Genetic diversity and amino acid sequence polymorphism in Helicobacter pylori CagL hypervariable motif and its association with virulence markers and gastroduodenal diseases

Abstract

Genetic variability in cagL gene especially within the Helicobacter pylori CagL hypervariable motif (CagLHM) may affect the development of gastric cancer. Therefore, this study was conducted to investigate the association of CagL diversity with clinical outcomes and with H pylori virulence markers. A total of 126 patients with different gastric diseases including non‐ulcer dyspepsia (NUD), peptic ulcer disease (PUD), gastric erosion (GE), and gastric cancer (GC) were enrolled. H pylori was cultured from gastric biopsies, and the isolates were screened for the presence of cagL, cagA, vacA, babA2, sabA, and cagPAI integrity by PCR. The amino acid polymorphisms of cagL were analyzed using DNA sequencing. We isolated 61 (48.4%) H pylori strains from 36 NUD, eight PUD, 12 GE, and five GC patients. Almost all isolates were cagL positive (97%), and their RGD, RHS, and SKIIVK motifs were highly conserved. Among 10 CagLHM variants identified, NEIGQ and NKIGQ were detected as the most prevalent sequences. Interestingly, a significant association was found between the presence of NKMGK and PUD (P = 0.002). Notably, the NEIGQ isolates with multiple C‐type EPIYA repeat that carried intact cagPAI correlated with disease risk for PUD, GE, and GC (P = 0.021). In conclusion, we identified novel variants of H pylori CagLHM sequences in Iranian population such as NKMGK, which was associated with disease risk for PUD. Further studies using a large number of strains are required to better clarify the function of certain CagLHM motifs in gastric carcinogenesis and disease outcome.

Characterization and genetic diversity of Helicobacter pylori type IV secretion system components, CagI and CagN and its association with clinical outcomes among Iranian patients

“…Ogawa et al discovered complete RGD motifs in CagL sequences were observed from all isolates, which possibly imply the importance of the RGD motif for CagL function [26]. A recent investigation on this topic was performed by Yadegar et al in Iran, in which almost 97% of H. pylori clinical strains contained cagL gene [29]. Furthermore, their ndings highlighted the importance of a common CagL hypervariable motif (CagLHM) such as NEIGQ along with multiple C-type EPIYA repeats, which was linked to PUD, GE, and GC with more severity compared to NUD.…”

“…The incubation was performed at 37°C for 3-7 days under a microaerophilic atmosphere (5% O 2 , 10% CO 2 and 85% N 2 ) in a CO 2 incubator (Innova ® CO-170; New Brunswick Scienti c, USA). The suspected colonies were identi ed as H. pylori based on colony morphology, Gram staining, positive reaction for oxidase, catalase and urease tests, and also by H. pylori gene-speci c PCR following the previously described protocols [28,29]. Pure cultures from con rmed isolates were kept in 0.5 ml of Brain heart infusion (BHI) medium (Merck, Germany) containing 15% glycerol plus 20% FCS, and stored at -80°C until further analysis.…”

Helicobacter pylori Virulence Factor Cytotoxin-Associated Gene A (CagA)-Mediated Gastric Pathogenicity

“…In a study, particular polymorphisms upstream of the RGD motif at amino acid residues 58–62, called the CagL hypervariable motif (CagLHM), were correlated with severe disease progression in a geographically dependent manner [ 51 , 52 ]. Recently, studies have also found CagL polymorphisms such as D58, K59, M60, E62, K122, and I134 and novel CagL variants, and shown their association with chronic gastritis and PUD [ 53 , 54 ].…”

Genetic variation in the cag pathogenicity island of Helicobacter pylori strains detected from gastroduodenal patients in Thailand

“…The integrity of cag-PAI was evaluated by determining the presence of several gene clusters within the cag-PAI region. The presence or absence of selected gene clusters was defined as an intact cag-PAI, a partially deleted cag-PAI, or complete absence of cag-PAI [26]. The complete absence of cag-PAI was confirmed by a PCR assay of cag-PAI empty site [26].…”