The Helicobacter pylori blood group antigen-binding adhesin facilitates bacterial colonization and augments a nonspecific immune response

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.

Epigenetic modulation of cytokine expression in gastric cancer: influence on angiogenesis, metastasis and chemoresistance

Cytokines are proteins that act in the immune response and inflammation and have been associated with the development of some types of cancer, such as gastric cancer (GC). GC is a malignant neoplasm that ranks fifth in incidence and third in cancer-related mortality worldwide, making it a major public health issue. Recent studies have focused on the role these cytokines may play in GC associated with angiogenesis, metastasis, and chemoresistance, which are key factors that can affect carcinogenesis and tumor progression, quality, and patient survival. These inflammatory mediators can be regulated by epigenetic modifications such as DNA methylation, histone protein modification, and non-coding RNA, which results in the silencing or overexpression of key genes in GC, presenting different targets of action, either direct or mediated by modifications in key genes of cytokine-related signaling pathways. This review seeks insight into the relationship between cytokine-associated epigenetic regulation and its potential effects on the different stages of development and chemoresistance in GC.

Effects of Helicobacter pylori infection on intestinal microbiota, immunity and colorectal cancer risk

Infecting about half of the world´s population, Helicobacter pylori is one of the most prevalent bacterial infections worldwide and the strongest known risk factor for gastric cancer. Although H. pylori colonizes exclusively the gastric epithelium, the infection has also been associated with various extragastric diseases, including colorectal cancer (CRC). Epidemiological studies reported an almost two-fold increased risk for infected individuals to develop CRC, but only recently, direct causal and functional links between the chronic infection and CRC have been revealed. Besides modulating the host intestinal immune response, H. pylori is thought to increase CRC risk by inducing gut microbiota alterations. It is known that H. pylori infection not only impacts the gastric microbiota at the site of infection but also leads to changes in bacterial colonization in the distal large intestine. Considering that the gut microbiome plays a driving role in CRC, H. pylori infection emerges as a key factor responsible for promoting changes in microbiome signatures that could contribute to tumor development. Within this review, we want to focus on the interplay between H. pylori infection, changes in the intestinal microbiota, and intestinal immunity. In addition, the effects of H. pylori antibiotic eradication therapy will be discussed.

Helicobacter pylori infection: a dynamic process from diagnosis to treatment

Helicobacter pylori, a gram-negative microaerophilic pathogen, causes several upper gastrointestinal diseases, such as chronic gastritis, peptic ulcer disease, and gastric cancer. For the diseases listed above, H. pylori has different pathogenic mechanisms, including colonization and virulence factor expression. It is essential to make accurate diagnoses and provide patients with effective treatment to achieve positive clinical outcomes. Detection of H. pylori can be accomplished invasively and noninvasively, with both having advantages and limitations. To enhance therapeutic outcomes, novel therapeutic regimens, as well as adjunctive therapies with probiotics and traditional Chinese medicine, have been attempted along with traditional empiric treatments, such as triple and bismuth quadruple therapies. An H. pylori infection, however, is difficult to eradicate during treatment owing to bacterial resistance, and there is no commonly available preventive vaccine. The purpose of this review is to provide an overview of our understanding of H. pylori infections and to highlight current treatment and diagnostic options.

Helicobacter pylori infection-A risk factor for lipid peroxidation and superoxide dismutase over-activity: A cross-sectional study among patients with dyspepsia in Cameroon

Background and Aim

There is an intimate relationship between oxidative stress and inflammation. Helicobacter pylori (H. pylori) infection leads to gastritis in almost all the hosts. So, we hypothesize that gastritis in H. pylori infection may be described as the accumulation of continuous oxidative damage.

Methods

The study was conducted from October 2020 to October 2021 at three reference health facilities in Cameroon. A total of 266 participants (131 males and 135 females) ranging from 15 to 88 years old with 48.28 ± 17.29 years as mean age were enrolled. Each participant gave a written informed consent and ethical committees approved the protocol. Biopsies samples were collected for H. pylori detection using histological examination and rapid urease test. Malondialdehyde (MDA) and glutathione (GSH) content, and catalase (CAT) and superoxide dismutase (SOD) activities were evaluated in serum as biomarkers of oxidative stress.

Results

Helicobacter pylori was detected in 71.80% of our sample population. Low income level was associated with higher GSH level (P = 0.0249) and having family history of gastric cancer to higher SOD activity (P = 0.0156). A significant higher MDA content (P < 0.0001) and SOD activity (P = 0.0235) was recorded among infected individuals compared with noninfected ones. A significantly higher MDA content and SOD activity was recorded among smokers (P = 0.0461) and participants older than 50 years old (P = 0.0491) with H. pylori positivity.

Conclusion

Our findings showed that H. pylori infection is associated with overproduction of reactive oxygen species and oxidative stress. The presence of this pathogen in elderly individuals or in smokers increased their risk for oxidative stress.

Outer Membrane Vesicles (OMVs) as Biomedical Tools and Their Relevance as Immune-Modulating Agents against H. pylori Infections: Current Status and Future Prospects

Outer membrane vesicles (OMVs) are lipid-membrane-bounded nanoparticles that are released from Gram-negative bacteria via vesiculation of the outer membrane. They have vital roles in different biological processes and recently, they have received increasing attention as possible candidates for a broad variety of biomedical applications. In particular, OMVs have several characteristics that enable them to be promising candidates for immune modulation against pathogens, such as their ability to induce the host immune responses given their resemblance to the parental bacterial cell. Helicobacter pylori (H. pylori) is a common Gram-negative bacterium that infects half of the world's population and causes several gastrointestinal diseases such as peptic ulcer, gastritis, gastric lymphoma, and gastric carcinoma. The current H. pylori treatment/prevention regimens are poorly effective and have limited success. This review explores the current status and future prospects of OMVs in biomedicine with a special focus on their use as a potential candidate in immune modulation against H. pylori and its associated diseases. The emerging strategies that can be used to design OMVs as viable immunogenic candidates are discussed.

