Variations in Helicobacter pylori Cytotoxin-Associated Genes and Their Influence in Progression to Gastric Cancer: Implications for Prevention

Helicobacter pylori (HP) is a bacterium that colonizes the human stomach and can establish a long-term infection of the gastric mucosa. Persistent Hp infection often induces gastritis and is associated with the development of peptic ulcer disease, atrophic gastritis, and gastric adenocarcinoma. Virulent HP isolates harbor the cag (cytotoxin-associated genes) pathogenicity island (cagPAI), a 40 kb stretch of DNA that encodes components of a type IV secretion system (T4SS). This T4SS forms a pilus for the injection of virulence factors into host target cells, such as the CagA oncoprotein. We analyzed the genetic variability in cagA and other selected genes of the HP cagPAI (cagC, cagE, cagL, cagT, cagV and cag Gamma) using DNA extracted from frozen gastric biopsies or from clinical isolates. Study subjects were 95 cagA+ patients that were histologically diagnosed with chronic gastritis or gastric cancer in Venezuela and Mexico, areas with high prevalence of Hp infection. Sequencing reactions were carried out by both Sanger and next-generation pyrosequencing (454 Roche) methods. We found a total of 381 variants with unambiguous calls observed in at least 10% of the originally tested samples and reference strains. We compared the frequencies of these genetic variants between gastric cancer and chronic gastritis cases. Twenty-six SNPs (11 non-synonymous and 14 synonymous) showed statistically significant differences (P<0.05), and two SNPs, in position 1039 and 1041 of cagE, showed a highly significant association with cancer (p-value = 2.07×10−6), and the variant codon was located in the VirB3 homology domain of Agrobacterium. The results of this study may provide preliminary information to target antibiotic treatment to high-risk individuals, if effects of these variants are confirmed in further investigations

Association of IL1B -511C/-31T haplotype and Helicobacter pylori vacA genotypes with gastric ulcer and chronic gastritis

<p>Abstract</p> <p>Background</p> <p>The association between proinflammatory cytokine gene polymorphisms and gastric diseases related to <it>Helicobacter pylori </it>varies by population and geographic area.</p> <p>Our objective was to determine if the <it>IL-1B </it>-<it>511 T>C </it>and -<it>31 C>T </it>polymorphisms and <it>H. pylori vacA </it>genotypes are associated with risk of chronic gastritis and gastric ulcer in a Mexican population.</p> <p>Methods</p> <p>We conducted endoscopic studies in 128 patients with symptoms of dyspepsia. We took two biopsies from the body, antrum, or ulcer edge from each patient, and classified our histopathological findings according to the Sydney System. <it>H. pylori </it>infection and <it>vacA </it>genotyping were accomplished via PCR from total DNA of the gastric biopsies. We confirmed the presence of anti-<it>H. pylori </it>serum IgG and IgM in 102 control subjects. In both case subjects and control subjects, the <it>IL-1B </it>-<it>511 T>C </it>polymorphism was genotyped by PCR-RFLPs and the <it>IL-1B -31 C>T </it>polymorphism was genotyped by pyrosequencing.</p> <p>Results</p> <p>Sixty-two point seven (62.7%) of the 102 control subjects were <it>H. pylori-</it>seropositive. Among the case subjects, 100 were diagnosed with chronic gastritis and 28 with gastric ulcer. We found that 77% of the patients with chronic gastritis and 85.7% of the patients with gastric ulcer were <it>H. pylori-</it>positive. The predominant <it>H. pylori </it>genotype was <it>vacA s1m1 </it>(58.4%) and the most frequent subtype was <it>vacA s1</it>. The -<it>511 TC</it>, (rs16944 -511 T>C) genotype and the -<it>511C </it>allele were associated with chronic gastritis (OR = 3.1, 95% CI = 1.4-6.8 and OR = 3.0, 95% CI = 1.4-6.0, respectively). The subjects carrying -<it>31T </it>(rs1143627 -31 C>T) were found to be at a higher risk of having chronic gastritis (OR = 2.8, 95% CI = 1.3-5.8). The <it>IL-1B </it>-<it>511C/-31T </it>haplotype was associated with chronic gastritis (OR = 2.1, 95% CI = 1.2-3.8) but not with gastric ulcer.</p> <p>Conclusions</p> <p>The <it>H. pylori vacA </it>genotypes identified herein were similar to those reported for other regions of Mexico. The <it>vacA s1m1 </it>genotype was not associated with gastric ulcer. In the southern Mexican population, the <it>IL-1B -511C </it>and -<it>31T </it>alleles and the -<it>511C/-31T </it>and -<it>511T/-31T </it>haplotypes are associated with increased risk of chronic gastritis and gastric ulcer.</p