Equine Intradermal Test Threshold Concentrations for House Dust Mite and Storage Mite Allergens and Identification of Stable Fauna THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Holly A. Roberts, D.V.M Graduate Program in Comparative and Veterinary Medicine The Ohio State University 2014 Master's Examination Committee: Dr. Gwendolen Lorch, Advisor Dr. Andrew Hillier Dr. Samuel Hurcombe Copyrighted by Holly A. Roberts 2014 Abstract The presence of house dust mites (HDMs) and storage mites (SMs) in the human environment has been established worldwide and both contribute to atopic disease consisting of atopic dermatitis, asthma and allergic rhinitis in some individuals. The Dermatophagoides, Acarus, Tyrophagus and Lepidoglyphus mite genera contribute to the pathogenesis of atopic disease. HDMs and SMs have also been implicated in atopic dermatitis in veterinary medicine. Extensive work has been done for canine mite induced allergic patients, but relatively little information is available for equine allergic patients. Intradermal testing is performed in veterinary patients to identify environmental antigens that cause disease with the intent of formulating allergen-specific immunotherapy. Equine HDM and SM intradermal test (IDT) threshold concentrations (TCs) for the Midwestern United States are unknown. The mite stable fauna for the Midwestern region of the United States has not been determined. The objectives of this study were to determine IDT TCs for HDM and SM species, to quantify mite-specific IgE concentrations in thirty-eight clinically normal horses over two seasons and to characterize the mite fauna of a stable in this region across three seasons. Subjective measurements of IDT reactions were used to determine the TCs for Dermatophagoides farinae, Dermatophagoides pteronyssinus, Acarus siro, Tyrophagus ii putrescentiae and Lepidoglyphus destructor. The reactions were scored using a scale of 0 to 4+. Allergen testing concentrations ranged from 1:320,000-1:20,000 w/v for HDMs and 1:160,000-1:5,000 w/v for SMs. Threshold concentrations were defined as the highest concentration of a mite allergen where ≤10% of horses had a positive subjective reaction (≥2+) at 15 min. Analysis of equine serum-specific IgE was performed using a commercially available allergen-specific IgE ELISA test. Specialized mite traps and modified flotation methods were used to collect mites in spring, late summer and winter from nine locations on one farm. Selected locations for mite collection represented the three different stabling environments used, bedding types, feed materials or combinations thereof. A single-baited mite trap was placed at each of the locations for a four-day period (96 h), while 200 g of material was gathered from each site on the fourth day for flotation. An acarologist morphologically identified and quantified the species of HDMs and SMs collected. Subjectively determined TCs were: 1:80,000 w/v for Dermatophagoides farinae in both seasons, 1:80,000 w/v in spring and 1:160,000 w/v in late summer for Dermatophagoides pteronyssinus, 1:40,000 w/v in spring and 1:20,000 w/v in late summer for Acarus siro, 1:20,000 w/v for Lepidoglyphus destructor in both seasons, and 1:20,000 w/v in spring and 1:10,000 w/v in late summer for Tyrophagus putrescentiae. In both seasons, at least one horse had a positive serum IgE result for each HDM or SM evaluated. Negative serum IgE concentrations for all mite species were present in 55% of iii horses in spring and 66% in late summer. At least one mite from all four genera specific to this study was identified. Tyrophagus mites were the most prevalent with Dermatophagoides mites being the least numerous. Collectively, Oribatida, Cheyletus, Glycyphagus and Tarsonemidae represented the majority of the genera detected. The determined TCs from our study differ from published recommendations for equine HDM and SM IDT dilution concentrations, suggesting the need to consider seasonal and regional influences on IDT TCs and reactivity. These results establish that horses stabled in the Midwestern United States are exposed to a diverse Acari population. Provocation and allergy testing of allergic horses with specific mite allergens would be necessary to determine the significance of these mites in relation to disease. iv Dedicated to Mom, Amy and Andy v Acknowledgements I would like to thank my thesis committee members, Dr. Andrew Hillier and Dr. Samuel Hurcombe, and especially my advisor, Dr. Wendy Lorch, for their support, guidance and expert advice on completing my research project and thesis. I would have never been able to complete my Masters program without their assistance. I would also like to thank Dr. Lynette Cole, Dr. Leigh