Our overall aim is to develop immunization constructs, vectors, and strategies which have the best chance of inducing protective immune responses to mutans streptococcal infections in susceptible pediatric populations. We have previously identified several glucosyltransferases (GTF) enzyme sequences which can induce immune response in rodents which will alter GTF activity and reduce subsequent dental caries. To enhance the induction of protective immune responses we will first identify sequences from glucosyltransferase (GTF) enzymes from S. mutans and S. sobrinus associated with potent Class II MHC binding in humans. Peptides based on these and on novel GTF epitopes, recently shown to influence catalytic activity and transitional state stability of the enzyme (activity associated) will be synthesized and evaluated for immunogenicity and protective effect. These epitopes, together with other functionally significant peptides derived from the catalytic and glucans binding domains of GTF previously shown to induce protective responses, well be incorporated into conjugate vaccines with tetanus toxoid (TT). Intranasal routes for mucosal immunization with TT- GTF peptide conjugate vaccine will be investigated for the ability to induce protective levels of immunity in the oral cavity in the well established rodent model of experimental dental caries. Since the intranasal route may be contraindicated in children with upper respiratory conditions such as asthma, the colo-rectal route of administration will also be explored using constructs combined with or without mucosal adjuvants such detoxified mutant E. coli enterotoxin (LT) or unmethylated CpG oligodinucleotides. The protective effect of systemic immunization with TT-GTF peptide conjugate vaccine studies will also be investigated as an approach to minimizing the frequency of visits required for childhood immunizations, since evidence suggests that this route of immunization can induce salivary IgA antibody in young children. Various of the mist effective peptide(s) as determined by TT-GTF peptide conjugate vaccine studies will be expressed recombinantly in attenuated Salmonella typhi vectors which can target these epitopes to appropriate mucosal inductive sites. Caries protection will be evaluated after intranasal immunization with these attenuated Salmonella vectors. Our goal is to design a vaccine that contains a combination of immunologically potent and functionally relevant epitopes, in formats, by routes, and with adjuvants that result in sustained levels of protection from dental caries and that will be acceptable for human use.
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