DOCSLIB.ORG

Discordant Antigenic Drift of Neuraminidase and Hemagglutinin in H1N1 and H3N2 Influenza Viruses

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Discordant Antigenic Drift of Neuraminidase and Hemagglutinin in H1N1 and H3N2 Influenza Viruses Discordant antigenic drift of neuraminidase and hemagglutinin in H1N1 and H3N2 influenza viruses Matthew R. Sandbultea, Kim B. Westgeestb, Jin Gaoa, Xiyan Xuc, Alexander I. Klimovc, Colin A. Russelld,e,DavidF.Burked, Derek J. Smithb,d,e, Ron A. M. Fouchierb, and Maryna C. Eichelbergera,1 aDivision of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892; bDepartment of Virology, Erasmus Medical Center, 3000 CA, Rotterdam, The Netherlands; cInfluenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30333; dDepartment of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; and eFogarty International Center, National Institutes of Health, Bethesda, MD 20892 Edited by Peter Palese, Mount Sinai School of Medicine, New York, NY, and approved November 8, 2011 (received for review August 23, 2011) Seasonal epidemics caused by influenza virus are driven by anti- and animal sera (14). In the present study, we use this assay to genic changes (drift) in viral surface glycoproteins that allow evasion characterize the antigenic drift of NA in human H1N1 and H3N2 from preexisting humoral immunity. Antigenic drift is a feature of viruses recommended for United States influenza vaccines over not only the hemagglutinin (HA), but also of neuraminidase (NA). the past ∼15 y (Table S1). In the NI assay, we used panels of ferret We have evaluated the antigenic evolution of each protein in H1N1 antisera against each wild-type H1N1 and H3N2 virus and virus and H3N2 viruses used in vaccine formulations during the last 15 y reassortants generated by reverse genetics to combine the tar- by analysis of HA and NA inhibition titers and antigenic cartography. geted NA and a mismatched HA of the H6 subtype. Use of these As previously shown for HA, genetic changes in NA did not always reassortants prevented false NI signals because of interfering HA lead to an antigenic change. The noncontinuous pattern of NA antibodies. We then constructed antigenic maps from the data- drift did not correspond closely with HA drift in either subtype. sets, using multidimensional scaling to position the antigens and Although NA drift was demonstrated using ferret sera, we show antisera on the map, as previously described (12). that these changes also impact recognition by NA-inhibiting anti- bodies in human sera. Remarkably, a single point mutation in the NA Results and Discussion of A/Brisbane/59/2007 was primarily responsible for the lack of Antigenic Characterization of the HA and NA of H1N1 and H3N2 MICROBIOLOGY inhibition by polyclonal antibodies specific for earlier strains. These Viruses. H6 reassortant viruses containing NA of historical as well data underscore the importance of NA inhibition testing to define as recent H1N1 and H3N2 vaccine viruses (Table S1) were used to antigenic drift when there are sequence changes in NA. measure NI titers of strain-specific ferret antisera. There was minimal NI cross-reactivity between the phylogenetically distant usceptibility to infection with circulating influenza viruses is early NAs and antisera raised against recent seasonal strains of Sdetermined to a large degree by the presence or absence of the classical H1N1 (Table S2) and H3N2 (Table S3) human lin- strain-specific functional antibodies elicited by prior infection or eages, demonstrating extensive antigenic drift since introduction vaccination. Influenza viruses constantly evade antibody-medi- of these subtypes. Ferret serum raised against A/California/7/2009 ated inhibition of replication by antigenic drift, an accumulation (CA/09), a representative 2009 H1N1 pandemic (H1N1pdm) vi- of mutations in epitopes of major surface proteins, HA and rus, demonstrated a robust homologous NI antibody titer with neuraminidase (NA) (1). Antigenic drift has been studied most very low cross-reactive titers against NAs of the long-established extensively for HA, although NA has also been observed to human seasonal H1N1 lineage (Table S2). undergo antigenic drift (2–4). NA-specific antibodies can reduce Phylogenetic trees, genetic maps based on amino acid se- viral replication and disease severity in mice (5) and chickens (6), quences, and antigenic maps were generated for HA and NA and have similarly been associated with resistance against in- of H1N1 (Fig. 1) and H3N2 (Fig. 2) viruses recommended for fluenza in humans (7, 8). Despite this correlation with immunity, inclusion in 1996–2009 seasonal influenza vaccines. Since NI antigenic drift of NA is not routinely examined. Early studies data had not previously been used to generate an NA antigenic with a few virus strains demonstrated discordant antigenic drift map, we first established that end-point NI titers provided suf- of HA and NA (4), suggesting the virus can overcome