Helicobacter pylori Infection, Its Laboratory Diagnosis, and Antimicrobial Resistance: a Perspective of Clinical Relevance

Despite the recent decrease in overall prevalence of Helicobacter pylori infection, morbidity and mortality rates associated with gastric cancer remain high. The antimicrobial resistance developments and treatment failure are fueling the global burden of H. pylori-associated gastric complications. Accurate diagnosis remains the opening move for treatment and eradication of infections caused by microorganisms. Although several reports have been published on diagnostic approaches for H. pylori infection, most lack the data regarding diagnosis from a clinical perspective. Therefore, we provide an intensive, comprehensive, and updated description of the currently available diagnostic methods that can help clinicians, infection diagnosis professionals, and H. pylori researchers working on infection epidemiology to broaden their understanding and to select appropriate diagnostic methods. We also emphasize appropriate diagnostic approaches based on clinical settings (either clinical diagnosis or mass screening), patient factors (either age or other predisposing factors), and clinical factors (either upper gastrointestinal bleeding or partial gastrectomy) and appropriate methods to be considered for evaluating eradication efficacy. Furthermore, to cope with the increasing trend of antimicrobial resistance, a better understanding of its emergence and current diagnostic approaches for resistance detection remain inevitable.

Incorporating Immunotherapy in the Management of Gastric Cancer: Molecular and Clinical Implications

Simple Summary

Gastric cancer is one of the most common malignant tumours worldwide, with the fifth and third highest morbidity and mortality, respectively, of all cancers. Survival is limited, as most of the patients are diagnosed at an advanced stage, and are not suitable for surgery with a curative intent. Chemotherapy has only modestly improved patients’ outcomes and is mainly given with a palliative intent. Immunotherapy has improved overall survival of patients with gastric cancer, and has thus become a new standard of care in clinic. In this review we discuss the strong molecular rationale for the administration of immunotherapy in this disease and analyse the clinical data supporting its use.

Abstract

Gastric cancer has a median survival of 11 months, and this poor prognosis has not improved over the last 30 years. Recent pre-clinical data suggest that there is high tumour-related neoantigen expression in gastric cancer cells, suggesting that a clinical strategy that enhances the host’s immune system against cancer cells may be a successful approach to improve clinical outcomes. Additionally, there has been an increasing amount of translational evidence highlighting the relevance of PD-L1 expression in gastric cancer cells, indicating that PD-1/PD-L1 inhibitors may be useful. Several molecular subgroups of gastric cancer have been identified to respond with excellent outcomes to immunotherapy, including microsatellite instable tumours, tumours bearing a high tumour mutational burden, and tumours related to a chronic EBV infection. In gastric cancer, immunotherapy has produced durable responses in chemo-refractory patients; however, most recently there has been a lot of enthusiasm as several large-scale clinical trials highlight the improved survival noted from the incorporation of immunotherapy in the first line setting for advanced gastric cancer. Our review aims to discuss current pre-clinical and clinical data supporting the innovative role of immunotherapy in gastric cancer.

Biomarker Characterization and Prediction of Virulence and Antibiotic Resistance from Helicobacter pylori Next Generation Sequencing Data

The Gram-negative bacterium Helicobacter pylori colonizes c.a. 50% of human stomachs worldwide and is the major risk factor for gastric adenocarcinoma. Its high genetic variability makes it difficult to identify biomarkers of early stages of infection that can reliably predict its outcome. Moreover, the increasing antibiotic resistance found in H. pylori defies therapy, constituting a major human health problem. Here, we review H. pylori virulence factors and genes involved in antibiotic resistance, as well as the technologies currently used for their detection. Furthermore, we show that next generation sequencing may lead to faster characterization of virulence factors and prediction of the antibiotic resistance profile, thus contributing to personalized treatment and management of H. pylori-associated infections. With this new approach, more and permanent data will be generated at a lower cost, opening the future to new applications for H. pylori biomarker identification and antibiotic resistance prediction.

From Helicobacter pylori infection to gastric cancer: Current evidence on the immune response

Gastric cancer (GC) is the result of a multifactorial process whose main components are infection by Helicobacter pylori (H. pylori), bacterial virulence factors, host immune response and environmental factors. The development of the neoplastic microenvironment also depends on genetic and epigenetic changes in oncogenes and tumor suppressor genes, which results in deregulation of cell signaling pathways and apoptosis process. This review summarizes the main aspects of the pathogenesis of GC and the immune response involved in chronic inflammation generated by H. pylori.

Acceptive Immunity: The Role of Fucosylated Glycans in Human Host-Microbiome Interactions

The growth in the number of chronic non-communicable diseases in the second half of the past century and in the first two decades of the new century is largely due to the disruption of the relationship between the human body and its symbiotic microbiota, and not pathogens. The interaction of the human immune system with symbionts is not accompanied by inflammation, but is a physiological norm. This is achieved via microbiota control by the immune system through a complex balance of pro-inflammatory and suppressive responses, and only a disturbance of this balance can trigger pathophysiological mechanisms. This review discusses the establishment of homeostatic relationships during immune system development and intestinal bacterial colonization through the interaction of milk glycans, mucins, and secretory immunoglobulins. In particular, the role of fucose and fucosylated glycans in the mechanism of interactions between host epithelial and immune cells is discussed.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

Development of Helicobacter pylori Whole-Proteome Arrays and Identification of Serologic Biomarkers for Noncardia Gastric Cancer in the MCC-Spain Study

BACKGROUND

Helicobacter pylori (H. pylori) is a bacterial carcinogen and the leading risk factor for noncardia gastric cancer (NCGC). Detecting antibodies against specific H. pylori proteins in peripheral blood can be applied to characterize infection and determine disease associations. Most studies analyzing the association between H. pylori infection and gastric cancer have focused on previously identified antigens, predominantly the virulence factor cytotoxin-associated gene A (CagA). Selecting antigens in an unbiased approach may, however, allow the identification of novel biomarkers.

