Comparative immunogenicity and protective effect against dental caries of a low (3800) and a high (185,000) molecular weight protein in rhesus monkeys (Macaca mulatta).

The immunogenicity and protective effect of two peptides derived from the human oral bacterium Streptococcus mutans (serotype c) was examined. Furthermore, the effect of immunization was examined in monkeys previously given fluoride in their diet and which had developed a low incidence of dental caries when offered a human type of diet containing about 15 per cent sucrose. The 3800 peptide streptococcal antigen (SA) has two major antigenic determinants, similar to those in the 185,000 SA I/II. Immunization with 10 (or 1) micrograms of the 3800 SA, made up in an aluminium-hydroxide adjuvant, induced a consistent increase in serum IgG, IgM and IgA antibodies to SA I/II throughout the period of investigation. Salivary-IgA antibodies were only slightly raised. Sequential examination up to 76 weeks showed a significantly lower incidence of dental caries and a lower proportion of Strep. mutans in the immunized compared with sham-immunized, control monkeys. Thus immunization with the 185,000 or 3800 SA can almost completely prevent dental caries in rhesus monkeys which otherwise develop a low incidence of caries.