Title: Potency, efficacy and antigenic mapping of H7 avian influenza virus vaccines against the 2012 H7N3 highly pathogenic avian influenza virus from Mexico Authors
|Wan, Xiu-Feng -|
|Xu, Yifei -|
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 17, 2014
Publication Date: N/A
Interpretive Summary: A virulent avian influenza virus caused an outbreak in chickens in Mexico in 2012. The virus caused severe disease and the authorities in Mexico decided to prepare and use a vaccine based on a local non-virulent virus isolate from 2006. Since time was short little initial testing could be conducted to determine if the selected vaccine strain was a good fit. Therefore studies were conducted to evaluate the dose of the official vaccines strain that was protective, and it was found that a standard dose was sufficient. Additionally, several other avian influenza virus isolates of the same subtype were tested for whether they could be used as vaccines as well. It was shown that several other closely related isolates would be adequate vaccines if needed.
Technical Abstract: 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 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 seed 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 as 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 virus were evaluated both to identify other potential vaccine strains and to characterize the relationship between genetic and antigenic distance with protection to 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 as the immunogenicity of the vaccine seed strain was also critical factor.