ADHESION OF ACTINOBACILLUS-ACTINOMYCETEMCOMITANS TO A HUMAN ORAL CELL-LINE

Two quantitative, rapid assays were developed to study the adhesion of Actinobacillus actinomycetemcomitans, an oral bacterium associated wi th periodontal disease, to human epithelial cells. The human oral carc inoma cell line KB was grown in microtiter plates, and adherent bacter ia were detected by an enzyme-linked immunosorbent assay with purified anti-A. actinomycetemcomitans serum and horseradish peroxidase-conjug ated secondary antibody or [H-3]thymidine-labeled bacteria. Adhesion w as found to be time dependent and increased linearly with increasing n umbers of bacteria added. Variation in the level of adhesion was noted among strains of A. actinomycetemcomitans. Adhesion was not significa ntly altered by changes in pH (from PPI 5 to 9) but was sensitive to s odium chloride concentrations greater than 0.15 M. Pooled human saliva was inhibitory for adhesion when bacteria were pretreated with saliva before being added to the cells. Pretreatment of the KB cells with sa liva did not inhibit adhesion. Protease treatment of A. actinomycetemc omitans reduced adhesion of the bacteria to KB cells. The data are con sistent with the hypothesis that a protein(s) is required for bacteria l adhesion and that host components may play a role in modulating adhe sion to epithelial cells.