Eliciting specific humoral immunity from a plasmid DNA encoding infectious bursal disease virus polyprotein gene fused with avian influenza virus hemagglutinin gene

• HA of AIV could be expressed by IBDV polyprotein gene in the same vector by replacing the VP3 gene of IBDV for HA gene of AIV.
• The location of expressed VP2 and HA in the transfected cells was in the cytoplasm and at cell membrane, respectively, which was the same in the transfected cells when VP2 or HA was expressed individually.
• The fusion protein VP24-HA could induce humoral immunity to VP2 and HA by DNA vaccination in specific pathogen free chickens.

DNA vaccine coding for infectious bursal disease virus (IBDV) polyprotein gene and that for avian influenza virus (AIV) hemagglutinin (HA) gene have been shown to induce immunity and provide protection against the respective disease. The present study was carried out to determine whether an IBDV polyprotein gene-based DNA fused with AIV HA gene could trigger immune response to both IBDV and AIV. After transfection, VP2 and HA were detected in the cytoplasm and at cell membrane, respectively, by immunofluorescent antibody double staining method, suggesting the fusion strategy did not affect the location of protein expression. VP4 cleavage between VP2 and HA was confirmed by Western blot, indicating the fusion strategy did not affect VP4 function in transfected cells. After vaccination in chickens, the DNA construct VP24-HA/pcDNA induced ELISA and virus neutralizing antibodies against VP2 and hemagglutination inhibition antibody against the HA subtype. The results indicated that a single plasmid construct carrying IBDV VP243 gene-based DNA fused with AIV HA gene can elicit specific antibody responses to both IBDV and AIV by DNA vaccination.