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Potency, Efficacy, and Antigenic Mapping of H7 Avian Influenza Virus Vaccines Against the 2012 H7N3 Highly Pathogenic Avian Invluenza Virus from Mexico

Erica Spackman, Xiu-Feng Wan, Darrell Kapczynski, Yifei Xu, Mary Pantin-Jackwood, David L. Suarez, David Swayne
Avian diseases 2014 v.58 no.3 pp. 359-366
Influenza A virus, antigenic variation, chickens, disease prevention, dose response, epitope mapping, genetic distance, hemagglutination, hemagglutination inhibition test, morbidity, mortality, pathogenicity, vaccination, viral vaccines, virulent strains, viruses, wild birds, Mexico
In the spring of 2012 an outbreak of H7N3 highly pathogenic (HP) avian influenza virus (AIV) occurred in poultry in Mexico. Vaccination was implemented as a control measure, along with increased biosecurity and surveillance. At that time there was no commercially available H7 AIV vaccine in North America; therefore, a recent H7N3 wild bird isolate of low pathogenicity from Mexico (A/cinnamon teal/Mexico/2817/2006 H7N3) was selected and utilized as the vaccine seed strain. In these studies, the potency and efficacy of this vaccine strain was evaluated in chickens against challenge with the 2012 Jalisco H7N3 HPAIV. Although vaccine doses of 256 and 102 hemagglutinating units (HAU) per bird decreased morbidity and mortality significantly compared to sham vaccinates, a dose of 512 HAU per bird was required to prevent mortality and morbidity completely. Additionally, the efficacy of 11 other H7 AIV vaccines and an antigenic map of hemagglutination inhibition assay data with all the vaccines and challenge viruses were evaluated, both to identify other potential vaccine strains and to characterize the relationship between genetic and antigenic distance with protection against this HPAIV. Several other isolates provided adequate protection against the 2012 Jalisco H7N3 lineage, but antigenic and genetic differences were not clear indicators of protection because the immunogenicity of the vaccine seed strain was also a critical factor.