Gray, Dr. Melanie Hnot, Deb Crosier and Dr. Natalie Theus for their support and friendship. I am forever grateful to all who got me through my residency and Masters. Additionally, I would have never gotten through my residency, my internship or vet school without the love and support of my family (Mom, Amy, Andy, Cookie, Warren, Melanie, Tracey, Clara, Ella, Nora, Bradley and Paige) and close friends (McCoy, Davis, Beth, Olga, Karalie, Emily, Lauren, Laura, Amy, Tara, Ricky, and the list goes on). A special out goes to Dr. Heather Davis for her constant pep talks, goodies and love that kept me going on my lowest of days as well as Dr. Tara McCoy for being like a sister, always pushing me to achieve and being the most bad ass vet. You all mean the world to me, and I love you! vi Vita December 2005...............................................B.S. Biology, University of Kentucky May 2010............................................ ...........D.V.M., Auburn University July 2011 to present .......................................Graduate Teaching and Research Associate, The Ohio State University Publications Roberts HA, Hurcombe SDA, Hillier A, et al. Equine intradermal test threshold concentrations for house dust mite and storage mite allergens and identification of stable acari fauna. Vet Dermatol 2014; 25: 124-136. Lorch G, Calderwood Mays MB, Roberts HA, et al. Sweat Hypersensitivity Induced Urticaria and Sebaceous Adenitis in an American Saddlebred. J Vet Intern Med 2013; 27: 1627-1632. Fields of Study Major Field: Comparative and Veterinary Medicine Studies in Dermatology vii Table of Contents Abstract............................................................................................................. ii Dedication ........................................................................................................ v Acknowledgement ........................................................................................... vi Vita .................................................................................................................. vii List of Tables ................................................................................................... xi List of Figures .................................................................................................. xii CHAPTER 1 Introduction …......................................................................... 1 CHAPTER 2 Literature review ..................................................................... 4 2.1 History of Allergy…………………………………………………. 4 2.2 Hypersensitivity Reactions in Humans..…………………………... 5 2.2.1 Type I Immediate IgE-Mediated Hypersensitivity............... 6 2.2.1.1 Immediate Phase Reactions……………………….. 6 2.2.1.2 Late-Phase Reactions……………………………… 8 2.2.2 Type II Antibody-Mediated Hypersensitivity……………... 8 2.2.3 Type III Immune Complex Hypersensitivity……………… 9 2.2.4 Type IV Delayed Hypersensitivity…………....……...……. 9 2.3 Atopic Disease in Humans…..……………………………...……... 10 2.3.1 Immunology of Atopic Disease…………………...… 10 2.3.2 Atopic Dermatitis……………………………...……. 12 2.3.3 Pathogenesis of Atopic Dermatitis…………………. 12 2.3.3.1 Barrier Dysfunction………………………… 13 2.3.3.2 Filaggrin Mutations………………………… 14 2.3.3.3 Antimicrobial Peptides……………………... 15 2.3.3.4 Role of Keratinocytes………………………. 16 2.3.3.5 Role of Dendritic Cells……………………... 17 2.3.3.6 Thymic Stromal Lymphopoietin…………… 19 2.3.3.7 JAK-STAT…………………………………. 20 2.3.3.8 Cytokines in Atopic Dermatitis….…………. 21 2.3.3.8.1 Newer Cytokines…………………… 21 viii 2.3.4 Pathogenesis of Pruritus in Atopic Dermatitis……………. 22 2.4 Equine Allergic Disease…………………………………………... 24 2.4.1 Equine Atopic Dermatitis………………………………… 24 2.4.1.1 Pathogenesis……………………………..….…..... 24 2.4.1.2 Clinical Signs…………………………….……….. 27 2.4.2 Equine Recurrent Urticaria……………………………….. 27 2.4.2.1 Pathogenesis…………………...…………………. 28 2.4.2.2 Clinical Signs………………………….………….. 29 2.4.3 Insect-Bite Hypersensitivity……………………………… 29 2.4.3.1 Pathogenesis……………………………………… 31 2.4.3.2 Clinical Signs…………………………………….. 35 2.5 Diagnosis Of Equine Allergic Disease…………………………….35 2.5.1 Allergy Testing…………………………………………… 36 2.5.1.1 Intradermal Testing…....…………….…………… 36 2.5.1.1.1 Threshold Concentrations……….……….. 39 2.5.2.1 Allergen-Specific Serum IgE Testing….………… 41 2.6 Treatment…………………………………………….…………… 42 2.6.1 Allergen-Specific Immunotherapy………….……………. 42 2.6.1.1 Mechanism of Action in Humans…….………….. 43 2.6.1.2 Mechanism of Action Veterinary Patients……….. 45 2.6.1.3 Patient Selection………………………….………. 45 2.6.1.4 Formulation………………………….…………… 46 2.6.1.5 Allergen Types…...………………….…………… 47 2.6.1.6 Administration…………………….……………… 49 2.6.1.7 Types of Immunotherapy…………....…………… 50 2.6.1.8 Adverse Effects…………………….…………….