METHODS

Using a combination of multiple spotting technique and cell-free, on-chip protein expression, we displayed the H. pylori genome (strain 26695) on high-density microarrays. Immunogenic proteins were identified by serum pool incubations and henceforth analyzed in individual samples. To test its applicability, we used sera from a multicase-control (MCC)-Spain study. Serologic responses between NCGC cases and controls were assessed by conditional logistic regression estimating ORs and 95% confidence intervals.

RESULTS

We successfully expressed 93% of the 1,440 H. pylori open reading frames in situ. Of these, 231 (17%) were found to be immunogenic. By comparing 58 NCGC cases with 58 matched controls, we confirmed a higher seroprevalence of CagA among cases (66%) than controls (31%). We further identified a potential novel marker, the Helicobacter outer membrane protein A (HopA).

CONCLUSIONS

In this study, we provide evidence that our H. pylori whole-proteome microarray offers a platform for unbiased de novo identification of serologic biomarkers.

IMPACT

Given its versatile workflow, antibody responses against other H. pylori strains and possible associations with diverse H. pylori-related outcomes can be systematically analyzed.

Pathogenesis and clinical management of Helicobacter pylori gastric infection

Helicobacter pylori (H. pylori) is a gram-negative bacterium that infects approximately 4.4 billion individuals worldwide. However, its prevalence varies among different geographic areas, and is influenced by several factors. The infection can be acquired by means of oral-oral or fecal-oral transmission, and the pathogen possesses various mechanisms that improve its capacity of mobility, adherence and manipulation of the gastric microenvironment, making possible the colonization of an organ with a highly acidic lumen. In addition, H. pylori presents a large variety of virulence factors that improve its pathogenicity, of which we highlight cytotoxin associated antigen A, vacuolating cytotoxin, duodenal ulcer promoting gene A protein, outer inflammatory protein and gamma-glutamyl transpeptidase. The host immune system, mainly by means of a Th1-polarized response, also plays a crucial role in the infection course. Although most H. pylori-positive individuals remain asymptomatic, the infection predisposes the development of various clinical conditions as peptic ulcers, gastric adenocarcinomas and mucosa-associated lymphoid tissue lymphomas. Invasive and non-invasive diagnostic methods, each of them with their related advantages and limitations, have been applied in H. pylori detection. Moreover, bacterial resistance to antimicrobial therapy is a major challenge in the treatment of this infection, and new therapy alternatives are being tested to improve H. pylori eradication. Last but not least, the development of effective vaccines against H. pylori infection have been the aim of several research studies.

Immunoinformatics approaches to explore Helicobacter Pylori proteome (Virulence Factors) to design B and T cell multi-epitope subunit vaccine

Helicobacter Pylori is a known causal agent of gastric malignancies and peptic ulcers. The extremophile nature of this bacterium is protecting it from designing a potent drug against it. Therefore, the use of computational approaches to design antigenic, stable and safe vaccine against this pathogen could help to control the infections associated with it. Therefore, in this study, we used multiple immunoinformatics approaches along with other computational approaches to design a multi-epitopes subunit vaccine against H. Pylori. A total of 7 CTL and 12 HTL antigenic epitopes based on c-terminal cleavage and MHC binding scores were predicted from the four selected proteins (CagA, OipA, GroEL and cagA). The predicted epitopes were joined by AYY and GPGPG linkers. Β-defensins adjuvant was added to the N-terminus of the vaccine. For validation, immunogenicity, allergenicity and physiochemical analysis were conducted. The designed vaccine is likely antigenic in nature and produced robust and substantial interactions with Toll-like receptors (TLR-2, 4, 5, and 9). The vaccine developed was also subjected to an in silico cloning and immune response prediction model, which verified its efficiency of expression and the immune system provoking response. These analyses indicate that the suggested vaccine may produce particular immune responses against H. pylori, but laboratory validation is needed to verify the safety and immunogenicity status of the suggested vaccine design.

Blood group antigen-Binding Adhesion2 (BabA2) gene in gastric tissue biopsies as a diagnostic biomarker for Helicobacter pylori infection

BACKGROUND

The Lewis (b) blood group antigen-Binding Adhesion2 (BabA2) has been reported to mediate the attachment of H. pylori to human.

AIM

assessment the diagnostic potential of detection of (BabA2) gene compared with immunostaining of Lewis (b) by specific mouse monoclonal antibodies in gastric biopsies from Egyptian Patients as a diagnostic maker for Helicobacter pylori infection.

MATERIALS AND METHODS

Fifty untreated patients suffering from dyspeptic complaints were enrolled in this study and underwent for upper gastro-duodenal endoscopy. Biopsies were taken for histological examination by (H&E) and immunohistochemical analysis for Lewis b by specific mouse monoclonal antibodies, and scoring of Lewis b expression in gastric tissue biopsy as well as molecular detection of BabA2 gene of H. pylori by PCR. Biochemical analysis was performed to detect the presence of H. pylori urease activity using Rapid Urease Test (RUT).

