Allergy Frontiers, Volume 5: Therapy and Prevention

Allergy Frontiers: Therapy and Prevention

Volume 5 Ruby Pawankar • Stephen T. Holgate Lanny J. Rosenwasser Editors

Allergy Frontiers: Therapy and Prevention

Volume 5 Editors Lanny J. Rosenwasser, M.D. Ruby Pawankar, M.D., Ph.D. Children’s Mercy Hospitals and Clinics Nippon Medical School UMKC School of Medicine 1-1-5 Sendagi, Bunkyo-ku 2401 Gillham Road Tokyo Kansas City, MO 64108 Japan USA

Stephen T. Holgate, M.D., Ph.D. University of Southampton Southampton General Hospital Tremona Road Southampton UK

ISBN: 978-4-431-99361-2 e-ISBN: 978-4-431-99362-9 DOI 10.1007/978-4-431-99362-9 Springer Tokyo Berlin Heidelberg New York

Library of Congress Control Number: 2009934782

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Springer is part of Springer Science+Business Media (www.springer.com) Foreword

When I entered the field of allergy in the early 1970s, the standard textbook was a few hundred pages, and the specialty was so compact that texts were often authored entirely by a single individual and were never larger than one volume. Compare this with Allergy Frontiers: Epigenetics, Allergens, and Risk Factors, the present six- volume text with well over 150 contributors from throughout the world. This book captures the explosive growth of our specialty since the single-author textbooks referred to above. The unprecedented format of this work lies in its meticulous attention to detail yet comprehensive scope. For example, great detail is seen in manuscripts dealing with topics such as “Exosomes, naturally occurring minimal antigen presenting units” and “Neuropeptide S receptor 1 (NPSR1), an asthma susceptibility gene.” The scope is exemplified by the unique approach to disease entities normally dealt with in a single chapter in most texts. For example, anaphylaxis, a topic usually confined to one chapter in most textbooks, is given five chapters in Allergy Frontiers. This approach allows the text to employ multiple contributors for a single topic, giving the reader the advantage of being introduced to more than one viewpoint regarding a single disease. This broad scope is further illustrated in the way this text deals with the more frequently encountered disorder, asthma. There are no fewer than 26 chapters dealing with various aspects of this disease. Previously, to obtain such a comprehensive approach to a single condition, one would have had to purchase a text devoted solely to that disease state. In addition, the volume includes titles which to my knowledge have never been presented in an allergy text before. These include topics such as “NKT ligand conjugated immunotherapy,” “Hypersensitivity reactions to nano medicines: causative factors and optimization,” and “An environmental systems biology approach to the study of asthma.” It is not hard to see that this textbook is unique, offering the reader a means of obtaining a detailed review of a single highly focused subject, such as the neuropeptide S receptor, while also providing the ability to access a panoramic and remarkably in-depth view of a broader subject, such as asthma. Clearly it is intended primarily for the serious student of allergy and immunology, but can also serve as a resource text for those with an interest in medicine in general.

v vi Foreword

I find it most reassuring that even though we have surpassed the stage of the one-volume, single-author texts, because of the wonderful complexity of our specialty and its broadening scope that has evolved over the years, the reader can still obtain an all-inclusive and comprehensive review of allergy in a single source. It should become part of the canon of our specialty. Phillip Lieberman, M.D. Foreword

When I started immunology under Professor Kimishige Ishizaka in the early 1950s, allergy was a mere group of odd syndromes of almost unknown etiology. An immunological origin was only suspected but not proven. The term “atopy,” originally from the Greek word à-topòs, represents the oddness of allergic diseases. I would call this era “stage 1,” or the primitive era of allergology. Even in the 1950s, there was some doubt as to whether the antibody that causes an allergic reaction was really an antibody, and was thus called a “reagin,” and allergens were known as peculiar substances that caused allergy, differentiating them from other known antigens. It was only in 1965 that reagin was proven to be an antibody having a light chain and a unique heavy chain, which was designated as IgE in 1967 with international consensus. The discovery of IgE opened up an entirely new era in the field of allergology, and the mechanisms of the immediate type of allergic reaction was soon evaluated and described. At that point in time we believed that the nature of allergic diseases was a mere IgE-mediated inflammation, and that these could soon be cured by studying the IgE and the various mediators that induced the inflammation. This era I would like to call “stage 2,” or the classic era. The classic belief that allergic diseases would be explained by a mere allergen- IgE antibody reaction did not last long. People were dismayed by the complexity and diversity of allergic diseases that could not be explained by mere IgE-mediated inflammation. Scientists soon realized that the mechanisms involved in allergic diseases were far more complex and that they extended beyond the conventional idea of a pure IgE-mediated inflammation. A variety of cells and their products (cytokines/chemokines and other inflammatory molecules) have been found to interact in a more complex manner; they create a network of reactions via their receptors to produce various forms of inflammatory changes that could never be categorized as a single entity of inflammation. This opened a new era, which I would like to call the modern age of allergology or “stage 3.” The modern era stage 3 coincided with the discovery that similar kinds of cytokines and cells are involved in the regulation of IgE production. When immu- nologists investigated the cell types and cytokines that regulate IgE production, they found that two types of helper T cells, distinguishable by the profile of cytokines they produce, play important regulatory roles in not only IgE production

vii viii Foreword but also in regulating allergic inflammation. The advancement of modern molecular technologies has enabled detailed analyses of molecules and genes involved in this extremely complex regulatory mechanism. Hence, there are a number of important discoveries in this area, which are still of major interest to allergologists, as can be seen in the six volumes of this book. We realize that allergology has rapidly progressed during the last century, but mechanisms of allergic diseases are far more complex than we had expected. New discoveries have created new questions, and new facts have reminded us of old concepts. For example, the genetic disposition of allergic diseases was suspected even in the earlier, primitive era but is still only partially proven on a molecular basis. Even the molecular mechanisms of allergic inflammation continue to be a matter of debate and there is no single answer to explain the phenomenon. There is little doubt that the etiology of allergic diseases is far more varied and complex than we had expected. An immunological origin is not the only mechanism, and there are more unknown origins of similar reactions. Although therapeutic means have also progressed, we remain far from our goal to cure and prevent allergic diseases. We have to admit that while we have more knowledge of the many intricate mechanisms that are involved in the various forms of allergic disease, we are still at the primitive stage of allergology in this respect. We are undoubtedly proceeding into a new stage, stage 4, that may be called the postmodern age of allergology and hope this era will bring us closer to finding a true solution for the enigma of allergy and allergic diseases. We are happy that at this turning point the editors, Ruby Pawankar, Stephen Holgate, and Lanny Rosenwasser, are able to bring out such a comprehensive book which summarizes the most current knowledge on allergic diseases, from epidemiology to mechanisms, the impact of environmental and genetic factors on allergy and asthma, clinical aspects, recent therapeutic and preventive strategies, as well as future perspectives. This comprehensive knowledge is a valuable resource and will give young investigators and clinicians new insights into modern allergology which is an ever-growing field. Tomio Tada, M.D., Ph.D., D.Med.Sci. Foreword

Allergic diseases represent one of the major health problems in most modern societies. The increase in prevalence over the last decades is dramatic. The reasons for this increase are only partly known. While in former times allergy was regarded as a disease of the rich industrialized countries only, it has become clear that all over the world, even in marginal societies and in all geographic areas—north and south of the equator—allergy is a major global health problem. The complexity and the interdisciplinary character of allergology, being the science of allergic diseases, needs a concert of clinical disciplines (internal medicine, dermatology, pediatrics, pulmonology, otolaryngology, occupational medicine, etc.), basic sciences (immunology, molecular biology, botany, zoology, ecology), epidemiology, economics and social sciences, and psychology and psychosomatics, just to name a few. It is obvious that an undertaking like this book series must involve a multitude of authors; indeed, the wide spectrum of disciplines relevant to allergy is reflected by the excellent group of experts serving as authors who come from all over the world and from various fields of medicine and other sciences in a pooling of geographic, scientific, theoretical, and practical clinical diversity. The first volume concentrates on the basics of etiology, namely, the causes of the many allergic diseases with epigenetics, allergens and risk factors. Here, the reader will find up-to-date information on the nature, distribution, and chemical structure of allergenic molecules, the genetic and epigenetic phenomena underlying the susceptibility of certain individuals to develop allergic diseases, and the manifold risk factors from the environment playing the role of modulators, both in enhancing and preventing the development of allergic reactions. In times when economics plays an increasing role in medicine, it is important to reflect on this aspect and gather the available data which—as I modestly assume— may be yet rather scarce. The big effort needed to undertake well-controlled studies to establish the socio-economic burden of the various allergic diseases is still mainly ahead of us. The Global Allergy and Asthma European Network (GA2LEN), a group of centers of excellence in the European Union, will start an initiative regarding this topic this year. In volume 2, the pathomechanisms of various allergic diseases and their classification are given, including such important special aspects as allergy and the bone marrow, allergy and the nervous system, and allergy and mucosal immunology.

ix x Foreword

Volume 3 deals with manifold clinical manifestations, from allergic rhinitis to drug allergy and allergic bronchopulmonary aspergillosis, as well as including other allergic reactions such as lactose and fructose intolerances. Volume 4 deals with the practical aspects of diagnosis and differential diagnosis of allergic diseases and also reflects educational programs on asthma. Volume 5 deals with therapy and prevention of allergies, including pharmacotherapy, as well as allergen-specific immunotherapy with novel aspects and special considerations for different groups such as children, the elderly, and pregnant women. Volume 6 concludes the series with future perspectives, presenting a whole spectrum of exciting new approaches in allergy research possibly leading to new strategies in diagnosis, therapy, and prevention of allergic diseases. The editors have accomplished an enormous task to first select and then motivate the many prominent authors. They and the authors have to be congratulated. The editors are masters in the field and come from different disciplines. Ruby Pawankar, from Asia, is one of the leaders in allergy who has contributed to the understanding of the cellular and immune mechanisms of allergic airway disease, in particular upper airway disease. Stephen Holgate, from the United Kingdom, has contributed enormously to the understanding of the pathophysiology of allergic airway reactions beyond the mere immune deviation, and focuses on the function of the epithelial barrier. He and Lanny Rosenwasser, who is from the United States, have contributed immensely to the elucidation of genetic factors in the susceptibility to allergy. All three editors are members of the Collegium Internationale Allergologicum (CIA) and serve on the Board of Directors of the World Allergy Organization (WAO). I have had the pleasure of knowing them for many years and have cooperated with them at various levels in the endeavor to promote and advance clinical care, research, and education in allergy. Together with Lanny Rosenwasser as co-editor-in-chief, we have just started the new WAO Journal (electronic only), where the global representation in allergy research and education will be reflected on a continuous basis. Finally, Springer, the publisher, has to be congratulated on their courage and enthusiasm with which they have launched this endeavor. Springer has a lot of experience in allergy—I think back to the series New Trends in Allergy, started in 1985, as well as to my own book Allergy in Practice, to the Handbook of Atopic Eczema and many other excellent publications. I wish this book and the whole series of Allergy Frontiers complete success! It should be on the shelves of every physician or researcher who is interested in allergy, clinical immunology, or related fields. Johannes Ring, M.D., Ph.D. Preface

Allergic diseases are increasing in prevalence worldwide, in industrialized as well as industrializing countries, affecting from 10%–50% of the global population with a marked impact on the quality of life of patients and with substantial costs. Thus, allergy can be rightfully considered an epidemic of the twenty-first century, a global public health problem, and a socioeconomic burden. With the projected increase in the world’s population, especially in the rapidly growing economies, it is predicted to worsen as this century moves forward. Allergies are also becoming more complex. Patients frequently have multiple allergic disorders that involve multiple allergens and a combination of organs through which allergic diseases manifest. Thus exposure to aeroallergens or ingested allergens frequently gives rise to a combination of upper and lower airways disease, whereas direct contact or ingestion leads to atopic dermatitis with or without food allergy. Food allergy, allergic drug responses and anaphylaxis are often severe and can be life-threatening. However, even the less severe allergic diseases can have a major adverse effect on the health of hundreds of millions of patients and diminish quality of life and work productivity. The need of the hour to combat these issues is to promote a better understanding of the science of allergy and clinical immunology through research, training and dissemination of information and evidence-based better practice parameters. Allergy Frontiers is a comprehensive series comprising six volumes, with each volume dedicated to a specific aspect of allergic disease to reflect the multidisciplinary character of the field and to capture the explosive growth of this specialty. The series summarizes the latest information about allergic diseases, ranging from epidemiology to the mechanisms and environmental and genetic factors that influence the development of allergy; clinical aspects of allergic diseases; recent therapeutic and preventive strategies; and future perspectives. The chapters of individual volumes in the series highlight the roles of eosinophils, mast cells, lymphocytes, dendritic cells, epithelial cells, neutrophils and T cells, adhesion molecules, and cytokines/chemokines in the pathomechanisms of allergic diseases. Some specific new features are the impact of infection and innate immunity on allergy, and mucosal immunology of the various target organs and allergies, and the impact of the nervous system on allergies. The most recent, emerging therapeutic strategies are discussed, including allergen-specific immunotherapy and anti-IgE treatment,

xi xii Preface while also covering future perspectives from immunostimulatory DNA-based therapies to probiotics and nanomedicine. A unique feature of the series is that a single topic is addressed by multiple contributors from various fields and regions of the world, giving the reader the advantage of being introduced to more than one point of view and being provided with comprehensive knowledge about a single disease. The reader thus obtains a detailed review of a single, highly focused topic and at the same time has access to a panoramic, in-depth view of a broader subject such as asthma. The chapters attest to the multidisciplinary character of component parts of the series: environmental, genetics, molecular, and cellular biology; allergy; otolaryngology; pulmonology; dermatology; and others. Representing a collection of state- of-the-art reviews by world-renowned scientists from the United Kingdom and other parts of Europe, North America, South America, Australia, Japan, and South Africa, the volumes in this comprehensive, up-to-date series contain more than 150 chapters covering virtually all aspects of basic and clinical allergy. The publication of this extensive collection of reviews is being brought out within a span of two years and with the greatest precision to keep it as updated as possible. This six- volume series will be followed up by yearly updates on the cutting-edge advances in any specific aspect of allergy. The editors would like to sincerely thank all the authors for having agreed to contribute and who, despite their busy schedules, contributed to this monumental work. We also thank the editorial staff of Springer Japan for their assistance in the preparation of this series. We hope that the series will serve as a valuable information tool for scientists and as a practical guide for clinicians and residents working and/or interested in the field of allergy, asthma, and immunology. Ruby Pawankar, Stephen T. Holgate, and Lanny J. Rosenwasser Contents

Part I Therapy and Prevention of Allergies

Allergen Avoidance and Prevention of Allergy ...... 3 Syed Hasan Arshad

Pharmacotherapy of Allergic Rhinitis ...... 19 Jeffrey M. Lehman and Michael S. Blaiss

Antihistamines in Rhinitis and Asthma ...... 37 Todor A. Popov

Antiallergic and Vasoactive Drugs for Allergic Rhinitis...... 51 Friedrich Horak

Antileukotrienes in Asthma and Rhinitis ...... 63 Anthony Peter Sampson

Mechanisms of Action of b2 Adrenoceptor Agonists ...... 91 Ian P. Hall and Ian Sayers

Alkylxanthines and Phosphodiesterase 4 Inhibitors for Allergic Diseases ...... 105 Mark A. Giembycz

Glucocorticoid Insensitive Asthma ...... 133 Sally E. Wenzel

Recalcitrant Asthma ...... 145 Sharmilee M. Nyenhuis and William W. Busse

Mechanisms and Management of Exercise-Induced Bronchoconstriction ...... 171 John D. Brannan and Paul M. O’Byrne

xiii xiv Contents

Use of Theophylline and Sodium Cromoglycate in Adult Asthma ...... 187 Hironori Sagara, Kenya Kouyama, Takeshi Fukuda, and Sohei Makino

New Insights into Allergen-Speciﬁ c Immunotherapy in Rhinitis and Asthma ...... 195 Giovanni Passalacqua and Giorgio Walter Canonica

Sublingual Immunotherapy in Allergic Rhinitis and Asthma ...... 217 Paul Potter

Anti-IgE in Allergic Airway Diseases: Indications and Applications ...... 227 Jennifer Preston DeMore and William W. Busse

Drug Delivery Devices and Propellants ...... 245 Bruce K. Rubin and James B. Fink

Update on the Management of Atopic Dermatitis/Eczema ...... 259 Sherrif F. Ibrahim, Anna De Benedetto, and Lisa A. Beck

Immunosuppressants as Treatment for Atopic Dermatitis ...... 291 Bartlomiej Kwiek and Natalija Novak

Management of Anaphylaxis ...... 311 Phillip Lieberman

Anaphylaxis: Are Regulatory T Cells the Target of Venom Immunotherapy? ...... 325 Marek Jutel, Mübeccel Akdis, Kurt Blaser, and Cezmi A. Akdis

Food Allergy: Opportunities and Challenges in the Clinical Practice of Allergy and Immunology ...... 335 Julie Wang and Hugh A. Sampson

Early Immunological Inﬂ uences on Asthma Development: Opportunities for Early Intervention ...... 347 Patrick G. Holt

Asthma and Allergy in Childhood: Prediction and Early Diagnosis ...... 365 Karin C. Lødrup Carlsen and Göran Wennergren

Early Interventions in Allergic Diseases ...... 379 L. Karla Arruda, Dirceu Solé, and Charles K. Naspitz Contents xv

Birth Cohort Studies for the Prevention of Allergy: New Perspectives—Where Do We Go from Now? ...... 397 Mascha Rochat and Erika von Mutius

Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma ...... 417 Susan L. Prescott

Recombinant Allergens for Therapy and Prevention: Molecular Design and Delivery of Allergy Vaccines ...... 433 Shyam S. Mohapatra and Shawna A. Shirley

Prevention of Allergic Diseases ...... 447 Leena von Hertzen and Tari Haahtela

Emerging Nonsteroidal Anti-Inﬂ ammatory Therapies Targeting Speciﬁ c Mechanisms in Asthma and Allergy ...... 465 Leif Bjermer and Zuzana Diamant

Part II Special Considerations in Children, Elderly and Pregnancy

Asthma and Rhinitis in Pregnancy ...... 485 Vanessa E. Murphy and Peter G. Gibson

Asthma in the Elderly ...... 499 Charles E. Reed

The Natural History of Childhood Asthma ...... 511 Miles Weinberger and Dirceu Solé

The Wheezing Infant and Young Child ...... 531 Peter J. Helms

Acute Severe Asthma in Children ...... 543 Barbara P. Yawn

Best Estimates of Asthma Control in Children ...... 565 Megan E. Partridge and William K. Dolen

Risk-Beneﬁ t of Asthma Therapy in Children: Topical Corticosteroids...... 577 Hugo P. Van Bever, Lynette P. Shek, and Daniel Y.T. Goh

Risk-Beneﬁ t of Asthma Therapy in Children: Nonsteroidal Anti-Inﬂ ammatory Drugs ...... 593 James P. Kemp xvi Contents

The Role of Inﬂ uenza Vaccination in Asthmatic Children ...... 611 Herman J. Bueving and Johannes C. van der Wouden

Treatment of Infants with Atopic Dermatitis ...... 621 Ulrich Wahn

Diagnosing Food Allergy in Children ...... 635 Dan Atkins

Diagnosis and Treatment of Latex Allergy ...... 653 Kevin J. Kelly and Brian T. Kelly

New Aspects of Peanut and Tree Nut Allergy ...... 675 Corinne A. Keet and Robert A. Wood

Allergic Fungal Sinusitis: Controversy and Evolution of Understanding with Therapeutic Implications ...... 695 Berrylin J. Ferguson and Arpita Mehta

Immunomodulatory Role of Bacillus Calmette-Guérin in the Prevention and Therapy of Allergy and Asthma ...... 713 Toluwalope O. Makinde, Againdra K. Bewtra, and Devendra K. Agrawal

Use of Theophylline and Sodium Cromoglycate in Pediatric Asthma ...... 727 Akihiro Morikawa

Antibody Deﬁ ciency Syndromes (Including Diagnosis and Treatment) ...... 737 Kenneth Paris, Lily Leiva, and Ricardo U. Sorensen

Index ...... 755 Contributors

Devendra K. Agrawal Departments of Biomedical Sciences, Internal Medicine, and Medical Microbiology and Immunology, Creighton University School of Medicine, CRISS II, Room 510, 2500 California Plaza, Omaha, NE 68178, USA Cezmi A. Akdis Swiss Institute of Allergy and Asthma Research (SIAF), Obere str. 22, CH-7270 Davos, Switzerland Mübeccel Akdis Swiss Institute of Allergy and Asthma Research (SIAF), Obere str. 22, CH-7270 Davos, Switzerland Syed Hasan Arshad Infection, Inflammation and Immunity Research Division, School of Medicine, University of Southampton, Mailpoint 810, Level F, South Block, Southampton General Hospital, Southampton SO16 6YD, UK L. Karla Arruda Division of Clinical Immunology, Department of Medicine, School of Medicine of Riberão Preto, University of São Paulo, Brazil Dan Atkins Department of Pediatrics, National Jewish Health, 1400 Jackson Street, Denver, CO80206, USA Lisa A. Beck Departments of Dermatology and Medicine, University of Rochester, 601 Elmwood Ave, Box 697, Rochester, NY 14642, USA Anna De Benedetto Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA Againdra K. Bewtra Department of Internal Medicine, Creighton University School of Medicine, CRISS II, Room 510, 2500 California Plaza, Omaha, NE, USA

xvii xviii Contributors

Leif Bjermer Department of Respiratory Medicine and Allergology, Heart and Lund Division, University Hospital of Lund, 221 85 Sweden Michael S. Blaiss Department of Medicine and Pediatrics, Division of Clinical Allergy and Immunology, University of Tennessee Health Science Center, 7205 Wolf River Blvd. Suite 200, Germantown, TN 38138, USA Kurt Blaser Swiss Institute of Allergy and Asthma Research (SIAF), Obere str. 22, CH-7270 Davos, Switzerland John D. Brannan Firestone Institute for Respiratory Health and the Department of Medicine, Michael G DeGroot School of Medicine, McMaster University, 50 Charlton Ave, East, Room T3213, Hamilton, ON, Canada L8N 4A6 Herman J. Bueving Department of General Practice, Erasmus MC, University Medical Center Rotterdam, Burg. S’Jacobsplein 51, 3015 CA Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands William W. Busse Division of Allergy and Immunology, Department of Medicine, University of Wisconsin; University of Wisconsin School of Medicine and Public Health, J5/219 CSC-2454, 600 Highland Avenue, Madison, WI 53792, USA Giorgio Walter Canonica Allergy and Respiratory Diseases, Department of Internal Medicine, Padiglione Maragliano, L.go R. Benzi 10, 16132 Genoa, Italy Karin C. L¿drup Carlsen Department of Paediatrics, Division of Woman and Child, Oslo University Hospital, Ullevål University Hospital, NO-0407, Oslo, Norway; The Faculty of Medicine, University of Oslo, Oslo, Norway Jennifer Preston DeMore University of Wisconsin School of Medicine and Public Health, J5/219 CSC-2454, 600 Highland Avenue, Madison, WI 53792, USA Zuzana Diamant Departments of Allergology and Pulmonology, Erasmus University Medical Center, Rotterdam, The Netherlands William K. Dolen Allergy-Immunology Section, Departments of Pediatrics and Medicine, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912, USA Contributors xix

Berrylin J. Ferguson Division of Sino-Nasal Disorders and Allergy, Department of Otolaryngology, University of Pittsburgh School of Medicine, The Eye and Ear Institute Building, 200 Lothrop Street, Suite 500, Pittsburgh, PA 15213, USA James B. Fink Independent Consultant, San Mateo, CF, USA Takeshi Fukuda Department of Pulmonary Medicine and Clinical Immunology, Dokkyo Medical University School of Medicine, Japan Peter G. Gibson Hunter Medical Research Institute, Level 3, John Hunter Hospital, Locked Bag #1, Hunter Region Mail Centre, Newcastle, NSW 2310, Australia Mark A. Giembycz Department of Pharmacology and Therapeutics, Institute of Infection, Immunity and Inflammation, Faculty of Medicine, University of Calgary, Calgary, AB, Canada Daniel Y.T. Goh Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore; University Children’s Medical Institute, National University Hospital, Singapore Tari Haahtela Skin and Allergy Hospital, Helsinki University Central Hospital, P.O. Box 160, 00029 HUS, Finland Ian P. Hall Division of Therapeutics and Molecular Medicine, University Hospital of Nottingham, Nottingham NG7 2UH, UK Peter J. Helms Department of Child Health, University of Aberdeen; Royal Aberdeen Children’s Hospital, Westburn Road, Aberdeen, Scotland AB25 2ZG, UK Patrick G. Holt Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia, Perth, Western Australia Friedrich Horak Ear Nose and Throat Department, Allergy Centre Vienna West, Medical University Vienna, Huetteldorferstrasse 46, A-1150 Vienna, Austria Sherrif F. Ibrahim Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA xx Contributors

Marek Jutel Swiss Institute of Allergy and Asthma Research (SIAF), Obere Street 22, CH-7270, Davos, Switzerland; Department of Clinical Immunology, Wroclaw Medical University, Traugutta 57, PL- 50-417 Wroclaw, Poland Corinne A. Keet Department of Pediatrics, Division of Pediatric Allergy and Immunology, Johns Hopkins University School of Medicine, Baltimore, MD, USA Brian T. Kelly Medical College of Wisconsin, 8700 W. Wisconsin Avenue Milwaukee, WI 53226, USA Kevin J. Kelly Department of Pediatrics, University of Missouri Kansas City School of Medicine, 2401 Gillham Road, Kansas City, MO 64108, USA James P. Kemp Department of Pediatrics, University of California School of Medicine, San Diego; Allergy and Asthma Medical Group and Research Center, 9610 Granite Ridge Drive, Suite B, San Diego, CA 92123, USA Kenya Kouyama Department of Respiratory Medicine, Dokkyo Medical University Koshigaya Hospital, Japan Bartlomiej Kwiek Department of Dermatology, Medical University of Warsaw, Warsaw, Poland Jeffrey M. Lehman Department of Medicine and Pediatrics, Division of Allergy and Immunology, University of Tennessee Health Science Center, 50 N. Dunlap, WPT Rm 401, Memphis, TN 38103, USA Lily Leiva Department of Pediatrics, Research Institute for Children 4th Floor, Louisiana State University Health Sciences Center; Jeffrey Modell Diagnostic Center, Children’s Hospital, 200 Henry Clay Avenue, New Orleans, LA 70118, USA Phillip Lieberman Division of Allergy and Immunology, Department of Medicine and Pediatrics, University of Tennessee, Memphis, 7205 Wolf River Boulevard, Suite 200, Germantown, TN 38138, USA Toluwalope O. Makinde Department of Biomedical Sciences, Creighton University School of Medicine, CRISS II, Room 510, 2500 California Plaza, Omaha, NE 68178, USA Sohei Makino Jobu Hospital for Respiratory Diseases, Japan Contributors xxi

Arpita Mehta Division of Sino-Nasal Disorders and Allergy, Department of Otolaryngology, University of Pittsburgh School of Medicine, The Eye and Ear Institute Building, 200 Lothrop Street, Suite 500, Pittsburgh, PA 15213, USA Shyam S. Mohapatra Division of Allergy and Immunology, Joy Airway Disease and Nanomedicine Research Center, Department of Internal Medicine, Department of Molecular Medicine, University of South Florida, College of Medicine and James A. Haley Veteran’s Hospital, Tampa, FL, USA Akihiro Morikawa Kitakanto Allergy Institute, Kibounoie Hospital, 22-4 Ohmama, Ohmama-machi, Midori, Gunma 376-0101, Japan Vanessa E. Murphy Hunter Medical Research Institute, Level 3, John Hunter Hospital, Locked Bag #1, Hunter Region Mail Centre, Newcastle, NSW 2310, Australia Erika von Mutius University Children’s Hospital, Lindwurmstr. 4, 80337, Munich, Germany Charles K. Naspitz Division of Allergy, Clinical Immunology and Rheumatology, Federal University of São Paulo, São Paulo, Brazil Natalija Novak Department of Dermatology and Allergy, University of Bonn, Sigmund-Freud- Strasse 25, 53105 Bonn, Germany Sharmilee M. Nyenhuis Division of Allergy and Immunology, Department of Medicine, University of Wisconsin, CSC 2454/J5-219, 600 Highland Avenue, Madison, WI 53792, USA Paul M. O’Byrne Firestone Institute for Respiratory Health and the Department of Medicine, Michael G DeGroot School of Medicine, McMaster University, 50 Charlton Ave, East, Room T3213, Hamilton, ON, Canada L8N 4A6 Kenneth Paris Department of Pediatrics, Research Institute for Children 4th Floor, Louisiana State University Health Sciences Center; Jeffrey Modell Diagnostic Center, Children’s Hospital, 200 Henry Clay Avenue, New Orleans, LA 70118, USA Megan E. Partridge Allergy-Immunology Section, Departments of Pediatrics and Medicine, Medical College of Georgia, 1120 15th Street, Augusta, GA, USA Giovanni Passalacqua Allergy and Respiratory Diseases, DIMI, University of Genoa, Italy xxii Contributors

Todor A. Popov Clinic of Allergy and Asthma, Alexander’s University Hospital, 1, Sv. Georgi Sofiyski St., 1431 Sofia, Bulgaria Paul Potter Allergy Diagnostic and Clinical Research Unit, University of Cape Town Lung Institute, George Street, Mowbray, Cape Town 7700, South Africa Susan L. Prescott School Paediatrics and Child Health Research, University of Western Australia, Perth, WA, Australia; Princess Margaret Hospital, P.O. Box D184, Perth, WA 6001, Australia Charles E. Reed Mayo Medical School, Rochester, MN, USA Mascha Rochat University Children’s Hospital, Lindwurmstr. 4, 80337, Munich, Germany Bruce K. Rubin Jessie Ball duPont Professor and Chairman of the Department of Pediatrics, Professor of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23219, USA Hironori Sagara Department of Respiratory Medicine, Dokkyo Medical University Koshigaya Hospital, Japan Hugh A. Sampson Division of Allergy and Immunology, Department of Pediatrics, Jaffe Food Allergy Institute, Mount Sinai School of Medicine, New York, NY, USA Anthony P. Sampson Division of Infection, Inflammation & Immunity (III), University of Southampton School of Medicine, The Sir Henry Wellcome Building (MP825), Southampton General Hospital, Tremona Road, Southampton, S016 6YD, UK Ian Sayers Division of Therapeutics and Molecular Medicine, University Hospital of Nottingham, Nottingham NG7 2UH, UK Lynette P. Shek Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore Shawna A. Shirley Department of Molecular Medicine, University of South Florida, College of Medicine and James A. Haley Veteran’s Hospital, Tampa, FL, USA Dirceu Solé Division of Allergy, Clinical Immunology and Rheumatology, Federal University of São Paulo, São Paulo, Brazil Contributors xxiii

Ricardo U. Sorensen Department of Pediatrics, Research Institute for Children 4th Floor, Louisiana State University Health Sciences Center; Jeffrey Modell Diagnostic Center, Children’s Hospital, 200 Henry Clay Avenue, New Orleans, LA 70118, USA Hugo P. Van Bever Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore; Department of Paediatrics, National University Hospital, 5 Lower Kent Ridge Road, 119074 Singapore Johannes C. van der Wouden Department of General Practice, Erasmus MC, University Medical Center Rotterdam, Burg.s’ Jacobsplein 51, 3015 CA Rotterdam, P.O. Box 2040, 3000 CA Rotterdam, The Netherlands Leena von Hertzen Skin and Allergy Hospital/ HUCH, P.O. Box 160, 00029 HUS, Finland Ulrich Wahn Department for Pediatric Pneumology and Immunology, Charité Berlin, Germany Julie Wang Division of Allergy and Immunology, Department of Pediatrics, Jaffe Food Allergy Institute, Mount Sinai School of Medicine, New York, NY, USA Miles Weinberger Pediatric Department, University of Iowa Hospital, 200 Hawkins Drive, Iowa City, IA 52242, USA Göran Wennergren Department of Paediatrics, Göteborg University, Queen Silvia Children’s Hospital, SE-416 85 Göteborg, Sweden Sally E. Wenzel University of Pittsburgh, NW 628 Montefiore, 3459 Fifth Ave., Pittsburgh, PA 15213, USA Robert A. Wood Department of Pediatrics, Division of Allergy and Immunology, Johns Hopkins University School of Medicine; Johns Hopkins Hospital, CMSC 1102, 600 North Wolfe Street, Baltimore, MD 21287, USA Barbara P. Yawn University of Minnesota; Olmsted Medical Center, MN, USA Part I Therapy and Prevention of Allergies Allergen Avoidance and Prevention of Allergy

Syed Hasan Arshad

Introduction

Definitions

Atopy is the inherited tendency to produce Immunoglobulin E (IgE) antibodies in response to exposure to allergens. This can be identified clinically by measurement of specific IgE to allergens in the serum or by skin prick test, where IgE bound to skin mast cells is detected. The atopic predisposition leads to a higher risk of development of allergic diseases such as allergic asthma and rhinitis, atopic dermatitis and some allergic food and drug reactions, specifically those that are IgE mediated. Epidemiological studies have shown that nearly 40% of the population in Western, developed countries are atopic [1] . However, not all subjects with atopy develop clinical manifestations. Some remain asymptomatic, while others develop various symptoms related to allergic diseases. The disease may also go into remission. Indeed, it is not uncommon for atopic children to grow out of one set of allergic diseases, usually food allergy and atopic dermatitis, only to be replaced by allergic asthma and rhinitis in later childhood. This is commonly known as atopic march. In this chapter, atopy will be considered as meaning both allergic sensitization and atopic/allergic disease. Primary prevention aims at reducing the development of disease in previously healthy subjects while secondary preventive measures seek to reduce morbidity in individuals with disease.

S.H. Arshad () Infection, Inflammation and Immunity Research Division, School of Medicine , University of Southampton , Mailpoint 810, Level F, South Block, Southampton General Hospital , Southampton , SO16 6YD , UK e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 3 DOI 10.1007/978-4-431-99362-9_1, © Springer 2010 4 S.H. Arshad

Risk Factors

The development of asthma and other allergic diseases is determined by gene– environment interactions. Those with the right combination of genes and appropriate environmental stimuli may develop the disease. Exposure to allergen is, of course, essential in the development of allergic sensitization and symptomatic diseases in atopic individuals. Other environmental factors may predispose to the phenotypic expression in genetically susceptible individuals and may include exposure to pollutants, dietary factors and infections.

At Risk Population

The high prevalence of allergic diseases, in the community, has become a major public health problem. There is an urgent need to devise effective methods to prevent the development of these disorders. Individuals who develop atopy are both genetically susceptible and have been exposed to appropriate allergens. Despite advances in identification of asthma and atopy genes, genetic manipulation to reduce the development of atopy may not be possible in the near future. Therefore, the focus has been on allergen avoidance as a means of preventing atopy. One of the difficulties in preventing atopy is that of identifying susceptible individuals, who would be at high risk and stand to benefit most from an effective intervention. For high-risk children, more intensive and expensive measures may be justified, if their effectiveness can be proven. At present, these individuals are identified by positive responses on skin prick test or presence of specific IgE in their serum, both indicating sensitization. However, by the time sensitization has developed it may be too late to intervene. Moreover, the onset of allergic manifestations is often during early childhood. Rapid advances in human genetics will result in better identification of at-risk children at birth or even earlier. Until then, most studies have relied upon family history of atopy as a means of identifying children at high risk of atopy and thus suitable for preventive measures. This is not entirely satisfactory as a significant number of allergy problems develop in individuals with no history of atopy in the immediate family.

Early Critical Period

Allergic diseases are common in early childhood and many children develop sensitization during the first 3 years of their life. This may be because pre-natal and immediate post-natal periods are critical in the development of the immune system. There is evidence to suggest that a maturational deficiency exists in the immune system during infancy in children who are at high risk due to family history of atopy [2] . Prevention of Allergy 5

It is likely that environmental exposures during this period will have a more profound influence on the developing immune system. It has also been argued that fetal exposure to allergens should be minimized in order to protect the developing immune system. A susceptible child will develop tolerance or sensitization depending on the type, amount and route of exposure of an allergen. Further exposure to the same allergens may lead to allergic reaction, which may be systemic or confined to one organ system. Thus, efforts at reducing allergens exposure to prevent atopy have primarily focussed on infancy and occasionally included the third trimester of pregnancy.

Allergen Exposure

Certain allergens are ubiquitous and most – if not all – of us are exposed to these allergens in varying degrees. For example, food allergens such as cows’ milk and egg are foreign proteins that children are often exposed to, early in life. The “normal” response of the immune system is that of tolerance and production of IgG antibodies. However, some but not all, susceptible individuals may produce IgE antibodies instead, detectable on skin prick test or radioallergosorbent test (RAST), which may lead to cow’s milk or egg allergy and may contribute to the development of atopic eczema. Similarly, exposure to house dust mite and pollen allergens is almost universal in temperate, humid climates and yet not all atopic individuals are sensitized to these ubiquitous allergens.

Exposure and Disease

Even among those with atopic heredity, it is not clear why exposure to some allergens induces tolerance, while others cause sensitization.This may depend on a number of factors like dose and route of exposure and these factors may act differently with different allergens. For example, for dust mite allergen there seems to be a dose response effect, where increasing level of exposure may increase the risk of sensitization [3] . However, there is some evidence that exposure to cat allergen may work differently where extremely low and high exposure may lead to tolerance while middle level exposure may increase sensitization [4] . Recent evidence also suggests that environmental exposure (through skin or airway) to some food allergens may cause sensitization, while oral route induces tolerance [5] . In this state of a relative lack of knowledge regarding critical issues, the evidence to support the hypothesis – if prevention of atopy is possible by allergen avoidance – would undoubtedly be patchy. Nonetheless, this idea remains attractive to the investigators across the world and several studies have been performed to test the effectiveness of allergen avoidance. There are several reasons for this. First, if exposure to allergen causes sensitization and subsequently clinical diseases, then it is logical to try to 6 S.H. Arshad reduce exposure to allergen to prevent atopy. Secondly, there have been successes with this approach, albeit in slightly different circumstances. For example, with the increased use of latex gloves, latex allergy became a considerable problem in 1980s and 1990s. With reduction in exposure, primarily with the increased use of latex free gloves and instruments, the prevalence of latex allergy has been reduced.

Primary Prevention

Food Allergen Avoidance

Breast Feeding

Cow’s milk is often introduced to the infant either as replacement or as supplement to breast feeding. Thus, cow’s milk allergy is relatively common in infancy with a prevalence of around 2–3% when strict criteria and/or challenge protocols were used for diagnosis [6] . Exclusive breast feeding, which avoids exposure to cows’ milk in early life, has been proposed as an atopy reducing measure for several decades. In 1930s, Grlulee and Sanford reported seven times higher incidence of eczema in children fed cow’s milk formula as opposed to those fed breast milk [7] . Since then, a large number of studies have produced conflicting results [8] . Most of these studies have been observational, as it is not considered ethical to randomize children into breast or formula fed groups. This and other methodological flaws (retrospective collection of information, short duration of follow-up, poor definition of outcomes) in studies may account for some of the controversial results. The weight of the evidence favors a protective effect of exclusive breast feeding for at least up to 3 months, on infantile wheeze and atopic eczema. There is no clear protective effect on asthma and rhinitis. The effect of exclusive breast feeding may be modified by atopic heredity. A recent study suggested that those with genetic predisposition had lower incidence of sensitization and allergic rhinitis with exclusive breast feeding, while children without such predisposition had an increased risk [9] . However, the effect of breast milk on immune system is more complex (e.g. protection against infection, nutritional factors such as omega-3 fatty acids) than simple avoidance of cow’s milk exposure. Breast feeding has numerous nutritional, immunological, and psychological advantages and should be recommended for all, irrespective of its effect on atopy prevention. In terms of allergen exposure, it is known for some time that breast fed infants are exposed to small amounts of food protein, ingested by the mother. These small quantities of food protein antigen carry a significant potential for sensitizing the infant at a very early age. Several randomized controlled trials (RCTs) have tested the hypothesis that maternal avoidance of highly allergenic food (such as dairy produce, egg, fish and nuts) during lactation may reduce susceptible infant’s Prevention of Allergy 7

Table 1 Randomized controlled trials of maternal avoidance of highly allergenic foods during lactation (with or without restriction during pregnancy) Duration of Study (year reported) Primary outcomes follow-up (years) Benefit Zeiger et al. (1989), Atopy 1 Cows’ milk allergy Zeiger and Heller (1995)a and AD reduced 7 No effect Herrmann et al. (1996) a AD b /food allergic 1 No difference sensitization Sigurs et al. (1992), AD 4 AD Hattevig et al. (1999) a 10 No difference a References: [10– 14] b AD atopic dermatitis

exposure to these allergenic foods through breast milk and thus prevent the development of atopy (Table 1 ). The results are variable with some studies showing a reduction in atopic diseases, especially in cow’s milk allergy and atopic eczema in early childhood, while others failed to show any protective effect [10– 14] . Although maternal avoidance diet during lactation is difficult to adhere to, none of the studies restricting maternal diet during lactation only [13, 14] , reported any adverse nutritional effects for mother or child. A Cochrane database review concluded that restricting maternal diet during lactation might be of some benefit in children at high risk of atopy [15] .

During Pregnancy

Fetus is also exposed to food ingested by the mother as cord blood mononuclear cells recognize and proliferate when stimulated by food (such as cows’ milk and egg) proteins. To prevent this sensitization, the protective effect of maternal avoidance of highly allergenic foods during late pregnancy was assessed in a prospective study [16, 17] . Restricting maternal diet (excluding cow’s milk and egg) during the third trimester of pregnancy seems to have little beneficial effect in genetically predisposed children. Indeed, there was some concern regarding the health of the mother and child, as the weight gain during pregnancy was lower than expected, and infants had slightly lower birth weight compared to the control group. Two RCTs combined the dietary restriction of highly allergenic foods (cow’s milk, egg, nuts, fish, and soy) during late pregnancy and lactation up to 6 months [10– 12] . There was a reduction in food allergic manifestations and atopic dermatitis at the age of 2 years in one study, but no long-term benefit beyond early childhood was observed. Weight gain during the third trimester was again a concern in mothers who practiced avoidance diet. 8 S.H. Arshad

Late Introduction of Solid Foods

Several observational studies have suggested that delaying the introduction of solid foods up to at least 6 months, thus avoiding infants’ exposure to potentially allergenic foods may reduce the occurrence of food allergy and atopic eczema in genetically predisposed children [18, 19] . On this basis, most atopy prevention guidelines recommend late (after 6 months) introduction of solid foods. Peanut is a specific example. Observational studies suggested that ingestion of peanut by the mother during pregnancy and early introduction of peanut in infants’ diet (e.g. peanut butter) might increase the risk of peanut allergy [20] . In the UK, mothers with a history of atopy in the immediate family were advised to avoid peanut during pregnancy and delay introduction in the child’s diet for up to 3 years. However, it is uncertain if peanut avoidance in early life has any effect on the prevalence of peanut allergy in children [21] . Importantly, no RCT has been done to address specifically the benefit of delayed introduction of solid foods. Most intervention studies have combined late introduction of solids with other intervention measures and thus it is difficult to know if this strategy alone has any protective effect. The evidence is weak to support a preventive effect of late introduction of solid foods, including peanut, as the sole intervention [21] . Indeed, a recent study suggests that oral ingestion of peanut may lead to tolerance rather than sensitization which is likely to occur through the environmental (skin, airway) route [5] .

Hydrolyzed Milk Formulae

In hydrolyzed milk formulae, protein is broken down into small peptides rendering it non-allergenic. The resulting small molecules loses epitops essential for IgE binding – a pre-requisite for IgE mediated allergic reaction. Extensive hydrolyzate contains only a tiny fraction of the remaining large size peptides, whereas partial hydrolyzate has significant amount of relatively large peptides with IgE binding capacity. These formulae are designed to be used as replacement therapy for children with allergy to cows’ milk. However, in children at high risk of atopy, who are not breast fed, hydrolyzed formulae can be used as a primary prevention strategy, avoiding early exposure to cows’ milk. A number of RCTs have been done to assess the preventive effect of replacing cows’ milk formula with a hydrolyzate from birth (Table 2 ). A reduction in cow’s milk allergy and atopic dermatitis in the first year has generally been documented but any longer term effect is uncertain [22– 26] . There is some controversy regarding the extent of hydrolysis needed for primary prevention. Overall, extensive hydrolyzate is considered more effective [26] . There is also some uncertainty regarding the differential effect of the type of protein (casein vs. whey) used to produce hydrolyzate [26] . Most RCTs indicate a greater preventive effect of extensively hydrolyzed casein formula on allergic manifestations. Overall, protein hydrolyzate, as supplement or alternative to breast feeding, reduces allergic manifestations (cow’s milk allergy and atopic eczema) during the first 2–3 years of life in children at high risk of atopy. These hydrolyzates have Prevention of Allergy 9

Table 2 Randomized controlled trials of the use of hydrolyzed milk formula for primary prevention of atopy Duration of Study (year reported) Primary outcomes follow-up (years) Benefit Mallet and Henocq Wheeze 1 No difference (1992)a 2 AD Marini et al. (1996) a ADc /recurrent 1 3-fold reduction in allergic wheeze manifestations Fukushima et al. (1997) a AD/cows’ milk 2 Significant reduction in allergy both diseases Chan et al. (2002) a AD 3 AD but not wheeze GINI b Study (2003)a AD/food allergy 1 AD reduced a References: [22– 26] b GINI German Infant Nutrition Intervention c AD atopic dermatitis shown to be nutritionally adequate for the need of the infant. However, these have not been shown to be superior to exclusive breast feeding. Most studies found that soy formula does not protect against allergy in high-risk infants [27] . In summary, avoidance of food allergens in early life, in children at high risk of atopy may reduce the development of cow’s milk allergy and atopic eczema in the first 2–3 years of life. Any additional protective long-term effect or reduction in asthma or allergic rhinitis remains uncertain.

Aeroallergens

Common aeroallergens include dust mites, pollens, furry pets, molds, and cockroaches (Table 3 ). Exposure to these allergens is known to cause morbidity in those with allergic diseases such as asthma, allergic rhinitis, and atopic eczema. There is less agreement if exposure to these allergens causes the development of these diseases in previously healthy children but the bulk of evidence favours the hypothesis [28] . Thus, it is likely that allergen avoidance could prevent the development of atopy (primary prevention) and may also reduce symptoms in those with allergic disease (secondary prevention).

House Dust Mite Allergen Avoidance

House dust mite is one of the most common indoor allergen. Dust mites reside in carpets, bedding, soft furnishings, and soft toys, and the allergen they produce in their faeces and body parts, enriches the dust collected in these items. With human activity, the dust – and with it, the mite allergen – gets airborne and inhaled. 10 S.H. Arshad

Table 3 Common airborne (inhalant) allergens Group Common allergens Dust mites Dermatophagoides pteronyssinus Dermatophagoides farinae Molds Cladosporium Penicillium Aspergillus Alternaria Pollens Grass Weed Tree Flower Domestic animals Cat Dog Rabbit Horse Insects Cockroach Birds Cockatiel Budgerigar Rodents Mouse Rat Hamster Guinea pig Gerbil

Exposure to dust mite allergen causes sensitization in genetically susceptible children in a dose dependent manner [3] and dust mite sensitization has been shown to increase the risk of future development of asthma and allergic rhinitis [29] . There is some evidence of a direct link between exposure to house dust mite and development of asthma [30] . Presuming that immediate post-natal period is a particularly critical time for allergen exposure to have it maximal effect on the developing immune system, most intervention studies have attempted to reduce infant’s exposure to dust mite allergen exposure from birth. Some of these studies have been carefully designed and executed, showing a reduction in the content of dust mite allergen in the collected dust in the intervention group [31– 38] . However, in most studies, this reduction in exposure did not have the desired effect of reducing the development of atopy (Table 4 ). Thus, recent evidence indicates that current avoidance measures, including mattress impermeable covers reduce dust mite allergen exposure, but this may not be sufficient to prevent clinical allergy. Longer term follow-up is required to make a firm conclusion, but it seems unlikely that current dust mite allergen avoidance measures are effective in achieving a significant reduction in the burden of atopy. Prevention of Allergy 11

Table 4 Randomized controlled trials evaluating the effect of house dust mite allergen avoidance on primary prevention of atopy Age at Allergen avoidance Outcome Study recruitment N measures at (years) Preventive effect on SPACE a,b Birth 696 Mattress covers provided 1 Allergic and advice given to sensitization reduce exposure to 2 No effect 2–4 years 636 dust mite and cigarette 1 Allergic smoke sensitization 5–7 years 242 1 Allergic sensitization MAASa,b Prenatal 620 Mattresses covers, HEPA c 1 Severe wheeze only filter, hard wood flooring and use of acarosan PIAMAa,b Prenatal 810 Mattress covers and 2 Nocturnal cough general advice only CAPSa,b Prenatal 616 Mattress covers and 1.5 No effect general advice 3 Dust mite sensitization a SPACE Study of Prevention of Allergy in Children of Europe, MAAS Manchester Asthma and Allergy Study, PIAMA Prevention and Incidence of Asthma and Mite Allergy Study, CAPS Childhood Asthma Prevention Study b References: [31– 38] c HEPA: High Efficiency Particulate Arresting

Other Aeroallergens

Although, dust mite is the most important allergen worldwide for asthma, other aeroallergens assume importance in various climates. For example, in the dry hot climate of Arizona, most subjects with asthma are sensitized to Alternaria Alternata , a common indoor mold. In Scandinavian countries, where dust mites do not thrive due to cold and dry environment, animals, particularly cat is a major allergen. Similarly, in inner cities of the US and other countries, cockroach allergen may cause most morbidity. No RCT has yet been carried out to assess the effect of reduction in mold, animal, or cockroach allergen in primary prevention of atopy. Another set of important aeroallergens are grass, tree and weed pollen, which causes seasonal allergic rhinitis and asthma. Observational studies provide evidence to support the view that early exposure to high levels of pollen may increase the risk of later development of seasonal allergic rhinitis [39] . However, an RCT to assess the effectiveness of primary prevention by reducing exposure to pollen would be extremely difficult to perform. 12 S.H. Arshad

Table 5 Randomized controlled trials assessing the effectiveness of combined food and environmental allergen avoidance on primary prevention of atopy Allergen avoidance Follow-up Study N measures at (years) Reduction in Isle of Wight 120 Breast feeding with 1 Asthma, eczema, Prevention Studya maternal dietary allergic sensitization restriction, hydrolyzed 2 Allergic sensitization formula, delayed 4 Allergic sensitization introduction of solids, 8 Asthma, allergic acaricide applications sensitization and mattress covers Canadian 545 Breast feeding, delayed 1 Asthma, allergic rhinitis Asthma Primary introduction of solids, 2 Asthma Prevention Study a reduction of dust-mite 7 Asthma (but not and pet allergen eczema or atopy) PREVASC a,b 443 Breast feeding, delayed 2 Asthma introduction of solids, hydrolyzed formula, reduction of dust-mite and pet allergen a References: [40– 43] b Prevention of Asthma in Childhood Study

Combined Approach

Reduction in one set of allergens, either food or dust-mite, does not seem to be highly effective in preventing atopy. Perhaps a comprehensive approach in allergen reduction is required (Table 5 ). This hypothesis was tested originally in the Isle of Wight prevention study where strict avoidance of highly allergenic food was combined with dust-mite allergen reduction in high risk infants [40] . These children have also been followed-up for the longest period (birth to 8 years). Overall, there has been significant reduction in allergen sensitization as well as clinical manifestations of atopy such as asthma, atopic eczema, and allergic rhinitis [41] . A Canadian study, which combined dust-mite avoidance with breast feeding and general environmental measures also showed a reduction in asthma but not allergic sensitization [42] . A recent Dutch study further supports this concept where high-risk infants developed less atopy when breast fed and avoided dust-mite and smoke exposure [43] . A recent review concluded that multi-faceted approach to allergen avoidance addressing both food and dust-mite allergen reduction may afford better protection to infants at high risk [44] .

Secondary Prevention

Secondary prevention aims to achieve better control of disease and improve prognosis by avoidance of exacerbating factors such as allergens and pollutants. Environment control, including allergen avoidance should be an essential part of the management of allergic disease. Prevention of Allergy 13

Occupational Allergens

Occupational allergen exposure may cause asthma, rhinitis, and dermatitis, which may be atopic or non-atopic. Reduction in exposure to occupational allergens, by changes in industrial processes or use of protective gear, is essential to reduce morbidity due to occupational disease. Latex allergy is one such example where use of non-latex gloves and other appropriate precautions has resulted in significant reduction in morbidity and mortality.

Food Allergens

Exposure to food allergens may cause relatively minor symptoms such as itching and numbness in the mouth, as occurs in oral allergy syndrome due to cross reactivity of certain fruits proteins with tree pollens. It may cause or exacerbate organ-specific disease such as atopic eczema. However, it may also result in severe and life threatening anaphylaxis. Prevention by avoidance of relevant food allergen remains the mainstay of treatment of food allergy. In children with cow’s milk allergy, extensive hydrolyzate is often tolerated and those with extreme sensitivity can be given amino-acid based formula. Once the diagnosis is made, detailed information regarding avoidance should be provided. Written information with a list of prepared or packaged food that may contain specific food allergens helps to reduce inadver- tent exposure. The patient should be taught how to glean relevant information from the packaged food labels. The services of a dietician may be invaluable. Accidental exposure often occurs outside home. Therefore people should also be encouraged to ask, when unsure, the details of the constituents of the meal, for example in a restaurant or at a dinner party. Nuts are particularly difficult to avoid as traces occur in many foods. For fear of litigation, manufacturers often label a vast number of packaged foods as “may contain traces of nuts,” which limits the choice of food available to those with nut allergy. Accurate labelling is also difficult due to uncertainty regarding the “minimal safe dose” i.e. the amount of a food, such as peanut, that can be regarded as safe for highly food allergic patients.

Aeroallergens

In subjects with allergic asthma and rhinitis, exposure to common allergens such as pollen, mold, and dust-mite is associated with increase in morbidity and risk of emergency care attendance. Most studies have focussed on avoidance of dust-mite allergen. In the 1980s, extreme measures such as removing children with asthma and dust-mite sensitivity to several thousand feet above sea level in Alps, where the environment was cold and dry (not suitable for dust-mite survival) resulted in significant improvement in asthma symptoms and bronchial hyper-reactivity [45] . 14 S.H. Arshad

Several RCTs have shown that it is possible to achieve a reduction in mite allergen exposure with environmental measures including the use of dust-mite allergen impermeable covers [46] . Some, but not all, studies have shown reduction in symptoms and/or need for medication [46] . Recent studies however, indicate that simply handing out dust-mite allergen mattress covers alone is not adequate for a clinically relevant benefit in asthma or rhinitis [47, 48] . What is needed is a comprehensive approach with identification and removal of allergens and pollutants in the patient’s environment, and specific advice and education on environmental control. In inner city homes, heavily infested with cockroaches, an intensive intervention and education program can achieve a significant and clinically relevant reduction in cockroach allergen levels [49] . Thus, allergen avoidance is feasible, and it is a desirable part of the allergy management program, in addition to pharmacotherapy and allergen specific immunotherapy.

Summary

The worldwide increase in the prevalence of atopy continues to underline the importance of primary prevention. Food allergy and atopic eczema, which is often associated with food allergy, is common in early childhood. Attempted reductions in exposure to food allergens, by breast feeding with or without maternal dietary restriction, delayed introduction of solid foods and the use of hydrolyzed milk formulae have at best achieved partial success. There has been some reduction in cow’s milk allergy, atopic eczema, and wheeze in the first 2 years of life, but this benefit is not sustained in later childhood. Simple, inexpensive and safe methods, such as prolonged and exclusive breast feeding, may be recommended for the whole population. However, apart from breast feeding, which has a number of other advantages, none of the other methods can be recommended for implementation on a wider scale for prevention of atopy. In some children who are at significantly higher risk, maternal dietary avoidance of allergenic foods may be advised, if dietary supervision is available. In these children, if breast feeding is not feasible, current evidence favours extensively hydrolyzed casein formula as a supplement or alternative to breast milk. Further research is urgently needed, especially large RCTs, to develop recommendations based on good scientific evidence. A number of RCTs have evaluated the effect of dust mite allergen avoidance in primary prevention of asthma. Dust-mite allergen avoidance methods have been applied from birth, as well as later in childhood. It has been clearly shown that reduction in exposure to dust mite allergen is possible with extensive environmental measures. However, this reduction does not translate into reduction in atopy. Any reduction in allergen sensitization has been modest and the effect on clinical manifestations of atopy, such as asthma and rhinitis, is generally disappointing. It can be argued that while multiple allergen exposure leads to sensitization, it is unrealistic to expect that intervention with avoidance of single allergen, such as dust-mite or even one group of allergen such as food allergens will result in Prevention of Allergy 15 significant reduction in atopy. Studies, which have applied multi-faceted allergen avoidance regime, have met with greater success. The Isle of Wight prevention study which assessed the effect of both food and dust mite allergen avoidance has shown that atopy can be significantly reduced and the benefit may continue into later childhood, years after active intervention is stopped. Other studies testing multiple allergen avoidance regimes have also shown significant benefit. Food allergen avoidance remains the only practical method to avoid morbidity in those with food allergic reactions. Patients should be told how to avoid food allergen in question, and provided with a list of alternative foods that can be safely consumed. Avoidance of aero-allergens may be even more difficult. Trials of dust mite avoidance measures, currently in practice, such as allergen impermeable mattress covers have not consistently shown to be of benefit. Those with animal allergy are often reluctant to give up their pets. Pollens, dust mites, molds, and cockroach allergens are ubiquitous in their appropriate environments. However, with rigorous environmental intervention, exposure can be reduced with significant improvement in symptoms and medication requirement for patients with asthma and allergic rhinitis.

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30. Sporik R, Holgate ST, Platts-Mills TA, Cogswell JJ. Exposure to house-dust mite allergen (Der p I) and the development of asthma in childhood. A prospective study. N Engl J Med 1990;323(8):502–7 31. Halmerbauer G, Gartner C, Schier M, Arshad H, Dean T, Koller DY, et al. Study on the prevention of allergy in Children in Europe (SPACE): allergic sensitization in children at 1 year of age in a controlled trial of allergen avoidance from birth. Pediatr Allergy Immunol 2002;13 (Suppl 15):47–54 32. Horak F Jr., Matthews S, Ihorst G, Arshad SH, Frischer T, Kuehr J, et al. Effect of mite- impermeable mattress encasings and an educational package on the development of allergies in a multinational randomized, controlled birth-cohort study – 24 months results of the Study of Prevention of Allergy in Children in Europe. Clin Exp Allergy 2004;34(8):1220–5 33. Tsitoura S, Nestoridou K, Botis P, Karmaus W, Botezan C, Bojarskas J, et al. Randomized trial to prevent sensitization to mite allergens in toddlers and preschoolers by allergen reduction and education: one-year results. Arch Pediatr Adolesc Med 2002;156(10):1021–7 34. Arshad SH, Bojarskas J, Tsitoura S, Matthews S, Mealy B, Dean T, et al. Prevention of sensitization to house dust mite by allergen avoidance in school age children: a randomized controlled study. Clin Exp Allergy 2002;32(6):843–9 35. Custovic A, Simpson BM, Simpson A, Kissen P, Woodcock A. Effect of environmental manipulation in pregnancy and early life on respiratory symptoms and atopy during first year of life: a randomised trial. Lancet 2001;358(9277):188–93 36. van Strien RT, Kerkhof M, Oldenwening M, de Jongste JC, Gerritsen J, Neijens HJ, et al., Prevention and Incidence of Asthma and Mite Allergy Study. Mattress encasings and mite allergen levels in the Prevention and Incidence of Asthma and Mite Allergy study. Clin Exp Allergy 2003;33(4):490–5 37. Mihrshahi S, Peat JK, Marks GB, Mellis CM, Tovey ER, Webb K, et al. Eighteen-month outcomes of house dust mite avoidance and dietary fatty acid modification in the Childhood Asthma Prevention Study (CAPS). J Allergy Clin Immunol 2003;111(1):162–8 38. Peat JK, Mihrshahi S, Kemp AS, Marks GB, Tovey ER, Webb K, et al. Three-year outcomes of dietary fatty acid modification and house dust mite reduction in the Childhood Asthma Prevention Study. J Allergy Clin Immunol 2004;114(4):807–13 39. Saitoh Y, Dake Y, Shimazu S, Sakoda T, Sogo H, Fujiki Y, et al. Month of birth, atopic disease, and atopic sensitization. J Investig Allergol Clin Immunol 2001;11(3):183–7 40. Arshad SH, Matthews S, Gant C, Hide DW. Effect of allergen avoidance on development of allergic disorders in infancy. Lancet 1992;339(8808):1493–7 41. Arshad SH, Bateman B, Sadeghnejad A, Gant C, Matthews SM. Prevention of allergic disease during childhood by allergen avoidance- The Isle of Wight prevention study. J Allergy Clin Immunol 2007;119(2):307–13 42. Chan-Yeung M, Manfreda J, Dimich-Ward H, Ferguson A, Watson W, Becker A, et al. A randomized controlled study on the effectiveness of a multifaceted intervention program in the primary prevention of asthma in high-risk infants. Arch Pediatr Adolesc Med 2000;154(7):657–63 43. Schönberger HJAM, Dompeling E, Knottnerus JA, Maas T, Muris JWM, van Weel C, et al. The PREVASC study: the clinical effect of a multifaceted educational intervention to prevent childhood asthma. Eur Respir J 2005;25(4):660–70 44. van Schayck OCP, Maas T, Kaper J, Knottnerus AJA, Sheikh A. Is there any role for allergen avoidance in the primary prevention of childhood asthma? J Allergy Clin Immunol 2007;119(6):1323–8 45. Piacentini GL, Martinati L, Fornari A, Comis A, Carcereri L, Boccagni P, et al. Antigen avoidance in a mountain environment: influence on basophil releasability in children with allergic asthma. J Allergy Clin Immunol 1993;92(5):644–50 46. Eggleston PA. Improving indoor environments: reducing allergen exposures. J Allergy Clin Immunol 2005;116(1):122–6 18 S.H. Arshad

47. Woodcock A, Forster L, Matthews E, Martin J, Letley L, Vickers M, et al. Control of exposure to mite allergen and allergen-impermeable bed covers for adults with asthma. N Engl J Med 2003;349(3):225–36 48. Terreehorst I, Hak E, Oosting AJ, Tempels-Pavlica Z, de Monchy JG, Bruijnzeel-Koomen CA, et al. Evaluation of impermeable covers for bedding in patients with allergic rhinitis. N Engl J Med 2003;349(3):237–46 49. Eggleston PA, Butz A, Rand C, Curtin-Brosnan J, Kanchanaraksa S, Swartz L, et al. Home environmental intervention in inner-city asthma: a randomized controlled clinical trial. Ann Allergy Asthma Immunol 2005;95(6):518–24 Pharmacotherapy of Allergic Rhinitis

Jeffrey M. Lehman and Michael S. Blaiss

Introduction

The primary goal of allergic rhinitis (AR) treatment is to alleviate symptoms, improve quality of life and prevent comorbidities. In addition to allergen avoidance there are several pharmacologic agents available: oral and topical H1 -antihistamines, intranasal glucocorticosteroids, leukotriene receptor antagonists, mast cell stabilizers, anticholinergic agents and decongestants. Medications used for AR are typically administered orally or intranasally. The intranasal route allows for higher concentrations of the drug to be delivered thus minimizing the systemic side effects. However, many patients with AR have an aversion to using nasal spray, and oral medications are typically used in these patients.

Oral H1 -Antihistamines

Histamine is an important chemical mediator of allergic inflammation and is released in large quantities from tissue mast cells and basophils upon antigen binding to IgE on the cell surface and crosslinking Fce RI (high affinity receptor for IgE) during the early allergic response [1, 2] . Histamine then acts in the nose to cause

J.M. Lehman Department of Medicine and Pediatrics, Division of Allergy and Immunology, University of Tennessee Health Science Center , 50 N. Dunlap, WPT Rm 401 , Memphis , TN 38103 , USA M.S. Blaiss () Department of Medicine and Pediatrics, Division of Clinical Allergy and Immunology, University of Tennessee Health Science Center , 7205 Wolf River Blvd. Suite 200 , Germantown , TN 38138 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 19 DOI 10.1007/978-4-431-99362-9_2, © Springer 2010 20 J.M. Lehman and M.S. Blaiss vasodilatation and increased vascular permeability, and stimulation of sensory nerves leading to the sensation of itching [1, 2] . This manifests clinically as sneezing, rhinorrhea, and pruritus [2] . There are at least four types of histamine receptors that have been identified. However, the majority of allergic responses are mediated via the H1 receptor [3] .

H1 -antihistamines are inverse agonists, rather than H 1-antagonists, that combine with and stabilize the inactive form of the H1 receptor leading toward a shift in equilibrium to the inactive state [3] . In addition to the inverse agonist effect at the

H1 receptor, the newer second-generation agents have both antiallergic and anti- inflammatory properties. They have been shown to inhibit the release of mediators from mast cells and basophils through a direct inhibitory effect on calcium-ion channels [4] . Pretreatment with an H 1 antihistamine has been shown to decrease the early response to an allergen challenge through decreasing the levels of proinflammatory cell adhesion molecules, cytokines, mediators such as histamine, leukotrienes, and prostaglandins [4– 8] .

First Generation H1 -Antihistamines

The first generation H1 antihistamines such as diphenhydramine, chlorpheniramine, brompheniramine and hydroxyzine are also referred to as the sedating antihistamines. These agents are effective in controlling the rhinorrhea, sneezing and pruritus associated with AR. Unfortunately these agents cross the blood-brain barrier producing undesirable side-effects such as central nervous system depression, sedation leading to impaired performance at home, work and school and cardiotoxicity [9– 11] . There are no long-term safety studies on the first generation antihistamines.

These agents have poor H 1 receptor selectivity and act on muscarinic receptors causing anticholinergic effects such as dry mouth, urinary retention, constipation and tachycardia [9] . The high risk to benefit ratio makes the first generation H 1 antihistamines a less attractive therapeutic option and are not recommended as first line therapy in AR.

Second Generation H1 -Antihistamines

The second generation antihistamines (Table 1 ), developed in the early 1980s, have improved H1 receptor selectivity, absent or decreased sedation, faster onset and longer duration of action and fewer adverse effects [11, 12]. To date, no clinically significant cardiotoxic effects have been reported for loratadine, desloratadine, fexofenadine, cetirizine and levocetirizine. In general, second generation antihistamines exhibit favorable pharmacokinetics. They have a relatively quick onset of action, near complete absorption, widespread tissue distribution with minimal CNS Pharmacotherapy of Allergic Rhinitis 21

Table 1 Available second generation H1 -antihistamines Usual pediatric daily dosage Usual adult daily dosage Sedation Oral Loratadine 2–5 yrs: 5 mg 10 mg Noa Desloratadine 6–11 mos: 1 mg 5 mg Noa 12 mos–5 yrs: 1.25 mg 6–11 yrs: 2.5 mg Cetirizine 6–11 mos: 2.5 mg 12 5–10 mg Yes mos–5 yrs: 2.5–5 mg Fexofenadine 6–11 yrs: 30 mg twice daily 60 mg twice daily; 120 mg No or 180 mg daily Levocetirizine 6–11 yrs: 2.5 mg 5 mg Yes Intranasal Azelastine 5–11 yrs: 1 spray twice daily 2 sprays twice daily Yes Olopatadine >12 yrs: 2 sprays twice daily 2 sprays twice daily Yes yrs years; mos months a Cause sedation at higher than recommended doses

penetration unlike first generation antihistamines, and relatively long half-life allowing for once daily dosing [13] . Several controlled trials of second generation

H1 antihistamines have been published and have shown overall relief of symptoms including sneezing, pruritus, rhinorrhea, and conjunctival symptoms, and improved quality of life [2, 14, 15] .

Cetirizine

Cetirizine is rapidly absorbed and achieves peak plasma concentration in ~1 h [3] .

In addition to H1 receptor antagonism, cetirizine was found to inhibit eosinophil chemotaxis during the allergic response and therefore blunted the late-phase reaction [16] . Cetirizine can cause an increased incidence of sedation at its recommended dose in patients aged 12 or older [17] . Cetirizine is classified as mildly-sedating and should not be prescribed to patients whose jobs require high psychomotor skills such as pilots. Cetirizine has been shown in numerous clinical trials to be more efficacious compared to placebo in the treatment of both seasonal allergic rhinitis (SAR) and perennial allergic rhinitis (PAR) [18– 23] . Cetirizine significantly improved QOL measures of general health, physical functioning, vitality, social functioning, and emotional and mental health within one week of treatment and continued up to 6 weeks [24] . 22 J.M. Lehman and M.S. Blaiss

Levocetirizine

Levocetirizine is the enantiomer of cetirizine. Levocetirizine, like cetirizine, has been shown to inhibit eotaxin-induced transendothelial migration of eosinophils in vitro, thus blunting the late phase response [16] . Levocetrizine shows lower sedating effects in clinical studies than cetirizine [25]. A randomized trial involving >400 patients with SAR found that levocetirizine significantly reduced symptom scores over an 8-week period [26] . A multinational placebo-controlled study found that levocetirizine significantly improved QOL over 6 months of treatment [11] . A large multicenter study in children with SAR and PAR found that 4–6 weeks of treatment with levocetirizine significantly improved symptoms and QOL [27] .

Loratadine

Loratadine has been found to blunt the early- and late-phase of allergic reactions [7] . Loratadine is a nonsedating antihistamine, and psychomotor tests confirm its safety at the recommended dosage (10 mg/day) [28] . However, performance studies with higher, off-label loratadine doses of 20 and 40 mg showed significant impairment and sedation in some objective performance tests compared with placebo [29] . Although the placebo controlled studies with loratadine are limited, two studies have shown that loratadine was superior to placebo in the treatment of AR [30, 31].

Desloratadine

Desloratadine, an active metabolite of loratadine, has been shown to inhibit IgE- mediated and non-IgE-mediated release of IL-4 and IL-13 from human basophils in vitro [32] . Like loratadine, desloratadine significantly reduces the symptoms of SAR. However, as in the case of loratadine, somnolence has been noted at higher- than-recommended doses [29] . Two multicenter, randomized, double-blind studies comparing the efficacy of desloratadine to placebo showed a statistically significant reduction in symptoms in patients with SAR over a 2-week study period [33, 34]. Desloratadine rapidly and safely reduced the symptoms of PAR, and its efficacy did not diminish during 4 weeks of treatment [35] . There have been no large clinical trials studying the effect of desloratadine on QOL. Pharmacotherapy of Allergic Rhinitis 23

Fexofenadine

Fexofenadine, the active metabolite of terfenadine, is a potent H1 receptor antagonist that does not display cardiotoxicity like its predecessor [36] . In addition to blocking

H1 receptors, in vitro and in vivo studies have shown that fexofenadine reduces allergic inflammatory responses mediated by mast cells, basophils, epithelial cells, eosinophils and lymphocytes [37] . Fexofenadine has also been shown to demonstrate anti-inflammatory activity through inhibition of ICAM-1 expression on nasal epithelium in vitro [20] . Numerous clinical trials have shown fexofenadine to be more efficacious than placebo for the symptoms of SAR [38– 44] . van Cauwenberge et al. [45] conducted a large multinational, double-blinded, placebo-controlled, 2 week trial of fexofenadine (120 mg once a day) versus loratadine (10 mg once a day) in patients with SAR. Individual symptoms were self-assessed and no difference in overall symptom scores was observed between fexofenadine and loratadine. However, fexofenadine significantly improved the individual symptoms of nasal congestion and itchy, watery, red eyes compared with loratadine. Fexofenadine has also been found to decrease work impairment and benefit emotions, sleep and practical problems [43] . Fexofenadine is a substrate for P-glycoprotein (P-gp), which is a membrane-bound transporter that inhibits absorption and promotes excretion [46] . Grapefruit juice has been found in vitro to inhibit P-gp activity and when consumed with grapefruit juice, the plasma concentration of fexofenadine can be decreased by up to 40% [47] . Conversely, when fexofenadine is taken in conjunction with ketoconazole and erythromycin, plasma levels may be increased, thus increasing the potential for adverse effects [48] . It is important to note that no serious adverse effects attributable to drug interactions with this second generation H1 antihistamine have been reported.

Intranasal H1 -Antihistamines

Topical second generation H1 -antihistamines (Table 1 ) are considered to be similar in efficacy to oral H1- antihistamines and are also considered as first-line therapy for mild-moderate AR [9, 11] .

Azelastine

Dose-ranging trials have shown a therapeutic onset of action within 3 h after initial dosing and persistence of efficacy over a 12-h interval. The most common side effects seen with azelastine at the recommended dose of two sprays per nostril twice a day, are bitter taste (19.7% vs. 0.6% placebo) and sedation (11.5% vs. 5.4% placebo) [49, 50] . Studies have shown that azelastine improved all symptoms in SAR and PAR including ocular symptoms, and can also reduce nasal congestion [9, 11, 51] . 24 J.M. Lehman and M.S. Blaiss

Azelastine has demonstrated efficacy in SAR [52– 54] , and in recent studies azelastine appears to be slightly superior to cetirizine [55] , desloratadine [56] , and fexofenadine [49] in its ability to reduce total nasal symptoms scores, including nasal congestion. An older study, however, did not find that azelastine was superior to cetirizine in seasonal AR [57] .

Olopatadine

Olopatadine nasal spray provided reductions in total nasal symptom scores at 30 min compared to placebo and maintained an effect for at least 12 h after dosing [58] . A multicenter, randomized, double-blind SAR study comparing olopatadine to placebo nasal spray found that olopatadine was an effective antiallergy medication that significantly improved the QOL of patients suffering from SAR [59] . Olopatadine nasal spray (0.4% and 0.6%) provided statistically significant improvements in AR symptoms compared with placebo regarding TNSSs and in quality-of-life variables in patients with SAR [60] . Olopatadine nasal spray administered twice daily was safe and well tolerated in adolescents and adults. Olopatadine was also found to be superior to placebo spray and mometasone furoate in reducing allergy symptoms associated with SAR [61] .

Intranasal Corticosteroids

Intranasal corticosteroids (INS; Table 2 ) are recommended as first-line therapy for moderate-severe AR [62] . Corticosteroids target the inflammatory mechanism of the early and late phase allergic processes and are therefore effective in treating most symptoms of AR including: congestion; sneezing; rhinorrhea and nasal pruritus [9, 11, 62] .

Table 2 Available intranasal corticosteroids Usual pediatric daily dosage Usual adult daily dosage Triamcinolone acetonide 2–5 yrs: 1 spray/nostril daily 6–12 yrs: 1–2 sprays/nostril daily 1–2 sprays/nostril daily 6–11 yrs: 2 sprays/nostril daily 2–4 sprays/nostril daily Budesonide 6–12 yrs: 1–2 sprays/nostril daily 1–4 sprays/nostril daily Fluticasone propionate ³ 4 yrs: 1–2 sprays/nostril daily 2 sprays/nostril daily Mometasone furoate 2–12 yrs: 1 spray/nostril daily 2 sprays/nostril daily Beclomethasone 6–12 yrs: 1–2 sprays/nostril twice 1–2 sprays/nostril twice diproprionate daily daily Flunisolide 6–14 yrs: 2 sprays/nostril twice 2 sprays/nostril daily twice-three times daily Fluticasone furoate >2–11 yrs: 1–2 sprays/nostril daily 2 sprays/nostril daily Ciclesonide ³ 12 yrs: 2 sprays/nostril daily 2 sprays/nostril daily yrs years; mos months; HFA hydrofluoroalkane Pharmacotherapy of Allergic Rhinitis 25

INS Compared with Placebo

When INS are compared to placebo, this treatment group shows improvement in all parameters examined. A randomized, double blind, 3-week study of 429 patients, 12 years and older with AR who were treated with triamcinolone acetonide 220 µg/ day showed a significant decrease in nasal congestion, discharge and sneezing compared to placebo [63] . In placebo-controlled, double blind studies of fluticasone propionate (100 µg twice daily or 200 µg/day), fluticasone propionate was significantly more effective than placebo in improving nasal and ocular symptoms and increasing the number of symptom free days [64] . A double blind, placebo controlled, randomized study of patients with AR comparing mometasone furoate versus placebo showed a significant decrease with mometasone furoate in total symptom scores, total nasal scores and individual nasal symptoms [65] . Fluticasone furoate (110 µg/day), was recently found to significantly improve nasal congestion, itching, rhinorrhea, and sneezing over a 2-week period when compared to placebo in children and adults greater than 12 years [66] . Ciclesonide for intranasal use is formulated in a hypotonic suspension, which has been shown in preclinical in vivo models to provide enhanced tissue uptake when compared with a traditional isotonic formulation [67] . In addition, the intranasal formulation of ciclesonide is preserved with potassium sorbate rather than benzalkonium chloride, which is used in many INSs. Benzalkonium chloride is believed to interfere with mucociliary transport and can lead to the development of hypersensitivity, rhinitis medicamentosa, and neutrophil dysfunction, though there are no clinical studies showing significant adverse effects in humans [68, 69] . Ciclesonide is administered as an inactive parent compound that is metabolized by endogenous esterases in the upper and lower airways to the pharmacologically active metabolite desisobutyryl- ciclesonide. A recent clinical study evaluated the efficacy of 200 µg of ciclesonide nasal spray administered once daily compared with that of placebo on nasal symptoms and signs of AR in adults and adolescents with SAR over a 28-day period. Intranasal ciclesonide was found to be superior to placebo in relieving nasal congestion, rhinorrhea, sneezing and itching [70] .

Comparison of Individual INS

Several studies have compared individual INS and it appears that there is no clinically significant difference in the efficacy of various INS. Welsh et al. compared beclomethasone diproprionate, 168 µg twice daily, versus flunisolide propionate, 100 µg twice daily, in patients with SAR and found the two drugs to be equally effective [71] . Similarly, trials comparing beclomethasone, flunisolide, triamcinolone and budesonide in patient with AR found them to be equally effective [72] . Beclomethasone dipropionate and fluticasone propionate have been compared in multiple trials. A two week study in patients with SAR found beclomethasone dipropionate to be as effective as fluticasone propionate [73] . A 3-week study in 26 J.M. Lehman and M.S. Blaiss patients with PAR found that beclomethasone and fluticasone propionate were equally effective [74] . Conversely, a 12-month study in patients with PAR found fluticasone propionate to be superior to beclomethasone diproprionate [75] . Onset of action of individual INS may differ. Recent studies suggest that fluticasone propionate, budesonide, mometasone and triamcinolone show clinical benefit within 1–2 days [71, 76–78] , whereas fluticasone furoate showed benefit within 8 h of administration [66] . Jen et al. [76] demonstrated that fluticasone propionate nasal spray was more effective than placebo within 12 h of treatment, although peak efficacy took several days to obtain. Similarly, one dose of triamcinolone acetonide provided symptom relief in patients with AR within 12 h of administration [78] . Mometasone furoate was found to provide relief of AR symptoms within 12 h [77] and budesonide was demonstrated to act within 3 h of administration, although maximum efficacy occurred within days to weeks [78] .

INS Compared with Oral H1 Antihistamines

A meta-analysis of 16 studies involving 2267 subjects (ages 12–75 years) with AR showed that INS produced significantly greater improvement with total nasal symptoms compared to oral H1 antihistamines [79] . Significant findings from this meta-analysis include: INS produced significantly greater relief of nasal congestion, decreased nasal discharge, and decreased nasal pruritus than oral H1 antihistamines. Two studies from this meta-analysis demonstrated that INS showed a modest but significant decrease in post-nasal drip compared to oral H1 antihistamines. However, there was no difference in ocular symptoms.

Adverse Effects of INS

The goal for an ideal AR therapy is an INS with a high therapeutic ratio (i.e., high efficacy, good tolerability, and low systemic bioavailability) [80, 81] . The systemic bioavailability of an INS is related to its deposition in the nasal cavity, followed by mucociliary clearance to the throat and, eventually, to the gastrointestinal tract; absorption from the mucosal surface can contribute up to 50% systemic bioavailability of the INS [80, 82] . The most common local side effects of INS, reported by 2–10% of patients, include burning, irritation, and drying. There have also been a few reported cases of nasal septal perforation [80, 83, 84] . Epistaxis, due to drying or thinning of the nasal mucosa, is another common local side effect associated with the use of INS and occurs in 17–23% of patients treated with INS and in 10–15% of patients treated with placebo in clinical trials [80, 85] . Interestingly, the incidences of epistaxis reported with placebo in clinical trials of INS are high as well; therefore, the physical trauma caused by the nasal spray application device, as well as the Pharmacotherapy of Allergic Rhinitis 27 formulation additives, most likely also contribute to epistaxis [80, 85] . To minimize epistaxis patients should be instructed on the proper technique for administration, which is to direct the spray away from the septum. Systemic exposure of INS occurs because of direct absorption of INS from the nasal mucosa as well as runoff down the throat to the gastrointestinal tract [80] . The major effect of corticosteroids on the hypothalamic-pituitary-adrenal (HPA) axis is the negative feedback effect caused by suppression of corticotrophin-releasing hormone and adrenocorticotropic hormone (ACTH) levels, leading to lower cortisol secretion and eventual atrophy of the adrenal cortex [80] . The majority of second- generation INS have little effect on HPA-axis function [80] . In pediatric patients with AR, treatment with fluticasone propionate 200 µg/day for 6 weeks did not suppress 12-h urine cortisol levels [86] . However, in another study of pediatric patients with PAR, intranasal fluticasone propionate 200 µg/day suppressed 12-h urine cortisol compared with placebo, whereas intranasal triamcinolone acetonide 110 µg/day did not [87] . Similarly, treatment with fluticasone propionate 200 µg/day for 4 days suppressed 12-h urinary-free cortisol secretion, whereas treatment with triamcinolone acetonide 220 µg/day or beclomethasone diproprionate 336 µg/day did not suppress cortisol levels [88] . In contrast, treatment with budesonide or mometasone furoate, each at a daily dose of 200 µg, or triamcinolone acetonide at a daily dose of 220 µg for 5 days did not have any suppressive effect on morning, 12-h, or 24-h plasma cortisol levels or on 12- and 24-h urinary free cortisol levels [89] . Finally, in children with PAR, treatment with intranasal budesonide 400 µg/day for 1 year and an aqueous suspension of budesonide 400 µg/day for an additional 6 months did not suppress morning plasma and 24-h urinary-free cortisol levels during the first and second year of treatment [90] . Effects of INS on the HPA axis are influenced by the frequency of drug administration. Once-daily administration of INS would have a negligible effect on the HPA axis [91] . A once-daily morning dosing regimen is very important in prepubertal children, in whom growth hormone secretion is pulsatile and nocturnal, with initiation of pulses corresponding to the normal late-evening low levels of plasma cortisol [80, 91]. Absorption of exogenous corticosteroid at this time from a twice- daily regimen could have a suppressive effect on growth hormone release [80] . Consistent with this observation, randomized, parallel-group, short-term studies of intranasal budesonide 200 µg given twice daily to 44 children with AR caused significant suppression of lower-leg growth [92] , whereas in another double-blind, parallel-group study of 38 children, budesonide 200 µg or 400 µg given once daily in the morning did not suppress lower-leg growth [93] . Inhaled corticosteroids have been shown to have significant effects on eyes resulting in glaucoma and subcapsular cataracts and on bone [94] . However, enough data are not available on the effects of INS on eyes or bone to draw a definitive conclusion [80] . A retrospective chart review study of 12 patients showed that INS use resulted in an increase in intraocular pressure and a significant reduction in intraocular pressure was observed after discontinuation [95] . In another study, similar effects on intraocular pressure were observed with intranasal or inhaled beclomethasone diproprionate [96] . 28 J.M. Lehman and M.S. Blaiss

In summary, currently available INS are effective and safe for the treatment of AR. However, the risk of side effects may be increased by high doses or prolonged exposure to more potent INS, especially in younger or older patients. Furthermore, there is a risk of an additive inhibitory effect on the HPA axis in patients receiving concomitant ICS and INS therapy [80] .

Leukotriene Modifying Agents

Leukotrienes appear to be important mediators of nasal allergic reactions, and their presence in the nose induces nasal obstruction [11] . Leukotrienes have significant proinflammatory effects as well as causing vasodilatation, increased vascular permeability, airway smooth muscle contraction, mucus secretion and chemoattraction towards eosinophils [62] . Therefore, they are involved in both the early and late phase allergic response. A meta-analysis demonstrated that montelukast, compared to placebo, demonstrated a moderate but significant reduction in relieving nasal symptoms in patients with AR, whereas INS induced a significant and substantial reduction in symptoms [97, 98] . A randomized, double-blind, placebo controlled trial comparing montelukast, loratadine and placebo in patients with SAR demonstrated that montelukast was more effective than placebo in improving scores for the primary endpoint of daytime nasal symptoms and the secondary endpoints of night-time, composite, and daytime eye symptoms, patient’s and physician’s global evaluations of AR, rhinoconjunctivitis and quality-of-life [99] . Loratadine also improved scores for the primary endpoint and the majority of the secondary endpoints. When analyzed by week, the treatment effect of montelukast was more persistent than loratadine over all 4 weeks of treatment. A combined analysis of three multicenter, randomized, double-blind, parallel-group studies was performed involving 1,862 patients with SAR, comparing montelukast to placebo over a two week treatment period. Montelukast significantly improved daytime nasal symptoms score and individual scores of congestion, rhinorrhea, itching, and sneezing compared with placebo [100] . A meta-analysis of seventeen randomized controlled trials involving 6,231 adults with SAR was performed to evaluate the effect of oral leukotriene receptor antagonists as monotherapy or combined with other drugs in the treatment of SAR [101] . Oral leukotriene antagonists significantly reduced daytime nasal symptoms, nighttime nasal symptoms, eye symptoms, and significantly improved quality of life compared with placebo. There were no significant differences between oral leukotriene antagonists and oral histamine H1 antagonists on nasal and eye symptoms, and quality-of-life. However, the authors found that leukotriene receptor antagonists were inferior to INS for decreasing daytime and nighttime nasal symptoms. The combination of leukotriene receptor antagonists plus histamine H1 antagonists produced greater relief of eye symptoms compared with histamine H1 antagonists alone. Finally, INS significantly reduced nasal congestion compared with leukotriene receptor antagonists plus histamine H1 antagonists. Therefore, the authors concluded Pharmacotherapy of Allergic Rhinitis 29 that leukotriene receptor antagonists were better than placebo, equivalent to oral histamine H1 antagonists, and inferior to INS for treating SAR. Alternatively, leukotriene receptor antagonists plus histamine H1 antagonists were more effective than histamine H1 antagonists alone but inferior to INS. In a multicenter, double-blind, randomized, parallel-group, placebo-controlled 2-week trial, 460 men and women, aged 15–75 years, with SAR were randomly allocated to receive one of the following five treatments: montelukast 10 or 20 mg, loratadine 10 mg, montelukast, 10 mg with loratadine 10 mg, or placebo, once daily in the evening [102] . Concomitant montelukast with loratadine significantly improved daytime nasal symptoms score compared to placebo. Compared with placebo, montelukast with loratadine also significantly improved eye symptoms, nighttime symptoms, individual daytime nasal symptoms, global evaluations, and quality of life.

Local Chromones

Mast cell stabilizers inhibit mast cell degranulation and thus inhibit the release of histamine and other mediators of the early phase of allergic inflammation. Cromolyn sodium, which is available over-the-counter, is generally not as effective as antihistamines or INS but has been shown to be superior to placebo in reducing symptoms of the early phase [62] . Cromolyn is likely to be more effective when administered just prior to contact with an allergen [11] . Although the safety profile of cromolyn is very good, the dosing interval of four times a day make this a less attractive option.

Local Anticholinergics

Double-blind, placebo-controlled studies have shown that ipratropium bromide is effective in controlling watery nasal discharge, but that it does not affect sneezing or nasal obstruction in perennial allergic and nonallergic (vasomotor) rhinitis [103, 104] . Anticholinergic side effects are uncommon and usually dose- dependent [11] .

Decongestants

Decongestants reduce nasal congestion by activating a -adrenergic receptors on the nasal vasculature leading to vasoconstriction [62] . Decongestants do not improve nasal itching, sneezing or rhinorrhea associated with AR. Oral decongestants such as ephedrine, phenylephrine, phenylpropanolamine and pseudoephedrine are the 30 J.M. Lehman and M.S. Blaiss most commonly used oral decongestants. Systemic side effects include irritability, dizziness, headache, tremor, insomnia as well as tachycardia and hypertension [11] . Patients with glaucoma or hyperthyroidism and elderly men with prostate enlargement are also at risk when using oral sympathomimetic decongestants. Pseudoephedrine was recently banned for Olympic athletes [105] . A recent study showed that the combination of pseudoephedrine and an antihistamine was significantly more effective in reducing total nasal symptoms than either agent alone [106] . There are very few randomized/controlled clinical studies on the effects of pseudoephedrine alone in AR. Topical decongestants, oxymetazoline and phenylephrine are also available over-the-counter. These medications can be effective with nasal congestion associated with AR. However, prolonged use (>10 days) of intranasal decongestants may lead to tachyphylaxis, a rebound swelling of the nasal mucosa and “drug-induced rhinitis” termed rhinitis medicamentosa [107] .

Summary

AR is a common chronic disorder that can significantly interfere with a patient’s QOL. The goals of treatment are to provide the patient with symptom relief and improvement in QOL with minimal number of side effects. Prescribing physicians must take into account patient preferences, symptoms and side effect profile. Lack of treatment or treatment with suboptimal therapy may result in reduced quality of life and compromise productivity at work or school. Many different classes of medications are now available, and they have been shown to be effective and safe in a large number of well-designed clinical trials. Table 3 provides a stepwise approach to the treatment of AR [11] .

Table 3 Management of allergic rhinitis Intermittent symptoms Persistent symptoms Milda Moderate/severe a Mild a Moderate/severeb • Oral or • Oral or • Oral or • INS and Oral

intranasal intranasal intranasal H1 or intranasal H1

H1 antihistamine H1 antihistamine antihistamine antihistamine or and/or and/or and/or LTRA • Oral/intranasal • Oral/intranasal • Oral/intranasal • Add decongestant for decongestant or decongestant or decongestant or blockage • LTRA • INS or • INS or • Add intranasal anticholinergic for • LTRA or • LTRA or • Intranasal • Intranasal rhinorrhea chromone chromone LTRA leukotriene receptor antagonist; ICS intranasal corticosteroid a Not in preferred order b In preferred order Pharmacotherapy of Allergic Rhinitis 31

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102. Meltzer EO, Malmstrom K, Lu S, Prenner BM, Wei LX, Weinstein SF, Wolfe JD, Reiss TF (2000) Concomitant montelukast and loratadine as treatment for seasonal allergic rhinitis: a randomized, placebo-controlled clinical trial. J Allergy Clin Immunol 105:917–22 103. Borum P, Mygind N, Schultz Larsen F (1979) Intranasal ipratropium: a new treatment for perennial rhinitis. Clin Otolaryngol 4:407–11 104. Wagenmann M, Naclerio RM (1992) Complications of sinusitis. J Allergy Clin Immunol 90:552–4 105. Bonini S, Bonini M, Bousquet J, Brusasco V, Canonica GW, Carlsen KH, Corbetta L, Cummiskey J, Delgado L, Del Giacco SR, Haahtela T, Jaeger S, Moretti C, Palange P, Passalacqua G, Passali D, Pedersen BK, Popov T, Rasi G, Ventura MT, Vignola AM (2006) Rhinitis and asthma in athletes: an ARIA document in collaboration with GA2LEN. Allergy 61:681–92 106. Pleskow W, Grubbe R, Weiss S, Lutsky B (2005) Efficacy and safety of an extended-release formulation of desloratadine and pseudoephedrine vs the individual components in the treatment of seasonal allergic rhinitis. Ann Allergy Asthma Immunol 94:348–54 107. Lockey RF (2006) Rhinitis medicamentosa and the stuffy nose. J Allergy Clin Immunol 118:1017–8 Antihistamines in Rhinitis and Asthma

Todor A. Popov

Histamine: Role in Health and Disease

Just several years after the concept “allergy” was coined about a century ago [1] , histamine was identified by Sir Henry Dale [2] and subsequently emerged as one of the most important allergy substrates. This marked the onset of a spiral of scientific achievements, which resulted in the development of multiple drug formulations used in the prevention and treatment of allergic disorders and in elucidation of the pleiotropic role histamine plays in health and disease. Histamine belongs to a group of locally produced tissue hormones (including serotonin and others) referred to as “autacoids.”1 It plays a vital role in the regulation of the many important functions related to circadian influences, adaptation to environment and stress. Conversely, histamine is intimately implicated in the pathogenesis of allergic diseases, which develop as defective systemic trait of genetically predisposed individuals and may have different organ expressions. Airway allergic morbidity in particular accounts for a lot of individual suffering and disability, and poses a substantial economic burden to society [3, 4] . Therefore, the correct prescription of existing antihistamine products and the development of new and more effective formulations devoid of unwanted effects are two important avenues in the global crusade to control these morbidities affecting millions of people. Endogenous histamine is produced in neurons as part of the histaminergic neuronal system originating in the tuberomamillary nucleus of the hypothalamus [5] . It is a low molecular weight amine, synthesized from l -histidine by the enzyme histidine decarboxylase. It plays a pivotal role in maintaining the state of wakefulness and alertness by modulating the firing potential of neurons in the cortex of the brain and by interfering with the neuronal excitation of other neurons using different transmitters: acetylcholine, serotonin, dopamine, g -aminobutyric acid (GABA), and

T.A. Popov () Clinic of Allergy and Asthma , Alexander’s University Hospital , 1, Sv. Georgi Sofiyski Street , 1431 Sofia , Bulgaria e-mail: [email protected] 1 From Greek: autoV = own, proper and akoV = medicinal product.

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 37 DOI 10.1007/978-4-431-99362-9_3, © Springer 2010 38 T.A. Popov noradrenaline. The cellular sources of histamine are mucosal and skin mast cells and basophils in the blood. These two cell types degranulate their histamine load as part of a classical IgE mediated reaction or under the influence of other non-IgE triggers, thus initiating local allergic or systemic anaphylactic reactions [6, 7]. Historically, a lot of effort has been invested in creating drugs countering the effects of histamine released from these cells. Many of these drugs, though, are lipophilic and penetrate the blood-brain barrier, antagonizing the effects of histamine in the central nervous system (CNS) with ensuing sedation and impairment of coordination [8, 9] .

Histamine Receptors and Agonists: Diversity of Action

Histamine exerts its multiple effects by coupling to receptors expressed on the membrane of cells in different tissues [10] . Four different receptors denoted sequentially as H1 –H4 [11– 14] have been identified and sequenced so far. Their structure, position in the genome and encoding differ substantially, which reflects the complexity of their biological role. Generally, these receptors are composed of seven transmembrane chains and when activated, they exert their cellular effects through the G-protein system, triggering in action second messengers specific for each receptor (Table 1 ). Interestingly, sometimes they display activity in the absence of agonists. This is important, as blocking this spontaneous activity may interfere with standard physiological functions. The H-receptors exhibit stereochemical differences, which can be recognized by different chemical compounds, referred to as specific receptor agonists. A big proportion of these invert the original effects of histamine by rendering the receptor – G-protein complex inactive, which categorizes them as “inverse” agonists [15] . However, as they abolish the effects of histamine, they are popularly known as histamine receptor antagonists. In 1937 Bovet and Staub described the first pharmaceutical formulation to counter the effects of histamine in guinea pig [16] . The compound was too toxic for subsequent clinical development, but still sparked a lot of enthusiasm for research. Five years later, the first product aiming to treat nasal and skin allergic symptoms appeared on the market. Some 40 drugs with similar pharmacological profile were introduced in clinical practice until 1980, which became subsequently known as first generation antihistamines. Based on their chemical structure, they were divided into ethylendiamines, ethanolamines, alkylamines, phenothiazines, pipera- zines and piperidines [17] . While this classification helped at a time when analogy was sought with the molecule of histamine, the introduction of bigger and more complex molecules of the second generation H 1 inverse agonists – some of which defy labeling into the scheme – make it rather useless.

The introduction of second generation of H1 inverse agonists (Table 2 ) in clinical practice brought about significant improvement in the quality of antihistamine treatment, as these drugs had improved pharmacokinetic and pharmacodynamic profiles. They hardly penetrate the blood-brain barrier, which make them relatively free of the most bothersome adverse effects of the first generation: drowsiness, Antihistamines in Rhinitis and Asthma 39 JNJ 7777120 Thioperamide Cimetidine secretion channels), regulating 2+ bone marrow eosinohils mechanisms of Ca neurotransmitter release chronotropic/ionotropic cardiac effects Smooth muscle contraction Increased vascular permeability Negative inotropic cardiac effect Mepyramine Release of neutrophils from the Function of mast cells and Involvement in inflammation Histaminergic neurons (block Histaminergic Stimulation of gastric acid Smooth muscle relaxation; positive Airways: smooth muscles, vascular endothelial cells hemopoietic lineage trachea peripheral nerves: Airways peripheral nerves: cells) vascular smooth muscle, dendritic cells Ubiquitous, specifically in: Bone marrow and cells of the Heart Central nervous system Airways: dendritic cells, Central nervous system Heart Gastrointestinal tract Dendritic cells Endothelial cells Gastric parietal cells (oxyntic Airways: mucous glands, Heart Central nervous system

2+ influx influx 2+ 2+ in intracellular cAMP in intracellular cAMP phosphatidyl-inositol: opening up Ca phospholipase C activation: or elevation in intracellular cAMP Ca of the formation cAMP: reduction of the influx Ca Distinctive features of the histamine (H) receptors [10, 13– 17]

H2 Through adenylate cyclase: elevation Table Table 1 Receptor H1 G-protein signaling pathway Through phospholipase C/ Location Function Specific inverse agonist H4 Through adenylate cyclase or H3 Through adenylate cyclase: inhibition 40 T.A. Popov

Table 2 Generations of histamine type 1 (H1 ) receptor inverse agonists introduced in clinical practice over the years

H1 receptor inverse agonists First generation Second generation Acrivastine Doxylamine Astemizolea Alimemazine Emedastine Cetirizine Antazoline Flunarizine Ebastine Betahistine Hydroxyzine Epinastine Brompheniramine Ketotifen Loratadine Carebastine Mebhydrolin Mizolastine Chlorpheniramine Meclozine Rupatadine Cinnarizine Mepyramine Terfenadine a Clemastine Mequitazine Cyclizine Methapyrilene “Modern” second generation Cyproheptadine Oxatomide Desloratadine b Dexchlorpheniramine Phenindamine Fexofenadinec Dexbrompheniramine Pheniramine Levocetirizine d Dimenhydrinate Promethazine Dimetindene Thiazinamium Diphenhydramine Tripelennamine Diphenylpyraline Triprolidine

Locally applied Azelastine e Ketotifen Levocabastinee Olopatadine e,f Epinastinee,f a Withdrawn in most countries due to increased risk of cardiotoxicity b Metabolite of loratadine c Metabolite of terfenadine d Enantiomer of cetirizine e Developed only as topical preparation f Registered only as eye drops lassitude, dizziness, incoordination. They also have other important advantages: higher specificity for the H1 receptors, no affinity for muscarinic, serotoninergic, dopaminergic, adrenergic and other receptors with the ensuing untoward symptoms, and longer half-life allowing once daily dosing regimen [18] . A setback to the process of fast and wide introduction of second generation antihistamines in routine clinical practice were reports of life threatening arrhythmias and fatalities associated with the intake of the early representatives of this class of drugs: astemizole and terfenadine [19] . These triggered intensive research to identify the mechanisms of these cardiotoxic effects. It turned out that they relate to the binding affinity of a K channel – -iKr – a potassium inward rectifying current coded by the Human Ether go-go Related Gene (HERG), which has high homology to the H1 receptor [15] . All second generation preparations were scrutinized in this respect with particular focus on the ability of higher doses to prolong the QT interval of the electrocardiogram (ECG) tracings. As it turned out, other second generation drugs did not affect the electrical activity of the heart. Astemizone and terfenadine were withdrawn from the market in most countries. Antihistamines in Rhinitis and Asthma 41

Meanwhile the quest for new drugs with improved pharmacokinetic and pharmacodynamic profiles continued and three novel H1 inverse agonists were added to the list: desloratadine, fexofenadine and levocetirizine. What they had in common was their origin from older second generation drugs – desloratadine and fexofenadine being active metabolites of terfenadine and loratadine respectively, and levocetirizine being the active enantiomer of cetirizine [20] . Suggestions were made to classify these new formulations as “third generation” antihistamines. However, as they do not present properties, which make them dramatically different from their predecessors and other members of this class, it is more reasonable to label them as

“modern second generation H1 inverse agonists,” while waiting for real third generation molecules to be created with novel (not necessarily antiallergic) properties (Table 2 ). It is conceivable that with the new molecular techniques and with all different histamine receptors and their splicing variants sequenced and visualized in three dimensions, new formulations will be tailored to create the prefect drugs to treat selectively the unwanted effects of histamine in allergic reactions.

Classifications of Allergic Rhinitis and Implications for Treatment

Allergic rhinitis is clinically defined as a symptomatic disorder of the nose, induced by an IgE-mediated inflammation after allergen exposure of the membranes lining the nose [5] . Its prominent features had been identified as early as 1929: “The three cardinal symptoms in nasal reactions occurring in allergy are sneezing, nasal obstruction, and mucous discharge” [21] . Nowadays nasal obstruction, rhinorrhea, nasal itching, and sneezing still form the basis of our clinical diagnosis, but these are supplemented by other subtler, simpler, and composite outcomes related to quality of life, impairment of social behavior, and the ability to cope with tasks in school and at the workplace. However, these are rather nonspecific signs and are shared with other forms of rhinitis related to different causes (infectious, occupational, medicinal, neurogenic, hormonal, etc.) or effectuated by various other non-IgE mediated mechanisms, shaping sophisticated classification tables with still more intricate algorithms for management of the respective conditions [5, 22] . The picture is rendered still more complex by considerations related to comorbidities like sinusitis, conjunctivitis, asthma, chronic cough, or to special conditions like pregnancy and lactation, specific aspects of childhood and advanced age. For many years allergic rhinitis has been subdivided to seasonal-associated to high pollen counts – and perennial – attributed mostly to indoor allergens. In 1999, a panel of experts suggested a more global perspective during a World Health Organization (WHO) supported workshop on Allergic Rhinitis and its Impact on Asthma (ARIA), accounting for places on Earth with perennial pollen allergens and others with seasonal indoor allergen fluctuations [5] . It was proposed that allergic rhinitis should rather be assessed based on continuity and severity of symptoms. Subjects with the “Intermittent” form would have symptoms for less than 4 days a 42 T.A. Popov week for less than 4 consecutive weeks, whereas patients with the “Persistent” form would have symptoms more than 4 days a week for more than 4 consecutive weeks. If symptoms do not affect in any way the daily performance and the night rest of subjects with either form, severity would be defined as “Mild;” otherwise it would range between “Moderate” and “Severe,” depending largely on the individual perception of the symptoms. Subsequently the new ARIA classification was validated by an epidemiological study, which demonstrated that intermittent and persistent allergic rhinitis represent a new different stratum of the disease with consequences reflecting on its management [23] . Pharmacological treatment provides the fastest and most effective way of getting rid of the annoying symptoms of allergic rhinitis. There is no doubt whatsoever, that the most widely used drugs are the H1 antihistamines and the topical nasal corticosteroids. Usually judgements about treatment strategies are made based on the rank- ing of symptoms by the patients themselves, the severity of their condition, the knowledge of the strengths and weaknesses of the different drug classes and the separate compounds within them, the overall individual profiles of the subjects, not disregarding relevant financial considerations. A starting point may be to allocate the patient to one of the two groups of the simple clinical classification of rhinitis patients – “sneezers and runners” and “blockers” [24] . “Sneezers and runners” have itching, sneezing, and rhinorrhea as their leading symptoms. As these symptoms are readily reproduced by a histamine nasal challenge, it is logical to assume that drugs antagonizing the histamine effects would have a good chance to be effective in these subjects. “Blockers” are more likely to respond to the predominantly anti- inflammatory action of corticosteroids. However, this conditional approach should not be regarded as a “rule of the thumb,” as individuals may respond differently to treatment options, and may have preference of one product over the other. The advent of pharmacogenetics may help identify subjects with a high likelihood to respond to different treatment modalities.

Antihistamines in the Treatment of Allergic Rhinitis: Beyond the Histamine Effects

By definition, patients with allergic rhinitis are sensitized to outdoor and/or indoor allergens. When they are subjected to exposures above certain threshold levels, it would unleash an IgE mediated reaction with a cascade of cellular, humoral, and neurogenic events set in motion with inflammation of the nasal mucosa as a net result. Many of the developing symptoms may be attributed to the direct action of histamine, as it is released in high quantities during the degranulation of mast cells [6] . This explains the beneficial effect from the application of antihistamines in allergic rhinitis, which is backed up by decades-long experience with the multitude of members of the big family of H1 receptor inverse agonists. However, after an early phase in the IgE mediated reaction, where degranulation of mast cells, respectively histamine, plays a critical role, there follows a late phase Antihistamines in Rhinitis and Asthma 43 reaction involving other cell types, with T cells and eosinophils taking the lead [25] . Once chronic inflammation sets in the airway mucosa, it is sustained even at times of relative remission, when house dust mite levels or pollen counts are at a minimum. This prepared the ground for introducion of the concept of “minimal persistent inflammation” [26, 27] . A beneficial effect of a second generation antihistamine on this kind of smoldering process without the dramatic involvement of histamine has been demonstrated [28] . Besides, evidence has emerged along the road that allergens, because of their enzymatic proteolytic activity, may directly activate epithelial cells to promote a Th 2 -immune response, inducing airway inflammation independent of IgE [29, 30] . Taken together, the discussed mechanisms shape nonspecific nasal hyperreactivity, which is an important feature of rhinitis and can be defined as an increased nasal response to a normal stimulus, resulting in sneezing, nasal congestion and secretion, either as single symptoms or in various combinations [31] . The good clinical effect of antihistamines in a condition, in which many factors in addition to histamine have a stake, has instigated research to establish possible mechanisms, by which they may influence inflammatory outcomes. It appears that at least some of these anti-inflammatory effects are also related to the H1 receptor, which exists in two forms – inactive and active – even in the absence of its natural agonist histamine [32] . The active form upregulates Nuclear Factor Kappa B (NF kB), which in turn migrates to the cell nucleus and affects transcription and subsequent production of many proinflammatory mediators and molecules such as Intercellular Adhesion Molecule 1 (ICAM-1), Vascular Cell Adhesion Molecule 1 (VCAM-1), inducible Nitric Oxide Synthase (iNOS), Interleukin 6 (IL-6) or

Granulocyte Monocyte Colony Stimulating Factor (GMCSF). H1 inverse agonists bring about stabilization of the inactive form of the receptor and thereby have a number of receptor dependent anti-inflammatory effects, which are characteristic of the whole class of drugs. There are also receptor independent effects, some of them achieved through competitive inhibition of the binding of calcium, which seem to be more compound specific (Table 3 ).

As already indicated in Table 2 , the family of H 1 receptor inverse agonists is rather numerous and heterogeneous. They possess features common to all the members, but also others that differentiate between subgroups within them. All of them antagonize the effects of histamine by coupling to H1 receptors, but the second generation representatives display much higher H1 receptor affinity for them. Most products are prescribed for oral use, but there are also topical preparations for nasal/ ocular application. Attempts have been made to rank the separate compounds based on their ability to block the histamine-induced wheal and flare reactions in the skin of volunteers [33– 35] . While a clear cut distinction between the separate formulations was established using this test system, clinical trials comparing effectiveness of antihistamines in subjects with allergic rhinitis could only pick marginal differences if any [36] . This discrepancy may be due to variable H1 blocking activity of different drugs, their additional antiallergic effects, and possibly, their differences in lipophilicity and tissue deposition. Moreover, it appears that not all H 1 antihistamines have similar effects on patients and thus nonresponders with one drug may respond favorably to another [37] . 44 T.A. Popov

Table 3 Properties of H 1 inverse agonists beneﬁ cial for the treatment of allergic rhinitis [5, 61, 62] Properties Relevant Clinical related to Mechanism of action to symptoms significance Effect on Antagonizing the effect of Rhinorrhea, Very high

H1 -receptor histamine at the level of nasal itching, nasal epithelium, glands, sneezing sensory nerves and vascular endothelium

Rendering the H1 receptor Nasal congestion, Not clear. inactive, thus precluding itching Demonstrated the activation of Nuclear in few trials at Factor Kappa B (NFk B) to doses higher trigger the production of than usual inflammatory mediators Direct Suppression of mediator Rhinorrhea, Difficult to effect on release from mast cells nasal itching, distinguish through competitive sneezing, from receptor inhibition of the binding of nasal mediated calcium congestion clinical effects

The second generation H 1 receptor inverse agonists have undisputed advantages over the first generation formulations. Therefore, it has been recommended that they should be considered as a first-choice treatment for allergic rhinitis when they are available and affordable [5] . Surprisingly, it has been found that they are more cost-effective than the cheap first generation products because of the cost of the associated sedation [38] . The onset of action of the second generation antihistamines occurs between 20 and 120 min after oral intake and covers 24 h (with the exception of acrivastin). Some individual compounds have specific properties, which need to be taken into account if related to important clinical effects.

Certain foods have been found to alter the absorption of some oral H 1 receptor inverse agonists, depending on their proclivity to interact with a 170 kDa plasma membrane phosphorylated glycoprotein known as P-glycoprotein (P-gp) or an Organic Anion Transport Polypeptide (OATP) [39] . By this mechanism, grapefruit, orange, and apple juices may decrease the oral availability of fexofenadine [40] . Some of the second generation antihistamines (but not cetirizine, levocetirizine and fexofenadine) undergo hepatic metabolism via the Cytochrome P450 (CYP3A) system and are transformed into active metabolites. As CYP3A is also involved in the metabolism of many chemically diverse drugs administered to humans, this can lead to unwanted and unexpected drug–drug interactions [41] .

Effectiveness of second generation H1 receptor inverse agonists in allergic rhinitis, particularly on rhinorrhea, nasal itching and sneezing, has been proven in many double blind placebo controlled clinical trials [5] . The “modern” second generation formulations (Table 2 ) nourished expectations that they may have an effect on nasal congestion [42– 44] . However, such an effect tended to be rather modest in comparison with local corticosteroids. Antihistamines in Rhinitis and Asthma 45

No significant tachyphylaxis has been reported with any of the second generation antihistamines so far.

Oral H1-antihistamines have been shown to be safe and effective in children and have been approved for very young ones [45, 46] .

Several H 1 antihistamines have been engineered (some of them exclusively) for topical application (Table 2 ). This administration route offers several advantages, like fast onset of their effect and the possibility of delivering high concentrations directly into the nose, avoiding or minimizing systemic effects. This approach is most appropriate in patients with symptoms confined to the nose, as multiple organ manifestations would require additional medication.

Antihistamines in Asthma: Same Airway Disease, but Dramatically Different

The links between nose and lung have been empirically recognized long ago, but only recently the ARIA report ascribed special importance to the similarities between the nasal and bronchial mucosa [47] . The concept of “one airway – one disease” was explored from different angles, emphasizing mostly the functional complementarity of upper and lower airways and the common immunological defect related to the systemic nature of allergic sensitization. It has been acknowledged that histamine may mimic all the important asthma symptoms and histamine challenges have been used for decades for the diagnosis of asthma. The role of histamine has been extensively studied, and its involvement in the development of bronchial airway inflammation well documented [48] . Histamine provokes bronchoconstriction by direct muscle stimulation, as well as indirect stimulation of airway parasympathetic afferent nerves. It increases vascular permeability through venular dilatation and extravasation of plasma proteins and leukocytes with resulting mucosal edema, produces cough by direct stimulation of H1 receptors on sensory nerves and mucus hypersecretion through H2 receptor stimulation on mucosal glands [49, 50] . It is also chemotactic for eosinophils and neutrophils and increases the reactivity of the bronchial epithelium. Despite all these compelling facts prompting the importance of histamine in asthma, treatment strategies relying on blocking of the histamine effect in the lower airways have been rather disappointing. No H1 receptor inverse agonist has gained peer review recognition of the Global Initiative for Asthma (GINA) experts, for inclusion as a treatment option of asthma in the international guidelines. Notwithstanding the lack of distinct therapeutic effect on asthma, studies have provided some modest pieces of evidence that antihistamines may not be so hope- less for asthma management after all. Most antihistamines produce some acute bronchodilation in subjects with reversible lower airway obstruction [51] . They also exert a positive effect on airway hyperresponsiveness [52] . While studies demonstrating anti-inflammatory effects of different antihistamine compounds may have questionable clinical relevance, some others on patients with both allergic 46 T.A. Popov rhinitis and asthma report some benefits regarding the asthmatic condition [53, 54] . Although for the present antihistamines are not recommended for the treatment of asthma, when used for rhinitis they may improve concomitant asthma. Apart from asthma and conjunctivitis, which go hand in hand with allergic rhinitis, other comorbidities like nasal polyps, adenoid hypertrophy, tubal dysfunction, otitis media with effusion, chronic cough, laryngitis, etc. are often present too. There is no solid evidence regarding a positive therapeutic effect of antihistamines in any of them.

Antihistamines in Children, Elderly and Pregnant Women with Rhinitis

Allergic rhinitis is one of the most common chronic diseases in all ages and walks of life. Beyond the plateau of adulthood, its management has specific features for the pediatric and geriatric populations. Nasal symptoms of mothers-to-be also need to be handled with special consideration to their future offspring.

Allergic rhinitis can have a serious negative impact on children. The H1 receptor inverse agonists present a viable option for its management, as they do not affect the growth and physical development. However, a critical aspect of their application in childhood may be related to their effects on the functions of the CNS at a time of vigorous learning, mental and emotional development. Allergic rhinitis may by itself affect learning ability and concentration [55] . Therefore choosing the most appropriate formulation, which should not additionally induce sedation and impairment, is a responsible task [56] . The second generation H1 receptor inverse agonists certainly offer a better chance to circumvent adverse effects, which involve a wide spectrum of symptoms from drowsiness and fatigue to paradoxical hyperactivity, insomnia, and irritability with the representatives of the first generation. While second generation drugs are considered effective and safe, there are few clinical trials (especially in infants) addressing all aspects of the application of the existing molecules in different age groups. Otherwise, pediatric treatment strategies do not differ substantially from the general principles discussed so far. Elderly patients with allergic rhinitis have typically multiple comorbidities, different metabolic rates, slowing further with the advance of age, and, subsequently higher risk to develop drug–drug interactions [57] . These circumstances should discourage prescription of first-generation antihistamines with their inherent anticholinergic and sedating effects on elderly subjects, particularly on those with impaired cognitive function. Second generation antihistamines should be the drugs of choice in advanced age too, with possible need for dosage adjustments in case of impaired hepatic metabolism and renal excretion. In women with perennial rhinitis, symptoms may improve or deteriorate during pregnancy [58] . A specific condition called “persistent hormonal rhinitis or rhinosinusitis” may develop in the last trimester of pregnancy in otherwise healthy women. Its severity parallels the blood estrogen level and symptoms disappear at delivery. Antihistamines in Rhinitis and Asthma 47

Treatment relies on the same drugs as in the general population of rhinitic subjects. Caution must be exercised when administering any medication during pregnancy, as most medications cross the placenta and could potentially exert teratogenic effect on the fetus [59] . For most drugs, limited studies have been performed only on small groups without long-term analysis. The American College of Obstetricians and Gynecologists and the American College of Allergy, Asthma, and Immunology have issued a joint position paper regarding the treatment of allergic rhinitis during pregnancy [60] . Based on safety data available before 2000, these organizations recommended chlorpheniramine, loratadine, and cetirizine as reasonable choices for allergic rhinitis management during pregnancy (ideally after the first trimester). However, the selection has to be further narrowed, based on the sedative and performance-impairing effects of first-generation agents, favoring the use of second- generation agents.

The Ideal Antihistamine: Basis for Comparison of all Existing Preparations

With the long list of existing antihistamines, it is quite frustrating to make judgements about relative potencies, clinical merits, and foreseeable risks in prescribing one product or another to individual patients. Recently an attempt was made to come up with definitions of the properties of an “ideal” antihistamine preparation to set a standard for future drug development [32] . The list of optimal characteristics of this utopic molecule used as a bench mark will also help physicians to form an opinion about pharmaceutical products they are about to add to their armamentarium.

The pharmacological properties should involve H 1 receptor selectivity, high potency, additional antiallergic/anti-inflammatory properties, no interactions with intestinal/liver enzymes, infectious agents and other drugs, no toxicity. Their onset of action should be rapid, lasting long enough to allow one daily application. The clinical efficacy should be high in all forms and severity levels of allergic rhinitis, in coping with all symptoms including nasal congestion, and acting on eye and subjective and objective asthma symptoms, affecting positively the long term asthma outcomes. The ideal preparation should be devoid of side effects , including those commonly registered with existing preparations – no sedation, cognitive or psychomotor impairment, no effects related to other CNS receptors, no cardiac arrhythmias, and no metabolic disturbances including weight gain. The ideal molecule should be proven effective and safe in special population groups : children of different ages, elderly people, pregnant and lactating women. Antihistamines bear potential for further improvement, which can favorably affect the quality of life of millions with allergic rhinitis. In the meantime, it is the responsibility of the healthcare professional to disseminate knowledge about treatment modalities and to upgrade management guidelines based on sound evidence. 48 T.A. Popov

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Antiallergic and Vasoactive Drugs for Allergic Rhinitis

Friedrich Horak

Introduction

Rhinitis is defined as the inflammation of the lining of the nose with one or more symptoms. The symptom profile of allergic rhinitis (AR) includes sneezing, itching of the eyes, nose, and throat, nasal obstruction, and rhinorrhoea. However, other problems and symptoms are also commonly associated with AR. For example, patients with seasonal AR commonly have conjunctivitis and may also have bronchial asthma. In central Europe, the association with bronchial asthma is greater with birch pollen allergy than grass pollen allergy. Headache and fatigue are other symptoms commonly associated with AR [1] . The most bothering symptom of AR is blocked nose, but loss of taste and smell are also associated symptoms. AR is linked with asthma; more than 30% of patients with perennial AR have signs of asthma, and about 75% of patients with allergic asthma also have perennial AR [2] . The upper and lower airway tracts are very closely related. The combination of symptoms in AR causes impairment of day-to-day physical, emotional, occupational, and social functioning. In particular, patients with perennial AR have severely impaired quality of life and some sleep disturbances, and the disease has a significant impact in terms of lost productivity [3] . Thus, symptom relief is a priority in AR. A complex system within the nasal vascular system controls nasal patency. Fenestrations within the subepithelial capillaries allow the rapid flow of water into the lumen for evaporation and heat loss. These are unique to this part of the respiratory tract. Other vessels that play an important part in the blocked nose include the capacitance vessels, which regulate airflow in the nose and are involved in congestion and decongestion. Arteriovenous anastomoses are responsible for temperature control.

F. Horak () Ear, Nose, and Throat Department , Medical University Vienna , Head of Allergy Centre Vienna West , Huetteldorferstrasse , 46, A-1150 Vienna , Austria e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 51 DOI 10.1007/978-4-431-99362-9_4, © Springer 2010 52 F. Horak

The effects of histamine and other mediators are closely related to this vascular system. For example, histamine acts on the postcapillary venules, causing plasma extravasation during the immediate and late phase of the allergic reaction by opening gaps in the intercellular junctions between the endothelial cells. A potent histamine antagonist could help reduce this activity. However, mediators other than histamine, such as bradykinin, prostaglandin D2 , leukotrienes, platelet activating factor, and others also cause plasma extravasation [4] . Thus, a drug that only possesses antihistamine activity would not completely inhibit this effect. During an allergic reaction, the diameter of capillaries increases dramatically within about 15 min. A similar effect occurs on vessels in the deeper layers of the mucous membrane. It is known that symptoms, particularly those of the long-acting late-phase reaction, lead to greater immunoglobulin (Ig)-G synthesis and increasing morbidity. Several mediators are responsible for the different parts of the late-phase reaction, including the 5-lipoxygenase enzyme, which is responsible for the synthesis of leukotrienes. The immediate-phase reaction is characterized by itching and sneezing, some discharge, and some congestion, whereas the late-phase reaction is characterized by nasal blockage, loss of smell, and nonspecific hyperreactivity. Antihistamines are active in reducing the immediate-phase reaction, particularly those symptoms induced mainly by histamine, such as itching, sneezing, and discharge. Some of the second-generation antihistamines are also active in the late phase, and may act by reducing 5-lipoxygenase activity, ICAM-1 expression, or IL-4 activity. Therefore, these modern antihistamines are not only H1 -receptor antagonists but also antiallergic drugs that are active in parts of the late-phase reaction.

Guidelines for the Treatment of AR

Prior treatment guidelines published by the International Rhinitis Management Working Group in 1994 recommended a stepwise approach to treating AR, starting with oral and/or topical antihistamines, particularly for mild and moderate disease [5] . More recently, the WHO ARIA (Allergic Rhinitis and its Impact on Asthma) workshop published a new classification of AR based on frequency, duration, severity, and influence on quality of life [6] . The pharmacologic treatment of AR proposed by ARIA is an evidence-based and stepwise approach. These recommendations have been subsequently modified and validated [7– 9] . However, the stepwise approach to treating AR, starting with oral and/or topical antihistamines followed by topically used steroids, was the same as described already in the early 1990s [5] .

Cornerstones of Rhinitis Treatment

1. Education of patients, parents, and their contacts Antiallergic and Vasoactive Drugs for Allergic Rhinitis 53

2. Allergen avoidance according to a recent allergy diagnosis 3. Pharmacotherapy

a. Oral H1 -receptor antagonists

b. Topical nasal H1 -receptor antagonists c. Topical nasal corticosteroids d. Systemic corticosteroids e. Antileukotrienes f. Sodium cromoglicate g. Anti-IgE h. Intranasal decongestants i. Oral decongestants 4. Speciﬁ c allergen vaccination (immunotherapy) The following sections will deal with “Pharmacotherapy of allergic rhinitis.”

Oral H1 -Receptor Antagonists

Because histamine release is a common feature of AR, antihistamines have been the treatment of choice. Since the early 1970s, the design and development of antihistamines have evolved, with the goal of improving specificity and reducing side effects.

First-generation H1 -antagonists (diphenhydramine, promethazine, hydroxyzine, chlorpheniramine, azatadine) represent a chemically heterogeneous group of agents that effectively reduced itch, nasal discharge, and sneezing, but not congestion, in patients with SAR. Because of their high lipophilicity and marked tendency to cross the blood–brain barrier, these agents were plagued with anticholinergic and CNS- related antihistamine side effects of dry mouth, sedation, and daytime drowsiness, and a tendency to cause urinary retention in the elderly [10– 12] . The use of these agents in treating allergic disease was further limited by their short plasma half-life

[11] . First-generation H1 -receptor antagonists are no longer used in AR.

There is a number of second-generation H1 -receptor antagonists in the market and some more under development: (1) acrivastine, (2) azelastine, (3) cetirizine, (4) bilastine, (5) desloratadine, (6) ebastine, (7) emedastine, (8) epinastine, (9) fexofenadine, (10) levocetirizine, (11) loratadine, (12) mizolastine, (13) norastem- izole, (14) rupatadine (astemizole and terfenadine were widely withdrawn from the market).

Compared to first-generation H1 -receptor antagonists, second-generation H1 - antagonists exert their antiallergic effects through multiple mechanisms, including suppression of the inflammatory response. However, the clinical relevance of these additional activities is still questionable [11, 13– 17] . Although second-generation

H 1-antagonists effectively reduced nasal itch, discharge, and sneezing, they did not reduce congestion in patients with AR satisfactorily [18– 20] . However, it is evident that few second-generation H1 -antagonists have some effect on nasal obstruction [21– 24] . 54 F. Horak

Nevertheless, some of the second-generation antihistamines (e.g. azelastine, cetirizine, levocetirizine) are associated with sedation and psychomotor impairment, but not in the same amount as first-generation drugs [25– 27] . Furthermore, drug– drug interactions raised major concerns with some of these agents, since coadminis- tration of terfenadine or astemizole with cytochrome P enzyme inhibitors (e.g. ketoconazole and erythromycin) resulted in significant cardiotoxicity and cardiac arrhythmias [11, 25] . Overall, second-generation antihistamines are much safer than the first-generation ones and have unquestionable advantages over them. According to the ARIA guidelines, antihistamines are the first choice of pharmacotherapy in mild to severe AR. Since 1985, more than 50 studies have compared the effects of different second- generation antihistamines in controlling the nasal symptoms of patients with AR. There was no consistent pattern of one antihistamine showing superiority over other antihistamines [28, 29] .

However, there is still a need for improved H1 -receptor antagonists for more effective treatment of allergic disease. A symptom reduction of about 40% more than placebo is clinically relevant but does not meet the patients’ need completely. Ideally, such agents should have an additional low potential for drug interaction and undesirable CNS-related side effects, combined with proven anti-inflammatory and decongestant properties.

Topical Nasal H1 -Receptor Antagonists

Because of the fast onset of action [30– 32] , topical nasal H1-receptor antagonists like azelastine, epinastine, ketotifen, or levocabastin are very useful as rescue medication. Their therapeutic effect is similar to oral antihistamines for all rhinitis symptoms and there is even some effect on conjunctival symptoms [33– 36] . Therefore, it also makes sense to use this topical treatment for mild AR as first line treatment, optionally combined with the topical treatment of allergic conjunctivitis. Furthermore, there is some information indicating the benefit of topical antihistamines for AR patients who do not respond to oral antihistamines [37, 38]. However, it is to be considered that topically used antihistamines do not improve symptoms due to histamine at other sites, such as lower airways or skin.

Topical Nasal Corticosteroids

There are some opposing positions in terms of the place of topical corticosteroids in the management of AR: These compounds may be used in second line in addition to antihistamines in terms of moderate to severe AR or as first line therapy for moderate to severe AR and treatment failures with antihistamines alone. Whatever, it is evident that intranasal corticosteroids are, to some extent, Antiallergic and Vasoactive Drugs for Allergic Rhinitis 55 superior to antihistamines [39] . However, although corticosteroids act by suppressing allergic inflammation at multiple points in the allergic cascade, their therapeutic potency is in the range of oral antihistamines, leading to a symptom reduction of about 50% only [40, 41]. In contrast to antihistamines, the onset of action is not before 6–12 h (topical antihistamines are active after 15–30 min, oral antihistamines are active after 30–90 min) and the maximal effect may not be apparent until after 2 weeks (5–7 days in terms of antihistamines) [42– 44] . In recent years, new corticosteroids, which offer greater topical efficacy with lower systemic absorption (triamcinolone acetonide, budesonide, fluticasone proprionate, mometasone fuorate) [45, 46], have been developed for nasal use. A new approach to decrease systemic side effects of corticosteroids is the development of the so-called “soft steroids” like loteprednol etabonate (just not on the market) [47, 48] .

Systemic Corticosteroids

Systemic oral corticosteroids are rarely indicated in the management of AR. They may be an option used briefly and supporting the conventional pharmacotherapy for uncontrolled symptoms only. A circadian rhythm, taking the drug before 8:00 a.m. (preferably every second day), would reduce the potency of side effects. The treatment should not last longer than 5–10 days, with a limit of 0.5 mg per kg. Systemic intramuscular depot corticosteroids are not recommended for AR at all. The risk/benefit ration is more than poor compared to other treatment options [49] .

Antileukotrienes

Besides histamine, which is the most important mediator of the allergic cascade, leukotrienes play an important role in allergic inflammation [50– 54] . Therefore, leukotriene receptor antagonists like montelukast or zafirlukast as well as leukotriene systesis inhibitors like zileuton can reduce the essential components of allergic inflammation in AR. These drugs are orally active, can be administered once daily, and provide a systemic approach to the management of patients with AR or bronchial asthma. The wide range of clinical effects favors the compound, especially when the AR is accompanied by allergic bronchial asthma. The majority of allergic asthmatics suffer from concomitant rhinitis. For this large group of patients, leukotriene receptor antagonists can be the suitable medication. Leukotriene receptor antagonists have confirmed efficacy in AR and have a level of therapeutic potency close to H1-receptor antagonists [55] . However, the response is less consistent than that observed for antihistamines. Moreover, synergistic benefits were documented with antihistamines in AR as 56 F. Horak well as with corticosteroids and long acting beta-2 agonists in bronchial asthma [56– 58] . As this synergistic effect is not clearly convincing in terms of the clinically relevant extent, this treatment option is still under discussion. Leukotriene receptor antagonists have their place in the therapy of AR if allergic bronchial asthma is co-morbid [59, 60] .

Sodium Cromoglicate

In recent times, the use of sodium cromoglicate or nedocromil is disputed. Although they have an excellent safety profile, their efficacy is limited and the need for frequent dosing is not compliant. Cromones are generally less effective than all other medications used for the treatment of AR [61, 62] . Children with mild symptoms of AR and only sporadic problems may take an advantage of the drug [63] .

Anti-IgE

A monoclonal antibody to IgE, omalizumab has been developed recently, only in the 1990s. It is a recombinant humanized form of a mouse antibody, and because it is humanized it does not generate immune responses in humans [64– 67] . This antibody is directed at the part of the IgE molecule that is normally obscured, when IgE is attacked, to the high-affinity receptor on the mast cells, and omalizulab is able to bind to and neutralize circulating IgE without causing mast call degranulation. Casale et al. showed that omalizumab suppresses serum IgE in patients with SAR, which is encouraging as serum IgE levels were correlated with symptom scores in the same study [68] . The clinical efficacy of omalizumab has since been confirmed in patients with SAR, as well as in various studies in patients with asthma [69] . Anti-IgE therapy, therefore, promises to be a useful addition to the treatment options in patients with allergies. However, due to the bad cost/benefit ratio, it will be restricted to some cases of severe bronchial asthma only. Further use may include treatment with immunotherapy in high-risk patients.

Intranasal Decongestants

The use of decongestants in AR may be beneficial in reducing the bothering symptom of blocked nose, but because of the potential risks of side effects and rhinitis medicamentosa they should be handled with utmost care. Currently available topical decongestants (ephedrine, xylometazoline, oxymetazoline) are limited by tachyphylaxis and they have the tendency to cause rebound congestion when discontinued [70– 72] . Antiallergic and Vasoactive Drugs for Allergic Rhinitis 57

Several combined preparations of intranasal decongestants with antihistamines are on the market. They have shown a greater efficacy than the drugs given separately [70] . However, these combinations have the same limitations and side effects as decongestants alone. Therefore, the use of all intranasal decongestants and their combinations is to be restricted to a maximum of 10 days only.

Oral Decongestants

Although oral decongestants do not suffer from a rebound effect, they are not free of problems. On the one hand, they are less effective than the topical medication and on the other, they are rich on side effects like insomnia, increase in blood pressure, and urinary retention. However, some slow-release preparations may have an efficacy up to 24 h [73, 74] . The safety and efficacy of pseudoephedrine is generally limited, with 240 mg per day . Antihistamine and decongestant combinations are on the market, with first- generation antihistamines and second-generation antihistamines like loratadine, desloratadine, cetirizine, and fexofenadine. They have shown a greater efficacy than the drugs given separately [75, 76] . Because of the side effects, oral decongestants and combined preparations are not generally recommended and should be used only in selected cases. In some states, there are restrictions on the availability of pseudoephedrine because it can be used to produce methamphetamine. Therefore, phenylephrine was suggested to substitute pseudoephedrine. Phenylephrine cannot be converted to methamphetamine and can be sold without restrictions. However, phenylephrine, at the FDA-approved dose of 10 mg for adults, is unlikely to provide relief from nasal congestion [77] .

Conclusion

Several effective medications for AR are on the market. They can be tailored for the individual patient in order to reduce the burden of allergy. The following guidelines may help. However, the efficacy of each preparation is limited and some patients still have residual symptoms. Therefore, there is still a need for more improvement and new molecules.

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Anthony Peter Sampson

Introduction

Leukotrienes are lipid mediators synthesized from arachidonic acid liberated from the membranes of activated inflammatory cells [1] . The subfamily of cysteinyl- leukotrienes (cys-LTs) represented by LTC4 , LTD 4 and LTE4 are the first inflammatory mediators to have a proven role in the pathophysiology of asthma [2] and which mimic many of the features of allergic rhinitis [3] . Antileukotriene drugs that block the synthesis of leukotrienes or antagonize cys-LT receptors have been licensed for asthma therapy in most countries in the last dozen years [4] , with some of these drugs also being registered for use in allergic rhinitis [2] . This chapter will outline the sources and actions of cys-LTs in allergic airway inflammation and the clinical evidence underlying the use of antileukotriene drugs in asthma and allergic rhinitis.

The Leukotriene Biosynthetic Pathway

Inflammatory processes in the allergic airway depend on a complex network of cellular interactions regulated by mediators of numerous chemical classes, including lipids. These include the leukotriene and prostanoid families of eicosanoids, which are derivatives of the 20-carbon polyunsaturated fatty acid – arachidonic acid. Arachidonate is usually found esterified in phospholipids in cellular membranes, particularly the nuclear envelope, and is metabolized to the potent neutrophil chemotaxin leukotriene (LT)B4 or to the bronchoconstrictor and proinflammatory cysteinyl-LTs (LTC4 , LTD 4 and LTE4 ) by the 5-lipoxygenase pathway (Fig. 1 ).

A.P. Sampson () Division of Infection, Inflammation & Immunity (III), University of Southampton School of Medicine, The Sir Henry Wellcome Building (MP825), Southampton General Hospital, Tremona Road, Southampton, SO16 6YD, UK. e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 63 DOI 10.1007/978-4-431-99362-9_5, © Springer 2010 64 A.P. Sampson is then 4 show the Y and X , by cells expressing ). 4 a

ght to donate arachidonate respectively, which together with respectively, 4 ) which liberates arachidonate from 2 receptors on target cell membranes, receptors on target 2 . Depending on cell-type, LTA . Depending on cell-type, LTA 4 (cPLA and LTE and LTE 2 4 or CysLT 1 receptor antagonists. From [1] with permission [1] receptor antagonists. From 1 hydrolase and/or to the first of the cysteinyl-LTs, LTC LTC hydrolase and/or to the first of cysteinyl-LTs, 4 concentrations activate cytosolic phospholipase A concentrations activate cytosolic phospholipase 2+ synthase. After cellular export by multidrug resistance-associated protein 1 (MRP1), extracellular synthase. 4 receptors and at nuclear peroxisome proliferator activated receptors (PPAR receptors and at nuclear peroxisome proliferator activated (PPAR 2 by cells expressing LTA by cells expressing LTA 4 and BLT and BLT 1 by gamma-glutamyl-transpeptidase (GGT) and dipeptidase forms LTD by gamma-glutamyl-transpeptidase (GGT) and dipeptidase forms LTD 4 acts at distinct BLT acts at distinct BLT 4 Stimuli that activate cells by increasing intracellular Ca

are termed sulphidopeptide-leukotrienes or cysteinyl-leukotrienes (cys-LTs). These act at specific CysLT These act at specific CysLT are termed sulphidopeptide-leukotrienes or cysteinyl-leukotrienes (cys-LTs). 4 while (non-cysteinyl) LTB while (non-cysteinyl) LTB respective sites of action the 5-LO inhibitor zileuton and lukast class CysLT converted to the potent neutrophil chemoattractant LTB converted to the potent neutrophil chemoattractant LTB cleavage of the peptide side-chain of LTC cleavage of the peptide side-chain LTC Fig. 1 the nuclear envelope and transfers it to the 5-lipoxygenase activating protein (FLAP) located within the membrane. FLAP is thou the nuclear envelope and transfers it to 5-lipoxygenase activating protein (FLAP) located within membrane. FLAP 5-lipoxygenase (5-LO), which translocates from the cytosol to convert arachidonate in two stages leukotriene (LT)A LTC LTC microsomal glutathione-S-transferase type II or a specific LTC microsomal glutathione-S-transferase type II or a specific LTC Antileukotrienes in Asthma and Rhinitis 65

Cellular Sources of Leukotrienes

The cells with the highest capacity to generate cys-LTs are subsets of myeloid leukocytes. In vitro, eosinophils preferentially or exclusively secrete LTC4 [5] , while monocytes generate both LTB4 and smaller amounts of LTC4 [6] . Mature blood basophils and human lung mast cells have a high capacity to generate LTC 4 [7] . In contrast to myeloid cells, the capacity of lymphocytes to generate LTs is contentious, but reports suggest that B-cells and T-cells can generate LTB4 de novo or by transcellular donation of LTA4 from myeloid cells, but cannot generate cys-LTs [8] . Within the airway, bronchial epithelial cells may also generate cys-LTs in relatively small amounts, either constitutively or following viral infection [9, 10] . Other structural cells, such as fibroblasts, smooth muscle cells, and endothelial cells may also generate cys-LTs or LTB4 , either de novo, or following transcellular donation by other cell-types of arachidonate, or of the intermediate LTA4 [11– 13] . Although such cell-types have a limited capacity to generate LTs, their numerical predominance may make them significant contributors to cys-LT levels within the airway as a whole.

Cysteinyl-Leukotriene Receptors

The actions of cys-LTs are mediated by specific CysLT receptors. Pharmacological studies in human bronchi originally identified a receptor at which both LTC4 and

LTD4 were full constrictor agonists, with LTD4 being the most potent, and this receptor was termed CysLT 1 [14] . The CysLT 1 receptor is the molecular target of the “lukast” class of antileukotriene drugs currently marketed for asthma therapy, including montelukast, zafirlukast, and pranlukast; such compounds failed to block contractile responses induced equipotently by LTC4 and LTD4 in human pulmonary veins, and this second receptor was termed CysLT 2 [15] . The dual antagonist

BAYu9773 can antagonize the CysLT2 receptor experimentally, but currently marketed antileukotriene drugs do not block the actions of cys-LTs at this receptor, which may include endothelial activation and the production of specific cytokine subsets by mast cells, as well as effects on other organ systems.

Human CysLT 1 and CysLT 2 receptors were both characterized at the molecular level in 1999–2000 [16– 18] (Table 1 ). Both are classical G-protein-coupled receptors (GPCR) with seven putative transmembrane regions, and their functional activation involves calcium mobilization. The CysLT2 receptor polypeptide shows 31% amino acid identity to Cys-LT1 . The molecular studies largely confirmed the previous pharmacological observations – at the CysLT1 receptor, LTD4 is approximately

10-fold more potent as an agonist of calcium mobilization than LTC4 or LTE4 . At

CysLT2 receptors, LTC 4 and LTD 4 are roughly equipotent, but both have lower potency for CysLT2 than LTD 4 has for the CysLT 1 receptor. The specificity of the

“lukast” antagonists for CysLT1 , and the dual antagonism of CysLT 1 and CysLT 2 by BAYu9773 were also confirmed by the molecular studies. There are distinct patterns 66 A.P. Sampson 41– 45, 54, 60] [16, 19– 21, 39, [17, 18, 21, 35, 61] vascular leakage, Th2 vascular leakage, cytokine synthesis, airway remodeling bleomycin-induced airway fibrosis, interleukin-8 release Pranlukast Zafirlukast MK-571 Bay u9773 Bay u9773 Endothelial activation,

4 Montelukast Bronchoconstriction, eosinophilia, Montelukast Ischemic neural injury [22] 4 4 > LTE >> LTE > LTE None Enhanced proliferation [56] 4 4 4 4 > LTC = LTD > LTD = LTD 4 4 4 4 Bay u9773 (partial) LTC LTC LTD LTD Uridine diphosphate monocytes), vascular endothelium eosinophils, basophils, some T-cells T-cells eosinophils, basophils, some Cysteinyl-leukotriene receptors

CysLT2 CysLT2 Brain, heart, spleen, leukocytes (e.g., GPR17 Brain, heart, kidney LTC Table Table 1 Receptor CysLT1 Cellular expression Bronchial smooth muscle, mast cells, Agonists Antagonists Actions References Sampson AP Allergy Frontiers rhinitis Antileukotriene drugs in asthma and allergic Unidentified Human bronchial fibroblasts LTC Antileukotrienes in Asthma and Rhinitis 67

of tissue expression for CysLT1 and CysLT2 receptors. CysLT1 is found mainly in airway smooth muscle, spleen, peripheral blood leukocytes (notably eosinophils and basophils), and pulmonary macrophages [16, 19, 20] . In contrast, large amounts of

CysLT2 mRNA are found in the heart (Purkinje fibers), brain, placenta, spleen and leukocytes, but little in the lung [17] . On grounds of structural homology, the CysLT receptors are classified as members of the nucleotide family of GPCRs that also includes purinergic (P2Y) receptors [21] . There is growing evidence that some members of this family are dual receptors, able to be activated both by cys-LTs and by nucleotides such as uridine diphosphate (UDP). The family also contains a number of orphan GPCRs, and one of these, known as GPR17, was recently identified as a dual CysLT/P2Y receptor [22] . GPR17 shows most activity in response to nanomolar concentrations of LTC4 and is also activated by micromolar concentrations of UDP. Intriguingly, GPR17 is expressed highly in brain and is associated with ischemic neural injury in a rat model; montelukast antagonizes the receptor and blocks the neural injury [22] . It is possible that further novel CysLT receptors will be identified and interactions between cys-LTs and nucleotide agonists may be functionally important in the inflamed airway.

Actions of cys-LTs in Asthma and Rhinitis

Bronchoconstriction

Leukotriene B4 has no bronchoconstrictor activity in normal or asthmatic human subjects [23] , but the cys-LTs are the most potent bronchoconstrictor mediators yet identified. In normal and asthmatic subjects, LTC 4 and LTD 4 are 400- to 10,000- fold more potent than histamine or methacholine, with a slower onset but a longer duration of action [24– 26] . Inhaled LTE4 is 10-fold less potent than LTC4 or LTD4 , but remains more potent than histamine. The bronchoconstrictor effects of cys-LTs are mediated by CysLT1 receptors.The cys-LTs appear to act equally on the central and peripheral airways. In asthmatic subjects, inhalation of cys-LTs may increase bronchial responsiveness to histamine or methacholine, with one report indicating increased histamine responsiveness up to seven days after LTE 4 inhalation [27] . In normal subjects, evidence of an effect of cys-LTs on methacholine responsiveness is contradictory. Cysteinyl-LTs do not affect responsiveness to exercise challenge or inhalation of distilled water.

Vascular Effects

In addition to bronchoconstriction, cys-LTs have a wide range of potent proinflammatory actions relevant to asthma and rhinitis, including effects on the vasculature. Cysteinyl-LTs directly increase endothelial permeability in human 68 A.P. Sampson post-capillary venules in vitro [28] . In mice, gene deletion experiments demonstrate the importance of the CysLT 1 receptor in acute vascular permeability increases, following IgE-dependent stimuli [29] . Unlike many other inflammatory autacoids, cys-LTs at high concentrations generally constrict arterioles in a number of organs; and in human skin, the wheal and flare are accompanied by a central pale area due to vasoconstriction at the injection site where the cys-LT concentrations are highest [30] . However, assessed by laser Doppler imaging, LTD 4 markedly increases overall blood flow in human skin, mediated at least in part by secondary release of histamine [31] . Laser Doppler fluximetry also showed that LTD4 increases blood flow in the nasal mucosa, accompanied by increased nasal resistance and reduced nasal airflow [32] . It seems likely that leukotriene- dependent increases in microvascular permeability contribute to edema in the allergic airway [33] . In addition to opening tight junctions between vascular endothelial cells, cys- LTs promote leukocyte-endothelial interactions. In human umbilical vein endothelial cells (HUVEC), cys-LTs enhance the rolling of polymorphonuclear leukocytes along the endothelium, by increasing expression of P-selectin on both leukocyte and endothelial cell surfaces [34] . CysLT 1 antagonists do not block the effect and this may be explained by the high expression of CysLT2 receptors on HUVECs [35] . Eosinophils overexpress a specific ligand for P-selectin that may produce selective endothelial adhesion of eosinophils relative to neutrophils [36] .

Leukocyte Recruitment

As well as on human bronchial smooth muscle, CysLT 1 receptors are also expressed on a number of inflammatory cell-types, including mast cells, basophils and eosinophils [19, 20] . In atopic asthmatic subjects, inhalation of LTE4 produces a 10-fold influx of eosinophils in the bronchial mucosa 4 h after inhalation, while there is no cellular response to concentrations of inhaled methacholine producing a similar degree of bronchoconstriction [37] . The eosinophilia persists for up to

6 weeks after a single LTE4 inhalation. Inhalation of LTD4 produces a modest increase in sputum eosinophils [38] .

Consistent with the in vivo data, nanomolar concentrations of LTD 4 cause selective migration of normal human eosinophils in vitro [39] , although the magnitude of the effect is moderate compared to that induced by eosinophilotactic chemokines., migratory responses of eosinophils to LTD4 may be further enhanced in asthmatic subjects by in vivo priming by eosinophilopoietic cytokines such as IL-5 [40] . Cysteinyl-LTs may also promote airway eosinophilia by reducing eosinophil apoptosis [41] or by enhancing their proliferation in the bone marrow and their release into the circulation [42] . These proliferative, chemotactic, and antiapoptotic effects of cys-LTs on eosinophils are mediated by CysLT1 receptors [43] . Antileukotrienes in Asthma and Rhinitis 69

Other Inflammatory Actions

The presence of CysLT1 receptors on other cell-types including mast cells, basophils, monocytes, dendritic cells, and activated T-cells suggests multiple roles of cys-LTs in allergic inflammation [44] . Mice rendered incapable of generating cys-LTs by deletion of the LTC4 synthase gene show reduced airway inflammation induced by inhaled allergen, with reductions in eosinophil counts, mast cell activation, Th2 cytokine production, and mucus gland hyperplasia [45] . Production of Th2 cytokines is also blocked in antigen-stimulated human mononuclear cells treated in vitro with the CysLT1 receptor antagonist pranlukast [46] . Nitric oxide (NO) is a key vasodilator mediator and a useful marker of inflammation [44] ; blockade of CysLT1 receptors reduces exhaled NO in asthmatic children [47] , although no effect is detectable in children with seasonal allergic rhinitis (SAR) [48] .

In vitro, LTC4 and LTD4 increase mucus secretion in human bronchial mucosal explants [49] , and reduce mucociliary clearance in human nasal epithelium [50] . The ability of cys-LTs to increase mucus secretion, blood flow, and resistance in the nasal airway complements the ability of histamine to cause profuse watery nasal secretions as well as itching and sneezing [51] . Together, cys-LTs and histamine effectively mimic allergic rhinitis symptoms.

Airway Remodeling

It is increasingly recognized that airway remodeling – including the proliferation of bronchial smooth muscle cells and myofibroblasts and the deposition of subepithelial collagen – is an important feature of asthma and that cys-LTs may have key roles in these processes [52] . An early study in rats showed that the increase in bronchial responsiveness induced by inhaled antigen, is related to an increased mass of bronchial smooth muscle, and both these increases are blocked by a CysLT1 antagonist, suggesting a mitogenic effect of cys-LTs on smooth muscle [53] . In vitro,

LTD4 greatly augments the proliferative effects of epidermal growth factor (EGF) on human airway smooth muscle (HASM) cells [54] . The proliferative effects may be mediated by CysLT1 receptors and involve modulation of the activity of insulin-like growth factor (IGF) [55] . Cys-LTs also markedly enhance the mitogenesis and proliferation of human bronchial fibroblasts induced by a range of growth factors; intriguingly, this effect is not Ca2+ -dependent and is not reduced by antagonists of

CysLT1 , CysLT 2 , GPR17 or P2Y receptors, suggesting that a novel CysLT receptor is responsible [56] . LTC4 further induces collagenase expression in human lung fibroblast cells and in primary fibroblasts in patients with idiopathic pulmonary fibrosis [57] , which may contribute to remodeling of extracellular matrix. The cys- LTs are also reported to be potent mitogens for human airway epithelial cells [58] , suggesting that they may be involved in epithelial repair processes. Studies that are more recent provide striking evidence of cys-LT involvement in airway fibrosis in mouse models. In an allergic mouse model, the CysLT1 antagonist 70 A.P. Sampson montelukast had modest effects on airway inflammation (e.g., eosinophil counts) induced by ovalbumin, but entirely prevented the airway smooth muscle hyperplasia and airway fibrosis induced during 75 days of exposure to the antigen [59] . In a second study, when montelukast was introduced only after remodeling had been induced by ovalbumin exposure over a similar period, it was nevertheless able to reverse these changes completely over the following 90 days, while dexamethasone had no effect [60] . In a mouse model of interstitial pulmonary fibrosis induced by bleomycin, deletion of the LTC4 synthase gene confirmed that cys-LTs are essential for fibrosis to develop; however, in contrast to the allergic mouse, the profibrotic changes were dependent on CysLT2 receptors in this model, while CysLT1 receptors were antifibrotic [61] . Clinical studies are required to determine whether blockade of CysLT1 or CysLT 2 receptors may prevent, reverse, or exacerbate airway fibrosis in asthma and other human airway diseases.

Leukotrienes in Biological Fluids

Leukotrienes can be quantified in biological fluids including urine, sputum, nasal lavage fluid, bronchoalveolar (BAL) lavage fluid, and exhaled breath condensate (EBC) using radio- or enzyme-immunoassays, often requiring prior purification with solid-phase extraction, immunoaffinity columns, or high performance liquid chroma- tography [62] . Urinary LTE4 levels, are elevated in asthmatic subjects with acute severe asthma after correction for variable dilution using creatinine concentration, but not allergic rhinitis [63] ; and in asthma the levels correlate with airflow limitation

[64] . BAL fluid levels of LTC4 rise along with other mast cell mediators within 5 min of inhaled allergen challenge, and urinary LTE4 levels are elevated during both the early and late phase responses [65, 66]. BAL fluid LTC4 levels also increase markedly after aspirin challenge in susceptible subjects, and in these aspirin-intolerant subjects, levels of cys-LTs in BAL fluid and EBC and urinary LTE 4 levels are persistently elevated even at baseline when compared to other asthmatics [67, 68], in whom baseline levels are usually indistinguishable from normal subjects. A number of studies also report elevated cys-LT levels in EBC in asthma [2] .

In the nasal airway, lavage fluid LTC4 levels and urinary LTE4 levels are raised in patients with SAR, after laboratory allergen challenge or natural allergen exposure

[69– 72] . Respiratory syncvtial virus infection also increases nasal LTC4 levels [73] .

Classes of Oral Antileukotriene Drug

Compounds that target the leukotriene pathway can be divided into leukotriene synthesis inhibitors (LTSI) – which target enzymes of the leukotriene synthetic pathway, most notably inhibitors of 5-LO or FLAP – and leukotriene receptor antagonists (LTRA) which may target either LTB4 receptors (B-LTRA) or cys-LT receptors (cysLTRA) (Table 2). The only LTSI that is licensed for asthma therapy Antileukotrienes in Asthma and Rhinitis 71 elevation, hepatotoxicity; dose interactions with theophylline, warfarin, propranolol syndrome syndrome; dose interactions with food, theophylline, warfarin syndrome Abdominal pain, liver enzyme Headache, abdominal pain, C-S Headache, abdominal pain, C-S 600 mg qid 20 mg bid Children years: 10 mg bid 5–11 6–14 years: 5 mg nocte Infants 2–5 years: 4 mg tablet nocte or 1–5 years: 4 mg granules nocte Adults: 10 mg nocte Children Adults: 225 mg bid Headache, abdominal pain, C-S allergic allergic rhinitis allergic rhinitis Asthma Adults and children >12 years: Asthma, Asthma, Asthma Adults and children >12 years:

1 1 1 inhibitor antagonist antagonist antagonist 5-LO CysLT Therapeutics Inc pharmaceuticals

a Merck & Co. CysLT AstraZeneca CysLT TM TM Critical Ono TM TM Oral antileukotriene drugs

Note: not all drugs or formulations are available in countries and indications may also vary Montelukast Singulair Pranlukast Onon Sampson AP Allergy Frontiers rhinitis Antileukotriene drugs in asthma and allergic Table Table 2 Generic name Zileuton Trade name Manufacturer Zyflo Type Indication Dosages a Adverse effects Zafirlukast Accolate 72 A.P. Sampson is zileuton (Zyflo), and the only licensed LTRAs are the cysLTRAs montelukast (Singulair), zafirlukast (Accolate), and pranlukast (Onon) – all three of which are highly selective antagonists of the CysLT1 receptor, but not the CysLT 2 receptor. It is not known whether the ability of zileuton to block LTB4 synthesis as well as that of LTC 4 confers additional therapeutic benefit. The availability of zileuton is restricted to some countries and its clinical use is hindered by the requirement of monitoring of liver function due to a risk of hepatotoxicity. Its use is also restricted by low patient compliance resulting from the four times daily dose regimen, although slow-release preparations are being developed. The remainder of this review will therefore focus mainly on the cysLTRAs, two of which (pranlukast, montelukast) are also registered for use in allergic rhinitis.

Antileukotriene Drugs in Provocation Studies

Allergen Bronchoprovocation

The currently marketed cysLTRAs are representatives of a third generation of compounds that emerged in the early 1990s. They were licensed in many countries later in that decade, starting with pranlukast in Japan in 1995. All are potent and selective CysLT1 antagonists that are able to displace the dose-response curve for inhaled

LTD 4 to the right by about 200-fold [74– 76] . A number of studies showed unexpected effectiveness of cysLTRAs in the allergen bronchoprovocation model, with the area under the curve (AUC) of the early airway response (EAR) being reduced by 75–80% compared to placebo [77, 78]. The remainder of the EAR is accounted for by histamine and PGD2 , with IgE-activated mast cells being the likely source of all three mediators [79] . CysLTRAs also reduce the AUC of the late airway response (LAR) by about 50%, but have only a modest inhibitory effect on the increased numbers of sputum eosinophils and increased airway responsiveness that follows the LAR [80] . They may therefore act by blocking the bronchoconstrictor effects of cys-LTs released by eosinophils and other infiltrating leukocytes, rather than by preventing the chemoattraction of these leukotriene-generating cells.

Exercise and Cold Air Challenges

CysLTRAs have also been investigated in challenges with exercise, cold air, and aspirin in susceptible subjects. The evidence for raised urinary LTE4 levels after exercise challenge is ambiguous, but cysLTRAs consistently reduce bronchoconstriction induced by exercise challenge or inhalation of cold dry air by approximately 30–60% in adults [81, 82] and children [83, 84]. In an 8-week study in adults, the protection against EIB afforded by montelukast was similar to that obtained by salmeterol. However, the efficacy of montelukast was sustained over the trial while that of salmeterol declined [85] . Antileukotrienes in Asthma and Rhinitis 73

Aspirin Challenge

Approximately 10–15% of asthmatics bronchoconstrict in response to oral or inhaled challenge with aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs can also trigger adverse rhinoconjunctival reactions in susceptible individuals, who have a high risk of nasal polyposis. Aspirin-intolerant patients are more likely to be female with onset usually in early middle age, and they often require significant glucocorticoid therapy for moderate-to-severe persistent asthma. As this is not eliminated by NSAID avoidance, the syndrome is best described as aspirin-exacerbated respiratory disease (AERD). The bronchoconstrictor and nasal responses are associated with cys-LT synthesis [86] , probably triggered by inhibition by NSAIDs of endogenous PGE2 synthesis, which normally suppresses 5-LO pathway activity [87] . Aspirin-intolerant subjects also show chronically elevated urinary LTE4 levels, which may be associated with enhanced

LTC 4 synthase expression in the upper and lower airway eosinophils [88, 89] and mast cell activation [90] . Bronchoconstriction induced by threshold doses of aspirin can be completely blocked by cysLTRAs [91] , but cysLTRAs only partially block bronchial reactions induced by larger aspirin doses [92] . The 5-LO inhibitor zileuton also reduces aspirin-induced bronchospasm associated with reduced urinary

LTE4 excretion and marked improvements in nasal symptoms [90] . In long-term studies in AERD, both a cysLTRA (montelukast) and the 5-LO inhibitor zileuton provided further improvements in lung function and symptom scores when added to existing therapy with inhaled and oral corticosteroids [93, 94] . In a 4-week study, montelukast also improved nasal symptoms and reduced nasal reactions to intranasal aspirin [95] . Despite the mechanistic links between AERD and the leukotriene pathway, no studies exist that demonstrate that cysLTRAs are more effective in AERD than in other asthma phenotypes.

Efficacy of Antileukotriene Drugs in Asthma

Acute Asthma

A number of studies showed that oral cysLTRAs and 5-LO inhibitors could produce rapid improvements in baseline lung function of up to 30% in patients with stable, mild-to-moderate persistent asthma, suggesting an inherent basal airway tone in asthma driven by cys-LTs [96] . The bronchodilator effect is additive to that obtained with short-acting beta-2 agonists [97] . The bronchodilator effect is greater and occurs more rapidly when montelukast is given by the intravenous route [98] , suggesting that intravenous cysLTRAs may be effective in status asthmaticus. A study in adult asthmatics with acute, severe asthma showed that intravenous montelukast added to standard therapy improved FEV1 after 10 min and at 2 h, with a lower requirement of beta-2 agonists and fewer treatment failures [99] . 74 A.P. Sampson

Although not available for intravenous use, short courses of oral montelukast reduce acute healthcare utilization, symptoms and school absences in children aged 2–14 years with intermittent asthma, when treatment is instigated at the onset of an acute exacerbation or upper respiratory tract infection [100] .

Chronic Asthma

Many long-term studies in adults and children (aged 6–14 years) with mild-to- moderate persistent asthma have demonstrated that, cysLTRAs improve FEV1 and secondary outcomes [1, 2, 96]. Typically, oral cysLTRAs over 2–6 months produce

7–16% increases in FEV 1 , with 30–50% reductions in symptom scores, night time awakenings, use of beta-2 agonists or oral corticosteroids, acute healthcare contacts, and days lost from work/school [101– 103] . Similar outcomes are seen with zileuton [104] . The benefits are observed in patients with or without concurrent inhaled corticosteroid therapy, and occur within hours or days.They are sustained over the duration of the trials, with a prompt return to baseline values on withdrawal of the cysLTRA. In a 12-month trial, oral montelukast therapy also reduced exacerbations and use of inhaled corticosteroids in children aged 2–5 years with intermittent asthma exacerbations associated with respiratory infection [105] .

Anti-Inflammatory and Remodeling Effects

CysLTRA has multiple anti-inflammatory effects in vitro and in animal models, including reductions in airway eosinophilia and the prevention of airway remodeling [59, 106]. In clinical trials, inflammatory markers are usually secondary to objective measures of lung function and subjective measures of disease severity, but multiple-dose studies of cysLTRAs consistently show modest (~30%) reductions in blood eosinophils in mild-moderate asthma and in SAR [48, 107] . CysLTRAs also reduce exhaled NO in children with asthma, although not in SAR [48, 49] . The effect is truly anti-inflammatory and not simply due to bronchodilation, as it is not mimicked by a short-acting beta-2 agonist, while it appears to be masked by ICS [108] . The impact of cysLTRA therapy on aspects of airway remodeling such as subepithelial fibrosis and smooth muscle hyperplasia has not been investigated in clinical trials. However, a study in mild asthmatic subjects found that oral montelukast for eight weeks marginally reduced the numbers of bronchial mucosal myofibroblasts induced by repeated low-dose inhaled allergen challenge, although this did not reach significance compared to placebo treatment [109] . Evidence that a cys- LTRA, but not a corticosteroid, can reverse established airway remodeling in mice makes such clinical studies a high research priority. Antileukotrienes in Asthma and Rhinitis 75

Comparison with Other Asthma Therapies

In adults with mild-to-moderate asthma, oral therapy with antileukotriene drugs has been reported to show improvements in lung function, beta-2 agonist use, and symptoms comparable to those obtained with sodium cromoglycate or oral theophylline [110, 111] . The most important comparative studies however are those with inhaled corticosteroids (ICS) and long-acting beta-2 agonists (LABA). Well-designed studies in persistent asthma of all severities in children [112] as well as adults [107, 113, 114] indicate that cysLTRA is not as effective on the average in improving FEV1 as low-dose ICS, including fluticasone and beclomethasone (Fig. 2a ), although the ICS is generally more effective on secondary outcomes. Nevertheless, the MOSAIC study in children aged 6-14 years with mild asthma failed to show statistically significant inferiority of montelukast to fluticasone in the number of rescue-free days [115] . In clinical trials, average responses to ICS may be skewed upwards by a small proportion (<10%) of steroid hyper-responders

(FEV 1 improvement >50%), with the majority of subjects showing a range of improvements similar to the LTRA [107] (Fig. 2b ). Commensurate with their

Fig. 2 (a ) Comparison of mean changes in forced expiratory volume in one second (FEV 1) in adult chronic asthmatics treated for 12 weeks with oral montelukast ( black circles ; 10 mg once daily; n = 354), inhaled beclomethasone ( black triangles; 200 m g twice daily by spacer; n = 233) or placebo ( open squares ) (n = 215). Dotted lines indicate patients switched from montelukast to placebo ( n = 52) or beclomethasone to placebo (n = 43) for a further 3-week washout period

Fig. 2 (continued) (b ) Distribution of treatment responses for FEV 1. Hatched bars indicate patients receiving montelukast (10 mg once daily) and white bars those receiving inhaled beclomethasone (200 m g twice daily). From [107] with permission

Fig. 3 Difference in FEV1 response in an 8-week crossover trial of inhaled fluticasone (100 m g twice daily) and oral montelukast (5 or 10 mg once daily) in asthmatic children aged 6–17 years. Only 45% of children experienced an FEV 1 improvement of 7.5% or greater, and of these, about one-quarter showed a better response to montelukast than to fluticasone. From [118] with permission Antileukotrienes in Asthma and Rhinitis 77 respective molecular mechanisms, the onset of action of cysLTRAs is more rapid than ICS, often within the first day of treatment, but the benefits of ICS overtake those of the cysLTRA after 2–3 weeks. In longer-term “open extension” studies, which mimic real-world asthma, the efficacy of cysLTRAs may improve relative to ICS due to better patient compliance with the nonsteroidal drug [116] . However, a study of hospitalizations and healthcare costs for 1 year following initiation of therapy in a practice setting showed lower costs and fewer hospitalizations for fluticasone compared to zafirlukast [117] . Individual patients may nevertheless have differing experiences with these drugs. In a crossover study comparing 8 weeks of inhaled fluticasone and oral montelukast in asthmatic children aged 6–17 years, only about half the children responded to therapy. Of the responders, more were likely to respond to fluticasone than to oral montelukast. However, in a significant minority montelukast was the superior drug, with favorable response to fluticasone being associated with blood eosinophilia, exhaled NO and serum IgE levels, and favorable response to the cysLTRA being linked to younger age and shorter disease duration [118] (Fig. 3 ).

