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Protection of commercial turkeys following inactivated or recombinant H5 vaccine application against the 2015U.S. H5N2 clade highly pathogenic avian influenza virus

Darrell R. Kapczynski, Matthew J. Sylte, Mary L. Killian, Mia K. Torchetti, Klaudia Chrzastek, David L. Suarez
Veterinary immunology and immunopathology 2017 v.191 pp. 74-79
Alphavirus, genes, vaccination, poults, antibodies, viruses, viral shedding, blood serum, disease outbreaks, control methods, hemagglutinins, hemagglutination, survival rate, Meleagrid alphaherpesvirus 1, epizootic diseases, Influenza A virus, turkeys, avian influenza, recombinant vaccines, cloaca, RNA, North America
Between December 2014 and June 2015, North America experienced the largest recorded foreign animal disease outbreak with over 47 million poultry dead or euthanized from viral exposure to a clade H5 highly pathogenic avian influenza (HPAI) epizootic. Soon after the epizootic began, the U.S. Department of Agriculture (USDA) began testing the efficacy of different vaccines as a possible future control strategy. The aim of these studies were to evaluate the efficacy three H5 vaccines to aid in control of HPAI in commercial turkeys. Three different vaccine technologies were evaluated for efficacy: 1) inactivated reverse genetic laboratory-generated virus encoding a clade H5 hemagglutinin (HA) gene (rgH5), 2) recombinant turkey herpesvirus encoding a clade 2.2. H5 HA (rHVT-AI), and 3) recombinant replication-deficient alphavirus RNA particle vaccine encoding a clade H5 HA (RP-H5). All vaccines tested significantly (P<0.01) increased survival rates between vaccinated and sham vaccinated groups of poults challenged with A/turkey/Minnesota/12582/2015 clade H5N2 HPAI. The rgH5 vaccine had detectable serum hemagglutination inhibition (HI) antibody against the challenge virus, and significantly reduced the frequency and level of viral shedding from oropharyngeal and cloacal swabs at days 2 and 4 post-challenge. Vaccination with only rHVT-AI or RP-H5 was not 100% protective, and failed to significantly reduce viral shedding post-challenge. A combined prime and boost strategy with the rHVT-AI and RP-H5, or rHVT-AI and rgH5, was 100% protective against lethal H5N2 HPAI challenge.Results of these studies led to USDA conditional approval of commercially available recombinant vaccines for use in turkeys as a control measure for clade H5 HPAI epizootics.