Comparison of an Adherence Domain and a Structural Region of Streptococcus mutans Antigen I/II in Protective Immunity against Dental Caries in Rats after Intranasal Immunization

Previous studies have identified an N-terminal saliva-binding region (SBR) on Streptococcus mutans surface antigen I/II (AgI/II) and suggested its importance in the initial adherence of S. mutans to saliva-coated tooth surfaces and subsequent development of dental caries. In this study, we compared the SBR with a C-terminal structural region of AgI/II (AgII) in their abilities to induce protective immunity against caries in rats. When SBR, AgII, or the whole AgI/II molecule was administered intranasally as a conjugate with the B subunit of cholera toxin (CT), in the presence of CT adjuvant, substantial levels of salivary immunoglobulin A anti-AgI/II antibodies were induced. Evaluation of caries activity showed that the SBR, though not as protective as the parent molecule, was superior to AgII and thus can be further considered as a component in a multivalent caries vaccine.