IMMUNOLOGICAL CHARACTERISTICS OF A SYNTHETIC PEPTIDE ASSOCIATED WITH A CATALYTIC DOMAIN OF MUTANS STREPTOCOCCAL GLUCOSYLTRANSFERASE

The immunogenicity of a multiple antigenic peptide construct consistin g of four copies of the synthetic 21-mer peptide DANFDSIRVDAVDNVDADLLQ was measured. The composition of this peptide was derived from a sequ ence in the N-terminal region of mutans streptococcal glucosyltransfer ases (GTFs) containing an aspartic acid implicated in catalysis. The p eptide (CAT) construct was synthesized as a tetramer on a lysine backb one and subcutaneously injected into Sprague-Dawley rats for polyclona l antibody formation or intraperitoneally injected into BALB/c mice, a nd then spleen cell fused with Sp2/0Ag14 murine myeloma cells for mono clonal antibody formation. The resulting rat antisera and mouse monocl onal antibodies reacted with CAT and with native GTF isozymes from Str eptococcus sobrinus and Streptococcus mutans (in enzyme-linked immunos orbent assay and Western blot [immunoblot] analyses). Functional inhib ition of the water-insoluble glucan synthetic activity of S. sobrinus GTF-I was demonstrated with an immunoglobulin M anti-CAT monoclonal an tibody (>80% inhibited) and with rat sera (approximately 17% inhibited ). The monoclonal antibody preparation also modestly inhibited the wat er-soluble glucan synthetic activity of an S. mutans GTF mixture. Thes e results suggest that the CAT peptide contains B-cell epitopes that a re similar to those of intact mutans streptococcal GTFs and has the po tential to elicit antibody that can inhibit GTF function. Thus,sequenc es within this peptide construct may have value for inclusion in a syn thetic dental caries vaccine.