Effect of specific antisera on adherence properties of the oral bacterium Streptococcus mutans

Antisera to Strep. mutans antigens B, glucosyltransferase (GTF) and a glucan-binding protein (GBP) reduced the build-up of this bacterium on glass surfaces in vitro; antiserum to antigen A and a control non-immune serum were without significant effect. The same sera were used to study the involvement of these antigens in cell-cell aggregation mediated by sucrose or water-soluble Dextran 2000. Antiserum to GTF and antigen B inhibited sucrose-dependent cell-cell aggregation of the organism by approximately 50 per cent; none of the antisera tested had any effect upon dextran-mediated aggregation. In the presence of sucrose, GTF and GBP became cell associated while the distribution of antigens A and B between culture supernatant and cell surface remained unchanged. Cells incubated in the presence of Dextran 2000 showed no change in the distribution of any of these antigens. It is concluded that the aggregation of Strep. mutans induced by sucrose or by dextran involves different cellular components. Consideration of these in-vitro results in relation to data from experiments in which macaque monkeys were immunized with purified Strep. mutans antigens suggests that inhibition of sucrose-dependent adherence is not the basis for protection against dental caries.