title: Using epidemics to map H3 equine influenza virus determinants of antigenicity.
abstract: Equine influenza is a major cause of respiratory infections in horses and causes widespread epidemics, despite the availability of commercial vaccines. Antigenic drift within the haemagglutinin (HA) glycoprotein is thought to play a part in vaccination breakdown. Here, we carried out a detailed investigation of the 1989 UK outbreak, using reverse genetics and site-directed mutagenesis, to determine the individual contribution of amino acid substitutions within HA. Mutations at positions 159, 189 and 227 all altered antigenicity, as measured by haemagglutination-inhibition assays. We also compared HA sequences for epidemic and vaccine strains from four epidemics and found that at least 8 amino acid differences were present, affecting multiple antigenic sites. Substitutions within antigenic site B and at least one other were associated with each outbreak, we also identified changes in loop regions close to antigenic sites that have not previously been highlighted for human H3 influenza viruses.
authors: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. Electronic address: alana.woodward@aht.org.uk.
authors: Alana
authors: A
authors: Woodward
authors: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. Electronic address: adam.rash@aht.org.uk.
authors: Adam S
authors: AS
authors: Rash
authors: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. Electronic address: elizabeth.medcalf@aht.org.uk.
authors: Elizabeth
authors: E
authors: Medcalf
authors: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. Electronic address: neil.bryant@aht.org.uk.
authors: Neil A
authors: NA
authors: Bryant
authors: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket CB8 7UU, UK. Electronic address: debra.elton@aht.org.uk.
authors: Debra M
authors: DM
authors: Elton
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation; D018604:Epitope Mapping; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D006734:Horse Diseases / Q000453:epidemiology / Q000821:virology*; D006736:Horses; D009980:Influenza A virus / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000276:immunology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D016415:Sequence Alignment; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus
keywords: Antigenic drift; Equine influenza; Hemagglutinin; Reverse genetics; Vaccine breakdown