The CagA toxin of Helicobacter pylori: abundant production but relatively low amount translocated

Helicobacter pylori CagA and CagT antibodies arrest the translocation of CagA into gastric epithelial cells

Cytotoxic-associated gene A (CagA) is a key virulence factor of Helicobacter pylori, associated with gastric ulcers and stomach cancer. The bacterium employs a Cag-type IV secretion system for translocation of CagA into the host cells. This study investigates the impact of CagA antibodies on CagA translocation into gastric epithelial cells in vitro. Our findings reveal that CagA synthesis and translocation across bacterial membranes is a continuous process initiated upon host-cell contact. Notably, the treatment of Helicobacter pylori with CagA-specific antibodies significantly inhibited the translocation of CagA into host cells during infection. These results suggest that the CagA antibody may serve as a potential therapeutic strategy to combat Helicobacter pylori pathogenesis. A similar result was obtained when CagT antibody was used under the same conditions. Notably, the CagT antibody exhibited a more pronounced pathoblocking effect, likely due to its accessibility on the bacterial surface as a structural component of Cag-T4SS. Taken together, this study provides insights into the therapeutic potential of CagA and CagT antibodies to mitigate Helicobacter pylori infection, while also advancing our understanding of the mechanisms involved in CagA translocation across the bacterial membranes to the host cell.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-025-04343-0.

A study of the association between Helicobacter pylori infection type and pancreatic cancer risk: A systematic review and meta‑analysis

Pancreatic cancer is a highly invasive malignant tumor with a complex pathogenesis that makes early diagnosis challenging. The potential association between Helicobacter pylori infection and pancreatic cancer risk has been noted; however, the available results are still highly divergent. The aim of the present study was to systematically evaluate the association between different types of H. pylori infection and pancreatic cancer risk as well as to explore the possible causes. A systematic search was conducted using the PubMed, Embase and Cochrane Library databases up to August 2023. The literature quality was evaluated using the Newcastle-Ottawa Scale. All studies that met the criteria were included in the overall meta-analysis to calculate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs). In addition, subgroup analyses were performed based on factors such as diagnostic criteria for H. pylori infection, study region, type of study design and CagA status. The effect of publication bias on the quantitative synthesis results was assessed using the trim-and-fill analysis, and sensitivity analyses were used to verify the robustness of the quantitative synthesis results. A total of 17 studies involving 67,910 participants, including 64,372 controls and 3,538 patients with pancreatic cancer, were included in the present study. The overall analysis showed that no significant association was observed between H. pylori infection and pancreatic cancer risk (OR, 1.15; 95% CI, 0.93-1.41). Further subgroup analyses, which did not consider the effects of study quality, diagnostic criteria, geographical distribution and the type of study design, did not produce new findings that contradicted the results of the overall analysis. CagA+ H. pylori infection did not significantly affect the risk of pancreatic cancer (OR, 0.95; 95% CI, 0.78-1.16), whereas CagA- H. pylori infection may be a possible risk factor for pancreatic cancer (OR, 1.24; 95% CI, 1.004-1.541). The H. pylori infection did not significantly increase the risk of pancreatic cancer. However, it is noteworthy that CagA- H. pylori infection could be a potential factor that elevated the risk of pancreatic cancer.

Hibiscus sabdariffa as a Novel Alternative Strategy Against Helicobacter pylori Infection Development to Gastric Cancer

Most gastric cancers (95%) are related to an initial Helicobacter pylori infection worldwide. Treatments against this pathogen include a mix of antibiotics, antimicrobials, and proton-pump inhibitors. Over time, H. pylori mutated, generating resistance to treatments and making it hard to combat its infection. The purpose of this review is Hibiscus sabdariffa, commonly known as hibiscus, as a potential agent for anti-H. pylori activity. Scientific interest has increased toward plant-derived bioactive compounds, which have the ability to enhance the antibiotic effect and can lead to the development of new drugs, such is the case for H. sabdariffa. In general, studies show that natural products, such as plant-derived bioactive compounds, can be used as alternative treatments from natural origin against the pathogen. The specific action mechanism of these bioactive compounds is still controversial, but it is suggested that they have an anti-inflammatory effect, and they also act as antibiotic coadjutants. Research has been conducted regarding different bioactive compounds such as polyphenols, epicatechins, alkaloids, and caryophyllenes. H. sabdariffa contains several of these compounds; therefore, more studies are needed to establish its effect against H. pylori.