Add-on Therapy and Steroid-Tapering Trials

The rationale of add-on therapy is the apparent inability of oral or inhaled corticosteroids to inhibit cys-LT synthesis in vivo in normal and asthmatic subjects, although most published studies are short-term [119– 121] . CysLTRA may therefore provide additional benefit when combined with ICS or oral corticosteroids, particularly as a shallow dose-response curve provides only marginal improvements with increased ICS dosages. Addition of a second drug like salmeterol, theophylline or a cysLTRA may therefore be preferable to increasing the ICS dosage. Add-on therapy can be examined in three contexts: (1) adding a cysLTRA to ICS therapy as an alternative to maintaining or increasing the ICS dosage in poorly- controlled asthma, (2) enabling the tapering of existing ICS dosage by adding a cysLTRA while maintaining good asthma control, and (3) comparison of cysLTRA plus ICS cotherapy against cotherapy with LABA plus ICS – typically salmeterol and fluticasone. Compared with low-dose beclomethasone alone, adding oral montelukast to therapy of patients with moderate asthma produced a modest improvement in FEV1 and consistent improvements in secondary outcomes [122] . In patients with severe asthma receiving high-dose ICS (>1600 m g/d of beclomethasone or equivalent), the addition of zafirlukast at double the standard dose (80 mg/d) similarly improved primary and secondary outcomes [123] . Similar results were seen when montelukast was added to budesonide in children [124] , although it failed to provide additional benefit in a short-term study in very severe asthmatics already taking three controller medications [125] . In steroid dose-doubling studies, adding oral montelukast has been shown to be at least as effective as doubling the daily dose of budesonide from 800 to 1600 m g/d 78 A.P. Sampson

Fig. 4 In the COMPACT study, adult asthmatics inadequately controlled on 800 mg of budesonide daily who were randomized to receive oral montelukast (10 mg daily) in addition to budesonide ( solid line ) showed a more rapid improvement in morning peak expiratory flow (AM PEF) than those randomized to receive a doubled budesonide dose (1600 m g daily; dashed line ). From [126] with permission in mild-to-moderate adult asthmatics, across a wide range of measures including time of onset, morning PEF, symptom scores, night-time awakenings, beta-2 agonist use and asthma QoL [126, 127] (Fig. 4 ). The combination of montelukast and budesonide is superior to doubling the budesonide dose in asthmatics with or without comorbid SAR [128] . Tapering studies suggest that asthma control can be maintained by adding a cysLTRA, while reducing ICS dosage [129, 130] . In the second of these studies, the ICS dose was carefully tapered to the lowest possible to maintain control during the run-in period, and adding montelukast allowed a further 47% reduction compared to 30% in the placebo group. An updated Cochrane meta-analysis supports the view that cysLTRAs are effective as add-on therapy and as steroid-sparing agents, but summarized their effects on lung function as being modest [131] . Finally, a number of conflicting studies have compared the combination of LTRA plus ICS versus a LABA plus ICS in patients poorly controlled on ICS alone. In one 48-week study, 2000 uncontrolled asthmatics on 200 m g/d fluticasone were randomized to receive in addition either montelukast (10 mg/d) or salmeterol (100 m g/d) [132] ; the combinations were equally effective on time to first asthma attack, asthma exacerbations, nocturnal awakenings, and asthma QoL, while the montelukast / fluticasone cotherapy was superior in reducing blood eosinophilia. The salmeterol / fluticasone combination was superior on lung function outcomes. Other studies of similar drug combinations also show better inflammatory marker outcomes with the LTRA/ICS combination and greater lung function improvements with the LABA/ICS combination [133– 136] . The latter phenomenon may be related to the usual clinical trial entry criterion of reversibility with a short-acting Antileukotrienes in Asthma and Rhinitis 79 beta-2 agonist; many asthmatics may not meet this criterion and it could therefore bias study populations towards patients most likely to show a strong bronchodilator response to a LABA. Overall, the differences between LTRA/ICS and LABA/ICS combinations may be clinically insignificant [137] .

Efficacy of Antileukotriene Drugs in Allergic Rhinitis

Monotherapy

Cysteinyl-LTs mimic many of the features of allergic rhinitis, particularly congestion and rhinorrhea [3] , with mast cells, eosinophils and basophils within the nasal mucosa all being likely sources of these mediators [72] . An early study of zafirlukast showed improvements in nasal congestion, and to a lesser extent rhinorrhoea and sneezing, in adult patients with acute SAR, with no effect on nasal itch or eye symptoms [138] . It was shown that zafirlukast reduced eosinophils in nasal lavage fluid and increased ciliary beat frequency in SAR patients [139] , reduced symptoms and improved tolerability of a cat allergen challenge [140] . In a 6-week winter study, daytime and nighttime nasal symptoms, global evaluations, and quality of life were improved by montelukast compared to placebo in patients with perennial allergic rhinitis [141] . A meta-analysis confirmed that montelukast and antihistamines are equally effective as monotherapies when compared with placebo for SAR symptoms and quality of life, but that both are inferior to intranasal corticosteroids [142] .

Combination Therapy

Rhinitis symptoms, particularly itch, are also associated with histamine release, and a combination of the cysLTRA montelukast and the antihistamine loratadine was better than either drug alone in a 2-week springtime study in SAR patients for symptoms including itch, rhinorrhoea, and sneezing; the exception was nasal congestion in which the combination proved no better than montelukast alone [143] . An autumn (fall) study however showed only modest benefits from adding montelukast to loratadine on nasal symptom scores and secondary outcomes [144] . The combination of montelukast and the antihistamine cetirizine has been shown to be as effective as the intranasal corticosteroid mometasone in improving SAR, particularly in domiciliary measures of nasal peak flow and symptom scores [145] (Fig. 5 ). A meta-analysis of eight large studies in SAR and PAR confirms that combining montelukast with an antihistamine is well-tolerated and generally more effective than either drug-type given as monotherapy, and that in many cases the combination is as effective as nasal steroids [146] . The meta-analysis also points to 80 A.P. Sampson

Fig. 5 In 22 patients with seasonal allergic rhinitis (SAR), the combination of oral montelukast (10 mg) with the histamine H1 receptor antagonist cetirizine (10 mg) given once daily produced a significant reduction in total nasal symptom score similar to that produced by the intranasal corticosteroid mometasone furoate (200 m g once daily). From [145] with permission the concomitant benefits of oral cysLTRA therapy in patients with comorbid asthma and allergic rhinitis, in line with the ARIA recommendations on treating allergic inflammation concomitantly in the upper and lower airways [147]

Safety, Compliance, and Adherence

Antileukotriene drugs are generally well tolerated in clinical trials and in routine clinical practice [148– 150] , with headache being the most frequently reported adverse event in large-scale prescription-event monitoring studies [150] . The 5-LO inhibitor zileuton is associated with a 3.5% incidence of serum alanine aminotrans- ferase levels rising above three times the upper limit of normal [104] , usually within the first 2–3 months of treatment. Hepatic function tests are therefore recommended over the first year of zileuton treatment, but cysLTRA do not produce a similar incidence of hepatic enzyme changes. Rare severe hepatic reactions have been reported with zafirlukast [151] , which also has pharmacokinetic interactions with food and with warfarin and theophylline that require dosage adjustments. Reports of a rare eosinophilic vasculitis (Churg–Strauss syndrome) emerging in patients initiated on cysLTRA therapy are usually accounted for by ill-advised concomitant reductions in systemic corticosteroid dosage that allow the unmasking of underlying eosinophilic disease [148, 152] . A similar phenomenon can occur with other antiasthma drugs [153] . Antileukotrienes in Asthma and Rhinitis 81

Variability in Clinical Response

Asthma and allergic rhinitis are inherently variable in intensity overtime. There is a perception however, of an unusually high variability in clinical response to cysLTRA therapy, but this is not entirely justified by the evidence. In routine clinical practice, 66% of asthmatics report lung function improvements, with 8% reporting a dramatic improvement [149] Lung function improvements with montelukast follow a bell-shaped (Gaussian) distribution with no evidence of distinct populations of responders and nonresponders [107] . The distribution of responses is very similar to that seen with low-dose inhaled beclomethasone in the same patients. In individual patients, the clinical response to antileukotriene therapy nevertheless shows consistency overtime [154] , suggesting a real biological basis for variability that may include genetic factors. Polymorphism in the 5-LO, LTC4 synthase and CysLTR2 genes has been linked to the clinical response to antileukotriene therapy in some studies [155– 158] but not in all [159] . LTC 4 synthase polymorphism is also linked with baseline lung function impairment in asthma [160] and allergic rhinitis susceptibility [161] . Genetic factors may also underlie the marked variability in bronchodilator response to beta-2 agonists and the predisposition of LABA to induce tolerance to short-acting beta-2 agonists used as rescue medication [162] . Overall, the heterogeneity of therapeutic response to antiasthma drugs is similar for glucocorticoids, beta-2 agonists, and antileukotriene drugs [154] . This heterogeneity reinforces the need for asthma management guidelines to be flexible to allow clinicians to tailor therapy appropriately to individual patients.

Summary

Antileukotriene drugs were developed in the 1990s to block the synthesis or activity of the leukotriene family of lipid mediators, which has well-established roles as potent bronchoconstrictor agents with additional proinflammatory effects on blood vessels, mucus glands, and leukocytes. The most successful antileukotriene drugs are the cysteinyl-leukotriene type 1-receptor antagonists (cysLTRA) which became available for clinical use in asthma management in the late 1990s and for allergic rhinitis in many countries since 2003. CysLTRAs are safe and effective oral prophylactic medications that, depending on national guidelines, can be used as controller monotherapy or as second-line therapy added to inhaled corticosteroids. Their use seems well supported by scientific rationale and by clinical evidence in exercise-induced bronchoconstriction, in aspirin-exacerbated respiratory disease, and in patients with concomitant allergic rhinitis. Further research may identify additional asthma phenotypes or genotypes that predict good clinical response to antileukotriene drugs. Clinical studies are also required to determine whether antileukotriene drugs can modify chronic processes of airway remodeling. 82 A.P. Sampson

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Ian P. Hall and Ian Sayers

Introduction

b2 adrenoceptor agonists have been the main stay bronchodilator agents used for the management of asthma for the last 50 years. These drugs have proven to be the most effective bronchodilators available. The first agent used widely in the management of asthma was isoprenaline (isoproterenol), a nonselective b adrenoceptor agonist. This was replaced by short acting b 2 adrenoceptor selective agents, often called SABAs; the main agents used are salbutamol (albuterol) and terbutaline.

More recently, long acting b 2 agonists (LABAs), which have a prolonged duration of bronchodilator effect, have been developed, the major examples being formoterol and salmeterol. A number of new LABAs are currently in development or phase II/III clinical trials, including agents such as indacaterol. This chapter deals with the molecular pharmacology underlying the control of b 2 adrenoceptor signalling.

Adrenoceptor Populations in the Airways

Human airways predominantly express b 2 adrenoceptors [1, 2] . However, three different human b adrenoceptors, namely b 1 , b 2, and b 3 adrenoceptors, exist, with different physiological roles. The b 1 adrenoceptor is responsible for predominantly mediating the cardiovascular effects of catecholamines, and the b3 adrenoceptor is expressed primarily in adipocytes and the cardiovascular system and is responsible for mediating metabolic and cardiovascular effects (see [3] for a review). A human

b 4 adrenoceptor has been hypothesized to exist, but, at present, the consensus view is that the pharmacological findings, which have been used to support the existence

I.P. Hall () and I. Sayers Division of Therapeutics and Molecular Medicine , University Hospital of Nottingham , Nottingham , NG7 2UH , UK e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 91 DOI 10.1007/978-4-431-99362-9_6, © Springer 2010 92 I.P. Hall and I. Sayers

of the putative b 4 adrenoceptor, are likely to be due to actions at different conformational states of the other known human b adrenoceptors [4] .

Molecular Genetics of the Human b 2 Adrenoceptor

The gene for the human b2 adrenoceptor is located on chromosome 5 q31–33 [5] .

The b2 adrenoceptor gene ( ADRB2) is an intronless gene, although interestingly at least one open reading frame is present in the 5 ¢ untranslated region of the gene: this codes for a short peptide also known as the b upstream peptide, or BUP

[6, 7] . The human b 2 adrenoceptor gene is relatively polymorphic, with two common nonsynonymous single nucleotide polymorphisms (SNPs), resulting in amino acid substitutions at codon 16 (Arg16Gly) and codon 27 (Gln27Glu). A rare polymorphism at codon 164 (Thr164Ile) has also been identified (Fig. 1 ). The promoter region for the gene also contains a number of SNPs including a SNP in the terminal codon of the 5¢ leader cistron (BUP), which may alter the ability of BUP to modulate translation [8, 9] . A full account of the effects of these polymorphisms can be found in volume 1, pages 205–225.

Structure–Function Relationships of the b 2 Adrenoceptor

The human b 2 adrenoceptor belongs to the superfamily of G protein coupled receptors (GPCRs), typified by rhodopsin like structures with seven transmembrane spanning domains, an extracellular N terminus, and an intracellular C terminus

Arg:39% Glu:43%

Met: <0.001%

Ile: 3%

Fig. 1 Schematic of the human b 2 adrenergic receptor with coding region polymorphisms shown. Allele frequencies for the nonsynonymous coding region SNPs are shown, derived from the UK population [56]. Figure adapted from [61] Mechanisms of Action of b2 Adrenoceptor Agonists 93

[5, 10] . Agonist binding is dependent upon the presence of key amino acid residues within the hydrophobic core of the receptor in the third, fourth, and fifth transmembrane spanning domains [10– 13] . The third intracellular loop contains amphiphilic regions important for coupling the stimulatory G protein Gs. This third intracellular loop, together with key residues on the long cytoplasmic tail of the receptor, are important sites for receptor regulation by phosphorylation [11– 16] . Following agonist binding to the receptor, downstreams signalling is dependent upon the binding of Gs to the receptor complex. Gs exists as heterotrimers of a and b g and subunits: following agonist binding, GDP is released from the a subunit of the complex, leading to the disassociation of the complex. The free a subunit of Gs is then able to stimulate adenylyl cyclase, which results in the elevation of cyclic AMP within the cell. Cyclic AMP, in turn, catalyses the disassociation of protein kinase A regulatory and catalytic subunits: the free catalytic subunit of protein kinase A then phosphorylates key downstream signalling proteins (reviewed in [17] ) (Fig. 2 ). Thus, the activation of protein kinase A mediates the majority of physiological responses driven by the stimulation of this pathway. In addition to physiological effects, which are protein kinase A dependent, there is some evidence that cyclic AMP /protein kinase A independent effects may also contribute to signalling. For example, free Gs a may interact directly with calcium activated potassium channels (BKCa) to stimulate channel activity independent of protein kinase A induced phosphorylation, although the latter also contributes to b agonist induced increases in channel activity [18] . Hence, while there is a good

Beta 2 adrenoceptor agonist BKCa

PKA

Fig. 2 Mechanisms underlying downstream signalling from the b 2 adrenoceptor. Adapted from [62]. See text for details. AC = adenylyl cyclase; BKCa = calcium activated potassium channel; PKA = Protein kinase A 94 I.P. Hall and I. Sayers relationship between the magnitude of cell cyclic AMP responses and physiological responses in general, some inconsistencies can be observed, for example, when comparing the effects of agents such as forskolin, which is able to elevate cell cyclic AMP content independent of receptor activation [18] . In addition, at least in some transformed cell systems, there is evidence that cyclic AMP/protein kinase A independent actions on downstream signalling cascades may result through stimulation of alternative pathways including interactions with the inhibitory G protein Gi and effects on gene transcription activated by MAP kinase dependent signalling pathways [19]. However, many of the transformed cell systems used to detect these effects have a marked overexpression of the b 2 adrenoceptor, and whether or not these effects are important in nontransformed cell systems, or in vivo, remains unclear. Although these cyclic AMP independent pathways may be important at least in some cell types for physiological responses, it is still the case that the vast majority of effects of b 2 adrenoceptor agonist stimulation are driven by cyclic AMP/protein kinase dependent effects. This signal is also regulated by the breakdown of intracellular cyclic AMP. The only known mechanism which catalyses cyclic AMP breakdown is activation of phosphodiesterase isoenzymes within the cell. The most important class of these enzymes in airway smooth muscle appears to be the type 4 phosphodiesterases (PDE4), and in particular, a specific splice variant, PDE4D5, which appears to act as a key gate keeper regulating cell cyclic AMP levels [20, 21]. For example, although PDE4D is a minor component of total tissue PDE activity, and PDE4D5 an even smaller component, inhibition of PDE4D5 by siRNA approaches produces marked effects on cyclic AMP cascades following b 2 adrenoceptor stimulation in airway smooth muscle, possibly, in part, related to the ability of the receptor complex to bind targeted PDE4D5 [21] .

Distribution of b 2 Adrenoceptor Expression

The b2 adrenoceptor is widely expressed in the airways being present in airway smooth muscle, bronchial epithelial cells, and a number of inflammatory cells including mast cells and alveolar macrophages [22, 23] .

Stimulation of the b2 adrenoceptor on airway smooth muscle results in cell relaxation. This is the most important effect of inhaled b 2 agonists in the airways and is responsible for the bronchodilation observed following the administration of inhaled b2 adrenoceptor agonists. There are a number of potential mechanisms underlying the relaxant effect of b 2 adrenoceptor agonists on airway smooth muscle: the most important of these are summarised in Table 1 (see also [24] for review).

The role of b2 adrenoceptors on epithelial cells has not been studied extensively. Stimulation results in altered ciliary beat frequency and ion (e.g. Cl− ) and water secretion, and may also modulate mediator release, though the importance of these mechanisms in vivo remains largely unexplored [25] . Stimulation of b 2 adrenoceptors on Mechanisms of Action of b 2 Adrenoceptor Agonists 95

Table 1 Effects of b 2 adrenoceptor agonists on airway smooth muscle Effects on contractile/relaxant signalling pathways : Inhibition of myosin light chain kinase (MLCK) activation Stimulation of Ca2+ uptake into sarcoplasmic reticulum Stimulation of Na+ /K + ATPase activity Inhibition of phosphatidylinositol 4,5 bisphosphate hydrolysis Inhibition of inositol trisphosphate induced Ca2+ release from intracellular stores Inhibition of Ca2+ entry through store and/or receptor operated channels Stimulation of Ca 2+ activated K+ channels (BKCa) Other effects : Stimulation of gene transcription via CREB activation Inhibition of cell proliferation/migration

mast cells results in the inhibition of mediator release: however, interestingly, b 2 agonists, at least in vitro, appear to increase IgE release from B cells. b 2 adrenoceptors are also likely to regulate vascular permeability in the small vessels present in the airway wall, though the importance of this effect in vivo remains unclear [26] .

Regulation of b 2 Adrenoceptor Expression

Both the expression and coupling of b2 adrenoceptors is closely regulated within the airways [27– 33] . The number of receptors present at the cell surface is dependent upon the balance between new receptor formation due to increased transcriptional activity of the ADRB2 gene and receptor internalisation and breakdown. Increased transcription may be partly due to the stimulation of cyclic AMP response elements in the promoter of the ADRB2 gene. Increased receptor expression is also likely to be, in part, due to the regulation of mRNA stability by AU rich regions in the 3¢ untranslated region of the gene. In contrast, longer term receptor activation, at least in tissue culture models, results in a loss of responsiveness, initially due to phosphorylation of the receptor by both protein kinase A dependent and protein kinase A independent (beta adrenergic receptor kinase or BARK dependent) pathways. Both of these kinase mediated responses result in the phosphorylation of key residues on the receptor, which, in turn, alters receptor coupling. BARK is a member of a large family of receptor kinases, namely the GRKs or GPCR kinases.

In the short term, b 2 adrenoceptor phosphorylation leads to dissociation from down stream signalling: however, prolonged receptor stimulation leads to receptor internalisation. Once internalised, the receptor can be recycled to the cell membrane or targeted to the proteosome for degradation [32, 33]. While these effects can clearly be demonstrated in both transformed and nontransformed cell culture models, their importance in the more dynamic environment of the airway wall again remains less clear. Receptor downregulation can be easily demonstrated ex vivo in peripheral blood mononuclear cells (PBMC) [34] , but has not unequivocally been demonstrated to date in vivo in structural cells in the human airway. 96 I.P. Hall and I. Sayers

b2 adrenoceptor expression and coupling can also be modulated by exposure to pro- and anti-inflammatory agents. Glucocorticoids have been shown to increase b 2 adrenoceptor expression in a number of model systems [35] , though the importance of this response in vivo in the human lung remains uncertain. In contrast, exposure to pro inflammatory mediators such as interleukin 1b , at least in the short term, results in reduced cyclic AMP responses to b 2 adrenoceptor stimulation in cultured cell systems [36] . It has also been demonstrated in primary human airway myofibroblast culture systems that b 2 adrenoceptor coupling is modulated by the extracellular matrix, with relatively smaller cyclic AMP responses to receptor stimulation when cells are grown in the presence of laminin compared with fibronectin [37] . This suggests that receptor coupling is controlled via integrin dependent adhesion mechanisms, an observation of particular interest, given the alterations in matrix composition seen following long term inflammation in the airway wall in chronic asthma.

Transgenic mice studies have added insights into the role of b 2 adrenoceptors in the airway. Mice with very high levels of overexpression of the human b 2 adrenoceptor show, as perhaps might be expected, reduced bronchoconstrictor responses to spasmogens [38, 39]. However, interestingly, mice with lower levels of overexpression show enhanced rather than reduced bronchoconstrictor responses to cholinergic stimulation [40] . This counter-intuitive effect may be related to homeostatic mechanisms being brought into play, which result in increased expression of key proteins involved in contractile signalling pathways in airway myocytes (e.g. phospholipase C) or in altered receptor expression of bronchoconstrictor receptors such as the histamine H1 receptor [40, 41].

Pharmacology of b Adrenoceptor Agonists

b 2 adrenoceptor agonists are predominantly based on the structure of adrenaline. All agents currently in clinical usage are composed of a benzene ring with a side chain of two carbon atoms and either an amine or a substituted amine head. Positions 3 and 4 on the benzene ring can be substituted by hydroxyl groups (OH), in which case the molecule becomes a catecholamine. Substitution of these hydroxyl groups, in general, makes the compound less potent, but does make the agent relatively resistant to metabolic degradation by the enzyme catechol O methyltransferase (COMT). Substitutions on the a carbon atom block oxidation by monoamine oxidases (MAO). The pharmacological effects of adrenaline and noradrenaline are believed in vivo to be predominantly terminated by uptake into sympathetic nerve endings (uptake 1), though catecholamine uptake into other sympathetically innervated tissues (uptake 2) may also contribute to some extent. Oxidation by MAO occurs predominantly in sympathetic nerve endings, while degradation by COMT occurs predominantly in tissues. Exogenously administered b 2 adrenoceptor agonists are conjugated with sulphates and glucuronides in the liver (and probably also the lung and gut wall), contributing to elimination (reviewed in [42] ). Mechanisms of Action of b 2 Adrenoceptor Agonists 97

There are some important differences in the lipophilicity of different agonists, which may, in part, underlie the longer duration of action of some LABAs. For example, salmeterol is a relatively lipophilic molecule, resulting in extensive pooling in the plasma membrane following drug exposure: the long duration of action is also probably related to the long lipophilic tail of the molecule inserting into the receptor agonist binding pocket.

Clinical Pharmacology of SABAs and LABAs

b2 adrenoceptor agonists, in clinical use, can be distinguished by their pharmacology in terms of duration of action and degree of agonism. As mentioned above, salbutamol (albuterol) and terbutaline are short acting agents (SABAs) with bronchodilator responses which reach a maximum within 1–2 min and last typically up to 4–6 h. In contrast, the long acting agents (LABAs) salmeterol and formoterol provide sustained bronchodilation over at least 12 h. These agents are frequently administered in combination inhalers, together with an inhaled corticosteroid. The new generation LABAs (such as indacaterol) have an even longer duration of bronchodilator effects [43] . These drugs can also be distinguished in terms of their pharmacology depending upon the degree of agonism at the cognate receptor. Thus, while terbutaline and formoterol are near full agonists compared to isoprenaline at the b 2 adrenoceptor, salbutamol and, to an even greater extent, salmeterol are partial agonists at least in cell systems expressing the b 2 adrenoceptor at physiological levels of expression [44] . The final point to consider is that salbutamol and formoterol exist as racemic mixtures (i.e., include both the R and S enantiomers), though the R enantiomer is the active component [45] . There have been concerns that the S-enantiomer may have detrimental effects rather than just being an ineffective inert component of the racemic mixture, though clinical evidence to support this idea is currently not available.

Clinical Effects

b 2 adrenoceptor agonists have two main effects on airway pharmacology in patients with asthma. Firstly, they provide short term bronchodilation, the extent of which is at least, in part, dependent on the degree of pre-existing bronchoconstriction. This effect is driven by relaxation of airway smooth muscle within the airway wall, with a resultant increase in airway calibre and hence, reduction in air flow limitation. The second effect of stimulation by b 2 adrenoceptor agonists is to inhibit bronchoconstrictor responses mediated by challenge with a wide range of airway irritants such as histamine, methacholine, cold air, and exercise. 98 I.P. Hall and I. Sayers

Safety of SABAs and LABAs

Despite the observations that b 2 adrenoceptor agonists provide the most effective bronchodilators available in the treatment of asthma, there is a long history of concern over the use of these agents. These concerns originally arose because of epidemiological studies showing the association between the use of isoprenaline and increased risk of asthma death or severe asthma exacerbations in the 1960s, and subsequent studies suggesting similar effects with the shorter acting b adrenoceptor agonist fenoterol [46, 47] : The latter data resulted in the withdrawal of fenoterol from the market in a number of countries. More recently, the FDA placed a black box warning on LABAs in the USA following the early termination of a study examining the efficacy of salmeterol (the SMART study), in which a small excess of deaths or severe exacerbations was seen in the treatment arm [48] . There are a number of possible mechanisms whereby SABAs and/or LABAs could potentially have caused these effects. Firstly, while inhaled b2 selective agonists are predominantly active within airways, some systemic absorption occurs and a number of studies have shown effects on relevant systemic physiological end points such as heart rate, hypokalaemia, and tremor, all of which are dose related (see for example [49] ). However, while these effects could potentially contribute to cardiovascular risk, particularly in patients with underlying cardiovascular disease, they would not explain the worsening of asthma control. Hence, attention has been concentrated on the possibility that tachyphylaxis (tolerance) to the effects of SABAs and LABAs may contribute to poorer control in at least some asthmatics [50] . Reduced responsiveness to SABAs and LABAs could potentially occur by alteration of their effectiveness in either (1) inducing bronchodilator effects or (2) in preventing bronchoconstriction. Both of these possibilities have been extensively studied. Although some studies have shown reduced bronchodilator responsiveness to acute administration of SABAs after a period of regular treatment with salmeterol or formoterol, in general, the effects observed have been small (see e.g. [51] ) and of doubtful clinical significance. However, more pronounced effects on the degree of bronchoprotection seen against bronchoconstructer challenge have been observed in, a number of studies. Maximum bronchoprotection to constrictor challenge is observed with b2 adrenoceptor agonists in the first 24 h after commencing treatment: this is followed by a reduction in the amount of bronchoprotection provided [52] . However, the amount of bronchoprotection observed, though relatively reduced, is still greater than that observed with placebo. This, therefore, seems unlikely to be the explanation underlying the observational studies suggesting poorer outcome in asthmatics.

It is clear that regular use of short acting b2 agonists is no more effective than ‘as required’ use of these agents [53] and hence, clinical guidelines for asthma, in general, do not recommend regular use of SABAs. However, the explanation for this difference, given the effectiveness of LABAs, is unclear, though it is conceivable that relatively rapid on/off effects at the receptor may be detrimental as com- Mechanisms of Action of b2 Adrenoceptor Agonists 99 pared to the long term receptor stimulation observed with LABAs. One other possibility, which has been suggested as a possible explanation of the SMART data, is that compliance with inhaled steroid may be reduced in some patients taking LABAs, due to symptomatic relief with LABAs, a subsequent reduction in inhaled steroid usage, and a consequent loss in anti-inflammatory effects.

There had been considerable attention recently paid to the possibility that b 2 adrenoceptor polymorphism may contribute to either disease risk [54– 56] , disease severity [56] , or treatment responses for patients on SABAs and LABAs. This is discussed in greater detail in volume 1, pages 205–225. From the clinical perspective, a large retrospective study and a subsequent prospective study on SABA usage suggested that in steroid naïve patients, individuals with the Arg16Arg genotype (approximately 15% of the Caucasian population), either failed to respond or deteriorated in terms of lung function parameters, symptoms scores, and relief medication usage while on regular treatment [57, 58] (Fig. 3). However, as discussed above, regular treatment with SABAs, particularly in steroid naïve patients, is not recommended currently under national asthma treatment guidelines such as those in use in the UK and USA and hence, while of academic interest, this effect is of limited clinical significance. A subsequent pilot study examining genotype and responses to LABAs suggested similar effects may be present in both steroid naïve patients and asthmatics taking inhaled corticosteroids [59] : however, a larger (retrospective) analysis of clinical trial data suggested no difference in outcome by genotype group in patients on combination LABA and corticosteroid treatment, implying the receptor polymorphism is unlikely alone to account for poorer treatment outcomes [60] .

Fig. 3 Effects of regular and as required salbutamol (albuterol) on lung function by ADRB2 genotype for Arg16Gly. Adapted from [57] DAM PEF = change in morning peak expiratory flow 100 I.P. Hall and I. Sayers

Therefore, in summary, it appears that small numbers of individuals with asthma taking b2 adrenoceptor agonists may be at risk of deterioration of their disease and (very rarely) death. However, these effects have not been convincingly shown for currently used SABAs or LABAs in patients on regular inhaled corticosteroid treatment.

Summary

The above review has dealt with the major mechanisms underlying the mode of action of b2 adrenoceptor agonists, and the modulation of these responses. This has been an active area of research over recent years, driven by the clinical importance of these agents and lingering concerns over safety. Over the next few years, a number of novel LABAs are likely to be introduced into clinical practice. This will undoubtedly lead to further evaluation of efficacy and safety issues: with this in mind, the profile of new agents in terms of their duration of action and degree of agonism should be carefully considered, as it is already clear from the data discussed above that not all LABAs are identical in terms of their pharmacology.

Acknowledgements Work in the authors’ laboratory is supported by Asthma UK and the Medical Research Council.

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Mark A. Giembycz

Introduction

Despite significant advances in our understanding of the pathogenesis of many allergic disorders, the etiology of allergy is still incompletely understood. However, both the World Allergy and World Health Organization [1] have identified and recognized the participation of immunoglobulin (Ig) E-driven mechanisms in many allergic diseases (Table 1 ). Since the incidence of allergy has reached epidemic proportions, it is very clear that drugs, which can prevent the overt and covert manifestations of allergic reactions and, ideally, suppress or even prevent the process of host sensitization can have a profound clinical and economic impact. While corticosteroids are considered the most effective antiallergic/anti-inflammatory drugs currently available, they are nonselective in action and not without adverse effects. Moreover, in diseases such as asthma, a significant proportion of patients who are treated with corticosteroids remain symptomatic [2] . Thus, new drugs with enhanced selectivity and improved side-effect profiles are clearly required. One group of drugs, which from a theoretical perspective, may exhibit powerful anti-inflammatory and immunomodulatory activity are inhibitors of certain of the cyclic nucleotide phosphodiesterase (PDE) isoenzymes that selectively degrade cyclic adenosine-3¢ ,5 ¢ - monophosphate (cAMP) and/or cyclic guanosine-3 ¢,5 ¢ -monophosphate (cGMP) [3– 9] . The prototype PDE inhibitors that have been used in the treatment of asthma for many years are the alkylxanthines of which theophylline is the most widely prescribed. The main beneficial activity of theophylline was originally attributed to its weak bronchodilator action. However, evidence accumulated in the 1990s suggested that this molecule might have anti-inflammatory activity at subbronchodilator doses [10– 12] . These, somewhat surprising data fuelled the idea that theophylline and, so- called, “second generation” PDE inhibitors could act as bronchodilators and potential antiallergic and/or anti-inflammatory agents [7, 13– 18] .

M.A. Giembycz () Department of Pharmacology and Therapeutics, Institute of Infection, Immunity and Inflammation, Faculty of Medicine , University of Calgary , 3330 Hospital Drive NW , Calgary , AB , Canada T2N 4N1 e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 105 DOI 10.1007/978-4-431-99362-9_7, © Springer 2010 106 M.A. Giembycz

Table 1 Allergic diseases where IgE- Asthma driven mechanisms are implicated Atopic and contact dermatitis Rhinitis Eczema Sinusitis Hypersensitivity pneumonitis Extrinsic alveolitis Angioedema and anaphylaxis Certain forms of migraine and gastrointestinal disorders Urticaria

The rationale for developing new PDE inhibitors has stemmed primarily from the realization that PDEs represent a highly heterogeneous group of enzymes,which are differentially expressed across different cell types and specific functional responses are almost certainly regulated. Accordingly, it was rapidly appreciated that the selective inhibition of a particular PDE isoenzyme may discretely alter the function of cells expressing that variant, and theoretically, specific functional responses within the same cell. Given the prevalence of allergic diseases as a whole, the potential clinical reward for developing a novel class of steroid-sparing drugs is very apparent. With respect to allergy and allergic diseases, the most relevant enzyme family is known as PDE4 (see Table 2 for taxonomy). Indeed, many of the World’s major pharmaceutical companies have an active PDE4 research program have developed highly selective inhibitors, many of which are currently undergoing clinical trials for asthma and other allergic inflammatory disorders ( Fig. 1 , 1-12; Table 3). The purpose of this chapter is to introduce cyclic nucleotide PDEs in general and then describe the salient characteristics and tissue distribution of PDE4 across cells that participate in allergic inflammatory reactions. Potential sites where PDE4 inhibitors could act to alleviate the acute and chronic manifestations of allergic disease, including clinical trials data, form the final part of this chapter. Readers interested in the more general aspects of PDE biology are directed to recent reviews on this subject [3, 4, 19] .

Generic Properties and Characteristics of Cyclic Nucleotide PDEs

Cyclic nucleotide PDEs (E.C. 3.1.4.17) comprise a large group of enzymes whose sole function is to hydrolyze, and thereby inactivate the biologically active cyclic purines, cAMP and cGMP (Fig. 2 ). PDEs which act on cyclic pyrimidine monophosphates have also been described (see [20] ), although investigators have tended to focus, almost exclusively, on the PDEs which hydrolyze cyclic purine nucleotides for which functionally important second messenger roles have unequivocally been established. A cyclic nucleotide PDE that hydrolyzed the 3¢ -ribose phosphate bond of cAMP to the catalytically inactive 5¢ -AMP was first identified in 1962 [21] . Since then, multiple families, and indeed, subfamilies of PDEs, which selectively act on cAMP and/or cGMP have been identified (see [3, 4] for reviews). The PDEs that metabolize cyclic Alkylxanthines and Phosphodiesterase 4 Inhibitors 107

Table 2 Properties and selective inhibitors of cyclic nucleotide phosphodiesterases Km ( m M) PDE family cAMP cGMP Selective inhibitors References 1 Ca2+ /Calmodulin- 0.3–124 0.6–6 SCH 57801, KS-505a [142] [143] stimulated IC-224 [144] 2 cGMP-stimulated 28–100 10–28 ENHA, Oxindole [145] [146] BAY 60-7550 [147] IC933 [144] PDP [148] 3 cGMP-inhibited 0.02–0.3 0.1–0.5 Siguazodan, SK&F [149] [150] 95654 [151] Cilostamide [152] Cilostazol 4 cAMP-specific 1–10 >50 Rolipram, Ro 20-1724 [153, 154] [155] Cilomilast [156] Roflumilast [157] Piclamilast [158] 5 cGMP-binding 280 3–7 Zaprinast , Sildenafil [159] [160] Vardenafil [161] Tadalafil [162] 6 Photoreceptor 600–700 15–17 None reported 7 Rolipram-insensitive, 0.01–0.5 NA BRL 50481, PF 332040 [163] [164, 165] cAMP-specific IC242 [166] 8 Rolipram-insensitive, 0.06 NA None reported cAMP-specific 9 Zaprinast-insensitive, 228 0.7–0.17 BAY 73-6691 [167] cGMP-specific 10 cAMP-inhibited (?) 0.22–1.1 13–14 None reported 11 Dual-selective 1–2 2–3 None reported NA reliable data not available purine nucleotides comprise at least 11 distinct families and can be distinguished by a number of criteria including substrate specificity, kinetic properties, responsiveness to endogenous allosteric regulators, and susceptibility to inhibition by various compounds and in primary amino acid sequence (Table 3 ). Molecular biological studies have discovered that many PDEs are separate gene products and express multivariant regulatory domains linked to highly conserved homologous catalytic sequences located near the C-terminus of the protein. Members of one family share 20–25% sequence homology with members of another family. Furthermore, at least six out of the 11 gene families can be divided in to subfamilies that are 70–90% homologous. At the end of 2006, more than 22 PDE genes were unequivocally identified. For further information on the molecular diversity of PDE isoenzymes, interested readers are directed towards a number of comprehensive reviews [3, 4, 22– 26] . A diagrammatic representation of the primary structure of cyclic purine PDEs is shown in Fig. 3. All mammalian PDEs essentially share the same structure: there is a central core located close to the C-terminus of the protein, which shares 25–35% homology between isoenzyme families and which features a highly conserved domain of some 270 amino acids. Studies performed in a number of laboratories indicate that this conserved region within the central core of all PDEs represents the 108 M.A. Giembycz

a H C 3 O OH H N HN O

O N N N N N N N O N N S O H C Cl 3 CH3 1 Arofylline 2 Tofimilast 3 Cilomilast

OH O CH HN CH 4 Cl 3 N O O O N O NH HO N N O Cl CH O O 3 N S O F F CH 4 Tetomilast 5 Roflumilast 6 ONO 6126 3 F

CH CH O N CH 3 3 N N 3 Cl O N CH 3 O CH3 O NH N O H C HO 3 O

O O Cl CH3 CH3 7 AWD-12-281 (GSK 842470) 8 Ibudilast 9 IC-485

b O R1 R H 2 O O O N H O N HN O NH2 N O N N Y O Z

CH3 H C 10 Atizoram 11 Cipamfylline 3 H C 3 H3C or Z = OOor OH P ONH2 OOH CH3 propionamide methyl propionate ethylphosphonic acid

12 CC-10004

Fig. 1 Chemical structures of PDE4 inhibitors which have been clinically evaluated in allergic diseases. The structure of CC-10004 has not been disclosed. Shown are predicted possibilities.

Only small substitutions are tolerated at R1 and methyl and difluromethyl are tolerated candidates.

Larger substitutions are tolerated at R2 and possibilities include cyclopropyl or cyclopentyl moieties. Y = O or H 2. Z = propionamide, methyl propionate or ethylphosphonic acid. See text and Ref. [107] for further details Alkylxanthines and Phosphodiesterase 4 Inhibitors 109 Isoenzyme selectivity Indication Development stage

ammatory disorders Representative PDE4 inhibitors for inﬂ

AlmirallGlenmarkPfizerONOOtsukaNycomedGlaxoSmithKlineGlaxoSmithKlineCelgene ArofyllineICOS Oglemilast (GRC 3886)MediciNovaGlaxoSmithKline/Leo Pharma (CP-325366) Tofimilast Cilomilast (SB 207499)Pfizer 61063) Cipamfylline (BRL ONO 6126 (GSK 842470) AWD-12-281 Data collated from Mealey & Bayes (2005) (OPC 6535) 4 Tetomilast Roflumilast 4 4 4 4 CC-10004 4 4 Ibudilast IC-485 Asthma, COPD 4 4 Atizoram (CP-80,633)Atopic Dermatitis Asthma, Asthma Atopic Dermatitis COPD Bronchitis COPD 4 4 4 Phase II Asthma, COPD 4 Asthma, COPD Phase III Phase II Atopic Dermatitis Asthma, Psoriasis, Atopic Dermatitis Multiple sclerosis Phase II Phase II Phase III Phase II/III COPD Phase III Phase II Phase III Discontinued Phase II Discontinued Table Table 3 Company Drug 110 M.A. Giembycz

NH NH2 2 N N

N N N N PDE N N

2+ cAMPH2O; Mg O 5’-AMP O OH OH

O OH HO O O P P O HO HO O

Fig. 2 CAMP hydrolysis by cyclic nucleotide phosphodiesterases

cAMP 5’-AMP cGMP 5’-GMP Allosteric/Small Molecule Phosphorylation Sites Binding Site (eg ERK-2 at S579 in PDE4D3 2+ (e.g. cGMP, Ca /calmodulin) and S651 in PDE4D5)

Phosphorylation Sites Catalytic 54 (eg PKA at S in PDE4D3) Domain

Targeting Domains Dimerisation (eg TAPAS-1 in PDE4A1) Domains

Fig. 3 General structure of mammaliam cyclic purine PDEs. Limited proteolysis and protein sequencing suggest that all mammalian PDEs so far examined contain a conserved central core that features the catalytic site. This region of PDE proteins is flanked, through putative hinge regions, by highly heterologous C- and N-termini. These are believed to express regulatory domains, dimerisation motifs, phosphorylation sites, and sequence information which determine the subcellular localization of PDEs. See text for further details. TAPAS Tryptophan Anchoring Phosphatidic Acid Selective catalytic site [27] . The central core of mammalian PDEs is linked via, so called, hinge regions to C- and N-terminal extensions (Fig. 3 ) which show relatively little sequence homology between PDE families [22] . This finding has led to the view that the nonconserved domains subserve regulatory functions of the protein [22] . Indeed, it is now appreciated that the N-termini of PDEs can feature binding sites for calmodulin (PDE1) and cGMP (PDEs 2, 5, 6, 10, 11) – so-called GAF domains 1 [28] , membrane-association domains (PDE3), subcellular targeting sequences (PDE4,

1 GAF and PAS [domains] are acronyms of the names of the first three groups of proteins identified to contain them, i.e. c G MP-regulated cyclic nucleotide phosphodiesterase, cyanobacterial A denylyl cyclase and E. coli transcription factor, F h1A (formate-hydrogen lyase), and P eriod circadian protein, A h receptor nuclear translocator protein and S ingle minded protein, respectively. Alkylxanthines and Phosphodiesterase 4 Inhibitors 111

PDE7), phosphorylation sites (most PDEs) that control catalytic activity, and PAS1 domains (PDE8) – involved in ligand recognition and protein–protein interactions. Similarly, sequences at the C-terminus express dimerization motifs (most PDEs exist as dimers; [29– 33] ) and/or are substrates for phosphorylation (e.g., [34, 35] ).

Phosphodiesterase 4

A cAMP-specific PDE that was inhibited by the alkoxybenzyl-substituted imidazoli- done, Ro 20-1724, but largely unaffected by cGMP was originally purified from canine kidney [36, 37] . It is now appreciated that this was the first report of a member of a large family of similar proteins collectively known as PDE4 isoenzymes. Since that original description, PDE4s have been purified and partially characterized from a number of sources including human monocytes [38] and human leukocytes [39] . Human recombinant proteins have also been heterologously expressed and purified to facilitate the identification of selective inhibitors by high throughput screening [40] . Without apparent exception, PDE4 isoenzymes are acid proteins (p I = 4–6) that exclusively hydrolyze cAMP (Table 3 ). In 1989 Davies and colleagues isolated and cloned the Drosophila melanogaster “dunce” gene and found that it encoded a PDE of the PDE4 family. In the same year, four rat cDNA homologues [41– 43] of the “dunce” cAMP PDE were identified, establishing a molecular basis for the observed heterogeneity of gene products within the PDE4 family. These clones represent transcripts of four different genes and are now named RNPDE4A, RNPDE4B, RNPDE4C, and RNPDE4D according to the nomenclature proposed by Beavo and colleagues (1994). Four human genes (A–D) have also been identified and many of their products studied in some detail (see [3, 4, 19] . An astonishing finding that emerged from the molecular cloning of PDE4 isoenzymes was the presence of mRNA transcripts of different sizes for each of the four variants (greater than 50 have been unequivocally identified at the time of writing) that are differentially expressed between tissues [3, 4, 23]. The basis for this profound heterogeneity of PDE4 isoenzymes is attributable to both alternative mRNA splicing and to the fact that PDE4 genes express multiple promoter regions, and therefore provide several potential start codons for the translation of the protein. Proteins encoded by each PDE4 gene may be either of the “short” or “long” form (see [3] ). Structurally, long PDE4 isoforms have an N-terminal domain, two, so-called, upstream conserved regions (UCR1 and UCR2; they are thought to mediate dimerization of long PDE4s [32] ), have a highly conserved catalytic centre and a unique C-terminus; in contrast, short PDE4 variants are truncated proteins that lack UCR1 [44] .

Therapeutic Indications of PDE4 Inhibitors

PDE4 inhibitors have been tested for efficacy in a number of immunological and immunodeficiency conditions including asthma, chronic obstructive pulmonary disease (COPD), Crohn’s disease, myasthenia gravis, atopic dermatitis, psoriasis, sys- 112 M.A. Giembycz

Table 4 Established PDE isoenzyme proﬁ les in human proinﬂ ammatory and immune cells implicated in allergic disorders Immune/proinflammatory cell PDE profile Mast cell 3, 4, 5, 7 Alveolar macrophage 1, 3, 4, 5, 7 T-Lymphocyte 1, 2, 3, 4, 5, 7, 8(?) B-lymphocyte 3, 4, 7 Eosinophil 4 Neutrophil 4, 7 Basophil 4, 7 Monocyte 1, 3, 4, 7 Platelet 1, 2, 3, 5 Epithelial cell 1, 2, 3, 4, 5, 7, 8 Endothelial cell 2, 3, 4, 5, 7 Dendritic cell 1, 3, 4, 7 Airway myocyte 1, 2, 3, 4, 5, 7, 8 Vascular myocyte 1, 2, 3, 4, 5, 7 temic lupus erythematosis, rheumatoid arthritis, diabetes and multiple sclerosis [45– 49] . Asthma, COPD, and to a lesser extent, atopic dermatitis/psoriasis are indications where development of PDE4 inhibitors is most advanced (Table 3 ). The rationale for developing compounds that attenuate PDE4 activity is based on three critical findings: (1) PDE4 is abundant and the major regulator of cAMP metabolism in almost every proinflammatory and immune cell (Table 4); (2) PDE4 inhibitors suppress a myriad of in vitro responses such as cytokine generation, free radical generation, degranulation, IgE production, proliferation, lipid mediator and histamine generation, and chemotaxis; and (3) PDE4 inhibitors are efficacious in animal models of inflammation [7] . If these observations hold in humans then, conceptually, PDE4 inhibitors should demonstrate pleiotropic inhibitory activity across proinflammatory and immune cell function. A further prediction is that inhibition of PDE4 should potentiate the effects of endogenous anti-inflammatory agents that increase cAMP such as catecholamines, prostaglandin E 2 and prostacyclin. Taken together, the preclinical pharmacology of these compounds provided a rational basis for the development of novel anti-inflammatory pharmaceuticals that may display steroid-like activity without associated adverse event.

Anti-inflammatory Effects of PDE Inhibitors In Vivo

The actions of theophylline and PDE4 inhibitors upon acute (IgE-mediated) and chronic (proinflammatory/immunocompetent cell-mediated) consequences of allergen provocation in vivo have, in general, been documented in some detail and include studies of passive cutaneous anaphylaxis (PCA), cell infiltration into sites of inflammation, and microvascular leakage. Alkylxanthines and Phosphodiesterase 4 Inhibitors 113

IgE-Mediated Processes

It seems unlikely that PDE inhibitors of any isoenzyme family reduce IgE levels in vivo . In humans, it is reported that ibudilast, which is an essentially nonselective PDE inhibitor [50] is without effect on IgE levels in asthmatic individuals [51] . Similarly, the elevated level of total serum IgE in a murine model of dermatitis caused by the repeated application of the hapten, 2,4,6-trinitro-1-chlorobenzene, is unaffected by oral administration of the PDE4 inhibitor, rolipram [52] . In contrast, PDE4 inhibitors exhibit efficacy at reducing PCA reactions in rats, mice, and guinea -pigs [53, 54] . Furthermore, rolipram is effective at reducing the infiltration of indium-labeled eosinophils into the skin of guinea pigs following a PCA reaction [55] . Collectively, these data imply that PDE4 inhibitors can suppress the degranulation of IgE-bearing leukocytes and, therefore, allergen-induced mediator release. Further support for this proposal derives from studies in sensitized guinea pigs where rolipram, administered intravenously, inhibits antigen – but not LTD4 -induced bronchoconstriction [56] . Thus, rolipram preferentially exerts an inhibitory influence at the level of mast cells and basophils rather than exerting a direct antispasmogenic action at the level of airways smooth muscle [56] .

Proinflammatory Cell Infiltration

Intravenous injection of a low dose of theophylline into a guinea pig model of allergic asthma immediately prior to antigen prevents both the immediate bronchoconstriction and the late phase reaction (LPR) [57] . Qualitatively identical results were obtained in an allergic sheep and rabbit model [58] . Independent experiments conducted with sensitized guinea pigs and rats have demonstrated that theophylline suppresses pulmonary eosinophil, and in the case of the rat, neutrophil recruitment which is believed to be intimately associated with the development of the LPR [59– 65] . In many of these studies, however, theophylline was administered acutely at a supra-therapeutic dose indicating that the observed effects may not be relevant to the clinical situation. In contrast, chronic treatment of guinea-pigs for seven days with therapeutically-relevant doses of theophylline is reported to effectively prevent PAF- and allergen-induced eosinophil recruitment [60, 66] . A large number of investigations (too many to describe individually herein) have evaluated the effect of PDE inhibitors on the infiltration of proinflammatory cells into the airways lumen, skin, and eye of guinea pigs, rats, and monkeys in response to a variety of dissimilar stimuli including allergen. For example, pretreatment of sensitized guinea pigs with zardaverine, a mixed PDE3/PDE4 inhibitor, markedly suppressed allergen-induced infiltration of eosinophils, macrophages, and neutrophils into the bronchoalveolar lavage (BAL) fluid to a level achieved with dexamethasone [67] . Comparable data has been reported for the PDE3/PDE4 inhibitor, benafentrine, on PAF- and allergen-induced pulmonary eosinophil recruitment in guinea pigs after chronic (6 days) dosing [60, 66] . Studies conducted more recently 114 M.A. Giembycz with rolipram and second generation PDE4 inhibitors including cilomilast (3 ), roflumilast (5 ) and AWD 12-281 ( 7 ) have corroborated those findings both in the airways and in allergic cutaneous reactions [68– 77] . Similarly, treatment of sensitized Cynomolgus monkeys with rolipram abrogates the pulmonary neutrophilia and eosinophilia, and airways hyperresponsiveness after multiple exposures to the antigen but is without effect on the immediate increase in airways resistance that follows acute antigen provocation [78] . Thus, these data are consistent with the findings that PDE4 inhibitors may be anti-inflammatory and act primarily to prevent the activation of immune cells in the lung rather than exerting an antispasmogenic or spasmolytic effect on the level of airways smooth muscle [56] .

Microvascular Leakage and Edema

It is well recognized that the microcirculation plays an important role in inflammatory reactions. Under normal conditions, the endothelium lining the postcapillary microvenules in the skin and bronchial circulation (capillaries in the pulmonary vasculature) is largely impermeable to blood cells and to macromolecules; but following a proinflammatory insult, localized arteriolar vasodilatation occurs with a consequent increase in blood flow. This effect is induced by the liberation of proinflammatory mediators such as histamine and tachykinins. An increase in capillary and microvenular pressure then ensues together with the liberation of other mediators such as leukotriene D4 , which directly contract the microvenular endothelial cells. Together, these effects, by increasing microvenular permeability, permit the loss of plasmaproteins from the vascular compartment. Furthermore, the resulting increase in osmotic pressure due to loss of solute from the circulation leads to marked fluid exudation and edema. In guinea pigs, theophylline reduces plasma exudation into the trachea, bronchi, and BAL fluid, but its efficacy may depend upon the nature and strength of the leak-evoking stimulus [79– 82] . With respect to PDE4 inhibitors, intravenous, oral, and intratracheal administration markedly attenuate PAF-induced microvascular leakage in both small and large airways, and into the BAL fluid of anaesthetized guinea pigs [81, 83, 84] . The finding that rolipram is active when given directly into the airways indicates an important local action in the lung, and highlights that systemic administration is not necessary for these compounds to exert an anti-inflammatory influence. This is an important observation, since the administration of PDE4 inhibitors by the inhaled route should reduce untoward side effects while maintaining efficacy. Svensjo and colleagues [85] reported that PDE4 and PDE3/PDE4 inhibitors attenuate the increase in microvascular permeability evoked by bradykinin in the hamster cheek pouch. Qualitatively identical results were obtained for the effect of rolipram, denbufylline, AWD12-281, cilomilast, and piclamilast on edema formation in the skin, and proinflammatory cytokine release evoked by Alkylxanthines and Phosphodiesterase 4 Inhibitors 115 a variety of stimuli including arachidonic acid, croton oil, and various irritant haptens [52, 68, 73–75, 86–89] .

Clinical Trials of Theophylline in Asthma

Until relatively recently, the therapeutic efficacy of theophylline in asthma was attributed to its weak bronchodilator activity. However, while theophylline is an effective bronchodilator, there is now increasing evidence that this drug may also exert an immunomodulatory action at plasma concentrations that do not affect airways smooth muscle tone (reviewed in [90] ). Several lines of investigation have lead to this conclusion. In essentially all studies, theophylline protects against the LPR following allergen provocation, implying that the emigration of proinflammatory and immunocompetent cells from the circulation into the lung and/or their subsequent activation is suppressed. Indeed, suppression of the LPR at nonbronchodilator doses (<10 mg/l) of theophylline is associated with a reduction in the typical increase in CD4+ and CD8+ T-lymphocytes. Theophylline also suppresses the activity of other proinflammatory and immune cells ex vivo including neutrophils and macrophages, which is positively correlated with the concentration of theophylline measured in the BAL fluid. Similar experiments have demonstrated that the number of activated eosinophils and CD4+ T-cells are reduced in allergic subjects given low dose theophylline, and that eosinophil accumulation in bronchial tissue in patients with atopic asthma is attenuated. All these changes are mirrored by improvements in lung function.

Clinical Trials of PDE4 Inhibitors in Asthma and Rhinitis

Asthma

PDE4 inhibitors have been shown to be effective in patients with exercise-induced asthma. Nieman and colleagues (1998) have reported the results of a randomized, placebo-controlled, double blind crossover trial with cilomilast in 27 patients with exercise-induced asthma. Subjects were randomized to receive cilomilast or placebo for 7 days followed by a 7 day washout and then the alternative treatment for 7 days. The primary efficacy variable was the maximum percentage decrease

(MPD) in forced expiratory volume in 1 s (FEV1 ) in response to exercise. In the placebo group the mean fall in FEV1 after exercise was 32.9%, which was significantly greater than the deterioration in lung function seen when the same subjects received a single dose of cilomilast (23.6% reduction in FEV 1 ). The improvement in lung function was incremental such that after 7 days of therapy, the MPD in

FEV 1 was further reduced to 21.8% [91] . There were also improvements in the 116 M.A. Giembycz

MPD in peak expiratory flow rate (PEFR), time to recovery after exercise, and percent protection against exercise-induced bronchoconstriction [91] . Similar data have been obtained with roflumilast. Sixteen patients with exercise- induced asthma were recruited into a placebo-controlled, randomized double blind, two-period cross-over study where placebo or roflumilast (500 mg od) was administered in random order for 28 days [92] . FEV 1 was measured before and repeatedly up to 12 min after the end of the exercise challenge. Blood was taken for determination of lipopolysaccharide (LPS)-induced tumor necrosis-a (TNF a ) released ex vivo as a surrogate marker of inflammatory cell activation. At the end of the study the mean fall in FEV1 in response to exercise was significantly reduced (by 41%) when compared to placebo [92] . Similarly, the median TNFa concentration was reduced by 21% during roflumilast treatment whereas it remained constant under placebo [92] , indicating that an anti-inflammatory plasma concentration of the drug had been achieved. Other trials of cilomilast in asthma have yielded equivocal results. In one of these, the results of a multicentre, placebo-controlled, double blind randomized parallel group study with cilomilast (5, 10 and 15 mg bid for 6 weeks) involving 283 patients taking inhaled corticosteroids concurrently was reported [93] . All patients had an FEV1 of approximately 66% as predicted, expressed a 12% or greater responsiveness to salbutamol, and had asthma that was inadequately controlled with inhaled corticosteroids [93] . Two hundred and sixty six patients completed the study. At the highest tolerated dose (15 mg bid) cilomilast as well as placebo, increased FEV1 from week 1 onwards and this effect was greater with the active treatment group [93] . However, the improvement in lung function failed to reach statistical significance at any time except at week 2 when the mean difference in trough FEV1 was 210 ml greater than in the placebo treatment group [93] . Improvements, relative to placebo, in forced expiratory flow at 25–75% of forced vital capacity (FEF25–75 ) and domiciliary PEFR were also detected; but again, statistical significance was not achieved. However, in the physicians’ global assessment, 59% of patients taking cilomilast (15 mg bid) were rated as “markedly improved” compared to 39% of patients given placebo, which was significant. Similarly, in the patients’ global assessment, 69% of patients in the active treatment group (15 mg bid) indicated that they were “markedly improved” compared to 41% of patients who received placebo [93] . An international (Germany, United Kingdom, France and South Africa), multicentre phase IIb double blind, parallel, 12 month efficacy, safety and tolerability study of cilomilast (10 and 15 mg bid) also evaluated 211 asthmatic patients between 19 and 70 years of age, which was an extension of three double blind randomized phase II studies of 4–6 weeks duration [94, 95] . One hundred and fifty eight patients received cilomilast and the rest were given placebo. Inclusion criteria included a history of episodic wheezing for at least 6 months, an FEV1 ³ 45% and £90% of predicted for height, sex and weight, and responsiveness to salbutamol ( ³12%) at time of screening. Clinically relevant and statistically significant improvements above placebo were seen in forced vital capacity (FVC) and PEFR, which were sustained from week 1 to the end of month 12. A consistent improvement Alkylxanthines and Phosphodiesterase 4 Inhibitors 117

in FEV1 was also noted but this did not reach statistical significance. Asthma symptom scores maintained in diaries also indicated a reduction in cough, wheeze, and breathlessness/chest tightness in the active treatment group when compared to placebo [94] . More encouraging data have been obtained with roflumilast. In particular, a trial in 23 subjects with mild asthma showed that roflumilast (250 or 500 m g od) given for 7–10 days reduced the early and late asthmatic reactions evoked by allergen challenge [96] . These are potentially exciting data as the suppression of LPR (43% in the 500 µg treatment group) indicates that the drug may have exerted a clinically relevant anti-inflammatory effect. Indeed, in many clinical trials of oral PDE4 inhibitors, a maximum level of lung function improvement is achieved within the first 2–4 weeks of treatment, implicating a nonbronchodilator mode of action. Further studies have also found that roflumilast improved FEV1 in subjects with mild to moderate asthma [97] ; it also reduced allergen-induced AHR to histamine [98] . One study has also found that roflumilast is as effective as an inhaled corticosteroid at improving lung function [99] . In that study, 499 asthmatic patients were randomized to receive either roflumilast (500 m g od) or beclomethasone dipropionate (200 µg bid) through a metered-dose inhaler for 12 weeks. At the end of the study, both treatment groups had significant and comparable improvements in FEV1 , FVC, and PEFR; asthma symptoms and b 2 -agonist use were also reduced. Finally, roflumilast has been shown to be effective in the treatment of allergic rhinitis [100] , which supports the idea that PDE4 inhibitors may have utility in treating a variety of allergic [and nonallergic] inflammatory disorders.

Clinical Trials of PDE4 Inhibitors in Psoriasis and Atopic/ Contact Dermatitis

Several selective and nonselective PDE inhibitors of varied structural classes have been evaluated in humans for efficacy in atopic dermatitis and/or psoriasis [101] .

Rolipram and Rolipram Analogues

Two small studies, conducted in the late 1970s, were designed to examine the ability of Ro 20-1724, applied topically, to improve psoriatic lesions [102] . In one of these, which involved 17 subjects, Ro-20,1724 or vehicle was applied as a cream (qid) under occlusion for 4 weeks, and the extent of the lesions assessed 2, 4 and 6 weeks after initiation of the study. Compared to vehicle, 75% of subjects at week 4 showed improvements in skin lesions with no obvious adverse events. In the second study, Ro 20-1724 (1%) was compared to the corticosteroid, triamcinolone acetonide cream, in 33 subjects. Again, lesions were improved in 77% of subjects, although the corticosteroid was more efficacious (94% improvement at week 4). 118 M.A. Giembycz

Cutaneous application of the archetypal PDE4 inhibitor, rolipram (0.5% and 1%; 20 min pretreatment) to eight volunteers has also shown to reduce erythema induced by Balsam of Peru , given topically, which contains the irritant cinnamic aldehyde [103] . Similar data was obtained with Ro 20,1724 [103] . Another rolipram analogue, atizoram (10 ), was evaluated in 20 subjects with atopic dermatitis [104] . In this double-blind, randomized study, atizoram (0.5%) or its petrolatum vehicle was applied as an ointment (bid) for 28 days on 200 cm 2 lesional areas. A statistically significant and clinical-relevant reduction in all proinflammatory parameters (i.e., erythema, induration/papulation, excoriation) was noticed within three days of treatment, which was preserved throughout the duration of the trial. At the end of the study 16 of the 20 sites treated with azitoram showed improvements in proinflammatory parameters compared to only 3 of the 20 sites to which vehicle had been applied.

Xanthines

Consistent with the data obtained with rolipram and Ro 20-1724, cutaneous application of caffeine and pentoxfylline (0.5% and 1%; 20 min pretreatment) has been shown to reduce erythema induced by Balsam of Peru , given topically [103] . Significantly, there was a positive correlation between the anti-inflammatory activity of these four PDE inhibitors and their ability to suppress PDE4 isolated from the HaCaT keratinocyte cell line [103] . In 2002, the results of a multinational and multicentre, placebo-controlled, double-blind, randomized, parallel group, proof-of-concept study with cipamfylline (11 ) was reported [105] . In this trial, 52 subjects with a diagnosis of atopic dermatitis were randomized to one of two treatment groups such that the effect of cipamfylline (1.5 mg/g) could be compared against vehicle and the moderately potent corticosteroid, hydrocortisone 17-butyrate (0.1%), applied as creams. Subjects were treated twice daily with a maximum application of 2 g/day for 14 days. Several inflammatory parameters were measured at the beginning of the study and at days 3, 7 and 14 including the degree of erythema, edema/papulation, oozing/crusting, excoriation and lichenification to provide a total severity score (TSS). The results of that trial demonstrated that cipamfylline was more effective than vehicle in reducing the TSS but was not as efficacious as hydrocortisone 17-butyrate [105] . Despite the topical application of cipamfylline, systemic exposure was recorded in 25% of subjects, which presumably precluded further trials at higher topical doses. In contrast, cipamfylline (2.5 mg/g) delivered topically as an ointment was not better than vehicle in reducing inflammation in an acute and chronic human model of contact dermatitis where sodium dodecylsulphate was used as irritant, and under experimental conditions where betamethasone 17-valerate was effective [106] . The reason for this discrepancy is unclear. Alkylxanthines and Phosphodiesterase 4 Inhibitors 119

Thalidomide Derivatives

C-10004 ( 12 ) is a thalidomide derivative in Phase II clinical trials for a number of allergic conditions including psoriasis [107] . In Phase I studies, C-10004 given orally in single and multiple doses (10 mg and 20 mg) was well tolerated in healthy volunteers and had a mild adverse-effect profile [107] . A Phase IIa trial has also established that C-10004 (20 mg) reduced both symptoms of psoriasis in a small population of subjects and reduced epidermal thickness – a primary efficacy endpoint measure – although this was not of a magnitude required by the United States Food and Drug Administration [101] . However, in this trial, C-10004 was not well tolerated, with adverse events (nausea, dizziness, and diarrhea) mirroring those reported for other PDE4 inhibitors including cilomilast and roflumilast (see Section on Adverse Events ).

Safety, Tolerability, Drug Metabolism and Pharmacokinetics of Theophylline and PDE4 Inhibitors: A Comparison

Table 5 shows a comparison of the drug metabolism, pharmacokinetics (DMPK), and clinical safety of theophylline and PDE4 inhibitors for which information is available. Perhaps the most striking difference is in the pharmacokinetics, which has implications for patient compliance and the extent to which the plasma concentration requires monitoring. At bronchodilator doses, intra- and intersubject variability to theophylline together with a low therapeutic ratio poses a significant clinical problem requiring careful titration with routine plasma monitoring to avoid serious cardiac and CNS side effects [108] . This is a particular problem with smokers, as polycyclic aromatic hydrocarbons present in vapor phase of cigarette smoke are known to induce drug metabolizing enzymes including CYP1A1 and CYP1A2 [109– 111] . As theophylline is principally metabolized by CYP1A2 [112, 113] , dose adjustments are often necessary to compensate for the increased clearance in cigarette smokers [114– 116] . Age is another factor that has a marked effect on the pharmacokinetics of theophylline. Indeed, the clearance of theophylline decreases 15–28% in the elderly when compared to young adults, which probably reflects a decrease in the elimination of theophylline by CYP1A2 [117– 119] . In contrast, the pharmacokinetics of cilomilast and roflumilast are linear, providing dose-proportional systemic exposure that is essentially unaffected by age and cigarette smoking status. This indicates that no dose adjustments will be necessary in elderly smoking subjects with COPD [108, 120, 121] . Despite producing bronchodilatation, theophylline is prone to cause adverse events. These are particularly pronounced when dosed to give plasma concentrations of 20 mg/l or greater, although these unwanted actions can be offset by gradually titrating the dose of theophylline until therapeutic levels are achieved [122] . 120 M.A. Giembycz

In contrast, a major benefit of PDE4 inhibitors in clinical trials is their superior safety and tolerability profile over theophylline. Although nausea and vomiting are common with PDE4 inhibitors, this is usually of moderate severity and is reported to be self-limiting [123] . Moreover, PDE4 inhibitors are generally well tolerated in both short- and long-term dosing trials with a low incidence of adverse events; they have no action on adenosine receptors, and with the exception of headache, are devoid of adverse cardiovascular activity [120, 121]. Nevertheless, despite these improvements over theophylline, there are still major safety concerns with current second generations PDE4 inhibitors at the doses believed necessary to impart therapeutic benefit (see Section on Adverse Events). Another significant clinical problem is that theophylline has a high potential for drug interactions [120, 121] . Thus, in addition to CYP1A2, theophylline is also metabolized, albeit to a lesser extent, by CYP2E1 and CYP3A4. Accordingly, many drug interactions may occur including all of those indicated in Table 5 . In contrast, PDE4 inhibitors have, in general, a far reduced propensity for drug interactions. With respect to cilomilast, none of the metabolic pathways largely involve cytochrome P450 enzymes (CYP1A2, CYP2D6, CYP3A4), which are most susceptible to competitive inhibition by other drugs [121] . Indeed, the only P450 enzyme implicated (CYP2C8), has few other substrates or inhibitors. Moreover, cilomilast does not inhibit any important hepatic cytochrome P450 enzymes in vitro [121] . The finding that, at steady state, cilomilast has no clinically meaningful effect on the pharmacokinetics of digoxin, theophylline, or prednisolone supports this data [121] . Conversely, neither theophylline nor Maalox Plus – an antacid commonly used in the elderly that contains salts of calcium, magnesium and/or alu- minium that can alter the absorption or bioavailability of some drugs – had any significantly influence on the pharmacokinetics of cilomilast [121] . Similar results have been reported for roflumilast. Thus, taken together these data demonstrate that the two most clinically advanced PDE4 inhibitors are not contra-indicated with commonly prescribed medications for asthma and can be safely coadministered with these drugs.

Adverse Events of Theophylline and PDE4 Inhibitors

Theophylline

Theophylline has a very low therapeutic ratio. This undesirable property is a major cause for concern, as adverse events tend to occur when the plasma concentration exceeds 20 µg/ml (110 µM). The most common adverse events include nausea, vomiting, gastro-intestinal irritation, and headache (probably due to PDE4 inhibition – see below). Other more serious, side effects such as CNS stimulation, diuresis, and cardiac arrhythmias occur at higher doses and may be due to the ability of theophylline to act as an adenosine A1 -receptor antagonist [122, 124] . Still higher plasma concentrations may precipitate convulsions and even death [122] . Alkylxanthines and Phosphodiesterase 4 Inhibitors 121

Table 5 A comparison of the mechanism of action, DMPK, safety and tolerability of theophylline and PDE4 inhibitors Theophylline PDE4 inhibitors a Mechanism of • Unclear (inhibition of PI-3Kd ; • Selective inhibition of action histone acetylation PDE4 status) • PDE inhibition only at high (>20 mg/l) doses DMPK Pharmacokinetics • Nonlinear • Linear providing dose • Significant intersubject proportional systemic variability affected by age, exposure smoking status and concomitant • Low intersubject variability medication necessitating plasma – no plasma monitoring monitoring required Absorption • Variable, depends on formulation • Oral formulations (od or bid)

• tmax ~1–2 h Bioavailability • Variable, depends on formulation • >80%, unaffected by food or antacids Half life • 7–9 h • 7–16 h depending on inhibitor Volume of distribution • 500 ml/kg • Low • plasma protein binding ~56% • High Clearance • ~400 ml/h/kg • Low • Affected by genetic factors, cigarette smoking, coexisting pathology and drugs that affect hepatic metabolism Metabolism • ~90% metabolized by liver • Negligible first pass hepatic (CYP1A2) metabolism Drug interactions • High potential for drug • Low potential for drug interactions including interactions propafenone, mexiletine, • Can be taken with other enoxacin, ciprofloxacin, drugs prescribed for asthma cimetidine, propranolol, oral and COPD contraceptives, erythromycin, rifampicin, phenytoin, carbamazepine, phenobarbitone, isoprenaline, tobacco smoke Excretion • 10% excreted unchanged via the • Depends on inhibitor kidneys Dosing adjustment • May be required in cigarette • None, accept in individuals smokers, the elderly, individuals with moderate hepatic and with liver disease and subjects severe renal impairment taking concomitant medication • Contraindicated in subjects • Contraindicated in individuals with severe hepatic with heart disease, seizure impairment disorders and gastro-esophageal reflux.

(continued) 122 M.A. Giembycz

Table 5 (continued) Theophylline PDE4 inhibitors a Clinical efficacy • Effective in a subset of patients • Phase III clinical trials with COPD ongoing • Nonbronchodilator doses effective in asthma; steroid sparing Safety and tolerability • Serious cardiovascular and CNS • No cardiovascular or CNS side-effects side-effects • GI irritation, nausea, insomnia in • Headache, nausea, 10–15% of patients vomiting, arteriopathy(?) a Details refer to cilomilast and roflumilast, which are in late Phase III clinical trials

PDE4 Inhibitors

Despite some encouraging data from Phase III studies in asthma, and the superior DMPK over theophylline, roflumilast and other PDE4 inhibitors are still hampered by a low therapeutic ratio. This limitation became clear early on in the development of these compounds with nausea, diarrhea, abdominal pain, vomiting, and dyspep- sia being the most common adverse events reported (reviewed in [120, 121]). For example, the number of subjects failing to complete all controlled trials of cilomilast conducted by GSK due to an adverse event was positively dose-related with gastrointestinal disturbances being the most prevalent [125] . Unfortunately, these unwanted actions, which are mediated both locally (i.e., in the gastrointestinal tract) and centrally, can be accounted for by the ubiquitous distribution of PDE4 isoforms across many tissues, and represent an extension of the pharmacology of PDE4 inhibitors that is typical of first generation compounds such as rolipram. Documentation of serious toxicities resulting from the oral administration of PDE4 inhibitors is relatively sparse. However, the most worrying potential toxicity generic to PDE4 inhibitors is arteritis. This condition is characterized by inflammation, hemorrhage and necrosis of blood vessels, and is believed to be irreversible in animals. Mechanistically, arteritis is thought to result from hemo- dynamic changes produced by excessive and prolonged vasodilatation of specific vascular beds, although the means by which PDE4 inhibitors cause certain vessels to become targets of inflammation is unknown. In nonhuman primates, studies with PDE4 inhibitors generally have not identified pathologies, including arteritis, similar to those reported in other species used for toxicology [126, 127] ; this has lead to a view that arteriopathies maybe nonprimate-specific. Indeed, rats and dogs may have an increased susceptibility to drug-induced vascular lesions because of the common occurrence of arteriopathies in these species [128, 129] . Consistent with this hypothesis, cilomilast is reported not to produce vascular lesions in primates whereas in rodents medial necrosis of mesenteric arteries is well documented [130] . However, a recent comprehensive toxicological study found that a PDE4 inhibitor, SCH 351591 produced in Cynomolgus monkeys, Alkylxanthines and Phosphodiesterase 4 Inhibitors 123 acute to chronic inflammation of small to medium sized arteries in many tissues and organs [131] . These findings of arteriopathy in primates, which were previously thought to be resistant to toxicity, have serious implications for human risk, and it is noteworthy that Merck in 2003 abandoned development of their lead PDE4 inhibitor (licensed from Celltech Group) due to an incidence of colitis, raising the possibility that it was secondary to arteritis [132] . Moreover, as asthma is a chronic disease requiring – in many subjects with moderate to severe disease – long-term therapy, a wide margin of safety will be needed because toxicity cannot be adequately monitored. The major problem for the physician is that presentation of mesenteric ischemia is vague in humans and diagnostic tools are poor. Indeed, attempts by the pharmaceutical industry to develop biomarkers of arteritis to assist the development of PDE4 inhibitors have, to date, been unsuccessful. However, perhaps some comfort can be derived from the knowledge that no clinically relevant effects have been produced in patients treated for many years with bronchodilator doses of theophylline (which produce medial necrosis of mesenteric vessels in rats [133, 134]), as well as more selective PDE4 inhibitors including rolipram and denbufylline [130] . Other adverse events generic to PDE4 inhibitors and of potential concern based on margin of safety calculations consist of testicular toxicity – manifested as degeneration of the epithelium lining the seminiferous tubules – hypertrophy, and hyperplasia of the adrenal cortex. It also includes focal myocardial necrosis, erosion of the gastrointestinal mucosa and squamous cell hyperplasia of the nonglandular stomach, which is indicative of an irritant action of cilomilast on the gut [130, 135, 136] . However, it is currently believed that these findings do not have clinical relevance. Indeed, there is no evidence from the Phase II or Phase III trials conducted to date that cilomilast at a dose 15 mg (bid) produces these adverse effects in humans.

Concluding Remarks

Many of the major pharmaceutical companies in the world have developed potent and novel “second generation” PDE4 inhibitors for the treatment of a number of allergic disorders (Table 3 ). There is abundant predictive evidence from preclinical studies that these new drugs demonstrate global anti-inflammatory activity with an improved therapeutic ratio [7, 121, 137, 138] . That said one must be cautious of this interpretation since only the acute effects of PDE4 inhibitors in animals have been demonstrated and whether they translate into a useful therapy in chronic human allergic diseases remains to be determined. Indeed, despite initial optimism, the disappointing results of a number of Phase III trials of PDE4 inhibitors indicate that dose-limiting adverse events are a major cause for concern and probably reflect an interaction with PDE4 expressed in “nontarget” tissues. An additional contributing factor also may lie in the knowledge that all PDE4 inhibitors currently in development, block PDE4D, which is believed to promote emesis [139 – 141] . 124 M.A. Giembycz

Nevertheless, by 2010 it is likely that results from clinical trials will reveal whether optimism in the therapeutic potential of this class of compounds was justified.

Acknowledgements The author is an Alberta Heritage Foundation for Medical Research (AHFMR) Senior Scholar and is funded by the Canadian Institutes of Health Research.

References

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Sally E. Wenzel

It has been understood for some time that, although the majority of patients with asthma respond well to corticosteroid (CS) therapy, a small subgroup exists in whom CSs either have no effect on asthma or its components, or in whom the dose required to cause an improvement, greatly exceeds the usual therapeutic range. As CSs are widely recognized as the most effective therapy currently available for asthma, a poor response to CSs may contribute to the development of severe asthma. However, GC insensitive asthma is not synonymous with difficult-to-treat asthma, as it has been recognized that child and adult asthmatics with a wide range of severity may exhibit a lower than expected response [1, 2]. Yet, it is the group of patients with difficult-to- treat asthma, who are also refractory to treatment with CSs, who likely contribute to nearly 50% of the economic burden of the disease [3] . For many years, CS insensitivity was described as being related to a direct abnormality in the glucocorticoid (GC) pathway (i.e., receptor, translocation, transcription factor binding). However, it is now understood that GC insensitive asthma is likely to be much more complex than originally described, with numerous other factors also contributing to an absent or diminished CS response, which may have little to do with molecular pathways. After defining GC insensitivity, this review will describe the current understanding of four potential reasons for GC insensitivity. These include: (1) abnormal activation of the GC receptor and its nuclear inhibitory effects, (2) the presence of a “different” inflammatory process that may not respond to CS therapy, (3) the lack of any inflammatory process and (4) the presence of an inflammatory process in a region of the lung, poorly accessible to inhaled therapy. A fifth reason for GC insensitivity also exists, namely, non-adherence/compliance with CS medications. However, that reason for GC insensitivity will not be discussed further in this chapter. This chapter will conclude with a section on approaches to treatment of GC insensitive asthma (Table 1 ) . The relative importance of each of these components to “GC insensitive asthma” is not yet known; but each subtype requires a different treatment approach. In fact, it is

S.E. Wenzel () University of Pittsburgh , NW 628 Montefiore, 3459 Fifth Ave. , Pittsburgh , PA 15213 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 133 DOI 10.1007/978-4-431-99362-9_8, © Springer 2010 134 S.E. Wenzel

Table 1 Mechanisms of GC insensitivity 1. Abnormal activation of the GC receptor and its nuclear inhibitory effects 2. The presence of a “different” inflammatory process that may not respond to CS therapy 3. The lack of any inflammatory process 4. The presence of an inflammatory process in a region of the lung poorly accessible to inhaled therapy likely that the classically associated reasons for GC insensitivity – those related to abnormalities in the GC pathway – occur in no more than 50% of the refractory asthma population [4– 6] . These patients are more likely to have the hallmark of persistent eosinophilic/lymphocytic inflammation despite high dose steroids, but very few studies have evaluated the level of airway inflammation in association with GC insensitivity. For the remainder of this chapter, “GC” will be used to describe the glucocorticoid pathway and its molecular biology, while “CS” will always refer to corticosteroids in relation to asthma therapy.

Definition of GC Insensitive Asthma

It is first important to define the term “GC insensitive asthma.” It is clear that this definition varies from study to study. However, “steroid resistance” was originally defined as the failure of an asthmatic patient to respond to high dose systemic/oral CS therapy. Specifically, patients were treated with methylprednisolone (40 mg) per day for 2 weeks and FEV1 response was determined. Those patients who failed to achieve a 15% improvement in FEV1 over that 2-week period were termed GC resistant [7, 8] . What has become increasingly clear is that absolute GC resistance is quite uncommon. In fact, most people with a poor response to GCs rather have a rightward shift in the dose response to GC therapy, requiring higher (and often unacceptably high) doses of GCs before a therapeutic response is seen. These patients might better be termed “poorly sensitive” as opposed to “insensitive.” Unfortunately, in many studies undertaken more recently, the details of the level of GC responsiveness in the mechanistic studies are limited. Similarly, in many of the “GC pathway” studies, little description exists regarding the background inflammatory process of the patient-subject’s disease.

Abnormal Activation of the GC Receptor and its Nuclear Inhibitory Effects (Table 2)

For many years, GC insensitive asthma was believed to be primarily due to a defect in GC receptors or their signaling mechanisms. One of the first identified abnormalities was the description of extremely rare individuals who lacked a functional GC receptor. Glucocorticoid Insensitive Asthma 135

These individuals, labeled as “Type 2” GC resistance, were completely lacking in response to GCs at any level and in any tissue. These rare individuals not only did not benefit from GCs, but they also did not suffer the side effects of GCs. However, in studies by Sher and colleagues, these patients were believed to account for no more than 5% of the GC insensitive population [9] . In contrast, the majority of the GC insensitive patients were described to have a Type 1 defect, meaning that they suffered the consequences of GC therapy through side effects in other tissues/ organs, but did not achieve an anti-inflammatory response in the lung [10] . These patients had low GC binding affinities and the defect was described to occur primarily on T-lymphocytes and monocyte/macrophages [9] . Interestingly, very small numbers of these patients were actually studied for the level of lung inflammation before or after CS therapy; however, there appeared to be an increase in eosinophilic inflammation in these patients, and a lack of suppression of Th2 cytokines, including IL-4 and -5 [10] . In recent studies, the mechanisms for this Type 1 defect have been further evaluated, with different groups defining different mechanisms for the process. These mechanisms have recently been extensively reviewed by Ito, et al., although direct comparisons are often difficult due to the different peripheral blood systems used [11] . Interestingly, although rare studies have evaluated the responses of lung cells to CSs, the majority of mechanistic studies have evaluated peripheral blood mononuclear cell response, including the basal response to GC stimulation, the impact of co-stimulatory factors on GC responses and the effects of IL-2 and -4 in combination, or IL-13 alone to induce GC insensitivity [12] . The comparability of these different systems remains questionable, and cross verification with either severity of asthma or the presence of “uninhibited” inflammation is lacking. Several studies have attempted to address the mechanisms behind the ability of these cytokines to blunt the usual steroid suppressive effects. In no case does it appear to be secondary to defects in the structure of the receptor [11] . However, two general theories have been proposed. The first suggests that in GC insensitive asthma there is an increase in a particular splice variant of the GC receptor, known as glucocorticoid (GR)-b . This GR- b is an isoform of the GC receptor which normally binds GC, but in which the signaling responses are generally blunted as compared to the more common form of the receptor – the GR-a . GR- b is produced when the last exon of the GR gene is altered through alternative splicing to produce a protein with a truncated carboxyterminus. Several studies have shown an increase in expression of GR-b , particularly on airway T-cells and macrophages; however, other studies have not been able to demonstrate such an increase [13– 15] . Of note, incubation of PBMCs with IL-2 and IL-4, while rendering them less GC sensitive, did not produce higher levels of GR-b expression [16] . Interestingly, while the finding of increased GR-b in GC insensitive asthma is controversial, it is clear that neutrophils express high levels of the GR- b isoform. As will be described later, neutrophils are present in higher numbers in severe, CS dependent asthma, and neutrophils are well known to be poorly responsive to CSs [17– 19] . Another theory holds that this blunted response is due to interference by proinflammatory signaling molecules such as AP-1, NF-kB, which interfere with the 136 S.E. Wenzel ability of GCs to prevent the translocation and binding of these molecules to the nucleus. Adcock and colleagues first observed that the GR in “steroid resistant” asthmatics did not bind to the DNA binding sites in the nucleus to the same degree that it did in steroid sensitive asthmatics. This diminished binding was suggested to be due to a diminished interaction of AP-1 with the GR in steroid resistant asthmatics, and an increase in AP-1 binding to DNA [20, 21] . However, in that study, there was no difference in GR binding to other transcription factors, such as NF-kB. Subsequently, one of the components of AP-1, c-fos, was shown to be increased in biopsies from GC insensitive asthmatics, with overexpression of c-fos associated with diminished DNA binding [22] . Further studies have suggested that activation of the mitogen activated protein (MAP) kinase jun-kinase (JNK) – which can activate both c-fos and its counterpart, c-jun, contributing to increased AP-1 levels – is also increased in GC insensitive asthma [23] . Mechanistically, activation of T-cells through the T-cell receptor (TCR) (alone) is inhibited by dexamethasone through a c-fos AP-1 pathway. However, when T-cells are activated by co-stimulatory molecules in conjunction with TCR, dexamethasone is no longer able to suppress lymphocyte proliferation, and simultaneously, c-fos is not inhibited. However, when some MAP kinase pathways (although not JNK pathways) were inhibited in the presence of dexamethasone, T-cell resistance was reversed [24] . While increases in GR-beta were not observed in response to IL-2/IL-4 treatment of PBMCs, others have reported that IL-2/IL-4 treatment increases the activation of another MAP kinase – p38 MAP kinase. Inhibiting p38 MAP kinase appears to restore the GC sensitivity of these cells to GCs, at least when measuring inhibition of granulocyte macrophage colony stimulating factor production in response to lipopolysaccharide (LPS) [25] . Interestingly, in most cases, the mechanisms for GC insensitivity are evaluated at the level of nuclear translocation and GC response element (GRE) binding. This would imply that the majority of the GC resistance is due to diminished GRE binding. However, as previously noted by Ito, et al., it is likely that the majority of immunosuppressive effects of GCs are not due to transrepression, but rather due to inhibition of transactivation. The role that altered GC-DNA binding plays in GC insensitive asthma associated transactivation of inflammatory cytokine expression remains poorly understood. As previously noted, almost all reported studies on the molecular mechanisms of GC insensitive asthma have focused on PBMCs, sometimes differentiated into T-cells and monocyte/macrophages (Table 2 ). Recently, a specific class of t-cells,

Table 2 Molecular mechanisms of GC insensitivity 1. Lack of GC receptor (Type 2 defect) 2. Low GC binding affinity with normal GC receptor numbers (Type 1 defect) (induced by IL-2, IL-4 and IL-13) a. Increase in GR-beta to GR-alpha ratio (not induced by cytokine exposure) b. Diminished binding of GR to pro-inflammatory transcription factors (c-fox, NF-kB) c. Increased activation of p38 MAP kinase d. Vitamin D dependent IL-10 deficiency e. Low histone deacetylase activity Glucocorticoid Insensitive Asthma 137

Treg cells has been identified by their expression of the transcription factor Foxp3. These cells are believed to be regulatory of adaptive immune responses, particularly Th2 immune responses. A current theory suggests that deficiency in Treg cells contributes to a Th2 response in asthma. In that regard, a recent study suggested that GCs are normally sufficient to induce the expression of the Treg associated cytokine, IL-10 from isolated CD4(+) T-cells when incubated in the presence of vitamin D [26] . In patients with GC insensitive asthma, there was reduction in IL-10 production, which could be rescued by pretreatment of the cells with dexamethasone, followed by vitamin D. The authors proposed that the mechanism for this effect was through an inhibition of loss of the GC receptor in the presence of dexamethasone alone [27] . This observation of loss of GC receptor expression in the response to dexamethasone is consistent with anecdotal reports of progressive loss of GC responsiveness in patients with severe asthma (Wenzel, unpublished observations). Interestingly, the authors proceeded to administer oral vitamin D to three GC insensitive subjects and were able to show in vitro that IL-10 production was enhanced. Although the clinical significance of these findings remains to be determined, several additional studies recently have suggested that increasingly severe forms of asthma may be associated with vitamin D deficiency and/or related genetic abnormalities [28] . The final “molecular mechanism” for GC insensitivity relates to changes in the epigenetics of the chromatin and was first described in chronic obstructive pulmonary disease (COPD) [29] . The overall hypothesis is based on the concept that inflammatory and oxidative stresses alter the chromatin structure in such a way as to maintain high levels of gene transcription over time. In COPD, Barnes and colleagues reported that activation of the enzyme, histone deacetylase (HDAC) 2 was reduced. The authors proposed that HDAC inactivity allowed persistent histone acetylation, which kept the chromatin in an “on” or active arrangement. They proposed that this HDAC activation was poorly inhibited by CS therapy in COPD, especially in lung tissue and alveolar macrophages, explaining the relative steroid “resistance in that disease as compared to asthma” [30] . Subsequently, patients with severe asthma were also evaluated for levels of histone acetyltransferases and HDAC-2. Similar to COPD, PBMCs from severe asthma subjects appeared to have a decrease in HDAC2 activity, which was related to their level of GC insensitivity in an in vitro assay of LPS induced cytokine release [31, 32] . While theophylline was reported to reverse some of these effects on HDAC inhibition, a therapeutic trial of theophylline in GC insensitive patients has not yet been performed [33] . Further, the interaction of alterations in histone acetylation with other theories of GC insensitive asthma, specifically overactivity of JNK/AP-1 and/or high level activation of T-cells through TCR and co-stimulatory molecules remains to be investigated. In virtually all reported cases of GC insensitive asthma, a direct link to the level of eosinophilic inflammation, a hallmark for poorly controlled asthma, is absent. Therefore, it is difficult to determine whether the effect in PBMCs actually predicts the lack of suppression of inflammation. In fact, when patients are selected for treatment with CS based on their level of eosinophilic inflammation, the response 138 S.E. Wenzel to CS therapy remains, albeit at higher doses, at least in severe asthma subjects [34, 35].Whether these higher doses overcome all or one specific molecular pathway described above remains to be determined.

GC Insensitivity Due to the Presence of a “Different” Inflammatory Process

Although GC insensitivity typically conjures up cellular level responses and molecular biology, it is highly likely that a good percentage of GC insensitivity is due to differences in the disease itself. As has long been appreciated, asthma is a highly heterogeneous disease. More recently, investigations have determined that not only is it clinically heterogeneous, but pathologically heterogeneous as well. As the definition of asthma involves the mere presence of symptoms in the face of reversible airflow limitation, many obstructive airway diseases can “mimic” or be mistaken for asthma. These diseases or syndromes include various bronchiolitic syndromes, COPD-smoking asthma overlap, and post-infectious bronchiolitis. In addition, a group of “severe asthmatics” exists in whom the inflammation is predominantly neutrophilic [19, 36] . In most, if not all of these syndromes, classical Th2/eosinophilic inflammation is only minimally present, and neutrophils may be the most common inflammatory cell. As previously noted, neutrophils are highly resistant to CS, and in fact, appear to increase in the face of CS therapy. Several studies suggest that those individuals with more neutrophilic inflammation are likely to be relatively GC insensitive [17, 37, 38] . In these cases, the insensitivity is likely due to the basic lack of responsiveness of the particular type of inflammation or inflammatory cell, as compared to an abnormality in the GC receptor pathway. An area of intensive current investigation for GC insensitivity is the smoking asthmatic. Several groups have now reported that response to CS therapy is blunted in smoking asthmatics [39, 40] . Smoking asthmatics have a higher level of neutrophilic as compared to eosinophilic inflammation [38] , which falls when smoking is discontinued. Interestingly, in that same study, CS responsiveness increased as neutrophil levels fell. Whether this neutrophilic inflammation contributes to a higher oxidative stress level is not yet clear; however, their FeNO levels are generally low [41] .

GC Insensitivity Due to the Lack of Any Inflammatory Process

In a smaller percentage of asthma subjects, very little migratory inflammatory cell- related inflammation can be found despite an evaluation of many lung compartments [6, 42, 43] . These patients have been reported to be more often female and obese. An additional group may consist of patients who once had a very active inflammatory process, but in whom the disease has progressed to a state where the Glucocorticoid Insensitive Asthma 139 inflammation has resolved, but poorly defined remodeling has occurred. This remodeling, in the form of epithelial abnormalities, smooth muscle hypertrophy/ hyperplasia or fibrotic/repair changes, could contribute to ongoing airway obstruction and symptoms in the absence of GC responsive elements. For instance, epithelial abnormalities in asthma have been shown to be moderately responsive to GCs [44] . Similarly, the subepithelial basement membrane, which is reported to be thicker in asthma, is only modestly impacted by CS treatment, even in high doses [45] . Whether these GC insensitive subjects might respond to therapies targeted towards a specific structural/remodeling element is not yet clear. However, those subjects with lower levels of eosinophilic inflammation are generally less symptomatic and at less risk of severe exacerbations than those with a “CS responsive” inflammation. Another group of asthmatics with lower than expected inflammation is the obese asthmatic [46] . Findings from a recent report suggested that an inverse relationship between FeNO and BMI exists, such that the higher the BMI, the lower the measurable inflammation. In that regard, a recent study compared the efficacy of an inhaled CS vs. a leukotriene receptor antagonist (LTRA) in obese asthmatics and reported that the relative efficacy of the CS was reduced as compared to the LTRA [47] . Finally, it is important to confirm the diagnosis of asthma. Vocal cord dysfunction can and has masqueraded as asthma – and particularly severe asthma – for many years and does not respond to CS therapy [48] .

GC Insensitivity Due to the Presence of an Inflammatory Process in a Region of the Lung Poorly Accessible to Inhaled CS Therapy

Identification of eosinophilic inflammation has traditionally been through sputum analysis or endobronchial biopsy. Additionally, exhaled nitric oxide (FeNO ) has been proposed as a tool to identify patients with persistent eosinophilic inflammation [49, 50] . In general, there are reasonable correlations of sputum or biopsy eosinophils with FeNO , even in patients on high doses of CS [50] . However, it is likely that neither is an adequate measure of eosinophilic (i.e., GC sensitive) inflammation in the distal lung. As noted in the previous section, up to 50% of severe asthma patients have low or no inflammation in these regions. In addition to having a disease that exists because of “non-inflammatory elements,” it is also possible that the inflammation exists beyond the reach of these more proximal airway approaches. In this regard, a systematic comparison of standard markers of inflammation in subjects with severe asthma comparing proximal to distal airways, revealed increased inflammation in the distal airway, as compared to the proximal airway [51] . Specifically, mast cells appeared to be dramatically increased in the distal lung, despite low levels in the proximal airways [52] . In a recent abstract, about 50% of severe asthma subjects previously identified as “non-eosinophilic” were found to have eosinophilic inflammation in the distal lung [53] . All these findings, 140 S.E. Wenzel support a recent study in which alveolar nitric oxide was measured and compared to standard measures of FeNO in patients with refractory asthma. Although the proximal measures of FeNO were not increased, assessments of nitric oxide at higher flow rates, believed to measure more distal nitric oxide levels were found to be significantly higher in these patients. These alveolar NO levels correlated with lavage eosinophils, but not sputum or bronchial wash, supportive of a distal source [54] . While the reasons for these differences are not clear, it is likely that the majority of today’s inhaled CS, with larger particle sizes, do not reach the distal lung. If severe asthma persists in some patients because of a strong distal component to their disease, then treatment with inhaled CS could leave a large portion of the inflammation undetected-or under treated. This lack of delivery of CS to the small airways could cause some asthmatics to present with GC insensitive asthma based on inadequate delivery to the region of interest.

Approaches to Therapy in GC Insensitive Patients

As noted earlier, GC insensitive asthma covers a range of patients, from mild to severe. Most therapeutic trials in GC insensitive asthma have focused on the severe patients, and often without any attempt to determine the “type” of GC insensitivity that is present. However, it can definitely be argued that before treating a patient with a cytotoxic drug, determining the type of GC insensitivity is very helpful. After confirming the diagnosis of asthma and evaluating adherence/compliance as best as one can (AM cortisol, pharamacy records, etc), determining: (1) the level of eosinophilic inflammation and later (2) the response to systemic steroids can give extremely helpful information. Eosinophilic inflammation can be measured in biopsy tissue, sputum and marginally, as FeNO [4, 50, 55]. Eosinophils in sputum may be the most robust indicator of airway eosinophils and strong support exists for the relationship between reduction in sputum eosinophils and improvement in asthma control [34, 35] . If there is any indication of persistent eosinophilic inflammation, then a trial of systemic steroids is warranted. This can be done using the standard approach of 40 mg of prednisone or methylprednisolone for 2 weeks or as an injection of high doses of triamcinolone. If little improvement in FEV1 and reduction in eosinophils occurs, then the patient likely is poorly responsive to GC, but truly sensitive. Treatment may require daily oral steroids, or even in extreme cases, monthly injections of CSs. Although trials of cytotoxic agents including methotrexate and cyclosporine have been carried out, the additional benefits of these medications over CS alone is marginal. Unfortunately, no currently indicated asthma therapy has specifically evaluated its efficacy as steroid sparing in patients with persistent eosinophilic inflammation despite high dose CS therapy. If there is any indication that the inflammation is more persistent in the distal lung, then treatment with systemic medications, including LTRA, 5 lipoxygenase inhibitors, and even theophylline, in addition to systemic CS or fine particle aerosol corticosteroids may offer some benefit. Glucocorticoid Insensitive Asthma 141

Patients with GC insensitive asthma because of cigarette smoking or obesity would be best advised to quit smoking and lose weight. However, in addition, there are data from small studies that LTRAs may offer some benefit in these patients [39, 47] . In patients in whom no eosinophilic inflammation (anywhere) is found, but in whom a neutrophilic inflammation is noted, additional higher doses of CS are not likely to be helpful. An evaluation for esophageal reflux and appropriate treatment is indicated, as is an evaluation for infection. Anecdotally, a 5-lipoxygenase inhibitor may have some efficacy in these patients, as well.

Conclusions

GC insensitive asthma describes a wide range of asthma patients and multiple mechanisms for the poor response. While intensive effort continues to understand the group of patients with GC insensitivity based on abnormalities in the GC pathway itself, many other mechanisms of GC insensitivity exist. For the clinician, it is important to differentiate one from the other to improve therapeutic options.

References

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Sharmilee M. Nyenhuis and William W. Busse

Introduction

Asthma is increasing in both prevalence and severity throughout the world [1] . Asthma affects approximately 8% of the adult population and up to 20% of the pediatric population in North America, Europe, and Australia [2] . The majority of these patients have mild to moderate persistent asthma that can be well controlled by environmental control measures and appropriate use of controller and reliever medications. It is estimated, however, that 5–10% of patients with asthma have severe disease that is recalcitrant to typical treatment modalities, including, in some cases, the administration of systemic corticosteroids. These patients have the greatest impairment in lifestyles, highest morbidity, and a disproportionate amount of health care cost associated with this disease [3– 5] . Women and minorities share these burdens disproportionately as well. Our understanding of the pathophysiology of this subset of asthma patients is poorly understood. Consequently, these patients need a careful evaluation to uncover risk factors and novel approaches to control the disease.

Definitions of Severe Asthma

To more fully classify and identify severe asthma, a recognized and uniform definition is necessary. Rackemann published a working classification of asthma in 1921 in which he grouped patients into having “extrinsic” or “intrinsic” asthma [6] . “Extrinsic” asthma patients were likely to be allergic to environmental allergens;

S.M. Nyenhuis Division of Allergy and Immunology, Department of Medicine , University of Wisconsin , Madison , WI USA W.W. Busse () Division of Allergy and Immunology, Department of Medicine, University of Wisconsin , 600 Highland Avenue , Madison , WI 53792 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 145 DOI 10.1007/978-4-431-99362-9_9, © Springer 2010 146 S.M. Nyenhuis and W.W. Busse this linkage could usually be identified through the patient’s history and by allergen skin tests. These patients usually developed their asthma before 30 years of age, and their disease was more labile. Complications of “extrinsic” asthma were usually due to infections, malnutrition, or psychological factors. Those with “intrinsic” asthma tended to develop asthma after 40 years of age and have more severe disease with a less clear-cut allergic component. It was theorized that “intrinsic” asthma might be sensitive to the bacteria residing in places such as nose, sinuses, tonsils, and gums, but this has been difficult to prove and, to some extent, largely abandoned [6, 7] . In addition, other factors have been thought to play a role in “intrinsic” asthma such as infections (bacterial or viral), a reflex from upper airways (polypoid sinusitis), or psychological factors such as anxiety or fatigue. Other disease considerations, which should be made in “intrinsic” asthma, include emphysema, tumors, or foreign bodies. This clinical classification scheme acknowledges the relative contribution of allergic and nonallergic mechanisms to asthma pathogenesis and suggests that asthma is a heterogeneous disease. When classifying patients as having severe asthma, many factors need to be considered such as symptoms, medication use, pulmonary function abnormalities, bronchial hyper-responsiveness, features of inflammation, consequences of the disease, frequency and severity of exacerbations, response to treatment, and health impact status (Table 1 ). Various clinical definitions of severe asthma have been proposed through national and international guidelines, working groups, and work- shops which incorporate the above factors [8] . An American Thoracic Society (ATS) sponsored Workshop made a comprehensive approach to establish a “working” definition of refractory asthma [9] . The definition was based on the medication requirements, asthma symptoms, frequency of asthma exacerbations, and degree of airflow limitations. Specifically, the definition required the need for patients to meet one of two major criteria (continuous high-dose inhaled corticosteroids or oral corticosteroids for > 50% of the previous year), and

Table 1 Features to consider in deﬁ ning severe asthma (from [8] , with permission from Elsevier) 1. Symptoms Exacerbations • Frequency • Severity 2. Medication use Response to treatment or intensity of treatment required to control symptoms 3. Pulmonary functions 4. Bronchial responsiveness 5. Airway inflammation 6. Development of airway remodeling 7. Consequences of disease • Respiratory failure • Hospitalizations • Impaired quality of life Recalcitrant Asthma 147 two of seven additional minor criteria (Table 2 ). The minor criteria include aspects of lung function, exacerbations, disease stability, and the use of one or more additional controller medications. In conjunction with these criteria, patients must have had other possible conditions excluded and adherence and exacerbation factors were fully considered [ 10] . This definition has recently been used by the NIH-sponsored Severe Asthma Research Program (SARP) which was established in 2000 to define the characteristics, mechanistic factors, potential approaches for study and treatment, and future research needs and directions of severe asthma [11] . SARP enrolled severe asthma patients across 8 centers in the United States who met the ATS Workshop criteria for severe asthma. Although, only 2 minor criteria (Table 2 ) were required to meet ATS criteria for severe disease, most of the severe asthma patients had 5–6 minor criteria present despite being on high doses of corticosteroids. In addition, the 2 minor criteria that best distinguished severe asthma from both mild and moderate asthma were ≥ 3 exacerbations requiring treatment with oral corticosteroids in the previous year and a history of endotracheal intubation. Therefore, with these findings from the SARP, the ATS Workshop definition has been shown to be helpful in classifying subjects with severe asthma, and establishes criteria to distinguish individuals with severe asthma [12] .

Table 2 ATS Workshop Consensus Deﬁ nition of Refractory Asthma (from [9] , with permission)a,b Major characteristics In order to achieve control to a level of mild-moderate persistent asthma: 1. Treatment with continuous or near continuous (≥ 50% of year) oral corticosteroids 2. Requirement for treatment with high-dose inhaled corticosteroids: Drug Dose ( µg / d ) Dose ( Puffs/d ) a. Beclomethasone > 1,260 > 40 puffs (42 µg/inhalation dipropionate > 20 puffs (84 µg/inhalation b. Budesonide > 1,200 > 6 puffs c. Flunisolide > 2,000 > 8 puffs d. Fluticasone propionate > 880 > 8 puffs (110 µg), > 4 puffs (200 µg) e. Triamcinolone acetonide > 2,000 > 20 puffs Minor Characteristics 1. Requirement for daily treatment with a controller medication in addition to inhaled corticosteroids, for example, long-acting b -agonist, theophylline, or leukotriene antagonist 2. Asthma symptoms requiring short-acting b -agonist use on a daily or near daily basis

3. Persistent airway obstruction (FEV 1 < 80% predicted; diurnal PEF variability > 20%) 4. One or more urgent care visit, for asthma per year 5. Three or more oral steroid “bursts” per year 6. Prompt deterioration with ≤ 25% reduction in oral or inhaled corticosteroid dose 7. Near fatal asthma event in the past a Requires that other conditions have been excluded, exacerbating factors treated, and patient felt to be generally adherent b Definition of refractory asthma requires one or both major criteria and two minor criteria 148 S.M. Nyenhuis and W.W. Busse

The European Network For Understanding Mechanisms Of Severe Asthma (ENFUMOSA) was established to better understand the severe asthma, but it also addressed the need for a definition of severe asthma. The ENFUMOSA group developed common methodology that was applied to recruit a cohort of severe asthma patients and a control group of mild-moderate asthma patients who were controlled on low-moderate doses of inhaled corticosteroids (ICS) for comparison [13] . Criteria for severe asthma required that patients were diagnosed by an asthma specialist by 45 years of age, received daily ICS for at least one year, and had evidence of variable airflow obstruction. The study further divided the patients into levels of severity by inhaled corticosteroid treatment and asthma exacerbations in the past one year. Controlled asthma was defined as those with mild-moderate disease controlled on ≤ 1,000 mcg/day of beclomethasone (median dose 666 mcg/day) for at least 1 year and no asthma exacerbations over the past one year. Severe asthma was defined as patients using ≥ 1,200 mcg/day of beclomethasone (median dose 1773 mcg/day) and had at least one asthma exacerbation in the past one year [13] . In summary, these study groups defined severe asthma as patients with signs of ongoing poor asthma control despite the treatment with high doses of corticosteroids. Severe asthma may often be easily confused with “poorly controlled” and “brittle” asthma. “Poorly controlled” asthma may represent a transient state of disease, in which symptoms may be improved with standard approaches to therapy while severe asthma represents a disease that is not responsive to standard treatment despite aggressive attempts at management [10] . “Brittle asthma” is often thought by many as a specific asthma phenotype. The term was first used in 1977 to describe patients with asthma who manifest a wide and chaotic variation in peak expiratory flow (PEF) despite high doses of inhaled corticosteroids [14] . The PEF pattern identified in brittle asthmatics did not show an obvious repeating pattern and was distinct from the controlled patterns of PEF variation seen in patients with uncontrolled asthma (Fig. 1 ). This variability in PEF and the chaotic pattern has been identified as a risk factor of death from an acute severe asthma attack. The initial definitions/classifications of brittle asthma were not considered sufficiently specific and have undergone much recalculation. Ayres and colleagues developed a new classification of brittle asthma which divides these patients into two types [15] . Type 1 is characterized by persistent and chaotic variability in the peak flow (> 40% diurnal variation for > 50% of the time over a period of at least 150 days) despite aggressive medical therapy (e.g., ICS of at least 1,500 mcg of beclomethasone). Type 2 brittle asthma is characterized by sudden acute attacks occurring in less than three hours without an obvious trigger on a background of apparent normal airway function or well controlled asthma. The type 1 patient is more likely to be female (2.5F:1 M), usually ranging between 18 and 55 years of the age. Patients with type 2 brittle asthma apparently have no sex difference. Type 1 brittle asthma is associated with increased sensitization to common allergens such as Dermatophagoides pteronyssinus. Type 2 brittle asthma may be triggered by exposure to aeroallergens such as Alternaria leading to sudden and severe asthma attacks. Recalcitrant Asthma 149

Fig. 1 Peak flow chart in a patient with type 1 brittle asthma before (open circles) and after (closed circles ) treatment with continuous subcutaneous terbutaline. Brittle Asthma defined as a diurnal peak expiratory flow (PEF) variability of >40% (from [15] , with permission)

Both types of patients often require hospital admissions but type 1 patients tend to use their health care resources more than type 2 patients. Type 1 brittle asthma β often fails to respond to inhaled 2 -agonists administered by nebulizer or long- β acting 2 -agonists. The asthma attacks in the type 2 brittle variant appear not to be controlled or prevented by steroids, and often do not respond fully to inhaled β 2 -agonists. Patients who have had near fatal asthma attacks may have a poor perception of worsening airway function, a feature that may be pertinent in both type 1 and 2 brittle asthma [15, 16] . These patients have been found to have an impaired hypoxic drive when their lung function is normal, suggesting that during an acute exacerbation they may not have a normal ventilatory response [17] . This defect often leads to a reduced awareness of the severity of attacks and a subsequent delay in getting appropriate therapy.

Risk Factors for Severe Asthma

Researchers have been trying to answer questions such as, “How does severe asthma develop?” and “What portends severe asthma?” To date, we have not been able to fully and satisfactorily answer these questions, but studies such as the Melbourne Epidemiological Study of Childhood Asthma will provide insight and more definitive answers to these questions in the near future. As asthma most commonly begins in infancy, age of onset appears to be the logical starting point to examine the natural history of asthma and the possible risk factors associated with severe and persistent asthma. The Melbourne Epidemiological Study is a large cohort of asthma, and control subjects who were enrolled at 7 years of age and 150 S.M. Nyenhuis and W.W. Busse

Table 3 Predictors of persistence and severity of childhood asthma (from [19] , with permission from Elsevier) More severe and frequent wheezing episodes during preschool age Onset during school age Family history of asthma and allergy Elevated serum IgE Early development of positive skin test results Early development of bronchial hyperresponsiveness Frequency of respiratory infections Lack of contact with older children Parenting difficulties Greater childhood psychological risk

have been followed for an additional 35 years [18] . Upon enrollment, the children were divided into 5 groups: (1) controlled, never wheezed; (2) mild wheezy bronchitis, fewer than 5 episodes; (3) wheezy bronchitis, 5 or more episodes; (4) asthma, not associated with infection; (5) severe asthma, onset before 3 years of age and persistent symptoms [19] [Table 3 ]. Over a 35 year period, the symptoms and

FEV1 in each of these groups continued to reflect the differences found in the severity categorization. The more severe the asthma was at 7 years of age, the more likely it was to persist to 42 years of age. In addition, the reduced lung function at 7 years of age was associated with continuing symptoms in the adult life, and a reduction in the lung function continued. Furthermore, the presence of hay fever, eczema, or positive skin tests increased the risk of more severe asthma in adult life. From the Melbourne Epidemiological Study and other pediatric cohorts, the persistence and severity of asthma in adults has been found to be mainly dependent on the severity of asthma as a child. Other factors, though, may also play a role in the severity of asthma in adults. For example, chronic sensitization to indoor (dust mites, cats, and/or cockroaches) and outdoor allergens may also result in more severe and persistent asthma. Of the allergens that have been studied in this relationship, Alternaria appears to be associated with a reduction in FEV1 even in the absence of asthma symptoms [20] . Aspirin exacerbated respiratory disease is also an important category of adult asthma. This often develops in the third and fourth decades of life and is found more commonly in women. This phenotype is characterized by persistent rhinitis, which usually appears before the onset of asthma, aspirin sensitivity, and nasal polyps that usually appear after the onset of asthma. In a multicenter study, The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR), severe or difficult-to-treat asthma patients had a lower post-bronchodilator FEV 1 compared with patients with non- aspirin-sensitive asthma a finding that may be the result of airway remodeling [21] . Furthermore, these patients usually require inhaled or systemic corticosteroids to control their disease. Recalcitrant Asthma 151

Not all adult asthma patients have a dramatic decline in lung function over time.

The decline in FEV 1 is proposed to be dependent on the severity of disease. The effect of inhaled corticosteroids on the deterioration of lung function has been studied and, thus far, ICS do prevent the loss of lung function [22] . The potential reasons for the deterioration in lung function are likely many, with airway remodeling being one possible contribution. Persistent inflammation and severity likely contribute to airway remodeling, which can increase airway obstruction in the absence of reversibility. In addition to airway remodeling, comorbid conditions such as tobacco use, allergen exposure, and bronchiectasis may contribute to the decline in lung function. Tobacco use may lead to chronic obstructive pulmonary disease. Prolonged allergen exposure, especially occupational agents like Western Red Cedar and diisocyanates, can cause irreversible changes in the airway [19] . Furthermore, bronchiectasis due to frequent infections or allergic bronchopulmonary aspergillosis can cause permanent loss of lung function and severe persistent asthma (Table 4 ). The risk factors of a disease are often divided into 2 groups: Genetic and environmental, that is, a gene-by environmental interaction. Taussig and colleagues have noted, the great variability and complexity of asthma suggest that the disease is not under the control of a typical Mendelian monogenic 2-allele locus, but that several major and minor loci are involved [23] . As several genes are most likely involved in asthma, the identification of risk factor genes for severe asthma is complex.

Genetic Risk Factors

Several genetic polymorphisms have been found in relationship to asthma and asthma severity. These polymorphisms have been found not only associated with the pathogenesis of severe asthma but also involved in the response to the treatment and disease progression of asthma. IL-4 is a major cytokine responsible for B-cell class switching from immunoglobulin M (IgM) to immunoglobulin E (IgE). Mutations in the IL-4 gene and the IL-4 receptor have found a link to a loss of lung function and near-fatal events [24, 25] .

Table 4 Predictors of persistence and severity of adult asthma (from [19] , with permission from Elsevier) Continued exposure to allergens including occupational agents Older age of onset Presence of aspirin sensitivity Socioeconomic status Smoking Coexisting diseases, including COPD, bronchiectasis, and (rarely) α -1 antitrypsin deficiency or allergic bronchopulmonary aspergillosis 152 S.M. Nyenhuis and W.W. Busse

Specifically, a nucleotide substitution in the IL-4 gene promoter at position −589 has been identified and is present in approximately 27% of the Caucasian population [26] . This polymorphism has been associated with life-threatening asthma episodes and low

FEV1 values in a Caucasian population [24, 25] . The gene encoding for the alpha subunit of the IL-4 (IL4RA) receptor also contains polymorphisms that have been associated with atopy and asthma. The nucleotide substitution occurs on the IL4RA receptor gene and has been found in 36% of Caucasians [27] . Sanford and colleagues found that the mutation in the IL4RA gene is a risk factor for reduced lung function in asthma but not of life-threatening asthma [24] . In addition, homozygosity of this mutation has also been associated with asthma subjects with severe disease, that is, FEV1 predicted < 60% [28] . Furthermore, the SARP study has suggested that polymorphisms in IL4RA are linked with both a high level of severe (intensive care unit/intubation) exacerbations and lower FEV1 [11] . ADAM33, another novel gene involved in the inflammatory response, has been found as a risk factor of asthma, bronchial hyperresponsiveness, and an accelerated decline in baseline lung function [29, 30] . ADAM33 is a disintegrin and metalloproteinase that is composed of multiple domains that allow the ADAM proteins to function in many cellular processes such as cell adhesion, proteolysis, signaling, proliferation, and differentiation. The expression of ADAM33 in vivo is increased in bronchial smooth muscle, myofibroblasts, and fibroblasts, thus, suggesting that this gene may play a role in the airway remodeling [31] . Furthermore, single nucleotide polymorphisms (SNPs) in ADAM33 are associated with a more rapid decline in FEV 1 in asthma over a 20 year period in a Dutch population [32] . An inverse correlation exists between FEV1 values and ADAM33 protein levels in Korean asthma subjects [33] . Further investigations into the role that these gene polymorphisms play in the pathogenesis of severe asthma may provide novel treatments. β agonists exert their effect by binding to the β 2-adrenergic receptor (β 2AR) on airway smooth muscle to cause bronchial relaxation. Polymorphisms in the β 2AR gene have been identified which may alter receptor function by changing the sensitivity, or regulation, of the receptor. The two most common polymorphisms of β2AR gene are Arg16Gly and Gln27Glu. Many studies have tried to evaluate the importance of these mutations to asthma susceptibility, phenotypes, and bronchial hyper-responsiveness [34] . Contopoulos-Ioannidis and colleagues compiled a meta-analysis to determine the strength of these polymorphisms with the aforementioned asthma characteristics [34] . The Gly16 allele of the β 2AR gene probably doubled the risk of nocturnal asthma and modestly increased asthma severity when compared to the Arg16 allele. The modest increase in asthma severity may be associated with a greater frequency of nocturnal asthma. Neither the Gly16 nor the Glu27 allele contributed to asthma susceptibility or to the intensity of bronchial hyper-responsiveness. Whether polymorphisms of the (2AR gene decrease responsiveness to beta agonists and these changes that influence the outcomes are still controversial. Gender differences and asthma have always been of interest. A reversal of the prevalence of asthma between the two sexes occurs in adolescence when asthma becomes more prevalent in girls. More recently, the importance of sex in severe Recalcitrant Asthma 153 asthma has been noted in TENOR and ENFUMOSA in which a striking prominence of females has emerged in severe asthma cohorts [15, 35] . The ENFUMOSA study also revealed a strong association with asthma exacerbations and the menstrual cycle with exacerbations occurring premenstrually [13] . In contrast, the SARP did not find women to be overly represented in the severe asthma group but did have similar findings with regard to the association between asthma exacerbations and menses [11] . Of note, both studies represent recruitment trials and not random sampling. Progesterone has been recognized to play a role in menstrual related asthma and can relax smooth muscle, thus contributing in the airway tone in women [36] . Furthermore, gonadotrophin releasing hormone (GnRH) may directly influence inflammatory responses in the airways. On the basis of these findings, a strong case can be made that further research should be undertaken to understand the factors that explain why women have more severe asthma.

Environmental Risk Factors

Several environmental allergens have been studied, but a clear link to allergen exposure and asthma severity has not been fully ascertained. Asthma patients with Alternaria sensitization have a higher risk of severe asthma and death [9] . Rosenstreich and colleagues studied the role of cockroach allergy in inner-city children. The combination of both cockroach allergy and high level exposure was associated with more frequent hospitalizations for asthma and asthma impairment [37] . Such studies provide information on the link between allergen sensitization and exposure; further studies are needed to prove a “cause and effect” relationship between environmental allergens and asthma severity. The ENFUMOSA cohort was developed to better define the pathophysiology of chronic severe asthma and included both severe and mild-moderate asthma patients to identify differences that may suggest specific risk factors for severe disease. Although, atopy is identified as a strong risk factor of asthma development, the evidence from the ENFUMOSA study and the SARP indicated atopy is less apparent in severe disease [11, 13] . The ENFUMOSA subjects had reduced total serum IgE, fewer positive skin prick tests and RASTs to common allergens and the absence of a family history of allergy (Fig. 2 ). Furthermore, ENFUMOSA suggests that other environmental factors may be more important, such as infections and exposure to Aspergillus fumigatus and Alternaria [15] .

Infections

The coexistence of asthma and sinusitis is well appreciated with up to 50% of patients with sinus disease also carrying a diagnosis of asthma [38] . The SARP was formed to understand the mechanisms that contribute to severe asthma [39] . In severe asthma, a higher incidence of sinus disease was found in severe asthma. In other 154 S.M. Nyenhuis and W.W. Busse

Fig. 2 Percentage of positive skin-prick tests to common aeroallergens in asthmatic patients with well-controlled (hatched bars ) or severe (open bars ) asthma. # total number of subjects in each group with at least one positive reaction. Local 1 and Local 2 indicate the two most frequent allergens specific to the geographical region. *p < 0.05, (from [13] , with permission)

studies, patients with severe asthma had prominent abnormalities on computed tomography (CT) scanning of the paranasal sinuses to suggest that sinonasal involvement may be a risk factor of asthma severity [40] . Ten Brinke and colleagues studied the relationship between sinonasal inflammation and bronchial mucosal inflammation in severe asthma [38] . Standard CT scans of the paranasal sinuses assessed mucosa thickness. Extensive disease was found in 24% of the severe asthma subjects (Table 5 ). Using different measurements to assess the bronchial inflammation, for example, sputum eosinophilia and exhaled nitric oxide (NO), they found a direct relationship between the sinonasal mucosa thickness and markers of bronchial inflammation (exhaled NO, blood eosinophils, and the % sputum eosinophils) (Table 6 ). Mechanisms by which sinus disease may exacerbate asthma are not established but include the enhancement of systemic airway inflammatory responses, direct deposition of inflammatory mediators and cytokines from the upper airways into the lower airways, and rhinobronchial reflexes [38] . The treatment of sinus disease in children and adults with severe or refractory asthma has led to better asthma control in these groups [41] . However, the linkage between sinusitis and asthma, particularly severe disease, is not established. Mycoplasma pneumoniae is a common cause of both upper and lower respiratory infection and can exacerbate asthma. This pathogen has been recovered from the Recalcitrant Asthma 155

Table 5 Characteristics of patients with severe asthma with and without extensive sinus disease (from [38] , with permission from Elsevier) Extensive sinus Limited sinus disease (n = 21) disease (n = 68) p value Age (y)a 50.4 ± 14.8 42.7 ± 13.1 0.02 Female sex (%) 61.9 69.1 0.54 Age at onset of asthma (y)b 35.0 (1.0–63) 11.5 (0.5–68) < 0.001 Asthma duration (y)b 12.0 (2–43) 23 (2–63) 0.01 Maintenance oral steroids (%) 38.1 26.9 0.33 Nasal corticosteroids (%) 57.1 30.9 0.03 Dose ICS (µg/d)b 1600 (1600–3600) 1600 (1600–6400) 0.50 Smoking history (pack years)b 1 (0–10) 0 (0–10) 0.09 History aspirin/NSAID sensitivityc 4/5 6/19 0.05 Positive atopic status (%) 47.6 63.2 0.20 ICS . Inhaled corticosteroids, beclomethasone equivalent; NSAID , nonsteroidal anti-inflammatory drug a Mean ± SD b Median (range) c Only 24 patients were reported to have used these medications

Table 6 Comparison of physiologic and inﬂ ammatory parameters in patients with severe asthma with and without extensive sinus disease (from [38] , with permission from Elsevier) Extensive sinus Limited sinus disease disease (n = 21) (n = 68) p value

a Baseline FEV1 /VC (% predicted) 70.2 ± 20.9 75.4 ± 21.5 0.33 TLC (% predicted)a 102.8 ± 15.7 97.5 ± 15.2 0.19 FRC (% predicred)a 132.1 ± 34.6 111.8 ± 33.9 0.03 a KCO (% predicted) 80.9 ± 18.4 94.3 ± 15.6 0.006 b PC 20 histamine (mg/mL) 1.09 ± 2.4 0.79 ± 2.8 0.63 Exhaled NO (ppb)c 27.1 (2–124) 8.5 (2–76) 0.002 Blood eosinophils (109 /L)c 0.44 (0.05–1.12) 0.17 (0.01–1.29) < 0.001 Sputum eosinophils (%)c 7.3 (0–59) 0.7 (0–14) 0.007 VC , Slow inspiratory vital capacity; TLC , total lung capacity a Mean ± SD b Geometric mean ± SD (in doubling doses) c Median (range)

FEV1 : Forced Expiratory Volume in 1 second FRC: Functional Residual Capacity

K co : Diffusing Capacity NO: Nitric Oxide

upper and lower airways of patients with chronic stable asthma and has been proposed as a contributory factor to asthma severity [42] . In addition, Chlamydia pneumoniae has also been identified as a possible risk factor for severe asthma. In children, C. pneumoniae infections have been associated with asthma exacerbations [41] . 156 S.M. Nyenhuis and W.W. Busse

The presence of this organism has been associated with persistent airflow limitation in nonatopic adult-onset asthma, disease severity and a poor clinical outcome, when detected in sputum and lung biopsies [43, 44] . There is also some evidence that infection with Chlamydia pneumonia is associated with asthma severity. Hahn and colleagues studied Chlamydiae in severe corticosteroid-dependent asthma patients and found treatment with macrolide antibiotics, such as clarithromycin or azithro- mycin, led to improved asthma control [41] . Further studies are needed to identify the exact role these infections play in asthma and its severity. Viral infections of the upper respiratory tract have long been recognized as one of the most important precipitants of acute severe exacerbation of asthma in children and adults [45] . Johnston and colleagues determined that 80–85% of school-aged children with wheezing episodes tested positive for a respiratory virus with, rhinovirus, the most common isolate [45] . Furthermore, Nicholson and colleagues demonstrated that approximately half of exacerbations in adults with asthma were associated with a viral infection [46] . Rhinoviruses (RV) are the cause of the common cold, but in the recent past, they were difficult to detect by standard virologic methods. With newer detection methods, such as reverse transcription polymerase chain reaction (RT-PCR), RV has been detected more frequently and are the predominant virus found in asthma exacerbations from a respiratory infection [45] . Respiratory viruses can have pro-inflammatory and immunomodulatory effects in the airways that could lead to asthma exacerbations [47] . When RV infects the epithelial cells of the airway, it initiates a cascade of events which inhibits viral replication and programmed cell death, and as a consequence effective viral elimination. In some asthma patients, there may be a defect in this process secondary to a deficiency in interferon-β production [44] . This deficiency can lead to the persistence of RV in the airways thus establishing a vicious cycle of pro-inflammatory responses that eventually causes tissue edema, lower airway obstruction, and heightened airway responsiveness. Furthermore, airway abnormalities from RV infection may last up to six months after an exacerbation in children. In infancy, an RV infection early in life is a strong predictor of subsequent wheezing, suggesting that RV might also be important in the pathogenesis and chronicity of asthma [44] . Studies have suggested that RV and its subsequent effects on the airway may also play a role in asthma severity. When RV infections occur in vivo , T helper-1 (Th1) responses are induced with the production of interferon-γ (IFN-γ ). There is also evidence that some asthma patients have reduced Th1 production. In addition, decreases in IFN-γ production to dust mites may be related to asthma severity and persistence [48] . Brooks and colleagues further proposed that a defective Th1 response to RV could be associated with clinical features of greater asthma severity. Their results were consistent with their proposed findings as Th1 responses to RV, γ γ as measured by IFN- or IFN :IL-5 ratio, correlated with methacholine PC20 and

FEV1 , respectively. They also noted an association between measures of asthma severity and IFN- γ generation to be limited to RV and not occur with other mitogens or tetanus toxoid [49] . These findings suggest that respiratory viruses may also Recalcitrant Asthma 157 play a role in asthma severity, and a defective Th1 response may be a factor. Additional research will have to be carried out to further characterize the role of RV in asthma severity.

Smoking

Cigarette smoking contributes to the severity of asthma. Asthma patients who are smokers are more symptomatic and have more frequent and severe exacerbations as well as an accelerated decline in lung function [10] . Furthermore, when the efficacy of both inhaled and oral corticosteroids in tobacco users with asthma was investigated, smokers were less responsive to short-term inhaled corticosteroid treatment. More recently, Tomlinson and colleagues found that cigarette smokers with asthma were relatively insensitive to long-term administration of low-dose inhaled corticosteroid therapy as well [50] . Finally, Chaudhuri and colleagues found similar results but in patients treated with short-term high-dose oral corticosteroids [51] . The mechanisms of corticosteroid resistance in tobacco smokers are poorly understood, but several possibilities have been proposed. First, smokers with asthma have increased sputum neutrophils when compared with nonsmokers with asthma [51] . Airway neutrophilia has been associated with a poor response to inhaled corticosteroids. Second, there is a change in the glucocorticoid α : β receptor ratio which may be caused by elevated levels of tumor necrosis factor-␣, a growth factor, often found in smokers [51] . Finally, smokers have decreased histone deacetylase activity which is required for glucocorticoids to exert their maximal suppression of cytokine induction [52] . Without a full suppression of cytokine induction, there may be an increase in inflammatory gene expression that leads to a decrease in response to treatment [52] .

Obesity

A recent large-scale epidemiologic study of severe/difficult-to-treat patients with asthma (TENOR) suggested that the body mass index increases with greater severity of disease in adults [35] . In this cohort of severe/difficult-to- treat asthma, 76% of the patients were obese or overweight. In the SARP cohort, patients with moderate asthma were equally as obese as patients in the severe asthma group, but this was not as large a group as TENOR [11] . Weight loss has been reported to improve lung volumes, but the relationship to airway obstruction, reactivity, and asthma symptoms has been more controversial [53, 54] . One must consider other comorbidities in this patient population, such as obstructive sleep apnea (OSA), as it may also affect overall lung function, and treat them as appropriate. 158 S.M. Nyenhuis and W.W. Busse

Gastroesophageal Reflux Disease (GERD)

Gastroesophageal reflux disease (GERD) affects almost 20% of adults in the United States on a daily basis. The prevalence of GERD is much higher in asthma reaching approximately 75% of this population [55] . GERD is considered an inciting factor of asthma symptoms as well as exacerbations. Esophageal acid reflux can elicit respiratory responses by causing decreases in airflow and oxygen saturation, and increases in respiratory resistance, minute ventilation, and respiratory rate. There are several mechanisms of esophageal acid-induced bronchoconstriction including a vagally-mediated reflex, heightened bronchial reactivity, and microaspiration. Esophageal acid can also elicit airway neurogenic inflammatory responses with the release of substance P, tachykinins, nitric oxide, and other cytokines. In asthma, there are factors that may promote GERD such as autonomic dysregulation, increased thoracic pressure, diaphragm dysfunction, and medications [55] . Asthma subjects have the evidence of autonomic dysregulation which can lead to a heightened vagal responsive. This increased responsiveness could also result in decreased lower esophageal sphincter (LES) pressure and transient relaxation of the LES, which is a main mechanism of GERD [55] . Secondly, chronic airflow obstruction causes a greater negative pleural pressure to increase the pressure gradient between the thorax and the abdominal cavity to promote reflux. Thirdly, hyperinflation can cause geometric flattening of the diaphragm to relax the LES and subsequently allow acid reflux into the esophagus. Finally, asthma medi- β cations, theophylline, and inhaled 2 -adrenergic agonist in some studies, have been noted to worsen GERD symptoms [55] . The significance of GERD to overall asthma management is still unresolved and further research is needed. A proposed management approach to GERD symptoms in adults with asthma includes a 3 month trial of high-dose proton pump inhibitor. If treatment failure occurs, a 24 hour esophageal pH test should be performed while monitoring symptoms. A precise link between GERD and a decline in asthma control is yet to be established as varying degrees of improvement in asthma have been observed with the treatment of GERD [41] .

Adherence

Problems with treatment adherence and hence apparent greater disease severity may be a factor in the loss of asthma control. It is no surprise that patients with the highest levels of adherence have significantly fewer exacerbations [56] . In addition, Milgrom and colleagues have suggested that poor control in children and adolescents is related to the adherence to corticosteroid therapy [57] . Prescription refills for ICS are approximately two to four canisters/year, implying that problems of adherence are not limited to severe asthma but occur across all severities [10] . Attempts to promote adherence to prescribed therapy should be made for all patients. If patients admit to poor adherence, the reasons should be established [56] . Recalcitrant Asthma 159

Table 7 Health Care Utilization Parameters in Psychiatric Cases and Noncases Among Patients with Severe Asthma (from [60] , with permission) Cases Noncases ( n = 21 ) (n = 77 ) Health Care Utilization Parameters n % n % p value GP visits: ≥ 4 last year 15 71.4 23 29.9 0.02 Chest physician visits: ≥ 4 last year 17 81.0 60 77.9 0.78 Emergency visits: ≥ 2 last year 15 71.4 24 31.2 0.01 Exacerbations: ≥ 2 last yeara 12/13 92.3 29/51 56.9 0.02 Hospital admissions: ≥ 2 last year 4 19.0 4 5.2 0.04 Maintenance of oral corticosteroids 8 38.1 26 33.8 0.71 Ever ICU admission 3 14.3 8 10.4 0.62 Ever mechanical ventilation 3 14.3 2 2.6 0.03 Definition of abbreviations : GP = general practitioner; ICU = intensive care unit a For the exacerbation analysis, only the 64 patients without maintenance oral steroids were considered

Finally, if adherence is a concern, even after a thorough patient history and asthma education, an early morning cortisol level may be checked to ascertain the level of cortisol secretion for patients on oral corticosteroids [10] . Previously, psychologic problems have been associated with near-fatal asthma, but more extensive studies have not substantiated this relationship [10] . Studies have also suggested that psychologic disease is not more common in severe asthma compared to society in general [58– 60] . However, patients with severe asthma, who frequently utilize health care, do exhibit more psychopathology (Table 7 ). The majority of the psychological abnormalities center on anxiety, depression, and a lack of trust for health care providers [61] . These psychological abnormalities often lead to noncompliance with medications, irregular follow-up, and suboptimal asthma management [60] . Other forms of psychopathology, such as bipolar disorder, personality disorders, and schizophrenia, have not been found to occur more often in patients with severe asthma [10] .

Histological Features of Severe Asthma

The role inflammation in the pathogenesis and pathophysiology of severe corticosteroid- dependent asthma continues to be an area of study. Wenzel and colleagues have found differences in the inflammatory pattern among asthma patients on high-dose inhaled glucocorticoids compared wiht milder asthma and normal controls [1, 62] [Table 8]. Eosinophils were found to be most prominent in the moderate severe asthma subjects (not on glucocorticoids) compared with the normal controls and severe asthma subjects (p < 0.007). Furthermore, the airway tissue of severe asthma subjects dependent on high doses of glucocorticoids had a two-fold higher concentration of neutrophils compared 160 S.M. Nyenhuis and W.W. Busse

Table 8 BAL cell differentials among asthmatics on high dose glucocorticoids (severe asthma) when compared with milder asthmatics and normal controls (from [1] , with permission) Total Cells Macrophages Lymphocytes Eosinophils a Neutrophils b Group (× 10 4 ) (× 10 4 ) (× 103 ) (× 10 3 ) (× 103 ) Normal (n = 6) 10.2 (7.9–11.8) 9.2 (7.1–10.9) 6.5 (4.8–10.0) 0 (0–0.3) 0.5 (0–1.5) Mild-moderate 10.0 (7.6–10.8) 7.8 (7.0–9.2) 3.0 (1.3–6.9) 2.3 (1.0–3.8) 1.0 (0–2.1) asthma (n = 12) Severe asthma 11.5 (8.2–21.3) 7.9 (6.6–17.2) 5.8 (3.9–16.7) 1.2 (0–2.1) 2.6 (1.2–8.7) ( n = 14) All values given as median with interquartile range a Significant difference among the groups, p < 0.007 b Significant difference among the groups, p = 0.032

Table 9 Sputum characteristics of severe asthmatics when compared with normal controls and milder asthmatics (from [63] , with permission)a Normal Mild asthma Moderate asthma Severe asthma Volume, ml 2.9 (2.5–3.2) 2.9 (2.2–3.6) 2.6 (1.9–3.2) 2.7 (2.1–3.5) TIC, × 10 6 /ml 0.67 (0.46–1.03) 1.10 (0.54–2.14) 1.36 (0.54–2.14) 1.87 (1.31–5.42) bc Tmac, × 106 /ml 0.43 (0.26–0.76) 0.66 (0.35–1.10) 0.55 (0.27–1.57) 0.53 (0.42–0.81) Tneu, × 106 /ml 0.22 (0.11–0.34) 0.25 (0.20–0.71) 0.64 (0.32–1.02) 1.20 (0.55–2.61) de Teos, × 106 /ml 0 (0–0) 0.03 (0.01–0.09) f 0 (0–0.06) 0.04 (0–0.33) g Tsq, × 10 6 /ml 0.20 (0.14–0.32) 0.18 (0.10–0.31) 0.17 (0.10–0.30) 0.20 (0.07–0.27) Macrophages, % 71.7 (57.8–78.6) 58.3 (47.7–66.1)g 49.9 (40.2–62.4) 33.1 (11.6–57.8) cd Neutrophils, % 27.7 (20.6–42.2) 35.4 (29.8–46.1) 48.9 (37.1–57.6) 53.0 (38.4–73.5) cg Eosinophils, % 0.0 (0.0–0.1) 4.2 (1.9–8.0)hi 0.5 (0–26) 4.5 (0.3–11.4) d Lymphocytes, % 0.2 (0.0–0.3) 0.2 (0.0–0.3) 0.0 (0.0–0.6) 0.0 (0.0–0.3) Squamous 22.5 (17.4–32.2) 18.8 (8.2–29.1) 13.9 (7.9–34.1) 6.1 (2.5–46.1) epithelium, % ECP, ng/ml 7.3 (0–24) 60.7 (29.6– 32.5 (7.5–84.5) 163.6 (90.2– 163.6) b 717)cj IL-8, ng/ml 0.3 (0.2–0.6) 1.5 (0.4–2.6) 1.9 (1.5–2.7) a 3.6 (2.3–5.8) de MPO, ng/ml 0 (0–2.5) 4.6 (0–23.2) 15.7 (4.2–32.4)e 26.0 (16.8–38.5) cd Definition of abbreviations: ECP = eosinophil cationic protein; IL-8 = interleukin-8; MPO = myclo- peroxidase; Teos = total eosinophil count; TIC = total inflammatory cell count; Tmac = total macrophage count; Tneu = total neutrophil count; Tsq = total squamous epithelial cell count a Data shown as medians with 25–75 percentiles shown in parentheses b p < 0.01 compared with normal c p <0.05 compared with mild asthma d p < 0.001 compared with normal e p < 0.01 compared with mild asthma f p < 0.01 compared with normal g p < 0.05 compared with normal h p < 0.001 compared with normal i p < 0.05 compared with moderate asthma j p < 0.01 compared with moderate asthma with moderate asthma group (not on glucocorticoids) and normal subjects. Jatakanon and colleagues have also detected higher concentrations of neutrophils in the sputum of severe asthma subjects when compared with normal subjects and milder asthma patients [63] [Table 9 ]. These findings suggest that in severe asthma Recalcitrant Asthma 161 requiring high doses of glucocorticoids inflammation persists, particularly neutrophilic, which may be due to the severity of the disease, glucocorticoid treatment, or undefined factors [1] . Oral corticosteroids increase the number of neutrophils in biopsy tissues and lavage specimens while effectively eliminating eosinophils. Unlike eosinophils, neutrophils are resistant to treatment with glucocorticoids. However, leukotriene and superoxide production may inhibit of neutrophil apoptosis. Glucocorticoids may also reduce the eosinophil/lymphocyte driven process while leaving behind or even augmenting a neutrophil mediated process [1] . Severe asthma is, however, likely to be a heterogenous population. To further characterize the different histopathologic mechanisms in severe asthma, Wenzel and colleagues studied severe asthma patients dependent on glucocorticoids and separated them into two histopathologic groups: Eosinophils present (low to moderate concentration of eosinophils on endobronchial biopsy compared with normal controls) and eosinophil absence (nearly absent eosinophils on endobronchial biopsy) [62] . The low eosinophil group had a lower FEV 1 % predicted (Tables 10 and 11 ). In contrast, the eosinophil positive subjects had a significantly higher incidence of respiratory failure and mechanical ventilation as well as thicker

Table 10 The physiologic characteristics of severe asthma patients dependent on glucocorticoids separated into two subgroups: (+) eosinophils and (–) eosinophils based on endobronchial biopsy (from [62] , with permission) Eosinophil (−)a Eosinophil (+) a ( n = 14) ( n = 20) p value

FEV 1, % pred 42 (33–58) 56 (34–66) 0.05 BD response, % 25 (12–50) 22 (15–35) 0.69 RV, % pred 191 (155–294) 210 (167–242) 0.95 Vtg, % pred 109 (93–150) 108 (393–131) 0.68 FVC/SVC 97 (89–100) 88 (71–94) 0.03 Definition of abbreviations : BD = bronchodilator; FVC/SVC = forced vital capacity/ slow vital capacity; RV = residual volume; Vtg = thoracic gas volume a Values are expressed as median (interquartile range)

Table 11 The clinical characteristics of severe asthma patients dependent on glucocorticoids separated into two subgroups: (+) eosinophils and (–) eosinophils based on endobronchial biopsy. (from [62] , with permission) Eosinophil (−) Eosinophil (+) ( n = 14 ) ( n = 20 ) p value Age, yr a 28 ± 3 34 ± 3 0.22 M/F 7/7 8/12 0.68 Cauc/AA + Hisp 12/2 16/4 0.67 Asthma duration, yr a 22 ± 3 19 ± 3 0.51 Steroid dose, mg/d a 27 ± 4 29 ± 5 0.85 Intubation (Y/N) 1/13 12/8 0.004 a Values are mean ± SEM. 162 S.M. Nyenhuis and W.W. Busse sub-basement membrane (SBM). The FVC/SVC ratio, (as a potential indicator of airway collapse during forced expiration) was lower (indicating more collapse) in the eosinophil positive group (p = 0.03). These findings suggest that there are at least two different and distinct pathologic processes, based on the presence or absence of eosinophils, which present clinically and physiologically as “severe, refractory asthma”. This information may have implications for the treatment of not only severe asthma but also asthma of all severity.

Management of Severe Asthma

When approaching a patient with recalcitrant asthma, there are at least four components to consider: (1) confirm the diagnosis of asthma, (2) evaluate and treat confounding or exacerbating factors, (3) evaluate possible asthma phenotypes, and (4) optimize the “standard” asthma pharmacotherapy [10] [Fig. 3 ]. Confirmation of the diagnosis of severe asthma includes an extensive history and physical examination, a set of full pulmonary function tests (pre- and post-bronchodilator spirometry, lung volumes, and diffusing capacity), total eosinophil count, allergy skin testing, serum IgE, and chest X-ray. Depending on the findings from the above testing, chest computed tomography scan, a standard methacholine challenge, and/or laryngoscopy may also be helpful. These diagnostic tests can help differentiate small changes related to interstitial disease and mixed obstructive/restrictive disease, as well as evaluate for allergic bronchopulmonary aspergillosis, emphysema, bronchiolitis obliterans, and vocal cord dysfunction (paradoxical adduction of the vocal cords during inspiration) [9] . Severe asthma should also be evaluated and treated for confounding/exacerbating factors as well. Diagnostic tests to identify these factors include: A pH probe to evaluate GERD; a sinus computed tomography to evaluate chronic sinusitis (bacterial/fungal), nasal/sinus polyps, or surgically amenable disease; a sleep study to evaluate for obstructive sleep apnea; allergy skin testing; and an early morning cortisol to evaluate compliance/adherence to oral corticosteroids [10] . Vocal cord dysfunction may coexist with asthma and may not only be in the differential diagnosis for asthma but also an exacerbating and coexisting factor. Once these confounding factors are identified, they should be treated as effectively as possible. Inhaled allergens (animal dander, pollens, and dust mites) can cause airway inflammation. Unfortunately, the evidence to suggest that avoidance of environmental triggers affects asthma control is varied [44] . Furthermore, adherence should be assessed often, including pill counts, prescription refills, direct questioning, or serological testing if the patient is on corticosteroids or theophylline [41] . Distinct phenotypes of severe asthma have begun to emerge. Further characterization of these phenotypes may lead to changes in treatment and approaches. For example, adult-onset asthma appears to be less involved with allergic reactions, making allergen avoidance unnecessary. In addition, aspirin sensitive asthma and Recalcitrant Asthma 163

Fig. 3 Algorithm of possible strategies and recommendation for managing patients with difficult to control asthma despite maximum combination treatment. *Includes C pneumoniae and M pneumoniae. CF = cystic fibrosis. COPD = chronic obstructive pulmonary disease. CHF = chronic heart failure. ABPA = allergic bronchopulmonary aspergillosis (from [44] , Reprinted with permission from Elsevier) 164 S.M. Nyenhuis and W.W. Busse occupational-related asthma are additional phenotypes that might benefit from specific therapies, such as aspirin desensitization, use of 5-lipoxygenase inhibitors, and removal from occupational exposures [64] . Furthermore, an eosinophilic phenotype of severe asthma has been characterized by the presence of eosinophilic inflammation directly on sputum analysis or biopsy microscopy or indirectly on exhaled nitric oxide levels [64] . A predominance of eosinophils suggests that these patients may be more responsive to higher doses of corticosteroids or alternative inflammatory medications. Ten Brinke and colleagues studied the effect of parenteral corticosteroids in a small group of severe asthma patients with an eosinophilic phenotype [65] . Their findings suggest that aggressive anti-inflammatory treatment with parenteral corticosteroids (i.e. 120 mg intramuscular injection of triamcinolone) can result in improvements in post-bronchodilator FEV1 and a decreased use of rescue medication (Fig. 4 ). Finally, if there is limited evidence of inflammation histologically or diagnostically (normal exhaled nitric oxide levels), anti-inflammatory therapy may be less beneficial in this group of patients [64] . It is also important to establish whether patients with severe asthma are receiving adequate treatment. Undertreatment is consistently recognized in fatal and near fatal asthma and can be an important contributor to poor asthma control [41] . Standard treatment of severe asthma as outlined by The Global Initiative for Asthma (GINA), includes high-dose inhaled corticosteroids combined with a long-acting β 2 agonist as the preferred add-on therapy [66] . Alternative therapies include 5-lipoxygenase inhibitors, cysteinyl leukotriene receptor antagonist, and sustained released theophylline which can be added onto the combination therapy [45] . Some patients may have persistent and refractory symptoms as well as poor lung function despite the use of high-dose ICS and long-acting β 2 agonists. In this group, it is important to perform a trial of oral corticosteroid therapy. A clinical assessment along with spirometry before and after the treatment course can provide

Fig. 4 Effect of treatment with intramuscular triamcinolone ( circles) or placebo ( squares ) on postbronchodilator Forced Expiratory Volume in 1 s (FEV1) ( left panel ) and on rescue medication score (right panel ) in 22 patients with severe asthma. ( Open symbols ) Patients using corticosteroids on a daily basis. (Closed symbols) Patients not using oral corticosteroids on a daily basis. Lines represent median values (from [65] , with permission) Recalcitrant Asthma 165 useful information to the patient’s responsiveness to corticosteroid therapy [64] . If the patient does respond to an oral corticosteroid burst, titration to the lowest amount of oral corticosteroids to maintain control or stabilize symptoms should be undertaken. In a subset of patients with severe asthma, prolonged or chronic use of oral corticosteroids will be required; in these circumstances, the addition of a steroid sparing drug should be considered. A number of agents have been tried, including gold, cyclosporine, and methotrexate, all with limited benefit at best. Methotrexate has been the most studied steroid-sparing agent in asthma. A Cochrane review of the benefit of adding methotrexate to oral corticosteroids in steroid-dependent asthmatics evaluated the available, but conflicting, data in the current literature [67] . By performing a systematic review with a meta-analysis, the authors concluded that methotrexate may have a small steroid sparing effect, but the overall reduction in daily steroid use was not large enough to diminish steroid-associated adverse effects or offset the adverse effects of methotrexate. The decision to use methotrexate in any patient must be based on an individual assessment of the risks and benefits specific to that patient. Intravenous immunoglobulin (IVIG) has well appreciated anti-inflammatory and immunomodulatory properties and has been used in numerous disorders such as thrombocytopenia, Guillane-Barre syndrome, and Kawasaki’s disease [68] . In some studies, the use of high-dose intravenous human immunoglobulin in steroid- dependent severe asthma has been shown efficacious in the reduction of oral corticosteroids and suppression of persistent inflammation [68, 69] . The variability in response as well as the cost and inconvenience of IVIG has prevented its widespread use in the treatment of steroid-dependent severe asthma [44] .

New Approaches to Treatment of Severe Asthma

Our increasing knowledge on the cellular mechanisms involved in asthma and a need for better asthma therapies have led to a focus on cellular and molecular targets in the treatment of severe asthma. Humanized monoclonal IgG1 blocking antibody directed to IgE (omalizumab) removes circulating and tissue IgE but also promotes the loss of high affinity IgE receptor on mast cells, basophils, and dendritic cells [44] . These effects decrease mast-cell activation and sensitivity to lead to a reduction in eosinophil influx and activation and finally the suppression of airway inflammation [See the Anti-IgE chapter by J. DeMore, this volume]. Several studies have shown omalizumab to be effective in the treatment of severe allergic asthma when symptoms are not controlled with standard therapies. The outcomes affected by omalizumab therapy include exacerbations, hospitalizations, symptoms, and asthma-specific quality of life [70] . Anti-IgE’s effectiveness in severe asthma, which is often nonatopic, is not fully defined and other targeted treatment options may need to be studied. Other approaches target cytokines that induce allergic airway, and include monoclonal antibodies to interleukin-5 (IL-5) and tumor necrosis factor- α (TNF-α ). IL-5 is a 166 S.M. Nyenhuis and W.W. Busse

T helper (Th) type 2 cytokine involved in eosinophil production, activation, and survival. The presence of activated eosinophils is a cardinal feature of the allergic inflammation and is often found in severe asthma. The use of humanized monoclonal antibodies against IL-5 (mepolizumab) significantly reduces blood and sputum eosinophils, but only diminishes bone marrow and airway biopsy tissue approximately 50% in over 20 weeks of treatment [71] . Mepolizumab does not affect pulmonary responses to inhaled allergen and indexes of asthma control. Kips and colleagues, however, found a small, but significant improvement in FEV1 with a 0.3 mg/kg dose; no other clinical improvements were seen [72] . Despite its profound effect on blood and sputum eosinophils, mepolizumab has not produced striking changes in clinical outcomes in severe asthma. TNF-α has become a therapeutic target in a wide range of chronic inflammatory disorders including rheumatoid arthritis and Crohn’s disease. Given its effects on inflammation, TNF-α has also gathered interest in asthma. TNF-α has been shown to promote not only the recruitment of neutrophils but also eosinophils into the airways [73] . Howarth and colleagues found elevated levels of TNF- α in induced sputum from patients with steroid-dependent asthma [73] . Etanercept, a soluble TNF- α receptor-IgG1Fc fusion protein, has been evaluated in severe asthma in small prospective studies [71] . The results of these studies have shown promise by improving symptoms, lung function, asthma-related quality of life and airway hyper-responsiveness. Erin and colleagues conducted a double-blind, placebo-controlled trial with infliximab, a recombinant human- murine chimeric monoclonal antibody, that specifically and potently binds and neutralizes soluble TNF-α and its membrane-bound precursor [74] . Infliximab was well tolerated and decreased exacerbations in moderate persistent asthma. Larger clinical trials with these promising anti-TNFα monoclonal antibodies in severe asthmatics are in progress to more fully define the role of TNF-α in asthma.

Conclusion

Severe asthma may reflect only a small proportion of patients but, they account for the majority of the cost and morbidity of the disease. The pathophysiology, phenotypes, and effective treatment modalities of severe asthma are not well understood. Multi-center prospective cohorts such as SARP and ENFUMOSA provided a starting point to better define severe asthma, its risk factors, histopa- thology, and possible new therapies. Ongoing and future prospective cohorts will, hopefully, gather further insight into the pathophysiologic mechanisms of severe asthma and phenotypes that can then be used to determine novel biomarkers and more effective biologic therapies. Recalcitrant Asthma 167

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60. ten Brinke A, Ouwekerk ME, Zwinderman AH, Spinhoven P, Bel EH (2001) Psychopathlogy in patients with severe asthma is associated with increased health care utilization. Am J Respir Crit Care Med 163:1093–1096 61. Kolbe J, Fergusson W, Vamos M, Garrett J (2002) Case-control study of severe life threatening asthma (SLTA) in adults: Psychological factors. Thorax 57:317–322 62. Wenzel SE, Schwartz LB, Langmack EL, Halliday JL, Trudeau JB, Gibbs RL, Chu HW (1999) Evidence that severe asthma can be divided pathologically into two inflammatory subtypes with distinct physiologic and clinical characteristics. Am J Respir Crit Care Med. 160:1001–1008 63. Jatakanon A, Uasuf C, Maziak W, Lim S, Chung KF, Barnes PJ (1999) Neutrophilic Inflammation in Severe Persistent Asthma. Am J Respir Crit Care Med 160:1532–1539 64. Wenzel, S and Szefler SS (2006) Managing severe asthma. J Allergy Clin Immunol 117:508–511 65. ten Brinke A, Zwinderman AH, Sterk PJ, Rabe KF, Bel EH (2004) “Refractory” Eosinophilic Airway Inflammation in Severe Asthma. Am J Respir Crit Care Med 170:601–605 66. Global Initiative for Asthma. Global strategy for asthma management and prevention. A six part management program. NIH publication number 02-3659 http://www.ginathma.org 67. Davies H, Olson L, Gibson P (2000) Methotrexate as a steroid sparing agent for asthma in adults. Cochrane Database Sys Rev 2:CD000391 68. Haque S, Boyce N, Thien FC, O’Hehir RE, Douglas J (2003) Role of intravenous immunoglobulin in severe steroid-dependent asthma. Intern Med J 33:341–344 69. Salmun LM, Barlan I, Wolf HM, Eibl M, Twarog FJ, Geha RS, Schneider LC (1999) Effect of intravenous immunoglobulin on steroid consumption in patients with severe asthma: A double-blind, placebo-controlled, randomized trial. J Allergy Clin Immunol 103:810–815 70. Niebauer K, Dewilde S, Fox-Rushby J, Revicki DA (2006) Impact of omalizumab on quality- of-life outcomes in patients with moderate-to-severe allergic asthma. Ann Allergy Asthma Immunol 96:316–326 71. O’Byrne PM (2006) Cytokines or Their Antagonists for the Treatment of Asthma. Chest 130:244–250 72. Kips JC, O’Connor BJ, Langley SJ, Woodcock A, Kerstjens HAM (2003) Effect of SCH55700, a humanized anti-human IL-5 antibody, in severe persistent asthma. Am J Respir Crit Care Med 167:1655–1659 73. Howarth PH, Babu KS, Arshad HS, Lau L, Buckley M, McConnell W, Beckett P, Al Ali M, Chauhan A, Wilson SJ, Reynolds A, Davies DE, Holgate ST (2005) Tumour necrosis factor (TNF a ) as a novel therapeutic target in symptomatic corticosteroid dependent asthma. Thorax 60:1012–1018 74. Erin EM, Leaker BR, Nicholson GC, Tan AJ, Green LM, Neighbour H, Zacharasiewisz AS, Turner J, Barnathan ES, Kon OM, Barnes PJ, Hansel TT (2006) The effects of a monoclonal antibody directed against tumor necrosis factor-a in asthma. Am J Respir Crit Care Med 174:753–762 Mechanisms and Management of Exercise- Induced Bronchoconstriction

John D. Brannan and Paul M. O’Byrne

Introduction

The term “exercise-induced asthma” has been used to describe the transient narrowing of the airways and the subsequent increase in airway resistance, which can occur during, though more commonly following, vigorous exercise [1] . Exercise is a trigger for bronchoconstriction in individuals with asthma, but is not considered an independent risk factor for the development of asthma. The term “exercise-induced asthma” can be misleading and in some individuals, symptoms and airway narrowing can develop as a result of acute vigorous exercise in the absence of other clinically recognized symptoms of asthma [2] . Thus, the term exercise-induced bronchoconstriction (EIB) is now generally preferred to be a more accurate reflec- tion of the underlying pathophysiology.

Epidemiology

EIB can occur in the majority of individuals with symptoms of asthma [3] . The epidemiology of EIB has been confined to specific populations that are easier to study, such as in school children [4] , athletes in high school [5] or college [6] , summer and winter elite athletes [7– 9] as well as army recruits [10] . The prevalence of EIB in the above populations has been reported to be between 7% and 50% depending on the type of sport and environment where the exercise is performed. Athletes in winter sports have generally been observed to have a higher prevalence of EIB than those engaged in summer sports. Longitudinal studies have demonstrated that the prevalence of EIB is increasing [11] and EIB is more common in urban environments

J.D. Brannan () and P.M. O’Byrne Firestone Institute for Respiratory Health and the Department of Medicine , Michael G DeGroot School of Medicine, McMaster University , 50 Charlton Ave, East, Room T3213 , Hamilton , ON , Canada L8N 4A6 e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 171 DOI 10.1007/978-4-431-99362-9_10, © Springer 2010 172 J.D. Brannan and P.M. O’Byrne than in rural environments [12] . Although associated with atopy [13] , EIB can occur in those who are nonatopic [14] . An important observation from many of these studies is that up to 40% of individuals with EIB have not had a diagnosis of asthma and most have normal lung function prior to exercising. Thus, symptoms and lung function can be poor predictors of EIB in these individuals. Further, findings in epidemiological studies suggest that EIB may be a precursor for the development of persistent asthma [15] . A worldwide survey of asthma reported that in more than 10,000 individuals who were currently taking asthma medications or had symptoms in the previous year, nearly half reported exercise-induced symptoms, suggesting poor asthma control [16] . There is little information with regard to mortality related to EIB in either the general population or elite athletes. A retrospective analysis in North America over a 7-year period reviewed 61 asthma deaths that were closely associated to a sporting event or physical activity [17] . Many of these deaths occurred in individuals with mild asthma, while the majority (81%) occurred in individuals who were younger than 21 years of age. Almost 60% of deaths occurred in individuals who were considered elite or competitive level athletes. An important and yet disturbing finding was that 10% of deaths occurred in individuals with no known history of asthma or EIB.

Pathogenesis

Early observations found that the intensity and duration of exercise as well as the temperature and humidity of the inspired air were important for the development of EIB [18] . During exercise, ventilation increases and the cooling and/or drying of the airways were considered important in causing exercise-induced airway narrowing. The osmotic and thermal effects of respiratory water loss are now thought to be the primary determinants for airway narrowing due to exercise [1] . This is supported by the finding that EIB is attenuated when the inspired air is more fully humidified and closer to body temperature and that EIB can occur when hot dry air is inspired [1] . The increase in the osmolarity of the airway surface is thought to result in the release of mediators of bronchoconstriction from inflammatory cells [19– 21] . These mediators (e.g., leukotrienes, prostaglandins, histamine) then act via specific receptors on the bronchial smooth muscle to cause contraction and airway narrowing. Both airway inflammation and airway hyperresponsiveness (AHR) are important features of EIB. Early evidence using pharmacotherapy to inhibit EIB provided significant insight into the potential role of inflammation on the airway response to exercise.

Inhaled b 2 agonists were the first drugs to be shown to protect against EIB [22] . While confirming the beneficial effects of inhaled b 2 agonists, it was later found that oral b 2 agonists were not effective at protecting against EIB, even though they caused bronchodilation [23] . This suggested that the superior efficacy of an inhaled b 2 agonist against EIB was due to an added benefit of acting directly on the airway surface. Management of EIB 173

It was suggested that the ability of a b 2 agonist to relax the airway smooth muscle and stabilize the mast cell provided an important duel mechanism for bronchoprotection [23] . This was supported by studies that demonstrated that sodium cromoglycate was also effective at inhibiting EIB, likely via inhibiting the release of mast cell mediators [24] . In addition, daily treatment with inhaled corticosteroids (ICS) reduced the severity of EIB, suggesting that airway inflammation was an important determinant of the presence and severity of EIB [25] . The involvement of inflammatory mediators such as the leukotrienes in sustaining airway narrowing due to exercise was later demonstrated using specific receptor antagonists for leukotrienes [26] . Direct evidence for airway inflammation in EIB has been provided by the finding of significantly more eosinophils in the sputum of asthmatics with EIB compared to those without EIB [27, 28] . Further, the severity of EIB is related to the number of eosinophils in both sputum and blood [27, 29] . There is also evidence that the levels of exhaled nitric oxide, a marker of nonspecific inflammation, are related to the airway response to exercise [30] and are associated with atopy [14] . There is increasing evidence that mast cell mediator release occurs in association with EIB. Studies attempting to measure mediators of bronchoconstriction have identified increases in arterial plasma histamine levels measured at the time of maximal airway narrowing to exercise [31] . Leukotriene E4 or the metabolite of prostaglandin D2 , 9 a , 11 b -PGF2 , a marker of mast cell release, are measured in urine [20, 21, 32] and sputum following EIB [33, 34] . An imbalance of bronchoconstricting leukotrienes and histamine compared to the bronchodilating mediator

PGE2 after exercise has also been suggested [34] . While it has been shown that EIB is not a cause of eosinophilic airway inflammation [35] , there may be an increased likelihood of airway injury as seen by the release of columnar epithelial cells in association with the severity of EIB [34] . Recently, it has been observed that nonasthmatics can release a variety of bronchoconstricting mediators following either exercise or surrogate tests that mimic EIB [36] . These observations have highlighted the importance of airway smooth muscle sensitivity in EIB. This has led to the suggestion that the development of EIB in elite athletes may be the result of chronic airway dehydration and airway damage due to regular high intensity exercise [37] . AHR to histamine or methacholine is often associated with airway narrowing due to exercise [29, 38] . However, in some cases, EIB can occur in the absence of AHR to either methacholine or histamine [4, 39] . It is known that a wide variety of mediators are involved in EIB and that leukotrienes are more potent at causing airway narrowing than methacholine or histamine [40] . This suggests that the airway smooth muscle in some individuals with EIB may be more sensitive to the bronchoconstricting effects of leukotrienes and other mediators. Allergen exposure has been shown to increase EIB. The percent fall in forced expiratory volume in 1 s (FEV1 ) after exercise in asthmatic children is more severe after allergen challenge [41] . The effect of allergen exposure on EIB is likely to be due to increases in airway sensitivity and the number of airway inflammatory cells (e.g., mast cells, eosinophils) following acute allergen exposure [42] . 174 J.D. Brannan and P.M. O’Byrne

Clinical Manifestations

The clinical presentations of EIB are the sudden onset of symptoms typical of asthma, such as wheeze, chest tightness, cough, and shortness of breath. Other nonspecific symptoms such as chest or abdominal pain, headaches, muscle cramps, fatigue, dizziness, poor exercise performance or “feeling out of shape” have also been described [43] . While those experiencing symptoms may seek medical assistance, it has been demonstrated that self reported symptoms are poor predictors of the presence or severity of EIB [6, 8] . A personal history or family history of asthma or allergic rhinitis may increase the likelihood of EIB [43] . EIB can occasionally occur during exercise itself and may be reflective of more severe EIB. However, bronchodilation can occur during exercise and last for 1–3 min following the cessation of exercise [44] . This is soon followed by bronchoconstriction with the maximum response seen 10–15 min after exercise, with spontaneous recovery of lung function often occurring by 60 min. In about 50% of the patients, the recovery from bronchoconstriction is followed by a refractory period, whereby there is a protective effect against further EIB if exercise is to be continued [45] . This protective effect usually lasts less than 4 h and is thought to involve the release of inhibitory prostaglandins in the airways [46, 47] . In some patients with very mild EIB, strenuous exercise may not cause clinically significant bronchoconstriction and the abnormal airway response to exercise is not reproducible.

Diagnosis

As symptoms and lung function are poor predictors of the presence or severity of EIB, the use of exercise challenge testing is recommended to identify EIB [48, 49] . In addition, there has been a need for the development of a surrogate test for EIB as there are some limitations to laboratory exercise challenge testing [50, 51] . As previously described, the major factors that determine the severity of EIB are pulmonary ventilation reached and sustained during exercise and the water content and temperature of the inspired air. Thus, any exercise challenge must control the rate of water loss from the airways by monitoring the ventilation during exercise and controlling the water content of the inspired air. As a result, exercise challenges have been standardized and conventionally involve 6–8 min of exercise on a treadmill or cycle ergometer [52] . A source of compressed dry air is recommended to standardize the inhaled air during exercise and minimize the water content for effective airway drying. During the period of exercise, a suitable level of intensity is assessed by monitoring the heart rate so that 80–90% of the predicted maximum heart rate is reached and sustained for at least 4 min. However, it is recommended that ventilation, which is the provoking stimulus, also be measured during exercise to achieve a ventilation rate of at least 40–60% of the predicted maximum voluntary ventilation (MVV) [52] . Management of EIB 175

FEV1 should be the primary outcome variable to assess the airway response to exercise. As the maximum response often occurs 6–8 min following exercise, the

FEV 1 should be measured before and at regular intervals for at least 20–30 min following exercise [52, 53] . EIB is identified if a 10% fall in FEV1 in adults and a

15% fall in FEV1 in children occurs following exercise [52] . It has proved difficult to standardize exercise testing among laboratories. Further, the sensitivity of these laboratory-based exercise tests to identify EIB, even when the inspired air is cool and dry, has been reported to be only 65% in treated adult asthmatics [53] and even less, at 22%, when compared to field exercise tests [54] . The surrogate bronchial provocation tests, which have been developed through the understanding of the mechanism of EIB, provide some advantages in the identification of EIB [50, 51] . Ecuapnic voluntary hyperpnea (EVH) for 6 min at 80% of MVV using dry air containing 5% CO2 is more likely to achieve a greater sensitivity to identify airway narrowing compared to a progressive exercise challenge [55] . Higher ventilation rates are achieved more rapidly with EVH than a progressive exercise challenge [50] . However, while EVH tests are recommended for athletes with normal lung function, they should be used with caution, since falls in FEV1 of more than 50% can occur in known asthmatics. The recently developed dose- response osmotic challenge tests have identified EIB in asthmatics and athletes, and can predict the severity of EIB in steroid naïve asthmatics [19, 56] . However, in a less clearly defined asthmatic population, AHR to methacholine and mannitol have demonstrated similar sensitivity [57] . The osmotic challenge tests can present a safe and less complex alternative for the identification of EIB that will respond to therapy [57, 58] .

Differential Diagnosis

Physiological dyspnea after exercise must be considered in patients with no evidence of EIB, particularly in those who derive no benefit from pretreatment with bronchodilators. Central airway obstruction, vocal cord dysfunction, laryngotrache- omalacia, parenchymal pulmonary disease, gastroesophageal reflux, and heart failure should also be considered in adult patients who suffer from atypical exercise- induced dyspnea (EID). The differential diagnosis is similar among children. In a retrospective review, treadmill exercise testing was performed on 142 children with EID, referred to a pediatric allergy and pulmonology clinic, who had no other signs of asthma or in whom treatment with b 2 agonists had failed [59] . Symptoms of EID were reproduced in 117 children (82%). Among these, only 11 (9%) had EIB defined by the presence of symptoms and a >15% decrease in FEV1 from baseline following exercise. Other diagnoses included normal physiologic exercise limitation (63%), restrictive abnormalities (13%), vocal cord dysfunction (11%), laryngomalacia (2%), and hyperventilation and supraventricular tachycardia, each in one patient. 176 J.D. Brannan and P.M. O’Byrne

Management

The combination of pharmacologic and nonpharmacologic intervention can be effective in preventing airway narrowing in the majority of patients with EIB. The major goal of this combination is to ensure that exercise is not avoided by patients with EIB. Asthmatics should exercise as much as desired, and should be encouraged by the fact that athletes, in spite of symptomatic asthma, have won Olympic medals and played professional sports. Improved understanding of the pathophysiology of EIB has resulted in general recommendations that can help reduce its severity. These measures are based upon observed relationships between the severity of bronchoconstriction and the following factors:

Pharmacological

Treatment of EIB has been primarily studied in patients with EIB and underlying asthma. Therapeutic options for patients with EIB as the only manifestation of AHR are not well researched. In general, if EIB occurs frequently in patients with poorly controlled asthma, the most important strategy is to improve overall asthma control. ICS and leukotriene-modifying agents are often useful in this regard.