host an- ficient sensitivity for the analysis. This process was done by tibody resistance by modifying either antigen. Although it is comparative analysis of end-point titers (inverse of the serum likely that NA’s drift is most often the result of antibody selec- dilution that inhibits NA activity ≥50%) and the precise 50% tion, antigenic change may on occasion be a consequence of a inhibition titer (IC50), the inverse of the serum dilution that functional change in HA (9). results in exactly 50% inhibition determined by nonlinear re- Vigilant surveillance by public health agencies is required to gression analysis (14) of ferret antisera generated in response to maximize the match between seasonal vaccine antigens and pre- H3N2 infection. The maps generated using these datasets were dominant circulating viruses (10, 11). At present, vaccine strain- very similar, with an excellent correlation of distances between 2 selection decisions are based on antigenic characterization of HA antigens on the map, r = 0.99 (Fig. S1). End-point NI titers coupled with HA and NA genetic data, also taking into consid- eration epidemiologic and human serologic data (11). Antigenic cartography using data from HA inhibition (HI) assays provides Author contributions: M.R.S. and M.C.E. designed research; M.R.S., K.B.W., J.G., and M.C.E. performed research; X.X., A.I.K., D.J.S., and R.A.M.F. contributed new reagents/analytic a tool to visualize and quantitate antigenic relatedness of the HAs tools; M.R.S., K.B.W., C.A.R., D.F.B., D.J.S., and R.A.M.F. analyzed data; and M.R.S., K.B.W., of circulating viruses (12) in relation to vaccine viruses. Antigenic R.A.M.F., and M.C.E. wrote the paper. characterization of NA can be performed using NA inhibition The authors declare no conflict of interest. (NI) assays to determine the extent of antibody-mediated in- This article is a PNAS Direct Submission. terference with enzyme activity (13), but the cumbersome nature Freely available online through the PNAS open access option. of the standard NI assay using large volumes of hazardous 1 To whom correspondence should be addressed. E-mail: [email protected]. chemicals has precluded routine analysis of NA. We recently gov. fi developed a miniaturized format of this assay and con rmed its This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. accuracy and sensitivity for analysis of NI antibody titers in human 1073/pnas.1113801108/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1113801108 PNAS Early Edition | 1of6 Downloaded by guest on September 27, 2021 Fig. 1. Comparison of the antigenic and genetic evolution of NA and HA of influenza A (H1N1) virus. (A and B) Phylogenetic trees of the coding region of NA (A) and HA1 (B) nucleotide sequences. A/Brevig Mission/1918 was chosen as outgroup for both trees. Scale bars roughly represent 10% of nucleotide sub- stitutions between close relatives. (C) NA and (D) HA genetic maps. The vertical and horizontal axes represent genetic distance, in this case the number of amino acid substitutions between strains; the spacing between grid lines is 3 amino acid substitutions. (E) NA and (F) HA antigenic maps based on NI and HI data, in which the viruses are shown as circles and antisera as squares. The spacing between grid lines is one unit of antigenic distance, correspondingto a twofold dilution of antisera in the NI and HI assays. The orientations of all maps were chosen to roughly match the orientation of the HI antigenic map in F, and the color-coding of viruses is consistent among all panels. were therefore used in subsequent analyses. We also showed that greater than the antigenic distance between the HAs of these there was good correlation between antigenic distance deter- viruses (2.0 units). From this observation, we speculate that the mined using NI data in tables and the antigenic distance de- abrupt antigenic change of N1 NA may have been a factor termined from map location (Fig. S2)(r2 = 0.95 for N1 and r2 = contributing to the dominance of H1N1 in many parts of the 0.86 for N2 antigens), providing confidence that the antigenic Northern Hemisphere during the 2007/08 season (15). maps are representative of the raw data. To confirm the location The antigenic drift of NA was also not proportional to number of antigens on the map, NI assays were repeated using a larger of amino acid changes for H3N2 viruses isolated from the mid- number of antisera. There was excellent correlation between the 1990s [A/Wuhan/359/95 (WU/95)] to the 2009/10 Northern location of antigens generated by analyses of the first and second hemisphere formulation [A/Uruguay/716/2007 (UY/07), an A/ datasets (Fig. S3)(r2 = 0.98 for both N1 and N2 antigens). Brisbane/10/2007-like virus], even though phylogenetic analysis of The raw NI data as well as the antigenic map show that the NA the NAs of these viruses shows a chronologic progressive evolu- of human H1N1 viruses was in antigenic stasis for over a decade, tion at the nucleotide level (Fig.
