T-cell, adhesion, and B-cell epitopes of the cell surface Streptococcus mutans protein antigen I/II.

The T-cell and antibody responses to a cell surface streptococcal antigen (SA I/II) were investigated in naturally sensitized humans. Serum antibody responses were directed predominantly to the N-terminal (residues 39 to 481) and central (residues 816 to 1213) regions of SA I/II which may be involved in bacterial adhesion to salivary receptors. T-cell responses were also directed predominantly towards the central region. The linear peptide relationship of the immunodominant and minor T- and B-cell as well as adhesion epitopes was mapped within residues 816 to 1213. Immunodominant T-cell and B-cell epitopes were identified within residues 803 to 853, which were separated in linear sequence from the adhesion epitopes (residues 1005 to 1044). Adhesion epitopes overlapped with minor B- and T-cell epitopes (residues 1005 to 1054 and 1085 to 1134). An immunodominant promiscuous T-cell epitope (residues 985 to 1004) was adjacent to an adhesion epitope (residues 1005 to 1024). The limited B-cell response to adhesion epitopes is consistent with the success of Streptococcus mutans in colonizing the oral cavity. The strategy of T-cell, adhesion, and B-cell epitope mapping has revealed a general approach for identifying components of subunit vaccines which may focus responses to critical functional determinants. Such epitopes of SA I/II may constitute the components of a subunit vaccine against dental caries.