title: Lewis epitopes on outer membrane vesicles of relevance to Helicobacter pylori pathogenesis.
abstract: BACKGROUND
  Helicobacter pylori extrudes protein- and lipopolysaccharide-enriched outer membrane vesicles from its cell surface which have been postulated to act to deliver virulence factors to the host. Lewis antigen expression by lipopolysaccharide of H. pylori cells has been implicated in a number of pathogenic roles. The aim of this study was to further characterize the expression of lipopolysaccharide on the surface of these outer membrane vesicles and, in particular, expression of Lewis antigens and their association with antibody production in the host.
  
  
  METHODS
  H. pylori strains were examined for outer membrane vesicle production using transmission electron microscopy and Lewis antigen expression probed using immunoelectron microscopy. Sera from patients were analyzed for cross-reacting anti-Lewis antibodies and, subsequently, absorbed using outer membrane vesicle preparations to remove the cross-reacting antibodies.
  
  
  RESULTS
  The formation of outer membrane vesicles by H. pylori was observed in both in vitro and in vivo samples. Furthermore, vesicles were produced following culture in either liquid or solid medium by all strains examined. Moreover, we observed the presence of Lewis epitopes on outer membrane vesicles using immunoelectron microscopy and immunoblotting. Circulating anti-Lewis antibodies were found in the sera of gastric cancer patients but not in the sera of H. pylori-negative control subjects. Absorption of patient sera with outer membrane vesicles decreased the levels of anti-Lewis autoantibodies.
  
  
  CONCLUSIONS
  Our results demonstrate the ability of H. pylori to generate outer membrane vesicles bearing serologically recognizable Lewis antigens on lipopolysaccharide molecules which may contribute to the chronic immune stimulation of the host. The ability of these vesicles to absorb anti-Lewis autoantibodies indicates that they may, in part, play a role in putative autoimmune aspects of H. pylori pathogenesis.
authors.affiliation: Department of Microbiology, National University of Ireland, Galway, Ireland.
authors.forename: Sean O
authors.initials: SO
authors.lastname: Hynes
authors.forename: Jacqueline I
authors.initials: JI
authors.lastname: Keenan
authors.forename: John A
authors.initials: JA
authors.lastname: Ferris
authors.forename: Heidi
authors.initials: H
authors.lastname: Annuk
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Moran
mesh_terms: D000907:Antibodies, Bacterial / Q000097:blood; D015551:Autoimmunity; D002473:Cell Wall / Q000276:immunology* / Q000648:ultrastructure; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000032:analysis*; D016481:Helicobacter Infections / Q000097:blood / Q000276:immunology / Q000382:microbiology*; D016480:Helicobacter pylori / Q000276:immunology* / Q000472:pathogenicity / Q000648:ultrastructure; D007983:Lewis Blood Group Antigens / Q000032:analysis* / Q000276:immunology; D016256:Lewis X Antigen / Q000032:analysis* / Q000276:immunology; D008854:Microscopy, Electron; D013274:Stomach Neoplasms / Q000097:blood / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000939:Epitopes; D007983:Lewis Blood Group Antigens; D016256:Lewis X Antigen; C094162:Lewis Y antigen