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Vaccine Protection of Turkeys Against H5N1 Highly Pathogenic Avian Influenza Virus with a Recombinant Turkey Herpesvirus Expressing the Hemagglutinin Gene of Avian Influenza

Kapczynski Darrell R., Dorsey Kristi, Chrzastek Klaudia, Moraes Mauro, Jackwood Mark, Hilt Debra, Gardin Yannick
Avian diseases 2016 v.60 no.2 pp. 413-417
immunity, gastrointestinal system, Meleagrid alphaherpesvirus 1, turkeys, Influenza A virus, animal health, gene expression, food availability, hemagglutinins, genes, avian influenza, recombinant vaccines, vaccination, viral load, cloaca, viral shedding, viruses, virulence, health foods
Outbreaks of H5 highly pathogenic avian influenza (HPAI) in commercial poultry are a constant threat to animal health and food supplies. While vaccination can enhance protection and reduce the spread of disease, there is considerable evidence that the level of immunity required for protection varies by subtype and virulence of field virus. In this study, the efficacy of a recombinant turkey herpesvirus (rHVT) vector vaccine expressing the hemagglutinin gene from a clade 2.2 AI virus (A/Swan/Hungary/4999/2006) was evaluated in turkeys for protection against challenge with A/Whooper Swan/Mongolia/L244/2005 H5N1 HPAI clade 2.2. One-day-old turkeys received a single vaccination and were challenged at 4 wk postvaccination with 2 × 10⁶ 50% embryo infectious dose per bird. The results demonstrate that following H5N1 HPAI challenge 96% protection was observed in rHVT-AI vaccinated turkeys. The oral and cloacal swabs taken from challenged birds demonstrated that vaccinated birds had lower incidence and titers of viral shedding compared with sham-vaccinated birds. From respiratory and gastrointestinal tracts, there was a greater than 6 log₁₀ reduction in shedding in vaccinated birds as compared with the controls. This study provides support for the use of a commercially available rHVT-AI vaccine to protect turkeys against H5N1 HPAI.