Prophylactic treatment of EIB prior to exercise, using inhaled b2 agonists and/or cromolyn or nedocromil sodium or leukotriene antagonists, should be considered in all patients with EIB.

b 2 Agonists

Inhaled b 2 agonists are the prophylaxis drug of choice to prevent and treat episodes of EIB in moderate to severe asthmatics. They are the most effective pharmacotherapy that can inhibit the severity of EIB. Two inhalations of a short acting b2 agonist (SABA) (e.g., salbutamol or turbutaline) or long acting b 2 (LABA) (e.g., formoterol) should be taken 5–10 min before exercise. These have been shown to reduce the fall in FEV1 by 70–80% [53, 60] . LABAs have a longer duration of bronchoprotection than SABAs. However, the LABA salmeterol has a slower onset of action and needs to be taken at least 30 min before exercise [61] . Furthermore, salmeterol is less effective in reversing EIB. However, equipotent doses of terbutaline, formoterol, or salmeterol appear to be equally effective in providing short- term control of EIB [62] . Patients with more severe asthma may require higher prophylactic doses of inhaled b 2 agonists or the addition of cromolyn or nedocromil sodium [63] . It should also be noted that not all patients have experienced this superior protective effect with a b 2 agonist and in these patients, other treatment strategies should be prescribed [64] . Children often present a difficult clinical situation by exercising vigorously Management of EIB 177 and intermittently throughout the day without treatment prior to exercise. In this setting, LABA can provide protection against EIB for most of the day [65, 66] . However, regular use of both LABA and SABA provide less effective protection against EIB than the prophylactic use of b 2 agonists [64, 67, 68] (Fig. 1 ). If patients forget to take prophylactic treatment for EIB or if they experience breakthrough symptoms despite treatment, bronchoconstriction should be treated with two to four inhalations of an inhaled b 2 agonist. However, recovery using a standard dose of rescue bronchodilator may also be limited by daily b 2 agonist therapy [64, 68] .

Cromoglycates

An alternative therapy is the prophylactic use of inhaled cromolyn or nedocromil sodium [69] . The bronchoprotective effect against EIB is immediate following inhalation. However, this protection does not extend beyond 2–3 h after treatment. As these drugs have a good safety profile and are well tolerated [69] , it has been proposed that the dose administered could be titrated to suit the individual [70] . In exceptional situations like very high performance athletes or patients exercising in extreme conditions (e.g., very cold, dry air), the combination of four inhalations of

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(L) 3.00 Treatment 2.75 Regular Pre-exercise Placebo Placebo 2.50 Salbutamol Placebo exercise 2.25 Placebo Salbutamol Salbutamol Salbutamol 2.00 pre post 0 102030405060 Treatment Time Post Exercise (min)

Fig. 1 Mean forced expiratory volume in 1 s (FEV 1) before and following a preexercise dose of 200 mcg of salbutamol or placebo followed by 5 min of constant work load exercise on a cycle ergometer in asthmatics with EIB. Exercise tests followed 7 days of regular treatment of 800 mcg per day of salbutamol and placebo. One week of regular treatment with salbutamol resulted in a decrease in baseline FEV1 , more marked EIB, and decreased protective effect of salbutamol on EIB. From [67] with permission 178 J.D. Brannan and P.M. O’Byrne

a b 2 agonist and four inhalations of cromoglycate is significantly more effective than either drug used alone [63] . Lower doses of nedocromil sodium are as effective as cromolyn sodium in protecting against EIB. However, they offer no clear advantage [69] .

Inhaled Corticosteroids

The most effective therapy to reduce the underlying pathology of asthma involves the use of ICS. While ICS may offer some improvement on EIB in the short-term [71] , they will have a greater improvement over weeks to months by decreasing the magnitude of bronchoconstriction that occurs with a given workload [72, 73] . Crossover studies of 4-week treatment periods of 100, 200, and 400 mcg per day of the ICS budesonide demonstrated a dose-dependent reduction in the response to exercise in asthmatic children [74] . However, improvements in symptoms and lung function were not dose-dependent and were observed to plateau at the lowest doses. More recently, it was shown that higher doses of ciclesonide over 3 weeks were more effective against EIB than lower doses [71] (Fig. 2 ). It was also demonstrated that these higher doses were superior in attenuating the elevated level of eosinophils observed in persons with more severe EIB [75] . This evidence suggests that persons

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Fig. 2 Individual data and the mean (SE) of the maximum decrease in FEV1 after exercise following 3 weeks treatment using four different doses of the inhaled corticosteroid ciclesonide (40,

80, 160, 320 mcg) in asthmatics with EIB. The maximum decrease in FEV 1 was reduced in all treatment groups and in most individuals before ( pre – open box) and following ( post – closed box) 3 weeks of ciclesonide. The greatest inhibition was seen using the highest daily dose of 320 mcg. From [71] with permission Management of EIB 179 with more severe EIB have more significant levels of airway inflammation and thus, may require a higher dose of ICS for effective inhibition of EIB. However, other studies in children have failed to demonstrate an ICS dose- dependent reduction in EIB, with doses of 100–200 mcg of budesonide per day or doses of 200–500 mcg of fluticasone per day [72, 76, 77] . For these reasons, a therapeutic trial of ICS is a reasonable approach in patients with EIB. Furthermore, if an objective measurement of a patient’s response to ICS is required, an exercise test or a surrogate test for EIB should be considered, as EIB is one of the last features of asthma to be resolved using regular ICS [73] .

The effects of combination therapy using inhaled b 2 agonists with ICS against EIB have not been extensively studied. One study has demonstrated a superior protective effect of salmeterol and fluticasone in persons with moderate EIB compared to fluticasone alone [78] . However, in many patients, the addition of a LABA did not completely inhibit EIB after 4 weeks of therapy [64, 78] .

Leukotriene-Modifying Agents

Antileukotrienes provide a therapeutic alternative in the setting of chronic asthma complicated by EIB. Leukotrienes play a significant role in EIB by contributing to and sustaining the reduction in lung function [26] (Fig. 3 ). Thus, treatment with a

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–20

–25 0357915202530354045 Time Post Exercise (min)

Fig. 3 The first evidence to demonstrate in asthmatics that the leukotriene receptor antagonist MK-571 administered intravenously inhibits EIB. Studies using oral montelukast have since demonstrated a similar protective effect on EIB, attenuating the reduction in FEV1 following exercise and causing rapid recovery to preexercise FEV1 values. From [26] with permission 180 J.D. Brannan and P.M. O’Byrne leukotriene modifying agent such as montelukast or an inhibitor of leukotriene synthesis such as a 5-lypoxygenase inhibitor can attenuate EIB [21, 79] . Protection against EIB is apparent even after a single dose of montelukast and recovery from post exercise bronchoconstriction is accelerated [80] . The long half-life of montelukast allows once-daily dosing to protect against EIB for up to 24 h [80] . Zileuton must be taken 4 times daily at present and while it demonstrates the same protection compared to montelukast, it has a shorter duration of action [79] . Leukotriene receptor antagonists appear superior to LABA when treating asthmatics with EIB, even in addition to regular ICS [81, 82] . In a blinded multicenter trial, asthmatics with EIB were randomly assigned to either montelukast or salmeterol for 8 weeks [83] . Therapy was protective within 3 days for both groups, however, tolerance to salmeterol developed. By 8 weeks, the bronchoprotective effect of montelukast had further improved. As previously mentioned, children with EIB can pose a therapeutic challenge, because they tend to exercise intermittently throughout the day and often neglect premedication with an inhaled b 2 agonist. Leukotriene receptor antagonists are an effective option in this setting.

Histamine (H1 ) Antagonists

Antihistamines have limited effectiveness in the treatment of EIB [84] . Limited protection has been reported in more severe EIB when exercise is at a higher intensity [85, 86] , but not in mild EIB [87] . The combination of antihistamines and antileukotrienes had no significant additive effect in either adults [87] or children [88] .

Dietary Modification

Diets rich in omega-3 fatty acids (e.g., fish oil), which have demonstrated anti- inflammatory activity, have not been conclusively demonstrated to be helpful in patients with asthma [89] . However, in athletes and asthmatics with EIB, there have been more promising results. In two randomized, double blind, crossover studies in athletes and asthmatics with mild EIB, 3 weeks of high dose fish oil supplementation significantly reduced the post exercise fall in FEV 1 [32, 33] . This occurred in association with a reduction in LTE4 and PGD 2 in the urine [32] and sputum [33] as well as IL-1b and TNF-a in blood [32] and sputum [33] . While no further improvement was seen in the preexercise FEV1 in this population with normal lung function, there was a reported decrease in the use of b 2 agonist. This suggests that in asthmatics with mild EIB, a diet enriched with omega-3 fatty acids may provide some benefit. Other studies have demonstrated attenuation of EIB with low salt diets [90] or increased dietary ascorbic acid (Vitamin C) [91] . However, these studies have also investigated persons with mild EIB and thus, it may be difficult to extrapolate these findings to persons who have more severe EIB, as observed in studies assessing the efficacy of established asthma pharmacotherapies [53, 75] . Management of EIB 181

Other Therapies

Other types of asthma therapy are not effective in protecting against EIB.

Anticholinergics [92] , oral b 2 agonists [23] , and methylxanthines [93] , when used alone, are ineffective at inhibiting EIB in the majority of patients. Several other treatment approaches have been tested and they demonstrate a protective effect against EIB. Inhaled furosemide [94] , prostaglandin E2 [95] , indomethacin [96] , and heparin [97] have been shown to protect against EIB. However, long-term clinical use of these compounds has not been directly compared with the prophylactic use of inhaled b 2 agonists. For this reason, their role in clinical practice is unclear.

Nonpharmacological

Avoiding exercise during periods of very cold weather, elevated airborne allergen, or high pollution, which may worsen EIB, should be recommended. Similarly, EIB is less severe when the inspired air is warmer and more humid. The use of a spe- cially designed face mask to trap expired water and humidify the inspired air can be of significant benefit when exercising in cold environments and may provide added benefit when used together with a b 2 agonist [98] . As previously described, a refractory period can occur and this has been used to recommend a warm up before exercise to prevent or minimize EIB. Exercising for 15 min at 60% of the maximum exercise intensity has been shown to reduce the severity of EIB, but will not inhibit the airway response [99] . However, it should be noted that nonsteroidal anti-inflammatory drugs can prevent any refractory period and thus, prevent any expected inhibition of EIB as a result of prior exercise [46] .

Conclusion

There are a variety of different approaches in choosing therapy to prevent EIB in the clinical setting. It is becoming increasingly clear that traditional clinical signs of asthma such as symptoms and lung function are poor predictors of the presence and severity of EIB. Thus, objective measures for EIB are useful in making informed decision to prescribe and monitor the benefits of therapy. In patients with uncontrolled asthma and those with persistent exercise-induced symptoms, treatment of the underlying inflammatory component of the disease using ICS is a first priority. If asthma is well controlled using ICS and EIB is the only manifestation of

AHR, EIB should be treated prophylactically with inhaled b 2 agonists or cromoglycates. Leukotriene-modifying agents are also effective and can be used in patients who refuse to take ICS because of unwanted side effects or fail to respond to ICS.

b 2 agonists remain the most effective treatment for acute episodes of EIB. Tolerance to the bronchoconstricting effects and the bronchodilator benefits of a b2 agonist 182 J.D. Brannan and P.M. O’Byrne

can occur with the frequent use of a b2 agonist, either with or without an ICS. Thus, using a cromolycate or leukotriene antagonist may be the best choice in this setting, as tolerance does not occur with regular use and side effects are minimal.

References

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Hironori Sagara, Kenya Kouyama, Takeshi Fukuda, and Sohei Makino

Introduction

Sustained-release theophylline is frequently used in Japan to treat asthma. Theophylline has a long history as a therapeutic drug. In the early twentieth century, Plavec et al. reported that theophylline has a positive inotropic action on the myocardium. Since 1937, when Herrman et al. confirmed its effectiveness for asthma attacks, theophylline has been primarily considered a bronchodilator. In the 1970s and 1980s, theophylline was mainly used for the long-term management of asthma in the United States. Since the 1990s, the mainstay of treatment for asthma in the United States shifted to inhaled corticosteroids or inhaled corticosteroids plus long-acting inhaled b 2 agonists (LABAs). The clinical positioning of theophylline was thus negatively affected. Since the latter part of the 1990s, however, evidence has accumulated that theophylline inhibits the airway inflammation characteristically found in asthma and can be used with inhaled corticosteroids to treat asthma. In this paper, we describe the clinical significance of sustained-release theophylline for the long- term management of asthma.

H. Sagara () and K. Kouyama Department of Respiratory Medicine, Dokkyo Medical University Koshigaya Hospital, Japan e-mail: [email protected] T. Fukuda Department of Pulmonary Medicine and Clinical Immunology, Dokkyo Medical University School of Medicine, Japan S. Makino Jobu Hospital for Respiratory Diseases, Japan

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 187 DOI 10.1007/978-4-431-99362-9_11, © Springer 2010 188 H. Sagara et al.

Properties of Sustained-Release Theophylline

Pharmacological Properties of Theophylline

Theophylline is metabolized by cytochrome P-450 enzyme systems in the liver. The rate of theophylline metabolism varies considerably among patients. The main metabolic pathways are demethylation and oxidation. Its metabolites are broadly distributed in the tissue and pass through the blood-brain barrier and placenta. The rates of protein binding range from 40 to 60%. In neonates with low serum albumin concentrations, elderly patients, and patients with cirrhosis, free theophylline concentrations may be higher than expected. Theophylline and its metabolites are excreted in the urine. The urinary excretion rate of unchanged theophylline is 10–15%. The urinary excretion rates of the main metabolites are about 50% for 1,3-dimethyl uric acid, 20% for 1-methyl uric acid, 15% for 3-methylxane, and less than 5% for 1-methyl xanthine. Generally, xanthine derivatives such as theophylline act on the central nervous system, heart, kidney, striated muscle, smooth muscle, and other organ systems. Theophylline most strongly acts on smooth muscle. Various actions, such as stimulation of the central nervous system, positive inotropic action, diuresis, cerebral vasoconstriction, and promotion of gastric-acid secretion can lead to side effects, depending on the dose and the response to theophylline. Theophylline acts primarily by phosphodiesterase inhibition and adenosine antagonism. Phosphodiesterase is a hydrolytic enzyme of cyclic adenosine monophosphate (AMP), which is produced from adenosine triphosphate by adenyl cyclase, and of cyclic guanosine monophosphate (GMP), which is produced from guanosine triphosphate by guanylate cyclase. The balance between the activities of these enzymes is regulated by intracellular concentrations of cyclic AMP and cyclic GMP. Theophylline inhibits phosphodiesterase, thereby elevating intracellular concentrations of cyclic AMP and relaxing airway smooth muscle. There are 11 phosphodiesterase isozymes, each with various subtypes [1, 2] . Each isozyme has a characteristic tissue distribution. Phosphodiesterase 4 is mainly found in inflammatory cells such as eosinophils, mast cells, and T cells. Theophylline is basically considered to be a nonselective phosphodiesterase inhibitor. There are three types of adenosine receptors. Adenosine stimulates guanylate cyclase activity, contracts airway smooth muscle, and stimulates the release of histamine from mast cells. Theophylline is thought to nonselectively block adenosine receptors on the surface of the cells, thereby inhibiting airway-smooth-muscle contraction. However, theophylline-induced bronchodilation and anti-inflammatory activity cannot be explained solely by phosphodiesterase inhibition and adenosine antagonism. Various types of selective phosphodiesterase inhibitors are now being developed, and their clinical usefulness in patients with chronic obstructive pulmonary disease is being studied. However, these selective phosphodiesterase inhibitors have not been shown to be clearly superior to theophylline in terms of therapeutic Use of Theophylline and Sodium Cromoglycate in Adult Asthma 189 activity or safety. Why theophylline is effective for asthma remains largely unknown [3] . Theophylline produces bronchodilation at serum drug concentrations from 5–15 m g mL−1 [4] . Theophylline alone is inferior to isoproterenol and adrenaline in terms of bronchodilation for asthma attacks [5] ; bronchodilatory activity is addi- tively enhanced by combining theophylline with b 2 agonists [6, 7] .

Anti-Inflammatory Effects of Theophylline

In 1994, Sullivan et al. reported that theophylline decreases activated eosinophil counts in the bronchial epithelium after allergen challenge in patients with asthma [8] . Attention subsequently focused on the anti-inflammatory effects of theophylline, and considerable progress has been made in understanding the mechanisms involved. The main mechanisms underlying the anti-inflammatory effects of theophylline are the augmentation of histone deacetylase activity (HDAC) and direct effects on eosinophils and other important inflammatory cells in asthmatic airways. Low concentrations of theophylline (below 2 m g mL−1 ) augment HDAC activity, inhibiting gene transcription activity. This mechanism is not involved in the anti-inflammatory activity of corticosteroids. Clinically, this independent mechanism of action is thought to underlie the complementation of the effects of inhaled corticosteroids by theophylline [9] . Theophylline induces apoptosis of eosinophils, whose survival is prolonged by interleukin-5 stimulation [10] , and inhibits effector functions such as specific granular protein secretion caused by the stimulation of receptors on the surface of eosinophils [11] . The first essential step in the accumulation of eosinophils in asthmatic airways is the adherence of circulating eosinophils to endothelial cells. We previously reported that theophylline at clinically recommended and higher concentrations significantly inhibits the adhesiveness of eosinophils in blood and the expression of adhesive molecules on endothelial cells [12, 13] . On the other hand, the authors of this chapter and others have confirmed that corticosteroids do not directly influence eosinophil adhesion or the expression of adhesive molecules on endothelial cells [14, 15] . The inhibition of eosinophil adhesion by theophylline is thought to compensate for the inability of steroids to control this step in the establishment of eosinophilic airway inflammation [13] . Many clinical studies have shown that theophylline inhibits eosinophilic airway inflammation in patients with asthma [16– 18] . This result was highly reproducible. In particular, the discontinuation of theophylline promotes eosinophil accumulation in the airways of patients with moderate, persistent asthma who are receiving inhaled corticosteroids [16] . Theophylline enhances the inhibitory effect of inhaled corticosteroids on eosinophilic inflammation in the majority of adults with asthma who are receiving a moderate dose of inhaled corticosteroids [17] . This finding shows that theophylline inhibits airway inflammation in patients with asthma who do not respond to steroids. In asthmatic airways, airway remodeling is believed to progress through the activation of fibroblasts induced by factors released from eosinophils, such as 190 H. Sagara et al. transforming growth factor- b. Theophylline suppresses the proliferation of fibroblasts induced by transforming growth factor-b stimulation and the expression of type I collagen messenger RNA [19] . To our knowledge, no study has examined the effects of theophylline on remodeling clinically. Available evidence suggests that theophylline inhibits airway remodeling by acting on both eosinophils and fibroblasts, the sources of fibrosis-associated molecules in asthma. Theophylline also inhibits neutrophilic inflammation, which commonly occurs in severe asthma [20, 21] . Studies performed in Europe and North America have repeatedly shown that eosinophilic inflammation persists and eosinophils accumulate in the airways of some patients with severe asthma and who receive high-dose steroids [22, 23]. The results of our previous studies in Japanese patients with asthma support this finding [24] . The mechanism of inflammation is complex, involving neutrophils and eosinophils. Dr. Nagata et al. previously reported that neutrophils markedly induce the passage of eosinophils through the basement membrane by promoting CXC chemokine-induced neutrophil migration [25] . They also confirmed that such intercellular interactions are inhibited by clinical concentrations of theophylline [26] . Such effects may contribute to the action of theophylline in severe asthma, as described below.

Safety of Theophylline

Generally, the optimal serum theophylline concentration is 5–15 m g mL−1 , producing a given level of bronchodilation [3] . As described below, there is convincing evidence that a serum theophylline concentration of 8–10 m g mL−1 is useful for the long-term management of asthma. Guidelines for the prevention and management of asthma issued by the immunology and allergy research group of the Ministry of Health, Labor and Welfare recommend a serum theophylline concentration of 5–10 m g mL−1 for elderly patients. Side effects are likely to occur when the serum theophylline concentration exceeds 15 m g mL−1 . Side effects include gastrointestinal symptoms such as nausea and vomiting, cardiac stimulation associated with tachycardias and arrhythmias, and central nervous symptoms such as restlessness and insomnia. Serious side effects such as convulsions can occur in elderly patients or in patients who concomitantly receive drugs that increase serum theophylline concentrations, as described below. In large studies of patients with asthma or chronic obstructive pulmonary disease who were 65 years or older, however, side effects occurred in 4.7% of the patients. The main side effects included gastrointestinal symptoms and palpitations; no patient had convulsions [27] . Theophylline is associated with cytochrome P-450-related drug interactions. Theophylline is a substrate of cytochrome P-450-IA2 (CYP1A2) and cytochrome P-450-IIIA4 (CYP3A4). Serum theophylline concentrations can increase when theophylline is used concomitantly with drugs that inhibit CYP1A2 and CYP3A4 activities, such as new quinolones, macrolides, diltiazem, and selective serotonin-reuptake inhibitors. In contrast, serum theophylline concentrations can decrease when theophylline is used concomitantly with drugs that promote CYP1A2 and CYP3A4 activities, such as rifampicin, phenytoin, and val- proic acid. Side effects can also be caused by the excessive consumption of bever- Use of Theophylline and Sodium Cromoglycate in Adult Asthma 191 ages containing caffeine, a xanthine derivative. Smoking elevates CYP1A2 activity and decreases serum theophylline concentrations. Most side effects can be avoided by monitoring serum theophylline concentrations. The dose of theophylline varies depending on the patient. In most average Japanese patients, serum theophylline concentrations of 5–15 m g mL−1 are obtained at a daily dose of 400 mg. If theophylline can be used safely and is confirmed to be effective, serum theophylline concentrations usually do not have to be measured in routine clinical practice.

Evidence Supporting the Effectiveness of Theophylline for the Long-Term Management of Asthma

Evidence Supporting the Concurrent Use of Theophylline and Inhaled Corticosteroids

Combination therapy with theophylline and inhaled corticosteroids is generally considered the standard of care for the long-term management of asthma. Japanese guidelines for the management and treatment of asthma recommend both drugs for the treatment of moderate or severe persistent asthma (step 3 or higher), but this regimen can also be used for mild persistent asthma (step 2). Inhaled corticosteroids and theophylline are thought to act on airway lesions in asthma through different mechanisms. In fact, evidence suggests that their clinical effects are additive. For example, some studies have compared the effectiveness of doubling the dose of inhaled corticosteroids with that of adding a low dose of sustained-release theophylline in patients with asthma unable to be controlled by moderate doses of inhaled corticosteroids. The improvement in asthmatic symptoms and respiratory function was equivalent or significantly better in the latter group [28– 31] . Evans et al. found that the addition of theophylline in a dose producing a mean serum drug concentration of 8.0–8.9 m g mL−1 produced a greater improvement in airflow limitation than did doubling the dose of budesonide (Pulmicort® ) in patients whose asthma was not adequately controlled by budesonide alone [28] . Ukena et al. reported that additional treatment with theophylline in a dose producing a mean serum drug concentration of 10 m g mL −1 in patients who are receiving inhaled corticosteroids is more clinically effective than doubling the dose of inhaled corticosteroids [29] . These results indicate that serum theophylline concentrations of 8–10 m g mL −1 are needed for sustained-release theophylline to be effective in patients with asthma poorly controlled by inhaled corticosteroids alone. As stated above, theophylline in a dose of 400 mg/day produces serum theophylline concentrations generally within the target range in most Japanese patients. However, a recent American study has reported that low-dose theophylline (300 mg/day) was more effective in improving symptoms in patients who were not receiving inhaled corticosteroids than in those who were concurrently receiving inhaled corticosteroids. Combined treatment with low-dose theophylline and inhaled corticosteroids improved pulmonary function, but did not significantly improve symptoms [32] . 192 H. Sagara et al.

Adequate clinical effectiveness thus requires an appropriate dose of theophylline, providing optimal serum drug concentrations. In a study directly comparing the effects of theophylline, formoterol (an LABA), and zafirlukast (a leukotriene receptor antagonist) in adults with asthma who poorly responded to moderate dose of inhaled corticosteroids, the improvement in asthmatic symptoms was better in the formoterol group during the first month of treatment. Subsequently, however, the differences among the groups became smaller and were no longer significant after 3 months of treatment [33] . The rapid improvement in symptoms associated with LABAs is expected because of their potent bronchodilatory activity. In contrast to LABAs, both theophylline and leukotriene receptor antagonists have anti-inflammatory activity, which may contribute to an improvement in asthmatic symptoms after a certain period. The results described above showed that theophylline is useful for the long-term management of asthma. The addition of theophylline is a viable treatment option for persistent asthma, which cannot be controlled by inhaled corticosteroids alone because theophylline inhibits the chronic airway inflammation characteristically found in asthma and prevents airway remodeling. Asthma requires long-term medical treatment. Theophylline is far less expensive than inhaled corticosteroids, an important factor in ensuring continued treatment.

Evidence Supporting the Effectiveness of Theophylline for Severe Asthma

In patients with severe asthma and are receiving oral steroids, the addition of theophylline significantly decreases symptom scores [34] . In contrast, the discontinuation of theophylline leads to exacerbations of asthma in a high proportion of patients [35] . High doses of inhaled corticosteroids and LABAs are generally used to treat severe asthma. However, a recent study reported that serum theophylline concentrations of 8–13 m g mL−1 significantly augmented salmeterol-induced bronchodilation in patients with severe asthma in whom the mean forced expiratory volume in 1 s was 57% of the predicted value [36] . The effectiveness of additional treatment with theophylline may be attributed to the fact that theophylline inhibits neutrophilic inflammation in severely asthmatic airways and interferes with the inflammatory mechanisms involving neutrophils and eosinophils, in addition to having bronchodilatory activity, as described above. Recent studies performed in the United States have shown that LABAs can have long-term negative effects on respiratory function and increase acute exacerbations of asthma, even in patients who concomitantly receive inhaled corticosteroids [37– 39] . In patients for whom the asthma cannot be controlled by combination therapy with inhaled corticosteroids and LABAs and were repeatedly hospitalized because of a poor response to inhaled short-acting b 2 agonists given on an emergency basis, baseline control status and the response to short-acting b 2 agonists markedly improved after switching from LABAs to theophylline [40] . In contrast to LABAs, theophylline does not act through receptors on the surface of cells. Use of Theophylline and Sodium Cromoglycate in Adult Asthma 193

Theoretically, a reduced response to theophylline with continued use of the drug (i.e., down-regulation) does not occur. In patients who do not respond well to LABAs, treatment regimens should be changed or theophylline should be given additionally. Taken together, currently available findings indicate that theophylline should be included in regimens for the long-term management of severe asthma, which cannot be controlled by high doses of inhaled corticosteroids and LABAs.

References

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18. Lim S, et al. Low-dose theophylline reduces eosinophilic inflammation but not exhaled nitric oxide in mild asthma. Am J Respir Crit Care Med 2001; 164: 273–276 19. Yano Y, Yoshida M, Hoshino S, et al. Anti-fibrotic effects of theophylline on lung fibroblasts. Biochem Biophys Res Comm 2006; 341: 684–690 20. Kraft M, Torvik JA, Trudeau JB, et al. Theophylline: potential anti-inflammatory effects in nocturnal asthma. J Allergy Clin Immunol 1996; 97: 1242–1246 21. Culpitt SV, de Matos C, Russell RE, et al. Effect of theophylline on induced sputum inflammatory indices and neutrophil chemotaxis in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2002; 165: 1371–1376 22. Wenzel SE, Schwartz LB, Langmack EL, et al. Evidence that severe asthma can be divided pathologically into two inflammatory subtypes with distinct physiologic and clinical characteristics. Am J Respir Crit Care Med 1999; 160: 1001–1008 23. The ENFUMOSA Study Group. The ENFUMOSA cross-sectional European multicentre study of the clinical phenotype of chronic severe asthma. Eur Respir J 2003; 22: 470–477 24. Kikuchi S, Nagata M, Kikuchi I, et al. Association between neutrophilic and eosinophilic inflammation in patients with severe persistent asthma. Int Arch Allergy Immunol 2005; 137: 7–11 25. Kikuchi I, Kikuchi S, Kobayashi T, et al. Eosinophil trans-basement migration induced by IL-8 and neutrophils. Am J Respir Cell Mol Biol 2006; 34: 760–765 26. Kikuchi I, Kikuchi S, Kobayashi K, et al. Theophylline Attenuates the Neutrophil-Dependent Augmentation of Eosinophil Trans-Basement Membrane Migration. Int Arch Allergy Immunol 2005; 137 (accepted for publication) 27. Ohta K, Fukuchi Y, Grouse L, et al. A prospective clinical study of theophylline safety in 3810 elderly with asthma or COPD. Respir Med 2004; 98: 1016–1024 28. Evans DJ, Taylor DA, Zetterstrom O, et al. A comparison of low-dose inhaled budesonide plus theophylline and high-dose inhaled budesonide for moderate asthma. N Engl J Med 1997; 337: 1412–1418 29. Ukena D, Harnest U, Sakalauskas R, et al. Comparison of addition of theophylline to inhaled steroid with doubling of the dose of inhaled steroid in asthma. Eur Respir J 1997; 10: 2754–2760 30. Wang Y, Eang C, Lin K, et al. Comparison of inhaled corticosteroid combined with theophylline and double-dose inhaled corticosteroid in moderate to severe asthma. Respirology 2005; 10: 189–195 31. Shah AR, Sharples LD, Solanki RN, et al. Double-blind, randomized, controlled trial assessing controller medications in asthma. Respiration 2006; 73: 449–456 32. American Lung Association Asthma Clinical Research Centers. Clinical trial of low-dose theophylline and montelnkast in patients with poorly controlled asthma. Am J Respir Crit Care Med 2007; 175: 235–242 33. Yurdakul AS, Caliir HC, Tunctan B, et al. Comparison of second controller medications in addition to inhaled corticosteroid in patients with moderate asthma. Respir Med 2002; 96: 322–329 34. Nassif EG, Weinberger M, Thompson R, et al. The value of maintenance theophylline in steroid-dependent asthma. N Eng J Med 1981; 304: 71–75 35. Brenner M, Berkowitz R, Marshall N, et al. Need for theophylline in severe steroid-requiring asthmatics. Clinical Allergy 1988; 18: 143–150 36. Vatrella A, Ponticiello A, Pelaia G, et al. Bronchodilating effects of salmeterol, theophylline and their combination in patients with moderate to severe asthma. Pulm Pharmacol Ther 2005; 18: 89–92 37. Wechsler ME, Lehman E, Lazarus SC, et al. National Heart, Lung, and Blood Institute’s Asthma Clinical Research Network. beta-Adrener-gic receptor polymorphisms and response to salmeterol. Ame J Respir Crit Care Med 2006; 173: 519–526 38. Martinez FD. Safety of long-acting beta-agonists -an urgent need to clear the air. N Engl J Med 2005; 353: 2637–2639 39. Salpeter SR, Buckley NS, Ormiston TM, et al. Meta-analysis: effect of long-acting beta-ago-nists on severe asthma exacerbations and asthma-related deaths. Ann Int Med 2006; 144: 904–912 40. Weinberger M, Abu-Hasan M. Life-threatening asthma during treatment with salmeterol. N Engl J Med 2006; 355: 852–853 New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma

Giovanni Passalacqua and Giorgio Walter Canonica

Historical Context

Allergen-specific immunotherapy (SIT) was introduced on an empirical basis about a century ago [1] , with the erroneous rationale of vaccinating against “airborne toxins.” Despite this wrong conception, the subcutaneous injection (SCIT) of pollen extracts proved capable of reducing the symptoms of hay-fever, and SIT (also termed “vaccine”) became one of the cornerstones of allergy treatment. After the discovery of IgE [2] , the mechanisms of SIT were investigated and its clinical efficacy was assessed in double blind placebo controlled trials [3] . From the 1960s until the end of the 1980s, there were no important changes in the practice of SIT that was invariantly given by SCIT, other than the introduction of the modified allergens or allergoids. In 1986, the British Committee for the Safety of Medicines (CSM)[4] reported 26 deaths due to SCIT and started a process of intense critical revision of this treatment, which led to the publication of the World Health Organization guidelines [5] . In these guidelines, indications, contraindications, risks, and benefits of SCIT were clearly stated, and SCIT was finally recognized as an effective treatment. Another important consequence of the CSM report was the strong impulse to search for safer modalities of immunotherapy. In this regard, the sublingual route (SLIT) was extensively studied and subsequently validated [5, 6] . SLIT can, therefore, be considered an important milestone in the history of SIT, since it really changed the clinical practice and originated an intense debate, which is still ongoing. Another revolution in the history of SIT was the discovery of Th1 and Th2 lymphocyte subsets [7] , which allowed elucidating the mechanisms of action and, in turn, opened new research pathways such as the use of adjuvants. Few years later, the T regulatory cells were also described [8] , leading to new immunotherapy approaches. In parallel to the clinical evolution, basic immunology techniques also

G. Passalacqua and G.W. Canonica () Allergy and Respiratory Diseases, Department of Internal Medicine , Padiglione Maragliano, L.go R. Benzi 10 , 16132 Genoa , Italy e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 195 DOI 10.1007/978-4-431-99362-9_12, © Springer 2010 196 G. Passalacqua and G.W. Canonica

The future of Immunotherapy (SCIT/SLIT) Food allergy INDICATIONS Latex Atopic dermatitis Liposomes PHARMACEUTICAL FORM Biolistic injection Mucoadhesive substances

Alum-alginates ADJUVANTS Bacterial wall derived DNA-adjuvants

Recombinant purified RECOMBINANT/ Hypoallergenic isoforms ENGINEERED Peptides Chimeric proteins c-DNA GENIC VACCINATION Plasmids Replicons

Fig. 1 Novel approaches for specific immunotherapy

evolved rapidly and provided the instruments to design and build specific molecules, such as the recombinant and engineered allergens, for immunotherapy (Fig. 1 ).

Injection Immunotherapy

Efficacy and Safety

The SCIT is well established and its indications, contraindications, limits, and practical aspects have been well defined in numerous guidelines [5, 6, 9, 10] . In the last 5 years, some new articles on the clinical efficacy and safety of SCIT have been published, all confirming the clinical effect in rhinitis and asthma due to mites, grass, birch, and ragweed. Interestingly, two clinical studies, one evaluating symptoms upon exposure [11] and one evaluating the response to a nasal provocation test [12] , demonstrated the dose-dependency of SCIT for clinical efficacy. Moreover, there are two meta-analyses of the efficacy of SCIT for both allergic asthma [13] and rhinitis [14] , which clearly confirm the efficacy of the treatment on symptoms and use of rescue medications. Concerning the safety aspects, a randomized study with grass and birch vaccines [15] found that systemic reactions with SCIT occurred in 3.3% of the injections New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 197 with grass and 0.7% of the injections with birch. A postmarketing surveillance [16] reported a rate of systemic reactions of 0.9% of the total doses and 3.7% of patients, whereas another survey on grass pollen SCIT reported an occurrence of systemic reactions in 2% of patients [17] . A retrospective study [18] on 65 patients receiving multiple vaccines and rush IT reported 38% systemic reactions with one severe episode. It is noteworthy that an e-mail survey of more than 17,000 physicians in the USA [19] reported a high rate of errors in administration (wrong patient or wrong dose).

Mechanisms (Fig. 2 )

It is well known since many years that SCIT is associated with an increase in allergen-specific IgG antibodies, particularly in the IgG4 subclass. More recent studies have extended these observations, with a special attention toward the biological effects of IgG. These effects include the IgG-dependent ability of postim- munotherapy serum to inhibit the binding of allergen-IgE complexes to B-cells, the blocking of subsequent IgE-facilitated allergen presentation with the activation of allergen-specific T-lymphocytes, and the prevention of allergen-IgE dependent activation of peripheral basophils [20– 22] . The effect of allergen-specific IgG may be explained either by competition for IgE-allergen binding or alternatively by an effect mediated via the inhibitory IgG receptor Fcg RIII, which is coexpressed with

IgE

IL-4 APC B-cell Th2

ALLERGEN Eosinophil

IL-5 Allergic b TGF inflammation IL-10 CD4 SIT T reg SIT IL-10

SIT IgG IFN- γ Th1 B-cell

Fig. 2 Putative mechanisms of action of immunotherapy. The solid red arrows indicate stimulation, the green dotted arrows indicate inhibition 198 G. Passalacqua and G.W. Canonica

Fc eRI on basophils, and inhibits post-IgE receptor signaling pathways following allergen binding [23, 24] . The allergic inflammation, typically accompanied by tissue eosinophilia, is regulated by Th2 lymphocytes that produce a distinct profile of cytokines. Studies over the past decade have confirmed the blunting of allergen- driven Th2 responses, including reductions in IL-4, IL-13, IL-5, and IL-9, in the periphery and /or within the target organs [25– 30] . These changes are associated with: a) immune deviation in favor of Th1 responses with an overproduction of IFN g and/or b) the emergence of a population of regulatory T-lymphocytes that produce the inhibitory cytokines IL-10 and/or TGFb [31– 33] . It is hypothesized that these regulatory T-cells act directly to suppress allergen-specific Th2 responses. Alternatively, IL-10 is a known switch factor for IgG4 production [34] , whereas TGF b favors IgA [35] and both of these antibody classes are increased in peripheral blood after SCIT [31] .

Long-Lasting Effect and Prevention

It is known since many years that injection immunotherapy maintains its beneficial effects for years after discontinuation. This long-term effect has been described in both open and controlled studies with a number of different allergens [36– 43] (Table 1 ). The long-lasting effect has been reported to persist for 3–6 years, but a recent follow-up study in 23 children described a 6-years effect after the discontinuation of grass SCIT [42] . Interestingly, the same children were evaluated again after 12 years and persistence of a moderate beneficial effect was still identified [43] . In two large retrospective studies [44, 45] , SCIT appeared to prevent the onset of new atopic sensitizations as determined by skin prick testing. This results confirmed those obtained previously in a small sample of monosesitized children [46] . In a large randomized, controlled, but not blinded, study of SCIT (the Preventative Allergy Treatment study, PAT), pollen immunotherapy reduced the risk of the onset of asthma in children who had allergic rhinitis and no asthma [47] . This preventive effect was observed to persist in the same patients for 2 years after the termination of SCIT [48] .

Table 1 Long-lasting effect of subcutaneous immunotherapy Author (ref) Allergen Patients Duration sit Long-lasting effect Mosbech (36) Grass 2.5 years 6 years Grammer (37) Ragweed 61 adult/children 4 months 2 years Hedlin (38) Cat/dog 32 adult/chidren 3 years 5 years Des Roches (39) Mite 40 adult 1–4 years 3 years Ariano (40) Parietaria 35 adult 4 years 4 years Durham (41) Grass 52 adult 3–4 years 3 years Eng (43) Grass 25 children 3 years 12 years New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 199

Sublingual Immunotherapy

Efficacy and Safety

SLIT is the natural evolution of the oral administration of allergens, proposed in the early 1970s and then abandoned [49] . The original rationale of the sublingual administration was to achieve an effective absorption of the allergen through the oral mucosa so that systemic side effects of the injections could be avoided or reduced. The rationale of the absorption was not supported by experimental data, but since the first controlled study [50] , SLIT was found to be effective in reducing symptoms and medication intake. Nowadays, there are more than 50 randomized trials of SLIT (for review see [51, 52] ), and several meta analyses of those studies [53– 55] . A summary of the evolution of SLIT is depicted in Fig. 3 . According to the literature, SLIT is effective in rhinitis and asthma due to the most common allergens, including mites, grasses, parietaria, ragweed, and olive. The clinical efficacy in rhinitis [55] and asthma [56] was also separately confirmed in pediatric patients in meta analyses. According to the evidence-based medicine rules [57] , the meta analyses confer to SLIT a grade of evidence Ia and the recommendation for its clinical use is A. Nonetheless, the opponents of SLIT argue that meta analyses collect together small studies that are highly heterogeneous in design, doses, and evaluation parameters. This can be true, but in the more recent

1970ties 1986, Scadding et al 1993. SLIT is ORAL IT 1st DBPC trial Mentioned in an EAACI pos pap

1998: WHO 1998, first 1997, Tari, SLIT is accepted Tablet SLIT 1st pediatric trial

2001: ARIA 2004 1st 2004: Preventive effect document META Compliance ANALYSIS

2005-2006: Large randomized controlled trials 2005: SLIT in children Studies on the mechanism of action below the age of 5

Fig. 3 The history of SLIT 200 G. Passalacqua and G.W. Canonica trials of sublingual immunotherapy for grass pollen-induced seasonal rhinitis, involving hundreds of patients, the magnitude of the effect, defined as the reduction in diary symptoms and rescue medication scores compared to placebo, was reported to vary from 24% to about 40% [58– 61] . Moreover, in these studies, a clear dose- response relationship was identified, similarly to SCIT. Of note is a recently published trial, which found that SLIT is not effective when utilized in a primary care setting [62] . This leads to concerns, mainly on the adequacy of patients’ choice made by GPs, rather than the efficacy of SLIT itself. There are few direct comparisons of SLIT versus SCIT. One double dummy study without the placebo group, conducted in grass pollen allergic patients, showed that the clinical efficacy of SLIT was equivalent to that of SCIT [63] . Another open comparative 12 months study in Alternaria tenuis allergic patients [64] found a significant clinical improvement in both groups (even greater with SLIT). There is also an open comparison between SLIT and SCIT in mite- allergic patients [65] , showing a better improvement with the subcutaneous route, especially for asthma symptoms, although SLIT well controlled rhinitis symptoms. This study is biased due to a clear imbalance between groups at the baseline, concerning asthma symptoms. Recently, a double-blind, double- dummy, placebo-controlled study compared SCIT and SLIT in birch pollinosis [66] . Symptoms and drug intake were reduced by about one third in the SLIT group and by half in the SCIT group, with no significant difference evident between treatments. However, there were six grade 3 and 4 reactions in the SCIT group and none in the SLIT group. The most relevant feature of SLIT is its safety, which still remains a concern with SCIT. In all the randomized controlled trials, SLIT was well-tolerated, the most frequent side effects being local (oral itching or swelling) or gastrointestinal (nausea, vomiting, diarrhea, and “stomach ache”). These side effects were generally described as either mild and self-limiting or manageable by a temporary dose reduction. The majority of these events were local, very mild, and self-resolving and systemic reactions were quite rare. It was suggested that the type and severity of adverse events are not directly related to the dose [67] , but the more recent studies clearly showed that the rate of untoward effects, although these effects are mild, is dose dependent [68] . According to an extensive review of the literature, 17 serious adverse events (mainly asthma) were reported [69] . Two cases of anaphylaxis were recently reported, one with nonstandardized mixtures of allergens [70] and the other with a rush administration of latex extract [71] . Some postmarketing surveys in children and adults [72– 76] are available (Table 2 ). Based on these large surveys, the overall rate of side effects was found to range between 3% and 18% of patients and was invariantly less than 1 reaction per 1,000 doses. Interestingly, the rate of adverse events in children below 5 years of age did not increase with respect to the other age classes [73, 76, 77] . This fact represents a relevant advantage, since, for SCIT, the age below 5 years is considered as a relative contraindication, due to the possible severity of the adverse events [5] . New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 201

Table 2 Post-marketing surveillance studies on the safety of SLIT Author Average AE% of AE/1,000 doses (ref) N pats Age range follow-up Allergens patients Di Rienzo 268 2–15 years 3 years 54% mites 3% 0.083/1,000 [69] 25% grass 6% parietaria 16% mixed Lombardi 98 >14 years 3 years 35% mites 7.5% 0.5/1,000 [72] 38% grass 23% parietaria 4% others Pajno [71] 354 5–15 years 3–4 years 42% mites 6% 0.15/1,000 20% parietaria 11% grass 7% olive 20% mixed Agostinis 36 3–5 years 2 years Mites 19 5% 0.07/1,000 [73] Grasses 17 Di Rienzo 70 3–5 years 2 years 62% mites 5.6% 0.2/1,000 [70] 22% grass 12% parietaria 4% others

Mechanisms

Until 5 years ago, only limited data were provided on the mechanism of action of SLIT, and these data were often controversial. In fact, in some studies, SLIT was associated with modest increases in IgG, transient increase in IgE, and suppression of eosinophil recruitment and activation in target organs [78– 82] . Nonetheless, other studies failed to demonstrate changes in systemic T-cell, and cytokine response [83, 84] or local changes in the sublingual mucosa [79] . More recently, the investigation specifically focused on the Th1/Th2 balance and the role of Treg cells. Two studies reported an increased production of the regulatory cytokine IL-10 [85, 86] after SLIT and another study showed a reduction of the Th2 cytokine IL-13 [87] . Savolainen et al demonstrated in vitro that SLIT reduces the expression of IL-5 and enhances the expression of IL-10 in PBMC stimulated with the allergen [88] . Overall, the clinical effects of SLIT resemble those of SCIT, and the data available suggest that the mechanisms of action are partially similar. Nevertheless, a more detailed definition of the mechanisms of action of SLIT is mandatory and it will probably represent a major research field. Concerning the biodistribution of allergens in humans, the earliest studies conducted with the radiolabeled Par j 1 allergen and its allergoid [89] clearly showed that the direct absorption of the allergen through oral mucosa is absent or negligible. Moreover, it was shown that the allergen persists for hours in the mouth, even after 202 G. Passalacqua and G.W. Canonica spitting or drinking. This suggests that the contact with the mucosa is crucial for the effect of SLIT. In fact, when the allergen is immediately swallowed (oral route), the clinical efficacy is poor or absent. In addition, it was consistently shown that the modified allergen, and not the native one, can be absorbed intact in small amounts in the bloodstream. These aspects were recently confirmed in allergic volunteers with the purified Der p 2 allergen and its allergoid [90] . This finding confirms that the biodistribution (no oral absorption, long persistence in the mouth, absorption of the intact allergoid) of allergens does not depend on the type of molecule.

Aspects Currently Under Investigation

There are some aspects of SLIT that need further experimental support, although the existing data are favorable. One aspect is the ability of SLIT to prevent the onset of new sensitizations and the onset of asthma, similarly to SCIT [45, 47] . Recently, in an open randomized trial, involving more than 500 patients, the rate of occurrence of new sensitizations was found to be 5.8% in the active group and 38% in the control group (p < 0.001)[91] . In an observational cohort study, not designed to evaluate SLIT, it was shown that among monosensitized patients treated with SLIT, only about 10% developed new sensitizations after 3 years, whereas this percentage was around 40% in patients receiving only drugs without SLIT [92] . More importantly, a study by Novembre et al [93] , performed on children, demonstrated that SLIT is capable of reducing the risk of asthma onset. In that study, 97 children with only rhinitis were subdivided into two groups, receiving either drugs or drugs plus SLIT for 3 years. In the active treatment group, asthma occurred in 6 the first year, 7 the second year, and 8 the third year. In the control group, the corresponding numbers were 6, 16 (P = 0.06), and 18 ( P = 0.04). Another randomized open controlled trial [94] involved 216 children (age 5–17 years) suffering from allergic rhinitis, with or without intermittent asthma. They were randomly allocated 2:1 to drugs plus SLIT or drugs only, and followed for 3 years. One hundred and ninety-six patients were evaluated at 3 years, and the occurrence of persistent asthma was 2/130 (1.5%) in the SLIT group and 19/66 (30%) in the control group. Finally, the long-term effect, which is well ascertained for SCIT, has been so far demonstrated for SLIT in a single open and nonrandomized study [95] . Another important concern about SLIT is the adherence, because the treatment is self-managed by the patient. The problem of adherence was systematically addressed in three studies employing the method of unscheduled phone interviews. In the first study [96] involving 126 patients, the overall adherence was around 95%. In another study [97] conducted in more than 400 patients, the adherence rate at 3 and 6 months was greater than 90% in about 75% of the patients. A similar study was conducted in a population of 70 children, and the results on compliance did not differ from the above mentioned in adults [98] . In view of the increasing attention that is paid to the economic aspects of the treatment strategies nowadays, a cost-effectiveness assessment of SLIT is mandatory. A pharmaco-economic pilot study [99] in children New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 203 reported a substantial reduction in all outcome measures (exacerbations, visits, absence from school, drugs, and school and parental work loss) during SLIT. Another large study in adults, which utilized a formal pharmaco-economic model, showed that SLIT in pollinosis leads to remarkable economic savings in terms of direct and indirect costs when compared to drug treatment alone [100] .

Future Developments

The good safety profile of SLIT is likely to allow the expansion of its indications to conditions different from respiratory allergy. Indeed, a recent study [80] demonstrated that SLIT is clinically effective in the treatment of IgE-mediated hazelnut allergy. Positive results were also reported with SLIT in latex allergy [101– 103] . Two randomized controlled trials of SLIT were conducted. The first one, on 12 children with latex allergy, reported a significant reduction of clinical symptoms at 12 months, accompanied by a decrease of symptoms related to cross-reacting foods [102] . The other randomized study [103] involved 35 adults with cutaneous and respiratory allergy to latex and it reported a significant improvement in both clinical manifestations after 12 years of SLIT. Finally, a randomized placebo-controlled trial conducted in 56 children with mite allergy and extrinsic atopic dermatitis, receiving SLIT for 18 months, described a significant reduction in the SCORAD (Fig. 4 ) and medication intake starting from month 9. The favorable effect was maintained until the end of SLIT, but was significant only in the mild and moderate form of the disease [104] . Another interesting aspect of SLIT is that the traditional slow updosing phase does not seem to be necessary. Indeed, there have been some reports with ultra rush (less than 2 h) updosing, showing that the rapid increase of the doses does not lead to an increase of side effects [105, 106] . A randomized trial compared the safety of the traditional updosing regimen with the no-updosing [107] regimen in 135 patients and found no difference in adverse events rate between the two groups. The most recent large randomized trials were all performed with the no-updosing regimen, and their results, in terms of safety, were as favorable as those of the studies involving the traditional route.

Novel Formulations and Routes of Administration

One of the possibilities to improve SIT is to modify the pharmaceutical form of administration. In this method, liposomes are regarded as a promising route of delivery since they resemble biological membranes and can also act as adjuvants [108] . The use of liposomes to encapsulate allergens for SCIT has been proposed. A randomized DBPC study with a liposomal mite vaccine showed clinical efficacy 204 G. Passalacqua and G.W. Canonica

SLIT (N=26) Placebo (N= 22) 0

–2

–4

–6

–8 * * * –10 * SCORAD vs baseline baseline vs SCORAD

Δ –12

0 3 6 9 12 15 18 months

Fig. 4 Double-blind, placebo-controlled study of SLIT for atopic dermatitis in 58 children. Change from baseline (delta SCORAD) in the two groups at the different time-points. The significant differences between groups are marked with an asterisk (from Ref. 104)

comparable to traditional vaccines as well as a good safety profile [109] . This treatment was also capable of reducing nonspecific bronchial hyperresponsiveness in mild asthmatics [110] . Another promising opportunity is represented by the needle-free epidermal administration of microparticles, the so-called “biolistic” administration. This route of delivery has been extensively studied for other kind of vaccinations [111] , but only recently proposed for the delivery of allergens. So far, only a single study has been conducted on mice, showing that the biolistic administration is able to induce a Th1 skew [112] . Finally, in the case of mucosal administration of allergens, such as that of SLIT, potential improvement could result from the bioadhesive vehicles [113] . These mixtures of organic molecules prolong the time of persistence of the active principle on the mucosa and can enhance their immunogenicity. So far, no study has been performed on humans with bioadhesive molecules.

Immunotherapy with Adjuvants

In immunology, adjuvants are classically non antigenic or non immunogenic substances, which, when coadministered with antigens, enhance their effects [114] . Thus, in the case of SIT, an effective adjuvant would allow the reduction in the amount of allergen to be administered. New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 205

Immunotherapy with Bacterial Adjuvants

The traditional adjuvants used in experimental immunology are usually irritant or toxic and therefore, are not suitable for human use. For this reason, extensive researches were made to identify proper adjuvants to be given with allergens [115] . One of the most promising adjuvants is a mixture of phospholipids derived from the cell wall of the nonpathogen bacterium Salmonella Minnesota. This adjuvant is called monophosphoril-lipid A (MPLA). MPLA has been shown to be non toxic, well tolerated, and capable of inducing a pronounced Th1 response in animals [116] and humans [117] . A double-blind, placebo- controlled study was conducted on an injection SIT with grass pollen extract adjuvanted with MPLA [118] , to be administered in only four injections. This study demonstrated a significant improvement in patients with allergic rhinitis, associated with immunological changes similar to those induced by traditional SCIT [119] . The same preparation was also tested, with favorable results, in children and adolescents, although the study was open and not controlled [120] . At present, the MPLA-adjuvanted immunotherapy is commercially available in several countries [121] .

DNA-Adjuvanted Immunotherapy

About 10 years ago, while attempting to vaccinate animals with the DNA encoding for the allergen, rather than with the allergen itself, it was noticed that the administration of DNA plasmids exerted a potent Th1-inducing effect [122] . The reasons for the adjuvant effect were identified as short repetitive sequences (CpG motifs) that are typical of the bacterial DNA [123] . These sequences, the so-called ISS-ODN (immunostimulatory sequences-oligodeoxynucleotide ), are typically recognized by the toll-like receptor 9, which is a component of the innate immunity [124] and activates the Th1 response to bacteria. It was immediately clear that ISS-ODN could represent a potent adjuvant for allergen immunotherapy [125] , and a DNA conjugated allergen, Amb a 1, was prepared for human administration [126] . This injected adjuvanted allergen was shown able, in an exploratory study in humans, to effectively redirect the allergen- specific immune response toward the Th1 phenotype [127, 128] . Recently, a phase II, double-blind, placebo-controlled trial with the DNA-conjugated ragweed allergen, conducted in 25 adults with rhinitis, reported a significant clinical benefit (reduction of symptoms and medication intake), which was maintained for two pollen seasons after vaccination [129] . The DNA adjuvanted immunotherapy seemed to be well tolerated and no untoward effect was described. 206 G. Passalacqua and G.W. Canonica

Immunotherapy with Peptides

The rationale behind this approach is that IgE recognizes the entire epitope of an allergen (i.e., conformational recognition), whereas antigen presenting cells and T cell receptors recognize the linear sequences. Thus, by giving, instead of the entire allergenic protein, only some peptides it is expected to obtain an immunogenic activity without the allergenic one. In fact, it was demonstrated in vitro that appropriate peptides derived from allergens were able to induce a functional inactivation of allergen-specific T helper cells [130– 132] . The first attempts with this kind of SIT were made with mixtures of short peptides derived by the Fel d 1 allergen of cats [133– 136] , at a dose variable from 7.5 to 750 mcg per injection. Unfortunately, in the aforementioned human trials, despite some efficacy on symptoms and measurable immunological changes, there were unexpected severe adverse events [134, 136] . Subsequently, other mixtures of short and partially overlapping peptides were used and, in the more recent studies, [137, 138] , there was a clear demonstration of clinical efficacy, with the reduction of symptoms upon cat exposure and the immunotherapy was well tolerated. A few small studies were also conducted with long peptides derived from the hymenoptera allergen Api m 1 [139– 141] , all showing a favorable immune response, despite the evaluation of clinical parameters only in one study [139] .

Recombinant and Engineered Allergens

The commercialized extracts for immunotherapy, although standardized, are heterogeneous mixtures of allergenic proteins and non-relevant components. In addition, there are numerous cross-reactivities within allergens. Thanks to the advances in molecular biology, it is now possible to synthesize many of the allergenic proteins, so that it would be also possible to vaccinate only with the relevant molecules. This is called “tailored immunotherapy.” There are numerous studies describing the characteristics and immunological effects of recombinant allergens [142] , but their clinical application has only been carried out in the last 2 years. A randomized, controlled trial of recombinant birch allergens resulted in reduced skin test responses and the inhibition of basophil histamine release [143] , whereas a trial of four recombinant grass allergens resulted in a decrease in seasonal symptoms and medication requirements compared to placebo treatment [144] . The molecular approach also offers the unique opportunity to synthesize allergens that are partly different from the naturally occurring ones (hypoallergenic isoforms). This can be achieved by numerous techniques such as site-directed mutagenesis [145] , but the final goal is to maintain the immunogenicity of a vaccine, while reducing/avoiding the capacity to bind allergen-specific IgE, thereby reducing the risk of IgE- dependent side effects. The most attractive perspective offered by genetic engineering is that of administering the genes encoding for the allergens instead of the allergens themselves. New Insights into Allergen-Specific Immunotherapy in Rhinitis and Asthma 207

This can be done using so-called replicons. Very recently, an effective vaccination with a replicons encoding for the major grass allergen was described in an animal model of allergy [146] . Molecular biology also allows building chimeric proteins that are a fusion of two or more different allergens. This has been done by constructing a fusion protein made by the Bet v 1 allergen, carrying the immunodomi- nant peptides of Phl p 1 [147] . This construct has been shown immunologically effective in an animal model, but studies in humans are still lacking.

Concluding Remarks

In the last 20 years, there has been an impressive blossoming of immunotherapy studies [148] . The most important novelty, from a clinical point of view, was the introduction of SLIT, which is now accepted as a viable alternative to injection immunotherapy. It is true that some points, such as the ideal patient, the extent of the long-lasting effect, and the preventative role [149] , need to be better detailed for SLIT. These aspects will represent the clinical challenge for the near future. It is important to remind that though SLIT is easy to manage, the self-administration itself requires a careful instruction and a detailed follow-up of the patients. Its prescription must be made only by a specialist, after the establishment of a detailed diagnosis and the careful evaluation of the expected benefit/cost ratio. This certainly applies also to injection immunotherapy. In parallel to the clinical developments of SLIT, the mechanisms of specific desensitization were clarified in increasing detail [150] . This prompted the explo- ration of new opportunities, such as the use of bacterial and DNA adjuvants, peptides [151] , and recombinant/engineered allergens. Although these approaches are still at the beginning stages in humans, they represent the frontier for the immediate future. Looking far ahead, the ultimate approach to immunotherapy is likely to be the “internal vaccination” via the administration of genes encoding for the allergens.

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Paul Potter

Introduction

Since the recognition and approval of sublingual immunotherapy (SLIT) by the World Health Organization and the European Association of Allergy and Clinical Immunology in 1998 [1, 2], there was been a worldwide interest in the use of this treatment for allergic diseases. Sublingual immunotherapy has been shown to be effective in rhinitis and asthma; it is extremely safe and unlike subcutaneous immunotherapy, represents a form of immunotherapy which can be used beyond the specialized allergy centers. Sublingual immunotherapy involves the daily administration of incremental amounts of a purified allergen, which is held under the tongue for 2 min and then swallowed. Optimal dosing regimens are still being explored, but typically doses are increased over 4 weeks to reach a maintenance dose, which is continued on alternate days for a 3 year period. The allergen may be administered as drops, as an oral spray, or as a rapidly dissolving tablet. Sublingual immunotherapy (SLIT) has been found to be effective for seasonal allergic rhinitis and in certain children with asthma. This review will consider current knowledge of the immunological changes which have been observed in patients undergoing SLIT, the clinical evidence of efficacy and safety of SLIT in allergic rhinitis and asthma and the current indications and limitations of its use in children and adults.

P. Potter () Allergy Diagnostic and Clinical Research Unit , University of Cape Town Lung Institute , George Street , Mowbray , Cape Town 7700 , South Africa e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 217 DOI 10.1007/978-4-431-99362-9_13, © Springer 2010 218 P. Potter

Mechanisms

During sublingual immunotherapy, patients achieve a state of tolerance or unresponsiveness to the allergens administered. Clinical observations and recent studies indicate that a state of long term tolerance may be occurring in phases which may be related to dosing and frequency of administration of the allergen. There is currently some debate as to whether SLIT activates the same immunological mechanisms, to induce tolerance to the allergen, as that occurs during subcutaneous immunotherapy (SIT). It is evident from the route of administration of the vaccine that Fc Epsilon bearing dendritic cells in the oral mucosa, which are not present in subcutaneous tissues, are involved in SLIT, but not in SIT. Clinically, an early phase of oral tolerance is achieved within weeks of initiating SLIT. Patients who initially react to the sublingual drops with oral itching for about 30 min after exposure report that the oral itching goes away within a few weeks and higher oral doses are tolerated without local clinical effects. The oral tolerance, so achieved, occurs before any appreciable tolerance to allergen exposure is perceived in end organs such as the nose, or the airways. Once they have achieved oral tolerance, patients may report early onset of tolerance in the end organ. This was typically observed in patients receiving preseasonal SLIT for pollen allergies within 3 months of initiating SLIT [3] . A similar acquisition of significant protection and tolerance to latex allergen [4] has been reported within 3 months of SLIT. Long lasting tolerance is achieved after 2–4 years of SLIT typically for perennial allergies (e.g., house dust mites), manifesting as asthma and/or rhinitis, and also for seasonal allergies. Tolerance is maintained for as long as 10 years after SLIT has been discontinued [5] . There are no published sequential long-term studies, which provide information on what happens immunologically during these phases of tolerance. Several cross sectional studies have been published, reporting changes in mediators, immunoglobulins, cytokines, and surface markers. These studies have been done at different time points, studying different molecules, in variable populations, receiving different allergen extracts, with different dosing schedules and in differing end organ diseases. Immunological changes observed to occur during SLIT are summarized in Table 1 . In studies where the immunological changes observed during SLIT have been compared directly with patients in a parallel group receiving SIT, the immune responses to SIT appear to be stronger [9, 10] . In the first instance immunological changes have been observed in the end organs of allergy, particularly the nose. Early reports that SLIT down regulates the expression of adhesion molecules on the nasal and conjunctival epithelial cells by Passalacqua et al. in 1998 [11, 12] have been confirmed by Silvestri et al. [13] in the studies of the expression of ICAM I in nasal epithelial cells. In the studies of Ippoliti [7] , falls in serum ECP and IL-13 are clearly demonstrated. In the studies of Marcucci et al. [8] , SLIT prevented the observed increase in nasal tryptase after allergen challenge, and a fall in allergen specific IgE, without any change in nasal ECP. Sublingual Immunotherapy in Allergic Rhinitis and Asthma 219

Table 1 Immunological changes observed during sublingual immunotherapy A Early (6 months) • Fall in serum ECP [7] • Fall in IL-13 [7] • Increased PHA stimulated IL-12 [6] • Increased Der p 1 stimulated IFNg [6] B Intermediate (10–12 months) • Fall in nasal allergen Specific IgE [8] • Reduction in nasal tryptase levels [8] • Increase in IL-10 [18] C Later (>18 months) • Reduction in late phase SPT responses (p = <0.003) [9] • Increase in IgG4/IgE ratios (p = 0.05) [9] • Fall in ICAM-I expression in nasal epithelial cells [10, 12, 13] • Reduction in methacholine responsiveness [10]

Lima [9] has reported a significant increase in IgG4/IgE ratios in certain patients receiving SLIT for over 18 months. The induction of “blocking” IgG antibodies has been reviewed by Wachholz and Durham [14] in patients undergoing SIT. It has been modulated that the induction of IgG antibodies with blocking activity may have a protective role, not only through the inhibition of allergen induced IgE mediated release of inflammatory mediators, but also through the inhibition of IgE facilitated antigen presentation to T cells. In most studies, although allergen specific IgE levels have not been influenced by SLIT, allergen specific IgG was shown to increase in studies by Tari et al. [15] . Allergen specific IgG4 increases are usually only observed after several months of immunotherapy and while some have considered these increases to be a para phenomenon following exposure to higher doses of allergen, further studies are required to understand whether they contribute to the development of tolerance in patients receiving SLIT. Although several clinical studies have shown a rapid onset of oral tolerance within months of the initiation of SLIT, there are no published immunological studies of this early period to explain this early tolerance development. It is probable that an alteration of certain TH2 responses occurs early at a cytokine level, reducing mast cell priming necessary for mediator release. At a systemic level , mechanisms for the induction of immunological tolerance are more likely to be related to changes in the regulatory T cell network. Although a reduction in late phase responses to allergen has been demonstrated in SLIT patients by Lima et al., a complete shift from a TH2 to a TH1 response to allergen has not been consistently shown to accompany successful immunotherapy, as evidenced by a persistence in IgE levels and an elevation in IgG4 levels during successful immunotherapy. The importance of IL-10+ CD4+ CD25+ T cells in the peripheral blood playing a regulatory role in allergic and nonallergic subjects requires further study in patients undergoing SLIT. IL-10 is a major regulatory cytokine of inflammatory responses and acts as a general inhibitor of both TH1 and TH2 cells in vitro and in vivo [16] . 220 P. Potter

IL-10 promotes IgG4 while TGF switches B cells toward IgA promoting IgA antibody production. For successful SIT induction of cells of the CD4+ CD25 type secreting IL-10 and TGF-B is essential for the suppression of allergen induced immune responses. Oral administration of antigens typically generates TGF B secreting T cells (Tr1/ Th3), which localize to the target organ and suppress inflammation in the local microenvironment [16] . Animal studies at the Pasteur Institute (Paris), Ben Mohamed L et al. [17] have shown that sublingual delivery of lipoproteins results in stronger systemic responses in lymph nodes and in the spleen than subcutaneous administration, without adjuvant. The mucosal route resulted in preferential induction of gamma interferon producing cells and of IgG2a antibodies, compared to the dominant IL-4 and IgG, responses from the subcutaneous route. However, using sublingual allergen immunotherapy, the presence of systemic immune effects on IgG4/IgE ratios (p = 0.05) and reduction in late phase SPT responses (p = 0.003) were not accompanied by changes in the sublingual epithelium or lamina propria for CD3+ cells, CD1a cells, CD68+ cells, or IL-2mRNA [9] . Oral dendritic cells have higher levels of FcER expression when compared with skin dendritic cells and activation of this receptor leads to secretion of IL-10 in monocytes. This unique environment in the oral mucosa contributes significantly to inflammatory suppression via the oral route. Its importance in SLIT remains to be explored. If allergens are given in high doses in a noninflammatory environment where there is a no co-stimulation by accessory molecules, immunological “suppression” rather than immune “activation” is favored Recently, the role of suppressive cytokines such as IL-10 and TGF-B as key molecules in the maintenance of peripheral tolerance has been highlighted. IL-10 enhances IgG4 and TGF-B enhances IgA secretion, while IgE production is suppressed by these cytokines. Allergens entering the mucosal surfaces are regulated by both IL-10 and TGF-B. Oral administration of antigen induces antigen specific TGF-B secreting T cells (Tr1/Th3), which localize to the target organ and suppress inflammation in the local environment. For bee venom SIT, Adkis et al. have found that an early increase in IL-10 (within a month) and an increase in TGF-B within 1 year correlates well with successful treatment and recently an increase in IL-10 was shown to accompany successful sublingual immunotherapy [18] . Pharmacokinetics of sublingual immunotherapy have been investigated by Bagnusco et al. [19] using 123 I labeled purified parietaria allergen (Par j 1) and sequential scintiscans, plasma radioactivity, and plasma chromatographs. It was found that allergen was retained up to 40 h in the oral mucosa and that native allergen could not be detected in the bloodstream after swallowing. Oral dendritic cells “retain” allergen and Fc Epsilon receptor bearing cells in the oral mucosa of allergic subjects, which may be important in the induction of tolerance during SLIT. Further, long-term sequential studies are required to understand the immunological mechanisms underlying successful sublingual immunotherapy. The application of Sublingual Immunotherapy in Allergic Rhinitis and Asthma 221 recent knowledge in peripheral tolerance mechanisms may well facilitate the development of more potent and effective sublingual vaccines [20] .

Clinical Evidence of Efficacy

SLIT is commercially available and used routinely in Europe, parts of the Middle East, Malaysia, Southern Africa, and in South America. In a recent update, Passalacqua and Canonica [21] reported on the clinical results of 36 double blind placebo controlled studies, which have been conducted on SLIT to date. Nine new studies [22– 30] had been published between 2004 and 2006. All of the studies confirmed that SLIT was effective in reducing the symptoms of rhinoconjunctivitis and when present, also concomitant asthma. In the recent large placebo controlled study by Niu et al. (2006) [22] the clinical efficacy of SLIT in asthmatic children with mite allergy was also confirmed. An important meta analysis of Wilson et al. (2005) [31] confirmed that sublingual immunotherapy was effective and safe for allergic rhinitis and highlighted the paucity of studies on SLIT in asthma and particularly in children. A new meta analysis of 10 pediatric studies has confirmed that SLIT is effective in reducing the rescue medication and symptom scores in children [32] , compared with placebo. In a review, comparing the clinical efficacy and safety of subcutaneous and sublingual immunotherapy, Malling [33] drew attention to the importance of using clearly defined selection criteria, extracts, dosing schedules, and outcome variables. Very few studies meet such criteria for direct comparison. The first methodologically optimal comparison between sublingual and subcutaneous immunotherapy evaluated over 2 years was reported by Khinchi et al. 2004 [34] . Despite a number of dropouts in this study of 71 subjects no significant difference in symptom and medication scores was observed among the groups using a commercial birch pollen extract as the allergen. The cumulative dose in the SLIT treated patients was 175 times the dose given subcutaneously in the first year. This study also drew attention to the importance in taking into consideration the pollen load in such a study. In the patients on SLIT, a reduction of 50% was observed, but in view of small numbers assessment of the statistical difference between SLIT and SLIT treated groups was not possible. The World Allergy Organization (WAO) has stressed the importance of conduct- ing methodologically sound studies in a recent WAO document [35]. In a new ARIA document (Allergic Rhinitis and its Impact on Asthma group, in co-operation with Ga2LEN (Global allergy and asthma European Network). Passalacqua and Durham have also conducted an update on allergen immunotherapy in which the evidence for efficacy, safety, and additional effects of sublingual immunotherapy is reviewed [36] . Clinical efficacy has been confirmed for SLIT for rhinitis for most of the common allergens including grasses, trees, ragweed, parietaria, and mites. For asthma a 2 year course of SLIT significantly reduced the severity of bronchial hyperresponsiveness [37] . 222 P. Potter

Since the meta analysis of Wilson [31] , further studies have confirmed the efficacy of SLIT in children with allergies to grass pollen [38, 39] and house dust mites [40] . SLIT is highly suitable for children for long term use because it is less invasive than subcutaneous injections. In a long term study of SLIT in children by Rienzo [5] , the prevalence of asthma was greatly reduced 4–5 years after discontinuation of the vaccine. The long term benefit may be particularly important in children with more severe symptoms [40] .

New Dosing Regimes

Although sublingual immunotherapy has been proven to be safe and efficacious for allergic conjunctivitis and in asthma optimal dosing regimens are still being explored. It is conventionally accepted that treatment doses up to 375 times of those used in subcutaneous immunotherapy are necessary for efficacy, but it is unclear if a time dose-response relationship exists. The frequency of SLIT administration may be crucial to its efficacy, and possibly more so than the cumulative dose. This hypothesis has been recently evaluated in an open study by Bordignon and Burasten [41] in which 64 patients with birch or grass pollen were studied using different regimes over a 2 year period. Some subjects received their immunotherapy drops 3 times daily. It was found that in patients who received their sublingual drops more frequently (3 × daily), the number of administrations correlated with the efficacy of SLIT as measured by antihistamine use. There was no increase in adverse effects and skin prick reactivity was modulated parallel to increased frequency of SLIT use. It was suggested that multiple daily doses may provide a much greater impact on the overall allergen absorption through the oral mucosa than the concentration of the allergen or its cumulative amount. Using this regime an induction phase of administration is avoided. Further studies are needed to compare such regimes with the usual “high dose” SLIT administration regimes. Availability of a new dissolving tablet form of SLIT also opens up greater possibilities of the wider use of SLIT, because of its stability, simplicity of administration and easiness of storage. Strategies to enhance the allergen presentation to local dendritic cells, e.g., by regulatory T cells should be intensified [42] .

Economic Evaluation

Few data are available on the pharmacoeconomic aspects of sublingual immunotherapy. In a new study by Bertho et al. (2006) [43] costs, clinical outcomes, and cost effectiveness of SLIT plus pharmacotherapy was compared with pharmacotherapy alone using data on approximately 2,000 patients. From both perspectives SLIT was less expensive and more effective than pharmacotherapy alone. Sublingual Immunotherapy in Allergic Rhinitis and Asthma 223

Safety

There is good evidence to support the excellent safety profile of SLIT. In more than 20 years of clinical trials and commercial usage no or fatal event has ever been reported [44] . Pooled safety data has been reviewed again by Canonica [45] in 2006. In the pooled data from 472 adults published by Andre et al. [46] , adverse occurred in 39% of individuals receiving active SLIT and 23% in the placebo groups. Adverse events were minor non-specific and mild systemic reactions and there were never any anaphylactic reactions. The main reason for stopping therapy in the few patients who dropped out (14 on active and 10 on placebo) was repeated buccal and abdominal discomfort. The most frequent side effect of SLIT was oral itching and swelling, which disappears within a few weeks. The gastrointestinal events appear to be dose related, but also disappear with time as tolerance is achieved. Seventeen systemic reactions have however been recently reported, including 2 cases of anaphylaxis [47, 48] when using non-standardised extracts [47] or a rush administration of a latex extract [48]

Psychological Stress and Response to SLIT

Psychological stress has recently been shown to play a role in atopy and to also affect the response to immune modulating therapies such as vaccinations with microbial agents. In a new study by Ippoliti et al. (2006) of 40 children with asthma undergoing SLIT, there was a higher prevalence of psychosocial stressing factors (divorced/absent parents, low income households, nonworking parents) among stressed children. All clinical parameters and ECP concentration improved after SLIT in all patients, but greater improvements in symptom score, peak expiratory flow, and ECP occurred in the nonstressed patients. Stress evaluation is a useful prognostic factor in immunotherapy, as it may also have a bearing on adherence to medications, particularly over the long term. It should, however, also be borne in mind that on chronic allergic illness can also in its own right result in chronic stress for the patients if untreated. Sublingual immunotherapy has great potential to improve the quality of life of such patients [49] .

Future Directions

Since the efficacy and safety of sublingual immunotherapy has been confirmed in numerous DBPC trials [22– 30] and meta analysis [32] , and according to a Cochrane review discussed in this chapter [31] , this form of therapy holds great promise for the future . Further research is required to determine optimal dosing and studies confirming efficacy of the new tablet formulations [50] are extremely important. Further studies on different tablet formulations are in progress. In the future, vaccine preparation strategies will focus on the use of biological or systemic adjuvants, which would improve the continuous allergen release and 224 P. Potter presentation to oral Langerhans cells. These may include regulatory T cell adjuvants. Further research is also required as to how to best select patients for sublingual immunotherapy and whether mixtures of allergens would have any efficacy in sublingual immunotherapy vaccines, since only about 20% of allergic subjects are monosensitive, and efficacy has only been confirmed to date for SLIT using mon- ovalent vaccines. For the purposes of marketing and registration it is also important that larger multicentre studies are conducted around the world to test efficacy and applicability of specific vaccines to allergy sufferers around the world. This is particularly important because of the potential for SLIT to be administered also by nonallergy specialists to allergy sufferers in the developing world, where there is a paucity of allergy expertise, but an increase in the prevalence in allergic disease, which parallels those that observed in the developed nations of the world.

References

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13. Silvestri M, Spallarossa D, Battistini E, et al. Changes in inflammatory and clinical parameters and in bronchial hyperactivity in asthmatic children sensitised to house dust mites following sublingual immunotherapy. J Investig Allergol Clin Immunol 2002; 12: 52–59 14. Wachholz P, Durham S. Mechanisms of immunotherapy IgG revisited. Curr Opin Allergy Immunol 2004; 4: 313–318 15. Tari MG, Marciano M, Monti G, et al. Efficacy of sublingual immunotherapy in patients with rhinitis and asthma due to house dust mites: a double blind study. Allergol Immunopath 1990; 18: 277–284 16. Adkis M, Schmidt-Weber C, Jutel M, Adkis L, Blaser K. Mechanisms of allergen immunotherapy. Allergy Clin Immunol Int J World Allergy Org 2004; 16: 65–69 17. Ben Mohamed L, Belkard Y, Loing E, Brahimi K, et al. Systemic immune responses induced by mucosal administration of lipo peptides without adjuvant. Eur J Immunol 2002; 32(8): 2274–2281 18. Ciprandi G, Fenoglio D, Cirilli I, Vizzacaro A, Ferreira A, Tosca MA. Induction of interleukin 10 by sublingual immunotherapy for house dust mites: a preliminary report. Ann Allergy Asthma Immunol 2005; 95: 38–44 19. Bagnusco M, Manani G, Passalacqua G, Motta C, Falagiani P. Absorption and distributions kinetics of the major parietaria judaica allergen (Par j 1) administered by non-injectable routes in healthy human beings. J Allergy Clin Immunol 1997; 100: 122–129 20. Jutel M, Adkis M, Blaser K, Adkis CA. Mechanisms of allergen specific immunotherapy: T cell tolerance and more. Allergy 2006; 61: 796–807 21. Passalacqua G, Canonica G. Sublingual immunotherapy: update 2006. Curr Opin Allergy Clin Immunol 2006; 6: 449–454 22. Tonnel AB, Scherpereel A, Douay B, et al. Allergic rhinitis due to house dust mites: evaluation of the efficacy of specific sublingual immunotherapy. Allergy 2004; 59: 491–497 23. Bufe A, Ziegler-Kirbach E, Stoeckmann E, et al. Efficacy of sublingual swallow immunotherapy in children with severe grass pollen allergic symptoms: a double-blind placebo-controlled study. Allergy 2004; 59: 498–504 24. Smith H, White P, Annita I, et al. Randomized controlled trial of high-dose sublingual immunotherapy to treat seasonal allergic rhinitis. J Allergy Clin Immunol 2004; 114: 831–837 25. Rolinck-Werninghaus C, Wolf H, Liebke C, et al. A prospective, randomized double-blind, placebo-controlled multicentre study on the efficacy and safety of sublingual immunotherapy (SLIT) in children with seasonal allergic rhinoconjunctivitis to grass pollen. Allergy 2004; 59: 1285–1293 26. Bowen T, Greenbaum J, Charbonneau Y, et al. Canadian trial of sublingual swallow immunotherapy for ragweed rhinoconjunctivitis. Ann Allergy Asthma Immunol 2004; 93: 425–430 27. Dahl R, Stender H, Rak S. Specific immunotherapy with SQ standardized grass allergen tablets in asthmatics with rhinoconjunctivitis. Allergy 2006; 61: 185–190 28. Niu CK, Chen WY, Huang JL, et al. Efficacy of sublingual immunotherapy with high-dose mite extracts in asthma: a multicentre, double-blind, randomized and placebo-controlled study in Taiwan. Respir Med 2006; 100: 1374–1383 29. Passalacqua G, Pasquali M, Ariano R, et al. Randomized double blind controlled study with sublingual carbamylated allergoid in mild rhinitis due to mites. Allergy 2006; 61: 849–854 30. Durham SR, Yang WH, Pedersen MR, et al. Sublingual immunotherapy with once-daily grass-allergen tablets: a randomised controlled trial in seasonal allergic rhinoconjunctivitis. J Allergy Clin Immunol 2006; 117: 802–809 31. Wilson DR, Torres L, Durham SR. Sublingual immunotherapy for allergic rhinitis. Allergy 2005; 60: 3–8 32. Penagos M, Compalati E, Tarantini F, Baena-Cagnani R, Huerta J, Passalacqua G, Canonica GW. Meta analysis of sublingual immunotherapy in pediatric patients. Ann Allergy Asthma Immunol 2006; 97: 141–148 33. Malling HR. Comparison of the clinical efficacy and safety of subcutaneous and sublingual immunotherapy: methodological approaches and experimental results. Current Opin Allergy Clin Immunol 2004; 4: 539–542 226 P. Potter

34. Khinchi MS, Poulsen LK, Carat F, et al. Clinical efficacy of sublingual and subcutaneous birch pollen allergen-specific immunotherapy: a randomized, placebo-controlled, double- blind, double-dummy study. Allergy 2004; 59: 45–53 35. Canonica W, Baena-Cagnani C, Bousquet J, Bousquet JP, Lockey RF, Malling HJ, Passalacqua G, Potter PC, Valovirta E. Recommendations for standardization of clinical trials with allergen specific immunotherapy for respiratory allergy. Statement of a WAO – World Allergy Organization Task Force. Allergy 2007; 62: 316–324 36. Passalacqua G, Durham S. In corporation with the Global Allergy and Asthma and European Network (Ga2Len) (2007). Allergic Rhinitis and its impact on asthma: Update on allergen immunotherapy. J Allergy Clin Immunol 119: 881–891. 37. Pajno GB, Passalacqua G, Vita D, Parmiani S, Barbeiro G. Sublingual immunotherapy abrogates seasonal bronchial hyperresponsiveness in children with parietaria induced respiratory allergy: a randomized controlled trial. Allergy 2004; 59(8): 883–887 38. Novembre E, Galli E, Landi F, Caffarelli C, Piffen M, De ME. Co-seasonal sublingual immunotherapy reduces the development of asthma in children with allergic conjunctivitis. J Allergy Clin Immunol 2004; 114: 851–857 39. Bufe A, Ziegler-Kirbach E, Stoeckman E, Heidermann P, Gehlhar K, Hollard Letz T. Efficacy of sublingual swallow immunotherapy in children with severe grass pollen symptoms: a double blind placebo controlled study. Allergy 2004; 59: 498–504 40. Marcucci F, Sensi L, Di GG, Salvatori S, Bernini M, Pecora S, et al. Three year follow up of clinical and inflammation parameters in children monosensitised to mites undergoing sublingual immunotherapy. Paediatr Allergy Immunol 2005; 16: 519–526 41. Bordignon V, Burastero SE. Multiple daily administration of low dose sublingual immunotherapy in allergic rhinoconjunctivitis. Ann Allergy Asthma Immunol 2006; 97: 158–163 42. Reider N. High dose sublingual immunotherapy: too much of the good! Ann Allergy 2006; 97: 125 43. Berto P, Passalacqua G, Crimi N, Frati F, Ortolani M, Senna G, Canonica GW. Ann Allergy Asthma Immunol 2006; 97: 615–621 44. Passalacqua G, Guerra L, Pasquali M, Lombard C, Canonica GW. Efficacy and safety of sublingual immunotherapy. Ann Allergy Asthma Immunol 2004; 93: 3–12 45. Canonica GW, Passalacqua G. Sublingual immunotherapy in the treatment of adult allergic patients. Allergy 2006; 61 (Suppl 81): 20–23 46. Ippoliti F, De Santos W, Volteranni A, Caritario N, Frattolillo D, Lucarelli S, Frediani S, Frediani T. Psychological stress affects response to sublingual immunotherapy in asthmatic children allergic to house dust mite. Paediatr Allergy Immunol 2006; 17: 337–345 47. Dunsky EH, Goldstein FM, Dvorin J, Bela-Canech G. Anaphylaxis to sublingual immunotherapy. Allergy 2006; 61: 1235. 48. Antico A, Pagan M, Crema A. Anaphylaxis by sublingual immunotherapy. Allergy 2006; 61: 1236. 49. Potter PC, Thomas H, Terblanche L. Quality of life as a monitoring index and global score as an outcome index in sublingual immunotherapy for allergic rhinitis. Curr Allergy Clin Immunol 2006; 19(3): 161 50. Didier A, Melac M, Combebias A, Andre C. Efficacy and safety of sublingual immunotherapy tablets in grass pollen rhinoconjunctivitis. J Allergy Clin Immunol 2006; 117: 721 (abstract) Anti-IgE in Allergic Airway Diseases: Indications and Applications

Jennifer Preston DeMore and William W. Busse

Introduction: Role of IgE and Anti-IgE Molecules

IgE plays a role in both the initial sensitization to antigen and the subsequent effects upon repeat exposure. For sensitization, inhaled antigen is ingested by antigen presenting dendritic cells that line the airway, and then processed and presented to antigen-specific T cells. The subsequent production of cytokines stimulates B cells to produce antigen-specific IgE, which then binds to the surface of mast cells and basophils via the high-affinity receptor for IgE, namely Fce RI [1] (Fig. 1a ). Upon repeat exposure to an inhaled antigen, there is cross-linking of IgE bound to the surface of mast cells and basophils. This interaction signals mast cells and basophils to degranulate, releasing mediators such as histamine, prostaglandin, and leukotrienes, and to stimulate chemokine and cytokine production. These mediators cause an early or acute phase reaction and, under some circumstances, can lead to a late-phase reaction. IgE is an immunoglobulin that consists of a variable and constant region. The variable region is the area that binds to the antigen. Within the constant region, CHe 3 contains the binding sites for the two different receptors, Fce RI and Fce RII (Fig. 2 ). Given the biological effects of IgE, a novel mechanism to treat allergic disease, including asthma, would be to block IgE and its actions. However, an antibody to IgE could either stimulate or block this molecule. The antibody could stimulate IgE if IgE were already bound to receptors on mast cells and basophils. If the antibody is subsequently attached to the bound IgE, it could cause the cross-linking of at least two IgE molecules with subsequent degranulation. Depending on the degree of degranulation, this response may result in an acute allergic reaction. However, if an antibody could block IgE from attaching to its receptors on mast cells and basophils, degranulation could be prevented. Omalizumab is such a molecule; it is an anti-IgE antibody that binds to IgE regardless of IgE specificity.

J.P. DeMore () and W.W. Busse University of Wisconsin School of Medicine and Public Health , J5/219 CSC-2454, 600 Highland Avenue , Madison , WI 53792 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 227 DOI 10.1007/978-4-431-99362-9_14, © Springer 2010 228 J.P. DeMore and W.W. Busse

Fig. 1 Pathophysiology of asthma: Aeroallergens initially interact with the immune system when they are taken up by dendritic cells (a ). This process occurs by phagocytosis and may be enhanced after initial sensitization by the binding of allergen-specific IgE to high-affinity receptors (Fce RIs) on the surface of dendritic cells. Dendritic cells process the allergen, bound to major-histocompatibility- Anti-IgE in Allergic Airway Diseases: Indications and Applications 229

Fig. 2 Mechanism of action of human anti-IgE: Anti-IgE neutralizes IgE by binding to the constant region 3 of the IgE heavy chain at a site (inset CH e 3, green circle ) that overlaps the binding sties for both Fc epsilon receptor I (Fc e RI, white square ) and Fce RII or CD 23 ( yellow square ). This prevents IgE from binding to its receptors. Anti-IgE and IgE form trimers and hexamers that may “sweep” away allergens (a ). Anti-IgE reduces IgE receptors on basophils and mast cells ( c ) as well as dendritic cells (d ). Its effects on CD23, on B cells bearing membrane bound IgE (mIgE) ( e), and on the differentiation of IgE producing plasma cells are unknown. (Adapted from Annual Review of Medicine, with permission ( [2] , p. C-1))

Fig. 1 (continued) complex (MHC) molecules, and present it to T cells. T cells are stimulated by the interaction of MHC-bound antigen with surface T-cell receptors, causing T-cell proliferation and the subsequent release of cytokines. These cytokines stimulate B cells to become plasma cells that produce IgE. B cells express low-affinity Fce receptors (Fc e RIIs); interaction of IgE with these receptors may influence B-cell differentiation and regulation of IgE synthesis. IgE produced by plasma cells binds to the surface of mast cells and basophils and, when cross-linked by allergen, induces degranulation and the release of inflammatory mediators. This process results clinically in an acute asthma attack. Omalizumab is a monoclonal anti-IgE antibody that binds to the Fc region of the IgE molecule (b ). In so doing, Omalizumab prevents IgE from binding to cell-surface receptors. Omalizumab is unable to bind to IgE molecules that are already bound to Fc e RIs; as a result, it cannot induce anaphylaxis. Reduced binding of IgE to Fce RIs on mast cells and basophils inhibits degranulation and the release of inflammatory mediators. There is also a marked downregulation of Fce RIs. Reduced IgE binding to Fce RI on dendritic cells may reduce the ability of these cells to process antigen efficiently. Reduced IgE binding to Fce RII on B cells is thought to alter B-cell differentiation and the regulation of IgE synthesis. All these effects may contribute to the prevention of acute exacerbations of asthma. (Adapted from New England Journal of Medicine, with permission. Copyright © 2006 Massachusetts Medical Society. All rights reserved ( [1] , p. 2690)) 230 J.P. DeMore and W.W. Busse

It attaches to the IgE molecule in the CH e3 region, which is the same region that contains the binding sites for Fc e RI and Fce RII. Omalizumab does not bind to IgA or IgG. Once Omalizumab is bound to IgE, the resulting complex is blocked from binding to either Fc e RI or Fc e RII receptors. It is thought that a conformational change takes place on the IgE molecule to prevent binding to receptors, but IgE can still bind another Omalizumab molecule for a total of 2 Omalizumab molecules/IgE molecule [2] (Figs. 1b and 2). Two antibodies were initially developed as anti-IgE molecules. Omalizumab was the antibody chosen for further development. Omalizumab, approved for use in moderate-to-severe asthma in the United States, is also known as rhuMAb-E25, rhuMab, or Xolair, and is a recombinant humanized monoclonal anti-IgE antibody of mouse origin. To produce Omalizumab, mice are immunized with human IgE, and their B cells are harvested and fused with myeloma cells, whereby a hybridoma is produced. The antibody is then humanized by grafting the light chains onto a human IgG1 molecule. The origin of the molecule is 95% human and 5% murine [2] .

Proof of Concept of Omalizumab Actions in Asthma

Boulet et al. [3] conducted a multicenter, randomized, double-blind, parallel group study, in which 20 allergic asthmatic subjects received either intravenous Omalizumab or placebo. They then underwent an inhaled antigen challenge to testvthe action of anti-IgE. The concentration of allergen that provoked a 15% fall in FEV1 during the early asthmatic response was first determined. Subjects in the

Omalizumab group required a double dose of allergen to cause a 15% fall in FEV1 compared to baseline values, indicating a blockage of IgE actions [3] . Subsequently, Fahy et al. [4] studied 19 allergic asthmatic subjects in a randomized, double-blind, parallel group study. After 9 weeks of anti-IgE treatment or placebo, the effects of allergen inhalation on the early- and late-phase response to inhaled antigen were measured. When the subjects received Omalizumab, there was a significant increase in the dose of allergen needed to induce an early response, and both the early- and late-phase falls in FEV1 were significantly reduced [4] . Both studies demonstrated that Omalizumab blocks the allergic airway response to inhaled antigen, and as a consequence, may be an effective treatment for asthma by reducing the allergic airway response to allergen.

Clinical Efficacy in Allergic Asthma

Omalizumab was initially studied in moderate-to-severe asthmatic patients in a phase I study [5] . Once the safety and tolerance in humans was determined, a phase II double- blinded, placebo-controlled, multicenter study was conducted, involving 317 subjects who required inhaled corticosteroids (ICSs) or oral corticosteroids for asthma treatment. Anti-IgE in Allergic Airway Diseases: Indications and Applications 231

In that study, the subjects received either intravenous placebo or low-dose or high- dose Omalizumab. Those treated with Omalizumab showed improved asthma symptom scores and a decrease in ICSs and beta-agonist use without a loss of asthma symptom control, an improved quality of life, and a trend toward the ability to discontinue oral corticosteroid use [6] .

Design of Studies

Cochrane Database of Systematic Reviews examined the efficacy of anti-IgE in subjects with chronic asthma. This review pooled data from 14 randomized controlled trials and totaled 3,143 mild-to-severe allergic asthmatic subjects. The inclusion criteria for the studies included a positive skin test to a perennial aeroallergen and serum IgE levels greater than 30 and lesser than 700 to 1,300 IU/mL. Seven studies examined anti-IgE therapy as an adjunct to either inhaled or oral corticosteroid use. These studies used a run-in phase, during which the corticosteroid dose was titrated to the minimal amount of medication necessary to maintain symptom control, referred to as the “stable steroid phase.” After Omalizumab treatment for a period of 12—28 weeks, some studies tried to further taper the corticosteroid doses of their subjects, adding a steroid tapering phase to the trial [7] .

Asthma Exacerbations

The Cochrane Review found that the frequency of asthma exacerbations reduced with Omalizumab use. Both the number of subjects experiencing an asthma exacerbation as well as the number of exacerbations experienced reduced. The reduction in frequency of asthma exacerbations was also seen despite the taper of ICSs [7– 12] . Even subjects with severe asthma experienced fewer exacerbations on Omalizumab treatment as well as a reduction in the number of severe exacerbations [11] . Hospitalizations for asthma also significantly reduced [8– 10] . In adults on Omalizumab, the duration of an asthma exacerbation was reduced to 7.8 days compared to the average duration of 12.7 days in the placebo-treated group [8] . In children, Omalizumab did not reduce the duration of the exacerbation. [10] .

Inhaled Corticosteroids

During the steroid tapering phase, the endpoint dose of ICS was reduced. In the Omalizumab-treated groups, a greater reduction in ICSs was noted when compared to the placebo group. This effect was seen in both adults and children [8– 12] . In adults, the Omalizumab-treated group was able to reduce their dose of ICSs by 75% 232 J.P. DeMore and W.W. Busse compared to 50% by the placebo-treated group [8] . Of note, the placebo-treated group also had quite a high percentage of individuals who were able to reduce their corticosteroid dose as well. Using a pooled analysis, the Cochrane Database found that the subjects on Omalizumab were able to decrease their ICSs by a mean value of 119 mcg/day which, though relatively small, was still a significant reduction when compared to placebo [7] . Studies also determined the frequency of a complete withdrawal of ICSs. Adults and children who took Omalizumab were more likely than placebo-treated subjects to discontinue ICS use completely [8– 12] . Overall, treatment with Omalizumab allowed for a reduction or total discontinuation of ICSs in some asthmatic subjects.

The Effect of Omalizumab on Other Medication Use, Including Beta-2 Agonists and Oral Corticosteroids

Subjects who received Omalizumab also required less rescue beta-2 agonist use [8– 12] . Pooled analysis found the reduction in rescue medication to be 0.63 and 0.74 puff/day in the steroid-stable and steroid-taper phases, respectively. No significant differences were seen in the reduction or withdrawal of oral steroids between the Omalizumab and placebo groups. In addition, a study examined a subgroup of subjects taking leukotriene receptor antagonists and found no additional effect to Omalizumab [7] .

Lung Function

There has been no consistent effect of Omalizumab on lung function. No differences in morning peak expiratory flow or FEV1 end of treatment values were noted between Omalizumab-treated and placebo-treated groups. However, two trials did note small, but not clinically significant, changes with Omalizumab on baseline

FEV1 values [11, 12] .

Quality of Life

Assessment of asthma-related quality of life was performed using the Asthma Quality of Life Questionnaire (AQLQ) at different phases throughout two of the 52-week trials. For those receiving Omalizumab, there were statistically significant improvements in all domains as well as the overall AQLQ score. The domains addressed included activity limitations, emotions, environmental exposure, and symptoms. Furthermore, the AQLQ improvement was clinically significant in a higher proportion of subjects in the Omalizumab-treated groups. Improvement was also found during the reduction of ICSs [13, 14] . Anti-IgE in Allergic Airway Diseases: Indications and Applications 233

Severe Asthma

Patients with severe asthma require either high doses of ICSs with long-acting beta-2 agonist or daily oral corticosteroids. Holgate et al. [15] investigated the effect of Omalizumab on severe asthmatic subjects on high-dose ICSs; more subjects in the Omalizumab group were able to significantly reduce their ICS dose. In addition, Omalizumab-treated subjects had fewer asthma exacerbations, but this effect did not reach statistical significance [15] . Humbert et al. also examined the effect of Omalizumab on severe asthmatic subjects. These subjects had a recent history of an exacerbation. The Omalizumab-treated group experienced less asthma exacerbations, fewer severe exacerbations, and a lower rate of emergency room visits [11] .

Children

Children with allergic asthma have also been found to benefit from treatment with Omalizumab. Milgrom et al. [10] evaluated children, 6–12 years of age, with moderate-to-severe allergic asthma. Compared to placebo treatment, more children who received Omalizumab were able to reduce their ICS dose, have a greater reduction in their ICS dose, and experience fewer asthma exacerbations. Asthma symptom scores and spirometry were relatively unaffected by active treatment. There was also a trend for children in the treatment group to miss fewer days of school [10] . A greater number of subjects treated with Omalizumab had clinically relevant improvements in their quality of life scores using the Pediatric AQLQ, limited to the domains of activities and overall quality of life [16] . Children who were treated with Omalizumab for a total of 52 weeks tolerated the medication well, with the same frequency of adverse events as those who received the placebo [17] .

Predictors of Response to Omalizumab

In the studies to evaluate the effects on asthma, some subjects have shown either minimal or no response to Omalizumab. Given this variability, it would be beneficial to know which patients are more likely to benefit from this treatment. Bousquet et al. [18] used two randomized, double-blind, placebo-controlled trials to retrospectively determine the predictors of response to Omalizumab. The best predictor of a positive response to Omalizumab was an emergency asthma treatment in the past year, which was defined as a hospital or emergency room visit or an urgent doctor visit. Subjects with FEV 1 of less than 65% predicted or receiving a high dose of ICS (equivalent to budesonide > 800 m g/day) were also more likely to respond to treatment. Baseline values of IgE were not found to predict a subject’s response to Omalizumab [18] (Fig. 3 ). 234 J.P. DeMore and W.W. Busse

Fig. 3 Venn diagram of odds ratios (corresponding 95% CIs) for response with Omalizumab relative to placebo for the composite definition of response, according to three high-severity baseline covariates. (Adapted from Chest, with permission conveyed through Copyright Clearance Center, Inc. ( [18] , p. 1384))

Asthma Guidelines

The National Asthma Education and Prevention Program Expert Panel (NAEPP) Report 3 addresses the use of anti-IgE therapy in asthma patients and recommends that practitioners consider anti-IgE as adjunctive therapy for patients, with severe persistent asthma and documented allergic disease, who are inadequately controlled on high dose ICSs and long-acting beta-agonist, i.e., step 5 or 6 therapy. In addition, patients who require oral corticosteroids, i.e., step 6, may also benefit from anti-IgE therapy (evidence B). The NAEPP asthma guidelines also state that patients, who are on step 4, have underlying allergies, and are on medium doses of ICSs and long- acting beta-agonist may also benefit from anti-IgE therapy in order to avoid the need for larger doses of corticosteroids. However, this recommendation lacks comparator trials and is considered evidence D [19] (Fig. 4 ).

Allergic Rhinitis

Allergic rhinitis is also an IgE-mediated disease that significantly impairs quality of life as well as productivity in school and work. Subjects with a history of ragweed-induced seasonal allergic rhinitis were enrolled and randomly given one of Anti-IgE in Allergic Airway Diseases: Indications and Applications 235

Fig. 4 National Asthma Education and Prevention Program Expert Panel (NAEPP) Report 3 addresses the use of anti-IgE therapy as an adjunct in asthma patients, with severe persistent asthma and allergies, who are inadequately controlled on high-dose inhaled corticosteroids and long-acting beta-agonist or who require oral corticosteroids. (Adapted from [19] , pending publication)

three doses of Omalizumab or placebo. Treatment was started prior to and continued through the ragweed pollination season. Subjects who received a 300 mg dose of Omalizumab experienced significantly less nasal and ocular symptoms and also needed less amounts of rescue antihistamine medication. Furthermore, rhinitis- specific quality of life scores improved even during the peak time of ragweed pollination. Serum values of lower free IgE levels also correlated with less severe nasal symptoms and need for rescue antihistamines [20] . A similar level of symptom control and reduction in rescue medication was seen in subjects, who were treated with Omalizumab, with seasonal allergic rhinitis to birch pollen. [21] . Patients with perennial allergic rhinitis may also benefit from Omalizumab. Over 16 weeks of treatment, subjects experienced a lower severity of nasal scores, reduced need for rescue antihistamine use, and improved rhinoconjunctivitis- specific quality of life. The nasal severity score was graded on a four-point scale from none to severe, based on the following four symptoms: sneezing, itchy, runny and stuffy nose [22] . An update of the pharmacologic treatment of allergic rhinitis by the Allergic Rhinitis and its Impact on Asthma (ARIA) Workshop Report has proposed that there exists level A evidence for anti-IgE treatment use in both seasonal and perennial rhinitis in adults as well as children [23] . 236 J.P. DeMore and W.W. Busse

Allergic rhinitis is very common in patients with asthma and, if present, may also complicate the management of asthma. There is evidence that by controlling symptoms of allergic rhinitis, asthma control may also improve. The shared pathogenesis of these two conditions and the shared upper and lower airway make targeting both diseases with one treatment an ideal concept in the approach to treatment [24] . Patients with allergic asthma and concomitant persistent allergic rhinitis were studied in the SOLAR trial. Subjects who received Omalizumab as add-on therapy experienced fewer asthma exacerbations and had a clinically significant improvement in both the AQLQ and the Rhinitis Quality of Life Questionnaire (RQLQ). However, the use of rescue medications, both short-acting beta-agonists and antihistamines, was similar between the groups [12] .

Mechanism of Action of Anti-IgE

Anti-IgE inhibits the binding of IgE to effector cells by attachment to circulating free IgE molecules. IgE molecules that are bound to anti-IgE are unable to bind to the receptors on the effector cells. Milgrom et al. [6] demonstrate the reduction in free IgE through the administration of intravenous Omalizumab to occur 1 h after dosing [6] . Besides inhibiting IgE binding on cells to Fce RI receptors, Omalizumab also decreases the number of high-affinity Fc eRI receptors. When Fce RI is on the cell surface, it is either bound to IgE, stabilizing the receptor to remain on the surface, or is internalized and degraded. If no IgE is bound to the receptor, it is internalized, degraded, and not available for IgE binding. This reduction in receptors was noted by MacGlashan and colleagues on basophils of subjects treated with Omalizumab [25] . The reduction in receptor density was significant with mean values at baseline of 220,000, going to 8,300 /basophil following treatment. When basophils from patients treated with Omalizumab were subsequently challenged with allergen, histamine release was reduced by 90% [25] . The receptors on mast cells were also reduced with the administration of Omalizumab. The reduction of Fce RI on mast cells occurred later than that observed with basophils, but the effects lasted longer due to the greater lifespan of mast cells [26] . Precursor dendritic cells, both subsets 1 and 2, are an earlier developmental stage of dendritic cells, and differentiate into dendritic cells upon migration into tissues. Precursor dendritic cells subsets 1 and 2 are associated with Th1 and Th2 immunologic responses, respectively. Both these dendritic cell subsets show a reduction of surface Fce RI expression following Omalizumab use. A tenfold decrease in free IgE corresponded to a 42 and 54% decrease in Fce RI on precursor dendritic cells subsets 1 and 2, respectively [27] . The reduction of IgE on these effector cells may diminish the patient’s response to an allergen as there is less antigen uptake. Allergen cannot be processed by the dendritic cell and presented to cells; consequently, this effect by Omalizumab could reduce IgE production and affect the ongoing sensitization to allergens. Anti-IgE in Allergic Airway Diseases: Indications and Applications 237

Omalizumab may also affect B cells, reducing the expression of the low-affinity receptor, Fc eRII. With a decrease in circulating IgE, IgE binding to Fce RII is also reduced and this effect is thought to subsequently affect B cell differentiation into plasma cells. With this Fce RII alteration in expression, IgE synthesis is thought to subsequently decline [1] . Omalizumab has other anti-inflammatory effects as well. Djukanovic et al. [28] found reductions in IgE-bearing cells in the airway mucosa biopsies and significant decreases in the mean percentage of sputum eosinophils with Omalizumab treatment. This decrease was coupled with a decrease in the submucosal cells of B lymphocytes, IL-4 staining cells as well as CD3+, CD4+, and CD8+ T lymphocytes. No improvement was observed in airway hyperresponsiveness with methacholine. However, all subjects had mild asthma. In addition to reducing serum-free IgE, Omalizumab decreases IgE in the airway mucosa of asthma subjects [28] . Noga et al. [29] , who previously found a decrease in circulating IL-13, also noted further anti-inflammatory effects with Omalizumab treatment. To further investigate the underlying mechanism, they found that the Omalizumab-treated group had increased Annexin V, a marker of eosinophil apoptosis, decreased GM-CSF+ lymphocytes as well as experienced a reduction in IL-2 + and IL-13 + lymphocytes with subsequent downregulation of cytokines IL-2 and IL-13. No differences were seen in IL-5, IFN- g , or TNF- a . Their findings suggest that the reduction in both tissue and circulating eosinophils caused by Omalizumab may occur by promoting apoptosis along with a reduction of GM-CSF, which normally supports eosinophil viability. The reduction in IL-2 is likely to affect the proliferation and activity of eosinophils. It is of interest that IL-5, which is an important growth factor for eosinophils, was unaffected by Omalizumab [29] .

Pharmacokinetics of Omalizumab

A dose-related decrease in circulating free IgE levels occurs with Omalizumab treatment. The clinical efficacy of Omalizumab has been shown to occur when free IgE levels are less than 10 IU/mL. To achieve this effect on IgE in the treated patient, the recommended dose schedule is 0.016 mg/kg/IU of serum IgE. Dosing is dependent on the weight of the patient and the initial total IgE level [30, 31] (Fig. 5 ). As Omalizumab is an IgG1 molecule, its serum half-life is 26 days, which is longer than IgE. When Omalizumab binds to IgE, the amount of total IgE increases, but the amount of free IgE decreases. With the administration of Omalizumab, there is an initial increase in total IgE. Currently, the measurement of free IgE is only a research tool and not available to assess treatment response. If patients experience a treatment interruption of less than 1 year, the dosing of Omalizumab should be based on the initial IgE prior to starting therapy, as total serum IgE changes with treatment. 238 J.P. DeMore and W.W. Busse

Fig. 5 Dosing schedule for subcutaneously administered Omalizumab, according to the baseline serum IgE level and body weight. The recommended dose is 0.016 mg/kg of body weight per international unit of IgE every 4 weeks, administered subcutaneously at either 4-week (italic) or 2-week (roman) intervals for adults and adolescents (persons 12 years of age and older) with allergic asthma. Dashes indicate that no dose should be prescribed. (Adapted from New England Journal of Medicine, with permission. Copyright © 2006 Massachusetts Medical Society. All rights reserved ( [1] , p. 2692))

The onset of action of Omalizumab depends on the route of administration. When given intravenously, a reduction in free IgE occurs within 1 h of Omalizumab administration [6] . When Omalizumab is given subcutaneously, 4 weeks are required for a significant reduction in the free IgE level [20] . The peak serum concentration of Omalizumab is seen 7–8 days after administration. Bousquet et al. [18] examined the time for a clinical response to Omalizumab. Of the patients who experienced improvement at 16 weeks of treatment, 61% showed some benefit by 4 weeks from initiating treatment. Of those benefiting from Omalizumab, 87% had an effect at 12 weeks. Based on these findings, the investigators recommend continuing treatment for at least 12 weeks to assess whether benefit will occur [18] . With the discontinuation of anti-IgE therapy, IgE levels return to their prior levels. Patients do not experience a “rebound” effect with a further elevated IgE. In fact, some patients had IgE levels below their pretreatment level when evaluated 1 year after the discontinuation of Omalizumab treatment. The basophils from these patients also showed a reduction of Fce RI compared to their pretreatment levels, but histamine release to antigen had returned to baseline values by 1 year [32] .

Safety of Omalizumab

The safety of Omalizumab has been examined in a number of clinical trials. Pooled data from the Cochrane Database found that the only statistically significant difference in adverse events was an increase in injection site reactions compared to placebo with the subcutaneous administration [7] . Anti-IgE in Allergic Airway Diseases: Indications and Applications 239

However, concerns have been raised recently that Omalizumab may cause anaphylaxis in some patients. In premarketing clinical trials, the incidence of anaphylaxis was three patients out of 3,507 or less than 0.1%. Since the approval by Food and Drug Administration in the United States, postmarketing data were collected until December 2005; during this time, 48 case reports of anaphylaxis were made. The estimated number of patients treated with Omalizumab by this time was 39,500, which gave a frequency of anaphylaxis of 0.1%. The case definition of anaphylaxis by the Food and Drug Administration was skin or mucosal tissue involvement with airway compromise, or a reduced blood pressure, with or without associated symptoms. A temporal relationship with Omalizumab administration, with no other identifiable cause, was needed to suggest a cause-and-effect relationship. The associated symptoms included bronchospasm, hypotension, syncope, urticaria, angioedema of the throat or tongue, dyspnea, cough, chest tightness, cutaneous angioedema, and generalized pruritus. The characteristics found in these case reports suggested that 71% of the patients with anaphylaxis experienced the onset of symptoms within 2 h of administration, while 13% of the reactions occurred up to 24 h later. Forty percent of the reported reactions occurred after the first dose of Omalizumab, while some reactions occurred following 2 years of therapy. Of the patients who experienced anaphylaxis to Omalizumab and were reported to have had a subsequent dosing, 56% experienced a repeat episode of anaphylaxis. Out of the symptoms noted with these reports of anaphylaxis, 96% of the cases had pulmonary involvement, such as bronchospasm, dyspnea, cough, or chest tightness. Thirteen percent were reported to experience hypotension or syncope. Some patients required oxygen or parenteral medications for treatment. Of these patients, 15% required hospitalization [33] . Due to concerns raised by these reports of anaphylaxis, the Food and Drug Administration in the United States recommended a boxed warning to the product. They also recommended that patients should be observed for 2 h after the administration of Omalizumab. These points are under consideration.

Neoplasms

Premarketing data had noted an elevated incidence of neoplasm in patients receiving Omalizumab. In the treatment group, 25 neoplasms were found in 20 of the 4,127 Omalizumab-treated patients for an incidence of 0.48%. In the control group, five neoplasms were found in five of 2,236 patients treated, at an incidence of 0.22%. In the treatment group, these tumors were diagnosed soon after Omalizumab was initiated and varied both in cell type and location, with no single type of neoplasm being more prevalent. The incidence of different types of neoplasm was comparable to the general population. A blinded review by independent oncologists found no link between Omalizumab treatment and neoplasm. An epidemiological study to follow the long-term effects of Omalizumab is currently underway [34] . 240 J.P. DeMore and W.W. Busse

Immune Complex and Antibodies

A theoretical concern of immune complex disease exists as IgE binds to anti-IgE; however, there has been no evidence of immune complex deposition or immune complex disease in the clinical trials. As IgE binds to anti-IgE, trimers or cyclic hexamers are formed. The cyclic hexamers that are formed are the size of naturally occurring IgM molecule and do not cause serum sickness or affect renal glomeruli. These immune complexes do not fix complement and are cleared by a low-avidity interaction between Fc gamma receptors of leukocytes and the reticuloendothelial system in the hepatic sinusoids [35] . Another concern was the development of antibodies to Omalizumab. In premarketing trials, only one subject developed IgG and IgA anti-Omalizumab antibodies; they resolved when re-evaluated 11 weeks later. This subject had received Omalizumab via an inhalation route. Subjects who received the drug via intravenous or subcutaneous route have not developed anti-Omalizumab antibodies [35] .

Helminth Infection

With the depletion of IgE during Omalizumab therapy, another concern was the enhanced susceptibility to parasitic infections. In premarketing trials, including 3,678 patients with 1,934 patient years, one helminth infection, namely pinworm, was reported. Since the approval of Omalizumab, there have been no spontaneous postmarketing reports of helminth infection in an estimated 39,000 patients [35] . To investigate the risk of intestinal helminth infection with Omalizumab treatment, a randomized, double-blind, placebo-controlled trial was conducted for 1 year with 137 patients, who were at high risk for parasite infection, in Brazil. Of those who experienced at least one infection, 50% were in the treatment group, while 41% were in the placebo group. Cruz et al. found a tendency toward an increased incidence of infection, but this tendency was not statistically significant. Compared to the placebo-treated group, subjects treated with Omalizumab had no difference in the time, severity, and morbidity of the infection or the response to treatment [36] .

Thrombocytopenia

In monkeys, thrombocytopenia occurred with supertherapeutic doses of Omalizumab. In comparison with adult monkeys, juvenile monkeys were more susceptible to a decrease in platelets at the same dose of Omalizumab. Premarketing trials showed that subjects had a decrease in platelet counts, but these declines were still within normal ranges and not necessarily associated with bleeding events. Anti-IgE in Allergic Airway Diseases: Indications and Applications 241

From postmarketing experience, one patient was reported to have severe thrombocytopenia, but as this was voluntarily reported, the true incidence of such reactions are unclear in comparison with the total number of patients who received this medication [35, 36] .

Summary

Anti-IgE therapy is a novel treatment for allergic airway diseases. Omalizumab was initially shown to affect early- and late-phase responses with antigen challenges. Clinical efficacy was demonstrated in both asthma and allergic rhinitis and in both adults and children in numerous well-designed, randomized, double-blind, placebo- controlled studies. The pharmacokinetics of Omalizumab have been examined and the safety of the medication has been studied. Further studies have helped elucidate the mechanism of action of Omalizumab and led to an insight into the pathophysiology of asthma.

References

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Bruce K. Rubin and James B. Fink

Introduction

Topical delivery of medications to the airway as medical aerosols is the first line treatment of asthma. Medical aerosols are produced by a range of devices and each device has its own characteristics, method of operation, and target patient population. Aerosol delivery can be a challenge as the structure of the airways is designed to minimize lung penetration of many aerosols found in the air around us; from dust and pollen to airborne pathogens. The smaller the airway, the greater the flow turbulence and therefore, the greater the volume of particles filtered. Thus, delivery of medical aerosols to children is often an order of magnitude less than adults [1] . This challenge is greater in asthma when there is airflow limitation, inflammation, excess mucus secretion, and airway remodeling [2] . Patient education for proper device use is as critical as proper device selection for effective therapy [3, 4] . In this chapter, we discuss the characteristics of aerosol devices and the best techniques for aerosol delivery in patients with asthma.

Aerosol Characteristics

An aerosol is a group of particles suspended in air. The lower the terminal settling velocity, the more stable the aerosol and the longer it remains in suspension. The settling velocity depends on both the particle size and density. Aerosol particle size

B.K. Rubin () Jessie Ball duPont Professor and Chairman of the Department of Pediatrics, Professor of Biomedical Engineering, Virginia Commonwealth University, Richmond, VA 23219, USA e-mail: [email protected] J.B. Fink Independent Consultant , San Mateo , CF , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 245 DOI 10.1007/978-4-431-99362-9_15, © Springer 2010 246 B.K. Rubin and J.B. Fink is usually reported as the mass median aerodynamic diameter (MMAD). For a uniformly spherical particle, this is defined as the particle diameter multiplied by the square root of the particle density. Because particles are non-uniform in density and shape, they are usually sized by their settling behavior on a series of baffles in a cascade impactor, yielding information about the MMAD and the particle size distribution or geometric standard deviation (GSD). The smaller the GSD, the greater the proportion of particles that will cluster around the MMAD. By convention, a GSD of less than 1.22 is called a monodisperse. Pressurized meter dosed inhalers (pMDI) and dry power inhalers (DPI) generally have a smaller GSD than that produced by jet nebulization [5] . Until recently, monodisperse aerosols have only been available for investigational use or for radioisotope studies of deposition. However, newer clinical devices produce a near monodisperse size distribution of particles. This could allow the targeting of particles to specific parts of the airway [6] . Because of variation in GSD, devices that generate similar MMAD may have different respirable mass, or volume percent of particles between 0.5 and 5 µm MMAD multiplied by the amount of aerosol inhaled at the mouthpiece. When a spacer or holding chamber is not used, up to 80% of the total emitted dose of a chlorofluorocarbon (CFC) powered inhaler deposits in the oral pharynx, leading to swallowing of medication, GI absorption, increased systemic effects, and loss of medication available to the lung. Oral pharyngeal deposition has been associated with thrush or laryngeal dysfunction with inhaled corticosteroids (ICS). Extremely fine particles, less than 0.5 µm MMAD, are so light that they may not sediment in the airway and can be exhaled. However, nanoparticles, less than 0.01 µm, such as those generated in the smoke of cigarettes, have the greatest penetration and retention in the lungs. Inertial impaction, gravitational sedimentation, and diffusion are the three major mechanisms of aerosol deposition and are particle size dependent. Inertial impaction is flow dependent and is the primary mechanism for deposition of particles larger than 3 µm. With high inspiratory flow, there is an increased tendency for even smaller particles to impact and deposit in the airway, while slow inspiratory flow allows larger particles to pass through the upper airways, into the lungs. The longer an aerosol particle resides in the airway, the greater the likelihood that it will deposit by sedimentation. It is for this reason that breath holding for 5–10 seconds is recommended after inhaling [7] . Diffusion primarily affects particles so small that Brownian motion is a greater influence on particle movement than gravity. Brownian movement results in both collision and coalescence of particles with both the surface of the airway and with other particles. The ability of a device to produce appropriately sized particles is a function of both how the device is designed as well as how the device is used. For example, spontaneous breathing results in 30% greater deposition of aerosol from a jet nebulizer than positive pressure breaths delivered by intermittent positive pressure ventilation or mechanical ventilation with the same nebulizer [8] . Drug Delivery Devices and Propellants 247

Aerosol Devices

Aerosol device delivery has been reviewed by a panel of the American College of Chest Physicians [9] . In this evidence-based review, it was determined that for most patients with asthma, nebulizers, DPI, and pMDI were equally effective in delivering aerosolized short-acting beta agonists if the device is used appropriately by the patient. Although equally effective, there are significant differences in the ability of patients to use these devices as well as differences in costs, convenience, portability, and particle generation characteristics.

Inhalers

Dry Powder Inhalers (DPI)

Concerns about the environmental impact of propellants used in pMDI have resulted in an increase in the development of new DPI devices. DPIs have the advantage of being small, portable, and intrinsically breath activated, with the medication delivered when inhalation begins. In early DPIs, the medication was milled to a respirable size (2–3 µm), loosely bound to a much larger carrier such as lactose, and sealed in capsules, which were punctured at the time of administration. Use of a large particle carrier makes it easier to store the medication in a form that can be “disaggregated” with a patient’s inspiratory effort during inspiration. Capsules and blister packets are used to store and protect the powder from ambient humidity. Alternatively, powder can be packed into cakes that act as a bulk reservoir, from which a single dose is then scraped at the time of administration. Once a capsule, packet, or cake is exposed to ambient humidity or humidity from exhaled breath caused by breathing back into the device, the powder clumps within milliseconds, resulting in reduced emitted doses [10] . If large enough, the powder clumping can reduce the delivery of doses that follow. Once the medication is scraped from a cake reservoir or liberated from a capsule or blister pack, it needs to be dispersed into an aerosol cloud. This can be done passively with energy provided by the patient or actively with energy provided by the device. Most DPIs used for asthma therapy are passive, meaning that the energy to disaggregate the powder comes from the patient’s inspiratory force, with the emitted dose varying with patient effort [11] . Thus, a tight seal is needed on the mouthpiece to produce an adequate inspiratory flow, and flow can be compromised during an acute asthma attack. The inspiratory flow required for optimal disaggre- gating can range from 15 to 90 LPM. Effective flow for the Diskus is at least 30 LPM, while higher resistance devices like the Turbuhaler (AstraZeneca) or the Spiriva Handihaler (Pfizer) require 60 LPM or more [12] . 248 B.K. Rubin and J.B. Fink

There are some DPI devices that can actively disaggregate and disperse the medication as a fine aerosol into a holding chamber, similar to those used for pMDI. The first of these was the Nektar powder delivery system for the administration of inhaled insulin (Exubera, Pfizer Pharmaceuticals) [13] . This type of active DPI tends to be more expensive than passive devices, and will not be initially available for asthma medications.

Pressurized Metered Dose Inhalers (pMDI)

Pressurized MDI were first developed in the 1950s by the Riker Company, now part of 3 M [14] . They used a metering device to “puff” a specific amount of medication from a multiple dose canister. Each canister has a reservoir that contains propellants, surfactants/dispersing agents, and a small amount of active drug. The traditional asthma “puffers” are the primary means of aerosol medication delivery worldwide and use of the pMDI with the valved holding chamber (VHC) is often considered the standard, by which other aerosol delivery devices are judged. The pMDI is one of the most cost-effective devices for inhaled medication delivery. It is conveniently light weight, portable, and multidose, and can be stored in any ori- entation without leakage. It will reliably provide consistent dosing during the canister life. Few changes were made to the traditional pMDI until the mandate to seek new, more environmentally friendly propellants [15] . Within the stratosphere, ozone is concentrated, protecting the surface from ultraviolet radiation. Once released, CFCs rise to the stratosphere, where they are gradually broken down by ultraviolet light and this depletes the stratospheric ozone. Pressurized MDIs have historically used the chlorofluorocarbons trichlorofluoromethane (CFC-11) and dichlorodifluo- romethane (CFC-12) as propellants, both of which are potent ozone-depleting substances. The Montreal protocol was adopted to reduce the emission of fluoro- carbons into the atmosphere, creating a requirement to develop alternative propellants to the traditional CFC-11 and CFC-12 used for pMDI in the early 1950s. The FDA announced that after 31 December 2008, the production and sale of single ingredient CFC pMDIs must cease. Hydrofluoralkene HFA134a (tetrafluroethane) is a substitute for CFC-12. It has a much lower potential for ozone depletion and is an acceptable alternative for CFCs under the Montreal protocol. HFA carrier pMDIs require a different metering valve with a smaller aperture, producing a finer particle size for many medications. The particle size is decreased for some lipophilic corticosteroids that dissolve into a solution in HFA134a. In some cases, the new valves can reduce the particle size from greater than 4 µm MMAD to about 1.2 µm, as is the case with beclomethasone dipropionate (BDP) [16] . Some steroids do not dissolve in the HFA carrier and so, the particle size for medications such as budesonide or fluticasone are about the same as that of CFCs [17] , and albuterol HFA does not have a smaller particle size than CFC. Most HFA pMDI are less affected by changes in temperature, and emit Drug Delivery Devices and Propellants 249 aerosol at a lower velocity, tending to reduce pharyngeal deposition [18] . It is probable that a change to HFA devices will require us to reexamine the age-related dose equivalence of CFC pMDIs [19] . One of the disadvantages of pMDI is that it is hard to tell how much medication remains in the canister. While some pMDI have an overfill of 10–15% of the nominal fill, the amount of drug emitted after the number of doses on the label can vary, alternating between the label dose and no dose at all [20] . Unfortunately, the residual carrier agents and propellants continue to make an audible sound and plume with each actuation; long after medication delivery has been compromised. In the past, some manufacturers had suggested that the amount of medication remaining in the canister could be ascertained by floating the canister in a bowl of water, but it has been shown that this is not only an unreliable method but also that water entering the valve stem can alter performance of the pMDI for subsequent doses [20] . The best alternative is to use a dose counter similar to that used in DPI so that patients will know how many doses remain within the canister. Beginning in 2006, all new pMDI that are introduced in the US market have been required to have a built-in dose counter. In the absence of a dose counter, the best way of determining how much medication remains is to keep a running count of doses used for rescue drugs taken on an as-needed basis. For medications like ICS that are taken on a consistent basis, patients should be instructed to calculate in advance the number of actuations and the number of puffs per day and to indicate directly on pMDI exactly when the canister is to be discarded. In reality, most patients do not do this, and are at risk of using their pMDI beyond their ability to provide consistent dosing. Environmental factors such as temperature can also contribute to inconsistent doses. CFC inhaler activation rapidly drops the canister temperature as the gas expands. As temperature of the canister drops, so does the emitted dose of the CFC pMDI [21] . This is why the pMDI canister should be warmed to hand temperature before use and patients should wait for 20 seconds between each activation. This may not be as great a problem with HFA propelled pMDI canisters.

Breath Activated pMDI

Breath activated pMDI have an inspiratory flow trigger that activates on inhalation only. This eliminates many problems with poor hand breath coordination, such as inhaling before or after the dose is emitted [22] . Because inspiratory flow is needed to activate these devices, the ability of a patient to use the device is age dependent. Maxair (pirbuterol) by 3-M (St. Paul, MN) and albuterol HPA (Teva) are available with the Autohaler and in Europe, the Easyhaler (Baker Norton Co., Eire) is available as a breath activated pMDI, with a triggering inspiratory flow required of about 30 LPM. An after-market device, the MD Turbo (TEAM Pharmaceuticals, Morrisville, NC) allows most pMDI with original boot from the manufacturer to be inserted in a device that provides breath actuation and a dose counter. 250 B.K. Rubin and J.B. Fink

Venturi Type Jet Nebulizers (JN)

Small volume nebulizers (SVNs) typically use the Venturi principle to generate aerosol. A jet of compressed gas is directed over a tube, drawing fluid from a reservoir and shearing the fluid into particles that are driven against a baffle, or the internal wall of the nebulizer. This causes large particles to impact and return to the reservoir, while smaller particles continue with the gas stream toward the patient. The efficiency of the SVN depends on the gas flow and the pressure driving the nebulizer. Higher flows generally produce smaller particles [23] . Typical home nebulizers use a gas source between 10 and 35 psi, while 50 psi is commonly used in hospitals. The requirement for a compressed gas source limits device portability. With few exceptions, medical compressors are relatively heavy and require mains electricity to operate, limiting portability. Several small battery-operated VN have been introduced and they can also be operated from 12 V or mains power sources. The SVNs available in the market have a wide range of efficiency, particle size, and output rate [24] . The amount of medication remaining in the nebulizer cup at the end of nebulization or at the start of sputtering is referred to as the nebulizer residual volume and this ranges from 0.5 to 1.8 mL [25] . Thus, greater the residual volume and smaller the initial fill volume, lesser the amount of medication available for nebulization and inhalation. The fill volume is particularly important for nebulizers that have a large residual volume. Medication should be placed in the nebulizer cup in unit doses. Nebulizers should be inhaled from an upright position as tilting the nebulizer cups can cause spillage, loss of medication, and ineffective nebulization. Nebulization should stop once the cup begins to sputter.

Breath Activated Nebulizers

Breath actuated nebulizers only produce aerosol during inspiration, with no loss between inspirations. Negative pressure at the start of inhalation drops a valve into place to allow nebulization to begin and stop when each inhalation is complete. These have the advantage of requiring smaller fill volumes because there is less medication lost, but often they take longer to completely nebulize a charge.

Large Volume Nebulizers (LVN)

Large volume nebulizers have been used primarily for continuous nebulization of beta agonist bronchodilators in the emergency department or intensive care unit. LVNs have a greater reservoir volume to allow aerosol to be generated for extended periods of time, although this may not be therapeutically advantageous [26] . Drug Delivery Devices and Propellants 251

Ultrasonic Nebulization

UN uses a vibrating piezoelectric crystal to produce cavitation in a reservoir containing a liquid formulation, producing standing waves that generate aerosols. Particle size and output rates vary with frequency and amplitude [27] . One of the advantages of UN is that a large volume of solution can be aerosolized in a relatively short period of time, but medications in suspension are poorly nebulized [28] . It can be difficult to detect when the piezoelectric crystal is cracked, caked with dry medication, or otherwise inoperable. Some crystals can become very hot through the process of vibrating and denature heat-sensitive medications, especially proteins. UNs are usually more expensive than other delivery devices. UNs are no more efficient at medication delivery than other devices and so, their use is not recommended for delivering therapeutic aerosols to ambulatory patients.

Vibrating Mesh Nebulizers (VM)

VM nebulizers generate aerosols by pushing or drawing fluid through a mesh containing more than 1,000 apertures. Liquid medication passes from the reservoir through the mesh and is transformed into discrete particles. VM nebulizers use a piezo-ceramic element to vibrate the mesh containing the apertures, but the VM typically operates at less than 10% of the frequency and power consumption of the standard UN used in the clinical setting, reducing the heat transferred to the formulation. Unlike UN, which does not effectively nebulize suspensions, the VM can nebulize any suspension as long as it can physically pass through the aperture. The particle size generated by the VM is directly related to the diameter of the aperture through which the medications pass [29] . The VM nebulizers are more efficient than jet or UN nebulizers, with less residual drug remaining in the nebulizer after administration is complete, making this the most efficient commercially available liquid aerosol generation technology. This is offset by the price, which is more than that of standard nebulizer systems.

Other New Nebulizer Technologies

There are promising nebulizer technologies in development. The Respimat (Boehringer Ingelheim) has been released in Europe as a hand-held multi-dose nebulizer, used to deliver tiotropium [30] . Aerosol generation through the use of electrostatic charge (Ventaira, Columbus, Ohio) has been shown to produce small, almost monodisperse particles. Another technology, which incorporates the rapid vaporization of molecules, including proteins, appears to produce highly respirable small particles. 252 B.K. Rubin and J.B. Fink

Accessory Devices

Accessory devices have been developed to enhance the function of aerosol delivery devices. These include spacers, valved holding chambers (VHC), actuation enablers, and dose counters. The pMDI is designed to operate with the actuator/ boot provided by the manufacturer. Accessory devices with “universal” actuators, that do not allow the use of the manufacturer’s actuator/boot, may have great variability in performance depending on the pMDI, drug, or propellant used [31] .

Spacers

A spacer is a simple tube or chamber that is placed at the end of the actuator boot letting the pMDI aerosol cloud expand and mature, reducing the speed of the aerosol plume, and allowing larger particles to evaporate or rain out before reaching the patient. Spacers can be as simple as a piece of tubing, a toilet paper roll, or a large plastic drink bottle that has been cleaned and a second hole added [32] . At their best, spacers can reduce pharyngeal deposition up to 9%. They also provide some protection from loss of aerosol when the pMDI is actuated immediately before inspiration. Unlike VHC, spacers do not improve coordination problems such as patient exhaling during the actuation of the pMDI. Some spacers are so small or poorly designed that there is a significant reduction in medication inhaled. In general, a spacer that has less than 100 mL of internal volume will reduce the available inhaled mass of drug from the pMDI [33] .

Valved Holding Chambers (VHC)

VHC are a great improvement over the spacer. VHC have a one-way valve that prevents medication loss if the patient exhales into the device. VHC also allow a patient to dissociate the coordination of medication inhalation with actuation. Several seconds of delay between actuation and inhalation of the medication will not appreciably reduce the amount of medication available to the lungs [34] The placement of the valve between the chamber and the patient’s airway also serves to further reduce pharyngeal deposition by two orders of magnitude compared to the pMDI alone (0.9% vs. 90%), and one order of magnitude over simple spacers (0.9% vs. 9%), thus, reducing side effects. VHC can also increase the available drug for inhalation by up to fivefold compared to the pMDI alone. The most effective VHC are either metal coated or made of electrostatic resistant plastics that carry little charge [35] . Desirable characteristics of VHC include a size large enough to allow the aerosol to develop and remain as a cloud until inhalation, an easy to open inhalation valve, Drug Delivery Devices and Propellants 253 the ability to accept a variety of pMDI boots into the device, a clear and straight aerosol flow path that decreases precipitation of aerosol within the device, construction using materials that are electrostatically reduced, and, of critical importance, a comfortable interface, either a mouthpiece or a mask, between the device and the patient [36] .

Masks

A variety of masks have been used for VHC; some of these are masks designed to be used for anesthesia or resuscitation, some have been adapted from adult use for children, while others have been specifically designed for inhalation using a VHC. The best masks have a low dead space, fit comfortably on the child’s face, and make a complete seal with a minimal amount of pressure [37] . For the child’s comfort, some masks incorporate an exhalation valve. However, the ability to make a complete and comfortable seal is most important. We can ensure that the mask is sealed on the face if we observe the VHC inhalation valve opening and closing with breathing.

Activation Enablers

Accessory devices have been designed to fit around the boot that holds the pMDI canister, making it easier to press and actuate the pMDI. These can be useful for elderly patients with arthritis or with poor grip strength, who find it difficult to actuate the canister.

Special Uses

Neonatal and Pediatric Aerosol Therapy

The smaller diameter of upper and lower airways in infants and children result in a greater percentage of particle impact in this range [38] . In addition, preferential nose breathing filters aerosol from inspired gas, reducing the mass of drug available for pulmonary deposition. There are few indications for administering asthma medication to neonates because asthma is not a neonatal disease. Asthma is also uncommon in infants in the first year of life, and during this period, asthma may not respond well to medications. Children under the age of 3 years are usually not able to make a good seal on a mouthpiece and inhale on command. For toddlers, it is best that medications be delivered 254 B.K. Rubin and J.B. Fink using a device that can be combined with a comfortable, closely fitting mask. Nowadays, that would mean using a nebulizer or pMDI and VHC with a mask. The crying and struggling child or infant has a short and high flow inhalation and a long exhalation, especially when screaming. This dramatically decreases the amount of medication in the lower respiratory tract and so, aerosol medication should not be given to a child who is upset, fighting the delivery device, or crying [39] . The face mask or mouthpiece appears to be equally effective when using a nebulizer [40] , but mouthpiece delivery is superior when using a pMDI and holding chamber, and a mouthpiece should be used for most children 3 years of age and older. Medication should never be given by “blow-by”; that is using a mouthpiece that is not in the child’s mouth or a mask that is held some distance in front of the face. Almost no blow-by medication makes it into the lungs [41] . Most children who are old enough to drink from a straw are able to place the device mouthpiece directly in their mouth. When aerosols are given using a mouthpiece, it is important that the patient breathes in slowly and deeply and that the tubing should not increase turbulence as may happen with corrugated tubing. If a child can use a mouthpiece effectively, there should be no reason for them to routinely take asthma medication through a nebulizer. Guidelines from the Global Initiative for Asthma (GINA), a collaboration of the National Heart, Lung, and Blood Institute (United States) and the World Health Organization [42] , recommend a pMDI with VHC plus face mask for infants, a pMDI with VHC plus mouthpiece for children 4–6 years of age, and a DPI, breath- actuated pMDI, or pMDI with VHC for children 6 years and older.

Emergency Department Aerosol Delivery for Acute Asthma

The goal of asthma therapy in the emergency department (ED) is to quickly reverse bronchospasm, improve airflow, and provide effective anti-inflammatory therapy. Fairly high doses of aerosol beta agonists are often administered with or without anticholinergic bronchodilators. Although there have been small studies that suggest that high doses of ICS can be nearly as effective as systemic corticosteroids for patients with acute asthma [43] , there is little to recommend ICS as a substitute for systemic corticosteroids, given the high doses that are needed. On the other hand, although subcutaneous or intravenous beta agonists are effective in treating acute asthma, they are no more effective than the same medications given by aerosol and there is an unacceptably high risk of side affects when beta agonists are administered systemically. It has been shown that bronchodilators given by pMDI and VHC are at least as effective as medication administered by jet nebulizers in the ED [44] . Although patients with mild acute asthma may obtain benefit using a DPI, this is not recommended for patients with decreased inspiratory flow. In patients with stable asthma, 4 inhalations of albuterol (440 µg nominal dose in the US; 500 µg nominal dose in the rest of the world) is therapeutically equivalent to 2.5 mg by nebulization. Drug Delivery Devices and Propellants 255

However, during acute asthma it may be necessary to initially increase the number of inhalations or the nebulized dose to achieve adequate bronchodilatation. With a higher initial dose of inhaled medications, bronchodilators are likely to be administered less frequently. The optimal dose and frequency of aerosol medication administration during acute moderate-to-severe asthma has not been established, and this is likely to be different for patients at different ages, with different durations of symptoms, and other mediations taken, such as ICS. Beta agonist bronchodilators can also be delivered by continuous nebulization by placing 10–20 mg of albuterol per hour in a large volume nebulizer (LVN) and administering this for extended periods of time (8–24 hours) [45] . Randomized controlled trials comparing continuous nebulization with intermittent lower dose nebulization or frequent inhalation of a pMDI with a VHC have not been reported. If continuous nebulization is used, it should be given with a comfortable and closely fitting mask because holding a mouthpiece in place for extended periods can be tiring during acute asthma. The mask must be vented in order to prevent re-breathing and carbon dioxide retention. The benefits of continuous nebulization decrease as the systemic anti-inflammatory drugs take effect. We recommend that if continuous nebulization is used in acute asthma, patients should be closely monitored for tremor and tachycardia, and should be evaluated frequently with the goal of returning them to intermittent pMDI and VHC as soon as possible. Data do not support the use of continuous nebulized bronchodilator therapy for patients with mild-to-moderate acute asthma.

Care of Devices

Jet Nebulizer Maintenance

JN should be routinely cleaned and should not have medication or nebulizer solution in them after treatment is completed, as this can be a reservoir for bacteria or fungus [46] . The nebulizer should be routinely checked for leaks and cracks. Older nebulizers tend to degrade over time [47] .

VHC Maintenance

VHC need to be checked to be sure that there are no objects that have entered the chamber during transport. Clear chambers make it easier to detect if there are foreign objects. The valve should be periodically examined to make sure it is not torn or stuck. This is particularly important for VHC where the valves are pegged (e.g. Optichamber) rather than using pliant flaps (e.g. Aerochamber). The mask should also be checked to make sure it is not torn and that it sits correctly on the holding chamber. VHC should be periodically washed with a mild liquid detergent. 256 B.K. Rubin and J.B. Fink

DPI and pMDI Maintenance

DPI need to be kept dry when they are not being used. The dose counter needs to be checked regularly. The mouth orifice needs to remain clean at all times. Once activated, the DPI should not be flipped as this will cause dumping of medication. Pressurized MDIs need to sit completely in the boot before activation. If not properly placed in the boot or if the canister does not go with the boot, this can compromise medication delivery. The canister should be replaced once per month. The boot should also be kept clean and free from foreign objects at all times.

Patient Education

One of the most important factors in the effectiveness of asthma medications is adherence to scheduled use. Nonadherence to prescribed ICS is a risk factor for acute severe and fatal asthma. Even during monitored clinical trials, full adherence to prescribed asthma therapy is estimated to be no more than 50% [48] . One of the most common reasons for nonadherence is the patient being unaware of the correct use of the device or the medication. A good way to ensure adherence is to teach the patient the correct use of medication, minimize the number of drugs and different frequencies of administration of their inhaled drugs, emphasize using the most important drug, reduce medication costs (financial and time), and suggest administration during those times in the day when they are performing routine activities, such as before brushing teeth. The use of medication and devices should be reviewed at every office visit and if there are questions, device use should be directly observed. The keys to good adherence are patient and caregiver education, and making medication use important, easy, and a routine part of the patient’s lifestyle [4] .

References

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30. Hochrainer D, Holz H, Kreher C, Scaffidi L, Spallek M, Wachtel H. Comparison of the aerosol velocity and spray duration of Respimat Soft Mist inhaler and pressurized metered dose inhalers. J Aerosol Med 2005;18:273–82. 31. Berry J, Heimbecher S, Hart JL, Sequeira J. Influence of the metering chamber volume and actuator design on the aerodynamic particle size of a metered dose inhaler. Drug Dev Ind Pharm 2003;29:865–76. 32. Zar HJ, Asmus MJ, Weinberg EG. A 500-ml plastic bottle: An effective spacer for children with asthma. Pediatr Allergy Immunol 2002;13:217–22. 33. Dolovich MA, MacIntyre NR, Anderson PJ, et al. Consensus statement: aerosols and delivery devices. American Association for Respiratory Care. Respir Care 2000;45:589–96. 34. Barry PW, O’Callaghan C. The effect of delay, multiple actuations and spacer static charge on the in vitro delivery of budesonide from the Nebuhaler. Br J Clin Pharmacol 1995;40:76–8. 35. Wildhaber JH. High percentage lung delivery in children from detergent-treated spacers. Pediatr Pulmonol 2000;29:389–393. 36. Rubin BK, Fink JB. Optimizing aerosol delivery by pressurized metered dose inhalers. Resp Care 2005;50:1191–97. 37. Shah SA, Berlinski AB, Rubin BK. Force-dependent static dead space of face masks used with holding chambers. Respir Care 2006;51:140–4. 38. Rubin BK, Fink JB. The delivery of inhaled medication to the young child. Pediatr Clin N Am 2003;50:1–15. 39. Iles R, Lister P, Edmunds AT. Crying significantly reduces absorption of aerosolised drug in infants. Arch Dis Child 1999;81:163–65. 40. Lowenthal D, Kattan M. Facemasks versus mouthpieces for aerosol treatment of asthmatic children. Pediatric Pulmon 1992;14:192–96. 41. Rubin BK. Bye-bye, blow-by. Resp Care 2007 August (in press). 42. GINA Global Strategy for Asthma Management and Prevention. Updated 2003 . NIH Publication NO 02-3659. 43. Nakanishi AK, Klasner AK, Rubin BK. A randomized controlled trial of inhaled flunisolide in the management of acute asthma in children. Chest 2003;124:790–94. 44. Cates CJ, Rowe BH. Holding chambers versus nebulisers for beta-agonist treatment of acute asthma (Cochrane Review). In: The Cochrane Library, 2000; Issue 2 (CD000052). Oxford: Update Software). 45. Colacone A et al. Continuous nebulization of albuterol (salbutamol) in acute asthma. Chest 1990;97:693–697. 46. Hamill RJ, Houston ED, Georghiu PR, Wright CE, Koza MA, Cadle RM, et al. An outbreak of Burkholderia cepacia respiratory tract colonization and infection associated with nebulized albuterol therapy. Ann Intern Med 1995;122:762–766 47. Standaert TA, Morlin GL, Williams-Warren J, Joy P, Pepe MS, Weber A, Ramsey BW. Effects of repetitive use and cleaning techniques of disposable jet nebulizers on aerosol generation. Chest 1998;114:577–86 48. Rubin BK. Adherence to asthma therapy: The “blocked receptor”. Pediatr Pulmonol 2004;37:36–37. Update on the Management of Atopic Dermatitis/Eczema

Sherrif F. Ibrahim , Anna De Benedetto , and Lisa A. Beck

Introduction

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that affects patients of all ages. The etiology is multifactorial, resulting from complex interactions of the immune system, environmental stimuli, and susceptibility genes. The prevalence of AD is increasing in industrialized nations, with as estimates as high as 20% of children and 3% of adults [1] . The financial and psychosocial cost of the disease is substantial [2] . Several studies have shown that AD in children is associated with a reduction in quality of life for patients as well as their families which is beyond that of other chronic diseases of childhood such as asthma, diabetes, and cystic fibrosis [3– 5] . The treatment of moderate to severe atopic dermatitis continues to be frustrating because of the lack of efficacy of most therapies and the chronicity of the disease. There are also potential side effects with most therapies – whether topical or systemic – and these risks must be weighed against the therapeutic benefit to the patient. Because the natural history of AD involves periods of waxing and waning severity, treatment plans are often dynamic and must change accordingly to reflect disease activity. Combination therapy is the rule, as the disease itself is the final manifestation of many contributing environmental and host factors. Commonly, trials of several different treatment modalities coupled with environmental measures are necessary before an effective, individualized regiman is achieved. The diagnostic criteria and pathophysiology of AD have been well described elsewhere [1, 7, 8] . This chapter will present the general approach to the patient with AD, including basic practice guidelines for all patients, as well as a review of many of the available topical and systemic agents. When possible, evidence

S.F. Ibrahim, A. De Benedetto, and L.A. Beck () Departments of Dermatology and Medicine , University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave. , 697 , Rochester , NY 14642 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 259 DOI 10.1007/978-4-431-99362-9_16, © Springer 2010 260 S.F. Ibrahim et al. will be presented that may support one treatment choice over another as well as a discussion of the impact that recent research may have on future treatment options.

Basic Approach to Therapy

Treatment of AD regardless of extent of involvement must address general good skin care practice as well as the education of the patient and care providers on the natural history of AD, environmental control measures, screening and treatment of associated atopic diseases (rhinitis, asthma, eosinophilic esophagitis, food allergy, and conjunctivitis), psychosocial support, and adjustment of expectations from various treatment approaches. The cornerstones of treatment involve emollients and other means of skin hydration to address the profound xerosis classically seen with the disease, as well as identification and avoidance of trigger factors. Further treatment decisions are based on severity, and typically include the addition of topical glucocorticoids and/or topical calcineurin inhibitors. In the case of moderate to severe AD, a systemic treatment option is often considered, and may only be needed for short periods of time to control flares. More recently, it has become increasingly evident that control of skin infections is critical for the successful management of this disease [9] . The development of AD is multifaceted, with each patient having specific triggers and necessitating treatment regimens that are highly individualized. Although topical steroids have historically carried the bulk of the therapeutic burden, the approach to treatment of AD patients should utilize combination therapy to address the multiple components (pruritus, inflammation, colonization/ infection) of the disease.

Avoidance of Exacerbating Factors

Exacerbating factors in AD include irritants and allergens – the latter typically evoking IgE-mediated inflammation. It is believed among patients with AD, that there are two forms of the disease – the more common “extrinsic” form (affecting 70–80% of patients) that is associated with IgE-mediated sensitivity to common allergens, and an “intrinsic” form (affecting 20–30% of patients) that develops in patients with normal IgE levels [10] . Allergen testing by skin prick and serum radioallergosorbent tests (RAST) can be helpful in the evaluation of AD patients. Up to 30% of children with moderate to severe AD may have underlying food allergy. Avoidance of foods implicated in either controlled challenges as well as in food allergen-specific CAP-RASTs have resulted in clinical improvement for some patients [11] . It is important to distinguish food intolerance from true food Update on the Management of Atopic Dermatitis/Eczema 261 allergy. Up to 25% of adults report having a food allergy, although the prevalence of IgE mediated disease in double-blind, placebo-controlled studies indicates this figure is less than 5% in adults and approximately 6% in children under 3 years of age [12– 14] . The most common food allergens are milk, eggs, peanuts, tree nuts, soy, fish, and wheat [15] . Clinical reactions to food in AD subjects include worsening of dermatitis – particularly in sensitized infants – either alone or associated with typical immediate-type allergic reactions such as urticaria, pruritis, gastrointestinal symptoms, or anaphylaxis. Several clinical studies have shown that elimination of relevant food allergens can lead to clinical improvement of the dermatitis [16, 17]. A large, controlled study in high-risk infants demonstrated that extensively versus partially hydrolyzed casein formula reduced AD severity by 50% in the first year of life [18, 19] . Interestingly, children with AD are often found to have positive skin tests for peanut despite being peanut naïve, and almost half of these peanut naïve children develop skin symptoms on oral peanut challenge [20] . This situation poses a challenge for counselling of parents as far as dietary restrictions and avoidance of foods are concerned. Because peanut allergy can theoretically be fatal without prior sensitization, the American College of Allergy recommends avoidance of peanut products before 3 years of age [21] . Ramesh has provided a recent thorough review of food allergy in children (Fig. 1) [13] .

BASIC SKIN CARE: Irritant / Allergen Avoidance and Skin Hydration

Control of skin infection / colonization

Anti-itch therapy

Systemic Rxs Topical Rxs Immunosuppressive Therapy Corticosteroids or Cakineurin Inhibitors Biologics

Dry skin Mild Moderate Severe Recalcitrant

Disease State

Fig. 1 Basic approach to the management of atopic dermatitis. Combination therapy is the mainstay of AD treatment. Milder cases can be controlled with emollient use and topical agents alone, while more advanced disease requires systemic therapy. Frequently, patients will require systemic therapy for defined periods of time during flares of AD. Control of skin colonization and infection by bacteria as well as anti-itch treatment are critical to limit the progression of the disease 262 S.F. Ibrahim et al.

Although children can outgrow good allergies, they may become sensitized to inhaled allergens as they become older [10, 22] . The avoidance of aeroallergens such as house dust mite has proven effective in relieving symptoms in some, but not all studies. It is likely that most AD patients are polyallergic, with reactivity to multiple aeroallergens, microbial antigens, as well as self-antigens [10] . The deficiency in epithelial barrier function seen in AD patients probably allows easy access for multiple allergens to encounter immune system players and drives the characteristic Th2 response. The resultant polyallergic state may explain why elimination or reduction of one or more allergens does not always lead to significant clinical improvements. There are numerous reports on the use of specific immunotherapy in the management of respiratory hypersensitivity conditions such as allergic rhinitis and asthma [23] . This approach is thought to induce allergen-specific tolerance by introducing the known allergen either sublingually or subcutaneously at increasing doses. There is growing evidence supporting the efficacy of this approach in subjects with AD. Werfel et al, demonstrated that sublingual immunotherapy improves dermatitis in atopic patients who are mono-sensitized to a specific allergen, and can reduce the need for topical corticosteroids [22] . Recent reviews by Novak and Bussman et al have examined the role of specific immunotherapy as it pertains to AD [24, 25]. Further refinement in immunotherapy and well-designed trials will undoubtedly clarify its role and utility in the management of atopic dermatitis. Beyond food and environmental allergies, several reports have demonstrated that contact (type IV) allergy may also play a role in the skin manifestations observed in patients with atopic dermatitis [26] . Although there has been some controversy in the role of patch testing in AD patients, multiple studies have shown high rates of positive patch test readings in atopic patients [27, 28]. Therefore, it is worthwhile to evaluate AD subjects with recalcitrant disease to determine if contact allergens are also contributing to their skin disease. This is often difficult, as patch testing requires large areas of clear skin (preferably on the back) in order to adequately perform and interpret the test. As a general rule, most clinicians suggest that AD subjects just avoid exposure to the most frequent contact allergens such as metals, fragrances, dyes, and neomycin sulfate [27, 29] .

Topical Treatments

Emollients

A feature observed in all AD patients is the loss of an effective skin barrier which, among other things, results in increased transepidermal water loss (TEWL), dry skin (xerosis), and in some, ichthyosis [30] . Defects in barrier function lead to greater exposure to environmental allergens, irritants, and likely play a role in AD subjects’ susceptibility to microbial colonization and infection. The extent of barrier Update on the Management of Atopic Dermatitis/Eczema 263 dysfunction has been shown to correlate with the degree of inflammation [31] . Furthermore, barrier dysfunction may also lead to systemic allergic responses such as airway hyperreactivity and progression along the atopic march [32] . Proper skin hydration can be maintained with regular application of emollients (i.e. creams or ointments) throughout the day, as well as the use of soaps with minimal defatting activity and a neutral pH [33] . Branda et al performed a study correlating irritation from several commonly used household soaps, and found that Dove™ products had the lowest scores on a normalized irritation index [34] . Although scientific data supporting the use of emollients is limited, one study has shown they have a steroid-sparing effect in mild to moderate AD [35] . Another study demonstrated that emollients containing ceramide, a lipid that is expressed at reduced levels in the epithelium from AD subjects, was more effective than placebo in children with recalcitrant the epithelium from AD [36] . In July 2003, the compound MAS063D (Atopiclair™ in the US, Zarzenda™ in the EU) was approved as a prescription medical device by the US Food and Drug Administration (FDA) to relieve the symptoms of AD and allergic contact dermatitis. This is a steroid-free cream whose main components are hyaluronic acid, a glycosaminoglycan found in normal connective tissue and known to induce tissue hydration; Vitis vinifera (common grape vine), which has anti-oxidants and anti-protease activity; telmesteine, which reduces free radicals formation and theoretically may protect against oxidizing agents that may contribute to epithelial damage. The rationale for using MAS063D in AD therapy is to protect AD skin from insult by free radicals and skin-damaging enzymes, and to improve barrier function by moisturizing the skin. However, only a few studies have been conducted to evaluate the safety and benefits of this compound in the management of AD and none of them have elucidated the mechanism by which it has its effect [37, 38]. Recently, the FDA has approved another nonsteroidal topical called MimyX Cream™ (Stiefel Laboratories, Inc, Coral Gables, FL) for the management of burning and itching associated with AD and other dermatitis for both adult and pediatric patients. The approval was based on data from safety and efficacy studies showing the moisturizer was equivalent to currently marketed products for reducing post-procedure (e.g. laser, photodynamic therapy) symptoms [39] . The major constituent in MimyX™ is N-palmitoylethanolamide, a fatty acid that has been reported to be deficient in AD subjects, and is a ligand for the cannabinoid receptor, CB2 [40] . Topical cannabinoid agonists have been shown to be effective and well-tolerated therapies for refractory pruritus, suggesting that N-palmitoylethanolamide and other related agents may be useful for treatment of itch [41] . Pilot studies in patients with AD have been promising; however, larger controlled trials will be needed to better characterize their efficacy and mode of action [42] . The filament aggregating protein called filaggrin, is an essential player in the formation of the cornified cell layer and maintenance of skin barrier function. Recent genetic studies have shown that null mutations in the gene encoding filaggrin are a strong and highly reproducible predisposing factor in the development of AD in European and Asian cohorts [43] . Howell et al demonstrated that filaggrin expression is reduced in acute AD lesions compared to nonlesional skin, indicating that patients may also have an acquired defect. They also demonstrated that differentiated keratinocytes, cultured in 264 S.F. Ibrahim et al. the presence of IL-4 and IL-13 had reduced filaggrin expression, suggesting that Th2 cytokines present in AD lesions may be responsible for the reduced filaggrin observed. This is another mechanism by which the barrier can become dysfunc- tional [44] .

Topical Steroids

Topical glucocorticoids have been the mainstay of therapy in the treatment of atopic dermatitis for over 40 years. They are rated on a scale from I to VII based on their relative potency in a cutaneous vasoconstrictor assay, with class I steroids being the most potent agents. Steroid class has been shown to correlate with clinical efficacy and side effects [46] . The utility of topical steroids has been demonstrated in a number of studies [46– 50] . A meta-analysis of 83 randomized, vehicle-controlled studies demonstrated that 80% of patients treated with topical steroids for less than one month reported a positive response (good or better on a symptom scale) [51] . Unfortunately, side effects are tightly linked with potency and include skin atrophy or thinning, striae and acneiform erup- tions [52] . As a general rule, mid to high potency agents should be used with caution on the face, flexural, and genital areas in most subjects or anywhere on the body in small children. Systemic adverse effects from topical steroids such as suppression of the hypothalamic-pituitary-adrenal axis (HPA) and Cushing’s syndrome are uncommon. Ellison et al have shown that HPA suppression was rare in pediatric subjects with moderate to severe AD, even after several years of regular use of mild to moderate potency topical steroids [53] . However, HPA suppression was found in those receiving potent topical glucocorticoids, or both topical and systemic steroids. Within this latter group, the authors identified a subgroup of AD patients with HPA suppression but no clinical improvement, implying that some patients may have glucocorticoid resistance that occurs only in the skin, and that this resistance may be inherent to disease pathophysiology [53] . Similarly, recent studies in AD subjects have shown a blunted HPA axis response with a low dose dexamethasone suppression test when compared to non-atopic controls [54, 55] . The authors speculated that a hyporeactive HPA could explain the link between atopic diseases and stress. Nevertheless, short courses of Class IV steroids are safe for up to 4 weeks in infants and young children based on the lack of demonstrable systemic effects [56] . Therefore topical corticosteroids, while effective, are limited in their use by their side effect profiles. This is of greater concern in subjects with AD, as their disease typically recurs in the same locations. Surprisingly, given their widespread use, it is unclear what the best application frequency is for topical steroids. There is no clear evidence to support the use of twice-daily over once-daily application [51, 57, 58] . It may therefore be reasonable to use once-daily corticosteroids initially in the treatment of AD patients. Update on the Management of Atopic Dermatitis/Eczema 265

Several reports suggest that intermittent application of topical steroids may be useful as a preventative strategy. In one study, application of 0.1% betamethasone valerate on unaffected skin twice weekly prevented subsequent flares at that site [59] . This effect may at least in part be due to a reduction in Staphylococcus aureus colonization which has been observed with topical steroid use [60] .

Topical Calcineurin Inhibitors

The topical calcineurin inhibitors (TCI), pimecrolimus and tacrolimus, are approved for the treatment of mild-to-moderate and moderate-to-severe AD, respectively. By inhibiting calcineurin, they prevent the translocation of the transcription factor, nuclear factor of activated T cells (NFAT) from the cytoplasm to the nucleus. This prevents the transactivation of many inflammatory cytokines including IL-1 b, -2, -3, -4, -5, GM-CSF, IFNg , and TNF-a that are thought to contribute to the development of AD [61] . Clinical trials have established the efficacy of these agents both as monotherapy and for their steroid-sparing effects [62, 63]. While they have not been shown to cause the skin atrophy seen with topical steroids, side effects can include transient burning, erythema, and pruritis, which typically improves after the first week of use [52] . In February of 2006, the FDA placed a black box warning in the package insert based on concerns that rare cases of malignancy (e.g. skin cancers and lymphoma) have been reported in patients using these medications although they acknowledge that a causal relationship has not been established [64] . The labeling states that these drugs should be used as second line treatments and their use in children younger than 2 years is not recommended. This action has resulted in considerable frustration within the dermatologic and allergy communities [65– 67] . In 2006, a group of AD experts concluded that the potential for adverse systemic effects from TCI is very low, and one should not forestall appropriate use of these agents in AD management [68, 69] . In a recent comprehensive review, Callen et al have summarized both published and FDA meeting reports on the safety of several topical therapies used in AD, and concluded that these medications are safe and well tolerated with only occasional, mild side effects such as burning and stinging upon application [49] . A nested case- control study examining the risk of lymphoma in AD patients following exposure to TCIs found no increased risk of malignancy from these agents. In AD patients who did develop lymphoma, the severity of AD was the main factor associated with this risk [70] . Ashcroft et al have performed a meta-analysis of both pimecrolimus and tacrolimus in the treatment of AD [71] . These agents were found to be effective, safe topical agents in the management of AD, but the authors note that additional data will be needed to determine the long term safety gains over the use of topical steroids. Ongoing Phase IV (post-marketing) studies with TCIs in AD patients will likely clarify the safety of these drugs. 266 S.F. Ibrahim et al.

Infection and Antimicrobial Treatments

Skin infections caused by a variety of bacterial, fungal, and viral microorganisms frequently modulate the course of AD and complicate the management of these patients. Defective skin barrier, reduced skin lipid content, increased skin surface pH, increased bacterial adhesion, and decreased production of antimicrobial peptides by skin cells, all contribute to an increased propensity for cutaneous colonization and infection in AD [72] . This colonization and infection is thought to stimulate the release of inflammatory cytokines from keratinocytes, further aggravating the disease. Therefore, reduction in the microbial burden often improves overall skin health in these patients. In-depth reviews by Drs. Leung and Wollenberg et al provide a more comprehensive discussion of infections in patients with AD [72, 73] .

Bacterial Infections

Of the bacteria commonly found on the skin, Staphylococcus aureus has been the best characterized. In certain studies, up to 100% of AD patients are colonized with S. aureus on the skin and/or nasal mucosa as compared to 5–30% of normal controls. Acute AD lesions contain higher numbers of S. aureus than chronic lesions, unaffected atopic skin, or skin from non-atopics [72] . Furthermore, up to 65% of the S. aureus isolates from AD patients are toxin-producing [9] . Many investigators feel that S. aureus colonization aggravates the inflammation and pruritus characteristic of AD. Toxins secreted by S. aureus can act as superantigens, activating T cells and increasing disease activity. Many AD patients also develop IgE antibodies directed against S. aureus toxins, causing greater disease severity [74] . Topical antiseptics (e.g. triclosan, chlorhexidine, bleach [sodium hypochlorite] [234]) have been shown to be effective in reducing skin colonization with S. aureus and/or improving clinical symptoms [75] . Topical antiseptics can be used as a component of emollients or in wet-wrap dressing therapy [9] . Use of topical antibiotics is in part, limited by a higher risk of sensitization against these agents in AD patients. Moreover, there are concerns about the rise of resistant strains of bacteria with continued use of topical and oral antibiotics [76] . Therefore, use of these agents is recommended for short durations (three weeks or less). There is some evidence that topical mupirocin may improve AD activity as well as reduce bacterial counts [77] . Intranasal mupirocin has also been successfully used for intranasal eradication and prophylaxis of S. aureus [78] . The addition of a topical antimicrobial agent to topical corticosteroid preparations has not shown a benefit beyond that of a topical steroid alone [79] . Several clinicians have suggested the use of dilute bleach baths (2 teaspoons of household bleach/gallon of water) to reduce skin colonization while minimizing the emergence of antibiotic resistance [80, 234]. Antibacterial soaps have also been shown to significantly improve skin lesions over placebo soap [81] . Newer antimicrobial approaches include the use of silver-coated textiles and silk fabric, which have anti-friction and antimicrobial action [82, 83] . Update on the Management of Atopic Dermatitis/Eczema 267

Systemic antibiotic therapy should be reserved for more advanced bacterial infections. Short-term therapy with first or second-generation cephalosporins or semisynthetic penicillins, are usually effective, as S. aureus is the most likely causative agent [84] . Unfortunately, reinfection is common after a course of antistaphylococcal therapy. Long term therapy should be avoided to limit the development of bacterial resistance. Community-associated methicillin-resistant S. aureus (CA-MRSA) is now identified in up to 30% of all skin and soft tissue infections [85, 86] . Our own studies have shown up to 14% of AD subjects are colonized with CA-MRSA, based on antibiotic sensitivities [235] . Growing antibiotic resistance will undoubtedly pose a significant threat to the treatment of bacterial infections in general, and will be an increasingly important issue for atopic patients in particular, given their high rates of colonization and frequent use of antimicrobials.

Viral Infections

Atopic dermatitis patients have an increased likelihood of developing severe skin infections from viruses that do not typically cause disseminated cutaneous infections in non-atopics [72] . The condition is named after the causative virus: eczema molluscatum from the molluscum contagiosum virus (MCV), eczema vaccinatum from the live vaccinia virus vaccine, and eczema herpeticum from the herpes simplex virus (HSV) type 1 or 2. The latter can cause disseminated infection in patients with several other skin conditions besides AD that are infected with HSV; however the term eczema herpeticum is reserved for disseminated HSV infection specifically in patients with AD. When it occurs in patients with other skin conditions, it is termed Kaposi’s varicelliform eruption [73] . Once again, disturbed skin barrier function, Th2 cell predominance, and lower levels of IFN- a are thought to contribute to the higher incidence of skin infections in AD patients. Eczema vaccinatum has been described in AD patients who have received the smallpox vaccine or more commonly had exposure to a recently vaccinated individual, which can cause a disseminated vaccinia eruption [73]. Therefore, a history of or active AD is a contraindication for smallpox vaccination. New attenuated strains of the virus are being developed, which may reduce the risk of this complication; but their efficacy towards preventing smallpox outbreaks is unknown [87– 89] . Eczema herpeticum can be quite serious, often requiring prompt medical attention. The patients at greatest risk for developing eczema herpeticum are those with more severe eczema, higher total IgE, and earlier age of onset [236] . There seems to be a genetic component, based on the fact that there is often a family history of this complication [90, 237] (unpublished data). Skin findings are accompanied by fever, lymphadenopathy, and malaise. Rarely, multi-organ failure may ensue including conjunctivitis, encephalitis, and meningitis [90]. Immediate treatment with systemic anti-virals such as acyclovir is necessary to minimize morbidity and mortality from the disease. Prior to the development of 268 S.F. Ibrahim et al. modern anti-virals, mortality from eczema herpeticum was reportedly as high as 75% [90] . Topical and systemic immunosuppressive treatments are contraindicated during acute phases of this condition. Suppression of recurrent HSV infection can be achieved with daily oral antiviral treatment [91] . Less severe viral skin infections in AD patients are caused by different strains of the human papilloma virus (HPV), and manifest as warts or verruca. The incidence of warts in AD patients has been estimated to be between 4 and 17% higher than in non-atopics [92] . A large variety of treatment modalities exist and have been reviewed extensively [93, 94]. Lesions of eczema molluscatum can resolve spontaneously; however treatment can accelerate the process and prevent autoinoculation. Treatment typically consists of destructive modalities similar to those suggested for HPV infections. Topical calcineurin inhibitors and topical steroids should be stopped in order to maximize host immune response [92] .

Fungal Infections

As with bacterial and viral infections, AD patients are also prone to fungal infections of the skin [95] . In particular, Malassezia spp. is known to colonize the skin of both healthy and atopic subjects, especially in seborrheic areas such as the face, and are implicated in exacerbation of AD [96] . Skin lesions of AD in patients with IgE to M. furfur have been shown to improve with antifungal treatment [95] . Additionally, atopic patients are more prone to develop chronic der- matophyte infections, and may show improvement in their AD when treated with antifungals [95] .

