[An anticaries experimental study of SD rat immunized by recombinant plasmid pEGFP-N1-Srv+ encoding the V-region of surface protein of Streptococcus mutans].

Purpose: An anticaries DNA vaccine pEGFP-N1-Srv+ was used to immunize rats by different immune pathways. The expression of recombinant plasmid in different tissues in vivo and the specific immune response and protection effects against dental caries were observed.

Methods: 20 SD rats were divided into 4 groups, immunized with the recombinant plasmid pEGFP-N1-SrV+ by submandibular gland-target injection(TSG), and intramuscular injection,respectively; then the expression of recombinant plasmid in different tissues were detected by immunohistochemistry technique. 24 SD rats were divided into 4 groups, immunized with recombinant plasmid pEGFP-N1-SrV+ of 100 μg, then boosted once after two weeks, through the same routes as above;then indirect ELISA technique was used to detect the specific antibodies. Keyes caries scores were used to evaluate the anticaries effects. The data was analyzed by using SPSS17.0 software package.

Results: (1)Recombinant plasmid was positively expressed in the muscle fibers and submandibular glands.(2)The specific salivary anti-SR IgA and serum IgG were detected, and the peak time of the antibodies level appeared 4 weeks after initial . At the 4th week, the levels of specific anti-SR antibodies were higher in the experimental group than that in the negative control group. The levels of salivary specific anti-SR IgA were significantly higher in TSG immunization group than that in the intramuscular injection group. (3)Keyes caries scores were not significantly different between the experimental groups and negative control groups. recombinant plasmid pEGFP-N1-Srv+ expressed in vivo and effectively increased specific salivary anti-SR IgA and serum IgG, and TSG immunization route significantly increased the specific salivary anti-SR IgA compared with the intramuscular immunization route;however, the recombinant plasmid pEGFP-N1-Srv+ alone can not protect the rats from dental caries.

Conclusions: The recombinant plasmid pEGFP-N1-SrV+ expressed in vivo and effectively increased specific salivary anti-SR IgA and serum IgC, and TSG immunization route significantly increased the specific salivary anti-SR IgA compared with the intramuscular immunization route; however, the recombinant plasmid pEGFP-N1-Srv+ alone can not protect the rats from dental caries.