Load more

Recommended publications
  • Dissecting Human Antibody Responses Against Influenza a Viruses and Antigenic Changes That Facilitate Immune Escape
    University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations 2018 Dissecting Human Antibody Responses Against Influenza A Viruses And Antigenic Changes That Facilitate Immune Escape Seth J. Zost University of Pennsylvania, [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Allergy and Immunology Commons, Immunology and Infectious Disease Commons, Medical Immunology Commons, and the Virology Commons Recommended Citation Zost, Seth J., "Dissecting Human Antibody Responses Against Influenza A Viruses And Antigenic Changes That Facilitate Immune Escape" (2018). Publicly Accessible Penn Dissertations. 3211. https://repository.upenn.edu/edissertations/3211 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/3211 For more information, please contact [email protected]. Dissecting Human Antibody Responses Against Influenza A Viruses And Antigenic Changes That Facilitate Immune Escape Abstract Influenza A viruses pose a serious threat to public health, and seasonal circulation of influenza viruses causes substantial morbidity and mortality. Influenza viruses continuously acquire substitutions in the surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). These substitutions prevent the binding of pre-existing antibodies, allowing the virus to escape population immunity in a process known as antigenic drift. Due to antigenic drift, individuals can be repeatedly infected by antigenically distinct influenza strains over the course of their life. Antigenic drift undermines the effectiveness of our seasonal influenza accinesv and our vaccine strains must be updated on an annual basis due to antigenic changes. In order to understand antigenic drift it is essential to know the sites of antibody binding as well as the substitutions that facilitate viral escape from immunity.
    [Show full text]
  • Through a Combination of Continual Antigenic Drift of Surface Proteins and High Transmission Rates the Identity of Circulating I
    Title: Computer-assisted vaccine design Hao Zhou, Ramdas S. Pophale, and Michael W. Deem Departments of Bioengineering and Physics & Astronomy Rice University Houston, TX, USA Abstract We define a new parameter to quantify the antigenic distance between two H3N2 influenza strains: we use this parameter to measure antigenic distance between circulating H3N2 strains and the closest vaccine component of the influenza vaccine. For the data between 1971 and 2004, the measure of antigenic distance correlates better with efficacy in humans of the H3N2 influenza A annual vaccine than do current state of the art measures of antigenic distance such as phylogenetic sequence analysis or ferret antisera inhibition assays. We suggest that this measure of antigenic distance could be used to guide the design of the annual flu vaccine. We combine the measure of antigenic distance with a multiple-strain avian influenza transmission model to study the threat of simultaneous introduction of multiple avian influenza strains. For H3N2 influenza, the model is validated against observed viral fixation rates and epidemic progression rates from the World Health Organization FluNet – Global Influenza Surveillance Network. We find that a multiple-component avian influenza vaccine is helpful to control a simultaneous multiple introduction of bird-flu strains. We introduce Population at Risk (PaR) to quantify the risk of a flu pandemic, and calculate by this metric the improvement that a multiple vaccine offers. Computer-assisted vaccine design Introduction Circulating influenza virus uses the ability to change its surface proteins, along with its high transmission rate, to flummox the adaptive immune response of the host. The random accumulation of mutations in the hemagglutinin (HA) and neuraminidase (NA) epitopes, the regions on surface of the viral proteins that are recognized by host antibodies, pose a formidable challenge to the design of an effective annual flu vaccine.
