title: Comparison of hamster and pony challenge models for evaluation of effect of antigenic drift on cross protection afforded by equine influenza vaccines.
abstract: BACKGROUND
  Vaccination and challenge studies in ponies are the most relevant experimental system for predicting whether strains included in equine influenza vaccines are relevant, but they are difficult to perform.
  
  
  OBJECTIVE
  In order to investigate the feasibility of using a small animal model, results of a cross-protection study in hamsters were compared with those from a previous pony challenge experiment.
  
  
  METHODS
  Animals were immunised with inactivated vaccines containing one of 4 strains of equine influenza A H3N8 subtype virus isolated over a 26 year period (1963 to 1989), then challenged with a 1989 strain.
  
  
  RESULTS
  Although there was no significant difference in titres of excreted virus between groups of vaccinated ponies, hamsters immunised with heterologous strains had significantly higher virus titres in the lung than hamsters vaccinated with the homologous strain. In both ponies and hamsters, the number of animals excreting virus was greater the earlier the isolation date of the vaccine strain, although this was only significant in the hamster study.
  
  
  CONCLUSIONS
  Despite differences, the overall conclusion of both the pony and hamster models was that heterologous vaccines may be less effective than homologous vaccines at preventing virus excretion.
  
  
  CONCLUSIONS
  Further validation is required, but the hamster model shows potential for preliminary assessment of the effects of antigenic drift on vaccine efficacy.
authors.affiliation: Animal Health Trust, Lanwades Park, Kentford, Newmarket, Suffolk CB8 7UU, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Daly
authors.forename: R J
authors.initials: RJ
authors.lastname: Yates
authors.forename: G
authors.initials: G
authors.lastname: Browse
authors.forename: Z
authors.initials: Z
authors.lastname: Swann
authors.forename: J R
authors.initials: JR
authors.lastname: Newton
authors.forename: D
authors.initials: D
authors.lastname: Jessett
authors.forename: N
authors.initials: N
authors.lastname: Davis-Poynter
authors.forename: J A
authors.initials: JA
authors.lastname: Mumford
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D000940:Antigenic Variation; D006224:Cricetinae; D003429:Cross Reactions; D006734:Horse Diseases / Q000517:prevention & control*; D006736:Horses; D009980:Influenza A virus / Q000276:immunology*; D007252:Influenza Vaccines / Q000276:immunology*; D008168:Lung / Q000821:virology; D008647:Mesocricetus; D023421:Models, Animal; D009976:Orthomyxoviridae Infections / Q000517:prevention & control / Q000662:veterinary*; D011897:Random Allocation; D014613:Vaccines, Attenuated / Q000276:immunology; D017201:Virus Shedding
chemical_list: D000914:Antibodies, Viral; D007252:Influenza Vaccines; D014613:Vaccines, Attenuated