Elucidating gastric cancer mechanisms and therapeutic potential of Adociaquinone A targeting EGFR: A genomic analysis and Computer Aided Drug Design (CADD) approach

Gastric cancer predominantly adenocarcinoma, accounts for over 85% of gastric cancer diagnoses. Current therapeutic options are limited, necessitating the discovery of novel drug targets and effective treatments. The Affymetrix gene expression microarray dataset (GSE64951) was retrieved from NCBI-GEO data normalization and DEGs identification was done by using R-Bioconductor package. Gene Ontology (GO) analysis of DEGs was performed using DAVID. The protein-protein interaction network was constructed by STRING database plugin in Cytoscape. Subclusters/modules of important interacting genes in main network were extracted by using MCODE. The hub genes from in the network were identified by using Cytohubba. The miRNet tool built a hub gene/mRNA-miRNA network and Kaplan-Meier-Plotter conducted survival analysis. AutoDock Vina and GROMACS MD simulations were used for docking and stability analysis of marine compounds against the 5CNN protein. Total 734 DEGs (507 up-regulated and 228 down-regulated) were identified. Differentially expressed genes (DEGs) were enriched in processes like cell-cell adhesion and ATP binding. Eight hub genes (EGFR, HSPA90AA1, MAPK1, HSPA4, PPP2CA, CDKN2A, CDC20, and ATM) were selected for further analysis. A total of 23 miRNAs associated with hub genes were identified, with 12 of them targeting PPP2CA. EGFR displayed the highest expression and hazard rate in survival analyses. The kinase domain of EGFR (PDBID: 5CNN) was chosen as the drug target. Adociaquinone A from Petrosia alfiani, docked with 5CNN, showed the lowest binding energy with stable interactions across a 50 ns MD simulation, highlighting its potential as a lead molecule against EGFR. This study has identified crucial DEGs and hub genes in gastric cancer, proposing novel therapeutic targets. Specifically, Adociaquinone A demonstrates promising potential as a bioactive drug against EGFR in gastric cancer, warranting further investigation. The predicted miRNA against the hub gene/proteins can also be used as potential therapeutic targets.

CagA toxin and risk of Helicobacter pylori-infected gastric phenotype: A meta-analysis of observational studies

BACKGROUND

Helicobacter pylori (H. pylori) is frequently associated with non-cardia type gastric cancer, and it is designated as a group I carcinogen. This study aimed to systematically review and meta-analyze the evidence on the prevalence of CagA status in people with gastric disorders in the Indo-Pacific region, and to examine the association of CagA positive in the risk of gastric disorders. This study focused on the Indo-Pacific region owing to the high disability adjusted life-years related to these disorders, the accessibility of efficient treatments for this common bacterial infection, and the varying standard of care for these disorders, particularly among the elderly population in the region.

METHODS

Relevant studies were identified in the health-related electronic databases including PubMed, Ovid, Medline, Ovid Embase, Index Medicus, and Google Scholar that were published in English between 1 January 2000, and 18 November 2023. For pooled prevalence, meta-analysis of proportional studies was done, after Freeman-Tukey double arcsine transformation of data. A random-effect model was used to compute the pooled odds ratio (OR) and 95% confidence interval (CI) to investigate the relationship between CagA positivity and gastric disorders.

RESULTS

Twenty-four studies from eight Indo-Pacific countries (Bhutan, India, Indonesia, Malaysia, Myanmar, Singapore, Thailand, Vietnam) were included. Overall pooled prevalence of CagA positivity in H. pylori-infected gastric disorders was 83% (95%CI = 73-91%). Following stratification, the pooled prevalence of CagA positivity was 78% (95%CI = 67-90%) in H. pylori-infected gastritis, 86% (95%CI = 73-96%) in peptic ulcer disease, and 83% (95%CI = 51-100%) in gastric cancer. Geographic locations encountered variations in CagA prevalence. There was a greater risk of developing gastric cancer in those with CagA positivity compared with gastritis (OR = 2.53,95%CI = 1.15-5.55).

CONCLUSION

Findings suggest that the distribution of CagA in H. pylori-infected gastric disorders varies among different type of gastric disorders in the study countries, and CagA may play a role in the development of gastric cancer. It is important to provide a high standard of care for the management of gastric diseases, particularly in a region where the prevalence of these disorders is high. Better strategies for effective treatment for high-risk groups are required for health programs to revisit this often-neglected infectious disease.