    [Show full text]
  • Antigenic Variation in Vector-Borne Pathogens
    Synopsis Antigenic Variation in Vector-Borne Pathogens Alan G. Barbour* and Blanca I. Restrepo† *University of California Irvine, Irvine, California; and †Corporación para Investigaciones Biológicas, Medellín, Colombia Several pathogens of humans and domestic animals depend on hematophagous arthropods to transmit them from one vertebrate reservoir host to another and maintain them in an environment. These pathogens use antigenic variation to prolong their circulation in the blood and thus increase the likelihood of transmission. By convergent evolution, bacterial and protozoal vector-borne pathogens have acquired similar genetic mechanisms for successful antigenic variation. Borrelia spp. and Anaplasma marginale (among bacteria) and African trypanosomes, Plasmodium falciparum, and Babesia bovis (among parasites) are examples of pathogens using these mechanisms. Antigenic variation poses a challenge in the development of vaccines against vector- borne pathogens. What Is Antigenic Variation? original antigen is archived in the cell and can be Immunodominant antigens are commonly used in the future. The adaptive immune system used to distinguish strains of a species of of an infected vertebrate selects against the pathogens. These antigens can vary from strain original infecting serotype, but that specific to strain to the extent that the strain-specific response is ineffective against new variants. One immune responses of vertebrate reservoirs example of antigenic variation occurs in determine the population structure of the B. hermsii, a cause of tickborne relapsing fever pathogen. One such strain-defining antigen is (4), which has a protein homologous to the OspC the OspC outer membrane protein of the Lyme protein of B. burgdorferi. However, instead of a disease spirochete Borrelia burgdorferi in the single version of this gene, each cell of B.
    [Show full text]
  • Evolution and Adaptation of the Avian H7N9 Virus Into the Human Host
    microorganisms Review Evolution and Adaptation of the Avian H7N9 Virus into the Human Host Andrew T. Bisset 1,* and Gerard F. Hoyne 1,2,3,4 1 School of Health Sciences, University of Notre Dame Australia, Fremantle WA 6160, Australia; [email protected] 2 Institute for Health Research, University of Notre Dame Australia, Fremantle WA 6160, Australia 3 Centre for Cell Therapy and Regenerative Medicine, School of Biomedical Sciences, The University of Western Australia, Nedlands WA 6009, Australia 4 School of Medical and Health Sciences, Edith Cowan University, Joondalup WA 6027, Australia * Correspondence: [email protected] Received: 19 April 2020; Accepted: 19 May 2020; Published: 21 May 2020 Abstract: Influenza viruses arise from animal reservoirs, and have the potential to cause pandemics. In 2013, low pathogenic novel avian influenza A(H7N9) viruses emerged in China, resulting from the reassortment of avian-origin viruses. Following evolutionary changes, highly pathogenic strains of avian influenza A(H7N9) viruses emerged in late 2016. Changes in pathogenicity and virulence of H7N9 viruses have been linked to potential mutations in the viral glycoproteins hemagglutinin (HA) and neuraminidase (NA), as well as the viral polymerase basic protein 2 (PB2). Recognizing that effective viral transmission of the influenza A virus (IAV) between humans requires efficient attachment to the upper respiratory tract and replication through the viral polymerase complex, experimental evidence demonstrates the potential H7N9 has for increased binding affinity and replication, following specific amino acid substitutions in HA and PB2. Additionally, the deletion of extended amino acid sequences in the NA stalk length was shown to produce a significant increase in pathogenicity in mice.
    [Show full text]
  • Recitation 21 – Fall 2018 (Note: the Recitation Summary Should NOT Be Regarded As the Substitute for Lectures) (This Material Is COPYRIGHT Protected.)
