title: Gonococcal lipooligosaccharide sialylation prevents complement-dependent killing by immune sera.
abstract: Previous investigators have demonstrated that a sialic acid residue is added to the terminal galactose moiety of gonococcal lipooligosaccharide (LOS) when incubated with 5'-CMP-N-acetylneuraminic acid. When this in vitro sialylation occurs, gonococci become resistant to the bactericidal activity of normal human serum. This is believed to result because the added sialic acid residue blocks the binding of bactericidal anti-LOS antibodies present in normal human serum. We extend these studies by demonstrating that sialylated gonococci also become resistant to the bactericidal effect of immune sera containing antibodies that recognize exposed components of the outer membrane besides LOS. Prevention of antibody binding to the organism was not the cause, since the same percentage of bactericidal antibodies to the major outer membrane protein, Protein I, can be absorbed with sialylated organisms as with wild-type organisms. In addition, gonococcal sialylation prevents opsonophagocytosis by antigonococcal antisera. The negative effect of sialic acid on the complement pathway might be the reason for the findings in this study.
authors.affiliation: Laboratory of Bacterial Pathogenesis and Immunology, Rockefeller University, New York 10021.
authors.forename: L M
authors.initials: LM
authors.lastname: Wetzler
authors.forename: K
authors.initials: K
authors.lastname: Barry
authors.forename: M S
authors.initials: MS
authors.lastname: Blake
authors.forename: E C
authors.initials: EC
authors.lastname: Gotschlich
mesh_terms: D000942:Antigens, Bacterial / Q000502:physiology*; D003165:Complement System Proteins / Q000276:immunology*; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid / Q000494:pharmacology; D003601:Cytotoxicity Tests, Immunologic; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007106:Immune Sera / Q000276:immunology*; D007108:Immune Tolerance / Q000502:physiology*; D066298:In Vitro Techniques; D008070:Lipopolysaccharides / Q000502:physiology*; D019158:N-Acetylneuraminic Acid; D009344:Neisseria gonorrhoeae / Q000276:immunology / Q000472:pathogenicity*; D010587:Phagocytosis / Q000187:drug effects; D012794:Sialic Acids / Q000494:pharmacology*; D016704:Synapsins / Q000494:pharmacology
chemical_list: D000942:Antigens, Bacterial; D007106:Immune Sera; D008070:Lipopolysaccharides; D012794:Sialic Acids; D016704:Synapsins; C023023:lipid-linked oligosaccharides; D003569:Cytidine Monophosphate N-Acetylneuraminic Acid; D003165:Complement System Proteins; D019158:N-Acetylneuraminic Acid