Production of goat milk antibodies against cell surface protein antigen-glucosyltransferase fusion protein of Streptococcus mutans

Passive immunization is an effective way to prevent infectious diseases in animals and humans. Several attempts have been made to obtain antibody that is effective against Streptococcus mutans using animals. In this study, we immunized pregnant goats with a protein derived from S. mutans. This organism produces two major colonization factors: cell surface protein antigen (PAc) and glucosyltransferases (GTFs). Inhibition of these two factors is predicted to provide protection against dental caries. We used a fusion protein, PAcA-GB, which fuses the saliva-binding alanine-rich region (PAcA) of PAc with the glucan binding (GB) domain of GTF-I, as an immunogen. Normal milk samples from goats that were immunized subcutaneously and re-immunized into lymph nodes contained high titers of antibody specific for the fusion protein. When compared with antibodies purified from nonimmunized milk, the goat IgG antibodies purified from immunized milk inhibited the adhesion of S. mutans to saliva-coated hydroxyapatite beads. Total glucan synthesis by GTF-I from S. mutans was strongly inhibited by goat IgG antibodies purified from the immunized milk.