Helicobacter pylori glycan biosynthesis modulates host immune cell recognition and response

Introduction

The pathogenic bacterium Helicobacter pylori has evolved glycan-mediated mechanisms to evade host immune defenses. This study tests the hypothesis that genetic disruption of H. pylori glycan biosynthesis alters immune recognition and response by human gastric epithelial cells and monocyte-derived dendritic cells.

Methods

To test this hypothesis, human cell lines were challenged with wildtype H. pylori alongside an array of H. pylori glycosylation mutants. The relative levels of immune response were measured via immature dendritic cell maturation and cytokine secretion.

Results

Our findings indicate that disruption of lipopolysaccharide biosynthesis diminishes gastric cytokine production, without disrupting dendritic cell recognition and activation. In contrast, variable immune responses were observed in protein glycosylation mutants which prompted us to test the hypothesis that phase variation plays a role in regulating bacterial cell surface glycosylation and subsequent immune recognition. Lewis antigen presentation does not correlate with extent of immune response, while the extent of lipopolysaccharide O-antigen elaboration does.

Discussion

The outcomes of this study demonstrate that H. pylori glycans modulate the host immune response. This work provides a foundation to pursue immune-based tailoring of bacterial glycans towards modulating immunogenicity of microbial pathogens.

Review of Phytochemical Potency as a Natural Anti-Helicobacter pylori and Neuroprotective Agent

Phytochemicals are plant secondary metabolites that show health benefits for humans due to their bioactivity. There is a huge variety of phytochemicals that have already been identified, and these compounds can act as antimicrobial and neuroprotection agents. Due to their anti-microbial activity and neuroprotection, several phytochemicals might have the potency to be used as natural therapeutic agents, especially for Helicobacter pylori infection and neurodegenerative disease, which have become a global health concern nowadays. According to previous research, there are some connections between H. pylori infection and neurodegenerative diseases, especially Alzheimer's disease. Hence, this comprehensive review examines different kinds of phytochemicals from natural sources as potential therapeutic agents to reduce H. pylori infection and improve neurodegenerative disease. An additional large-scale study is needed to establish the connection between H. pylori infection and neurodegenerative disease and how phytochemicals could improve this condition.

Unwelcome guests - the role of gland-associated Helicobacter pylori infection in gastric carcinogenesis

Helicobacter pylori (H. pylori) are Gram-negative bacteria that cause chronic gastritis and are considered the main risk factor for the development of gastric cancer. H. pylori have evolved to survive the harsh luminal environment of the stomach and are known to cause damage and signaling aberrations in gastric epithelial cells, which can result in premalignant and malignant pathology. As well as colonizing the gastric mucus and surface epithelial cells, a subpopulation of H. pylori can invade deep into the gastric glands and directly interact with progenitor and stem cells. Gland colonization therefore bears the potential to cause direct injury to long-lived cells. Moreover, this bacterial subpopulation triggers a series of host responses that cause an enhanced proliferation of stem cells. Here, we review recent insights into how gastric gland colonization by H. pylori is established, the resulting pro-carcinogenic epithelial signaling alterations, as well as new insights into stem cell responses to infection. Together these point towards a critical role of gland-associated H. pylori in the development of gastric cancer.

Serum Calprotectin and B-cell activating factor are potential biomarkers for Helicobacter pylori infection

Humans always mount a robust immune response to the bacterial infection caused by Helicobacter pylori, which causes various gastrointestinal tract infections. Calprotectin (CALP) and B-Cell Activating Factor (BAFF) are inflammatory biomarkers having a role in the gastrointestinal neutrophilic response to bacterial infection. The study was designed to assess serum CALP and BAFF as inflammatory biomarkers in H. pylori infection and peptic ulcer patients. The current study comprised 112 people, including 62 H. pylori-infected patients (34 men and 28 women) who were clinically diagnosed with H. pylori infection via testing positive for the H. pylori stool antigen test; they were compared to a control group of 50 healthy people (34 men and 16 women) who were age and gender-matched to H. pylori-infected patients. The serum level of CALP and BAFF were assayed using the ELISA technique. The biochemical parameters were statistically compared between patients and controls by unpaired Man-Whitney U t-test and Receiver Operating Characteristic (ROC) curve analysis. There was a significant elevation of serum CALP in H. pylori-infected patients [116.4(120.7), p=0.0132] in comparison to healthy controls [99.50(115.8)]. Similarly, there was a significant elevation of serum BAFF concentration in H. pylori-infected patients [485.7(367.1), p=0.0014] in comparison to healthy controls [444.5(513.0)]. The ROC curve analysis suggests serum CALP and BAFF as reasonable inflammatory biomarkers for H. pylori infection with statistically significant (p=0.0135, p=0.0015) area under the ROC curve of (0.6361, 0.6748), respectively. CALP and BAFF are potent inflammatory biomarkers involved in the development and etiology of H. pylori infection. Serum CALP and BAFF levels could be used as biomarkers for chronic inflammation induced by H. pylori. CALP and BAFF biomarkers can be combined to diagnose and predict the prognosis of H. pylori infection.

