title: Evidence supporting the inclusion of strains from each of the two co-circulating lineages of H3N8 equine influenza virus in vaccines.
abstract: Two lineages of antigenically distinct equine influenza A H3N8 subtype viruses, American and European, co-circulate. Experiments were conducted in ponies to investigate the protection induced by vaccines containing virus from one lineage against challenge infection with homologous or heterologous virus. Regression analysis showed that vaccinated ponies with average pre-challenge single radial haemolysis (SRH) antibody levels (i.e. 45-190mm2) had a higher probability of becoming infected if they were vaccinated with virus heterologous to the challenge strain than if they were vaccinated with homologous virus. Field studies in Thoroughbred racehorses also showed that SRH antibody levels of >/= 150mm2 induced by vaccines containing a European lineage strain are protective against infection with a virus from the same lineage, but that the same or higher antibody levels may not be protective against an American lineage virus. In conclusion, vaccines should contain virus strains representative of both H3N8 subtype lineages to maximise protection against infection.
authors.affiliation: Centre for Preventive Medicine, Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK. janet.daly@aht.org.uk
authors.forename: Janet M
authors.initials: JM
authors.lastname: Daly
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Yates
authors.forename: J Richard
authors.initials: JR
authors.lastname: Newton
authors.forename: Andrew
authors.initials: A
authors.lastname: Park
authors.forename: William
authors.initials: W
authors.lastname: Henley
authors.forename: James L N
authors.initials: JL
authors.lastname: Wood
authors.forename: Nick
authors.initials: N
authors.lastname: Davis-Poynter
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Mumford
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D000956:Antigens, Viral / Q000032:analysis; D006389:Hemagglutinins, Viral / Q000235:genetics; D006734:Horse Diseases / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D006736:Horses; D053123:Influenza A Virus, H3N8 Subtype; D009980:Influenza A virus / Q000145:classification* / Q000235:genetics / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D009976:Orthomyxoviridae Infections / Q000453:epidemiology / Q000517:prevention & control* / Q000662:veterinary* / Q000821:virology; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D014611:Vaccination / Q000662:veterinary
chemical_list: D000914:Antibodies, Viral; D000956:Antigens, Viral; D006389:Hemagglutinins, Viral; D007252:Influenza Vaccines