Vaccine protection of chickens against antigenically diverse H5 highly pathogenic avian influenza isolates with a live HVT vector vaccine expressing the influenza hemagglutinin gene derived from a clade 2.2 avian influenza virus

Abstract

Vaccination is an important tool in the protection of poultry against avian influenza (AI). For field use, the overwhelming majority of AI vaccines produced are inactivated whole virus formulated into an oil emulsion. However, recombinant vectored vaccines are gaining use for their ability to induce protection against heterologous isolates and ability to overcome maternal antibody interference. In these studies, we compared protection of chickens provided by a turkey herpesvirus (HVT) vector vaccine expressing the hemagglutinin (HA) gene from a clade 2.2 H5N1 strain (A/swan/Hungary/4999/2006) against homologous H5N1 as well as heterologous H5N1 and H5N2 highly pathogenic (HP) AI challenge. The results demonstrated all vaccinated birds were protected from clinical signs of disease and mortality following homologous challenge. In addition, oral and cloacal swabs taken from challenged birds demonstrated that vaccinated birds had lower incidence and titers of viral shedding compared to sham-vaccinated birds. Following heterologous H5N1 or H5N2 HPAI challenge, 80-95% of birds receiving the HVT vector AI vaccine at day of age survived challenge with fewer birds shedding virus after challenge than sham vaccinated birds. In vitro cytotoxicity analysis demonstrated that splenic T lymphocytes from HVT-vector-AI vaccinated chickens recognized MHC-matched target cells infected with H5, as well as H6, H7, or H9 AI virus. Taken together, these studies provide support for the use of HVT vector vaccines expressing HA to protect poultry against multiple lineages of HPAI, and that both humoral and cellular immunity induced by live vaccines likely contributes to protection.

Natural recombination in alphaherpesviruses: Insights into viral evolution through full genome sequencing and sequence analysis

“…Currently, natural recombination has not been assessed in BoHV-1 or herpesvirus of turkeys (HVT) but live vaccines using these viruses are in widespread use in the cattle and poultry industries, respectively, with the latter being used as vaccine vector to express exogenous proteins from other avian pathogens (Kapczynski et al, 2015;Li et al, 2011;Roh et al, 2016). Examining natural recombination in these two viruses should be included in future research in order to determine potential risks to animal health.…”

Viral vector-based influenza vaccines

“…HVT encoding the HA gene of an A(H5N1) virus afforded protection from infection with various A(H5N1) viruses. [122][123][124] Similarly, a recombinant HVT-H7 vaccine protected chickens against infection with the homologous A (H7N1) virus. 125 Since chickens are often vaccinated at very young age (1 day after birth), maternal antibodies against the vector or against the protein encoded by the transgene could influence vaccine efficacy.…”

Live poultry vaccines against highly pathogenic avian influenza viruses

“…This vaccine protected vaccinated birds from challenge with the homologous and heterologous HPAIVs of H5N1 and H5N2 subtypes [19]. Recombinant HVT provided higher protection than the inactivated vaccine in the form of oil-in-water emulsion produced from a similar strain [20].…”