Antimicrobial Peptides

Antimicrobial peptides (AMP) are naturally occurring peptides that have been shown to possess anti-bacterial and anti-viral properties. They have generated considerable interest because of their potential therapeutic use against a variety of pathogens. In the epidermis, AMPs are secreted by keratinocytes and they are considered an integral part of the cutaneous innate immune system [97] . Several groups have noted that AD subjects have diminished AMP production which likely contributes to the susceptibility of AD subjects to skin colonization/infections [98– 101] . Manipulation of AMP expression could be a valuable approach to control microbial infections in AD subjects. In recent years, synthetic cationic steroid antibiotics, modeled after the chemical structure of AMP, have been developed for treatment of multi-drug resistant bacteria [102] . Leung et al., have recently shown in an in vitro model that these agents are effective anti-viral compounds capable of limiting Vaccina virus infection [103] . Other studies have shown that the induc- Update on the Management of Atopic Dermatitis/Eczema 269 tion of AMP is mediated by 1,25-dihydroxyvitamin D3 and the vitamin D receptor [104] . Studying the role of high-dose vitamin D and its effects on AMP production and other aspects of innate immunity in subjects with AD, is an area of active investigation by several groups.

Anti-Itch Treatment

Pruritus is the most distressing feature of AD, and the itch-scratch cycle perpetuates the disease. Scratching causes injury to the skin resulting in the release of inflammatory mediators that could themselves fuel the itch, as well as contributing to further barrier impairment and skin infections. The etiology of pruritus in AD is poorly understood, and consequently, highly effective therapy is not available. Current therapies rely on nonspecific approaches to reducing itch such as topical agents, oral antihistamines, and phototherapy. New developments in the study of pruritus may lead to better, targeted therapy and are briefly discussed below. Topical corticosteroids and TIMs have been shown to improve pruritus [105, 106] . Anti-pruritic effects are believed to relate to the inhibition of local inflammatory cytokines. In addition, the use of emollients with or without oatmeal baths and wet- wraps may reduce the frequency and/or amount of steroid application. Topical doxepin cream (Zonalon™, Bradley Pharmaceuticals, Fairfield NJ) has been used in subjects with AD and other pruritic conditions with variable results [107] . Doxepin is a tricyclic antidepressant drug, with strong anti-H1 and -H2 actions. Several studies have reported a short-term (1 week) improvement in itch, but no improvement in AD severity beyond this period [108] . The addition of topical doxepin to topical corticosteroids has been shown to induce a significantly faster and more substantial reduction in pruritus than corticosteroids alone [109] . Long-term studies on the efficacy of topical doxepin treatment are not available. The sedating effects observed even after fairly limited body surface area applications have limited the usefulness of this treatment. The effectiveness of oral antihistamines for pruritus control in AD patients is often debated [110, 111] . H1 and H2 antagonists have been utilized by many practitioners in the management of the intense pruritis frequently observed in AD. While evidence-based reviews have found insufficient evidence to recommend the use of antihistamines in AD [112] , it is our opinion that the soporific effects of the older generation antihistamines are helpful in preventing or minimizing scratching that typically escalates in the evening. Antihistamines may also be useful as, they are effective in treated a variety of comorbid conditions frequently seen in association with AD such as allergic rhinitis, conjunctivitis, and asthma [113, 114] . Beyond the oral and topical treatment modalities discussed above, phototherapy with ultraviolet (UV) radiation has been used successfully to treat AD. Several variations of phototherapy have been described including narrowband UVB (311 nm), broadband UVB, UVA1 (340–400 nm), psoralen plus UVA (PUVA 320–400 nm), 270 S.F. Ibrahim et al. balneophototherapy, climatotherapy, and extracorporeal photopheresis, although PUVA and UVB are most widely used [115, 116]. Phototherapy is effective when used in conjunction with topical steroids, thereby reducing the total dose of both treatment approaches [117] . There is increasing evidence supporting the efficacy and safety of narrow-band UVB in the management of AD [118– 120] . Narrow-band UVB is an effective adjuvant treatment for moderate to severe atopic dermatitis and the treatment is usually well tolerated, although its mechanism of action is still unclear. Several studies suggest that UVB has immunomodulatory effects, such as blocking the function of antigen presenting cells, and inducing the release of TNF-a and IL-10 by keratinocytes [121] . Interestingly, new evidence suggests that UVB rather than UVA may stimulate expression of the antimicrobial peptide LL-37, likely through a Vitamin D-mediated pathway [122] . Furthermore, T-cells within the epidermis seem to be susceptible to UVB-induced apoptosis [123] . Long-term safety of narrowband UVB phototherapy in AD patients will need to be monitored, particularly in its relationship to the development of cutaneous malignancy. As a general rule, phototherapy should be reserved as a second-line treatment in adults and used cautiously in children under 12 years old, as there is little information about long term side-effects in this age group. Advances in cellular and molecular biology have revealed new insight into the biology of itch, particularly in AD patients. Opioid receptors are known to play a central role in the modulation of itch, both centrally and peripherally [124] . Naltrexone, an opiate receptor antagonist has been used in treatment of recalcitrant pruritic diseases. AD patients have been shown to benefit from treatment with both oral and compounded topical preparations [125– 127] . Other recent advances in the etiology of itch may provide alternative approaches to treatment. Sonkoly et al demonstrated a significant increase in the expression of IL-31 in atopic skin as compared to psoriatic skin. IL-31 is a T-cell derived cytokine that elicits severe pruritus and dermatitis in a murine model. It was shown that staphylococcal superantigen rapidly induced IL-31 expression in atopic individuals, providing a link between staphylococcal colonization, T-cell activity, and pruritus in patients with AD [128] . This study provides a new target for the development of effective anti-itch therapies, and also supports the notion that antimicrobial agents may have a role in the treatment of pruritus. Sun et al have recently demonstrated that the gastrin-releasing peptide receptor plays an important role in the itch sensation centrally [129] . Thus, perhaps a combination of approaches including the reduction of bacterial burden, central modification, and peripheral blockade of itch mediators may ultimately be the most effective treatment approach for the intense pruritus that defines AD.

Systemic Immunosuppressive Therapy

Atopic dermatitis results from an abnormal inflammatory response, therefore many systemic immunosuppressive agents have been used successfully in its management. In general, systemic therapies are reserved for refractory cases in order to minimize Update on the Management of Atopic Dermatitis/Eczema 271 the risks associated with long-term immunosuppression. Most of the systemic medications currently used for treatment of moderate to severe AD are not FDA approved for this indication. Each requires close follow-up and some degree of clinical and laboratory monitoring to ensure that side effects are detected as early as possible. No single agent has proven superior to others, and therefore agents that are highly effective in one patient may not be suitable for another. Trials of several different systemic agents may be necessary before finding the best therapy for a given patient. Likewise, some patients may only need systemic agents for a limited time as “induction therapy” to reach an acceptable level of symptom control before switching to a maintenance regimen [130] . Patients who are refractory to multiple treatments should undergo skin biopsy and other investigations to ensure that the diagnosis of AD is accurate.

Systemic Steroids

Although oral corticosteroids have been used in the treatment of inflammatory skin conditions for over 50 years, few randomized studies have been performed in subjects with AD. The decision to use systemic steroids should not be taken lightly given the numerous systemic side effects including diabetes, hypertension, osteoporosis, cataracts, and avascular necrosis, as well as the risk of relapse upon steroid discontinuation [7] . Short courses of systemic steroids (less than four weeks duration) can be helpful in cases of acute flares of dermatitis; however they should be avoided during periods of rapid adolescent growth to minimize risk of permanent growth retardation [131] and even in the worst cases should be limited to at most 2–3 courses per year. The equivalent of 20–40 mg of prednisone daily for 2 weeks is typically sufficient to relieve severe flares, but the precise dosing and length of treatment is variable, influenced by factors such as bodyweight, disease severity, access to steroid-sparing agents and continued exposure to allergens. Withdrawal of steroids should be gradual to minimize the chances of rebound flares and HPA disruption.

Methotrexate

Methotrexate (MTX) is an antimetabolite that competes with folic acid for dihydro- folate reductase, an enzyme that catalyzes folic acid into reduced folate cofactors necessary for DNA synthesis. It has been used for many years to treat cancer as well as autoimmune and inflammatory diseases including psoriasis [132] . By disrupting folate metabolism, MTX inhibits proliferation of rapidly dividing cells such as keratinocytes and T cells. Several studies have indicated that MTX is effective and well-tolerated in AD subjects with moderate-to-severe disease and is comparable in efficacy to other second-line therapies [133– 136] . Bateman et al demonstrated a 272 S.F. Ibrahim et al. dose-dependent reduction in allergen-specific T cells that correlated with clinical response of AD to MTX [137] . The therapeutic approach used for AD is similar to that used for psoriasis. After baseline laboratories are checked (complete blood count, liver function tests) a test dose of 2.5 or 5 mg is administered with repeat laboratory values drawn 5–7 days later. If tolerated, the dose is then increased by 2.5–5 mg weekly until a therapeutic dose that typically falls between 15 and 25 mg/week is reached. The MTX dose for the week is taken in its entirety on one day, with 1 mg of folic acid given on non- MTX days to reduce potential side effects [138] . Nausea, anorexia, fatigue, myelosuppression, pneumonitis, and liver disease are among the potentially toxic effects of MTX. Although patients typically have laboratory monitoring monthly or bimonthly, there have been reports of liver damage occurring in the setting of normal liver function tests. For this reason, the American Academy of Dermatology guidelines recommend a liver biopsy after a cumulative methotrexate dose of 1.5 gm [139] . However recent data has suggested that this figure may be too conservative and patients without preexisting risk factors could potentially receive as high as 4.0 gm before undergoing liver biopsy [140] . MTX has been approved for children older than 2 years with juvenile rheumatoid arthritis, and appears to be well tolerated in the pediatric population [141] .

Oral Calcineurin Inhibitors

Oral calcineurin inhibitors have been utilized extensively as systemic immunosuppressive agents in solid organ transplant recipients. Their mode of action has been discussed in the TCI section above. Several clinical trials have shown the efficacy of CyA in the treatment of AD in both children and adults at doses of 3–5 mg/kg/ day [142– 147] . In one study, relapse of AD after discontinuation of CyA was reported, but the mean scores for disease activity and extent of disease were less than baseline values [148] . Short courses of CyA have also been shown to induce remission in pediatric patients, indicating that treatment plans should be individualized to the patient [144] . Dose-dependent side effects of cyclosporine include – but are not limited to – nephrotoxicity, hypertension and hyperlipidemia, which are why most clinicians limit its use to less than one year. In one study, increases in serum creatinine of over 30% were seen in 7 of 73 (10%) of AD patients treated with CyA and 8% of patients experienced a rebound phenomenon in their dermatitis upon discontinuation of treatment [149] . Although it has been suggested that tolerability of CyA may be better in children [150] , other studies have suggested that it may diminish bone mass in the pediatric AD population [151] . Neoral, a microemulsion of CyA with improved pharmacokinetic properties, has been shown to have a faster onset of action and higher initial efficacy in AD [152] . Oral pimecrolimus is a newer generation calcineurin inhibitor that prevents the dephosphorylation of NFAT as described in the topical calcineurin inhibitor section above. A double-blind, placebo-controlled trial with oral pimecrolimus Update on the Management of Atopic Dermatitis/Eczema 273

(10 mg, 20 mg or 30 mg twice daily for 12 weeks) has recently been completed. This trial has demonstrated significant improvement in the Eczema Area and Severity Index (EASI) scores for the 60 mg per day group compared to placebo. No nephrotoxicity or hypertension was observed during the trial period [152] . A nonhuman primate study with this formulation of pimecrolimus demonstrated an occurrence of lymphoma in monkeys exposed to a dose which represented 30 times the maximum recommended human dose. This finding has lessened the enthusiasm for clinical development of oral pimecrolimus [153] . Tacrolimus (FK506, Prograf) is a macrolide immunosuppressant produced by the soil fungus Streptomyces tsukubaensis with similar mode of action as the other calcineurin antagonists, but 10–100 times more potent than CyA [154, 155]. Like CyA, it is commonly used in solid organ transplant recipients to prevent rejection. Oral tacrolimus has been shown to be effective in inflammatory skin disorders including AD. However its potential side effect profile including infections, hypertension, hyperglcemia, hyperkalemia, nephrotoxicity, neurotoxicity, and increased risk of neoplasia has limited its use in dermatology, although its safety has been shown to be comparable if not superior to that of CyA in the transplant population [154, 156–159] . More controlled trials will be necessary to elucidate its utility in AD and other dermatologic disorders. Sirolimus (rapamycin) is not a calcineurin inhibitor like pimecrolimus, tacrolimus, or CyA, yet acts in a related fashion. Unlike the tacrolimus-FKBP12 complex which inhibits calcineurin, the sirolimus-FKBP12 complex inhibits the mammalian target of rapamycin (mTOR) and downstream players. This pathway is known to have a role in cellular growth and proliferation, and study of mTOR inhibitors has received immense scientific interest as potential cancer therapies [160] . Sirolimus is a larger molecule than pimecrolimus or tacrolimus, thereby precluding its use as a topical agent [161] . Unlike the calcineurin inhibitors, sirolimus does not exhibit renal toxicity, and thus can be used in conjunction with these agents. Reitamo et al demonstrated its use in the treatment of psoriasis in conjunction with CyA to reduce the dose and toxicity associated with the latter medication [162] . Side effects associated with sirolimus include lipid abnormalities, elevated liver enzymes, and thrombocytopenia [163] . Its utility and safety in dermatology has yet to be determined beyond preliminary studies that have been published to date [164, 165] . Notably, a new calcineurin inhibitor, ISA247 (Isotechnika, Inc., Scottsdale, AZ) is currently being studied in organ transplantation and psoriasis [166, 167]. It is significantly more potent that CyA, but appears to have less toxicity. Its role in treatment of AD has not been evaluated.

Mycophenolate Mofetil

Mycophenolate mofetil (Cellcept) is an inhibitor of inosine monophosphate dehydrogenase (IMP) that preferentially depletes guanine nucleotides in T and B lymphocytes, thereby limiting their proliferation. Several small, open-label studies of 274 S.F. Ibrahim et al. mycophenolate mofetil have demonstrated good efficacy and safety profiles in children and adults with severe AD [168– 172] . Mild headaches, gastrointestinal complaints, and fatigue are the most frequent side-effects associated with its use. Elevated liver enzymes have been reported [173] . Dosing in adults usually starts at 500 mg twice daily and increases to 1–1.5 gm twice daily as needed, based on efficacy and side effects. Maximum benefit can take 8–12 weeks. A new IMP inhibitor, VX-148 (Vertex Pharmaceuticals, Inc., Cambridge, MA) is currently being tested in patients with hepatitis C and psoriasis and appears to be a potent immunosuppressive agent with good pharmacological activity and bioavailability in a murine model [174] .

Azathioprine

Azathioprine (Imuran, GlaxoSmithKline) is an immunosuppressant drug that is metabolized into 6-mercaptopurine and 6-thioinosinic acid that acts through the inhibition of purine synthesis and cell proliferation. A double-blind, placebo- controlled crossover trial of 37 patients with severe AD showed an improvement in symptoms and reduction in the disruption of work/daytime activities after treatment with azathioprine; however 12 patients discontinued the medication secondary to side effects. Gastrointestinal disturbances and leucopenia were the major side effects. Other side effects associated with its use include fevers, rigors, myalgias, arthralgias, hepatotoxicity, and possibe increased risk of malignancies [175– 177] . Meggett et al demonstrated a 37% improvement in AD severity in a double-blind, randomized, control trial with azathioprine [178] . The side effects of azathioprine typically limit the enthusiasm for this therapy in AD. Genetic polymorphisms in the enzyme, thiopurine methyltransferase (TPMT) have been linked to individual differences in azathioprine side effects – particularly bone marrow toxicity – and it is suggested that patients undergo testing prior to initiation of the drug so that dose adjustments can be made [179] . Recommended dose of azathioprine for dermatologic disorders is 1–3 mg/kg/day in persons with normal TPMT activity. Azathioprine has demonstrated equal efficacy and safety profile in children as in adults with AD [180, 181] . An additional study has demonstrated clinical improvement of AD associated with a substantial reduction in serum total IgE in AD patients treated with azathioprine [182] . Regular monitoring of liver function and complete blood count is recommended.

Biologics

A new era of highly targeted therapeutic agents has emerged. These agents target specific components of the immune response and this approach holds the promise of reduced side effects as compared with conventional immunosuppressive medications discussed above. Update on the Management of Atopic Dermatitis/Eczema 275

Many of these drugs are recombinant proteins such as antibodies or soluble receptors, and are truly at the forefront of medical treatment of the disease.

Interferon-g (rIFN-g )

Recombinant interferon-g (IFNg ) was one of the first immunobiologics studied as a treatment for AD. The rational for IFNg therapy is to restore the balance between Th1 and Th2 cytokines, as IFN-g suppresses the expression and actions of Th2 cytokines such as IL-4 and IL-13, which play a key role in IgE production, eosinophilia, and the initiation of AD. It was somewhat surprising that treatment with IFN g was not shown to lower serum IgE levels in patients with atopic dermatitis treated for 12 weeks. Instead, the clinical improvement noted, correlated with decreases in absolute white blood cell and eosinophil counts [183– 185] . The exact mechanism of action of IFNg in the treatment of AD is unclear. A randomized, placebo-controlled trial of 83 severe AD patients demonstrated improvements in symptom scores and physicians’ overall response evaluation [186] . Headaches, myalgias, and chills developed in roughly half of those receiving active treatment. Treated patients were then enrolled in an open label trial and followed for more than 2 years, and no significant adverse events were reported [185] . Although IFNg therapy has not been FDA approved for the treatment of AD, its off-label use by some clinicians is reserved for treatment of acute flares in patients with moderate-to-severe AD [187] . Further studies to determine which AD patients are more likely to respond to IFNg , optimal dosing strategy and long-term safety are needed. For these reasons, as well as for cost reasons, and the flu-like symptoms commonly observed with this therapy, it is not commonly used.

Intravenous Immunoglobulin (IVIg)

IVIg is a plasma product pooled from 10,000 to 20,000 donors containing Ig molecules [188] . It has been used successfully in the treatment of primary immunodeficiencies, Kawasaki’s Disease and idiopathic thrombocytopenic purpura. The mechanism of IVIg’s anti-inflammatory action is not fully understood but is thought to involve both the Fc and antigen binding portions of the Ig molecule [188] . Several small case series’ and trials have shown efficacy in the treatment of AD [189– 193] . A meta-analysis by Jolles concluded that an improvement was observed in 61% of patients treated with IVIg, that adults were less likely to respond than children (48% vs 90%), and the duration of response was longer in children. It was also shown that IVIg as adjunctive therapy was more effective than monotherapy in adults (59% vs 0%), whereas monotherapy was effective in 90% of children [188] . Dose ranges of IVIg varied from 0.4–2 g/kg for 1–11 cycles. 276 S.F. Ibrahim et al.

IVIg is generally well tolerated, with most side effects occurring within an hour of infusion such as flushing, myalgia, arthralgia, headache, fever, chills, nausea, vomiting, chest tightness, wheezing, changes in blood pressure, tachycardia, and aseptic meningitis. Anaphylaxis is rare, but can occur in the setting of IgA deficient patients [188] . Furthermore, conflicting views have been expressed as to whether or not variability exists between different brands and preparations of IVIg [194, 195] . Certainly, further studies are needed to better characterize the role of IVIG in treatment of severe AD.

Tumor Necrosis Factor (TNF)a inhibitors (Etanercept – Enbrel®, Amgen; Infliximab – Remicade®, Centocor; Adalimumab – Humira®, Abbott)

Tumor Necrosis Factor (TNF)- a inhibitors are being used successfully to treat a variety of inflammatory conditions including psoriasis, rheumatoid arthritis, and inflammatory bowel disease. TNFa induces the expression or release of a variety of proteins relevant for the development of AD lesions, including the endothelial adhesion molecule, E-selectin, which facilitates the homing of the cutaneous lymphocyte antigen (CLA) positive memory T cells to the skin [196] . In addition, TNF a induces the production of chemokines important for the attraction of inflammatory cells to lesions of AD including thymus activation regulated chemokine (TARC [CCL17]), macrophage derived chemokine (MDC [CCL22]), and monocyte chemotactic protein (MCP)-4 [CCL13]. Interestingly, studies have failed to demonstrate an increased level of TNF in leukocytes or in serum of atopic dermatitis patients [197, 198] , whereas several groups have shown TNF immunoreactivity in lesional skin [199, 200] . Based on these findings, one can theorize that TNF antagonisms may be advantageous in the treatment of AD by decreasing adhesion molecule expression and recruitment of inflammatory cells to dermatitic lesions. Etanercept, a soluble TNF-receptor, and infliximab, a chimeric monoclonal antibody, are currently used to treat the cutaneous and musculoskeletal features of psoriasis. Recent studies have shown that TNF antagonism may be beneficial in some subjects with poorly controlled asthma [201, 202]. Remarkably little is known about how such drugs affect cutaneous allergic inflammation. To address this question, we recently employed the intradermal allergen challenge model to evaluate the clinical and cellular effects of etanercept on the acute and late phase reactions observed in this model [203] . The results from 10 subjects demonstrated that etanercept had no effect on the size of late phase reactions, cellular influx, or endothelial adhesion molecule expression, which is in agreement with the relatively poor clinical efficacy of this class of immunosuppressives in the treatment of atopic dermatitis [204, 205]. Nevertheless, there was an unexpected reduction in the size of the acute phase reactions, suggesting that etanercept can affect mast cell degranulation or its downstream effects, making this a potentially useful drug in the treatment of urticaria. To date, no studies of adalimumab in AD have been conducted. Update on the Management of Atopic Dermatitis/Eczema 277

Anti-LFA agents (Efalizumab – Raptiva®, Genentech-Xoma)

Efalizumab was a recombinant humanized monoclonal antibody that binds to the integrin subunit, CD11a. CD11a is the a subunit of lymphocyte function-associated antigen-1 (LFA-1), a cell surface molecule on T cells that mediates the adhesion to intracellular adhesion molecule (ICAM)-1. ICAM-1 is expressed on antigen presenting cells as well as endothelial cells and keratinocytes. Therefore, by blocking the LFA-1/ICAM-1 interaction, efalizumab inhibited T-cell activation as well as migration into inflammatory sites such as the skin [206] . In acute AD, the CLA+ CD4+ cell predominates, and releases local mediators that drive inflammation and recruitment of other inflammatory cells. Efalizumab was FDA approved for the treatment of moderate to severe chronic plaque psoriasis [196] . Recently, a few case reports and series demonstrated successful treatment of severe and refractory AD with efalizumab [207– 209] . In 2007, an investigator-initiated, prospective, open-label, pilot study conducted on 10 subjects with severe AD, was published [210] . Six out of ten subjects reached at least 50% improvement in EASI score. Overall, efalizumab was well tolerated. There were three significant adverse events during the course of this study, including thrombocytopenia, viral gastroenteritis, and a subject with worsening of disease beyond baseline levels after drug discontinuation. In early 2008 it became clear that patients receiving efalizumab were at increased risk for the development of progressive multifocal leukoencephalopathy (PML) and because of this risk Genentech voluntarily withdrew this drug from the US market in June of 2009.

Anti IgE Agents (Omalizumab – Xolair®, Genentech)

Omalizumab is a recombinant humanized IgG monoclonal antibody that binds specifically to the Fc eRI binding site on soluble human IgE, irrespective of allergen-specificity. It does not bind cell-surface bound IgE, thereby reducing the risk of anaphylaxis [211] . Several important mechanisms of action have been demonstrated, including reduction in free IgE levels, reduction in surface-bound IgE on basophils, mast cells and dendritic cells, and reduction in allergen-triggered response in basophils and mast cells [212, 213] . Omalizumab was FDA approved in June of 2003 for use in patients 12 yrs of age and older, with moderate to severe allergic asthma. Given the clinical benefits seen in trials with anti- IgE approaches in allergic diseases such as asthma, allergic rhinitis, and food allergy [211, 214] , and levels of serum IgE having been demonstrated to correlate with the severity of atopic dermatitis [215] , trials in subjects with atopic dermatitis seem warranted [216] . Two small case series have investigated the use of omalizumab in atopic dermatitis – one demonstrated benefit while the other showed no effect [217– 220] . 278 S.F. Ibrahim et al.

Notably, the serum IgE varied considerably among treated patients. In the study with the positive clinical response with omalizumab, serum total IgE values were substantially lower than in the study that showed no clinical response. Nevertheless, most of the subjects reported to date have been significantly under dosed based on the fact that they have all had rather elevated total IgE values. Current FDA recommendations for dosing of Xolair in an average-sized adult will only allow for neu- tralization of serum IgE levels up to 700 IU/ml. Therefore it is not too surprising that clinical improvement was not observed in many of these AD studies where the IgE levels far exceeded this cut off. Unfortunately, the AD patients with severe disease who are in need of new therapeutic options typically have extremely high serum IgE levels that omalizumab – based on current FDA regulations – cannot neutralize. Nevertheless, a randomized, controlled trial of omalizumab in AD patients with serum IgE levels within the appropriate dosing range (< 700 IU/ml) would define the relevance of IgE and its receptors in AD. If IgE pathways prove to be critical for the development of the disease, this and related compounds would provide a viable steroid-sparing treatment option for those moderate to severe AD patients with high serum IgE levels.

Alternative Approaches

Probiotics

Probiotics are cultures of live microorganisms including Lactobacillus and Bifidobacterium species which, upon ingestion, may provide benefit by improving the balance of the intestinal microflora. They have shown promise in the prevention and perhaps treatment of allergic diseases, including AD [221, 222] . Their mechanism of action is unknown but is thought by some to be related to the fact that intestinal flora of allergic children may be different from that of healthy infants [223, 224] . It has been shown that probiotics improve the mucosal barrier function and thereby reduce leakage of antigens through the mucosa, or have other direct influences on the immune system [225] . In one study, 159 expectant mothers with a personal or family history of atopic disease were randomized to 2 capsules of 109 Lactobacillus species or placebo. Offspring of the active treatment group were 50% less likely to manifest AD symptoms compared to offspring in the placebo-treated group [224] . In another study, 56 infants with moderate to severe AD were randomized to Lactobacillus fermentum or placebo. After 8 weeks of therapy, the group which received the probiotic had significant improvement in tits Severity Scoring of Atopic Dermatitis (SCORAD) index [222] . While some have ques- tioned the findings of these studies, this continues to be an active area of research [226, 227] . Update on the Management of Atopic Dermatitis/Eczema 279

Gamma linoleic Acid (GLA)

Gamma linoleic acid (GLA), also known as fatty acid, omega-6 fatty acid, and evening primrose oil, has been studied as an adjuvant in AD treatment. Several studies have shown a defect in essential fatty acids (EFA) metabolism in AD patients’ reduction rate of conversion of dietary EFAin their active metabolites [228] . Polyunsaturated fatty acids are essential components of all cell membranes as well as precursors of eicosanoids, which may play an important role in inflammatory and immunological processes of AD [229] . A recent meta-analysis of clinical trials demonstrated that evening primrose oil had a beneficial effect on pruritis, crusting, edema, and erythema in AD patients, which is apparent between 4 and 8 weeks after treatment [230] . However, the magnitude of this effect was reduced in association with increasing frequency of potent steroid use. Although unlikely to have utility as monotherapy, use of GLA and associated compounds may prove useful in the treatment of AD.

Psychological Interventions

Several psychological interventions have been used in management of AD. One of the goals of this approach is to break the itch-scratch cycle that exacerbates the disease and negatively impacts quality of life [231] . These interventions include behavioral management, relaxation therapy, and cognitive behavioral therapy (i.e. mindfulness). Unfortunately few research studies have been conducted to assess the efficacy of such approaches. One controlled trial addressed the effect of hypnotherapy or biofeedback as compared to placebo in AD children, and concluded that there was no difference between the two relaxation techniques. Both however induced a significant reduction from baseline in severity of AD [232] . Given the anecdotal evidence of patients with AD reporting worsening of their disease during times of stress and other preliminary findings, further studies into the contribution of psychological factors to the course of AD will be of interest to the dermatologic community.

Conclusions

Atopic dermatitis is a complicated disease that is a challenge to manage. Fortunately, as our understanding of the disease process at the molecular and cellular level increases, so too does our armamentarium of treatment options. By recognizing and avoiding triggers of the disease, maintaining good skin care practice, and deciding upon the best course of treatment that offers maximal relief of symptoms while minimizing side effects, the physician and patient can together determine the appropriate course of treatment. 280 S.F. Ibrahim et al.

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223. Weston S, Halbert A, Richmond P, Prescott SL. Effects of probiotics on atopic dermatitis: a randomised controlled trial. Arch Dis Child 2005;90(9):892–7. 224. Kalliomäki M, Kirjavainen P, Eerola E, Kero P, et al. Distinct patterns of neonatal gut microflora in infants in whom atopy was and was not developing. J Allergy Clin Immunol 2001;107(1):129–34. 225. Kalliomaki M, Salminen S, Arvilommi H et al. Probiotics in primary prevention of atopic disease: a randomized placebo-controlled trial. Lancet 2001;357(9262):1076–9 226. Madsen K. Probiotics and the immune response. J Clin Gastroenterol 2006;40(3):232–4. 227. Williams HC. Two “positive” studies of probiotics for atopic dermatitis: or are they? Arch Dermatol 2006;142(9):1201–3. 228. Williams HC. Prevention of atopic eczema: a dream not so far away? Arch Dermatol 2002;138(3):391–2. 229. Horrobin DF. Essential fatty acid metabolism and its modification in atopic eczema. Am J Clin Nutr 2000;71(1 Suppl):367S–72S. 230. Ziboh VA, Miller CC. Essential fatty acids and polyunsaturated fatty. acids: significance in cutaneous biology. Annu Rev Nutr 1990;10:433–10. 231. Morse NL, Clough PM. A meta-analysis of randomized, placebo-controlled clinical trials of Efamol evening primrose oil in atopic eczema Where do we go from here in light of more recent discoveries. Curr Pharm Biotechnol 2006;7(6):503–24. 232. Horne DJ, White AE, Varigos GA. A preliminary study of psychological therapy in the management of atopic eczema. Br J Med Psychol 1989;62(Pt 3):241–8. 233. Sokel B, Kent CA, Lansdown R, Atherton D, Glover M, Knibbs J. A comparison of hypnotherapy and biofeedback in the treatment of childhood atopic eczema. Contemp Hypnosis 1993;10(3). 234. Huang JT, Abrams M, Tlougan B et al. Treatment of Staphylococcus aureus colonization in atopic dermatitis decreases disease severity. Pediatrics. 2009;123(5):e808–14. 235. Warner J, McGirt LY, Beck LA. Biomarkers of Th2 Polarity and Disease Severity are Predictive of Staphylococcal Colonization in Atopic Dermatitis Subjects. Br J Dermatol 2008;160(1):183–5. 236. Beck LA, Boguniewicz M, Hata T, Schneider LC, Hanifin J, Gallo R, Paller AS, Lieff S, Reese J, Zaccaro D, Milgrom H, Barnes KC, Leung DY. Phenotype of atopic dermatitis subjects with a history of eczema herpeticum. J Allergy Clin Immunol 2009; 25. [Epub]. 237. Gao P-S, Rafaels NM, Hand T, Murray T, Boguniewicz M, Hata T, Schneider L, Hanifin JM, Gallo RL, Gao L, Beaty TH, Beck LA, Barnes KC, Leung DY. Filaggrin Mutations that Confer Risk of Atopic Dermatitis Confer Greater Risk for Eczema Herpeticum. J Allergy Clin Immunol 2009 (accepted). Immunosuppressants as Treatment for Atopic Dermatitis

Bartlomiej Kwiek and Natalija Novak

Introduction

Atopic dermatitis (AD) is a chronic inflammatory skin disease affecting about 20% of children and up to 3% of adults worldwide. The clinical manifestation of AD is based on the interaction of specific genetic predispositions with a large number of environmental factors. Treatment of AD depends on the course and severity of the disease as well as the most important trigger factors such as aero- or foodallergens, microbial pathogens or other exogenous and endogenous influences [1] . Here we provide an overview of the mode of action of different immunosuppressants, which are frequently used as treatment for AD.

Glucocorticosteroids

Nearly 60 years ago, the Nobel Prize for Physiology and Medicine was awarded for isolation and synthesis of cortisol, the physiological prototype of all synthetic glucocorticosteroids (GCS) and its introduction as an anti-inflammatory drug. The use of local and systemic GCS in dermatology and in particular as a treatment for AD started some years later [2, 3] . Nowadays, topical GCS are still the first line therapy for AD in cases in which anti-inflammatory treatment is required [4] . Both efficacy and safety of local and systemic GCS are connected with a wide spectrum of effects and include anti-inflammatory actions, which are related to their physiological role as modulators of the natural response of our immune system to stress and infectious stimuli. A large number of synthetic derivatives of GCS with a wide spectrum of anti-inflammatory properties and differences in their capacity to penetrate skin

B. Kwiek Department of Dermatology, Medical University of Warsaw, Warsaw, Poland N. Novak () Department of Dermatology and Allergy , University of Bonn , Sigmund-Freud-Strasse 25 , 53105 Bonn , Germany e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 291 DOI 10.1007/978-4-431-99362-9_17, © Springer 2010 292 B. Kwiek and N. Novak have been developed until now. This diversity in the character of GCS has to be taken into account when interpreting in vivo and in vitro studies on the mechanisms of GCS.This diversity might provide quite different results or data which might seem to be conflicting at first sight.

GCS Signaling

Cortisol and GCS are small lipophylic agents, which easily penetrate cell membranes and invade the cytoplasm, where they can bind to the glucocorticosteroid receptor (GR). Ligation of GCS to GR is followed by the nuclear translocation of the GCS–GR complex. This process is regulated by chaperones from the heat shock protein (hsp) family and immunophilins [5, 6] . Among several variants of GR, which are a product of alternative splicing and translation, GR-a targets the GCS regulated genes, while GR-b exerts regulatory functions and is responsible for GCS resistance [7, 8] . Once the activated GCS–GR complex enters the nucleus, it forms a homodimer and interacts with the glucocorticosteroid responsive element (GRE) on DNA-specific sequences in the promoter region of GCS regulated genes It either activates transcription at the positive GRE site or suppresses transcription via the negative GRE site. The process of activation of anti-inflammatory genes is called “transactivation” and induces the expression of annexins (including annexin/lipocortin-1), secretory leuko-protease inhibitor (SLPI), inhibitor of nuclear factor-k B (NF- k B) (I k B- a ), mitogen-activated kinase phosphatase-1 (MKP-1), glucocorticoid-induced leucine zipper protein (GILZ), and interleukin (IL)-10 [9] . Additionally, direct contact of DNA-activated GR influences other transcription factors or coactivator molecules by protein-protein interactions, which results in gene suppression called “transrepression.” This process includes the inhibition of NF-k B, activating protein-1 (AP-1) and signal transducers, and activators of transcription (STAT) family proteins. GR protein undergoes several posttranscriptional modifications including phosphorylation, which is important for the GCS response [10] . GCS action is related to chromatin remodeling by regulation of histone acylation or deacy- lation, which results in gene transcription or repression [9] . Further on, GCS influence the mRNA stability of inflammatory proteins, thus modulating post transcriptional steps of inflammatory responses [11] . However, some of the clinical responses (in particular the rapid responses) observed with GCS are most likely not based on transcription-related mechanisms but rather a result of nongenomic mechanisms such as the modulation of GR expression itself or cell membrane fluidity [12, 13]

GCS and the Th1/Th2 Balance

GCS influence both the level of cytokines and the response to cytokines, and favor immune responses of the Th2 type, while blocking immune responses of the Th1 type [14– 20] . It is supposed that GCS block interleukin (IL)-12 related STAT-4 Immunosuppressants 293 phosphorylation of T cells in vitro, [17] which in addition to the inhibition of interferon (IFN)-g production in GCS treated skin, favor Th2 immune responses [21] . GCS suppress interferon regulatory factor (IRF) -1, -3 and -7 gene expression in peripheral blood mononuclear cells (PBMC) [22] and increase granulocyte- macrophage colony stimulating factor (GM-CSF) receptor expression on monocytes in vitro [23] . In accordance with findings concerning a Th2 shift upon GCS treatment, increased IgE synthesis by B cells in response to GCS treatment has been described [20] . Despite these results, the efficacy of GCS in the early Th2 dominated phase of AD could be explained mostly by their inhibitory effect on the production of so-called initial phase cytokines such as tumor necrosis-a and interleukin-1 b, as well as the Th2 cytokines IL-3, IL-4, IL-5, GM-CSF and reduction of the expression the high affinity receptor for IgE (Fce RI) on mononuclear cells [11, 24] . GCS do not only exert immunosilencing functions on the cytokine network [14] . In addition they promote the expression of regulatory/anti-inflammatory mediators including IL-10 and the respective IL-10 receptor (IL-10R), transforming growth factor (TGF)-b receptors I, II, III [22] and thymosin-b 4 [25] by a variety of immunocompetent cells. GCS have been shown further to promote the development and function of regulatory CD4+ CD25 + FOXP3 + T cells (Treg) in asthma patients [26] . This is of particular importance considering the latest findings on the role of Treg in the pathogenesis of autoimmune and allergic diseases [27] . Evidence of a deregulation of Treg in AD skin has been provided very recently [28] , supporting the idea of a GCS related induction of Treg functions as a potential mode of action of GCS in AD. However, mild GCS such as hydrocortisone did not influence the number of FOXP3+ T cells in AD skin [29] .

GCS and Antigen Presentation

One of the most striking effects of systemic and topical GCS is a random depletion of all CD1a+ epidermal dendritic cells (DC) [30] , including Langerhans Cells (LC) and inflammatory dendritic epidermal cells (IDEC) [31, 32] . Monocytes are direct precursors of LC and IDEC [33, 34] . Therefore induction of monocytopenia [35] , apoptosis of monocytes as early DC precursor’s [36, 37] and inhibition of the recruitment of DC precursors in AD could be of importance for GCS related depletion of DC from the epidermis. Downregulation of monocyte chemoattractants, such as macrophage derived chemokine (MDC), IL-16 and the chemokine regulated upon activation, normal T cells expressed and secreted (RANTES) [38– 40] contribute to this process. Lately, a nonmyeloid subtype of DC, called plasmacytoid DC (PDC), was described and characterized by a CD1a- CD123 + BDCA2+ phenotype. PDC are believed to play an important role in innate immune responses to viral infections by secreting high amounts of type I interferons, and coordinating innate and acquired immune processes. Deregulated distribution of PDC in blood, dermal and epidermal compartment of AD subjects compared to healthy individuals or individuals 294 B. Kwiek and N. Novak with other chronic inflammatory skin diseases has been shown [41– 43] . Further on, modified expression of Fce RI and altered IFN-a and IFN- b production by PDC of AD patients could be of importance to impaired responses to viral infections observable in subgroups of AD patients. Besides the influence of GCS on myeloid DC, topically applied GCS deplete PDC from the dermis of lesional AD skin. Clinical significance of this finding for both efficacy and potential side effects of GCS in AD, such as increased susceptibility to viral skin infections, remains to be evaluated [44] .

GCS and Leucocyte Migration

The atopy patch test (APT) is a model for the cutaneous allergic response in AD. It was shown that leucocytes influx into the skin after epicutaneous application of aeroallergens during the APT can be inhibited by GCS [21, 45] . Migration of immun- competent cells to the skin is a multistep process orchestrated by several chemokines, and chemokine receptors and associated with the presence and activity of adhesion molecules. GCS are strong suppressor of adhesion molecule expression in vitro and in vivo, including the suppression of ICAM, VCAM and E-selectin on endothelial cells [21, 46] . This phenomenon seems to be limited to GCS with moderate to strong potency, while mild GCS applied topically does not exert these effects [47] . Some GCS affect additionally adhesion molecule expression on circulating leukocytes. Together, this might result in the inhibition of leukocytes adhesion to endothelial cells and thereby recruitment of leukocytes to the site of inflammation [48] . The production of chemokines by PBMC and epidermal cells has been shown to be affected by GCS in several studies [38, 49, 50] . Topical treatment with GCS leads to decreased serum levels of TARC/CCL17(Thymus and activation regulated chemokine), macrophage derived chemokine (MDC)/CCL22, IL-16 and eotaxins for instance [40, 51, 52] . GCS reduce leukocyte infiltration in the epidermis and dermis [21] and the like- lihoodof re-triggering eczema after GCS application is directly dependent on the intensity of leukocyte infiltration. Consequently, the rationale behind this mode of treatment could be to keep the number of infiltrating leukocytes low and prevent relapses of AD by repetitive application of GCS.

GSC and Cell Viability/Skin Barrier

Besides the influence on leucocytes migration, induction of apoptosis of several inflammatory cells in the skin and the circulation is of importance for the reduction of inflammatory cell recruitment which goes along with GCS treatment. GCS have been shown to induce apoptosis of monocytes, macrophages, myeloid DC, PDC and T cells [31, 32, 37, 53]. Immunosuppressants 295

In addition to the induction of apoptosis of leucocytes, GCS are also capable of protecting cells from programmed cell death [54] . It is assumed that this bivalent function of GCS is related to their physiological role in both immunosupression and protection of inflamed tissue from inflammation induced destruction, and is believed to be mediated by Bcl-2 family proteins. T cell mediated keratinocyte apoptosis plays a major role in the pathogenesis of AD [55] . Activated T cells have been shown to release IFN-g , which upregulates the expression of Fas on the surface of keratinocytes. In the next step, keratinocyte apoptosis is induced by the interaction of Fas ligand expressed by activated T cells with its respective receptor (Fas/CD95) on the surface of keratinocytes. GCS can inhibit this process mainly by reducing T cell activation; but given in high doses, GCS affect T cell mediated apoptosis and in addition induce directly the cell death of keratinocyte [56] . Topical GCS were shown to decrease enhanced transepidermal water loss in AD skin and improve disease related disruption of skin barrier [57] . This is most likely related to their influence on the viability of keratinocytes [56] and the reduction of inflammatory cytokines in the skin, which indirectly impair the skin barrier function [58] . The lesional and nonlesional skin of AD patients is highly colonized with microbes such as Staphylococcus aureus bacteria. Upon treatment of AD with GCS, the level of S. aureus colonization drops significantly [59] . This might be a consequence of a GCS-restored skin barrier followed by hiding of extracellular matrix molecules known to act as adhesins to S. aureus (e.g., fibronectin, collagens, fibrinogen, elastin, or laminin) [60, 61] . S. aureus produced superantigens are able to activate T cells, bridging T cell receptor (TCR) and major histocompatibility class (MHC) II molecules directly regardless their clonality. In contrast to regular antigen related TCR activation, which can be blocked by GCS, superantigen induced TCR related PBMC proliferation was shown to be resistant to GCS blockade in vitro [62, 63] . Additionally, S. aureus superantigens are able to induce the inactive variant GRb , which leads to GCS resistance.

GSC and Mast Cells/Eosinophils

Increased numbers of skin infiltrating mast cells is a typical feature of AD and is associated with increased serum levels of soluble stem cell factor (sSCF), which promotes migration, differentiation and maturation of mast cells [64] . GCS deplete mast cells from the skin after 3 weeks of topical treatment [65] . Simultaneously the levels of sSCF and the soluble form of its receptor (tyrosine kinase transmembrane receptor – KIT) decrease [64] . Eosinophilia and elevated levels of eosinophil granule proteins are typical features of active AD, especially the allergic/extrinsic subtype which goes along with a high number of sensitizations and elevated serum IgE levels. GCS decrease the level of serum IL-5, the main and selective growth, differentiation, activation and 296 B. Kwiek and N. Novak chemotactic factor for human eosinophils. GCS also decrease the level of IL-5 secreted by stimulated human T cells in vitro [66] . Lower levels of IL-5 in response to GCS treatment shorten the survival of skin eosinophils and reduce eosinophil infiltration of the skin [67] . Depletion of eosinophils upon GCS treatment also results from decreased chemotactic signals other than IL-5, such as eotaxin-3 (CCL26), IL-16 [68] and reduction of the expression of the adhesion molecules ICAM-1(CD54) and ICAM-3 (CD50), important for eosinophil activation and recruitment [69] mediated by GCS.

Cyclosporine

The immunosuppressive drug Cyclosporine A (CsA) was introduced in 1978 in transplantation medicine, to prevent organ rejection [70] . CsA binds to cyclophillin and blocks the activation of T cells by preventing the production of cytokines which support the proliferation of T cells such as IL-2 [71] . Nowadays, CsA is also used as a treatment for severe cases of AD, and its safety and efficacy has been proven in several studies [72, 73] . One of the most prominent features of AD is the strong infiltration of the skin lesions with activated CD4+ T cells. Immunhistological investigations have shown that the dermal infiltrate is mainly composed of CD4+ and CD8 + cells with a CD4/CD8 ratio similar to that found in the peripheral blood [74] . It is well known that the human immune system harbours a powerful army of cutaneous T cells bearing the cutaneous lymphocyte antigen (CLA) on their surface, which enables them to be immediately recruited into the skin on invasion of foreign antigens. Cyclosporine treatment significantly reduces the number of CD4+ / CLA + and CD3+ /CLA + T cells in the peripheral blood of treated AD patients, while the number of CD3 + , CD4 + and CD8 + cells as well as CD8 + /CLA + T cells remains unchanged. Reduced numbers of CD14 + , CD25 + , CD36 + and IL-8 producing inflammatory cells are detectable in the skin of AD patients after therapy with CsA, indicating a decreased infiltration of activated cell types in response to the CsA treatment [75] . Reduced production of the proinflammatory cytokines IL-6 and IL-8 by PBMC isolated from the peripheral blood of children treated with CsA has been shown, indicating a reduced activation of different cell subtypes not only in the skin but also in the blood in response to CsA treatment [76] .

CsA and Keratinocytes

Fas ligand mediated keratinocyte apoptosis has been supposed to play a major role in the pathogenesis of AD [55] . Interestingly, this process has been shown to be partially prevented by CsA treatment, which is mainly a result of the CsA related reduction of the activation state of T cells [56] . Immunosuppressants 297

CSA and Leukocyte Migration

Chemokines expressed by endothelial cells act on leukocytes rolling on the endothelium and increase the affinity of leukocyte integrins to their ligands. Integrin activation is critical for the adherence of leukocytes to the endothelium and migration towards a chemical gradient into extravascular tissue. In acute AD, enhanced serum levels of several chemokines such as CCL2/MCP-1 (monocyte chemoattractant protein-1), CCL4/MIP-1b (macrophage inflammatory protein), CCL5/RANTES (regulated on activation, normal T cell expressed and secreted), CCL11/Eotaxin, CCL17/TARC, CCL22/MDC, CCL26/eotaxin-3, CCL27/CTACK (cutaneous T cell attracting chemokine) and CX3CL1 /Fractalkine and other chemotactic factors like IL-16 and soluble CD30 (sCD30) have been observed [74] . These chemokines are supposed to contribute to the chemotaxis of eosinophils and Th2 cells as well as being precursors of skin DC from the blood into the peripheral tissue. Evidence of a counteraction of CsA on the recruitment of inflammatory cells arises from studies showing a reduced amount of the chemokines CCL22 and CCL17 produced by monocyte-derived DC, derived from monocytes of AD patients after treatment with CsA, and by PBMC stimulated with house dust mite allergens and coincubated with CsA in vitro [49] . Both chemotactic factors have been shown further to correlate with the disease activity of AD [77] . CCL17 as ligand of the CC-chemokine receptor (CCR)-4, induces cutaneous lymphocyte trafficking in AD [78] , while CCL22 is mainly produced by DC and macrophages, and induces migration of DC and CD4+ T cells [79] . As a correlate of these findings, serum levels of CCL17 and CTACK profoundly decrease during systemic treatment with CsA [80] . The amounts of sCD30 [81, 82] , eosinophilic cationic protein as an indicator for eosinophil activation [83] and soluble E-selectin are reduced in the blood of AD patients treated with CsA [84] . Another characteristic feature of most AD patients is the Th2 overbalance, mirrored by elevated serum levels of Th2 cytokines and Th2 prone micromilieu in the skin in the acute phase of the disease as well as increased serum levels of total and allergen- specific IgE. The Th2 dominated cytokine pattern of T cells in the peripheral blood of patients treated with CsA changes, showing reduced production of the Th2 cytokines interleukin IL-4, IL-5 and IL-13, indicating that a partial restorage of the Th2 overbalance in AD is achievable by CsA [85] .

CsA and IgE Autoreactivity

There is some evidence that an important subgroup of patients with AD, which benefits from treatment with CsA might belong to the group of AD patients who have developed IgE autoreactivity. Immunoglobulin E autoreactivity has been implicated as an important immunopathogenetic factor in AD in the last few years. Molecular analysis of allergens has revealed striking similarities between environmental allergens and human proteins, leading to the hypothesis that autoimmune reactions 298 B. Kwiek and N. Novak might play a role [86] . IgE-reactive autoantigens directed against human proteins have been cloned from human epithelial copy DNA (cDNA) expression libraries and have been found to primarily represent intracellular proteins [87] . Autoantigens characterized for AD are Hom s 1-5 and DSF70 [88] . These autoantigens seem to act as adjuvants to the immunological mechanisms in AD patients with elevated IgE levels, as they have been detected in IgE-immune complexes of AD sera. The release of autoallergens from the damaged tissue, putatively triggered by mechanical factors such as scratching, could trigger responses mediated by mast cells, T cells, and IgE. Since IgE autoreactivity is already detectable in a subgroup of children with severe sensitizations against food- or aeroallergens, the manifestation of IgE autoreactivity and the decision, whether an individual may have a chronic persistent course until adulthood or clearance of the disease during childhood seem to take part already in infancy [89] . IgE autoallergen levels decrease as a consequence of successful treatment with CsA [90] . This finding indicates that CsA might suppress the activity of T cells which support the production of IgE autoantibodies and reduce the contact of autoreactive B cells with autoantibodies leading to reduced IgE autoreactivity [90] . However, which of the CsA induced effects described here represent rather primary mechanisms of CsA acting directly on target cells or rather secondary phenomena that might go along with a general decrease of the disease activity induced by CsA, remains to be clarified.

Calcineurine Inhibitors

CsA, tacrolimus, and pimecrolimus share common molecular targets. They inhibit the function of calcineurine, the enzyme that dephosorylates NFAT [91] . CsA binds calcineurine indirectly by interaction with cyclophilin, a member of the immunophilin family, while another immunophilin – FKBP-12 is a binding molecule for both tacrolimus and pimecrolimus [92] . Although the role of immunophilins associated with their enzymatic peptidyl prolyl cis/trans isomerases (PPI) activity is multidirec- tional, their influence on Ca++ /Calmoduline/Calcineurine/NFAT is why they have been named as calcineurine inhibitors (CNI). Binding calcineurine by the immunophilin-calcineurine inhibitor complex prevents dephosphorylation and nuclear translocation of NFAT. This leads to inhibition of the transcription of proinflammatory cytokines in T cells. NFAT and NFAT family members as well as calcineurine and immunophilins are integral parts of a high number of immunocompetent cells.

CNI and T cells

NFAT signaling in T cells is involved in both Th1 and Th2 differentiation and proliferation of T cells. Thus, inhibition of NFAT results in the blockade of these processes. It was shown that tacrolimus blocks IL-2 synthesis and proliferation of Immunosuppressants 299

T cells in AD [93] . Both topical tacrolimus and pimecrolimus were shown to inhibit Th1 and Th2 cytokine production (IL-5, IL-13, IL-10 and IFN-g ) by CD4+ and CD8 + T cells in AD skin and strongly reduce the T cell infiltration [94, 95] . Whether CNI induce T cell apoptosis directly or indirectly remains to be clarified [96] . In contrast to systemic use of CNI, topical application of these compounds has only minimal effects on circulating lymphocyte numbers [94, 95] . The reduction of lymphocyte infiltrates after CNI treatment are partially the effect of decreased expression of adhesion molecules on endothelial cells [47] together with decreased production of chemotactic factors, such as IL-16 in tacrolimus treated skin and ccl!/ in PBMC from AD patients [49, 97] . In contrast to GCS, tacrolimus is capable of blocking superantigen stimulated T cell proliferation thus representing an alternative therapy in the case of GCS resistance [98] . Interestingly tacrolimus does not only exert inhibitory functions on cytokine production, but has shown to act synergistically on Treg from AD patients to inhibit T cell proliferation. Additionally topical application of tacrolimus leads to increased numbers of TGF-b producing Treg, which can be of importance to the immunoregulatory and anti-inflammatory effects of this compound [29] .

CNI and Antigen Presentation

The clinical picture of eczematous skin in AD implicates the role of allergic reactions of the delayed type. Understanding the central role of IgE bearing DC on one hand and introduction of APT as a model for AD on other hand, have provided important background information for therapeutic strategies which target the process of antigen uptake and presentation in AD. Recent findings have proved that different subtypes of DC are affected in their phenotype and functions by CNI. In contrast to GCS, topical CNI do not deplete epidermal CD1a+ DC [31, 32, 94, 95, 99] . Interestingly, while the total number of myeloid DC in the skin remains unchanged after treatment with CNI, IDEC are rapidly depleted from the epidermis simultaneously with the improvement of the skin lesions. Considering the role of IDEC in perpetuating and amplifying the Fce RI related allergic response [100] this phenomenon could be one of the central events responsible for topical CNI efficacy. Both tacrolimus and pimecrolimus do not profoundly change the number of LC in the epidermis, which might be of importance for preservation of the postulated role of LC in the maintenance of local tolerance. In contrast to the different influence of GCS and CNI on myeloid DC, GCS and pimecrolimus were shown to homoge- nously deplete PDC from the dermis [44] . Despite impact of CNI on DC balance, they profoundly modulate the function of DC. CNI reduce MHC II and costimulatory molecule expression of DC, impair the stimulatory properties of DC toward T cells and inhibit DC maturation. This is the case of in vitro generated DC treated with CsA and tacrolimus [101, 102] as well as ex vivo isolated LC from the skin of AD patients treated with tacrolimus, [103] while the functional inhibition of human DC induced by pimecrolimus was minimal [104] . However, it was shown that pimecrolimus modulates DC in the 300 B. Kwiek and N. Novak murine system [105] . While IL-12 production by human monocyte derived DC was not affected by pimecrolimus treatment [36] , tacrolimus inhibited IL-12 secretion by DC in both mouse [101] and human models [106] . Antigen presentation by epidermal DC in AD is related to the presence of Fce RI on the DC surface and so called antigen focusing results in the amplification of the allergic response to antigens. In this context, tacrolimus was shown to reduce the expression of Fc eRI on LC and IDEC in the lesional skin of AD, and might therefore be responsible for the reduction of the antigen-uptake and presentation process in AD [99] .

CNI and Eosinophils

IL-5 synthesis was found to be downregulated by tacrolimus and CsA in PBMC and T cells [66, 107] . During AD treatment with systemic CsA, the blood count of CD4+ IL-5+ and CD8 + IL-5+ cells decreases together with a reduction of the eosinophilia [85] . In skin treated topically with CNI, IL-5 is downregulated in both CD4+ and CD8+ cells together with a lowered level of eotaxin, CCR3, RANTES and IL-16, which could be of importance for the reduction of eosinophil recruitment to AD skin [94, 95, 97, 108] . Decrease of IL-5 in the skin is accompanied by a decrease of the serum level of this cytokine and can be important for a reduced generation of eosinophils from the bone marrow.

CNI and Effector Cells

The function, survival, and proliferation of mast cells are heavily impaired by CNI [109] . Topical CNI inhibits Fce RI-mediated production of histamine, eicosanoids, and cytokines (including IL-4 and TNF-a ) by mast cells and basophils [110, 111] while the total number of mast cells in the skin remains unaffected [94, 95] .

CNI and Keratinocytes

Keratinocytes are involved in the pathophysiology of AD by secreting enhanced amounts of GM-CSF, IL-1, TNF-a , and inducible nitric oxide synthase (iNOS). CNI was shown to inhibit GM-CSF and iNOS production by human AD keratinocytes [56, 112] . Additionally topical tacrolimus was shown to induce the release of anti-inflammatory mediators such as TGF-b from keratinocytes and upregulates IL-10R [112, 113] . CNI inhibit T cell mediated apoptosis of keratinocytes [56] , which might be responsible for a reduced spongiosis observable after topical application of CNI [94, 95] . Immunosuppressants 301

While tacrolimus and pimecrolimus do not influence the viability of keratinocytes directly [112, 114] , tacrolimus reduces keratinocytes proliferation [112, 114, 115] .

Mycophenolate Mofetil

Mycophenolate mofetil (MMF) is a 2-morpholinoethyl ester of mycophenolic acid, which selectively and reversibly inhibits inosine monophosphate dehydrogenase and suppresses de novo synthesis of purine in T and B cells. Mycophenolic acid inhibits leukocyte recruitment and their adhesion to endothelial cells [116] . Successful treatment of adults - and in a few studies also of children with AD -with MMF has been reported [116– 118] . Therefore, MMF has been suggested as alternative therapy for moderate to severe AD mainly for recalcitrant forms of AD in single cases. However, sufficient data from double-blind placebo controlled studies including a high number of AD patientsis necessary to confirm these results. Side effects of MMF treatment include dose-dependent nausea, vomiting, diarrhoea, abdominal pain, and bone marrow suppression with increased risk of infection. Further on, case reports of liver enzyme abnormalities in treated patients exist [119] . Concerns about the use of MMF in AD have been raised due to the high bacterial colonization in AD patients on one hand and the enhanced risk of infections as a side effect of the drug on the other hand [120] . Therefore careful risk benefit analysis resulting from controlled studies with MMF in AD and detailed knowledge about the mode of action of MMF in ADare indispensable, to assess the value of MMF as a treatment for AD.

Methotrexate

Methotrexate (MTX) has been used for the treatment of T cell mediated skin disorders such as psoriasis or rheumatoid arthritis for a long time. In some small studies, a putative effect of MTX as treatment for adult patients with moderate to severe AD has been provided with clinical improvement in 70% of the patients after 3 months [121] . Significant improvement of disease activity in 52% of the cases from baseline and quality of life of the patients has been shown in another, open-label dose- ranging study using MTX in adult patients with moderate to severe AD [122, 123 ]. MTX is an antimetabolite, which has profound anti-inflammatory activities. MTX increases the concentration of adenosine and binds to anti-inflammatory adenosine receptors. Adenosine acts as endogenous mediator of anti-inflammatory mechanisms and mediates cytokine expression as well as upregulation of adhesion molecule expression. Therefore, the anti-inflammatory effects of MTX might lead to improvement of AD in a subgroup of patients. As a consequence, the exact mode of action of this treatment in AD has to be studied in more detail in the future. 302 B. Kwiek and N. Novak

Intravenous Immunoglobulines

Intravenous immunoglobulines (IVIG) was administered for the first time over 50 years ago to patients with antibody deficiencies. Since then a high number of inflammatory and autoimmune disorders have been treated with IVIG. A few studies in which IVIG have been used as a monotherapy for children with AD [124] or as adjunctive therapy in adults with AD [125] have shown a positive clinical effect derived by IVIG on the severity of AD. The positive effect of IVIG on AD is not completely surprising, looking at the main cells and structures targeted by IVIG, which play a central role in the pathogenesis of AD. Primary target cells of IVIG are antigen presenting cells (APC) such as dendrite cells (DC). IVIG attenuate DC differentiation and maturation, and downregulate the expression of costimulatory molecules essential for T cell stimulation [126, 127] . Further, IVIG functionally block Fc receptors but increase the functions of inhibitory Fc gamma RIIB [128] . Dose dependent effects of IVIG on induction and prevention of apoptosis of peripheral blood cells by the death receptor Fas (CD95) has been shown and might represent another mode of action of IVIG of relevance in AD [129] . Comparable to GCS and CNI, IVIG are able to reduce T cell mediated keratinocyte apoptosis [56] . One major point of relevance for AD might be the enhanced steroid sensitivity induced by IVIG and achievable GCS sparing effects [131] . However, the relatively high price and the consideration of the cost-benefit ratio as well as the relatively low experience and studies in a broad number of patients with AD preclude IVIG from their use as standard therapy in the clinical practice for a high number of AD patients so far.

Biologicals

Biologic agents are proteins which can be extracted from animal tissue or synthesized in large quantities with the help of recombinant DNA techniques. Several drugs have been designed to treat inflammatory skin disorders by targeting specific cells, cytokines, or interactions between ligands and receptors [132] . Efalizumab is a humanized monoclonal antibody to the alpha-1 integrin CD11a, which is a component of LFA1 on the surface of T cells. The interaction between LFA1 on T cells and ICAM-1 on APC represents an important costimulatory signal which induces T cell activation. ICAM-1 on endothelial cells also interacts with LFA-1 on circulating T cells. This interaction is necessary for the migration of T cells into inflamed skin. The effect of efalizumab bases not only on the inhibition of the interaction of APC and T cells, but also on the inhibition of the migration of T cells to the skin and the binding of T cells to endothelial cells [133] . Due to its potential to inhibit T cell activation, Efalizumab is being now used in open-label pilot studies for the treatment of AD with relatively good clinical results in comparison to other biologicals in a majority of treated patients [134, 135]. However, double blind placebo controlled studies including a high number of AD patients are required to decide Immunosuppressants 303 whether Efalizumab or other biologics might represent alternative treatments for specific subgroups of AD patients.

Conclusion

Research of the last years has profoundly improved our knowledge regarding the mode of action of immunosuppressants in AD. Together with the increasing knowledge gained on the subject of the complex pathophysiology of AD, novel therapeutic strategies taking different AD subtypes into consideration need to be developed to supplement our current repertoire of immunmodulators and optimize the treatment of AD.

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Phillip Lieberman

The Prevention of Anaphylactic Episodes

General Preventive Measures

Obviously, anaphylaxis is an unavoidable aspect of the practice of medicine. With the growing use of polypharmacy and the present epidemic of allergic disease, its incidence is increasing [1] . Although it is not possible to prevent all such episodes, some general preventive measures can reduce the frequency and severity of these events (Table 1 ). Prior to the administration of any drug, a thorough drug allergy history should be obtained. Interpretation of this history requires knowledge of the biochemical and immunologic cross-reactivity amongst drugs. When a history of an allergic reaction to a drug is present, a substitute, non-cross reactive medication should be administered when possible. Because parenteral administration of medication usually produces more severe reactions than oral administration, the oral route should be used whenever possible. When parenteral administration is required, the patient should be observed for 20–30 min after the injection is given. Although anaphylactic reactions due to drug mislabeling are rare, such instances have been recorded. In our mobile society where patients remove drugs from their original containers and repackage them, especially when traveling, such instances can occur more often. Therefore proper labeling of drugs is essential, and whenever a drug is suspected as the cause of an episode, the contents of the container from which it was taken should be checked against the label.

P. Lieberman () Division of Allergy and Immunology, Departments of Medicine and Pediatrics , University of Tennessee, Memphis , 7205 Wolf River Boulevard, Suite 200 , Germantown , TN 38138 USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 311 DOI 10.1007/978-4-431-99362-9_18, © Springer 2010 312 P. Lieberman

Table 1 Measures to reduce the incidence of anaphylaxis and anaphylactic deaths General Obtain thorough history for drug allergy. Avoid drugs that have immunologic or biochemical cross-reactivity with any agents to which the patient is sensitive. Administer drugs orally rather than parenterally when possible. Check all drugs for proper labeling. Keep patients in the office 30 min after injections. For Patients at Risk Make sure all medical charts are clearly labeled for drug allergies. Have patient wear and carry warning identification such as jewelry and/or wallet cards. Teach self-injection of epinephrine and caution patients to keep an epinephrine kit with them. Discontinue beta-adrenergic blocking agents, angiotensin-converting enzyme (ACE) inhibitors, ACE blockers, monoamine oxidase inhibitors, and certain tricyclic antidepressants when possible. Use preventive techniques when patients are required to undergo a procedure or take an agent that places them at risk. Such techniques include pretreatment, provocative challenge, and desensitization.

Preventive Measures for Patients at Risk

Medical charts should be clearly labeled, denoting a patient’s drug allergies. All patients at risk should carry identifying information such as a wallet card and/or identifying jewelry. Jewelry can be obtained from Medic Alert (2323 Colorado Road, Turlock, California 95382, www.medicalert.org). All patients at risk for anaphylaxis should be supplied with automatic epinephrine injector kits. It should be emphasized that they must keep the kit with them at all times. It is well known that patients fail to keep such kits with them, and even when they have them available, are reluctant to use them [2] . It has also been documented that diligent efforts to educate patients on the importance of keeping epinephrine available can improve adherence rates regarding maintaining the availability of epinephrine and its appropriate utilization [3] . Patients at risk for anaphylaxis should avoid, if possible, taking certain classes of medication (Table 2 ). These include beta-blockers [4] , ACE inhibitors [5] , monoamine oxidase inhibitors, and tricyclic anti-depressants [6, 7]. In addition, there is at least a theoretical admonition against such patients taking angiotensin blocking agents. Beta-blockers are contraindicated because they prevent and/or alter the effects of epinephrine administered for therapy or produced by the body during the natural compensatory response to hypotension. ACE inhibitors prevent the degradation of kinins, which play a role in the production of anaphylactic events and also interfere with the natural compensatory response to hypotension by preventing the production of angiotensin II [5] . Angiotensin blocking agents also interfere with the action of angiotensin II, thus blocking a natural response to hypotension. Monoamine Treatment of Anaphylaxis 313

Table 2 Drugs which should be avoided in patients who are at risk of anaphylactic events (e.g., insect sting hypersensitive patients, patients with recurrent idiopathic anaphylaxis, etc.) Drug Potential adverse effect Beta-adrenergic Diminishes the effect of exogenously administered blockers epinephrine and endogenously manufactured epinephrine that occurs as a response to hypotension. ACE inhibitors Blocks the destruction of kinins which can play a role in the production of anaphylactic events as well as prevents the production of angiotensin II which occurs as a compensatory response to hypotension. Angiotensin receptor May block the effect of angiotensin II, synthesized as a response blockers to hypotension, at its receptor site. Monoamine oxidase Prevent the degradation of epinephrine, thus complicating the inhibitors choice of dose. Tricyclic antidepressants Prevent the reuptake of catecholamines at neuronal endings, thus again complicating the choice of dose of epinephrine

oxidase inhibitors and tricyclics complicate the dosing of epinephrine. The former does so by preventing its degradation, and the latter by preventing re-uptake of catecholamines at neuronal endings, thus exaggerating the effect of exogenously administered sympathomimetic amines [6, 7] . Of course in some instances it is necessary to administer a drug or a diagnostic agent to a patient who has had a previous reaction to administration of this drug or agent. In these instances published protocols employing desensitization, provocative challenges, or pretreatment regimens should be employed.

Management of the Acute Event

Treatment Administered in a Medical Facility

It is believed that prompt initiation of therapy prevents fatalities. Therefore rapid recognition with immediate onset of treatment is essential. The steps of therapy may be divided into those which should be “reflexive” in nature and therefore performed immediately, and those which may be initiated after further evaluation (Table 3 ). It is important to stress that the steps noted in Table 3 are subject to the discretion of the physician managing the care of the patient. Variations in their sequence and performance would depend on clinical judgment. To initiate therapy, the medications and apparatus for treatment must be available. There have been a number of position statements listing drugs and equipment which should be on hand for the management of anaphylaxis [5] . Table 4 is a sum- mation of these suggestions with revisions. Table 5 is a list of drugs and other agents used in the treatment of anaphylaxis with suggested dosages. 314 P. Lieberman

Table 3 Treatment of anaphylaxis Requires immediate action Place lying flat on back with legs elevated Assess airway and secure if needed Ventilate if required Initiate High flow oxygen Rapid assessment of level of consciousness Vital signs Administer epinephrine 0.01 mg/kg to a maximum of 0.5 mg in anterolateral thigh Obtain intravenous access with large bore needle if hypotension present Treatment that can be instituted later after further evaluation For continued hypotension consider: Intravenous fluids Vasopressors other than epinephrine If wheezing present: Administer albuterol ventilation If patient is unresponsive and receiving beta-adrenergic blocker, consider: Atropine for bradycardia Glucagon for hypotension Ipratropium inhalation for wheezing not responsive to albuterol For cutaneous symptoms as well as possibly hypotension, consider: H1/H2 blockers Corticosteroids

Table 4 Equipment and medication needed for treatment of anaphylaxis in the ofﬁ ce Primary Tourniquet 1- and 5-ml disposable syringes Oxygen tank and mask/nasal prongs Epinephrine solution (aqueous) 1:1,000 (1-ml ampules and multidose vials) Epinephrine solution (aqueous) 1:10,000 (commercially available preloaded in a syringe) Diphenhydramine injectable Ranitidine or cimetidine injectable Injectable corticosteroids Ambu-bag, oral airway, laryngoscope, endotracheal tube, No. 12 needle Intravenous setup with large bore catheter IV fluids: 2,000 ml crystalloid, 1,000 ml hydroxyethyl starch Aerosol beta 2 bronchodilator and compressor nebulizer Glucagon Normal saline 10-ml vial for epinephrine dilution Electrocardiogram Supporting Suction apparatus Dopamine Sodium bicarbonate (continued) Treatment of Anaphylaxis 315

Table 4 (continued) Primary Aminophylline Atropine IV “setup” with needles, tape, and tubing Non-latex gloves Optional Defibrillator Calcium gluconate Lidocaine Neuroleptics for seizures

Table 5 Drugs and other agents used in the treatment of anaphylaxis Drug Dose and route of administration Comment Epinephrine IMa : 1:1,000 0.3–0.5 ml IM Initial drug of choice for all lateral thigh (adult); 1:1,000 episodes; should be given 0.01 mg/kg or 0.1–0.3 ml IM immediately; may repeat q lateral thigh (child) 5–15 min IV b : 0.1–1.00 ml of 1:1,000 If no response to IM aqueous epinephrine diluted in administration and patient 10 ml normal saline IV (see text in shock with cardiovascular for details) collapse consider intravenous administration Alternatively, an epinephrine infusion can be prepared by adding 1 mg (1 ml) of 1:1,000 dilution of epinephrine to 250 ml of D5W to yield a concentration of 4.0 mcg/ml. This solution is infused at a rate of 1–4 mcg/min (15–60 drops per minute with a microdrop apparatus) [60 drops per minute = 1 ml = 60 ml/h] ), increasing to a maximum of 10 mcg/min. Antihistamines Diphenhydramine 25–50 mg IM or IV (adult); 12.5– Route of administration depends 25 mg PO, IM, or IV (child) on severity of episode Ranitidine 1 mg/kg IV ranitidine Cimetidine 4 mg/kg IV cimetidine Cimetidine should be administered slowly because rapid administration has been associated with hypotension; doses shown are for adults; dose in children less well established (continued) 316 P. Lieberman

Table 5 (continued) Drug Dose and route of administration Comment Corticosteroids Hydrocortisone 100 mg−1 g IV or IM (adult), Exact dose not established; other 10–100 mg IV (child) preparations such as methylprednisolone can be used as well; for milder episodes, prednisone 30–60 mg may be given (see text) Drugs for resistant bronchospasm Aerosolized Dose as for asthma Useful for bronchospasm not beta- agonist responding to epinephrine (albuterol, levalbuterol) Aminophylline Dose as for asthma Rarely indicated for recalcitrant asthma bronchospasm; beta- agonist is drug of choice Volume expanders Rate of administration titrated Crystalloids 1,000–2,000 ml rapidly in adults; against blood pressure response (normal saline 30 ml/kg in first hour in for IV volume expander; or Ringer’s children. after initial infusion, further lactate) administration requires tertiary Colloids 500 ml rapidly followed by slow care monitoring; in patients (hydroxyethyl infusion in adults who are beta-blocked larger starch) amounts may be needed Vasopressors Dopamine probably the drug of Dopamine 400 mg in 500 ml dextrose 5% choice, but other agents have in water as IV infusion; been successfully employed 2–20 mcg/kg/min (see text). The rate of infusion Norepinephrine 0.5–20 mcg/min should be titered against the Phenylephrine 20–200 mcg/min blood pressure response; Vasopressin 0.04 units/min or 2.4 units/h continued infusion requires intensive care monitoring Drugs employed in patients who are beta-blocked Atropine sulfate 0.3–0.5 mg IV; may repeat every Glucagon is probably the drug of 10 min to a maximum of 2 mg choice with atropine useful only in adults for treatment of bradycardia. Glucagon Initial dose of 1–5 mg IV Ipratropium might be considered followed by infusion of as an alternative or added to 5–15 mcg/min titrated against inhaled beta-adrenergics for blood pressure wheezing. Ipratropium Inhaled a IM = intramuscular b IV = intravenous

Immediate Measures

As noted, the initial step in the management of anaphylaxis is a rapid assessment of the patient’s status with emphasis on evaluation of the airway and state of consciousness. If the airway is compromised it should be secured immediately and ventilation should be initiated if necessary. The patient should be placed in the Treatment of Anaphylaxis 317 supine position with legs elevated, and vital signs should be obtained. Variations in the Trendelenburg position may be necessary if the patient is wheezing severely and dyspneic. When the antigen has been injected in the arm, a tourniquet proximal to the injection site should be considered. However, there is no proven efficacy of this procedure. If such a tourniquet is utilized, care should be taken to release it every five minutes (for a minimum of three minutes) during therapy. It should be left in place no longer than 30 min. Oxygen should be started at a high flow rate. In children, an estimate of the patient’s weight should be made to help guide dosage decisions. Epinephrine is the drug of choice and should be administered simultaneously while the patient is being assessed. The route of administration depends on the severity of the reaction. In most instances the intramuscular route can be utilized. The site of administration should be the anterolateral thigh (vastus lateralis muscle). The adult dose is 0.3–0.5 ml (0.3–0.5 mg) of a 1:1,000 solution. In children, the dose is 0.01 mg/kg. These dosages can be repeated two to three times as needed at 5 to 15-min intervals.

Measures Initiated After Further Evaluation

When severe hypotension is present, especially if there is cardiac collapse, and no response to intramuscular administration, epinephrine should be administered intravenously. Numerous intravenous regimens have been suggested [5] . Regardless of the dose and regimen employed, care should be taken and the patient should be monitored for arrhythmias. The dose administered depends on the severity of the episode and should be titrated against the response. There is evidence in animal models [8] and humans [9, 10] that a continuous infusion is superior to bolus administration. However, simple bolus administration has been utilized successfully. The intravenous bolus preparation can be prepared by diluting 0.1 ml (0.1 mg) of a 1:1,000 aqueous epinephrine solution in 10 ml of normal saline. This 10 ml dose can be infused over 5–10 min. There are a number of suggestions for constant intravenous infusion. Epinephrine can be prepared for constant infusion by adding 1 ml (1 mg) of a 1:1,000 dilution of epinephrine to 250 ml of D5W to yield a concentration of 4.0 mcg/ml. This solution is infused at a rate of 1–4 mcg/min (15–60 drops per minute with a microdrop apparatus [60 drops per minute equals 1 ml equals 60 ml/h]), increasing to a maximum of 10.0 mcg/min for adults and adolescents. For children, a dosage of 0.01 mg/kg may be infused (up to a maximum dose of 0.3 mg) [11] . An alternative method of infusion, which can be used when an infusion pump is available, has been recommended by Brown, et al., who conducted a prospective study of the treatment of human anaphylaxis induced by insect sting [12] . This is the only dose response study, known to the author, that compares the dose administered with the improvement in blood pressure . Brown, et al. recommended 1 mg (1 cc) of epinephrine 1:1,000 diluted in 100 ml administered intravenously by infusion pump. 318 P. Lieberman

The initial rate was 30–100 ml/h. Subsequent administration was titrated up or down depending upon the patient’s response and the side effects. The infusion was stopped 30 min after resolution of symptoms and signs. It should be emphasized that if intravenous epinephrine is given, cardiovascular monitoring is indicated. In the absence of the ability to gain intravenous access, sublingual injection (rather than subcutaneous or intramuscular) has been suggested as an alternative route because of the rich vascularity of this area [5] . The same dose utilized for intramuscular injection could be given in the posterior third of the sublingual area. A number of reports have presented evidence that other vasopressors may be helpful if there is a lack of response to epinephrine. These agents include dopamine [5] and vasopressin [13] . The use of vasopressin was given further credence by a study comparing vasopressin and epinephrine for cardiopulmonary resuscitation. In this study, the effects of vasopressin were similar to those of epinephrine in the management of ventricular fibrillation and pulseless electrical activity, but superior in patients with asystole. Vasopressin, in this setting, followed by epinephrine, was postulated to be more effective than epinephrine alone in the treatment of refractory cardiac arrest [14] . However, another trial failed to find vasopressin improved survival in cardiac arrest [15] . Unfortunately, hypotension does not always respond to vasopressor treatment, regardless of the agent used. Hypotension can persist even in the face of maximal vasoconstriction. In this instance, it is believed to be caused by a shift of fluid from the intravascular to the extravascular space. In such cases, the mainstay of treatment should be the restoration of intravascular volume. This is best accomplished by the rapid administration of large volumes of fluid. It has been debated whether colloids or crystalloids should be used, and there are arguments to support both forms of therapy [5] . However, the most important component of fluid therapy is not the composition of the fluid itself, but rather the rate of administration. Large volumes of crystalloid are often required. For example, 1,000–2,000 ml of lactated ringers or normal saline should be given rapidly. In an adult, depending on the blood pressure, a rate of 5–10 ml/kg in the first five minutes has been suggested. Children can receive up to 30 ml/kg of crystalloid solution in the first hour. The alternative to crystalloid therapy is the colloid, hydroxyethyl starch. Adults can receive rapid infusion of 500 ml followed by a slow infusion thereafter. In patients taking beta- blocking agents, the necessary volume of fluid and rate of infusion may be much greater. For example, 5–7 L may be needed before stabilization occurs. Of course, patients requiring a large volume of fluid should be monitored closely and should be in a tertiary medical facility. An interesting observation regarding the potential benefit of methylene blue for refractory hypotension occurring during an anaphylactic event was recently reported [16] . In a case of refractory hypotension occurring during an anaphylactic event due to the administration of protamine and not responding to standard therapy, the intravenous administration of 100 mg of methylene blue reversed hypotension and restored normal pulmonary artery pressure within minutes. In addition to the significance of this observation regarding the potential of methylene blue as a treatment for refractory hypotension, it also supports the contention that nitric Treatment of Anaphylaxis 319 oxide is an important mediator of hypotension in some patients with anaphylaxis because methylene blue acts by inhibiting the production of nitric oxide. Patients receiving beta-adrenergic blocking agents may present other problems. They are often resistant to standard therapeutic regimens. They can experience refractory hypotension, bradycardia, and relapsing manifestations. In such patients, both inotropic and chronotropic functions of the heart are suppressed, resulting in bradycardia with marked hypotension. They can be resistant to epinephrine and other vasodepressors. Atropine and glucagon have been recommended for therapy in patients with beta-adrenergic blockade. Atropine is useful only for bradycardia; it exerts no beneficial effect on the inotropic function of the heart. Atropine sulfate can be administered intramuscularly or subcutaneously in a dose of 0.3–0.5 mg every 10 min to a maximum of 2 mg. Glucagon, a polypeptide hormone produced by the alpha cells of the pancreas, has both inotropic and chronotropic effects on the heart. The inotropic effect does not depend upon catecholamines or their receptors and is therefore unaltered by beta-adrenergic blockade. For this reason, glucagon may be the drug of choice in patients who are beta-blocked. The dose of glucagon is 1–5 mg intravenously as a bolus, followed by an infusion of 5–15 mcg/ min titrated against the clinical response. The administration does not produce myocardial irritability. Its cardiotonic effects can be seen within the first 5 min, and become maximal between 5 and 15 min after a single 5 mg bolus. The most common side effects of glucagon administration are nausea and vomiting. Resistant bronchospasm can be treated with inhaled ipratropium bromide and/or aminophylline. Antihistamine therapy can be useful as adjunctive treatment given with epinephrine [17] . Although antihistamine therapy is not life-saving, it can be effective in the treatment of cutaneous manifestations as well as hypotension. A combination of H1 and H2 antagonists may be superior to an H1 antagonist alone [17] . Both intramuscular and intravenous routes can be used depending on the severity of the event. The role of corticosteroids in the management of anaphylaxis has not been clearly elucidated. Based on an extrapolation of their effect on other allergic diseases, however, there is a rationale for their use. It has been suggested that they may be effective in preventing recurrences, especially the biphasic response [18] . Nonetheless other studies have not substantiated the beneficial effect of corticosteroids in this regard [19] . There is no established dose or drug of choice. Suggested intravenous doses for severe episodes are seen in Table 5 . In addition, it is probably wise to give oral prednisone (30–60 mg) to patients who have experienced milder episodes of anaphylaxis and have been discharged from therapy.

Treatment in the Field by the Patient

Treatment in the field is of course initiated by the patient. It consists of the immediate administration of epinephrine by automatic epinephrine injector. Intuitively it would seem that such therapy would be administered routinely and appropriately. 320 P. Lieberman

However, such is not the case. Over the past several years a number of investigations have uncovered problems regarding the prescription of epinephrine by physicians and the use of this drug by patients. In many instances physicians fail to prescribe automatic epinephrine injectors for individuals who have experienced a previous event [5] , and when prescriptions are given, incorrect instructions regarding the use of the injector are not uncommon [5] . Patients themselves, as noted, fail to keep epinephrine with them and even when they do have it often do not administer it appropriately [20] . These problems mandate attention to the education of patients at risk regarding the use of epinephrine and emphasis regarding the necessity to keep injectors with them at all times. The route of choice of administration of epinephrine in the outpatient setting is the anterolateral thigh (vastus lateralis muscle). Such administration produces a more rapid rise to peak plasma levels than administration via the deltoid or by subcutaneous injection in the arm [21] . Another problem with field administration of epinephrine is that patients fail to refill their prescriptions and therefore their injectors become out of date. Simons and associates have shown that out of date EpiPens still function in spite of the fact that their plastic sheaths may show sign of wear. In most instances they found that the epinephrine, even though out of date, was not discolored and no precipitants were visible. Nonetheless there was some decrease in bioavailability, which depended on several factors, including the length of time the epinephrine had been out of date. However, because such injectors still show potency it is suggested that patients administer the drug in spite of the fact that the injector may not be in date [22] . Episodes that occur in the field may require more than one injection of epinephrine. This may be related to the severity of the episode or to a recurrence after an asymptomatic phase (biphasic reaction). Two injections may be required anywhere from 16% to approximately 33% of cases [23] . Thus it is wise in most instances to prescribe at least two automatic epinephrine injectors. The patient should be told that if epinephrine is required, he/she should immediately go to the nearest medical facility (preferably someone else should drive the patient) and should take the second injection if he/she has not improved after 5–10 min and has not yet reached the medical facility. In cases where hypotension has occurred during previous episodes, the patient should also lie flat with feet elevated if possible. In such instances, patients should be told to always keep a cellular telephone with them in case they are not able to travel to an emergency facility. In this instance, they should contact an emergency medical management team to transport them to such a facility.

The Observation Period After Resolution of Symptoms

Although there are no controlled trials establishing the ideal observation period after successful treatment of an event, recognition that biphasic reactions can occur has resulted in recommendations for more prolonged observation in certain cases [19, 24] . Treatment of Anaphylaxis 321

Table 6 Indications for prolonged observation (8–24 h after resolution of symptoms) in episodes of anaphylaxis • Moderate to severe reaction • Episode in an asthmatic with wheezing • Ingested antigen (possibility of continued absorption) • Previous history of a biphasic response

Resuscitation guidelines [24] have been established to guide physicians regarding the observation period. These are noted in Table 6 .

Fatalities

First of all, it is important to realize that the level of severity of a previous reaction is not necessarily predictive of the severity of a future event . That is, repeat reactions can be more severe than initial reactions, and fatalities have occurred in patients who have experienced an initial mild event [25] . Death can be due to several causes. The majority are either respiratory or cardiovascular in nature. However, death can be due to disseminated intravascular coagulation [25] . It is important to note that death can occur in the field setting in spite of appropriate therapy with epinephrine. Pumphrey and Gowland [26] studied 48 deaths between 1999 and 2006. Nine of the patients who died used epinephrine correctly. One of these used three injections. Two of the patients who did use epinephrine correctly had outdated injectors. As noted previously, death could occur in patients with previous mild reactions. Over one-half of the deaths in this series occurred in patients where the previous reaction had been classified as mild. In a previous study by Pumphrey [27] , he noted that four deaths were associated with the patient assuming an upright or sitting posture after having been recumbent. He attributed these deaths to the “empty heart syndrome” with the heart contracting in the absence of blood in the ventricles because of decreased venous return occurring when the patient sat up or stood up. Another factor in Pumphrey’s series was the food related to anaphylactic events. He found that tree nuts and peanuts were the most common foods involved. Asthma was also a risk factor. In a series evaluated by Rotskoff, et al. [28] , it was concluded that elderly patients with comorbid diseases are at risk, and that a rapid onset of symptoms after exposure might also be a risk factor. As in Pumphrey’s series, of note is the fact that there was a death in spite of the fact that epinephrine was administered appropriately and in time. In an ongoing series of fatalities, Bock, et al. [29] reported a group of 32 individuals who died with food-induced anaphylaxis. They also found nuts and peanuts to be the most common foods associated with anaphylactic deaths. However, deaths also occurred because of other foods including shellfish in their series. All of the subjects who had data evaluated had asthma. Four of their 32 reported cases had epinephrine administered in a timely and appropriate manner. From a review of these data, several risk factors for death emerge. These are summarized in Table 7 . 322 P. Lieberman

Table 7 Risk factors for fatal reactions • Asthma • Elderly with comorbid conditions • Teenagers (perhaps because they have a decreased adherence rate in regard to carrying automatic epinephrine injectors with them) • Food allergy to tree nuts and peanuts • Rapid onset of symptoms after exposure to responsible agent • Injected antigen • Assuming the sitting or standing posture prior to complete cardiovascular stabilization

References

1. Warner JO (1997) Anaphylaxis; the latest allergy epidemic. Pediatr Allergy Immunol 18:1–2 2. Lieberman P (2003) Use of epinephrine in treatment of anaphylaxis. Curr Opin Allergy Clin Immunol 3:313–318 3. Webb L, Lieberman P (2006) Anaphylaxis: a review of 601 cases. Ann Allergy Immunol 97:39–43 4. Lieberman P, Kemp SF, Oppenheimer J, Lang DM, Bernstein IL, Nicklas RA (2005) Letter reply. J Allergy Clin Immunol 116:933–936 5. Lieberman P (2003) Anaphylaxis and anaphylactoid reactions. In: Allergy: Principles and Practice, edition 6, Adkinson F, Yunginger J, Busse W, Bochner B, Holgate S, Simons FER (eds) (Mosby, an affiliate of Elsevier, US) pp 1497–1522 6. Physicians Desk Reference (PDR) (2005) Thomson, page 1186 7. Physicians Desk Reference (PDR) (2005) Thomson, page 732 8. Mink SN, Simons FER, Simons KJ, et al. (2004) Constant infusion of epinephrine, but not bolus treatment, improves haemodynamic recovery in anaphylactic shock in dogs. Clin Exp Allergy 34(11):1776-1783 9. Gei A, Pachecho L, Van Hook J (2003) The use of continuous infusion of epinephrine for anaphylactic shock during labor. Obstet Gynecol 102:1332–1335 10. Brown SGA (2005) Cardiovascular aspects of anaphylaxis: implications for treatment and diagnosis. Curr Opin Allergy Clin Immunol 5:369–364 11. Lieberman P, Kemp S, Oppenheimer J, Lang D, Bernstein I, Nicklas R (2005) The diagnosis and management of anaphylaxis: an updated practice parameter. J Allergy Clin Immunol 115:S483–S523 (supplement) 12. Brown SGA, Blackman KE, Stenlake V, Heddle RJ (2004) Insect sting anaphylaxis; prospective evaluation of treatment with intravenous adrenaline and volume resuscitation. Emerg Med J 21:149–154 13. Schummer W, Schummer C, Wippermann J (2004) Anaphylactic shock: is vasopressin the drug of choice? Anaest 101:1025–1027 14. Wenzel V, Krismer AC, Arantz HR(2004) A comparison of vasopressin and epinephrine for out of hospital cardiopulmonary resuscitation. N Engl J Med 350:105–113 15. Stiell IG, Herbert PC, Wells GA (2001) Vasopressin versus epinephrine for in hospital cardiac arrest: a randomized controlled trial. Lancet 358:105–109 16. Sheth SS, Del Duca D, Ergina P, Clarke AE (2007) Methylene blue as a treatment for refractory anaphylaxis. J Allergy Clin Immunol 17. Lin RY, Curry A, Pesola G (2000) Improved outcomes in patients with acute allergic syndromes who are treated with combined H1 and H2 antagonists. Ann Emerg Med 36:462–468 18. Ellis AK, Day JH (2007) Incidence and characteristics of biphasic anaphylaxis: a perspective evaluation of 103 patients. Ann Allergy Asthma Immunol 98:64–69 Treatment of Anaphylaxis 323

19. Lieberman P (2005) Biphasic anaphylactic reactions. Ann Allergy Asthma Immunol 95:217–226 20. Sicherer S, Simons EFR (2005) Quandaries in prescribing emergency action plans and self- injectable epinephrine for first-aid management of anaphylaxis in the community. J Allergy Clin Immunol 115:575–583 21. Simons FE, Gu X, Simons KJ (2001) Epinephrine absorption in adults: intramuscular versus subcutaneous injection. J Allergy Clin Immunol 108:871–873 22. Simons FER, Gu X, Simons KJ (2000) Outdated EpiPen and EpiPen Junior autoinjectors: past their prime? J Allergy Clin Immunol 105:1025–1030 23. Kelso JM (2006) A second dose of epinephrine for anaphylaxis: how often needed and how to carry? J Allergy Clin Immunol 117(2):464–465 24. Soar J, Deakin C, Nolen J (2005) European Resuscitation Council guidelines for resuscitation 2005, Section 7. Cardiac arrest in special circumstances. Resuscitation 6751:S135–S170 (supplement). 25. Pumphrey RSH (2004) Fatal anaphylaxis in the UK, 1992-2001. In: Anaphylaxis (publication of The Novartis Foundation, John Wiley & Sons Ltd, summary of Novartis Foundation Symposium 257, 2004. John Wiley & Sons Ltd, the Atrium, Southern Gate, Chichester, UK), pp 116–132 26. Pumphrey RSH, Gowland M (2007) Further fatal allergic reactions to food in the United Kingdom, 1999-2006. J Allergy Clin Immunol 19:1018 27. Pumphrey RSH (2003) Fatal posture in anaphylactic shock. J Allergy Clin Immunol 112:451– 452 (Letter to Editor) 28. Rotskoff BD, Greenberger PA, Lifschultz B (2003) Fatal anaphylaxis: postmortem findings and associated comorbid disease. J Allergy Clin Immunol 111:S101 (abstract) 29. Bock SA, Munoz-Furlong A, Sampson HH (2007) Further fatalities caused by anaphylactic reactions to food, 2001–2006. J Allergy Clin Immunol 119:1016–1018 Anaphylaxis: Are Regulatory T Cells the Target of Venom Immunotherapy?

Marek Jutel , Mübeccel Akdis , Kurt Blaser , and Cezmi A. Akdis

Abbreviations

SIT Specific immunotherapy VIT Venom immunotherapy PIT Peptide immunotherapy

TReg T regulatory Tr1 Type-1 T regulatory

Introduction

The immunological mechanism of venom immunotherapy (VIT) was unclear for a long time. VIT has been demonstrated to influence the deviated immune response in allergic individuals in a specific manner and eventually redirect the immune system towards normal immunity. A rise in allergen-blocking IgG antibodies, particularly of the IgG4 class, which supposedly block allergen and IgE-facilitated antigen presentation [1] , the generation of IgE-modulating CD8+ T cells [2] and a reduction in the numbers of mast cells and eosinophils, including the release of mediators [3, 4] were shown to be associated with successful allergen-specific immunotherapy (SIT). Later on, SIT was found to be associated with a decrease in IL-4 and IL-5 production by CD4 + T helper (Th) 2 cells [5, 6] , and in some experimental conditions with a

M. Akdis, K. Blaser, and C.A. Akdis Swiss Institute of Allergy and Asthma Research (SIAF) , Obere Street 22 , CH-7270 , Davos , Switzerland M. Jutel () Swiss Institute of Allergy and Asthma Research (SIAF), Obere Street 22, CH-7270, Davos, Switzerland; Department of Clinical Immunology , Wroclaw Medical University , Traugutta 57 , PL-50-419 , Wroclaw , Poland e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 325 DOI 10.1007/978-4-431-99362-9_19, © Springer 2010 326 M. Jutel et al. shift towards increased IFN-g production [7– 9] . Distinct Th1 and Th2 subpopulations of T cells counter-regulate each other and play a role in distinct diseases [10] . The mechanism of repolarization of specific T cell activity from dominating Th2- type towards Th1-type, as observed during VIT had been a matter of controversy. A new light was shed when a further subtype of T cells, with immunosuppressive function and cytokine profiles distinct from either Th1 and Th2 cells, termed regulatory/ suppressor T cells (TReg ) has been described [11, 12]. The evidence for their existence in humans has been demonstrated [13, 14] . In addition to Th1 cells, TReg cells are able to inhibit the development of allergic Th2 responses and play a major role in allergen-SIT [13, 15] (Fig. 1 ). Recent studies have also demonstrated that peripheral T-cell tolerance is crucial for a healthy immune response and successful treatment of allergic disorders [13– 15] . The crucial role of TReg cells in the induction of allergen-specific peripheral tolerance during VIT has been well documented. Thus, the basis for new developments in SIT has been created.

Fig. 1 Induction of Immune deviation towards T Reg cell response leads to peripheral tolerance in allergen-specific immunotherapy and healthy immune response. T Reg cells utilize multiple suppressor factors to regulate undesired activity of effector cells. IL-10 and TGF-b suppress IgE production and induce non-inflammatory Ig isotypes IgG4 (more relevant in venom SIT) and IgA, respectively. Furthermore, these two cytokines directly suppress allergic inflammation induced by effector cells such as mast cells, basophils, and eosinophils. In addition, TReg cells inhibit Th2 cells, which can no longer provide cytokines such as IL-3, IL-4, IL-5, and IL-13. These cytokines are required for the differentiation, survival, and activity of mast cells, basophils, and eosinophils ( red line : suppression, black line : stimulation) TReg Cells and Venom Immunotherapy 327

Types of TReg Cells and Allergic Responses to Insect Venoms

Generation of allergen-specific CD4+ T helper cells is responsible for the development of allergic diseases. Under the influence of interleukin (IL)-4 (IL-4), naive T cells activated by APC differentiate into Th2 cells [10, 16] . Once generated, effector Th2 cells produce IL-4, IL-5, and IL-13 and mediate several regulatory and effector functions. These cytokines induce the production of allergen-specific IgE by B cells, development and recruitment of eosinophils, production of mucus, and contraction of smooth muscles [10] . The degranulation of basophils and mast cells by IgE-mediated cross-linking of receptors is the key event in type 1 hypersensitivity, which may lead to chronic allergic inflammation. Importantly, although Th2 cells are responsible for the development of allergic diseases, Th1 cells may contribute to chronicity and effector phase in allergic diseases [17– 19] . The cardinal difference between venom allergy and true atopic diseases like allergic rhinitis, asthma, and atopic dermatitis is the lack of many chronic events of allergic inflammation leading to tissue injury and remodeling [20] . Peripheral T-cell tolerance to allergens, which is characterized by functional inactivation of the cell to antigen encounter, can overcome both acute and chronic events in allergic reactions. It is well established that TReg cells suppress immune responses via cell- to-cell interactions and/or the production of suppressor cytokines [12, 13, 21] . Peripheral T-cell tolerance is characterized mainly by generation of allergen- specific TReg cells, suppressed proliferative and cytokine responses against the major allergen [14, 22, 23]. Type-1 T regulatory (Tr1) cells are defined by their ability to produce high levels of IL-10 and TGF-b [12, 24] and suppress naive and memory T helper type 1 or 2 responses. There is now clear evidence that IL-10- and/or TGF-b - producing Tr1 cells are generated in vivo in humans during the early course of allergen-SIT, suggesting that high and increasing doses of allergens induce Tr1 cells in humans [13, 15, 25]. Regulatory/suppressor Th3 cells, which produce high levels of TGF-b , and variable amounts of IL-4 and IL-10 upon activation with appropriate antigen or anti-CD3 antibody are indicated in mucosal tolerance [26] . + + + CD4 CD25 TReg cells constitute 5–10% of peripheral CD4 T cells and express the IL-2 receptor a chain (CD25) [27] . They can prevent the development of autoimmunity and transplantation rejection indicating that the normal immune system contains a population of professional TReg cells involved in active mechanism of immune + suppression [21, 28] . There are other TReg cells including CD8 TReg cells, which may − − + play a role in oral tolerance [29] , double negative (CD4 CD8 ) TCRa b T Reg cells that mediate tolerance in several experimental autoimmune diseases [30] and g d TReg cells which can play a role in the inhibition of immune responses to tumors [31] . In addition, a regulatory role for IL-10-secreting B cells and dendritic cells has been recently suggested [32] . Some other cells may also show possible regulatory function. It has been demonstrated that natural killer cells, epithelial cells, macrophages, and glial cells express suppressor cytokines such as IL-10 and TGF-b . Although their role has not been coined as professional regulatory cells, these cells may efficiently contribute to the generation and maintenance of a regulatory/ suppressor-type immune response [33] . 328 M. Jutel et al.

Role of TReg Cells During Natural Tolerance and Venom SIT

Changes in immune response to bee venom (BV) has been intensively investigated during VIT, PLA-peptide immunotherapy (PLA-PIT) [6, 34– 36] . Successfully treated patients develop specific T cell unresponsiveness against the entire PLA allergen as well as the T cell epitope-containing peptides. The decreased proliferative responses did not result from deletion as they were restored by addition of IL-2 and IL-15. The same anergic state of specific T cells has been observed in protected hyperimmune individuals such as bee keepers [13] . Since, stimulation of anergized cells in the presence of IL-4 induce recovery of a Th2 cytokine pattern typical for an allergy, the microenvironmental conditions regulate T cell phenotypes in VIT. Thus, successful SIT may be more difficult to achieve in an established polyspecific allergy and atopy. The unresponsive state of specific cells results from increased IL-10 secretion [13] . The cellular origin of IL-10 was demonstrated as the antigen- specific T cell population and activated CD4+ CD25+ T cells, Tr1 lymphocytes as well as monocytes, and B cells [13] .

The allergic status of the patients might affect the efficacy of TReg -mediated T cell unresponsiveness. Mamessier and colleagues have shown that in less severe subjects (grade I and II – according to Mueller scale) increase in frequency of CD4 + CD25+ T cells appeared early but was delayed in more severe subjects (grade III–IV). Also IL-10-producing T cells increased gradually in both groups but were in a lower frequency in more severe patients. Accordingly, in the study of

Bellinghausen et al. it has been shown that function of T Reg in wasp venom allergic subjects is dependent on allergen concentration with different thresholds for individual patients and much lower threshold for non-allergic individuals [34] . It has been shown that tolerance to aeroallergens is associated with activation of

TGF- b -secreting TReg [15] . This, however, has not been shown during VIT. Discrepancies in the mechanisms of control of immune response to venoms and to aeroallergens might be different routes of natural allergen exposure, with the involvement of mucosal immune system in the latter case. IL-10 also plays an inhibitory role on IgE and effector cells of allergic inflammation (Fig. 1 ). However, VIT does not abolish the capacity by B cells to produce specific IgE and IgG4 antibodies; the ratio of specific IgE to IgG4 decreases up to 100-fold. VIT-induced IL-10 counter-regulates antigen-specific IgE and IgG4 antibody syntheses. It is a potent suppressor of both total and allergen-specific IgE, while simultaneously IgG4 formation is increased [13] . Thus, IL-10 regulates specific isotype formation and skews the specific response from an IgE to an IgG4 dominated phenotype. Similar findings suggesting induction of IgG4 by T Reg cells have been observed in other allergies [23, 37] . Most patients are protected against bee stings already at an early stage of VIT which is not paralleled by changes in antibody formation. It has been shown that lower amounts of mediators of anaphylaxis (e.g., histamine or sulphidoleukot- rienes) are released during VIT [7] . These effects may be attributed to direct suppressive effect of IL-10 on effector cells (mast cells, basophils). Thus, the role of TReg Cells and Venom Immunotherapy 329

TReg cells is not limited to suppression of T H2 cells. Peripheral tolerance uses multiple mechanisms to suppress allergic inflammation. Apparently, TReg cells contribute to the control of allergen-specific immune responses by suppression of antigen- presenting cells that support the generation of effector T H 2 and TH 1 cells; suppression of T H 2 and T H 1 cells; suppression of allergen-specific IgE and induction of

IgG 4 and/or IgA; suppression of mast cells, basophils, and eosinophils; and interaction with resident tissue cells [38] . Peptide immunotherapy (PIT) is another attractive approach for investigation of peripheral T-cell tolerance in humans. In the clinical study using PIT in BV allergy with a mixture of short peptides that directly represented the T cell epitopes (17,

12, and 11 amino acids) of the BV major allergen, phospholipase A 2 were administered [39] . The study showed modulation of the immune response against the whole allergen inducing specific T cell tolerance and a decrease in the specific

IgE:IgG4 ratio [39] . Several ongoing studies suggest the role of TReg cells and their cytokines in PIT [40, 41] . One recent study has shown that VIT is associated with a progressive expansion of circulating regulatory T cells, supporting a role for these cells in tolerance induction. A significant progressive increase in both the proportion and the absolute numbers of regulatory T cells defined as CD25bright and/or Foxp3+ CD4+ T cells was demonstrated [42] . Moreover, after multiple bee stings, venom antigen-specific Th1 and Th2 cells show a switch towards IL-10-secreting Tr1 cells [43] . Recently, an important role of antihistamine pretreatment in enhancement of clinical efficacy of VIT has been indicated [44] . Considerable evidence has emerged to suggest that histamine participates in the immune regulation of the inflammatory response in several diseases. As a small molecular weight monoamine that binds to four different G-protein-coupled receptors, histamine has recently been demonstrated to regulate several essential events in the immune response [45– 47] . Histamine receptor (HR) 2 is coupled to adenylate cyclase and studies in different species and several human cells demonstrated that inhibition of characteristic features of the cells primarily by cAMP formation dominates in HR2- dependent effects of histamine [48] . Histamine released from mast cells and basophils by high allergen doses during SIT interferes with the peripheral tolerance induced during SIT in several pathways. Histamine enhances Th1-type responses by triggering the HR1, whereas both Th1- and Th2-type responses are negatively regulated by HR2. Human CD4 + Th1 cells predominantly express HR1 and CD4 +Th2 cells express HR2, which results in their differential regulation by histamine [45, 46] . Histamine induces the production of IL-10 by DC 18. In addition, histamine induces IL-10 production by Th2 cells [49] , and enhances the suppressive activity of TGF- b on T cells [50] . All three of these effects are mediated via HR2, which is relatively highly expressed on Th2 cells and suppresses IL-4 and IL-13 production and T cell proliferation [45, 46] (Fig. 2 ). Apparently, these recent findings suggest that HR2 may represent an essential receptor that participates in peripheral tolerance or active suppression of inflammatory/immune responses. Histamine also regulates antibody isotypes including IgE14. High amount of 330 M. Jutel et al.

HR2: induction of humoral immunity and HR2 suppression of cellular induction of IL-10 immunity. suppression of IL-12 prdominant HR2 low HR1 suppressed specific IgE Th2 or tolerance suppressed HR1-deleted mice show inducing DC Th2 cytokines increased specific IgE tolerance

Th2

H monocytes and dendritic cells modulation are suppressed of B cell via HR2 antibody histamine production

Fig. 2 Histamine released during allergen-SIT plays a suppressive role on monocytes and monocyte-derived dendritic cells via HR2 (DC). Th2 cells express predominant HR2, which acts as the negative regulator of proliferation, and suppression of IL-4 and IL-13 production, suggesting a role for HR2 on T cells for peripheral tolerance. Histamine also modulates antibody production by directly effecting B cell antibody production as a co-stimulatory receptor on B cells and enhances humoral immune responses via HR2. Allergen-specific IgE production is differentially regulated in HR1- and HR2-deficient mice. HR1-deleted mice show increased allergen-specific IgE production, whereas HR2-deleted mice show suppressed IgE production allergen-specific IgE is induced in HR1-deleted mice. In contrast, deletion of HR2 leads to a significantly less amounts of allergen-specific IgE production, probably due to direct effect on B cells and indirect effect via T cells. After multiple stings HR2 was up-regulated on specific Th2 cells. HR2 displays a dual effect by directly suppressing allergen-stimulated Th2 cells and increasing IL-10 production [43] . The long-term protection from honeybee stings by terfenadine pretreatment during rush immunotherapy with honeybee venom in a double-blind, placebo-controlled (DBPC) trial was analyzed [51] . After an average of 3 years, 41 patients were re-exposed to honeybee stings. Surprisingly, none of the 20 patients who had been given HR1-antihistamine pretreatment, but 6 of the 21 given placebo, had a systemic allergic reaction to the re-exposure by either a field sting or a sting challenge. This highly significant difference suggests that antihistamine pretreatment during the initial dose-increase phase may have enhanced the long-term efficacy of immunotherapy. In a prospective DBPC study using levocetirizine pretreatment during VIT, it has been shown that in allergen-specific T cells HR1/HR2 ratio was decreased after 21 days of treatment. However, this was prevented by levocetirizine. In addition, IL-10 levels were higher in the levocetirizine group [52] . Expression of HR1 on T lymphocytes is strongly reduced during ultra-rush immunotherapy, which may lead to a dominant expression, and function of tolerance-inducing HR2 administration of antihistamines decreases the HR1/HR2 expression ratio, which may enhance the suppressive effect of histamine on T cells. In a mice model it has TReg Cells and Venom Immunotherapy 331 been shown that Clemastine increased IgE production while decreasing IgG2a production against BV [53] . This Th2 shift of the humoral response appeared to be caused by reduced IFN- g and enhanced IL-4 secretion from allergen-specific T cells. However, the doses of antihistamines used were 103 -fold the regular doses used in humans. Further studies are required to substantiate these promising findings supporting the role of histamine signaling in the modulation of the immune response. These findings account for possible recommendation of antihistamine pretreatment in the induction phase of all VIT patients.

Conclusion

There is growing evidence supporting the role for TReg cells and/or immunosuppressive cytokine – IL-10 as a mechanism, by which venom-SIT and healthy immune response to venoms is mediated leading to both suppression of Th2 responses, ensuring a well-balanced immune response, and a switch from IgE to IgG4 antibody production (Fig. 1 ). These mechanisms can be better used by improvement of vaccines including recombinant allergens, immunogenic peptides, or immune reactive adjuvants along with elaboration of more efficacious, rapid desensitization protocols as well as antihistamine pretreatment.

Acknowledgments The authors’ laboratories are supported by the Swiss National Foundation Grants: 32-112306, 32-65436, 32-105865 and Polish National Science Committee Grant No. 1387/PO5/2000/19.

References

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Julie Wang and Hugh A. Sampson

Introduction

Food allergy affects up to 6% of children and 3–4% of adults in the United States (1) , and remains the leading cause of outpatient anaphylaxis in most surveys (2) . The prevalence of food allergy is greatest in the first 2 years of life and decreases with age. The most common food allergens causing reactions in children include milk, egg, wheat, soy, peanuts, tree nuts, fish, and shellfish. While the majority of children outgrow their allergy to milk, egg, wheat and soy, allergies to peanut, tree nuts, fish and shellfish are often life-long. Although any food can cause anaphylaxis, the most commonly implicated foods for severe allergic reactions are peanuts, tree nuts, fish, and shellfish (3) . Currently, there are no treatments that can cure or provide long-term remission from food allergy. The mainstay of management consists of avoidance and education as well as providing emergency medications for the treatment of allergic reactions. This approach is generally effective; however, avoidance can be quite difficult as several of these food allergens are ubiquitous in our diets; thus, patients and their families experience a significant negative impact on their quality of life. Therefore, there are several new strategies currently being investigated with the aim of long-term treatment and possible cure.

J. Wang and H.A. Sampson () Division of Allergy and Immunology , Department of Pediatrics, Jaffe Food Allergy Institute , Mount Sinai School of Medicine , New York , NY , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 335 DOI 10.1007/978-4-431-99362-9_20, © Springer 2010 336 J. Wang and H.A. Sampson

Allergen-Specific Immunotherapy

Allergen Immunotherapy

Subcutaneous Immunotherapy (SCIT)

Subcutaneous immunotherapy (SCIT) that has been used since 1911, is standardized and is highly efficacious for allergic rhinitis, asthma, and insect sting allergy (4) . Moreover, its efficacy persists after discontinuation of immunotherapy. Thus, SCIT is an attractive treatment option for food allergy given its efficacy and safety in other allergic disorders. The first successful use of SCIT for food allergy was reported by Freeman in 1930 in a fish-allergic patient (5) . Subsequently, no new reports emerged until the 1990s when a few groups reported their experience with SCIT for peanut allergy (6) . In a double-blind, placebo-controlled trial of rush immunotherapy in peanut allergic patients, three patients were able to complete the study. There was a 67–100% decrease in symptoms induced by double-blind, placebo-controlled food challenge (DBPCFC) and 2–5-log reduction in end-point skin prick tests to peanut extract in these patients. Only one placebo patient completed the study; there was no change in DBPCFC symptom score or skin test sensitivity for this individual. However, the study had to be terminated prematurely because of a severe adverse reaction and the rate of systemic reaction with the rush immunotherapy protocol was 13.3%. Another study of SCIT for peanut allergy was published by Nelson et al. (7) , in 1997. This group treated six peanut allergic patients with a rush protocol and patients were on maintenance immunotherapy for 1 year. For comparison, six untreated controls were used. All patients treated with immunotherapy had improved tolerance as demonstrated by DBPCFC and decreased sensitivity on skin test as compared to controls who showed no change. However, only three patients were able to reach the maintenance dose during this trial. The remaining three patients required dose reductions because of systemic side effects. This resulted in either partial or complete loss of protection. Overall, systemic reactions were common both during the initial rush protocol and with maintenance injections (39%). Bullock et al. (8) reported a case of successful desensitization for peanut allergy. They also examined immunologic parameters in their patient and found increased peanut-specific IgG4 levels. Specific IgE levels declined from pretreatment levels, but still remained significantly elevated. Overall, these studies demonstrate that SCIT can lead to increased tolerance; however, unacceptably high rates of adverse systemic reactions is a significant disadvantage to this method. In addition, there are no long-term studies investigating whether the increased tolerance persists after discontinuation of treatment, as it does for aeroallergen immunotherapy. Since the pollen-fruit syndrome (PFS) is, in many cases, due to cross-reactivity with pollens, SCIT would seem to be a logical treatment for PFS as well. A study of birch immunotherapy for apple allergy in 49 birch pollen sensitive adults with Food Allergy: Opportunities and Challenges 337 apple-induced PFS found a reduction of oral symptoms in 84% and decreased skin test sizes in 88%, but an increase in apple-specific IgE was observed in 38% (9) . None of the control subjects reported a reduction in PFS symptoms or showed a decrease in skin test reactivity at follow-up. This study was limited by the self- reported symptoms and lack of placebo controls. Another study of birch SCIT found decreased symptoms (based on DBPCFC) and skin test sizes in the treated group, but there was no placebo SCIT group for comparison (10) . Instead, the comparison was made with a group of patients who used medication for symptomatic treatment. A case report of a patient with improved oral symptoms to fennel, cucumber, and melon after 3.5 years of SCIT with grass, mugwort, and ragweed was also reported (11) . In contrast, several studies have not shown similar efficacy of immunotherapy for PFS. Bucher et al. (12) placed 15 adults on SCIT for birch to treat PFS to apple and hazelnut. Open challenges were performed before and after SCIT. The authors found limited benefit of immunotherapy with birch for PFS. Similarly, another study found no benefit of subcutaneous and sublingual immunotherapy to birch for PFS to apple (13) . A pediatric study from Sweden indicated no beneficial effect of birch SCIT or oral immunotherapy for food allergic symptoms (14) . In addition to difficulties in objective evaluations for improvement in symptoms, there is no consensus for target doses; thus, SCIT remains an unproven therapeutic approach for PFS.

Oral Immunotherapy (Specific Oral Tolerance Induction, SOTI)

Since there is a high incidence of adverse reactions with SCIT, alternative routes of immunotherapy administration are being explored to improve the risk–benefit ratio. There is an expanding body of literature that reports a high rate of efficacy with oral immunotherapy (75–86%) (15– 17) . Several studies have been published for trials with various food allergens. A trial of egg oral immunotherapy in non-anaphylactic patients was published. Buchanan et al. (18) treated seven patients with a modified rush immunotherapy with build-up to a daily maintenance dose of 300 mg. The patients were kept on maintenance dose for the duration of the study. Four patients who passed a DBPCFC at the end of the 24-month trial underwent a second DBPCFC after 3–4 months without immunotherapy; two patients passed this second DBPCFC. The authors found a significant increase in egg-specific IgG, but no change in egg- specific IgE post-treatment. All tolerated significantly more egg than at the study onset, with two patients demonstrating oral tolerance. Of note, this study did not include control patients, was not blinded, and only included children without a history of anaphylaxis to egg. Patriarca et al. (19) reported on a larger group of patients who received immunotherapy to a variety of food allergens. In this study, 42 patients with food allergy underwent sublingual–oral desensitization to milk, egg, fish, wheat, apple, and/or beans. Ten patients who refused to participate in the desensitization protocol and remained on elimination diets served as the control group . Six patients in the treatment 338 J. Wang and H.A. Sampson group dropped out of the study due to poor compliance. Another four patients stopped the protocol because of continued symptoms not controlled by oral antihistamines or cromolyn sodium. All of the remaining patients (85.7%) had negative DBPCFCs, which were performed at the completion of the desensitization protocol. Prophylactic oral antihistamines or cromolyn sodium was administered to 11 patients (30.6%) who experienced mild side effects. Patients were maintained on therapy, so it is unclear whether any of these patients achieved tolerance or whether they reached a desensitized state. One of the main criticisms of these studies has been the non-randomized nature of the trials. Two studies incorporated randomization into their trial design, but neither were blinded or placebo-controlled. Morisset et al. (20) studied 57 children with cow’s milk allergy and 84 children with egg allergy. For the milk-allergic group, 27 children were randomized to oral immunotherapy and 30 children continued avoidance diets. Post-treatment, there was significant improvement in clinical tolerance and decrease skin test reactivity in the group treated with oral immunotherapy. For those with egg allergy, 49 underwent egg oral immunotherapy and 35 children continued avoidance diets. There was an improvement in clinical tolerance; however, this did not reach statistical significance. The egg immunotherapy group did demonstrate decreased skin test size and specific IgE after treatment. Staden et al. (21) performed a randomized study of oral immunotherapy in 45 children with food allergy to egg or milk. The children were randomly assigned to one of two groups, 25 to specific oral tolerance induction (SOTI) and 20 to continue the elimination diet. At the end of 18–24 months, the children underwent DBPCFC and then a repeat challenge 2 months later (off SOTI). There was a similar rate of complete tolerance between the two groups (36% for those on SOTI, 35% for those adhering to an elimination diet). However, another seven patients in the SOTI group developed partial tolerance and could include some egg or milk as part of their regular diets. The authors suggested that this partial tolerance provides a larger margin of safety for these children from accidental ingestions. Also, these children have improved quality of life since additional food products are included in their diets. Overall, 64% of the SOTI group achieved improved tolerance after treatment. All patients in the SOTI arm did experience side effects; however, all were considered mild to moderate. Four children had systemic reactions; these were treated with oral antihistamines and corticosteroids. No severe systemic reactions occurred. The authors cautioned that SOTI requires close continuous supervision of the children by an allergist. They also identified certain factors that reduced the threshold for SOTI-induced allergic reactions, which included exercise, respiratory tract infections, and the pollen season if the patient is pollen-allergic, during the dose- escalation and maintenance phases of therapy. Skripak et al. [42] performed the first double-blind, placebo-controlled oral immunotherapy study for milk allergy in children. Twenty children were randomized and 12 completed 3–4 months of active immunotherapy. After treatment, the threshold for reactions to milk was increased for all children on active OIT. Although no significant changes in specific IgE levels or skin prick test results were observed, there was Food Allergy: Opportunities and Challenges 339

a significant increase in milk-specific IgG and IgG4 in the active group. The majority of participants experienced reactions during the post-OIT food challenge, demonstrating that complete protection from allergic reactions due to milk was not achieved. All participants continued daily intake of milk, therefore, it is unclear whether any OIT participants achieved tolerance rather than desensitization to milk. Longo et al. [43] demonstrated that OIT can be safe and effective for highly milk allergic children in their OIT trial. After 1 year, 36% of the OIT group had unre- stricted diets, and more than half (54%) were able to tolerate limited amounts of milk (ranging from 5–150mL). Adverse reactions were common and occurred in all children on OIT. This study demonstrated that OIT can be effective even for those with the most severe allergies. The authors noted that although adverse events were common, in cases of persistent milk allergy and a high risk of accidental exposures and reactions, the risks of treatment may be acceptable. Recently, Jones et al. [44] reported an open-label peanut (OIT) study in which desensitization was successful in 93% of patients. Declines in skin prick tests and peanut-specific IgE levels and increases in peanut-specific IgG4 were observed. A significant decrease in basophil activation was detected, as well as increases in several cytokines, including IL-10 and IL-5, suggesting that OIT does not cause the typical downregulation of Th2 and upregulation of Th1 profiles. Furthermore, T-cell microarrays demonstrated downregulation of apoptotic genes, indicating a potential role for apoptosis in OIT. These studies show that oral immunotherapy is a promising treatment option for food allergy. However, evidence to date do not demonstrate that apparent improvements in tolerance are due to true induction of oral tolerance and not the natural history of food allergy. Further trials using placebo-controls and mechanistic studies should provide insight.

Sublingual Immunotherapy (SLIT)

Sublingual immunotherapy, which has been demonstrated to be safe and effective treatment for allergic rhinitis and asthma, is another attractive option for the treatment of food allergy. The first case of successful SLIT for the treatment of food allergy was reported by Mempel et al. (22) for a patient with kiwi anaphylaxis. Enrique et al. (23) published a randomized double-blind, placebo-controlled study investigating SLIT for hazelnut allergy. Twelve patients were treated with SLIT for 5 months using the sublingual-discharge technique. Six patients had symptoms consistent with pollen-fruit syndrome (PFS) to hazelnut and five patients had a history of anaphylaxis to hazelnut (one participant withdrew consent on the first day of SLIT). The SLIT extract contained Cor a 1 (Bet v 1 homologue) and Cor a 8 (lipid transfer protein). Eleven patients received placebo. Significant increases in threshold of sensitivity to hazelnut allergen were observed following treatment with hazelnut SLIT. There was also an increase in hazelnut-specific IgG4 and IL-10 after treatment in the active group. The systemic reaction rate was low (0.2%) and only occurred during the build-up phase. Treatment with antihistamine was sufficient. 340 J. Wang and H.A. Sampson

Local reactions occurred in 7.4% and consisted mostly of oral pruritus. As for the other routes for immunotherapy, further studies are needed to assess the long-term efficacy of this technique, optimal treatment doses and duration, as well as its applicability to other allergenic foods. A recent randomized, double-blind, placebo-controlled clinical trial of SLIT for peach allergy also reported promising results of improved allergen tolerance that was associated with decreases in skin test reactivity and significant increases in IgE and IgG4 to Pru p 3. [45] A multicenter study investigated the effects of birch pollen SLIT for PFS. [46] Twenty patients with pollen-associated apple allergy received SLIT for 1 year. Although improvement in nasal provocation scores to birch pollen was seen in 9 patients, there was no significant improvement in their apple-induced oral symptoms. Furthermore, there was no change in specific IgE or IgG4 to the major apple allergen, Mal d 1 after treatment, suggesting that SLIT with birch pollen may have no clinical effect on associated apple allergy. Overall, immunotherapy still appears to be a viable option for the treatment of food allergy, especially as safer routes of administration are being explored. Certainly, additional randomized, placebo-controlled studies are necessary to determine the true efficacy of this method and to standardize extracts, protocols, and durations of treatment. In addition, studies to elucidate the mechanisms of this treatment will provide insight into whether treatment is inducing true oral tolerance.

Modified Recombinant Vaccines

Since significant adverse effects occurred with conventional immunotherapy for peanut, modified recombinant food proteins are being investigated for use in allergen-specific treatment of food-induced anaphylaxis. Modified peanut allergens, in which the primary sequences of IgE-binding epitopes of the major peanut proteins (Ara h 1, 2, 3) are altered using site-directed mutagenesis to decrease IgE binding capacity, have been engineered. These recombinant proteins stimulate T cells from peanut allergic individuals to proliferate, but have greatly reduced IgE-binding capacity as compared to wild-type peanut protein (24, 25) . Heat-killed Escherichia coli (HKE) producing recombinant peanut proteins have been shown to have protective effects in a murine model of peanut anaphylaxis (26) . Peanut-sensitized mice were treated with HKE containing modified Ara h 1–3 (HKE-MP123; low, medium, and high doses), HKE-containing vector alone, or placebo. Mice treated with HKE-MP123 demonstrated reduced symptom scores during peanut challenge as compared to the placebo-treated group. The medium and high dose HKE-MP123 treated groups were protected for up to 10 weeks post-treatment. The high-dose treated group demonstrated the most significant decrease in IgE levels and decreased production of IL-4, IL-5, IL-13, and IL-10, and increased IFN-g and TGF-b production by splenocytes. The proposed mechanisms involve Th1 cytokines and/or T regulatory cells suppressing Th2 cell activation and mast cell/basophil mediator release on re-exposure to antigen (27, 28) . The HKE-mAra h 1–3 has been manufactured in Food Allergy: Opportunities and Challenges 341 a GMP facility clinical trials have been initiated for use in man and is undergoing final toxicology studies prior to submitting an IND application to the FDA.

Peptide Immunotherapy

The use of food allergen peptide immunotherapy has also shown potential. These peptide fragments contain T cell epitopes, but are not of sufficient length to crosslink IgE and, therefore, cannot trigger mast cell or basophil activation. A preliminary study using pepsin-digested peanut peptides showed the ability to induce IFN- g (Th1 cytokine) in a concentration-dependent manner (29) . In a murine model of peanut allergy, Li et al. (30) were able to demonstrate that mice receiving immunotherapy with peptides containing IgE epitopes to Ara h 2, a major peanut protein, prior to allergen challenge experienced only mild allergic reactions as compared to sham-treated mice, which exhibited severe anaphylactic reactions. In addition, the treated mice had smaller drops in rectal temperatures and lower plasma histamine levels than the sham-treated mice. Although these preliminary studies demonstrate this technique to be a promising approach to the treatment of food allergy, validat- ing the stability and uniformity of peptide mixtures for use in human poses a significant challenge.

Immunostimulatory Sequence-Conjugated Protein Immunotherapy

Immunostimulatory sequences (ISS), such as CpG oligodeoxynucleotides, bound to proteins can act as adjuvants to promote switching to a Th1 response (31) . ISS conjugated to allergenic proteins may be more immunogenic and less allergenic. Initial studies with ragweed allergen showed that immunotherapy with ISS in combination with Amb a 1, the major ragweed allergen, promoted Th1 responses and reduced allergenicity in mice, rabbits, and primates (32) . Horner et al. (33) immunized C3H/HeJ mice with either a plasmid encoding beta-galactosidase (beta-gal) or beta-gal protein plus an immunostimulatory sequence oligodeoxynucleotide (ISS-ODN). The mice then underwent a sensitization protocol to beta-gal. Mice immunized with beta-gal plus ISS-ODN were protected from developing fatal anaphylaxis and had lower plasma histamine levels after allergen challenge compared to the group treated with beta-gal protein alone. A similar approach is being investigated in a murine model of peanut-induced anaphylaxis (34) . Mice were immunized with either ISS-linked Ara h 2 (a major peanut protein) or ISS-linked Amb a 1 prior to sensitization with peanut. The mice were then challenged with Ara h 2 five weeks after initial sensitization. Mice treated with ISS-linked Ara h 2 had lower symptom scores and lower plasma histamine levels following challenge with Ara h 2 compared to the mice treated with ISS-linked Amb a 1. The investigators also noted a significantly higher Ara h 2-spe- 342 J. Wang and H.A. Sampson cific IgG2a level in the ISS-linked Ara h 2 treated mice, but there was no significant difference in specific-IgE or IgG1 levels between the two groups. These findings suggest that immunostimulatory sequence-conjugated protein immunotherapy may be an effective method of preventing the development of food allergy.

Plasmid DNA Immunotherapy

Another approach to immunomodulate allergen-induced anaphylaxis utilizes allergen gene immunization. Roy et al. (35) synthesized DNA nanoparticles containing the gene for Ara h 2, a major peanut allergen, by complexing plasmid DNA with chitosan and orally administered these nanoparticles to mice. Immunized mice demonstrated less severe and delayed anaphylactic responses following challenge compared to mice treated with “naked” DNA or those that were unimmunized. These mice also had decreased IgE levels, lower plasma histamine, and lesser vascular leakage. This approach may also be effective in preventing the development of peanut allergy, but concerns regarding the use in humans is a potential disadvantage of this technique.

Allergen Non-Specific Immunotherapy

Anti-IgE

Treatment with anti-IgE antibodies has been investigated in a double-blind, randomized, dose-ranging trial in 84 patients with a history of peanut allergy (36) . Patients were randomized to receive either TNX-901 (150, 300, or 450 mg of anti-IgE antibodies) or placebo. Patients who received the highest dose (450 mg) of anti-IgE, monthly for 4 months, had a significant decrease in symptoms with peanut challenge as compared to the placebo group. The median threshold of sensitivity to peanut increased from less than 1 peanut (178 mg) to almost 9 peanuts (2.8 gms). Therapy was well-tolerated. However, while 25% of patients were able to tolerate over 20 peanuts following therapy, another 25% failed to develop any change in tolerance to peanut following treatment. Recently, investigation of another anti-IgE preparation, omalizumab (Xolair®, Genentech), has been at least temporarily discontinued (37) .

Herbal Medicine

Alternative approaches have also been shown to have beneficial effects on food allergy in murine models. The Traditional Chinese Herbal Medicine formula, FAHF-2, has protective effects on peanut-sensitized mice. Peanut-allergic mice Food Allergy: Opportunities and Challenges 343 treated with FAHF-2 had no signs of anaphylaxis after peanut challenge, but all sham-treated mice had severe symptoms of anaphylaxis, decreased rectal temperatures, elevated plasma histamine, and marked vascular leakage (38) . The clinical effects were associated with decreased peanut-specific IgE levels and Th2 cytokine production (IL-4, IL-5, IL-13). The protective effects of FAHF-2 were demonstrated to last up to 6 months post-therapy, which represents about 25% of the life-span of the mouse (39) . These results were initially based on mice given the FAHF-2 during peanut sensitization, but recent studies have demonstrated that FAHF-2 can induce tolerance to peanut in mice with established peanut allergy. This protection persisted for 4 weeks post-treatment and was associated with decreased production of IL-4 and IL-5, but increased IFN- gamma (40) . Studies with human T cells have also been performed to investigate the effect of FAHF-2. Purified human PBMCs were obtained from peanut-allergic individuals and stimulated with crude peanut extract in the presence and absence of FAHF-2. The cells stimulated in the presence of FAHF-2 had a decrease in antigen-dependent T-cell proliferation. There was also a dose-dependent decrease in Th2 cytokine production (IL-5 and IL-13) and increase in IFN-g production, indicating that FAHF-2 specifically inhibits the Th2 response (41) . Recently, the U.S. FDA approved a botanical drug IND for FAHF-2 and a Phase I trial is currently underway.

Summary and Conclusions

The current accepted treatment strategy for food allergy is strict avoidance of the offending allergens and education regarding the use of epinephrine and an emergency plan in cases of accidental ingestions or exposures. While this method is generally effective, these pose a significant negative impact on the quality of life of both patients and their families. Therefore, the development of new therapies for food allergy that are safer and more effective are essential. We have described several promising approaches being investigated, which will hopefully provide long-term treatment options and potentially a cure for food allergy.

References

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Patrick G. Holt

Introduction

The prevalence of atopic disease, in particular atopic asthma, has increased markedly in developed countries over the last 20 years. The rate of this increase has slowed significantly over the last few years and may be approaching a plateau, suggesting that the bulk of subjects with susceptible genotypes in current birth cohorts may already be responding maximally to the environmental factors which are responsible for driving the disease process. The resulting impact of these environmentally induced changes in asthma prevalence on health care systems in the developed countries is extremely high. An increasingly wide body of epidemiological evidence suggests that the countries of the developing world are no longer immune to this epidemic, as lifestyle changes associated with economic expansion recreate the patterns of environmental risk factors which drive disease in the developed world. The long term solution to this problem clearly does not lie in the development of more and better symptomatic treatments, but instead requires a more radical series of approaches aimed at reduction of the overall burden of disease [1] . This chapter reviews developments in the recent literature on asthma etiology, which collectively suggest a range of testable strategies for primary and secondary prevention of atopic asthma. The recent key findings are those emerging from cross-sectional and prospective cohort studies on atopic disease pathogenesis in pediatric populations.These indicate that the major gene x environment interactions responsible for disease inception occur during early childhood, when the immune functions underlying the inflammatory effector mechanisms which ultimately drive

P.G. Holt () Telethon Institute for Child Health Research , Centre for Child Health Research, the University of Western Australia , Perth , WA , Australia e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 347 DOI 10.1007/978-4-431-99362-9_21, © Springer 2010 348 P.G. Holt disease pathogenesis are undergoing final maturation. It is clear that the kinetics of this immune maturation process varies markedly within human populations, and these variations represent important determinants of susceptibility to development of atopic diseases. This chapter briefly summarizes the evidence supporting this general concept, and discusses intervention strategies aimed at prophylaxis of atopy, which arise from these findings.

Postnatal Development of Immune Competence

It is well established that infancy is a period of attenuated immune competence, resulting from a broad range of maturational deficiencies in immune regulatory and effector mechanisms [2– 4] . Recent research indicates that these deficiencies are not evenly distributed throughout the immune system. In particular, it is evident that the most profound immune maturational defect in fetal, and neonatal life is within the T-helper (Th)-1 arm of the adaptive immune system, skewing overall immune function towards the Th2 phenotype [5] . This represents an evolutionary adaptation to protect the fetoplacental unit from the toxic effect of Th1 cytokines such as IFNg , which potentially may be produced locally in cellular immune responses triggered as a result of histoincompatibility between mother and fetus, and/or arising from responses to infections. Th1 responses in this milieu are recognized as a major cause of fetal loss [5, 6] . A broad range of immunoregulatory mechanisms operate at the fetomaternal interface to prevent such T-cell-mediated responses reaching significant levels. These include constitutive production within the placenta by cells such as tropho- blasts of Th1 inhibitory and Th2 trophic molecules including IL-4, IL-10 [7] , progesterone [8] and PGE2 [7] . These mechanisms are further bolstered by local production of regulatory molecules which inhibit T-cell activation such as tryptophan metabolites [9] and IL-10 [10] , together with expression on local tissues of FasL [11] which is a potent trigger of apoptosis in preactivated T-cells. After birth, the confrontation of the newborn by a microbially hostile environment dictates the necessity for selective upregulation of Th1-associated effector mechanisms, as these are central to host antimicrobial defence and hence survival.This is necessitated because levels of protective maternal antibody progressively wane in the infant. The initial signals of postnatal upregulation of Th1 functions are provided by normal microbial exposure, particularly involving commensal organisms that colonize the gastrointestinal tract GIT during early infancy [12, 13] . Specific molecular signature molecules including lipopolysaccharide (LPS) and microbial nucleic acids are recognized via the TOLL family of receptors expressed on cells of the innate immune system [14] , and these interactions trigger production of a range of Th1-inducing maturation factors including IL-12 and IL-23 by cell populations such as monocytes and (in particular) dendritic cells (DC). This series of microbial-driven interactions leading Potential Strategies for Asthma Prevention 349 to production of immune maturation-enhancing molecules provides a plausible set of mechanisms for the Hygiene Hypothesis which has been invoked as a contributing factor in changing patterns of disease expression over recent time [15] . However it is also becoming clear that microbial exposure is also of central importance in driving maturation of T-regulatory cell (Treg) function, which is also attenuated at birth (reviewed in [16] ), and moreover may be further reduced in infants at high risk of atopy [17] . The capacity to produce both Th1 and Th2 cytokines increases in normal subjects during infancy, but this maturation process typically appears to be initiated earlier and initially progresses faster for the Th2 cytokines, maintaining the fetal-like Th2-skewed pattern of immune function [18, 19]. The basis for persistence of this response phenotype during infancy appears to be multifactorial and involves the functions of several cell types. However the rate- limiting cells may be within the DC population, which at birth are dominated by DC2 cells which selectively drive Th2 differentiation, maintaining the pattern established during fetal life [20] . DC are present in only relatively low numbers in the infant circulation, in particular the plasmacytoid DC population [21] . Moreover, the antigen presentation (APC) functions of circulating DC remain markedly attenuated throughout infancy, and continue to skew T-cell activation responses towards the Th2 profile [22] . It is also important to note the results of animal model studies demonstrating that maturation of DC populations in mucosal tissues in the lung and airways progresses slowly during the preweaning period [23, 24], and the overall kinetics of this process is determined by intensity of exposure to environmental (including infectious) irritants [24] . Postmortem studies on tissues from infant airways suggest a comparable pattern of microbial-driven maturation of this important regulatory population in humans [25] . Given the central importance of airway mucosal DC in both the initiation of sensitization to aeroallergens and in reactivation of Th2-memory cells responsible for driving the asthma late phase response [26, 27] , it is feasible that infection-driven maturation of this DC population may have long term consequences in relation to pathogenesis of atopic asthma. It is also evident that the functional competence of the CD4+ T-cell system matures relatively slowly in most normal infants. In particular, the capacity of infant CD4 + Th-cells to develop stable clones is low relative to adults, and their ability to secrete both Th1 and Th2 cytokines is comparably diminished, though the degree of attenuation is greatest for Th1 cytokines, notably IFN g [28] . The principal mechanism(s) underlying this developmental attenuation is/are intrinsic to the T-cells themselves and are independent of APC function [28] . In particular, hypermethylation of CpG motifs in the proximal promoter of the IFN g gene is a defining feature of neonatal naive CD4+ T-cells and limits capacity for rapid upregulation of IFN g gene expression in these cells [29] . It is notable that CPG methylation in the IFN g promoter is less marked in CD8+ T-cells and NK cells during infancy,and IFNg responses of these cell types are less attenuated than in their CD4 + T-cell counterparts [29– 31] . 350 P.G. Holt

Recent Thymic Emigrants (RTE) and the Conundrum of Intrauterine Sensitisation to Allergens

Findings from many laboratories including the author’s (reviewed in [32] ) suggesting the presence of allergen responsive T-cells in cord blood have stimulated debate on the potential for transplacental priming against dietary and inhalant allergens (e.g., see [33] ). However, recent studies which have addressed in more detail the issue of the precise identification of allergen responsive cells in cord blood (e.g., [34] ) seriously question earlier conclusions. In particular, it has been known for some time that the bulk of T-cells in the blood of human neonates express a range of unique markers not found in adult T-cells, in particular intracellular T-cell receptor (TcR) excision circles [35, 36] . These cells are RTE, and they slowly decline proportionately within the circulating T-cell population over infancy and early childhood as they are replaced by conventional (“mature”) naive T-cells from the thymus, and/or via slow homeostatic turnover. Recent studies from our group have demonstrated an unexpected contribution from these immunologically naive RTE to early postnatal T-cell responses in vitro. Notably, we have demonstrated that the CD4 + T-cells in cord blood which respond in vitro to environmental allergens via proliferation and cytokine production appear to be exclusively CD45RA- immunologically, immunologically naive RTE [16] . The basis for this apparent nonspecific reactivity to allergens appears to be structural alterations in the TcR of RTE which enable “promiscuous” low affinity interactions with a broad range of antigens, as opposed to the high specificity and high affinity of such reactions by genuine T-memory cells. These low affinity interactions trigger initial rapid proliferation and initial cytokine production by the RTE, which is then terminated via apoptotic death unless cytokines such as IL-4 or IL-7 are present at high concentrations to “rescue” the cells [16] . A comparable response pattern has been observed in neonatal CD8+ T-cells in mice [37] . A potentially important byproduct of these responses is activation of Treg cells which are present in the neonatal circulation, but are initially functionally inert until activated [37] .

Immune Maturation and Genetic Risk for Atopic Disease

Earlier studies in our laboratory established that the kinetics of postnatal maturation of CD4+ Th-cell cytokine response capacity in children at high genetic risk (HR) of atopy (i.e., positive family history) was slower than in low risk (LR) children with negative family history [28] . This was independent of APC activity, and was most marked for Th1 cytokines, resulting in exaggeration in the HR children of the devel- opmentally normal pattern of Th2 skewing [28] . These observations have been confirmed in many independent labs [32] . This attenuation appears to be due at least in part to polymorphisms in genes encoding microbial pattern recognition receptors such as CD14 and TLR2, which are more frequent in HR children [38, 39] . Potential Strategies for Asthma Prevention 351

However, the key to the role of this attenuation in relation to atopy pathogenesis is timing. Notably, the life period during which Th2 function is differentially low in HR children coincides with the time at which initial “priming” of allergen-specific CD4+ T-cell memory responses is most commonly initiated [34, 40– 42] . Attenuated cross- regulation from Th1 cytokines in this period may accordingly favor development of Th2 polarized memory. It is important to note that the maturational Th1 defect in HR children is restricted to CD4+ Th-cells, and we have reported that the activity of cytokine secreting CD8 + T-cells in infants who develop early atopy is enhanced relative to those who remain free of sensitization [30] .This is reflected by changing patterns of IFN g gene promoter methylation in CD8+ T-cells [31] . The exaggerated attenuation of Th1 function in HR infants may have consequences not directly related to atopic sensitisation. For example, a number of studies have shown that vaccine responses in HR children are less than in the population at large. In particular, antibody responses to pneumococcal vaccine are reduced [43] and T-cell memory to BCG vaccination in these children is short-lived relative to nonatopics [44] . T-cell responses to antigens in the DTaP vaccine during infancy are relatively Th2- polarized [18] . Moreover, in addition, reduced capacity to secrete Th1 cytokines in these children is associated with increased risk of respiratory viral infections during infancy, in particular RSV [18, 45] . Recent studies from our group and others have emphasized the importance of the temporal “window” in relation to these mechanisms. It is noteworthy that in many HR children who initially express attenuated Th1 function, the underlying maturation process rapidly accelerates beyond 12 months of age to the extent that a major subset of these children eventually become hyperproducers of both Th1 and Th2 cytokines [18] . By 6 years of age this is evident in the responses of atopic children to both vaccine antigens and allergens [2] , and this pattern is even more marked by 12 years of age [46] . This finding may have implications for asthma pathogenesis in the light of evidence suggesting a positive link between bronchial hyperresponsiveness and excessive Th1 cytokine production in atopic children [47] .

Pathways Leading to Development of Wheeze in Childhood: Towards a Rational Basis for Development of Effective Prevention Strategies

Findings from prospective studies on children exemplified by two large birth cohorts in Perth [48, 49] and the Tucson cohort [50] provide the basis for the schema shown in Fig. 1 The control focus of this schema is the conundrum of why progression to development of significant persistent wheezing disease amongst children who become sensitized to inhalants is restricted to a subset of only around 25–30% of this population [51] . The distinguishing feature of these children appears to be early development of sensitization [52, 53] accompanied by the development of wheezing lower respiratory infections (wLRI) during infancy [49, 50]. These two causes of airway inflammation appear to interact synergistically to drive asthma development, as the highest risk of development of persistent asthma is seen in 352 P.G. Holt lants and severe lower ynergistically to maximize ynergistically ASTHMA PERSISTENT nostimulatoty vaccines) nostimulatoty 9.0-13.0 mucosal immune functions) ~2.0 wheeze wheeze 2.0-4.0 intermittent intermittent (anti-inflammatory drugs) (anti-inflammatory ing tolerance ing tolerance induction) pertubation of lung of pertubation growth/differentiation Odds Ratios for asthma at age 6 years 6 asthma at age for Odds Ratios otics, probiotics, immu probiotics, otics, non-specific stimulation of stimulation non-specific 4 4 persistent intercurrent low-moderate moderate-severe crease risk for asthma development, and these two and development, crease risk for asthma airway inflammation airway inflammation airway lergy-induced inflammation inflammation lergy-induced sensitisation by stimulat by sensitisation consolidation of allergen specific Th2 memory) specific Th2 of allergen consolidation (specific anti-virals; (specific anti-virals; se ensuing disease risk. Odds Ratios derived from Refs 34,49 exposure infancy infection repeated 3 LRT Th2 memory al maturation of immune functions (e.g. prebi of immune functions al maturation exposure 5 consolidation spread and rapid clearance tolerance Th2 priming Prospective birth cohort studies indicate that early sensitisation to inhalants and severe lower + + 2 URT viral infection allergen 1 2. atopic of initial (prevention Immunoprophylaxis 4.5.al or viral- airways against growing Protection of LRT infections severe Protection against 3. (SIT or SLIT to prevent Early immunotherapy Potential asthma prevention strategies 1.postnat Stimulation of Legend : Legend : (LRT) infections can independently in tract respiratory synergistically to maximi can interact factors in immune infunction immune maturational defect(s) maturational Risk for asthma development during early childhood Prospective birth cohort studies indicate that sensitization to inha

Fig. 1 ensuing disease risk. Odds Ratios derived from [34, 49] infections can independently increase risk for asthma development, and these two factors interact s respiratory tract (LRT) ensuing disease risk. Odds Ratios derived from [34, 49] Potential Strategies for Asthma Prevention 353 children who experience both atopic sensitization and multiple severe infections during infancy [49, 54]. Our most recent findings [34, 48] have narrowed this “window” period of maximum risk to sensitisation to below 2 years of age. It is hypothesized that the occurrence of these inflammatory events during infancy in the period of rapid postnatal lung growth perturbs underlying cellular differentiation programs, thus disturbing the development of key structure: function relationships in lung and airway tissues which are central to development of normal respiratory function. The resulting abnormal functional phenotype “tracks” into later life and may eventually manifest as persistent asthma [54] .

Strategies for Primary and Secondary Prevention of Persistent Atopic Asthma: Current and Future Options

The central feature of the model in Fig. 1 is the requirement of synergism between the atopy and infection pathways in order to generate maximal risk of persistent asthma development. Accordingly, attenuation of either pathway has the theoretical potential to prevent progression to persistent disease. In principle, a broad range of approaches directed toward this aim are testable with the information and resources currently available, and these are discussed below.

Rational for Early Intervention Strategies for Asthma Prevention

Previous indications [52, 53] that the severity of the asthma-associated sequelae of atopy is inversely related to age of initial sensitization have been further supported by more recent findings by our group. Notably, we have recently shown that synergism between early viral infections and atopic sensitization in relation to subsequent asthma risk is only seen if sensitization occurs below 2 years of age [55] . Furthermore, the earlier children are sensitized, the more intense are their allergen-specific Th2 cytokine responses later in childhood [56] . Additionally, recent prospective birth cohort studies tracking into the teen years have clearly demonstrated that persistent wheeze at 6 years of age tracks stably into the late teen years [57] . These observations argue strongly that the key period for protection of HR children against the asthma- promoting effects of airway inflammation is during early childhood. In this context, one of the key potential targets for early intervention is the process of primary allergic sensitisation. Relevant to this strategy, there is a continuing debate concerning precisely when relevant T-cell priming against allergens actually commences. In particular, earlier studies including our own (reviewed in [33] ) have demonstrated putative allergen-responsive T-cells in cord blood, suggesting that T-cell priming may occur transplacentally. However we have since demonstrated 354 P.G. Holt

[16] that T-cells apparently responding to allergens in cord blood were not Th-memory cells but instead immature thymic emigrants which interact nonspecifi- cally with protein antigens. More recently, we have shown in a prospective cohort study tracking allergen-specific T-cell memory in children, that stable Th-memory to mite allergen does not develop until beyond 6 months of age [34] . This argues that allergen-specific interventions should only be initiated postnatally. However, this may not necessarily apply to interventions targeted at innate immunity, given the recent report suggesting that maternal exposure to microbial stimuli during pregnancy may contribute towards lowering risk of atopy in their offspring via effects on postnatal development of TLR functions [58] .

Targeting Postnatal Maturation of Immune Competence

The range of immune functions shown to be attenuated in children in the period of infancy during which allergen specific T-cell sensitization most commonly occurs, has expanded progressively over the last decade. Of particular interest are findings showing that one of the key factors limiting early T-cell competence is innate immune function [4] . A recent example is the report from our group demonstrating that the principal factor limiting the expression of Th-memory responses to vaccine antigens in vitro was attenuated antigen presentation activity by DC [22] . Numerous studies have reported that these developmental deficiencies are more pronounced in HR infants, and these include observations related to monocytes, DC, Th-cells, and most recently T-reg cell populations [17] . With regard to testable treatments aimed at promoting maturation of immune functions during infancy (intervention point #1 in Fig. 1 ) , there is continuing interest in modulation of gastrointestinal tract (GIT) colonization with the commensals that normally drive this postnatal process. Earlier claims of positive findings with probiotics in infants [59] have stimulated numerous follow-up trials which have met with mixed success, but at the time of writing this chapter the most recently published studies do not show consistent protection against AD or atopy [60– 62] . There is also increasing interest in the potential of “prebiotic” oligosaccharides, the feeding of which is suggested to promote colonization of commensals with probiotic activity such as bifidobacteria [63] , and one study has reported reduced AD in infants treated with prebiotic for 6 months [64] . It is also pertinent to note recent claims from a trial involving prebiotic administration to women during pregnancy followed by subsequent combined prebiotic/probiotic treatment of their infants, which reportedly showed protection against eczema at 2 yrs of age [65] . An alternative approach also being studied in some centres involves attempts to boost immune competence in older HR children with more potent microbial stimuli derived from killed microorganisms, including the use of mycobacterial vaccines. Recent attempts to replicate findings of clinical efficacy from the use of M. Vaccae vaccine have yielded at best only very modest positive effects [66] or equivalence to placebo [67] . It is possible that such stimuli may be of more benefit in younger Potential Strategies for Asthma Prevention 355 age groups, but this remains to be tested. There are also increasingly widespread attempts to utilize orally delivered microbial extracts in this context, particularly in relation to protection against early infections.This approach is discussed in greater detail below in relation to protection against infections.

Protection against the Induction and Persistence of Allergic Sensitization

Immunotherapy targeted at increasingly younger age groups, aimed either at desensitization per se or at prevention of progression from mild to severe atopic disease, is being widely practised. Much of the impetus for expansion of activity in this area is being provided via recent promising findings in children as young as 3 years with sublingual immunotherapy (SLIT; [68] ) which obviates compliance-related problems associated with use of subcutaneous immunotherapy (SIT). A more radical approach is currently being tested by our group, under the aus- pices of the NIH Immune Tolerance Network (ITN; www.immunetolerance.org) in conjunction with collaborators in Melbourne and New York, with extensions planned to European sites. This approach derives from the concept developed here [69] that aeroallergen sensitization during infancy was the result of a failure of immunological mechanisms operative in the oropharyngeal and upper respiratory mucosae which normally promote development of protective tolerance to inhaled allergens. A comparable process operates in the GIT and protects against sensitization to dietary allergens. The concept being tested is that enhancing the intensity of allergen exposure of the oropharyngeal mucosa in nonsensitized HR infants employing allergens given repeatedly as sublingual drops will enhance this tolerance process, thus reducing both sensitization and subsequent asthma (intervention #2 in Fig. 1 ) . The overall active treatment period is 1 year, with a 3 year follow-up. The results of this trial on prevention of sensitization of immunologically naive infants will not be known for at least 4 years. However, in the interim, results are becoming available from a variety of alternative trial approaches focusing on later stages of the atopic march i.e., attempts to attenuate or reverse the allergic phenotype in children who are already sensitized (intervention #3 in Fig. 1 ) . The principal rationale for this approach is provided via the clear connection (reviewed [70] ) between early allergic rhinitis and subsequent development of bronchial asthma in children. Direct support for this concept comes from the 5 year follow-up of a recent large trial in 6–12 year old children demonstrating significant SIT-mediated protection of pollen allergic rhinitic children from progression to asthma [71] . It has been claimed earlier that SIT can also protect children against sensitization to “bystander” allergens which were not part of the SIT treatment [72] .This claim has also gained further recent independent support [73] . As noted above, a major focus of current interest in this area is the use of SLIT, and a range of reviews are available which summarize recent (largely positive) findings ( [68, 74, 75] ; see also individual studies [76– 78] ). 356 P.G. Holt

Early Treatment with Anti-Inflammatory Drugs to Blunt the Asthma-Promoting Effects of Airway Inflammation in Children

As noted in Fig. 1 , the highest level of risk for development of persistent asthma stems from interactions between viral and inhalant allergy-induced inflammation on early postnatal lung growth and differentiation. It seems likely that this would be a cumulative process, and hence any measures which successfully reduce the overall burden of inflammatory damage during this period should potentially be of benefit to the prevention of asthma development (intervention #4 in Fig. 1) . However the selection of effective drugs for use in the relevant young age groups involved, represents a major unresolved issue. In this regard it is highly pertinent to note the conclusions from a recent large trial on 2 year treatment of HR children aged 2–3 years with inhaled corticosteroid (ICS), which did not change later development of asthma symptoms after cessation of treatment [79] . Earlier studies on the long term use of ICS in childhood had reached similar conclusions [80, 81]. The precise reasons for the failure of steroids in this context remain to be explained, particularly in view of their known potency as anti-inflammatory agents. One possible explanation involves potential ICS-mediated side effects on DC functions. Notably, we have demonstrated previously that postnatal development of the airway mucosal DC networks which control immunological homeostasis in the lung and airways is inhibited by ICS [24, 82]. These cells regulate host responses to pathogens including viruses, and also the balance between tolerance and immunity to inhaled nonpathogenic antigens including aeroallergens. It is accordingly feasible that the negative effects of ICS in this regard may outweigh the benefits accruing from their anti-inflammatory activity. The leukotriene receptor antagonist Montelukast has also been used in young children, but while providing short term symptomatic relief in viral bronchiolitis [83, 84] , it did not prevent development of persistent disease. We have previously argued that drugs selectively targeting individual components of the Th2-associated inflammatory cascade also merit trial in these younger age groups [1] , but the paucity of safety data in the relevant age groups again remains an issue.

Protection Against Early Respiratory Viral Infections: The Ultimate Challenge

As noted in the schema in Fig. 1 , airways inflammation arising from early lower respiratory tract viral infections is a major contributor to risk for early development of persistent asthma, and the key viruses in this context appear to be RSV and Rhinovirus [48] . The relative contributions of each virus at the population level cannot currently be precisely quantified, but both are clearly significant in disease Potential Strategies for Asthma Prevention 357 pathogenesis [55] . Protection of HR infants against these infections during infancy thus represents a prime target for asthma prophylaxis (intervention #5 in Fig. 1 ) , Based on animal studies, in the case of RSV it is claimed that specific properties of the virus-associated F protein endows it with unique capabilities to stimulate bystander Th2 immunity and hence to interact directly with atopic processes [85] . Recent human-based evidence, including the demonstration of increased hospitalization risk for bronchiolitis in infants with AD following RSV infection [86] and increased Th2 reactivity in infants in the wake of RSV infection [87] , is consistent with this postulate. No vaccines are currently available for either virus, but a humanized monoclonal antibody against RSV is available which has been shown to be effective in prevention of RSV bronchiolitis in HR infants [88– 90] . A higher affinity version of the antibody (known as Numax®; [91] ) has recently undergone successful multicentre trials and merits evaluation in the context of the viral pathway in Fig. 1 . There is clearly a need for development of other types of antiviral drugs for use in this context in these young age groups, but at present the available options are somewhat limited. However one class of preparations is being employed with some success in related contexts, and may merit investigation for protection against early asthma development. Notably, several competing bacterial-derived immunostimulants are in current use in a range of clinical settings including pediatrics. The two best known are OM-85 [92] and Ribomunyl [93] , both of which are given orally. Their precise mechanism(s) of action remain to be defined, but it appears feasible that they may function via stimulation of recirculating effector cells (such as Th-cells and B-memory cells) which are part of the common mucosal immune system. OM-85 has undergone successful trials for reduction of risk for infection-induced exacerbations in adult COPD patients [94] , and has been used extensively for prevention of acute respiratory infections in young children [95, 96] . Ribomunyl has been reportedly used in children with comparable success [84] , particularly in the prevention of recurrent respiratory infections, including during infancy [97] .

Conclusions

The current paradigm for asthma treatment, notably aggressive treatment of clinically relevant established disease with selective and nonselective anti-inflammatory drugs, does not represent the ideal long term solution to the increasingly expensive public health problems posed by the asthma epidemic. Instead, early identification of children at HR of asthma development, and intervention in advance of the establishment of persistent disease, has potential to markedly reduce the overall burden of disease in the community. A range of potential early intervention options are undergoing testing internationally, and it appears likely that the overall approach will eventually enter the ranks of “standard” treatments for HR children. 358 P.G. Holt

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Karin C. Lødrup Carlsen and Göran Wennergren

Why Should We Predict Disease?

Clinicians would be at a great advantage if they at an early stage could identify the children who would develop asthma or other allergic disease in the future and who would remain or become healthy in later childhood and adult life. Then, resources could be focused more towards those with likely persistent disease to ensure optimal relevant management. For the scientists, identifying children who will go on to develop a disease, could provide a strong basis for understanding disease development as well as for giving appropriate advice to the community on how to prevent or diminish the potential harmful influences whenever possible. Parents need to know at the earliest possible stage whether or not their coughing or wheezing child is starting a life long career in allergic diseases, or if the symptoms are passing with a healthy outcome. Thus, appropriate early management, primary or secondary prevention, and prognosis estimates, all point to the necessity or value of trying to predict any disease. However, this has proven difficult. A PubMed search (October 2007) with the four index words: predict , asthma (or allergy ), birth , child gave 17 hits (for both outcomes), of which none attempted to use factors known at birth for predicting asthma or allergy in children. On the other hand, evaluation of early life factors (infancy and early childhood) for predicting the same outcomes have been more widely reported, although relatively rarely with significant predictive capacities

K.C.L. Carlsen () Department of Paediatrics, Division of Woman and Child , Oslo University Hospital, Ullevål University Hospital , NO-0407 , Oslo , Norway; The Faculty of Medicine , University of Oslo , Oslo , Norway e-mail: [email protected] G. Wennergren Department of Paediatrics , Queen Silvia Children’s Hospital, Göteborg University , SE-416 85 , Göteborg , Sweden e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 365 DOI 10.1007/978-4-431-99362-9_22, © Springer 2010 366 K.C.L. Carlsen and G. Wennergren

(see below). Thus, there is a need to discuss what prediction entails: from a statistical and conceptual point of view, as well as from a clinical and scientific point of view, in relation to allergic disease development. Furthermore, early diagnosis of allergic disease is closely connected to prediction. Optimal management will depend upon an earliest possible diagnosis, and early appropriate diagnosis improves the likelihood of prognosis estimates. The present chapter will therefore concentrate upon factors that increase or decrease the likelihood of allergic disease at present or in the future, as well as discussing possible models for predicting prognosis in established diseases. However, the discussion will be limited to prediction within childhood up towards early adulthood.

Some Definitions and Considerations

Table 1 outlines some of the statistical terms central to diagnostic tests or prediction. The term “predictors” are commonly used in statistical models for analysing associations between one outcome and several factors, such as in regression models.

Table 1 Deﬁ nitions of the central terms used for consideration of prediction Sensitivity: The probability of the test finding disease among those who have the disease or the proportion of people with disease who have a positive test result. Sensitivity = true positives/(true positives + false negatives) Specificity: The probability of the test finding NO disease among those who do NOT have the disease or the proportion of people free of a disease who have a negative test. Specificity = true negatives/(true negatives + false positives) Positive Predictive Value (PPV): The percentage of people with a positive test result who actually have the disease. Positive predictive value = true positives/(true positives + false positives) Negative Predictive Value (NPV): The percentage of people with a negative test who do NOT have the disease. Negative predictive value = true negatives / (true negatives + false negatives) Likelihood Ratio: The likelihood that a given test result would be expected in a patient with a disease compared to the likelihood that the same result would be expected in a patient without that disease. Likelihood Ratio Positive (LR+) : The odds that a positive test result would be found in a patient with, versus without, a disease. Likelihood Ratio Positive (LR+) = Sensitivity / (1 - Specificity). The probability of a test result being positive in a person with the disease divided by the probability of a test result being positive in a person without the disease. Likelihood Ratio Negative (LR-): The odds that a negative test result would be found in a patient without, versus with, a disease. Likelihood Ratio Negative (LR-) = (1- Sensitivity) / Specificity. The probability of a test result being negative in a person who has the disease, divided by the probability of a negative test result in a person who doesn’t have the disease Prediction and Early Diagnosis 367

However, only rarely do authors state how much of the explained variability of the outcome is identified by all the factors included in the models. Thus, a “predictor” in such cases is more likely to reflect the potential effect upon the outcome by the risk factor in question, rather than the ability of the factor to predict the outcome. Thus, a consideration of prediction models may be necessary to understand the difference. With statistical approaches to assess whether or not a factor may increase or decrease the risk of disease, we often use the term odds ratio, or relative risk. Prediction models are generally used to assess the likelihood of a certain outcome in an individual if they fulfil the criteria (factors) listed in the model. The odds ratio or relative risk estimates how much the presence of a factor increases or decreases the risk, as compared to the absence of the factor. To predict the dichotomous event of asthma (or allergy), the appropriate statistical analysis is a logistic regression analysis [1] . The logit model (logistic regression analysis) has several appealing properties, including that the coefficients determined for each independent variable in the model have a simple interpretation in terms of odds ratios, being a type of risk measure that under certain assumptions can be compared to relative risk. Furthermore, the probability of a subject having asthma or not at a certain time point is easily estimated. However, the generalised measure of predictive power, also known as Nagelkerke’s R2 (R squared, that may be interpreted as the proportion of variance explained by the independent variables) is rarely reported. Some of the disadvantages of such models include the fact that estimations of odds ratios involve successive approximations, and in complex diseases there is usually not one single “correct” solution. Secondly, if the standard error of the estimate is more than three times the value of the estimate, the results should be interpreted with caution. If the dispersion differs among groups of subjects, the estimated coefficients tend to shrink towards 0. This unobserved heterogeneity and the magnitude of the estimated coefficients will be conservative, and all relevant covariates should preferentially be included. Finally, all complex models should always be assessed for the model fit, and statistical advice [1] is recommended.

Prediction Versus Risk Factors

In order to employ a risk assessment for prediction, it must be noted that a risk factor has to be extremely strongly associated with a disease within a population if it should be of any screening value [2] . It has been stated that even a relative odds of 200 between highest and lowest fifths yields a detection rate of no more than 56% for a 5% false positive rate, provided, distribution of the screening variable is approximately Gaussian with similar SD in affected and unaffected people [2] . Thus, it is reasonable to ask if any of the currently known risk factors for asthma or allergy has any potential for predicting disease in an individual. As an example, family allergic history, a traditional “predictor” or at least highly significant risk factor for allergic diseases [3] , is losing ground in relation to asthma with the current 368 K.C.L. Carlsen and G. Wennergren asthma epidemic [4, 5] . Although children born into families with allergies or asthma are at increased risk of the diseases, the majority of children with disease appears to come from families without parental allergic diseases [5] . Other risk factors that have been relatively consistently associated with asthma, such as exposure to tobacco smoke products and to house dust mites [6] or indoor dampness [7] are not very accurate for predicting asthma in any individual child, although the risk of asthma is increased. Predicting capacity may depend not only on the strength of association between the factor and the outcome, but also at what stage of life prediction is attempted in relation to the age by which the outcome is defined. Or put in another way: when do we have the “true” answer of an outcome? This is particularly relevant for allergic diseases, which may appear at any age, although the majority of asthma has been symptomatic in the first few years of life [8] , whereas allergy to some foods like egg and milk are common in the first 1 or 2 years of life, decreasing thereafter [9] in most children. The precision of prediction is likely to be inversely related to the time between prediction point and outcome. For instance, estimated prediction by a clinical score of obstructive airways disease during early childhood, for asthma in school age [10] may be more successful than for asthma in adulthood. Likewise, recurrent wheezing during pre-school years is more likely to predict current asthma during school age than post puberty, after which the gender shift in asthma incidence is well recognised [11] . Thus, not only is the time at which prediction is attempted important per se, but the older the child, the more relevant information is likely to be available to create prediction models. And likewise, the older the individual, the more likely an outcome is to represent the “truth”, particularly in diseases such as asthma, which is greatly heterogeneous during early childhood [12] . On the other hand, an objective factor such as cord blood immunoglobulin E (IgE) appeared to better predict atopy at 7 years than did serum IgE during infancy [13] . It could therefore be useful to consider time of prediction in relation to birth, at debut of disease, in school age, during puberty and early adulthood, with outcomes during pre-school age, school age, early and late adulthood. Prediction of outcomes demands a high degree of specification of phenotypes, since risk factors may differ for non-allergic vs allergic asthma and asthma vs allergic sensitisation or for lung function decline. In the following, we will describe some of the tools (Table 2 ) that have been used for prediction or to identify predictors (risk factors), and subsequently discuss the current status of predictive models for asthma and allergic diseases.

