Expression of the Foot-and-Mouth Disease Virus VP1 Protein Using a Replication-Competent Recombinant Canine Adenovirus Type 2 Elicits a Humoral Antibody Response in a Porcine Model

To develop a new type vaccine for Foot-and-Mouth Disease (FMD) prevention by using canine adenovirus as vector, the VP1 cDNA of Foot-and-Mouth Disease Virus (FMDV) type O strain China 99 was amplified by RT-PCR and cloned into pEGFP-C1 by replacing the GFP gene with the VP1 cDNA, resulting in an expression plasmid pVP1-C1. The expression cassette of VP1 composed of the CMV promoter, the VP1 gene and the SV40 early mRNA polyadenylation signal was recovered by Nsi I / Mlu I digestion of pVP1-C1 and cloned into the Canine adenovirus type-2 (CAV-2) genome in which E3 region was partly deleted by removing the Ssp I- Ssp I fragment. The recombinant virus (CAV-2-VP1) was obtained by transfecting the recombinant CAV-2-VP1 genome into MDCK cells with Lipofectamine 2000. Immunization trial in pigs with the recombinant virus, CAV-2-VP1, showed that CAV-2-VP1 could stimulate a specific immune response to both FMDV and the vector virus. Immune response to the VP1 and FMDV after VP1 expression was confirmed by ELISA, western blotting analysis and neutralization test. It was indicated that CAV-2 may serve as a vector for FMD vaccine development in pigs.