Host-microbiota interactions and oncogenesis: Crosstalk and its implications in etiology

A number of articles have discussed the potential of microbiota in oncogenesis. Several of these have evaluated the modulation of microbiota and its influence on cancer development. Even in recent past, a plethora of studies have gathered in order to understand the difference in microbiota population among different cancer and normal individuals. Although in majority of studies, microbiota mediated oncogenesis has been primarily attributed to the inflammatory mechanisms, there are several other ways through which microbiota can influence oncogenesis. These relatively less discussed aspects including the hormonal modulation through estrobolome and endobolome, production of cyclomodulins, and lateral gene transfer need more attention of scientific community. We prepared this article to discuss the role of microbiota in oncogenesis in order to provide concise information on these relatively less discussed microbiota mediated oncogenesis mechanisms.

Seminars in immunology special issue: Nutrition, microbiota and immunity The unexplored microbes in health and disease

Functional characterization of the microbiome's influence on host physiology has been dominated by a few characteristic example strains that have been studied in detail. However, the extensive development of methods for high-throughput bacterial isolation and culture over the past decade is enabling functional characterization of the broader microbiota that may impact human health. Characterizing the understudied majority of human microbes and expanding our functional understanding of the diversity of the gut microbiota could enable new insights into diseases with unknown etiology, provide disease-predictive microbiome signatures, and advance microbial therapeutics. We summarize high-throughput culture-dependent platforms for characterizing bacterial strain function and host-interactions. We elaborate on the importance of these technologies in facilitating mechanistic studies of previously unexplored microbes, highlight new opportunities for large-scale in vitro screens of host-relevant microbial functions, and discuss the potential translational applications for microbiome science.

Immune Thrombocytopenia Induced by Helicobacter pylori Infection: A Case Report and Literature Review

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by the production of autoantibodies against the platelet surface antigens. ITP is a diagnosis of exclusion and is further categorized into primary and secondary ITP. The etiology of primary ITP is idiopathic, and secondary ITP is caused by infections and autoimmune disorders. Among infectious etiology of ITP, human immunodeficiency virus, herpes virus, and hepatitis B and C virus are common. Helicobacter pylori (H. pylori) is a rare cause of ITP, and the relationship between ITP and H. pylori is highlighted in the literature. We report a case of ITP in an adult female who presented with hematemesis and petechial rash in the lower limbs. Her initial laboratory results demonstrated thrombocytopenia, and the results of her gastric biopsy and stool antigen were positive for H. pylori. She was diagnosed with ITP induced by H. pylori because additional causes of ITP were not identified. Her clinical improvement and platelet recovery after initiating H. pylori eradication therapy were consistent with H. pylori-induced ITP.

Helicobacter pylori Pathogenicity Islands and Giardia lamblia Cysteine Proteases in Role of Coinfection and Pathogenesis

