Mechanism of C. trachomatis attachment to eukaryotic host cells.

A novel trimolecular mechanism of microbial attachment to mammalian host cells was characterized for the obligate intracellular pathogen Chlamydia trachomatis. Using purified glycosaminoglycans (GAGs) and specific GAG lyases, we demonstrated that a heparan sulfate-like GAG present on the surface of chlamydia organisms is required for attachment to host cells. These observations were supported by inhibition of attachment following binding of heparan sulfate receptor analogs to chlamydiae and by demonstrating that chlamydiae synthesize a unique heparan sulfate-like GAG. Furthermore, exogenous heparan sulfate, as an adhesin analog, restored attachment and infectivity to organisms that had lost these attributes following treatment with heparan sulfate lyase. These data suggest that a GAG adhesin ligand mediates attachment by bridging mutual GAG receptors on the host cell surface and on the chlamydial outer membrane surface.