Bovine milk antibodies against cell surface protein antigen PAc-glucosyltransferase fusion protein suppress cell adhesion and alter glucan synthesis of Streptococcus mutans

Cell surface protein antigen (PAc) and glucosyltransferases (GTF) produced by Streptococcus mutans are considered major colonization factors of the or ganism, and the inhibition of these factors is thought to prevent dental ca ries. In this study, 8-mo-old pregnant Holstein cows were immunized with fu sion protein PAcA-GB, a fusion of the saliva-binding alanine-rich region (P AcA) of PAc with the glucan binding (GB) domain of GTF-I, an enzyme catalyz ing the synthesis of water-insoluble glucan from sucrose. High titers of im munoglobulin antibodies specific for the fusion protein were found in norma l milk after reimmunization, and they persisted for similar to 3 mo. The im munoglobulin G (IgG) antibodies against PAcA-GB were purified from immunize d milk. The antibodies significantly inhibited the adhesion of S. mutans ce lls to saliva-coated hydroxyapatite beads. IgG antibodies purified from imm unized milk also inhibited total glucan synthesis by cell-associated GTF pr eparation and GTF-I from S, mutans, The immunized milk may be useful as a m eans of passive immunization for the prevention of dental caries in humans.