Identification of a repeated epitope recognized by human serum antibodies in a surface protein antigen of Streptococcus mutans

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Abstract
This study determined the antigenic determinants of a 190‐kDa surface protein antigen of Streptococcus mutans that is involved in the initial attachment to the tooth surface. In 5 subjects, the reactivities of serum antibodies to 7 overlapping surface protein antigen fragments covering the entire antigen molecule and 19 sequential overlapping synthetic 19‐mer peptides covering the entire A‐region of the surface protein antigen were examined with enzyme‐linked immunosorbent assay (ELISA). The study showed that the A‐region of the antigen is strongly immunogenic in humans and contains several widely distributed epitopes. In addition, an amino acid sequence of the one of dominant epitopes in a certain subject was identified as LTAENTAI with ELISA inhibition assays using the relevant truncated peptides. This epitope was located both at the positions from L‐346 to 1–364 and L‐430 to E‐437 of the antigen molecule, and serum antibodies against the epitope were found in 3 of the 5 subjects.