RESULTS

: Out of 50 gastric biopsies, 41 biopsies were positive for histological, Immunostaining for Lewis b expression and urease activity test (RUT) for H pylori. RUT showed a sensitivity of 87.8%, specificity 88.9%, positive predictive value (PPV) 97.2%, and negative predictive value (NPV) 61.5%. BabA2 gene results revealed that, out of 41 positive biopsied cases, 39 (95.1%) were positive by the PCR test for BabA2 gene. And all 9 negative biopsies (100%) for H pylori negative for BabA2gene so the sensitivity and specificity of BabA2 gene detection in gastric biopsies by PCR were 95.1% and 100%; respectively.

CONCLUSION

: BabA2 gene detection in gastric tissue biopsies could be suggested as a diagnostic biomarker to be included among the other biomarkers routinely performed for clinical diagnosis of H. pylori infection.

Role of polymorphisms in genes that encode cytokines and Helicobacter pylori virulence factors in gastric carcinogenesis

The Helicobacter pylori (H. pylori) infection is a determinant factor in gastric cancer (GC) development. However, the infection outcomes are variable and depend on both host and bacterial characteristics. Some host cytokines such as interleukin (IL)-1β, IL-1Ra, IL-8, IL-10 and tumor necrosis factor-α play important roles in the host immune system response to the pathogen, in the development of gastric mucosal lesions and in cell malignant transformation. Therefore, these host factors are crucial in neoplastic processes. Certain polymorphisms in genes that encode these cytokines have been associated with an increased risk of GC. On the other hand, various virulence factors found in distinct H. pylori bacterial strains, including cytotoxin-associated antigen A, vacuolating cytotoxin, duodenal ulcer promoting gene A protein, outer inflammatory protein and blood group antigen binding adhesin, have been associated with the pathogenesis of different gastric diseases. The virulent factors mentioned above allow the successful infection by the bacterium and play crucial roles in gastric mucosa lesions, including malignant transformation. Moreover, the role of host polymorphisms and bacterial virulence factors in gastric carcinogenesis seems to vary among different countries and populations. The identification of host and bacterium factors that are associated with an increased risk of GC development may be useful in determining the prognosis of infection in patients, what could help in clinical decision-making and in providing of an optimized clinical approach.

Helicobacter pylori-induced miR-135b-5p promotes cisplatin resistance in gastric cancer

Helicobacter pylori infection is a major risk factor for the development of gastric cancer. Aberrant expression of microRNAs is strongly implicated in gastric tumorigenesis; however, their contribution in response to H. pylori infection has not been fully elucidated. In this study, we evaluated the expression of miR-135b-5p and its role in gastric cancer. We describe the overexpression of miR-135b-5p in human gastric cancer tissue samples compared with normal tissue samples. Furthermore, we found that miR-135b-5p is also up-regulated in gastric tumors from the trefoil factor 1-knockout mouse model. Infection with H. pylori induced the expression of miR-135b-5p in the in vitro and in vivo models. miR-135b-5p induction was mediated by NF-κB. Treatment of gastric cancer cells with TNF-α induced miR-135b-5p in a NF-κB-dependent manner. Mechanistically, we found that miR-135b-5p targets Krüppel-like factor 4 (KLF4) and binds to its 3' UTR, leading to reduced KLF4 expression. Functionally, high levels of miR-135b-5p suppress apoptosis and induce cisplatin resistance. Our results uncovered a mechanistic link between H. pylori infection and miR-135b-5p-KLF4, suggesting that targeting miR-135b-5p could be a potential therapeutic approach to circumvent resistance to cisplatin.-Shao, L., Chen, Z., Soutto, M., Zhu, S., Lu, H., Romero-Gallo, J., Peek, R., Zhang, S., El-Rifai, W. Helicobacter pylori-induced miR-135b-5p promotes cisplatin resistance in gastric cancer.

Lotus tetragonolobus and Maackia amurensis lectins influence phospho-IκBα, IL-8, Lewis b and H type 1 glycoforms levels in H. pylori infected CRL-1739 gastric cancer cells

PURPOSE

Attachment of Helicobacter pylori to the mucous epithelial cells and the mucous layer is said to be a crucial step for infection development. Sugar antigens of gastric mucins (MUC5AC, MUC1) can act as receptors for bacterial adhesins. The aim of the study was to investigate if Lotus tetragonolobus and Maackia amurensis lectins influence the level of MUC1, MUC5AC, Lewis b, H type 1, sialyl Lewis x, phospho-IκBα and interleukin 8 in Helicobacter pylori infected gastric cancer cells.

MATERIALS AND METHODS

The study was performed with one clinical H. pylori strain and CRL-1739 gastric cancer cells. To assess the levels of mentioned factors immunosorbent ELISA assays were used.

RESULTS

Coculture of cells with bacteria had no clear effect on almost all examined structures. After coculture with H. pylori and lectins, a decrease of the level of both mucins, Lewis b and H type 1 antigens was observed. Lectins addition had no effect on sialyl Lewis x. Maackia amurensis caused slight increase of phospho-IκBα while interleukin 8 level was decreased.

CONCLUSIONS

Lotus tetragonolobus and Maackia amurensis lectins can mediate in binding of Helicobacter pylori to gastric epithelium.