    7.016: Fall 2018: MIT 7.016 Recitation 21 – Fall 2018 (Note: The recitation summary should NOT be regarded as the substitute for lectures) (This material is COPYRIGHT protected.) Summary of Lectures 32 (12/3) & 33 (12/5): Viruses: Viruses are obligate intracellular parasites. They consist of a protein coat (capsid) surrounding a genome, which encodes for proteins. These may include structural or coat proteins, other proteins necessary to get inside the host cell and make copies of the viral genome and the proteins that provide the virus with the anti–host defense system. Non-enveloped/ naked viruses do not have a lipid bilayer surrounding their capsid. They typically dock onto a protein on the surface of the target cells and inject their genomes into the host. Enveloped viruses have a lipid bilayer. They fuse their own membrane with the host membrane, such that the entire viral particle is endocytosed into the host cell. Once a virus is inside its host, it takes over the host machinery and uses it to make coat proteins and viral genomes. The genomes are then packaged into the coats and the new viral particles escape from the host cell either by lysing the cell or budding off from the cell. Viral genomes can be composed of either DNA or RNA. They can be single-stranded or double- stranded. There are two types of single stranded RNA viruses: plus (+) stranded or minus (-) stranded. The plus (+) stranded RNA genome can be directly read and translated by the host cell translation machinery. So these viruses bring only their genome, with no additional proteins, into the host cells at the time of infection.
    [Show full text]
  • Antigenic Drift in Type a Influenza Virus
    Proc. Natl. Acad. Sci. USA Vol. 76, No. 3, pp. 1425-1429, March 1979 Immunology Antigenic drift in type A influenza virus: Peptide mapping and antigenic analysis of A/PR/8/34 (HONI) variants selected with monoclonal antibodies (antigenic variants/hemagglutinin/peptide maps/amino acid changes) W. G. LAVER*, W. GERHARDt, R. G. WEBSTERf, M. E. FRANKELO, AND G. M. AIR* *Department of Microbiology, John Curtin School of Medical Research, Australian National University, Canberra, Australia; tThe Wistar Institute of Anatomy and Biology, 36th Street at Spruce, Philadelphia, Pennsylvania 19104; and tDivision of Virology, St Jude Children's Research Hospital, P.O. Box 318, Memphis, Tennessee 38101 Communicated by Robert M. Chanock, December 11, 1978 ABSTRACT Variants of A/PR/8/34 (HONI) influenza virus, quence (7, 8). It is likely that many of these changes are unre- having hemagglutinin molecules with probably a single altered lated to the antigenic differences between the HAs, so that antigenic determinant, were isolated by growing the virus in analysis of natural variants may not reflect the differences in the presence of the monoclonal hybridoma antibody PEG-1. The variants were analyzed by peptide mapping and characterized antigenic determinants. By using monoclonal antibodies, we antigenically by using PEG-i and four other monoclonal hy- have been able to select variant viruses in which the changes bridoma antibodies to PR8 hemagglutinin. Peptide maps of the in sequence of the HA polypeptides have a better chance of large hemagglutinin polypeptide, HAI, from 8 out of 10 variants being restricted to those affecting the determinant recognized showed a single changed peptide.
    [Show full text]
  • The Development and Use of a Poxvirus Vector System to Protect Pigs Against Swine Influenza Virus Patricia Louise White Foley Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1998 The development and use of a poxvirus vector system to protect pigs against swine influenza virus Patricia Louise White Foley Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Agriculture Commons, Animal Sciences Commons, Immunology and Infectious Disease Commons, Medical Immunology Commons, Microbiology Commons, and the Veterinary Pathology and Pathobiology Commons Recommended Citation Foley, Patricia Louise White, "The development and use of a poxvirus vector system to protect pigs against swine influenza virus " (1998). Retrospective Theses and Dissertations. 12192. https://lib.dr.iastate.edu/rtd/12192 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. tNFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly firom the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted.
