Variable experiences in immunization of rats against Streptococcus mutans-associated dental caries

Abstract

Studies were conducted to test possible immunization of rats against Streptococcus mutans strain 6715-associated dental caries. Rats were infected with streptomycin-resistant virulent 6715 after formalin-killed cells of 6715 were injected subcutaneously distant from the salivary glands. High humoral agglutinin titres were elicited and a salivary antibody response was observed both by agglutination and by indirect fluorescent antibody techniques. No differences could be detected in the recoveries of Strep. mutans from the teeth or in the amount of dental plaque on the teeth between infected-immunized and infected-un-immunized animals. Smooth surface caries was essentially dependent on infection by 6715. Sulcal caries, while not dependent upon infection by strain 6715, was augmented by it. There was an apparent although variable protection of rats against caries associated with Strep. mutans infection. The immunization regimen was associated not only with reduction of smooth surface caries scores, but also with reduction of sulcal caries scores when the contribution of Strep. mutans to the sulcal disease was most prominent. Absence of weight variations between animal groups suggested that the observed caries reductions could not be ascribed to alteration in food intake resulting from the immunization regimen.