Helicobacter pylori is a well-known human-specific stomach pathogen that infects more than half of the world’s population. The infection with this bacterium can cause a variety of gastrointestinal problems, including chronic gastritis, peptic ulcers, and even cancer. H. pylori is a highly infectious bacterium. H. pylori causes an increase in gastric mucosa pH or gastric mucosa intestinal metaplasia. These modifications in the stomach environment are necessary for G. lamblia colonization to occur. Giardia lamblia is a flagellate protozoan parasite that can cause giardiasis in humans and other mammals. It dwells in the duodenum and upper jejunum. Globally, over 280 million cases of human giardiasis are predicted to occur each year. Simultaneous human colonization by G. lamblia and H. pylori is a typical occurrence since the viruses’ predisposing factors are similar in both groups. Giardiasis is a parasitic infection that affects both children and adults worldwide. Infection with Giardia is more common in underdeveloped countries. Globally, more than 200 million cases of giardiasis are detected each year. In contrast, the presence of G. lamblia in the host body triggers an immunological response comparable to that of H. pylori, with lymphocytes strongly polarized towards Th1. As a result, their combined presence exacerbates host tissue damage. The major goal of this seminar is to describe the pathophysiology, immunology, and clinical aspects of G. lamblia and H. pylori coinfection using a comprehensive search of PubMed, Lancet, and Google Scholar sources. Upper gastrointestinal problems such as upper abdominal pain, abdominal bloating, nausea, vomiting, epigastric pain/burning, and belching are all caused by both organisms. Differentiation by physical examination is impossible in people infected with both bacteria. For this coinfection distinction, a laboratory diagnosis is required. G. lamblia and H. pylori, when present together, have a synergistic effect on the host and can cause serious damage. As a result, researchers should delve deeper into the mechanics underlying this potential microbial interaction.

Immune thrombocytopenic purpura secondary to Helicobacter pylori

Immune thrombocytopenic purpura is a disorder characterized by decreased platelet count that may be secondary to infectious or autoimmune etiologies. We present a patient with upper gastrointestinal bleeding complicated by severe thrombocytopenia. Endoscopy revealed gastritis with pathology positive for Helicobacter pylori. Platelet count normalized after triple antibiotic therapy. The precise mechanism by which H. pylori causes immune thrombocytopenic purpura remains unclear; however, there are several plausible mechanisms. This case highlights the importance of keeping H. pylori in the differential in patients presenting with thrombocytopenia.

Kinetics of CagA type IV secretion by Helicobacter pylori and the requirement for substrate unfolding

Type IV secretion of effector proteins is an important principle for interaction of human pathogens with their target cells. The corresponding secretion systems may transport a multitude of effector proteins that have to be deployed in the respective spatiotemporal context, or only a single translocated protein, as in the case of the CagA effector protein produced by the human gastric pathogen Helicobacter pylori. For a more detailed analysis of the kinetics and mode of action of CagA type IV secretion by H. pylori, we describe here, a novel, highly sensitive split luciferase-based translocation reporter which can be easily adapted to different end-point or real-time measurements. Using this reporter, we showed that H. pylori cells are able to rapidly inject a limited amount of their CagA supply into cultured gastric epithelial cells. We have further employed the reporter system to address the question whether CagA has to be unfolded prior to translocation by the type IV secretion system. We showed that protein domains co-translocated with CagA as protein fusions are more readily tolerated as substrates than in other secretion systems, but also provide evidence that unfolding of effector proteins is a prerequisite for their transport.

The Role of Formyl Peptide Receptors in Permanent and Low-Grade Inflammation: Helicobacter pylori Infection as a Model

Formyl peptide receptors (FPRs) are cell surface pattern recognition receptors (PRRs), belonging to the chemoattractant G protein-coupled receptors (GPCRs) family. They play a key role in the innate immune system, regulating both the initiation and the resolution of the inflammatory response. FPRs were originally identified as receptors with high binding affinity for bacteria or mitochondria N-formylated peptides. However, they can also bind a variety of structurally different ligands. Among FPRs, formyl peptide receptor-like 1 (FPRL1) is the most versatile, recognizing N-formyl peptides, non-formylated peptides, and synthetic molecules. In addition, according to the ligand nature, FPRL1 can mediate either pro- or anti-inflammatory responses. Hp(2-20), a Helicobacter pylori-derived, non-formylated peptide, is a potent FPRL1 agonist, participating in Helicobacter pylori-induced gastric inflammation, thus contributing to the related site or not-site specific diseases. The aim of this review is to provide insights into the role of FPRs in H. pylori-associated chronic inflammation, which suggests this receptor as potential target to mitigate both microbial and sterile inflammatory diseases.

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

Helicobacter pylori causes persistent infection in the gastric epithelium of more than half of the world’s population, leading to the development of severe complications such as peptic ulcer diseases, gastric cancer, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Several virulence factors, including cytotoxin-associated gene A (CagA), which is translocated into the gastric epithelium via the type 4 secretory system (T4SS), have been indicated to play a vital role in disease development. Although infection with strains harboring the East Asian type of CagA possessing the EPIYA-A, -B, and -D sequences has been found to potentiate cell proliferation and disease pathogenicity, the exact mechanism of CagA involvement in disease severity still remains to be elucidated. Therefore, we discuss the possible role of CagA in gastric pathogenicity.

