Intranasal immunization against dental caries with a Streptococcus mutans-enriched fimbrial preparation

Streptococcus mutans has been identified as the major etiological agent of human dental caries. The first step in the initiation of infection by this pathogenic bacterium is its attachment (i,e., through bacterial surface pro teins such as glucosyltransferases, P1, glucan-binding proteins, and fimbri ae) to a suitable receptor. It is hypothesized that a mucosal vaccine again st a combination of S. mutans surface proteins would protect against dental caries by inducing specific salivary immunoglobulin A (IgA) antibodies whi ch may reduce bacterial pathogenesis and adhesion to the tooth surface by a ffecting several adhesins simultaneously. Conventional Sprauge-Dawley rats, infected,vith S, mutans at 18 to 20 days of age, were intranasally immuniz ed with a mixture of S, mutans surface proteins, enriched for fimbriae and conjugated with cholera toxin B subunit (CTB) plus free cholera toxin (CT) at 13, 15, 22, 29, and 36 days of age (group A). Control rats were either n ot immunized (group B) or immunized with adjuvant alone (CTB and CT [group C]), At the termination of the study (when rats were 46 days of age), immun ized animals (group A) had significantly (P < 0.05) higher salivary IgA and serum IgG antibody responses to the mixture of surface proteins and to who le bacterial cells than did the other two groups (B and C), No significant differences were found in the average numbers of recovered S, mutans cells among groups. However, statistically fewer smooth-surface enamel lesions (b uccal and lingual) were detected in the immunized group than in the two oth er groups, Therefore, a mixture of S, mutans surface proteins, enriched wit h fimbria components, appears to be a promising immunogen candidate for a m ucosal vaccine against dental caries.