Adherence of Multiple Serovars of Chlamydia trachomatis to a Common Receptor on HeLa and McCoy Cells Is Mediated by Thermolabile Protein(s)

Abstract

Several aspects of the adherence of purified elementary bodies (EB) of Chlamydia trachomatis to HeLa and to McCoy cells were examined using different techniques, including an ELISA. Serovar-specific, biotinylated monoclonal antibodies were used to detect cell-bound chlamydiae. In addition, purified chlamydiae were biotinylated and their adherence properties were studied. The assays were done at 4 "C to exclude the energy-dependent internalization of the cell-bound EB and host-cell membrane recycling that occur at 37 "C. Saturation kinetics were routinely observed at 4 "C, and the rate of adherence remained linear for approximately 60 min. Lineweaver-Burk analysis of the kinetics data showed that adherence of any one serovar was competitively inhibited by other serovars of C. trachomatis. This competition for the same receptor on the two alternative hosts, HeLa and McCoy, was also seen when the adherence assays were done at 37°C in the presence of sodium azide, an energy poison that inhibits endocytosis of cell-bound chlamydiae. Chlamydiae exposed to 56 "C for 5 min, or treated with low doses of trypsin, failed to exhibit competitive inhibition, having suffered considerable loss of the ability to adhere to host-cells. These data suggest that heat-and trypsin-labile chlamydial moieties participate in the adherence reaction, and that oculo-genital serovars of C. trachomatis, including that of lymphogranuloma venereum, attach to the same receptor on the host-cell membrane.

Selection of Mutant Cell Lines Resistant to Infection byChlamydia trachomatisandChlamydia pneumoniae

“…Evidence has been presented to support receptor-mediated (microfilamentindependent) endocytosis of chlamydiae into clathrin-coated pits, as well as microfilament-dependent uptake into non-clathrin-coated vesicles (9,10,16,23). However, receptor binding is both saturable and highly sensitive to proteolytic treatment of the host cell surface (2,22), suggesting that a protein component of the host plasma membrane is critical for this interaction. To date, no host cell receptor(s) to which chlamydiae bind has been identified, with the exception of a possible role for the estrogen receptor complex (6).…”

Entry of the Lymphogranuloma Venereum Strain ofChlamydia trachomatisinto Host Cells Involves Cholesterol-Rich Membrane Domains

“…The mechanism responsible for Chlamydia internalization by host cells involves heparan sulfate glycosaminoglycans, which could either bridge a chlamydial ligand to a host cell receptor (48) or be host cell receptors for chlamydiae (42). Previous studies have indicated that there are saturable and trypsin-sensitive binding sites for chlamydiae on host cells (6,46). Interestingly, most of the heparan sulfate proteoglycans on the cell surface are attached to the membrane by a GPI anchor (31).…”

Mechanisms of Chlamydia trachomatis Entry into Nonphagocytic Cells

“…Chlamydiae are responsible for a wide range of diseases in humans, including lymphogranuloma venereum, pelvic inflammatory disease, conjunctivitis, urethritis, cervicitis, pneumonia, psittacosis, and possibly atherosclerosis (49). Chlamydia infection begins with the attachment of the elementary body (EB) to a eukaryotic cell by interaction with a proteinaceous host component (5,6,57). After attachment, chlamydiae are internalized into the cell by an unknown mechanism resembling endocytosis, upon which Chlamydia-derived vesicles mature into a specialized parasitophorous vacuole, or inclusion, that is nonfusogenic with endosomal and lysosomal membranes.…”