Cross-strain protection of a targeted anti-caries DNA vaccine pGJA-P/VAX

Objectives: A surface protein antigen and glucosyltransferases are two major virulence factors of cariogenic organisms. They are both structurally and immunologically similar between Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus). The aim of this study was to investigate whether a targeted anti-caries DNA vaccine pGJA-P/VAX, which was constructed against the glucan-binding domain of S. mutans GTF and the A-P fragment of S. mutans PAc, could induce cross immune responses to S. sobrinus and protect S. sobrinus infected rats from dental caries. Methods: pGJA-P/VAX was formulated with Chitosan to form particles at 4 to 6 micron. Twelve 18-day-old female rats were placed into 2 experimental groups of six animals each as follows: Group A, infected with S. sobrinus, immunized with Chitosan-pGJA-P/VAX complex; and group B, infected with S. sobrinus, immunized with Chitosan-pVAX1 (the vector) complex. All rats were immunized by the intranasal route on day 28 and boosted 2 weeks later. At 78 days of age, serum and saliva samples were collected for ELISA. And the caries activity was determined by the Keyes method. Results: The salivary anti-PAg and anti-GTF IgA levels of group A (1:8 and 1:7 respectively) were significantly higher than those of group B (1:3) (P<0.05). While no significant differences were observed in the serum antibody responses (P>0.05). The rats of group A displayed significantly fewer enamel lesions than those of group B (P<0.05), and the caries lesion reduction was 21.02%. No significant difference was observed in either dentinal slight or dentinal moderate lesions (P>0.05). Conclusions: pGJA-P/VAX induced significant mucosal immune responses to S. sobrinus antigens via the intranasal route. It could prevent S. sobrinus infected rats from dental caries to a certain extent. Supported by NSFC grant 30271416.