INDUCTION OF IMMUNE-RESPONSES TO FUNCTIONAL DETERMINANTS OF A CELL-SURFACE STREPTOCOCCAL ANTIGEN

Antibodies directed against the cell surface adhesin, termed streptoco ccal antigen I/II of Streptococcus mutans can protect against dental c aries. Streptococcal antigen I/II (SA I/II) interacts with salivary gl ycoproteins and promotes adhesion to the tooth surface. Topical applic ation of monoclonal antibodies which recognize a domain within residue s 816-1213 (fragment 3) prevents colonization by S. mutans in primates . In this study the immunogenicity and antigenicity of fragment 3 was investigated in five strains of mice. Fragment 3 induced an immune res ponse following immunization with whole cells of S. mutans in all stra ins of mice. Immunization with recombinant fragment 3 also induced T-c ell proliferative and antibody responses both to fragment 3 and to the SA I/II. Antibody responses to the previously defined adhesion determ inants (residues 1005-1044) were weak or undetectable. Immunization of three representative strains of mice with a recombinant polypeptide ( residues 975-1044) comprising this adhesion epitope and an adjacent T- cell epitope (residues 975-1004) elicited both T- and B-cell responses to the polypeptide and to native SA I/II. The B-cell epitopes overlap ped with the adhesion determinant. These findings provide a means of d irecting immune responses to functional determinants of SA I/II.