Helicobacter pylori virulence factors: relationship between genetic variability and phylogeographic origin

MicroRNAs in Helicobacter pylori-infected gastric cancer: Function and clinical application

Gastric cancer (GC) is the leading cause of cancer-related death worldwide, and it is associated with a combination of genetic, environmental, and microbial risk factors. Helicobacter pylori (H. pylori) is classified as a type I carcinogen, however, the exact regulatory mechanisms underlying H. pylori-induced GC are incompletely defined. MicroRNAs (miRNAs), one of small non-coding RNAs, negatively regulate gene expression through binding to their target genes. Dysregulation of miRNAs is crucial in human cancer. A noteworthy quantity of aberrant miRNAs induced by H. pylori through complex regulatory networks have been identified. These miRNAs substantially affect genetic instability, cell proliferation, apoptosis, invasion, metastasis, autophagy, chemoresistance, and the tumor microenvironment, leading to GC development and progression. Importantly, some H. pylori-associated miRNAs hold promise as therapeutic tools and biomarkers for GC prevention, diagnosis, and prognosis. Nonetheless, clinical application of miRNAs remains in its infancy with multiple issues, including sensitivity and specificity, stability, reliable delivery systems, and off-target effects. Additional research on the specific molecular mechanisms and more clinical data are still required. This review investigated the biogenesis, regulatory mechanisms, and functions of miRNAs in H. pylori-induced GC, offering novel insights into the potential clinical applications of miRNA-based therapeutics and biomarkers.

Identification, Genome Sequencing, and Characterizations of Helicobacter pylori Sourced from Pakistan

The stomach's colonization by Helicobacter pylori (H. pylori) results in gastritis, ulcers, and stomach cancer. Frequently, pain is treated with medication, but resistant H. pylori infections are not. Therefore, it is important to find pharmacological targets and improved treatments for resistant H. pylori strains. The aim of the current study was sampling, identification, drug susceptibility testing following genome sequencing and comparative genome-wide analysis of selected H. pylori strains from Pakistan with three representative strains for virulence and drug-resistant characteristics. Based on culture, biochemistry, and molecular biology, 84 strains of H. pylori were identified, which made up 47% of the enrolled cases. Among all H. pylori strains, the highest resistance was reported for metronidazole with 82 H. pylori strains (98%), followed by clarithromycin with 62 resistant strains (74%). Among metronidazole-resistant strains, 38 strains (46%) were also resistant to clarithromycin, contributing 61% of clarithromycin resistant cases. Two strains, HPA1 and HPA2, isolated from 'gastritis' and 'gastric ulcer' patients, respectively, were further processed for WGS. The draft genome sequences of H. pylori strains HPA1 and HPA2 encode 1.66 Mbp and 1.67 Mbp genome size, 24 and 4 contiguous DNA sequences, and 1650 and 1625 coding sequences, respectively. Both the genomes showed greater than 90% similarity with the reference strain H. pylori ATCC 43504/PMSS1. The antibiotic-resistant genes were identified among all the strains with overall similarity above 95%, with minor differences in the sequence similarity. Using the virulent gene data obtained from the Virulence Factor Database, 75 to 85 virulent genes were identified in the five genome assemblies with various key genes such as cytolethal distending toxin (cdt), type IV secretion system, cag PAI, plasticity region, cell-motility- and flagellar-associated genes, neutrophil-activating protein (HP-NAP), T4SS effector cytotoxin-associated gene A (cagA), and urease-associated genes ureA and ureB, etc. Sequence similarity between the virulence factors found in this study and reference genes was at least 90%. In summary, the results of our study showed the relationship between clinical results and specific H. pylori strains' (HPA1 and HPA2) genetics such as antibiotic resistance and specific virulence factors. These findings provide valued understanding of the epidemiology of H. pylori-associated diseases. Moreover, identification and genomics analysis have provided insights into the epidemiology, genetic diversity, pathogenicity, and potential drug resistance genes of H. pylori strains, offering a foundation for developing more targeted and effective medical interventions, including anti-virulent medications.

Vaccination against Helicobacter pylori - An approach for cancer prevention?

The gram-negative bacterium Helicobacter pylori is the most common chronic bacterial infection and the main cause of gastric cancer. Due to the increasing antimicrobial resistance of H. pylori, the development of an efficacious vaccine is a valid option to protect from disease or infection and ultimately prevent gastric cancer. However, despite more than 30 years of research, no vaccine has entered the market yet. This review highlights the most relevant previous preclinical and clinical studies to allow conclusions to be drawn on which parameters need special attention in the future to develop an efficacious vaccine against H. pylori and thus prevent gastric cancer.