Coimmunization with recombinant epitope-expressing baculovirus enhances protective effects of inactivated H5N1 vaccine against heterologous virus.

H5N1, a highly pathogenic avian influenza virus (HPAIV), poses a significant threat to poultry and human health. However, currently available inactivated influenza vaccines are less efficacious against viruses that display antigenic drift. In this study, we constructed a recombinant baculovirus (BV-HMNN) expressing four conserved antigen epitopes: H5N1 hemagglutinin stem area amino acids 76-130 (HA2 76-130); three tandem repeats from the ectodomain of the conserved influenza matrix protein M2 (3M2e); nucleoprotein amino acids 55-69 (NP55-69); and nucleoprotein amino acids 380-393 (NP380-393). We evaluated the immunogenicity and protective efficacy of coimmunization with an inactivated avian influenza virus vaccine (Re6) and the recombinant baculovirus (BV-HMNN) against heterologous viral infection in specific-pathogen-free chickens. The chickens immunized with both vaccines (Re6+BV-HMNN) achieved complete protection, was significantly greater than that of chickens vaccinated with Re6 alone. BV-HMNN-supplemented vaccination also reduced viral shedding more effectively than nonsupplemented vaccination. We conclude that coimmunization with both vaccines was superior to immunization with the inactivated vaccine alone in inducing cross-protection against heterologous H5N1 virus.