INHIBITION OF GLUCOSYLTRANSFERASE ACTIVITIES OF STREPTOCOCCUS-MUTANS BY A MONOCLONAL-ANTIBODY TO A SUBSEQUENCE PEPTIDE

Preliminary analysis indicated that a 19-amino-acid peptide sequence ( 435 to 453 of GtfC) within a highly conserved region of the glucosyltr ansferases of the cariogenic streptococci might be functionally import ant (J.-S. Chia, S.-W. Lin, T.-Y. Hsu, J.-Y. Chen, H.-W. Kwan, and C.- S. Yang, Infect. Immun. 61:1563-1566, 1993). To obtain antipeptide mon oclonal antibodies (MAbs), the 19-amino-acid peptide was conjugated to bovine serum albumin and used as an antigen in BALB/c mice. Six immun oglobulin G-secreting hybridoma clones, CJSm18-S1 to -S6, specifically reacted with this peptide and with purified GtfC and GtfD but not wit h bovine serum albumin in an enzyme-linked immunosorbent assay. The co ncentrated hybridoma supernatant of all six MAbs inhibited GtfC enzyma tic activity but failed to inhibit GtfD, although GtfD contains the sa me peptide sequence. Further analysis of a purified immunoglobulin G2b MAb from one of the clones, CJSm18-S3, confirmed that this MAb specif ically inhibited GtfC enzymatic activity for insoluble-glucan synthesi s in a dose-dependent manner. CJSm18-S3, even at high concentrations, had no effect on GtfD, which synthesizes water-soluble glucan exclusiv ely. Furthermore, the in vitro sucrose-dependent adherence of Streptoc occus mutans was also inhibited by CJSm18-S3 in a dose-dependent manne r. Our results indicate that the peptide containing the N-terminal con served region of glucosyltransferases is functionally important for bo th enzymatic activity and bacterial adherence.