Genetic diversity and functional analysis of oipA gene in association with other virulence factors among Helicobacter pylori isolates from Iranian patients with different gastric diseases

Helicobacter pylori (H. pylori) is one of the most genetically diverse bacterial pathogens that persistently colonizes the human gastric epithelium. This remarkable genomic plasticity may act as a driving force for successful adaptation and persistence of the bacteria in the harsh gastric environment. Outer inflammatory protein A (OipA) encoded by oipA gene (HP0638/hopH) is a member of the outer membrane proteins (OMPs) of H. pylori involved in induction of IL-8 secretion and is associated with development of peptic ulcer and gastric cancer. Expression of OipA is regulated by phase variation within a CT dinucleotide repeat motif of the oipA gene. In this study we carried out direct DNA sequence analysis of 53 amplified fragments to investigate the oipA "On/Off" status among Iranian H. pylori isolates from patients with various gastric diseases. The prevalence of cagL, cagA, EPIYA motifs, vacA alleles, babA2 and sabA genotypes as well as cagPAI integrity of the isolates were determined by PCR. Our results demonstrated a high prevalence of strains with functional oipA status (79%) and significant associations were found between functional oipA and cagA (P = 0.027) and vacA s1m1 (P = 0.022) genotypes. The vacA s1m2 genotype was also found to be statistically associated with PUD (P = 0.0001). Interestingly, we showed that H. pylori strains with intact cagPAI co-expressed oipA gene in a significant synergistic relationship (P < 0.01). However, no significant association was observed between the functional oipA status and clinical outcomes (P > 0.05). In conclusion, our findings denotes great diversity in the number and pattern of CT dinucleotide repeats of oipA among Iranian H. pylori strains. The synergistic link between functional oipA and other important virulence factors is proposed to be critical in the pathogenesis of H. pylori, which needs further studies with a larger number of samples.

vacA s1m1 genotype and cagA EPIYA-ABC pattern are predominant among Helicobacter pylori strains isolated from Mexican patients with chronic gastritis

Purpose

Virulent genotypes of Helicobacter pylori vacA s1m1/cagA⁺/babA2⁺ have been associated with severe gastric diseases. VacA, CagA and BabA are polymorphic proteins, and their association with the disease is allele-dependent. The aims of this work were: (i) to determine the prevalence of H. pylori by type of chronic gastritis; (ii) to describe the frequency of cagA, babA2 and vacA genotypes in strains from patients with different types of chronic gastritis; (iii) to characterize the variable region of cagA alleles.

Methodology

A total of 164 patients with chronic gastritis were studied. Altogether, 50 H. pylori strains were isolated, and the status of cagA, babA2 and vacA genotypes was examined by PCR. cagA EPIYA segment identification was performed using PCR and sequencing of cagA fragments of six randomly selected strains.

Results/Key findings

The overall prevalence of H. pylori was 30.5 %. Eighty percent of the isolated strains were vacA s1m1, and the cagA and babA2 genes were detected in 74 and 32 % of the strains, respectively. The most frequent genotypes were vacA s1m1/cagA⁺/babA2^- and vacA s1m1/cagA⁺/babA2⁺, with 40 % (20/50) and 28 % (14/50), respectively. In cagA⁺, the most frequent EPIYA motif was -ABC (78.4 %), and EPIYA-ABCC and -ABCCC motifs were found in 10.8 % of the strains. A modified EPIYT-B motif was found in 66.6 % of the sequenced strains.

Conclusion

H. pylori strains carrying vacA s1m1, cagA⁺ and babA2^- genotypes were the most prevalent in patients with chronic gastritis from the south of Mexico. In the cagA⁺ strains, the EPIYA-ABC motif was the most common.

Overexpression of serine protease HtrA enhances disruption of adherens junctions, paracellular transmigration and type IV secretion of CagA by Helicobacter pylori

BACKGROUND

The serine protease HtrA is an important factor for regulating stress responses and protein quality control in bacteria. In recent studies, we have demonstrated that the gastric pathogen Helicobacter pylori can secrete HtrA into the extracellular environment, where it cleaves-off the ectodomain of the tumor suppressor and adherens junction protein E-cadherin on gastric epithelial cells.

RESULTS

E-cadherin cleavage opens cell-to-cell junctions, allowing paracellular transmigration of the bacteria across polarized monolayers of MKN-28 and Caco-2 epithelial cells. However, rapid research progress on HtrA function is mainly hampered by the lack of ΔhtrA knockout mutants, suggesting that htrA may represent an essential gene in H. pylori. To circumvent this major handicap and to investigate the role of HtrA further, we overexpressed HtrA by introducing a second functional htrA gene copy in the chromosome and studied various virulence properties of the bacteria. The resulting data demonstrate that overexpression of HtrA in H. pylori gives rise to elevated rates of HtrA secretion, cleavage of E-cadherin, bacterial transmigration and delivery of the type IV secretion system (T4SS) effector protein CagA into polarized epithelial cells, but did not affect IL-8 chemokine production or the secretion of vacuolating cytotoxin VacA and γ-glutamyl-transpeptidase GGT.

CONCLUSIONS

These data provide for the first time genetic evidence in H. pylori that HtrA is a novel major virulence factor controlling multiple pathogenic activities of this important microbe.

Helicobacter pylori BabA in adaptation for gastric colonization

Helicobacter pylori (H. pylori) as a causative agent of gastric complications, is well adapted for the colonization of gastric mucosa. Although the infectious process depends on several factors, the adhesion to the gastric mucosa is the first and important step. Among several outer membrane proteins, BabA is one of the significant protein involving in many inflammatory processes in addition to its role in the attachment for the persistent colonization. We performed a PubMed search using the key words: “babA”, “pylori”, “gastric complications”, “homologous recombination”, “slipped strand mispairing”; a total of 249 articles were displayed. Of these we mainly focused on articles with the full text in English and published between 2005 and 2016. H. pylori BabA is involved in binding with receptors; however, its synthesis is regulated by phase variation. In this review we confirm that H. pylori babA can be modulated at the molecular and functional levels to adapt to the stress within the gastro-intestinal tract.

The Gastric Microbiome and Its Influence on Gastric Carcinogenesis: Current Knowledge and Ongoing Research

Gastric malignancies are a leading cause of cancer-related death worldwide. At least 2 microbial species are currently linked to carcinogenesis and the development of cancer within the human stomach. These include the bacterium Helicobacter pylori and the Epstein-Barr virus. In recent years, there has been increasing evidence that within the human gastrointestinal tract it is not only pathogenic microbes that impact human health but also the corresponding autochthonous microbial communities. This article reviews the gastrointestinal microbiome as it relates primarily to mechanisms of disease and carcinogenesis within the upper gastrointestinal tract.