Whole Genome Sequencing Reveals Virulence Potentials of Helicobacter pylori Strain KE21 Isolated from a Kenyan Patient with Gastric Signet Ring Cell Carcinoma

Helicobacter pylori (H.pylori) infection is etiologically associated with severe diseases including gastric cancer; but its pathogenicity is deeply shaped by the exceptional genomic diversification and geographic variation of the species. The clinical relevance of strains colonizing Africa is still debated. This study aimed to explore genomic features and virulence potentials of H. pylori KE21, a typical African strain isolated from a native Kenyan patient diagnosed with a gastric cancer. A high-quality circular genome assembly of 1,648,327 bp (1590 genes) obtained as a hybrid of Illumina Miseq short reads and Oxford Nanopore MinION long reads, clustered within hpAfrica1 population. This genome revealed a virulome and a mobilome encoding more than hundred features potentiating a successful colonization, persistent infection, and enhanced disease pathogenesis. Furthermore, through an experimental infection of gastric epithelial cell lines, strain KE21 showed the ability to promote interleukin-8 production and to induce cellular alterations resulting from the injection of a functional CagA oncogene protein into the cells. This study shows that strain KE21 is potentially virulent and can trigger oncogenic pathways in gastric epithelial cells. Expended genomic and clinical explorations are required to evaluate the epidemiological importance of H. pylori infection and its putative complications in the study population.

Role of vacuolating cytotoxin A in Helicobacter pylori infection and its impact on gastric pathogenesis

Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.

N-terminal region of Helicobacter pylori CagA induces IL-8 production in gastric epithelial cells via the β1 integrin receptor

Introduction. Helicobacter pylori is associated with gastrointestinal disease, most notably gastric cancer. Cytotoxin-associated antigen A (CagA), an important virulence factor for H. pylori pathogenicity, induces host cells to release inflammatory factors, especially interleukin-8 (IL-8). The mechanism by which C-terminal CagA induces IL-8 production has been studied extensively, but little is known about the role of the N-terminus.

Aim. To investigate the effect of CagA303–456aa (a peptide in the N-terminal CagA) on IL-8 production by gastric epithelial cells.

Methodology. CagA303-456aa was produced by a prokaryotic expression system and purified by Strep-tag affinity chromatography. An integrin β1 (ITGB1)-deficient AGS cell line was constructed using the CRISPR/Cas9 technique, and NCTC 11637 cagA and/or cagL knockout mutants were constructed via homologous recombination. The levels of IL-8 production were determined by enzyme-linked immunosorbent assay (ELISA), and p38 and ERK1/2 phosphorylation were examined by Western blot.

Results. CagA303-456aa induced IL-8 expression by AGS cells. IL-8 induction by CagA303-456aawas specifically inhibited by ITGB1 deficiency. Notably, CagA303-456aa activated the phosphorylation of both p38 and ERK1/2, and blocking p38 and ERK1/2 activity significantly reduced IL-8 induction by CagA303-456aa. ITGB1 deficiency also inhibited the activation of p38 phosphorylation by CagA303-456aa. Finally, experiments in CagA and/or CagL knockout bacterial lines demonstrated that extracellular CagA might induce IL-8 production by AGS cells.

Conclusion. Residues 303–456 of the N-terminal region of CagA induce IL-8 production via a CagA303-456–ITGB1–p38–IL-8 pathway, and ERK1/2 is also involved in the release of IL-8. Extracellular CagA might induce IL-8 production before translocation into AGS cells.

Helicobacter pylori Virulence Factors Exploiting Gastric Colonization and its Pathogenicity

Helicobacter pylori colonizes the gastric epithelial cells of at least half of the world's population, and it is the strongest risk factor for developing gastric complications like chronic gastritis, ulcer diseases, and gastric cancer. To successfully colonize and establish a persistent infection, the bacteria must overcome harsh gastric conditions. H. pylori has a well-developed mechanism by which it can survive in a very acidic niche. Despite bacterial factors, gastric environmental factors and host genetic constituents together play a co-operative role for gastric pathogenicity. The virulence factors include bacterial colonization factors BabA, SabA, OipA, and HopQ, and the virulence factors necessary for gastric pathogenicity include the effector proteins like CagA, VacA, HtrA, and the outer membrane vesicles. Bacterial factors are considered more important. Here, we summarize the recent information to better understand several bacterial virulence factors and their role in the pathogenic mechanism.

