Immune responses of two recombinant adenoviruses expressing VP1 antigens of FMDV fused with porcine granulocyte macrophage colony-stimulating factor

Foot-and-mouth disease (FMD) is a highly contagious and economically devastating vesicular disease of cloven-hoofed animals. In the present report, we constructed and characterized the immune responses conferred by two recombinant adenoviruses expressing VP1 epitopes (three amino acid residues 21–60, 141–160 and 200–213 in VP1, designated VPe) or VP1 protein of FMDV fused with porcine granulocyte macrophage colony-stimulating factor (named rAd-GMCSF-VPe and rAd-GMCSF-VP1). Seven groups of female BALB/c mice each containing 18 mice were inoculated subcutaneously twice at 2-week intervals with the recombinant adenoviruses. Then the protective efficacy of the two adenoviruses was detected in guinea pigs and swine. The results showed that the highest levels of FMDV-specific T cell proliferation, IFN-γ and IL-4 could be induced by rAd-GMCSF-VPe expressing fusion GMCSF-VPe, and the highest level of FMDV-specific humoral immune responses could be induced by rAd-GMCSF-VP1 expressing fusion GMCSF-VP1 in mice. All guinea pigs and swine co-administrated with rAd-GMCSF-VPe and rAd-GMCSF-VP1 were protected from viral challenge, even though the neutralizing antibody titers were significantly lower than those in the group inoculated with inactivated FMD vaccine. It demonstrated that co-administration of rAd-GMCSF-VPe and rAd-GMCSF-VP1 might be attractive candidate vaccines for preventing FMDV infection.