Helicobacter pylori as an oncogenic pathogen, revisited

Gastric cancer is an inflammation-associated malignancy aetiologically related to infection with the bacterium, Helicobacter pylori, which is considered a necessary but insufficient cause. Unless treated, H. pylori causes life-long acute and chronic gastric inflammation resulting in progressive gastric mucosal damage that may result in gastric cancer. The rate of progression from superficial gastritis, to an atrophic metaplastic mucosa, and ultimately to cancer relates to the virulence of the infecting H. pylori as well as host and environmental factors. H. pylori virulence is a reflection of its propensity to cause severe gastric inflammation. Both mucosal inflammation and H. pylori can cause host genomic instability, including dysregulation of DNA mismatch repair, stimulation of expression of activation-induced cytidine deaminase, abnormal DNA methylation and dysregulation of  micro RNAs, which may result in an accumulation of mutations and loss of normal regulation of cell growth. The difference in cancer risk between the most and least virulent H. pylori strain is only approximately 2-fold. Overall, none of the putative virulence factors identified to date have proved to be disease-specific. The presence, severity, extent and duration of inflammation appear to be the most important factors and current evidence suggests that any host, environmental or bacterial factor that reliably enhances the inflammatory response to the H. pylori infection increases the risk of gastric cancer.

Helicobacter pylori Outer Membrane Protein-Related Pathogenesis

Helicobacter pylori colonizes the human stomach and induces inflammation, and in some cases persistent infection can result in gastric cancer. Attachment to the gastric mucosa is the first step in establishing bacterial colonization, and outer membrane proteins (OMPs) play a pivotal role in binding to human cells. Some OMP interaction molecules are known in H. pylori, and their associated host cell responses have been gradually clarified. Many studies have demonstrated that OMPs are essential to CagA translocation into gastric cells via the Type IV secretion system of H. pylori. This review summarizes the mechanisms through which H. pylori utilizes OMPs to colonize the human stomach and how OMPs cooperate with the Type IV secretion system.

Cytokine networks and their association with Helicobacter pylori infection in gastric carcinoma

Cytokine networks as dynamic networks are pivotal aspects of tumor immunology, especially in gastric cancer (GC), in which infection, inflammation, and antitumor immunity are key elements of disease progression. In this review, we describe functional roles of well-known GC-modulatory cytokines, highlight the functions of cytokines with more recently described roles in GC, and emphasize the therapeutic potential of targeting the complex cytokine milieu. We also focus on the role of Helicobacter pylori (HP)-induced inflammation in GC and discuss how HP-induced chronic inflammation can lead to the induction of stem cell hyperplasia, morphological changes in gastric mucosa and GC development.

Oxidative Stress Resulting From Helicobacter pylori Infection Contributes to Gastric Carcinogenesis

Helicobacter pylori is a gram-negative, microaerophilic bacterium that infects the stomach and can lead to, among other disorders, the development of gastric cancer. The inability of the host to clear the infection results in a chronic inflammatory state with continued oxidative stress within the tissue. Reactive oxygen species and reactive nitrogen species produced by the immune and epithelial cells damage the host cells and can result in DNA damage. H pylori has evolved to evoke this damaging response while blunting the host's efforts to kill the bacteria. This long-lasting state with inflammation and oxidative stress can result in gastric carcinogenesis. Continued efforts to better understand the bacterium and the host response will serve to prevent or provide improved early diagnosis and treatment of gastric cancer.

Comparative Genomics of H. pylori and Non-Pylori Helicobacter Species to Identify New Regions Associated with Its Pathogenicity and Adaptability

The genus Helicobacter is a group of Gram-negative, helical-shaped pathogens consisting of at least 36 bacterial species. Helicobacter pylori (H. pylori), infecting more than 50% of the human population, is considered as the major cause of gastritis, peptic ulcer, and gastric cancer. However, the genetic underpinnings of H. pylori that are responsible for its large scale epidemic and gastrointestinal environment adaption within human beings remain unclear. Core-pan genome analysis was performed among 75 representative H. pylori and 24 non-pylori Helicobacter genomes. There were 1173 conserved protein families of H. pylori and 673 of all 99 Helicobacter genus strains. We found 79 genome unique regions, a total of 202,359bp, shared by at least 80% of the H. pylori but lacked in non-pylori Helicobacter species. The operons, genes, and sRNAs within the H. pylori unique regions were considered as potential ones associated with its pathogenicity and adaptability, and the relativity among them has been partially confirmed by functional annotation analysis. However, functions of at least 54 genes and 10 sRNAs were still unclear. Our analysis of protein-protein interaction showed that 30 genes within them may have the cooperation relationship.

Importance of the C-terminal histidine residues of Helicobacter pylori GroES for Toll-like receptor 4 binding and interleukin-8 cytokine production

Helicobacter pylori infection is associated with the development of gastric and duodenal ulcers as well as gastric cancer. GroES of H. pylori (HpGroES) was previously identified as a gastric cancer-associated virulence factor. Our group showed that HpGroES induces interleukin-8 (IL-8) cytokine release via a Toll-like receptor 4 (TLR4)-dependent mechanism and domain B of the protein is crucial for interactions with TLR4. In the present study, we investigated the importance of the histidine residues in domain B. To this end, a series of point mutants were expressed in Escherichia coli, and the corresponding proteins purified. Interestingly, H96, H104 and H115 were not essential, whereas H100, H102, H108, H113 and H118 were crucial for IL-8 production and TLR4 interactions in KATO-III cells. These residues were involved in nickel binding. Four of five residues, H102, H108, H113 and H118 induced certain conformation changes in extended domain B structure, which is essential for interactions with TLR4 and consequent IL-8 production. We conclude that interactions of nickel ions with histidine residues in domain B help to maintain the conformation of the C-terminal region to conserve the integrity of the HpGroES structure and modulate IL-8 release.

