Expression of the capsid protein of porcine circovirus type 2 in Lactococcus lactis for oral vaccination.

Diseases associated with porcine circovirus type 2 (PCV2) infections are becoming a major problem for the swine industry worldwide. The capsid protein (Cap) of PCV2 is an antigen important for both early diagnosis and development of vaccines. In this study, Lactococcus lactis was used as vehicle to deliver the PCV2 antigen in an attempt to develop oral vaccine. A cap gene with a deleted nuclear localization signal sequence (dcap) was cloned into an Escherichia coli/L. lactis shuttle vector pSEC: LEISS under the control of a nisin promoter. Intracellular and extracellular expression of the dCap was confirmed by Western blot analysis. Significantly higher levels of PCV2-specific IgG in the sera of mice were observed upon oral administration of strain cultures expressing the PCV2 antigen. These results suggest that it is feasible to use L. lactis as an antigen delivery vehicle for developing oral vaccines against PCV2 infection.