Neisseria gonorrhoeae (GC) is a human pathogen that adheres to and invades genital surfaces. Although pili are required for the initial adherence, the interaction of GC with epithelial cells is also promoted by a family of outer membrane proteins, the opacity (Opa) proteins such as OpaA protein from strain MS11. Studies have demonstrated that the interaction of the OpaA GC with epithelial cells involves binding to heparan sulfate attached to syndecan receptors. However, other Opa proteins interact with CEA gene family member 1 (CGM1) or biliary glycoprotein (BGP), members of the CD66 antigen family. In this study, we demonstrate that, in addition, the 180-kD carcinoembryonic antigen (CEA) is a receptor for Opa proteins. This conclusion was based on the following observations. First, transfected HeLa cells expressing CEA (HeLaCEA) and the CEA-expressing colon cancer cell line (LS 174T) bound and subsequently engulfed the Opa+ bacteria. These interactions were inhibited by anti-CEA antibody, but could not be inhibited by addition of heparin. Furthermore, OpaI E. coli directly bound purified CEA. We also compared the adherence and invasion by Opa+ bacteria of CD66 transfected HeLa cells: HeLa-BGPa, HeLa-CGM6, HeLa-NCA, HeLa-CGM1a, HeLa-CEA, and HeLa-Neo serving as negative control. Using OpaI as the prototype, the relative ability of the transfected HeLa cell lines to support adherence was (CEA = BGPa >CGM1a >NCA >>CGM6 = Neo). The ability to mediate invasion of the transfectant cells was (CGM1a >CEA >BGPa >NCA >CGM6 = Neo). Among the Opa proteins tested, OpaC proved to be bifunctional, able to mediate adherence to both syndecan receptors and to CD66 antigens.

Our recent studies have shown that the dendritic cell-specific ICAM nonintegrin CD209 (DC-SIGN) specifically binds to the core LPS of Escherichia coli K12 (E. coli), promoting bacterial adherence and phagocytosis. In this current study, we attempted to map the sites within the core LPS that are directly involved in LPS-DC-SIGN interaction. We took advantage of four sets of well-defined core LPS mutants, which are derived from E. coli, Salmonella enterica serovar Typhimurium, Neisseria gonorrhoeae, and Haemophilus ducreyi and determined interaction of each of these four sets with DC-SIGN. Our results demonstrated that N-acetylglucosamine (GlcNAc) sugar residues within the core LPS in these bacteria play an essential role in targeting the DC-SIGN receptor. Our results also imply that DC-SIGN is an innate immune receptor and the interaction of bacterial core LPS and DC-SIGN may represent a primeval interaction between Gram-negative bacteria and host phagocytic cells.

Neisseria gonorrhoeae (GC) or

SummaryNeisseria gonorrhoeae attaches to host epithelial cells via pili and opacity-associated (Opa) outer membrane proteins. Pilus-gonococci (Gc) of strain MS11 adhere to both human and nonhuman cells, but only when particular Opa proteins are expressed; OpaA + variants adhere best, OpaC § variants are next best, and the seven other Opa + variants adhere poorly or not at all. The adherence of OpaA + Gc to Chinese hamster ovary (CHO) cells is inhibited by heparin or heparan sulfate (HS), but not by chondroitin sulfate. OpaA + Gc do not adhere to CHO cells devoid of HS proteoglycans; low concentrations of heparin restore OpaA + Gc adherence to these HS-deficient CHO cells and high concentrations inhibit it. 3H-heparin binding to whole Gc parallels their adherence abilities (OpaA § > OpaC + > OpaH § >> Opas B, D, E, F, G, I = Opa-= 0). Opa proteins separated by SDS-PAGE also bind 3H-heparin. These data suggest that adherence of pilus-, Opa + Gc involves HS-proteoglycan of eukaryotic cells.