Development of Passive Immunization System Against Dental Caries by Hen Egg Yolk Antibodies of Streptococcus Mutans.

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The effect of polyclonal egg yolk antibodies (yIgG) raised against whole cells, cell-free (CF) glucosyltransferase (GTase), cell-associated (CA) GTase, surface protein antigen (PAc) of serotype c S. Mutans was examined in terms of in vitro inhibition of virulence-related factors of S. mutans and protection of S. mutans-infected rats against the development of dental caries. Hens (18 weeks old) were immunized with formalintreated whole cells, purified CF-GTase, CA-GTase or PAc together with Freund complete adjuvant. yIgG was purified by ammonium sulfate precipitation followed by DEAE-Sephacel column chromatography or fractional precipitation with ethanol. Purified yIgG was found to be a 220-kDa protein, which was dissociated into H and L chains upon addition of 2-mercaptoethanol. yIgG to whole cells gave a heavy aggregation of the organisms of S. mutans, while yIgG to CF-and CA-GTase specifically inhibited the enzymatic activity of these GTases, respectively. yIgG to CA-GTase and whole cells was found to suppress clearly the cell adherence of S. mutans to a glass surface. Specific-pathogen-free Sprague-Dawley rats that had been infected heavily and repeatedly with S. Mutans and fed diet #2000 induced severe dental caries, while rats fed diet #2000 containing>0.1% yIgG to CA-GTase resulted in a statistically significant reduction in dental plaque accumulation and caries development. Administration of yIgG to CF-GTase failed to protect against caries. These results clearly suggest that yIgG to S. mutants CA-GTase specifically inhibited a virulence factor of this organism, i. e. Insoluble glucan synthesizing CA-GTase, resulting in a significant drop in the development of dental caries.