Table 2 Tools used for predicting allergic diseases 1. Questionnaires 2. Blood analyses (Cord blood IgE, early specific IgE, sCD14, IFN-g , IL-4 etc) 3. Skin prick tests 4. Clinical diseases expression 5. Lung function 6. Family history 7. Constructed prediction models Prediction and Early Diagnosis 369

Tools for Prediction

Questionnaires are widely used due to the simplicity of distribution, but have the major drawback that specified phenotypes may be difficult to verify without objective test measures. Prediction may subsequently have less ascertained outcomes, and recall bias (in retrospective studies) may clearly influence the accuracy of prediction. For example, in some instances, such as in the Tasmanian birth cohort follow-up study, the outcomes in adulthood were established by questionnaires and analysed in relation to investigations in the subjects at age 7 years [14] . In this study, asthma as well as atopic eczema identified by age 7 years, female gender, maternal asthma and early or frequent asthma attacks at 7 years were predictors for adult asthma, with mean OR of about 1.4–1.7 [14] . However, the predictive capacity of each factor was not discussed, although a child with none of the risk factors had a 7% chance of having current asthma as an adult, whereas each risk factor was associated with about a 50% increase in risk, resulting in a chance of current asthma in adulthood of 11% with one risk factor, 16% with two risk factors present and so on. The predicted chance was greater than 50% in only 0.5% of all the children and in 5% of the children with parent reported asthma, with similar risk assessments for current atopic asthma [14] . Blood analyses have commonly been used for predicting asthma, allergic rhinitis, atopic eczema and combined allergic disease as well as lung function. Most common among blood tests are the use of cord blood IgE or serum total or specific IgE to predict asthma and allergy [3, 13, 15– 22] , with variable results. However, although total IgE has been assessed as a predictor on its own [15, 23], the results have demonstrated limited or little value for identification of later atopic disease expression [13] . Specific IgE antibodies (s-IgE) used to detect allergic sensitisation has been reported from many studies to precede atopic disease [13, 17, 18, 24, 25] , or to predict obstructive airways disease at the time of s-IgE measurement [13, 26, 27] . Furthermore, the use of s-IgE measurements at 6 months of age in high risk infants with a specifically designed paediatric allergy panel test was reported to precede atopic diseases by 5 years with a very high positive predictive value, but the usefulness of the test was limited by a low sensitivity (approximately 24%) [28] . The usefulness of measuring s-IgE in the first or second year of life for predicting allergic rhinitis or food allergy in school age or early adulthood is less well elucidated, but is likely to be hampered by low sensitivity of identifying s-IgE at least as inhalant allergens at this particular age. Eosinophils and their secretory proteins such as eosinophils cationic protein (ECP) have also been used to predict development and persistence of asthma and other atopic diseases [13, 18, 21, 29–39] . The predictive role of the eosinophils in asthma and other allergic diseases has been debated, and in the mid-1990s serum ECP was extensively studied. However, although serum ECP appeared useful to predict persistence of wheeze after 2 years [21] , Øymar demonstrated that neither 370 K.C.L. Carlsen and G. Wennergren eosinophils count, nor ECP could be used to predict asthma among infants admitted to hospital with their first bronchiolitis [29] . Some early studies suggested that high interleukin 4 (IL-4) in cord blood [40] , and low interferon-g (IFN-g ) [41, 42] during infancy was associated with increased risk of asthma in later childhood, although the Swedish study by Borres et al [40] found no association between IFN-g and atopic disease by 18 months. Skin prick tests (SPT) have been used in most birth cohort studies of asthma and allergy [43, 44] , as well as in many other prospective studies with similar focus [45, 46] , to assess the risk of atopic diseases in children demonstrating early allergic sensitisation. In line with this, a positive SPT to egg at 1 year (in a high risk population) had a high predictive capacity for atopic eczema and moderate predictive capacities for allergic rhinitis, asthma and any atopic disorder at 7 years [13] . However, since the number of children sensitised to aeroallergens in this age is low [47] during the first 2 years of life, positive SPT as a predictor is likely to be flawed by low sensitivity. For prediction of food allergy tolerance development, one study found that the size of wheal was associated with the prognosis of peanut allergy tolerance in one retrospective study in young children [48] , whereas others found that SPT responses could not predict loss of symptomatic food allergy [46] . Clinical disease expression is probably more a marker of disease than a predictor, although scores have been made to try to predict persistence of disease [10, 22] . However, in high risk infants, a truly predictive assessment was reported in 1995 by Zeiger et al in a prospective randomised study of maternal and infant food allergy avoidance among 165 children followed from birth to 7 years of age [13] . Food allergy demonstrated at 4 years doubled the risk of asthma or allergic rhinitis at 7 years, whereas food sensitisation (assessed with skin prick tests) at age 4 and 12 months presented a high predictive capacity for atopic dermatitis, and moderate predictive capacities for allergic rhinitis, asthma or any atopic disorder at 7 years [13] , much in line with the findings from another birth cohort study (the German MAS study) [49] . In the latter study, Bergmann et al [50] identified that atopic dermatitis in the first 3 months was a risk factor for aeroallergen sensitization at 5 years, modified by a positive family history for atopic diseases which increased the risk. Although these risk factors were also significantly associated with the manifestation of allergic airway disease, the positive predictive value for this outcome at age 5 years was only 50%. Early symptoms of obstructive airways disease are, quite expectedly, a risk for later asthma. It seems that infants and young children with wheezing severe enough to need hospital treatment are at particular risk for asthma later during childhood and early adulthood [51– 54] . Thus, recent follow-up studies from Finland and Sweden show that infants and young children who react with wheezing during viral infections, have a clearly increased risk of asthma not only at school age but also in early adulthood [53, 54]. In these subjects, who were hospitalised before the age of 2 years due to wheezing, asthma prevalence at age 17–20 years was 30–43%, depending on the asthma definition used, compared with 11–15% in the control groups [53, 54] . The strongest risk factors for presence of asthma in early adulthood in these children with early wheezy bronchitis/bronchiolitis, were current allergy, Prediction and Early Diagnosis 371 bronchial hyper-responsiveness and female gender [54] . Independent infantile risk factors were female gender and passive smoking [54] . The connexion between prenatal smoke exposure and asthma appeared to be mediated via the development of bronchial hyper-responsiveness [55] . Smoke exposure in infancy on the other hand, was associated with an increased risk of active smoking in early adult age, which is in turn linked to asthma [55] . Lung function measurements have been assessed for predictive capacity of asthma or asthma like phenotypes for several decades, whereas the associations between lung function at, or shortly after birth and obstructive airways disease in later childhood and early adulthood have been studied in a limited number of studies only [56– 58] . Equipment to measure infant lung function has been available from the 1980s, and the first infants who had such measurements are subsequently currently in their early adulthood. The most common measure, often regarded as the “gold standard” for infant lung function measures is the partially forced flow- volume measurements, often referred to as the “squeeze-jacket technique” giving the resultant parameter flow at (estimated) functional residual capacity ( Vmax FRC) [59– 61] . However, other techniques such as measurements of tidal flow-volume loops giving the t PTEF / tE (time to reach peak expiratory flow to total expiratory time) that are simpler to use and which do not require sedation have been used for neonatal measures of lung function [62– 64] , with recent predictive results reported during school age [58] . In a prospective birth cohort study, assessing a history of asthma and current asthma at 10 years from lung function measured at 2 days of age, demonstrated that in children with low t PTEF /t E (<0.20) and reduced compliance of the respiratory system (Crs) (below median), almost 45% had asthma by 10 years, and 28% had current asthma at 10 years of age, respectively [58] . On the other hand, this means that among these children starting life with reduced lung function, 55% never had asthma and approximately 70% of children did not have current asthma at 10 years of age.

Looking at each lung function measure separately, t PTEF /t E <0.20 had the best positive and negative predictive value (PPV and NPV) of 31.3 and 85.1, respectively, with an OR of 1.90 (1.06–3.42) for a history of asthma by 10 years [58] . Among other studies that assessed the value of early lung function for later asthma, the Tucson study described persistently reduced lung function from 3 months to 6 years of life among children with transient early wheezing, compared to children with never wheeze, persistent wheezing and late onset wheezing [60] . However, the predictive capacity of early lung function was not discussed. Several, but not all [65] studies reported that reduced lung function in the first few months of life (prior to clinical disease) increased the risk of bronchiolitis [66] or asthma in pre-school age [64, 67, 68] . Furthermore, not all studies have shown associations between early life lung function measures and assessments in later childhood. Reduced VmaxFRC at a few months of life was not significantly associated with wheezing after 3 years in the Tucson study [60] , and flow limitation in infancy was a predictor of increased wheeze [57] , but not asthma at 6 and 11 years [57] in the Perth study. Others described the association between infant and later lung function through childhood [69] and into adulthood [56] demonstrating a great degree of tracking of 372 K.C.L. Carlsen and G. Wennergren lung function (i.e. later lung function is largely dependent upon pre-morbid lung function), and with little change after adjusting to clinical wheezy phenotypes [56, 69] . It is not clear whether using lung function in sub-groups, i.e. with a positive family history of atopy will improve the predictive capacity on an individual level, since data are currently lacking. Family history . Parental history of asthma seems to have better predictive value for future asthma in the child [22, 70, 71] , than family history of atopy [54] . Prediction models or indices have been developed and reported in a few studies. Clough et al [72] developed models to predict 12 months persistent wheezing in infant wheezers, with maximal predictive value (78%) when they included personal atopy, parental atopy, age and cytokine studies. On the other hand, in the Tucson Children’s Respiratory Study, Castro-Rodriguez et al [22] developed two clinical indices at 3 years of age to define risk of asthma in school age, finding active asthma on at least one time-point between 6 and 13 years in 76% and 59% of children with their positive stringent and loose index models, respectively. Their indices included characteristics of wheezing 0–3 years, doctor’s diagnosed parental asthma or eczema, wheezing unrelated to colds, eosinophilia, or allergic rhinitis. Later, the criteria in this Asthma Predictive Index have been slightly modified [70] . To the major criteria, i.e. parental history of asthma and physician diagnosed atopic dermatitis, allergic sensitization to ³ 1 aeroallergen have also been added. Among the minor criteria, allergic sensitization to milk, egg, or peanuts have replaced physician-diagnosed allergic rhinitis [70] . So far, only one study [10] (to the authors’ knowledge) has included severity of (frequency and/or persistence) and/or hospital admissions for obstructive airways disease (OAD) within the first 2 years of life in the predictive model, giving PPV and NPV of 55% and 92%, respectively for a history of asthma or current asthma with a severity score of 6–12 compared to zero. Noticeably, the score applied at 1 year of age (OAD by 1 year) did not significantly predict 10-year outcomes [10] , suggesting that not only the first, but also the second year of life is an important determinant of later airways disease. The use of the Castro-Rodriguez score (slightly modified) in the latter birth cohort study resulted in a maximum PPV of 48% and NPV of 86%in the Oslo study, including blood tests and parental atopy [10] . Thus, clinical atopic disease expression appears good predictors of later atopic disease, particularly early OAD for later asthma (during childhood), whereas other atopic phenotypes, such as atopic dermatitis appear less valuable as predictor for asthma. Thus, the few risk models that have been used for early prediction of asthma outcomes in school age mainly [10, 22, 72] vary greatly in their predicting capacity, and it is not known how appropriate these models may be for outcomes in early adulthood. To summarise the discussion on whether or not we can predict asthma or allergy, it is clear that most of the known risk factors for atopic diseases are of little value to predict future asthma or allergy in healthy, young individuals. On the other hand, early manifestation of atopic diseases, most noticeably early wheeze, early food or inhalant allergy and atopic eczema are phenotypes that increase the risk of later asthma, allergic rhinitis or allergic sensitisation, but with varying predictive capacity. Prediction and Early Diagnosis 373

To date, the best predictive capacity for asthma appears to be obtained for an eight- year follow-up time after determining a severity score of OAD based upon frequency and severity of asthma episodes by 2 years of age. For the future, prediction models should include discussions related to gender, particularly for outcomes pre or post puberty. Furthermore, in the near future, it is likely that including genetic predisposition will improve predictability of the models, since this is likely to modify the effects of risk factors upon asthma, allergic rhinitis, atopic eczema or food allergies.

Early Diagnosis

Why is early diagnosis important? First of all, careful diagnosis is likely to lead to optimalised management, and, in view of the discussion above, give an indication of prognosis. By early and thorough diagnostic considerations, it is likely that research into disease development improves, particularly in relation to uncovering risk as well as protective factors for each of the atopic or allergic phenotype expressions. When known, accurate diagnosis at an early age may prompt appropriate environmental advice (particularly in secondary and tertiary prevention), and facilitate a discussion on what the benefits and costs are of different management strategies. The allergy march has been much discussed, and indicates a progression from one phenotype to the next. However, as is well recognised, any of the phenotypes maybe present without co-existing phenotypes, or they may appear in duet or in multiplex within a very short time period. Furthermore, the expression of disease may be undulating, such as atopic eczema and food allergy, but which is also seen with asthma. Thus, it would be necessary to consider the following phenotypes: early wheeze versus asthma, atopic eczema, allergic rhinitis, food allergies, allergic sensitisation versus allergic diseases and combined allergic diseases. The natural course of allergic diseases has been widely described, and include several or all of these phenotypes [24, 46, 49, 73– 78] . Commonly, atopic eczema and/or food allergy appears within the first year of life, often with concurrent wheezy lower respiratory tract infections. Thereafter follows asthma and/or allergic rhinitis whilst the atopic eczema and food allergy often go into remission during the pre-school years. Since each of these manifestations may appear on its own, or be part of complex disease, it is important to consider the extent to which one disease may be a marker of one of the other diseases or not. For instance, recurrent wheezing in a one-year-old child with atopic eczema is more likely to be the debut of persistent asthma than if the child had no other atopic manifestation. A very interesting question is whether early diagnosis and early treatment alters the natural course of the disease, in addition to giving symptom control? A Danish study in the beginning of the 1990s indicated that early treatment with inhaled corticosteroids improved lung function development in children with asthma [79] . More recent studies have not found effects on the natural course of the asthma disease or development of lung function [80– 83] . However, even if early treatment 374 K.C.L. Carlsen and G. Wennergren does not alter the natural course of the disease, the benefits with early treatment in terms of symptom control are motivation enough for stressing the importance of early diagnosis.

Acknowlegement The authors wish to thank Petter Mowinckel for his contribution to the discussion of statistical considerations of prediction.

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L. Karla Arruda , Dirceu Solé , and Charles K. Naspitz

Introduction

Atopy has been defined as the genetic predisposition to develop IgE antibody responses to a variety of common environmental allergens. Clinically, atopy is expressed by asthma, allergic rhinoconjunctivitis and atopic dermatitis. It has been recognized that the “atopic march” evolves from food allergy and atopic dermatitis in the first 2 years of life, followed by asthma and allergic rhinitis. Over the past 30 years, the prevalence of allergies and asthma has increased significantly in developed countries, and asthma is one of the most common chronic diseases in children. Evidence indicates that environmental factors acting early in life, including respiratory viral infections, exposure to pets and microbial products, day-care attendance, breast feeding, and exposure to allergens, tobacco smoke and other pollutants, are key events for establishment of sensitization and development of chronic, persistent symptoms of allergic diseases [1] . It is thought that gene–environment interactions play a crucial role in these processes. Therefore, attempts to successfully prevent development of allergic diseases should be a priority. At present, there are no genetic markers for atopy or asthma which could be used routinely in clinical practice and family history of atopy has been used to identify children genetically at-risk of developing allergic diseases. These children from high-risk families have been the focus of most of the intervention studies. In this chapter, we discuss risk factors for development of sensitization and allergic disease, focussing on preventive strategies for allergies and asthma at an early age.

L.K. Arruda () Division of Clinical Immunology, Department of Medicine, School of Medicine of Ribeirão Preto , University of São Paulo , Av. Bandeirantes 3900 , Ribeirão Preto , SP 14049-900 , Brazil e-mail: [email protected] D. Solé and C.K. Naspitz Division of Allergy, Clinical Immunology and Rheumatology , Federal University of São Paulo , São Paulo , Brazil

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 379 DOI 10.1007/978-4-431-99362-9_23, © Springer 2010 380 L.K. Arruda et al.

Risk Factors for Allergies and Asthma

Respiratory Viruses, Wheezing, Allergen Sensitization and Asthma

Infections with respiratory viruses, particularly human rhinovirus (HRV) and respiratory syncytial virus (RSV) are leading causes of lower respiratory tract (LTR) illnesses associated with wheezing in children. Although acute wheezing episodes may be severe enough to require hospitalization, majority of children presenting wheezing illnesses early in life will no longer wheeze by the age of 6 [2] . However, in a proportion of these children, early-life-wheezing is a clinical manifestation of asthma. Respiratory viral infections have been implicated in the pathogenesis of asthma in several ways: during infancy, certain viruses have been linked to inception of the asthma phenotype; in children with established asthma, viral respiratory infections play a significant role in triggering acute exacerbations that might lead to hospitalizations and frequent outpatient visits; in children with repeated infections due to day-care attendance or contact with older siblings, respiratory viruses may have a paradoxical effect of reducing long-term risk of allergy and asthma, through alterations of cytokine response profiles. In the first 3 years of life, most LRT illnesses with wheezing are associated with infection by RSV. In the northern hemisphere, RSV accounts for 60–80% of wheezing episodes in children younger than 2 years of age [3] . It has been shown that children who wheeze with RSV infection in early life have lower level of lung function prior to infection [2] . Most children have serum RSV antibody by the age of 2, yet reinfections are common. Although risk of subsequent wheezing after RSV may decrease significantly with age, recurrent episodes of wheezing due to active RSV infections may occur throughout childhood. Transmission requires close contact, and occurs either by large-particle aerosols or by contamination of hands and inoculation into the eye or nose, with an average incubation period of 2–8 days [4] . More recently, the role of HRVs in causing acute wheezing has been appreciated. HRVs are small, nonenveloped, positive-strand RNA viruses in the family Picornaviridae , with over 100 identified serotypes with minimal cross-antigenicity [5] . HRV infects only higher primates, and causes illness only in humans, with replication restricted to the respiratory epithelium [6] . In temperate climates, HRV has been estimated to cause up to 80% of autumn colds [5, 7]. In tropical countries, available evidence indicates that HRV is frequently associated with acute respiratory illnesses (ARI). HRV transmission requires close exposure and occurs mainly by hand-to-hand contact, followed by self-inoculation into the eye or nose. It can also be transmitted by airborne spread. Once HRV reaches the nasal cavity, infection occurs in virtually 100% of susceptible subjects; and approximately 75% of those infected develop illness after 1–2 days incubation [5] . Sensitive PCR-based assays have established the importance of HRV as the cause of LRT illnesses, in addition to upper respiratory tract symptoms. A recent study with in situ hybridization applied to lower airway biopsy specimens has demonstrated presence of HRV in the LTR of 45% of a group of children 3–26 months of age with recurrent respiratory symptoms [8] . Early Interventions in Allergic Diseases 381

Other viruses have also been associated with wheezing LRT illnesses in children at lower frequencies, including influenza, human parainfluenza viruses, human coronavirus, adenovirus, human metapneumovirus, and the recently identified human bocaviruses (HBoV) – however at a lower frequency [9] . In keeping with observations made in temperate climates, it has been shown that infection with respiratory viruses and family history of allergy, were independently associated with wheezing among infants [10] . Results of this case-control study carried out in Ribeirão Preto, a city in southeast Brazil, revealed that, in the group of children under 2 years of age, respiratory viruses were detected in 60.8% of wheezing infants versus 13.3% of controls, and RSV was detected in 39% wheezing children and none of the controls. Rhinovirus RNA was found in 20.2 and 10% of the wheezing and control children, respectively, though this difference was not significant (p = 0.21). The frequency of RSV was lower than that reported in temperate regions (39% versus 60–80%). However, considering the subgroup of infants 0–6 months-old, 61% tested positive for RSV antigen. RSV infections were predominantly found in the months of February to May, corresponding to late summer and early to midfall, indicating that the virus occurs in a different seasonal pattern as compared to that of the northern hemisphere. In the group of children 2–12 years of age, respiratory viruses were not significantly associated with wheezing [10] . In the United States, Heymann et al have shown that viral infections, especially HRV, were the dominant risk factor for wheezing among children hospitalized before the age of 3 [11] . In their study, 84% of wheezing children p = 3 years-old were positive for virus, compared to 54% of controls ( p < 0.001); RSV was the dominant pathogen in the winter months among children 2 years-old or younger; however, rhinovirus was detected more often among wheezing children hospitalized in the other months of the year (58%) as compared to controls (26%, p < 0.04) [11] . One important issue would be whether infections with respiratory viruses particularly RSV and HRV occurring early in life could function as triggers or “adjuvants” for subsequent development of sensitization and persistent symptoms of allergic diseases. The rational for this hypothesis would be the potential of these infections to induce significant damage to the airways which might facilitate penetration of allergen(s) and/or trigger events related to airway remodeling. RSV enters the cell by fusion of the viral envelope with the cell membrane, and causes syncytia formation as a result of fusion of the infected cells to adjacent ones. Replication in the bronchiolar epithelium causes necrosis of ciliated cells, peribron- chiolar inflammation with abundant lymphocytes and macrophages, and impairment of secretion clearance, resulting in small airway obstruction and the hyperinflation characteristic of bronchiolitis. Clinically, involvement of the LRT is characterized by tachypnea, dyspnea, cough, expiratory wheezing, air trapping, hyperaeration of the lungs on chest X-rays, and intercostal muscle retractions and cyanosis [4] .The pathogenesis of HRV infection is based on the release of cytokines, chemokines, and inflammatory mediators triggered by productive viral replication in a limited number of cells. A number of chemokines, particularly CXCL8 (IL-8), CCL3 (macrophage inflammatory protein 1a ) and CCL5 (RANTES) are major mediators released during respiratory viral infections, which could recruit virus-specific T-cells as well as allergen-specific T-cells that in turn could augment 382 L.K. Arruda et al. any ongoing allergic response in the lung [12, 13]. It has been speculated that the contemporaneous occurrence of cycles of viral-induced and allergen-induced inflammation in the airways during the period of rapid lung growth and remodeling in infancy interacts synergistically to disrupt underlying tissue differentiation programs. This interaction could result in deleterious changes in ensuing respiratory functions, which may then manifest as persistent wheeze and/or asthma [14] . Studies have shown association of RSV bronchiolitis and other early respiratory tract infections with recurrent wheezing or symptomatic asthma during the first 4–7 years of life [15, 16] . A long-term study carried out in Tucson, Arizona, revealed an association of LTR infection caused by RSV early in life with persistent wheezing at 3 and 6 years of age; however, this effect was lost at age 13 [17, 18] . Besides RSV, HRV [19] may be potentially implicated in the subsequent development of childhood asthma. Lemanske et al. have shown that, in a group of 285 children at high risk of asthma, studied during the first 3 years of life, infection with HRV in the first year was the greatest risk factor for persistent wheezing in the third year [20] . The authors showed that 63% of children who wheezed during rhinovirus season continued to wheeze in the third year, as compared to only 20% of all other infants (OR = 6.6). A study in Finland revealed that infants hospitalized for rhinovirus-induced wheezing presented a fourfold higher risk of asthma in school age, as compared to wheezing infants from whom no rhinovirus was identified. Children with atopic dermatitis were especially likely to develop wheezing during HRV infections [21] . These studies highlight the previously unrecognized potential role of rhinovirus infection occurring in early life in the onset of asthma. Follow-up of children 0–2 years of age who participated in the emergency room study in Brazil [22] revealed that, after 2 years, 52% presented persistent wheezing. In contrast to studies carried out in temperate regions, viral infections were not a risk factor for persistent wheezing. On the other hand, early sensitization particularly to mites and cockroach, at 2–4 years of age, and exposure to high levels of cockroach allergen in the home in the first 2 years of life were both strong and independent risk factors for persistence of wheezing. It has been consistently shown that early allergen sensitization becomes a major risk factor for wheezing exacerbations and hospitalizations for wheezing after age 3 [17, 22– 25] . It is thought that IgE-mediated inflammation found in most children with persistent symptoms of asthma is a key factor in causing lung function impairment and airway remodeling. Previous studies in Brazil have shown that day-care centers and schools, in addition to homes, are sources of significant exposure to mite and cockroach allergens, which might contribute to sensitization [26, 27]. Heymann et al have demonstrated that sensitization to house dust mites and other aeroallergens was an important risk factor for hospital admissions for wheezing and adverse responses to viral infections, particularly those caused by rhinovirus, in 3–18 years old children [11] , highlighting the synergistic effect of sensitization, allergen exposure, and concomitant viral infection in augmenting inflammatory responses in the airways [28] . The possibility that viral and atopy-associated inflammation may interact synergistically to drive asthma pathogenesis has been raised recently by Kusel et al. [14] . Results of this community-based cohort, involving 198 children followed from Early Interventions in Allergic Diseases 383 birth to 5 years, revealed that acute LTR infection caused by rhinovirus or RSV in the first year of life interacted with atopy in infancy (sensitization £ 2 years-old) to promote later asthma [14] . It is well recognized that exacerbations of asthma, in patients with established disease, are often triggered by respiratory viral infections, particularly those caused by rhinovirus. In asthmatic patients, persistence of HRV up to 6 weeks following infection or exacerbation of asthma, has been reported [29, 30] , suggesting that an aberrant immune response to HRV may be involved in the development of acute exacerbations in atopic individuals with asthma. Also, coexistence of atopy enhances the clinical effect of HRV infection, increasing intensity and duration of bronchial hyperreactivity [31] . Finally, it has been suggested that repetitive viral infections might confer protection to development of asthma, based on their ability to skew the immune system away from the Th2-type response [13, 15]. Day-care attendance and/or siblings significantly increased the likelihood of occurrence of RSV or rhinovirus infections, and increased the risk of rhinovirus-induced wheezing at an early age. Neonatal interferon (IFN)-g responses were lower in infants with high frequency of respiratory infections; conversely, frequent infections were associated with a smaller decline of IFN-g responses during the first year of life, indicating that pre- existing immunologic factors may influence the expression of viral infections in infancy [15] .

Breast Feeding

Exclusive breast feeding for at least 4 months has been associated with protection against development of asthma or atopic diseases [32, 33], but other studies have failed to demonstrate protection by breast milk [34] . Bottcher et al. [35] found no relationship in levels of cytokines (IL-4, IL-5, IL-6, IL-8, IL-10, IL-13, IL-16, IFN- g , TGF- b 1, TGF- b2), chemokines (RANTES, eotaxin) or secretory IgA in breast milk, and development of sensitization or allergic symptoms, or levels of salivary IgA during the first 2 years of life.

Endotoxin

Endotoxin is a constituent of the outer membrane of gram-negative bacteria, found ubiquitously in nature, being present in most indoor environments as a component of house dust. Endotoxin stimulates the release of potent proinflammatory cytokines. Exposure to high levels of endotoxin in dust is associated with induction of asthma in sensitive patients [36, 37] . It has been demonstrated that bacterial endotoxin is capable of producing Th1- associated cytokines, IFN-g , and IL-12 and therefore, has the potential to decrease 384 L.K. Arruda et al. allergen sensitization. Chronic endotoxin exposure, before polarized T-cell responses are established, might be expected to protect against allergen sensitization by continuously enhancing Th1-type lymphocyte development [38] . This assumption has been partially confirmed by studies in humans showing that exposure to high levels of endotoxin in early life was associated with protection against allergic sensitization [39, 40] . An experimental study with pregnant BALB/c mice has shown that combined exposure to endotoxin during prenatal and postnatal phases suppressed allergen- specific sensitization (IgE production), eosinophilic airway inflammation (reduced numbers of eosinophils in bronchoalveolar lavage fluids), and in vivo airway reactivity in response to methacholine. The suppression of allergen-mediated inflammatory responses was associated with increased Toll-like receptor and T-bet expression by lung tissues and a shift toward predominantly Th1 immune responses [41] . Similar results were observed by Wang and McCusker [42] . The relationship of exposure to microbial agents (endotoxin, fungal agents, and other microbial contaminants) early in life (3 months of age) and the development of atopic sensitization and physician-diagnosed asthma and wheeze in the first 4 years of life, in children of atopic mothers, was investigated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study. A significant reduction in the development of asthma was associated with early exposure to these substances [43] . Children who were born and raised in a farm environment and exposed to poul- try and livestock were reported to have lower prevalence of asthma and/or allergic diseases in comparison to those living in urban area [44, 45] . Until recently, exposure to high levels of endotoxin was associated with exposure to farm animals, presence of pets in home, number of people living in the house, and cleaning habits [46] . However, results of a study carried out on children from rural areas in Europe, evaluating farm-related exposures and health outcomes, revealed that levels of endotoxin and extracellular polysaccharides were associated with health outcomes independent of farm exposures [47] . It has recently been shown by Simpson et al. that the impact of endotoxin may be genetically determined [48] . In the setting of a birth cohort study, increasing endotoxin exposure was associated with reduced risk of allergic sensitization and eczema, and increased risk of nonatopic wheeze, only in children with the CC genotype at −159 of the CD14 gene [48] .

Pet Ownership

Several prospective birth cohort studies have raised the issue of whether keeping of pets , particularly keeping of dogs or cats, might decrease the risk of developing sensitization to those allergens and have confirm these results in part [49– 51] . A systematic review of the scientific literature concerning keeping of pets within the first 2 years of life and prevalence of asthma has shown that exposure to pets Early Interventions in Allergic Diseases 385 was associated with increased risk of asthma and wheezing in children older than 6 years of age and a tendency for protection in those aged below 6 years [52] . In a recent study, a protective effect of early exposure to cat was documented [53] ; however it hasn’t happened unanimously and some bias of selection may have accounted for the results. So, the protective effect observed might be attributable to allergen or other exposures associated with pet ownership (eg. Endotoxin), but may in part be due to the prior removal of pets in families where children are sensitized or symptomatic or in families with a positive history for atopy at the time the child was born [49] . Platts-Mills and colleagues [54] while evaluating the immune response among 226 children, 47 of whom had asthma and airway hyperresponsiveness, have demonstrated that increasing the exposure to house dust mites was associated with an increase in frequency of sensitization to dust mite allergen. The highest category of exposure to cat allergen though was associated with decreased frequency of sensitization and higher prevalence of IgG antibody to Fel d 1. However, the occurrence of sensitization to dust mite or cat allergens was the strongest independent risk factor for asthma (mite OR = 4.2; cat OR = 6.1).

Tobacco Smoke

Maternal tobacco smoking during gestation is an important avoidable risk factor associated with elevated levels of IgE in cord blood, subsequent asthma and allergic diseases in childhood [55– 57] , and reduction of pulmonary function in children [58] . Increased production of IL-13 by cord blood cells has been found in newborns whose mothers had smoked during gestation as compared with those who never smoked [56] . Macaubas et al. [59] reported a direct relationship of maternal tobacco smoking with both low concentrations of IL-4 and IFN-g in cord blood and increased risk of wheezing by age 6 years. A recent experimental study on BALB/c mice has shown that daily in utero exposure to maternal tobacco smoking was associated with exacerbation of subsequent adult responses to initial allergen exposure [60] . There is a strong body of evidence to support the role of exposure of children to environmental tobacco smoke (ETS) in increasing the incidence of asthma, wheeze, cough, bronchitis, bronchiolitis, pneumonia, and impaired pulmonary function. ETS increases both the prevalence and severity of asthma, as judged by increases in the frequency of attacks, the number of emergency room visits, and the risk of intubation [55, 57] . The risk associated with parental smoking seems to be greater at younger ages. Although a dose–response relationship between ETS exposure and respiratory outcomes has been demonstrated, at present there is no threshold dose of ETS exposure below which an effect will not occur, and therefore active intervention measures and policies to reduce or eliminate children’s exposure to ETS should be strongly encouraged [55] . Polymorphisms in the proinflammatory cytokine genes tumor necrosis factor-a (TNF) and lymphotoxin-a (LTA) have been associated with asthma and atopy in some 386 L.K. Arruda et al. studies. Secondhand smoke and ozone both stimulate TNF production. In a recent study, Wu et al. genotyping six tagging single nucleotide polymorphisms (SNPs) in TNF and LTA have observed that genetic variation in TNF may contribute to childhood asthma and that association may be modified by parental smoking [61] . A home-based, individualized, intervention study [62] carried out among inner city children with atopic asthma which included education and remediation for exposure to both allergens and ETS, resulted in reduction of asthma associated morbidity.

Therapeutic and Preventive Strategies

Perspectives of Treatment and Prevention of Respiratory Viral Infections

Few specific interventions are available to reduce the impact of respiratory viruses. No vaccine is currently available for RSV prophylaxis. The disease enhancement caused by formalin-inactivated vaccine in the 1960s plus results of more recent unsuccessful trials of live-attenuated vaccines, have significantly slowed progress toward an RSV vaccine. Passive immunization/immunoprophylaxis with monthly infusions of RSV immunoglobulin or monthly intramuscular injections of humanized monoclonal antibody, during the RSV season, reduced the incidence and severity of RSV infections in high-risk children including those preterm babies less than 6 months-old, children with congenital heart disease, and children less than 2 years with bronchopulmonary dysplasia [4] . The large number of HRV serotypes with minimal cross-antigenicity has hampered the development of an HRV vaccine. It may be possible to reduce exposure to HRV by washing of hands after contact with a cold sufferer or after handling objects that may have been contaminated with respiratory secretions [5] . Immunization with formalin-inactivated or live-attenuated multivalent influenza virus vaccines and chemoprophylaxis for influenza virus A are the methods available for preventing influenza. Influenza vaccine is used prior to the influenza season. The inactivated vaccine has an approximate 70–90% efficacy in preventing illness in healthy children and adults. In summary, there are virtually no effective strategies targeted at the respiratory viruses for treatment or prevention of viral-induced wheezing illnesses in children. However, evidence indicates that treatment of lung inflammation with inhaled corticosteroids or blocking viral-induced overproduction of leukotrienes with leukotriene-receptor antagonist Montelukast may be effective in decreasing severity and frequency of viral-induced wheezing in young children with recurrent or persistent symptoms [63, 64] . A double-blind, controlled trial (PREVIA study) investigated the effect of treatment with Montelukast for 12 months in 2–5 years-old children with intermittent asthma. Approximately half of these children were positive for at least one respiratory virus, including HRV, coronavirus, and RSV in their nasal Early Interventions in Allergic Diseases 387 aspirates during exacerbations of symptoms. The results showed that Montelukast had a beneficial effect, decreasing frequency of exacerbations, increasing time between acute wheezing episodes, and reducing the need for inhaled corticosteroids during exacerbations [64] .

Environmental Interventions in Genetically Predisposed Infants

Preventive strategies have focused on manipulating the environment of high-risk individuals as an attempt to reduce the prevalence of allergies and asthma in children. At present, six primary prevention controlled studies are in progress [65] . The longest follow-up reported has been from the Isle of Wight study [66] . In this randomized, controlled study, a group of 120 high-risk infants was recruited prenatally, and development of allergic diseases and sensitization to common allergens was assessed at ages 1, 2, 4 and 8 years. Intervention included strict elimination of common food allergens (dairy products, egg, wheat, nuts, fish, and soy) to the age of 12 months. Lactating mothers followed the same restriction diet (except wheat) for the duration of breast feeding. Extensively hydrolyzed formula was given as a supplement to the child from birth, or when breast feeding was discontinued before 9 months. Stringent allergen avoidance measures were also instituted at birth, aimed at reducing exposure to house dust mites. Repeated measurement analysis showed a sustained preventive effect of allergen avoidance on asthma, atopic dermatitis, and sensitization to allergens over the period of the first 8 years of life, and on allergic rhinitis at age 8 [67] . Therefore, the conclusion was that stringent avoidance of mite and food allergens applied to high-risk children in infancy were beneficial and resulted in reduction of allergic sensitization and clinical manifestations of allergy, beyond the period of avoidance [67] . Likewise, outcome of the Canadian Primary Prevention Study on high risk infants has been reported at age 7 years, showing that intervention during the first year of life, comprising avoidance of mite, pet allergens and ETS, as well as dietary regimen, resulted in reduction of asthma symptoms and asthma diagnosed by a pediatric allergist in the intervention group. In the Canadian study, no significant effect of intervention was observed for bronchial hyperreactivity, allergic sensitization, allergic rhinitis, or atopic dermatitis at age 7 years [68] . Initial results from other cohorts look promising; however further follow-up will be necessary before any recommendations can be made [65] . Results of the Manchester Asthma and Allergy Study (MAAS) have been reported up to the age of 3, and showed that stringent mite and pet allergen avoidance measures starting during gestation, resulted in decrease in severe wheezing and exercise induced wheezing at age 1, and improved pulmonary function in the intervention group at age 3. However sensitization to mites was increased at 3 years of age [69] . In the Study of Prevention of Allergy in Children in Europe (SPACE), environmental control measures aimed at reducing exposure to dust mite allergens at birth and education failed to prevent sensitization at age 2 [70] . Another study looking at the effects of mite avoidance measures during gestation and education. The PIAMA study, showed a modest benefit 388 L.K. Arruda et al. of reduction of cough apart from colds at 2 years of age [71] . The results of the Childhood Asthma Prevention Study (CAPS), carried out in Australia, revealed that house dust mite allergen avoidance in conjunction with supplementation of diet with omega-3 fatty acids (abundant in fish and canola-based oils), applied to children with high risk of asthma, resulted in decrease in cough and sensitization to mites at 3 years of age , with no significant differences in wheeze [72] . The conclusion of these prospective studies so far is that environmental measures taken to decrease exposure to dust mite allergens, even if started during gestation, appear to have limited beneficial effects. However, dust mite avoidance in conjunction with stringent dietary avoidance measures applied to high-risk infants of highly motivated families, may result in prevention of sensitization and clinical manifestations of allergy up to 8 years. Follow-up of some of the studies is still too short to allow more definitive recommendations.

Pharmacological Treatment

The prophylactic treatment with an antihistamine, ketotifen, in atopic dermatitis patients was followed by a fourfold reduction in incidence of asthma related symptoms, mainly in those with high levels of serum total IgE [73] . Similar results were observed among children with high risk of developing asthma. The incidence of asthma in preasthmatic patients treated with ketotifen was 9% versus 31% in the placebo group [74] . Warner et al. have evaluated long-term treatment with cetirizine as a preventive tool for the onset of asthma in children aged less than 2 years with atopic dermatitis and without asthma, in a double-blind, randomized, placebo-controlled trial (the Early Treatment of the Atopic Child, ETAC study). At the end of 18 months of active treatment, they observed a significant reduction in the onset of asthma among grass pollen-sensitized infants and dust mite-sensitized infants. These differences were sustained only for the grass pollen-sensitized infants after 18 months of treatment interruption. They concluded that cetirizine truly delays or, in some cases, prevents the development of asthma in a subgroup of infants with atopic dermatitis sensitized to grass pollen and, to a lesser extent, to house dust mite [75] . More recently, preliminary results of the Early Prevention of Asthma in Atopic Children (EPAAC) study, shows that the use of levocetirizine daily for 18 months was safe among atopic children 12–24 months of age [76] . On the whole, these studies indicate that the antihistamines ketotifen, cetirizine, and levocetirizine are safe for use in very young atopic children, and that they may have a role in preventing development of asthma in some of these children, particularly those with atopic dermatitis, and those allergic to house dust mite and grass pollen at an early age [76] . The hypothesis that early introduction of inhaled corticosteroids in young children at high risk of developing asthma could change the natural history of the disease has been investigated. A recent study in preschool children at high risk of asthma revealed that 2 years of treatment with inhaled corticosteroid was highly effective in reducing symptoms and asthma exacerbations, though the benefit was Early Interventions in Allergic Diseases 389 no longer present during a third treatment-free year, indicating that corticosteroids may not have disease modifying effects [63] . In this trial, the Prevention of Early Asthma in Kids (PEAK), 285 children aged 2–3 years were randomized to receive either 88 mcg Fluticasone twice daily for 2 years or placebo, and at the end of the second year, treatments were interrupted. Clinical and functional differences favoring the children treated with inhaled Fluticasone disappeared a few weeks after discontinuation of regular treatment. Recently, two other studies carried out in the United Kingdom and Denmark [77, 78] reached similar conclusions as the PEAK trial: very early treatment of asthma with inhaled corticosteroids, even before the persistent form of the disease has become evident, does not change the natural clinical course of the disease, and does not seem to affect the level of lung function attained at the end of follow-up, despite the fact that this form of treatment is very effective in controlling asthma symptoms while in use [79] .

Allergen-Specific Immunotherapy

Specific immunotherapy (SIT) administered by the subcutaneous route is an efficient treatment for IgE-mediated disease to defined allergens [80] . Beneficial effects of SIT in children have been demonstrated in preventing new sensitizations in children monosensitized to mites [81, 82] and in slowing the progression to asthma in those with seasonal allergic rhinitis, sensitized to pollen allergens (the PAT study) [83] . Follow-up of children with allergic rhinitis sensitized to birch or grass pollens, who underwent SIT for 3 years [83] showed that the effect of SIT in preventing development of asthma was still evident 2 years after SIT was discontinued [84] . Concerns regarding the use of SIT in asthma include the possibility of severe anaphylaxis; however guidelines have been developed to minimize risks of reaction [80] . Sublingual immunotherapy (SLIT) is increasingly being regarded as an efficient tool for the treatment of patients with asthma and/or rhinitis, as indicated by results of meta-analysis of studies carried out in children and adults [85] . The increased safety and ease of administration of SLIT makes this strategy very attractive as a form of early intervention in young children with IgE-mediated disorders, which could modify the natural course of allergic diseases. Studies addressing the use of SLIT in young children however have not been reported. Issues including standardization of the vaccines, establishment of effective doses and schedules for administration, compliance, and better understanding of mechanisms of action and magnitude of efficacy need further research [85] .

Conclusions

Evidence suggests that events taking place between 2 and 3 years of age might be crucial determinants in the development of allergies and asthma [86] . Strategies to prevent development of sensitization and progression to disease or to elicit long 390 L.K. Arruda et al.

Table 1 Recommendations based on the World Allergy Organization Project Report and Guidelines on Prevention of Allergy and Allergic Asthma – primary prevention Infants without a special risk for allergic diseases Exclusive breast feeding for 6 months is recommended by the WHO: if a supplement is needed, a conventional cow-milk-based formula is recommended (B) No special maternal diet during pregnancy or lactation (A) Avoidance of solid foods until 6 [4] months of age (B) Avoidance of exposure to tobacco smoke (also during pregnancy) (B) Infants with a high risk for allergic diseases Exclusive breast feeding for at least 6 months: if a supplement is needed, a documented hypoallergenic formula is recommended for the first 4 months of life; after the age of 4 months, high-risk children can receive the same nutrition as nonhigh-risk children (A) No special maternal diet during pregnancy or lactation (A) Avoidance of solid foods until 6 [4] months of age (B) Environmental measures Avoidance of tobacco smoke (also during pregnancy) (B) Reduction of allergen exposure early in life (house dust mites, furred pets, cockroaches) (B) Avoidance of damp housing conditions (C) Avoidance of pollutants (C)

Table 2 Recommendations based on the World Allergy Organization Project Report and Guidelines on Prevention of Allergy and Allergic Asthma – secondary prevention Avoidance of tobacco smoke (B) Patients who have perennial asthma, rhinitis, or eczema and who are allergic to house dust mites or animal dander should try to reduce their exposure to the relevant allergens (A, B). Recommended measures include: Removal of relevant pets Reduction of indoor relative humidity below 50% if possible Encasing of mattresses with documented protective coverings Washing of pillows in hot water (>55°C) regularly or encasing of pillows with documented protective coverings Washing of bedding in hot water (>55%) regularly (every 1–2 weeks) Removal of carpets in bedroom

lasting remission of symptoms are strongly desirable. However, current environmental interventions and treatment modalities with pharmacotherapy do not meet these expectations. According to the recent published World Allergy Organization Project Report and Guidelines on Prevention of Allergy and Allergic Asthma document [87] , some evidence-based recommendations can be highlighted (Tables 1 and 2 ).

Acknowledgments Dr. L. Karla Arruda’s research on risk factors for asthma in children in Brazil is supported by FAPESP and CNPq, Instituto de Investigação em Imunologia, L.K.A. and D.S. are recipients of CNPq scholarships. Early Interventions in Allergic Diseases 391

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72. Peat JK, Mihrshahi S, Kemp AS, Marks GB, Tovey ER, Webb K, Mellis CM, Leeder SR. Three-year outcomes of dietary fatty acid modification and house dust mite reduction in the Childhood Asthma Prevention Study. J Allergy Clin Immunol 2004;114:807–13 73. Iikura Y, Naspitz CK, Mikawa H, Talaricoficho S, Baba M, Sole D, Nishima S. Prevention of asthma by ketotifen in infants with atopic dermatitis. Ann Allergy 1992;68:233–6 74. Bustos GJ, Bustos D, Bustos GJ, Romero O. Prevention of asthma with ketotifen in preasthmatic children: a three-year follow-up study. Clin Exp Allergy 1995;25:568–73 75. Warner JO; ETAC Study Group. Early Treatment of the Atopic Child. A double-blinded, randomized, placebo-controlled trial of cetirizine in preventing the onset of asthma in children with atopic dermatitis: 18 months’ treatment and 18 months’ posttreatment follow-up. J Allergy Clin Immunol 2001;108:929–37 76. Simons FE; Early Prevention of Asthma in Atopic Children (EPAAC) Study Group. Safety of levocetirizine treatment in young atopic children: An 18-month study. Pediatr Allergy Immunol 2007;18:535–42. Epub 2007 Jun 11 77. Murray CS, Woodcock A, Langley SJ, Morris J, Custovic A; IFWIN study team. Secondary prevention of asthma by the use of Inhaled Fluticasone propionate in Wheezy INfants (IFWIN): double-blind, randomized, controlled study. Lancet 2006;368:754–62 78. Bisgaard H, Hermansen MN, Loland L, Halkjaer LB, Buchvald F. Intermittent inhaled corticosteroids in infants with episodic wheezing. N Engl J Med 2006;354:1998–2005 79. Martinez FD. Asthma treatment and asthma prevention: a tale of 2 parallel pathways. J Allergy Clin Immunol 2007;119:30–3 80. Bousquet J, Lockey R, Malling HJ, Alvarez-Cuesta E, Canonica GW, Chapman MD, Creticos PJ, Dayer JM, Durham SR, Demoly P, Goldstein RJ, Ishikawa T, Ito K, Kraft D, Lambert PH, Lowenstein H, Muller U, Norman PS, Reisman RE, Valenta R, Valovirta E, Yssel H. Allergen immunotherapy: therapeutic vaccines for allergic diseases. World Health Organization. American academy of Allergy, Asthma and Immunology. Ann Allergy Asthma Immunol 1998;81:401–5 81. Des Roches A, Paradis L, Menardo J-L, Bouges S, Daurés J-P, Bousquet J. Immunotherapy with a standardized Dermatophagoides pteronyssinus extrat. VI. Specific immunotherapy prevents the onset of new sensitizations in children. J Allergy Clin Immunol 1997;99:450–3 82. Pajno GB, Barbeiro G, De Luca F, Morabito L, Parmiani S. Prevention of new sensitization in asthmatic children monosensitized to house dust mite by specific immunotherapy. A six year follow-up study. Clin Exp Allergy 2001;31:1392–7 83. Möller C, Dreborg S, Ferdousi HA, Halken S, Høst A, Jacobsen L, Koivikko A, Koller DY, Niggemann B, Norberg LA, Urbanek R, Valovirta E, Wahn U. Pollen immunotherapy reduces the development of asthma in children with seasonal rhinoconjunctivitis (the PAT-Study). J Allergy Clin Immunol 2002;l09:251–6 84. Niggeman B, Jacobsen L, Dreborg S, Ferdousi HA, Halken S, Høst A, Koivikko A, Koller D, Norberg LA, Urbanek R, Valovirta E, Wahn U, Möller C; PAT Investigator Group. Five-year follow-up on the PAT study: specific immunotherapy and long-term prevention of asthma in children. Allergy 2006;61:855–9 85. Pajno GB. Sublingual immunotherapy: the optimism and the issues. J Allergy Clin Immunol 2007;119:796–801 86. Kurukulaaratchy RJ, Matthews S, Arshad SH. Does environment mediate earlier onset of the persistent childhood asthma phenotype? Pediatrics 2004;113:345–50 87. Host A, Boner A, Odhiambo J, Custovic A, Lockey R. Preventive measures: early interventions In: Joahansson SGO, Haahtela T (eds) Prevention of Allergy and Allergic Asthma – World Allergy Organization Project Report and Guidelines. Karger, Basel, 2004, pp135–151 Birth Cohort Studies for the Prevention of Allergy: New Perspectives—Where Do We Go from Now?

Mascha Rochat and Erika von Mutius

Introduction

There has been an increase in the prevalence of asthma and other allergic diseases in both industrialized and developing countries over the past decades [1] . In population based studies, prevalence estimates of asthma, atopic dermatitis, and allergic rhinitis vary from 7–10%, 15–20%, and 15–20%, respectively [2, 3] , and different increase rates of each of these diseases have been reported in countries around the world [1, 4] . The reasons for this increase are still largely unknown, but interactions between various types of environmental exposures in populations with distinct genetic backgrounds have been proposed [1] . Allergic diseases have therefore become a major public health problem as well as a burden to health care resources, and they not only adversely affect the quality of life of millions of children and adults, but most importantly can be life-threatening in their most severe form. An urgent need to formulate strategies, leading to a reduction of their morbidity and mortality is thus required. This reduction could be achieved through primary or secondary prevention, and much research in both areas has been undertaken.

Study Design

A necessary prerequisite for effective primary prevention measures is to know the different determinants of allergic diseases. Many determinants have been studied, discovered and defined through different study types during the last decades; but as described below, each of these study designs has distinct advantages and disadvantages, and should be adopted after due consideration.

M. Rochat and E. von Mutius () University Children’s Hospital , Lindwurmstr. 4 , 80337 , Munich , Germany e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 397 DOI 10.1007/978-4-431-99362-9_24, © Springer 2010 398 M. Rochat and E. von Mutius

Cross-Sectional Studies

Most of the risk and protective factors such as housing conditions (dampness), allergen exposure, active and passive smoking, pet keeping, breastfeeding or viral infections were primarily identified through cross-sectional or retrospective studies. The term cross sectional study is used to describe a study design that measures the prevalence of exposures and diseases in a given population simultaneously. The potential of cross-sectional studies is to generate hypotheses and, in case of consistent findings across numerous studies, suggest causal relations, particularly, if dose- response patterns can be observed. They are, however, limited in their capacity to describe a time sequence between potential risk factors and health effects. The fact that they can be done in a relatively short period of time and are less expensive than cohort studies confers advantages.

Cohort Studies

To assess whether a time sequence, meaning the necessity for the cause to precede the outcome, is present, the study design should be prospective and include accepted well- defined diagnostic criteria and outcome measures, a sufficient duration of follow-up, and a proper sample size for adequate statistical evaluation [5] . In Ancient Rome, a cohort was one of ten divisions of a Roman military legion and was constituted with young men of similar age coming from one region. Members were often injured or killed in service but were not replaced. The cohort was then disbanded when the term of enlistment was over [6] . Historically, the term “cohort” was introduced into epidemiological studies in 1935 by Dr. Wade Frost, the leading US-American epidemiolo- gist of the time [7] . He used the term to describe what would now be called generation studies. Over the years, its current meaning slowly emerged and a cohort study is now a well defined study design. A cohort study tracks outcome(s) forward in time. At the beginning of the observation period, the probands can be divided into two or more groups based on exposure, treatment, and/or risk factors. The groups are then followed for a period of time and the incidence of the outcome(s) is documented. The cohort can be drawn from the general population or a population at high risk for developing the respective disease. A birth cohort is a cohort of individuals born within a given period of time. It is often used to define a cohort of children followed since birth (or since pregnancy). Unfortunately cohort studies are very expensive and time consuming, and absence of follow-up may cause major problems.

Observational Birth Cohort Studies

Observational cohort studies are considered “natural” experiments where the natural course is observed. Several observational birth cohort studies investigating allergies were initiated during the last decades. The aims were to identify risk factors that Birth Cohort Studies for the Prevention of Allergy 399 could be modified to prevent or limit the development of allergic diseases; and predictors to target potential prevention strategies in the susceptible population.

Interventional Birth Cohort Studies

For conclusive proof of evidence for causal relationships, well-designed, double- blind randomised controlled trials or interventional cohort studies including a control for confounders, as well as proper registration of compliance and follow-up of dropouts are required [5] . In interventional studies, two or more groups are recruited at the beginning of the trial and one or more interventions are initiated. At least one group is left to its natural course and is used as a control. All groups are then followed for a given period of time. Unfortunately, interventional studies with proper randomisation and double blinding are not always possible. The effect of breastfeeding or maternal smoking, for example, cannot be tested by means of randomised controlled trials for obvious ethical reasons. Even though interventional studies can address either the general population or children at high risk of developing allergic diseases, most of them have been performed on high risk children to maximize the benefits, reduce the expense of recruiting a large population, and obtain maximum co-operation from the parents. The definition of high risk is, however, very heterogeneous. Some studies used a questionnaire based approach asking about allergy or asthma in first degree relatives (mother, biological father, siblings). Others confirmed the diagnosis with laboratory tests (specific IgE, skin-prick test or elevated cord blood IgE). Similarly, hereditary was defined either as single or multiple. In general, interventions aiming at the prevention of allergies can be categorized into two aspects: “avoidance” and “immune deviation”. The “avoidance” concept is based on the expectation that by avoiding allergens during the critical period of sensitization, the immune system will not react to these allergens later on and allergic diseases will not occur. The “immune deviation” concept postulates that the immune system can be “educated” to develop tolerance to environmental allergens. During the last decades, there have been an increasing number of prospective interventional birth cohorts, testing either one or multiple of the known risk or protective factors. Most of them have been based on the avoidance concept.

Defining Allergies

As mentioned above, the determinants of allergic diseases are a prerequisite for preventive measures, but a precise definition of the disease is equally mandatory. Even though such a statement seems obvious, it is in fact a challenge to define an allergic “outcome”, as the term allergy describes various diseases among which asthma, allergic rhinitis and atopic dermatitis are the most common. But other diseases such as urticaria or food allergy can also be found under this umbrella term. 400 M. Rochat and E. von Mutius

Therefore, different research groups reporting on allergies may actually be reporting on very different disease entities. Atopic diseases were originally grouped under one term because they are associated with an elevation of either total or specific immunoglobulin E (IgE) (also termed “atopy”). This association is, however, loose and many patients with “atopic” illnesses have normal IgE levels and lack specific IgE antibodies in their serum. The relevance of allergic sensitization as an outcome is furthermore to be debated since not many children with a positive allergy test either as prick or RAST test are asymptomatic [8] . Given this ambiguity, the EAACI recently revised the nomenclature and proposed standard definitions in 2001 and subsequently in 2004 [9] . But, as these have not always been used, comparisons between the different studies are often difficult, if not impossible. This may partly explain why controversial results emerge from different studies. To complicate matters even further, some diseases have been divided into different phenotypes. Asthma, for example, which is a chronic inflammatory disorder of the airways that can cause recurrent episodes of wheezing, breathlessness, chest tightness, and cough in susceptible individuals has been shown to begin in early life with wheezing symptoms. Based on the time of onset, the natural course and the different risk factors and determinants, wheezing children can be grouped into at least three different phenotypes: transient wheezers (present only in the first 3 years of life); persistent wheezers (beginning in the first 3 years and persisting beyond 3 years of age); and late-onset wheezers (beginning between 3 and 6 years of age) [10] . Taking into account these different phenotypes, it can be postulated that asthma may not be one disease but rather a syndrome and that distinct mechanisms underlie the apparently equivalent clinical manifestations.

Natural Course of Allergic Illnesses

It is very important to take into consideration the natural course of the disease when evaluating potential preventive measures. Even though no clinical symptoms are detectable at birth, recent studies show evidence that food and inhalant allergens can reach the fetal circulation [11] . However, the role of this exposure in determining subsequent patterns of immunologic memory and disease is conflicting [12, 13] . In infancy, the main allergic outcomes are atopic dermatitis, gastrointestinal symptoms and recurrent wheezing, whereas asthma and allergic rhinoconjunctivitis are the main diseases later in childhood [14] . Adverse reactions to foods, mainly cow’s milk, hen’s egg, peanut, wheat and soy protein are most common in the first years of life, whereas allergy to inhalant allergens such as house dust mites, animal dander and pollen mostly occurs later [15] . Recent findings from the German Multicentre Allergy Study (MAS) birth cohort suggest that in most cases asthma does not follow a first manifestation of atopic dermatitis claimed as “atopic march”. Rather, in most cases both conditions are either manifest in an individual child or the infant is only affected by one illness. The combination of conditions results in more severe asthma as well as more severe eczema, and lung function parameters are significantly reduced in these children at school age [16] . Birth Cohort Studies for the Prevention of Allergy 401

Risk Factors and Protective Exposures

Prospective birth cohorts have helped us greatly to understand the natural history of allergic diseases by following a cohort of either high risk children or children representative of the general population for various periods of time. Additionally, most of them have studied, and reported specific risk or protective factors. These factors are briefly detailed below, with an emphasis on the ones that have been studied in interventional studies.

Nutrition

Maternal Diet

There is strong evidence that maternal dietary allergens can cross the placental barrier and pass into the breast milk [17, 18] . The hypothesis, that reduced maternal allergen intake may reduce fetal allergen exposure and thus avoid early sensitization was therefore tested in a number of studies. Mothers were asked to refrain from consuming a varying number of allergenic products (cow’s milk, eggs, peanuts, fish, citrus fruits) [19– 21] either during pregnancy, lactation or both [19– 22] for a period of time ranging from four weeks to a few months. Despite the variety of study approaches, no conclusive evidence of a preventive effect of maternal dietary restrictions during pregnancy or lactation on the development of allergic diseases was observed [19– 23] . On the contrary, potential adverse effects on maternal nutritional status and on gestational weight gain, fetal growth and preterm birth have been observed [23] . As maternal dietary interventions did not have an effect on the development of allergic diseases, other dietary habits were investigated. The substantial shift in dietary fatty acid intake in many populations around the world favouring n-6 polyunsaturated fatty acid (PUFA) (margarine, vegetable oil) over n-3 PUFA (oily fish) resulted in the hypothesis that the intake of certain fatty acids may increase the risk of developing allergies. Observational studies assessing maternal dietary intake during the last 4 weeks of pregnancy [24] or the PUFA content of breast milk [25] concluded that low levels of n-3 PUFA intake correlated with the development of allergic diseases or atopic eczema during the first two years of life. These findings were, however, not confirmed when using skin test reactivity as an outcome [26] . Interventional studies are needed before any firm recommendation can be issued.

Breastfeeding

A recent review of the literature [27] reported a protective effect of exclusive breastfeeding on the development of allergic diseases especially among high risk children. Even though one long-term prospective birth cohort confirmed these findings [28] , 402 M. Rochat and E. von Mutius several recent long-term observational birth cohort studies not included in the previously published meta-analyses have shown breastfeeding to be a risk factor for the development of allergic diseases mainly in high risk children [29] . Matheson et al [30] followed a cohort from childhood to middle-age and concluded that “in high risk children, breast-feeding, although important for the protection of the infant against early wheezing illness (asthma), eczema, and food allergies, does not appear to protect against the development of asthma, allergic rhinitis, or food and inhalant allergies in the long term”. Truly randomised interventional birth cohorts on exclusive breastfeeding cannot be performed for ethical reasons, but Kramer et al [31] used a similar approach and performed a cluster randomised trial by selecting at random study areas in Bellarussia where breastfeeding was promoted. The investigators followed 13,889 children up to the age of 6 years. Children in the interventional sites were significantly more likely to be breastfed and by the age of 6 years no protective effect of prolonged and exclusive breastfeeding on asthma or allergy was found.

Hypoallergenic Infant Formula

If breastfeeding is not possible, products with highly reduced allergenicity based on hydrolysed protein or amino acid mixtures can be used as a substitute. A number of interventional cohort studies on different formulas have been undertaken. Most of the studies were performed in high risk populations, only a few were in the general population. The study designs and formulas under investigation differed considerably between the studies, which rendered comparisons difficult [32] . Cow’s milk was compared to hydrolyzed or extensively hydrolyzed casein formula or to partially hydrolyzed or extensively hydrolyzed whey formula in different combinations. Taken together, the results indicate that a hydrolysed formula is not superior to exclusive breastfeeding for the prevention of allergy. Among high risk infants who cannot be exclusively breastfed, there is some evidence to suggest that prolonged feeding with a hydrolysed formula as compared to a cow’s milk formula reduces transiently the incidence of infant and childhood atopic dermatitis, but not asthma in the first years of life [33] . Longitudinal studies following children up to school age are needed to see whether there is any prolonged benefit from such interventions.

Infantile Diet

The evidence that introduction of solid foods to infants before 4 months of age increases the risk of allergic diseases is conflicting. In general, there is insufficient evidence to suggest that on its own, the early introduction of solids to infants is associated with an increased incidence of asthma, food allergy and allergic rhinitis. Unfortunately, many studies lack a rigorous design and are thus susceptible to multiple biases. No evidence was found to support a delayed introduction Birth Cohort Studies for the Prevention of Allergy 403 of solid foods beyond the sixth month of life for the prevention of atopic dermatitis or atopic sensitization [34] . However, there is a consistent association between the persistence of eczema and the introduction of solid foods before age 4 months that is supported by long term follow-up studies and the dose-dependent nature of the association. Furthermore, it is also noteworthy that the preventive effect of breastfeeding and hydrolyzed formulas was only observed in studies including avoidance of complementary foods during at least the first 4 months of life [35] . Clearly, additional evidence from well designed randomised longitudinal studies is needed to endorse recommendations on delayed solid food introduction in infancy. Prospective studies investigating the potential effects of other dietary factors such as fish oil, omega-3 fatty acids, antioxidants (vitamin C, vitamin E and selenium), magnesium or sodium which have been found to be either protective or risk factors in cross-sectional studies are still awaited.

Probiotics

Observational studies have found a correlation between the colonization of the gastrointestinal tract with lactobacillus as well as eubacteria and a decrease in allergic diseases [34] . During the last years, interventional birth cohorts have therefore examined the effect of different doses of probiotics (live microbial food ingredients) on the development of allergic diseases. All studies were conducted on high risk infants and each studied a different probiotic bacterial strain. After administering either the probiotics Lactobacillus GG, Lactobacillus reuteri or a mixture of four probiotics and one prebiotic to pregnant women and subsequently to their offspring for the first 6 [36, 37] and 12 [38] months, three studies saw a protective effect on the incidence of eczema [36] and atopic eczema [37, 38] up to the age of 2 [37, 38] and 7 years [36] . One survey administered Lactobacillus acidophilus to infants during the first 6 months, but not to their mothers during pregnancy [39] . The authors found an increase in atopic eczema, but did not see an effect on the cumulative incidence of eczema at the age of 12 months. Whether these contrasting results are attributable to different bacterial strains or to the postnatal administration remains unclear. Moro et al. showed a beneficial effect of a mixture of prebiotic oligosaccharides (GOS/FOS) added to bottle fed infants in reducing the incidence of atopic eczema during the first six months of age [40] . Taken together, the current evidence suggests that probiotics might have a preventive effect on the development of eczema. However, in our opinion, a number of issues remain unanswered which preclude firm recommendations on the use of probiotics for the prevention of allergies: which is the best probiotic strain? What is the optimal dose? Is there any effect among children from the general population without a family history of atopic diseases in first degree relatives? Is this preventive effect prolonged into childhood years? Are other allergic illnesses such as asthma and hay fever also amenable to prevention by the administration of probiotics? 404 M. Rochat and E. von Mutius

Environmental Factors

As mentioned above, two concepts prevail with respect to potential preventive strategies. One concept is based on the rationale of risk factor avoidance, particularly of allergen avoidance. The other complementing concept is based on the identification of protective factors, in particular the hygiene hypothesis postulating that “allergies may be the result of a misdirected immune response in the absence of infection” [41] . Many, mostly cross-sectional studies aiming at the identification of harmful and protective environmental exposures for the development of allergies have been performed. In the following sections we will focus on cohort studies investigating either avoidance or immune modulation pathways.

Environmental Tobacco Smoke

Environmental tobacco smoke (ETS) exposure either during pregnancy or early life is one of the most consistent risk factors for the development of respiratory symptoms, wheezing and asthma [1] . Active smoking has been associated with the onset of asthma in adolescents and adults in a number of studies [1] . Exposure to ETS is therefore the most important preventable inducer and trigger of asthma. Because of the consistence of findings across numerous populations worldwide, the avoidance of ETS is warranted for the prevention of asthma and other respiratory diseases. There is less evidence, however, to suggest that ETS exposure also affects the incidence of atopic sensitisation.

Traffic Related Pollution

While it is well accepted that air pollution in general can trigger symptoms in children with established asthma [42] , its influence on the development of allergies is not clear. Cross sectional studies have shown strong evidence to support an association between air pollutants associated with traffic exposure and respiratory health, however, the evidence is conflicting regarding the development of allergic diseases and atopic sensitization. To our knowledge there are only two observational cohort studies among children investigating traffic pollution and health outcome at the ages of two and four years, respectively. As acknowledged by the authors, the short duration of follow-up, limits the interpretation of the results, and the positive relation with wheezing, asthma, and sensitization to food allergens must therefore be interpreted with caution [43, 44] .

Inhaled Allergens

The level of aeroallergen exposure varies according to the geo-economic situation. House dust mite (HDM) is the most important allergen in humid climates; pet allergens might be more relevant in colder countries; Alternaria species prevail in dry Birth Cohort Studies for the Prevention of Allergy 405 climates and cockroach is one of the dominant allergens in inner-city areas in the US. These allergens have been investigated in numerous studies over the past decades, because their exposure affects a persons risk of developing IgE antibodies against them [45] . Without allergens in the environment, specific sensitization towards that allergen cannot occur. In a German birth cohort, the levels of HDM and cat allergen concentrations in domestic carpet dust were strongly related to the development of atopic sensitization towards these allergens in the first 3–7 years of life [46] . A clear dose-response relationship was found as well as a strong effect modification by the familial background, for atopic diseases. In the group of children with a positive family history of atopy, mite allergen concentration below 750 ng/gm dust resulted in a 3% sensitization rate, whereas in the group of children without a positive family exposure up to 25,000 ng/mg dust was associated with a sensitization rate of 3%. These findings indicate that no general exposure threshold for allergic sensitization can be proposed. As might be expected HDM exposure was not related to the propensity of mounting IgE responses towards other environmental antigens. Likewise, the propensity to develop asthma may not be affected by levels of environmental allergen exposure. This notion is supported by findings from prospective cohort studies where no relation between the level of exposure to HDM and the incidence of asthma and persistent wheeze was found [45] . However, the interaction of higher indoor allergen exposure and the development of atopic sensitization towards these allergens in the first 3 years of life resulted in more severe asthma [47] . Recent findings from a number of interventional studies have further corroborated these notions. In the interventional studies, HDM reduction measures were initiated either during pregnancy or at birth, and the children were followed until the ages of 7–8 years old. Although a reduction of HDM could be documented after radical allergen reduction measures were undertaken, the results of one study showed an increased risk in mite sensitization at the age of 3 years, an increase in atopic dermatitis and no significant differences in respiratory symptoms between the interventional and the control groups by the age of 8 [48] . Other studies, using more practical interventional measures such as mattress covers, showed no protective effect on the prevalence of asthma and atopic sensitization up to the age of 2 years [49, 50] . In inner-city areas in the US comprehensive environmental interventions to decrease indoor allergen levels, including cockroach and dust-mite allergens, resulted in reduced asthma-associated morbidity among 5 to 11 year old children [51] .

Pets

As with other allergens, exposure to pet allergen increases the risk of subsequent specific sensitization and thus potentially increases the incidence of allergic diseases. This notion was challenged in 1999 by studies showing that early life exposure to pets was associated with a lower prevalence of allergic rhinitis and asthma at school age and reduced cat sensitization as well as atopy in adulthood. A review of the associations between pet exposure, asthma and asthma like 406 M. Rochat and E. von Mutius symptoms was therefore undertaken by Apelberg in 2001 who concluded that in children over 6 years of age there was a significant increase in the risk of asthma or wheezing, but in children younger than 6 years, exposure to pets had a protective effect [52] . Since then, there have been a number of prospective studies showing a reduced risk of allergic diseases or allergic sensitization in children exposed to cats or dogs in infancy, but consistency among these studies is lacking. Parental, mostly maternal history of asthma or atopy seems to exert significant effect modification with pet exposure being a risk factor in high risk children and a protective factor in low risk children. Additionally, there seems to be marked differences between different animal species, with exposure to dogs showing a more consistent pattern of protection than exposure to cats [53] . An interesting question in analyzing the relationship between pet exposure and allergic sensitization or allergic disease is whether it is exposure to high levels of allergens given off by the pet or exposure to an undefined environmental factor(s) related to the pet that contribute(s) protectively to the determination of the outcome, presumably by effects on the maturation of the immune system [54] . Furthermore, these results must be regarded with caution because of the possibility of reverse causation due to already implemented avoidance strategies in families with atopic heredity. As of today, the available literature does not provide conclusive guidance regarding the effects of pet exposure early in life.

Family Size/Day Care

Among the most consistent associations is Strachan’s original observation that exposure to siblings reduces the risk of developing allergic diseases such as hay fever and eczema [55] . Whether this effect is attributable to an increase of the number of infections transmitted by “unhygienic” contact with older siblings or due to other unknown factors associated with an increased number of pregnancies is unknown. In the absence of a large family, exposure to children in early child care seems to have a similar protective effect [56] . Several observational studies have confirmed these findings in recent years [57, 58] . One cross-sectional study from Kramer et al. found an association between day- care attendance in the first year of life and the development of allergic diseases in single child families [59] . Positive associations were reported in two prospective birth cohorts. Celedon et al. found an inverse association between day care attendance in the first year of life and total serum IgE levels at the age of two [60] , and eczema, as well as asthma and recurrent wheezing in the first 6 years of life among high risk children. This effect was not seen among offsprings of mothers with a history of asthma, where day care attendance was associated with an increased risk of wheezing [61] . In the Tucson birth cohort, young children’s exposure to other children in or out of the home was found to result in more frequent wheezing in the first few years of life and subsequently to decreased levels of serum IgE concentrations, skin test reactivity and to protection against the development of asthma and frequent wheezing later in childhood [62] . Birth Cohort Studies for the Prevention of Allergy 407

Infections

Few prospective birth cohorts have investigated the potential effect of early infections on the development of atopy [63– 66] . Three studies showed a protective effect, while no effect was seen in one survey. With respect to wheeze and asthma, studies investigating the effect of early life respiratory tract infections must be interpreted with caution. Bias by reverse causation is likely to occur since viral infections are the most potent trigger of asthma exacerbations. Respiratory syncitial virus (RSV) may, however, be particularly associated with asthma. A number of studies have consistently shown that children with a history of RSV bronchiolitis have an increased risk of developing repeated wheezing and asthma up to school age. Whether the RSV infection is the culprit or whether the determining factor is an asthmatic’s susceptibility to develop (severe) bronchiolitis after RSV infection remains unresolved. A recent cohort study provided some evidence that both arguments may be justified [67] . Findings from cross-sectional studies, mainly based on serological results, have suggested that other infectious agents such as hepatitis A, herpes, EBV, salmonella, helicobacter pylori, mycobacteria and lactobacilli [68] may be linked to the development of allergies. However, little is known from prospective studies.

Microbial Exposures in the Environment

There is increasing evidence from cross-sectional studies to suggest that an environment rich in microbial compounds may protect from the development of allergic diseases. So far, few prospective studies have investigated the role of such exposures and these studies have focussed on assessing endotoxin, the cell wall component of gram negative bacteria. Two prospective birth cohorts found that endotoxin exposure in infancy among high risk children was associated with an increased incidence of wheeze and inconsistently with an increased incidence of atopic dermatitis, but not rhinitis or atopy in the first years of life [69, 70] . In contrast, another study showed that prenatal exposure to endotoxin was associated with a reduction in cord blood immunoglobulin E production suggesting that maternal cytokine production modulates the foetal immune cells [71] . But the infant’s exposure to endotoxin had no protective effect on the development of atopy until the age of 2 years [72] . These discrepancies between studies might be explained by recent data from a birth cohort showing that exposure to endotoxin exerts a protective effect only in individuals with a particular genetic background (CC genotype for CD14/_159) [73] .

Antibiotics/Vaccinations/Paracetamol

Antibiotics and vaccinations have been postulated to interfere with the immune response in the developing immune system and thus to enhance the development of allergic diseases. But here again, results from observational cohort studies are conflicting. 408 M. Rochat and E. von Mutius

While no association has been found between antibiotics and the subsequent development of asthma in a number of prospective birth cohorts and recently summarised in a meta-analysis [74] , some prospective birth cohorts have shown a positive association between antibiotics administered during pregnancy or lactation and the development of allergic diseases in the offspring [75, 76] . According to the hygiene hypothesis, infections might confer protection from the development of allergic illnesses. Following this argument, it was proposed that vaccinations may play a role in the incidence of allergic disorders. However, two recent reviews of the literature came to the conclusion, that there is no epidemiological evidence to suggest an association between infant vaccinations and the development of allergic diseases [77, 78] . Since 2000, cross sectional, case control and ecologic studies have analysed and consistently reported a dose response association between paracetamol (acetaminophen) use and the development of wheeze and asthma. One possible mechanism might be mediated by an imbalance in the oxidant/antioxidant equilibrium leading to oxidant damage in the lung [79] . Reverse causation may, however, significantly bias these associations. Since paracetamol is given for fever and infectious diseases, the reported associations may merely reflect the strong relation between viral infections and asthma. In this context it is interesting to note that a prospective birth cohort found an association between paracetamol administered during late pregnancy and the development of asthma, wheeze and elevated total IgE by the age of 6–7 years [80] .

Multifaceted Interventional Studies

The studies described above used a monofaceted approach, studying one protective exposure or one preventive measure. Overall, the results of theses studies are rather disappointing. One explanation might be that the development of complex diseases, such as allergic illnesses, is attributable to a number of environmental influences. Accordingly, the avoidance of one single factor may not be sufficient. Some studies have therefore used a multifaceted approach, asking the parents to avoid or eliminate various known risk factors. All were performed among high risk children. The Isle of Wight study started the intervention postnatally. The investigators combined dietary restrictions in the lactating mothers and their children during the first year of their life with HDM reduction measures. The results at the age of 8 years suggest that such a combined approach is mostly effective for reducing atopy and may prevent some cases of childhood asthma depending on the phenotypic characteristic of the child [81] . The Canadian Childhood Asthma Primary Prevention Study used a combination of dietary restrictions in the mothers during pregnancy and lactation and encouraged them to breast-feed and delay the introduction of solid foods during the first year of life of their children. Additionally, intervention measures introduced before birth and during the first year of life included avoidance of HDM, pets, environmental tobacco smoke and day care facilities. The results showed a significant reduction in the prevalence of asthma and asthma symptoms, but not allergic rhinitis, atopic dermatitis, atopy or bronchial hyperresponsiveness at 7 years Birth Cohort Studies for the Prevention of Allergy 409 of age. Since there was no difference between the groups for the objective parameters and since the controls could not be blinded towards the intervention, the preventive effect may at least in part be attributable to some underreporting in the active arm [82] . The Prevention of Asthma in Children study (PREVASC) combined prenatal HDM and pet allergen avoidance strategies with dietary interventions and restrictions in passive smoking. The results showed no effective reduction in asthma- like symptoms at the age of two years [83] . The Australian Childhood Asthma Prevention Study (CAPS) combined a reduction in HDM allergen measures with dietary fatty acid supplementation. The results at 5 years showed that the measures did not prevent the onset of asthma, eczema or atopy. As in other studies the reduction of HDM increased the risk of eczema [84] .

Secondary and Tertiary Prevention in Cohort Studies

There have been a number of studies investigating the potential of secondary and tertiary preventive measures through medications aiming at either preventing the onset of disease among predisposed subjects such as the Early Treatment of the Atopic Child (ETAC) study or at the prevention of a chronic course of asthma. The ETAC study, a multi-centre European double-blind, randomised, placebo-controlled study, investigated the potential of cetirizine (antihistamine) to prevent the development of asthma in infants with atopic dermatitis. However, this trial failed since no effect on asthma prevention was seen in the active arm [85] . The hypothesis that the treatment with inhaled corticosteroids at the onset of infant asthma might improve long-term asthma outcome is built on the observation that in many asthmatic children an ongoing chronic inflammatory process is associated with a loss of lung function by early childhood which extends into adult life. Within a birth cohort, a subsample of infants was randomised after either one prolonged (> 1 month) or two medically confirmed wheezy episodes to a treatment with Fluticasone propionate twice daily or to a control group. At the age of 5 years, the results showed that the early use of inhaled corticosteroids had no effect on the natural history of asthma or wheeze later in childhood and did not prevent lung function decline or reduce airway reactivity [86] . Likewise, a nested interventional study of another cohort showed that early intermittent inhaled budesonide therapy had no effect on the progression from episodic to persistent wheezing and no short-term benefit during episodes of wheezing in the first three years of life [87] .

Conclusion

Birth cohort studies investigating determinants of allergic illnesses have substantially contributed to our understanding of the natural course of allergic diseases and associated features. They have identified a number of potential harmful and protective determinants, but consistency across populations is often lacking. Recommendations on a 410 M. Rochat and E. von Mutius population level, based on these findings, can in our opinion, only be issued for tobacco smoke avoidance for the prevention of asthma and other respiratory conditions. With respect to eczema and food allergy, the administration of hypoallergenic milk formula can be recommended for high risk children if prolonged breastfeeding is not possible. All other strategies have to be scrutizined in view of the results obtained so far.

Where do we go from now?

The lack of understanding of the significant determinants of allergic illnesses may be attributable to a number of reasons [1] . A basic requirement for the demonstration of a causal relation between an exposure and a disease is the temporal sequence of events. Only exposures occurring before the first symptoms of an illness can influence its inception. Birth cohorts have the advantage of documenting temporal sequences and thus facilitating conclusions on causal relations. But the disparity and heterogeneity of findings in the literature are remarkable, and reflect the complexity of allergic diseases. Environmental exposures potentially causing the new onset of allergies are likely to occur during fetal life and early childhood. Any potential risk factor is likely to interact with an underlying, genetically determined pathway resulting in the manifestation of disease. But the mechanisms underlying allergic illnesses are not fully understood. This lack of understanding may in part be attributable to the fact that allergic illnesses are a syndrome of many diseases rather than one entity. The context in which exposures occur and interact with a subject’s individual pathophysiological pathways is another important factor in the causation of allergies. Variation in these pathways is determined by genes. Environmental exposures interact with these pathways. However, these interactions do not occur in isolation. Pathways have more than one component and the function of each component is determined by the gene or genes contributing to and regulating the processes. If in fact more than one pathway leads to the development of allergies, then not only many genes with small individual contributions, but also many environmental factors and gene–environment interactions will eventually be found to contribute to disease manifestation. Hence, different contexts in which a number of different exposures interact with various genetic backgrounds in a range of racial or ethnic groups will eventually result in changes in the incidence of allergies. The challenge in the years to come will be to integrate complex interactions between multiple exposures and numerous genetic variants to achieve an understanding of the causation of asthma.

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59. Kramer U, Heinrich J, Wjst M, Wichmann HE (1999) Age of entry to day nursery and allergy in later childhood. Lancet 353(9151):450–4 60. Celedon JC, Litonjua AA, Ryan L, Weiss ST, Gold DR (2002) Day care attendance, respiratory tract illnesses, wheezing, asthma, and total serum IgE level in early childhood. Arch Pediatr Adolesc Med 156(3):241–5 61. Celedon JC, Wright RJ, Litonjua AA, Sredl D, Ryan L, Weiss ST, Gold DR (2003) Day care attendance in early life, maternal history of asthma, and asthma at the age of 6 years. Am J Respir Crit Care Med 167(9):1239–43 62. Ball TM, Castro-Rodriguez JA, Griffith KA, Holberg CJ, Martinez FD, Wright AL (2000) Siblings, day-care attendance, and the risk of asthma and wheezing during childhood. N Engl J Med 343(8):538–43 63. Illi S, von Mutius E, Lau S, Bergmann R, Niggemann B, Sommerfeld C, Wahn U (2001) Early childhood infectious diseases and the development of asthma up to school age: a birth cohort study . Bmj 322(7283):390–5 64. Zutavern A, von Klot S, Gehring U, Krauss-Etschmann S, Heinrich J (2006) Pre-natal and post-natal exposure to respiratory infection and atopic diseases development: a historical cohort study. Respir Res 7:81 65. Nafstad P, Brunekreef B, Skrondal A, Nystad W (2005) Early respiratory infections, asthma, and allergy: 10-year follow-up of the Oslo Birth Cohort. Pediatrics 116(2):e255–62 66. Ramsey CD, Gold DR, Litonjua AA, Sredl DL, Ryan L, Celedon JC (2007) Respiratory illnesses in early life and asthma and atopy in childhood. J Allergy Clin Immunol 119(1):150–6 67. Gern JE, Brooks GD, Meyer P, Chang A, Shen K, Evans MD, Tisler C, Dasilva D, Roberg KA, Mikus LD, Rosenthal LA, Kirk CJ, Shult PA, Bhattacharya A, Li Z, Gangnon R, Lemanske RF, Jr. (2006) Bidirectional interactions between viral respiratory illnesses and cytokine responses in the first year of life. J Allergy Clin Immunol 117(1):72–8 68. Schaub B, Lauener R, von Mutius E (2006) The many faces of the hygiene hypothesis. J Allergy Clin Immunol 117(5):969–77; quiz 978 69. Park JH, Gold DR, Spiegelman DL, Burge HA, Milton DK (2001) House dust endotoxin and wheeze in the first year of life. Am J Respir Crit Care Med 163(2):322–8 70. Gillespie J, Wickens K, Siebers R, Howden-Chapman P, Town I, Epton M, Fitzharris P, Fishwick D, Crane J (2006) Endotoxin exposure, wheezing, and rash in infancy in a New Zealand birth cohort. J Allergy Clin Immunol 118(6):1265–70 71. Heinrich J, Bolte G, Holscher B, Douwes J, Lehmann I, Fahlbusch B, Bischof W, Weiss M, Borte M, Wichmann HE (2002) Allergens and endotoxin on mothers’ mattresses and total immunoglobulin E in cord blood of neonates. Eur Respir J 20(3):617–23 72. Bolte G, Bischof W, Borte M, Lehmann I, Wichmann HE, Heinrich J (2003) Early endotoxin exposure and atopy development in infants: results of a birth cohort study. Clin Exp Allergy 33(6):770–6 73. Simpson A, John SL, Jury F, Niven R, Woodcock A, Ollier WE, Custovic A (2006) Endotoxin exposure, CD14, and allergic disease: an interaction between genes and the environment. Am J Respir Crit Care Med 174(4):386–92 74. Marra F, Lynd L, Coombes M, Richardson K, Legal M, Fitzgerald JM, Marra CA (2006) Does antibiotic exposure during infancy lead to development of asthma?: a systematic review and metaanalysis . Chest 129(3):610–8 75. Kummeling I, Stelma FF, Dagnelie PC, Snijders BE, Penders J, Huber M, van Ree R, van den Brandt PA, Thijs C (2007) Early life exposure to antibiotics and the subsequent development of eczema, wheeze, and allergic sensitization in the first 2 years of life: the KOALA Birth Cohort Study. Pediatrics 119(1):e225–31 76. Jedrychowski W, Galas A, Whyatt R, Perera F (2006) The prenatal use of antibiotics and the development of allergic disease in one year old infants. A preliminary study . Int J Occup Med Environ Health 19(1):70–6 77. Gruber C, Nilsson L, Bjorksten B (2001) Do early childhood immunizations influence the development of atopy and do they cause allergic reactions? Pediatr Allergy Immunol 12(6):296–311 Birth Cohort Studies for the Prevention of Allergy 415

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Susan L. Prescott

Introduction

As asthma and allergic diseases reach epidemic proportions, there is an urgent need to identify early the logical targets for strategies to reverse this trend. The frequent onset of disease within the first months of life necessitates early interventions. While it has been well recognized that allergic disease is multifactorial, conventional allergy prevention strategies have largely centered around avoidance of allergens and irritants with disappointing results. More recently, there has been a shift in focus to the role of immunomodulatory factors both as aetiologic factors and as possible avenues of early treatment and/or prevention [88] . Preliminary studies suggest that other environmental exposures (such as infection [1] , maternal diet [2, 3] , and smoking [3, 4] ) can modify early immune function, although the mechanisms are not clear (Fig. 1 ). While potential genetic polymorphisms are of great importance in understanding the complex gene-environmental interactions during this period, genomic programming cannot account for the rising rates of disease. There has been a consequential shift in interest to environmental factors that may influence early immune development potentially through epigenetic modification in gene expression. This includes potentially environment-driven changes in the patterns of DNA methylation in proximal gene promoters, chromatin remodeling, histone modifications, and/or non-coding RNA interactions that can alter the patterns of gene expression and clinical phenotype (Fig. 1 ) [89] . With rising disease rates, there is a continuing urgency to identify the pathways involved and to explore and monitor the effects of early interventions that could

S.L. Prescott () School of Paediatrics and Child Health Research , University of Western Australia , Perth , WA , Australia Princess Margaret Hospital , P.O. Box D184 , Perth , WA , 6001 , Australia e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 417 DOI 10.1007/978-4-431-99362-9_25, © Springer 2010 418 S.L. Prescott

Environmental Factors

Pollutants Diet Allergens

OTHER? Microbes Epigenetic modification

Genetic predisposition

Effects on Immune Development

Clinical Phenotype

Fig. 1 Effects of environmental factors on immune development

favorably influence immune development and prevent allergic disease. This review explores the role of a range of novel immunomodulatory strategies including dietary interventions (including fatty acids, antioxidants, and prebiotics), the use of microbial agents (including probiotics, mycobacteria and other bacterial adjuvants), as well as the role of allergen immunotherapy for the primary prevention of disease. In this context, “primary” prevention refers to measures that may reduce the development of manifest allergic disease in individuals who have not previously had any evidence of disease. This review does not address conventional strategies, or strategies to alter the expression of already established disease.

The Need for Early Interventions for Allergy Prevention

Allergic disorders including atopic dermatitis, food allergies, allergic rhinitis, and asthma, are collectively among the most common diseases in western societies. Rates of allergic sensitization are now reaching 40% in industrialized regions, with the same concerning trends now apparent in many developing societies. This highlights the urgent need to determine underlying mechanisms and to develop effective, preferably non-invasive and cost effective strategies to prevent disease and reverse these trends. Any strategy that reduces the burden of disease (even slightly) could have an enormous impact in a global context. Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma 419

Limitations of Current Strategies

Until recently, most of the interest has focused on the role of allergens in the development of disease. Although evidence was limited, this was the basis for recom- mending avoidance of allergenic” foods and indoor allergens (particularly house dust mites and pets) for primary allergy prevention. However, the results of intervention studies using these strategies have been disappointing (as summarized elsewhere [5] ) or even paradoxic [6] . It now appears more likely that other factors are likely to influence the development of sensitization rather than allergen encounter per se. This has led to a growing focus on the potential role of other immunomodulatory factors including microbial products and dietary nutrients. Other novel allergy prevention studies are focusing on the potential role of controlled allergen administration (immunotherapy) rather than on allergen avoidance (as above). Notably, there are also studies underway to assess the role of regular, early exposure to potentially allergenic foods (such as peanut) to induce tolerance. Although this approach is the exact opposite of existing “avoidance” approaches, there is a strong logical basis for pursuing this method of preventing allergic disease, as discussed further below.

Identifying Target Populations for Prevention Strategies - the Need for Better Allergy Predictors

Children born into atopic families are more likely to develop allergic diseases (50–80% risk) compared to those with no family history of atopy (20%). These children are commonly described as “high risk” for the purpose of prevention strategies, as there are currently no other more accurate (e.g. biological) markers of allergic risk. As potentially more effective interventions for disease prevention are developed (such as primary sublingual immunotherapy), it will become more crucial to more accurately identify children who will develop disease. The development of allergic disease is frequently preceded by immunologic differences that are already evident in the neonatal period [7– 12] . The most consistently observed difference has been reduced T cell production of IFNg [7– 12] , suggesting that relative T cell immaturity may be an important contributor to disease development. Although it is not clear whether this T cell “defect” is primary or secondary to antigen presenting cell immaturity, our findings (below) support the presence of intrinsic differences in T cells from neonates with subsequent allergic disease. Despite the relationships between Type 1 (Th1) IFNg production and allergy risk [7– 12] , this has not been a reliable predictive marker because it (along with other functional measures) relies on inherently variable in vitro culturing systems with potent polyclonal stimulants that potentially distort patterns of response [13] . There are currently no other biological markers that have any established predictive value [13] . Cord blood IgE (CB-IgE), the only neonatal marker to be extensively 420 S.L. Prescott evaluated as a likely predictor context, was shown to be unreliable in this context (reviewed in [13] ). Although the specificity of this test ranged between 60 and 70% in several studies, the sensitivity (26–47%) and positive predictive value (22–42%) were generally very poor in predicting allergic disease [14– 17] . For the first time, we recently discovered that the ‘fingerprint’ pattern of neonatal T cell PKC isozyme expression significantly predicts subsequent allergic disease (as detailed in [18] ), and that the predictive effect was stronger than any other biological marker. Moreover, we have demonstrated that an intervention designed to prevent allergic disease (maternal dietary supplementation with fish oil) significantly modified the expression of the same neonatal PKC pathway (discussed further below and in [18] ). These findings provide a strong basis for investigating this pathway further as a potential neonatal screening test for allergy prediction and potential target for prevention. Until these and other markers are further investigated, “family history” of allergic disease remains the only crude predictor of allergic disease in use, with variable specificity (48–67%) and sensitivity (22–72%) and a positive predictive value generally less than 40% [14– 16] . Using receiver- operator curves (ROC), we recently determined that a neonatal PKCz level of £ 62% of adult control levels was able to predict allergic disease with a sensitivity of 80% and a specificity of 63% (and an accuracy of 71%, the proportion of correctly classified individuals based on subsequent outcomes) [18] as shown on Fig. 2 . We are now exploring the value of this parameter as a disease predictor in larger cohort studies.

Using neonatal PKCζ in the prediction of subsequent allergic disease

ROC Cu rve 1.00

Sensitivity = 80% .75

.50

.25

0.00 0.00 .25 .50 .75 1.00 1 - Specificity

Specificity = 63%

PKCζ <62.3% (of control) predicted disease with optimal specificity and sensitivity

Fig. 2 Sensitivity and Specificity of PKCz in predicting allergic disease Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma 421

Novel Non-Invasive Strategies Using Dietary Nutrients to Prevent Disease

Dietary factors are among the leading candidates in the rising rates of allergic disease [19] . Modern diets differ in many respects from more traditional diets, with more complex, processed, and synthetic foods and less fresh fish, fruits, and vegetables. As a result, there have been many changes in the intakes of various dietary components. These changes include decreased consumption of omega 3 PUFA (n-3 PUFAs), antioxidants and nondigestable oligosaccarides (prebiotics), and fer- mented foods (containing probiotics). These factors are also of particular interest as they have the potential to modulate inflammatory responses, and may promote oral tolerance (Fig. 3 ). However, while most studies have focused on the specific role of individual factors, it is important to recognize that this “single component” approach does not fully address the “composite effects” of diets and dietary changes (or interaction with other environmental factors). It remains essential to recognize the overall complexity of dietary changes in the wider context.

( 1 ) The role of dietary fatty acids and fatty acid supplements Modern diets contain less essential n-3 PUFA and elevated levels of n-6 PUFA, and similar changes are seem in infant diets with parallel changes in breast milk composition [20] . The initial studies to link these trends to the rise in allergic disease noted protective relationships between the consumption of oily fish in childhood and the development of asthma and wheeze [21– 23] , although there has been some evidence to the contrary [24] . Several studies of maternal diet during pregnancy have also reported reduced risk of childhood eczema [25] and asthma [26, 27] , with high maternal consumption of n-3 PUFA from fish oil. A large UK cohort (n = 1,238) also suggested a link between cord blood n-3:n-6 levels and higher risk for eczema and late onset wheeze, however that these associations were not significant after Dietary Factors that may influence tolerance:

Diet / Environment • Pattern of food allergen exposure (Gut flora) (timing, dose, interval)

• Factors affecting colonisation Systemic - prebiotics immune - probiotics tolerance (gut maturity / permeability / pH)

•Other immunomodulatory factors: - breast feeding - fatty acids - antioxidants - role of dietary contaminants?

Fig. 3 Dietary Factors that may influence tolerance 422 S.L. Prescott adjustment for multiple comparisons [28] . Collectively, these studies indicate PUFA have immunological properties that may regulate early immune development. In keeping with this, a recent Boston cohort study reported associations between cord blood immune responses and maternal fatty acid levels in pregnancy [29] . There is also a strong immunological basis for the observations, including anti- inflammatory effects of n-3 PUFA on wide-ranging aspects cellular function including antigen presenting cell (APC) function, T cell function, and the production of inflammatory products (prostaglandins and leukotrienes), as reviewed elsewhere [30] . This logically stimulated interest in the potential benefits of n-3 PUFA (fish oil) supplementation in early life for modulating early immune function and preventing allergic inflammation. These notions have been supported by observed effects of maternal fish oil supplementation on neonatal immune function [2, 31] . Most recently, we have noted that maternal fish oil supplementation was associated with significantly higher neonatal expression of a key T cell intracellular signaling molecule (PKC zeta; P = 0.014), whereas most other isozymes were reduced by fish oil supplementation [32] . Most notably, increased PKC zeta expression was associated with significantly reduced risk of allergic disease in later infancy [32] . This marker may not only be of value as a “predictive tool”, but may also be of value in assessing effectiveness of interventions aimed at allergy prevention, and needs to be investigated further. Despite the immunological effects and epidemiologic associations, there have been few intervention studies to examine the role of fish oil supplementation in allergy prevention. Currently, there has only been one published study to specifically address this (although others are anticipated soon), and the results were disappointing. The Childhood Asthma Prevention Study (CAPS) studied the effects of a daily supplement of tuna fish oil (500 mg oil/day; along with margarines and cooking oils rich in n-3 fatty acids) in infants at high risk of allergy (based on family history). The control group received a placebo supplement plus polyunsaturated margarines and cooking oils. This intervention commenced at 6 months of age or at weaning (which ever occurred first). Although early assessment indicated a reduction of respiratory symptoms (wheeze, coughing) at 18 month [33] and 3-years [34] , there was no reduction in the development of atopy, asthma, or other allergic disease by five years of age [35] . The only other randomized controlled trial to report effects of fish oil supplementation of allergy prevention was designed to assess the effects of maternal fish oil supplementation during pregnancy (3.7 g n-3 PUFA/day) on neonatal immune function. In addition to the immunomodulatory effects, there was also a threefold reduction in the clinical detection of egg sensitization (OR = 0.34, P = 0.055) by one year of age. Although there was no difference in the propensity to develop atopic dermatitis, infants in the fish oil group had significantly less severe disease (OR = 0.09, P = 0.045) [2] . However, this study was too small to be conclusive. A more recent study has now also shown a significant reduction both in food allergy and IgE-associated eczema in children fish oil whose mothers were supplemented with daily fish oil from the 25 weeks gestation to 3–4 months of breastfeeding (compared with a placebo group) [90] . The only study to assess long term allergy outcomes has been a recently published 16 year follow-up of children involved in a pregnancy fish oil supplementation study (originally performed to assess pregnancy outcomes such as gestational length {Olsen, Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma 423

1992 #594}), which showed a reduction in subsequent asthma [91] . Currently there are several more studies in progress (in Europe and Australia), which are specifically designed to assess this, and the results are awaited with great interest. Until this has been addressed more definitively, fish oil supplementation cannot be recommended specifically for allergy prevention.

( 2 ) The role of antioxidants Recent dietary changes also included declining intakes of antioxidants (such as vitamin C, vitamin E, beta-carotene, zinc, and selenium). Although there is no evidence that these trends are “causally” associated, there have been preliminary epidemiological studies that suggest an association between lower intakes of antioxidant rich foods (such as fresh fruits and vegetables) with deficit effects on pulmonary function [36] , and increased risk of wheeze in both adults [37] and children [38, 39] . It has been hypothesized that these epidemiological associations may reflect a protective effect of antioxidant rich diets in the development of allergic diseases such as asthma [40, 41] . Although the full effects of antioxidants in immune development have not been thoroughly documented, the immunological properties of antioxidants have supported this hypothesis. Dendritic cells have been shown to promote the development of regulatory T cells in vitro in the presence of vitamin C and E antioxidants [42] . Studies in humans have also demonstrated that by favorably altering the ‘redox’ status of cells, antioxidants can enhance IL-12 production by APC [43] , favor development of T helper cell type 1 (Th1) responses, and inhibit the development of allergic type 2 (Th2) responses. Speculation that these dietary changes could possibly have beneficial effects on developing immune responses has been the rationale for examining the relationship between antioxidant exposure during pregnancy and early childhood. One of the first studies to examine this noted an inverse relationship between cord blood mononuclear cell proliferative responses to allergens and maternal vitamin E intake during pregnancy [3] . Although the significance of this is not clear, this provided preliminary evidence that maternal dietary factors could potentially have antenatal influences and could be implicated in the increasing propensity for allergic symptoms in early childhood. Since then, the same group has reported that low maternal intake of vitamin E in utero is associated with an increased risk of developing childhood wheeze, asthma, and eczema by two and five years of age [40, 44] . More recently, they have also shown that maternal vitamin D intake during pregnancy may have the potential to reduce early childhood wheezing [45] . A Boston study has also reported that maternal intakes of vitamin E and zinc were negatively associated with wheezing at two years of age, although they did not observe any correlations between antioxidant intake and the risks of eczema in the same children [46] . Relationships between allergic disease and other antioxidant levels, such as vitamin C, have been inconsistent. Some studies have suggested negative associations (increased risk of wheezing) with increased vitamin C intake [44] , while others have demonstrated beneficial decreases in the risk of wheeze [38, 47] . It is likely that maternal antioxidant intake during pregnancy does influence the antioxidant status of the developing fetus and potentially modulates the risk and development of childhood atopy [3, 48, 49] . It is also possible that this could influence or 424 S.L. Prescott alter developing immune functions in the neonate. However, without any randomized controlled trials, this is difficult to prove definitively. Until these concepts are better understood, and concerns about potential adverse effects of antioxidant supplementation [50] are addressed, there is currently no place for specific antioxidant vitamin supplementation specifically for allergy prevention. Importantly, it is likely that fresh foods (such as fruits and vegetables) may have additional ‘protective’ properties that cannot be replicated by specific vitamin supplements, many of which may be synthetic [51] . Thus, while the potential role of antioxidants in immune regulation is unclear, it is best to advocate a healthy balanced diet rather than specific vitamin supplementation.

( 3) The role of dietary prebiotic and probiotic supplements Colonization of the intestinal tract is essential for development of normal immune tolerance. This has generated great interest in the role of dietary supplements that can favorably modify intestinal flora. Animal models have clearly demonstrated that impaired intestinal colonization can lead to failed oral tolerance and predisposition to inflammatory diseases [52] . In humans, pre-symptomatic differences in perinatal intestinal colonization patterns have also been documented in children who subsequently develop allergic disease [53, 54] . “Probiotics” are the main dietary supplements that have been used to favorably influence colonization. These are live commensal micro-organisms that (at an optimal dose) exert health benefits. The first study to explore the effect of probiotics in allergy prevention was performed by a Finnish group [55] . They administered Lactobacillius rhamnosus (or a placebo) to mothers (starting 2–4 weeks before delivery) and to infants in the first 6 months of life. The probiotic was associated with a 50% reduction in the incidence of eczema [55] ; although the cumulative effect on eczema was still evident at 4 years [56] , there was no reduction in respiratory allergy, IgE levels, or allergic sensitization. However, a number of methodical concerns have been raised [57] making the results difficult to interpret. There are now more than 16 other published studies and at least four other studies in progress to examine the effects of various probiotic strains for allergy prevention, most using direct infant supplementation as recently reviewed [92, 93] . The first of these (using a Lactobacillus acidophilus ) failed to show any reduction in allergic disease despite changes in colonization, but instead reported an increase in sensitization and in IgE-associated atopic eczema [58] . The second study used a combination of strains (and prebiotic galacto-oligosaccharides) to show a reduction in atopic eczema, but no effects on sensitization or other allergic disease [59] . The third study, showed no effect of Lactobacillus reuteri on the prevention of allergic disease or sensitization [60] . However, subgroup analyses showed that probiotics were associated with less IgE-associated atopic eczema and less sensitization in a subgroup with atopic mothers. The results of more recent studies have been summarised elsewhere [92, 93]. Explanations for the varied results between studies include host factors (including genetic differences in microbial responses and allergic predisposition) and other environmental factors, such as general microbial burden, individual microbiota, diet (including consumption of prebiotic substances), and treatment with antibiotics. As more studies are completed, these factors are likely to make robust meta-analyses problematic to Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma 425 perform. Despite all the immunomodulatory effects described in experimental models, so far, none of these studies has shown any clear effect on preventive sensitization or any allergic disease other than eczema. One important concern is the potential for contamination of these supplements with milk antigens during the manufacture process, which may pose a risk for children highly allergic to milk proteins [61] . It seems unlikely that supplementation with a single strain can influence the complex intestinal microbial population. This has lead to a focus on dietary substrates that can influence the growth profile of intestinal microflora, most notably nondigestable, but fermentable oligosaccharides (prebiotics). These substrates favor beneficial bacterial species (including bifidobacteria and lactobacilli). The first trials for allergy prevention are only just emerging and show promising results [62] . Moro et al. recently reported that “prebiotic” supplementation with a mixture of galacto- and long chain fructo-oligosaccharides for the first six months of life in high risk formula fed infants significantly increased bifidobacteria colonization (but had no effect on lactobacilli). This effect on colonization was associated with a significant reduction in the development of atopic dermatitis. In summary, while there is a sound theoretical basis for exploring the preventative effects of probiotics and prebiotics, further studies are needed before specific recommendations are appropriate.

Novel Strategies using other Microbial Products

Reduced early microbial exposure in early life has become a leading candidate to explain the escalating rate of allergic disease. Infants depend on “signals” from the microbial environment to mature both Th1 and regulatory immune function. These signals, mediated through pattern-recognition receptors such as toll like receptors (TLR), appear essential to achieving the immunological balance required for (a) pathogens protection and (b) normal immune tolerance. These strategies have been used very successfully in vaccines against infectious diseases, and may also logically play a future role in the prevention of noninfectious immune diseases. (a) The role of CpG and other adjuvants in allergy “vaccinations” Broadly speaking, bacterial adjuvants such as immunostimulatory sequences (ISS) unmethylated cytosine and guanosine CpG motifs have more “Th1 polarizing” effects in mature individuals. Although these are not presently used in current vaccines, there has been growing interest in the potential role of these adjuvants in promoting perinatal Th1 responses. This is clearly of interest not only in enhancing early protection from infection, but also, as a strategy, in inhibiting the development of Th2 allergic responses in high risk infants. This remains largely theoretical at present, and there is ongoing concern about other unpredictable effects on the developing immune system. In established allergic disease, bacteria have also been used as adjuvants in allergen immunotherapy for many decades [63] . There are now many studies that demonstrate that CpG immunostimulatory sequences of oligodeoxynucleotides (ISS-ODN) inhibit airways inflammation, eosinophilia, IgE responses, 426 S.L. Prescott

Th2 (IL-5) responses and bronchial hyper-reactivity, and remodeling [64– 66] . In mice, the administration of ISS-ODN coupled to rag weed allergen (Amb a 1) induced a Type 1 sustained biased (IFNg ) response to Amb a 1, with concurrent IgE suppression [67] . Notably, it appears that this strategy will be more effective in down-regulating developing rather than established immune responses [67] . (b) Potential concerns about the use of immune adjuvants in infants Bacterial-derived adjuvants are already used extensively in existing infant vaccines to enhance immune responses against infectious disease. While adjuvants are very broadly regarded as Th1 or Th2 promoters, responses are often mixed and not exclusively polarized. However, Recent studies in animals suggests that “Th1 adjuvants” (such as complete Freund’s adjuvant [CFA]) have paradoxical effects in neonatal animals [68] with inhibition of murine Th1 responses (IgG2a, IL-2, and IFN g responses) and enhanced Th2 (IL-5) responses. In human neonatal mononuclear cell cultures, we recently demonstrated that CpG motifs not only enhance Th1 IFNg responses to vaccines antigens (and other environmental proteins such as house dust mite antigen), but also result in significantly enhance Th2 responses to these proteins. This suggests that CpG may not have the same Th1 polarizing effects in neonates, and needs to be investigated further. Thus, ethical considerations and uncertainties about long term effects are likely to delay the investigation of similar strategies in children, particularly in the absence of existing disease. (c) The use of mycobacterial products As potent Th1 immunostimulants, mycobacteria antigens have also been considered as agents for both prevention and treatment of allergic disease (reviewed in [69] ). In sensitized animals, mycobacteria have also been associated with improved pulmonary function [70] , reduced airways inflammation [71] , eosinophilia [72] , and expression of adhesion molecules [73] . Although the mechanisms are not clear, there is some evidence in animals that mycobacterium give rise to allergen specific CD4+CD45B-low regulatory cells that mediate a reduction in airways inflammation through the production of TGF b and IL-10 [74] . In humans, BCG vaccination has also been associated with reduced total and specific IgE in allergic individuals [75– 77] , and improved lung function in asthmatics [78] . Intradermal administration of mycobacteria has previously been used therapeutically in children with existing atopic dermatis with some success [79] . In newborns, BCG can influence immune responses to other antigens (vaccine antigens) promoting both Th1 and Th2 responses [76] . Although BCG administration in the neonatal period does not appear to reduce the risk of developing allergic disease [80, 81] , as with many other agents, the role of mycobacterial antigens for disease prevention still needs to be investigated further. (d) Role of bacterial endotoxin administration Natural exposure to endotoxin (typically in association with animals) has been associated with reduced allergy risk in some [82] but not all studies [83] . To the author’s knowledge, there is only one study, still in progress, that is investigating the effects of endotoxin administration in a randomized controled trial. The results are not yet known. Novel Immunomodulatory Strategies for the Prevention of Atopy and Asthma 427

(e) Genetic polymorphisms in microbial recognition could inﬂ uence effectiveness of these interventions Genetic studies presently provide evidence that functional variations in aspects of TLR microbial signaling may be associated with the expression of the allergic phenotype. Specifically, polymorphisms in the gene coding for CD14 (involved in LPS signaling through TLR4) have been linked to total serum IgE levels [84] . More recently, a TLR2 genetic polymorphism was shown to have a protective effect on asthma [85] . Notably, the “protective” effect was only seen when children were raised in environments with “high” microbial burden, illustrating the interactive effects of genetic and environmental factors on these pathways. Together these findings suggest that functional genetic polymorphisms in microbial recognition pathways could result in individual variation in the effectiveness of microbial products in disease prevention.

The Role of Allergen Immunotherapy

Other new allergy prevention studies are focusing on the potential role of controlled allergen administration (immunotherapy) rather than allergen avoidance. Concepts of an integrated mucosal immune system have been used to explain the remote effects of both “natural” tolerance and tolerance “induced” by mucosal immunotherapy. In the respiratory tract, the bulk of ambient aeroallergen exposure occurs in the “upper” airway. Under normal conditions, this appears to result in the generation of a CD4+CD25+ regulatory T cells and low level Th1 responses. This is the basis for the therapeutic use of mucosal allergen administration to induce systemic tolerance, and has been most successful using a sublingual route (sublingual immunotherapy [SLIT]). There are a growing number of reports of clinical benefits in established disease, including those of children [86] . There is also preliminary evidence that SLIT may reduce the risk of asthma developing in children with allergic rhinitis [87] . Novel studies are now planned to examine the effects of SLIT for primary prevention of aeroallergen sensitization. In this proposed randomized controlled trial, 200 children (aged 18 months to 3 years and at high risk of developing allergic respiratory disease) will receive inhalant allergen SLIT (house dust mite, cat, and timothy grass) or a placebo for 12 months. These children will already have evidence of allergic disease (food allergy or atopic dermatitis) but no sensitization to inhalants. The children will be monitored for 3 years, aiming to detect a 50% reduction in IgE and allergic Th2 responses to allergens, as well as a 50% reduction in asthma (www.immunetolerance.org/research/ allergy/trials/holt.html ).

Future Directions

Currently, our capacity to prevent allergic disease is constrained by limited understanding of disease pathogenesis and aetiological factors, particularly of the early exposures responsible for the recent increase in allergic disease. As the specific 428 S.L. Prescott pathways involved in disease pathogenesis are more clearly defined, it will be possible to develop more efficient (possibly molecular) targets for intervention and more accurately identify infants who will otherwise go on to develop disease.

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79. PD Arkwright, TJ David. Intradermal administration of a killed Mycobacterium vaccae suspension (SRL 172) is associated with improvement in atopic dermatitis in children with moderate-to-severe disease. J Allergy Clin Immunol 2001;107(3):53 80. JS Alm, G Lilja, G Pershagen, A Scheynius. Early BCG vaccination and development of atopy. Lancet 1997;350(9075):400–3. 81. IL Strannegård, LO Larsson, G Wennergren, Ö Strannegård. Prevalence of allergy in children in relation to prior BCG vaccination and infection with atypical mycobacteria. Allergy 1998;53(3):249–54. 82. E von Mutius, C Braun-Fahrländer, R Schierl, J Riedler, S Ehlermann, S Maisch, M Waser, D Nowak. Exposure to endotoxin or other bacterial components might protect against the development of atopy. Clin Exp Allergy 2000;30(9):1230–4. 83. G Bolte, W Bischof, M Borte, I Lehmann, HE Wichmann, J Heinrich. Early endotoxin exposure and atopy development in infants: results of a birth cohort study. Clin Exp Allergy 2003;33(6):770–6. 84. M Baldini, IC Lohman, M Halonen, RP Erickson, PG Holt, FD Martinez. A Polymorphism in the 5’ flanking region of the CD14 gene is associated with circulating soluble CD14 levels and with total serum immunoglobulin E. Am J Respir Cell Mol Biol 1999;20(5):976–83. 85. W Eder, W Klimecki, L Yu, E von Mutius, J Riedler, C Braun-Fahrlander, D Nowak, FD Martinez. Toll-like receptor 2 as a major gene for asthma in children of European farmers. J Allergy Clin Immunol 2004;113(3):482–8. 86. SM Sopo, M Macchiaiolo, G Zorzi, S Tripodi. Sublingual immunotherapy in asthma and rhinoconjunctivitis; systematic review of paediatric literature. Arch Dis Child 2004;89(7):620–4. 87. E Novembre, E Galli, F Landi et al. Coseasonal sublingual immunotherapy reduces the development of asthma in children with allergic rhinoconjunctivitis. J Allergy Clin Immunol 2004;114(4):851–7. 88. SL Prescott, VL Clifton. Asthma and Pregnancy: emerging evidence of epigenetic interactions in utero. Curr Opin Allergy Clin Immunol 2009;9(5):417–26. 89. D Martino, SL Prescott. Silent mysteries: epigenetic paradigms could hold the key to conquer- ing the epidemic of allergy and immune disease. Allergy 2009; in press. 90. C Furuhjelm, K Warstedt, J Larsson, M Fredriksson, MF Bottcher, K Falth-Magnusson, et al. Fish oil supplementation in pregnancy and lactation may decrease the risk of infant allergy. Acta Paediatr 2009;98(9):1461–7. 91. SF Olsen, ML Osterdal, JD Salvig, LM Mortensen, D Rytter, NJ Secher, et al. Fish oil intake compared with olive oil intake in late pregnancy and asthma in the offspring: 16 y of registry- based follow-up from a randomized controlled trial. Am J Clin Nutr 2008;88:167–75. 92. H Johannsen, SL Prescott. Practical prebiotics, probiotics and synbiotics for allergists: how useful are they? Clin Exp Allergy 2009; in press. 93. SL Prescott, B Björkstén. Probiotics for the prevention or treatment of allergic diseases. J Allergy Clin Immunol 2007;120:255–62. Recombinant Allergens for Therapy and Prevention: Molecular Design and Delivery of Allergy Vaccines

Shyam S. Mohapatra and Shawna A. Shirley

Introduction

Advances in the knowledge of the cellular and molecular basis of immunity have led to a thorough understanding of the immunologic features that characterize an allergic response. All humans can mount an IgE antibody (Ab) response to a parasite, but some genetically predisposed or atopic individuals mount this response to common antigens to which they are exposed either by inhalation, ingestion or by contact with the skin [1] . These non-parasitic antigens, called allergens, induce persistently elevated levels of specific IgE Ab and stimulate a Type-I immediate hypersensitivity [2, 3] . Common allergens include dust, plant and tree pollens, pet dander and food. Although a specific sample of pollen or house dust contains numerous antigens, only a few of them induce a specific IgE Ab response and are considered allergens. The epitope structure will determine if an antigen is an allergen [2– 7] . Some, but not all antigens have epitopes that stimulate a Th2-like response, which induces an IgE Ab response [6] . Several factors contribute to the immune response to the allergens including the amount and the route of antigen exposure [4, 5, 7], the type of antigen-presenting cell [1, 8, 9], and the cytokine milieu. IFN-g will promote a Th1-like immune response, whereas IL-4 will promote a Th2-like response. Other factors to consider are the host immune response genes and environmental cofactors, such as adjuvants. These may bias the immune response to allergens towards a Th2-type response.

S.S. Mohapatra () Division of Allergy and Immunology, Joy Culverhouse Airway Disease and Nanomedicine Research Center, Department of Internal Medicine , University of South Florida , College of Medicine and James A. Haley Veteran’s Hospital , Tampa , FL , USA e-mail: [email protected] S.A. Shirley Department of Molecular Medicine , University of South Florida , College of Medicine and James A. Haley Veteran’s Hospital , Tampa , FL , USA

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 433 DOI 10.1007/978-4-431-99362-9_26, © Springer 2010 434 S.S. Mohapatra and S.A. Shirley

Recombinant Allergens

Recombinant allergens provide a safe alternative to traditional natural allergens used for immunotherapy. They can be consistently produced as defined molecules of high purity and quality in unlimited amounts with defined physiochemical, biological and immunologic characteristics [10] . There are several disadvantages to the traditional allergens used in allergen immunotherapy. They are contaminated with unwanted materials or allergens from other sources which may prime Th2 responses and induce new sensitizations. Their compositions vary widely from batch-to-batch, and may lack or contain important allergens in lower amounts, overall, making the results of such therapy not predictive and often leading to decreased efficacy (Table 1 ) . Recombinant allergens were first described by Thomas et al. in 1988 when they cloned and expressed Der p 1 in E. coli [11] . To date, more than 100 of the major allergens have been cloned from diverse sources, such as mites, animals, molds, insects, foods and grass, weed and tree pollens using bacterial or phage vectors [12– 14] . The emergence of gene cloning, gene expression, DNA sequencing, the polymerase chain reaction (PCR), peptide synthesis, and peptide sequencing technologies in the late 1980s, have allowed the characterization and study of allergens and helped in determining their primary structures. The cloning of some of the allergen-cDNAs enabled the production in virtually unlimited amounts of the corresponding recombinant allergens in E. coli for use in basic and clinical studies [15] . The recombinant allergens that are synthesized by yeast and the baculovirus systems efficiently bind to IgE Abs, presumably due to

Table 1 Critical factors involved in recombinant allergen synthesis Steps involved in synthesis Critical factors for success Step 1 Clone cDNAs for relevant allergen Characterize native allergens Characterize physiochemically and Identify the isoallergens (if any) immunologically Compare with the native allergens Determine if it is a major AL. and their isoforms Characterize epitopes Step2 Produce rALs in large quantities in Confirm the allergen(s) glycosylation either E. coli , yeast, insect cells or mammalian cells Step 3 Modify allergens and test in animal Test in one small and one large animal models. Structure-modified model and/or relevant human cell allergens (only T cell epitopes or culture models T cell epitopes with modified B cell epitopes) Step 4 Formulate vaccine and test single Singly or in combined form should or multiple allergens. Perform decrease significant (>70%) Ab and safety study (phase I) and in T cell response for that group of vitro and in vivo study of human allergens responses Step 5 Clinical efficacy (phase-II) Randomized DBPC trials are needed Ab , antibody; AL, allergen; rAL , recombinant allergen; DBPC , double-blind placebo-controlled Recombinant Allergen Vaccines 435 the glycosylation of the recombinant proteins, which allows for appropriate folding, similar to that of the native proteins. For a majority of allergens, their precise function is unknown. However, for allergens with a known primary structure or with available amino acid sequence data, their homology with other known proteins in the database is known [16, 17] . Recombinant allergens can be produced as wild- type allergens that exactly mimic the properties of the natural allergens or as modified variants with enhanced properties such as increased immunogenicity and decreased allergic reactivity. They can also be produced as hybrid molecules that represent complex allergen sources by incorporating the epitopes of several allergens into a single molecule [18] . The production of overlapping recombinant and synthetic peptides in milligram amounts has allowed the determination of the complete repertoire of epitopes, which recognize B and T cell lymphocytes for many allergens, such as mites, cat and the pollens of trees, ragweeds and grasses. Furthermore, site-directed mutagenesis, in conjunction with PCR, permits the synthesis of allergens and peptides with the desired amino acid substitutions, which are devoid of IgE binding ability [19] . The B cell epitopes, utilizing the human IgE binding epitopes, are identified by analyses including antibody binding, molecular modeling, and X-ray crystallogra- phy. The T cell epitopes of many allergens have been identified by T cell proliferation assay, using peripheral blood mononuclear cells, and/or T cell lines and clones. Further, the knowledge of the primary structures of allergens and their B and T cell epitopes led to the determination of cross-reactivities among different allergens [20– 23] . These studies indicate that: (1) the major allergens have a number of epitopes, (2) the B and T cell epitopes appear to overlap, and (3) the epitopes recognized by various individuals differ. Whereas some epitopes are immunodomi- nant, other epitopes are of minor importance in mounting a persistent allergen-specific immune response [13] . In sharp contrast to natural allergen vaccines, the recombinant allergen vaccines possess well-defined physicochemical and immunologic properties and can be produced with consistently reproducible characteristics that permit monitoring of treatment and investigation of mechanisms. However, each allergen will be a separately regulated product, similar to other recombinant cytokines and proteins used as therapeutics. The risks involved in using recombinant allergens are associated with their production in E. coli or insect cells and the potential for mutations to be caused during the production process. However, recombinant allergens offer tremendous potential for allergy diagnostics as multi-allergen tests using marker allergens can be developed to facilitate the faster diagnosis and accurate prescription of immunotherapy [13, 24] .

Recombinant Allergy Vaccines

The availability of recombinant allergens make it possible to monitor, diagnose and treat allergic patients. They also allow the creation of novel allergy vaccines. The rationale is that, modified recombinant allergen vaccines provide a safer and more 436 S.S. Mohapatra and S.A. Shirley effective vaccine with fewer injections than what is currently available with natural allergen extracts. A list of recombinant allergen-based vaccines can be found in a review article by Lindhart and Valenta [25] . In a mouse model, vaccination with a multi-epitopic recombinant allergen induced allergen-specific immune deviation from a Th2-like to a TH1-like response [26] . In another study, the treatment of primed mice with a recombinant allergen vaccine did not decrease IgE Ab responses; however it increased specific IgG1 and IgG2a Ab isotypes [27] . Interestingly, recombinant allergen treatment enhanced IgG2a and IgG1 Ab production to crude Kentucky Blue grass allergens (kALs). A comparison of the cytokine responses showed that the recombinant allergens induced significantly higher levels of IFN-g and specific IgG2a Abs compared to kALs [27] . In the clinical realm, the potential advantages of recombinant allergens include the administration of allergens in optimal doses, an increase in the safety of allergen immunotherapy by mutating allergens to modify or eliminate IgE binding epitopes by using aqueous, enteric coated, liposome-packed, polymerized, or N-formyl- methionyl-leucyl-phenylalanine-conjugated allergen vaccines for immunotherapy [28– 31] . The clinical studies with recombinant allergens conducted to date are listed in Table 2 . Grass allergen vaccines comprise a few major allergens, each of which contributes significantly to the allergic response. In an elegant study, a cocktail of recombinant allergens were used to substitute extract-based immunotherapy of grass allergy and provided the proof of concept for the feasibility of patient-tailored immunotherapy. The clinical benefit of the treatment was associated with the promotion of IgG4 and reduction of IgE antibodies consistent with the induction of IL-10-producing Treg cells reported for extract-based specific immunotherapy [32] . Similar studies have been performed with recombinant birch allergens using either a combination of recombinant allergens or their modified derivatives [33– 36] . Most of these studies have been performed in Europe for grass and tree pollen allergens in a limited number of patients. None of these studies has shown significantly greater improvement compared to natural allergen mixtures. Further studies need to be conducted to indicate their reproducibility.

Molecular Design of Allergy Vaccines

It is important to consider the underlying mechanisms of allergen-specific immunotherapy when designing allergy vaccines. One approach could be to modulate the T helper cell response to promote a Th1-like response as opposed to the Th2 response or inducing immunosuppressive Treg cells to promote tolerance. Another approach could be to use active vaccination that promotes the IgG response while suppressing or eliminating the IgE response. DNA-based allergen (AL-DNA) vaccines may be useful to treat allergic patients [26, 37– 39] . Allergens cloned into suitable plasmids (pAL), would be utilized. In mice, such therapy shifts allergen-specific immunity from a Th2- response to a Recombinant Allergen Vaccines 437 [44] [33– 35] [36] effective effective IgG response. Decreased cutaneous and nasal sensitivity to rBet v 1 fragments. Th1 response to rBet Increased v 1 trimers 53% lower medication score compared to control group Decreased IgE cells Treg Increased IL-10 and , natural Birch pollen allergen , natural Birch pollen allergen nBet v 1 Allergen Allergen (pollen) No. of patients Center Results Ref. Birch n = 124 Birch Multi n Blunting = 51 of seasonal IgE, Robust Single Increase in IgG1 and IgG4 A , recombinant major Birch pollen allergen; , recombinant major Birch pollen allergen; rBet v 1 trimers and placebo (1 pre-seasonal Rx) trimers and placebo Bet v mix Immunotherapy trials with recombinant allergens Immunotherapy trials with recombinant allergens

, recombinant allergens; , recombinant allergens; design Study description Table 2 Study Study design DBPC Compare a mixture of rALs with DBPC placebo Compare rBet v 1 and nBet Timothy grass n = 62 Birch Single 147 = Increase n IgG4 Multi rBet v 1 and nBet are equally [32] DBPC Compare rBet v 1 fragments, Open Compared rBet v 1 fragment variants with rALs 438 S.S. Mohapatra and S.A. Shirley

Th1-like response, similar to the cytokine changes that occur in allergic patients after allergen immunotherapy. Although, allergen-DNA vaccines may be advantageous, clinical trials involving these vaccines have not been completed and the potential adverse effects of these vaccines in humans are unknown. Hybrid vaccines contain fusion molecules of two or more allergen epitopes or derivatives from single or multiple sources in a single vaccine. These molecules are engineered using recombinant DNA technology [40] and studies reveal they show low IgE binding activity, but retain the complexity of their T cell epitopes [41– 43] . Although no clinical trials with hybrid vaccines have been carried out, animal models show promising results [42] . Wild-type allergen vaccines are engineered to resemble the natural allergen. They will have the same relevant B and T cell epitopes and allergenic properties of the natural molecules. Clinical studies have shown that these recombinant allergen vaccines are just as effective as the natural allergen [44] . Hypoallergenic allergen derivatives are recombinant allergens that have been modified to reduce the allergenic activity of the molecule, but preserve the immunogenicity and T cell epitopes. The decrease in allergenicity reduces the IgE effects, which allow higher doses of the derivatives to be given in comparison to the natural counterpart. The steps toward designing a recombinant allergen-based vaccine are outlined in Fig. 1 . First, the source of allergen must be selected followed by the isolation of the cDNAs coding for the relevant regions. This is done by extracting RNA, tran- scribing it into cDNA and expressing it in a phage library which is then screened with IgE from allergic patients. This yields a mixture of allergens that equal the natural allergens of the source. The clinical relevance of each allergen is evaluated by skin testing in different populations; then relevant recombinant allergens are selected for vaccine formulation. Preclinical evaluations are carried out based on mixtures of allergens, hybrid molecules consisting of recombinant allergens equal- ing the natural allergens or genetically engineered derivatives having reduced allergenic activity. The final step is to carry out double-blind, placebo-controlled (DBPC) immunotherapy trials [25] .

Delivery of Allergy Vaccines

Recombinant allergens are less immunogenic than natural allergens, therefore it is essential to use an adjuvant to deliver the vaccine. Some examples of adjuvants used for recombinant allergen delivery include emulsions such as aluminum hydroxide (alum), cytokines, nanoparticles, and CpG DNA. One important aspect of treatment of allergic disease is the method of administration of the drugs to patients. While traditional immunotherapy utilizes a parenteral route, new approaches involving administration of allergen to specific tissues, such as local nasal, sub-lingual and local lung immunotherapy have been investigated. Recombinant Allergen Vaccines 439

Fig. 1 Steps involved in designing recombinant allergen-based vaccines

Cytokines

Th1-like cytokines IFN-g and IL-12 have the potential to convert allergen-specific Th2-like responses to Th1-like responses [26, 45–47] . IL-12 has been suggested as an adjuvant for vaccination against diseases in which the Th2 profile predominates. The administration of a fusion protein vaccine consisting of ovalbumin (OVA) and 440 S.S. Mohapatra and S.A. Shirley

IL-12p40 reduced OVA-specific IgE responses in vivo [48] . IFN g is a pleiotropic Th-1 cytokine that downregulates Th2-associated airway inflammation and hyperresponsiveness (AHR). Since allergic subjects produce relatively low amounts of IFN g, we investigated the ability of chitosan-IFNg pDNA nanoparticles (CIN) for in situ production of IFN-g and examined its in vivo effects [49] . In a mouse model of allergy, CIN reduced OVA-induced inflammation and AHR. Production of IFN- g was increased after CIN treatment, while the Th2-cytokines, IL-4 and IL-5, and OVA-specific serum IgE were reduced compared to controls. AHR and eosinophilia are also significantly reduced by CIN therapy. CIN was found to inhibit epithelial inflammation within 6 hours of delivery by inducing apoptosis of goblet cells.

CpG DNA

Prokaryotic DNA sequences are rich in unmethylated cytosine-phosphoguanosine (CpG) dinucleotides. CpG DNA can be co-administered with antigen in the form of synthetic oligonucleotides which are able to activate both innate and adaptive immune responses through toll-like receptor 9 (TLR9) signaling. For natural allergens, CpG oligos have to be injected with the allergen; however, they can be directly linked with recombinant allergen cDNA. Utilization of CpG oligos as an adjuvant has been reported in a murine model of allergy and asthma [50] . The immunostimulatory profile of these adjuvants can be adjusted by chemical modifications. These sequences tend to induce a Th1-like cytokine response [51] . Synthetic CpG motifs linked to the major ragweed allergen Amb a 1 redi- rected ragweed-specific Th2 responses to Th1 responses as evidenced by increased IFN-g , CXCL-9 and CXCL-10 expression in a placebo-controlled clinical study [52] .

Live Bacillus Calmette-Guerin BCG

Bacillus Calmette-Guerin (BCG) has been suggested as an adjuvant for allergen immunotherapy. Vaccination simultaneously with live BCG and a recombinant grass allergen [37] induced allergen-specific immuno-deviation, i.e., a fivefold decrease of total IgE Abs and a tenfold decrease in specific IgE Abs, with a concomitant tenfold increase in IgG2a Ab synthesis (Mohapatra et al., unpublished data). Splenocytes of mice stimulated in vitro with Kentucky blue-grass allergens after the mice had been vaccinated with BCG and then 21 days after with the recombinant allergen, produced significantly higher amounts of IFN-g (unpublished data). Also, a live vaccine to treat allergic diseases using a recombinant (BCG) expressing allergens has been proposed [37] . Recombinant Allergen Vaccines 441

Live Vectors

Allergen genes expressed in the appropriate hosts may be used as live vaccines, which stimulate the immune system toward a Th1-like response. For example, oral immunization with Salmonella typhimurium expressing a Bet v 1-cDNA promoted IgG2a instead of the default IgE Ab responses [39] . However, IgG2a responses specific for Bet v 1 could be detected in only 10% of the immunized mice. These experimental approaches appear promising and may lead to effective allergy vaccines.

Nanoparticles

The application of nanotechnology for targeting drugs and macromolecules to specific tissues or cells is one of the most important areas in nanomedicine research [53] . Evidence shows that chitosan, a natural biocompatible cationic polysaccharide extracted from crustacean shells, has the potential to be a safe and effective carrier for genes and drugs. It has strong immunostimulatory properties, low immunogenicity [54] , anticoagulant activity [54] , wound-healing properties [55] , and antimicrobial properties [55] . Chitosan is nontoxic, nonhemolytic, slowly biode- gradable and has been widely used in controlled drug delivery [56– 60] . Chitosan also increases transcellular and paracellular transport across the mucosal epithelium [61] and, thus, may facilitate mucosal allergen delivery and modulate immunity of the mucosal and bronchus-associated lymphoid tissue (Fig. 2 .). Research from our laboratory has shown that plasmid DNAs can be encapsulated in chitosan to effectively transfer and express genes in lung cells [49] . Chitosan is also effective in delivering peptides. We have successfully encapsulated the allergen OVA in chitosan. These particles when delivered to mice orally desen- sitize the animals (data unpublished).

Nanocomplexes Lung GFP Expression

Fig. 2 Nanocomplexes effectively deliver DNA to lungs after oral administration 442 S.S. Mohapatra and S.A. Shirley

Roy et al. reported an immunoprophylactic strategy using oral allergen-gene immunization to modulate peanut antigen-induced murine anaphylactic responses. Plasmid DNA encoding a dominant peanut allergen gene was coupled to chitosan and delivered orally resulting in transduced gene expression in the intestinal epithelium. Nanoparticle delivery of the allergen resulted in reduced anaphylaxis. This shows oral chitosan−DNA nanoparticles are effective in modulating murine anaphylactic responses, and may be useful as a prophylactic for food allergy [62] . Chitosan, therefore, appears to be a good candidate for the safe mucosal delivery of recombinant allergen molecules for immunotherapy. Modifications can be made to chitosan that will enhance its muco-adhesiveness and overall efficacy [63, 64] . Also, the complexes are thermally stable and can be stored at room temperature and reconstituted with water when needed.

Future of Immunotherapy

Recombinant allergens and their corresponding cDNAs could be used to prevent allergen-specific IgE responses. As stated previously, vaccination of mice with a multi-epitopic recombinant allergen, induced an allergen-specific Ab response that was long lasting, despite several booster immunizations [27] . Alternatively, plasmids expressing allergens could also be utilized for prophylactic vaccination. The immunization of rats with a mite allergen-cDNA cloned in a plasmid vehicle resulted in an AL-specific IgG2a and a Th1-like response with no detectable IgE. This was in marked contrast to immunization with an allergen, which induced an IgE antibody response [65] . These studies suggest that immunization with allergen- cDNA(s) may provide a novel type of prophylactic vaccine against allergic diseases. About a quarter of the population is genetically predisposed to develop allergic disease and with advances in the identification of genes it may be possible to develop methods to predict atopic predisposition. This, in turn, may allow for vaccination of predisposed individuals to prevent sensitization from exposure to specific allergens.

Concluding Remarks

Molecular cloning of allergens has advanced the knowledge of their primary structures and has enabled them to be produced in virtually unlimited quantities for potential diagnosis and treatment of allergic disease. Furthermore, availability of these recombinant allergens has led to the possibility that new ways to prevent or treat allergy may utilize them or even plasmid DNAs that encode allergens. It will be necessary to demonstrate the effectiveness and safety of these vaccines in humans before these new forms of therapy can be used in routine treatment. Allergic conditions are complex, and it is naive to think that one form of AL-specific Recombinant Allergen Vaccines 443 immunotherapy will be effective to treat all allergic conditions. Nonetheless, it is prudent that all new technologies be explored for the diagnosis and treatment of allergic diseases.

Acknowledgement The authors would like to thank the support by Joy McCann Culverhouse endowment to the division of Allergy and Immunology and Mabel and Ellsworth Simmons Professorship to SSM.

References

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Leena von Hertzen and Tari Haahtela

Introduction

Accumulating evidence indicates that an environment rich in microbes in childhood reduces the risk of developing atopic disease in later life [1] . Along with urbanization, the perpetual coexistence of environmental microorganisms with man has been severely disturbed, with unexpected consequences. It has been elegantly shown that continuous stimulation of the innate immunity cells by commensals and saprophytes is necessary for the proper development and maintenance of mucosal homeostasis [2] . Such continuous stimulation of the immune system through the skin, respiratory tract and gut is thought to activate the regulatory network, which in turn seems to be decisive in the development of tolerance and in the prevention of inflammation associated with atopic conditions and harmful Th2 responses [3, 4] . Allergy and asthma epidemic still continues in many western countries [5] , whereas in some other, less affluent areas, it may have only started [6, 7] . Numerous studies have provided evidence that allergen avoidance is not the right strategy to reverse the rising trends in asthma and allergy prevalence. Avoidance of inhalant allergens is difficult, often impossible, and the results from avoidance interventions have not been encouraging [8– 10] . As to food antigens, excessive avoidance in early life can be harmful and prevent or weaken the development of regulatory mechanisms. Virtually, the only possibility to reduce the allergy burden in a population is to strengthen those mechanisms that are involved in the development and maintenance of tolerance. Patients must be treated, but the strategies to reduce the allergy burden should focus on prevention and preventive treatment. In this chapter, the development of tolerance in the context of environmental factors, and the means by which allergies might be reduced at the national level are discussed.

L. von Hertzen () and T. Haahtela Skin and Allergy Hospital , Helsinki University Central Hospital , P.O. Box 160, 00029 HUS , Finland e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 447 DOI 10.1007/978-4-431-99362-9_27, © Springer 2010 448 L. von Hertzen and T. Haahtela

Factors in the Environment that May Confer Protection

Epidemiological studies have identified a number of factors that may confer protection against allergies, most associated, more or less, with the hygiene hypothesis. These studies have been extensively reviewed earlier (e.g., in [11, 12] ), and are not repeated here. Nonetheless, the strongest and most consistent evidence comes probably from studies performed among farmers’ children and those living in nonaffluent areas in simple living conditions. Currently more than 30 studies have shown that farming environment, particularly in early life is associated with reduced risk for atopic disease in later life [1] . Similarly, data from the former socialistic countries indicate that atopic diseases are inversely related to affluence and urbanization [13, 14] . Common to both farming and nonaffluent environment is the heavy daily exposure to saprophytes and other microorganisms. Along with increasing affluence and urbanization, a dramatic shrinking in the diversity of ecosystems and species has occurred [15] , and this concerns, not only macrobiology but microbiology as well. Thus far, the focus in microbial exposure-allergy – studies has largely been on endotoxin (lipopolysaccharide, LPS), the major cell wall component of gram-negative bacteria, and numerous studies have reported an inverse association between endotoxin levels in house dust and occurrence of atopic disease, although dose, route and timing of exposure may significantly affect the outcome [16, 17] . However, gram- negative bacteria are likely to represent only a minor part of all bacteria in the environment, as gram-positive bacteria, particularly members of the phylum Actinobacteria (including genera such as Streptomyces , Mycobacterium , Corynebacterium , Bifidobacterium ), have been found to predominate in soils and natural waters in different geo-climatic areas [18– 20] . The other phylum of gram-positive bacteria, Firmicutes (e.g., genera such as Staphylococcus , Streptococcus , Lactobacillus , Lactococcus), are also widely distributed in the environment and animals [21] . The significance of endotoxin as an environmental immunomodulator may have been overestimated, while the role of gram-positive bacteria largely ignored. The concept of the crucial role of saprophytes particularly from the gram-positive lineage in conferring protection against allergies has gained further momentum from several dietary studies. These include studies on (1) farm milk, (2) raw vegetable and fresh fruit, and (3) natural water consumption.

Farm Milk Consumption

A large body of data [22– 27] , albeit not all [28] have revealed the unpasteurized milk/ farm milk may confer protection against sensitization and atopic disease. Riedler [24] and Barnes [27] in two independent studies were among the first to show that farm milk consumption in early life is associated with reduced rates of sensitization and/or atopic disease. After that the results have been replicated in four more studies [22, 23, 25, 26] , two of which in large populations. A British study among nearly 4,800 school children [23] showed that current unpasteurized milk consumption was inversely associated with eczema symptoms and atopy. The effect was seen in all children, Prevention of Allergic Diseases 449 independent of whether farmers’ children or not, and present regardless of the frequency of farm milk consumption. By contrast, farming status, early or current farm animal exposure, barn/stable exposure and endotoxin exposure were not associated with atopy in that study. Further, the most recent study with 15,000 European school children [22] revealed that farm milk consumption ever in life was associated with reduced rates of atopic diseases and sensitization to pollens and food allergens. The associations were, in line with the study by Perkin [23] , found in all children and independent of farm-related coexposure. No other farm products inversely associated with atopic diseases or related symptoms, could be identified [22] . Which factor(s) in farm milk might mediate this relative strong protection against atopy and atopic diseases? It is well established that raw milk from a healthy cow after milking includes saprophytes derived from the cow (udders), soil or milking equipments. The microbial content normally is at the level of 100–1000 bacteria/ml, and the proportion of gram-positive bacteria of all those bacteria in milk is as high as >80%, Micrococcus (phylum Actinobacteria) and Staphylococcus (phylum Firmicutes) being the dominant genera. The proportion of gram-negative bacteria is very low, <10%, as is that of fungi (<10%) [29] . By contrast, the shop- purchased milk is likely to lose its immunomodulatory capacity during processing comprising separation, pasteurization and homogenization, of which separation (gathering of fat and microbial cell wall components considered as “rubbish”) may have the greatest impact in this respect.

Raw Vegetable and Fresh Fruit Consumption

Another line of evidence of the impact of environmental saprophytes comes from studies investigating the relationship between raw vegetable and fresh fruit consumption and the occurrence of atopic disease. Data are accumulating to support the notion that consumption of such vegetables/fruits may reduce the risk of atopic disease [28, 30– 34] . Remes [28] went further and found that the inverse association between vegetable consumption and atopy was stronger for vegetables grown on the own or a nearby farm than for vegetables bought from the grocery store. By contrast, the consumption of boiled vegetables showed no association with atopy. These findings suggest that soil saprophytes associated with recently collected vegetables rather than various phytochemicals or even vitamins are involved in this protective effect [28] . Indeed, intake of vitamin supplementation or cod liver oil in infancy has even been associated with increased sensitization rates in later life [32] .

Natural Water Consumption

We found recently, as part of the Karelia Allergy Study that the numbers of microorganisms in drinking water collected from school kitchens was inversely associated with atopy among children in the respective schools [35] , in line with the limited 450 L. von Hertzen and T. Haahtela earlier data [36– 38] . Most Russian Karelians use untreated surface water from lake Ladoga as domestic water. This water may be brought to a boil, but major bacterial components, e.g., endotoxin, teichoic acids, muramic acids, are heat-resistant [35] , and are to a large extent likely to retain their immunobiological activity after heat- ing. Several studies have indeed shown that both viable and nonviable bacteria and their components are immunologically active [39, 40] . Analysis of chemical markers (muramic acids; a marker of peptidoglycan, 3-OH-fatty acids; a marker of endotoxin) of the bacteria in Karelian drinking waters revealed that the content of muramic acids was 3-fold higher as compared with that of 3-OH-fatty acids, pointing further to the significance of gram-positive bacteria rich in peptidoglycan as environmental immunomodulators [35] . Saprophytes in natural waters largely reflect the microbiota in soil (members in the phylum Actinobacteria), as soil bacteria have been found to gain access to waters even during low run periods [41] As shown earlier, the Russian Karelians are protected from atopy and atopic diseases [14] . Drinking water may have great impact on the development of tolerance as the exposure occurs on a daily basis throughout the life. In sum, the urban man-made environment clearly cannot provide all the microbial stimulation, in terms of quantity and diversity, that appears to be necessary for the proper development of the immune system and tolerance, nor the modern man’s immune system been able to adapt to this kind of microbial deprivation in this short time. Microbial deprivation concerns not only saprophytic bacteria but also fungi, protozoans, helminths and microscopic mites as well.

Tolerance

In guidelines and consensus reports concerning asthma and allergy, hardly any attention has thus far been paid to tolerance. Currently, tolerance is one of the hot topics in allergy research worldwide, information is growing exponentially and many breakthroughs in tolerance-immunology research have recently been made (reviewed e.g., in [42– 44] ). The concept of T cells that have the ability to actively suppress the function and proliferation of many other cells is not new [45, 46] . However, only 30 years later, the specific role of these suppressive T cells, renamed regulatory T cells, in the development of tolerance could be unraveled.

Definition of Tolerance

Tolerance can be categorized as immunological and clinical tolerance . Immunological tolerance refers to an antigen-induced condition, in which the immune response is greatly silenced. This can be primary tolerance, acquired prenatally or in infancy through the first contacts with the antigen/allergen, or secondary tolerance, in which an earlier developed allergy disappears transiently or permanently. Prevention of Allergic Diseases 451

Clinical tolerance refers to a condition, in which there are no clinical symptoms, irrespective of sensitization to the allergen. In the following, the term “tolerance” refers to immunological tolerance.

Mechanisms Involved in the Development of Tolerance

The development of tolerance may involve several different mechanisms, depending e.g., on the dose and route of exposure. The mechanisms include (1) anergy (under particular conditions, T cells do not die but persist as functionally inactive effector cells), (2) clonal deletion (activation-induced T cell death) , (3) immune deviation and, (4) active suppression by T reg cells [47, 48] , of which especially the last one, has been the subject of an intensive research worldwide during the past years. Recent data suggest that both thymus-derived natural T reg cells expressing the transcription factor Foxp3, and peripherally induced T reg cells (with or without Foxp3) acting via cytokines IL-10 and/or TGF-b have a physiological role in protection against allergic disease in humans [49] . For the induction of the latter, mucosal surfaces and skin provide a favorable environment [50] . There are several excellent reviews that have outlined the most recent data of T reg cells and the regulatory network (e.g., [49, 51– 53] ). Here, we will highlight some recent findings of major relevance to tolerance.

Bell-Shaped Curve

It was earlier widely believed that the dose-response curve for different allergens/ bioparticles is different. For example, for house dust allergen, the occurrence of sensitization and respiratory symptoms was considered to increase linearly with increasing exposure, whereas for cat allergen, a nonlinear dose-response curve was proposed [54] . The emerging picture, however, now is that a nonlinear dose- response curve (Fig. 1 ) may be a rather universal phenomenon, although the matter is still debated [55] . To date, a bell-shaped curve has been identified for endotoxin [56] , fungal 1-3-b -glucans [57] , cat and dog allergens [55, 58, 59] , rat and mouse allergens [60– 62] and house dust mite allergens [59, 63, 64] . Even the relationship between parasites and atopic diseases appear to be nonlinear; at low levels of exposure, atopic diseases and related symptoms are positively associated with exposure whereas at high levels of exposure, parasites appear to confer protection against atopic disease. In addition to dose, type of the parasite and duration of the infection (stage of chronicity) are likely to be involved [65] . This nonlinearity in dose- response curve may partly explain discrepancies between some studies of helminths/pets and allergy [65, 66]. 452 L. von Hertzen and T. Haahtela

Prevalence of atopy/ atopic disease

Exposure

Fig. 1 The bell-shaped curve in the development of tolerance

Toll-Like Receptors in the Development of Tolerance

Identification of microorganisms in environmental exposure (e.g., those in house dust, drinking water, milk) is pivotal from the perspective of their immunomodulatory capacity, and is the prerequisite for the development of novel bacteria-based prevention strategies. Toll-like receptors are a family of conserved receptors that recognize microbial molecular patterns. These Toll-like receptors (at least 10 in humans) are particularly expressed by antigen presenting cells (APC) of the innate immune system, and capture microbes and microbe-derived components as part of the first line immune defense system. As discussed above, bacteria particularly from the gram-positive lineage appear to predominate in the environment; in soil, natural waters, raw milk, and even in house dust of people living in a microbe-rich area [67] . The role of gram-positive bacteria as immunomodulators must thus be significant. The main immunostimulatory cell wall components in gram-positive bacteria are (lipo)teichoic acids and peptidoglycans [68– 70] . Peptidoglycan is present in virtually all bacteria, but in high amounts, up to 50% of the dry weight of cell walls, in gram-positives. It consists of a polymeric glycan chain with alternating N -acetylmuramic acid and N- acetylglucosaminyl monomers cross-linked by short peptide subunits [1, 70] . Teichoic acids are water soluble polymers containing ribitol or glycerol residues joined through phosphodiester linkages. In lipoteichoic acids there is a single lipid side chain anchored to the ribitol or glycerol backbone [1] . Similarly to endotoxin, peptidoglycan and lipoteichoic acids induce the release of proinflammatory cytokines including TNF-a , IL-1, and IL-6 [68, 70] . It is now well established that gram-positive bacteria and their cell wall components are captured by TLR2 (albeit small fragments of peptidoglycan appear to be recognized by cytosolic intracellular receptors NOD1 (nucleotide-binding oli- gomerization domain) and NOD2 [71, 72] . TLR2 also recognizes mycobacteria, Prevention of Allergic Diseases 453 various mycobacterial cell wall components and fungal zymosan [73] and b -glucan [74– 76] , all these structures are abundantly found in soil and natural waters. In addition, protozoan glycosylphosphatidyl-inositol anchors are recognized by TLR2 [70] . Indeed, TLR2 is the member of the TLR family with the highest number of different ligands identified to date. Early analyses in humans revealed significantly increased TLR2 mRNA accumulation in the lung, spleen and peripheral blood mononuclear cells (PBMC) as compared to other tissues [70] . Several lines of evidence suggest that TLR2 and probably also TLR9 (the receptor for bacterial DNA (CpG motifs)) are particularly involved in the development of tolerance [77– 80] , although differences between respiratory and oral tolerance in this respect may exist [81] . TLR2 ligation on human DCs was shown to lead to a rapid release of IL-10, the cytokine central to the development of tolerance [82, 83] , and in higher concentrations than in TLR4 or TLR7 ligation [77] . Further, only TLR2, but not TLR4 or TLR9, ligation on regulatory T (T reg) cells resulted in T reg cell proliferation, clonal expansion and changes in their function in murine models [78, 84] . Interestingly, ligation of TLR2 on PBMNs from atopic individuals was found to prevent the Th2 immune response after exposure to allergen ex vivo [79] . The significance of TLR2 expression and polymorphism in conferring protection against atopic disease among farmers’ – but not among nonfarmers’children- has been shown earlier [85, 86] , underscoring the impact of environment in determing the risk of the disease for certain polymorphism [87] . We have found that nasal administration of microbe-rich barn dust to BALB/c mice, induced significantly higher TLR2 mRNA expression in lung epithelial cells as compared with urban house dust. The difference was also significant, albeit of lower magnitude, for TLR9 expression, whereas for TLR4 expression, no significant differences between these two dusts could be found [M Leino, unpublished], which, in line with the studies by Eder and Lauener [85, 86] , suggests a central role of TLR2 in a microbe-rich environment and in the development of tolerance. Most recently, a German study [88] showed that TLR2 controls mucosal inflammation by restoring epithelial barrier function. Oral treatment of mice with intestinal injury using a TLR2 ligand was able to suppress mucosal inflammation and restore mucosal homeostasis. Not only T reg cells but also dendritic cells (DCs) (and their secreted cytokines IL-10 and TGF-b ), are the key players in the regulatory network. A prominent role in determining whether tolerance is induced or not, has been found for DCs, in close interplay with T cells [89, 90] . There is now considerable evidence that the lack/presence of costimulatory and other signals (lack referring to immature DCs) and the lack/presence of regulatory cytokines IL-10 and TGF- b at the site of induction contribute to DCs’ ability to induce Treg cells and tolerance [90] . Pulmonary DCs, accumulating immediately above and beneath the basement membrane of the respiratory epithelium [89] , comprise a unique subset of DCs, called plasmacytoid DCs (pDCs), which appear to be crucial in maintaining tolerance to inhaled harmless antigens. Murine models have shown that when pDCs have been depleted, inhalation of normally inert OVA led to the development of all the major features of asthma. In addition, when transfer of allergen-pulsed pDCs prior to sensitization to 454 L. von Hertzen and T. Haahtela allergen was performed, asthma could not be induced (reviewed in [89] ). In humans, only the plasmacytoid subset, not conventional DCs, express TLR9 [91] , the receptor of unmethylated DNA (CpG oligonucleotides) abundant in bacteria, mites and other invertebrates [92, 93] . Accumulating data indicate a role for TLR9 particularly in the development of respiratory tolerance [80, 94] . Moseman et al. [80] showed in human cells ex vivo that TLR9 stimulation on pDCs by its ligand, CpG-oligonucleotides, generated T reg cells which suppressed T-cell proliferation in an antigen-nonspecific manner, expressed Foxp3 and produced a T reg cell cytokine profile.

Healthy Immune Response vs. Allergic Immune Response

The normal immune response to harmless antigens/allergens is tolerance without the appearance of Th2 cytokines and specific IgE antibodies [89, 90] . In high/ repeated antigen exposure, antigens are not able to fully activate the DCs which in turn may lead to T cell deletion and the development of T reg cells [89] . This tolerance in healthy individuals is mediated by dendritic cells, T reg cells and the suppressive cytokines IL-10 and TGF-b [82] . It is now widely accepted that the balance between allergen-specific T reg cells and Th2 cells is decisive in the development of allergy. After exposure, both healthy individuals and those with allergy show Th1, Th2 and T reg cells, but the relative proportions of these subsets vary; in healthy individuals, specific T reg cells are consistently found to be the dominant subset, whereas in atopics, the proportions of specific Th2 cells are greatly increased [95, 96] . In addition, the function of T regs may be impaired in allergic conditions [97] . Successful specific immunotherapy (SIT) has been found to largely restore the balance in T cell subsets [82] . IL-10 is induced and increasingly secreted by SIT, which, in addition to inducing the generation of T reg cells, suppresses both total and specific IgE and simultaneously increases IgG4 production [96] . A healthy immune response to an allergen (Der p1) is characterized by increased specific IgA and IgG4 levels, low levels of specific IgG1 and trace amounts, if any, of specific IgE [98] . T reg cells, through their secretion of IL-10 and/or TGF- b , are involved in the development of tolerance in several ways: they (1) suppress the function of DCs (and other APCs) to become inactive, tolerogenic, (2) suppress the function and proliferation of Th1 and Th2 cells, (3) suppress specific IgE but increase specific IgG4 and/or IgA production, (4) suppress mast cells, basophils and eosinophils, and (5) interact with resident tissue cells [96] . However, in addition to IL-10 and/or TGF- b , T reg cells may use different mechanisms to regulate T cell proliferation/ function and to control immunopathologies; this may be related to the level of inflammation [83, 99] . An interesting question remains as to whether there are differences in mechanisms involved in the development of tolerance between individuals who are sensitized Prevention of Allergic Diseases 455 but otherwise healthy (clinical tolerance; a condition frequently seen e.g., among the Russian Karelian children) and those without any sensitization at all.

Can Tolerance Be Restored in Atopic Individuals?

Data obtained thus far, mainly from animal models have provided evidence that administration of an antigen systemically under certain conditions can restore tolerance and prevent the development of respiratory allergic disease in sensitized animals (reviewed in [90] ). Even allergen-induced inflammation in murine models of asthma could have been ameliorated by repeated administration of allergen locally into the respiratory tract, although results obtained from murine models need to be taken cautiously [90] . Dose and duration of antigen exposure may be the crucial determinants here. Nonetheless, recent results from studies of sublingual immunotherapy among sensitized children have been encouraging and support the view obtained from animal models; tolerance could be restored and the development of asthma prevented at least in children [100] .

Primary Prevention

An initiative “Prevention of Allergy and Allergic Asthma” was taken up some years ago by the World Allergy Organization (WAO), in collaboration with the World Health Organization (WHO), to prepare strategic guidelines that would provide a sound basis for practical action for authorities, health care professionals, patient organizations, and patients, to decrease the burden of allergy and asthma at a national level [101] . The general principles presented in the paper was targeted to act as a draft for local guidelines to be developed, and was based on scientific evidence and the WHO categorization on the strength of evidence. Preventive measures concerning primary, secondary and tertiary prevention are comprehensively considered in the WAO/WHO guidelines [101] . The focus of this discussion is on primary prevention, i.e., how to strengthen tolerance against allergens and prevent sensitization at the population level. Primary prevention measures by WAO/WHO and the strength of evidence are presented in Table 1 . The evidence is strongest in showing that there is no need of special diet for lactating mothers. Convincing evidence also indicates that smoking in pregnancy and exposure to environmental tobacco smoke in early life is deleterious with respect to allergies, whereas breast-feeding for 4–6 months may prevent or dampen – although not consistently shown in all studies- the development of atopic disease in later life (reviewed in [101] ). As to the avoidance of pets in high risk families, recent data show that even in genetically predisposed children, tolerance to inhalant allergens may develop, provided that the exposure is high enough [59] . 456 L. von Hertzen and T. Haahtela

Table 1 Primary prevention measures (WAO/WHO) Category Measure of evidence Smoking and exposure to environmental tobacco smoke should be avoided, (B) particulary during pregnancy and early childhood Tobacco smoke should be removed from work places (B) Damp housing conditions should be avoided, and indoor air pollutants should be (C) reduced (C) Breast-feeding should be continued until 4–6 months (B) No special diet is needed for the lactating mother (A) In high-risk children, exposure to inhalant allergens should be reduced. Note: (B) the most recent data, however, indicate that even high-risk children may develop tolerance against allergens; the dose-response curve appears to be bell-shaped [59] Highly irritant agents in occupational settings should be avoided. In case this is (C) not possible, measures to prevent employee exposure should be implemented A Evidence from meta-analysis of several or at least one randomized controlled trial(s) B Evidence from at least one controlled study without randomization or from other type of quasi- experimental study, or extrapolated recommendation from category A evidence C Evidence from nonexperimental descriptive studies, such as comparative, correlation and case- control – studies, or extrapolated recommendation from category A or B evidence

Measures for secondary prevention and the strength of evidence are shown in Table 2. Thus far, evidence is vague, and mostly no direct evidence-based data are available. Reduction of exposure to indoor allergens in the case of sensitized young children is recommended to prevent onset of allergic disease. Monosensitization to indoor allergens has been suggested to be the intermediate phase from nonatopy to polysensitisation and overt allergic disease [102] . This is, however, unlikely to be a universal pattern, as occurrence of atopic disease and atopy in general has remained low e.g., in Russian Karelia in repeated surveys [14, 103] and in generational analyses [14] , irrespective of relatively high monosensitisation rates to house dust mite allergen among Russian children. Altogether, effective means for primary and secondary prevention are either lacking or are too vague to make a change. From the public health point of view, the preventive measures should be effective, easy to implement and cause no harm. This is difficult to achieve, and at the moment no active preventive measures are recommended anywhere. Giving child-bearing mothers, infants and children pre- and probiotics is an interesting approach. The first results of probiotic studies were quite promising [104] , but the issue has become controversial as negative results have also been published [105, 106] . It must be emphasized that the term “probiotic” does not refer to any single bacterium species, and the effects are strain- specific. Recently, two studies with moderately positive results have been published [107, 108] . Modulation of the innate immunity by microbial, saprophytic components along with the most important airborne allergens (e.g., grass and birch pollen, cat and dog) in high-risk infants may offer a promising option. It could even be Prevention of Allergic Diseases 457

Table 2 Secondary prevention measures (WAO/WHO) Category of Measure evidence Atopic eczema in infants and children should be treated to prevent respiratory (D) allergy Upper respiratory disease (rhinoconjunctivitis) should be treated to reduce risk of (D) development of asthma In young children already sensitized to indoor allergens, exposure should be (B) reduced to prevent onset of allergic disease Employees should be removed from occupational exposure if they have (C) developed symptoms associated with occupational allergic sensitization B Evidence from at least one controlled study without randomization or from other type of quasi- experimental study, or extrapolated recommendation from category A evidence C Evidence from nonexperimental descriptive studies, such as comparative, correlation and case- control – studies, or extrapolated recommendation from category A or B evidence D Expert opinion of the Prevention of Allergy and Allergic Asthma working group [100] or extrapolated recommendation from category A, B or C evidence

possible to treat drinking water and milk with immunostimulatory saprophytic components without risking the population with infections.

The Finnish Allergy Programme 2008–2018 Launched

Occurrence of allergic diseases in Finland, similar to many other western countries, has reached alarming high levels. This rise in prevalence has continued for more than 40 years, without any changes in trends [109] . Sensitization rates to one or more common allergens among Finnish school children are currently approaching 50% [14] . Already in the early 1990s, the situation for asthma was considered serious enough to give an impetus for a National 10-year Asthma Programme, carried out in 1994–2004. This concrete, pragmatic action plan with simple goals resulted in improvements in several outcome measures and showed that a change for the better can be achieved with this kind of public health action plan [110] . In the wake of the successful asthma programme, the time for a national allergy programme to decrease the burden and costs of allergy has now been considered to be highly opportune. It is necessary to unify diagnostics and treatment practices nationally. In addition, the issue of allergy is associated with much of imagined allergy and unnecessary avoidance of allergens, both of which should be reduced in the population. It has become increasingly clear that the rising prevalence of allergic disease cannot be reversed by allergen avoidance. Tolerance against allergens must be strengthened in the population, in addition to strengthening treatment to control the allergy in those with true and severe allergic disease. The Finnish Allergy Programme was launched in April 2008. 458 L. von Hertzen and T. Haahtela

Goals and Focus

Generally, the Programme is targeted to (1) decrease the burden of allergic disease on individuals and society, (2) decrease costs attributable to allergic disease, and to (3) improve treatment and control of patients with severe allergies. The Finnish Allergy Programme focuses on endorsing health and tolerance. It includes six ambitiously defined goals, tools to achieve the goals and an evaluation plan to assess the outcome and process [111] . The key messages of the Programme are:

( 1 ) Endorse health, not allergy ( 2 ) Strengthen tolerance ( 3 ) Adopt a new attitude to allergy. Avoid allergens only if mandatory ( 4 ) Recognize and treat severe allergies early. Prevent exacerbations ( 5 ) Improve indoor air quality. Stop smoking In allergy, there is now “law of worsening,” i.e., a mild allergy does not commonly develop to a severe one. Many children also outgrow their allergies. Adopting a new attitude – from avoidance to tolerance – is necessary. On the other hand, patients with severe disease must be treated better than before. The Allergy Programme emphasizes the importance of early recognition and treatment of patients with severe allergies. An important, albeit often neglected issue in allergy, is psychological tolerance. Imagined (pseudo-) allergy is common among people, and the Finnish Allergy Programme aims at reducing even this by strengthening psychological tolerance; mild allergy can be considered as a personal trait or characteristic rather than a disease that needs specific measures.

Conclusion

An urban environment appears to lack elements that are necessary for the proper development of tolerance. Accumulating evidence indicates that the interplay between dose, timing and nature of exposure and the genetic composition of the host is decisive in determining the immune response in an individual. Much attention during the past 10 years has been devoted to endotoxin as an environmental immunomodulator. However, gram-negative bacteria appear to play only a minor part of the microbiota in different environments, and the role of bacteria of the gram-positive lineage as well as other microorganisms, fungi, protozoans, mites, algae etc., should in this respect be examined. Nonetheless, one of the key issues in the development of tolerance seems to be the diversity of microorganisms in our environment. Could occurrence of allergies be reduced in western populations? A large body of data shows that allergen avoidance – besides the fact that it is often impossible – seems not to be the right strategy. Animal models have provided encouraging Prevention of Allergic Diseases 459 evidence that broken tolerance can be restored, and second-generation probiotic products (mixtures of four or more probiotic strains completed possibly with yeasts) and other bacteria-based prevention products may be the more successful tools in the future. Meanwhile, a 10 year Allergy Programme targeted to reduce the burden of allergies through education of health professionals and population is implemented in Finland. The focus of this Programme is on prevention and children, and the main issue will be the strengthening of tolerance in early life. To change the old dogmas is the major challenge.

Acknowledgments The authors thank Professor Tapani Alatossava, University of Helsinki, for fruitful discussions, and the Allergy Foundation for partly funding this work.

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Leif Bjermer and Zuzana Diamant

Introduction

Our current understanding of asthma pathophysiology has changed considerably during the last 20 years. From being regarded as an inflammatory disorder mainly affecting the central airways, asthma is now recognized as a heterogeneous, systemic disorder, involving the respiratory tract from nose to peripheral airways. Chronic inflammation in asthma is associated with the development of structural changes within the airways (the so-called “remodelling”) and airway hyperresponsiveness. While most asthma phenotypes are easily controlled with fairly low doses of corticosteroids, others appear more or less steroid-resistant. Inflammation involving mast cells and neutrophils is an example of such underlying mechanisms. Another example of corticosteroid resistance is over production of cysteinyl leukotrienes or tumour necrosis factor (TNF) -a in other asthma phenotypes [1, 2] . All together, this motivates the search for more systemic therapies, complementary to corticosteroid treatment. In this chapter, we will highlight some present and future nonsteroidal therapies, all given by systemic route.

Anti-Leukotrienes

In 1940, Kellaway and Trethewie discovered the “slow reacting substance of anaphylaxis”, which appeared to constitute leukotrienes. Leukotrienes are metabolites of the arachidonic acid, constituent of the membrane phospholipids, via the

L. Bjermer () Department of Respiratory Medicine and Allergology , Heart and Lung Division, University Hospital of Lund , 221 85 Lund , Sweden e-mail: [email protected] Z. Diamant Departments of Allergology and Pulmonology, Erasmus University Medical Center , Rotterdam , The Netherlands e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 465 DOI 10.1007/978-4-431-99362-9_28, © Springer 2010 466 L. Bjermer and Z. Diamant

5-lipoxygenase (LO) pathway [3]. Apart from their bronchoactive properties, leukotrienes have been shown to induce several other features of asthma, such as airway hyperresponsiveness, airway inflammation and potentially, even airway remodelling both in healthy and asthmatic individuals [4–6] . The discovery of leukotrienes introduced a new target for the treatment of asthma. In the second half of the 1990s, the leukotriene synthesis inhibitor (LTSI), zileuton, and the leukotriene receptor antagonists (LTRAs), pranlukast, zafirlukast and montelukast entered into clinical practice representing a novel class of anti-asthma therapy [7] . Through antagonism of cysteinyl leukotrienes (cysLTs) at the CysLT1-receptor within the airways and on inflammatory cells, LTRAs combine anti-inflammatory – mainly anti-eosinophilic – activity with mild bronchodilator and bronchoprotective properties [4] . In asthma, while both LTSI and LTRA have been shown to be similarly effective, blocking the synthesis of both the cysLTs and leukotriene (LT)B4 , LTSI may have additional potential in LTB4 -driven conditions, such as the more severe asthma, COPD and cardiovascular disease [8, 9] . Presently, LTRAs are implicated in all treatment steps for asthma, mainly as add-on therapy [10]. Recently, their application has been extended to virally induced bronchoconstriction in children and to the “combined allergic rhinitis and asthma syndrome” (CARAS) [11, 12] . Moreover, more specific applications of LTRAs imply the mainly cysLTs-driven asthma phenotypes including the Aspirin-Exacerbated Airway Disease (AERD) and smoking or obese asthmatics [1, 2, 13].

Anti-Prostanoids

Prostanoids are also derived from arachidonic acid through the cyclooxygenase (COX) pathway. Both thromboxane A2 (TxA2) and prostaglandin D2 (PGD2) have shown to be involved in allergic inflammation, and the effects are mediated mainly through three different receptors: TP (Thromboxane A2-receptor), DP (D-prostanoid receptor) and CRTH2 (chemoattractant receptor homologous-molecule expressed on T-helper type-2 cells). TxA2 is produced through the enzyme thromboxane synthase, and the primary target for its action is the TP-receptor. Introduced to the market in Japan in 1992, Ozagrel was the first TxA2 synthesis inhibitor reducing airway hyperresponsiveness to acetylcholine and leukotriene D4 [14] . Another anti-TxA2 drug, Seratrodast, is available for the treatment of asthma in Japan since 1997 [15, 16] . Both the DP and the CRTH2 receptors can be stimulated by PGD2 and both receptors are often expressed on the same cells. While the CRTH2 receptor on eosinophils, mast cells and basophils has a pro-inflammatory action, the DP receptor counteracts the CRTH2 effect. However, the interaction between these two receptors is very complex and there are examples of opposite effects, i.e., antagonizing DP receptor acting pro-inflammatory and vice versa [17] . Interestingly, even though PGD2 cannot discriminate between DP and CRTH2 receptors, there are several selective CRTH2 receptor antagonists being developed. Ramatroban was initially developed as a TP-receptor antagonist, but was found to Nonsteroidal Therapy in Asthma & Allergy 467 act also as a CRTH2 receptor antagonist. Modest, though beneficial effects have been reported when applied in allergic rhinitis and asthma, the drug has been registered in Japan as a controller of allergy [18]. Presently, more potent and selective CRTH2 receptor antagonists are being tested in clinical trials of asthma, with promising effects [19, 20] .

Phosphodiesterase Inhibitors

Phosphodiesterase (PDE) includes 11 isoenzymes with various biological activities [21] . In pulmonary medicine, PDE4 and PDE5 are of particular interest. The latter exhibits its mode through interaction with cGMP, and together with PDE1, they are mainly responsible for breaking down gCMP in vascular smooth muscle cells [22] . Sildenafil is a potent PDE5 inhibitor and has been found to be effective in the treatment of pulmonary hypertension. It is conceivable to assume that the same drug may have effect in preventing vascular remodelling, a common phenomenon in both asthma and COPD [21]. The mode of PDE4 action is primarily by converting cAMP to 5’AMP and the different enzymes exert different biological effects dependent on localisation in different cell compartments. PDE4 is a family of 4 distinct sub-enzymes: PDE4A, B, C and D where PDEA, B and D are expressed on various inflammatory cells and structural cells [21]. The PDE4 antagonists were initially believed to be a further development of theophylline, used in asthma and COPD treatment since 1937 [23] . The aim was to find a drug with fewer side effects and drug interactions. Two PDE4 antagonists, Cilomilast (Ariflo®) and Roflumilast (Daxas®), have made it all the way to phase III trials. Both drugs have been shown to modestly reduce early and late inflammatory responses after allergen challenge and to improve airway hyperresponsiveness and lung function [24] .

