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-gamma 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.