The effect of polyclonal egg yolk
immunoglobulin G antibodies (yIgG) raised against whole cells, cell-free (CF)
glucosyltransferase (
GTase), or cell-associated (CA)
GTase of serotype c Streptococcus 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
formalin-treated whole cells, purified CF-
GTase, or CA-
GTase together with Freund's complete adjuvant. In addition, yIgG to
surface protein antigen was used in some in vitro experiments for comparison with other
antibodies. 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 heavy and light chains upon addition of
2-mercaptoethanol. yIgG to whole cells and
surface protein antigen gave a heavy aggregation of S. mutans organisms, while yIgG to CF- and CA-
GTase specifically inhibited the enzymatic activity of the respective
GTase. yIgG to CA-
GTase and whole cells was found to clearly suppress the adherence of S. mutans cells to a glass surface. Specific-pathogen-free Sprague-Dawley rats that had been infected heavily and repeatedly with S. mutans and fed diet no. 2000 developed severe
dental caries, while rats fed diet 2000 containing greater than or equal to 0.1% yIgG to CA-
GTase showed a statistically significant reduction in
dental plaque accumulation and caries development. Administration of yIgG to CF-
GTase and whole cells 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 reduction in the development of
dental caries.