Borrelia burgdorferi bind to epithelial cell proteoglycans

Borrelia burgdorferi adhere to mammalian cells in vitro but neither the ligand(s) nor the receptor(s) has (have) been clearly established. Using an in vitro attachment-inhibition assay, a B. burgdorferi attachment mechanism has been identified. Heparin, heparan sulfate, and dermatan sulfate reduced the attachment of virulent B. burgdorferi strain 297 to HeLa cells by approximately 60%. In addition, virulent, but not avirulent, B. burgdorferi strains B31, N40, and HB19 demonstrated heparin attachment-inhibition. Attachment to Chinese hamster ovary cells deficient in heparan sulfate proteoglycans was reduced by 68% compared to attachment to wild-type cells and was identical to attachment at maximum heparin inhibition to the wild-type cells. Pretreatment of HeLa cell monolayers with heparitinase, heparinase, and chondroitinase ABC, but not with chondroitinase AC, reduced borrelial attachment by approximately 50%. A moderately high affinity, low copy number, promiscuous B. burgdorferi glycosaminoglycan receptor was demonstrated by equilibrium binding studies. A 39-kD polypeptide, purified by heparin affinity chromatography from Triton X-100 extracts derived from virulent borrelia, was a candidate for this receptor. These studies indicate that one mode of B. burgdorferi attachment to eukaryotic cells is mediated by a borrelial glycosaminoglycan receptor attaching to surface-exposed proteoglycans on mammalian cells.