A new Helicobacter pylori vacuolating cytotoxin determinant, the intermediate region, is associated with gastric cancer

Gastroenterology. 2007 Sep;133(3):926-36. doi: 10.1053/j.gastro.2007.06.056. Epub 2007 Jul 3.


Background & aims: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / metabolism
  • Adenocarcinoma / microbiology*
  • Amino Acid Sequence
  • Bacterial Proteins / analysis
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Biomarkers / metabolism
  • Case-Control Studies
  • Helicobacter pylori / genetics
  • Helicobacter pylori / pathogenicity*
  • Humans
  • Iran
  • Molecular Sequence Data
  • Mutation / genetics
  • Polymorphism, Genetic
  • Predictive Value of Tests
  • Stomach Neoplasms / metabolism
  • Stomach Neoplasms / microbiology*
  • United Kingdom
  • United States
  • Virulence / genetics


  • Bacterial Proteins
  • Biomarkers
  • VacA protein, Helicobacter pylori