The overall objective of this proposal is to investigate the functional aspects of naturally occurring human salivary IgA and serum IgG and IgM antibodies in inhibiting virulence factors of Streptococcus mutans which are important in dental caries formation. Our laboratory and others have shown that oral immunization of humans and experimental animals with S. mutans or pruified S. mutans antigens induces increased levels of specific salivary IgA antibodies, reduced numbers of plaque-adherent S. mutans and decreased numbers of carious lesions suggesting that IgA antibodies inhibit some or all of the essential steps in S. mutans-induced cariogenicity such as adherence, aggregation, formation of Alpha 1-3 (insoluble) and Alpha 1-6 (soluble) linked glucans or synthesis of lactic acid. Populations of caries-resistent and caries-active subjects will be recruited and parotid saliva and serum will be collected. The salivas and sera will be clarified, the immunoglobulins precipitated with 50% (NH4)2SO4 and purified by affinity chromatography and used to treat S. mutans cells and culture supernatant enzymes (serotypes c and g) in vitro in order to determine if the purified antibodies will inhibit S. mutans growth, adherence to glass surfaces, aggregation, acid production from sucrose and glucose, synthesis of insoluble and soluble glucans and/or glucosyltransferase (GTF), fructosyltransferase (FTF), lactate dehydrogenase (LDH), phosphotransferase (PTS), dextranase and invertase activities. Previously we have shown that saliva and serum from rabbits and rats immunized with S. mutans whole cells or ribosomal preparations inhibited S. mutans growth, acid production from sucrose and glucose-PTS activity suggesting that salivary and serum antibodies inhibit growth and production of acids by interfering with PTS and/or other S. mutans enzyme activities. Furthermore, the levels, specificities and isotypes of parotid salivary and serum antibodies from caries-resistent and caries-active subjects to various S. mutans antigens will be established using an enzyme-linked immunosorbent assay. These studies should provide valuable information on the function of Anti-S. mutans antibodies important in caries protection and the nature of the S. mutans antigen(d) most relevant in inducing protective immunity.
