Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2012
Publication Date: 4/1/2012
Citation: Kapczynski, D.R., Esaki, M., Dorsey, K.M., Jackwood, M.W., Prajitno, T., Gardin, Y. 2012. Protective efficacy of a recombinant HVT-H5 vaccine against lethal H5N1 and H5N2 avian influenza challenge [abstract]. 8th International Symposium on Avian Influenza. CDROM. Interpretive Summary:
Technical 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 (e.g. expressing AI genes) are gaining use for their ability to induce protection against heterologous isolates. Historically, protective immunity against highly pathogenic AI (HPAI) depends largely on antibody development against the HA glycoprotein. In these studies, we compared protection of chickens provided by a recombinant turkey herpesvirus (rHVT) vaccine expressing the HA gene from a clade 2.2 H5N1 strain (A/swan/Hungary/4999/2006) against homologous H5N1, as well as, heterologous H5N1and H5N2 HPAI challenge. In the first set of experiments, groups of birds were subcutaneously vaccinated at day of age and challenged four weeks later with a homologous H5N1 isolate, A/whooper swan/Mongolia/L245/2005. The results demonstrated all vaccinated birds were protected from mortality following challenge, with lower incidence and titers of viral shedding compared to sham-vaccinated birds. To examine protection against genetically distant HPAI, birds were challenged with either a H5N1 of Indonesian origin (A/chicken/West Java Subang/29/2007) or a H5N2 HPAI Mexican isolate (A/chicken/Queretero/14588-19/1994). In those studies, 80-95% of birds receiving the rHVT vaccine at day of age survived challenge, with fewer birds shedding virus after challenge. Interestingly, only low levels of cross reactive HI antibody titers were observed against the heterologous viruses prior to challenge. Taken together, these studies provide support for the use of rHVT vaccines expressing HA to protect poultry against multiple lineages of HPAI.