Deletion of the Single Putative N-glycosylation Site of the Porcine Circovirus Type 2 Cap Protein Enhances Specific Immune Responses by DNA Immunisation in Mice

The immunogenicity of a putative N-linked glycosylation site located at amino acids 143-145 (N143YS) of the porcine circovirus 2 (PCV2) Cap protein was investigated. Eukaryotic vectors expressing wild-type PCV2 Cap (pCap) and N-linked glycosylation site mutant Cap (pCap-m) were constructed and the immunogenicity of these proteins was determined following DNA vaccination in BALB/c mice. pCap-m elicited significantly higher Cap-specific T lymphocyte proliferative activity, percentage of CD8(+) T cells, ratio of immunoglobulin (Ig) G2a:IgG1 and levels of interferon-γ compared to pCap (P<0.05). These results indicate that deletion of the N-glycosylation site in the PCV2 Cap protein enhances specific immune responses and may have a role in Cap-based DNA vaccines with enhanced immunogenicity.