title: A new Helicobacter pylori vacuolating cytotoxin determinant, the intermediate region, is associated with gastric cancer.
abstract: OBJECTIVE
  Helicobacter pylori is the main cause of peptic ulceration and gastric adenocarcinoma. The vacuolating cytotoxin gene, vacA, is a major determinant of virulence. Two naturally polymorphic sites in vacA, the signal region and midregion, are well-characterized determinants of toxicity and markers of pathogenesis. The aim of this study was to characterize a new vacA polymorphic site, the intermediate (i) region.
  
  
  METHODS
  The vacA i-region was identified and characterized by constructing isogenic vacA exchange mutants and determining their vacuolating activity on HeLa, AGS, and RK13 cell lines. The vacA i-region types of H pylori isolates from patients undergoing routine endoscopy were determined by nucleotide sequencing and allele-specific polymerase chain reaction.
  
  
  RESULTS
  Two i-region types were identified, i1 and i2, and both were common among 42 Western clinical isolates. Interestingly, only naturally occurring s1/m2 strains varied in i-type; s1/m1 and s2/m2 strains were exclusively i1 and i2, respectively. Vacuolation assays showed that i-type determined vacuolating activity among these s1/m2 strains, and exchange mutagenesis confirmed that the i-region itself was directly responsible. Using a simple i-region polymerase chain reaction-based typing system, it was shown for 73 Iranian patients that i1-type strains were strongly associated with gastric adenocarcinoma (P < 10(-3)). Finally, logistic regression analysis showed this association to be independent of, and larger than, associations of vacA s- or m-type or cag status with gastric adenocarcinoma.
  
  
  CONCLUSIONS
  Together these data show that the vacA i-region is an important determinant of H pylori toxicity and the best independent marker of VacA-associated pathogenicity.
authors.affiliation: Wolfson Digestive Diseases Centre and Institute of Infection, Immunity and Inflammation, University of Nottingham, Nottingham, England.
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Rhead
authors.forename: Darren P
authors.initials: DP
authors.lastname: Letley
authors.forename: Marjan
authors.initials: M
authors.lastname: Mohammadi
authors.forename: Nawfal
authors.initials: N
authors.lastname: Hussein
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Mohagheghi
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Eshagh Hosseini
authors.forename: John C
authors.initials: JC
authors.lastname: Atherton
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000382:microbiology*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D016480:Helicobacter pylori / Q000235:genetics / Q000472:pathogenicity*; D006801:Humans; D007492:Iran; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011110:Polymorphism, Genetic; D011237:Predictive Value of Tests; D013274:Stomach Neoplasms / Q000378:metabolism / Q000382:microbiology*; D006113:United Kingdom; D014481:United States; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D015415:Biomarkers; C074689:VacA protein, Helicobacter pylori