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Research Project: Control Strategies to Prevent and Respond to Diseases Outbreaks Caused by Avian Influenza Viruses

Location: Exotic & Emerging Avian Viral Diseases Research

Title: Efficacy of recombinant H5 vaccines delivered in ovo or day of age in commercial broilers against the 2015 U.S. H5N2 clade 2.3.4.4c highly pathogenic avian influenza virus

Author
item Kapczynski, Darrell
item CHRZASTEK, KLAUDIA - ORISE FELLOW
item Shanmugasundaram, Revathi
item ZSAK, ANIKO
item SEGOVIA, KAREN - ORISE FELLOW
item SELLERS, HOLLY - UNIVERSITY OF GEORGIA
item Suarez, David

Submitted to: Virology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2023
Publication Date: 12/15/2023
Citation: Kapczynski, D.R., Chrzastek, K., Shanmugasundaram, R., Zsak, A., Segovia, K., Sellers, H., Suarez, D.L. 2023. Efficacy of recombinant H5 vaccines delivered in ovo or day of age in commercial broilers against the 2015 U.S. H5N2 clade 2.3.4.4c highly pathogenic avian influenza virus. Virology Journal. 20(1):298. https://doi.org/10.1186/s12985-023-02254-1.
DOI: https://doi.org/10.1186/s12985-023-02254-1

Interpretive Summary: Highly pathogenic avian influenza (HPAI) virus is a constant threat to the U.S. poultry industry. Between December 2014 and June 2015, the U.S. experienced the largest recorded foreign animal disease outbreak with approximately 47 million birds dead or euthanized from infection with a H5Nx HPAI virus. The economic impact of this outbreak is an estimated $3.3 billion USD to the U.S. poultry industry, and resulted in trade partners banning U.S. poultry imports. During the outbreak, the ability of vaccines to protect commercial chickens from HPAI was unknown. In this study, we investigated two recombinant H5 avian influenza vaccines for protection of broiler chickens. The results demonstrate that while both were effective, one was superior when delivered in ovo into the developing embryo. This route of vaccination would be consider optimal since it can be applied in a mass application to commercial poultry. Overall, this data can be used to develop intervention strategies to protect commercial broiler flocks from future HPAI outbreaks.

Technical Abstract: Background: Avian influenza is a highly contagious, agriculturally relevant disease that can severely affect the poultry industry and food supply. Eurasian-origin H5Nx highly pathogenic avian influenza viruses (HPAIV) (clade 2.3.4.4) have been circulating globally in wild birds with spill over into commercial poultry operations. The negative impact to commercial poultry renewed interest in the development of vaccines against these viruses to control outbreaks in the U.S. Methods: The efficacy of three recombinant H5 vaccines delivered in ovo or day of age were evaluated in commercial broilers challenged with the 2015 U.S. H5N2 clade 2.3.4.4c HPAIV. The recombinant vaccines included an alphavirus RNA particle vaccine (RP-H5), an inactivated reverse genetics-derived (RG-H5) and recombinant HVT vaccine (rHVT-AI) expressing H5 hemagglutinin (HA) genes. In the first experiment, in ovo vaccination with RP-H5 or rHVT-AI was tested against HPAI challenge at 3 or 6 weeks of age. In a second experiment, broilers were vaccinated at 1 day of age with a dose of either 107 or 108 RP-H5, or RG-H5 (512 HA units (HAU) per dose). Results: In experiment one, the RP-H5 provided no protection following in ovo application, and shedding titers were similar to sham vaccinated birds. However, when the RP-H5 was delivered in ovo with a boost at 3 weeks, 95% protection was demonstrated at 6 weeks of age. The rHVT-AI vaccine demonstrated 95 and 100% protection at 3 and 6 weeks of age, respectively, of challenged broilers with reduced virus shedding compared to sham vaccinated birds. Finally, when the RP-H5 and rHVT vaccines were co-administered at one day of age, 95% protection was demonstrated with challenge at either 3 or 6 weeks age. In the second experiment, the highest protection (92%) was observed in the 108 RP-H5 vaccinated group. Significant reductions (p < 0.05) in virus shedding were observed in groups of vaccinated birds that were protected from challenge. The RG-H5 provided 62% protection from challenge. In all groups of surviving birds, antibody titers increased following challenge.