Application of ORF3 Subunit Vaccine for Avian Hepatitis E Virus

SIMPLE SUMMARY: Avian hepatitis E has been widespread in many countries in the last few years and has caused immense economic losses to the poultry industry worldwide. There are still no commercial avian hepatitis E virus (HEV) vaccines so far. ORF3 protein subunit vaccines for HEV strain in laying hens and broilers were prepared, respectively, in this study; and the challenge protection test confirmed that the vaccine could reduce the viral shedding in feces after HEV infection; it provides necessary technical reserve for the prevention and control of avian HEV under existing conditions. ABSTRACT: Avian hepatitis E virus (HEV) is the main etiologic pathogen of chicken big liver and spleen disease which is widely prevalent in China in recent years. However, due to the lack of a highly effective culture system in vitro, a genetically engineered subunit vaccine is the main direction of vaccine development. In this study, ORF3 genes of VaHEV strain from laying hens and YT-aHEV strain from broilers were amplified, respectively, and ORF3 protein was successfully expressed by Escherichia coli prokaryotic expression system. The serum samples were collected periodically to detect avian HEV antibodies by indirect immunofluorescence after specific pathogen free chickens immunized with the two proteins and their mixed proteins, the results showed that all serum samples were positive for antibodies to avian HEV. The antibody-positive chickens were artificially challenged with the cell-adapted strain YT-aHEV strain. The chickens from the immunized control group were infected successfully; no fecal detoxification was detected in the immunized group. In this study, two representative strains of ORF3 subunit vaccines of laying hens and broilers were prepared by prokaryotic expression, the immune effects of different proteins of these were evaluated through immunization and challenge studies in vivo, which provided a new technical possibility for prevention and control of avian HEV.