Development of inhibitory peptide in adherence of periodontopathic bacteria to dental plaqu

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We previously showed that P.gingivalis fimbriae specifically bind to salivary acidic proline-rich proteins (PRP) and that the active domain in PRP is PQGPPQ.In this study, we examined the effect of synthetic peptide (PQGPPPQGGRPQGPPQGQSPQ ; pepPRP-C) corresponding to C-terminal region in PRP on the interaction between fimbriae and salivary proteins. The pepPRP-C significantly inhibited the binding of fimbriae to basic proline-rich glycoproteins (PRG)-coated hydroxyapatite (HAP) beads as well as to PRP on HAP beads. In the overlay assay, the pepPRP-C clearly diminished the interactions between the fimbriae and the various salivary components, including PRPs, PRGs, and the components with smaller molecular sizes. Moreover, pepPRP-C inhibited the coaggregation of P.gingivalis with various streptococcal strains, suggesting that this peptide may act as an effective inhibitor against P.gingivalis adherence to dental plaque. Then the recombinant Streptococcus gordonii secreting pepPRP-C was generated as a model of a possible approach to prevent the oral colonization of P.gingivalis. A duplicate DNA fragment (pepPRP-C) encoding pepPRP-C was obtained by self-complementary annealing of synthetic oligonucleotides. PepPRP-C was connected downstream to a promoter and a gene encoding a signal peptide of Streptococcus downei glucosyltransferase 1 in frame. The linked fragments were inserted into the plasmid pMNK-4 derived from pVA838. The constructed plasmid was transformed to S.gordonii G9B, which successfully secreted the recombinant pepPRP-C (r-pepPRP-C). The concentrated bacterial culture supernatant containing r-pepPRP-C inhibited the binding of P.gingivalis cells and fimbriae to PRP up to 72% and 77%, respectively. The r-pepPRP-C concentrate also inhibited the coaggregation of P.gingivaLis with various streptococcal strains. Therefore, the pepPR? -C secretion system might be available for prevention against P.gingivalis-induced periodontitis.