Anti-IgE

Subcutaneous Omalizumab (a humanized monoclonal antibody, RhuMab-E25) has recently been registered as add-on therapy for the treatment of therapy-resistant, severe allergic asthma*. The mechanisms of action comprise reducing circulating serum IgE and down-regulating high-affinity IgE-receptors (Fce RI) on mast cells and basophils [25]. Dosing is based on total serum IgE levels in combination with body weight. Since too high levels of anti-IgE may induce the formation of immune complexes, the cut-offs for these parameters have been set at 700 IE mL−1 and 150 kg, respectively [26]. In early clinical trials of asthma, Omalizumab has been shown to effectively reduce both the early and late phase responses following inhaled allergen [27]. In phase III trials, Omalizumab effectively improved disease control and allowed reduction of (topical) corticosteroids in two-thirds of the patients with allergic

* 2002 in Australia, 2003 in US and 2007 in Europe. 468 L. Bjermer and Z. Diamant asthma and/or allergic rhinitis [28–30] . However, despite its proven effectivity, the major drawbacks of this novel treatment modality comprise its subcutaneous administration (every 2–4 weeks) and high costs. Future applicability of anti-IgE in combination with immunotherapy is presently being explored for its immunotherapy-saving and (hence) safety-enhancing potential in allergic asthmatics [31, 32]. Presently, anti-IgE treatment is under investigation for another potential indication: food allergy [33].

Allergen Specific Immunotherapy

Allergen specific immune therapy (ASIT) has been introduced by Noon in 1911 to induce tolerance to relevant allergens. The first successful attempt to induce tolerance to pollen allergens by sub-dermal injections was performed by Freeman at the Saint Maries hospital in London [34] . ASIT has been found to be effective not only in hay fever but also in asthma with allergy for pollen or house-dust mite that cannot be controlled by standard therapy [35]. ASIT is mostly administered by specialists as sub-dermal injections, requiring a building-up period followed by a maintenance period of 3–5 years. The protocol used varies depending on local tra- dition and the number and type of allergens delivered. Rush desensitization may be applied in mono-allergy and it is important to quickly reach a maintenance dose and a certain degree of protection. Examples of different protocols are shown in table (Table ASIT-number). Ultra-rush desensitization, reaching the maintenance dose already on day one, may also be applied in specific settings both as injectable and sub-lingual therapies [36, 37] . Concomitant uncontrolled asthma (FEV1 lower than 70% of predicted) is a relative contraindication to ASIT as asthma may temporarily deteriorate, especially during the step-up phase [38] . On the other hand, ASIT may decrease asthma severity and if started early, even prevent the development of asthma in susceptible patients with allergic rhinitis [39] . Today, ASIT both as injection and as sub-lingual therapies, is documented for allergic rhinitis with or without concomitant asthma. When safety instructions and protocols are followed, both treatments are safe and well-tolerated. Although sub-lingual therapy has the advantage of being simpler to administrate and requires less safety precautions, overall, the documented efficacy is considerably less than for subcutaneous ASIT [40, 41] .

Anti-Cytokine Therapy

The production of cytokines is regulated by regulatory T-cells (T-reg cells) and until recently two major pathways were considered: the T-helper (TH) type 1 and 2 pathways, with the latter being more associated with allergic sensitization, production of IgE and activation of eosinophils [42, 43]. Thus, the therapeutic strategy should Nonsteroidal Therapy in Asthma & Allergy 469

o be racts time

Strength Quick (one allergen) (1 ½ month step-up)

time

Strength Standard-short (max 2 allergens) (3 months step-up)

time

1.0 week 16 ml Allergen Specific Immunotherapy Step-up Schedule Specific Immunotherapy Step-up Schedule Allergen

Increase interval length Increase interval length 2 weeks 4 weeks 6 weeks The strategy should be chosen depending on the number of ext specific immunotherapy. Example of dosing schedules for allergen 100 SQ 100 SQ 100 SQ 1,000 SQ 1,000 0.2 SQ 1,000 0.4 SQ 10,000 0.6 SQ 0.2 10,000 SQ 0.4 week 10,000 1 SQ 0.8 week 10,000 2 SQ 0.15 week 3 1,00,000 SQ 0.3 week 4 100 1,00,000 SQ SQ 0.6 week 5 week 6 1,000 100 1,00,000 SQ SQ SQ 0.8 1,000 SQ 0.1 week 1,00,000 7 SQ 1,0000 SQ 0.2 week 1,00,000 8 SQ 1,0000 SQ 1,0000 0.4 SQ 0.8 week 1,00,000 9 SQ 0.3 week 11 0.6 0.8 1,00,000 0.2 SQ week 0.2 12 0.8 1,00,000 SQ week 0.4 13 0.4 1,00,000 1,00,000 week SQ SQ 1 week week 0.1 14 2 week 1,00,000 3 SQ week 0.2 week 15 4 1,00,000 SQ 0.4 week 0.6 etc) must als 5 and clinical factors (concomitant asthma, disease severity, week other factors such as type of allergen used. However, 6 1,000 SQ 10,000 0.8 week considered. SQ 7 10,000 SQ 10,000 1.0 week SQ 8 10,000 week week SQ 1,00,000 9 10 SQ 100 SQ 0.2 0.1 1,00,000 week SQ 11 0.2 0.4 1,00,000 week SQ 12 0.15 1,00,000 0.8 SQ 1,00,000 SQ 0.3 day day 1 1 day 0.6 4 0.2 day 4 1.0 week 2 0.8 day 7 week 3 week day 4 1 week 6 week 5 Table Table 1 Standard (4 months step-up) Strength 470 L. Bjermer and Z. Diamant be directed towards inhibiting type 2 associated cytokines such as IL-4, 5 and 13 and promoting type 1 associated cytokines, such as IL-9, 10, 12 and interferon (IFN)-gamma. Recently, the TH-1 and 2 hypotheses have been challenged with the discovery of other T-regulatory pathways, such as TH17 [44]. In asthma, the predominance of TH1 or TH2 pathway is also dependent on the individual phenotype: while the more mild allergic asthma is mainly of the TH2 type, the more severe sub-sets involve inflammatory mediators more linked to the TH1 pathway [45].

Anti-TNF-a

TNF- a is stored in granulae of macrophages and mast cells and released via IgE- dependent mechanisms [46] . Other important TNF sources are eosinophils, neutrophils and epithelial cells [47] . Increased expression of TNF-α has been found in bronchoalveolar lavage cells from asthmatic subjects [48]. In addition, increased levels of TNF-α have been measured in BAL fluid from allergic asthmatics following allergen challenge [49] . Anti-TNF- a therapy either by Infliximab, a chimeric anti-TNF antibody, or Etanercept, a soluble TNF-a receptor, has shown promising effects in several studies of severe persistent asthma, as these patients are relatively resistant to treatment with corticosteroids, expressing a T-helper-1 cell cytokines profile [50]. A recent study in patients with severe persistent asthma reported substantial improvement in airway hyperresponsiveness, quality of life scores and post-bronchodilator FEV1 following 10 weeks of treatment with subcutaneous Etanercept [51]. Another study in severe asthmatics showed similar results after 12 weeks of open label treatment [45] . Interestingly, Etanercept failed to protect against allergen-induced airway inflammation and airway hyperresponsiveness in patients with mild to moderate persistent asthma, who have a different TH-cell profile [52]. Thus, further studies are needed before this targeted treatment approach can be more widely recommended.

Anti-IL-5

Interleukin (IL)-5 is secreted by activated CD4 positive T-lymphocytes and has a central role in eosinophil activation and chemotaxis [53]. Inhalation of interleukin-5 is known to cause eosinophilic inflammation and to induce airway hyperresponsiveness in patients with asthma [54]. Thus, several in vitro and in vivo studies support the central role of IL-5 in both the allergic and asthmatic (airway) inflammations. In an allergen challenge study, Leckie and colleagues pre-treated 24 males with atopic mild persistent asthma with intravenously administrated monoclonal interleukin-5 antibody (SB-240563) in a randomized placebo-controlled design [55]. However, despite dramatic reduction in the number of eosinophils in both blood and induced sputum, anti-IL-5 treatment failed to reduce both the allergen-induced late response Nonsteroidal Therapy in Asthma & Allergy 471

(LAR) and the allergen-induced airway hyperresponsiveness. These observations are in contrast with the pre-treatment with inhaled corticosteroids, reducing both the allergen-induced airway inflammation and the allergen-induced airway responses [56]. In a previous study in asthma, Haselden et al. already showed similar discrepancy between airway hyperresponsiveness and inflammatory reaction [57]. In this study, eight patients with a documented LAR to cat allergy were injected with cat allergen (Fel d 1) extract. However, no increase in eosinophils or TH2-type lymphocytes could be found in the bronchoalveolar lavage of these patients at 6 hours post-allergen [57] . These studies provided evidence that eosinophils may be merely an epi-phenomenon and hence may not play a predominant role in the pathophysiology of asthma, as was previously assumed. Another possible explanation could be that the anti-IL-5 effect on sputum and blood eosinophils does not fully reflect the situation within the deeper lung tissue. In a biopsy study, Flood-Page and co-workers found limited effect of anti-IL-5 treatment on tissue eosinophils in patients with active asthma [58] . In a more recent study, anti-IL-5 therapy with Mepolizumab failed to provide additional asthma control on top of moderate doses of inhaled corticosteroids in patients with persistent asthma, despite a significant reducing effect on sputum eosinophils [59]. Thus, the limited clinical efficacy of anti-IL-5 treatment may be due to the limited efficacy of the compounds tested so far or to a compensatory mechanism partly neutralizing the anti-IL-5 effect in the lung tissue. Alternatively, 2 recent placebo-controlled studies report beneficial effects of one year add-on treatment with intravenous mepolizumab in patients with severe refractory eosinophilic asthma [115,116] . In the first study with 9 patients with prednisone-dependent, eosinophilic asthma, mepolizumab reduced the number of sputum eosinophils and allowed tapering off prednisone [115]. Furthermore, in the other study in 61 asthmatics, add-on mepolizumab significantly reduced the number of blood and sputum eosinophilis along with significant reduction of the number of severe asthma exacerbations and improvement in quality of life (AQLQ scores) [116]. These data suggest that refractory airway eosinophilia may be a prerequisite for a potential response to (longterm) anti-IL-5 treatment.

Anti-IL-4 and Anti-IL-13

Parallel with IL-5, interleukin-4 (IL-4) is another key cytokine in the TH-2 dominated inflammation. IL-4 activates B-cells to differentiate into plasma cells secreting IgE [60, 61] . Furthermore, IL-4 enhances the secretion of eotaxin and increases the expression of adhesion molecules such as VCAM-1, which is known to be important for eosinophil recruitment and activation [62]. Increased serum levels of IL-4 have been reported in patients with allergic asthma, and allergen provocation has been shown to increase IL-4 levels in bronchoalveolar lavage [63]. Furthermore, inhalation of IL-4 has been shown to increase the numbers of eosinophils in induced sputum [64]. A free secreted form of IL-4 receptors naturally occurs in the serum of patients with active allergic asthma. This receptor has been shown to act as an antagonist to IL-4 and consequently prevents the activation of cells expressing IL-4 receptors [62] . A recombinant IL-4 receptor (RHUIL-4, 472 L. Bjermer and Z. Diamant

Nuvanc™; Immunex™) has been used in clinical studies in patients with allergic asthma. In one placebo-controlled parallel study, 62 patients with moderate persistent asthma, while on a maintenance dose of inhaled corticosteroids (ICS), were treated with inhaled RHUIL-4 (once per week for 12 weeks) and could successfully reduce or completely taper off their treatment with ICS [65]. Furthermore, treatment with recombinant IL-4 receptor resulted in a reduction of asthma symptoms and improved quality of life [65] . Presently, various anti-IL-4 approaches are being explored in allergic disease.

Anti-IL-13

The alpha chain of the IL-4 receptor forms an important signalling pathway for both IL-4 and IL-13 [66] . Thus, both cytokines share important biological activities. Interleukin-13 and IL-4 interact with respiratory epithelium, induce production of eotaxin and thus promote eosinophilic inflammation in animals [67] . They also interfere with COX-2 activity in epithelial cells, down-regulating the production of PGE2 [68] . Moreover, both cytokines increase the expression of VCAM, important for adherence and recruitment of T-lymphocytes and eosinophils to the lung tissue [69] . It has also been shown that both cytokines can induce similar biological activity independent of each other [70] . Thus, for optimal efficacy, it seems important to block both cytokines. Several combined anti-IL-4/IL-13 antibodies have shown promising results in animal models of asthma [71] . Until recently, there were no published human studies.

Anti-IL-9

Interleukin (IL)-9 was originally described as mast-cell growth factor due to its ability to enhance the survival of primary mast cells and to induce the production of their pro-inflammatory cytokine IL-6 [72, 73]. IL-9 induces mast-cell secretion of a number of proteases and the expression of high-affinity IgE receptor expression (Fce RI-a ) on T helper cell clones [74]. As mast cells are believed to play a crucial role in airway fibrosis and remodelling, IL-9 has received increased attention as a potential target in asthma therapy. Administration of anti-IL-9 systemically prevented the increase in airway hyperresponsiveness and eosinophilic response in mice after allergen challenge [75] . Presently, anti-IL-9 treatment is being tested in early clinical trials.

IL-10

Interleukin (IL)-10 is known to suppress the production of a number of proinflammatory cytokines such as IL-1b , TNF- a and GM-CSF and chemokines such as RANTES and eotaxin [76]. Furthermore, IL-10 inhibits the production of nitric oxide (NO) and appeared to block the effects of IL-5 [77]. Asthmatic patients have Nonsteroidal Therapy in Asthma & Allergy 473 been shown to have a decreased ability to secrete IL-10 [78, 79]. Furthermore, a pronounced suppression was demonstrated in patients with difficult-to-treat asthma [80], while the levels of IL-10 increased in asthmatic children successfully treated with inhaled corticosteroids [81]. Until recently, recombinant IL-10 has only been shown to be effective in patients with Crohn’s disease [82]. No studies in asthma have been reported so far.

Recombinant IL-12

Interleukin (IL)-12 is mainly secreted by activated macrophages [83] and is also released by epithelial cells in asthmatics with active airway inflammation [84].

IL-12 stimulates TH 0 lymphocytes towards the TH1 pathway and suppresses the TH2 response. It is known that subjects with allergic asthma have lower concentrations of IL-12 in their serum [85]. Low concentration of IL-12 has also been found in umbilical cord blood from infants predisposed to atopy [86]. These children also appeared to have low production of IFN- g, another important factor predisposing to TH-1 dominated inflammation [87, 88] . In vivo experiments in mice have shown that pre-treatment with IL-12 can prevent the increase of eosinophilic inflammation and the development of airway hyperresponsiveness following antigen challenge [89]. However, IL-12 may also have a dual response dependent on the timing of treatment. While IL-12 in the early phase of allergen sensitization may be protective, the introduction of IL-12 in a later stage may enhance even the allergic asthmatic reaction [90] . In a placebo-controlled study by Bryan and colleagues, 39 patients with allergic asthma were treated with recombinant IL-12 in weekly increasing doses for 4 weeks. In the group treated with IL-12, it was possible to prevent the allergen-induced eosinophilic inflammation. Furthermore, a tendency towards improvement in airway hyperresponsiveness after allergen provocation was seen together with a tendency to reduced late phase-induced inflammation. Unfortunately, the treatment was associated with a number of clinically relevant side effects, the most common one being flue-like symptoms occurring after each injection. Hence, 6 out of 19 subjects were withdrawn from the study due to unacceptable side effects [91].

Conclusion Anti-Cytokine Therapy

The cytokine network in asthma is complex and dependent on the site, duration or timing of the intervention. The latter is exemplified by IL-12 with a potentially dual response. In addition, different asthma phenotypes may require different (custom- ized) anti-cytokine therapy: an example is anti-TNF that seems to be effective in asthmatics with predominantly TH1 inflammatory mechanisms, including more severe disease, obese and/or smoking asthma patients [50, 92] . 474 L. Bjermer and Z. Diamant

Probably, blocking more than one cytokine pathway is needed to obtain sufficient efficacy. Another challenge is the dosing, as has been demonstrated with anti-IL-5 treatment. This is a drawback for anti-cytokine treatment, since the production of monoclonals is expensive. Alternative strategies for antibody production have been tested, i.e., peptide-based vaccination and induction of neutralizing antibodies. These strategies require much lower doses and thus have a potential of being more cost effective [93–95].

Probiotics

Following the concept of TH1 and TH2 imbalance and the hygiene hypothesis, immunostimulation with TH1 promoting microbes (i.e., probiotics) has been advocated during the last decade [96]. In this context, two major strategies have been tested: immunostimulating DNA sequences and active bacterial cultures, usually Lactobacilli (LB) and Bifid bacteria, given as food supplements. Probiotics delivered to high-risk mothers during the last months of pregnancy and during the first 6 months after delivery have been shown to reduce the risk for development of allergy and atopic dermatitis in newborns. This effect is maintained during the first years of life [97] and is of special interest as atopic dermatitis is a strong risk factor for later development of asthma in predisposed children [98]. Several species of Lactobacilli have been tested and the effect by one strain may not necessarily apply for another, i.e., it is not a “class effect”. In Kaliomäki’s studies, LB Rhamnosus GG (LGG) was used. In another recent study with a similar design, LB Streuveri reduced the number of IgE-related dermatitis, while the cumulative incidence of eczema was the same in both treatment groups [99]. In a third study using LB Acidophilus (LAVRI-A1), no difference in the incidence of atopic dermatitis could be found between the treatment groups. Unexpectedly, the degree of sensitization to allergens, including milk allergy, was higher in the probiotic group, despite a higher degree of Lactobacilli colonization [100]. Hence, this type of prevention of allergic diseases needs further research, considering both the lactobacillus strains but possibly the timing of intervention as well, before it can be generally recommended as a primary preventive tool, even in a risk population.

Heparins

Heparin and related compounds have been shown to possess immunomodulator properties, attenuating the allergic airway inflammation in various species, including humans [101]. The anti-inflammatory properties may at least partly be explained by their anionic polyelectrolyte structure and are (mostly) not associated with anti-thrombotic activity [100,102]. In asthma, repeated doses of inhaled Nonsteroidal Therapy in Asthma & Allergy 475 unfractionated heparin (UFH) have been shown to reduce the allergen-induced early and late asthmatic airway responses [103]. Similarly, in allergic rhinitis, intranasal UFH has been found to protect against adenosine monophosphate (AMP)- and allergen-induced nasal symptoms and the associated nasal mast-cell release and eosinophilia/ECP, respectively [104, 105]. In the past decade, low molecular weight heparins (LMWH) have been introduced into clinical practice. LMWH possess superior pharmacological and immunomodulator properties to UFH. In (pre)clinical models of asthma, LMWH have been shown to possess potent (dose-dependent) anti-inflammatory effects (by reducing mast cell-induced mediator release and by reducing tissue eosinophilia by T-cell modulation) in various species in vivo [100 + refs therein, [106, 107]. In asthmatic patients, inhaled LMWH (5000 IU anti-FXa/daily, for 2 weeks) has been shown to reduce the number of inflammatory cells and mediators/cytokines in bronchoalveolar lavage fluid [108]. In another study, a dose- dependent protection of ascending single inhaled dose of LMWH (enoxaparin) was found against exercise-induced bronchoconstriction (EIB) [109]. In this study, the maximum inhaled dose of LMWH (2 mg kg−1 ) was more effective than inhaled UFH (80,000 IU, equals 7.5 mg kg−1 ) against EIB and there were no anti-thrombotic effects at any of the doses tested [108]. A recent study by Duong and colleagues evaluated the effects of a single nebulized dose of a heparin- derived hypersulfated disaccharide devoid of anti-coagulant activity (IVX-0142) on allergen-induced airway responses and airway inflammation [110]. Overall small and statistically not significant effects on all outcome parameters were observed – probably due to ineffective dosing. Application of heparin and related compounds for treatment of asthma and related disorders awaits further research.

Other Potential Anti-Asthma Targets

Multiple signal transduction pathways are involved in airway inflammation with one of the key signalling pathways being phosphoinositide 3-kinase (PI3K). There are several isoforms of the PI3Ks, and especially the PI3Kg and d isoforms play an important role in the expression and activation of inflammatory mediators, inflammatory cell recruitment, immune cell function, airway remodelling and corticosteroid insensitivity in asthma and COPD [111, 112]. In this respect, these two isoforms may act as novel targets for therapeutic intervention in asthma and/or COPD. In vivo studies in these target populations are expected in the coming years. Other immunomodulator strategies in asthma are toll like receptor 9 (TLR-9) antagonists and CpG-, non-CpG- and antisense oligodeoxynucleotides [113, 114]. Some of these drugs have already entered phase I or II studies, but little data have been published so far. 476 L. Bjermer and Z. Diamant

Fig. 1 Different treatment strategies derived from the TH1/TH2 hypothesis. One strategy is to promote the immune system to direct towards the TH1 pathways, another to block TH2 promoting signals. A third strategy is to block disease specific (TH2 associated) mediators

Conclusion

Since asthma was recognized as an inflammatory disease of the airways responsive to corticosteroids, our understanding of the concept of inflammation has changed considerably. As the inflammation has been found to extend beyond the airways and not all components appeared to respond to corticosteroid treatment, an urgent need came to find more disease-specific treatment modules devoid of disturbing side effects. The hygiene hypothesis, even though recently revised, has provided a base for constructing a large number of treatment strategies outlined in figure (Fig. 1 ) from TH1 promoting microbes and cytokines to blocking TH2 associated cytokines and disease-specific mediators, mainly amending the TH2 pathway. However, the nature of asthma is heterogeneous and complex, hence it requires totally different approaches for the prevention and treatment of early, mild and more severe disease.

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100. Taylor AL, Dunstan JA, Prescott SL. Probiotic supplementation for the first 6 months of life fails to reduce the risk of atopic dermatitis and increases the risk of allergen sensitization in high-risk children: a randomized controlled trial. J Allergy Clin Immunol. 2007; 119 (1):–91 101. Diamant Z, Page CP. Heparin and related molecules as a new treatment for asthma. Pulm Pharmacol Ther. 2000; 13:1–4 102. Ludwig RJ, Alban S, Boehncke WH. Structural requirements of heparin and related molecules to exert a multitude of anti-inflammatory activities. Mini Rev Med Chem. 2006; 6 (9):1–23 103. Diamant Z, Timmers MC, Van der Veen H, et al. Effect of inhaled heparin on allergen- induced early and late asthmatic responses in patients with atopic asthma. Am J Respir Crit Care Med. 1996; 153 (6 Pt 1):1–5 104. Vancheri C, Mastruzzo C, Armato F, et al. Intranasal heparin reduces eosinophil recruitment after nasal allergen challenge in patients with allergic rhinitis. J Allergy Clin Immunol. 2001; 108 (5):–8 105. Zeng D, Prosperini G, Russo C, Spicuzza L, Cacciola RR, Di Maria GU, et al. Heparin attenuates symptoms and mast cell degranulation induced by AMP nasal provocation. J Allergy Clin Immunol. 2004; 114 (2):–20 106. Seeds AE, et al. The effect of inhaled heparin and related glycosaminoglycans on allergen- induced eosinophil infiltration in guinea-pigs. Pulm Pharmacol. 1995; 8(2–3):97–105 107. Zeng D, Prosperini G, Russo C, Spicuzza L, Cacciola RR, Di Maria GU, et al. Heparin attenuates symptoms and mast cell degranulation induced by AMP nasal provocation. J Allergy Clin Immunol. 2004; 114 (2):–20 108. Passowicz-Muszynska E, Jankowska R, Krasnowska M. [The effect of inhaled low molecular weight heparin on cell composition in bronchoalveolar lavage fluid and serum levels of soluble receptor IL-2 in bronchial asthma patients] Pol Merkuriusz Lek 2002; 12 (69):–20(Polish) 109. Ahmed T, Gonzalez BJ, Danta I. Prevention of exercise-induced bronchoconstriction by inhaled low-molecular-weight heparin Am J Respir Crit Care Med. 1999; 160 (2):–81 110. Duong M, Cockcroft D, Boulet LP, Ahmed T, Iverson H, Atkinson DC, Stahl EG, Watson R, Davis B, Milot J, Gauvreau GM, O’Byrne PM. The effect of IVX-0142, a heparin-derived hypersulfated disaccharide, on the allergic airway responses in asthma. Allergy 2008; 63 (9):1–201 111. Doukas J, Eide L, Stebbins K, Racanelli-Layton A, Dellamary L, Martin M, Dneprovskaia E, Noronha G, Acevedo LM, Soll R, Wrasidlo W, Cheresh DA. Aerosolized Phosphoinositide 3-Kinase {gamma}/{delta}Inhibitor TG–115 as a Therapeutic Candidate for Asthma and Chronic Obstructive Pulmonary Disease. J Pharmacol Exp Ther. 2008; [Epub ahead of print] 112. Park SJ, Min KH, Lee YC. Phosphoinositide 3-kinase delta inhibitor as a novel therapeutic agent in asthma. Respirology. 2008; 13 (6):–71 113. Dorn A, Kippenberger S. Clinical application of CpG-, non-CpG-, and antisense oligodeoxynucleotides as immunomodulators. Curr Opin Mol Ther. 2008; 10 (1):10–20 Review 114. Kline JN, Krieg AM. Toll-like receptor 9 activation with CpG oligodeoxynucleotides for asthma therapy. Drug News Perspect. 2008;21 (8):–9 115. Nair P, Pizzichini MM, Kjarsgaard M, Inman MD, Efthimiadis A, Pizzichini E, Hargreave FE, O’Byrne PM. Mepolizumab for prednisone-dependent asthma with sputum eosinophilia. N Engl J Med. 2009 Mar 5;360(10):985–93 116. Haldar P, Brightling CE, Hargadon B, Gupta S, Monteiro W, Sousa A, Marshall RP, Bradding P, Green RH, Wardlaw AJ, Pavord ID. Mepolizumab and exacerbations of refractory eosinophilic asthma. N Engl J Med. 2009 Mar 5;360(10):973–84 Part II Special Considerations in Children, Elderly and Pregnancy Asthma and Rhinitis in Pregnancy

Vanessa E. Murphy and Peter G. Gibson

Introduction

Asthma and rhinitis are common medical conditions that complicate pregnancy. Asthma can have an adverse impact on pregnancy outcomes, and pregnancy can modify the clinical status of pre-existing asthma and rhinitis. Coordinated medical and antenatal care that combines optimal medication use with self-management skills and careful monitoring of the mother and her baby form the basis of effective management of asthma and rhinitis in pregnancy.

Asthma During Pregnancy

Asthma prevalence is around 10% in the adult female population, and between 8 and 12% of pregnant women in the UK and Australia report asthma during pregnancy. The clinical status of asthma is often altered by pregnancy. Women may experience a worsening of asthma during pregnancy, an improvement in asthma, or no change in clinical asthma status [1, 2] . Exacerbations of asthma are also common and affect many pregnant women with asthma [3, 4] .

Asthma Control

Asthma control is an important variable to assess during pregnancy, since changes in asthma control may necessitate changes in asthma therapy [5, 6] (Table 1 ). A large prospective study of changes in asthma symptoms during and immediately

V.E. Murphy and P.G. Gibson () Hunter Medical Research Institute , Level 3, John Hunter Hospital , Locked Bag #1, Hunter Region Mail Centre , Newcastle , NSW 2310 , Australia e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 485 DOI 10.1007/978-4-431-99362-9_29, © Springer 2010 486 V.E. Murphy and P.G. Gibson

Table 1 Clinical assessment of asthma during pregnancy Asthma control Night waking Daytime symptoms Activity limitation Reliever use Exacerbations Frequency Severity Lung function Airflow limitation Co-morbidity Rhinitis Gastroesophageal reflux Obesity Self-management skills Inhalation device technique Education Adherence Self-monitoring Action plan

after pregnancy found that there was a significant increase in asthma symptoms such as wheezing, sleep disturbance, and activity limitation from asthma between 25 and 32 weeks of gestation in those women whose asthma worsened [2] . Among women whose asthma improved during pregnancy, there was a decrease in wheeze and little change in sleep/activity interference. However, in all women, there was a significant improvement in wheezing and interference with sleep, and activity from asthma between 37 and 40 weeks of gestation. More than half of the women who had worsening of asthma during pregnancy showed an improvement in the postpartum period, while worsening of asthma at postpartum was observed in 87% of women who had improvements in pregnancy [2] .

Asthma Exacerbations

Asthma exacerbations occur during pregnancy and can be severe requiring hospitalization in up to 6% of women [4] . Preventing exacerbations is an important goal of asthma treatment. During pregnancy, between 20 and 36% of women have exacerbations of asthma requiring medical intervention [3, 7]. Exacerbations can occur at any time during gestation, but are more common in the late second trimester [1, 3, 8]. Severe exacerbations during labor are rare. The exacerbation rate during pregnancy increases with increasing asthma severity [1, 3, 7]. Murphy et al. described severe exacerbations among 8% of women with mild asthma, 47% of women with moderate asthma, and 65% of women with severe asthma [3] . Other risk factors for asthma exacerbation during pregnancy include inadequate prenatal care, viral infection [3] , Asthma and Rhinitis in Pregnancy 487 rhinitis [9] , obesity [10] , medication nonadherence, and the lack of appropriate treatment with inhaled corticosteroids (ICS) during pregnancy [3, 8, 11]. Conditions such as gastroesophageal reflux, rhinitis, and sinusitis may worsen during pregnancy, in turn exacerbating asthma. Treatment of these conditions is recommended as a component of asthma management during pregnancy [5] . Changes in asthma during pregnancy are variable and are not necessarily consistent from one pregnancy to another. When successive pregnancies in women with asthma were examined, only 60% of women followed the same course of asthma in the second pregnancy as the first, suggesting that there is a determinant of asthma which differed in the two pregnancies [2] . Interestingly, the course of rhinitis during pregnancy correlated with the course of asthma during pregnancy, with rhinitis worsening or improving in more than 50% of patients whose asthma had also worsened or improved, respectively [9] . Systemic factors such as IgE which can affect both the upper and lower airways may, therefore, be an important determinant of changes that occur in asthma and rhinitis during pregnancy [9] . Fetal sex has also been suggested as a relevant factor, where female fetal sex has been associated with deteriorating asthma in pregnancy [12] .

Lung Function During Pregnancy

Several studies of airway function during pregnancy report no changes in spirometry, but improvements in methacholine airway responsiveness are observed to occur in asthmatic women during the second trimester of pregnancy [13] . Pregnancy itself leads to changes in lung volumes that do not appear to have a major impact on asthma. These changes include decreases in total lung capacity and functional residual capacity, reduced chest wall compliance, and increased tidal volume and minute ventilation resulting in decreased arterial pCO2 concentration as an effect of progesterone-induced heightened respiratory drive.

Rhinitis During Pregnancy

Symptoms of rhinitis are common during pregnancy. Between 18 and 30% of pregnant women report rhinitis symptoms during pregnancy. These symptoms may represent pre-existing rhinitis, the development of pregnancy rhinitis, or less common causes of rhinitis such as viral or bacterial infection, eosinophilic non-allergic rhinitis, nasal polyposis, or rhinitis medicamentosa. The course of rhinitis may vary during pregnancy. In patients with co-existing asthma and rhinitis, there is reasonable concordance between pregnancy-induced changes in asthma and changes in rhinitis [9] (Fig. 1 ). 488 V.E. Murphy and P.G. Gibson

30 Rhinitis Improved Rhinitis Same 20

% of women of % Rhinitis Deteriorated 10

0 Asthma Asthma Improved Worse

Fig. 1 Change in rhinitis among women with asthma who experienced an improvement or worsening of asthma during pregnancy (Adapted from [9] ).

Allergic Rhinitis

Allergic rhinitis is common in pregnancy, and like asthma, the course can vary with up to one-third of women experiencing a deterioration in allergic rhinitis symptoms during pregnancy [14] . In women with pre-existing rhinitis, disease severity may change as a result of pregnancy. For example, a worsening of nasal symptoms was observed in 34% of pregnant women with pre-existing rhinitis, an improvement in 15%, and no change in 45% [9] . The recently revised international consensus panel, ARIA (Allergic Rhinitis and Its Impact on Asthma), has developed a rhinitis classification, and has recommended a step-wise approach to the treatment of allergic rhinitis based on the severity and duration of symptoms [15] .

Pregnancy Rhinitis

There is a specific form of rhinitis that develops during gestation. Pregnancy- associated rhinitis is defined as symptoms of nasal obstruction and rhinorrhea that develop during pregnancy, lasting for at least 2 months, and disappearing postpartum. The incidence of rhinitis associated with pregnancy was estimated to be 9% [16] . The mechanisms of pregnancy rhinitis are not known, but may be hormonally induced or due to changes in nasal hyperreactivity. The treatment of pregnancy rhinitis involves simple measures such as sleeping with the head of the bed elevated to avoid the increase in nasal congestion that occurs in the supine position, nasal saline washings, and nasal alar dilation using external devices. Asthma and Rhinitis in Pregnancy 489

Snoring and Rhinitis in Pregnancy

There is an emerging recognition that snoring and obstructive sleep apnea (OSA) can be important complications during pregnancy [17, 18] . Additionally, OSA is linked to pre-eclampsia [17, 19] . Rhinitis can impact on these associations. While the nose does not usually contribute substantially to total upper airway resistance, the swelling of the nasal mucosa due to congestion of the submucosal capacitance vessels that occurs during pregnancy may significantly reduce nasal airflow. With pregnancy there is also a reduction in upper airway dimensions, and pre-existing nasal conditions such as structural defects and rhinitis can increase nasal resistance. The consequences of this are nasal obstruction and an impairment of nasal breathing, especially when supine and during sleep. Treatment of allergic rhinitis with nasal corticosteroid reduced the apnea–hypopnea index and improved nasal resistance in OSA patients [20] . These studies suggest that in addition to an assessment of rhinitis and its severity, it is important to enquire about snoring and daytime sleepiness in pregnant women with rhinitis, as this may indicate accompanying OSA. If OSA occurs during pregnancy, treatment with nasal continuous airway pressure is well tolerated and effective.

Maternal and Fetal Complications of Asthma in Pregnancy

Epidemiological studies provide varying results for the risk of maternal complications in pregnant women with asthma. The effect of asthma control and treatment may explain these differing results, with increased risks of complications generally associated with poor asthma control, asthma exacerbations, or undertreatment of asthma during pregnancy (Table 2 ).

Low Birth Weight

Women with an exacerbation of asthma during pregnancy have a 2.5-fold increased odds of delivering a low birth weight baby (<2,500 g) [4] . An increased risk of intrauterine growth restriction or low birth weight in asthmatic pregnancies was found in

Table 2 Pregnancy adverse effects associated with complicated asthmaa Low birth weight Pre-term labor Pre-eclampsia Severe asthma exacerbation a Complicated asthma is identified by poor control, need for oral corticosteroid, or severe exacerbation 490 V.E. Murphy and P.G. Gibson a meta-analysis of four studies where women did not use ICS for asthma treatment during pregnancy [21] . Conversely, a meta-analysis of data where some or all women had used ICS during pregnancy found no significantly increased risk of low birth weight compared to control [21] . These analyses suggest that the use of ICS medication for asthma treatment during pregnancy may protect against low birth weight.

Preterm Birth

Preterm labor is more common in pregnant women with severe asthma and in those needing oral corticosteroids for asthma exacerbations [22– 24] .

Pre-eclampsia and Pregnancy induced hypertension

Pregnant women with asthma have been identified as being at increased risk of pre-eclampsia or pregnancy induced hypertension [8, 22, 25, 26] . The rate of pre- eclampsia was reported to be higher among oral steroid users compared to women with asthma who did not use oral steroids. Several studies have also found that the risk of pre-eclampsia is increased in women with poor asthma control [27– 29] . In a large prospective study [30] where asthma was actively managed and subjects were well characterized, there was no effect of asthma on any of the outcomes examined, namely pre-eclampsia, perinatal mortality, low birth weight, preterm delivery, and congenital malformations. This study and others of women with closely managed asthma lead to the conclusion that well controlled asthma does not have significant adverse effects on either the mother or baby. Maternal allergic rhinitis has not been associated with adverse pregnancy outcomes [31] .

Congenital Malformations

The data on the effect of maternal asthma on congenital malformations is reassuring. Of the eight cohort studies examining congenital malformations among women with asthma, seven studies found no adverse effect and only one historical cohort study demonstrated a significantly increased odds of malformations in women with asthma compared to a control group of women without asthma [22] .

Perinatal Mortality

Although two studies in the 1970s found a significant effect of maternal asthma on perinatal mortality [32, 33] , many of deaths were to women with severe asthma that Asthma and Rhinitis in Pregnancy 491 was characterized by recurrent exacerbations during pregnancy. Since then, eight cohort studies have reported no increased risk of still birth and perinatal or neonatal mortality in women with asthma [8, 24, 30, 34– 38] .

Management of Asthma and Rhinitis During Pregnancy

Managing Asthma and Rhinitis

The goals of asthma and rhinitis management during pregnancy are to ensure normal fetal maturation while maintaining maternal quality of life by minimizing symptoms and limitations to activity, preventing exacerbations, maintaining near normal lung function and minimizing medication use and adverse side effects from medications [5] . Guidelines recommend the use of ICS for all women with persistent asthma, following a step-wise approach to therapy to achieve asthma control [5] . A randomized controlled trial that compared the use of inhaled beclomethasone and oral theophylline for the prevention of asthma exacerbations during pregnancy in women with moderate asthma found fewer side effects with inhaled beclomethasone and that the exacerbation rate was similar with both treatments [39] . Prospective studies also report that the risk of exacerbations of asthma during pregnancy was reduced by the use of ICS medication [8, 11] . Recommendations for asthma management during pregnancy include regular medical review and asthma monitoring with the obstetrician’s involvement. Education about how to self-manage asthma is an important component. Early detection of changes in lung function and asthma control is vital and women should receive education about asthma monitoring at home, and they should be provided with a written asthma action plan outlining how to respond to changes in their asthma and when to seek medical advice [5] . Monitoring and treatment of rhinitis is recommended to minimize complications. A simple visual analog scale has been found to be a useful tool to assess rhinitis symptoms in primary care [40] (Fig. 2 ).

Treatment of Asthma Exacerbations During Pregnancy

Current guidelines on the management of asthma during pregnancy recommend treating exacerbations aggressively as a severe asthma attack presents more of a risk to the fetus than the use of asthma medications due to the potential for fetal hypoxia [5] . Studies suggest that pregnant women may be undertreated during severe exacerbations and consequently experience on-going symptoms of an asthma exacerbation. Management of an asthma emergency during pregnancy should involve both close monitoring of lung function and fetal activity. Oxygen saturation should be maintained above 95% with close cooperation between the 492 V.E. Murphy and P.G. Gibson

10 9 8 7 Visual 6 analogue 5 scale (cm) 4 3 2 1 0 intermittent mild persistent mod persistent

Fig. 2 Visual analog scale values (cm) for categories of allergic rhinitis, assessed using ARIA guidelines. Solid line indicates cut-point for detecting more severe rhinitis (Adapted from [40] ).

respiratory specialist and obstetrician [5] . In a randomized trial of therapy for severe asthma exacerbation during pregnancy, women received methylprednisolone with intravenous aminophylline or methylprednisolone alone at the time of admission to hospital [41] . Women receiving aminophylline reported more side effects, without any improvement in the length of hospital stay. On discharge, the women were randomized to receive inhaled b 2 -agonist with either oral steroid taper alone (40 mg reduced by 8 mg daily) or ICS (beclomethasone) plus oral steroid taper. The readmission rate was reduced by 55% with the inclusion of ICS on discharge [41] . This study supports the use of corticosteroids during and after hospitalization for asthma exacerbation in pregnancy.

Safety of Drug Treatments for Asthma and Rhinitis

b 2 -Agonists

There is a significant amount of reassuring data on the safety of short-acting

b 2-agonists, particularly albuterol during pregnancy [5] . Studies have found no significant differences in perinatal mortality, congenital malformations, preterm delivery, and low birth weight in asthmatic women who used short-acting b 2 -agonists compared to women who used no treatment for asthma during pregnancy [42] . A reduced risk of pregnancy induced hypertension, but not pre-eclampsia, was reported for women with asthma using rapid acting b 2 -agonists [28] . Limited data is available on the use of long-acting b2 -agonists during pregnancy and no studies Asthma and Rhinitis in Pregnancy 493

have addressed the use of combined inhaled corticosteroid and long-acting b 2 -agonist preparations in asthmatic pregnant women.

Inhaled Corticosteroids

Inhaled corticosteroids have an acceptable safety profile among pregnant women with asthma and studies recommend that women whose asthma is well controlled on ICS should continue to use these during pregnancy [5, 43] . The majority of studies that address the safety of ICS use in pregnancy have been conducted in women using budesonide [5] . Other ICS drugs have not been shown to be unsafe and studies so far indicate that the use of ICS for asthma during pregnancy does not result in any adverse outcomes for the fetus [44] . In fact, by maintaining asthma control, ICS use may protect against some adverse outcomes, such as low birth weight [11, 21] . One study described a weak but significantly increased risk of malformations in women using any drugs for asthma during pregnancy, compared to the rate of malformations in the whole population [45] . A recent Canadian study of a large cohort of women with asthma found no increased risk of malformations in users of high-dose ICS [46] . Interestingly, there was a significantly reduced risk of malformations among users of moderate-dose ICS compared to nonusers [46] .

Intranasal Corticosteroids

Intranasal corticosteroids are recommended therapy for allergic rhinitis in pregnancy because of their acceptable safety profile and efficacy [47] . A recent review considered that the safety profile of intranasal budesonide was at least comparable to inhaled budesonide [48] .

Oral Corticosteroids

The effects of oral corticosteroids on pregnancy are not well described and the role of important variables such as the dose of oral steroid used, the timing and length of use during pregnancy remain unclear. Some cohort studies find a significant association between oral steroid use and pre-eclampsia [49] , preterm delivery [23, 24] , and reduced birth weight. Maternal oral corticosteroid use, particularly during the first trimester, appears to result in an increased risk of cleft lip in neonates [50] . None of the studies were specifically conducted in women with asthma. The current recommendation is that asthma be well managed so as to avoid the need for rescue oral steroid medication [43] . However, when required for the treatment of a severe exacerbation during pregnancy, the possible risks described are still less than the risks of severely uncontrolled asthma which may result in maternal and/or fetal death [5, 43] . 494 V.E. Murphy and P.G. Gibson

Leukotriene Receptor Antagonists

There is very limited data on the safety of leukotriene receptor antagonists in pregnancy. One study found no increased risk for preterm delivery, gestational diabetes, pre- eclampsia or pregnancy loss [51] ; however, there was a small decrease in birth weight among users of leukotriene receptor antagonists, and in comparison to women without asthma, there was an increase in the prevalence of major structural anomalies. Leukotriene receptor antagonists are not specifically recommended for use during pregnancy in current guidelines due to the limited data available [5] .

Antihistamines

Antihistamines are effective therapy for allergic rhinitis, especially in treating nasal itch and discharge. The older agents have a longer history of use during pregnancy, and one review recommends these agents be used as first-line for rhinitis in pregnancy when an antihistamine is required [52] . A position statement recommended that cetirizine or loratadine could be considered for use in pregnancy, after the first trimester, in women who required topical antihistamine therapy and were not able to tolerate older antihistamines such as chlorpheniramine [53] . A practical approach is to use intranasal corticosteroids such as budesonide as first-line therapy of allergic rhinitis in pregnancy.

Nasal Decongestants

While nasal decongestants are effective in relieving nasal obstruction, there is concern regarding their potential for causing rhinitis medicamentosa, and there have been concerns about their safety during pregnancy. More recent data is reassuring in this regard [54] . ARIA recommends that they be used with caution during pregnancy [15] , and not as first-line therapy.

Conclusions

Asthma and rhinitis are common problems in pregnancy. The clinical course of asthma and rhinitis may be altered by pregnancy, and uncontrolled asthma can have an adverse impact on outcomes for the mother and her baby. Optimal management of these conditions in pregnancy requires good communication between health professionals and patients, together with education, monitoring, and appropriate pharmacotherapy. There are research opportunities to identify the mechanisms of pregnancy-induced changes in asthma and rhinitis, as well as defining optimal management strategies for pregnant women with asthma and rhinitis. Asthma and Rhinitis in Pregnancy 495

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Charles E. Reed

Introduction

Despite the similarity of national and international guidelines for diagnosis and treatment of all ages, asthma in the elderly is a very different problem than asthma in children or younger adults. Diagnosis in this age group is particularly difficult because elderly patients frequently have coexisting lung diseases that contribute to the development of irreversible airway obstruction. Treatment is more difficult because of adverse effects of medications, especially on the heart. And death from asthma and other complicating lung diseases increases with age. There are three kinds of questions about asthma in the elderly: WHAT? HOW? and WHY? WHAT? questions are about epidemiology: What is the frequency, age of onset, death rate? HOW? questions are about the diagnosis and treatment: How do we diagnose and treat asthma in the elderly? WHY? questions are about pathogenesis: Why is the airway obstruction incompletely reversible in so many elderly patients? Why do they develop it when they do? Why do older individuals more often develop asthma that is intrinsic rather than allergic? Why in severe asthma are some segmental bronchi completely occluded with mucus plugs? The WHAT and HOW questions have been reasonably well answered [1– 5] . Some answers to the WHY questions may be found in the innate immune response to agents from the environment.

Diagnosis

National and international guidelines concur on the criteria for diagnosis of asthma and that these criteria are similar at all ages. The history includes episodic shortness of breath, cough and sputum, and wheezing. These symptoms are typically worse at

C.E. Reed () Emeritus Professor of Medicine , Mayo Medical School 9193 Bald Eagle Road , P.O. Box 158 , Boulder Junction , WI 54512 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 499 DOI 10.1007/978-4-431-99362-9_30, © Springer 2010 500 C.E. Reed night and often disturb sleep. Shortness of breath and wheezing after exercise or exposure to cold air or airborne irritants is a frequent symptom. Association with allergen exposure is less common in mature adults and when it develops in the middle-aged and elderly it is often occupational. Intrinsic asthma is often associated with rhinosinusitis and polyps and acute exacerbations from aspirin and related nonsteroidal anti-inflammatory drugs. In addition to the laboratory tests appropriate for all elderly individuals, blood tests should include a complete blood count and IgE level. Asthma is typically associated with eosinophilia unless it is under treatment with corticosteroids. Most elderly patients have moderately elevated IgE even if skin tests are negative. As a minimum, pulmonary function tests include spirometry before and after bronchodilators. If there is a suspicion of emphysema or interstitial lung diseases, then diffusing capacity should be added. Methacholine challenge is rarely indicated – only if the spirogram is normal and the diagnosis is in doubt. Chest X-ray, electrocardiograms, and cardiac ultrasound are needed to define other lung and heart diseases. Airway obstruction is often incompletely reversible, even after a course of corticosteroids. If the irreversible component is severe, computerized tomography (CT) is indicated to define the presence of additional lung diseases. Guidelines also stress that the diagnosis should include an evaluation of severity (mild, moderate, or severe) because management is linked to severity. The NAEPP working group report, Considerations for Diagnosing and Managing Asthma in the Elderly, summarizes their recommendations as follows:

DIFFERENTIAL DIAGNOSIS OF ASTHMA IN THE ELDERLY • The differential diagnosis of episodic chest symptoms in the elderly expands as cardiovascular disease and other forms of chronic lung disease become more prevalent. • In addition, the coexistence of asthma with other chronic cardiovascular or lung diseases may complicate the diagnosis. • It is important not to misdiagnose asthma as COPD because asthma has a different natural history and a better prognosis with treatment. • Because elderly patients with asthma can also have chronic, persistent airflow obstruction with poor bronchodilator responsiveness, a trial of therapy with corticosteroids may be necessary to establish that there is reversible airflow obstruction [1] .

After the diagnosis of asthma is established the history must probe into possible environmental causes. These include outdoor allergens, pets, damp or water damaged houses or other buildings, and past or present occupational exposures. Skin tests or serum IgE antibody tests confirm the history of asthma provoked by allergy. It is my personal opinion that allergy tests should be done on all elderly patients to identify environmental exposures that can be controlled. Also, they provide reassur- ance if they are negative. In the past decades, asthma was underdiagnosed in the elderly [6] , but now it is often overdiagnosed, either in patients with COPD with no reversibility or eosinophilia, or in patients whose only symptom is chronic day-time cough. Thus, epidemiological studies based on physicians’ diagnosis or patients’ recollection of asthma are Asthma in the Elderly 501 difficult to interpret. Also, for studies of the epidemiology of a disease it is traditionally assumed that a patient has only one disease – for example, either asthma or COPD. In the elderly, this assumption is simply not true, as the Dutch hypothesis stated many years ago [7] . After all, many asthmatic patients smoke, and nothing prevents a person with COPD from developing asthma too. Furthermore, many environmental exposures include both bacterial endotoxin (a well described occupational cause of chronic bronchitis and emphysema) and allergens. Cigarette smoke itself contains endotoxin [8] .

Onset and Prevalence

Asthma may have begun early in life and persisted into old age, or it may begin late in life. Most individuals who had mild to moderate asthma in earlier years have a remission, but more severe disease tends to persist or recur. The incidence rate for elderly individuals is the same as younger adults, about one per thousand per year [9] . The reasons for late onset asthma have not yet been fully defined. Unlike asthma beginning in childhood there is no familial correlation. It has been generally considered that asthma beginning after the fourth decade is more often intrinsic, and not likely to be IgE-mediated unless the exposure to the agent is new. However, some, but not all, studies of patients who developed asthma after age 65 reported that many had allergy and elevated IgE [10– 13] . Smoking is a risk factor, both for onset and persistence. Living or working in damp or water damaged buildings is an important risk factor for asthma development in children and working adults [14, 15] . Presumably this extends to the elderly. An important aspect of the onset of asthma in the elderly is that the obstruction becomes irreversible shortly after diagnosis or even before [16, 17] . Asthma prevalence in the elderly is about 6.5% [18] . Prevalence is somewhat greater than in young adults, presumably because the incidence rate exceeds the remission rate. Retrospective studies about whether incidence and prevalence of asthma in recent years has increased in the elderly are difficult because of changing criteria for diagnosis. In the Rochester, MN, community study based on information in the medical record rather than physicians’ diagnosis, the incidence in the elderly did not change between the years 1964 and 1984 [19] .

Course

Asthma that persists from earlier years remains fairly stable. However, asthma beginning in the elderly is more severe, more progressive, and less reversible [17, 20] .

In the Tucson community-based longitudinal study, the FEV1 declined rapidly shortly after diagnosis, but then remained relatively stable with treatment. The rate of decline increases with age. Quality of life is impaired, even in those patients with good bronchodilator response. Remission is less common than it is in younger adults [18] . 502 C.E. Reed

Death

The death rate of individuals with asthma is similar to the general population; it increases strikingly with age [21] . Unfortunately, epidemiological studies of deaths caused by asthma that are based on death certificates are unreliable [22] . In the Rochester community study, a death certificate diagnosis of asthma had a high specificity (99%), but low sensitivity (42%) [23] . Patients who have coexisting lung diseases have a higher death rate [24, 25] . Death from the cardiac effects of asthma medications enhanced by hypoxemia remains a problem, though less now that large doses of theophylline are no longer used [26, 27] .

Management and Treatment

The goal is to maintain the best quality of life possible. Patient (or caregiver) education is the key to success since achievement of optimum results requires the patient to take responsibility for day-to-day management. Details of the treatment program and criteria for evaluating its success in meeting the goal are, of course, individualized, carefully tailored to the patient’s social and physical environment, to the severity of the asthma, and to the presence of coexisting lung and heart diseases. Guidelines recommend that each patient be given individualized written instructions. The NAEPP working group report lists the following key points to consider [1] .

MANAGEMENT OF ASTHMA IN THE ELDERLY • Quality of life and the ability to live independently are important considerations in asthma management plans for the elderly. Each patient’s personal objectives should be explored and incorporated in treatment goals. • Desired therapeutic and clinical outcomes may be more difficult to achieve in elderly patients with asthma. Normal lung function may either be unattainable or be attainable only with potentially dangerous, high pharmacologic doses. Treatment goals may need to be modified to maintain a desirable quality of life. Conversely, some elderly patients do not appreciate the possibilities treatment offers, and they may have unnecessarily accommodated their lifestyles to their perceived limitations. It is important, therefore, to set realistic goals for therapy. • Medication for asthma management is similar for all ages, but ipratropium bromide may be useful, especially for those elderly patients who have chronic obstructive pulmonary disease or who experience tremor, angina, or arrhythmia from beta-2 agonists. • Because compliance with multiple therapies – for both asthma and coexisting diseases and conditions – may be difficult, elderly patients often need special education and training in using asthma medications and devices. • The potential for drug interactions is greater in elderly patients with asthma because these patients are likely to be on multiple medications for other conditions, particularly heart disease. — Beta-2 agonist and theophylline use should be monitored carefully because they can cause tachyarrhythmias and aggravate ischemic heart disease. — If theophylline is used, it should be used with caution, especially in patients with congestive heart failure. — Systemic corticosteroids may aggravate congestive heart failure and lower serum potassium with potentially adverse cardiac effects. — Corticosteroids in high doses may reduce bone mineral content and may accelerate development of osteoporosis. Asthma in the Elderly 503

INTERACTIONS AMONG EFFECTS OF AGING, ASTHMA, AND COEXISTING DISEASES • Differentiating the normal physiologic, psychologic, and psychosocial changes that accompany aging processes from abnormal changes that accompany age-associated diseases or asthma is difficult. • Normal aging-associated changes in lung structure are likely to exaggerate asthma symptoms. These changes sometimes make it difficult to distinguish clearly between asthma and COPD, especially in patients who have smoked. • Patients with COPD often have a reversible component to their condition, and asthma medications may relieve some symptoms and improve the patient’s quality of life. • Elderly patients may have a decreased response to influenza immunization as well as to pneumococcal vaccine and tetanus toxoid. • Patient education and asthma management plans for elderly patients should take into consideration possible decreased ability to handle multiple complex stimuli, memory problems, loss of coordination, and muscle strength that make it difficult to use metered- dose inhalers, hearing and visual difficulties, sleep disturbances that may impair cognitive function, and depression. • Adverse asthma reactions from medications related to polypharmacy are greater in the elderly. It is important to ask what other medications the elderly patient with asthma is taking. Particularly hazardous are beta adrenergic blocking agents (even ophthalmologic preparations) and, in some patients, nonsteroidal anti-inflammatory drugs and antidepressants.

Several points deserve elaboration. • The environment should be considered and optimized. Avoid active or passive smoking. Control exposure to household allergens. Identify and correct water damage and dampness in the home. See below for a more detailed discussion of the effects that airborne agents in these environments have on the innate immune inflammatory response. • Because many patients have glaucoma and cardiovascular diseases they are taking beta adrenergic blocking drugs that increase the severity of the asthma. Even eye drops may do so in some patients. • Learning how to inhale aerosol medications is difficult, although dry powder inhalers are easier to use than metered-dose inhalers. The patient’s inhalation technique should be checked at each follow-up visit. Elderly people tend to forget and often need several coaching sessions. • Anticholinergic aerosols are valuable bronchodilators for the elderly because they have less cardiovascular effects than beta adrenergic agonists. The long acting beta agonists are somewhat more likely to cause adverse cardiac effects, both because they are long acting and because they are less beta-2 selective [26, 27]. Unfortunately though, studies in younger adults have shown that while most asthmatic patients respond as well to anticholinergic as to beta-2 adrenergic agonists, as many as 25–30% of patients do not respond at all Therefore, the individual’s response must be validated by spirometry before and 20–30 min after inhalation. • Although bronchodilating levels of theophylline have been responsible for fatal cardiotoxicity, lower levels inhibit mast cell degranulation and inflammation [27a] . 504 C.E. Reed

• As discussed below mast cell proteases and cytokine production play a major role in airway inflammation and fibrosis. Therefore, levels not greater than 5 mg/L should be considered as anti-inflammatory supplements to aerosol corticosteroids. • Many guidelines recommend that asthma control be monitored with daily peak flow measurements at home. However, the guidelines specifically for the elderly indicate that in this age group the usefulness of home peak flow monitoring is limited [1] . However, spirometry at each follow-up visit is indicated. Inexpensive hand-held instruments make this as simple in the examining room as blood pressure measurements for hypertension. • Overdosage with oral corticosteroids can occur in patients with coexisting irreversible airway obstruction in the attempt to maximize lung function. The peripheral blood eosinophil count is a useful guide in this circumstance. Optimal anti-inflammatory efficacy is attained when the total eosinophil count is about 50–100/mm3 . If it is lower the corticosteroid dose may be too high. • Coexisting lung diseases that should be identified and considered in the management of patients with irreversible airway obstruction include: COPD, bronchiectasis (including allergic bronchopulmonary aspergillosis, ABPA), linear fibrosis, and even carcinoma of the lung [28] . Computerized tomography (CT) is indicated to identify the cause of irreversibility.

Irreversibility

The majority of elderly patients with asthma have a substantial degree of irreversibility. In a random sample of Mayo Clinic patients 65 years of age or older with asthma, only about 20% achieved an FEV1 better than 80% of predicted value; another 20% achieved less than 50% predicted. This impairment was not related to the duration of the illness [17] . Why is the airway obstruction irreversible in so many elderly asthmatics? It is due to several distinctly different pathologies. 1. Airway remodeling from the inﬂ ammation of asthma 2. Coexistence of COPD with centilobular and paraseptal emphysema 3. Bronchiectasis 4. Segmental linear pulmonary ﬁ brosis Although studies employing high-resolution CT scans have not been specifically designed to assess the reasons for irreversibility in the elderly, considerable information has been published about irreversibility in adults irrespective of age. Airway remodeling with collagen deposition beneath the basement membrane, smooth muscle hypertrophy, and hyperplasia of mucus glands affects the entire airway from main stem bronchi to bronchioles. Edema, vascular dilatation, and increased number of blood vessels also contribute to the thickening of the airway wall [29] . CT reveals the bronchial wall thickening and alveolar air trapping. The obstruction from remodeling increases with the severity and duration of asthma. Asthma in the Elderly 505

Although treatment with aerosol corticosteroids reduces it in the large airways, aerosol corticosteroids have less effect in the small peripheral bronchioles. This treatment may not prevent the loss of reversibility in all patients [30] . Emphysema, characteristic of COPD and distinguishable from air trapping, is present in the CT scans of many patients with irreversible asthma, especially those who smoke. In nonsmokers emphysema in elderly asthmatic patients is associated with the duration of the disease [31] . Bronchiectasis is characteristic of the complication of asthma, ABPA. In this disease, the high-resolution CT of the chest demonstrates multiple areas of bronchiectasis and is a useful radiologic tool. Some other asthma patients have bronchiectatic airways, but not to the extent seen in or of the same character as those in ABPA [32] . In ABPA, the bronchiectasis typically is central while in other asthmatic patients bronchiectasis more often occurs in more peripheral bronchi. CT scans of patients with long standing severe asthma showed that many had both central and peripheral bronchiectasis, and that these abnormalities were more common in intrinsic than allergic asthma [33] . Segmental linear fibrosis is a common complication of lung infections including ABPA. Rarely, it is a result of Churg Strauss syndrome. Why do some patients with asthma develop emphysema? Because they smoke, of course. But another cause of emphysema is occupational exposure to airborne endotoxin [34, 35] . So the history of elderly patients with irreversible asthma should include enquiry into occupations with endotoxin exposure. In addition, endotoxin is present in many indoor environments, particularly homes with dogs or high humidity, so the present home environment should be considered, too [36] . The innate immune response to endotoxin involves the binding of the lipopolysaccaride molecule to CD14 on the cell membrane where it activates toll-like receptor 4 leading to production of cytokines like TNFa and chemokines like IL-8. IL-8 attracts and activates neutrophils and the neutrophil elastase destroys the elastic tissue of the alveoli causing emphysema. Patients with asthma, particularly intrinsic asthma, have increased frequency of MZ and SZ alpha-1 antitrypsin phenotypes [37] . This deficiency presumably increases the frequency of emphysema, but direct studies are yet to be done. Why do only some individuals develop asthma, especially intrinsic asthma? And why do they develop it when they do? Asthma probably has the most complex pathogenesis and cell biology of any disease in medicine. It has no single cause. It results from the interaction between many different agents in the environment and many different genes. Expression of many of these genes and function of their products is influenced by exposure to environmental agents [38] . After the environmental stimuli enter the airways they initiate the airway hyperresponsiveness and inflammation through multiple complex interacting inter- and intracellular signaling pathways [39] . Damp or water damaged buildings is the source of many of these stimuli [14, 40– 43] . Microorganisms and mites growing in the damp environment not only produce allergens but also molecules that act through innate rather than humoral immunity. 506 C.E. Reed

In addition to the innate immune inflammation resulting from endotoxin inhalation, a second form of innate immunity resulting from the action of serine and cysteine proteases stimulating on specific receptors has emerged as an important mechanism of rhinitis and asthma. Endogenous proteases (thrombin, trypsin, and tryptase), acting on specific cell membrane molecules, protease-activated receptors (PARs), activate platelets and play a critical role in angiogenesis and fibrosis of wound healing, including airway remodeling. Information about exogenous proteases has expanded our understanding of allergic inflammation [44] . Proteases are present in many airborne allergenic particles. These proteases are not only allergens evoking an IgE response, but also promote production of IgE antibodies to proteins that otherwise would not elicit a Th2-type response [45, 46]. In addition, they can cause inflammation directly via PARs. This stimulation of inflammation includes recruitment and activation of eosinophils and degranulation of mast cells. In this respect, it can be considered as a variety of innate immunity directed particularly against parasites and arthropods [47, 48] . It is similar to toll-like receptor innate immunity in not requiring antibody production. But it differs in being directed against pathogens too large to be phagocytosed. The toxic products of eosinophils and the proteases of mast cell granules attack multicellular parasitic organisms directly. The important airborne proteases are from mites and molds. When molds germinate their hyphae produce digestive enzymes including proteases. Mite proteases are closely related between species. Group 1 (e.g., Der p1) are cysteine proteases; groups 3, 6, and 9 are serine proteases. All of them stimulate cytokine production by epithelial cells and degranulate eosinophils [49– 51] . Molds not only grow in damp indoor environments, but can also germinate on the respiratory epithelium. Ponikau and associates have reported that 96% of nasal cultures of patients with chronic rhinosinusitis are positive for common fungi, particularly alternaria, aspergillus, and cladosporium [52] . Normal control subjects had similar frequency of positive cultures, but the chronic hyperplastic rhinitis patients had hyphae in the mucus of 86% of specimens, indicating that the fungi were growing on the mucosa [53] . Subsequently, they reported that extracts of mucus and nasal tissue from these patients attracted peripheral blood eosinophils in a tissue culture, and that the eosinophils from patients with chronic rhinosinusitis were more responsive than those from healthy controls [54] . Protease stimulation of PARs presumably is the mechanism for rhinosinusitis and polyp formation. Proteins in extracts of molds, especially alternaria, induced activation, IL-8 production, and degranulation of normal eosinophils through Ga protein pathways [55] . Proteases from aspergillus and alternaria stimulate respiratory epithelial cells to produce IL-6 and IL-8 [56, 57] . Do molds geminating on the bronchial epithelium similarly cause asthma? And could localized superficial germination of aspergillus produce the localized bronchial gland hyperplasia that leads to segmental bronchial occlusion by mucus plugs? Aspergillus is cultured from the sputum of many patients with asthma who do not have ABPA, so the hypothesis is worth testing. Environmental proteases act primarily on the epithelial cells and mast cells. Expression of PAR-2 is increased on respiratory cells of asthmatics, and presumably Asthma in the Elderly 507

Table 1 Brief summary of innate immunity Th1-like Th-2 like Stimulus Endotoxin Serine and cysteine proteases Airborne sources Gram-negative bacteria Mites and molds Target organisms Bacteria and viruses Helminths and arthropods Receptors Toll-like receptors (TLRs) Protease-activated receptors (PARs) Primary cells involved Macrophages/monocytes Epithelial cells, mast cells Cytokines generated TNF a , INF g , IL-6, IL-10, IL-12 IL-6,IL-4, IL-13 Chemokines generated IL-8 Eotaxins Adhesion molecules ICAM-1 ICAM-1, VCAM-1 generated Leucocytes attracted Neutrophils, monocytes, Eosinophils, monocytes, lymphocytes lymphocytes Granulocytes activated Neutrophils Eosinophils, mast cells Increased immunoglobulin IgG IgE production Tissue effects Loss of alveolar elastic tissue, Basement membrane collagen goblet cell hyperplasia production, smooth muscle hypertrophy, bronchial gland hypertrophy, angiogenesis, increased noxioception increases the response to airborne proteases. It is not yet known whether this occurs before or after the development of asthma [58] . Much research is still needed about the genetics of these pathways, and how they may differ from “normal.” Table 1 summarizes the effect of these two pathways of innate immunity on asthma, COPD, and the combination of the two. One of the important effects is increased ICAM-1 on the respiratory epithelium that binds rhinovirus and increases viral respiratory infections.

Summary and Conclusions

Asthma is a common and complex illness in the elderly. Unlike asthma in children and young adults it often occurs in combination with other lung diseases – COPD, bronchiectasis, and linear segmental fibrosis. Even patients with recent onset of asthma have a substantial degree of irreversible airway obstruction. It is important to determine the reasons for the irreversibility. Management is also complicated by coexisting cardiovascular and other problems. Current evidence-based guidelines provide valuable basis for individualizing management, but in my opinion do not stress sufficiently on the importance of controlling environmental exposures. Although the studies linking damp or water damaged buildings to development of asthma have included only children and working adults, it is reasonable to assume 508 C.E. Reed that these exposures also make asthma worse in the elderly and can even cause its onset. Agents growing in water damaged or even just humid environments can cause airway inflammation and emphysema through two pathways of innate immunity: gram-negative bacterial endotoxin and mite and mold digestive proteases. At present the most practical way for physicians to check the on this is to ask the patient to look for it in their houses. Measurements of endotoxin and proteases in both settled dust and airborne particles are available, but only in research laboratories. Studies of the clinical value of these assays are needed. In order to reduce its severity, management of asthma in the elderly, particularly control of smoking and damp environment, needs to begin much earlier in life.

References

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40. Etzel R, Rylander R (1999) Indoor mold and children’s health. Environ. Health Perspect. 107 Suppl 3:463 41. Dangman KH, Bracker AL, Storey E (2005) Work-related asthma in teachers in Connecticut: association with chronic water damage and fungal growth in schools. Conn. Med. 69:9–17 42. Rao CY, Riggs MA, Chew GL, Muilenberg ML, Thorne PS, Van Sickle D, Dunn KH, Brown C (2007) Characterization of airborne molds, endotoxins, and glucans in homes in New Orleans after Hurricanes Katrina and Rita. Appl. Environ. Microbiol. 73:1630–1634 43. Jaakkola MS, Nordman H, Piipari R, Uitti J, Laitinen J, Karjalainen A, Hahtola P, Jaakkola JJ (2002) Indoor dampness and molds and development of adult-onset asthma: a population- based incident case-control study. Environ. Health Perspect. 110:543–547 44. Reed CE, Kita H (2004) The role of protease activation of inflammation in allergic respiratory diseases. J. Allergy Clin. Immunol. 114:997–1008 45. Gough L, Campbell E, Bayley D, Van Heeke G, Shakib F (2003) Proteolytic activity of the house dust mite allergen Der p 1 enhances allergenicity in a mouse inhalation model. Clin. Exp. Allergy 33:1159–1163 46. Kheradmand F, Kiss A, Xu J, Lee SH, Kolattukudy PE, Corry DB (2002) A protease-activated pathway underlying Th cell type 2 activation and allergic lung disease. J. Immunol. 169:5904–5911 47. Donnelly S, Dalton JP, Loukas A (2006) Proteases in helminth- and allergen-induced inflammatory responses. Chem. Immunol. Allergy 90:45–64 48. Pollock KG, McNeil KS, Mottram JC, Lyons RE, Brewer JM, Scott P, Coombs GH, Alexander J (2003) The Leishmania mexicana cysteine protease, CPB2.8, induces potent Th2 responses. J. Immunol. 170:1746–1753 49. Miike S, Kita H (2003) Human eosinophils are activated by cysteine proteases and release inflammatory mediators. J. Allergy Clin. Immunol. 111:704–713 50. Tomee JF, van Weissenbruch R, De Monchy JG, Kauffman HF (1998) Interactions between inhalant allergen extracts and airway epithelial cells: effect on cytokine production and cell detachment. J. Allergy Clin. Immunol. 102:75–85 51. Iraneta SG, Duschak VG, Rodriguez SM, Seoane MA, Albonico JF, Alonso A (1999) Proteinase and gelatinolytic activities of house dust mite and cockroach extracts. J. Investig. Allergol. Clin. Immunol 9:235–240 52. Ponikau JU, Sherris DA, Kern EB, Homburger HA, Frigas E, Gaffey TA, Roberts GD (1999) The diagnosis and incidence of allergic fungal sinusitis. Mayo Clin. Proc. 74:877–884 53. Taylor MJ, Ponikau JU, Sherris DA, Kern EB, Gaffey TA, Kephart G, Kita H (2002) Detection of fungal organisms in eosinophilic mucin using a fluorescein-labeled chitin-specific binding protein. Otolaryngol. Head Neck Surg. 127:377–383 54. Wei JL, Kita H, Sherris DA, Kern EB, Weaver A, Ponikau JU (2003) The chemotactic behavior of eosinophils in patients with chronic rhinosinusitis. Laryngoscope 113:303–306 55. Inoue Y, Matsuwaki Y, Shin SH, Ponikau JU, Kita H (2005) Nonpathogenic, environmental fungi induce activation and degranulation of human eosinophils. J. Immunol. 175: 5439–5447 56. Borger P, Koeter GH, Timmerman JA, Vellenga E, Tomee JF, Kauffman HF (1999) Proteases from Aspergillus fumigatus induce interleukin (IL)-6 and IL-8 production in airway epithelial cell lines by transcriptional mechanisms. J. Infect. Dis. 180:1267–1274 57. Kauffman HF, Tomee JF, van de Riet MA, Timmerman AJ, Borger P (2000) Protease- dependent activation of epithelial cells by fungal allergens leads to morphologic changes and cytokine production. J. Allergy Clin. Immunol. 105:1185–1193 58. Knight DA, Lim S, Scaffidi AK, Roche N, Chung KF, Stewart GA, Thompson PJ (2001) Protease-activated receptors in human airways: upregulation of PAR-2 in respiratory epithelium from patients with asthma. J. Allergy Clin. Immunol. 108:797–803 The Natural History of Childhood Asthma

Miles Weinberger and Dirceu Solé

Introduction

The natural history of a disease is defined as a set of interactive processes that involves the underlying defect, the susceptible individual, and the environment. These three variables influence the global process that results in the human response. The result is persistence of the pathophysiology, recovery, or death [1] . Two sequential phases can be identified, the pre-pathogenic period (dependent on the host, the environment and the agent) and the pathogenic period. Asthma is a complex disease with several rather distinct clinical patterns that make the study and discussion of its natural history a challenging task.

Definition of Asthma

In order to discuss the natural history of asthma, it first becomes necessary to define the clinical entities that we call asthma. There is by no means universal acceptance of a definition for asthma. Moreover, there are sufficiently different clinical patterns, clinical manifestations, and natural history that it is best to refer to specific asthma phenotypes when discussing the natural history [2] . This chapter will address specifically the natural history of the most common phenotypes that begin in childhood. What is asthma? This question is of particular importance in evaluating respiratory disease in the young child, where euphemisms for asthma including reactive

M. Weinberger () Pediatric Department , University of Iowa Hospital , 200 Hawkins Drive , Iowa City , IA 52242 , USA e-mail: [email protected] D. Solé Division of Allergy, Clinical Immunology and Rheumatology , Federal University of São Paulo , São Paulo , Brazil

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 511 DOI 10.1007/978-4-431-99362-9_31, © Springer 2010 512 M. Weinberger and D. Solé airway disease (RAD), wheezy bronchitis, obstructive bronchitis, recurrent bronchiolitis, etc. have been common. Sometimes, describing or defining asthma is like the parable of the blind men describing the elephant who felt it was like a tree, a snake, or a rope depending on whether they were feeling a leg, the trunk, or the tail. As with the perception of the blind men examining only one part of the elephant, asthma is sufficiently diverse that its perception depends on the experience of the observer. Some have suggested that, like love, it can’t be defined, but it’s recognizable when confronted [3] . The complexity and challenge of defining asthma have been discussed extensively by Sears [4] . In examining the 12 definitions and references in his review, a common theme to all is the presence of airway disease that varies over time either spontaneously or as a result of treatment. A committee of the American Thoracic Society agreed upon the definition that “Asthma is a disease characterized by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by a widespread narrowing of the airways that change in severity either spontaneously or as a result of therapy” [5] . This definition was expanded by a subsequent committee of the American Thoracic Society to include “The major symptoms of asthma are paroxysms of dyspnea, wheezing and cough, which may vary from mild and almost undetectable to severe and unremitting...” [6] . That definition and others, most notably that of Simon Godfrey, added to the definition that the airflow obstruction and clinical symptoms are largely or completely reversed by treatment with bronchodilators or corticosteroids [7] . Inflammation was introduced into the definition by Hargreave [8] and subsequently incorporated into the National Asthma Education Program Expert Panel Reports from the US National Institute of Health [9, 10] . However, a definition based on inflammation is not helpful in differential diagnosis or early disease identification since noninvasive measures of inflammation are neither readily available nor well-validated. This is especially true for young children in whom even the ability to make physiologic measurements is limited. Moreover, inflammation is not persistent in the common nonatopic asthma phenotype characterized by an intermittent viral respiratory infection-induced pattern of illness [11] . For a definition of a disease to be useful, it should provide a basis for making the diagnosis. While airway inflammation is certainly a characteristic for chronic phenotypes of asthma, the value of including this as a major component of the definition has been challenged. McFadden and Gilbert commented, “Airway inflammation and hyperresponsiveness....are not unique to this illness. The usefulness of these characteristics in defining asthma is unclear” [12] . This issue is discussed further by Brusasco et al. who argued that airway narrowing in asthma is not necessarily related to airway inflamation [13] . Asthma has thus proved challenging to define because of the diversity in its clinical presentation, variability of its clinical course, and absence of any specific diagnostic test. The ability to define asthma is essential for both study of the disease and for diagnosis. The reported prevalence and natural history of childhood asthma vary greatly depending on how asthma is defined for the purpose of diagnosis in epidemiologic and natural history studies [14, 15] . The challenge of defining asthma The Natural History of Childhood Asthma 513 becomes greatest in the very young child. While there is an absence of an internationally accepted criteria for the definition of asthma in early childhood, birth cohort studies have nonetheless been attempted using various criteria to define asthma or potential asthma [16] . Martinez has emphasized the heterogeneity of asthma and the identification of specific phenotypes based on patterns of natural history and presence of early allergic sensitization [17] .

When does Asthma begin?

While asthma can begin at almost any age, the childhood asthma phenotypes most commonly begin in infancy with a viral respiratory infection that causes the lower airway inflammatory disease with consequent wheezing and coughing that is commonly known as bronchiolitis. The most common cause of this initial wheezing episode is respiratory syncytial virus (RSV), but rhinovirus, parainfluenza, and metapneumovirus are other common cold viruses that can also initiate the first episode of lower airway disease in susceptible infants [18] . As many as 3% of infants in the U.S. have been hospitalized annually because of lower respiratory illness from these infections [19] . While it is premature to call the first episode of such symptoms asthma, this initial viral respiratory infection induced lower airway obstruction in infancy is often the harbinger of more to come, consistent with a diagnosis of asthma. In fact, when the onset of symptoms consistent with asthma was examined in an epidemiologic study of the population in the vicinity of Rochester Minnesota by investigators at Mayo clinic, the predominance of children with asthma had their onset during the first year of life (Fig. 1 ) [20] .

7000 6000 5000 4000 3000

2000 Number per 10,000 children 10,000 per Number 1000 0 <1 1 - 4 5 - 14 Age of onset (years)

Girls Boys

Fig. 1 Age- and sex-adjusted incidence of asthma onset in a population-based epidemiologic study in Rochester, Minnesota (adapted from Yunginger et al) [20] 514 M. Weinberger and D. Solé

When an Infant Gets a VRI

Genetic and prenatal factors

URI only Bronchiolitis

No recurrent LRI with VRI Atopy Chronic (persistent) Recurrent LRI with VRI ( intermittent asthma ) asthma

Fig. 2 Clinical consequences of initial infection following one of the common cold viruses in infancy. URI – upper respiratory illness; LRI – lower respiratory illness; VRI – viral respiratory infection (reproduced with permission) [24]

Thus, when a healthy baby becomes infected with one of these common cold viruses, as virtually all of them eventually do, most get only the typical coryza. A substantial minority experience bronchiolitis, the most common cause of hospitalization during the first year of life. Of those who experience bronchiolitis, about 25–50% subsequently have symptoms of an intermittent pattern of asthma manifested by recurrent wheezing only in association with subsequent viral respiratory infections [21, 22] . While clinical experience and natural history studies suggest that the majority of such children remit later in childhood, some continue to have recurrent or chronic symptoms consistent with a diagnosis of asthma throughout childhood, and some also continue into adult life [23] (Fig. 2 ) [24] .

Who gets Asthma?

A component of the natural history of asthma is identifying who is at risk for having asthma. An asthma phenotype is present in approximately 25% of the offspring of a parent with asthma [25] . Further evidence for a genetic influence on the asthma phenotype is seen in twin studies wherein there is a higher concordance in monozygotic twins compared with dizygotic twins, even though both twins share the same environment [26, 27] . But the concordance even in identical twins is not much over 50%. Both genetics and environment therefore appear to contribute to asthma. The Natural History of Childhood Asthma 515

The genetics are complex with apparently separate contributions to airway hyperresponsiveness and IgE mediated sensitivity to inhalant allergens [28] . Airway reactivity or hyperresponsiveness is considered a hallmark of asthma [29] . Persistence of asthma beyond the pre-school years has been found to be associated with increased airway responsiveness in early life [30] . However, airway hyperresponsiveness is not diagnostic of asthma. Airway hyperresponsiveness to a cholinergic stimulus is found with increased frequency in nonasthmatic parents of children with asthma at a frequency, suggesting that such responsiveness is transmitted as an autosomal-dominant trait that is a necessary but not sufficient biologic variable to cause clinical asthma [31, 32] . Total IgE production appears to have strong genetic determination based on the observations of very high concordance in monozygotic twins and lesser concordance in dizygotic twins, both of whom should have similar environmental exposures [33] . However, less well studied is the genetics of antigen specific IgE. Other genetic variables that can affect the phenotypic manifestations of atopic sensitization include the affinity of IgE receptors on target cells, the interaction of IgE with the receptors, IgE-induced release of mediators, and end-organ responsiveness. Despite their clinical usefulness as an aid to the assessment of diseases affected by atopic sensitization, neither the size of allergy skin tests nor the titer of antigen-specific IgE on in vitro tests reliably predicts either disease or severity. Although IgE mediated inhalant sensitivity tends to develop later than ingestant sensitivity in early childhood, Wilson et al. found cockroach sensitivity in 29%, dust mite in 10%, cat in 10%, and Alternaria in 4% among 49 asthmatic infants under one year of age [34] . Arshad and Hide examined the development of atopic related findings in a prospective study of 1,167 infants [35] . They found that dust mite positive skin tests were more prevalent in formula fed infants. While positive skin tests to animal epidermals were more prevalent among infants exposed to the respective animals, they did not find that exposure to animals influenced the prevalence of clinical disorders. However, Lindfors et al., in a case control study of 193 children with asthma aged one to 4 years, did find that high dose exposure to cat and/or dog resulted in an increased risk of asthma with indoor dampness and exposure to environmental tobacco smoke having apparent synergistic effect [36] . In a subsequent report, they described a dose-response relationship between cat exposure and sensitization to cat but not to dog [37] . Sears et al. found a relationship between children born in winter and sensitization to cats and house dust mites [38] . Sherrill et al., in a prospective longitudinal study in Tucson, found an association between sensitization before age 8, as determined by skin testing, and symptoms of asthma, whereas those who developed positive skin tests only after age 8 did not differ in frequency of asthmatic symptoms from those never sensitized [39] . Similar results were reported in a longitudinal study of 2,166 children by Chen et al [40] . While Nelson et al. found an association of many positive skin tests among 1,041 school age children with “mild to moderate” asthma, these investigators found that only dog, cat, and Alternaria mold correlated independently with increased lower airway hyperresponsiveness as measured by methacholine challenge, though not with decreased pulmonary function [41] . Although this latter study did not involve 516 M. Weinberger and D. Solé

% wheezing at year 3 year at wheezing % 20

0 RSV Season (Dec-Jan) Both Seasons None RV Season (Mar-Nov)

Season of First Wheezing as Infant

Fig. 3 Wheezing illnesses consistent with asthma at age 3 as predicted by initial viral respiratory infection induced lower wheezing illness in infancy (adapted from Lemanske et al) [42] pre-school age children, it indicates that some inhalant allergens appear to be more asthmagenic than others. Thus, getting asthma is a function of genetic and environmental variables, not all of which are known. While those with a viral respiratory infection-induced intermittent pattern appear to have a familial predisposition, the genetics of that pattern are not well-studied. Both airway hyperresponsiveness and IgE mediated sensitivity to inhalant allergens in infancy appear to be predictors of those who eventually have persistent symptoms.

Natural History of Early Childhood Asthma

While a viral respiratory infection is the cause of common first wheezing episodes in an infant (Fig. 2 ) and as respiratory syncytial virus (RSV) receives considerable attention because of its major contribution to seasonal epidemics of bronchiolitis, it is rhinovirus-induced bronchiolitis that appears to be a better predictor of those infants likely to experience recurrent wheezing episodes consistent with asthma [42] . When a wheezing illness was associated with the seasons for RSV or rhinovirus during the first year of life, rhinovirus was identified as a greater predictor for recurrent symptoms consistent with asthma than RSV when evaluated at age 3 (Fig. 3 ). Rhinovirus-induced bronchiolitis has also been reported to be associated with a high risk of asthma at 6 years of age [43] . The Natural History of Childhood Asthma 517

Fig. 4 Hospital discharge rates for asthma from the National Center for Health Statistics, Center for Disease Control, as the first-listed, by age group and year – United States, 1980–1999 (adapted from Akinbami et al ) [51]

Beyond the first episode of viral respiratory infection induced wheezing in infancy, viral respiratory infections continue to be a major cause of subsequent asthma exacerbations at all ages [44– 48] . These recurring viral respiratory infections appear to be the major risk factor for the large increase in hospital admissions for asthma that occurs in every autumn [49] . Pre-school age children have a particularly high frequency of viral respiratory infections, with most getting 3–8 infections per year and 10–15% getting 12 or more per year [50] . This is the likely explanation for a frequency of asthma hospitalization in the pre-school age group that far exceeds that of older children and adults. The rate of hospitalization for asthma among the U.S. children of age 1–4 years has been about 1 in 200 children compared with 1 in 500 children 5–14 years, and 1 in 1000 for individuals 15–24 years of age (Fig. 4 ) [51] . Various studies have evaluated factors associated with persistence of asthma from infancy (Table 1 ). The longest-term clinical course of asthma in young children was a prospective study with repeated evaluations for up to 35 years [52] . In 1963, all children entering first grade in Melbourne Australia had a medical examination that included a short questionnaire and interview. As part of that questionnaire, parents were asked if their child had experienced episodes of wheezing or asthma during their pre-school years and whether that had been associated with a viral respiratory infection. Based on that survey, an overall community prevalence for asthma symptoms in childhood was estimated to be about 20%, a rate similar to that described more recently in the U.S [14, 53, 54] . A stratified sample was then randomly selected in the following year from the approximately 30,000 7-year-old children previously surveyed. This included 105 2nd graders who had never wheezed to serve as controls, 75 with less than 5 episodes of wheezing with viral respiratory infections, 104 with 5 or more episodes of wheezing with viral respiratory infections, and 113 with recurrent wheezing not limited to association with viral respiratory infections. Three years later, the investigators entered 83 children 518 M. Weinberger and D. Solé adulthood with no lung impairment. function impairment, seen by age 14 y and not progressive. Nasal symptoms at age 1y age 2y, multiple time points than never wheezers. never or transient wheezers, along with more eczema, rhinitis eosinophils, parental asthma. Persistent asthma in childhood more likely to show modest lung Atopy increases risk for more severe disease. Maternal asthma, Parental smoking at Recurrent URI at age 2y, Chronic childhood atopic (up to 4y) Airway hyperresponsiveness Persistently low lung function Sensitization to house dust mites Female sex Smoking Maternal asthma, maternal smoking during pregnancy Reduced airway function in early infancy Atopy Parental asthma Reduced airway function in early infancy Level of lung function stabilized in all groups by age 6y Atopy more prevalent in persistent and late-onset wheezers than Age at entry and conclusion (y) Summary of factors related to persistence [59] a 168 7–42 Episodic childhood asthma tends to resolve in adolescence and and control subjects Longitudinal studies of childhood asthma persistence

Isle of Wight [74] BC 1,456 0–10 Never atopic Table Table 1 Location Sample type Manchester [71] Perth N [72] BC subjects BC [73] Tucson BC 690 Melbourne [52] 156 0–5 Children with wheezing 826 0–11 Poor lung function at age 0–22 3 y Increased airway responsiveness early and persistent wheezers have lower flows at Transient Dunedin [59] BC 613 9–26 Early age of onset of wheezing The Natural History of Childhood Asthma 519 age 4y function associated with a loss of lung function at school age. hyperresponsiveness life) inversely associated with atopy at school age. asthma at age 7 y. rhinitis at age 7 y associated with allergic hyperresponsiveness at age 11y smoking at age 4y Female gender Moderate to persistent asthma has early deterioration of lung in the first 3 y of life was Sensitization to perennial allergens was associated with bronchial High exposition to aeroallergens PD-bronchiolitis before age of 1y was significantly associated with More than 3 episodes of runny nose in the 1st y life was Passive smoking Female gender, Asthma in early adulthood Current allergy Early wheezing disorder, Bronchial hyperresponsiveness Female gender in infancy Bronchial Early sensitization to inhalant allergens Male sex, Eczema at age 4ys, Family history of eczema, Parental Delayed childhood atopic (up to 10y) Family history of urticaria, Maternal asthma Dog ownership at < 2 to 17–20 < Asthma in childhood Age at entry and conclusion (y) Summary of factors related to persistence 401 controls 101 patients and 100 0–22 y Persistent wheezing at age 11 505 0–7 PD-croup and more than 2 episodes of PD-ear infections (1st y due to wheezing and control subjects newborns newborns Risk factors for asthma 18,156 0–44 Parents with asthma Group [78– 80] Modified from [81] Germany [62] BC BC = Birth cohort, PD Physician-diagnosed, y year N = number, 1,314 0–13 Göteborg Göteborg [76] Children hospitalized Poole [77] ECRHS Study High atopy risk Location Sample type Brigham [75] High risk of asthma N subjects a 520 M. Weinberger and D. Solé from the same population who had chronic asthma. These children with severe chronic asthma, now 10-years-old, had a history of onset before age 3 with persistent symptoms at the time of entry with barrel chest deformity and/or FEV 1 that was 50% or less than the forced vital capacity. All groups of children were re-evaluated at ages 14, 21, 28, 35, and 42 years [55– 58] . The subsequent spot prevalence of continued wheezing episodes was 12% at ages 14 and 21. However, 75% percent of the stratified samples followed longitudinally, an estimated 15% of all children, had infrequent episodes, while 25%, an estimated 5% of all children, had frequent episodes. Only an estimated 0.5% of all children had chronic or persistent asthma based on their survey. Forty percent of the initial children followed were free of respiratory symptoms by age 10, and 50% were asymptomatic by age 14. The remainder continued into adult life, but symptoms were rarely troublesome, usually only present with viral respiratory infections or exercise. However, 10% who had ceased wheezing in childhood had recurrences as young adults, and some of those had troublesome symptoms. Those with chronic or persistent wheezing had growth failure and delayed puberty but eventually attained normal adult height. While 50% of this group improved considerably at puberty, most did not become totally asymptomatic. When the subjects were examined at 42 years of age, a correlation between the nature of the symptoms in childhood and the subsequent outcome was apparent (Fig. 5 ). Over half of those with symptoms of asthma limited to an association with viral respiratory infection prior to age 7 were asymptomatic at age 42. A substantial

100 80 60 40

20 Percent of patients of Percent 0 <5 w VRI 5+ w VRI w/o VRI chronic Childhood pattern of asthma at age 7

Persistent asthma Frequent episodic asthma Infrequent episodic asthma No recent asthma

Fig. 5 Clinical expression of childhood asthma at age 42 years among a stratified random sample from a population of 30,000 children surveyed at entry to 1st grade, about 20% of whom had symptoms consistent with asthma. The sample included 105 2nd graders who never wheezed, 75 with less than 5 episodes of wheezing with viral respiratory infections (<5 w VRI), 104 with 5 or more episodes of wheezing with viral respiratory infections (5+ w VRI), 113 with recurrent wheezing not associated with viral respiratory infections (w/o VRI), and 83 children from the same population who had severe chronic asthma (chronic). (adapted from Phelan et al) [52] The Natural History of Childhood Asthma 521 number were still having episodic asthma, and a few had developed persistent asthma. Nevertheless, the frequency of all patterns of active asthma at age 42 years was greater among those in whom wheezing without viral respiratory infection had been reported in childhood. About half of those with chronic asthma as children continued to have persistent symptoms at age 42, with only 11% reporting no recent asthma. Repeated measurements of forced expiratory volume at one second (FEV1 ) to age 42 did not differ significantly from controls among the two groups of children who had only wheezing with viral respiratory infection. Those with chronic asthma generally had significant decrements in the FEV1 that persisted but were not progressive (Fig. 6 ). It is notable that the patients in this 35 year study who began with asthma in their pre-school years had, for the most part, little in the way of what today would be considered optimal treatment. The initial identification of these patients occurred prior to the introduction of inhaled corticosteroids, cromolyn, or even optimal use of oral theophylline. The investigators did not intervene in the patients’ care, limiting their involvement to the interval assessments and recommendations communi- cated only to the patients’ physicians. However, the authors commented that the recommendations were rarely followed. This longitudinal study therefore provides unique data regarding the natural history of asthma, beginning in the pre-school years, that was generally untreated by current standards. Another longitudinal study of childhood asthma followed to adulthood was performed in New Zealand [59] . This study involved a complete birth cohort born in

110

100

70 Percent of predicted of Percent

60 7 10 14 21 28 35 42 Age in years Controls <5 w VRI 5+ w VRI w/o VRI Chronic

Fig. 6 One second forced expiratory volume (FEV 1 expressed as percent of predicted) for children over time by classification of childhood asthma at the time of recruitment. The categories of asthma at the time of entry into the study included those with <5 wheezing episodes with viral respiratory infections (<5 w VRI), those with ³ 5 episodes with VRI (5+ w VRI), those with episodic wheezing without VRI (w/o VRI), and those with severe persistent asthma (chronic), and controls from the same cohort (adapted from Phelan et al) [52] 522 M. Weinberger and D. Solé

20 Percentage of patients of Percentage

0 Relapsed Wheezing Intermittent wheeze Persistent Wheezing Remission Never or once

Fig. 7 Outcomes at age 26 years among 613 study members who provided respiratory data at every assessment (adapted from Sears et al) [59]

Dunedin, New Zealand from April 1972 to March 1973. Of 1128 children born during that period, 1037 were available at age 3 and were seen every 2 years between 3 and 15 years of age and then at 18, 21, and 26 years of age. Of those, 613 completed every assessment. These 613 were considered to be generally representative of the base cohort. Persistent wheezing at age 26, defined as wheezing reported at each of the visits, was reported in almost 15% of that 613. Wheezing that stopped and then relapsed, defined as reported at two or more visits followed by the absence of reporting at one or more visits and then reported as present at all previous visits, occurred in 12%. Wheezing in remission at age 26, reported at two or more visits followed by the complete absence at all subsequent visits, occurred in 9.5% (Fig. 7 ). Those with reported wheezing at each visit and those identified as having relapsed were found to be more likely to have allergic sensitivity to dust mites and cat allergen, increased airway hyperresponsiveness, and lower lung function that those whose wheezing did not persist or relapse. While pulmonary function was somewhat lower in those with persistent or relapsed wheezing, the rate of decline was similar for all (Fig. 8 ). These data appear to be consistent with other cohort studies [52, 60, 61] . In the German Multicentre Allergy Study that followed birth cohort of 1,314 children born in 1990 in five German cities from birth to 13 years of age, Illi et al. studied the role of allergic sensitization and allergen exposure early in life on the development and clinical course of asthma [62] . Consistent with previous studies, they demonstrated that early exposure and sensitization, as evidenced by determination of the presence of specific IgE, were predictive of persistent symptoms The Natural History of Childhood Asthma 523

Fig. 8 Mean ({+/−}SE) FEV1:FVC ratios measured at 9, 11, 13, 15, 18, 21, and 26 years in male (Panel A) and female (Panel B) study members, according to the pattern of wheezing (reproduced with permission from Sears et al) [59]

Fig. 9 Prevalence of wheeze from birth to age 13 years in children with any wheezing episode at school age (5–7 years), stratified for atopy at school age (reproduced with permission from Illi et al) [62] beyond age 5 (Fig. 9 ). Decreased lung function was also apparent in those who were sensitized by age 5. Subsequent to age 5, sensitization and exposure had much less effect. 524 M. Weinberger and D. Solé

In several studies of the natural history of asthma, female sex has been described as a risk factor for persistence of asthma from childhood to adulthood [59, 63– 65] . In a sex-specific analysis of airway responsiveness over time utilizing data from 941 participants from the Children’s Asthma Management Program [66] , who were enrolled in a 4 year observational study. Airway responsiveness to methacholine was observed to improve in males but not females after age 11 [67] . These data are consistent with the loss of male predominance for asthma prevalence postpuberty.

Can the Natural History of Asthma be Altered?

Two studies represent major attempts to favorably alter the natural course of asthma in wheezy infants. In a British study with the acronym IFWIN (Inhaled Fluticasone propionate in Wheezy Infants), a randomized, double-blind controlled trial of 100 m g of fluticasone twice daily was started in young children, median age 1.2 years, at the first sign of wheeze [68] . The purpose was to test the hypothesis that loss of lung function and worsening asthma could be prevented. After the initial doses were started, subsequent increases based on clinical need or decreases because of absence of symptoms occurred while the children were followed until 5 years of age. Two hundred children began treatment of whom 173 (85 given fluticasone and 88 placebo) continued treatment until evaluation at age 5 years. No significant differences were seen between the fluticasone and placebo groups at 5 years of age in current wheeze, physician-diagnosed asthma, use of asthma medication, lung function, or airway reactivity. In a U.S. study identified by the acronym PEAK (Prevention of Early Asthma in Kids), 285 children of 2–3 years of age with a positive predictive index, defined by specific clinical characteristics [69] , which placed them at risk for future persistent asthma, were randomized to fluticasone (2 inhalations of Flovent 44) delivered through a valved holding chamber or matched placebo [70] . During the 2 years of treatment, those receiving the inhaled corticosteroids (n = 143) had fewer symptoms than those receiving placebo (n = 142). However, when treatment was stopped at the end of 2 years, the frequency of symptoms in those receiving fluticasone gradually increased to match with that of those who had been receiving the placebo (Fig. 10 ). Thus, this study was consistent with the British study in demonstrating no alteration in the natural course of asthma. While treatment with an inhaled corticosteroid for a 2 year period was beneficial in decreasing the frequency of symptoms, there were no lasting effects once treatment was stopped.

Other Asthma Phenotypes in Childhood

The previous discussions have addressed the natural history of essentially two very common asthma phenotypes, those whose asthma is limited to recurrent episodic illness wherein viral respiratory infections are the inciting factor and those who also The Natural History of Childhood Asthma 525

Fig. 10 Bimonthly proportion of episode-free days during a two-year treatment period and a subsequent observation period following random assignment of pre-school age children (mean age 3 years) with a positive predictive asthma index [69] to fluticasone (n =143) or placebo (n =142) aerosol (reproduced with permission from Guilbert et al) [70]

develop inhalant allergy mediated by IgE to specific inhalant allergens. The former tends to remit or improve beyond age 6, while the latter are those most likely to continue with persistent symptoms. While published evidence for the natural history of other childhood asthma phenotypes is not available, at least two others clinical patterns of asthma can be identified. Children with no prior history can be seen developing asthma exclusively when exposed to inhalant allergens. No history of asthma or wheezing illnesses may be present early in life. Symptoms from this pattern of asthma may be manifest exclusively as seasonal allergic asthma from seasonal inhalants or asthma only upon exposure to a nonseasonal inhalant such as cat allergen. The long term pattern for this phenotype is less well-characterized although perhaps some of those are in the category described by Phelan [52] as wheezing without viral respiratory infections (Fig. 5 ). 526 M. Weinberger and D. Solé

Less frequent and even more poorly characterized with regard to the natural history is nonatopic asthma that begins in adolescence. This appears to be more common in girls than in boys and contributes to the gradual greater prevalence of asthma in boys than girls before puberty to the more equal distribution of asthma seen among the genders in adults.

Summary

While diagnosis of asthma is essential for studying the epidemiology and natural history, there has been controversy regarding a precise definition. However, all of the various definitions refer to airway obstruction that is largely reversible, either spontaneously or as a result of treatment. While there has been an emphasis on including inflammation in the definition, it has not generally been useful as a means of identifying asthma for the purposes of diagnosis. Beyond the diagnosis of asthma is the requirement to characterize the clinical patterns of asthma that distinguishes the various phenotypes. The most common phenotypes of asthma in childhood begin with a viral respiratory infection in infancy, followed by recurrent episodes of lower airway disease from subsequent common cold viruses. The development of specific IgE to inhalant allergens is a major distinguishing factor for those most likely to have persistent disease that continues throughout childhood and often into adult life. For the majority of those early wheezers and coughers with viral respiratory infections who do not develop allergic antibody, improvement or remission by school age is common. Less is known of the natural history of other phenotypes, such as those who only have asthma during exposure to allergens. These include those with seasonal allergic asthma and others who experience asthma only upon specific environmental exposures. Another childhood phenotype less well-characterized with regard to the natural history is the onset of nonallergic asthma in adolescence, more common in girls than boys, which contributes to the evolvement of more equal numbers of asthma among the genders in adult compared with the greater prevalence among boys during childhood.

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74. Kurukulaaratchy RJ, Matthews S, Arshad SH (2006) Relationship between childhood atopy and wheeze: What mediates wheezing in atopic phenotypes? Ann Allergy Asthma Immunol 97:84–91 75. Ramsey CD, Gold DR, Litonjua AA, Sredl DL, Ryan L, Celedon JC (2007) Respiratory illness in early life and asthma and atopy in childhood. J Allergy Clin Immunol 119:150–156 76. Goksör E, Amarak M, Alm B, Gustafsson PM, Wennergren G (2006) Asthma symptoms in early childhood – what happens then? Acta Paediatr 95:471–478 77. Rhodes HL, Thomas P, Sporik R, Holgate ST, Cogswell JJ (2002) A birth cohort study of subjects at risk of atopy: Twenty-two-year follow-up of wheeze and atopic status. Am J Respir Crit Care Med 165:176–180 78. deMarco R, Locatelli F, Cerveri I, Bugiani M, Marinoni A, Giammanco G (2002) Incidence and remission of asthma: A retrospective study on the natural history of asthma in Italy. J Allergy Clin Immunol 110:228–235 79. de Marco R, Pattaro C, Locatelli F, Svanes C (2004) Influence of early life exposures on incidence and remission of asthma throughout life. J Allergy Clin Immunol 113:845–852 80. de Marco R, Marcon A, Jarvis D, Accordini S, Almar E, Bugiani M, Carolei A, Cazzoletti L, Corsico A, Gislason D, Gulsvik A, Jõgi R, Marinoni A, Martínez-Moratalla J, Pin I, Janson C (2006) Prognostic factors of asthma severity: A 9-year international prospective cohort study. J Allergy Clin Immunol 117:1249–1256 81. Shapiro GG (2006) Among young children who wheeze, which children will have persistent asthma? J Allergy Clin Immunol 118:562–564 The Wheezing Infant and Young Child

Peter J. Helms

Although the notion that childhood wheezing illnesses, particularly those presenting in infancy and early childhood (children less than 5 yrs), may have different causes is not new, studies in recent years have revealed and rediscovered a number of distinct wheezing conditions in this early phase of life [1] (Table 1 ). The highest prevalence of recurrent wheezing is found in the first years of life and according to long-term population-related prospective birth cohort studies, up to 50% of all infants and children below the age of 3 years will have at least one such episode [2] . Wheezing in this early period of life is often transient, and 60% of children with mild intermittent infantile wheeze will become asymptomatic in later childhood [3] . On the other hand infants with more severe recurrent wheezing have a higher risk of developing persistent asthma particularly if they are also atopic [4] . However, both the incidence and period prevalence of wheezing decreases significantly with increasing child age [5] . Wheezing, a required feature to make the diagnosis of asthma, is generated by turbulent airflow in an obstructed medium to large airways in which transitional or turbulent airflow can occur. In small peripheral airways where linear bulk flow is absent or minimal not enough energy is available to generate oscillation of the airway wall and hence wheezing occurs. However the narrowing of small peripheral airways is usually associated with gas trapping and hyperinflation, which can result in dynamic compression of larger airways, with consequent airflow obstruction and, if a critical airway diameter is reached, with wheezing. Wheezing may therefore be caused both by alterations in the large airways themselves or by changes in the balance of pressures that control airway diameter. If localized, these alterations are usually associated with monophonic wheezing, whereas generalized intraluminal or extraluminal airway involvement is associated with polyphonic wheezing.

P.J. Helms () Department of Child Health, University of Aberdeen; Royal Aberdeen Children’s Hospital, Westburn Road , Aberdeen , Scotland , AB25 2ZG , UK e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 531 DOI 10.1007/978-4-431-99362-9_32, © Springer 2010 532 P.J. Helms

Table 1 “Asthma” syndromes in early childhood Infants(< 1 yr) Young children (1–5 yrs) Maternal smoking Atopic Asthma Prematurity Viral (Wheezy Bronchitis) Post Bronchiolitis Cough Viral wheeze Exercise induced

The airways of infants and young children are also more susceptible to obstruction because of their smaller size and the soft ribcage that offers poor support for the underlying lung, which recoils to volumes more likely to cause airway closure [6] .

Interpretation of Wheeze

Wheeze is commonly regarded by parents as a term describing many different respiratory sounds [7– 10] which at least in part, explains the heterogeneity in outcomes for early wheeze reported in longitudinal studies [11, 12] . A large airway rattle is the noise most commonly confused with wheeze [7] and is thought to be independent of asthma [13] ; hence the advice that wheeze should be confirmed and documented by a competent health care professional before assigning a diagnosis of asthma [14] .

Infant Wheeze

Although the highest incidence of asthma-like symptoms occurs during the first years of life and in most cases symptoms first develop during infancy and early childhood [15] , early epidemiological studies performed in the 1950’s suggested that wheezing episodes occurring in infancy were largely unrelated to the persistence of symptoms during the school age years [16] . Whereas a proportion of symptomatic infants and very young children have pre-existing reductions in airway function [1] , this clearly defined group in no way explains all the symptomatology present in this young population. Wheezing is a heterogeneous condition in infancy and most subjects who present at an early age will remit by school age with only a small proportion of approximately 20% progressing to classical atopic asthma in mid-childhood. If a strategy will ever be developed for the primary (or secondary) prevention of persistent wheezing in infancy and childhood, better characterisation of the main wheezing phenotypes of infancy will be required. Therefore, and until non-invasive markers that allow a better assessment of the nature of the inflammatory reaction in the airway become part of routine practice, only population risk factors that cannot be easily applied at the individual patient level can be used. The Wheezing Infant and Young Child 533

The most important known risk factor for frequent symptoms and reduced lung function in early life is maternal smoking during pregnancy [17, 18] although most studies suggest that exposure to tobacco smoke products in-utero is mainly associated with an increased risk of wheezing in early life (see subsequent section on environmental factors).

Early Wheezing and Prematurity

Associations among wheezing, lung function, and prematurity is unclear [19, 20] . There is evidence that infants born prematurely (especially those requiring mechanical ventilation) have both increased risk of wheezing during viral infections in early life and persisting lower levels of lung function. The association between prematurity and the development of persistent airway bronchial hyperresponsiveness (BHR) is less clear, and schoolchildren with a history of prematurity do not seem to be more atopic or to be more likely to exhibit non specific BHR [21] . Whether lower levels of lung function are the consequence of prematurity or are otherwise involved in the complex disease mechanisms contributing to premature delivery is not yet understood.

Wheezing after RSV Bronchiolitis

In addition to the role of rhinovirus the respiratory syncytial virus (RSV) has continued to receive much attention as a possible contributor not just to exacerbations but also to the early origins of wheezing illness. Long term studies have confirmed that bronchiolitis (the main diagnosis associated with RSV infection in early life) is associated with continuing respiratory morbidity and airways hyperresponsiveness independent of atopy [22] and that infants with severe enough bronchiolitis to require hospital admission are likely to continue with symptoms into early adolescence [23] . However other studies have found that for less severe disease presenting in the community and not requiring hospital admission the increased prevalence of wheezing gradually diminishes with advancing child age so that by age 13 no additional risk is evident [24] . The possibility that RSV or other viruses may interact with the immune and respiratory systems in early life to initiate the complex mechanisms leading to asthma and allergic sensitisation continues to be a matter of considerable study and debate. RSV infection by itself cannot be a “cause” for asthma, as more than 90% of all children are infected with RSV during the first 3 years of life. It is more likely that, if RSV can trigger the “asthmatic process”, this will occur in subjects who are predisposed either by their genetic background or by events occurring before their first encounter with RSV that have “primed” systemic and/or local immune responses. 534 P.J. Helms

Recurrent Symptoms Beyond Infancy

A sizeable proportion of young children who present with wheezing provoked by intercurrent infections or by exercise or with recurrent cough do have asthma, and careful attention to the clinical history and to the settings in which symptoms are reported can distinguish a number of distinct phenotypes. Treating all children as if there were destined to become atopic asthmatics and at risk of persistent disease is arguably unnecessary particularly as many symptomatic children will subsequently experience complete resolution during later childhood. However this optimistic note needs to be tempered by the observation that asthma has a labile long term course with a tendency for resolution and re-emergence in the same individual with time [25] .

Atopic Asthma

Early identification of classical atopic asthma with its associated chronic airway inflammation may be of great significance as this type of wheezing illness often persists into adult life [26] and is generally more severe than other wheezing and recurrent lower respiratory symptoms that present in infancy and early childhood. A family history of atopic disease has been found to predict persistence in some [27, 28] but not in all [29] long term follow-up studies. Attempts have been made to identify and monitor atopic status by assessment of the granular proteins, eosinophilic cationic proteins (ECP), and eosinophil protein X (EPX). However although this approach can identify individuals with active atopic disease it reflects eosinophil activation from all body sites not just the lung [30] and consequently has a limited role in predicting and following the development of asthma. There are as yet no reliable predictors available to confidently identify the risk of developing atopic asthma and the likelihood of persistence when an individual first presents with symptoms. Indeed studies in infants and young pre-school children [31, 32] confirm clinical impressions that the presence or absence of specific sensitisation to common inhaled allergens are poor predictors of the subsequent development of established asthma in contrast to the situation in school age children in whom BHR and atopy are strongly associated [33, 34] .

Viral Associated Wheeze

Until the 1980’s the terms wheezy bronchitis (WB) [35] and chronic bronchitis of childhood in North America [36] , were commonly used to describe school age children with recurrent wheezing and cough predominantly provoked by intercurrent respiratory tract, presumed viral, infections, in contrast to children with multi- trigger wheeze (MTW) more characteristic of atopic asthma. The Wheezing Infant and Young Child 535

The “wheezy bronchitis” diagnostic label fell into disfavour during the 1970’s with the observation that asthma and wheezing illness were often unrecognised and therefore not afforded the benefit of medical treatment [37] . The move towards an all inclusive label of asthma was supported by an influential follow up study from Melbourne Australia which could not clearly separate children with wheezy bronchitis from children with classical atopic asthma [38] . However it needs to be remembered that the diagnostic label of wheezy bronchitis was originally used in children of school age rather than in infants and young children and that a more widely accepted term for such infants and young children is “viral associated wheeze”. The limited data from airway sampling that is available in this young symptomatic age group supports the separation of a viral wheeze syndrome from classical atopic asthma in that the types of airway inflammation appear to be different [39] . Although it has become fashionable to label all wheezy illnesses as asthma and assume that eosinophilic airway inflammation is present, it is clear that there are different outcomes for the different wheezing syndromes and that the historical separation of wheezy bronchitis or what has been termed “viral associated wheeze” (VAW) from the classical largely atopic one should be reconsidered [40] .

Cough

Cough without wheeze is a common finding in epidemiological studies in childhood and appears to decrease with age [41] and although a common feature of asthma has been shown to be responsive to anti asthma treatment in several small, highly selected groups [42– 44] it is not clear whether these symptoms presenting on their own form part of the same syndrome [42, 45] . The epidemiological evidence, which shows approximately equal sex ratios for cough, in contrast to the male preponderance of wheeze, suggests that there are important differences in the determinants of recurrent cough alone and wheeze in this age group. The lack of association between cough without wheeze and atopy or BHR raises important questions as to whether this group should be considered alongside those children with wheeze, atopy, and BHR. Studies of bronchoalveolar lavage (BAL) [46] and induced sputum [47] also demonstrate that this type of airway inflammation is generally different from that seen in classical atopic asthma in that the major inflammatory cell type tends to be the neutrophil rather than the eosinophil. There is also evidence that a maternal history of bronchitis is a more significant risk factor for non wheezy cough than a paternal history of asthma [48] . Persistent cough may reflect an increased susceptibility to viral respiratory infection, which may have a heritable component. It is intriguing to speculate whether this susceptibility involves mechanisms related to those involved in virus-associated wheeze in infancy and to what extent the two groups of children with virus-associated wheeze in infancy and cough in later childhood may be linked. Although the short to medium term prognosis for those with cough alone appears to be good [49] the longer term implications of this pattern of lower respiratory illness (which may 536 P.J. Helms previously have been described as “bronchitis” or “pneumonia”) for the development of adult obstructive lung disease may be less favourable [50, 51] . Such children may be at increased risk not only from viral infection but also from other factors such as environmental tobacco smoke [52] or air pollution. Standard asthma therapy for isolated and troublesome cough without wheeze has shown no better response than placebo [53] again suggesting that this symptom without associated wheeze is distinct from asthma. Any child with cough and persistent sputum production also needs careful assessment to exclude alternative diagnoses including late presenting cystic fibrosis, ciliary dyskinesia, inhaled foreign body, congenital lung malformations, and selective immune deficiency [54] . Further prospective studies of well characterised families are likely to help in the identification of the heritable and environmental influences contributing to this troublesome symptom and its relationship, if any, to adult obstructive lung disease.

Major Environmental Factors

Human rhinoviruses are responsible for the majority of asthma exacerbations [55, 56] and respiratory syncytial virus is a common cause of severe symptoms in infants [57] . Severe respiratory infections are associated with persistence later in childhood [58] , and such children should be protected from re-exposure if at all possible. Infection can damage the airway epithelium, induce inflammation, and stimulate both an immune reaction and airway hyperresponsiveness [59, 60] . Once the infection resolves, hyperresponsiveness remains for a considerable length of time [61] . Passive exposure to tobacco smoke is one of the strongest domestic and environmental risk factors for developing recurrent coughing/wheezing or asthma symptoms at any age during childhood [2] . Tobacco smoke increases oxidative stress and stimulates inflammation in both the lower and upper airways. In addition, maternal smoking during pregnancy results in impaired lung growth in the developing fetus, which may be associated with wheezing early in life [62] . In existing asthma, active smoking is associated with disease persistence [62, 63] and although tobacco smoke is harmful to everyone, its detrimental effects are relatively greater in younger children. Avoiding tobacco smoke is therefore one of the most important factors in asthma prevention and particularly in early childhood when dependence on parents or carers who are active smokers places the child at a greater risk of exposure [64] .

Airway Inflammation and Remodelling

Airway remodeling is a general term describing chronic, possibly non-reversible changes that occur in the airways of patients with asthma. These include smooth muscle hypertrophy, angiogenesis and increased vascularity, chronic inflammatory cell infiltration, goblet cell hyperplasia, collagen deposition, thickening of the basement The Wheezing Infant and Young Child 537 membrane, and reduced elasticity of the airway wall [65] . Although such abnormalities have been described in both adults and children, they are less extensively characterized in childhood [66– 68] . Evidence of remodeling has been described in children with post-viral wheeze, but there is evidence that the changes do not begin until after infancy [69] . Remodeling may be enhanced by elements of a Th2 immune response [70, 71] although early treatment (from 2 or 3 years of age) with ICS does not appear to change the course of the disease [72] . Although bronchial biopsy and BAL have proved useful in adult patients in clarifying pathogenic mechanisms, there are practical and ethical difficulties in performing similar studies in children.

Persistence and Resolution

There are as yet no screening tests that can be used at first presentation to separate those individuals who are at risk of long term chronic airway inflammation and airway remodelling from those with transient symptoms associated only with viral infections although some features can be used to identify children with high or relatively low risk of persistent disease (Table 2 ). It is widely believed that the presence or absence of a family history of atopic disease has high positive and negative predictive value in establishing a diagnosis of asthma whatever the age of presentation. However this assertion, based as it is on large epidemiological studies and on the likelihood of familial transmission of the atopic trait, can only provide indications of the likely long term outcome. Evidence from serial cross-sectional and family studies in the same community suggests that much of the increase in the prevalence of childhood wheezing has come from what in the past would have been considered to be “low risk” families with little or no atopic history [73, 74] and from the youngest age group, under 5 years of age, where objective assessment of atopy with skin prick tests and/or specific RAST tests have a low predictive value for disease persistence at the individual patient level [75] . The large number of infants and young children presenting with recurrent symptoms suggestive of asthma, and with likely resolution of symptoms in the majority not only poses problems for the clinician in offering a long term prognosis but also in deciding the best initial therapy.

Table 2 Prognostic factors in early childhood For Resolution For Persistence Presentation in infancy Presentation after age 2–3 yrs Viral precipitants only Many provoking factors Male Female Intermittent episodes Persistent symptoms No personal atopy Personal Atopy (Eczema) No family atopy Family atopy Mild symptoms Severe symptoms 538 P.J. Helms

Implications for Therapy

As the confident diagnosis of asthma remains difficult, particularly in young children, the timing of introduction of prophylactic therapy and in particular inhaled corticosteroids (ICS) remains a challenge. A significant proportion of recurrently wheezy infants and very young children appear to have impaired airway function rather than atopy, in contrast to the situation in later childhood where atopy is more strongly associated with wheezing illness. This uncertainty has to be set against the association of decline in lung function with atopy and the likelihood that this may be modulated by chronic airway inflammation and airway remodelling. The large number of infants and young children presenting with recurrent symptoms suggestive of asthma, and with likely resolution of symptoms in the majority, clearly poses problems for the clinician in offering a long term prognosis and in deciding the best initial therapy. For the young child or infant with episodic viral induced wheeze and no interval symptoms the LTRA Montelukast should be considered before initiating ICS [76] . The problem would be completely resolved if there were no concerns about the long term use of prophylactic ICS. However, with the recognition that asthma is a chronic inflammatory airway disease there is now widespread consensus for the early introduction of ICS [14] . Whole population data suggests that the early use of ICS protects against exacerbations leading to hospitalisation [77] and this appears to be supported by declining rates of hospital admissions despite increasing whole population prevalences [78] . These observations suggest that either asthma is less severe than it used to be or that it is being well controlled in primary care with appropriate doses of ICS. With the high population prevalence of asthma and wheezing illness in childhood it is not surprising that a large proportion of the whole child population are being prescribed ICS on a regular basis. Bearing in mind that the majority of pre-school children will become asymptomatic by mid-childhood there is an urgent need to identify those with chronic airway inflammation, and by inference, increased risks of airway remodelling, as the benefits of continuing long term ICS therapy may be most beneficial and possibly disease modifying in such children.

Conclusions

Although wheezing illness is at its most prevalent in infancy and early childhood its self-limiting nature in the majority poses considerable challenges in offering a long term prognosis and in initiating long term prophylaxis. There is an urgent need to develop simple and reliable measures that can identify the presence of allergic airway inflammation as it is in this group of infants and young children that early use of ICS might modify the long term course of the disease. In the meantime when parents ask the question “will he/she grow out of it” all that can be offered in response are the relative risks based on the age of presentation, gender, and presence or absence of atopy (Table 2 ). Essentially this advice remains at the level of probability The Wheezing Infant and Young Child 539 rather than certainty although several factors associated with both a good and poor long term prognosis can be identified. Factors associated with resolution include early age of presentation, exacerbations only in the presence of intercurrent respiratory infections, and no associated atopic features. Less favourable features include presence of atopy, multiple provoking factors for wheeze, and the acquisition of the smoking habit (Table 2 ). The recognition of the major types of recurrent symptoms often brought together under the diagnostic label of asthma and the risk factors that contribute to long term prognosis should be included in decisions as to the most appropriate therapy. Among these the early identification of sensitisation to common inhalent allergens is important as this pattern of sensitisation appears to be associated with persistent disease. Further understanding of the patho-physiology of the different wheezing syndromes in infancy and childhood, their natural histories, and responses to therapy are clearly required. In addition to the identification of the environmental and genetic determinants underlying asthma in its various forms, the relationship, if any, between the wheezing syndromes presenting in childhood and adult chronic obstructive pulmonary disease requires urgent answers.

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Barbara P. Yawn

Definition

“Acute asthma” is often used to describe an asthma exacerbation or asthma attack. Whatever term is chosen these are episodes of rapid onset and progressive worsening of breathlessness, wheezing, cough, and chest tightness, individually or in combination.

Expiratory airflow as measured by spirometry (FEV1 ) or peak expiratory flow (PEF) decreases. Inflammatory cell influx into the lung assessed by sputum eosinophils and exhaled nitrous oxide increases [1– 4] . In more severe attacks blood oxygenation levels measured by pulse oximetery or arterial blood gases will also fall [5, 6] . Acute asthma or an asthma exacerbation is not the same as loss of asthma control. The exacerbation is usually of rapid onset and progressive while loss of control is more gradual and often does not continue to progress [7– 9] . Severe acute asthma can occur in children with good or poor control. The striking lack of PEF variation during exacerbations, as compared to increased variability usually seen with poor asthma control, suggests there may be differences in the beta 2 -adrenoceptor function between these conditions [7] . The severity of acute asthma is based on the level of functional disability (talking, ambulating, alertness), vital signs (respiratory rate, pulse and blood pressure and color), physical examination findings (wheezing and use of accessory chest wall muscles), lung function measurements, and measures of oxygenation in moderate to severe acute episodes [9– 14] . The rapidity of symptom onset may also be useful in infants and young children unable to provide objective lung function measures [15] . Assessment of inflammatory markers adds little additional information [4, 16– 20] . Table 1 [6, 10, 21– 27] provides a summary of metrics to assess the severity of acute asthma. Infants and young toddlers are at greater risk of developing respiratory failure during a moderate or severe exacerbation because of greater peripheral airway resistance, fewer collateral channels of ventilation, airway smooth muscles extending further into the peripheral airways resulting in longer areas of airway narrowing, less elastic recoil of the alveoli, and a mechanical disadvantage of the diaphragm.

B.P. Yawn () Adjunct Professor, University of Minnesota, Director of Research, Olmsted Medical Center e-mai: [email protected]; [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 543 DOI 10.1007/978-4-431-99362-9_33, © Springer 2010 544 B.P. Yawn

Table 1 Acute severe ASTHMA Respiratory Arrest Severe Imminent Symptoms Breathlessness While at rest (infant—stops feeding) Sits upright Talks in Words or short cries Cannot speak Alertness Usually agitated Severe Signs Respiratory rate Often > 30/minute Guide to rates of breathing in awake children: Normal rate by age < 60/minute infants up to 1 year < 50/minute young children up to 2 years < 40/minute children up to 12 <30/minute older than 12 years Use of accessory Usually Paradoxical suprasternal muscles; thoracoabdominal retractions movement Wheeze Usually loud; throughout inhalation Absence of wheeze and exhalation Pulse/minute > 120 Bradycardia Normal rate < 160/minute (infant) < 120/minute (child) < 110/minute (adult) Pulsus paradoxus Often present Absence suggests > 25 mm Hg (adult) respiratory muscle 20–40 mm Hg (child) fatigue Functional Assessment PEF < 40% < 25%

% predicted or % personal Note: FEV1 and PEF often cannot Note: PEF testing may best be obtained during severe not be needed in exacerbations. very severe attacks

PaO2 (on air) < 60 mm Hg: possible cyanosis and/or

PCO 2 ³ 42 mm Hg: possible respiratory failure (see text)

SaO2 % (on air) at sea level < 90%

Epidemiology of Severe Acute Asthma in Children

Most of the 6–18% of the world’s children [28– 31] diagnosed with asthma will never have a severe acute asthma episode. However, 5–10% will have at least one severe exacerbation with 1–2% having multiple severe exacerbations. Black children Acute Severe Asthma in Children 545

Table 2 Risk factors for life-threatening or fatal acute asthma include • Prior intubation and mechanical ventilation for acute asthma [34] • Two or more hospitalization for asthma in the past 12 months, • Hospitalization or emergency department visit for asthma within the past 1 month, • Lack of clear and accessible instructions for recognizing and dealing with deteriorating signs and symptoms (e.g. written asthma action plan) • Use of rescue or reliever medications on average of 3 or more times each day [35] • Sensitivity to Alternaria. • Use of or recent discontinued use of daily oral steroids [9] • No current use of inhaled corticosteroids [36] • History of non-compliance with medication plan [9, 37– 44] and certain subgroups of Latino children (e.g. in the U.S., Puerto Rican children) appear to have more severe and more rapid onset acute asthma episodes [28, 32] . The scope of the impact of race and genetic receptor polymorphisms on symptoms perception, treatment failures, and disease progression remain controversial in adults and almost no information is available related to children [32– 35] . The risk factors for life threatening asthma are shown in Table 2 [36– 42] . Children with severe or difficult to control asthma are most likely to have a life threatening or severe exacerbation, yet most severe exacerbations occur in the 80% of children with mild to moderate asthma. This group of children with mild asthma and severe exacerbations have been identified as a potential distinct phenotype [43] . Risk factors for severe asthma include a previous episode of severe or life threatening asthma lower socio-economic status, poor access to medical services, use of illicit drugs, parent mental illness, and heavy exposure to major irritants and toxins such as biomass fuel use in poorly ventilated homes [9, 44– 47] . Some biomarkers may suggest increased risk for severe exacerbations including increased number of circulating eosinophil progenitor cells [48] or the number of cytokines in broncho- alveloar lavage (BAL) fluid [49] . Neither is practical for daily practice and the only feasible assessment currently available, FeNO, is of limited value in predicting exacerbations and not recommended for primary care use [50, 51] .

Recognition and Treatment of Severe Acute Asthma

Early treatment of acute asthma requires early recognition by the child and parent. Treatment should be aimed toward rapid relief of airflow obstruction and hypoxemia. Early recognition (6 hours or less) may decrease the progression to severe acute asthma and hospitalization [26] . Treatment can begin at home or school but in any child with a history of severe exacerbation, treatment is best continued at an acute care facility such as an emergency department [52, 53] . Initial treatment will include use of the child’s rapid reliever. Increased doses of inhaled corticosterids (e.g. doubling the dose) have been shown to be of little value. Very high doses such as quadrupling may help but having a child use 8 or more puffs of an ICS is difficult [54– 57] . 546 B.P. Yawn

Children with a history of more than one moderate to severe exacerbation who live more than 30 minutes from acute care may benefit from having oral steroids at home. Some children with signs of moderate to severe exacerbations may present to the physician’s or nurse’s office. It is important that all office staff know the warnings signs of acute asthma and have protocols to follow to allow them to provide the necessary immediate evaluation and care including immediate access to an examination room to check vital signs, pulse oximetery, and provide oxygen if available . Staff must have permission to interrupt the medical staff to seek immediate support and care. Few clinics have the resources necessary to complete the monitoring and treatment of a severe exacerbation [58] and plans to transfer the child should be made immediately. The decision of what type of transport to use is based on local resources. Some parents will directly call for emergency transport [59] . In the office and emergency transport vehicle, treatment should include inhaled short acting bronchodilators and oxygen [60, 61] . A mask or holding chamber added to the inhaler or a nebulizer is often required because the child is unable to coordinate breathing and inhaler initiation because of his/her young age, rapid respirations, or marked distress [62– 64] . Only in the most extreme situations and when no other resources are available should subcutaneous epinephrine or terbutaline be used [65, 66] . Treatment should never be delayed for transport [67] . Although three bronchodilator treatments within the first hour is considered maximal treatment, home treatment should be repeated in the office or ambulance since inhaled bronchodilator without mask or holding chamber may have delivered little if any effective therapy. Non-medical remedies such as pursed lip breathing may calm some children during an exacerbation but does not improve lung function [10] . Other home remedies such as drinking large volumes of liquids, breathing warm moist air or use of over the counter anti-histamines or cold remedies are NOT recommended and may aggravate the acute episode and frustrate the child who is unlikely to be willing to drink or use oral medications during a severe episode [10] . All emergency medical services transport or ambulance teams should have standardized protocols that allow treatment with therapy beyond short acting beta agonist therapy including use of ipratropium bromide and systemic corticosteroids [61, 68– 70] . In addition, the transport team must be taught to assess for imminent respiratory failure and have skills and equipment to provide ventilatory assistance and support when required. Spirometry and peak flow assessment (PFA) are often impossible outside of the hospital [71] .

Assessment in the Emergency Department or Acute Care Facility

When a child arrives in the ED, basic therapy such as oxygen and bronchodilator therapy is begun while completing critical evaluation of vital signs, severity of episode, and oxygenation levels [Table 3 ]. While beginning treatment with the presumed diagnosis of asthma, other reasons for airflow obstruction must be ruled Acute Severe Asthma in Children 547

Table 3 Therapies for severe asthma exacerbations Recommended: Always: Oxygen, Inhaled short acting broncho-dilators, oral corticosteroids As needed : Intravenous magnesium sulfate, Heliox Not recommended: Never use : Sedatives, Mucolytic drugs, Excessive hydration Rarely : Methylxanthines by any route of administration, Antibiotics out including aspiration of a foreign body, anaphylaxis from something such as a peanut allergy, or a cardiovascular event (congenital heart disease) since beta agonists will not help these problems and may aggravate cardiovascular events. In older children, the use of illicit drugs or a severe panic attack should also be considered while initiating respiratory therapy [72– 75] . A short set of questions directed to the parent(s) should explore asthma history including previous hospitalization or ICU admission for asthma, any history of severe food or insect sting allergy, recent history of choking on solid foods, or a history of congenital heart disease [76] . In some areas the label of asthma is seldom applied to infants and so it may be necessary to inquire about diagnoses of reactive airway disease or recurrent broncho-spasm [59] . The general goals of treatment are the same worldwide but are best adapted and implemented locally on the basis of available resources and community needs [77, 78] . When a child meets the criteria for a severe exacerbation, an immediate decision must be made whether to continue therapy in the ED or transfer the child to the hospital. Immediate transfer to an intensive care unit (ICU) if available, is appropriate for children at risk of death [Table 2 ] and for infants with severe exacerbations. A respiratory rate of 60 or greater, inspiratory plus expiratory wheezing, the rare child with a silent chest (too little air movement for auscultation) [79] , or oxygen saturation of < 90% should lead to immediate hospitalization rather than treatment and evaluation in the emergency department. If a child is able to perform spirometry, any value < 25% of the predicted one that improves by < 10% within the first 15 minutes after the first bronchodilator treatment in office or in ED, is an indication for immediate transfer to the hospital and if available, an intensive care unit (ICU), bypassing extensive evaluation in the ED, regardless of other signs and symptoms [10]. Fever is not uncommon in infants with acute asthma as many asthma exacerbations result from viral infections. The presence of a fever in an infant with an asthma exacerbation does not automatically require either antibiotics or hospitalization [21] .

First Line Care in the ED

Figure 1 provides an overview of treatment once the immediate decision has been made to provide therapy in the ED. Most exacerbations will begin to improve with therapy over a period of 1–3 hours with a combination of oxygen, bronchodilators and systemic corticosteroids to combat inflammation. 548 B.P. Yawn

Fig. 1 Management of Severe Acute Exacerbation

Oxygen saturation should be kept > 95% in all infants and children. Hypoxemia may be obvious from nail bed or peri-oral cyanosis but usually requires an objective measure. Non-invasive measures such as pulse oximetery are appropriate for rapid initial assessment [7, 23, 80, 81] , but may need to be followed by arterial blood gases to also assess acidosis in respiratory failure or when assisted ventilation is used. Oxygen delivery should be by face mask since most infants and children with severe acute asthma will be mouth-breathing and a nasal cannula will have little effect. Oxygen tents should not be used for acute therapy since the period of time required to raise the oxygen level in the tent can be quite extended . Acute Severe Asthma in Children 549

The oxygen can be combined with nebulized short-acting beta-2-agonists given continuously over the first hour of therapy for rapid reversal of airflow obstruction [53, 82, 83] . Blow-by therapy is not recommended as the amount of drug inhaled into the lungs is usually quite low. A child who has already used multiple doses of beta2 -agonist over the past few hours may still respond to the same therapy delivered more effectively. Use of leva-albuterol may increase the bronchodilator effect [55, 84– 88] . Continuous and prolonged administration of bronchodilators provides some incremental bronchodilation [82, 89– 95] . However, if additional therapy is required after three or more doses of short-acting beta2 -agonists, short acting anticholinergic bronchodilators such as ipratropium bromide can be tried [89, 96] . The duration of action of a short-acting bronchodilator can be significantly shortened during an exacerbation [82] , so continuous treatment is usually recommended [97] . After prolonged use of beta agonists, the possibility of lactic acidosis should be considered and appropriate monitoring of serum pH can be done using capillary blood [98] .

The History and Physical Examination

A brief but more thorough history and physical should be done making sure to include the child in any queries whenever possible [Table 4 ] [10, 99] . Despite the need for health professionals to move rapidly and monitor closely, it is important to address the child’s and family’s fears of death and treatments such as nebulizers and steroids. It is not difficult to imagine the fear and anxiety a child or parent is experiencing amidst all of the ED or hospital activities. The physical examination is an ongoing process that is done initially to determine the severity of the acute asthma response to immediate therapy and then to look for triggers and co-morbid conditions such as pneumonia, pneumothorax, pneumomediastinum [100, 101] , congenital heart disease, epiglotitis, Respiratory Syntical Virus (RSV) infection, extrinsic and intrinsic tracheal narrowing, vocal cord dysfunction, gastro-intestinal reflux, anemia, non-respiratory infections such as parasites, or gastrointestinal infections which can be evaluated by chest radiograph, chest auscultation, a complete blood count, or other special tests.

Table 4 Brief history for severe acute asthma • Onset and possible triggers • Rapidity of progression • Current medications and all medications stopped or decreased recent • Prior ED, urgent care or hospital visits for asthma in past 2 years • Timing of prior severe episodes of asthma • Any other current problems or illnesses–upper respiratory infections, heart disease, cystic fibrosis, tuberculosis, etc. • Any exposure that may have been related–tobacco smoke, food, animals • Specific child and parent concerns or fears 550 B.P. Yawn

Stress and systemic corticosteroids elevate the polymorphonuclear leukocyte count within 1–2 hours [102] . For oxygen saturation levels less 95% and children on assisted ventilation, arterial blood gases are required for monitoring levels of oxygen, carbon dioxide, and pH. Venous (capillary) PCO2 may be useful for identifying levels of > 45 mm but should be confirmed by arterial testing [25] .

Ongoing ED Care

As soon as feasible, such as after the completion of the first nebulizer treatment or as the nebulized drug is being prepared, the infant or child should receive glucocorticosteroids (0.5–1 mg of prednisolone/kg or equivalent) that can be given in a single dose (best in severe exacerbations) or divided over a 24-hour period [53, 102– 105] . An estimated weight is sufficient for dosing the glucocorticosteroids. However, it is important to use doses determined by weight for all medications since the group defined as “children” can vary from a few kilograms to 50 or 60 kilograms. Inhaled corticosteroids, even at high doses, are not a substitute for oral or intravenous corticosteroids in children during a severe exacerbation [105] . Even children on daily oral steroids prior to the exacerbations benefit from a burst of high dose steroids [9] . During severe exacerbations additional therapies may be required such as a switch to anti-cholinergic bronchodilators [32, 89] . Epinephrine (adrenaline) is rarely indicated even for severe asthma exacerbations except when anaphylaxis or angioedema are also present [106] . Some data are available on magnesium sulfate and heliox and older therapies like theophylline [107– 111] . There is no role for theophylline in treating severe asthma exacerbations. In fact any child who has been using theophylline for asthma should be evaluated for theophylline toxicity [110, 111] . Inhaled magnesium sulfate therapy has not been shown to be of value [107, 108] , but intravenous magnesium sulfate (usually give as 2 gm over 20 minutes) can be used in children aged 8–12 and older with severe exacerbations, specifically those with initial FEV1 of 25%–30% of predicted and those whose FEV1 does not increase to above 60% of predicted after 1 hour of therapy [45, 100, 101, 105] . Magnesium sulfate is given intravenously (25–75 mg/kg with maximum does 2 grams over 20–30 minutes) to children with very severe or severe and worsening exacerbations. Two meta-analyses suggest that when added to conventional therapy it can be very helpful in children who present with FEV1 < 40% of predicted [52, 112] . Others report that magnesium sulfate is useful only in those with FEV1 < 25% of predicted [113] . Although not all studies have found positive results [114– 116] the use of magnesium sulfate in a child with a very severe exacerbation who is not responding to other therapies, or is faced with impending respiratory failure, or who is intubated is appropriate. The therapy is a single dose. Because magnesium sulfate toxicity results in muscle paralysis checking reflexes and observing for rapidly increasing respiratory muscle “fatigue” is important in a child who is given Acute Severe Asthma in Children 551 magnesium sulfate and is not intubated. The half life of magnesium sulfate can be quite long and the reflexes should be reassessed before considering extubation [114] . Nebulized magnesium sulphate combined with short acting beta agonist has not been shown to be of benefit [117] . Theoretically the low density of helium should improve the ability of an oxygen- helium mixture to get past marked airway obstruction [118] . However, two studies in children combined in a meta-analysis with 4 studies in adults, did not find any improvement in any outcome measures after use of heliox [119] . More recent work using a larger number of children, found some improvement in children given heliox driven nebulization of albuterol compared to children given only oxygen driven albuterol nebulization [109, 120– 122] . Therefore, a trial of heliox in children with life threatening or worsening severe exacerbation appears indicated. Very little data is available regarding the benefits of heliox driven non-invasive bilevel positive pressure ventilation and what is available concludes that it is not helpful [123] but that it may show promise [124] . Use of intravenous beta agonist has failed to show definitive improvement over inhaled beta-agonists [125] and may increase the risks of cardio-toxicity. However, in the child who is intubated, intravenous beta-agonist may be tried if therapy continues to be ineffective even when the child has respiratory support [126] . Due to the risk of cardio-toxicity, intravenous isoproterenol is not recommended [127] . Intravenous montelukast is not readily available in most sites but when available may be tried in children with severe or life-threatening exacerbations when conventional therapy is not working or begins to cause side effects such as cardio-toxicity [128] . One study of IV montelukast found significant improvement in pulmonary function within 10 minutes [128] . Use of oral montelukast does not have a place in emergency treatment of a severe exacerbation or in respiratory failure because the onset of action is 90 minutes or longer [129, 130] . In refractory cases of respiratory failure with severe airway obstruction, human recombinant human deoxyribonuclease (rhDNase) has shown some promise in small trials but should only be used in the context of a trial [131] . Concurrent administration of multiple drugs by nebulization is not recommended but may be required in ‘real world” care. The interaction of multiple drugs administered simultaneously in the same nebulizer is not well understood [132] . If multiple drugs are being given simultaneously and the child is not responding as anticipated, the switch to administering one drug at a time should be considered. Despite the child’s agitation, sedatives should never be given to the child with acute severe asthma prior to use of assisted ventilation. Mucolytic drugs may increase coughing and decrease oxygenation. Chest physiotherapy and the Asian practice of coining may increase the child’s discomfort and restrict respiratory efforts. The need for hydration should be individually determined. Most older children (12 and above) seldom require significant rehydration and fluid overload must be avoided. However, mouth breathing can lose large volumes of fluids in infants and young children who may become dehydrated. In the concern over respiratory status, monitoring of other systems can be overlooked, which is why written protocols and assessment checklists can be helpful. 552 B.P. Yawn

Monitoring Response to Therapy

Decisions to transfer a child to the hospital or to discharge the child can be complex decisions [Figure 1 ]. A child with marked hypoxemia who is unresponsive to oxygen and bronchodilator therapy within 15–30 minutes (oxygen saturation remains < 90%) should be hospitalized [6, 23, 81] . Unfortunately, objective lung function measurements can be helpful for children 5 years and older but difficult to obtain until the initial therapy has provided some relief for the child with a severe exacerbation [71] . One small study suggests that if a child’s peak flow remains at < 40% of predicted 15 minutes after initiation of therapy, he/she will require hospitalization [133] . None of the published severity assessment scores are perfect in predicting the need for hospitalization [6, 21, 71, 134– 136] . Children who continue to meet the criteria for a severe exacerbation [Figure 1 ] after 1 hour of intensive therapy in the ED, should be considered for hospitalization (86% required hospital). For those infants and children who still meet the criteria for a moderate exacerbation after 1 hour of intensive therapy, the rate of eventual hospitalization is about as high as 84%. But for those who have improved sufficiently to meet the criteria for mild exacerbation after 1–2 hours in the ED, only 18% will require hospitalization [26] . In very busy emergency departments where staff observation cannot be continuous, asking parents to help in assessment is useful [22] . Using the multi-faceted assessments for judging the severity of the exacerbation (vital signs, child’s ability to do simple functions like talk or cry, the measure of oxygenation, and if possible lung function) guides monitoring continuously with formal reassessments every 15–60 minutes.

Consideration of Hospital Based Therapy

When it is necessary to admit infants or children to the hospital for severe acute asthma, most cases are admitted to an intensive care unit where they can be closely monitored. In smaller hospitals, the ICU may not be familiar with care of infants and children. The decision to have the child remain in the local hospital versus transport to a center with more experience in caring for children should be made as soon as possible. If physicians are unsure regarding transfer, the referral center should be called to discuss possible transfer and method of transport.

Respiratory Failure

On rare occassions an infant or child arrives at the care site in respiratory failure, with apnea, or in a coma requiring immediate intubation and ventilatory assistance. More commonly respiratory failure develops over minutes to hours despite therapy [Table 5 ]. The etiology may be failure to respond to therapy or worsening of the obstructive process owing to continuation of the triggering event such as pneumonia Acute Severe Asthma in Children 553

Table 5 The signs of impending respiratory failure include • Inability to speak or cry due to respiratory distress, • Altered mental status such as failure to respond to parents, • Intercostal muscle retractions with inhalation, • Worsening fatigue often laying flaccid in parents arms or on the examination table

• Elevated PCO 2 (> 42 mm Hg). or respiratory muscle fatigue. Infants and very young children have limited respiratory muscle reserve and may develop respiratory failure suddenly. Without access to blood gases, clinical judgment alone must be used to determine when to intubate. If you are considering intubation it is best to proceed with intubation immediately. In any child respiratory failure can progress rapidly and is often difficult to reverse. Intubation with controlled oxygenation allows time to identify and treat the trigger(s) for the episode, prevent damaged to multiple organs from hypoxemia, and let the child to rest while reversing airway obstruction. External ventilation such as bagging may have very limited ability to move air sufficiently in and out of the lungs owing to the high pressures that can be required. As soon as intubation is considered a possibility, a physician experienced in intubation of infants or children should be consulted and arrangements to transfer to an intensive care setting should be made if feasible. Whenever possible, consultation should be done before an emergency intubation is required. Many hospitals now have evaluation teams that can be called for consultation prior to a respiratory or cardiac arrest and that help with not only evaluation but practical matters such as bringing the proper equipment for intubation of small children or infants and portable ventilator equipment. It is appropriate to intubate the child in the emergency department or regular hospital room and then transfer to an intensive care unit if immediate intubation is required. Transport of the child to an intensive care unit should never delay intubation. If intravenous access has not already been established it should be immediately after intubation. Management of mechanical ventilation of children with severe refractory asthma is complicated and beyond the scope of this chapter. Care of a child on a ventilator should be managed in consultation with an expert. If this expertise is not available within your hospital and transport to a hospital with this expertise is not feasible, consultation and support may be available by telephone and or internet interactions.

Prevention and Discharge Planning

Once the child or infant is stabilized in either the emergency department or the hospital, it is important to identify the trigger for this episode, provide at least minimal education regarding early identification of severe asthma, identify and make follow up appointment, and consult other available support services. Figure 2 provides a check list that can be used to remind the physicians and nurses to complete all the tasks. 554 B.P. Yawn

M.D./R.N. Intervention Dose/Timing Education/Advice Initials

Inhaled medications Select agent, dose, and . Teach purpose (MDI + spacer/holding frequency Teach technique chamber) (e.g., albuterol)

Beta2-agonist Emphasize need for 2-6 puffs q 3-4 hr prn spacer/ holding Corticosteroids chamber Medium dose Check patient technique Oral medications Select agent, dose, and Teach purpose Teach frequency (e.g., side effects prednisone 20 mg bid for 3-10 days)

Peak flow meter Measure a.m. and p.m. Teach purpose Teach PEF and record best of technique Distribute three tries each time peak flow diary

Follow-up visit Make appointment for Advise patient (or follow-up care with caregiver) of date, primary clinician or time, and location of asthma specialist appointment within 7 days of hospital discharge

Action plan Before or at discharge Instruct patient (or caregiver) on simple plan for actions to be taken when symptoms, signs, and PEF values suggest recurrent airflow obstruction

Fig. 2 Checklist for Discharge

Other services that should be considered include social services to explore insurance coverage or help with costs of needed medications, home visiting nurses to re- affirm education and help identify potential asthma irritants and triggers in the home, and mental health support if there are signs of depression or marked anxiety. Depending on the family structure, it may be important to include grandparents, siblings or other relatives, and care givers in this education. The education provided in the emergency department is often very limited. However, in the event of a severe exacerbation, staff should be available to educate the parents and, when appropriate, the child about the basics of asthma care, inhaler techniques, and reasons for use of medications including the concepts of anti- inflammatory medications and those used for quick relief [Table 6 ]. After a severe exacerbation, no child or infant should leave the hospital or emergency department without medications or prescriptions for systemic corticosteroids, inhaled or nebulized Acute Severe Asthma in Children 555

Table 6 Brief teaching should focus on • What asthma is • The usual triggers for asthma • Need for regular asthma visits in the outpatient setting • Review of discharge medications, (check literacy levels) • Plan to follow for worsening asthma (can use asthma action plan) [137] • Peak flow meter may be helpful corticosteroids, and, if old enough, long acting bronchodilators and either inhaler (with or without mask) for quick relief or nebulized quick reliever medication and a follow up appointment [137] . When feasible, an infant or child who has experienced a severe asthma exacerbation should consult an asthma specialist (allergist, pulmonologist, or general physician who has special training in asthma care) [10, 138– 141] . All children who are discharged from the ED or hospital following a severe exacerbation should have both actual drugs and prescriptions for all required medications for at least 30 days. No ED or hospital personnel should assume that the children will receive their immediately needed asthma medications from their usual physician or any specialist to whom they have been referred. In several studies such follow up appointments occur less than 30% of the time in the U.S and seldom within less than 14–28 days [142, 143] . It is however, important to stress the need for regular office based follow up of asthma. Children with fewer general practice contacts in a year are at increased risk of fatal asthma [144] , and having a follow-up visit within 30 days of an asthma emergency department visit decreased the ED and hospital readmission rate for the next 90 days [145] . Finding time and personnel with the training to educate parents and the child are often difficult. However, the rate of recurrence of severe exacerbations is also high (up to 50%) [143] and the time and stress required to care for a child with another severe asthma exacerbation is likely to be much greater than finding the time and staff to provide at least minimal prevention education before discharge from the first episode. Education in the intensive care unit when a child is intubated may be provided even to parents who appear too upset to learn. Providing some minimal information about how to prevent a re-visit to the ICU is often worth including during the time spent caring for and monitoring the child. Providing parents with support from pastoral staff or faith based support staff can also help with the treatment of the child and support for the family. Early recognition requires that parents and children know what signs and symptoms may herald an exacerbation, when those signs and symptoms suggest a severe exacerbation, and what action should be taken and how quickly the action should be initiated [26] . Written asthma action plans have been used for that purpose and appear to provide patients and families the needed support in deciding when and where to seek medical care and what treatment to begin while coming to medical care services [46, 47] . Similar education can be accomplished without written information and may be necessary in low literacy areas. Like written information, verbal instructions require repeated reinforcement, which requires repeated visits and may be difficult to achieve. 556 B.P. Yawn

Although the format of the written action plan may vary, the content has become relatively standard. For signs and symptoms, the ability to perform common activities helps patients, families, and health professionals determine the severity of the acute episode [See Figure 1 ]. For example, the level of breathlessness increases with severity from breathlessness during activity, breathlessness at rest precluding even the ability to speak more than one or two words at a time, and in infants precluding the ability to feed. Most children become very agitated with rapid breathing (over 30 breaths per minute), use of accessory respiratory muscles, and a pulse that may be twice the normal range. Drowsiness, confusion, and bradycardia are signs of impending respiratory failure and represent a medical emergency. Many parents and children learn to identify a typical pattern of acute asthma episodes that either begin slowly and build over hours or that begin and build over minutes [39, 47] . Identifying this pattern is important for any child with recurrent exacerbations since it provides a guide to the rapidity with which the family must react, whether they should transport the child by car or ambulance, whether they can go to the physicians office, or should immediately proceed to a hospital, emergency department, or acute care center. Children with severe exacerbations or those with rapidly deteriorating symptoms should be cared for in an acute or emergency medical setting where services for cardiac and respiratory support including ventilatory support are immediately available [53, 103] . Novel new therapies that are being tested to prevent recurrence of severe acute asthma include macrolides to reduce neutrophilic inflammation, perhaps by eliminating chronic lower respiratory track infection or carrier status [146] , anti-IgE in older children with marked allergic disease [147– 150] , and anti-TNF-alpha therapy [151, 152] . The most invasive therapy that does not work on inflammatory pathway but directly on the lung tissue is bronchial thermoplasy that uses controlled heat from a high radio-frequency source [153] and has been used primarily in adults with moderate success.

Summary

Early recognition and treatment is imperative to the successful resolution of a severe asthma exacerbation. Written protocols, flow algorithm and team evaluation management can facilitate care of acute severe asthma. The care of the exacerbation is not finished until plans have been initiated to prevent the next severe exacerbation.

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Megan E. Partridge and William K. Dolen

Asthma is a disease caused by the chronic inflammation with resulting airway hyper-responsiveness and reversible obstruction. Although the underlying pathophysiology of the condition is similar in adults and children, differences exist between these two populations because the pediatric lung is not just a smaller version of the adult lung. Because of a narrower airway, children may have asthma symptoms when exposed to stimuli that an adult may tolerate without symptoms. Since the pediatric lung is still developing, chronic inflammation may result not only in current asthma symptoms, but also in a permanent decrease in lung function [1] . On the global level, asthma prevalence is increasing at a disproportionate rate in children, compared to adults. Asthma has become the most common chronic disease of childhood, affecting approximately 9 million children less than 18 years of age [2] .

Asthma Severity Versus Asthma Control

Asthma severity and control are related, but different, concepts. The clinician assesses asthma severity prior to, and in the course of, treatment. It can be considered as an underlying personal characteristic of the disease that remains fairly constant despite therapy [3, 4] . Severity is defined on the basis of asthma symptoms, frequency of rescue medication use, measures of pulmonary function, and the degree to which asthma interferes with daily activities. The term “severity” can refer to the overall severity of the disease or to the severity of a particular exacerbation. In those patients being treated with daily maintenance medications, severity is assessed by the amount of medication needed to sustain asthma control. In contrast, the concept of asthma control relates to the adequacy of the current asthma management [3] . Asthma control has been defined in a variety of ways. In general, asthma

M.E. Partridge and W.K. Dolen () Allergy-Immunology Section , Departments of Pediatrics and Medicine, Medical College of Georgia , 1120, 15th Street , Augusta , GA 30912 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 565 DOI 10.1007/978-4-431-99362-9_34, © Springer 2010 566 M.E. Partridge and W.K. Dolen control refers to the control of disease manifestations, highlighting the dynamic nature of the disease by including response to therapy and triggers [5] . Unfortunately, there is no global consensus on the definition of asthma control and no single marker of adequate control [6] . According to the 2005 practice parameter on asthma control published by the Joint Task Force of the American College of Allergy, Asthma and Immunology and the American Academy of Allergy, Asthma and Immunology, the assessment of asthma control should be based on symptoms, sleep disturbance, use of rescue medications, limitations on daily activities, lung function, and patient and physician assessment of control [7] . Well-controlled asthma (Table 1 ) is defined by having asthma symptoms less than twice per week, rescue medication use twice a week or less, lack of nighttime symptoms, no limitations on daily activities, and normal lung function. The patient and physician should also agree that asthma is well controlled and physicians should frequently reassess their patients since asthma control will change over time [7] . Although they are two separate concepts, asthma severity and asthma control are closely related. For example, a patient who has severe asthma can still be well controlled, whereas a patient with mild asthma can be poorly controlled. This hypo- thetical inverse relationship has been demonstrated in a study of long-term asthma control using several markers of asthma severity, including use of oral steroids, frequency of hospitalizations for asthma, and number of unscheduled visits for asthma. Furthermore, in patients with severe asthma, asthma control is possible with effective control strategies [8] . As appreciation for the adverse health effects of asthma on the population has increased, so too has the need to identify patients at high risk of asthma exacerbations. It is important for clinicians caring for these patients to have a pragmatic approach to assess asthma so that they can identify high-risk patients. The 1991 National Heart, Lung, and Blood Institute (NHLBI) guidelines for the diagnosis and management of asthma emphasized that assessment of asthma severity is the best tool to guide asthma care [9] . The 1995 Global Initiative for Asthma (GINA) guidelines also focused on assessment of asthma severity. The GINA guidelines classify asthma into mild intermittent, mild persistent, moderate persistent, and severe persistent asthma on the basis of symptoms [10] .

Table 1 Well-controlled asthma Asthma symptoms twice a week or less Rescue bronchodilator use twice a week or less No nighttime or early morning awakening No limitations on exercise, work, or school Well-controlled asthma by patient and physician assessment Normal or personal best PEF or FEV1 Modified from “National Asthma Education and Prevention Program Expert Panel Report: Guidelines for the Diagnosis” [7] Best Estimates of Asthma Control in Children 567

In the past several years, an increasing focus on the importance of assessing asthma control, instead of asthma severity, has been reflected in newer guidelines [11] . The 2006 revision of the GINA guidelines was based on concepts of asthma control. The NHLBI asthma guidelines expected to be published in 2007 will probably include recommendations on the assessment of asthma control. Unlike past guidelines, these new guidelines are expected to provide recommendations on asthma management for children 0–4, 5–11, and ³ 12 years of age and will also provide recommendations on assessing asthma while on controller medications. Pediatric asthma is unique, making caring for this population of asthmatics a special challenge. Since reduction in the lung function starts early in life [12] , it is essential to address asthma control before this decline begins. The prognosis of adult asthma may be determined at least in part by asthma control during childhood [13, 14] . Estimates of pediatric asthma control should aid practitioners as they strive for optimal disease control in children.

Assessment of Asthma Control Using Subjective Measures

Symptom Assessments

Asthma symptom assessments (Table 2 ) alone are not a reliable measure of asthma control. The blunted perception of dyspnea found in chronic asthma is a contributing factor [15] . There is a poor correlation between perceived asthma symptoms and measured peak expiratory flow rates (PEFRs) in up to 60% of asthmatic adults (17–76 years) [16] . A similar lack of asthma perception has been found in children; less than 20% improvement in the visual analog scale scores after bronchodilator administration may identify a patient as a “poor perceiver.” [17] In contrast, other patients report significant asthma symptoms despite normal spirometry values. A study of more than 1,500 adults demonstrated a low correlation

Table 2 Interim asthma history for assessing asthma control How has your asthma been doing since your last visit? How has it been doing in the past week? Do asthma symptoms limit your exercise? What kind of exercise do you do? Do asthma symptoms affect school or play? How often do you cough? Is it due to asthma? How often do you wake up at night? Is it due to asthma? How often do you have other asthma symptoms? How often do you use your rescue inhaler? Do you feel that your asthma is in control? The Asthma Control Test [28] asks similar questions in a way that permits quantification of the response 568 M.E. Partridge and W.K. Dolen between daytime symptoms and forced expiratory volume in 1 second (FEV1) and PEFR measurements in 40% of patients [18] . Thus, symptoms may improve without a corresponding improvement in lung function, and lung function may improve without an improvement in asthma symptoms [19] . Despite this lack of correlation, the assessment of perceived asthma symptoms is an important component in the overall assessment of asthma control. In a study of over 3,000 adults, symptom frequency was the major determinant of a patient’s perception of asthma burden. Severity of asthma symptoms, frequency of exacerbations, and interference with activity were less strongly associated with a patient’s perception of asthma burden [20] . This is a disturbing finding, from a management perspective, since physicians often rely on the assessment of patient symptoms for the diagnosis and treatment of asthma.

Quality of Life Measures

Asthma affects overall quality of life in a number of ways. Surveys of children show that asthma limits their daily activities, causes them to miss school, and results in limitations on activity while at school. Asthma is the leading cause of childhood disability; its prevalence has increased at almost twice the rate of all other chronic illnesses of childhood combined [21] . Asthma patients are twice as likely as the general population to experience depression, and patients with depression are three times less likely to take prescribed medications; therefore, they have a higher risk of poor health outcomes in the future [1, 22, 23] . Depression is an important issue of asthma since it is related to quality of life, medication adherence, and risk of hospitalization [24] . Identifying and addressing these issues are important components of asthma care, and there are standardized measurement instruments to help clinicians achieve this goal. These tools attempt to quantify patient-reported symptoms in order to construct valid and reproducible measures of a subjective outcome. Tools available to physicians for the standardized assessment of an asthmatic’s quality of life include generic measures and asthma-specific measures. These health related quality of life (HRQOL) assessments focus primarily on disease burden in regards to overall physical and functional status, psychological status, effects on social interactions, and economic factors [25] . The 1992 Juniper Asthma Quality of Life Questionnaire (AQLQ) is an asthma- specific tool used to assess quality of life impairment in adult asthmatics [26] . The Pediatric AQLQ was adapted from the Juniper AQLQ. Analysis of this clinical instrument demonstrated that this test could detect significant differences in the quality of life of patients whose asthma control had changed in one direction or the other. Furthermore, results were reproducible in patients with stable asthma followed over time [26, 27] . Other validated tools can aid clinicians in assessing a patient’s subjective report of asthma symptoms. These include the Short Form-12 (SF-12) to assess generic Best Estimates of Asthma Control in Children 569 quality of life, the Mini AQLQ and the Asthma Outcomes Monitoring System (AOMS) to assess asthma severity, and the Asthma Control Test (ACT) to assess asthma control. The ACT was first developed for the use in adults and children over 12 years of age. This test has also been validated for the use in children 4–11 years of age. Using input from caregiver and child, this questionnaire can identify children whose asthma is inadequately controlled (sensitivity 68%, specificity 74%) [28] .

Healthcare Utilization

Morbidity from asthma is a major contributor to health care costs in the United States. In 1998, the economic burden of asthma in the United States was estimated at 12.8 billion dollars annually [29] . A population-based survey done in 1987 found that children 1–17 years of age with asthma used 3.1 times as many prescriptions, had 1.9 times as many outpatient visits, 2.2 times as many emergency department visits, and 3.5 times as many hospitalizations as children without asthma. Costs incurred by these children from healthcare utilization were almost three times that of the nonasthmatic children surveyed, demonstrating the significant impact of asthma on healthcare costs [30] . More severe asthma and non-compliance with NHLBI guidelines is associated with increased healthcare utilization [29] . Although only 20% of asthmatics have frequent exacerbations, these patients account for over 80% of total direct asthma costs [29, 31] . Tracking other healthcare utilization trends can be a way to monitor asthma control. In a retrospective observational study of over 60,000 patients, prescription claims for asthma medications and emergency room visits or hospitalizations were tracked in order to assess asthma control in this population. Patients were defined as well as controlled if they had fewer than four claims for beta-agonists, no oral steroid claims, and no ER visits or hospitalizations for asthma. During a 3-year period, 73% of patients had evidence of at least one episode of uncontrolled asthma. Fluctuations in asthma control occur even in patients with previously well-controlled asthma, which could be detected by monitoring resource utilization and administrative claims [32] . Healthcare utilization data can also be used to predict poor outcomes. A systematic review of the literature published between 1960 and 2004 on the risk factors associated with near fatal and fatal asthma in children and adults found several characteristics that predict a poor outcome. Increased use of medications such as beta-agonists via metered dose inhalers (OR = 1.67, 95% CI 0.99–2.84, P = 0.057), nebulizers (OR = 2.45, 95% CI 1.52–3.93, P = 0.0002), and oral steroids (OR = 2.71, 95% CI 1.34–5.51, P = 0.006) were predictors of fatal or near fatal asthma. A history of a hospital admission (OR = 2.62, 95% CI 1.04–6.58, P = 0.04) and/or intensive care unit admission (OR = 5.14, 95% CI 1.91–13.86, P = 0.001), and mechanical ventilation due to asthma (OR = 6.69, 95% CI 2.80–15.97, P = 0.0001) were also predictors of near fatal and fatal asthma [33] . 570 M.E. Partridge and W.K. Dolen

Monitoring the asthma medication use alone can serve as a marker for asthma exacerbations. A review of Medicaid claims data by over 31,000 adults over a 2-year period observed a significant positive association between emergency room visits or hospital admissions for asthma and filling a prescription for a short acting beta-agonist in the immediate period following the visit [34] .

Assessment of Asthma Control Using Objective Measures

Monitoring the Peak Expiratory Flow Rate

Monitoring the PEFR is a routinely used tool to assess airflow obstruction, since the various available devices are portable, inexpensive, and fairly easy to use (Table 3 ). There are, however, limitations to its use. The PEFR reflects the obstruction of the larger airways. PEFR monitoring is not reliable in children 3–5 years of age [35] and is not reproducible even when used in healthy children [36] . Nevertheless, past asthma guidelines have encouraged the use of PEFR in asthma home monitoring, and PEFR monitoring can result in fewer asthma exacerbations when used in combination with asthma education [36] . Children aged 7–14 years who were randomized to management based on monitoring either PEFR alone or PEFR plus symptom assessments had no differences in mean symptom score, lung function, PEF, and quality of life scores. During acute exacerbations, PEFR monitoring did not influence self-management decisions [37] . In some studies, PEFR monitoring is no more useful than monitoring asthma symptoms alone and is satisfactory as long as the results are applied to the individual’s asthma status at baseline [38, 39] . Although the PEFR may function best as a temporary monitoring device in the setting of an acute asthma exacerbation, it provides only a rough estimate of lung function. When used alone, it may not contribute significantly to asthma management and is not useful in the majority of childhood asthmatics [36, 40] . However, it may be useful in children who are poor perceivers to help identify triggers of their asthma [36] and provide a rough early warning of an asthma exacerbation. Use of a PEFR diary as an objective measure of lung function has been a recommendation by the asthma guidelines. Unfortunately, actual compliance with keeping an asthma diary has been estimated at approximately 20%, compared with patient reported compliance of 95%. Diaries can be inaccurate, falsified, and inconsistent [37] .

Table 3 Selected objective measures of asthma control Home monitoring of peak expiratory flow rate and/or FEV1 Forced expiratory spirometry Impulse oscillometry Sputum eosinophil counts Measurement of eNO Best Estimates of Asthma Control in Children 571

Forced Expiratory Spirometry

Other measures of pulmonary function (Table 3 ), specifically the FEV1, provide objective and more reliable data to the provider regarding the current degree of airway obstruction. It is easy to perform, reproducible, and is considered the gold standard of lung function tests in asthma. There are relatively inexpensive hand-held devices that will measure the FEV1. The FEV1 may indicate the risk of a future exacerbation [41] , may be used to predict progressive decline in lung function over time [42] , and may predict persistence of obstructive disease later in life [43] . In children and adults, the absolute value of the FEV1 should be followed over time, since the prediction equations have an unavoidable amount of statistical noise and are substantially affected by errors in entering age or height. The predicted FEV1 values used in the NHLBI guidelines may not be sensitive enough to accurately classify pediatric asthma patients as mild intermittent or persistent, moderate persistent, and severe persistent categories. A study performed at National Jewish Medical and Research Center found that FEV1 values are lower than predicted throughout childhood and that most children with asthma have FEV1 values within the normal range for their age. The mean FEV1 value in this population of children, including severe asthmatics, evaluated at a tertiary care center was 84% of predicted, well within what is considered the normal range. Therefore, when used alone, FEV1 is not a reliable measure of obstructive lung disease in children [44] . Another method for assessing the lung function, impulse oscillometry, does not require active patient participation. It can measure airflow resistance even in children who are unable to cooperate with the conventional lung function testing. It is reproducible in children 3–6 years of age, and the lung function measures obtained correlate well with values obtained from spirometry [45] . It is not a widely available technique and is therefore not routinely used in the clinical setting.

Sputum Eosinophil Counts

At this time, the counting of sputum eosinophils is primarily a research tool used in adults. Since there is correlation between the cellular components obtained in adult sputum analysis and those obtained in children, it is another potentially useful measure of asthma control in children [46] . Its use is limited to children older than 6 years of age, primarily due to the technical difficulties in cooperating with the maneuver and to low tidal volumes [47] . However, children with asthma, either well controlled or poorly controlled, have a significantly higher number of sputum eosinophils than children without asthma [48] . There is some correlation between sputum eosinophilia, defined as >2.5% eosinophils on sputum analysis [48] , and an increase in the frequency of asthma exacerbations [49] . Reducing sputum eosinophils into the normal range with use of inhaled steroids can decrease the number of asthma exacerbations [50] . Sputum eosinophilia may also predict the need for future asthma treatment. The CAMP study established that children with higher sputum eosinophil counts had more steroid bursts than children with lower counts [51] . 572 M.E. Partridge and W.K. Dolen

Difficulties associated with the performance of sputum analysis include the following: it is a time consuming procedure; there are time constraints since sample analysis must done with 2 h of collection; and there are few clinical laboratories that can perform sample analysis [52] . Until these limitations can be addressed, this will remain a research tool.

Measurement of Exhaled Nitric Oxide

The level of exhaled nitric oxide (eNO) can be a useful marker of airway eosinophilia that, in contrast with analysis of induced sputum, is easier to perform. It is a potentially practical measure of airway inflammation in children, though its use is currently limited by equipment costs and questions about standardization and reproducibility. Currently, eNO has been primarily used in the diagnosis of asthma, being most valuable in differentiating asthma, in which eNO is elevated, from other conditions such as chronic obstructive pulmonary disease or gastroesophageal reflux disease, in which eNO is low. Measurement of eNO has been used to assess asthma control and to predict the clinical response to changes in the dosage of inhaled corticosteroids [53, 54] . As a marker of asthma severity as outlined by the NHLBI guidelines [55] , eNO levels increase with the loss of asthma control [56] and decrease in a linear manner with adequate treatment [57] . The precise role for eNO measurement in routine asthma follow-up is still being determined.

Is Asthma Control Possible?

