Enhanced immunogenicity of an anti-caries vaccine encoding a cell-surface protein antigen of Streptococcus mutans by intranasal DNA prime-protein boost immunization

The present study aimed to enhance the specific anti-caries immunity induced by DNA prime-protein boost strategy for an A-P fragment of a cell-surface protein antigen of Streptococcus mutans (PAc).

BALB/c mice were immunized with DNA prime-protein boost, DNA-DNA or protein-protein regimens by the intranasal route, using combinations of plasmid vector (pCIA-P) that express PAc protein and a pure secretec recombinant PAc protein (rPAc). Then, a gnotobiotic mouse model was constructed 2 weeks after the last immunization, and specific immune responses in vivo and their protection against dental caries were observed.

The present study revealed stronger antibody responses in the DNA prime-protein boost group compared to those elicited by either DNA-DNA vaccination or protein-protein vaccination. In particular, PAc-specific antibody concentrations were improved significantly after boosting the pCIA-P DNA-primed mice with rPAc. Moreover, protection against S. mutans challenge was obtained in the mice treated with the DNA prime-protein boost vaccination, as demonstrated by a significant reduction in S. mutans colonization compared to control mice and animals immunized with the DNA-DNA vaccination or protein-protein vaccination.

The results obtained in the present study suggest that the intranasal DNA prime-protein boost vaccination regimen is a novel strategy for the practical application of DNA vaccine against dental caries.