Basic study for development of DNA vaccine against dental caries

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Streptococcus mutans possesses three glucosyltransferase (GTF) enzymes that coordinate to synthesize adhesive glucan, which facilitates adhesion and accumulation of S. mutans cells to tooth surfaces. Thus, GTFs are considered to be a major virulence factor of dental caries. We constructed DNA vaccines against GTFs and then attempted to determine their immunogenicity. Two functional domains of GTFs, the catalytic (CAT) and glucan-binding (GBD) domains, were used as targets of the DNA vaccines.DNA fragments coding these domains were amplified by PCR and ligated into an eukaryotic expression vector, pcDNA3, which resulted in the DNA vaccine plasmids pcDNA3/CAT and pcDNA3/GBD. A mouse embryo cell line, NIH 3T3, was transfected with either pcDNA3/CAT or pcDNA3/GBD and the expressions of mRNA and recombinant proteins for CAT or GBD in the transfected cells were subjected to reverse transcription-PCR (RT-PCR) and Western blot analyses, respectively. Using RT-PCR, CAT-and GBD- specific mRNA was detected in pcDNA3/CAT and pcDNA3/GBD transfected cells, while Western blot analysis also revealed that the CAT- and GBD- specific recombinants were expressed in the respective cells. Our results indicated that these DNA vaccines expressed recombinant proteins as antigens in mammalian cells and possessed the ability to induce immune responses.