Asthma control is achievable in the majority of patients, despite the degree of asthma severity. Bateman and Bousquet analyzed eight randomized, double-blind parallel studies of nearly 2,800 patients with poorly controlled asthma on their current therapy and of all asthma severity classifications. Asthma control, as defined by the asthma guidelines, was assessed after treatment with fluticasone, salmeterol, or combination therapy. They found that the proportion of patients achieving asthma control for a given therapy was similar despite the asthma severity, suggesting that asthma control can be attained even in severe asthma [58] . The Gaining Optimal Asthma Control (GOAL) study was a randomized, stratified, double-blind, parallel-group study, of 3,421 patients who were treated with fluticasone propionate or salmeterol/fluticasone. Treatment decisions were made based on rigorous adherence to the asthma guidelines until total control or well controlled asthma was achieved. In patients treated with either salmeterol/fluticasone or fluticasone for 1 year, total control was achieved in 41 and 28%, respectively, while good control was achieved in 71 and 59%, respectively. Patients treated with salmeterol/fluticasone had fewer exacerbations in 1 year and had more significant improvements in the quality of life measures than those patients treated with fluticasone alone. The conclusion of this study was that a majority of patients Best Estimates of Asthma Control in Children 573 with uncontrolled asthma can attain asthma control by the use of management strategies proposed in the asthma guidelines [59] . Although asthma control is possible in a majority of patients, variability in response to therapy is observed. This may be due to an array of factors that result in heterogeneity of the asthma phenotype [60] . These factors include, but are not limited to, presence of allergic sensitization, environmental triggers such as air pollution and viral infections, genetic polymorphisms that might affect response to therapy, and behavioral factors such as medication compliance [61, 62] . As a result of the multiple factors involved, asthma control is variable not only between individual patients, but also within a single patient [19] . The complex nature of asthma requires the use of multiple approaches in the evaluation and management of these patients. Assessment of control should take multiple parameters into consideration since reliance on any single measure is likely to overestimate the level of control [58] . A more complete understanding of the genetic and environmental basis for this variability in asthma phenotypes might allow simpler approaches to maximizing therapy and assessing control.

Achieving Asthma Control

The development of GINA and national guidelines has given physicians around the world access to specific expert opinions on best asthma management practices [10] . Despite the availability of these recommendations, the use of these guidelines in daily clinical practice has fallen short of the goals outlined in the guidelines. In a worldwide study published in 2006, asthma control in children was evaluated in relation to recommendations put forth by the GINA guidelines. Only a small percentage of children have a good control of their asthma. In addition, many patients are not being managed according to the recommendations of the guidelines. Internationally, there is wide variation in asthma management practices, such as use of written asthma action plans, performance of lung function testing, and use of inhaled steroids [6] . The Asthma Insights and Reality (AIR) survey was performed in 29 countries; it included 7,786 adults and 3,153 children [63] . In all of the countries studied, there was suboptimal control of asthma. Significant numbers of patients reported limitations in daily life, missed school and work days, continued asthma symptoms, and healthcare utilization.

Improving Asthma Control

Another important finding from the AIR survey was that one of the reasons for suboptimal asthma control was that patients do not understand the basics of the disease or the management of their asthma [63] . This observation generated development of a global, quantitative survey, the Global Asthma Physician and Patient (GAPP) survey, to examine barriers to optimal asthma care. Results from interviews with 574 M.E. Partridge and W.K. Dolen over 5,550 patients and physicians from over 16 countries found that perceptions about time spent on asthma education, the effectiveness of patient communication, and medications compliance issues differed between patients and physicians, highlighting a need for improvement in patient centered care [64] . Working toward asthma control in children should be a cooperative effort among the patient, parent, and physician. Education of patients, parents, and physicians is essential in attaining this goal. Patients and parents need to be able to recognize asthma symptoms and understand the treatments used in managing asthma at home. They also need to understand the importance of attaining optimal asthma control. Asthma education programs and events can be organized within communities to provide information on aspects of disease management and proper medication use [6] . Physicians need to address barriers to medication compliance, such as concerns about adverse effects of medications, in order maximize compliance. Early and aggressive treatment with anti-inflammatory medications should be initiated according to recommendations in published guidelines and should be reviewed regularly with patients [64] . Physicians should be aware that patient and parental perception of the level of asthma control can often be inaccurate, with overestima- tion of the level of control and underestimation of disease severity. Therefore, physicians may need to assess asthma control using several different measures (both subjective and objective) of control. Since physicians, parents, and patients can have inappropriately low expectations of the level of achievable asthma control, reexamination of asthma control goals with a more optimistic outlook may be needed [6] . Effective cooperation among the clinicians, parents, and patients provides the best chance for optimal asthma control and may reduce disease-related morbidity and mortality among children with asthma.

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Hugo P. Van Bever , Lynette P. Shek , and Daniel Y.T. Goh

Inhaled corticosteroids (ICS) are now considered the most effective asthma therapy, and are first-line therapy for control of asthma in both children and adults [1– 4] . In the past, ICS were mainly used in children with severe persistent asthma. Nowadays, they are also recommended for the treatment of mild to moderate persistent asthma, and in most countries, ICS have become first-line treatment, even for very young children [5] . However, ICS still fail to enjoy a favorable reputation in terms of safety and tolerability [6] . Many patients (and parents) have a “steroid phobia” that is based on the local and systemic adverse events from high-dose ICS or oral corticosteroids, leading to poor compliance [7– 9] . A number of ICS have been developed and made available to treat asthma over the last 30 years. They include beclomethasone dipropionate (BDP), budesonide (BUD), fluticasone propionate (FP), triamcinolone acetonide (TA), flunisolide (FLUN), mometasone furoate (MF), and ciclesonide (CIC) [10] . Each has unique physiochemical properties that confer distinct pharmacologic characteristics regarding potency, efficacy, safety, tolerability, lung deposition, receptor binding, lipophilicity, and esterification (Table 1 ). In children, the best studied ICS to date are BPD and BUD [11] . Therefore, many of the data and references mentioned in this chapter will be from studies on BPD and BUD. The newest ICS is ciclesonide (CIC), of which many studies in asthmatic children were published [12] recently. A recent study by Pedersen et al. concluded that ciclesonide’s safety and efficacy profile in asthmatic children is similar to that of fluticasone propionate [13] .

H.P. Van Bever () Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore; Department of Paediatrics, National University Hospital, 5 Lower Kent Ridge Road, 119074 Singapore e-mail: [email protected] L.P. Shek Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore D.Y.T. Goh Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, University Children’s Medical Institute, National University Hospital, Singapore

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 577 DOI 10.1007/978-4-431-99362-9_35, © Springer 2010 578 H.P. Van Bever et al.

Table 1 Comparison of the pharmacokinetic and pharmacodynamic features of a number of ICS Parameters BPD BUD FP CIC MF Oral bioavailability <1% 11% <1% <1% < 1% Pulmonary deposition 51% 28% 16% 52% 14% On-site activation somewhat no no yes no Receptor binding affinity 53 935 1,800 12 1,235 Esterification no yes no yes no Lipophilicity moderate low high very high Protein binding: free fraction (%) 87; 13 88; 12 90; 10 99; 1 99; 1 *T ½ h 0.5 2.8 7.8 0.36 4.5 *Vd, L 20 183 318 207 Clearance, L/h 15 84 69 152 53.5 *T1/2 h = half-life / Vd = volume of distribution Modified from Cerasoli F. Developing the ideal inhaled corticosteroid. Chest, 2003, 130:54S–64S Characteristics of Inhaled Corticosteroids

Effects of Inhaled Corticosteroids

Glucocorticoids are lipophilic molecules, exerting effects on many different cell types, and whose underlying mechanisms of action have been well described (Table 2 ) [14, 15] .

Similarities and Differences in Inhaled Corticosteroids

The potency of ICS varies widely. Relative topical potencies of ICS are as follows: FP – CIC > BUD > BPD > TA. Agents demonstrating an improved pharmacokinetic

Table 2 Effect of glucocorticoids on transcription of genes* Increased transcription – Lipocortin-1 – b 2-adrenoceptor – Endonucleases – Secretory leukocyte inhibitory protein Decreased transcription – Cytokines (IL-1, IL-2, IL-3, IL-4, IL-5, IL-6, IL-8, IL-11, IL-12, IL-13, TNF-alfa, GM-CSF, RANTES, monocyte inhibiting protein-1-alfa) – Inducible nitric oxide synthetase (iNOS) – Inducible cyclo-oxygenase (COX-2)

– Inducible phospholipase A2 (cPLA2 ) – Endothelin-1

– NK 2 receptors – Adhesion molecules (ICAM-1) *Adapted from: Barnes PJ (1997) Glucocorticoids. In: Kay AB, editor. Allergy and allergic diseases. Blackwell Science Ltd, London, pp. 619–641 Risk-Benefit of Asthma Therapy in Children: Topical Corticosteroids 579 profile (i.e. high clearance rate, high volume of distribution, and a high level of protein binding, together with a short elimination half-life and a long terminal half- life) have the potential to offer an improved therapeutic index as a result of increased receptor affinity, slower absorption from the lung following inhalation, and rapid systemic clearance [11] . The amount of systemic absorption depends not only on the actual dose administered, but also on the mode of delivery [1, 16, 17] . In a study by Agertoft and Pedersen, lung deposition between BUD inhaled from a Turbuhaler and FP inhaled from a Diskus (GlaxoSmithKline, London, UK) was compared in asthmatic children [18] . The mean lung deposition of BUD from a Turbuhaler was 30.8%, and of FP from a Diskus was 8%. This study indicates that to make rational comparisons between various ICS preparations possible, knowledge of interaction of drug preparation and delivery device in determining oral versus lung deposition is essential. Metered-dose inhalers containing hydrofluoroalkane (HFA) propellants are now replacing inhalers containing chlorofluorocarbon (CFC) propellants [19] . A glucocorticoid administered by means of an HFA propellant will have enhanced deposition in the peripheral airways and will have a different benefit/risk ratio than the same glucocorticoid administered in the same dose by means of a chlorofluorocarbon propellant. BDP through a HFA-MDI produces a clinically equivalent therapeutic response at half the dose of BDP through CFC-MDI, but with similar or less systemic activity, measured by studies of the HPA axis [20] . Although various ICS are believed to have similar clinical efficacy when used at equivalent therapeutic doses, differences in pharmacokinetics affect their safety profiles. The percentage of drug that is systemically available after oral administration has been estimated to be less than 1% for FP, 10.6% for TA, 11% for BUD, and 41% for BPD. Studies in asthmatic children in which the efficacy of the five currently available ICS has been compared directly on a microgram per microgram basis are not available [10, 21] . However, by extrapolating from published studies, it appears that ICS have similar clinical efficacy despite their distinct pharmacologic and pharmacokinetic profiles (Table 3 ). In contrast, they may differ with regard to their benefit/risk ratios.

Table 3 Clinical pharmacology of a number of ICS Percent of Plasma glucocorticoid Topical: elimination active after systemic Oral Inhalation half-life after first-pass Binding potency bioavailability bioavailability inhalation (h) metabolism affinity** ratio BDP 15 25 0.1 6.5* ? 0.4 0.1 BUD 11 28 2.3–2.8 6–13 9.4 1.00 FP <1 16 3.7–14.4 <1 18 25.00 TA 23 22 1.5–3.6 22 3.6 0.05 FLUN 20 39 1.6 21 1.8 0.05 From: Simons FER (1998) Benefits and risks of inhaled glucocorticoids in children with persistent asthma. J Allergy Clin Immunol 102:S77–84 *Beclomethasone dipropionate (0.1) is hydrolyzed to beclomethasone monopropionate (6.5) in vivo **Binding affinities are relative to dexamethasone 580 H.P. Van Bever et al.

Benefits of Inhaled Corticosteroids in Children

Overview of Efficacy of Inhaled Corticosteroids

A large number of studies have been performed in asthmatic children, showing that ICS have an important role in the maintenance treatment of childhood asthma [1, 2, 22] . In short, ICS are able to inhibit asthmatic symptoms, to reduce the need for reliever treatment, to improve the lung function (short-term), and to decrease bronchial hyperresponsiveness [23] . The onset of effect of ICS is not immediately. Symptoms usually begin to improve within days, but obtaining optimal control of symptoms can take weeks. Improvement in pulmonary function takes even longer, and airway hyperresponsiveness continues to improve even after months or years of regular treatment [24, 25] . However, both in preschoolers and in older children, effectiveness starts disappearing within weeks of discontinuing ICS [26, 27] . Moreover, it was shown that continuous use of ICS has no effect on the course of an acute severe asthma attack [28] . ICS have also been successfully used in the treatment of acute asthma [29, 30] . Data suggest that ICS have early beneficial effects (within 1–2 h) when they are used in multiple doses administered in time intervals < or = 30 min [31] . The efficacy is better with high doses given repeatedly during the initial phase of the exacerbation [32] . In comparison with oral prednisone, however, FP was found to be less effective in children with severe acute asthma [33] . Furthermore, it was shown that FEV1 in children with mild to moderate asthma, in the emergency department, improves faster on oral (prednisolone 2 mg/kg) than on a high dose of ICS (2 mg of FP) [34] . Similar findings were reported on FLUN, which happened to be less effective in acute asthma than prednisone [35] .

Early Intervention with Inhaled Corticosteroids

Based on theoretical grounds, it can be assumed that treatment with ICS may be more effective if started early during the course of childhood asthma, in an attempt to stop the inflammatory process, rather than after symptoms have been present for several years. In an open, but controlled study by Agertoft and Pedersen, a significant relationship between the duration of asthma at the start of BUD and the annual increase in FEV1 during BUD therapy was found. After 3 years of treatment with BUD, children who started this therapy later than 5 years after the onset of asthma had significantly lower FEV1 than the children who received BUD within the first 2 years after the onset of asthma [36] . In the START study is demonstrated that long- term, once-daily treatment with a low-dose of BUD decreases the risk of severe exacerbations and improves asthma control in patients with mild persistent asthma of recent onset [37] . However, the START study was unable to show that early administration of ICS has major benefits as compared to administration during later Risk-Benefit of Asthma Therapy in Children: Topical Corticosteroids 581 phases of asthma. Furthermore, many young children will outgrow their asthmatic symptoms spontaneously, and do not need ICS [38– 40] .

Failure to Respond to Inhaled Corticosteroids

Persistent asthmatic symptoms in children usually respond extremely well to ICS treatment. If symptoms persist, despite ICS treatment, the following issues should be considered: (1) poor compliance to treatment, (2) poor inhalation technique, (3) family dysfunction and psychosocial problems, including inability to afford the medication, and (4) physician error (diagnosis is not asthma, but vocal cord dysfunction or hyperventilation syndrome, or there are untreated co-morbidities, such as chronic sinusitis or gastro-esophageal reflux) [41, 42] . Rarely, persistent inflammation (i.e. undertreatment of extremely severe asthma), abnormal glucocorticoid pharmacokinetics, or true glucocorticoid resistance is responsible for the child’s persistent symptoms [43] .

Risks of Inhaled Corticosteroids in Children

Potential adverse effects of ICS have been reported and are listed in Table 4 .

Effect of ICS on Linear Growth and Bone Metabolism

For many years, systemic corticosteroids have been known to be potent inhibitors of linear growth, exerting their suppressive effects at virtually every level of a child’s growth axis [44] . Consequently, it was appropriate to carefully examine potential effects of ICS on childhood growth. However, it is important to emphasize that height measurements must be interpreted carefully because persistent severe

Table 4 Potential adverse effects of ICS in children – Growth delay – HPA axis dysfunction – Bone turnover (breakdown, formation, density) – Connective tissue effects: skin thinning, easy bruising – Posterior subcapsular cataracts – Metabolic changes (impaired insulin tolerance, increases glucose, hyperlipidemia) – Disseminated or opportunistic infection (e.g., varicella) – Behavioral/psychiatric effects – Local effects: irritation (cough), oropharyngeal candidiasis, dysphonia 582 H.P. Van Bever et al. asthma on itself may result in delayed onset of puberty and preadolescent deceleration of height velocity [45, 46] . Mild-to-moderate asthma on itself of duration of 4–7 years seems not adversely affect linear growth. Significant growth suppression occurs only when asthma is persistent and of at least moderate severity [47] . Linear growth can be described as short-term (weeks to months), intermediate term (6–12 months), and long-term (final adult height) [46] . A delay in short-term growth has been reported during treatment with ICS, by using kenmometry studies of lower-leg length growth [10, 46, 48] . Knemometry measurements must be interpreted with caution, however, because their predictive value with regard to long-term growth is unknown. There are still conflicting data as to whether some children with mild to moderate asthma have delayed intermediate-term growth during treatment with ICS. A number of studies, including several with a randomized, double-blind, placebo- controlled design, have suggested that some delay may occur with BPD doses as low as 400 µg/day, and that this effect occurs within the first 6–12 weeks of treatment [25, 49– 58] . There are fewer intermediate-term growth studies of other ICS, although it seems that BUD and FP (200 µg/day) can exhibit potentially the same effects as BPD [54, 55, 57, 59– 61] . Most of the studies on the effects of ICS on growth have been performed in prepubertal, late school-aged children, and only a limited number of studies have been performed in young children [62] . A large prospective, randomized trial in asthmatic children aged 1–3 years (n = 625) compared 1-year safety and efficacy of FP (100 m g twice daily) to that of sodium cromoglycate, and added important knowledge in this area [63] . There was no significant difference in mean adjusted growth rates between the two groups. Delayed intermediate-term growth seems to be not associated with decreased growth hormone secretion or impaired HPA axis function [57, 58] . Decreased concentrations of osteocalcin have been found, but correlations with linear growth delay were imperfect [58] . In contrast, the outcome of a meta-analysis, analyzing 21 studies, of the effects of ICS on intermediate-term growth showed that BPD did not have any effect, even at high doses for long therapy durations, or in children with severe asthma [64] . Early studies of BPD given for decades to children with moderate or severe asthma were also reassuring, as were more recent studies with BUD in which slight delay in linear growth was either found, or if found, was attributed to prepubertal growth deceleration rather than to ICS [36, 65– 68] . There are no prospective, randomized, rigorously controlled, double-blind studies on the effect of ICS on long-term linear growth . In one retrospective cohort study, it was suggested that the attainted adult height of asthmatic children treated with ICS is not significantly different from the adult height of those not treated with these medications [69] . A number of other studies came to similar conclusions [66, 70– 72] . ICS appear to have little effect on bone architecture or bone turnover [73–75] . Cross-sectional studies of children treated with ICS have reported normal bone mass or bone mineral density (BMD) and normal blood markers of bone Risk-Benefit of Asthma Therapy in Children: Topical Corticosteroids 583 metabolism [75, 76] . One cross-sectional study of 1,041 asthmatic children, 5–12 years old, examined whether mild-moderate asthma on itself sufficient to produce a decrease in baseline lung function is associated with an adverse effect on BMD, as determined by dual-energy x-ray absorptiometry (DEXA). In this group, the mean BMD was 0.65 ± 0.10 SD g/cm 2 for the population. The use of oral corticosteroids within the previous 6 months did not adversely affect BMD. The authors concluded that mild-moderate asthma of duration as long as 4–7 years in children does not adversely affect BMD [77] . In another study, on 174 asthmatic children, treated with FP 200 m g/d or nedocromil sodium for 24 months, no differences were found in BMD, determined by DEXA measurements of the lumbar spine and femoral neck [78] . Finally, a large population-based cohort of children aged 4–17 years in the United Kingdom on incidence rates of fractures among children taking ICS, compared to a group only on bronchodilators and a reference group, could not find any increased risk for fractures in children taking ICS, after adjusting the results for indicators of asthma severity [79] .

Effect of ICS on the HPA Axis

During treatment with recommended doses of ICS, the risk of adrenal insufficiency is very low, as most routine tests of HPA axis function are normal [80, 81] . However, more sensitive tests, such as serial early morning cortisol measurements, the area under the curve of 24-hour serum cortisol measurement, or 24-hour urine free cortisol measurements, might show evidence of HPA axis suppression [82, 83] . A recent series of case reports from the United Kingdom of adrenal insufficiency showed the potential side effects of high doses of ICS [84] .

Other Potential Adverse Effects of ICS

Other systemic adverse effects of ICS treatment in recommended doses are extremely uncommon. Posterior subcapsular cataract was not detected in children with a median age of 13.8 years inhaling a median dose of BPD or BUD of 750 µg/ day (12.9 µg/kg/day) for a median duration of 5 years, with infrequent supplemental oral glucocorticoids [85] . Side effects, such as skin rash and conjunctivitis, occurred at low frequencies, similar to placebo or comparator drugs [86] . Rarely, reports of behavioral disturbances and other adverse central nervous system have been published [87] . Furthermore, disseminated infections, such as disseminated varicella, are extremely rare in children taking ICS, and the association between the two has never been proven [88] . An altered carbohydrate and lipid metabolism have been 584 H.P. Van Bever et al. reported after high doses of ICS [89] . Rare cases of hypertrichosis have been reported that were associated with usage of ICS [90] .

Maximizing the Benefits and Minimizing the Risks

It is very important to maximize the benefits and minimize the risks of ICS in children with persistent asthma. The following guidelines may be helpful: (1) recommend the lowest dose that will achieve asthma control, (2) monitor height velocity and pulmonary function on a regular basis, and (3) for BDP and other ICS with little inactivation by first-pass metabolism, reduce oropharyngeal deposition and systemic absorption by encouraging children to rinse and expectorate after inhalation, and add a spacer device. According to the Global Initiative on Asthma (GINA), each individual asthmatic child should be assessed to establish his or her current treatment regimen, adherence to the current regimen, and level of asthma control [91] .

Inhaled Corticosteroids in Infants

Wheezing is a common symptom of infancy, affecting 25–30% of them [92, 93] . However, not all wheezy infants have asthma, and most of them will outgrow their symptoms. On the other hand, it has been shown that chronic asthma can start during infancy [39] . Therefore, infantile wheezing has to be considered as a heterogeneous disease, in which, among others, two major types of wheezing can be distinguished: viral-induced wheezing and wheezing that is associated with allergy. [94] . The treatment of wheezing infants is largely ignored in the different asthma guidelines, such as The Global Initiative for Asthma (GINA), and there are no international guidelines for the management of acute bronchiolitis [95] . The general trend nowadays, however, is to prescribe ICS to young wheezy children, although the majority do not need that kind of treatment. Randomized, controlled studies on the long term effect of inhaled corticosteroids in those wheezy infants with an unfavorable prognosis are urgently needed. In a number of studies, the effectiveness of ICS in young asthmatic children was shown, although not all studies showed clinical beneficial effects [96– 98] . Moreover, recent studies were unable to demonstrate significant long-term effects of ICS in young asthmatic children [27, 99, 100] . These findings are very similar to the findings in older asthmatic children, showing that once ICS are stopped, asthma symptoms do re-occur [26] . Moreover, in a recent study on the effect of FP, 200 µg/day, in preschool children with recurrent respiratory symptoms (i.e. cough, shortness of breath, wheeze) in a general practice setting, no effect was found during a 6 month treatment period [101] . ICS were also unable Risk-Benefit of Asthma Therapy in Children: Topical Corticosteroids 585 to prevent post-bronchiolitic wheezing when given during the acute phase of bronchiolitis [102] .

Combining Inhaled Corticosteroids with Long-Acting Beta-Agonists in Children

For patients whose asthma is not controlled on ICS monotherapy, current recommendations advocate the addition of add-on therapy. For many clinicians, the preferred add-on is a long-acting b -agonist (LABA) such as formoterol or salmeterol. In the Pediatric Asthma Controller Trial (PACT), fluticasone monotherapy was superior to fluticasone/salmeterol combination therapy for asthma control in patients with mild to moderate persistent asthma [103] . In another study of 177 children aged 6–16 years, the authors found no additional benefit of adding salmeterol to a daily dose of 400 m g beclomethasone in a group of children with moderate persistent asthma who were compliant with medication [104] . However, another study of 630 children aged 4–11 years showed improved lung function in those treated with combination of budesonide and formoterol (whether in the same or separate inhaler) compared with ICS alone [105] . Overall, analysis of randomized control trials of LABAs in children showed little to no added protection from asthma exacerbations in patients treated with LABAs compared with ICS alone [106, 107] . The use of LABAs has been brought to the spotlight recently because of the health advisory by the US Food and Drug Administration in 2005 ( http://www.fda.gov/cder/ drug/advisory/LABA ). The FDA mandated that all products containing LABAs are required to carry the warning that these medicines may increase the chance of severe asthma episodes, and death when these episodes occur. This advisory came about because of data from the Salmeterol Multicenter Asthma Research Trial (SMART), which showed that asthma-related death in adults was 4.4 times more likely in the salmeterol group compared to the placebo group [108] . With the current level of knowledge regarding LABAs, appropriate use of ICS first is recommended, which should be adequate in most patients with mild to moderate asthma [109] .

Conclusion: Treatment with ICS in Asthmatic Children: Risk or Benefit?

Except for a slight delay in short-term and intermediate-term growth, ICS are able to inhibit asthmatic symptoms, and to reduce the need for reliever treatment, without causing important systemic adverse effects when administered in recommended doses (Table 5 ). The only limitation found was that ICS seem to have no major positive effect on lung function parameters in asthmatic children. However, ICS are much less likely to cause adverse effects than are oral glucocorticoids, the only 586 H.P. Van Bever et al.

Table 5 Major messages on the usage of ICS in childhood asthma ICS in childhood asthma are... 1. Safe/effective/ not too expensive, and are therefore 1st choice treatment to prevent asthma symptoms 2. Free of major side effects when given in appropriate doses 3. The best medication to prevent symptoms of asthma, but have no major effect on existing symptoms 4. Not necessary in most infants with wheezing, as most of them will grow out of their wheezing and don’t need ICS 5. Preferred to be prescribed without a LABA, which should be avoided, especially in young children other medications that prevent and control asthma symptoms to the same extent [47] . However, no ICS is absolutely free from adverse effects, especially when the manufacturer’s recommended doses are exceeded [110] . Treatment with ICS has allowed most children with persistent asthma, even those with severe disease, to be free of symptoms and to have a normal lung function. The considerable long-term benefits of ICS are worth the relatively minor risks, but the risks must be minimized as much as possible.

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80. Bisgaard H, Nielsen MDD, Andersen B, Andersen P, Foged N, Fuglsang G, et al. (1988) Adrenal function in children with bronchial asthma treated with beclomethasone or budesonide. J Allergy Clin Immunol 81:1088–1095 81. Prahl P (1991) Adrenocortical suppression following treatment with beclomethasone dipropionate and budesonide. Clin Exp Allergy 21:145–146 82. Nicolaizik WH, Marchant JL, Preece MA, Warner JO (1994) Endocrine and lung function in asthmatic children on inhaled corticosteroids. Am J Respir Crit Care Med 150:624–628 83. Philip M, Aviram M, Lieberman E, Zadik Z, Giat Y, Levy J, et al. (1992) Integrated plasma cortisol concentration in children with asthma receiving long-term inhaled corticosteroids. Ped Pulmonol 12:84–89 84. Todd GR, Acerini CL, Buck JJ, et al. (2002) Acute adrenal crisis in asthmatics treated with high-dose fluticasone propionate. Eur Respir J 19:1207–1209 85. Simons FER, Persaud MP, Gillespie CA, Cheang M, Shuckett EP (1993) Absence of posterior subcapsular cataracts in young patients treated with inhaled corticosteroids. Lancet 342:776–778 86. Geller DE (2007) Clinical side effects during aerosol therapy: cutaneous and ocular effects. J Aerosol Med 20 (suppl 1):S100-S109 87. Connett G, Lenney W. Inhaled budesonide and behavioural disturbances. Lancet 338:634–635 88. Choong K, Zwaigenbaum L, Onyett H (1995) Severe varicella after low dose inhaled corticosteroids. Pediatr Infect Dis J 14:809–811 89. Turpeinen M, Sorva R, Juntunen-Backman K (1991) Changes in carbohydrate and lipid metabolism in children with asthma inhaling budesonide. J Allergy Clin Immunol 88:384–389 90. de Vries TW, de Langen-Wouterse JJ, de Jong-Van den Berg LT, Duiverman EJ (2007) Hypertrichosis as a side effect of inhaled steroids in children. Pediatr Pulmonol 42:370–373 91. Bousquet J, Clark TJ, Hurd S, Khaltaey N, Lenfant C, O’byrne P, Sheffer A (2007) GINA guidelines on asthma and beyond. Allergy 62:102–112 92. Taussig LM, Wright AL, Holberg CJ, Halonen M, Morgan WJ, Martinez FD (2003) Tucson Children’s Respiratory Study: 1980 to present. J Allergy Clin Immunol 111:661–675 93. Tan TN, Lim DLC, Chong YS, Lee BW, Van Bever HP (2005) Prevalence of allergy-related symptoms in the second year of life. Ped Allergy Immunol 16:151–156 94. Martinez FD (2002) What have we learned from the Tucson Children’s Respiratory Study? Paediatr Respir Rev 3:193–7 95. Chavasse RJ, Bastian-Lee Y, Seddon P (2002) How do we treat wheezing infants? Evidence or anecdote. Arch Dis Childh 87:546–7 96. Devulapalli CS, Haaland G, Pettersen M, Carlsen KH, Lodrup Carlsen KC (2004) Effect of inhaled steroids on lung function in young children: a cohort study. Eur Respir J 23:869–75 97. Chavasse RJ, Bastian-Lee Y, Richter H, et al. (2001) Persistent wheezing in infants with an atopic tendency responds to inhaled fluticasone. Arch Dis Childh 85:143–8 98. Van Bever HP, Schuddinck L, Wojciechowski M, Stevens WJ (1990) Aerosolized budesonide in asthmatic infants: a double blind study. Pediatr Pulmonol 9:177–180 99. Bisgaard H, Northman Hermansen B, Loland L, et al. (2006) Intermittent inhaled corticosteroids in infants with episodic wheezing. N Engl J Med 354:1998–2005 100. Murray CS, Woodcock A, Langley SJ, Morris J, Custovic A (2006) Secondary prevention of asthma by the use of Inhaled Fluticasone propionate in Wheezy Infants (IFWIN): double- blind, randomised, controlled study. Lancet 368:754–762 101. Schokker S, Kooi EM, de Vries TW, Brand PL, Mulder PG, Duiverman EJ, van der Molen T (2007) Inhaled corticosteroids for recurrent respiratory symptoms in preschool children in general practice: randomized controlled trial. Pulm Pharmacol Ther Jan 23 (in press) 102. Blom D, Ermers M, Bont L, van Aalderen W, van Woensel J (2007) Inhaled corticosteroids during acute bronchiolitis in the prevention of post-bronchiolitic wheezing. Cochrane Database Syst Rev 24, CD004881. Risk-Benefit of Asthma Therapy in Children: Topical Corticosteroids 591

103. Sorkness CA, Lemanske RF Jr, Mauger DT, Boehmer SJ, Chinchilli VM, Martinez FD, Strunk RC, Szefler SJ, Zeiger RS, Bacharier LB, Bloomberg GR, Covar RA, Guilbert TW, Heldt G, Larsen G, Mellon MH, Morgan WJ, Moss MH, Spahn JD, Taussig LM, and the Childhood Asthma Research and Education Network of the National Heart, Lung, and Blood Institute (2007) Long-term comparison of 3 controller regimens for mild-moderate persistent childhood asthma: the Pediatric Asthma Controller Trial. J Allergy Clin Immunol 119:64–72 104. Verberne AAPH, Frost C, Duiverman EJ, Grol MH, Kerribijn KF (1998) Addition of salmeterol versus doubling the dose of beclomethasone in children with asthma. Am J Respir Crit Care Med 158:213–219 105. Pohunek P, Kuna P, Jorup C, De Boeck K (2006) Budesonide/formoterol improves lung function compared with budesonide alone in children with asthma. Pediatr Allergy Immunol 17:458–65 106. Bisgaard H (2003) Effect of long-acting b2 agonists on exacerbation rates of asthma in children. Pediatr Pulmonol 36:391–8 107. Lee DK, Currie GP, Hall IP, Lima JJ, Lipworth BJ (2004) The arginine-16 beta2-adrenoceptor polymorphism predisposes to bronchoprotective subsensitivity in patients treated with formoterol and salmeterol. Br J Clin Pharmacol 57:68–75 108. Nelson HS, Weiss ST, Bleecker ER, Yancey SW, Dorinsky PM; SMART Study Group (2006) The Salmeterol Multicenter Asthma Research Trial: a comparison of usual pharmacotherapy for asthma or usual pharmacotherapy plus salmeterol. Chest 129:15–26 109. Martinez FD (2005) Safety of long-acting beta-agonists--an urgent need to clear the air. N Engl J Med 353:2637–9 110. Todd G, Dunlop K, McNaboe J, Ryan MF, Carson D, Shields MD (1996) Growth and adrenal suppression in asthmatic children treated with high-dose fluticasone propionate. Lancet 348:27–29 Risk-Benefit of Asthma Therapy in Children: Nonsteroidal Anti-Inflammatory Drugs

James P. Kemp

Introduction

Asthma is a chronic inflammatory disease of the airways, and anti-inflammatory treatment is an integral part of asthma treatment for both adults and children. Current international asthma management guidelines recommend low-dose inhaled corticosteroids (ICS) or a leukotriene modifier for children over age 5 and low-dose ICS for children age 5 and younger, who require a controller medication [1, 2] . While the guidelines list ICS as being the most effective controller medications [1, 2] , for many children, nonsteroidal anti-inflammatory treatments are an effective alternative to or adjunctive therapy with ICS to achieve asthma control. Nonsteroidal anti-inflammatory treatments used in childhood asthma include the leukotriene modifiers, cromolyn, nedocromil, ketotifen, theophylline, and, for children age 12 and older, omalizumab. This chapter will cover the benefits and risks of these nonsteroidal anti-inflammatory drugs for treatment of asthma in children. Other than the leukotriene modifiers and omalizumab, most of these agents have been in use for longer than ICS. Nonetheless, their mechanisms of action are not fully understood, and their efficacy is not always well-defined, particularly for children.

General Principles

The goals of asthma therapy are to enable each child to maintain normal activities of daily living (at school, at play) as well as physical activities (sports, outdoor games); to reduce or eliminate daytime symptoms (cough, wheeze) and nocturnal

J.P. Kemp () Department of Pediatrics, University of California School of Medicine, San Diego , Allergy and Asthma Medical Group and Research Center, 9610 Granite Ridge Drive, Suite B , San Diego , CA 92123 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 593 DOI 10.1007/978-4-431-99362-9_36, © Springer 2010 594 J.P. Kemp disturbance from asthma (cough, awakenings); and to minimize or eliminate need for reliever medication as well as the occurrence of asthma exacerbations. These goals have been emphasized in the new guidelines as indicators of asthma control [1, 2] . Another important goal, particularly true in pediatric medicine, is to avoid any adverse effects of treatment. Evidence from surveys worldwide suggests that asthma treatment goals are often not met: parents and children frequently overestimate the control of disease, accepting activity limitations and the presence of asthma symptoms as being usual or normal [3, 4] . Selection of asthma treatment in previous years has been guided by four pre- defined levels of asthma severity (intermittent, mild persistent, moderate persistent, and severe persistent) as per the asthma management guidelines [5– 8] , and most of the information in this chapter refers to these categories. More recently, the 2006 Global Initiative for Asthma (GINA) guidelines propose treatment selection according to the classification by the level of asthma control, namely controlled, partly controlled, and uncontrolled (Table 1 ) [1, 2] . This classification accounts for the fact that responsiveness to treatment is also a measure of asthma severity [9] . Asthma control is thus a treatment goal as well as a measurement to guide treatment selection. Asthma control is a parameter that should be periodically assessed for each patient to serve as the basis for subsequent treatment decisions [9] . Therapy for asthma should be individualized for each child. Asthma is now understood to be a heterogeneous disorder, with different asthma phenotypes that each may respond differently to therapy [10] . Moreover, children can manifest asthma differently at different ages, for example, symptoms in preschool children are often episodic rather than persistent and may be precipitated by viral respiratory tract infection [11] . Finally, as risk factors for developing asthma are identi-

Table 1 Classiﬁ cation of asthma by level of control (From [2] , with permission) Partly controlled Controlled (Any measure Characteristic (All of the following) present in any week) Uncontrolled Daytime symptoms None (twice More than twice/ Three or more or less/week) week features Limitations of activities None Any of partly Nocturnal symptoms/ None Any controlled awakening asthma present Need for reliever/rescue None (twice More than in any week treatment or less/week) twice/week Lung function (PEF Normal <80% predicted or a or FEV1 ) personal best (if known) Exacerbations None One or more/year b One in any week c a Lung function testing is not reliable for children 5 years and younger b Any exacerbation should prompt review of maintenance treatment to ensure that it is adequate c By definition, an exacerbation in any week makes it an uncontrolled asthma week Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 595 fied – including atopic dermatitis, a family history of asthma or allergy, and early allergic sensitization – primary prevention of asthma can be considered for high- risk children [12] . An important area identified for future research is to reach a better understanding of the mechanisms leading to airway inflammation, airway remodeling, altered pulmonary function, and bronchial hyper-responsiveness that characterize asthma [13] . A longer duration of asthma in children has been associated with lower lung function as well as more asthma symptoms and greater need for rescue b -agonist [14] . Thus, the question arises whether early intervention can change lung function outcomes: To treat or not to treat? Evidence thus far suggests that early treatment can reduce morbidity but does not change lung function outcomes [15, 16] . For 1-month-old infants with episodic wheezing, early introduction of 2-week courses of ICS with each wheezing episode did not halt the progression from episodic to persistent wheezing, nor was the proportion of symptom-free days over 3 years of treatment increased [15] . For children 2–3 years of age, regular ICS therapy for 2 years reduced symptoms and asthma exacerbations but did not alter lung function or development of asthma symptoms during a third year without treatment [16] . Studies using a mouse model of asthma have produced intriguing results with regard to airway remodeling [17, 18] . In this model, the typical changes of airway remodeling, including subepithelial fibrosis and smooth muscle cell layer thickening, are induced by allergen administration. Administration of montelukast, a type 1 cysteinyl leukotriene receptor antagonist (LTRA) reversed these structural changes, while administration of dexamethasone did not; both montelukast and dexamethasone reversed airway eosinophilia and goblet cell metaplasia [18] . How these findings translate to clinical practice will be of immense interest . But, currently, the findings indicate that multiple inflammatory processes are involved in asthma and not all patients respond equally well to the same treatment. The roles in childhood asthma therapy of nonsteroidal anti-inflammatory agents will continue to be shaped by the results of ongoing and future research. Dosages of these agents for children are summarized in Table 2 .

Cromolyn Sodium and Nedocromil

Mechanism of Action

Cromolyn sodium and nedocromil are inhaled agents formerly known as mast cell stabilizers. Their effects in asthma include the modulation of inflammatory cell activity – suppression of inflammatory mediator release from mast cells and suppression of activation of inflammatory cells – as well as the reduced firing of sensory neurons [5, 19, 20] . These effects are thought to be mediated by regulation of chloride channels [19, 20] . 596 J.P. Kemp

6 year old ³ 2 h after meals ); ³ –1 12 year old. 12 year old. 2 year old ³ ³ ³ 4 week to evaluate effects; for 4 week to evaluate effects; 1 week; for children 8 week to evaluate effects 8 week to evaluate effects ³ ³ ³ 1 h before or selection and administration intervals ³ 150 mg per injection site (goal 5–10 mg L starting and periodically during therapy children Monitor for possible anaphylaxis. maximum Store under refrigeration; For children Monitor serum concentration at peak Monitor hepatic transaminases before Take Take Many drug interactions Use for Use for once daily; /day divided –1 –1 /day divided 3–4 times/day –1 every 2 or 4 weeks (dose based on baseline IgE level and body weight) 3–4 times/day; and slowly increase to 10 mg kg 12 year old: 150–375 mg subcutaneously 12 year old: 1 year old: start at 5 mg kg 15 year old: 10 mg once daily; 12 year old: 20 mg twice daily 12 year old: 600 mg four times daily For children 3 year old: 1 mg 2 times/day ³ ³ <45 kg: start at 12–14 mg kg ³ >45 kg: start at 300–400 mg once daily ³ 6–14 year old: 5 mg once daily; 6 months to 5 years old: 4 mg once daily ³ year old: 10 mg twice daily 5–11 2 inhalations (each 0.8 mg) 4 times/day 1 ampule by nebulizer 4 times/day ³ ³ 6 months to 3 years: 0.5 mg 2 times/day ammatory agents used for treating childhood asthma ammatory agents used for treating childhood asthma 150 mg omalizumab upon reconstitution tablets; 100-, 200-, 300-, 400-mg extended-release capsules 150 mg/15 mL 150 mg/15 mL tablets; 10 mg tablets 100- and 200-mg capsules; Elixir and solution: 80 mg/15 mL; and Syrup: 80 mg/15 mL Nebulizer solution 20 mg/2 mL Nebulizer solution 20 mg/2 mL syrup: 1 mg/5 mL syrup: 1 mg/5 mL 400- and 600-mg controlled release a Dosages of nonsteroidal anti-inﬂ

Prescribers of theophylline are advised to read prescribing information for each specific product guide on appropriate dose

Omalizumab vial containing Single-use, 5 mL Zafirlukast 10- and 20-mg tablets Table Table 2 Agent Cromolyn sodium Metered-dose inhaler: 8.1 and 14.2 g Available formulations Dosage Antileukotrienes Montelukast 4-mg granules; 4- and 5-mg chewable Notes and comments a Zileuton 600 mg tablets Nedocromil sodium Metered-dose inhaler: 16.2 g 2 inhalations (each 1.75 mg) 2–4 times/day Use for Ketotifen 1 mg tablets; Theophylline Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 597

Benefits and Place in Therapy

Cromolyn and nedocromil have been used for many years in treating mild to moderate asthma in childhood [21] . The use of these agents for treating childhood asthma has gradually diminished since about 1990 with the widening use of ICS. In fact, the most recent GINA guidelines [1] for both children and adults characterize the role of cromolyn and nedocromil in long-term treatment of asthma as being “limited.” This conclusion is based on results of a recent systematic review of placebo-controlled trials indicating that there is insufficient evidence that sodium cromoglycate (cromolyn) has beneficial effects as maintenance therapy in childhood asthma [22] . Similarly, for nedocromil, a recent meta- analysis of placebo-controlled trials concludes that further study is warranted to establish the place of nedocromil in childhood asthma therapy [23] . Despite these data, the clinical experience of the author indicates that these agents are effective for some children who take them regularly. Other reported uses for cromolyn and nedocromil are as add-on therapy with ICS and for preventing exercise-induced bronchoconstriction (EIB). When taken by inhalation before exercise, nedocromil reduces the severity and duration of EIB and is associated with minimal to no side effects (Fig. 1 ) [24] . The efficacy and tolerability of cromolyn are similar to those of nedocromil when used for preventing EIB [25] . On average, the effects of these agents are less than those of short-acting b-agonists for preventing EIB; however, owing to individual variation in response and their good safety profile, cromolyn and nedocromil may be alternatives for some patients with EIB [26] .

Fig. 1 Results of six studies evaluating nedocromil to prevent exercise-induced bronchoconstriction: treatment effects of nedocromil and placebo on the time course of exercise-induced asthma.

Data are mean maximum fall in forced expiratory volume in 1 s (FEV 1 ) and 95% confidence interval. Squares , placebo; diamonds , nedocromil (From [24] , with permission) 598 J.P. Kemp

Cromolyn and nedocromil have an excellent safety profile. The minimal incidence of side effects associated with these agents may be perhaps due to the maintenance of a normal resting physiological state by their preventing chloride channel activation [20] .

Risks and Drawbacks

Both cromolyn and nedocromil are administered by inhalation, and both may produce a cough upon inhalation. Moreover, the bitter taste of nedocromil, noted by 25–30% of patients, may be objectionable to some children. The route (inhalation) and frequency of administration (three to four times daily with cromolyn) may be associated with reduced compliance with therapy [27, 28] .

Ketotifen

Mechanism of Action

Ketotifen is an orally administered antiallergic compound that has been used for many years in some countries for managing allergy, asthma, and atopic dermatitis.

The effects of ketotifen are not fully elucidated but include histamine H1 -receptor antagonism and inhibition of the release of proinflammatory mediators from mast cells and neutrophils [29] . In addition, ketotifen stimulates nitric oxide synthase activity, which suggests that its antiallergic effect may be in part mediated through the formation of nitric oxide [29] .

Benefits and Place in Therapy

Ketotifen is not included in the 2006 GINA Workshop Report or pediatric Pocket Guide [1, 2] . The following statement appears in the 2005 report: “The evidence on the effects of ketotifen in children is insufficient to warrant its use.” [5] Nonetheless, a recent Cochrane review of placebo-controlled trials of ketotifen therapy for asthma or wheezing in children (aged 4 months to 18 years) concludes that ketotifen used as sole or add-on therapy improves the control of asthma and wheezing for children with mild and moderate asthma [30] . The authors note that many children in the trials had atopy and thus the results cannot be extrapolated to all children with asthma. In one small placebo-controlled study, ketotifen was administered long term to infants considered to be at high risk of developing asthma [31] . After 3 years of therapy, 9% of those receiving ketotifen (4/45) and 35% of those receiving placebo Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 599

(14/40) had developed asthma, suggesting that ketotifen may affect the onset of asthma in some preasthmatic children [31] .

Risks and Drawbacks

Ketotifen may be more efficacious for children with a history of atopy. Transient sedation and weight gain are reported side effects of ketotifen [30] . This agent has a long onset of activity that can make the evaluation of clinical benefits difficult.

Theophylline

Mechanism of Action

The best-understood effect in asthma of the methylxanthines is bronchodilation via relaxation of bronchial smooth muscle secondary to phosphodiesterase inhibition with resulting increases in cAMP. Results of recent studies indicate that theophylline also has modest anti-inflammatory properties in asthma [32– 34] . Interestingly, it appears that the anti-inflammatory effects are evident at lower plasma concentrations (5–10 mg L–1 ) than the bronchodilatory effects, which first appear at 10 mg L–1 [33] . Mechanisms of the anti-inflammatory effects are currently being elucidated and include the induction of histone deacetylase (HDAC) activity by theophylline [32] . This effect appears to be synergistic with the effects of corticosteroids, which recruit HDAC to the site of active inflammatory gene transcription, where HDAC inhibits inflammatory gene transcription by inhibiting the acetylation of core histones [32] . This activation of HDAC by theophylline may possibly overcome a form of steroid resistance that occurs when oxidative stress reduces HDAC activity [32, 33] .

Benefits and Place in Therapy

Oral theophylline is the methylxanthine in most common clinical use and has been prescribed for decades for childhood asthma. Theophylline reduces asthma symptoms and the need for rescue medication in children as young as 18 months [1, 35] . In the most recent GINA guidelines [1] , the recommendations for theophylline administration are as monotherapy or as add-on therapy with inhaled or oral corticosteroids [1] . The guidelines note that the efficacy of theophylline is less than that of low-dose ICS, similar to the findings of a recent Cochrane review, which suggest that xanthines are suitable as first-line controller therapy only when ICS are not available [35] . The results of this meta-analysis found insufficient evidence to 600 J.P. Kemp support the use of theophylline as add-on therapy and called for further studies in this area [35] . In developed countries, where its use has fallen substantially since the introduction of ICS, theophylline is often reserved for use as add-on therapy for patients with moderate to severe asthma not controlled adequately with ICS [36] . In developing countries where ICS are difficult or too expensive to obtain, theophylline is often still used as first-line asthma therapy for children. Theophylline is orally administered, inexpensive, and widely available. As discussed above, its bronchodilating effects are now thought to be accompanied also by anti-inflammatory effects, which may or may not be clinically relevant.

Risks and Drawbacks

The therapeutic index of theophylline is relatively narrow. Therapeutic plasma concentrations in children are 5–10 mg L –1, while symptoms of toxicity may appear at plasma concentrations of ³20 mg L –1 [33] . The most common side effects are anorexia, nausea, vomiting, and headache [37] . At high concentrations, central nervous system toxicity can manifest as seizures. Absorption and clearance of theophylline may be variable [35] ; both are affected by genetic and environmental factors, including febrile illness [1] . Theophylline is metabolized by hepatic cytochrome CYP1A2 [33, 38] . Thus, the clearance of theophylline decreases with concurrent administration of macrolide (e.g., erythromycin) and quinolone antibiotics, resulting in increased plasma concentrations. Conversely, the clearance increases with concurrent administration of hepatic microsomal enzyme inducers, including phenobarbital and phenytoin. Plasma theophylline concentrations should be monitored for children receiving doses higher than 10 mg kg –1/day and those receiving other medications that may affect theophylline clearance.

Leukotriene Modifiers

Mechanism of Action

Included in this class are the LTRA, antagonists of the type 1 cysteinyl leukotriene

(cysLT1 ) receptor – montelukast, zafirlukast, and pranlukast – as well as the 5-lipoxygenase inhibitor zileuton, which inhibits leukotriene synthesis. Known also as the antileukotrienes, the leukotriene modifiers exert their effects through interference with the action of the cysteinyl leukotrienes or their synthesis. The cysteinyl leukotrienes are a group of compounds, formerly called the slow- reacting substance of anaphylaxis (SRS-A), that have many effects in asthma and allergic inflammation. These effects, which are thought to be mediated primarily Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 601

through the cysLT1 receptor, include airway smooth muscle contraction and bronchoconstriction, mucus secretion, increased vascular permeability, edema, recruitment of inflammatory cells, and promotion and maintenance of the inflammatory response in both upper and lower airways [39, 40] . In addition, recent data suggest that cysteinyl leukotrienes contribute not only to promoting but also to maintaining airway remodeling in asthma [17, 18, 39] . The synthesis and effects of cysteinyl leukotrienes appear to be relatively independent of regulation by exogenous corticosteroids [39] . This fact suggests that leukotriene modifiers could provide alternative or additive benefit to that provided by ICS.

Benefits and Place in Therapy

The most recent GINA guidelines list leukotriene modifiers as providing clinical benefit, although usually less than that obtained with low-dose ICS, for children ³ 5 years old at all levels of asthma severity [1] . The listed indications of antileukotrienes for children with asthma in the guidelines include it as controller therapy, to prevent EIB (approved for 15–18 years olds in the US), as add-on therapy for children with asthma inadequately controlled by low-dose corticosteroids, and to reduce viral-induced exacerbations for children aged 2–5 years [1] . In addition, montelukast relieves the symptoms of allergic rhinitis (AR) and thus can be administered for children as young as 2 years with concomitant asthma and AR, common comorbidities [40] . The LTRA montelukast and zafirlukast are used most commonly worldwide; pranlukast is used most commonly in Japan; and zileuton is available only in the United States [41, 42] . There are no comparative trials of the leukotriene modifiers. Of these agents, montelukast has been studied most extensively for its role in treating childhood asthma, while zileuton has not been studied and is not approved for children <12 years old. In published clinical trials, montelukast monotherapy has shown efficacy in children as young as 2 years [43– 46] and is approved for use in some countries down to 6 months and in the USA down to 1 year, while zafirlukast is approved for use in children as young as 5 years [47] . Clinical benefits of these agents included significant improvements in FEV1 , rescue b -agonist use, days with asthma exacerbations, quality-of-life assessments, and peripheral eosinophil levels. Of note, these clinical trials enrolled mostly children with mild to moderate asthma. Adding a leukotriene modifier to ICS is an alternative to increasing the dose of ICS [1, 43] . In one study of children with corticosteroid-dependent asthma [48] , the addition of montelukast to therapy produced a small additive effect on lung function and a 23% reduction in asthma exacerbation days. The anti-inflammatory effect of montelukast appears to be additive to that of ICS, as measured by improvements in measures of airway inflammation recorded with the addition of montelukast therapy for children with corticosteroid-dependent asthma [49, 50] . 602 J.P. Kemp

5 Montelukast 0 Placebo –5 –10

% Change –15 1

(Mean ± SE) –20 FEV –25

–30 0 5 10 15 30 45 60 Time After Exercise (Minutes)

Fig. 2 Mean percent change in FEV 1 from pre-exercise FEV 1 at time points from 0 to 60 min after exercise (From [51] , with permission)

Relief of EIB in childhood is important to enable planned as well as spontaneous physical activity. Both montelukast and zafirlukast are effective in preventing EIB in children from 6–14 years of age, and the effect of montelukast is maintained throughout the 24 h dosing interval (Fig. 2 ) [51– 53] . Montelukast also reduces the symptoms and inflammatory mediators of AR in children with concomitant asthma and AR [54– 56] . Observational studies show reduced use and cost of asthma rescue and allergy medication for children with concomitant AR who receive montelukast [54, 57] . For very young children (10–26 months) with early childhood asthma, montelukast has a positive effect on lung function, airway inflammation, and symptom scores [58] . Moreover, montelukast therapy in one study was shown to reduce viral-induced asthma exacerbations in preschool children with intermittent asthma [59] . Short-term studies comparing montelukast with ICS for children with mild to moderate asthma have tended to favor ICS [60– 64] , although for children with mild persistent asthma the clinical benefits of montelukast and ICS are relatively similar [63, 65] . Moreover, the results of observational studies suggest that the “real world” effectiveness of montelukast may be similar to that of ICS for children with mild persistent asthma [54, 57, 66] . This could result, in part, from improved compliance with the oral dose relative to the inhaled route of administration of ICS [66, 67] . Responsiveness of individual patients to ICS or montelukast therapy is variable (Fig. 3 ) [60, 61] . For children aged 6–17 years with mild to moderate persistent asthma and those who are younger and have a shorter disease course tend to respond favorably to montelukast. Instead, those with lower pulmonary function and higher levels of markers of allergic inflammation respond more favorably to ICS [61] . Variability in responsiveness to montelukast therapy appears at least in part to be influenced by genetic variations, which are currently being characterized [68, 69] . Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 603

Fig. 3 Difference in asthma control days between fluticasone propionate and montelukast (fluticasone minus montelukast) for individual participants. Each line designates a single participant (From [60] , with permission)

Finally, slowing of growth is not an issue for children receiving leukotriene modifiers whereas it remains an issue for those receiving ICS [16, 64, 65] .

Risks and Drawbacks

The LTRA have a good safety and tolerability profile [70] . Churg-Strauss syndrome is very rare in children, and causality has not been established [71] . The bioavailability of zafirlukast is affected by food intake and thus, this LTRA must be taken at least 1 h before or 2 h after food; administration is twice daily. Drawbacks to the use of zileuton include frequent administration (two to four times daily) and its metabolism by hepatic cytochrome P450 enzymes; thus, monitoring of hepatic transaminases is recommended monthly during the first 3 months and then for every 2–3 months for the first year of therapy, and periodically thereafter [72] . 604 J.P. Kemp

Omalizumab

Mechanism of Action

Asthma symptoms during childhood are often associated with elevations in total serum IgE levels [73] . Omalizumab is a monoclonal anti-immunoglobulin E (anti- IgE) that reduces circulating IgE levels and has multiple anti-inflammatory effects at the tissue level, including decreased airway eosinophilia and downregulation of IgE receptor expression on basophils and mast cells [74] .

Benefits and Place in Therapy

The role of omalizumab in childhood asthma therapy is currently being defined, as most of the clinical trials to date have enrolled adult and adolescent patients [1] . Omalizumab therapy has the greatest beneficial effect for patients with severe asthma; it also shows efficacy in clinical studies for treating moderate to severe allergic asthma and allergic rhinitis [74, 75] . Omalizumab is approved in many countries for use in patients ³ 12 years old with moderate to severe or severe allergic asthma that is not controlled with ICS. In a preliminary trial enrolling children 6–12 years old with moderate to severe allergic asthma requiring ICS [76] , omalizumab therapy was effective in reducing asthma exacerbations and the need for ICS. Moreover, levels of fractional exhaled nitric oxide, a marker of airway inflammation, did not rise during ICS dose reduction among children receiving omalizumab in a small substudy [77] , indicative of an anti-inflammatory effect of omalizumab in this age group.

Risks and Drawbacks

The drawbacks of therapy with omalizumab are the high cost, the need for refrigeration, and the injectable route of administration. Moreover, at least 0.2% of patients receiving omalizumab have experienced an anaphylactic reaction, and thus the US Food and Drug Administration has recently added a Black Box warning about the risk of anaphylaxis to the prescribing information. Omalizumab is administered as a subcutaneous injection every 2 or 4 weeks. During 1 year of administration to children aged 6–12 years with allergic asthma, other than severe injection site reactions, adverse effects of omalizumab occurred with no greater frequency than with placebo, and no serious adverse effects were recorded [78] . Risk-Benefit of Nonsteroidal Anti-inflammatory Drugs 605

Conclusions

While ICS remain the first-line choice for treating childhood asthma, nonsteroidal anti-inflammatory agents are an attractive alternative for some patients due to the drawbacks of ICS use – particularly the inhaled route of administration (difficult for some patients) and parental and patient fears of side effects. Moreover, the use of nonsteroidal anti-inflammatory agents as add-on or alternative therapy may address the limitations of ICS with regard to efficacy and compliance in some patients. Results of ongoing research will guide future recommendations for childhood asthma therapy. Issues and questions of particular interest with regard to the positioning of nonsteroidal anti-inflammatory agents in childhood asthma therapy include the following: • How to best identify children who will develop persistent asthma • How to halt the progression to persistent asthma over time • How to best treat intermittent wheezing in infants and preschool children • How to best treat children with asthma and concomitant rhinitis • How to best treat patients showing poor responsiveness or lack of compliance to ICS and • How to promote compliance with asthma therapies in the teenage years. A better understanding of the genetic mechanisms and environmental-gene interactions influencing the pathophysiology of asthma will help to better define optimal therapies for different phenotypes of childhood asthma. Equally important, a better understanding of how airway remodeling develops will help to identify the means of reversing this process and improving lung function for pediatric patients.

Acknowledgments Writing support was provided by Elizabeth V. Hillyer, with funding support from Merck and Co., Inc., Whitehouse Station, NJ, USA. The views expressed are solely those of the author, and the author had full control over the content and the preparation of the manuscript.

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65. Becker AB, Kuznetsova O, Vermeulen J, Soto-Quiros ME, Young B, Reiss TF, Dass SB, Knorr BA (2006) Linear growth in prepubertal asthmatic children treated with montelukast, beclomethasone, or placebo: a 56-week randomized double-blind study. Ann Allergy Asthma Immunol 96:800–807 66. Bukstein DA, Luskin AT, Bernstein A (2003) “Real-world” effectiveness of daily controller medicine in children with mild persistent asthma. Ann Allergy Asthma Immunol 90:543–549 67. Weinberg EG, Naya I (2000) Treatment preferences of adolescent patients with asthma. Pediatr Allergy Immunol 11:49–55 68. Whelan GJ, Blake K, Kissoon N, Duckworth LJ, Wang J, Sylvester JE, Lima JJ (2003) Effect of montelukast on time-course of exhaled nitric oxide in asthma: influence of LTC4 synthase A(-444)C polymorphism. Pediatr Pulmonol 36:413–420 69. Lima JJ, Zhang S, Grant A, Shao L, Tantisira KG, Allayee H, Wang J, Sylvester J, Holbrook J, Wise R, Weiss ST, Barnes K (2006) Influence of leukotriene pathway polymorphisms on response to montelukast in asthma. Am J Respir Crit Care Med 173:379–385 70. Bisgaard H (2001) Leukotriene modifiers in pediatric asthma management. Pediatrics 107:381–390 71. Boyer D, Vargas SO, Slattery D, Rivera-Sanchez YM, Colin AA (2006) Churg-Strauss syndrome in children: a clinical and pathologic review. Pediatrics 118:e914–e920 72. Critical Therapeutics Inc (2005) Zyflo (zileuton tablets) Prescribing Information; Available at http://www.criticaltherapeutics.com/pat_pi.html 73. Sherrill DL, Stein R, Halonen M, Holberg CJ, Wright A, Martinez FD (1999) Total serum IgE and its association with asthma symptoms and allergic sensitization among children. J Allergy Clin Immunol 104:28–36 74. Holgate S, Casale T, Wenzel S, Bousquet J, Deniz Y, Reisner C (2005) The anti-inflammatory effects of omalizumab confirm the central role of IgE in allergic inflammation. J Allergy Clin Immunol 115:459–465 75. Holgate ST, Djukanovic R, Casale T, Bousquet J (2005) Anti-immunoglobulin E treatment with omalizumab in allergic diseases: an update on anti-inflammatory activity and clinical efficacy. Clin Exp Allergy 35:408–416 76. Milgrom H, Berger W, Nayak A, Gupta N, Pollard S, McAlary M, Taylor AF, Rohane P (2001) Treatment of childhood asthma with anti-immunoglobulin E antibody (omalizumab). Pediatrics 108:E36 77. Silkoff PE, Romero FA, Gupta N, Townley RG, Milgrom H (2004) Exhaled nitric oxide in children with asthma receiving Xolair (omalizumab), a monoclonal anti-immunoglobulin E antibody. Pediatrics 113:e308–e312 78. Berger W, Gupta N, McAlary M, Fowler-Taylor A (2003) Evaluation of long-term safety of the anti-IgE antibody, omalizumab, in children with allergic asthma. Ann Allergy Asthma Immunol 91:182–188 The Role of Influenza Vaccination in Asthmatic Children

Herman J. Bueving and Johannes C. van der Wouden

Introduction

Asthma is the most occurring chronic disease in children. Asthma related genes and environmental factors play a role in the etiology. Nowadays, asthma is regarded as a chronic inflammatory disease of the airways instead of solely a reversible airway obstruction. Asthma is often diagnosed on specific symptoms such as chest tightness, wheezing, dyspnea, and coughing. It is likely that, rather than a single disease entity, asthma consists of related, partially overlapping syndromes. The first symptoms often are experienced before the age of 5. Children with the highest risk have a family history of atopy and/or asthma. Viral infections with symptoms of wheezing acquired in the first year of life may be associated with the risk of developing asthma later on [1] . However, making the diagnosis with a reasonable certainty that is supported by spirometry is only possible from the age of 6 onward. More than 50% of children with a period of wheezing earlier on in life are not diagnosed as having asthma at the age of 6 [2] . The use of rescue and anti-inflammatory medication has largely altered the prospects of asthma patients and has improved their quality of life. Thus, nowadays, most asthma patients lead a normal life without restrictions. Disease control achieved by the asthmatics is an important predictor of the likelihood of complications of the disease [3] . However, asthma exacerbations neither respond to inhaled steroids nor can they substantially be prevented in this way [4, 5] . Only the use of oral corticosteroids seems to be unmistakably effective in case of exacerbations [6, 7] . Children with asthma are believed to be prone to more severe respiratory illness than healthy children when infected with airway pathogens. Influenza is the only (lower) respiratory tract infection in humans for which a vaccine has existed for decades. The guidelines of most Western and developing countries advise to vaccinate patients with asthma, including children [8] .

H.J. Bueving () and J.C. van der Wouden Department of General Practice , Erasmus MC, University Medical Center Rotterdam , Burg. s’Jacobsplein 51 3015 CA Rotterdam, P.O. Box 2040, 3000 CA, Rotterdam , The Netherlands e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 611 DOI 10.1007/978-4-431-99362-9_37, © Springer 2010 612 H.J. Bueving and J.C. van der Wouden

So, administering influenza vaccination to children may prevent the development of asthma and when having asthma may prevent subsequent morbidity, health use, and complications. In this contribution, we will address the current state of affairs regarding the effect of influenza infection in children and the effectiveness of influenza vaccination in children with asthma.

Influenza: Incidence and Clinical Impact

Viral infections, including influenza, have long been associated with asthma exacerbations. The influenza viruses are classified in three genera, labeled A, B, and C. Only types A and B cause considerable epidemics. Every year influenza viruses change their genome partially, which is called antigenic drift. Because of different subtypes and antigenic drift, formerly built-up natural immunity or vaccine-initiated immunity will not provide protection throughout subsequent seasons. Three types of influenza A viruses are known to infect humans and transmit from human to human: H1N1, H2N2, and H3N2. Estimates for the seasonal incidence of influenza vary, depending on the methods used. To reliably assess influenza, the presence of influenza virus should coin- cide with symptomatic disease. However, in reports on the impact of influenza outbreaks, proxy measures are often used, such as isolated serologic incidence rates, rates of influenza like illness, and complications. Seasonal incidence measured in that way varies from 0–48% [9] . But for discussing the overall impact of influenza and protective measures such as vaccination, one should obviously use an average incidence. The best estimates for an average incidence come from two prospective long-term open population studies. Reported incidences are 4.6% (children aged 0–19 years) respectively 9.5% (children aged 0–5 years) [9– 11] . The overall picture is that in healthy children in the majority of cases influenza can be characterized as a self-limiting disease. The mechanism by which influenza causes asthma exacerbations is not yet known precisely. Postulations vary from direct infection to indirect induction of inflammatory responses [12] . Influenza primarily infects the lower respiratory tract, but also causes systemic symptoms (fever and malaise) and upper respiratory tract (URT) symptoms. Studies in asthmatic children report varying incidences, suggesting that between 30 and 80% of exacerbations are due to a virus [13– 15] . Viruses found are rhinovirus, coronavirus, respiratory syncytial virus (RSV), influenza virus, and an assortment of other viruses. Rhinovirus is most frequently associated with exacerbations of asthma. We found three studies that assessed the incidence of influenza-related respiratory illness in asthmatic children while confirming the presence of influenza by culture. This “hard” incidence was found to be 11.5% for both influenza A and B in 48 unvaccinated children (aged 2–14 years) under the surveillance of an asthma Influenza Vaccination in Asthmatic Children 613 clinic in Japan [16] . Three children (6%) were hospitalized for pneumonia. In another, community-based, study 18% of schoolchildren (aged 9–11 years) had influenza-related asthma exacerbations but no serious complications occurred [14] . Asthma exacerbations as well as episodes of URT symptoms lasted for about 7 days and did not differ between viruses detected. In the placebo arm of a trial in asthmatic children over two seasons, the incidence of laboratory-confirmed influenza-related asthma exacerbations was found to be 5%, again no serious complications occurred [17] . Influenza-related URT episodes lasted 8 days whereas influenza-related asthma exacerbations lasted 11 days. Incidences in children with asthma as reported here are between 5 and 18%. Although the one small study, with children under the surveillance of an asthma clinic, found a hospitalization rate of 6%, no complications were found in the above mentioned community-based study on asthmatic children not in the placebo arm of the study that recruited patients in general practice. Of all viral induced exacerbations, influenza accounted for 3.6% respectively 2% of lower respiratory tract (asthma) episodes [14, 15] . In conclusion, the incidence of influenza-related asthma exacerbations in children and its complications have not been extensively investigated. However, an observational study in children of 1–14 years over several seasons did not find excess morbidity diagnosed as asthma exacerbations [18] . The consequences of influenza infection in asthmatic children can be a rise in morbidity (e.g., exacerbations), more physician visits, the use of medication and hospitalizations or death. As some of these consequences are rare, data are only available from large observational studies [19] . Furthermore, quality of life may also be affected [15] . Because influenza can cause all kinds of illness in children, whether healthy or not, only part of the consequences of infection will be associated with asthma.

Availability and Immunogenicity of Vaccines

Two main types of influenza vaccine are available for the prevention of influenza: the trivalent inactivated vaccine (TIV) for parenteral use and the trivalent cold adapted live attenuated vaccine (CAIV) for intranasal administration. Both vaccines are highly immunogenic and induce adequate immune response with a high level of seroprotection. Inactivated vaccine has been licensed for children with asthma, while cold adapted vaccine has not yet been licensed for asthmatic patients. Unlike vaccination, natural infections with influenza provide an immune response on several levels, i.e., secretory antibodies (IgA) present at the mucosal surface, serum antibodies (IgG) and stimulate T-cells directed at the influenza virus. Immune resistance is a lifelong one against the specific strain and provides partial protection against antigenic drifts. Inactivated vaccine only produces serum protection while live attenuated vaccine mimics natural infection better by also providing mucosal antibodies. There is limited evidence that live attenuated vaccines also give some protection against antigenic drifts of the influenza virus [20] . 614 H.J. Bueving and J.C. van der Wouden

Although efforts are being made to develop an influenza vaccine with a broader spectrum and long-lasting immune response, research has only recently started, and success is not guaranteed [21] .

Adverse Effects of Influenza Vaccination

Safety and tolerability of inactivated vaccine in children with asthma, especially regarding exacerbations of asthma, are nowadays well established [22– 24] . Cold adapted live attenuated vaccine also is generally well tolerated in children and adolescents with asthma [25, 26] ; nevertheless, an increased risk of asthma/reactive airway disease in children younger than 36 months of age is of potential concern [27] . Even egg allergy should no longer be an absolute contraindication for influenza vaccination [28] .

Effectiveness

The effect of inactivated influenza vaccination in preventing clinical symptoms is a much-debated item [29] . Over the past years, live attenuated vaccines have been developed, tested, and used for intranasal administration. The less invasive route, of course, is a benefit in administering the vaccine. Besides, there is hope that the induced mucosal IgA immune response will provide a better protection against infection. In a large multicenter trial, a direct comparison between intramuscular inactivated and intranasal live attenuated vaccine in children with asthma [26] was made in which the live attenuated vaccine was 53% more efficacious in preventing influenza infection. However, as the authors correctly state, because there was no placebo group, the absolute efficacy cannot be calculated. A systematic review indicates that vaccines can have an efficacy of 65% for TIV and 79% for CAIV in reducing serologically confirmed cases of influenza in healthy children, i.e., by comparing pre and postseason antibody titers. However, when using symptom- based outcomes, i.e., influenza-related disease, the vaccines showed an efficacy of only 28% for inactivated and 38% for live attenuated vaccine [30] . Moreover, in case of a mismatch between the vaccine composition and the natural virus, efficacy probably will be much lower or absent. In asthmatics, few studies shed light on the clinical effect of inactivated influenza vaccine (Table 1 ). Observational studies report varying and sometimes even contradictory outcomes. In a retrospective cohort study, effectiveness was only reached for severe asthmatics in a separate analysis, whereas analysis of the whole group revealed an increase of asthma exacerbations [31] . In another study, effectiveness on physician diagnosed acute respiratory disease episodes including otitis media was only significant in asthmatic children under 6 years of age and no effectiveness was found on any children [32] . A third retrospective cohort study showed Influenza Vaccination in Asthmatic Children 615 significant effect significant effect quality of life or frequency of asthma attacks found, three hospitalizations in control and two in vaccine group significant increase in exacerbations in all seasons Results all children showed no Some distinct effects on the Some distinct effects No differences in the severity No differences Results total vaccine group

a a severe asthmatics only 1996–1997 OR clinic visits 2.9 OR ED visits 2.0 OR hospitalizations 1.9 (NS) 1999–2000 2000–2001 OR 0.43 (NS) Adjusted incidence rate ratio results 1993–1994 0.78 (NS) Subgroup analysis 1–6 years 1995–1996 1996–1997 OR 0.45 1999–2000 2000–2001 OR 1.24 (NS) Vaccine Vaccine effectiveness 1992–1993 0.49 1994–1995 0.59 1995–1996 0.65 placebo Peculiarities Season(s) and key results vaccine/ placebo uenza vaccine in asthmatic children uenza vaccine in asthmatic children (ED) visits, hospitalizations for asthma quality of life compared with baseline in influenza positive weeks, influenza confirmed by culture or PCR in emergency department or in emergency hospital like illness, pneumonia, bronchitis, bronchiolitis, asthma exacerbations, otitis media exacerbations, influenza confirmed by culture or PCR confirmed by culture Minimal important difference in Minimal important difference Children with asthma Febrile episodes, influenza controlled trial controlled trial clinical trial Age in years Study type Main outcome Clinical effectiveness of inactivated inﬂ Clinical effectiveness

= Not Significant NS [32] 0–12 Retrospective cohort Clinic visits, emergency department

[30] 1–6 Retrospective cohort Asthma exacerbations evaluated [31] 1–12 Retrospective cohort Combined endpoint: influenza [15] 6–18 Randomized Table Table 1 Article a [17, 23] 6–18 Randomized [16] 2–14 Non-randomized 616 H.J. Bueving and J.C. van der Wouden that children in the vaccine group unexpectedly had a significantly increased risk of asthma related clinic visits and ED visits [33] . Although in one small prospective non-randomized study in a tertiary asthma clinic center a positive effect was found on febrile episodes, clinical efficacy for asthmatics has not been established yet at the highest level of evidence [23] . For asthmatic children in a prospective randomized controlled study, no positive clinical effect of vaccination on asthma exacerbations was found [17] . However, a distinct effect on the quality of life in influenza-related episodes in asthmatic children was reported [15] . In conclusion, of the few studies in this area, most show a suboptimal design, and uncertainty remains about the degree of protection vaccination offers against influenza-related symptoms such as asthma exacerbations.

Vaccine Uptake in Children with Asthma

According to most national and international guidelines, people with moderate or severe asthma should be vaccinated [8] . However, definitions of asthma vary because of differences in the standardization of severity subcategories and because of differences in the views of physicians and patients on the severity of the disease. Besides, asthma in individual patients varies in degree of severity over the years, so when asthma patients have been vaccinated once, it does not mean that they will always need to be vaccinated. Asthma is a disease with an increasing incidence and is, both in absolute and relative numbers, one of the major disease categories to receive influenza vaccination, especially in children [34] . Despite the proven absence of serious side effects, vaccination uptake in asthmatic children, though differing worldwide, is far from optimal [35, 36] . Fear that vaccination causes illness and doubts about the benefits and effectiveness of influenza vaccination, are still, despite of vast opposite evidence, important reasons for patients and physicians to refrain from vaccination [37] .

Cost Effectiveness of Influenza Vaccination

When determining cost effectiveness of influenza vaccination, several seasons should be considered and included in the analysis of cost-effectiveness. However, an overall incidence of influenza-related illness between 4.6 and 9.5% in children [9– 11] as found before or 5% [17] or even 18% [14] as found in asthmatic children is a difficult starting point. Using these figures, disregarding clinical relevance and assuming protective effectiveness of vaccination to be 100%, 22 children (0–19 years), 11 children (0–5 years),or 20 children (6–18 years) respectively six children (9–11 years) with asthma would have to be vaccinated in order to prevent influenza- related illness in one child. Because the effectiveness of influenza vaccination is of Influenza Vaccination in Asthmatic Children 617 course lower than 100% and clinical relevance has to be taken into account, the numbers needed to treat will be higher than calculated here. For instance, in healthy subjects, a clinical effectiveness of the vaccine of just 28% for TIV and 38% for CAIV was found [30] . When extrapolating, this fact alone at least triples the above mentioned numbers needed to treat. In asthmatics, there is no evidence about the degree of protection vaccination provides against influenza-related asthma exacerbations [23] . When assuming a 5% incidence and taking into account the upper boundary of the confidence interval in this study, a maximum protection rate of 34% can be derived [17] . Thus, vaccinating 59 children with asthma could prevent only one influenza-related asthma exacerbation.

Conclusion

Although intuitively the best option for preventing influenza and subsequent clinical deterioration in children with asthma seems to be vaccination, no unequivocal evidence for its effectiveness is present. CAIV could prove to be a better alternative than the current TIV, when it is released for asthmatic children. Although from a pathophysiological point of view influenza is believed to be a threat for asthmatic children, very few data are available about this subject. Future research should first of all focus on a long-term observational research, spanning multiple seasons, to determine the real impact of influenza in children with (and without) asthma. Regarding vaccination, CAIV seems to be an improvement, although it still has to be delivered yearly, a huge logistic operation. Future research into influenza vaccination will understandably be focussed on broad-spectrum and long-lasting vaccines. If this goal is ever reached, it will make preventing influenza infections much easier.

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7. Weinberger M (2003) Treatment strategies for viral respiratory infection-induced asthma. J Pediatr. 142:S34–S38 8. van Essen GA, Palache AM, Forleo E, Fedson DS (2003) Influenza vaccination in 2000: recommendations and vaccine use in 50 developed and rapidly developing countries. Vaccine 21:1780–1785 9. Bueving HJ, van der Wouden JC, Berger MY, Thomas S (2005) Incidence of influenza and associated illness in children aged 0–19 years: a systematic review. Rev Med Virol. 15:383–391 10. Monto AS, Koopman JS, Longini IM, Jr. (1985) Tecumseh study of illness. XIII. Influenza infection and disease, 1976–1981. Am J Epidemiol. 121:811–822 11. Neuzil KM, Zhu Y, Griffin MR, Edwards KM, Thompson JM, Tollefson SJ, Wright PF (2002). Burden of interpandemic influenza in children younger than 5 years: a 25-year prospective study. J Infect Dis. 185:147–152 12. Tan WC (2005). Viruses in asthma exacerbations. Curr Opin Pulm Med. 11:21–26 13. Minor TE, Dick EC, DeMeo AN, Ouellette JJ, Cohen M, Reed CE (1974) Viruses as precipitants of asthmatic attacks in children. JAMA 227:292–298 14. Johnston SL, Pattemore PK, Sanderson G, Smith S, Lampe F, Josephs L, Symington P, O’Toole S, Myint SH, Tyrrell DA, et al. (1995) Community study of role of viral infections in exacerbations of asthma in 9-11 year old children. BMJ 310:1225–1229 15. Bueving HJ, van der Wouden JC, Raat H, Bernsen RM, de Jongste JC, van Suijlekom-Smit LW, Osterhaus AD, Rimmelzwaan GF, Molken MR, Thomas S (2004) Influenza vaccination in asthmatic children: effects on quality of life and symptoms. Eur Respir J. 24:925–931 16. Sugaya N, Nerome K, Ishida M, Matsumoto M, Mitamura K, Nirasawa M (1994) Efficacy of inactivated vaccine in preventing antigenically drifted influenza type A and well-matched type B. JAMA 272:1122–1126 17. Bueving HJ, Bernsen RM, de Jongste JC, van Suijlekom-Smit LW, Rimmelzwaan GF, Osterhaus AD, Rutten-van Molken MP, Thomas S, van der Wouden JC (2004) Influenza vaccination in children with asthma: randomized double-blind placebo-controlled trial. Am J Respir Crit Care Med. 169:488–493 18. Fleming DM, Pannell RS, Elliot AJ, Cross KW (2005) Respiratory illness associated with influenza and respiratory syncytial virus infection. Arch Dis Child. 90:741–746 19. Belshe R, Lee MS, Walker RE, Stoddard J, Mendelman PM (2004) Safety, immunogenicity and efficacy of intranasal, live attenuated influenza vaccine. Expert Rev Vaccines. 3:643–654 20. Hampson AW, Osterhaus AD, Pervikov Y, Kieny MP (2006) Report of the second meeting on the development of influenza vaccines that induce broad-spectrum and long-lasting immune responses, World Health Organization, Geneva, Switzerland, 6–7 December 2005. Vaccine 24:4897–4900 21. The American Lung Association Asthma Clinical Centers (2001) The safety of inactivated influenza vaccine in adults and children with asthma. N Engl J Med. 345:1529–1536 22. Cates CJ, Jefferson TO, Bara AI, Rowe BH (2004) Vaccines for preventing influenza in people with asthma. Cochrane Database Syst Rev. CD000364 23. Bueving HJ, Bernsen RM, de Jongste JC, van Suijlekom-Smit LW, Rimmelzwaan GF, Osterhaus AD, Rutten-van Molken MP, Thomas S, van der Wouden JC (2004) Does influenza vaccination exacerbate asthma in children? Vaccine 23:91–96 24. Redding G, Walker RE, Hessel C, Virant FS, Ayars GH, Bensch G, Cordova J, Holmes SJ, Mendelman PM (2002) Safety and tolerability of cold-adapted influenza virus vaccine in children and adolescents with asthma. Pediatr Infect Dis J. 21:44–48 25. Fleming DM, Crovari P, Wahn U, Klemola T, Schlesinger Y, Langussis A, Oymar K, Garcia ML, Krygier A, Costa H, Heininger U, Pregaldien JL, Cheng SM, Skinner J, Razmpour A, Saville M, Gruber WC, Forrest B (2006) Comparison of the efficacy and safety of live attenuated cold-adapted influenza vaccine, trivalent, with trivalent inactivated influenza virus vaccine in children and adolescents with asthma. Pediatr Infect Dis J. 25:860–869 Influenza Vaccination in Asthmatic Children 619

26. Bergen R, Black S, Shinefield H, Lewis E, Ray P, Hansen J, Walker R, Hessel C, Cordova J, Mendelman PM (2004) Safety of cold-adapted live attenuated influenza vaccine in a large cohort of children and adolescents. Pediatr Infect Dis J. 23:138–144 27. Zeiger RS (2002) Current issues with influenza vaccination in egg allergy. J Allergy Clin Immunol. 110:834–840 28. Jefferson T (2006) Influenza vaccination: policy versus evidence. BMJ 333:912–915 29. Jefferson T, Smith S, Demicheli V, Harnden A, Rivetti A, Di Pietrantonj C (2005) Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet 365:773–780 30. Kramarz P, Destefano F, Gargiullo PM, Chen RT, Lieu TA, Davis RL, Mullooly JP, Black SB, Shinefield HR, Bohlke K, Ward JI, Marcy SM (2001) Does influenza vaccination prevent asthma exacerbations in children? J Pediatr. 138:306–310 31. Smits AJ, Hak E, Stalman WA, van Essen GA, Hoes AW, Verheij TJ (2002) Clinical effectiveness of conventional influenza vaccination in asthmatic children. Epidemiol Infect. 128:205–211 32. Christy C, Aligne CA, Auinger P, Pulcino T, Weitzman M (2004) Effectiveness of influenza vaccine for the prevention of asthma exacerbations. Arch Dis Child. 89:734–735 33. Erhart LM, Rangel MC, Lu PJ, Singleton JA (2004) Prevalence and characteristics of children at increased risk for complications from influenza, United States, 2000. J Pediatr. 144:191–195 34. Daley MF, Beaty BL, Barrow J, Pearson K, Crane LA, Berman S, Kempe A (2005) Missed opportunities for influenza vaccination in children with chronic medical conditions. Arch Pediatr Adolesc Med. 159:986–991 35. Gnanasekaran SK, Finkelstein JA, Hohman K, O’Brien M, Kruskal B, Lieu T (2006) Parental perspectives on influenza vaccination among children with asthma. Public Health Rep. 121:181–188 36. Lin CJ, Nowalk MP, Zimmerman RK, Ko FS, Zoffel L, Hoberman A, Kearney DH (2006) Beliefs and attitudes about influenza immunization among parents of children with chronic medical conditions over a two-year period. J Urban Health. 83:874–883 37. Neuzil KM, Wright PF, Mitchel EF, Jr., Griffin MR (2000) The burden of influenza illness in children with asthma and other chronic medical conditions. J Pediatr. 137:856–864 Treatment of Infants with Atopic Dermatitis

Ulrich Wahn

Atopic dermatitis (AD) is a chronic inflammatory pruritic skin disease that affects a large number of children in industrialized countries [1] . The 12 month prevalence in 11-year-old children, as studied in the Global International Study of Asthma and Allergies in Childhood trial, ranged from 1 to 20%, with the highest prevalence typically found in Northern Europe [1, 2] . In 45% of children, the onset of AD occurs during the first 6 months of life, during the first year of life in 60%, and before the age of 5 years in at least 85% of the affected individuals. In those children with onset before the age of 2 years, 20% will have persisting manifestations of the disease, and an additional 17% will have intermittent symptoms by the age of 7 years (Fig. 1 ). A risk factor for persistent AD symptoms is the severity of disease in infancy [3] . The clinical pattern of AD varies with age. Infants typically present with erythematous papules and vesicles on the cheeks, forehead, or scalp, which are intensely pruritic. The childhood phase typically occurs from 2 years of age to puberty. Children are less likely to have the exudative lesions of infancy and instead exhibit more licheni- fied papules and plaques representing the more chronic disease and involving the hands, feet, wrists, ankles, and antecubital and popliteal regions.

Genetic and Other Risk Factors for AD

Parental atopy, in particular AD, is significantly associated with the manifestation and severity of early AD in children [4] . It has been estimated that over half of the overall disease risk can be accounted for by genetic determinants. During the last years, several AD suceptibility genes have been identified. They encode proteins of different functional classes underlining the complexity of the AD pathogenesis [5– 7]

U. Wahn () Department for Pediatric Pneumology and Immunology , Charite, Berlin , Germany e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 621 DOI 10.1007/978-4-431-99362-9_38, © Springer 2010 622 U. Wahn

Fig. 1 The natural history of AD from infancy to childhood obtained from the prospective birth cohort study Multicenter Atopy Study [3]

Environmental factors also play a role in the development of AD. Exposure to aeroallergens (pets, mites, and pollen) has been clearly shown to increase the risk factors for AD and AD severity. Sensitization to food allergens (cow’s milk and hen’s eggs) is associated with infantile AD and is related to disease severity. Food allergen sensitization is also predictive for persistence of symptoms throughout childhood. Only in a minority of those with food sensitization (up to 33% of patients with moderate-to-severe disease of all age groups) are food allergens of clinical relevance, as demonstrated by food challenge studies. Children with AD are at high risk of allergic asthma and allergic rhinitis. Of those with AD during the first 2 years of life, 50% will have asthma during subsequent years. The severity of AD, including early sensitization to food, increases the risk of asthma and allergic rhinitis. The exact mechanism for the progression of the disease in children with AD is unknown; however, it appears to be a complex interaction of genetics, environmental exposure, and sensitization. For children with a family history of atopy, early AD, and sensitization, almost all are expected to have asthma.

Pathophysiology

The pathophysiology of AD is the product of a complex interaction between various susceptibility genes, host environments, infectious agents, defects in skin barrier function, and immunologic responses. Activation of T lymphocytes, dendritic cells (DCs), macrophages, keratinocytes, mast cells, and eosinophils is characteristic of AD skin inflammatory responses [8, 9] . Treatment of Infants with Atopic Dermatitis 623

In about 80% of adult patients with AD, the disease is associated with increased serum IgE levels (>150 kU L–1 ), sensitization against aeroallergens and food allergens, and/or concomitant allergic rhinitis and asthma. AD is characterized by dry skin, even involving nonlesional skin and increased transepidermal water loss. In particular, ceramides serve as the major water-retaining molecules in the extracellular space of the cornified envelope, and the barrier function of these complex structures is provided by a matrix of structural proteins, which are bound to ceramides. A reduced content of ceramides has been reported in the cornified envelope of both lesional and nonlesional skin in patients with AD. Changes in stratum corneum pH levels have been found in patients with AD and might impair lipid metabolism in the skin [10] . Overexpression of stratum corneum chymotryptic enzyme is also likely to contribute to the breakdown of the AD epidermal barrier. This would allow penetration of irritants and allergens, which trigger an inflammatory response, thus contributing to the cutaneous hyperreactivity characteristic of AD. The increased susceptibility to irritants in patients with AD might therefore represent a primary defect of epidermal differentiation compounded by the presence of inflammation-induced skin damage [11] .

Triggers of AD

Allergens

Placebo-controlled food challenge studies have demonstrated that food allergens can induce eczematoid skin rashes in a subset of infants and children with AD. In some patients, urticarial reactions can trigger the itch-scratch cycle that flares this skin condition. Children with food allergy have positive immediate skin test responses or serum IgE directed to various foods, particularly egg, milk, wheat, soy, and peanut. Food allergen-specific T cells have been cloned from the skin lesions of patients with AD, providing direct evidence that foods can contribute to skin immune responses. In addition, it is well established that food can exacerbate AD both through allergic and nonallergic hypersensitivity reactions [12, 13] . Furthermore, direct contact with the skin (e.g., in the preparation of meals or when feeding infants) might be an important factor for the aggravation of eczema. Beyond the age of 3 years, food allergy is frequently outgrown, but sensitization to inhalant allergens is common [14] .

Microorganisms

Most patients with AD are colonized with S. aureus and experience exacerbation of their skin disease after infection with this organism [15– 19] . In patients with AD with bacterial infection, treatment with antistaphylococcal antibiotics can result in 624 U. Wahn reduction of skin disease. An important strategy by which S. aureus exacerbates AD is by secreting toxins called superantigens, which stimulate activation of T cells and macrophages. Most patients with AD make specific IgE antibodies directed against staphylococcal superantigens, which correlate with skin disease severity [20, 21] . Superantigens also induce corticosteroid resistance, thereby complicating their response to therapy.

Irritant Factors

Frequently, rough or woolly clothing leads to mechanical irritation and exacerbation of AD and eczema. Chemical irritants like skin-cleansing agents should also be considered but can only be satisfactorily identified by means of avoidance.

Diagnostic Work-Up

The investigation of exacerbating factors in AD involves a patient history, specific skin and blood tests, and challenge tests, depending on the degree of the disease severity and on the suspected factors involved.

Food

Both SPTs and measurement of specific IgE can be used to assess sensitization to a food. Diagnostic sensitivity and specificity vary considerably among different foods, reading systems, and age groups. A decision point discriminating between clinical relevance of sensitization (with challenge as the gold standard) has been developed with regard to specific IgE and SPTs to egg, milk, peanut, and others foods in children. Decision points can be helpful in making the decision to perform oral challenges. However, the need for challenges has to be decided on an individual basis [22– 26] . Other invalidated tests, such as lymphocyte cytotoxicity tests, the basophil degranulation test, or measurement of serum IgG (or subclasses) should not be used. APT is primarily a tool to investigate the mechanisms of eczema in the skin. However, APT can also reveal sensitization in patients with AD and might identify a subgroup of such patients. An elimination diet should not be recommended for a patient solely on the basis of a positive APT response to a food [27] . All the above mentioned tests require specialist knowledge in their performance and interpretation. Standardized, physician-supervised food challenges provide the most accurate diagnostic tool. However, it should be noted that patients can present with reactions at least 24 h after a food challenge, and the challenge settings and protocol should Treatment of Infants with Atopic Dermatitis 625 be appropriately designed; for example, in case of a negative challenge response, the skin of the patient should be examined the following day [28, 29] .

Treatment

The long-term management of AD presents a clinical challenge and includes basic and topical treatment [30] as well as in subgroups of infants, systemic treatment as well as specific allergen avoidance. For optimal disease management, regular medical supervision, together with education of the patient or care providers and appropriate psychosocial support, is needed. In selected patients, hospitalization might be of great benefit, especially in centers with a multidisciplinary team approach [31, 32] .

Basic Treatment

Basic therapy of AD should comprise optimal skin care, addressing the skin barrier defect with regular use of emollients and skin hydration, along with identification and avoidance of specific and nonspecific trigger factors. Nonspecific irritants include contactants, such as clothing made from occluding or irritating synthetic or wool material. Further irritating factors are soaps and hot water temperature during showering or bathing. Contacts with water should be minimized, moderately heated water should be used, and mild syndets with an adjusted pH value (acidified to pH 5.5–6.0 in order to protect the acid mantle of the skin) should be used for cleansing [33, 34] . Further treatment, on the basis of disease severity, includes the addition of multiple therapeutic agents in a step-wise fashion (Fig. 2 ). A combination of different

Fig. 2 Stepwise management of patients with atopic dermatitis (AD). TCS , topical corticosteroides; TCI , topical calcineurin inhibitors; CyA cyclosporine A. * Over the age of 2 years [8] 626 U. Wahn topical agents might be indicated. In cases of severe AD that cannot be controlled with topical treatment, systemic treatment options might need to be considered.

Topical Treatment

Emollients

A key feature of AD is severe dryness of the skin caused by a dysfunction of the skin barrier with increased transepidermal water loss. This is typically accompanied by intense pruritus and inflammation. The regular use of emollients is important for addressing this problem, and together with skin hydration, it represents the mainstay of the general management of AD. Emollients should be applied continuously, even if no actual inflammatory skin lesions are obvious. Because different emollients are available, selection criteria, such as the individual skin status, seasonal and climatic conditions, and the time of day, should be considered for optimizing the patients’ basic treatment. ‘‘Water-in-oil’’ or ‘‘oil-in-water’’ emulsions might be substituted to support the skin barrier function. Emollients containing polidocanol are effective in reducing pruritic symptoms. Adjuvant application of topical preparations with urea allows for intensive hydration of the skin, whereas salicyl acid can be added to an emollient for the treatment of chronic hyperkeratotic lesions.

Topical Glucocorticosteroids

Topical glucocorticosteroids are still an important tool for the treatment of acute flare-ups. Over recent years, the risk of adverse effects induced by topical steroids could effectively be reduced by optimizing application protocols and using new steroid preparations with improved risk/benefit ratios and lower atrophogenic potential, such as prednicarbate, mometasone furoate, fluticasone, and methylprednisolone aceponate [35, 36] . For the topical use of glucocorticosteroids, different therapeutic schemes have been established: intermittent use might be as effective as an initial therapy with a high potent steroid followed by a time-dependent dose reduction or change over to a lower potent preparation [37] . The choice of an adequate vehicle is important to achieve the optimal therapeutic effect. Recent data indicate that in children and adults, an application of corticosteroids (fluticasone) on unaffected skin twice weekly prevents further flare-ups of AD [38] . Aside from an anti-inflammatory effect, treatment with topical steroids contributes to a reduction of skin colonization with S. aureus and therefore might affect a further trigger factor of AD [39, 40] . The side effects of uncontrolled topical steroid use, particularly on delicate skin areas, are well documented, and therefore topical steroid preparations should be applied not more than twice daily as short-term therapy for acute eczematous lesions. Treatment of Infants with Atopic Dermatitis 627

In children, only mild to moderately potent steroid preparations should be used. In general, during acute flares, steroids should be used in combination with baseline emollient skin care to avoid steroid overuse and steroid-related side effects.

Topical Calcineurin Inhibitors (TCIs)

The TCIs pimecrolimus and tacrolimus allow a steroid-free, anti-inflammatory topical therapy of AD [41, 42] . In both animal and human studies, both molecules demonstrated an immunomodulatory activity. Currently, in the United States and Europe, pimecrolimus cream (1%) [43] and tacrolimus ointment (0.03%) [44] are only approved for the treatment of AD in children aged 2 years and older. Tacrolimus ointment (0.1%) is only approved for use in adults. The anti-inflammatory potency of 0.1% tacrolimus ointment is similar to a corticosteroid with moderate potency, whereas 1% pimecrolimus cream is less active [45] . Thus far, no trials have been published comparing pimecrolimus 1% with a mild corticosteroid. Both agents proved to be effective, with a good safety profile for a treatment period of up to 2 years with pimecrolimus and up to 4 years with tacrolimus [46– 48] . An occasionally observed side effect with TCIs is a transient burning sensation of the skin. In a comparative study of the local side effects of 0.03% tacrolimus ointment vs. 1% pimecrolimus cream in children, pimecrolimus achieved better local tolerability than tacrolimus [49] . Preliminary studies indicate that treatment with TCIs is not associated with a risk of skin atrophy. Therefore, they are a useful alternative for the treatment of sensitive skin areas, such as the face and intertriginous regions [50] . Generalized viral infections, such as eczema herpeticum or eczema molluscatum, have been observed during TCI treatment. It is unclear whether a trend for increased frequency of viral superinfections with use of TCIs really exists. Although there is no evidence of a causal link of cancer and the use of TCIs, the United States Food and Drug Administration has issued a black-box warning for pimecrolimus (Elidel; Novartis, Basel, Switzerland) and tacrolimus (Protopic; Astellas, Deerfield, Ill) because of a lack of long-term safety data. Furthermore, the new labeling states that these drugs are recommended as second-line treatments and that their use in children younger than 2 years of age is currently not recommended. Longterm safety studies with TCIs in patients with AD, including infants and children, are ongoing.

Wet-Wrap Therapy

A wet layer of cotton dressing, which is then covered with tubular bandages applied over emollients in combination with antiseptics or topical steroids, has been shown to be beneficial in cases of exacerbated AD skin lesions. A more practical alternative approach using clothing rather than bandages has also been described in detail [51– 53] . 628 U. Wahn

Topical Antimicrobial Therapy

The skin of patients with AD is heavily colonized with S. aureus , even at uninvolved sites. Toxins secreted by the majority of S. aureus on the skin behave as superantigens and, as discussed in the pathophysiology section, can directly influence the disease activity, although clinical signs of bacterial superinfection might be absent. Topical antiseptics, such as triclosan (2,4,4’-trichloro-2’-hydroxydiphenyl ether) or chlorhexidine, offer the advantage of a low sensitizing potential and low resistance rate [54] . They can be used in emollients or as part of an additional wet-wrap dressing therapy. The topical use of triclosan has been shown to be effective in significantly reducing skin colonization with S. aureus and skin symptoms. An irritative, photo- allergenic, phototoxic, mutagenic, or carcinogenic potential of triclosan has not been observed. The use of silvercoated textiles and silk fabric with a durable antimicrobial finish can reduce S. aureus colonization and eczema severity. These new options are still under investigation [55] . The addition of a topical antimicrobial agent to a topical steroid preparation has been shown to result in greater clinical improvement than a topical steroid alone. Interestingly, AD seems not to be associated with a higher risk of sensitization against topical antimicrobials. Because of deficient skin barrier function, patients with AD are exposed to a higher risk of recurrent bacterial superinfections of the skin. For the treatment of mild and localized forms of this secondary infection, a topical antibiotic treatment might be beneficial. Although erythromycin and fusidic acid have been widely used in Europe, high resistance rates of S. aureus to erythromycin have resulted in a preferential use of fusidic acid [56] . Topical fusidic acid has proved to be very effective against S. aureus because of its low minimal inhibitory concentration and good tissue penetration. However, long-term therapy with fusidic acid is suspected to be responsible for increasing resistance. Therefore, a restricted topical application for only short periods of about 2 weeks is advisable. For intranasal eradication of methicillin-resistant S. aureus , topical mupirocin has been shown to be effective.

Systemic Treatment

Antimicrobial Treatment

Systemic antibiotic treatment is indicated for widespread bacterial secondary infection, (primarily S. aureus) [57] . First- or second-generation cephalosporins or semisynthetic penicillins for 7–10 days are usually effective. Erythromycin- resistant organisms are fairly common, making macrolides less useful alternatives [58, 59] . In cases of penicillin or cephalosporin allergy, clindamycin or oral fusidic acid are possible alternatives. Unfortunately, recolonization after a course of anti- Treatment of Infants with Atopic Dermatitis 629 staphylococcal therapy occurs rapidly. Maintenance antibiotic therapy, however, should be avoided because it might result in colonization by methicillin-resistant organisms. Infection of the skin with the herpes simplex virus in the form of an eczema herpeticum (Kaposi’s varicelliform eruption) represents a severe and possibly life- threatening complication of AD, requiring a systemic antiviral treatment with acyclovir or other antiviral agents (e.g., valacyclovir) [60] . Recent findings underline the pathogenetic importance of a fungal colonization as a trigger factor. Contradictory data have been published about the efficacy of a systemic treatment of AD with ketoconazole, and although it is assumed that selected patients with AD might benefit from a topical or systemic antimycotic therapy, the effect of a therapeutic intervention needs to be better defined by further studies [61] .

Systemic Corticosteroids

Although oral corticosteroids are commonly used for many different skin diseases, few randomized clinical trials have been performed in patients with AD thus far. It is well known that relapse after the discontinuation of oral steroids is often observed. Corticosteroids in the form of a long-term oral therapy are associated with a series of well-documented side effects (e.g., disturbance of growth, cataracts, and development of lymphopenia). In cases of acute flare-up, patients might benefit from a short course of systemic therapy with corticosteroids, but long-term use in infants and children should be avoided [62, 63] .

Cyclosporin A

As with TCIs, cyclosporin A (CyA) inhibits calcineurin-dependent pathways, resulting in reduced levels of proinflammatory cytokines, such as IL-2 and IFN- g . Multiple clinical trials have shown CyA to be an effective treatment for adult and childhood AD, and although relapse after discontinuation of therapy is often observed, posttreatment disease severity often does not return to baseline levels [64– 66] . Despite the effectiveness of oral CyA in the treatment of AD, because of the possible side effects, particularly renal toxicity, the use of CyA should be limited to patients with severe refractory disease, contraindications must be excluded, and blood pressure and laboratory parameters must be monitored closely. The treatment can be performed in the form of a short- or long-term therapy with high-dose (3–5 mg/kg/d) or low-dose (2.5 mg/kg/d) administration, depending on the patients’ individual medical conditions. The principle of treatment should be to aim for the lowest effective dose and the shortest treatment period because toxicity is related to 630 U. Wahn both of these factors. In children, it should be considered that vaccinations might not be effective during immunosuppression.

Antihistamines

The therapeutic value of antihistamines seems to reside principally in their sedative properties, and they are useful as a short-term adjuvant to topical treatment during relapses associated with severe pruritus. Although there are no large controlled studies to date, newer nonsedating antihistamines seem to have little or no value in atopic eczema [67– 69] .

Diet

There is no universally recommended diet for infants with AD. Dietary restrictions should only be recommended in cases of an established diagnosis of food hypersensitivity. International guidelines for the diagnosis of food hypersensitivity have been published. As regards food-induced eczema, it is important to note that the predictive value of a positive case history is lower than that of food-induced immediate reactions.

Education

The goal of the patients’ education should be living with atopic dermatitis by means of an empowered patient or, in the case of infants and young children, a caregiver who can work as a partner with the doctor in selfmanaging their own or their children’s disease. Education to enhance disease knowledge, psychologic improvement in disease perception, and scratch control behavior modification, together with regular daily treatment, will lead to better skin care. This improvement in disease control will restore family dynamics, and the patient and family will cope better and have an overall improvement in quality of life. Additionally, education should be aimed at reducing doctor shopping, facilitating a better partnership between the doctor and the patient-parent, and decreasing the long-termcosts of chronic disease treatment. From the recent controlled studies, there is the general impression that positive outcomes are dependent on the time spent with parents and the qualification of the trainer. Sharing personal experiences in managing AD was helpful in 80% of those parents who attended the program conducted by Staab et al. [70] . A 12-lesson educational program described positive outcomes after 1 year, including diminished fear of topical corticosteroid cream use. In a recent German Treatment of Infants with Atopic Dermatitis 631 multicenter study, 820 children with AD were randomized into an intervention group (n = 443) and a control group ( n = 377). The intervention group underwent a 12 h education program on an outpatient basis. After 1 year, the overall Severity Score for Atopic Dermatitis (SCORAD) measure, quality of life, scratching index, and adherence to treatment showed statistically significant improvement. Fundamentally, each patient with AD should be educated on various aspects of the disease. For economic and practical reasons, structured education will target patients with moderate and severe chronic AD and their parents. Structured patient education should enable both patient and parent to have realistic short-term goals, enter a process of problem solving, accept living with their disease, appropriately use available social support, and enhance their own motivation for therapy.

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15. Abeck D, Mempel M. Staphylococcus aureus colonisation in atopic dermatitis and its therapeutic implications. Br J Dermatol 1998;139:13–16 16. Arikawa J, Ishibashi M, Kawashima M, Takagi Y, Ichikawa Y, Imokawa G. Decreased levels of sphingosine, a natural antimicrobial agent, may be associated with vulnerability of the stratum corneum from patients with atopic dermatitis to colonization by Staphylococcus aureus . J Invest Dermatol 2002;119:433–439 17. Breuer K, Kapp A, Werfel T. Bacterial infections and atopic dermatitis. Allergy 2001;56:1034–1041 18. Leung DY. Infection in atopic dermatitis. Curr Opin Pediatr 2003;15:399–404 19. Rippke F, Schreiner V, Doering T, Maibach HI. Stratum corneum pH in atopic dermatitis: impact on skin barrier function and colonization with Staphylococcus aureus . Am J Clin Dermatol 2004;5:217–223 20. Leung DYM, Harbeck H, Bina P, Reiser RF, Yang E, Norris AD, et al. Presence of IgE antibodies to staphylococcal enterotoxins on the skin of patients with atopic dermatitis: evidence for a new group of allergens. J Clin Invest 1993;92:1374–1380 21. Novak N, Allam JP, Bieber T. Allergic hyperreactivity to microbial components: a trigger factor of ‘‘intrinsic’’ atopic dermatitis? J Allergy Clin Immunol 2003;112:215–216 22. Celik-Bilgili S, Mehl A, Verstege A, Staden U, Nocon M, Beyer K, et al. The predictive value of specific immunoglobulin E levels in serum for the outcome of oral food challenges. Clin Exp Allergy 2005;35:268–273 23. Osterballe M, Bindslev-Jensen C. Threshold levels in food challenge and specific IgE in patients with egg allergy: is there a relationship? J Allergy Clin Immunol 2003;112:196–201 24. Sampson HA. Food allergy – accurately identifying clinical reactivity. Allergy 2005;60(Suppl 79):19–24 25. Sampson HA. Update on food allergy. J Allergy Clin Immunol 2004;113:805–819 26. Sampson HA. Utility of food-specific IgE concentrations in predicting symptomatic food allergy. J Allergy Clin Immunol 2001;107:891–896 27. Darsow U, Laifaoui J, Kerschenlohr K, Wollenberg A, Przybilla B, Wuthrich B, et al. The prevalence of positive reactions in the atopy patch test with aeroallergens and food allergens in subjects with atopic eczema: a European multicenter study. Allergy 2004;59:1318–1325 28. Bindslev-Jensen C, Ballmer-Weber BK, Bengtsson U, Blanco C, Ebner C, Hourihane J, et al. Standardization of food challenges in patients with immediate reactions to foods – position paper from the European Academy of Allergology and Clinical Immunology. Allergy 2004;59:690–697 29. Breuer K, Heratizadeh A, Wulf A, Baumann U, Constien A, Tetau D, et al. Late eczematous reactions to food in children with atopic dermatitis. Clin Exp Allergy 2004;34:817–824 30. Ainley-Walker PF, Patel L, David TJ. Side to side comparison of topical treatment in atopic dermatitis. Arch Dis Child 1998;79:149–152 31. Boguniewicz M, Nicol N. Conventional therapy. Immunol Allergy Clinics N Am 2002;22:107–124 32. Darsow U, Lubbe J, Taieb A, Seidenari S, Wollenberg A, Calza AM, et al. Position paper on diagnosis and treatment of atopic dermatitis. J Eur Acad Dermatol Venereol 2005;19:286–295 33. Loden M. Role of topical emollients and moisturizers in the treatment of dry skin barrier disorders. Am J Clin Dermatol 2003;4:771–788 34. Subramanyan K. Role of mild cleansing in the management of patient skin. Dermatol Ther 2004;17:26–34 35. Kerscher MJ, Hart H, Korting HC, Stalleicken D. In vivo assessment of the atrophogenic potency of mometasone furoate, a newly developed chlorinated potent topical glucocorticoid as compared to other topical glucocorticoids old and new. Int J Clin Pharmacol Ther 1995;33:187–189 36. Korting HC, Kerscher MJ, Schafer-Korting M. Topical glucocorticoids with improved benefit/ risk ratio: do they exist? J Am Acad Dermatol 1992;27:87–92 Treatment of Infants with Atopic Dermatitis 633

37. Thomas KS, Armstrong S, Avery A, Po AL, O’Neill C, Young S, et al. Randomised controlled trial of short bursts of a potent topical corticosteroid versus prolonged use of a mild preparation for children with mild or moderate atopic eczema. BMJ 2003;30:768 38. Berth-Jones J, Damstra RJ, Golsch S, Livden JK, Van Hooteghem O, Allegra F, et al. Twice weekly fluticasone propionate added to emollient maintenance treatment to reduce risk of relapse in atopic dermatitis: randomised, double blind, parallel group study. BMJ 2003;326:1367 39. Nilsson EJ, Henning CG, Magnusson J. Topical corticosteroids and Staphylococcus aureus in atopic dermatitis. J Am Acad Dermatol 1992;27:29–34 40. Stalder JF, Fleury M, Sourisse M, Rostin M, Pheline F, Litoux P. Local steroid therapy and bacterial skin flora in atopic dermatitis. Br J Dermatol 1994;131:536–540 41. Ashcroft DM, Dimmock P, Garside R, Stein K, Williams HC. Efficacy and tolerability of topical pimecrolimus and tacrolimus in the treatment of atopic dermatitis: meta-analysis of randomised controlled trials. BMJ 2005;330:516 42. Breuer K, Werfel T, Kapp A. Safety and efficacy of topical calcineurin inhibitors in the treatment of childhood atopic dermatitis. Am J Clin Dermatol 2005;6:65–77 43. Elidel [package insert]. Basel, Switzerland : Novartis Pharmaceuticals Corp.; 2006 44. Protopic [package insert]. Deerfield, IL: Astellas Pharma Manufacturing Inc.; 2006 45. Harper J, Green A, Scott G, Gruendl E, Dorobek B, Cardno B, et al. First experience of topical SDZ ASM 981 in children with atopic dermatitis. Br J Dermatol 2001;144:781–787 46. Hultsch T, Kapp A, Spergel J. Immunomodulation and safety of topical calcineurin inhibitors for the treatment of atopic dermatitis. Dermatology 2005;211:174–187 47. Paul C, Cork M, Rossi AB, Papp KA, Barbier N, de Prost Y. Safety and tolerability of 1% pimecrolimus cream among infants: experience with 1133 patients treated for up to 2 years. Pediatrics 2006;117:118–128 48. Wahn U, Bos JD, Goodfield M, Caputo R, Papp K, Manjra A, et al. Efficacy and safety of pimecrolimus cream in the long-term management of atopic dermatitis in children. Pediatrics 2002;110:e2 49. Kempers S, Boguniewicz M, Carter E, Jarratt M, Pariser D, Stewart D, et al. A randomized inverstigator-blinded study comparing pimecrolimus cream 1% with tacrolimus 0.03% in the treatment of pediatric patients with moderate atopic dermatitis. J Am Acad Dermatol 2004;51:515–525 50. Queille-Roussel C, Paul C, Duteil L, Lefebvre MC, Rapatz G, Zagula M, et al. The new topical ascomycin derivate SDZ ASM 981 does not induce skin atrophy when applied to normal skin for 4 weeks: a randomized, double-blind controlled study. Br J Dermatol 2001;144:507–513 51. Foelster-Holst R, Nagel F, Zoellner P, Spaeth D. Efficacy of crisis intervention treatment with topical corticosteroid prednicarbat with and without partial wet-wrap dressing in atopic dermatitis. Dermatology 2006;212:66–69 52. Mallon E, Powell S, Bridgman A. ‘‘Wet-wrap’’ dressings for the treatment of atopic eczema in the community. J Dermatolog Treat 1994;5:97–98 53. Ricci G, Patrizi A, Bendandi B, Menna G, Varotti E, Masi M. Clinical effectiveness of a silk fabric in the treatment of atopic dermatitis. Br J Dermatol 2004;150:127–131 54. Sporik R, Kemp AS. Topical triclosan treatment of atopic dermatitis. J Allergy Clin Immunol 1997;99:861 55. Gauger A, Mempel M, Schekatz A, Schafer T, Ring J, Abeck D. Silver-coated textiles reduce Staphylococcus aureus colonization in patients with atopic eczema. Dermatology 2003;207:15–21 56. Verbist I. The antimicrobial activity of fucidic acid. J Antimicrob Chemother 1990;25(Suppl B):1–5 57. Boguniewicz M, Sampson H, Harbeck R, Leung DYM. Effects of cefuroxime axetil on S. aureus colonization and superantigen production in atopic dermatitis. J Allergy Clin Immunol 2001;108:651–652 634 U. Wahn

58. Hoeger PH. Antimicrobial susceptibility of skin-colonizing S. aureus strains in children with atopic dermatitis. Pediatr Allergy Immunol 2004;15:474–477 59. Ravenscroft JC, Layton A, Barnham M. Observations on high levels of fusidic acid resistant Staphylococcus aureus in Harrogate, North Yorkshire, UK. Clin Exp Dermatol 2000;25:327–330 60. Wollenberg A, Zoch C, Wetzel S, Plewig G, Przybilla B. Predisposing factors and clinical features of eczema herpeticum: a retrospective analysis of 100 cases. J Am Acad Dermatol 2003;49:198–205 61. Lintu P, Savolainen J, Kortekangas-Savolainen O, Kalimo K. Systemic ketoconazole is an effective treatment of atopic dermatitis with IgE-mediated hypersensitivity to yeasts. Allergy 2001;56:512–517 62. Aylett SE, Atherton DJ, Preece MA. The treatment of difficult atopic dermatitis in childhood with oral beclomethasone dipropionate. Acta Derm Venereol Suppl 1992;176:123–125 63. Anonymous. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Lancet 1998;351:1225–1232 64. Berth-Jones J, Finlay AY, Zaki I, Tan B, Goodyear H, Lewis-Jones S, et al. Cyclosporine in severe childhood atopic dermatitis: a multicenter study. J Am Acad Dermatol 1996;34:1016–1021 65. Hauk PJ, Leung DYM. Tacrolimus (FK506): new treatment approach in superantigen- associated diseases like atopic dermatitis? J Allergy Clin Immunol 2001;107:391–392 66. Zaki I, Emerson R, Allen BR. Treatment of severe atopic dermatitis in childhood with cyclosporin. Br J Dermatol 1996;135(Suppl 48):21–24 67. Diepgen TL. Early Treatment of the Atopic Child Study Group. Long-term treatment with cetirizine of infants with atopic dermatitis: a multi-country, double-blind, randomized, placebo-controlled trial (the ETAC trial) over 18 months. Pediatr Allergy Immunol 2002;13:278–286 68. Wahlgren C-F, Hagermark O, Bergstrom R. The antipruritic effect of a sedative and a non- sedative antihistamine in atopic dermatitis. Br J Dermatol 1990;122:545–551 69. Warner JO. ETAC Study Group. A double-blinded, randomized, placebo-controlled trial of cetirizine in preventing the onset of asthma in children with atopic dermatitis: 18 months’ treatment and 18 months’ posttreatment follow-up. J Allergy Clin Immunol 2001;108:929–937 70. Staab D, Diepgen T, Fartasch M, Kupfer J, Lob-Corzilius T, Ring J, et al. Age-related, structured education programmes improve the management of atopic dermatitis in children and adolescents: results of the German Atopic Dermatitis Intervention Study (GADIS). BMJ 2006;332:933–938 Diagnosing Food Allergy in Children

Dan Atkins

Introduction

One of the most basic and satisfying roles of a parent is to feed their child. As a result, feeding behaviors and responses to food ingestion are among the most scrutinized aspects of a child’s life. Because of this careful monitoring, in addition to the frequency with which children eat throughout the day, it is not surprising that parents frequently attribute their child’s symptoms to food ingestion. As a result, clinicians who provide medical care for children are routinely called upon to provide advice and accurately distinguish an adverse reaction to a food from some other cause of symptoms. The consequences of inaccurately labeling a food as a cause of symptoms include delaying appropriate treatment for another disorder or needlessly removing a food from the diet which could have adverse nutritional and social consequences. In those situations where symptoms are triggered by food ingestion, determining which type of an adverse reaction to a food is responsible is important because of the implications regarding the mechanism involved, the likelihood of reproducibility, and the prognosis.

Features of IgE-Mediated Food Allergy

Although IgE-mediated reactions have been reported to a wide variety of foods, milk, egg, peanut, wheat, and soy account for the majority of reactions in young children, whereas peanuts, tree nuts, fish, and shellfish are the most common food allergens in older children, adolescents and adults [1] . A history of food allergy or other allergic disease in immediate family members, as well as a personal history

D. Atkins () Department of Pediatrics, National Jewish Health , 1400 Jackson Street , Denver , CO 80206 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 635 DOI 10.1007/978-4-431-99362-9_39, © Springer 2010 636 D. Atkins

Table 1 Symptoms and signs often associated with IgE-mediated reactions to foods by organ system Skin Flushing, pruritus, urticaria, angioedema, eczema Gastrointestinal tract Oropharyngeal pruritus and edema, abdominal cramping, nausea, vomiting, diarrhea Respiratory tract Nasal congestion, nasal pruritus, rhinorrhea, repetitive sneezing, laryngeal edema, wheezing, coughing, shortness of breath Cardiovascular system Hypotension, tachycardia, palpitations, chest pain Neurological system Changes in level of consciousness Behavioral Irritability (preceding or in combination with other symptoms)

of eczema, asthma, allergic rhinitis or animal dander sensitivity, increases the likelihood of IgE-mediated food allergy. Symptoms involving the skin, gastrointestinal tract, respiratory tract and, less frequently, the cardiovascular system, either individually or in combination, typically begin during or within minutes to a couple of hours of food ingestion (see Table 1 ). The severity of symptoms varies from annoying to life threatening with individual reactions lasting from minutes to hours. Biphasic reactions, consisting of improvement after an initial reaction followed by a later resur- gence of symptoms, and severe protracted reactions, although reported in children, are the exceptions rather than the rule. Depending upon the sensitivity of the patient and the route and extent of exposure, symptoms may gradually resolve without treatment or respond to the administration of epinephrine or an antihistamine, although more than one dose is occasionally required. Subsequent exposures to the offending food typically trigger reactions similar in onset and progression when a comparable dose of allergen is ingested. Inconsistencies in the timing and severity of allergic reactions to the same food may result from a difference in the route of exposure or amount consumed, denaturation of a food allergen during food preparation, cross-contact with other foods, factors that impact digestion or absorption such as vomiting, changes in the patient’s level of sensitivity or the ingestion of medications such as antihistamines that can mask symptoms. In rare instances, the ingestion of a food must be accompanied by another stimulus in order for an IgE-mediated reaction to occur. Food-dependent exercise-induced anaphylaxis is an interesting example where anaphylaxis is provoked by exercise within several hours of ingestion of a specific food [2– 4] . Ingestion of the specific food not followed by exercise does not cause symptoms even though the patient usually has a positive skin test to the food. Alternatively, exercise not preceded by ingestion of the specific offending food is well tolerated, except in rare cases where the ingestion of any meal prior to exercise triggers symptoms. A wide variety of foods have been implicated in causing these reactions such as fish, shellfish, wheat, celery, mushrooms, and fruit [5, 6] . The typical age of patients with food-dependent exercise-induced anaphylaxis extends from adolescence through the late thirties Diagnosing Food Allergy in Children 637 with women outnumbering men. The mechanism responsible for these reactions remains to be defined. This entity should be considered when reactions occur only following exercise preceded by food ingestion. Skin testing the patient to foods ingested shortly before the exercise preceding the reaction may aid in identification of the offending food [7, 8] . Another interesting IgE-mediated entity is the pollen-food allergy syndrome which is encountered in patients sensitized to pollens containing allergens that cross react with those found in fresh fruits and vegetables [9, 10] . Even though ingestion of the fresh food causes symptoms, cooking usually denatures these typically heat-labile allergens so that the same fruit or vegetable can be tolerated. Although the list of described pollen-food syndromes continues to grow, the more common clinically encountered examples include ragweed pollen sensitive patients who experience symptoms with the ingestion of melons or banana, birch pollen sensitive patients who experience symptoms when eating apple, hazelnut, celery, carrots, or raw potato, and mugwort pollen sensitive patients who react upon ingesting fresh apples, celery, peanuts or kiwi [11] . The syndrome was initially called the oral allergy syndrome with reference to the typical pattern of rapid onset pruritus and mild edema localized to oropharyngeal tissues. Because some patients experience significant laryngeal edema or symptoms extending beyond the oropharynx, including anaphylaxis, this name has been considered misleading and the pollen-food allergy syndrome has been proposed as a suitable alternative [12] .

Features of NonIgE-Mediated Food Allergy

The most commonly observed nonIgE-mediated food allergies in children present primarily with abdominal complaints that vary depending upon the location of the gastrointestinal tract involved. The family and personal history of other allergic diseases are often unrevealing. Typical presenting symptoms include abdominal pain, nausea, vomiting, diarrhea, bloody stools, early satiety, food refusal, and failure to thrive. The timing of symptom onset in relation to food ingestion is delayed in comparison to that observed in IgE-mediated reactions. As a result, identifying the culprit food is sometimes difficult, resulting in persistent symptoms until the offending food is identified and removed from the diet. Examples of these entities include allergic proctocolitis, food protein-induced enterocolitis syndrome (FPIES), and celiac disease. Allergic proctocolitis is a benign disorder encountered in formula and breast fed infants brought for evaluation because of stools streaked with blood [13] . Frequently implicated foods include milk and soy although occasionally other foods in the breast feeding mother’s diet are causative. Removal of the offending foods from the diet usually results in symptom resolution within 72 h and typically the food can be tolerated in the diet by a year of age. Infants with FPIES present with frequent vomiting, diarrhea, and failure to thrive while the culprit food remains in the diet. 638 D. Atkins

Although milk and soy are frequently causative, other foods such as cereals, vegetables, and meats have also been implicated [14, 15] . Children with this disorder may also present acutely with bouts of profuse vomiting and diarrhea beginning approximately 2 h after exposure to the offending food. Because of lethargy associated with these reactions in addition to hypovolemic shock observed in approximately 20%, the symptoms are often initially attributed to infection rather than food allergy until the reaction recurs upon subsequent food exposure. Treatment includes fluid resuscitation rather than epinephrine or antihistamines. The development of tolerance with age is the rule. Attempts at reintroduction of the food in the diet should be medically supervised with an intravenous line in place. Children with celiac disease classically present as infants or young children with recurrent vomiting, steatorrhea and failure to thrive as a result of chronic inflammation of the small bowel mucosa resulting from immunologic reactivity to gliadin peptides present in wheat, rye and barley [16] . The diagnosis is made using serologic screening tests along with typical findings on small intestinal biopsy and demonstration of improvement upon removal of gluten from the diet. Once the diagnosis is confirmed, lifelong dietary avoidance of gluten is indicated. Combined disorders that are both IgE- and nonIgE-mediated include primarily the allergic eosinophilic gastrointestinal disorders such as allergic eosinophilic gastroenteritis and eosinophilic esophagitis. Eosinophilic esophagitis can present from infancy through adulthood with difficulty feeding, failure to thrive, vomiting, epigastric pain, dysphagia, and food impaction [17] . The majority of patients have a positive family and personal history of other allergic disease along with positive skin tests to foods, although relatively few experience food-induced anaphylaxis. The diagnosis is made by the demonstration of 15 or more eosinophils per high power field on esophageal mucosal biopsies following an adequate period of high dose acid suppression. Favorable clinical responses have been observed in response to treatment with elimination diets and swallowed topical steroid preparations. The evaluation of nonIgE-mediated and combined food allergies is often best accomplished through the cooperative efforts of both an allergist and a gastroenter- ologist. In addition to efforts to identify the causative food, the accurate diagnosis and management of these disorders often requires upper endoscopy and/or colonos- copy to document the type and degree of inflammation present.

Evaluation of the Food Allergic Child

History

The goal of the history is to generate a list of suspected or potential culprit foods along with a thorough description of all symptoms considered to be food related and the timing of those symptoms in relation to food ingestion. Important aspects of the history are listed in Table 2 . This information is then evaluated for features consistent with food allergy, some other type of adverse reaction to a food such as Diagnosing Food Allergy in Children 639

Table 2 Important aspects of the food allergy history Suspected foods · List of suspected foods · Route of exposure Ingestion Contact Inhalation Injection · Amount ingested Estimated threshold dose · Manner of preparation Raw Cooked Added spices Mixed with other foods Preservatives · Simultaneously ingested foods · Illness in others ingesting the same foods · Review of current diet Ingested foods tolerated since the reaction Ingested foods not eaten since the reaction Description of reactions · Timing of symptom onset in relation to food ingestion · Associated factors Exercise Medication use · Symptoms · Severity · Duration Uniphasic Biphasic Protracted · Treatment provided · Response to treatment provided · Reproducibility of reaction on subsequent exposure · Timing of last reaction Other aspects · Psychological impact of reaction Anxiety level · Level of preparedness for future reactions a toxic, metabolic or pharmacologic reaction, or another etiology unrelated to food ingestion. If food allergy is suspected, the next step is to decide whether the described reactions are consistent with IgE-mediated or nonIgE-mediated reactions or a combination of the two. This decision impacts further evaluation because skin testing and/or the measurement of serum food-specific IgE aids in identifying the causative food or documenting sensitization to a suspected food only when an IgE- mediated reaction is involved. 640 D. Atkins

Review of the child’s diet should focus on identifying foods the child refuses to eat in addition to those that are tolerated. Although specific or multiple food refusal in young children with limited verbal ability is often attributed to behavior, careful questioning and a thorough physical examination is indicated to rule out other potential causes. Infants and toddlers often refuse foods to which they are allergic because of oropharyngeal tingling and burning, a metallic taste, abdominal pain or nausea triggered by the ingestion of these foods. Children with active esophagitis or dysphagia may avoid solid foods swallowed as a bolus because of pain associated with esophageal distention or spasm. Other potential causes of food refusal in children include chronic or intermittent aspiration resulting from swallowing disorders or oral tactile defensiveness in which certain food textures are not tolerated. Ongoing weight loss or failure to thrive, and not responding to dietary intervention to provide adequate caloric intake should prompt further evaluation to rule out other disease.

Physical Examination

The focus of the physical examination varies depending upon the acuity of the patient’s presenting symptoms. In the less acute setting, the physical examination involves a search for findings suggestive of other allergic disease such as allergic shiners, conjunctival injection, clear rhinorrhea, nasal congestion with a pale, edema- tous nasal mucosa, a transverse nasal crease, wheezing or patches of eczema as their presence increases the likelihood of coexistent IgE-mediated sensitivity to foods. Careful monitoring of growth parameters at the initial visit and over time is indicated for food-allergic children. Weight loss or failure to thrive is rarely encountered in children with IgE-mediated sensitivity to only a few foods or those less pervasive in the diet. However, children with nonIgE mediated or mixed gastrointestinal allergy, young children with food refusal or those on severely restricted diets because of suspected or documented multiple food allergy may present with failure to thrive. When children present for evaluation in the midst of an acute allergic reaction to a food the upper and lower airway should be assessed immediately for the presence of airway obstruction due to laryngeal edema or bronchospasm as severe laryngeal edema and bronchospasm refractory to treatment are common causes of death in food-induced anaphylaxis [18, 19] . Continuous monitoring of the oxygen saturation during these reactions is advised. Other airway findings such as marked nasal congestion, repetitive sneezing, profuse clear rhinorrhea, hoarseness, stridor, coughing, accessory muscle use, nasal flaring, and wheezing should be noted. Close monitoring of the vital signs and physical examination for changes suggestive of impending shock such as delayed capillary refill or changes in mental status is indicated as refractory shock is the other major cause of death from these reactions [20] . Cutaneous changes including flushing, generalized pruritus, angioedema, urticaria, and flaring of eczema are often encountered along with gastrointestinal findings of oropharyngeal edema, increased or decreased bowel sounds, abdominal tenderness, vomiting and/or diarrhea. However, the absence of Diagnosing Food Allergy in Children 641 cutaneous symptoms does not rule out the possibility of food-induced anaphylaxis. In addition, FPIES should be considered in children presenting with hyopovolemic shock caused by persistent vomiting and diarrhea beginning several hours after exposure to the offending food.

Skin Testing

When findings on the history and physical examination suggest an IgE-mediated reaction, skin testing is indicated. Skin testing to foods is performed using commercial food extracts, freshly prepared food extracts or the “prick to prick” technique where the fresh food is initially pricked with the skin test device followed immediately by pricking the child’s skin [21, 22] . The latter two techniques are most often used when testing for sensitivity to fruits or vegetables that contain labile allergens susceptible to degradation during the extraction process, when a commercial extract of the suspected food is available, or when the skin test to a commercial extract is negative in contrast to a highly suggestive history. Skin testing with fresh extracts prepared from different portions of a meal eaten immediately prior to a reaction can help identify foods or ingredients worthy of further investigation. Reactions to a freshly prepared extract caused solely by irritation of the skin are ruled out by testing others not sensitive to the food with the same extract. Prick-skin testing to foods is safe as systemic symptoms resulting from prick-skin testing are exceedingly rare, even in subjects with a history of anaphylaxis. In contrast, intradermal skin testing to foods is discouraged because the results are less reliable and intradermal testing carries a greater risk of systemic reactions [23] . In most situations skin test selection is based on foods implicated by the history or limited to common food allergens or those that might cross react with the suspected food. Barriers to skin testing are few, but include widespread skin disease or the inability to discontinue medications such as antihistamines that interfere with skin reactivity. Even in these situations, skin testing can usually be post- poned until treatment results in adequate clearing of the skin or medications can be withheld long enough to enable testing. The definition of a food skin test as positive when a wheal 3 mm in diameter larger than the negative saline control is observed and is based on initial studies in children by Bock in the late 1970s [24] . Using these criteria, the positive predictive accuracy of a properly performed food-skin test is considered less than 40%, suggesting that many children with a positive skin test to a food can ingest the food without ill effects [24] . Sporik et al., evaluating a large cohort of children with a median age of 3 years with skin testing followed by food challenges calculated skin-test diameters to peanut (>8 mm), cow’s milk (>8 mm) and egg (>7 mm) with positive predictive accuracies approaching 95% [25] . Extrapolation of their findings to other populations is discouraged because of potential differences in age, extracts, and techniques used, but their results demonstrate that as the mean wheal diameter used to define a positive skin test increases, although a decrease in sensitivity in encountered, an increase in specificity 642 D. Atkins is observed. Like other investigators, they found no correlation between skin test size and reaction severity. Thus, skin test size does not predict the severity of the reaction. Because of the poor positive predictive accuracy of skin testing, removing a previously tolerated food from the diet based on skin test results alone is rarely recommended. However, a positive skin test can pinpoint foods worthy of further investigation and is highly suggestive of a diagnosis when accompanied by an appropriate history as exemplified by the child who experiences a significant reaction shortly after the ingestion of an isolated food, particularly if a similar reaction has recurred with subsequent exposures. Alternatively, the negative predictive accuracy of a properly performed skin test is greater than 95% [26] . When the history is highly suggestive but the skin test to the suspected food is negative, further evaluation such as repeating the skin test with the same extract, verifying the potency of the extract used, skin testing with a freshly prepared extract of the suspected food, testing for the presence of serum IgE specific for the food, and reviewing the history for other potential causes is required. Thus, skin testing is a quick, efficient method of documenting or ruling out IgE-mediated sensitivity to a food when quality extracts are applied using proper technique and the child has not taken medications known to interfere with testing.

Atopy Patch Testing

Skin testing and the measurement of serum food-specific IgE antibodies are not beneficial in the evaluation of children with nonIgE mediated reactions where nonIgE-mediated immune mechanisms are involved. In recent years, the utility of the atopy patch test (APT) has been explored for the evaluation of children with atopic dermatitis [27] , eosinophilic esophagitis [28] , FPIES [29] and others with gastrointestinal symptoms suspected of being food-related, but not IgE-mediated [30] . Milk, egg, soy, and wheat are the foods most commonly evaluated for testing with the APT. The APT consists of applying the intact food allergen to noninflamed skin on the back under occlusion in a small aluminum cup. The patch test is removed after 48 h and any reaction at the site is assessed and recorded 20 min later and again 24 h after patch test removal. Reactions are graded based on the degree of erythema and the presence of papules or vesicles. Although usually well tolerated, irritant reactions and contact urticaria have been reported [31] . The utility of the APT in the evaluation of food allergic patients remains a topic of debate [32– 35] . At this point the interest lies in the potential utility of this test in identifying the responsible foods in patients with nonIgE mediated gastrointestinal disorders such as FPIES or mixed reactions involving both IgE- and nonIgE-mediated mechanisms as seen in eosinophilic esophagitis and atopic dermatitis. Aspects that hinder wider use of the APT include the lack of standardization of the procedure including the lack of standardized reagents or how best to prepare them in addition to the time and expertise required for the accurate performance of the test [31] . Diagnosing Food Allergy in Children 643

Laboratory Testing

Laboratory assays to measure the amount of unbound food allergen-specific IgE circulating in the serum are beneficial for the evaluation of the child suspected of IgE-mediated food allergy and who have extensive skin disease, when medications that interfere with skin testing cannot be withheld, or in a variety of other circumstances, such as the unavailability of an extract or in situations involving a highly suggestive history but a negative skin test. Another primary use of these assays is to help determine whether a food challenge is indicated. Although the sensitivity of skin testing and selected immunoassays is comparable [36] , the performance of a skin test is advised before food challenge in the child with a highly suggestive history and a negative immunoassay. Levels of food allergen-specific IgE in an individual child are obtained longitudinally to monitor for potential changes in sensitization. As with skin tests, food allergen-specific IgE levels are helpful in predicting the likelihood of a reaction, but do not predict reaction severity. One of the most widely used and evaluated immunoassays for the measurement of food-specific IgE is the CAP-RAST system (CAP-FEIA [Pharmacia, Uppsala, Sweden]), which measures the amount circulating allergen-specific IgE in the serum in kilounits of allergen-specific IgE per liter (kUA /L). In 1997, in a retrospective study analyzing the sera of food allergic children in light of highly suggestive histories or the results of food challenges, Sampson and colleagues reported predictive threshold levels for several of the commonly allergenic foods including milk, egg, peanut, and fish [37] . Patients with values higher than the calculated threshold values had a 95% likelihood of reacting upon ingestion of the food. In a subsequent prospective study Sampson evaluated 100 children by history, oral food challenges and measuring allergen-specific IgE levels to egg, milk, peanut, soy, wheat and fish [38] . This study was undertaken to determine if the 95% predictive decision points for egg, milk, peanut, and fish determined in the previous study were accurate. Using the previously defined predictive decision points, more than 95% of the food allergies to these foods in this population of children were correctly identified. These diagnostic decision points have been further investigated and refined and their use in clinical settings has significantly reduced the need for food challenges [39] . CAP-RAST levels above which 95% or more of children would be expected to react have been reported for several of the major food allergens. Children less than 2 years of age with a CAP-RAST to egg greater than 2 kU A /L or a CAP RAST to milk greater than 5 kUA /L have a greater than 95% chance of reacting on challenges. For older children, the decision points for foods commonly causing allergic reactions are as follows: egg 7 kU A /L, milk 15 kU A /L, peanut 14 kU A /L, tree nuts

~15 kUA /L, and fish 20 kUA /L. However, individual patient CAP-RAST results often fall in an indeterminate zone below the diagnostic threshold, but above the value predicting tolerance. In addition, since these decision points have been determined for relatively few foods, threshold values for a given suspected food may not have been established. As a result of these and other nuances, food challenges remain an important tool for documenting the link between the ingestion of a suspected food and the onset of symptoms. 644 D. Atkins

Elimination Diets

Elimination diets vary significantly depending upon the number of foods removed from the diet and become more difficult to construct as more foods or those pervasive in the diet come under suspicion. Limited elimination diets, removing only a few highly suspected foods are the simplest to prepare, particularly when foods not widely distributed throughout the diet are implicated. Oligoantigenic diets are constructed by limiting the diet to only a few foods rarely reported to cause reactions. Elemental formulas are the mainstay of elemental diets. Oligoantigenic and elemental diets are used when uncertainty about which foods cause symptoms exists or when a large number of foods are suspected. Elemental diets are useful in infants, but adherence to these diets is often difficult to maintain beyond infancy. When oligoantigenic and elemental diets are used, foods are added back to the diet individually at selected intervals accompanied by symptom monitoring. Tolerated foods are left in the diet, while those associated with a return of symptoms are removed. One food-associated disorder in which the use of elemental diets has been shown to be of particular benefit is eosinophilic esophagitis where improvement in 98% of children placed on elemental diets has been reported [40] . Lack of improvement on a diet free of suspected foods suggests either nonadherence, the need to consider other foods, or a cause other than food allergy. However, once the diagnosis of food allergy is firmly established, constructing an appropriate palatable elimination diet that meets the child’s nutritional requirements is an integral aspect of current treatment. Overzealous elimination of foods from the diet has been associated with adverse physical and psychological consequences in children [41, 42] . For example, children on dairy-free diets have been shown to have difficulty meeting their requirements for calcium, vitamin D and phosphorous [42] . As a result, consultation with a registered dietician to provide a complete nutritional assessment and patient education regarding label reading, food preparation, hidden sources of food allergens, and alternative nutrient sources is preferred.

Food Challenges

Oral food challenges are performed to document the presence or lack of clinical reactivity to a specific food and are categorized into open, single-blind, or double-blind depending upon who is aware of the contents of each dose given during the challenge. Placebo controls are often added during the performance of single- blind and double-blind challenges. The oral food challenge selected and whether placebos are used depends upon the need to control for patient and/or observer bias. The DBPCFC, where neither the child, the child’s family nor the medical team is aware of the contents of the challenge, remains the challenge of choice in the research setting as it best controls for both patient and observer bias. Single- Diagnosing Food Allergy in Children 645 blind placebo-controlled food challenges (SBPCFC), where only the medical staff knows the contents of challenge doses, are performed to eliminate bias on the part of the child and/or the child’s family. In an open food challenge (OFC), because the food is offered as it is usually eaten, both the child and medical staff know which and how much food is being given. A significant benefit of the OFC is the relative ease of performance as masking the challenge food is unnecessary, thereby significantly reducing preparation time. In most clinical situations an OFC suffices when objective symptoms are used to determine whether the challenge is positive. Oral food challenges provide the answers to a variety of clinical questions. If the culprit food is not obvious after a thorough history and attempts to document sensitization or when more than one food is implicated based on the history and test results, food challenges are indicated to determine which, if any, of the suspected foods cause symptoms. Accurately identifying the causative food prevents future reactions and avoids the needless elimination of foods from the diet. Food challenges are also performed to prove that a food can be safely returned to the diet. The majority of children, who as infants and toddlers were allergic to milk, egg, soy or wheat, develop tolerance to these foods as they age. In addition, about 20% of children with allergic reactions to peanut in the first years of life outgrow their sensitivity [43] . Toddlers found to be allergic to a specific food at an early age and during the course of their initial evaluation have evidence of sensitization to other foods they have not eaten are often kept on diets eliminating these foods through the first years of life. A thorough exposure history combined with information obtained from skin testing and an immunoassay for the level of food allergen-specific IgE is used to determine if and when to challenge children to these foods. When immune mechanisms other than IgE-mediated sensitivity are suspected, as exemplified by the FPIES, a food challenge may be the only accurate means of verifying the diagnosis [15] . In this situation, the challenge should be performed with an intravenous line in place. There are relatively few contraindications to the performance of a food challenge. They are not advised in a child with a history of a previous life threatening reaction without sufficient evidence to document a significant decrease in the level of sensitivity. Challenging a child with unstable asthma is ill advised and those with severe eczema should have their eczema appropriately controlled before being challenged. With a previous severe reaction to a food rarely encountered in the diet or if the child dislikes the food and would chose to continue avoidance, the potential benefit is unlikely to outweigh the risks of challenge. Children frightened by the consideration of a food challenge often benefit from working with a psychosocial clinician before a food challenge is performed. Decisions about who should be challenged are finalized only after a thorough discussion with the child and the child’s family regarding the rationale for challenge along with a review of the potential benefits and risks. A retrospective analysis of 253 failed food challenges performed in a tertiary care center to the common food allergens milk, egg, peanut, soy, or wheat in addition to the experience of other centers routinely performing these challenges provides evidence of safety when performed in a medical setting with the necessary 646 D. Atkins medications and equipment available along with personnel experienced in the treatment of anaphylaxis [44] . In preparation for a challenge the history of previous suspected reactions to the food is reviewed and an interim history and physical examination is performed to document that the child is medically stable. Food challenges are performed by feeding gradually increasing doses of the suspected food at predetermined time intervals until objective symptoms occur or a normal portion of the food ingested openly is tolerated. In blinded studies the challenge food is disguised in another food the child will ingest. Typical total doses are the normal age adjusted single serving amounts or 8–10 g when freeze-dried or powdered foods are utilized. When freeze-dried or concentrated foods are used, the potential for alteration of labile allergens must be taken into consideration. Standardized recipes for DBPCFC to milk, soy, cooked egg, raw whole egg, peanut, hazelnut, and wheat in their usual edible form and validated by professional panelists in a food laboratory have been published [45] . Although the dosing and interval between doses are often established based upon the child’s history, different formats have been used successfully in different centers [46, 47] . If subjective symptoms are encountered after a dose, reasonable options include a longer wait before administering the next dose, repeating the previous dose or halting the challenge. A food challenge is completed when the child has an observable reaction or a normal portion of the food ingested openly is tolerated. The observation period following completion of the challenge depends upon several factors including the immune mechanism involved, the timing, severity and duration of previous reactions, whether the child reacted and the severity of the reaction plus the level of concern regarding biphasic anaphylaxis. Usually children are observed until they have been asymptomatic for a couple of hours after a reaction or for about 2 h after the last dose if the food was tolerated. Children with nonIgE mediated reactions such as the food-protein induced enterocolitis syndrome or other delayed reactions are observed longer. The implications of the challenge results should be thoroughly reviewed with the child and the child’s family and all questions thoroughly answered. If the challenge is negative including the challenged food regularly in the diet is encouraged.

Management of the Food Allergic Child

Current management of the food-allergic child consists of the dietary avoidance of culprit foods and developing a plan for the prompt treatment of reactions resulting from accidental exposure. An individualized approach taking into consideration the immunologic mechanism involved, the age of the child, the severity of previous reactions, the current suspected degree of sensitivity, and the number of implicated foods is required. Dietary avoidance is accomplished by providing a palatable, nutritionally adequate elimination diet, along with education regarding label read- Diagnosing Food Allergy in Children 647 ing, and a review of potential sources of accidental exposure. Diets eliminating foods pervasive to the diet or multiple foods are best constructed by a skilled dietician experienced in working with children with food allergies. Reliable resources for obtaining further information, such as the Food Allergy and Anaphylaxis Network ( www.foodallergy.org ), are invaluable. Wearing a medical information bracelet or necklace or carrying a card that identifies the child as food allergic and lists the child’s food allergies helps prevent reactions and can save precious time if the child is found unconscious or incom- municative. A Food Allergy Action Plan that lists the steps to take in case of a reaction including the order and doses of all medications to be administered as well as contact information for family members and health care providers should be provided. This plan should be developed and thoroughly reviewed with the children, their family members, and all other caretakers. The delayed administration of epinephrine has been associated with fatal allergic reactions to foods [18, 19] . As a result, an epinephrine auto-injector along with thorough instruction regarding when and how to use it should be provided to the families of children considered to be at risk for food-induced anaphylaxis. Features of the history that prompt providing an epinephrine auto- injector include a previous severe reaction or one involving the respiratory or cardiovascular system; generalized urticaria or angioedema during previous reactions; coexistent asthma; allergy to peanuts, nuts, fish, or shellfish; or a history of other family members with severe allergic reactions to foods [48] . Injection of the epinephrine dose intramuscularly into the lateral thigh is advised based upon studies demonstrating improved absorption by this route over subcutaneous administration [49] . Epinephrine auto-injectors are currently available in doses of 0.15 and 0.30 mg with the 0.15 mg dose suggested by the manufacturer for children weighing 15–30 kg and 0.30 mg recommended for those over 30 kg; however, physician discretion regarding dosing is advised based upon the history. Auto-injector use is preferred over the use of an epinephrine ampule and syringe to avoid delay in administering the dose and reduce the potential for significant dosing errors [50] . Providing more than one auto-injector is generally recommended, particularly in situations where access to medical care is limited or could be delayed. Once an epinephrine auto-injector is used, emergency medical services should be notified for the transport of the patient to the appropriate medical facility. Other medications commonly available to patients for use in the immediate treatment of allergic reactions to foods include oral antihistamines and inhaled bronchodilators. Antihistamines carried for the first aid treatment of allergic reactions should be chewable or liquid preparations to reduce the time required for absorption. Appropriate doses of these medications and when to use them should be reviewed. The first aid treatment of food-induced anaphylaxis including the rationale for epinephrine administration has been reviewed by Simon [51] . Although epinephrine is the drug of choice for the treatment of anaphylactic reactions to foods, it does not reverse the symptoms of nonIgE-mediated reactions such as food protein-induced enterocolitis where the mainstay of therapy is fluid replacement. 648 D. Atkins

Upon arrival at a medical facility for treatment of an allergic reaction to a food, the patient should be rapidly assessed and supportive care provided as indicated. Oxygen should be rapidly provided for any evidence of respiratory distress. If 10–15 min has elapsed since the initial dose and if the reaction persists or is progressing, another dose of epinephrine should be given. Patients presenting with hypotension should receive intravenous fluids with consideration for instituting vasopressor therapy. If antihistamines have not been given or symptoms persist, an additional dose of antihistamine should be administered and the use of an H2 blocker considered. Other supportive care such as bronchodilator therapy for patients with bronchospasm should be provided as indicated. Consideration of factors that inhibit response to therapy, such as beta blocker use, is encouraged in patients unresponsive to standard treatment. Intravenous glucagon may effectively treat hypotension in patients on beta blocker therapy who are not responding to the vasopressor effects of epinephrine [51] . Before the patient with food-induced anaphylaxis is released from medical care, the means for obtaining an epinephrine auto-injector should be provided along with appropriate teaching and arrangement for follow-up with an allergist. Long-term management of the food allergic child involves at least annual monitoring for evidence of newly developed tolerance or the acquisition of new food allergies through focused interim histories and evaluation of the results of immunoassays for food-specific IgE or skin testing when indicated. Other important aspects of long term follow-up include analyzing the diet for nutritional adequacy, monitoring growth parameters, reviewing the first aid treatment of allergic reactions to foods, and discussing the burden of illness while providing psychological support. The psychological impact on children and their families is a frequently ignored aspect of food allergy often successfully managed with appropriate psychosocial intervention, resulting in a significant improvement in quality of life.

Future Directions

Promising results observed in recent studies suggest that improved diagnostic methods and treatments other than merely avoiding the offending food are forthcoming. For example, examination of specific epitopes or the number of epitopes on specific food allergens recognized by a patient’s food-specific IgE may improve the ability to predict the likelihood of the eventual development of tolerance or the potential for severe reactions [52– 55] . In addition, a variety of immunotherapeutic approaches including oral immunotherapy [56– 58] , sublingual immunotherapy [59] and immunotherapy using altered allergens administered with specific adjuvants [60] are under investigation as are novel therapies including treatment with humanized monoclonal anti-IgE antibodies [61] and a modified Chinese herbal therapy [62] . The findings of these and other studies underway to better define the immune mechanisms involved in the development of oral tolerance as well as food allergy suggest that viable therapies will become available within the next decade. Diagnosing Food Allergy in Children 649

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Kevin J. Kelly and Brian T. Kelly

Introduction

The diagnosis and treatment of latex allergy is one of the most challenging problems confronting the clinician. Because natural rubber latex is a plant derived product of Hevea brasiliensis, variations in allergen total content, quantity of specific allergens in finished products, and variations in the individual allergens may occur during collection, storage and manufacture of finished rubber products. Thus, not all rubber products will result in sensitization or clinical reactions in patients. Because the human immune system is highly variable, an individual will not always react in the same manner when encountering an allergen such as latex. For example, a cluster of anaphylactic reactions in patients with spina bifida characterized in the early 1990s, resulted in one out of every eight individuals undergoing surgery over a single year for spina bifida developed intra-operative anaphylaxis. However, many latex allergic individuals in this cohort had multiple surgeries during a period when latex precautions were not known to be necessary. Despite this lack of precaution, some surgeries resulted in severe anaphylaxis while other surgeries were performed without incident in the same individual using latex products [1, 2] . Having a complete understanding of the clinical manifestations of latex allergy is necessary to make a correct diagnosis and plan of treatment. This chapter builds on the presentation in a chapter from volume 3[132] that outlines a comprehensive review about the clinical manifestations of latex allergy. To obtain complete knowledge of the subject, a review of latex allergens, available tests, and therapy will be outlined.

K.J. Kelly () Department of Pediatrics, Children’s Mercy Hospitals and Clinics , 2401 Gillham Road , Kansas City , MO 64108 , USA e-mail: [email protected] B.T. Kelly Medical College of Wisconsin , 8700 W. Wisconsin Avenue Milwaukee , WI , 53226, USA

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 653 DOI 10.1007/978-4-431-99362-9_40, © Springer 2010 654 K.J. Kelly and B.T. Kelly

Latex Allergens

Over 2000 lactiferous (latex producing) plants are known to exist in the world. Natural rubber latex (NRL) is produced by the tropical tree H. brasiliensis from the plant family- Euphorbiaceae. Multiple flowering lactifer plants come from this family and are well recognized by the general public (Table 1 ) . One of the most common examples is Euphorbia pulcherrima or poinsettia. Cis -1,4-polyisoprene, is the reason that the latex of H. brasiliensis is harvested and is contained in an estimated 40,000 finished products. Figure 1 –d depicts the harvesting, collection and method of production of dipped latex products. Field latex, which usually contains about 1–2% protein, varies its protein content by clonal origin of the rubber plants, climatic factors, soil types, fertilizers, and yield enhancers used for the rubber cultivation [3– 5] . The trees grow optimally in a tropical humid environment where the temperature remains 20–28° C resulting in a variety of microorganisms, especially fungi, and insects that invade and can injure and kill the tree. The latex itself may act in self defense against both the invading organisms and the damage inflicted during tapping by unique wound sealing property [3– 5] . Beneath the surface of the cambium layer of the bark, the specialized lactifer cells form a tube-like or capillary circulation network throughout the rubber tree. The cytoplasm of the lactifer cells is secreted (the latex) when the cell is injured. It contains numerous defense related proteins and enzymes that are integral in the protection of the plant, biosynthesis of polyisoprene, and coagulation of latex. As might be predicted from other plants, defense proteins and enzymes are frequent causes of allergic sensitization and clinical reactions especially with foods [3] . The proteins present in latex may induce IgE mediated immune responses in latex allergic patients and, due to the cross-reactivity of some of these latex allergens, in fruit allergic and some vegetable and pollen sensitized patients [3– 5] . Over 200 proteins have been identified in latex with hevein (50%) and hevamine (30%) making up the majority of these proteins [6, 7] . However, only hevein is recognized as a significant allergen that causes disease in humans. The latex also contains lipids, carbohydrate and inorganic salt or metal ions such as potassium, manganese, calcium, sodium, zinc, copper and iron [8] . The majority of the proteins present in freshly harvested latex are detected in finished latex products either in their natural configuration or an altered configuration which may lead to

Table 1 Common plants of the Euphorbiaceae family Genus/species Common name Acalypha hispida Chenile plant Acalypha wilkesiana Jacobs coat Euphorbia splendens Crown of thorns Manikot esculenta Tapioca Ricinus communis Castor bean Euphorbia pulcherrima Poinsettia Hevea brasiliensis Rubber tree Diagnosis and Treatment of Latex Allergy 655

a b

Fig. 1 ( a ) A worker precisely cuts the bark of the Hevea brasiliensis tree, injuring the lactifer cells. The cells and circulation of the latex secrete a milky white latex rich in cis -1,4 polyisoprene. (Reproduced with permission from [4] .) (b ) Latex is collected from the H. brasiliensis tree by injuring the lactifer circulation. The latex is secreted and collected in a pail with ammonia and thiuram to prevent coagulation. (Reproduced with permission from [4] .) (c ) Latex is harvested and then brought to a collection station for transport and storage. (Reproduced with permission from [4] .) ( d ) Latex gloves are made by a dipping method with insertion of a porcelain former crated with a coagulant on the surface. The latex forms a thin film, which is then cross worked by sulfur heat vulcanization (Reproduced with permission from [4] )

the formation of neo-antigens [8– 10] . Treatment of latex with chemicals such as ammonia will increase the formation of protein fragments. In two-dimensional gel electrophoresis of nonammoniated latex, over 240 separate proteins or peptide fragments have been identified. However, the sera from latex allergic patients recognize and bind to only 25% of these proteins with IgE antibody [9] . The analysis of latex proteins by SDS PAGE demonstrated a wide range of peptides with molecular masses of 5–200 kDa [10] . The allergens of molecular weight in ranges of 11, 14, 18, 24, 27, 35, 66 and 100 kDa, have been found to be the most significant allergens affecting patients [11, 12] . Interestingly, multiple proteins of different molecular sizes exhibited binding specificity for either health care worker sera, spina bifida patient sera or both in IgE immunoblot [13, 14] . With the modern advancement in protein purification and molecular biology techniques, a number of latex proteins have been isolated, cloned and purified to 656 K.J. Kelly and B.T. Kelly

Table 2 Immunological characterization of Hevea brasiliensis latex allergens Molecular Accession Significance Allergens Allergen name weight (kDa) number Function as allergens Hev b 1 Elongation 14.6 X56535 Rubber Major factor 58 biosynthesis Tetramer Hev b 2 1,3-glucanase 34/36 U22147 Defense protein Major Hev b 3 Elongation factor 23 AF 051317 Rubber Major biosynthesis AJ223388 Hev b 4 Microhelix 50–57 n.a Defense protein Major complex 100–115 Dimer Hev b 5 16 U51361 - Major U42640 - Hev b 6.01 Prohevein 20 M36986 Defense protein Major Hev b 6.02 Hevein 4.7 M36986 Defense protein Major Hev b 6.03 C-terminal 14 M36986 Defense protein Major hevein Hev b 7 Patatin 42.9 AJ220388 Defense protein Minor homologue Inhibit rubber biosynthesis Hev b 8 Latex profiling 14 Y15402 Structural protein Minor Hev b 9 Latex enolase 51 AJ132580 - Minor Hev b 10 Mn superoxide 26 L11707 - Minor dismutase AJ249148 Hev b 11 Class 1 chitinase 33 AJ238579 Defense protein Minor Hev b 12 Lipid transfer 9.3 AY057860 Defense protein Major protein Hev b 13 Latex esterase 42 P83269 - Major

homogeneity [15] . This is critical in developing sensitive and specific immunodi- agnostic tests. Based on their IgE binding properties, the Allergen Nomenclature Subcommittee of IUIS has accepted thirteen proteins as latex allergens (ftp:// biobase.dk/pub/who-iuis/allergen. list) (Table 2 ).

Functional Properties of Latex Allergens

Biological Properties

The characterized proteins in Hevea latex have four basic functions: polyisoprene elongation, plant defense, enzyme function, or service as structural proteins. As is the case with other plant allergens, many of the Hevea allergens have enzyme functions or defense functions. The biologic functions of the latex allergens will be reviewed first. Diagnosis and Treatment of Latex Allergy 657

Polyisoprene Elongation

Hev b 1, also known as rubber elongation factor (REF), facilitates the enzyme prenyltransferase in the adding of several thousands of isoprene subunits to the polyisoprene chains [16, 17] . In the process of centrifugation of latex, three layers are formed. The upper layer contains rubber particles of large and small size. The middle layer is an aqueous layer that contains many proteins. The bottom layer contains lutoids and organic and inorganic materials. Hev b 1 is tightly bound to large rubber particles (>350 nm in diameter) in the interface between the insoluble upper layer consisting of polyisoprene molecules and the aqueous layer. Hev b 3 is another REF homolog. In contrast to Hev b 1, which is on the surface of large particles, it is present on the surface of the small rubber particles (<70 nm in diameter) and participates in the synthesis of long chain polyisoprene [18] . Hevein (Hev b 6.02) is the most abundant protein of Hevea latex and is found in the lutoid fraction after centrifugation [19] . Released from the cells when the plant is damaged, hevein interacts with glycoprotein receptors on the sacs around the rubber particles resulting in the coagulation of latex [20] . Hev b 7, a cytosolic protein with esterase activity, acts by inhibiting rubber biosynthesis through restriction of isoprenyl diphosphate incorporation [21] .

Plant Defense Functions

Defense related proteins are a series of protective proteins produced by higher plants to guard themselves against various stresses including invading organisms such as fungi. The proteins include families of cross-reactive plant allergens that are responsible for inducing primary allergic reactions and secondary reactions as is seen in the latex-fruit syndrome. The defense proteins identified as allergens in latex include 1,3-glucanase, microhelix complex, prohevein, patatin homolog, class 1 chitinase, and lipid transfer protein. The latex allergen, Hev b 2 with b -1,3-glucanase property, catalyzes the hydrolytic cleavage of polymers of b -1,3-glucans. These glucan polymers are part of the essential cell wall component of most of the fungi. Hence, this cleavage protein appears to involve in plant protection against the fungal infection by degrading the cell walls of fungal pathogens [22, 23] . Another major structural component of the cell wall of many fungi and of the exoskeleton of insects is chitin. Multiple plants produce chitinases, which are proteins common in a wide variety of seed producing plants, and are involved in hydrolytic cleavage of chitin. A more recently characterized latex allergen, Hev b 11 shows endochitinase activity and is likely involved in hydrolytic cleavage of chitin in either fungi or insects. The cross-reactivity among the class 1 endochitinases from avocado, banana, chestnut and latex has been associated with latex-fruit syndrome but may also be due to a hevein domains within the protein [23– 25 .] Hevamine, a basic protein from the lutoid fraction of latex and not accepted as an official allergen, is classified as a defense-related enzyme with both chitinase and lysozyme activity [26] . Hevamine catalyzes cleavage of b -1,4-glycosidic bonds 658 K.J. Kelly and B.T. Kelly in chitin as well as sugar moieties within the cell surface peptidoglycans, but may not have lysozyme activity as once identified [27] .

Common Enzymes and Structural Proteins

Hev b 5 is proline-rich protein with a 46% amino acid sequence homology to an acidic protein from kiwi [28, 29 .] Latex profilin, Hev b 8, is an actin binding protein that is likely to be involved in organization of an actin network of Hevea latex plant’s cytoskeleton [30 .] The latex enolase, Hev b 9 is a necessary enzyme within the glycolytic pathway while Hev b 10 with MnSOD activity protects the plant against highly toxic oxygen radical produced during the phagocytic processing of foreign organisms [15] .

Immunologic Properties

The immunologic properties of individual latex allergens have been evaluated by immune responses in either health care workers or patients with spina bifida since those individuals make up the majority of subjects found to have clinical disease. Most importantly, the immune responses have been evaluated using purified recombinant allergens in these groups. The allergens that the general population reacts to are likely to parallel these current observations. The results of these studies confirm the specificity and reli- ability of purified allergens in the immuno-diagnosis of latex allergy. The identified Hevea allergens have been classified as minor and major allergens depending on their reactivity with sera from various groups of latex allergic patients (Table 2 ).

Immune Responses to Rubber Biosynthesis Proteins

The three allergens most involved in rubber biosynthesis include Hev b1, Hev b 3, and Hev b 7. What is most interesting is the dichotomy of reactions seen between health care workers (HCW) and spina bifida (SB) patients to this particular group of allergens. Spina bifida patients tend to react frequently to Hev b 1 and Hev b 3 while other at risk groups do not seem to react as frequently. Whether this is due to genetic differences, surgical exposure timing, or route of exposure to the allergens is unclear. Hev b 1 (Rubber elongation factor): REF appears in a native configuration as a tetramer of molecular mass of 58 kDa on large rubber particles. The monomer has been cloned and purified as a 137 amino acid long protein. Hev b 1 is a major allergen reacting with 81% of latex sensitized SB patients and 50% of health care workers (HCW) [31] . In a multicenter study using RAST and ELISA assays, 13–32% of HCW and 52–100% of SB patients with latex allergy showed strong IgE binding Diagnosis and Treatment of Latex Allergy 659 with Hev b 1 [32] . Regardless, this is a very important allergen in patients with spina bifida and must be in sufficient quantity for diagnosis in this group of subjects. Hev b 3 (small rubber particle protein): This protein with strong IgE binding reactivity in patients with SB and latex allergy is associated with the small rubber particles (<75 nm) in latex [33– 36] . Clinical and immunological reactivity of Hev b 3 with serum IgE in HCW is less frequent and weaker than in SB patients [34, 36] . The amino acid sequence homology is 47% when compared to another major allergen for SB patients (Hev b 1) [34] . More importantly, preincubated latex allergic sera with Hev b 1 showed more than 80% ELISA inhibition to solid phase Hev b 3. This clearly indicates the presence of similar conformational allergens in these proteins [36] . In addition, a recombinant form of Hev b 3 expressed in bacterial system exhibits specific binding to antilatex IgE from SB patients [37] . Hev b 7 (patatin like protein): Patatin is an important potato allergen (Sol t 1) and is a major storage protein in potatoes. Hev b 7 is a 46 kDa protein with patatin homology and has IgE binding reactivity with 23% HCW with latex allergy but has not been demonstrated to be a major allergen for patients with SB [38– 41] . Although both HCW and SB patients exhibited IgE binding with Hev b 7, this allergen recognized only a small group of patients, for whom IgE antibody against other major latex allergens could not be detected [40] . Hev b 7 has two biologic functions. It inhibits rubber biosynthesis but also has hydrolase and esterase activity which inhibits the growth of invertebrate pests. Thus, it may also be classified as a defense-related protein. Although Hev b 6.01–6.03 has latex coagulation activity, it will be presented under defense-related proteins.

Immune Responses to Defense-Related proteins

Higher plants have a defense system of proteins that are compared frequently to the immune system of animals, but in reality are significantly different. In fact, a number of these proteins can be induced by different techniques outlined in Table 3 which could increase the allergen content of harvested latex. Static defense proteins (e.g., storage proteins) may exert antifungal activity or (e.g., lectins) antimicrobial activity. Pathogenesis-related proteins (PR-proteins) are encoded by the host plant but are

Table 3 Harvesting and manufacturing procedures that may affect latex allergen content in ﬁ nished natural rubber products Latex allergen enhancement Latex allergen reduction Frequent tapping of rubber tree Reduced tapping frequency Hormone treatment (e.g., ethepon) High temperature vulcanization Defense protein induction Prolonged vulcanization time Low temperature vulcanization No powder Dipping process Pre and Post vulcanization leaching Storage time shortened Acid coagulation Cornstarch donning powder Halogenation 660 K.J. Kelly and B.T. Kelly

Table 4 Pathogenesis Related proteins that may cross-react with Hevea latex proteins Family Class Source Protein name PR-2 B -1-3-Glucanases Latex, banana Hev b 2 PR-3 Class I Chitinase Latex, avocado, banana, Cas s 5, Hev b 11, Pers a 1 chestnut PR-4 Chitinases Latex Hev b 6 PR-8 Class III Chitinases Latex Hevamine PR-14 Lipid transfer proteins Latex, apple, apricot, Amb a 6, Cas s 8, Cor a 8, Hev b cherry, chestnut, 12, Mal d 3, Pru ar 3, Pru av hazelnut, peach, 3, Pru d 1, Pru p 3, plum, ragweed induced only in pathological situations (e.g., tapping of a latex tree). There are 14 identified families of PR-proteins with defense function and many are associated with food allergy, cross-reactions in pollen induced food allergy and the latex-fruit syndrome. Thus, it is important to understand the type of defense protein that are allergens in NRL, in order to predict which fruit and environmental allergens will cause clinical cross-reactivity. A list of the PR-families and the relevant latex allergen that belongs to these families of proteins is presented in Table 4 . The Hevea latex allergens that have defense-related functions include Hev b 2, Hev b 4, Hev b 6.01-6.03, Hev b 7 (see above), Hev b 11, Hev b 12, and Hev b 13 [42– 54] . Most latex allergic patients recognize one or more of these allergens and their potential cross-reactions with fruit proteins account for the multiple patients who have serious allergic reactions after ingestion of a food with such proteins. In addition, hevamine, a common protein that is not officially accepted as an allergen, is also a defense-related protein that some individuals develop IgE antibody against. Hev b 2: This basic b-1,3-glucanase can be isolated from B serum containing lutoids of Hevea latex. The native protein exhibits significant IgE binding with latex sensitized patients including both SB and HCW [42, 43] . Depending on the method used, the IgE reactivity may range from 20–61% of patients with clinical symptoms from latex allergen content [32] . The recombinant Hev b 2 over expressed in prokaryotic expression system, failed to react with IgE from sera of latex allergic patients [15] . The reason for the nonreactivity of recombinant Hev b2 may be due to the lack of glycosylation and posttranslational modifications comparable to the native protein. Foods such as banana, potato and tomato may contain b -1,3-glucanase activity but it is not clear if this is truly the protein resulting in cross-reactions [18] . Peptide sequencing shows similarity to tobacco and tomato endo-b -1,3-glucanase. Hev b 4: The microhelix component of latex or Hev b 4 has been identified in the bottom fraction lutoids; it was purified and discovered to be a major latex allergen reported by Sunderasen [33] . It is an acidic protein and under reducing condition appeared as a broad band in the range of 50–57 kDa. Although 65% of HCW were found to have significant IgE against this component, only 14% of these patients showed PBMC stimulation to Hev b 4 [32, 40] . Unfortunately, it has not been cloned and expressed and its function is likely to be a defense protein but further work must be done to prove this. Diagnosis and Treatment of Latex Allergy 661

Hev b 5 : Two independent investigator groups cloned and expressed Hev b 5, an acidic protein with a molecular mass of 16 kDa [28, 29] . It has 46% homology with an 18.9 kD protein from kiwi and is presumed to be partially responsible for clinical reactions to this fruit in latex allergic patients. This protein is a major allergen with strong IgE binding reactivity with both HCW and SB patients. In serologic assays, as many as 92% of HCW and 56% patients with SB showed IgE binding with the recombinant form of Hev b 5. In addition, the strong IgE binding property of Hev b 5 is witnessed by significant histamine release from basophils among latex allergic patients [28, 40] . Hev b 6 (prohevein) : Hev b 6.01 is one of the most abundant proteins in the lutoid bodies of Hevea latex. It has two distinct domains, a 4.7 kD C-terminal domain (Hev b 6.02) and an N-terminal 14 kD peptide (Hev b 6.03). Prohevein has strong reactivity with IgE from HCW and SB patients with latex allergy [32] . In immunoblot and ELISA, the 43 amino acid long N-domain exhibits IgE binding with significantly higher number of latex sensitized patients when compared to the 144 amino acid long C-domain of Hev b 6. The results of skin test reactions correlated well with the in vitro IgE to latex allergens [14, 44, 45] . Epitope mapping of the prohevein molecule revealed more IgE binding regions near the N-terminal end of the protein [45] .

