Risk assessment of pathological conditions caused by circulating H. pylori strains

Abstract

In recent years, there has been an increase in the prevalence of inflammatory and destructive diseases of the gastroduodenal zone, which is primarily explained by Helicobacter pylori (H. pylori) infection. One of the main factors of H. pylori pathogenicity is presence of cytotoxin-associated gene — CagA. It is known that CagA-positive H. pylori strains are associated with the development of atrophy, tumor invasion and rapid metastasis. A number of recently published studies have revealed that CagA is a polymorphic gene which contains a different number of repetitive sequences located in the 3’ region. Each repetitive region of CagA contains Glu-Pro-Ile-Tyr-Ala (EPIYA) profiles including tyrosine phosphorylation. Depending on the sequence of the EPIYA profile, there are 4 segments: EPIYA-A, EPIYA-B, EPIYA-C, EPIYA-D, each containing a repetitive region. Geographical features of the prevalence of H. pylori strains depending on the sequence of EPIYA have been revealed: EPIYA-A region of the western isolates of this bacterium is associated with EPIYA-A, EPIYA-B, EPIYA-C segments, while the eastern CagA-positive H. pylori isolates are characterized by the A-B-D type of the CagA gene. Data illustrating the strong correlation between the western CagA-positive H. pylori strains, which have a repeating EPIYA-C segment, and the development of precancerous states, as well as gastric cancer, are presented. H. pylori strains containing simultaneously A-B motives of EPIYA or one C-type of the CagA gene are associated with a 7-fold increase of risk of gastric cancer compared to CagA-negative strains; presence of two or more EPIYA-C motives is associated with a 30-fold increase of this risk.