Functional Analysis of thecagPathogenicity Island inHelicobacter pyloriIsolates from Patients with Gastritis, Peptic Ulcer, and Gastric Cancer

Abstract

Helicobacter pylori is the causative agent of a variety of gastric diseases, but the clinical relevance of bacterial virulence factors is still controversial. Virulent strains carrying the cag pathogenicity island (cagPAI) are thought to be key players in disease development. Here, we have compared cagPAI-dependent in vitro responses in H. pylori isolates obtained from 75 patients with gastritis, peptic ulcer, and gastric cancer (n ‫؍‬ 25 in each group). AGS gastric epithelial cells were infected with each strain and assayed for (i) CagA expression, (ii) translocation and tyrosine phosphorylation of CagA, (iii) c-Src inactivation, (iv) cortactin dephosphorylation, (v) induction of actin cytoskeletal rearrangements associated with cell elongation, (vi) induction of cellular motility, and (vii) secretion of interleukin-8. Interestingly, we found high but similar prevalences of all of these cagPAI-dependent host cell responses (ranging from 56 to 80%) among the various groups of patients. This study revealed CagA proteins with unique features, CagA subspecies of various sizes, and new functional properties for the phenotypic outcomes. We further showed that induction of AGS cell motility and elongation are two independent processes. Our data corroborate epidemiological studies, which indicate a significant association of cagPAI presence and functionality with histopathological findings in gastritis, peptic ulcer, and gastric cancer patients, thus emphasizing the importance of the cagPAI for the pathogenicity of H. pylori. Nevertheless, we found no significant association of the specific H. pylori-induced responses with any particular patient group. This may indicate that the determination of disease development is highly complex and involves multiple bacterial and/or host factors.

Subcellular and Functional Proteomic Analysis of the Cellular Responses Induced by Helicobacter pylori

“…The scattering hummingbird phenotype has been described as indicative of the translocation of CagA, the most important virulence factor of H. pylori, into epithelial cells, inducing host cellular growth changes (10,34). In addition, translocated CagA activates the nuclear factor-B (NFB) signaling pathway and leads to increased production of cytokines, such as IL-8.…”

Functional Cytotoxin Associated Gene A in Helicobacter pylori Strains and Its Association with Integrity of Cag-pathogenicity Island and Histopathological Changes of Gastric Tissue

“…Our results represented more conserved pathogenicity locus in severe gastritis patients, even among the strains with lower repeats of EPIYA motif. However, involvement of other H. pylori virulence factors or host factors also seems probable (25,(57)(58)(59)(60).…”

“…Diversity of cag-PAIs among different H. pylori strains, encouraged researchers to use cag-PAI typing as a molecular typing method to study its association with their pathogenic capacity in infected patients (23)(24)(25). Diversity of this PAI could be screened for the presence or absence of noted genes or defined deletions and insertions.…”

Expression of CagL from Helicobacter pylori and Preliminary Study of its Biological Function

“…This microorganism has been categorized as class I carcinogen by the World Health Organization [1]. The pathogenesis of H. pylori mainly depends on the exposure of several bacterial factors, including cytotoxin-associated gene A (CagA), the type IV secretion system (T4SS), vacuolating cytotoxin A, outer inflammatory protein A and several adherence factors, to the host [4][5][6].…”

“…Helicobacter pylori (H. pylori) is a gram-negative, spiralshaped, microaerophilic bacterium that colonizes the human gastric mucosa and is recognized as the causative agent of chronic active gastritis, gastric and duodenal ulcers or lymphoma of the MALT (mucosa-associated lymphoid tissue) system, and is a risk factor for the development of adenocarcinoma [1][2][3]. This microorganism has been categorized as class I carcinogen by the World Health Organization [1].…”