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Title: Variation in protection of four divergent avian influenza virus vaccine seed strains against eight clade 2.2.1 and 2.2.1.1. Egyptian H5N1 high pathogenicity variants in poultry

Author
item Spackman, Erica
item Swayne, David
item Pantin Jackwood, Mary
item WAN, XIU-FENG - Mississippi State University
item TORCHETTI, MIA KIM - Animal And Plant Health Inspection Service (APHIS)
item HASSAN, MOHAMMAD - National Laboratory For Veterinary Quality Control On Poultry Production
item Suarez, David
item Sa E Silva, Mariana

Submitted to: Influenza and Other Respiratory Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2014
Publication Date: 10/4/2014
Publication URL: http://handle.nal.usda.gov/10113/59861
Citation: Spackman, E., Swayne, D.E., Pantin Jackwood, M.J., Wan, X., Torchetti, M., Hassan, M., Suarez, D.L., Sa E Silva, M. 2014. Variation in protection of four divergent avian influenza virus vaccine seed strains against eight clade 2.2.1 and 2.2.1.1. Egyptian H5N1 high pathogenicity variants in poultry. Influenza and Other Respiratory Viruses. doi: 10.1111/irv.12290.

Interpretive Summary: A severe form of bird flu has become entrenched in some parts of the world, including Egypt. Vaccination of chickens and other poultry has been used as a control measure, however the virus has changed so that the original vaccines are no longer as effective as they were initially. In order to determine which vaccines are most effective against the new strains, we have compared how well current local strains work as vaccines in comparison to the original vaccines and viruses. The old vaccines protected better against the old strains than the newer strains as expected. The newer, local strains did not provide complete protection against the new strains. This data suggests that the newer strains may have changed so that they do not elicit an adequate immune response, therefore they would not make good vaccines. A second part of the study was to look at the relationships of the main structural coat protein of the virus among the vaccines and isolates. The expectation is that the more closely related the virus coats are between a vaccine and virus the better the protection will be. We did not observe this relationship in this data.

Technical Abstract: Highly pathogenic (HP) H5N1 avian influenza virus (AIV) was introduced to Egyptian poultry in 2006 and has since become enzootic. Vaccination has been utilized as a control tool, but for a variety of reasons the disease has not been eradicated. In 2007, an antigenically divergent hemagglutinin sub-clade, 2.2.1.1, emerged from the original clade 2.2.1 viruses. Objectives: The objective was to evaluate four diverse AIV isolates as vaccines in chickens, including two commercial vaccines and two additional contemporary isolates, against challenge with numerous clade 2.2.1 and clade 2.2.1.1 H5N1 HPAIV Egyptian isolates to assess the variation in protection among different vaccine and challenge virus combinations. Methods: Vaccination-challenge studies with four vaccines and up to eight challenge strains with each vaccine for a total of 25 vaccination-challenge groups were conducted with chickens. An additional eight groups served as sham vaccinated controls. Mortality, mean death time, morbidity, virus and pre-challenge antibodies were evaluated as metrics of protection. Hemagglutination inhibition data was used to visualize the antigenic relatedness of the isolates. Results and conclusions: Although all but one vaccine-challenge virus combination significantly reduced shed and mortality as compared to sham vaccinates, there were differences in protection among the vaccines relative to one another based on challenge virus. This emphasizes the difficulty in vaccinating against diverse, evolving virus populations, and the importance of selecting optimal vaccine seed strains for successful HPAIV control.