Identification and preliminary characterization of saliva-interacting surface antigens of Streptococcus mutans by immunoblotting, ligand blotting, and immunoprecipitation

The ability of surface protein antigens of Streptococcus mutans to interact with salivary components was examined by Western blot and immunoprecipitation methods. Immunoblotting of S. mutans OMZ175 wall-associated antigens revealed 10 major antigens, designated according to their estimated molecular weights. Four of them, with molecular weights of 135,000, 125,000, 120,000, and 115,000 in their denaturated form, bound salivary components. This property was further investigated by immunoprecipitation experiments: the reactivity with saliva was confirmed for antigens with molecular weights of 135,000, 125,000, and 120,000 in their native form, and their locations on the bacterial cell surface were established. These three antigens were characterized as glycoproteins; they directly bound concanavalin A, and pronase abolished their antigenicity, which was partly retained after treatment with NaIO4. Because of their distribution in several other stains of S. mutans, it will be of interest to study their possible implication in the mechanism of attachment of streptococcal strains to saliva-coated tooth surfaces.