Study of the correlation between the vacA genotype of Helicobacter pylori, the VacA product and gastroduodenal disease

Abstract

OBJECTIVE: To determine vacA genotypes and the vacuolating cytotoxin (VacA) activity of Helicobacter pylori strains isolated from patients with chronic gastritis (CG), peptic ulcers (PU) and gastric cancer (GC), and to investigate the relationship between the vacA genotypes of H. pylori, their product, VacA, and gastroduodenal diseases. METHODS: Sixty-two H. pylori strains were isolated from patients with CG (27 cases), PU (24 cases) and GC (11 cases) as diagnosed by either endoscopy or surgical pathology. The vacA genotypes of the H. pylori strains were tested by polymerase chain reaction (PCR). HeLa cell assays for VacA activity were carried out using a 20-fold concentrated culture supernatant of H. pylori in vitro. Culture supernatants of H. pylori strain NCTC 11637 and culture supernatants without H. pylori were used as positive and negative controls, respectively. RESULTS: All 62 H. pylori strains contained the vacA gene. The signal sequence and mid-region gene of the 62 H. pylori strains were s1a and m2 types, respectively. Mosaicism in vacA alleles was type s1a/m2 exclusively. The total rate of VacA expression in vitro was 37.1%; the rates of VacA expression in H. pylori strains isolated from patients with CG, PU and GC were 33.33, 29.17 and 63.64%, respectively. The proportion of strains expressing VacA in patients with GC was higher than those in patients with CG and PU, but the difference in VacA expression rates in CG, PU and GC strains was not significant (P > 0.05). CONCLUSIONS: The vacA genotype of H. pylori cannot be used to predict the clinical consequences of infection with that strain of H. pylori. Moreover, the VacA activity of H. pylori in vitro cannot be used to predict whether subjects infected with H. pylori will be more likely to develop CG, PU or GC. No correlation between vacA genotype and VacA expression was found in the present study.