The immunogenicity of various peptide antigens inducing cross-reacting antibodies to a cell surface protein antigen of Streptococcus mutans

A cell surface protein antigen (PAc) of Streptococcus mutans may be involve d in the binding of bacteria to the tooth surface, and has long been focuse d upon as a candidate for a preventive vaccine of dental caries. Previously the peptide PAc (365-377) was shown to raise an antibody in B10.D2 mice wh ich inhibited the binding of salivary components to the PAc molecule. Using this peptide as a unit peptide, two constructs based on multiple antigenic peptides, and several types of tandem repeats of two or three copies were synthesized to estimate the immunogenicity of these peptides. Increase in t he immunogenicity was observed for all constructs with the use of an adjuva nt compared to the unit peptide alone. However, the tandem repeat construct s generally induced antibody production in the absence of adjuvant, while t he multiple antigenic peptide constructs did not induce antibody production under the same condition. Although such a phenomenon may be restricted to this particular peptide sequence, these results may influence the strategy for the design of peptide vaccines.