Coimmunization with Complementary Glucosyltransferase Peptides Results in Enhanced Immunogenicity and Protection against Dental Caries

Abstract

ABSTRACT Peptide constructs from the catalytic (CAT) and glucan-binding (GLU) regions of the mutans streptococcal glucosyltransferase enzymes (GTF) can provide immunity to dental caries infection. A strategy of coimmunization was tested to determine whether protection could be enhanced. Rats were immunized with one of the previously described peptide constructs from the CAT or GLU region of the GTF of mutans streptococci or coimmunized with a combination of these constructs (CAT-GLU). Coimmunized animals demonstrated significantly higher serum immunoglobulin G (IgG) and salivary IgA antibody levels to CAT or GTF than rats immunized with either construct alone. To assess the functional significance of coimmunization with these constructs, animals were immunized as above or with Streptococcus sobrinus GTF and then infected with S. sobrinus to explore the effects of immunization on immunological, microbiological, and disease (dental caries) parameters. Serum antibody from the communized group inhibited S. sobrinus GTF-mediated insoluble glucan synthesis in vitro above that of the individual-construct-immunized groups. Immunization with CAT or GLU constructs resulted in significantly reduced dental caries after infection with S. sobrinus compared with sham-immunized animals. Coimmunization produced greater reductions in caries than after immunization with either CAT or GLU. Also, significant elevations in lymphocyte proliferative responses to CAT, GLU, and GTF were observed after coimmunization with CAT-GLU compared with the responses after immunization with the individual constructs. The results suggested that increased numbers of memory T cells, which could proliferate to CAT, were generated by coimmunization. The experiments support the functional significance of these GTF domains in dental caries pathogenesis and present coimmunization as a simple alternative to intact GTF to enhance protective immunity against cariogenic microorganisms.