CHARACTERIZATION OF PREPARATIONS ENRICHED FOR STREPTOCOCCUS-MUTANS FIMBRIAE - SALIVARY IMMUNOGLOBULIN-A ANTIBODIES IN CARIES-FREE AND CARIES-ACTIVE SUBJECTS

The ability of bacteria to adhere to salivary pellicle coated enamel t ooth surfaces is a critical step in oral bacterial colonization. Oral bacteria adhere to receptors of host origin in salivary pellicle. Stre ptococcus mutans has been identified as the major etiological agent of human dental caries and composes a significant proportion of the oral streptococci in carious lesions. Bacterial fimbriae are small (100 to 300 nm) hairlike appendages emanating from the cell surface. Preparat ions enriched for S. mutans fimbriae were isolated by a shearing techn ique and alternating high- and low-speed centrifugations. A representa tive fimbrial preparation had two distinct double bands comprising fou r proteins of approximately 100 to 200 kDa and one faint band at 40 kD a on reducing sodium dodecyl sulfate polyacrylamide gel electrophoresi s/immunoblots and had demonstrable glucosyltransferase activity. Rabbi t antisera raised against the preparation specifically stained the fuz zy coat of S. mutans, demonstrating short fimbria-like structures prot ruding 100 to 200 nm from the cell surface. Controls without antifimbr ia antibody did not exhibit this staining. There were significantly hi gher (P less than or equal to 0.05) levels of salivary immunoglobulin A, but not serum immunoglobulin G. antibodies to the enriched S, mutan s fimbria preparation by enzyme-linked immunosorbent assay from caries -free subjects than from caries-active subjects. The results suggest t hat S, mutans fimbriae may be an important adherence factor to which c aries-free subjects mount a protective salivary immune response.