    [Show full text]
  • Evolution and Ecology of Influenza a Viruses ROBERT G
    MICROBIOLOGICAL REVIEWS, Mar. 1992, p. 152-179 Vol. 56, No. 1 0146-0749/92/010152-28$02.00/0 Copyright © 1992, American Society for Microbiology Evolution and Ecology of Influenza A Viruses ROBERT G. WEBSTER,* WILLIAM J. BEAN, OWEN T. GORMAN, THOMAS M. CHAMBERS,t AND YOSHIHIRO KAWAOKA Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, 332 North Lauderdale, P.O. Box 318, Memphis, Tennessee 38101 INTRODUCTION ............ 153 STRUCTURE AND FUNCTION OF THE INFLUENZA VIRUS VIRION .153 Components of the Virion.153 PB2 polymerase.154 PB1 polymerase.154 PA polymerase ........... 154 Hemagglutinin.154 Nucleoprotein .155 Neuraminidase.155 Ml protein ............................................... 155 M2 protein .155 Nonstructural NS1 and NS2 proteins.155 Influenza Virus Replication Cycle.156 RESERVOIRS OF INFLUENZA A VIRUSES IN NATURE.156 Influenza Viruses in Birds: Wild Ducks, Shorebirds, Gulls, Poultry, and Passerine Birds.156 Influenza Viruses in Pigs.158 Influenza Viruses in Horses ....................P 159 Influenza Viruses in Other Species: Seals, Mink, and Whales.159 Molecular Determinants of Host Range Restriction.160 Mechanism for Perpetuating Influenza Viruses in Avian Species.161 Continuous circulation in aquatic bird species.161 Circulation between different avian species.161 Persistence in water or ice.161 Persistence in individual animals .161 Continuous circulation in subtropical and tropical regions .161 EVOLUTIONARY PATHWAYS.161 Evolutionary Patterns among Influenza A Viruses.161 Selection Pressures
    [Show full text]
  • Exploiting Pan Influenza a and Pan Influenza B Pseudotype Libraries for Efficient Vaccine Antigen Selection
    Article Exploiting Pan Influenza A and Pan Influenza B Pseudotype Libraries for Efficient Vaccine Antigen Selection Joanne Marie M. Del Rosario 1,2,3,†, Kelly A. S. da Costa 1,† , Benedikt Asbach 4 , Francesca Ferrara 1,5 , Matteo Ferrari 3,6, David A. Wells 3,6, Gurdip Singh Mann 1, Veronica O. Ameh 7,8, Claude T. Sabeta 8,9, Ashley C. Banyard 10 , Rebecca Kinsley 3,6, Simon D. Scott 1 , Ralf Wagner 4,11, Jonathan L. Heeney 3,6, George W. Carnell 3,6 and Nigel J. Temperton 1,3,* 1 Viral Pseudotype Unit, Medway School of Pharmacy, The Universities of Greenwich and Kent at Medway, Chatham ME4 4BF, UK; [email protected] (J.M.M.D.R.); [email protected] (K.A.S.d.C.); [email protected] (F.F.); [email protected] (G.S.M.); [email protected] (S.D.S.) 2 Department of Physical Sciences and Mathematics, College of Arts and Sciences, University of the Philippines Manila, Manila 1000, Philippines 3 DIOSynVax, Cambridge CB3 0ES, UK; [email protected] (M.F.); [email protected] (D.A.W.); [email protected] (R.K.); [email protected] (J.L.H.); [email protected] (G.W.C.) 4 Institute of Medical Microbiology and Hygiene, University of Regensburg, 93053 Regensburg, Germany; [email protected] (B.A.); [email protected] (R.W.) 5 Vector Development and Production Laboratory, St. Jude Children’s Research Hospital, Memphis, TN 38105, USA 6 Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK 7 Department of Veterinary Public Health and Preventive Medicine, College of Veterinary Medicine, Federal University of Agriculture Makurdi, Makurdi P.M.B.