Analysis of virulence diversity of 73 Helicobacter pylori strains isolated in Guizhou province, China

The present study aimed to investigate the virulence diversity of Helicobacter pylori (H. pylori) in major ethnic groups residing in Guizhou province, China, and its association with clinical outcomes. Gastric mucosal biopsies were collected from the pylorus of patients with gastrointestinal disorders. H. pylori was identified by colonial morphology, Gram staining, a urease test and H. pylori‑specific 16S rRNA gene fragment PCR amplification. DNA was extracted from pure culture and used for virulence gene analysis. The cytotoxin associated gene A (cagA), vacuolating cytotoxin A (vacA) and induced by contact with epithelium gene A (iceA) genes were analyzed by polymerase chain reaction analysis. The cagA gene was further analyzed through sequencing of the C‑terminal region containing EPIYA motifs, and phylogenetic analysis of the cagA C‑terminal variable region was performed using MEGA 6.0 software. In the present study, 73 H. pylori strains were isolated from clinical samples. cagA genotypes were detected in all strains, namely cagA‑AB, ‑ABC, ‑ABD and ‑BD genotypes were found in five (6.85%), three (4.11%), 63 (86.30%) and two (2.74%) isolates, respectively. Phylogenetic analysis showed that there was a clustering association between the cagA‑AB and cagA‑ABC genotypes, and between the cagA‑ABD and cagA‑BD genotypes. In terms of the frequency of the four EPIYA or EPIYA‑like motifs, the most predominant was EPIYA (92.92%), followed by EPIYT (3.77%), ESIYA (2.83%) and ESIYT (0.47%). The predominant vacA genotype was s1c/m2 (65.75%), and the predominant iceA genotype was iceA1 (79.45%). There were no associations between the H. pylori cagA, vacA or iceA genotypes and clinical outcomes. No significant difference was found in the distribution of these genotypes according to the age, ethnicity or location of residence of patients. In conclusion, H. pylori isolated from patients in Guizhou region, China, showed a unique genotype, which was mainly East Asia‑type cagA (ABD), vacA s1c/m2 genotype or iceA1‑postiive. These results provide important information on the distribution of H. pylori virulence genotypes in Guizhou province, China.

Creation and Initial Characterization of Isogenic Helicobacter pylori CagA EPIYA Variants Reveals Differential Activation of Host Cell Signaling Pathways

The polymorphic CagA toxin is associated with Helicobacter pylori-induced disease. Previous data generated using non-isogenic strains and transfection models suggest that variation surrounding the C-terminal Glu-Pro-Ile-Tyr-Ala (EPIYA) motifs as well as the number of EPIYA motifs influence disease outcome. To investigate potential CagA-mediated effects on host cell signaling, we constructed and characterized a large panel of isogenic H. pylori strains that differ primarily in the CagA EPIYA region. The number of EPIYA-C motifs or the presence of an EPIYA-D motif impacted early changes in host cell elongation; however, the degree of elongation was comparable across all strains at later time points. In contrast, the strain carrying the EPIYA-D motif induced more IL-8 secretion than any other EPIYA type, and a single EPIYA-C motif induced comparable IL-8 secretion as isolates carrying multiple EPIYA-C alleles. Similar levels of ERK1/2 activation were induced by all strains carrying a functional CagA allele. Together, our data suggest that polymorphism in the CagA C-terminus is responsible for differential alterations in some, but not all, host cell signaling pathways. Notably, our results differ from non-isogenic strain studies, thus highlighting the importance of using isogenic strains to study the role of CagA toxin polymorphism in gastric cancer development.

Structural Insights into Helicobacter pylori Cag Protein Interactions with Host Cell Factors

The most virulent strains of Helicobacter pylori carry a genomic island (cagPAI) containing a set of 27-31 genes. The encoded proteins assemble a syringe-like apparatus to inject the cytotoxin-associated gene A (CagA) protein into gastric cells. This molecular device belongs to the type IV secretion system (T4SS) family albeit with unique characteristics. The cagPAI-encoded T4SS and its effector protein CagA have an intricate relationship with the host cell, with multiple interactions that only start to be deciphered from a structural point of view. On the one hand, the major roles of the interactions between CagL and CagA (and perhaps CagI and CagY) and host cell factors are to facilitate H. pylori adhesion and to mediate the injection of the CagA oncoprotein. On the other hand, CagA interactions with host cell partners interfere with cellular pathways to subvert cell defences and to promote H. pylori infection. Although a clear mechanism for CagA translocation is still lacking, the structural definition of CagA and CagL domains involved in interactions with signalling proteins are progressively coming to light. In this chapter, we will focus on the structural aspects of Cag protein interactions with host cell molecules, critical molecular events precluding H. pylori-mediated gastric cancer development.

