Hyaluronan, a possible ligand mediating Treponema denticola binding to periodontal tissue

Binding of Treponema denticola ATCC 35405 to glycosaminoglycans, fibrinogen, type I collagen and porcine periodontal ligament epithelial cells was studied using an enzyme-linked immunosorbent assay. T. denticola bound to hyaluronan (hyaluronic acid) and its hexameric fragments. whereas little or no binding was detected to chondroitin-4-sulfate or dermatan sulfate proteoglycan. Binding of T. denticola to hyaluronan gradually increased during the 2-h incubation time. In contrast, binding to fibrinogen and type I collagen was more rapid, peaking within 5 min. T. denticola also bound to microbeads coated with hyaluronan and formed visible aggregates in solution. Pretreatment of the bacteria with hyaluronan or fibrinogen inhibited binding to hyaluronan. Gelatin, bovine serum albumin, chondroitin-4-sulfate, chondroitin-6-sulfate, heparin, dermatan sulfate, glucuronic acid, N-acetylglucosamine and N-acetyl-galactosamine did not inhibit binding. Binding was also inhibited by heating T. denticola and by pretreatment of the spirochetes with sodium periodate, phenylmethylsulfonyl fluoride, and p-chloromercurybenzoic acid. All these treatments also inhibited the chymotrypsin-like activity of T. denticola. Hyaluronan strongly inhibited binding of T. denticola to epithelial cells, whereas the other glycosaminoglycans and N-acetyl-glucosamine did not. The results show that T. denticola binds to hyaluronan, possibly by a mechanism involving the chymotrypsin-like surface protein of T. denticola.