Synthetic vaccines have been used to confer immunity on humans and also to orally elicit secretory antibody and mucosal protection. The overall aim of this proposed series of experiments will be to develop a synthetic vaccine which will be effective in protecting against dental caries. We will investigate enzymatic fragmentation of S. sobrinus and S. mutans GTFs in order to identify the epitopes on intact GTF to which human salivary antibody reacts. We will prepare human IgA and IgG antibody pools to S. sobrinus GTF and enzymatically digest GTF species and investigate epitopes associated with glucan-binding sites and with a catalytic site. We have outlined the structures of synthetic peptides which contain functionally relevant and structurally conserved regions of the glucosyltransferase enzymes derived from S. sobrinus and S. mutans. Theoretically, antibody directed to these structures will have enhanced potential to interfere with enzyme function and thereby inhibit dental caries. Particularly promising is the peptide containing a catalytic site of GTF. We will determine whether epitopes present on synthetic peptides react with (antigenicity), or elicit(immunogenicity) antibody that inhibits a function of the intact enzyme. The presence of functional activity of these peptides will be verified and compared to fragments from the parent molecules. Each peptide will be analyzed for antigenicity with human salivary IgA and serum antibody to GTFs. The ability of these peptides to generate protective immunity in an experimental dental caries model using both local and oral antigen administration will be investigated. We will also investigate the effects of synthetic peptide immunization on infection and disease caused by species of mutans streptococci other than species from which the peptide was derived. The most effective protective component(s) will be incorporated into a composite vaccine which will also be tested for protection in this system. The composite vaccine will incorporate all the protection-eliciting features of the GTF moieties and also the B and T cell epitopes required to initiate and sustain an immune response without any potentially harmful components. We will utilize both hybrid and MAP technologies to produce these composite vaccines. This proposal holds promise for further understanding of the relationship of GTF to dental caries and, most importantly, for the development of a dental caries vaccine for use in humans which is safe and elicits long-lasting protective immune response.
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