Relationship of vacA genotypes of Helicobacter pylori to cagA status, cytotoxin production, and clinical outcome

Background. Mosaicism in vacA alleles with three distinct families of vacA signal sequences (sla, s1b and s2) and two distinct families of middle region alleles (ml and m2) has been reported. It was suggested that the vacA sla genotype was closely associated with duodenal ulcer disease and with high cytotoxin production. The aim of this study was to evaluate the role of vacA genotyping with respect to gastric inflammation and injury, cytotoxin activity, and clinical presentation. Methods. H. pylori from patients with gastritis, peptic ulcer disease, or gastric cancer were characterized by vacA typing by polymerase chain reaction (PCR) and DNA sequencing. In vitro cytotoxin activity was assessed by vacuolation assay using Vero cells as well as with Hela cells. Results. Four hundred ninety-one strains were tested. vacA genotype s1a/m1 was present in more than 95% of strains independent of presentation with gastritis, peptic ulcer, or gastric cancer. No vacA genotype was associated with high average cytotoxin activity. The s2/m2 isolates had low or absent cytotoxin activity. All cagA negative strains (n = 18) were sla strains and both s2/m2 strains were cagA positive. One strain that was a recombinant of mi and m2 strains was identified and had low cytotoxin activity. The nucleotide and amino acid sequences between original mi strains and Japanese mi strains (new mi strains) were about 85% and 81%, respectively. Strains with the new mi genotype had nucleotide and amino acid sequences similarity of more than 96%. There was no difference in cytotoxin activity between strains with the Western type mi and the new type mi genotype. Conclusion. In this as in other reported studies (approximate to 1500 patients overall) vacA genotype was strongly but not exclusively associated with the presence of cagA. Overall, the studies did not support a role for vacA genotyping in relation to cytotoxin activity, virulence, histologic finding, or risk of a particular H. pylori disease. vacA genotype sl is likely to be a surrogate marker for the presence of the cag pathogenicity.