The Helicobacter pylori Autotransporter ImaA Tempers the Bacterium's Interaction with α5β1 Integrin

The human pathogen Helicobacter pylori uses the host receptor α₅β₁ integrin to trigger inflammation in host cells via its cag pathogenicity island (cag PAI) type IV secretion system (T4SS). Here, we report that the H. pylori ImaA protein (HP0289) decreases the action of the cag PAI T4SS via tempering the bacterium's interaction with α₅β₁ integrin. Previously, imaA-null mutants were found to induce an elevated inflammatory response that was dependent on the cag PAI T4SS; here we extend those findings to show that the elevated response is independent of the CagA effector protein. To understand how ImaA could be affecting cag PAI T4SS activity at the host cell interface, we utilized the Phyre structural threading program and found that ImaA has a region with remote homology to bacterial integrin-binding proteins. This region was required for ImaA function. Unexpectedly, we observed that imaA mutants bound higher levels of α₅β₁ integrin than wild-type H. pylori, an outcome that required the predicted integrin-binding homology region of ImaA. Lastly, we report that ImaA directly affected the amount of host cell β1 integrin but not other cellular integrins. Our results thus suggest a model in which H. pylori employs ImaA to regulate interactions between integrin and the T4SS and thus alter the host inflammatory strength.

Hydrogen Metabolism in Helicobacter pylori Plays a Role in Gastric Carcinogenesis through Facilitating CagA Translocation

A known virulence factor of Helicobacter pylori that augments gastric cancer risk is the CagA cytotoxin. A carcinogenic derivative strain, 7.13, that has a greater ability to translocate CagA exhibits much higher hydrogenase activity than its parent noncarcinogenic strain, B128. A Δhyd mutant strain with deletion of hydrogenase genes was ineffective in CagA translocation into human gastric epithelial AGS cells, while no significant attenuation of cell adhesion was observed. The quinone reductase inhibitor 2-n-heptyl-4-hydroxyquinoline-N-oxide (HQNO) was used to specifically inhibit the H2-utilizing respiratory chain of outer membrane-permeabilized bacterial cells; that level of inhibitor also greatly attenuated CagA translocation into AGS cells, indicating the H2-generated transmembrane potential is a contributor to toxin translocation. The Δhyd strain showed a decreased frequency of DNA transformation, suggesting that H. pylori hydrogenase is also involved in energizing the DNA uptake apparatus. In a gerbil model of infection, the ability of the Δhyd strain to induce inflammation was significantly attenuated (at 12 weeks postinoculation), while all of the gerbils infected with the parent strain (7.13) exhibited a high level of inflammation. Gastric cancer developed in 50% of gerbils infected with the wild-type strain 7.13 but in none of the animals infected with the Δhyd strain. By examining the hydrogenase activities from well-defined clinical H. pylori isolates, we observed that strains isolated from cancer patients (n = 6) have a significantly higher hydrogenase (H2/O2) activity than the strains isolated from gastritis patients (n = 6), further supporting an association between H. pylori hydrogenase activity and gastric carcinogenesis in humans.

IMPORTANCE

Hydrogen-utilizing hydrogenases are known to be important for some respiratory pathogens to colonize hosts. Here a gastric cancer connection is made via a pathogen's (H. pylori) use of molecular hydrogen, a host microbiome-produced gas. Delivery of the known carcinogenic factor CagA into host cells is augmented by the H2-utilizing respiratory chain of the bacterium. The role of hydrogenase in carcinogenesis is demonstrated in an animal model, whereby inflammation markers and cancer development were attenuated in the hydrogenase-null strain. Hydrogenase activity comparisons of clinical strains of the pathogen also support a connection between hydrogen metabolism and gastric cancer risk. While molecular hydrogen use is acknowledged to be an alternative high-energy substrate for some pathogens, this work extends the roles of H2 oxidation to include transport of a carcinogenic toxin. The work provides a new avenue for exploratory treatment of some cancers via microflora alterations.