Before any successful evaluation of anti-caries immunity can be effected, a suitable animal model must be available; sufficient data should be at hand with this model with respect to a) the immune response (IR), b) pathogenesis of superinfected cariogenic bacteria, c) overall sensitivity to caries attack, d) specificity of attack and e) adequate data concerning antibody and immunoglobulin levels and complement in key fluids including serum, saliva and milk. Such a model has been developed in our laboratory during the past 2 1/2 years with young, Antibiotic-Controlled (A.C.) rats. An understanding of effective caries immunity to S. mutans in young A.C. rats will be of principal concern in this proposal. By selective use of mutants of S. mutants in this system, coupled with serological studies, we will evaluate surface antigens of importance in virulence; these components will be isolated and purified by gel filtration, ion-exchange and immunoadsorbent chromatography. Following successful isolation, the IR to these antigens will be evaluated by quantitative immunodiffusion, precipitation and passive hemagglutination. Coupled with studies following different routes of antigen stimulation, we will develop the most efficient and practical schedule for induction of the salivary s- IgA response. Studies will be undertaken to evaluate the role of non- specific factors which could augment the overall response of these rats to S. mutans. Levels of lysozyme, lactoferrin and peroxidase will be determined in saliva following injection with S. mutans. In addition, in vitro experiments will determine synergistic activity of s-IgA and lysozyme, lactoferrin or peroxidase on a) growth inhibition, b) bactericidal and c) lytic activities on S. mutans.