Avian influenza outbreaks have placed a tremendous economic burden on the poultry industry, necessitating the need for an effective vaccine. Although multiple vaccine candidates are available, its development is hindered by several drawbacks associated with the vaccine platforms and as such, more improvements to the vaccines are needed. Therefore, in this study, the vaccine efficacy in the murine models was assessed prior to evaluation in chickens. An oral recombinant baculovirus (rBV) vaccine expressing influenza hemagglutinin (HA) (A/H5N1) was generated and its efficacy was investigated against homologous avian influenza infection in mice. Our results confirmed that oral administration of rBVs enhanced the level of virus-specific antibodies in the sera following boost immunization. Upon challenge infection with a lethal dose of highly pathogenic avian influenza virus (HPAI, H5N1) virus, a marked increase in mucosal IgG and IgA were observed. Drastically increased antibody secretory cell responses from the bone marrow cells and splenocytes of vaccinated mice were observed, in addition to the strongly elicited germinal center responses in the lungs and the spleens. Vaccinated mice showed significantly reduced lung pro-inflammatory cytokine responses, lung viral loads, body weight loss, and mortality. Though mice were only partially protected upon challenge infection, these results highlight the potential of orally administered rBVs expressing the HA as a vaccine candidate for controlling avian influenza outbreaks.
Keywords: Avian influenza virus; Mucosal immunity; Oral delivery; Protection; Recombinant baculovirus.
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