    [Show full text]
  • The Search for Protective Host Responses
    AIDS Viruses of Animals and Man ow does a host usually develop nately, appear to be resistant to destruc- The Search a state of protection against an tion by complement. H invading virus? Three major Studies performed in my laboratory host responses to invading viruses in- in 1987 showed no evidence of ACC clude activation of complement, produc- activity in humans at various stages tion of neutralizing and complement- of AIDS despite the presence of large Protective fixing antibodies, and cell-mediated im- amounts of antibody directed against mune responses. Traditionally, when both HIV and HIV-infected cells. The Host a new viral disease is recognized in a absence of ACC is also documented in species, efforts to understand the pro- visna-maedi. No ACC activity has been Responses tective immune states are derived from reported for the other animal-lentivirus its surviving members. These individ- systems mentioned here. Both my lab uals serve as immune benchmarks, and and others have shown that human com- subsequent studies often reveal impor- plement is incapable of inactivating HIV tant clues to the eventual production of either directly or in the presence of neu- a vaccine. Here we will review studies tralizing antibody. Recently, we have of the major antiviral immune responses discovered a heat-sensitive serum factor to HIV and see that none of them are in various laboratory and wild animal completely effective, although some av- species that does inactivate the human enues of developing traditional vaccines AIDS virus in vitro. Further studies are for AIDS are still open. underway to characterize this factor, or factors, and to understand how to recruit Complement.
    [Show full text]
  • Can We Predict the Limits of SARS-Cov-2 Variants and Their Phenotypic Consequences?
    Can we predict the limits of SARS-CoV-2 variants and their phenotypic consequences? As eradication of SARS-CoV-2 will be unlikely, we have high confidence in stating that there will always be variants. The number of variants will depend on control measures. We describe hypothetical scenarios by which SARS-CoV-2 could further evolve and acquire, through mutation, phenotypes of concern, which we assess according to possibility. For this purpose, we consider mutations in the ‘body’ of the virus (the viral genes that are expressed in infected cells and control replication and cell response), that might affect virus fitness and disease severity, separately from mutations in the spike glycoprotein that might affect virus transmission and antibody escape. We assess which scenarios are the most likely and what impact they might have and consider how these scenarios might be mitigated. We provide supporting information based on the evolution of SARS-CoV-2, human and animal coronaviruses as well as drawing parallels with other viruses. Scenario One: A variant that causes severe disease in a greater proportion of the population than has occurred to date. For example, with similar morbidity/mortality to other zoonotic coronaviruses such as SARS-CoV (~10% case fatality) or MERS-CoV (~35% case fatality). This could be caused by: 1. Point mutations or recombination with other host or viral genes. This might occur through a change in SARS-CoV-2 internal genes such as the polymerase proteins or accessory proteins. These genes determine the outcome of infection by affecting the way the virus is sensed by the cell, the speed at which the virus replicates and the anti-viral response of the cell to infection.
    [Show full text]
  • The Influenza Virus: Antigenic Composition and Immune Response
    Postgrad Med J: first published as 10.1136/pgmj.55.640.87 on 1 February 1979. Downloaded from Postgraduate Medical Journal (February 1979) 55, 87-97. The influenza virus: antigenic composition and immune response G. C. SCHILD B.Sc., Ph.D., F.I.Biol. Division of Viral Products, National Institute for Biological Standards and Control, Holly Hill, Hampstead, London NW3 6RB Summary capricious epidemiological behaviour of the The architecture and chemical composition of the causative virus and perhaps also the nature of the influenza virus particle is described with particular immune response in man to influenza antigens. reference to the protein constituents and their genetic control. The dominant role in infection of the surface Antigenic composition of the virus proteins - haemagglutinins and neuraminidases - Studies of the single-stranded, negative-strand, acting as antigens and undergoing variation in time RNA genome of the influenza A virus have revealed known as antigenic drift and shift is explained. The the existence of 8 species of RNA molecules (gene immuno-diffusion technique has illuminated the inter- segments) in the virus (McGeoch, Fellner and relationships of the haemagglutinins of influenza A Newton, 1976; Palese and Schulman, 1976a). viruses recovered over long periods of time. The Ho Each gene segment provides the code for one of the and H1 haemagglutinins are now regarded as a single 8 virus specific proteins synthetized in infected sub-type with H2 and H3 representing the haemag- cells. Seven of these proteins are integrated into glutinins of the 1957 and 1968 sub-types. Animal influenza virus particles. Table 1 summarizes the by copyright.
    [Show full text]