ATTACHMENT OF FUSOBACTERIUM-NUCLEATUM TO FIBRONECTIN IMMOBILIZED ON GINGIVAL EPITHELIAL-CELLS OR GLASS COVERSLIPS

To LEARN MORE ABOUT COLONIZATION OF THE ORAL EPITHELIUM by Fusobacteri um nucleatum and the role of fibronectin in mediating adhesion of this microorganism, we studied attachment of this bacterium to cultured gi ngival epithelial cells that were coated With exogenous, purified plas ma fibronectin. The three strains of F. nucleatum studied adhered in l arge numbers to epithelial cells that had been coated with fibronectin , compared with buffer-coated control cells. Bacterial adherence was a lso enhanced when epithelial cells were coated with whole human saliva . However, cells coated with saliva depleted of fibronectin did not fa cilitate adhesion of bacteria. Bacterial adhesion was restored when pu rified fibronectin was added back. We also tested adherence of bacteri a to coverslips coated with fibronectin, saliva, and saliva depleted o f fibronectin. The bacteria adhered to coverslips coated with fibronec tin or whole human saliva, but did not adhere to coverslips coated wit h fibronectin-depleted saliva. Bacterial adhesion to coverslips was re stored upon addition of purified fibronectin to the fibronectin-deplet ed saliva. Bacterial attachment to fibronectin-coated coverslips was f ound to be temperature-dependent, with maximal adhesion observed at 37 degrees C. Pre-treatment off. nucleatum with soluble fibronectin inhi bited attachment of the bacteria by 92%, whereas pre-treatment with bo vine serum albumin had no effect. Pre-treatment of bacteria with lamin in or type IV collagen caused moderate inhibition of attachment by 60% and 50%, respectively. Treatment of fibronectin-coated coverslips wit h Fab fragments of anti-fibronectin IgG blocked the attachment of F, n ucleatum by 93%. Fab fragments of the other antisera tested had no inh ibitory effect. The data suggest that the attachment of F. nucleatum t o fibronectin-coated coverslips or epithelial cells is a specific bind ing event between fibronectin and one or more molecules on the bacteri al surface. Interaction of F, nucleatum with fibronectin, a component of saliva, may play a role in adhesion and establishment of this perio dontal pathogen in the gingival sulcus.