Helicobacter pylori strains harboring babA2 from Indian sub population are associated with increased virulence in ex vivo study

Background

The babA2 gene along with the cagA and vacA of Helicobacter pylori has been considered as a risk factor for the disease outcome in certain populations. This study was aimed to understand the role of babA2 of H. pylori with the background of cagA and vacA in disease manifestations in Indian sub population.

Methods

A total of 114 H. pylori strains isolated from duodenal ulcer (DU) (n = 53) and non-ulcer dyspepsia (NUD) patients (n = 61) were screened for the prevalence of these virulence markers by PCR. The comparative study of IL-8 production and apoptosis were done by co-culturing the AGS cell line with H. pylori strains with different genotypes. Adherence assay was performed with babA2 positive and negative strains. Two isogenic mutants of babA2 were constructed and the aforesaid comparative studies were carried out.

Results

PCR results indicated that 90.6 % (48/53), 82 % (50/61) and 73.6 % (39/53) strains from DU patients were positive for cagA, vacA, and babA2, respectively. Whereas the prevalence of these genes in NUD subjects were 70.5 % (43/61); 69.8 % (37/53), and 65.6 % (39/61), respectively. Although adherence to AGS cells was comparable among strains with babA2 positive and negative genotypes, but the triple positive strains could induce highest degree of IL-8 production and apoptosis, followed by the cagA⁻/vacA⁻/babA2⁺ strains and triple negative strains, respectively. The wild type strains showed significantly higher IL-8 induction as well as apoptosis in ex vivo than its isogenic mutant of babA2.

Conclusion

PCR study demonstrated that there was no significant association between the distribution of babA2 genotype or of triple positive strains and disease outcome in this sub population. The adherence assay showed that there was no significant difference in the extent of adherence to AGS cells among babA2 positive and negative strains. But the ex vivo study indicated that the triple positive or even the babA2 only positive strains are involved in increased virulence. The wild type strains also exhibited increased virulence compared to the babA2 mutant strains. This inconsistency demonstrated that bacterial genotype along with host genetic polymorphisms or other factors play important role in determining the clinical manifestation of H. pylori infections.

Characterisation of worldwide Helicobacter pylori strains reveals genetic conservation and essentiality of serine protease HtrA

HtrA proteases and chaperones exhibit important roles in periplasmic protein quality control and stress responses. The genetic inactivation of htrA has been described for many bacterial pathogens. However, in some cases such as the gastric pathogen Helicobacter pylori, HtrA is secreted where it cleaves the tumour‐suppressor E‐cadherin interfering with gastric disease development, but the generation of htrA mutants is still lacking. Here, we show that the htrA gene locus is highly conserved in worldwide strains. HtrA presence was confirmed in 992 H. pylori isolates in gastric biopsy material from infected patients. Differential RNA‐sequencing (dRNA‐seq) indicated that htrA is encoded in an operon with two subsequent genes, HP1020 and HP1021. Genetic mutagenesis and complementation studies revealed that HP1020 and HP1021, but not htrA, can be mutated. In addition, we demonstrate that suppression of HtrA proteolytic activity with a newly developed inhibitor is sufficient to effectively kill H. pylori, but not other bacteria. We show that Helicobacter  htrA is an essential bifunctional gene with crucial intracellular and extracellular functions. Thus, we describe here the first microbe in which htrA is an indispensable gene, a situation unique in the bacterial kingdom. HtrA can therefore be considered a promising new target for anti‐bacterial therapy.

Differential inflammatory response to Helicobacter pylori infection: etiology and clinical outcomes

The bacterial pathogen Helicobacter pylori commonly colonizes the human gastric mucosa during early childhood and persists throughout life. The organism has evolved multiple mechanisms for evading clearance by the immune system and, despite inducing inflammation in the stomach, the majority of infections are asymptomatic. H. pylori is the leading cause of peptic ulcer disease and gastric cancer. However, disease outcomes are related to the pattern and severity of chronic inflammation in the gastric mucosa, which in turn is influenced by both bacterial and host factors. Despite over 2 decades of intensive research, there remains an incomplete understanding of the circumstances leading to disease development, due to the fascinating complexity of the host-pathogen interactions. There is accumulating data concerning the virulence factors associated with increased risk of disease, and the majority of these have pro-inflammatory activities. Despite this, only a small proportion of those infected with virulent strains develop disease. Several H. pylori virulence factors have multiple effects on different cell types, including the induction of pro- and anti-inflammatory, immune stimulatory, and immune modulatory responses. The expression of multiple virulence factors is also often linked, making it difficult to assess the meaning of their effects in isolation. Overall, H. pylori is thought to usually modulate inflammation and limit acute damage to the mucosa, enabling the bacteria to persist. If this delicate balance is disturbed, disease may then develop.