Hev b 8 (Profilin)

Prolifin, an actin binding protein, is involved in the formation of actin network of plant exoskeleton. The purified latex profilin when used in skin prick testing showed positive reactions in all the 24 SB patients and 6 of 17 HCW with latex allergy. Interestingly, latex derived profilin showed cross-reactivity with IgE among 36 patients with ragweed allergy, but the clinical relevance of this is unclear [30] .

Hev b 9 (Enolase)

Hev b 9 is most abundant in the aqueous layer of latex [7, 15] . A high degree of cross-reactivity can be expected because of the homology of enolases present in different organisms. However, unpublished work from our laboratory on sera from 26 HCW with latex allergy failed to demonstrate any IgE binding with the recombinant latex Hev b 9 and fungal enolases.

Hev b 10 (Manganese Superoxide Dismutase )

This highly conserved enzyme (MnSOD) has been reported from a number of fungi, bacteria and human beings as well [7, 15] . Although MnSOD from the fungus Aspergillus fumigatus demonstrated significant IgE binding with sera from allergic aspergillosis, 662 K.J. Kelly and B.T. Kelly one out of 26 latex allergic patients demonstrated IgE antibody binding with latex MnSOD (unpublished results). The limited study also indicates that in spite of the sequence similarities with MnSOD from other sources, the latex derived MnSOD showed only low levels of cross allergenicity with the corresponding mold enzyme.

Hev b 11 (Endochitinase)

Chitinases and lysozymes constitute about 25% of the proteins in the lutoid fraction of NRL. The class 1 chitinase shares homology with N-terminal hevein domain, and also shares epitopes with chitinases from avocado and banana [24, 25] . As of now, the cross-reactivity and immune responses of Hev b 11 in latex allergic patients are minor contributors to disease.

Hev b 12 (Lipid Transfer Protein)

Lipid transfer proteins with antifungal and antibacterial activity are named for their ability to transfer phospholipids from liposomes to mitochondria and are widely distributed in the plant kingdom. This class of proteins is the most important allergen in the Prunoideae fruits such as peach, cherry, apricot, and plum. This may help explain the cross-reactivity seen in stone fruits in latex allergic health care workers [54] .

Hev b 13 (Latex Esterase)

The biologic role of this protein is not as well defined but it is one of the major allergens found in natural and finished latex products that HCW react to [55] . This important allergen correlates well with the allergenic content of finished latex gloves and has been proposed to be one of four allergens used in a standard to measure immunological allergenic content of manufactured products [56] .

Diagnosis of Latex Allergy

The diagnosis of latex allergy in an individual patient requires a trained medical provider to take a complete medical history, perform a physical examination, and then supplement the clinical conclusions with appropriate testing. An algorithm that outlines one method of approaching a diagnosis of latex allergy is included in Fig. 2 . It should be noted that epicutaneous skin testing or serologic testing for antilatex IgE in the absence of a clinical history and physical exam are not adequate for an accurate Diagnosis and Treatment of Latex Allergy 663

An Algorithm for the Diagnosis of Latex Allergy

Latex Allergy Evaluation Medical History Physical Examination

Asymptomatic * Immediate symptom Delayed symptom Dermatitis, urticaria, angioedema, rhinitis, Acute or Chronic asthma, anaphylaxis Dermatitis

STOP No latex allergy Testing Indicated Testing indicated Testing not indicated Anti-latex IgE by serology Patch test (dermatitis) Patch test Patch SPT Serology Testing Negative STOP - Testing Positive Testing Positive Testing Negative Do Further testing No further testing** Latex allergy confirmed Contact Dermatitis Irritant Dermatitis***

Skin Prick Test

Dilute extract of latex glove

Testing Negative Testing Positive No further testing Further testing Latex allergy confirmed

Use Challenge Test

Testing Negative Testing Positive No further testing No latex allergy Latex allergy confirmed

Fig. 2 An algorithm for the diagnosis of latex allergy. This figure illustrates a diagnostic algorithm for the diagnosis of latex allergy in the United States where no diagnostic skin test reagent is cleared for use by the food and drug administration. (Reproduced with permission from [4] .) *Spina bifida patients should be cared for in a latex safe environment from birth. **If occupation worker – pulmonary function testing and methacholine challenge. In other countries outside the US, a licensed skin test reagent has been used as the procedure of choice for initial diagnostic testing. ***Some reports in the medical literature implicate latex proteins as a cause of contact dermatitis. No standardized reagent is available for such testing that does not include potential contamination from additive chemicals 664 K.J. Kelly and B.T. Kelly diagnosis of latex allergy since each of those tests has variable sensitivity, specificity, positive predictive value, and negative predictive values. Testing for latex allergy has been hindered in the US by the lack of a standard reagent clearance through USFDA. Despite a multicenter skin test study that confirmed one nonammoniated reagent to be reliable and safe, no licensed product has been forthcoming [57, 58] . Skin Testing: Skin testing has been the most sensitive and predictive test for confirming a diagnosis of latex allergy. Achieving the highest sensitivity has required the use of more than one source material for latex (e.g., natural latex nonammoniated and a latex glove extract) [57– 65] . In one series, the sensitivity of using two source materials was 100%, specificity of 99%, and a negative test having 100% predictive value in concluding that a patient was not allergic to latex [63] . The reason for failure of a skin test reagent to be approved in the US may relate to the frequency of adverse reactions to epicutaneous testing with latex allergen. Early information demonstrated that skin testing resulted in a high rate of systemic reactions not seen with other allergens approved for skin testing [64, 65] . More importantly, this high rate of reaction was confirmed in a comparative retrospective study from the Mayo Clinic where the rate of systemic reactions to latex was 228/100,000 latex skin tests while reactions of this nature to other allergens was 72/100,000 penicillin skin tests and 23/100,000 aeroallergen tests [66] . This represents a 10-fold elevated risk of systemic reactions to latex skin testing compared to aeroallergen tests. Even the multicenter skin test study with clone 600 latex resulted in 16% of subjects having a systemic, albeit mild, reactions to skin testing [57, 58] . Standardized extracts were not used in any of the studies associated with anaphylactic events except the multicenter skin test study [58] . Comparisons of latex extracts, made using different techniques, indicated that the protein content obtained from a single glove can vary over 2-fold, depending on the extraction method. Other factors, such as temperature, salt concentration and detergent activity can also affect extraction efficiency [67] . In addition, the stability of the different latex antigens is variable. Since the antigen content of gloves can vary several 100-fold, unstandardized extracts may contain vastly different amounts of latex protein. Furthermore, the measurable content of specific allergens is likely to be even more unpredictable. Therefore, a significant portion of the risk associated with latex skin tests can be attributed to the use of uncharacterized extracts. One further approach to this problem is the use of recombinant latex allergens for skin testing, which may be nearly as sensitive and specific as crude uncharacterized latex [68] . Although the algorithm in Fig. 2 , recommends skin testing, it may be safest to perform with a commercial latex standardized reagent such as the Stallergenes S.A. (Marseilles, France) used in Europe.

In Vitro Testing for Latex Allergy

The vast majority of in vitro testing for latex allergy has used methods for detecting antilatex specific IgE antibody circulating in the serum of patients. These range from the use of research laboratory prepared enzyme linked immunosorbent assays Diagnosis and Treatment of Latex Allergy 665

Table 5 Performance of speciﬁ c IgE serology tests Positive predictive Negative predictive Method Sensitivity (%) Specificity (%) value (%) value (%) Hycor HyTECH 91.6 73.3 71.4 a 92.3 DPC AlaSTAT 73.3b 97.2 95.0 83.4 Pharmacia CAP 76.3b 96.7 94.3 85.0 a The HyTECH test will result in an approximate 27% false positive rate b Both the AlaSTAT and CAP methods will result in a 24–27% false negative rate

(ELISA) to commercial methods as seen in the Pharmacia UniCAP FEIA (Pharmaceia, Peapack, NJ), AlaSTAT (Diagnostic Products Corporation, Los Angeles, Ca), and Hycor HYTECH (Hycor Biomedical, Inc., Garden Grove, Ca) systems [58– 60, 69– 87] . As predicted, these systems all have their benefits and problems associated with them. Early use of the CAP system from Pharmacia resulted in lower sensitivity and false negative results in patients [59, 60, 69– 71] . Modification of the allergen and even using allergen extracted from a Baxter Triflex glove enhanced the sensitivity to 82% [71] . A second approach to improve the performance of the commercial assay is to add recombinant allergens as may be done with the skin test reagents [77] . One of the most important studies compared the performance of the three commercially available serologic assays for latex specific IgE in 117 clinically allergic individuals and 195 clinically nonallergic controls [82] . When compared to skin test, both the Pharmacia CAP and AlaSTAT had similar sensitivity of 76% and 73% respectively with 97% specificity. Unfortunately, 25% of the latex-sensitized cases had false negative results. HyTECH had a significantly lower specificity of 73% which indicates that 27% of the positive results are erroneous (Table 5 ). Using this information, screening studies for latex allergy in a population with a low prevalence of latex allergy, these tests may cause a significant number of false positive reactions which makes these tests undesirable for this activity without a follow-up definitive test. Other in vitro methods of diagnosing latex allergy have included basophil histamine release, CD 63 activation of basophils, and lymphocyte proliferation methods [40, 45, 79, 88– 95] . These assays are more specific but lack sensitivity. Their most useful activity has been to identify specific IgE epitopes and T-cell epitopes as noted in Table 6 [91– 98] . These tests have not become useful clinical tools although genetic altering of strongly allergenic epitopes may be useful in down regulating and inducing tolerance by immunotherapy in latex allergic subjects.

In Vivo Provocation Testing

In addition to using serologic testing or skin prick testing in diagnosing latex allergy, it is sometimes necessary to understand whether a specific allergen or latex product reported by clinical history is truly responsible for the symptoms or clarify discor- dant serum and skin test results. There have been many versions of provocation tests 666 K.J. Kelly and B.T. Kelly

Table 6 Epitopes of latex allergens Allergens IgE Epitopes/Source T cell epitopes/source References Hev b 1137 aa 30-49, 46-64, 121-137/HCW 95 2-11,16-25,36-55, 61-70 40 65-74,90-108/HCW & SB 31-49, 91-109/ PBMC 95 Hev b 3 208 aa 10-24,13-27,48-59,55-69, 96 100-114, 103-114, 147- 169 160-171,178-189 / Spina Bifida T cell clones 2-17, 29-38,41-50,60-69, 40 85-94, 103-112,118-127, 138-147,159-168,179-188/ HCW & SB Hev b 5 46-65,109-128/ 97 HCW T cell clones 15-22, 28-32, 50-56, 76-81 100 90-95,132-139 /HCW 101 Hev b 6 N-domain 13-24,29-36 102 C domain 62-69,74-81 134-139, 164-171/HCW N-domain 19-24,25-37 49 C-domain 60-66,76-79, 79-82, 82-96, 98-103,164-172/HCW & SB for diagnosing latex allergy. These have included glove use tests using standardized gloves used in the multicenter latex skin test study [57] . In addition, multiple investigations have used a “latex glove wearing” test with or without a coupled inhalation test [99, 100] . The critical value of the provocation test is making certain that objective measurable or observable reactions are measured. These may include such things as urticaria, angioedema, or pulmonary function changes. Some investigators have chosen to use inhalation challenges alone or mucous membrane contact. These have been progressive, graded challenges and are currently only standardized in research settings. Trouble with blinding the challenge is difficult but has been accomplished using a hooded exposure chamber [101, 102] .

Prevention and Treatment of the Patient with Latex Allergy

Numerous scientists, clinicians, and industry experts have spent the last 15–20 years on prevention of latex allergy by reducing sensitization i in patients who are at highest risk of developing this devastating problem. Thus, the focus has been on prevention strategies for children who have spina bifida, individuals who require multiple surgeries, as well as health care workers and other occupations that require contact with natural rubber latex gloves. Some general principals of prevention and care of the latex allergic patient are listed in Table 7 . Diagnosis and Treatment of Latex Allergy 667

Table 7 Latex safe precautions in a hospital and clinical setting in documented or suspected latex allergy Only nonlatex glove use Allergy alert band for the patient “Latex safe precautions” on door to patient room Check all medical devices for latex content No latex contact to skin or mucosal surfaces of patient (no source for inhalation) No intravenous valves inline Inject medication via stopcock devices instead of injector ports on tubing Operating room – schedule as the first case of the day if powdered gloves in prior use in O.R. Multiple dose vials – take top off or change needle after drawing up medication Premedication – not necessary when strict latex safe precautions used Ideal – latex gloves used should be powder free and low in allergen for nonlatex allergic patients Ban powdered latex products manufactured by dipping process from building (e.g., balloons) Tables 1 , 2 , 3 , and 7 (Reproduced with permission from [4]

The prototype patient for prevention of latex allergy is the infant born with spina bifida. As early as 1993, experts suggested guidelines modeled after the prevention program implemented by the author of this article at the Children’s Hospital of Wisconsin [103] . These measures included such things as complete abstinence of latex materials used in the care of these patients from birth. This especially meant no latex gloves, catheters, dressings, tape or other medical devices that contained latex in the hospital and home setting. Given the level of disability and the vast number of surgeries in these subjects, it was quite a daunting task that is now considered routine care. Because these recommendations were so far from the normal care of at risk subjects, an opinion article to vastly change care and prevent latex allergy was published in 1996 [104] . Given that over 40,000 devices and materials contained natural rubber latex as a component, stopping all use of latex containing materials became impractical. Information about latex allergen content of these materials as well as analysis of the devices reported to cause allergic reactions to latex, reported to the USFDA center for devices and radiologic health, seemed to be the best approach to prevention. Avoiding the use of latex materials that were made by a dipping process with short vulcanization times and low heat was the most likely strategy to prevent allergic reactions. Indeed, the concept of “latex safe” environments vs. “latex-free” environments turned out to be safe, practical and ideal for patients with latex allergy [105] . Further observations in Canada, Europe and USA noted that airborne latex was created by cornstarch donning powder from latex gloves which continued to sensitize and cause allergic reactions not only in patients but health care workers [106– 127] . In fact, sensitization in health care workers may not only occur from direct wearing of latex gloves but through inhalation of airborne particles that carry latex allergen [110, 112– 120] . This became such an emotional and critical issue, one author suggested that prevention of latex allergy was an exercise in “principled medical center leadership” [117] . A number of investigators in the above referenced articles noted a high content of latex allergen from the source materials. In fact, the allergen content in dipped products has been reduced according to the industry by 668 K.J. Kelly and B.T. Kelly as much as 1000-fold since the early 1990s (Personal communication: Mr. Milt Hinsch, SSL Medical, Atlanta, Georgia). This has led to a marked reduction is the prevalence of latex allergy in health care workers and reduction in the use of products that emit airborne latex [127] . The care of the patient with latex allergy requires that individual to avoid personal contact of the skin and mucous membranes with latex materials. In addition, they should only enter areas where airborne latex allergen is controlled by use of nonpowdered latex products. If they are a health care worker, they should use nonlatex gloves and only work in areas where either powder-free latex gloves are used routinely or nonlatex gloves are used. Rarely, immunotherapy is a consideration for cure of latex allergy. However, the side effects of such therapy, length of time to achieve tolerance, and lack of a standard reagent make this therapy relatively futile [128– 130] . Promise of modified allergens to make immunotherapy safer and more effective is on the horizon [131] .

Summary

The diagnosis and treatment of latex allergy requires astute clinical skills, recognition of patterns of latex induced reactions and cross-reactions, and clinical judgment when interpreting test results. Ultimately, confirmation of a diagnosis of latex allergy lies with the clinician.

References

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Corinne A. Keet and Robert A. Wood

Introduction

In recent years, as our understanding of peanut and tree nut allergy has increased, the potential for real therapies has expanded greatly. Hope for a cure for peanut and other food allergies is on the horizon. At the same time, the rates of peanut and tree nut allergy have continued to increase, and much remains to be learned about these potentially deadly allergies. Recent news headlines have been filled with talk of a peanut allergy “epidemic.” Schools and airplanes have become battlegrounds over what measures need to be taken to ensure safety for peanut allergic patients. A 2005 news story about a peanut allergic Canadian teenager who died after kissing her boyfriend only amplified these concerns [1] . Behind these headlines, the data do point to an increase in peanut and tree nut allergy, along with other allergies. In the UK, admissions for anaphylaxis from food allergy have increased by 500% since 1990 [2] . In the US, a survey conducted in 1997 and again in 2002 showed a doubling of the rate of peanut and tree nut allergy in children from 0.6 to 1.2%, mostly as a result of increases in peanut allergy, while the rates of peanut and tree nut allergy in adults did not change significantly. This suggests that overall rates will further increase in the coming years as these children become adults [3, 4] . At present, approximately 1% of the US population is estimated to be allergic to peanuts or tree nuts [3] . Based on data from a large registry, the median age of first reaction to peanut is 18 months and to tree nuts is 36 months. For 74% with peanut allergy and 68% with tree nut allergy, the first allergic reaction was also the first known exposure to the nut [5] . Peanut and tree nut allergies tend to be more severe than other food allergies, and more than half of the participants in that registry

C.A. Keet and R.A. Wood () Department of Pediatrics, Division of Pediatric Allergy and Immunology , Johns Hopkins University School of Medicine; Johns Hopkins Hospital , CMSC 1102, 600 North Wolfe Street , Baltimore , MD , 21287 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 675 DOI 10.1007/978-4-431-99362-9_41, © Springer 2010 676 C.A. Keet and R.A. Wood reported anaphylactic reactions. Food allergy has a significantly negative impact on the life of a child and his or her family. In one survey, food allergy’s effects on quality of life were similar to chronic diseases such as juvenile diabetes [6] . Peanut and tree nuts are responsible for the majority of food related anaphylaxis fatalities in the US and UK, with 50–60% of fatalities caused by peanuts and 15–30% caused by tree nuts [7– 10] . Threshold studies have demonstrated that peanut allergic patients can react to as little as 100 m g of peanut orally, a quantity that can easily be accidentally ingested even by those attempting to strictly avoid peanuts [11] . Avoidance and, when it fails, prompt treatment with epinephrine and other medications are currently the only available means to deal with peanut and tree nut allergy. This situation, however, is changing. In this chapter, we review some of the current developments in our understanding of risk factors for peanut and tree nut allergy, epitope specificity and cross-reactivity, diagnosis, natural history, and emerging treatments.

Environmental and Genetic Factors

At this time, the reasons for the increase in peanut and tree nut allergy remain unclear. On one hand, peanut and tree nut consumption is increasing as their nutritional benefits become more widely known. More pregnant and nursing women are thought to eat nuts than in the past, exposing the developing immune system to these allergens [12] . On the other hand, overall rates of allergy have increased in the past 2–3 decades, outpacing changes in consumption patterns. Moreover, certain populations eat peanuts at high rates but do not seem to suffer from significant peanut allergy. One theory that has received much attention is the so called “hygiene hypothesis,” postulating that the developing immune system requires infectious stimuli in order to develop into a nonallergenic phenotype. Supporting this theory, children who grow up on a farm, have older siblings, and are enrolled in daycare at young ages have lower rates of allergic disease [13, 14] . In experimental mice, allergy is induced in a germ-free environment, because the presence of normal intestinal microflora seems to promote tolerance [15] . Endotoxins, or lipopolysaccharides, found in certain gram negative bacteria, are potent stimulators of the immune system and are hypothesized to direct the immune system in a Th1, or nonallergic, direction [16] . Although many details about the allergic response remain to be elucidated, it is generally thought that the allergic response is characterized by so-called Th2 helper T cells that produce the inflammatory cytokines Il-4, Il-5, Il-13, which in turn promote eosinophilia and IgE production [17] . In contrast, tolerance occurs in a Th1 dominated milieu. At birth, the infant’s immune system is immature, and is characterized by Th2 predominance. High-dose allergen and endotoxin exposure are thought to assist in the redirection to Th1 responses as the infant grows [18] . Although evidence has continued to accumulate to support the hygiene hypothesis, more and more gaps in this theory emerge, making it clear that other factors must also be in play. New Aspects of Peanut and Tree Nut Allergy 677

Genetics

Although environmental factors are important in the development of food allergy, it is also clear that genetic factors play a key role in determining who is affected by peanut and tree nut allergy. These factors, however, cannot explain the recent rapid increase in allergy since the gene pool changes over generations, not decades. Siblings of peanut allergic patients are more likely to develop peanut allergy themselves, as are children of atopic mothers [12, 19, 20] . In an attempt to quantify the genetic contribution to the risk of peanut allergy, Sicherer et al. identified 58 twin pairs in which at least one member was peanut allergic. Among the 14 monozygotic pairs, 9 were concordant for peanut allergy, compared to 3 of 44 dizygotic pairs. From these numbers, they estimated the heritability of peanut allergy to be 82% [21] . Given these data, it appears that genetic factors were important but not sufficient for allergy development, and that certain environmental conditions must have contributed to the development of the peanut allergy. Identifying which genes are responsible for the level of heritability is an ongoing project. Work on the genetic basis of food allergy has proceeded along several lines. Linkage analyses have identified chromosomal areas on which candidate genes lie, while our current understanding of pathophysiology and extreme phenotypes has provided other avenues of study.

Linkage Analyses

Starting with an Amish population in the early 1990s, chromosome 5q31 was linked to total IgE levels [22] . In further studies, this area was found to be linked to bronchial hyperresponsiveness in a Dutch population [23] , asthma and atopy in a Japanese population [24] , circulating eosinophils in a US population [25] , total IgE and eosinophil numbers in an Australian population [26] , mite-sensitive asthma in a Japanese population [27] , atopic dermatitis in a Swedish population [28] , and atopic symptoms in Dutch [29] and various US populations [30] . Although these findings failed to be replicated in a variety of African American, European and Australian populations [31– 35] , chromosome 5q31 has received particular interest because it contains genes for IL4, IL5, and IL13, all of which are cytokines involved in the Th2 driven allergic response, as well as CD14. The CD14 receptor is a membrane-bound and soluble receptor found on the surface of immune cells, which interacts with one of the toll like receptors (TLR4) and binds to lipopolysacchiride (endotoxin) and other infectious antigens. CD14 is thought to play a role in modulating the Th1/Th2 balance, and genetic variations have been linked to asthma, total IgE levels, and atopy [36] . For development of asthma, the risk conferred by specific polymorphisms of this gene may be related to environmental conditions [37] . Woo et al. tested the CD14 gene for an association with food allergy in a US population, and found an association between one polymorphism 678 C.A. Keet and R.A. Wood and food allergy, especially in Caucasian subjects [38] . In contrast, a recent study in Japan found no association between polymorphisms in this area and food allergy [39]. Detailed analyses of environment/genotype interactions have not been done for food allergy. Chromosome 12q has also been linked with total serum IgE and atopy in several populations [28, 30, 40] . One gene that is found in this area, Signal Transducer and Activator of Transcription – 6 (STAT-6), is involved in the signaling pathway that involves Il-4 and Il-13 in the upregulation of Th2 cytokines and antibody class switching to IgE. A polymorphism in this gene was associated with nut allergy when a group of nut allergic patients in the UK were compared to blood donor controls. Moreover, homozygosity for this polymorphism was associated with increased risk of severe nut reactions [41] . Other candidate areas are 2q, 6p, 7q, 11q, 17q, and 22q, although the data are very preliminary [30, 42, 43] .

HLA

The major histocompatibility complex (MHC) received early and sustained attention as an area possibly involved in the genetic risk for food allergy because of its centrality to the immune response. The genes for the Human Leukocyte Antigens (HLA) , the human version of the MHC, code for two classes of HLA receptor, Class I and II. Class I genes are expressed by most cells, while class II gene expression is usually limited to antigen presenting cells, including B cells, macrophages, and dendritic cells. Certain HLA alleles put individuals at higher risk of specific autoimmune diseases. For example, the presence of the B27 allele is associated with a high risk of ankylosing spondylitis, while the DR3 allele is associated with a variety of autoimmune connective tissue and endocrine disorders, with relative risks varying from 2.5 to 12 [44] . The mechanism of this association is thought to be related to the differential affinity of certain HLA chains for self-peptides. Theoretically, a similar mechanism could be at work in food allergy; certain HLA alleles could code for chains that have high affinity for the nut epitopes that are known to be allergenic. Lack of those alleles would mean that the allergenic epitopes are not presented to T cells, and the proteins escape immune detection. Several authors compared patients with various food allergies to healthy controls, and found an association with specific HLA alleles and the food allergy in question. However, it was not clear whether the HLA alleles were associated with underlying atopy or cross-reactive pollen allergy, or whether they were truly associated with the food allergy in question [45] . Three other recent studies looking at peanut allergy in particular failed to find a strong association with any HLA allele and peanut allergy, although the data suggest some tentative links [45– 47] . The studies done so far used serologic type to classify HLA alleles; an alternative approach would be to look at the actual peptide-binding groove. This approach was successful in finding an HLA association with the latex-fruit syndrome in New Aspects of Peanut and Tree Nut Allergy 679 one study. For nut allergy, it would be more difficult because of the broader sensitization patterns [48] .

SPINK5

Another way to approach the genetic study of allergy is to take an extreme phenotype with a known genetic cause and then look at that gene to see if polymorphisms might be responsible for milder phenotypes. Such an approach was used for the SPINK5 gene (serine protease inhibitor Karzal type 5). Mutations in this gene cause Netherton syndrome, which is a rare recessive disease consisting of congenital ichthyosis with defective cornification, hair abnormalities, and atopic disease. Immunologically, this syndrome is characterized by Th2 skewed responses. Proceeding from this knowledge, researchers have linked this gene to atopic dermatitis and asthma. A study of Japanese children linked a specific polymorphism in this gene to food allergy. The link could be due to problems with mucosal or skin integ- rity, or, alternatively, could relate to problems with the immune system which originate in the thymus [49] . The SPINK5 gene is located on chromosome 5q32, close to several genes for interleukins and other immunoregulatory proteins [50] .

Peanut and Tree Nut Allergens

Identification of the major peanut and tree nut allergens is important in the design of new treatments and diagnostic tests for peanut and tree nut allergy, assists in the monitoring for contamination, and forwards our understanding of cross-reactivity. As the case of the Brazil nut allergen Ber e 1 shows, lack of knowledge of nut allergens can lead to dangerous choices when it comes to modifying foods [51] . Like so many aspects of food allergy, our knowledge is partial, and the coming years will likely see major advances in this area. Most peanut and tree nut allergens are seed storage proteins. As a rule, they are broadly resistant to denaturation by the type of enzymatic reactions normally found in the GI tract. Typically, they serve in defense roles for the plant. Several major families of nut allergens include vicilins, legumins, and 2S albumins. The vicilin and legumin proteins share a beta-barrel conformation and are part of the cupin superfamily. Lipid-transfer proteins (LPS), profillins and heveins are panallergens broadly found in pollens, nuts, seeds, fruits, and vegetables, and are responsible for some of the IgE mediated cross-reactivity between these disparate substances [52, 53] . In the US and Europe, the most common tree nuts to which patients report allergy are walnut, cashew, almond, pecan, Brazil nut, hazelnut, macadamia nut, pistachio, and pine nut, although only walnut, cashew, almond, Brazil nut and hazelnut have been well studied [3, 54] . A more detailed review of the proteins responsible for tree nut allergy was published in 2003 [52] ; here we will focus on the common nuts 680 C.A. Keet and R.A. Wood and their major allergens (defined as proteins that show IgE binding with more than 50% of allergic patients).

Peanut

The peanut, or arachis hypogaea, is native to South America. Remnants from tombs in Peru dating from as early as 1200 bc show evidence of cultivation of peanuts, and by the time the Conquistadors arrived in the Americas, cultivation of peanuts was widespread throughout Central and South America [55] . The peanut is a legume related botanically to beans and peas but not to tree nuts. The important peanut allergens are named Ara h 1–8, and peanut oleosin has also been identified as a peanut allergen. Over 90% of peanut allergic patient’s sera bind intensely to either Ara h 1 or 2 [56] . Of these proteins, purified Ara h 2 has been shown in various experiments to bind to more sera of patients with peanut allergy, to be a more potent stimulator of basophils, to have greater ability to crosslink IgE in peanut allergic patients’ sera, and to cause more reaction on skin testing of peanut allergic patients compared to Ara h 1 [56, 57] . In addition, anti-Ara h 2 accounts for a larger percentage of total antipeanut IgE than anti-Ara h 1 in peanut allergic patients [56] . Thus, Ara h 2 appears to be more important in the allergic response to peanut than Ara h 1. An important caveat is that a recent study found that Ara h 1 is actually found as an oligomeric structure rather than a trimeric protein, as was previously thought [53] . Because most of these studies used Ara h 2 that was purified as a trimeric protein, further studies using the oligomeric protein may show different results. Although severity of peanut allergy has not been shown to be related to binding to any specific peanut protein, it has been linked to the diversity of epitope binding of a patient’s serum [58, 59] .

Hazelnut

The hazelnut tree is native to Europe and Asia, and allergy to hazelnut seems to be more common in Europe than in the US, where hazelnut products, although increasing in popularity, are not the staple that they are in parts of Europe. There are several different types of hazelnut allergy. In areas where birch and other trees of the family Betulaceae (alder, hazel and hornbean) are endemic, such as northern Europe, a pollen-associated food allergy wherein patients are initially sensitized to the tree pollen is common. Cor a 1, a hazelnut allergen, shares significant homology with Bet v 1, the birch pollen allergen [52] . This hazelnut allergy is frequently characterized by the oral allergy syndrome; patients with systemic allergy are less likely to be birch allergic [60] . Subcutaneous immunotherapy (SCIT) for pollen allergy reduces the hazelnut allergy in patients with both allergies [61, 62] . New Aspects of Peanut and Tree Nut Allergy 681

Mugwort pollen is also thought to be cross-reactive with hazelnut, likely related to distinct allergenic proteins [52] . The allergens responsible for nonpollen-related allergy to hazelnut have not been as well characterized. Among the proteins that have been shown to be important, an 11S globulin named Cor a 9 that reacted with sera from 86% of nonpollen allergic hazelnut allergic patients in the US. This protein has homology with the cashew nut allergen Ana o 2, the peanut allergen Ara h 3, and soybean glycein [63] . Another allergen is a LPS named Cor a 8, which reacted with 62–77% of Spanish patients’ sera in another study [64] . Several other proteins may also be important for allergy, but they have not yet been analyzed in such depth.

Walnut

Trees in the walnut family are found throughout the world. The so-called English walnut is actually native to the area that spans Southeast Europe, Southwest and central Asia, and southern China, and is much more widely consumed in the US than the native black walnut. In the US, walnut is the most common tree nut allergy [3] . Several proteins have been identified as important allergens. In one study, 75% of walnut allergic patients reacted with a recombinant 2S albumin precursor named rJug r 1. This protein is similar to allergens in Brazil nut, castor bean, cottonseed, and mustard seed. Another allergen, Jug r 2, reacted with 60% of walnut allergic patients’ sera in a separate study. This vicilin protein has 75% homology with the peanut allergen Ara h 1. Yet another protein, Jug r 4, a legumin, reacted with 57–65% of sera from walnut allergic patients [52, 65] . In a study of Italian patients with confirmed walnut allergy, the major allergen was a lipid-transfer protein, now called Jug r 3, which bound 78% of the patients’ sera. These patients generally had severe allergy, and were also often allergic to other fruits with LTPs, including stone fruits, apple, grape, corn, and hazelnut [66] .

Almond, Cashew and Brazil Nut

The almond was domesticated at least 4,000 years ago in the Near East; Tutankhamen’s tomb in Egypt, which dates from 1325 bc, contained almonds [67] . Almonds are the most commonly eaten tree nut in the United States, with a per capita consumption of more than ½ lb per year [68] . The most fully described almond allergen is amandin, a legumin which forms 65–70% of the extractable proteins in almonds. In one unpublished study, more than 50% of almond allergic patients’ sera are bound to this protein [52] . The cashew tree is native to Brazil, and is now grown widely throughout tropical regions. Two major allergens have been identified. Ana o 1 is a vicilin to which about 50% of cashew allergic patients react. It forms a relatively small part of the 682 C.A. Keet and R.A. Wood extractable protein, only about 5%. Ana o 2, also called anacardein, accounts for 50% of the extractable protein in the cashew, and is a legumin-like seed storage protein. About 62% of allergic patients react to the recombinant form of the protein, rAna o 2 [52, 69] . Finally, Brazil nut, although not a commonly consumed nut in the United States, is thought to be a major allergen in the UK [54] . A 2S albumin, Ber e 1, has been identified as an allergen for this nut. The protein is rich in methionine and was cloned and introduced to soybean in order to increase the nutritional value of the soybean. Eight of nine tested Brazil nut allergic patients reacted to the genetically modified bean, none to soybeans themselves, causing serious concerns about this genetically modified crop [51] . The Ber e 1 augmented soybean project was stopped for concerns about food allergy. Further work on identifying other allergens is ongoing.

Cross-Reactivity

Whether in practice- or population-based prevalence studies, 20–50% of peanut allergic patients are also allergic to tree nuts [3, 54] . As with other food allergies, more patients are sensitized than are actually allergic; Clark and colleagues reported in a large series of nut allergic patients that by age ten, 86% were sensitized to multiple nuts, while 47% were actually multi-allergic clinically. In that study, as time went on, more subjects developed multiple allergies and sensitizations. Unfortunately, they did not separate out peanut allergy from other nut allergies, so specific cross-reactivity patterns could not be assessed [70] . In Sicherer et al.’s survey study in the US, 45% of tree nut allergic patients were allergic to more than one nut [3] . There are several mechanisms that might account for simultaneous allergy to peanuts and tree nuts. Since peanut and tree nuts are botanically unrelated, it had been thought that this was simply a manifestation of an underlying allergic phenotype reacting to multiple potent allergens. However, there is now emerging data that the cross-reactivity is more likely the result of homologous epitopes between peanut and tree nuts. At present, the data on cross-reactivity between peanut and tree nuts are not entirely clear. Goetz et al. found limited cross-reactivity between pistachio and walnut with peanut, but not between peanut and other tree nuts [71] . In contrast, de Leon and others in Australia found that preincubation of sera from peanut allergic patients with extracts from almond, Brazil nut, and hazelnut inhibited binding to peanut, and that basophils coated with peanut-specific antibodies were activated by contact with almond and Brazil nut extracts [72] . Moreover, they found that IgE specific for recombinant Ara h 2 are bound to almond and Brazil nut extracts, indicating that this protein may be responsible for some of the cross-reactivity previously described [73] . New Aspects of Peanut and Tree Nut Allergy 683

In some series, over 25% of children with peanut allergy have a history of allergy to other, nonnut foods, most commonly milk and egg. This phenomenon is likely attributable to underlying atopy rather than cross-reactivity [54] . Peanuts are botanically closely related to other legumes, and extensive cross-reactivity has been found on serologic and skin testing. Nonetheless, clinical cross-reactivity is uncommon [74, 75] .

Tree Nut Allergy

Tree nuts appear to have more significant epitope homology. Using ELISA inhibition assays, Goetz et al. defined two groups of cross-reactive tree nuts. Walnut, pecan, and hazelnut were strongly cross-reactive, while hazelnut, cashew, Brazil nut, pistachio, and almond were moderately cross-reactive. These cross-reactivities followed botanical classification. Walnut, pecan, and hazelnut are members of the same botanical subclass, and walnut and pecan, which showed the strongest cross-reactivity, are members of the same family, Juglandaceae. Among the other group, cashew and pistachio, which are both members of the botanical family Anacardiaceae, showed the strongest cross-reactivity [71] . Clinical cross-reactivities have not been established at this level of detail; most nut allergic patients are counseled to avoid all nuts, and systemic oral food challenges have not generally been conducted.

Diagnosis

Diagnosis of peanut and tree nut allergy is generally done through diagnostic testing guided by history. Allergen specific IgE levels and skin testing are the most important tests, but because they lack specificity, they must be taken in context of the patient’s exposure and reaction history. Food challenges, while the gold standard, are not usually necessary to establish the clinical diagnosis of a nut allergy since the clinical reactions tend to be so dramatic.

Skin Testing

For skin testing, although a wheal size of greater than 3 mm is generally considered positive, this cutoff has a low positive predictive value in an unscreened population. For example, Clark and Ewan analyzed 1,000 patients with allergy to at least one tree nut or peanut. They found that of the 660 patients with skin prick tests between 3–7 mm, 54% were allergic and 46% were tolerant to that tree nut or peanut by clinical history [76] . In order to try to avoid the need for food challenges in patients who have an unclear history by making skin testing more specific, several researchers 684 C.A. Keet and R.A. Wood have investigated whether using an increased diameter size helps diagnosis. Wheal diameters above 8 mm were found to be over 95% accurate for predicting a positive food challenge to walnut, peanut, Brazil nut, and almond [76– 78] . Others report even higher cutoffs [79] . Ho et al. reported that for children younger than 2 years old being tested for peanut allergy, a wheal diameter of 4 mm was 95% predictive. Commercial extracts can vary widely in concentration of the major allergic proteins [80] . Finally, anaphylaxis to skin testing, although extremely rare, has been reported [81, 82] . Recently, recombinant peanut proteins have been developed for use in skin testing. Preliminary study shows some promise of a product with more consistent properties. With recombinant proteins, it may also be possible to predict the degree of severity of reaction based on the number of peanut proteins to which a patient reacts. Thus far, linking severity of clinical reactivity with diagnostic parameters has proved difficult. Larger scale testing of the recombinant peanut proteins for skin testing is still needed to determine their clinical utility [83] .

IgE Levels

Serum assays of allergen specific IgE are also more sensitive than specific. Peanut has been most extensively studied; for children undergoing food challenge, Perry et al. found that 50% pass when the level was <2 kUa/L [84] , while Fleischer et al. found that 58% of patients with TN-IgE level of 5 kUa/L or less and 63% with TN-IgE levels of 2 kUa/L or less passed food challenges [85] . Sampson and Ho reported a level of 15 kUa/L for 95% of subjects to have a positive food challenge [86, 87] . Clark and Ewan confirmed Sampson’s results for peanut and extended it to tree nuts as well [76] .

Possibilities for Remission

Recent data have revised our thinking about whether peanut and tree nut allergy can be outgrown. In several studies, approximately 20% of patients with peanut allergy do outgrow their allergy, including some who had initially had severe allergy. Patients who initially had PN specific IgE levels below 10 kUa/L were more likely to eventually outgrow the allergy. In addition, patients who had strictly avoided peanuts, who had initial reactions involving only the skin, and who did not have a history of eczema were more likely to outgrow their allergies, although these factors were not sufficient to predict which patients would outgrow their allergies [88, 89] . Current PN-IgE levels were predictive of an outgrown allergy. Fifty five percent of patients passed food challenges when their PN-IgE levels fell below 5 kUa/L, although 63% passed with PN-IgE below 2, and only 35% of those between 2 and 5 passed. New Aspects of Peanut and Tree Nut Allergy 685

Optimal results from food challenges can thus be expected with PN-IgE levels below 2 [89] . Fleischer et al. continued to follow the patients who had passed food challenges showing that they had outgrown their peanut allergy for a median of 2 years. They found that 7.9% of 38 patients had recurrence of reactions to peanut. All reactions occurred in patients who consumed peanut infrequently or in limited amounts, and thus the authors recommend that patients who have outgrown their peanut allergy eat peanut frequently, but also carry epinephrine indefinitely. For tree nut allergy, 8.9% of 101 patients aged greater than 4 with a history of prior reactions outgrew the allergy. Fifty eight percent of those with tree nut specific IgE levels of 5 kUa/L or less passed the food challenges, compared to 63% of those with tree nut IgE levels of 2 kUa/L or less [85] . Interestingly, resolution of allergy did not occur in any patients who had reacted to more than two different nuts in the past [90] .

Avoidance

In the absence of effective therapies to cure peanut and tree nut allergy, avoidance of the allergen remains vitally important. Peanuts and tree nuts are frequently hidden ingredients in baked goods, candy, and snack foods, and restaurants are also common sites of accidental exposure [7, 9] . A new labeling law, the food allergen labeling and consumer protection act (FALCPA), requires that common allergenic foods be identified in ingredient lists for commercial foods. This law, which was implemented in 2006, defines the common allergenic foods as milk, eggs, fish, crustacean shellfish, soybeans, wheat, peanuts, and tree nuts [91] . Accidental inclusion of allergenic ingredients is not covered by the law, nor is the use of pre- cautionary labels.

Treatments

Recent years have seen the initial development of several promising strategies for treatment of food allergy. Because there is no space to discuss all of the avenues of current research here, we focus on a few treatments that have shown the most promise thus far.

Immunotherapy

For almost 100 years, since well before IgE was identified, allergy has been treated with immunotherapy. The injection of increasing quantities of purified allergen, an 686 C.A. Keet and R.A. Wood example of specific immunotherapy, has been most successful for inhaled allergens. Although the precise mechanisms of immunotherapy remain incompletely known, there are some consistent findings and promising avenues for further research. SCIT has been studied the most. In multiple studies, it has been shown to elicit IgG (mostly IgG1 and IgG4), and sometimes IgA antibodies, with less consistent effects on IgE. Regulatory T cells have been a topic of more recent interest. These cells include CD4+CD25+ cells from the thymus, as well as Tr1 cells, Th3 cells, and CD3+ cells, which are induced in the periphery. These cells are thought to down regulate both Th1 and Th2 responses by both direct cell contact and immunosuppressive cytokines such as Il-10 and TGF- b . Dendritic cells seem to play a critical role in inducing these cells. There is some evidence that these cells are important in the induction of tolerance by immunotherapy, but the data remain incomplete [92, 93] . For food allergy, injected immunotherapy has been much less successful. Although there have been case reports of successful treatment of peanut allergy with injected immunotherapy [94] , in a placebo-controlled trial of SCIT for peanut allergy, most patients had repeated systemic reactions to the treatment, some severe [95] . In recent years, sublingual and oral immunotherapy have emerged as promising alternatives. When used for respiratory allergy, sublingual immunotherapy is better tolerated, with fewer systemic reactions than with oral immunotherapy [96] . However, both strategies have been tested with some foods, with promising preliminary results. For egg allergy, Buchanan et al. conducted an open trial of oral immunotherapy in egg allergic patients who had not had anaphylactic reactions. Over 2 years of treatment, all subjects tolerated significantly higher doses of eggs, and four of seven passed a full oral food challenge to egg. However, after 3–4 months of an egg restricted diet, only two maintained full tolerance to egg [97] . For cow’s milk, an Italian study found that 71% of 21 patients were successfully desensitized to cow’s milk, while another 14% tolerated lower maintenance doses; [98] and in a French study, 4 of 8 patients with milk allergy originally enrolled were able to reintroduce dairy into their diets following 6 months of immunotherapy. Adverse reactions, while common in these studies, were not severe [99] . Enrique et al. conducted a placebo-controlled trial of sublingual immunotherapy in 23 hazelnut allergic patients. After 8–12 weeks of therapy, the mean quantity of hazelnut required to provoke symptoms increased from 2.29 to 11.56 g after 8–12 weeks of treatment, and 50% reached the highest dose of hazelnut (20 g). Systemic reactions occurred in 0.2% of subjects during the build up phase of the study [100] . There have been several case reports of successful oral desensitization to peanut [101, 102] , and interim results of an ongoing trial are promising [103] . Duration of therapy, optimal dosages, route, and selection of patients who have most potential to benefit are all variables that are yet to be determined. In another attempt to create a safer kind of immunotherapy, researchers are modifying allergenic proteins so that they stimulate T cells without cross- linking IgE and causing mast cell and basophil degranulation. Both peptide fragments and mutated proteins that lack affinity for IgE are being used. Mutated proteins have had some effectiveness in a mouse model, while peptide New Aspects of Peanut and Tree Nut Allergy 687 fragments were effective when used in cat-allergic patients [104] . Human trials of modified peanut will be starting soon.

Anti-IgE

Another area of active interest is the use of anti-IgE monoclonal antibodies. These antibodies form complexes with membrane-bound and free IgE without allowing cross-linking, and thus prevent the IgE on B cells from interacting with mast cells and basophils. This, in turn, prevents the release of the mediators of immediate allergy. One such antibody, omalizumab, was approved by the US FDA in 2003 for treatment of allergic asthma, but has not yet been studied for food allergy. A similar drug, however, TNX-901, was studied for peanut allergy. In this study, Leung et al. randomized peanut allergic volunteers to different doses of the medication. TNX- 901 or placebo was given subcutaneously every 4 weeks for 4 months. Oral-food- challenge threshold doses of peanut increased in a dose-dependent manner, and at the highest dose, the threshold for reaction to peanut increased from approximately one half peanut to almost nine peanuts [105] . TNX-901 is no longer in development, but trials of omalizumab for peanut allergy will hopefully be done. In addition, trials are underway to see if treating patients with omalizumab prior to immunotherapy for respiratory allergies will result in fewer side effects and greater efficacy [106] . If successful, this method could extend to food immunotherapy. Despite the positive results of studies thus far, there are limitations to the potential of this medication for treatment of peanut and nut allergy. First, some subjects even on the highest dose of TNX-901 did not develop any protection. Second, continued treatment would be needed since protection from anaphylaxis would disappear once treatment is stopped. Third, although the threshold for anaphylaxis was increased so that most patients would likely not be at risk for accidental exposure, they would still have to avoid peanuts. Finally, monoclonal antibodies are very expensive, and for a medication that would have to be used for life, the cost could be prohibitive. In addition, there have been recent reports on post-marketing data of anaphylaxis from omalizumab [107] .

Herbal Treatments

Herbal remedies have been used to control allergic symptoms for centuries in Asia. Although the Traditional Chinese literature does not describe food allergy or treatments for it, researchers, encouraged by suppression of other allergic responses by Chinese herbs, have developed a mixture of Traditional Chinese herbs for treatment of peanut allergy. In initial murine trials of this combination, food allergy herbal formula–1 (FAHF-1), peanut-induced anaphylaxis was blocked. In these animals, IgE levels, peanut-induced lymphocyte proliferation, and synthesis of 688 C.A. Keet and R.A. Wood the inflammatory cytokines IL-4, IL-5, and IL-13 were all reduced [108] . Because of regulatory concerns about two of the herbal components of FAHF-1, they modified the compound, and tested the new mixture, FAHF-2, again in the same murine peanut allergy model. In the treated peanut allergic mice, there were no signs of anaphylaxis after challenge with peanut for at least 5 weeks post therapy. Newer, unpublished, results have found protection for as long as 6 months in mice with established peanut allergy [109] . The clinical findings were associated with significantly reduced splenocyte production of Il-4, Il-5, and Il-13 and enhancement of IFN-gamma upon peanut stimulation in vitro, consistent with a suppression of Th2 and increase in Th1 responses. The herbal compound appeared to have no adverse effects on the mouse, even at the highest dose that they could feed the animal, and did not appear to cause overall immune suppression, although other aspects of the immune response of treated animals have yet to be studied. The mechanism by which this compound works is not known. Animal studies of this herbal compound have been very promising, and research is ongoing [110] .

Conclusions

In recent years, we have learned many things about peanut and tree nut allergy. Several potential genetic risk factors for food allergy have been identified, many peanut and tree nut allergic epitopes have been classified, helping our understanding of cross-reactivity, and the best use of skin testing and specific IgE for diagnosis has been clarified. We have learned that peanut and tree nut allergy can be outgrown, and now have guidelines for testing patients who might have outgrown their allergies. Most promising, several potential therapies for food allergy are now undergoing study, and the prospects for effective treatment in the coming years is very real.

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Berrylin J. Ferguson and Arpita Mehta

Introduction

Fungal rhinosinusitis can be categorized into distinct forms on the basis of histopa- thology. The invasive manifestations are fulminant or rapidly progressing, chronic or indolent, and granulomatous. The noninvasive manifestations are fungus balls and allergic fungal sinusitis (AFS). A noninvasive and controversial category introduced within the last decade resembles AFS; however, patients are not allergic and are termed nonallergic eosinophilic fungal rhinosinusitis (NA-EFRS). AFS or NA-EFRS is the subject of this chapter and will be contrasted to eosinophilic sinus disease in which fungi are absent. Classically, AFS is defined as the histopathologic presence of eosinophilic mucin containing fungal hyphae retrieved from the nose or paranasal sinuses from patients who demonstrate IgE mediated allergy to the fungus. Patients with AFS often have asthma, peripheral eosinophilia, nasal polyps, and allergic rhinitis. The nose and sinus contents contain green, sticky or tan mucin plugs, which when examined pathologically reveal eosinophilic mucin, Charcot Leyden crystals, degenerating inflammatory cells, and sparse hyphae (Fig. 1 ). The presence of hyphae is considered to be important in making the diagnosis; however, hyphal presence is often sparse and the diagnosis of AFS may be missed due to sampling error [1] . The absence of fungus histopathologically or of allergy has lead to two additional categorizations: (1) Nonfungal eosinophilic mucin rhinosinusitis (NF-EMRS) in which fungi are not seen or cultured and are NOT considered to be of etiologic importance [2] (Fig. 2 ) and (2) Nonallergic eosinophilic fungal rhinosinusitis (NA-EFRS) in which fungi are present and believed to be causal in the pathophysiology through nonallergic mechanisms [3] .

B.J. Ferguson () and A. Mehta Division of Sino-Nasal Disorders and Allergy , Department of Otolaryngology, University of Pittsburgh School of Medicine, The Eye and Ear Institute Building, 200 Lothrop Street, Suite 500 , Pittsburgh , PA 15213 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 695 DOI 10.1007/978-4-431-99362-9_42, © Springer 2010 696 B.J. Ferguson and A. Mehta

Fig. 1 High power photomicrograph of AFS demonstrating hyphae in eosinophilic mucin and a conidia in hematoxylin and eosin (H&E) (original magnification × 100). Frequently, special fungal stains are required to identify hyphae. It is unusual to see conidia

Fig. 2 Low power photomicrograph of nonfungal eosinophilic mucin rhinosinusitis (NF-EMRS) showing eosinophilic mucin. Special stains for fungus (not shown) were negative. (25×)

The therapy for AFS includes surgery as well as topical and systemic steroids. Topical and systemic antifungals, leukotriene modulators, immunotherapy following surgical extirpation, and anti-IgE may be useful in individual patients. Recidivism and recurrence are frequent in the absence of medical therapy. Allergic Fungal Sinusitis 697

Historical Aspects

AFS was initially recognized clinically in 1976 by Safirstein as an inflammatory condition of the nose and sinuses associated with thick, sticky, eosinophilic mucin which grew out of aspergillus [4] . In 1981, Miller, in abstract form, noted the histopathologic similarity of the sinus manifestation to the already well-recognized pulmonary pathology of Allergic Bronchopulmonary Aspergillosis (ABPA) [5] . Independently, 2 years later, Katzenstein described this association in a series of six cases. None of these early reports had fungal culture data and based their terminol- ogy of allergic aspergillus sinusitis on the histologic appearance of the fungus and its resemblance to aspergillus [1] . We now appreciate that many fungi, in addition to Aspergillus species, are associated with AFS and that histologically it may be impossible to differentiate between fungal species [6] . The term allergic fungal sinusitis was coined in 1989 [7] . In 1998, Manning showed, in a case control study, that all the patients with AFS associated with Bipolaris displayed elevated IgE to Bipolaris , in contrast to controls in which this was present in only a minority of patients [8] .

Confusion and Controversy over the Diagnosis of AFS Categorization

The confusion over the role of fungus in the etiology of chronic rhinosinusitis (CRS) was heightened by the assertion of Ponikau and colleagues in the late 1990s that fungi were responsible for most cases of CRS. They reported that 93% of patients undergoing sinus surgery had both eosinophilic mucin and fungus present by nasal lavage sampling. Ponikau based his conclusion of a nonallergic etiology of eosinophilic fungal sinusitis on the fact that less than half of his sample of almost 100 patients with eosinophilic mucin and fungal presence were allergic. In this same report, Ponikau also noted that fungus could be grown from the nasal washings of 100% of normal controls [3] . They proposed that cell mediated responses provoked by fungus in susceptible host was responsible for eosinophilic fungal rhinosinusitis (EFRS). In order to highlight the nonallergic nature of Ponikau’s proposed categorization, we refer to this as nonallergic eosinophilic fungal rhinosinusitis (NA-EFRS). Since the proposal of Ponikau that fungus was causal in nearly all cases of CRS, there have been three large studies that compare the demographics of eosinophilic sinus disease relative to presence or absence of fungus with conflicting findings. In 2000, Ferguson reported that the eosinophilic mucin rhinosinusitis without fungus differed significantly in clinical characteristics of patients with AFS, although overlap existed [2] . Ferguson’s database was a comprehensive literature review of AFS and NF-EMRS combined with a database of patients from northeastern United States. The review compared 69 NF-EMRS patients with 431 patients with AFS and found 698 B.J. Ferguson and A. Mehta that AFS patients were significantly younger (30.7 years compared with 48.0 years), less likely to have asthma (41% compared with 93%), less likely to have aspirin sensitivity (13% compared with 54%), less likely to have bilateral disease (55% versus 100%), and had significantly higher total IgE levels (mean 1,941 mg/dL with a range of 12–13,084 mg/ dL) compared with NF-EMRS patients (mean, 267 mg/ dL with a range of 14–1,162 mg/dL). Over 90% of this database was drawn from North America [2] . In 2006, Saravanan prospectively categorized 70 patients in northern India undergoing sinus surgery and found that 36 of 70 (51%) patients had AFS, 12 of 70 (17%) had NF-EMRS, 4 (6%) had fungus balls, and the remaining 18 had noneosinophilic CRS from other causes. Similar to the report by Ferguson, the mean age of the AFS patients was younger than the NF-EMRS (28 ± 13 years versus 41 ± 10 years) and bilateral disease was less common in the AFS group (75% versus 100%), but these findings did not achieve statistical significance. Bony erosion (100% versus 40%) and heterogeneity of densities on CT scan (97% versus 67%) were significantly more common in the AFS group compared to the NF-EMRS [9] . In Adelaide, Australia, a prospective evaluation of 188 patients with EMRS found that patients with classic AFS were significantly younger than patients with other forms of EMRS; however, there was no difference in the subgroups in any other parameters examined including presence of aspirin sensitivity, bilaterality of disease, immunoglobulin levels, or asthma. Virtually 100% of all AFS patients have bilateral disease in southern Australia [10] . Possible explanations for the differences between these three large series include the impact of differences introduced by climate, genetic susceptibility, and socioeconomic factors. In the Ferguson literature and retrospective review, 93% of the patients were from North America, while the two large prospective series were from a single location. Saravanan’s study represented patients from central northern India, and Pant’s study was of patients from Adelaide, Australia. It is possible that in northern India and southern Australia conditions could exist that lead to a higher mold inoculum and more frequent bilateral disease.

Epidemiology and Geography

Allergic fungal sinusitis incidence varies geographically [11] . Endemic areas include areas of high humidity in the United States along the Mississippi River and in the South, in Northern India (51% undergoing sinus surgery), Adelaide Australia (8.6% undergoing sinus surgery) [2, 9, 12], and areas of the Persian Gulf. In 1998, the highest reported rate in the United States was in Memphis, Tennessee, where 20% of surgical endoscopic sinus cases were for AFS. Memphis lies on the other side of the Mississippi River, a few hundred miles downstream from St. Louis, Missouri, where in 1983 Katzenstein was the first to report on the incidence of AFS, 6.2% of all surgical sinus cases. Most telling is the absence of AFS in certain regions such as the Northwestern part of United States where there is a Allergic Fungal Sinusitis 699 cooler climate. The presence of mold spores is necessary for AFS to occur. The geographic variation in incidence of AFS could be secondary to differences in mold counts. Outdoor mold spore counts vary widely geographically and seasonally. Other sources of mold exposure include damp basements, bathrooms, humid- ifiers, and possibly air conditioning units. Air conditioning is more common and more utilized in the southern United States and in the Persian Gulf where there is high incidences of AFS.

Pathophysiology Similarities and Differences of AFS to ABPFD

AFS is thought to be the pathophysiological nasal/sinus equivalent of allergic bronchopulmonary aspergillosis (ABPA), yet differences exist between these two entities which have a similar histopathologic appearance. ABPA is more precisely called allergic bronchopulmonary fungal disease (ABPFD), since fungi in addition to Aspergillus can cause this disease. Both ABPA and AFS require an individual genetically predisposed to mold allergy that is exposed by inhalation to the mold spore. The spore must elude mucociliary clearance or expulsion by sneezing or coughing for a time period which is long enough to allow germination. It is estimated that an average person inhales 5.7 × 107 spores of various species within a 24-h period [13] . Occasionally, due to the maxillary transport disruption, dryness, or a large inoculum, the mold spore may not be cleared. In a susceptible and allergic individual, germination increases the antigenicity of the fungus [14] , leading to increased production of allergic mucin in which the fungus continues to grow. This leads to a “positive feed-back loop” in which growth of the antigenic fungus induces the production of more allergic mucin, which leads to increased growth of antigenic fungus (Fig. 3 ). The sticky allergic mucin resists clearance by normal mucociliary action, and the inflammatory cytokine milleaux promotes the growth of nasal polyps. If the mold spore randomly gets lodged in just one side of the nose, unilateral AFS will develop. The fungi most frequently associated with AFS are those with rapid germination rates. Antigenicity for most of the fungi associated with AFS increases with germination. At body temperature, Alternaria may germinate within as little as 2 h [15] . Pant found that fungal IgE levels were similar in patients with NF-EMRS and fungal allergy compared to patients with AFS [16] . This implies that presence of fungal allergy alone is not sufficient for the development of AFS. Patients also have fungal allergy without EMRS. Thus, IgE to fungal antigens in patients with NF-EMRS may represent cases in which fungi have not become entrapped in the nose or sinuses. In other words, the mucociliary/host defenses have been adequate to prevent entrap- ment of fungal spores or a co-factor such as superantigen may be absent. Recently, the controversy involving the definition of AFS has been intensified by reports of mucosal invasion as indicated by granulomatous inflammation and branching septate fungal hyphae in the submucosal tissues in patients with presumed extensive AFS [17, 18] . 700 B.J. Ferguson and A. Mehta

AFS + feed back loop Germinates quickly in Inhaled mucous, spore, Possible Not superantigen cleared producing By MCT bacteria co- More mucous factor stimulated

↑ Hyphal Growth + ↑ Antigenic antigenicity increases stimulation More mucous stimulated

Fig. 3 Diagram of positive feedback cycle in which an inhaled spore becomes trapped in the nose or sinus of a susceptible host. Allergic mucin is secreted. The spore germinates and grows in the mucin, increasing the antigenic stimulation, resulting in an increased production of mucin

Proteases and Fungal Sinus Disease

Gibson proposed that the pathophysiology of ABPA is not only one of IgE mediated reactions to fungal antigens, which stimulates the Th2 pathway leading to eosinophilic infiltrate, but that the presence of aspergillus proteases promote epithelial activation and a potent chemokine response that induces neutrophilic airway inflammation [19] . The effect of fungal proteases on sinus mucosa is largely unexplored but may be an additional mechanism in which fungi can stimulate inflammation independent of an IgE mediated/allergic pathway. Kita has shown that fungus can cause eosinophil degranulation independent of IgE mediated mechanisms [20] . In addition, the same investigators have shown that peripheral blood monocytes (PBMC’s) from patients with CRS respond to the supernatant of Alternaria with the production of IL-5 independent of an IgE mediated mechanism. This does not occur in patients without CRS [21] . It is possible that this is not an immunologically mediated reaction but is caused by fungal proteases, which could lead to nonallergic fungal ECRS. Proteases in fungi interact with nasal epithelial cells and enhance the production of inflammatory cytokines in vitro. These cytokines induce the migration of eosinophils and neutrophils. Shin reported that nasal polyp cells produce inflammatory cytokines in vitro on fungal exposure which is associated with the increased expression of protease activated receptors [22] . Allergic Fungal Sinusitis 701

Superantigen and Genetic Predisposition

In 2001, Schubert proposed that the presence of superantigens might be a condition which would lead to the cytokine mileaux, which would predispose to the generation of IgE against fungal presence leading to AFS. It is known that staph superantigens are important in perpetuating atopic dermatitis. Subsequently, several investigators have shown that staph superantigens are present in at least some of the patients with nasal polyposis [23– 25] . Not only do superantigens upregulate susceptible T-cells but may be responsible for B-cell activation. Superantigens enhance the TH2 response which leads to the isotype class switching of immunoglobulin synthesis favoring the production of IgE not only to the superantigens but also potentially to other foreign proteins, which may be present incidentally, such as fungus [26] . Wormald’s laboratory in Australia recently demonstrated that peripheral blood lymphocytes (PBL) from patients with CRS, both with and without nasal polyps as well as with normal controls, expressed significantly more interferon gamma (INF- g ) and a more modest increase in IL-5 when exposed to staphylococcal exo- toxin (superantigen) Type B (SEB). This was enhanced by the addition of fungal extracts (Aspergillus and Alternaria ). Unlike Shin’s study, no significant increase in IL-5 was seen upon exposure to just fungal extracts in Wormald’s study . They concluded that SEB exerted a proinflammatory effect on PBLs and fungal extracts may act synergistically to promote this action [27] . In AFS, the currently proposed mechanisms would involve Th2 associated cytokine such as IL-5, and not necessarily a Th1 cytokine such as INF-g . Whether AFS patients’ PBLs respond differently than CRS patients would be of interest. PBLs on exposure in vitro to SEB or fungal extracts have not been studied. Both ABPA and AFS are associated with certain class II genes of the major histocompatibility complex (HLA-DR2 and HLA-DR5, respectively). Not all patients with AFS have this genotype nor do all patients with this genotype develop either ABPA or AFS. Schubert reported that HLA-DQB1*03 was significantly a more frequent finding in patients with AFS than in chronic sinusitis without fungus; both were elevated compared to normal controls [28] . Such a finding is compatible with a role for bacterial superantigen exposure to genetically susceptible patients leading to the nonspecific upregulation activation of T-cells, which can set the stage for a TH2 mediated reaction to fungus that may be present incidentally [29] (Table 1 ).

Table 1 Pathogenesis of allergic fungal sinusitis Currently required elements Probably or possibly required Noninvasive fungal growth Superantigen from bacterial coinvestigation Eosinophilic mucin HLA subtype susceptible to superantigen stimulation Type I allergy to fungus cultured 702 B.J. Ferguson and A. Mehta

Fig. 4 Photomicrograph of eosinophilic mucin with nests of bacteria and hyphae. (hematoxylin and eosin) (original magnification × 100). In inset, hyphae are demonstrated by silver stain, the most sensitive stain for detection of fungi. (original magnification × 40)

Recently, Ferguson reported statistically significant association of bacteria with fungus in eosinophilic mucin compared to the presence of fungus without associated bacteria (Fig. 4 ). This may be evidence for a co-pathogenic role for bacteria, which presumably could produce superantigen required for AFS to occur or it may represent an incidental association [30] . A recent report by Orlandi and colleagues showed differences in genes present or activated in AFS compared to NF-EMRS. This is a preliminary study of a small number of cases that offers a potentially attractive method of categorizing EMRS, which might overcome current confusion generated by overlapping clinical characteristics and potentially lead to selective therapeutic interventions [31] .

IgE Levels and Associated Fungal Findings

In both AFS and ABPA, high levels of serum IgE are usually seen, and these levels fluctuate with disease activity. It is possible to encounter low levels of IgE, particularly in patients with quiescent disease [32] . Kuhn found that total IgE was both more specific and sensitive than fungal specific IgE for predicting persistence or recurrence of AFS [33] . The most common fungi associated with AFS vary geographically. In the southern United States, AFS is commonly associated with Bipolaris species. This antigen is not available commercially, and most clinicians substitute Helminthosporium during allergy antigen testing owing to its cross reactivity [34] . The most common Allergic Fungal Sinusitis 703 fungi associated with AFS, for which commercial assays for serological screening exist, are species of Helminthosporium , Aspergillus , Alternaria , and Curvularia . Elevated IgE and IgGs to the fungus are common in ABPFD. The precipitating antibodies (IgG) that are integral to a Gell and Coombs Type III reaction can be found in over 90% of ABPFD patients. Interestingly, there has been no similar demonstration of immune complexes and the development of AFS. Another difference between ABPFD and AFS is the absence of AFS in patients with cystic fibrosis. Between 6 and 25% of patients with cystic fibrosis are reported to have ABPFD [35] , while ABPFD as a whole afflicts only 1% of all asthmatics.

Fungal Culture

In order to determine the fungal cause of AFS, a culture must be obtained. Over homogenization of the specimen will prevent fungal growth. Nasal washes resulted in fungal recovery from nearly everyone’s nose, and whether the fungus is causative or incidental is impossible to determine [3] . Therefore, most investigators rely on cultures obtained from the eosinophilic or allergic mucin. Associated fungal causes vary geographically. In North America, most cases of AFS are caused by dematiaceous or pigment producing species such as Bipolaris , Exserohilum robatum, Curvularia lunata, and Alternaria . In northern India, the majority of AFS cases are caused by Aspergillus flavus, and in the Persian Gulf countries, Aspergillus species predominate.

Clinical Presentation

Associated clinical findings include a male predominance, nasal polyps, unilateral presence in half of the cases in North America, and asthma (40–61%). Sinus CT findings which are characteristic of AFS do not exclude other causes of eosinophilic sinus disease. This is discussed more fully under the radiographic subsection. In children with growing faces, remodeling of the facial skeleton to develop prop- tosis is common. Patients may relate blowing out the mucin plugs and complain of unilateral or bilateral nasal obstruction. Visual loss has been reported rarely in patients with sphenoid involvement. Dhiwakar et al. suggest that the combination of nasal polyposis, CT scan with heterogeneity and bone erosion, and specific elevated fungal IgE titer have high preoperative predictive value for AFS [36] . Most authors report nasal polyps in all forms of eosinophilic sinus disease, and therefore it may be sensitive but not specific for the diagnosis of AFS. AFS can occur or reoccur in the absence of nasal polyps. The five criteria described by Bent and Kuhn for the diagnosis of AFS include those which are part of the classic definition: Type I hypersensitivity to fungi and eosinophilic mucin with noninvasive hyphal presence as well as two additional clinical findings: A characteristic radiograph and nasal polyps. These two latter 704 B.J. Ferguson and A. Mehta findings are usually present in patients with AFS, but AFS can occur in their absence [37] . Asthma, when present with AFS, is usually mild and not steroid dependent, although there are case reports of concomitant ABPA associated with AFS [38] .

Radiological Findings

Computed tomography (CT) imaging of the sinuses is the modality of choice to diagnose AFS. The most common finding is central areas of high attenuation, which represent the eosinophilic mucin surrounded by densities of lesser attenuation that represent mucosal thickening and nasal polyps (Fig. 5 ). Mukherjig et al. performed a retrospective study examining the CT scans of 45 patients with AFS. Areas of hyperattenuation were found in all patients, 51% had bilateral findings and 20% had bony erosion and local extension of disease. Nussenbaum et al. reviewed 142 AFS patients’ CT scans and also found a 20% incidence of bony erosion, most commonly involving the lamina papyracea.

Fig. 5 Coronal CT of AFS showing opacification of the right maxillary sinus and ethmoid. Note the heterogenicity of densities with the denser material representing the mucin plugs and the lighter density representing nasal polyp or mucosal thickening Allergic Fungal Sinusitis 705

The ethmoid sinus was most commonly involved, although multiple sinuses were frequently involved and often expanded by the mucin. In northern India, both bony erosion and heterogeneous opacity with sinus expansion on CT scan were significantly more common in patients with AFS versus other forms of sinusitis. 100% of patients with AFS in this series demonstrated bony erosion. This high incidence of bony erosion may reflect the socioeconomic differences in which patients are not seen until they have developed advanced disease [9] . Magnetic resonance imaging of AFS frequently shows a hypointense central T1 signal, central T2 signal void, and increased peripheral T1/T2 enhancement. Thus, the diagnosis of a sinus abnormality could be missed due to the signal void if only an MRI scan is obtained. These findings are not specific for AFS and may be found in other eosinophilic sinus conditions. CT should be the primary mode of assessment for AFS to acquire important information regarding bony landmarks.

Treatment

The initial treatment in AFS is usually surgical. This provides pathologic material in order to make the diagnosis as well as the material for culture. In the absence of medical therapy, recurrence rates as high as 100% have been reported. Therefore, medical adjunctive therapy such as steroid, antifungal, and immunotherapy are utilized to improve the prognosis [39] (Table 2 ). Systemic steroids given before surgical therapy may diminish the eosinophilic component of the disease, and the pathologist may erroneously report nothing more than a fungus ball. Once steroids are withdrawn, the eosinophilic nature returns and the histopathologic diagnosis of AFS can be made. Numerous fungi are responsible for AFS. The causative organism may be recovered from air samples of the residences of the affected patients [40] . The rate of re-inoculation after treatment accounts for some of the high recurrence rates.

Surgical Management

Surgery is required to establish the diagnosis of AFS, remove the inciting fungal pathogen, reestablish physiological drainage, and preserve healthy mucosa. By fulfilling these goals, medical therapy can be optimized and control the disease.

Table 2 Therapy of allergic fungal sinusitis Definitely helpful Probably or possibly helpful Not helpful or unclear Steroids, systemic, or topical Immunotherapy Topical amphotericin B Surgery Oral antifungals* Leukotriene modulators Nasal lavage anti IgE* Calcineurin inhibitors Antibiotics *demonstrated efficacy in ABPA 706 B.J. Ferguson and A. Mehta

There are two surgical approaches toward the sinuses, external and endoscopic. Before the introduction of endoscopic techniques in the mid 1980s, AFS was approached externally through Caldwell-Lucs, external ethmoidectomies, and frontal sinus trephination or obliteration procedures. Endoscopic techniques are now primarily utilized [41] . This requires obtaining a preoperative CT scan within a few weeks of the operation to clearly demarcate any bony dehiscences and to identify the regions of disease. A microdebrider, which is a powered instrument with an oscillating blade attached to suction, facilitates the removal of the sticky tenacious mucin. The microdebrider’s trap allows easy collection of tissue for establishing diagnosis [42] . A microdebrider should not be used, or used only with great caution, in areas of bony dehiscence. Computer assisted navigational systems facilitate safe surgery in areas where landmarks have been obscured [43] . In refractory cases, stripping of nasal mucosa to remove presumed biofilm and irreversibly diseased tissue may prevent further recurrences. Aggressive and mutilating surgery should be avoided. Occasionally, frontal sinus obliteration is required.

Medical Management

Steroid therapy is the mainstay of ABPA and AFS, but because systemic steroids carry risk therapy, use should be limited [44] . The usual starting dose is 60–40 mg a day, which is then tapered over weeks to months [45] . Kupferberg et al. report that postoperative systemic steroids significantly reduce the recurrence of AFS and that doses less than 15 mg every other day lead to recurrence [46] . Schubert and Goetz in a series of consecutive AFS patients found that oral steroids given within the first 2 years postoperatively significantly delayed revision surgery [34] . Systemic steroids have potential for significant problems short-term including insomnia, personality change, diabetes, psychosis, or exacerbation of a peptic ulcer. Long-term usage may lead to osteoporosis, avascular necrosis of the hip, cataract formation, glaucoma, and hypertension. The risks associated with systemic steroids in children are growth retardation and potential irreversible bone growth loss; therefore, lower doses of 0.5–1 mg/kg per day are recommended [46] . Topical corticosteroids have limited systemic bioavailability and are usually part of the long-term management of AFS patients. Intranasal steroid sprays are usually more beneficial after surgery, when there is greater access to the affected nasal mucosa [47] .

Antifungal Therapy

Early nonrandomized, noncontrolled studies reported 70% improvement in symptoms and CT scans after irrigation of the nose with 20 mL of amphoterocin B 20 twice a day for 4 months. Studies to assess the effect of intranasal antifungals have evolved. (Table 3 ) In the best designed study to date, Ebbens et al. reported no benefit from usage of amphotericin irrigation either objectively of subjectively [48] . Allergic Fungal Sinusitis 707 usitis; CRS = chronic NP, 0% severe NP, NS difference, objectively, subjectively, or by QOL or by QOL subjectively, objectively, NS difference, Imp in 75% g/mL × 6 months × g/mL 8% imp in CT g/ m m g/mL × 13 g/mL weeks m L spray qid × 8 weeks × spray qid L NS imp* m 100 mL × x > 3 mL months 25 mL amphotericin B bid 25 mL 20 ml bid 100 20 ml bid 100 = 116 N = 24 = 20 ml bid 100 = 74 200 N N R,DB,PC,MC without AFS Entry criteria Design Amp B dose Result Studies of topical amphotericin B in CRS Studies of topical amphotericin B in CRS

DB = double blinded; PC = placebo controlled; QOL = quality of life; ESS = endoscopic sinus surgery; AFS = allergic fungal sin allergic = AFS endoscopic sinus surgery; = quality of life; ESS = placebo controlled; QOL = double blinded; PC NR = nonrandomized; NB = nonblinded; R = randomized; = MC = multicenter DB rhinosinusitis; = nasal NP polyp Table 3 [48, 55– 58] Ebbens – 2006 CRS, prior ESS, Ponikau – 2005 CRS R,DB,PC Table Table 3 Ricchetti – 2002 Nasal polyps – 2004 Weschta 74 = NR,NB N AFS without NP R,DB,PC 4 weeks × 20 ml bid 1:1,000 Resolution of polyps in 42–62% mod & mild Ponikau – 2002 CRS NR,NB n = 51 708 B.J. Ferguson and A. Mehta

In the pulmonary equivalent of the disease, ABPA, the antifungal intraconazole at a dose of 200 mg BID for 16 weeks, was shown to significantly improve the disease in a randomized placebo controlled multicenter study [49] . No benefit with high-dose oral terbinafine was shown in a randomized placebo controlled multicenter study of patients with CRS not restricted to AFS [50] .

Immunotherapy

Initially, immunotherapy was considered to be contraindicated in AFS due to its theoretical potential to worsen the disease through the formation of immune complexes. Goldstein was the first to suggest that immunotherapy may prevent recurrences [51] . Mabry and colleagues initially showed that fungal specific immunotherapy following endoscopic sinus surgery for AFS did not cause harm. Subsequently, they performed a retrospective review and found that patients who received 3 years of immunotherapy experienced a significant reduction in recurrence compared to patients who did not receive immunotherapy [52] . Marple et al. further expanded this study and followed AFS patients for at least 4–10 years and found that regardless of whether patients received immunotherapy or not, most patients were in remission [53] .

Anti-IgE

The humanized monoclonal antibody to the Fc portion of IgE, omalizumab, is currently approved for patients with severe allergic asthma. There are no reports of usage in patients with AFS, although the senior author has seen a case which responded within a week of initiating with omaluzimab. Recently, van der Ent et al. reported that a patient with ABPA responded dramatically and rapidly following a single dose of omalizumab [54] .

Other Modalities

Antibiotics have on occasion been reported to improve AFS, but there are no trials to support their use for this indication. If AFS does require the presence of a bacterial superantigen, then perhaps antibacterial therapies may have a role, but that role remains to be elucidated. If superantigen stimulation is important, the calcineurin inhibitors may have a role, as they do in atopic dermatitis, in which picrolimus and tacrolimus have proven efficacy. They have not been studied for this indication. Saline lavages remain unstudied for this condition, but have a prominent role in most physicians’ armamentarium, to be used before the application of a topical steroid. Saline irrigations are widely utilized in India for these conditions. Allergic Fungal Sinusitis 709

Discussion

In summary, our understanding of the pathophysiology of these various histopathologic forms of sinusitis characterized by eosinophilic mucin with presence or absence of fungus and IgE mediated hypersensitivity is incomplete and evolving. In 1999, noninvasive fungus was shown to be present in the majority of patients with ECRS, as well as by culture in most normals. Thus, fungal presence or fungal allergy alone is insufficient to make the diagnosis of AFS. It is the host’s eosinophilic response to these ubiquitous fungi, which leads to the clinical findings of AFS (nasal polyps, allergic mucin plugs, characteristic double densities radiographically). It is likely that the inflammatory cascade which leads to AFS is a multifactorial event, requiring IgE mediated sensitivity (atopy), specific T-cell HLA receptor expression, exposure to specific fungi, disruption of local mucosal defense mechanisms, and possibly co-stimulation with bacterial superantigens.

References

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Toluwalope O. Makinde , Againdra K. Bewtra , and Devendra K. Agrawal

Abbreviations

g d T-cell Gamma-delta T-cell NKT cells Natural killer T-cell

TH 1 Helper type-1 T-cell

Treg cells T-regulatory cell.

Introduction

There has been an increased prevalence and severity of asthma in recent decades. This increase in episodes of allergic asthma has been more evident in westernized nations where most infectious diseases have been markedly reduced by early immunization programs and extensive use of antibiotics [1] . Better diagnosis and exposure to conventional allergens have not been able to sufficiently explain the increased incidence of asthma. A substantial shift in genome does not occur in the span of only a few decades, and so genetic predisposition has also been ruled out as a major factor contributing to the observed increase in atopic diseases [1] . Paradoxically, several investigators have observed an inverse relationship between

T.O. Makinde Department of Biomedical Sciences , Creighton University School of Medicine , CRISS II , Room 510, 2500 California Plaza , Omaha , NE 68178 , USA A.K. Bewtra Department of Internal Medicine , Creighton University School of Medicine , CRISS II , Room 510, 2500 California Plaza , Omaha , NE 68178 , USA D.K. Agrawal () Departments of Medical Microbiology and Immunology, Biomedical Sciences, and Internal Medicine, Creighton University School of Medicine , CRISS II , Room 510, 2500 California Plaza , Omaha , NE 68178 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 713 DOI 10.1007/978-4-431-99362-9_43, © Springer 2010 714 T.O. Makinde et al. atopic diseases, such as asthma, and exposure to infectious pathogens including Mycobacterium bacilli [2] . Many immune cells and mediators contribute to the development and exacerbation of allergic response and asthma. It is, therefore, not surprising to see the development of numerous drugs to combat the disease. None of these therapies has a curative effect and there still remains a cohort of patients who are unresponsive to these treatments [3] . This warrants continued research in this area to develop more effective therapeutic approaches with minimal side effects to control this debilitat- ing disease. In the following sections, we critically reviewed the role of BCG in preventing a T helper (TH ) 2 response, its effect on immune cells, and its efficacy as a potential therapeutic agent to control allergy and asthma.

Hygiene Hypothesis

According to the “hygiene hypothesis,” the relative lack of infections early in life could promote the development of allergic diseases in genetically predisposed individuals [4] . However, it is important to note that not all infectious diseases contribute to the observed decrease in atopic conditions. For instance, respiratory syncytial virus (RSV) infection in early childhood may increase the risk for subsequent allergen sensitization and asthma [5] . Microbial infections that stimulate cell-mediated immune response are likely candidates for the inhibitory effect in the development of allergy and asthma.

Bacillus Calmette-Guérin

Bacillus Calmette-Guérin (BCG) is a live, genetically attenuated strain of Mycobacterium bovis ( M. bovis ), a bacterium that causes tuberculosis (TB)-like disease in cows. This vaccine was developed in the early part of the twentieth century and is still used as the primary means of immunization against TB. This vaccine is a strong inducer of T H1 immune response, and also activates cytotoxic T-cells and natural killer (NK) cells [2] .

Therapeutic Effects of BCG

BCG-vaccinated children experienced a significant decrease in overall mortality when compared to children that were not vaccinated with BCG. BCG vaccine- induced prevention of TB deaths is an insufficient explanation for this decrease in mortality [6] . Apart from its use as a TB vaccine, BCG also has proven therapeutic efficacy and applications in several other diseases such as HIV and cancer [7– 9] . BCG and Immunomodulation 715

Of relevance to this chapter is the protective role of BCG against the development of allergic and asthmatic response.

BCG in Allergy and Asthma

Analysis of the health records of children in Guinea-Bissau, West Africa, showed that early BCG vaccination of children in this region significantly reduced their susceptibility to atopic diseases [10] . However, this protective effect was most evident in children who were vaccinated during the first weeks of life, indicating the importance of an early intervention for inducing its protective effect [11] . This theory is not supported by an epidemiological study conducted in Denmark where no correlation was observed between the age of BCG vaccination and the risk of asthma development [12] . Neonatal vaccination with BCG induced a protective effect that lasted up to 14 years postvaccine administration, suggesting that the neonatal conditioning of the immune response may have a long term effect [13, 14] . Consistent with several other findings in experimental animals, we have also shown that BCG and M. vaccae , both have a protective effect on ovalbumin (OVA)-induced bronchoconstriction, bronchoalveolar lavage eosinophilia, airway hyperresponsiveness, and IL-4 production in a murine model [15] . IL-12 level is increased after BCG vaccination. However, endogenous IL-12 may contribute to airway eosinophilia [16] . Thus, it is unclear whether the protective effect of Mycobacterium in allergy and asthma is indeed via increase in IL-12 levels and warrants further investigation. In our subsequent study, BCG administration reversed established late allergic response without affecting early allergic response, BAL fluid IL-4 levels, or antigen-specific IgE level [17] . Although a previous study showed that the systemic administration of BCG also lowered antigen-specific IgE level [18] , others have observed results similar to ours [19] . These findings suggest that along with its preventive role BCG may also have a therapeutic effect in allergic asthma.

Factors Regulating Efficacy of BCG as an Anti-Asthma Therapy

There is significant discrepancy in the observations, both in clinical and experimental models, on the efficacy and duration of the effect of BCG as an anti-allergic or anti-asthmatic vaccine [13, 14] . Furthermore, the efficacy observed in many animal models has not been convincingly reproduced in humans. This could be due to many factors that might regulate the effect of BCG. The efficacy of BCG vaccine- induced tolerance was found to be most effective when administered very early in life [11– 13] . Prior exposure of the child to mycobacterial antigens [20] , genetic predisposition [21] , BCG strain [8] , dosage [22] , and route of administration [23] all play significant roles in the efficacy of BCG therapy. 716 T.O. Makinde et al.

BCG-Induced Immunoregulation and Airway Remodeling

Neonatal BCG vaccination attenuated inflammation and mucus production in a murine asthmatic model [24] . In our laboratory, although BCG suppressed AHR and inflammation, we did not observe a significant effect on subepithelial fibrosis [25] . It is, however, surprising that although there is proven efficacy for BCG-induced protective effect against allergy and asthma, a recent study found that BCG-induced apoptosis in BEAS-2B cells [26] . Another study found that BCG-induced human b -defensin-2 mRNA in airway epithelial cells [27] . The defensins are components of the innate immune system, and bridge innate and acquired immune responses by recruiting dendritic cells (DCs) and T-cells to the sites of microbial infection [27] . Thus, more studies are required to fully establish the role of BCG in chronic asthma.

TH 1/TH 2 Concept

TH 2 cells produce and secret cytokines such as IL-4, IL-5, IL-9, and IL-13 and these cytokines play a central role in the development of allergic reaction and airway hyperresponsiveness. On the other hand, TH 1 cytokines, including IL-2, IFN- g , and

TNF- b , support cell-mediated immunity [28] . A predisposition to a TH 1 response would prevent the development of allergic response in the form of atopy that is associated with a TH 2 response (Fig. 1 ) [2] .

PLASMA PLASMA MEMBRANE MEMBRANE STAT3 IL-10 R IL-10 Secretion Cytokines NFκB ?

TLR2/CD14 IL-10

IL-12 TH2 Cell In IL-4 milieu IL-4 BCG BCG TReg Cell In IL-10 milieu IL-10 antigen TCR MHC II IFN-γ TH1 Cell In IL-12 milieu IL-12 Secretion IFN-γ IL-12R IFN-γ Secretion

Inhibits IL-4 production IFN-γR Inhibits IL-4 production NAÏVE T CELL DENDRITIC CELL OR MACROPHAGE

Fig. 1 Differentiation of naïve T-cell into TH 1, T reg or T H 2 depending on the cytokine milieu.

IL-12 and IFN-g secretion from dendritic cells (DCs) or macrophages support a TH 1 polarization.

IL-10 secretion supports a Treg response, and IL-4 milieu supports a T H 2 response. Both IL-10 and

IFN- g would inhibit production of IL-4, hence block TH 2 response BCG and Immunomodulation 717

In Japan, children with positive TB bacilli skin test, induced by BCG vaccination at birth, had reduced incidence of allergy and asthma [29] . Also, children with a positive delayed hypersensitivity tuberculin skin test response had serum cytokine concentrations suggestive of a predominant TH 1 response, in contrast to the TH 2 cytokine profile seen in children with a negative tuberculin skin test [29] . In another study,

BCG vaccination at birth induced a memory-like TH 1 immune response [30] .

Growing Skepticism on the TH 1/TH 2 Concept

Although there is evidence supporting the TH 1/TH 2 concept in the pathogenesis of allergy and asthma, recent findings refute the hypothesis. Elevated levels of both

T H 1 and T H2 cytokines have been observed in the blood and airways of asthmatic subjects [31] . Airway hyperresponsiveness and airway inflammation (except eosinophil infiltration) enhanced by high-doses of lipopolysaccharide can be completely inhibited in the absence of TH 1 cytokine [32] . Both TH 1 and TH 2 cytokines following antigen challenge recruit endothelial cell progenitor cells in the lung and are associated with increased angiogenesis in the lung [33] . Several studies have shown BCG-induced protective effect to an atopic reaction without a clear shift toward a TH 1 response. In one of these studies, although the protective effect was accompanied by increased IFN-g levels, IL-5 remained elevated [34] . In a recent study BCG upregulated the mRNA expression of cytokines that support both T H 1 and TH 2 responses including TNF-a , iNOS, IL-6, and IL-12 from alveoli macrophages [35] . Also M. vaccae induced its protective effect against the development of a TH 2 response through a mechanism independent of IFN-g [36] .

This suggests that the TH 1/TH 2 balance in mycobacterial immunoregulation of atopic reaction may not stand alone [36] . There may be a potential role for other immune cells in the therapeutic effects of mycobacterial antigens. + + After BCG treatment, the percentage of CD4 CD25 (Treg ) cells in the peripheral blood of asthmatic mice was significantly increased. IL-10 production was also increased [37] . Interestingly, increase in CD8+ cell population, in conjunction with

T H1 cells, correlated with the protective effect of BCG [38] . The potential role of other immune cells in BCG vaccine-induced immunomodulation will be discussed in the following section.

Role of Other Immunoregulatory Cells

T reg Cells

A study in Malawian children found that apart from absence of cases of sepsis, children with BCG scar had a higher ratio of IL-10-producing to IL-4-producing T-cells, as well as a higher ratio of IL-10 producing to IL-6 producing monocytes 718 T.O. Makinde et al.

Table 1 Immunomodulatory role of cytokines in Bacillus Calmette-Guérin (BCG) vaccine- induced tolerance Cytokine Source Role in BCG protection + IFN- g T H 1cells, g d T-cells, and CD8 Suppress T H 2 cytokine release T-cells, NK, NKT + + TGF- b T reg cells (CD4 CD25 cells) Context-based immune activation or alteration + + IL-10 T reg cells (CD4 CD25 cells) Inhibits cytokine release to support

both T H 1 and T H 2 response

IL-12 APCs Enhances T H 1 polarization

in their blood compared to children without BCG scarring [39] . A recent study found that BCG administration enhanced the generation of Treg cells and IL-10 production [40] . In another study, heat-killed M. vaccae administration induced the generation of T reg cells. Several studies, including studies in our laboratory have found that T reg have an immunomodulatory effect in preventing the overt inflammation that is associated with a TH 2 response (Fig. 1 ) [41] . A study found that BCG- treated DCs enhanced the production of IL-12 and IL-10. However, it did not suppress the production of IL-5, a T H2 cytokine [42] . Another recent study found that DCs matured in the presence of BCG showed enhanced IL-10 and diminished IL-12 production. The same DCs primed naïve T-cells to develop into IL-10- producing T-cells, with no T H 1 or TH 2 bias [43] . Tregs can suppress allergic T H 2 response either by cell–cell contact or by secretion of mediators such as TGF-b and IL-10, both of which can function as anti-inflammatory cytokines [44] [Table 1 ]. TGF- b can activate or alter the immune system depending on experimental model and the micro-environment [45] .

CD8+ T-Cells

BCG vaccination of human newborns induced a specific, functional CD8+ T-cell response. Specific MHC class restricted CD8 + T-cells capable of producing IFN- g , TNF- a , and perforin have been found in the peripheral blood of BCG-vaccinated persons (Fig. 2 ) [46, 47] . Although T-cells, NK cells, and macrophages produce IFN- g , CD4+ and CD8 + are considered to be the primary sources of IFN- g , with CD4 + T-cells being more important than CD8 + T-cells [48, 49] . Nonetheless, CD8+ T-cell is still a significant player in mycobacterial immunoregulation. Deficiency in CD8+ T-cells results in decrease in host defense against mycobacterial infection [49– 51] . Vaccination of human newborns with BCG induces a specific CD8+ T-cell response, although it was quantitatively smaller than the BCG-induced CD4+ T-cell response [52] . In this study, BCG increased production of IFN-g and cytotoxic proteins from CD8 + T-cells [52] . BCG can also induce the generation of memory CD8 T-cells that produced IFN-g [53] . BCG and Immunomodulation 719

BCG Vaccination

APC IL-12, 1L-4, 1L-10, TGF-β

Activates

? + ? + ? T o NKT ? T o γδ CD8 TRCD8 H TRNKT H NK T cell

? ?

γ γ IFN-γ IL-10 IFN-γ IL-10 IFN- IFN-

Promotes TH1 Promotes TReg response response

Fig. 2 Bacillus Calmette-Guérin (BCG) vaccination leads to activation of antigen presenting cells (APC) and subsequent cytokine release with enhanced production of IL-10 and IFN-g from + + CD8 , TR CD8 , NKT, TR NKT, NK, g d-T cells. These cytokines promote either a TH 1 or Treg response g d -T Cells

g d -T cells are important component of the innate and adaptive immune response. After exposure to pathogens, g d-T cells proliferate robustly, producing cytokines, and effector molecules important for inhibiting the proliferation of intracellular pathogens [54, 55] . g d-T cells can mediate both positive and negative immunoregulatory effects [56] . g d-T cells are enriched in epithelial surfaces and mount potent, early responses to invading pathogens. g d-T cells provide a nonredundant early source of IFN-g , which enhances IL-12 production by DCs, leading to conditioning of the immune system away from a TH 2 response (Fig. 2 ). g d-T cells respond to antigen presented by antigen presenting cells (APCs) but are not restricted by conventional MHC class I or class II [57, 58]. Apart from secretion of IFN- g , g d -T cells also express several chemokines and chemokine receptors that enable them to migrate to epithelial surface to recruit other immune cells [54, 59, 60] . BCG vaccination enhances human g d -T cell responsiveness to mycobacteria suggestive of a memory cell-like phenotype [20] . g d -T cells also provided helper function for Mycobacterium -specific CD4 + and CD8+ T-cells [20] . g d -T cells depletion inhibited CD4 + and CD8+ T-cell expansion, but did not prevent IFN-g production [20] . CD4+ T-cells provide important helper function for the expansion of g d -T cells induced by mycobacterial extract, suggesting interdependence between the two [55, 61] . In the absence of CD4+ T-cells, IL-2 was able to induce g d -T cell expansion. This suggests that IL-2 secretion from CD4+ T-cells may have been 720 T.O. Makinde et al.

responsible for g d-T cells expansion [61] . This may also suggest a link between T H 1 cells that produce high amount of IL-2 and g d -T cells.

NKT Cells

BCG vaccination induced IL-21 expression by human peripheral blood mononuclear cells (PBMCs) in, at least in part, NKT cell-dependent fashion [62] . BCG-activated PBMCs significantly reduced IgE production by human B cells [62] . Another study observed a change in the density of CD4+ NKT cells following BCG injection and shift in their cytokine production from IL-4 to IFN-g (Fig. 2 ) [63] . However, BCG induced an early expansion of V a14-NKT cells in the liver, lungs, and spleen in murine model. These NKT cells initially produced IFN- g but change in NK1.1 expression led to subsequent shift to IL-4 production [64] . Reports from another study suggest that while NKT cells contribute to IFN-g secretion, the expansion in IFN- g producing T-cells is essentially responsible for the increased level of IFN-g observed following BCG injection [65] .

Antigen Presenting Cells

DCs and macrophages both function in antigen presentation and contribute to the cytokine milieu after a mycobacterial infection [2] . Depletion of macrophage in

OVA-sensitized mice led to decreased production of TH 1 cytokines particularly

IFN- g and increased production of TH 2 cytokines including IL-4 and IL-5 [66] . DCs matured in the presence of BCG exhibited an increase in IL-10 production and diminished IL-12 production. These DCs further primed naïve CD4+ T-cells to develop into IL-10 producing T-cells [43] . The expression of CD80, CD86, CD40, IL-12, and IL10 was upregulated in BCG-treated DCs, although IL-5 production was not suppressed [42] . This is consistent with other findings according to which BCG interaction with DCs results in direct cell maturation and activation, with increased production of cytokines including IL-12 and IL-10 [67– 69] . IL-12 induces TH 0-cells for increased production of IFN-g and decreased production of IL-4 and IL-5 [70] . IL-10 is an anti-inflammatory cytokine and it inhibits the secretion of cytokines, including IL-12 [67, 71] .

Role of NRAMP and TLRs

NRAMP1

Natural resistance-associated macrophage protein 1 gene (Nramp1 ) encodes antibacterial resistance and has been linked to increased risk of atopic reaction [72] . Nramp1-resistant mice had macrophages that were somewhat activated under resting BCG and Immunomodulation 721 condition, and therefore showed a high resistance to intracellular pathogens. Nramp1 gene encodes a membrane protein involved in cation transport [73] . Nramp1 influences the efficacy of mycobacterial treatment in allergy and asthma [74] . NRAMP1 affects both T-cell-mediated responses and macrophage activation [74] . Nramp1 has been associated with IL-10 production, suggesting a link with Treg activity [73] . Following OVA sensitization and challenge, Nramp1 resistant mice showed lower levels of T h 2 cytokines, IgE, and mast cell granules compared to congenic Nramp1 susceptible mice [73, 75] .

Toll-Like Receptors

Toll-like receptors (TLRs) are expressed both on T-cells and APCs [76, 77]. Leukocyte cells from a farmer’s children expressed significantly higher amount of mRNA encoding for TLR2 and CD14 than those from nonfarmers [78] . TLR2 activation leads to release of inhibitory IL-12 p40 dimers and IL-23. IL-23 pro- low motes the proliferation of CD45RB T-cells, which might include Treg cells [79] . TLRs are involved specifically in the recognition of the bacteria. Mycobacteria tend to activate TLR2s, an interaction that is facilitated by CD14 [80] . Under in vitro conditions BCG can induce maturation of DCs by activating the TLRs present on DCs [81, 82] . Additionally, BCG infection also enhanced migration of DCs via TLRs to mediastinal lymph nodes, where they can engage in a robust activation of naive T-cells [83] . Depending on the level of TLR activation, DCs can induce the production of IL-12 [84] . On the other hand, TLR-mediated signaling leads to the release of CC chemokines and eotaxin, which then recruit eosinophils [85] .

Conclusion

Experimental and clinical studies show significant efficacy of BCG in the prevention and therapeutic application in atopic diseases. BCG can activate various cells, leading to the secretion of several mediators including IL-12, IL-10, IFN-g , and under certain circumstances TH 2 cytokines. The surrounding cytokine milieu is important in determining the direction of the allergen-specific immune response. Thus, depending on the type of cell first encountered and the micro-environment, the protective and the therapeutic effect of BCG could be modulated to induce T H 1 and T reg cells. There is renewed effort in the development of recombinant BCG strains that promote the secretion of pro-T H 1 cytokine like IL-12 and IL-18. Indeed, a recombinant BCG strain expressing human IL-12 protein was successfully constructed [86] . Also, recombinant BCG expressing mouse IL-18 showed a synergistic effect on BCG induction of IFN-g , GMCSF, and decreased production of IL-10 in splenocytes [87] . 722 T.O. Makinde et al.

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Akihiro Morikawa

Introduction

Theophylline and sodium cromoglycate are old drugs used in the treatment of asthma, but in some patients, they are still useful for maintenance therapy. Theophylline is not only a bronchodilator, but also has anti-inflammatory effects [1] due to multiple mechanisms including adenosine receptor antagonism and epigenetic influences over inflammatory gene expression both of which occur at lower concentrations (5–10 µm ml-1 ). In Japan, slow release theophylline is still used as a controller therapy except in infants with asthma [2] . Sodium cromoglycate produces only minimal side effects and is also used as a controller in persistent asthma, especially in infantile asthma.

Theophylline

Pharmacological Properties

Physiological Effects

Theophylline was first introduced into asthma therapy as a bronchodilator, and an increasing acute bronchodilator response was shown in early dose–response studies. Theophylline directly relaxes human airways smooth muscle in vitro and, like b 2-agonists, acts as a functional antagonist, preventing and reversing the effects of all bronchoconstrictor agonists [3] . Theophylline may also have an additional effect on mucociliary clearance through a stimulatory effect on ciliary beat frequency and

A. Morikawa () Kitakanto Allergy Institute, Kibounoie Hospital 22-4 ohmama, ohmama-machi, Midori, Gunma 376-0101, Japan e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 727 DOI 10.1007/978-4-431-99362-9_44, © Springer 2010 728 A. Morikawa water transport across the airway epithelium [4] . Aminophylline, theophylline derivative, increases diaphragmatic contractility and reverses diaphragm fatigue, although an effect of theophylline on respiratory muscles remains unclear [5] .

Anti-Inflammatory Effects

There is an increasing evidence that theophylline has anti-inflammatory effects in asthma [6] . In patients with asthma, intravenous theophylline inhibits the late response to allergen challenge [7] . A reduced infiltration of eosinophils and CD4+ lymphocytes into the airways were observed after allergen challenge subsequent to theophylline, suggesting an inhibitory effect of theophylline on the chronic inflammatory response [8, 9] . In patients with mild asthma, theophylline reduced the numbers of eosinophils in bronchial biopsies, bronchoalveolar lavage, and induced sputum [10] . These anti-inflammatory effects of theophylline in asthma are seen at concentrations around 5 m g ml-1 , which is below the dose (10–20 m g ml -1 ) wherein significant clinically useful bronchodilatation is evident.

Molecular Mechanisms of Theophylline Effects

PDE Inhibition

The molecular mechanism of bronchodilatation is likely explained by phosphodiesterase (PDE) inhibition, resulting in an increase in cAMP by inhibition of PDE3, PDE4, and in cyclic guanosine 3’, 5’-monophosphate by inhibition of PDE5, but relatively high concentrations are needed for maximal relaxation [11] . Indeed, therapeutic concentrations of theophylline exhibit only 5–10% inhibition of total PDE activity in human lung extracts [12] . Theophylline has no selectivity for any particular isoenzyme, such as PDE4, which is the predominant PDE isoenzyme in inflammatory cells that mediates anti-inflammatory effects in the airways.

Adenosine Receptor Antagonism

Theophylline is a potent inhibitor of adenosine receptors at therapeutic concentrations, with antagonism of A1- and A2-receptors [13] . In an in vitro study, adenosine constricts airway smooth muscle of patients with asthma via the release of histamine and leukotrienes, suggesting that adenosine releases mediators from sensitized mast cells [14] . Inhaled adenosine monophosphate causes bronchoconstriction in subjects with asthma, and this is prevented by therapeutic concentrations of theophylline [15] . However, this does not necessarily prove that adenosine receptor antagonism is important for its antiasthma effect. Use of Theophylline and Sodium Cromoglycate in Pediatric Asthma 729

Other Effects

Selective maxi-K channels inhibitor, charybdotoxin, reduces bronchodilator effect of theophylline in human airways, suggesting that theophylline opens these maxi-K channels via an increase in cAMP [16] . Several other effects of theophylline have been described, including an increase in circulating catecholamines, inhibition of calcium influx into inflammatory cells, inhibition of prostaglandin effects, promotion of apoptosis of T-lymphocytes, release of interleukin-10, antagonism of tumor necrosis factor-alpha, and prevention of the translocation of the proinflammatory transcription factor nuclear factor-k B into the nucleus [17] . These effects may be mediated via PDE inhibition, although this has not been seen at the low doses that are effective in asthma.

Therapeutic Use

Although the efficacy of theophylline is less than that of inhaled glucocorticosteroids, theophylline has been shown to be effective as add-on treatment to inhaled glucocorticosteroids in children older than 5 years. It is significantly more effective than placebo at controlling day and night symptoms and improving lung function [18– 20] . Add-on treatment with theophylline has been found to improve asthma control and reduce the maintenance glucocorticosteroid dose necessary in children with severe asthma treated with inhaled or oral glucocorticosteroids [21, 22] . Maintenance treatment offers a marginal protective effect against exercise-induced bronchoconstriction [23] . A few studies in children of 5 years and younger also suggest some clinical benefit. Most clinical evidence regarding the use of theophylline in children has been obtained from studies in which plasma theophylline levels were maintained within the therapeutic range of 5–10 m g ml-1 . Sustained-release products are preferable for maintenance therapy, since they enable twice-daily dosing. Plasma theophylline concentrations should be measured, when doses more than 10 mg kg-1 /day are used. The Japanese Pediatric Guidelines (JPGL) 2005 guidelines for asthma recommend that slow-release theophylline can be used as an add-on therapy to patients not controlled by low doses of inhaled corticosteroids in children older than 5 years [24] . Several clinical studies have demonstrated that adding theophylline to inhaled corticosteroids in patients with mild to moderate asthma who are not controlled gives equivalent or better asthma control than doubling the dose of inhaled corticosteroids [25– 27] . Although long-acting inhaled b 2-agonists are more effective as an add-on therapy, theophylline is still useful in the management of severer patients at Steps 3 and 4 of the JPGL2005 guidelines [24] . Its benefits have been demonstrated by clinical improvement after addition of theophylline in patients not controlled even on high doses of inhaled corticosteroids [28] . 730 A. Morikawa

In the management of acute severe asthma, intravenous aminophylline has been superseded by the use of high doses of short-acting b 2-agonists delivered by nebulizer or metered dose inhaler with spacer, as this is more effective and safer. The JPGL 2005 guidelines recommend that drip infusion of intravenous aminophylline is usually reserved for children 2 years and older with severe exacerbations who do not respond adequately to b 2-agonist therapy [24] .

Epigenetics

Acetylation of core histones is associated with activation and transcription of inflammatory genes and is regulated by coactivator molecules that have intrinsic histone acetytransferase activity [29] . Proinflammatory transcription factors, such as nuclear factor-k B and activator protein-1, bind to coactivator molecules and activate this enzyme. In asthmatic airways, there is an increase in nuclear factor-B activation and an increase in histone acetyltransferase activity. Histone acetylation is reversed by histone deacetylases (HDAC), and there is a reduction in HDAC activity in asthmatic airways [30] . Theophylline activates HDAC activity and therefore suppresses the expression of inflammatory genes [31] . This effect is seen at therapeutic concentrations of theophylline (10.6–10.5 M) but is lost at higher concentrations (10.4 M). The effect is blocked by the HDAC inhibitor trichostatin A. A significant increase in HDAC activity is seen in bronchial biopsies after treatment of patients with asthma with low doses of theophylline (mean plasma concentration – 5 m g ml -1 ). It is not yet certain whether HDAC are the direct target of theophylline as several other nuclear proteins are coprecipitated in these inflammatory gene complexes [32] . The mechanism whereby low concentrations of theophylline activate HDAC are not yet known, but it is not mediated by either PDE inhibition or adenosine receptor antagonism because PDE inhibitors (nonselective, PDE4 and PDE3 inhibitors) and adenosine A1- and A2-receptor antagonists do not mimic this action of theophylline. Low concentrations of theophylline markedly potentiate the anti-inflammatory effects of corticosteroids in vitro, with a potentiation of 100-fold to 1,000-fold [31] , and this may underlie the benefit of low-dose theophylline added to low or high doses of inhaled corticosteroids seen in clinical studies of patients with asthma.

Sodium Cromoglycate

Introduction

A histamine antagonist is useful for controlling symptoms of immediate allergic reactions, but only partially effective in bronchial asthma, allergic rhinitis, and Use of Theophylline and Sodium Cromoglycate in Pediatric Asthma 731 atopic dermatitis. The reasons why an inhibitor of histamine is only partially effective are that many kinds of chemical mediators contribute to the inflammatory processes underlying these diseases. An attractive and advantageous procedure to prophylaxis is to prevent production or release of many kinds of chemical mediators by inhibiting response of mast cells and basophils sensitized to specific antigen. The first anti-allergic drug is sodium cromoglycate. This agent mainly inhibits antigen-induced release of histamine from human pulmonary mast cells [33] . However, there is no report about sodium cromoglycate and nedocromil from the viewpoint of epigenetics.

Pharmacological Properties

Sodium cromoglycate, the disodium salt of 1, 3-bis (2-carboxychromone -5-yloxy)- 2-hydroxy-propane, is the following structure shown in Fig. 1a . Sodium cromoglycate was synthesized first as the smooth muscle relaxant from a chromone benzopyrone of plant origin (Ammi visnaga). After some modification, it was revealed that sodium cromoglycate has a novel mechanism of action, namely, inhibition of release of histamine and other autacoids. Furthermore, it has been recently demonstrated that sodium cromoglycate inhibits the release of tumor necrosis factor a (TNF- a) from rat mast cells [34] . In addition, it also inhibits IL-5 and TNF- a production from human lung specimens, suggesting that it acts as an anti- inflammatory drug [35] . Nedocromil, a compound with a similar chemical and

a NaOOC O O COONa

O OCH2CHCH2O O OH CROMOLYN SODIUM b H3CCH2 CH2CH2CH3 NaOOC N O COONa

O O NEDOCROMIL SODIUM Fig. 1 Structure of cromolyn and nedocromil 732 A. Morikawa biological property, became available and proved the efficacy [36] . Nedocromil sodium is the following structure shown in Fig. 1b. It is generally more effective than sodium cromoglycate in animal model and human beings.

Pharmacologic Effects

Sodium cromoglycate inhibits the release of histamine and other autacoid, e.g., leukotriene, from sensitized human lung during IgE mediated allergic responses. This effect is not likely to be restricted to the antigen-antibody reaction. It can be observed when tested with other secretagogues such as compound 48/80, dextran, phospholipase A, and calcium ionophore A23187. Recently, several anti-allergic drugs including glucocorticosteroid, anti-leukotriene receptor antagonist, and sodium cromoglycate have been used for the treatment of asthma. The major mechanism of anti-inflammatory action of glucocorticosteroid is inhibition of cytokine production by T-lymphocytes. Whether sodium cromoglycate has the same mechanism as glococorticosteroid or not is unclear. Matsuse et al. reported the inhibitory effects of sodium cromoglycate on antigen-induced cytokine production by peripheral blood mononuclear cells from patients with atopic asthmatics in vitro. They concluded that sodium cromoglycate has antigen-specific anti-allergic inflammatory effects [37] .

Absorption, Fate and Excretion

Sodium cromoglycate is very poorly absorbed after oral administration and inhalation. By inhalation, only about 10% amount of sodium cromoglycate penetrates deep into the lungs and is absorbed into the blood, where its half-life is about 80 min. This drug is not metabolized and is exerted unchanged, about half in the urine and half in the bile [38] .

Toxicity

Sodium cromoglycate, generally, is well tolerated by patients, and adverse reactions are infrequent. Sometimes, dizziness, dysuria, joint swelling and pain, nausea, headache, and rash are encountered. Such reactions have been reported at a frequency of less than 1 in 10,000 patients. Very rare instances including laryngeal edema, angioedema, urticaria, and anaphylaxis also have been documented. The safety of sodium cromoglycate for use during pregnancy was established by Kaiser Study [38] . Use of Theophylline and Sodium Cromoglycate in Pediatric Asthma 733

Therapeutic Use

The main use of sodium cromoglycate is in the prophylactic treatment of bronchial asthma. Clinical efficacy of sodium cromoglycate is well established in patients with mild to moderate asthma [39] . It is noted that although sodium cromoglycate is effective in all patients, younger patients tend to respond better than adult. Pediatric studies of sodium cromoglycate from 1970s to 1980s focused on comparison with theophylline, which at the time was the drug of first choice in USA for treating children with asthma [40] . Sodium cromoglycate inhibits both immediate and late asthmatic responses when challenged with antigen or exercise. Both sodium cromoglycate and nedocromil prevent exercise-induced bronchoconstriction in children and adult [41, 42] . Furthermore, combination of nebulized sodium cromoglycate and beta-2 agonist twice-daily gave good control of symptoms in children with severe, intractable asthma [43] . In 1980s, it is revealed that the pathophysiology of bronchial asthma is the chronic inflammation of the airway [44] . Inhaled glucocorticosteroids are currently the most effective anti-inflammatory medications for the treatment of asthma. An anti-inflammatory effect of sodium cromoglycate and nedocromil is weak, and these drugs are less effective than a low dose of inhaled glucocorticosteroid in both adult and children [45] . For this reason, the role of these drugs in long-term treatment of asthma in adult and children is limited. Because of limited efficacy, sodium cromoglycate is not recommended for the treatment of asthma in the GINA guideline 2006 [46] . However, nedocromil may allow a reduction of steroids in patients receiving high doses of inhaled glucocorticosteroids. In addition, sodium cromoglycate is very safe and attenuate bronchospasm induced by exercise or cold air.

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8. Sullivan P, Bekir S, Jaffar Z, Page C, Jeffery P, Costello J. Anti-inflammatory effects of low- dose oral theophylline in atopic asthma. Lancet 1994; 343:1006–1008 9. Jaffar ZH, Sullivan P, Page C, Costello J. Low-dose theophylline modulates T-lymphocyte activation in allergen-challenged asthmatics. Eur Respir J. 1996; 9:456–462 10. Kraft M, Torvik JA, Trudeau JB, Wenzel SE, Martin RJ. Theophylline: potential anti- inflammatory effects in nocturnal asthma. J Allergy Clin Immunol. 1996; 97:1242–1246 11. Rabe KF, Magnussen H, Dent G. Theophylline and selective PDE inhibitors as bronchodilators and smooth muscle relaxants. Eur Respir J. 1995; 8:637–642 12. Poolson JB, Kazanowski JJ, Goldman AL, Szentivanyi A. Inhibition of human pulmonary phosphodiesterase activity by therapeutic levels of theophylline. Clin Exp Pharmacol Physiol. 1978; 5:535–539 13. Pauwels RA, Joos GF. Characterization of the adenosine receptors in the airways. Arch Int Pharmacodyn Ther. 1995; 329:151–156 14. Bjorck T, Gustafsson LE, Dahlen SE. Isolated bronchi from asthmatics are hyperresponsive to adenosine, which apparently acts indirectly by liberation of leukotrienes and histamine. Am Rev Respir Dis. 1992; 145:1087–1091 15. Feoktistov I, Polosa R, Holgate ST, Biaggioni I. Adenosine A2B receptors: a novel therapeutic target in asthma? Trends Pharmacol Sci. 1998; 19:148–153 16. Miura M, Belvisi MG, Stretton CD, Yacoub MH, Barnes PJ. Role of potassium channels in bronchodilator responses in human airways. Am Rev Respir Dis. 1992; 146:132–136 17. Tomita K, Chikumi H, Tokuyasu H, Yajima H, Hitsuda Y, Matsumoto Y, Sasaki T. Functional assay of NF-kappaB translocation into nuclei by laser scanning cytometry: inhibitory effect by dexamethasone or theophylline. Naunyn Schmiedebergs Arch Pharmacol. 1999; 359:249–255 18. Katz RM, Rachelefsky GS, Siegel S. The effectiveness of the short- and long-term use of crystallized theophylline in asthmatic children. J Pediatr. 1978; 92(4):663–667 19. Bierman CW, Pierson WE, Shapiro GG, Furukawa CT. Is a uniform round-the-clock theophylline blood level necessary for optimal asthma therapy in the adolescent patient? Am J Med. 1988; 85(1B):17–20 20. Pedersen S. Treatment of nocturnal asthma in children with a single dose of sustained-release theophylline taken after supper. Clin Allergy. 1985; 15(1):79–85 21. Nassif EG, Weinberger M, Thompson R, Huntley W. The value of maintenance theophylline in steroid-dependent asthma. N Engl J Med. 1981; 304:71–75 22. Brenner M, Berkowitz R, Marshall N, Strunk RC. Need for theophylline in severe steroid- requiring asthmatics. Clin Allergy. 1988; 18(2):143–150 23. Magnussen H, Reuss G, Jorres R. Methylxanthines inhibit exercise-induced bronchoconstriction at low serum theophylline concentration and in a dose-dependent fashion. J Allergy Clin Immunol. 1988; 81(3):531–537 24. Morikawa A, Nishima S. Japanese Pediatric Allergology. The Japanese Pediatric Guidelines (JPGL) 2005. Kyowa Kikaku, Tokyo, 2005 25. Evans DJ, Taylor DA, Zetterstrom O, Chung KF, O’Connor BJ, Barnes PJ. A comparison of low-dose inhaled budesonide plus theophylline and high-dose inhaled budesonide for moderate asthma. N Engl J Med. 1997; 337:1412–1418 26. Ukena D, Harnest U, Sakalauskas R, Magyar P, Vetter N, Steffen H, Leichtl S, Rathgeb F, Keller A, Steinijans VW. Comparison of addition of theophylline to inhaled steroid with doubling of the dose of inhaled steroid in asthma. Eur Respir J. 1997; 10:2754–2760 27. Lim S, Jatakanon A, Gordon D, Macdonald C, Chung KF, Barnes PJ. Comparison of high- dose inhaled steroids, low dose inhaled steroids plus low dose theophylline, and low dose inhaled steroids alone in chronic asthma in general practice. Thorax 2000; 55:837–841 28. Rivington RN, Boulet LP, Cote J, Kreisman H, Small DI, Alexander M, Day A, Harsanyi Z, Darke AC. Efficacy of slow-release theophylline, inhaled salbutamol and their combination in asthmatic patients on high-dose inhaled steroids. Am J Respir Crit Care Med. 1995; 151:325–332 29. Urnov FD, Wolffe AP. Chromatin remodeling and transcriptional activation: the cast (in order of appearance). Oncogene 2001; 20:2991–3006 Use of Theophylline and Sodium Cromoglycate in Pediatric Asthma 735

30. Ito K, Caramori G, Lim S, Oates T, Chung KF, Barnes PJ, Adcock IM. Expression and activity of histone deacetylases (HDACs) in human asthmatic airways. Am J Respir Crit Care Med. 2002; 166:392–396 31. Ito K, Lim S, Caramori G, Cosio B, Chung KF, Adcock IM, Barnes PJ. A molecular mechanism of action of theophylline: induction of histone deacetylase activity to decrease inflammatory gene expression. Proc Natl Acad Sci USA 2002; 99:8921–8926 32. Ito K, Barnes PJ, Adcock IM. Glucocorticoid receptor recruitment of histone deacetylase 2 inhibits IL-1b -induced histone H4 acetylation on lysines 8 and 12. Mol Cell Biol. 2000; 20:6891–6903 33. Altounyan, REt C. Inhibition of experimental asthma by new compound, disodium cromoglycate, “Intal”. Acta Allergol (Kbh), 1968; 51:677–693 34. Bissonette EY, Enciso JA, Befus AD. Inhibition of tumor necrosis factor-alpha (TNF-alpha) release from mast cells by the anti-inflammatory drugs, sodium cromoglycate and nedocromil sodium. Clin Exp Immunol. 1995; 105:78–84 35. Matsuo N, Shimoda T, Matsuse H, Obase Y, Asai S, Kohno S.Effects of sodium cromoglycate on cytokine production following antigen stmulation of a passively sensitized human lung model. Ann Allergy asthma Immunol. 2000; 84:72–78 36. Holgate ST. Clinical evaluation of nedocromil sodium in asthma. Eur J Respir Dis Suppl. 1986; 147:149–159 37. Matsuse H, Shimoda T, Matsuo N, Obase Y, Fukushima C, Asai S, Kohno S. Sodium cromoglycate inhibits antigen-induced cytokine production by peripheral blood mononuclear cells from atopic asthmatics in vitro. Ann Allergy Asthma immunol. 1999; 83:511–515 38. Goodman LS, Gilman A. The Pharmacological Basis of Therapeutics sixth ed. Macmillan Inc., NY, 1980, 621 39. Shatz M, Zeiger KS, Berstein IL, Johson CL. Therapy with cromolyn sodium. Ann Intern Med. 1978; 89:228–233 40. Tasche MJ, Uijen JH, Bernsen RM, de Jongste JC, van den Wouden JC. Inhaled disodium cromoglycate(DSCG) as maintenance therapy in children with asthma:a systematic review. Thorax 2000; 55:913–920 41. Hambleton G,Weinberger M, taylor J, Cavanaugh M, Ginchansky E, Godfrey S, Tooley M, Bell T, Greenberg S. Comparison of cromoglycate (cromolyn) and theophylline in controlling symptomed of chronic asthma. A collaborative study. Lancet 1977; 19:381–385 42. Kelly K, Spooner CH, Rowe BH. Nedocromil sodium versus sodium cromoglycate for preventing exercise-induced bronchoconstriction in asthmatics. Cochrane Database Syst Rev. 2000; 4:CD002731 43. Spooner CH, Spooner GR, Rowe BH. Mast-cell stabilizing agents to prevent exercise-induced bronchoconstriction Cochrane Database Syst Rev. 2003; 4:CD002307 44. Furusho k, Nishikawa K, Sasaki S, Akasaka T, Arita M, Edwards A. The combination of nebulized sodium cromoglycate and salbutamol in the treatment of moderate-to-sevre asthma in children. Pediatric Allergy Immunol. 2002; 13:209–216 45. Guevara JP, Duchame FM, Keren R, Nihtianova S, Zorc J. Inhaled corticosteroids versus sodium cromoglycate in children and adult asthma. Cochrane Database Syst Rev. 2006; 19(2):CD003558 46. Busse WW, Lemanske RF, Jr. Asthma. N. Eng J Med. 2001; 344:350–362 47. Global Strategy for Asthma Management and Prevention 2006. National Institute of Health, National Heart, Lung, and Blood Institute Antibody Deficiency Syndromes (Including Diagnosis and Treatment)

Kenneth Paris , Lily Leiva, and Ricardo U. Sorensen

Introduction

Antibody deficiency syndromes range from an absence of all immunoglobulins (agammaglobulinemia) to milder, but clinically relevant, deficiencies of specific antibodies in patients with normal immunoglobulin concentrations. In clinical practice, physicians encounter many forms of antibody deficiencies that do not fit the strict criteria for each syndrome that has been defined by several expert groups in primary immunodeficiencies [1, 2]. We recognize that antibody deficiencies are the most frequently reported immunodeficiencies in different areas of the world [3] and antibody deficiencies are the most frequently encountered immunodeficiencies in clinical immunology practice. The antibody deficiencies with the least clinical impact are found at the highest frequency in the population. For example, IgA deficiency, which can be observed in asymptomatic individuals, is the most frequently encountered immunodeficiency [4] while agammaglobulinemias are relatively rare. There may be a common misconception that the less frequent severe antibody deficiency syndromes are not relevant in clinical practice. However, early diagnosis of an antibody deficiency requires awareness and a thorough evaluation and may prevent permanent sequelae from the severe infections that can occur.

Antibody-Mediated Immunity

Immunity to infection with pathogenic organisms is, in part, provided by the antibodies produced by B cells. In conjunction with the complement system, antibodies enhance the ability of polymorphonuclear cells (PMN’s) and macrophages to engulf and kill

K. Paris (), L. Leiva, and R.U. Sorensen Department of Pediatrics, Research Institute for Children 4th Floor , Louisiana State University Health Sciences Center, Children’s Hospital , 200 Henry Clay Avenue , New Orleans , LA , USA; Jeffrey Modell Diagnostic Center , Children’s Hospital , 200 Henry Clay Avenue , New Orleans , LA 70118 , USA e-mail: [email protected]

R. Pawankar et al. (eds.), Allergy Frontiers: Therapy and Prevention, 737 DOI 10.1007/978-4-431-99362-9_45, © Springer 2010 738 K. Paris et al. these microorganisms. With regards to extracellular pathogens such as Streptococcus pneumoniae, Haemophilus influenza, Staphylococcus aureus, and viruses, these antibodies can protect the host prior to infection and clinical disease. More thorough protection against intracellular pathogens is provided by cell-mediated immunity. These pathogens include viruses, mycobacteria, salmonella, fungi such as Pneumocystis jirovicii and protozoa like Toxoplasma gondii . Cellular immune function should be evaluated when infections caused by these organisms are present. Immunity is provided by the three major immunoglobulins namely IgG, IgA, and IgM each having unique characteristics which convey protection. IgM is the first isotype synthesized by B cells in response to antigen stimulation. It is a pentamer with a large size and therefore remains within the vascular space. It is produced at highest concentrations during acute infections, and helps control blood borne disease. Its half life is approximately 5–6 days and therefore it does not confer long term protection against infection. IgG, in contrast to IgM, provides long term protection. IgG is also present in the greatest concentration within the intravascular and extravascular spaces. Four subclasses of IgG are recognized – each with its own structure, function and relative concentration within the circulation [5] . IgG1 and IgG3 are the subclasses produced predominantly in response to protein antigens, whereas anti-polysaccharide antibodies are predominantly found in IgG2. IgG4 is the subclass found in the least concentration. 60–65% of the total IgG is comprised of IgG1, 20–25% is IgG2, 5–10% is IgG3 and IgG4 is 3–6%. There is a wide range of normal values for both total IgG concentrations and for each subclass. Normal values vary widely according to patient age. IgA is the only immunoglobulin which is normally secreted into body secretions, mainly in the gastrointestinal and respiratory tracts. Production of IgA usually occurs in response to antigens encountered within the lumens of those organs. The main function of secretory immunoglobulin is to prevent microbial and foreign antigens (e.g., food) from penetrating the gut, respiratory and other mucosa. IgA is critical for mucosal immunity, although in its absence, other immunoglobulins also offer this protection. Discussion of antibody deficiencies requires a brief review of B cells and the development of humoral immunity. B cells mature in an antigen independent and antigen dependent manner. Development of the B cell is dependent on various enzymes and on the production of immunoglobulin chains within the B cell. For example, the enzyme B cell tyrosine kinase is essential for the progression of development from immature to mature B cells. The early stages of development can be identified by internal expression of various immunoglobulin chains and receptors [6] . These same receptors and immunoglobulin chains are later expressed on the cell surface, and are markers for later stages of B cell maturation. The ultimate development of B cells into plasma depends on exposure to antigen. These plasma cells then secrete large amounts of specific antibodies. Additionally, the complex interaction of the B cell with CD40L on T cells initiates the switch from IgM production to IgG and IgA. Various forms of the hyper-IgM syndrome have been described where this switch does not occur, leading to high Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 739 amounts of IgM and low IgG and IgA. Memory B cells are produced after antigen exposure as well, and the immunodeficiency known as CVID is associated with a defect in production of these cells. Immunoglobulin production changes throughout the lifetime. Immunoglobulin production is lowest immediately after birth, but increases during the first years of life. Active transport of IgG across the placenta during the third trimester of pregnancy causes high IgG concentrations immediately after birth. The half-life of this maternal IgG is approximately 20–30 days, and IgG levels decrease until synthesis of IgG by the infant surpasses catabolism. This occurs sometime after 3 months of age. Exposure to new antigens stimulates the production of specific IgM and subsequently IgG and IgA. Transient hypogammaglobulinemia of infancy is thought to be a defect in this normal “maturation” of the immune system with eventual normalization of IgG levels by 2 years of age. This maturation is reflected in the development of responses to protein and polysaccharide antigens. The ability to produce antibodies to protein antigens is present at birth, while the responses to polysaccharide antigens develop during the first 2 years of life.

Clinical Aspects of Antibody Deficiency

The hallmark of antibody deficiency is recurrent infection with gram positive and encapsulated gram-negative organisms. These infections may be mild in nature, or consist of single severe infections such as pneumococcal sepsis, CNS infection or similar invasive infection. Recurrent otitis media may be the only clinical early manifestation of agammaglobulinemia, the most severe form of antibody deficiency [7] . Additionally, serious complications of routine infections such as mastoiditis (otitis media), empyema (pneumonia) or abscess (meningitis) may also signal an antibody deficiency [8] . In the congenital or transient deficiencies of infancy, it is usual for these infections to begin at approximately 4–6 months of age due to the loss of maternal IgG. Infections with specific bacteria are also a component of some antibody deficiencies. A life threatening meningoencephalitis is seen in children with x-linked agammaglobulinemia [9] . Mycoplasma infections have been described in patients with chronic pulmonary infections that were resistant to typical antibiotic therapy or who had concomitant arthritis [9] . IgA deficient patients may have recurrent Giardia lamblia infection. Autoimmunity and other blood dyscrasias are noninfectious manifestations of antibody deficiency syndromes. Both x-linked agammaglobulinemia and x-linked hyper-IgM syndrome are associated with neutropenia. Chronic thrombocytopenia has been described in some phenotypes of CVID as well. The idea that patients with antibody deficiencies appear ill is false. Most patients develop normally, likely because of long asymptomatic periods or mild disease. This is especially true of common variable immunodeficiency which may develop and become symptomatic later in life. 740 K. Paris et al.

At times, the clinical presentation of antibody deficient patients mimics allergic diseases such as asthma and allergic rhino-sinusitis. The sequelae of these diseases often provide an environment conducive for bacterial super infection, even in the immuno competent host. Therefore, patients with antibody deficiencies have been diagnosed as having allergic asthma and they have even been subjected to long periods of allergy immunotherapy because of wheezing associated with recurrent bronchitis. Antibody deficiencies may co-exist with allergies, aggravating the susceptibility to recurrent infections. In practical terms, this means that a high index of suspicion is necessary to detect the presence of antibody deficiency syndromes.

General Evaluation of Antibody-Mediated Immunity

The evaluation of the immunological phenotype of antibody deficiency syndrome is based on the results of the following tests: • Quantitative immunoglobulins (IgG, IgA, IgM, and IgE) • IgG subclass concentrations • Specific antibody titers against protein antigens including tetanus and diphtheria toxoids (and possibly H. influenzae ) • Antibody titers against pneumococcal polysaccharide antigens • Occasionally measurement of isohemagglutinins • Circulating B lymphocytes The measurement of IgG subclass concentrations is controversial since age plays an important role in defining the normal concentrations of all IgG subclasses and must always be considered in the interpretation of results. A minimum of two determinations obtained at an interval of at least 1 month is recommended before a diagnosis of IgG subclass deficiency can be confirmed. Also, the clinical relevance of an isolated IgG subclass deficiency is not well established. However, the finding of a subclass deficiency in association with either IgA deficiency or poor response to polysaccharide antigens may be indicative of the eventual development of a more serious deficiency such as CVID. Total circulating IgA is measured as part of an immunoglobulin panel including IgM, IgG, and IgA. Measuring IgA subclasses or secretory IgA is usually not necessary since it is seldom useful. Perhaps the most important part of the evaluation of humoral immunity is the determination of the ability to produce specific antibodies after natural infection with a microbial pathogen, or in response to vaccination. Diphtheria and tetanus toxoids, viral vaccines and multivalent S. pneumoniae conjugate and polysaccharide vaccines are part of the recommended immunization schedule for every child, making the response to these antigens a convenient marker for immunocompetence. Evaluation of specific antibody titers requires a careful immunization history. If antibody concentrations to one or more vaccine antigens are low and immunization Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 741 is incomplete or not recent, active immunization should be used to evaluate the antibody response. It is important to note that a “protective” antibody concentration is not the same as a normal immune response. For example, while the protective anti-tetanus antibody titer is ³ 0.1 IU ml–1 , most normal children will generate titers at least tenfold higher. A review of the assessment and clinical interpretation of polysaccharide antibody responses has recently been published by the authors and is a guide to this component of the evaluation of antibody deficiencies [10] . In short, the evaluation of the response to polysaccharide vaccines requires a precise history of prior pneumococcal immunization with both the heptavalent conjugate pneumococcal vaccine (PCV-7) and or the 23-valent pneumococcal polysaccharide vaccine (PPV). The response to pure polysaccharides can be evaluated after 2 years of age by measuring antibodies against pneumococcal serotypes present only in the pure polysaccharide vaccine (Table 1 ). Pneumococcal immunization as an evaluation tool is favored

Table 1 Comparison of pneumococcal polysaccharide serotypes found in commercially available pneumococcal vaccines Serotypes Vaccines Danish # US # PPV PCV-7 1 1 X 2 2 X 3 3 X 4 4 X X 5 5 X 6B 26 X X 7F 51 X 8 8 X 9N 9 X 9V 68 X X 10A 34 X 11A 43 X 12F 12 X 14 14 X X 15B 54 X 17F 17 X 18C 56 X X 19A 57 X 19F 19 X X 20 20 X 22F 22 X 23F 23 X X 33F 70 X PPV = 23 Valent polysaccharide vaccine PCV-7 = Heptavalent conjugate vaccine Shaded Rows = Serotypes included in PPV and PCV-7 742 K. Paris et al. because it combines the enhancement of specific immunity to these common respiratory pathogens with the evaluation for the syndrome of specific antibody deficiency. Protection against infection and even colonization has been associated with antibody concentrations ³ 1.3 µg ml–1 (or 200–300 ng of antibody N/ml) [11, 12] . When patients have received gamma globulin or other plasma products, it is possible to test for antibody responses to the neoantigen bacteriophage Phi X174 which is available at specialized centers [13] . B cell enumeration is not performed unless an abnormality in immunoglobulin concentrations is already established. B cell percentages need to be determined by flow cytometry using monoclonal antibodies against specific B cell markers (CD19, CD20). Most patients fit within one of the deficiency phenotypes listed under classification of antibody deficiencies. The measurement of immunoglobulins and specific antibodies allows the inclusion of most patients in one of the deficiency phenotypes listed under classification of antibody deficiencies. For several immunoglobulin deficiencies, e.g., mild IgG deficiencies, selective IgA deficiencies and IgG subclass deficiencies, the clinical relevance is determined by the severity and frequency of infections and by the status of specific antibodies against protein and polysaccharide antigens. For patients who do not fit well into classic deficiency phenotypes, it is best to define both the immunoglobulin and the specific antibody status, e.g., selective IgA deficiency with or without specific antibody deficiency, when describing these patients.

Antibody Deficiency Syndromes

Agammaglobulinemia

Agammaglobulinemia occurs when there are significant decreases in all major classes of immunoglobulins. Agammaglobulinemia is diagnosed when there is serum IgG usually less than 200 mg dl –1 (2g L –1) and IgM and IgA are generally less than 20 mg dl–1 and CD19+ B cells are below 2% [2, 7] . Cell mediated function is normal. These patients present with respiratory infections such as otitis media, sinusitis and pneumonia. The infections may be severe in approximately 20% of patients. The onset of infections usually corresponds with the decrease in IgG levels at approximately 3–6 months of age when catabolism of maternal IgG leaves affected infants hypogammaglobulinemic. In isolated agammaglobulinemia, there is usually no sign of a T cell deficiency, and infections with opportunistic infections are rare. X-linked agammaglobulinemia is an immune deficiency affecting males due to mutations in the B-cell tyrosine kinase (BTK) gene located on Xq 21.3-22 [14, 15] . Mutations result in absent BTK mRNA in neutrophils or monocytes and absent BTK protein in monocytes or platelets. BTK mutation analysis confirms the diagnosis of XLA. The presence of male relatives with less than 2% B cells also suggests XLA as the diagnosis. It is the most common form of agammaglobulinemia. Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 743

There are cases of patients with higher concentrations of immunoglobulins than usual who have been diagnosed with BTK mutations later in life [16] . A history of male family members with recurrent infections is not always present since spontaneous mutations occur as well. S. pneumoniae and H. influenza cause the majority of infections in these patients. When present, central nervous system ECHO virus infections are characteristic of XLA, and are difficult to treat. A characteristic finding in patients with XLA is the absence of tonsils and lymph nodes. Patients who have had multiple infections are prone to the development of bronchiectasis [17] . This complication is seen despite treatment with gamma globulin and antibiotics. The autosomal recessive agammaglobulinemias are rare, but present with similar manifestations as XLA. There are several mutations within the genes involved in B cell maturation that cause ARA. Mutations in C mu heavy chain, signal-transducing molecule Ig-alpha, surrogate light chain Ig lambda-like peptide, or BLNK (the cytoplasmic adapter protein B cell linker protein) should be investigated when male patients are evaluated with a phenotype consistent with XLA but whose BTK is normal. These proteins are important in the maturation of B cells from the pro-B to pre-B cell stage. Additionally, female patients with agammaglobulinemia and affected patients with a family history of consanguinity should be evaluated for these mutations.

Hyper-IgM Syndrome

In the hyper IgM syndrome, there is usually a striking increase in IgM, with absence of IgG and IgA, due to defects in class switching. Some forms of the hyper IgM syndrome are caused by mutations in enzymes present in B cells, and so are considered to be purely antibody deficiencies. These two enzymes, AICDA (activation induced cytidine deaminase) and UNG (uracil DNA glycosylase) are involved in class switch recombination after the interaction of CD40L with CD40 on the B cell. Infections seen in this syndrome are similar to those in patients with agammaglobulinemia. The most common form of the hyper-IgM syndrome is caused by absence of CD40 ligand (CD40L) on T cells, which is important in class switching from IgM production to IgG and IgA. There are other forms caused by mutations in NEMO (NF-KB essential modulator). These are combined T and B cell immunodeficiencies and will not be discussed here.

Common Variable Immunodeficiency Disease (CVID)

CVID has an onset of above 2 years of age and affects both sexes. Patients have a hypogammaglobulinemia and variable T cell abnormalities, although infection with intracellular pathogens is unusual. CVID is diagnosed by a decrease of at least 744 K. Paris et al.

2 SD below the mean for age in two out of three of the major isotypes (IgM, IgG, and IgA), and by absent isohemagglutinins and/or poor response to protein and polysaccharide vaccines. B cells are normal, or only mildly decreased. Other defined primary and secondary causes of hypogammaglobulinemia need to be excluded [2] . Because the phenotype of CVID is variable, patients who have a decrease of at least 2 SD below the mean for age in only one of the major immunoglobulin isotypes but fulfill all other criteria may have CVID. In all patients with a persistently low IgG concentration and diarrhea (or the nephrotic syndrome), an IgG loss must first be ruled out. IgG-loss syndromes can be detected by evaluation of urine for proteinuria and IgG, determination of alpha 1-antitrypsin clearance in stool, by assessment of total protein and albumin concentrations and by calculating the half-life of IgG after an infusion of IgG [18] . Recurrent infections, cancer and autoimmune disease are common in patients with CVID [19, 20] . The age of clinical onset of CVID is quite variable, with some patients diagnosed in childhood and others diagnosed at any time during adulthood. Its late onset causes it to be the most common primary immunodeficiency diagnosed in adults. Clinical presentation generally occurs in the first three decades of life and serum immunoglobulin concentrations may increase or decrease over time leading to changes from IgA deficiency to CVID [21] . There are two incidence peaks around 2–5 and 16–20 years of age [22] . CVID is one of the most frequent human immunodeficiencies with incidences ranging from 1:10,000 in Sweden to 1:30,000 individuals [19, 20] . The infections seen in CVID are similar to other antibody deficiencies, with some unique exceptions. The majority of infections are caused by S. Pneumoniae , Moraxella catarrhalis , and H. influenzae . Giardia lamblia can cause clinical disease in patients with CVID. In addition to the infectious complications, patients with CVID have a propensity for the development of autoimmunity. This includes ITP, autoimmune hemolytic anemia, rheumatoid arthritis, SLE, autoimmune thy- roiditis, vitiligo, and primary biliary cirrhosis [23] . An inflammatory bowel disease has also been associated with CVID, and can cause splenomegaly, chronic diarrhea and malnutrition [24] . A sarcoid-like granulomatous disease involving lungs, liver and spleen can be confused with lymphoma [25] . Malignancies in general are found at increased rates in CVID patients. There was a 23-fold increased risk for malignant lymphoma and a 50-fold increase in gastric cancer among 377 patients with hypogammaglobulinemia, primarily CVID [26] . A 100-fold increased risk for lymphoma was noted in 98 CVID patients who were followed for up to 13 years [27] . Because CVID is a heterogenous disease with variable phenotypes, a single causative defect is not found. Familial inheritance occurs in up to 25% of cases, but most are sporadic [28] . The disease may have different presentations within the same family. It may also appear to skip generations, suggesting variable penetrance. IgA deficiency alone may be found in one family member, while other affected individuals have a hypogammaglobulinemia of 2 isotypes. Current efforts to identify mutations responsible for the development of CVID, focus on T and B cell costimulatory molecule and markers of B cell differentiation. For example, a deficiency of switched memory B cells in patients with an autosomal recessive form of Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 745

CVID is due to mutations in the inducible costimulator gene [29] . Susceptibility loci for CVID have been identified on chromosome 5p [30] and in the major histocompatibility complex region on chromosome 6p [31] .

Transient Hypogammaglobulinemia of Infancy

The clinical phenotype of transient hypogammaglobulinemia of infancy (THI) has not been clearly defined, and different criteria are offered by different authors [32– 34] . IgG levels are low compared to published norms for age, but are higher than those seen in agammaglobulinemia, and B cell numbers are normal. Immunoglobulin levels normalize by 2–3 years of age, which makes this a diagnosis that can only be made retrospectively. The age of patients being considered for this diagnosis should be between 6 months and 3 years of age. If only IgG is below 2SD for age, specific antibodies are normal and the infections are mild, it is possible to reassure the parents that a transient hypogammaglobulinemia of infancy is the most likely diagnosis and that follow-ups at 6 month intervals until the IgG normalizes is all that must be done. Infants presenting with diminished immunoglobulins who are otherwise immunologically normal might better be described by a broad, inclusive term such as hypoimmunoglobulinemia of early childhood [35] . Protective antibodies against tetanus and diphtheria toxins and H. influenza capsular polysaccharide also suggest that the hypogammaglobulinemia will be transient. Since some patients have eventually developed persistent antibody deficiencies [35, 36] , follow up is necessary. In all patients with hypogammaglobulinemia detected in the first 2–3 years of life, a careful family history and regular follow-up is recommended until the diagnosis of transient hypogammaglobulinemia can be documented retrospectively. The need for IgG replacement therapy is generally not necessary for these patients, although very frequent infections may warrant this treatment. In this case, careful monitoring of IgG trough levels while keeping the IgG dose and infusion intervals constant allows clinicians to determine when there has been a significant increase in the patient’s own IgG production to stop IgG replacement treatment.

Selective IgA Deficiency

Selective IgA deficient patients have a serum IgA of less than 7 mg dl–1 (0.07 g L–1 ), but normal serum IgG and IgM. This deficiency can only be diagnosed reliably after 4 years of age [2] because IgA deficiency cannot be differentiated from absent or low IgA concentrations seen in normal individuals less than 4 years old. As for hypogammaglobulinemia in this age group, IgA concentrations should be followed at 6–12 month intervals until an IgA deficiency is definitively ruled out. 746 K. Paris et al.

Within selective IgA deficiency, it is possible to differentiate between patients in whom no IgA is detected even by very sensitive methods and those who have low but detectable IgA concentrations. The former group is at a higher risk for developing anti-IgA antibodies upon exposure to any blood product containing IgA, since no tolerance to this protein has been developed. Patients older than 4 years, who have a serum IgA below 2 SD of normal concentrations but above 7 mg ml –1 , fall into an ill-defined category requiring further evaluation and follow-up only if they are symptomatic. As a group, many individuals with IgA deficiency are asymptomatic. Some patients with IgA deficiency have an increased incidence of upper respiratory tract infections, allergies, celiac-like enteropathy and autoimmune disease including SLE, rheumatoid arthritis, pernicious anemia and others [37] . The clinical manifestations associated with IgA deficiency in a given patient tend to remain constant with little tendency to develop other problems, e.g., patients who present with an autoimmune condition do not tend to develop recurrent infections. Patients with IgA deficiency who have recurrent infections should be evaluated for other associated antibody abnormalities, like IgG2 subclass or specific antibody deficiencies, or chronic allergic manifestations which may also predispose them to recurrent infections. Considering all its clinical forms including asymptomatic patients, selective IgA deficiency was the most common PID phenotype identified in many areas of the world [37] . The frequency of IgA deficiency in normal individuals (blood bank donors) varies from 1:396 to 1:2170 [4] and is somewhat higher in patients with recurrent infections, malignant, or autoimmune diseases [38] .

IgG Subclass Deficiencies

IgG subclass deficiencies can be found as isolated abnormalities or in combination with other immune deficiency syndromes like IgA deficiency, ataxia telangiectasia, the Wiskott Aldrich syndrome and multiple other immunodeficiencies [39] . Since IgG2, IgG3, and IgG4 do not contribute a large percentage to total IgG, they may be deficient without a decrease in total IgG serum concentrations. The severity of clinical manifestations, e.g., recurrent infections, is not related to the degree of IgG subclass deficiency. Asymptomatic patients with a complete IgG subclass deficiency due to g heavy chain deletions have been described [40] . Because of the difficulties in obtaining reliable IgG subclass determinations [8] , the diagnosis of an IgG subclass deficiency should always be confirmed by repeated testing at least 1 month apart. The ability to produce and maintain adequate concentrations of specific antibodies to protein and polysaccharide antigens is more important than IgG subclass concentrations. IgG subclass deficiencies should be followed at regular intervals since they may be transient [41, 42] . Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 747

IgG1 Subclass Deficiency

IgG1 constitutes 60–70% of total IgG, therefore IgG1 deficiencies nearly always cause a hypogammaglobulinemia.

IgG2 Subclass Deficiency

IgG2 deficiencies are a heterogeneous group of abnormalities which includes various degrees of severity and persistence. Deficient IgG2 may occur as an isolated abnormality or in combination with IgG4 and/or IgA deficiencies. IgG2 deficiency is one of the most frequently identified abnormalities in patients with recurrent infections [43] . Deficiencies in IgG2 may lead to recurrent sinopulmonary infections, otitis media, and disseminated pneumococcal disease [44, 45] . The high prevalence of recurrent infections in patients with IgG2 deficiency is likely due to the special relationship between IgG2 and polysaccharide antibodies. Most of the response to pneumococcal polysaccharides can be found in the IgG2 subclass [46, 47] . Not surprisingly, patients with IgG2 subclass deficiency have several abnormalities in the production of anti- polysaccharide antibodies, including responses to a restricted number of polysaccharides within the pneumococcal vaccine [42] , poor immunological memory [42] , and lack of development of specific antibodies of the IgG2 isotype [48] .

IgG3 Subclass Deficiency

IgG3 deficiency also has been described in patients with recurrent sinopulmonary infections [45] . Persistent IgG 3 deficiency is infrequently identified in patients with recurrent infections [43] .

IgG4 Subclass Deficiency

Many normal infants and children have very low or absent concentrations of IgG4, so this deficiency cannot be reliably diagnosed in children <10 years old [49] . Clinical relevance of an IgG4 deficiency is unlikely due to its small contribution to total IgG.

Specific Antibody Deficiency with Normal Immunoglobulins

We now recognize deficiencies in response to pure polysaccharides and also, increasingly, to conjugated polysaccharide antigens. These deficiencies are typically diagnosed based on the response to pneumococcal polysaccharides. Ideally, 748 K. Paris et al. one should be able to measure the response to immunization by obtaining pre- and post-immunization antibody concentrations. This is rarely possible for the response to pneumococcal serotypes present in the heptavalent conjugated pneumococcal vaccine, (PCV-7) since most children have received one or more doses of this vaccine before evaluation. This problem is obviated by using an interpretation of antipneumococcal antibody concentration results based both on antibody increases over pre-immunization concentrations (immune response) and on final concentrations of antibodies after immunization, regardless of increase from pre-immunization concentrations (antibody concentration). Adequate responses to individual pneumococcal polysaccharides can be arbitrarily defined as a post-immunization antibody concentration ³ 1.3 µg ml–1 or at least fourfold over baseline [50] . The syndrome of specific antibody deficiency is then defined using the combined response to all serotypes tested [10] . Some unimmunized patients in all age groups fail to demonstrate protective antibody titers to any pneumococcal serotype tested. This is unusual in individuals above two years of age who typically develop these antibodies in response to clinical or subclinical infections. Most adults have protective antibodies to all or at least 80% of serotypes tested, even before immunization with PPV. The overwhelming majority of these patients have a vigorous response to immunization. Therefore, low preimmunization antibody titers may not predict an underlying immunodeficiency. Immunocompetence cannot be differentiated from immunodeficiency without immunization and retesting after immunization.

Selective Anti-Pure (Non-Conjugated) Polysaccharide Antibody Deficiency

Specific antibody deficiency with normal immunoglobulins is a primary immunodeficiency of unknown etiology [51– 54] . It is frequently found in patients evaluated for recurrent infections, but the prevalence is unknown [43, 55] . Selective anti-polysaccharide antibody deficiencies are also frequent in patients with IgG subclass deficiencies [42] , combined immunodeficiencies, congenital asplenia and in acquired conditions like HIV infection and splenic deficiency. Specific antibody deficiencies can also be seen in some patients with Down syndrome [43] , the Netherton syndrome [56] and other congenital abnormalities that are constitutively associated with immunoglobulin or antibody deficiencies. The diagnosis of specific antibody deficiency with normal immunoglobulins (SADNI) should be considered in patients >2 years of age with recurrent upper and/ or lower respiratory tract infections and normal, IgG, IgA, and IgM concentrations. Since most children have received the pneumococcal conjugate vaccine, diagnosis requires the demonstration of an abnormal IgG antibody response to pneumococcal serotypes present exclusively in the polysaccharide vaccine [3, 8] . Antibody Deficiency Syndromes (Including Diagnosis and Treatment) 749

IgG replacement is an option for patients with proven recurrent infections and documented specific antibody deficiency. Prophylactic antibiotics are also used, keeping in mind the risk of developing antibiotic resistance. When the severity of infections warrants the use of IgG replacement treatment, it is wise to tell patients that the treatment will be stopped after a period of time and that the immune response will have to be reevaluated 4–6 months after discontinuation of IgG replacement. In children, improvement in responses to the polysaccharide vaccine may occur after treatment with intravenous immunoglobulins for 6–24 months [57] . This may be due to the maturation of the immune response with increasing age. Any one of these forms of specific antibody deficiency may be transient or permanent. Transient forms are common in children 2–5 years of age. The natural history of these syndromes is usually benign if they are properly managed, although failure to treat infections can lead to complications such as chronic sinusitis or mastoiditis. Further insights into the pathogenesis of this syndrome in different patients should eventually result in a more reliable assessment of the risk for persistent immune abnormalities and recurrent infections in some of these patients.

Treatment of Antibody Deficiencies

The comprehensive management of patients with antibody deficiencies is complex. It requires an understanding of the risks and complications that are associated with each of the individual diseases. Infections are treated with appropriate antibiotics, ideally based on sensitivity profiles of causative bacteria. The other mainstay of treatment is either intravenous or subcutaneous gamma globulin. When given IV, the usual interval between infusions is every 3–4 weeks. For the subcutaneous route, more frequent infusions such as once or twice weekly, results in more uniform plasma IgG levels. Specialists are also required to be familiar with monitoring IgG dosing and infusion rates, as well as preventing and treating infections when they occur. Infections occur despite the best treatment plans due to the wide variety of causative agents and variable resistance patterns of the bacteria. The indication for IgG is absolute for patients with agammaglobulinemia, CVID and the hyper-IgM syndrome. When bronchiectasis is present, even in more mild antibody deficiencies, it is also required . Selective IgA deficiency is not an IVIG replacement therapy although in some cases, poor IgG specific antibody production, with or without IgG2 subclass deficiency may coexist and IVIG may be used. Intravenous IVIG can pose a risk of anaphylaxis for IgA deficient patients who have anti-IgA antibodies [58] . Live vaccines are not recommended in infants with known hypogammaglobulinemia. Most immunizations are unnecessary during IgG replacement treatment. The usual starting dose for IgG replacement is 400–600 mg IgG/kg every 3 or 4 weeks. The trough level of IgG should be at least 500 mg dL–1 [59] . Patients with known bronchiectasis or other pulmonary complications require trough levels >800 mg dL–1 to improve pulmonary outcome [60] . 750 K. Paris et al.

Clinical Staging of Complications

After diagnosis and initiation of treatment, it is necessary to consider complications of the patient’s underlying disease. These complications are often secondary to the frequent infections suffered by these patients, and may be present even at the time of diagnosis. Treatment choices may be dependent on their presence or absence, such as IgG dosing in patients with bronchiectasis. Sinus CT scans should be done in patients with a history of chronic sinusitis, and cultures of sinus contents considered, to direct therapy. High resolution chest CT scans should be performed to evaluate for bronchiectasis, even in patients without a significant history of lower respiratory infections. Subclinical or chronic low grade infections may also cause scarring. GI complaints, especially in patients with CVID should prompt evaluation by a specialist via endoscopy when an etiology is not readily found. If patients with CVID or other antibody deficiencies have clinical signs of an autoimmune disorder, evaluation of autoantibodies should be performed.

Summary

Antibody deficiencies are the most common form of primary immunodeficiency found worldwide. Recognition of the t signs and symptoms of these disorders is important in order to diagnose and treat patients before complications develop. Because the impact of immune deficiency on individual patients is great, physicians should have a low threshold for evaluating these disorders despite knowing that in the majority of cases the results will be normal.

References

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A Antihistamines, 19, 37, 311 Adjuvant, 205 first generation, 20 Adverse effects, 38 second generation, 20–21 Adverse reactions to foods, 635 Anti-IgE, 51, 467 Aerosol therapy, 245 monoclonal antibodies, 687 Agonists, 38 therapy, 335 Airway deposition, 245 Anti-IL-4, 471 Airway hyperresponsiveness, 171 Anti-IL-5, 470 Airway inflammation, 171, Anti-IL-9, 472 187, 536 Anti-IL-13, 471, 472 Airway remodelling, 69, 536, 716 Anti-inflammatory effect, 187 Airway smooth muscle, 69 Antileukotrienes, 51, 63 Allergen bronchoprovocation, 72 Antimicrobial treatment, 621 Allergenic peptides, 206 Antioxidants, 423 Allergens, 3, 417–428 Anti-prostanoids, 466 avoidance, 419–420, 447 Anti-THF-α, 470 immunotherapy, 195, 427 Apoptosis, 187 Allergen specific immunotherapy, 468 Arachidonic acid, 63 Allergic disease, 379, 417–428 Aspergillus, 695 Allergic fungal sinusitis, 695 Aspirin-exacerbated respiratory disease Allergic inflammation, 105 (AERD), 73 Allergic rhinitis, 41, 51, 63 Aspirin intolerance, 70 management of, 30 Asthma, 3, 45, 63, 91, 105, 145, 171, 187, prevalence, 397 217, 347, 365, 379, 465, 511, 531, 543, treatment, 19, 42 611, 713, 727 Allergy, 347, 365, 397, 713 control, 565, 593 definition, 399–400 control test, 565 epidemic, 418 exacerbations, 74 prediction, 419–420 phenotypes, 511 prevention, 417 prevalence, 397 programme, 457–459 programme, 457 Almond, 681 symptoms, 74 Alternaria, 695 syndromes, 532 Amphotericin B topical, 695 Asthma quality of life questionnaire Anaphylaxis, 325 (AQLQ), 565 Antibiotics, 407–408 Asthmatic children, 577 Antibodies, 737 Asthmatic infants, 577 Anti-cytokine therapy, 468 Atopic asthma, 534 Antifungals, 695 Atopic dermatitis, 203, 259, 291, 621

755 756 Index

Atopic dermatitis prevalence, 397 Cord blood, 417–428 Atopic dermatitis/psoriasis, 105 Corticosteroids, 51 Atopy, 3, 379 Cough, 535 Avoidance, 3 Cromolyn, 593 Azelastine, 23 Cross-sectional studies, 398 Cyclic AMP, 91 Cyclosporine A, 291 B CysLT1 receptor, 66 Bacillus Calmette-Guérin (BCG), 426, 713 CysLT2 receptor, 66 B cells, 737 Cysteinyl-leukotrienes, 66 BEAS-2B, 716 Cytokines, 417–428 β 2 Adrenoceptor, 91 Cytosine-phosphoguanosine (CpG), 425 β 2 Agonists, 171 Beclomethasone, 76 Bell-shaped curve, 451 D Beta agonists, 245 Day care, 406 Birth, 365 Death, 499 Birth cohort, 397 Decongestants, 51 Blocking antibodies, 197 Definition, 145, 217 Brazil nut, 682 Definition of GC insensitive asthma, 134 Breastfeeding, 401–402 Dendritic cells, 453, 718 Bronchial hyperresponsiveness, 171 Dermatitis, 105 Bronchoalveolar lavage (BAL), 70 Desensitisation, 217 Bronchoconstriction, 67 Desloratadine, 22 Bronchodilation, 91 Diagnosis, 365, 531 Diet and nutrition, 421–422 Digital airway inflammation, 139 C Disease prevention, 347 Calcineurin antagonists, 259 DNA-adjuvanted, 205 Calcineurin inhibitors, 291, 621 Dogs, 406 Cancer, 714 Drinking water, 449 Cardiotoxic effects, 40 Drug delivery, 433 Cashew, 681 Dry powder inhalers, 245 Cats, 406 CC chemokines, 721 CD14, 677 E CD40, 720 EAACI, 400 CD86, 720 Eczema, 259 CD4+ T-cell, 719 Edema, 68 CD8+ T-cell, 719 Education, 621 Cetirizine, 21 Efficacy, 195 Chemoattractant receptor homologous- Elderly, 46, 499 molecule 2 (CRTH2) receptor Emergency care, 543 antagonists, 467 Emollients, 259 Children, 46, 365, 531, 543, 611 Endothelial cells, 68 Chitosan, 433 Endotoxin, 426, 448, 499, 676, 677 Chlorofluorocarbons, 245 Environment, 3, 448 Chromosome 5q31, 677 Environmental factors, 404, 536 Chromosome 12q, 678 Environmental tobacco smoke, 404 Chronic inflammation, 105 Eosinophilic mucin rhinosinusitis, 695 Classification, 145, 217 Eosinophils, 65, 171, 187 Co-existing lung diseases, 499 Eosinophils and mast cells, 171 Cohort studies, 398 Epidemiology, 397, 499 Common variable immune deficiency, 737 Epigenetics, 137, 417–428 Index 757

Epinephrine, 311 H1-receptor antagonists, 51 Exacerbation, 543 H1-receptor inverse agonist generations, 41 Exercise-induced bronchoconstriction, 72 Human leukocyte antigens (HLA), 678 Exercise-induced bronchospasm, 171 Hydrofluoralkene, 245 Exhaled breath condensate (EBC), 70 Hydrolyzed formula, 402 Exhaled nitric oxide, 565 Hygiene hypothesis, 397, 676, 714 Hypoallergenic infant formula, 402 Hypogammaglobulinemia, 737 F Family size, 406 Farming, 448 I Farm milk, 448 Ideal antihistamine, 47 Fatty acids, 417 IFN-γ, 720 Fexofenadine, 23 Immune deficiency, 737 Fluticasone, 76 Immune development, 418 Food Allergen Labeling and Consumer Immune system development, 347 Protection Act (FALCPA), 685 Immunodeficiency, 737 Food allergens, 635 Immunoglobulin E (IgE), 365, 684, 695, Food allergy, 335 715, 737 herbal formula, 687, 688 Immunomodulation, 417, 713 hypersensitivity, 635 Immunomodulatory factors, 417 Food intolerance, 635 Immunostimulatory sequence-conjugated Fungus, 695 protein immunotherapy, 335 Fungus ball, 695 Immunosuppressives, 259 Immunotherapy, 217, 325, 425, 695 Impulse oscillometry, 565 G Inducible nitric oxide synthase (iNOS), 717 Gammaglobulin, 737 Infantile diet, 402–403 Gene-environmental interactions, 417 Infants, 417 Genetic polymorphisms, 427 Infections, 407 Genetics, 3 Inflammation, 42 Genetics of asthma, 511 Influenza, 611 Glucocorticoid (GC), 259 Inhaled allergens, 404–405 insensitivity, 136 Inhaled beta-adrenergic agents, 311 receptor α, 135 Inhaled corticosteroids, 75, 171, 245, 577 receptor β, 135 Innate immune inflammation, 499 Glucocorticosteroids, 291, 621 Interleukin G-protein, 38 IL-2, 716 Guidelines, 543 IL-5, 716 IL-6, 717 IL-10, 472, 473, 721 H IL-12, 721 Hazelnut, 680, 681 IL-23, 721 Hazelnut immunotherapy, 686 Intervention, 397 Heparins, 474 Interventional birth cohort studies, 399 Hevea brasiliensis, 653 Intraconazole, 695 Histamine, 37 Intranasal antihistamines, 23 Histamine inverse receptor agonists, 38 Intranasal corticosteroids, 24, 25 Histamine receptors, 38 adverse effects of, 26, 27 Histaminergic neuronal system, 37 Intravenous fluids, 311 Histology, 145, 217 Intravenous vasopressors, 311 Histone deacetylase (HDAC), 187 Intrinsic asthma, 499 Host defense, 718 Invasive fungal sinusitis, 695 House dust mite, 404 Irreversible obstruction, 499 758 Index

J Muramic acid, 450 Jet nebulizers, 245 Mycobacteria, 426

K N Karelia Allergy Study, 449 Naïve T-cell, 718 Ketotifen, 593 Nanotechnology, 433 Natural course of allergic diseases, 400 Natural history, 511 L Nedocromil, 593 Lactating women, 47 Netherton syndrome, 679 Lactobacillus, 403 Neutrophilic asthma, 138 Latex allergen avoidance, 653 Nitric oxide (NO), 69, 311 Latex allergy, 653 NKT, 720 Leukocytes, 65 Non-IgE-mediated food allergy, 635

Leukotriene B4, 67 Nonsteroidal anti-inflammatory, 593 Leukotriene modifiers, 28, 593 Nonsteroidal anti-inflammatory drugs Leukotriene receptor antagonists, 171, 466 (NSAID), 73 Leukotrienes, 63, 465 NRAMP1, 720 Leukotrienes and histamine, 171 Nutrition, 401 Leukotriene synthesis inhibitors, 466 Levocetirizine, 22 Linkage analysis, 677 O Lipopolysaccharide, 717 Observational birth cohort studies, 398–399 5-Lipoxygenase, 63 3-OH-fatty acids, 450 Long-acting beta-2 agonists (LABAs), 75, 91 Olopatadine, 24 Long lasting effect, 198 Omalizumab, 593, 687 Loratadine, 22 Oral food challenge, 335 Low molecular weight heparins (LMWH), 475 Oral immunotherapy, 335, 686 Lung function, 365 Oral tolerance, 217, 335

M P Major histocompatibility complex (MHC) Paracetamol, 408 class 1, 718 Parasites, 451 Mast cells, 65 PDE4, 105 Mast cell stabilizers PDE4 inhibitors-adverse events, 105 anticholinergics, 29 Peak expiratory flow rate, 565 chromones, 29 Peanut, 680 decongestants, 29 Peanut allergy oral and intranasal, 29 cross-reactivity, 682 Maternal diet, 401 incidence, 675 Mechanisms, 195 Peanut and tree nut allergens, 679 subcutaneous immunotherapy Peanut and tree nut allergy (SCIT), 197 diagnosis, 683 sublingual immunotherapy (SLIT), 201 prognosis, 684, 685 Methylene blue, 311 Peanut immunotherapy, 686 Microbial exposures in the environment, 407 Peptide immunotherapy, 335, 686 Mitogen activated protein (MAP) kinases, 136 Peptidoglycans, 452 Modern second generation H1 inverse Perception of asthma, 565 agonists, 41 Pets, 405–406 Montelukast (Singulair™), 71 Pharmacotherapy, 171 Multicentre Allergy Study (MAS), 400 Phosphodiesterase, 105 Multifaceted interventional studies, 408–409 Phosphodiesterase inhibitors, 467 Index 759

Phosphodiesterase 4 inhibitors, 105 Skin testing, 653, 683 Phosphoinositide 3-kinase (PI3K) Sodium cromoglycate, 75, 727 inhibitors, 475 Specific immunotherapy, 454 Phototherapy, 259 SPINK5, 679 Polysaccharide antigens, 737 Spirometry, 565 Polymorphisms, 91, 453 Sputum analysis, 565 Polyunsaturated fatty acid, 401 Sputum eosinophilia, 565 Pranlukast (Onon™), 71 Step-up schedule immunotherapy, 469 Prebiotics, 424 Steroids, 695 Prediction, 365 Study design, 397 Pregnancy, 417–428 Subcutaneous immunotherapy, 335 Pregnant women, 46 Sublingual, 217 Prematurity, 533 Sublingual immunotherapy, 199, 200, 335, 686 Pressurized metered dose inhalers, 245 Systemic therapy, 465 Prevention, 3, 379, 433, 611 Prevention of asthma, 198, 202 Prevention products, 459 T Primary prevention, 417–428, 456 T cells, 325 Probiotics, 403, 424, 474 and eosinophils, 43 Prognosis, 365 subsets, 454 Proinflammatory mediators, 43 γδ-T Cells, 719 Protease-activated receptors, 499 Teichoic acids, 452 Psychological tolerance, 458 Tertiary prevention, 409 PUFA, 421–422 Thalidomide derivative-C-10004, 105 P2Y purinergic receptors, 67 T helper-1 (TH1) cells, 470, 716 T helper-2 (TH2) cells, 470, 676, 716 Theophylline, 75, 105, 187, 593, 727 R Therapeutics, 499 Radio allergosorbent test (RAST), 653 Therapy, 433 Recombinant allergens, 206, 207, 433 Therapy GC insensitive asthma, 140 Recombinant IL-12, 473 Therapy infants, 538 Recombinant protein immunotherapy, 686 TNX-901, 687 Recombinant proteins, 684 Tolerance, 447, 450 Regulatory T cells, 453 Tolerance restoration, 455 Respiratory infection, 347 Toll-like receptors, 425, 452, 721 Respiratory syncytial virus (RSV), 407, 714 Toll like receptors 9 (TLR-9) Review, 565 antagonists, 475 Rhinitis, 217 Topical treatment, 621 Risk-benefit, 593 Traditional Chinese Medicine, 335 Risk factors, 145, 217, 365, 379 Traffic related pollution, 404 Roflumilast, 105 Transforming growth factor (TGF-β), 719 RSV bronchiolits, 533 Treatment, 145, 217, 259, 291, 531 Tree nut allergy cross-reactivity, 682 S incidence, 675

Safety, 201 Treg Cells, 717

Saprophytes, 448 Treg NKT, 719 Secondary prevention, 409, 456 Tregs, 137 Severe, 145, 217 Tuberculosis, 714 Severe asthma, 543 Tumor necrosis-α (TNF-α), 716 β β β Short acting 2 adrenoceptor selective agents Tumor necrosis- (TNF- ), 717 (SABAs), 91 Type I resistance, 135 Signal transducer and activator of Type II resistance, 135 transcription-6 (STAT-6), 678 Types of GC insensitivity, 133 760 Index

V infants, 532 Vaccinations, 407–408 interpretation, 532 Vaccines, 611 mechanism, 533 Venom, 325 prognosis, 537 Viral respiratory infections, 511 risk factors, 537 Viral wheeze, 534 Wheezing, 531 Virus, 365 World Allergy Organization (WAO), 455 Vitamin C, 423 World Health Organization (WHO), 455 Vitamin D, 423 Vitamin E, 423 X Xanthines, 105 W Walnut, 681 Well-controlled asthma, 565 Z Wheeze Zafirlukast (Accolate™), 71 bronchitis, 535 Zileuton (Zyflo™), 71