NATURAL PROTEOGLYCAN RECEPTOR ANALOGS DETERMINE THE DYNAMICS OF OPA ADHESIN-MEDIATED GONOCOCCAL-INFECTION OF CHANG EPITHELIAL-CELLS

Many bacterial pathogens possess a complex machinery for the induction and/or secretion of factors that promote their uptake by mammalian ce lls. We searched for the molecular basis of the 60- to 90-min lag time in the interaction of Neisseria gonorrhoeae carrying the heparin-bind ing Opa adhesin with Chang epithelial cells. Infection assays in the p resence of chloramphenicol demonstrated that the Opa-mediated gonococc al infection of Chang cells required bacterial protein synthesis when the microorganisms were derived from GC agar but not when grown in liq uid media. Further analysis indicated that contact with agar ingredien ts rather than the growth state of the microorganisms determined the i nfection dynamics. DEAE chromatography of GC agar extracts and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses and testin g of collected fractions in infection assays identified negatively cha rged high-molecular-weight polysaccharides in the agar as inhibitors o f the cellular infection. Electron microscopy showed that agar-grown g onococci were surrounded by a coat of alcian blue-positive material, p robably representing accreted polysaccharides. Similar antiphagocytic material was isolated from bovine serum, indicating that in biological fluids gonococci producing the heparin-binding Opa adhesin may become covered with externally derived polysaccharides as well. Binding assa ys with gonococci and epithelial proteoglycan receptors revealed that polysaccharides derived from agar or serum compete with the proteoglyc ans for binding of the heparin-binding Opa adhesin and thus act as rec eptor analogs. Growth of gonococci in a polysaccharide-free environmen t resulted in optimal proteoglycan receptor binding and rapid bacteria l entry into Chang cells. The recognition that gonococci with certain phenotypes can recruit surface polysaccharides that determine in vitro infection dynamics adds a different dimension to the well-recognized biological significance of genetic variation for this pathogen.