Recombinant infectious bursal disease virus expressing Newcastle disease virus (NDV) neutralizing epitope confers partial protection against virulent NDV challenge in chickens

• Recombinant IBDV viruses expressing NDV neutralizing epitope were generated.
• The biological characterization and stability of the rescued viruses were evaluated.
• The recombinant IBDVs provided some protection against IBDV and NDV challenge.
• The recombinant IBDVs induced antibody responses against IBDV and NDV in chickens.

In this study, the regions in the infectious bursal disease virus (IBDV) genome that are amenable to the introduction of a sequence encoding a virus-neutralizing epitope of Newcastle disease virus (NDV) hemagglutinin-neuraminidase (HN) protein were identified. By using the reverse genetics approach, insertions or substitutions of sequences encoding the NDV epitope were engineered in the exposed loops (PBC, PHI and PAA′PAA′) of the VP2 capsid protein and the N terminus of the nonstructural VP5 protein as well as the pep7a and pep7b regions of the pVP2 precursor of a commonly used IBDV vaccine strain, Gt. Three recombinant IBDVs expressing the NDV epitopes were successfully rescued in the PBC, pep7b and VP5 regions and the expressed epitope was recognized by anti-HN antibodies. Genetic analysis showed that the IBDV recombinants carrying the NDV epitopes were stable in cell cultures and in chickens. Animal studies demonstrated that the IBDV recombinants were innocuous in chickens. Vaccination with the recombinant viruses generated antibody responses against both IBDV and NDV, and provided 70–80% protection against IBDV and 50–60% protection against NDV. These results indicate that the recombinant IBDV has the potential to serve as a novel vaccine vector for other pathogens. In future studies, it is worth considering research to improve IBDV vector vaccine to get complete protection and safety of animals and humans.