The effect of amino acid spacers on the antigenicity of dimeric peptide-inducing cross-reacting antibodies to a cell surface protein antigen of Streptococcus mutans

In the course of developing a synthetic peptide vaccine for dental caries, we identified a unique 13-mer peptide named PAc(365-377), TYEAALKQYEADL, as a minimum peptide inducing cross-inhibiting antibodies to a cell surface p rotein antigen (PAc) of Streptococcus mutans. However, the peptide could ha rdly induce the production of antibody in the absence of adjuvant. Thus usi ng this peptide as a unit peptide, tandem constructs of dimeric unit peptid e with or without spacer amino acid residues were synthesized, and their an tigenicities were examined in B10.D2 mice. Significant augmentation of anti genicity was obtained in all of the dimeric unit peptides with spacers, esp ecially for lysine spacers. In addition, analysis for crossreactivity of an ti-construct antibodies against a set of double valine-substituted analogue s of the unit peptide revealed that the di-lysine spacer might be more effe ctive in inducing the cross-reacting antibodies to rPAc.