ANTIGENICITY AND IMMUNOGENICITY OF A SYNTHETIC PEPTIDE DERIVED FROM AGLUCAN-BINDING DOMAIN OF MUTANS STREPTOCOCCAL GLUCOSYLTRANSFERASE

The immunogenicity and antigenicity of a multiply antigenic peptide co nstruct containing four copies of the synthetic peptide TGAQTIKGQKLYFK ANGQQVKG were measured in rodents and humans, respectively. The compos ition of this peptide construct (termed GLU) was derived from a major repeating sequence in the C-terminal region of mutans streptococcal gl ucosyltransferases that synthesize water-insoluble glucan (GTF-I). The GLU peptide elicited high levels of serum immunoglobulin G antibody t o GLU after subcutaneous injection into Sprague-Dawley rats. These ant isera also reacted with intact GTF isozymes from Streptococcus sobrinu s and Streptococcus mutans (by enzyme-linked immunosorbent assay [ELIS A] and Western blot [immunoblot] analyses) and with an 87-kDa glucan-b inding protein from S. sobrinus (by Western blot). The synthesis of fi lter-retained glucan by GTF-Sd of S. sobrinus could be inhibited (30%) by preincubation with anti-GLU rat serum. Splenic and lymph node lymp hocytes from rats injected once with S. sobrinus GTF isozymes demonstr ated significant proliferation after 5 days of culture with GLU. The G LU peptide reacted with 4 of 29 human parotid saliva samples and 5 of 29 human serum samples (by ELISA). These results suggest that the GLU peptide contains B- and T-cell epitopes that are similar to those of i ntact mutans streptococcal GTFs and possibly certain other glucan-bind ing proteins as well. Furthermore, since antibody to this epitope(s) a ppears to inhibit GTF function, sequences within this peptide construc t may have value for inclusion in a synthetic dental caries vaccine.