Helicobacter pylori vacA i region polymorphism but not babA2 status associated to gastric cancer risk in northwestern Iran

Helicobacter pylori-specific genotypes have been strongly associated with an increased risk of gastric cancer (GC). The aim of the present work was to study the associations of H. pylori virulence factors, vacA i region polymorphisms and babA2 status with GC risk in Azerbaijan patients. The DNA extracted from gastric biopsy specimens was used to access the babA2 and vacA genotypes. Overall, babA2 was present in 85.39 % (76/89) of H. pylori strains: 19 out of 24 (79.16 %) strains from GC, 16 out of 17 (94.14 %) strains from peptic ulcer disease (PUD) and 41 out of 48 (85.14 %) strains from chronic gastritis. No significant association was found between babA2 genotype and clinical outcomes (P > 0.05). i1 vacA polymorphism was detected in 46/89 (51.68 %) strains: in 21/24 (87.5 %), 6/17 (35.29 %) and 19/48 (39.58 %) patients with GC, PUD and chronic gastritis, respectively. i2 allele was detected in 43 (48.31 %) out of all 89 strains examined: 3 (14.28 %) of 24 strains from GC, 11 (64.71 %) of 17 from PUD, and 29 (60.42 %) of 48 strains from chronic gastritis. In this study, multiple linear regression analysis confirmed the strong association of i1 allele with GC (partial regression correlation 0.455 ± 0.101; P = 0). Results of multiple logistic regression analysis showed that vacA i1 genotype was significantly associated with GC compared with a control group (gastritis) (odds ratio 13.142, 95 % CI 3.116-55.430; P = 0). Findings from the measurement of H. pylori babA2 and vacA genotypes indicate a strong correlation between the vacA i1 allele and GC risk in the Azerbaijan area of Iran.

Correlation of ABH blood group antigens secretion with Helicobacter pylori infection in Pakistani patients

OBJECTIVES

A and B blood group antigens are fucosylated carbohydrate present on human erythrocytes and body secretions. Their presence in body secretions depends on the expression of a dominant allele of secretor gene FUT2 and is correlated with susceptibility to various infectious and non-infectious diseases. We investigated the correlation of blood group and ABH antigen secretion with Helicobacter pylori infection and gastroduodenal symptoms and analysed the distribution of babA gene among ABH secretors and non-secretors.

METHODS

Two hundred and ninety patients who underwent gastroduodenal endoscopy during 2011 to 2012 participated. Gastric biopsy, saliva and blood samples were obtained from every patient. Gastric biopsies were subjected to rapid urease test and PCR for the detection of H. pylori and babA gene. Blood grouping and ABH antigens secretions were determined by Lewis blood group phenotyping and haemagglutination inhibition test.

RESULTS

50.34% of patients were ABH antigen secretors and 45.51% non-secretors. Distribution analysis of blood group revealed that 40 blood group B, 67 blood group A 20 blood group O and 19 blood group AB patients secreted ABH antigens in saliva. Fifty-six blood group O, 19 blood group B, 32 blood group A and 17 blood group AB patients were non-secretors. Gastroduodenal complaints were common among non-secretors. Sixty-two percent of patients with a combination of duodenal ulcer and gastro-oesophageal reflux and 54% of patients with gastritis were non-secretors. Of 290 samples, 31.02% were positive for H. pylori. Thirty percent of these tested positive for babA gene; the majority belonged to non-secretor blood group O.

CONCLUSIONS

Our results suggest that the infection of H. pylori is correlated with ABO blood groups and blood group antigens secretion in body fluids.

Higher glucose level can enhance the H. pylori adhesion and virulence related with type IV secretion system in AGS cells

BACKGROUND

Hyperglycemia increases the risk of gastric cancer in H. pylori-infected patients. High glucose could increase endothelial permeability and cancer-associated signaling. These suggest high glucose may affect H. pylori or its infected status.We used two strains to investigate whether H. pylori growth, viability, adhesion and CagA-phosphorylation level in the infected-AGS cells were influenced by glucose concentration (100, 150, and 200 mg/dL).

RESULTS

The growth curves of both strains in 200 mg/dL of glucose were maintained at the highest optimal density after 48 h and the best viability of both strains were retained in the same glucose condition at 72 h. Furthermore, adhesion enhancement of H. pylori was significantly higher in 200 mg/dL of glucose as compared to that in 100 and 150 mg/dL (p < 0.05). CagA protein also increased in higher glucose condition. The cell-associated CagA and phosphorylated-CagA was significantly increased in 150 and 200 mg/dL of glucose concentrations as compared to that of 100 mg/dL (p < 0.05), which were found to be dose-dependent.

CONCLUSION

Higher glucose could maintain H. pylori growth and viability after 48 h. H. pylori adhesion and CagA increased to further facilitate the enhancement of cell-associated CagA and phosphorylated CagA in higher glucose conditions.

Associations of a TLR4 single-nucleotide polymorphism with H. pylori associated gastric diseases in Iranian patients

OBJECTIVE

Helicobacter pylori (H. pylori) is associated with gastric ulcer and gastric adenocarcinoma. Polymorphisms in the host genes coding for toll-like receptors (TLRs) may influence the innate and adaptive immune response to the infection, affecting the susceptibility to H. pylori or the disease outcomes. But the details and association to different polymorphisms and different clinical expressions in patients infected with H. pylori (different clinical expression of H. pylori infection) remain unclear.

METHODS

A case-control study consisting of 195 patients with H. pylori infection and 241 H. pylori uninfection was conducted. Genomic DNA was extracted and genotypes of TLR4Asp299Gly polymorphism were assessed through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Presence of cagA was evaluated using PCR.

RESULTS

TLR4 (Asp299Gly) G and DG alleles frequency in H. pylori infected population was significantly higher in the chronic gastritis group than in the chronic active gastritis group (P=0.021; OR, 2.409; 95% CI, 1.124-5.162). Grade mononuclear (MN) infiltration in H. pylori infected patients with DG genotype of TLR-4 Asp299Gly increased significantly. CagA positivity was more frequently associated with chronic active gastritis (P=0.017, OR=2.26, 95% CI=1.144-4.462) and grade polymorphonucler (PMN) infiltration.

CONCLUSION

TLR-4 Asp299Gly G allele substitution may be modified pattern of immune response in the gastric mucosa of H. pylori infected patients and may be H. pylori infected patients with gastritis have increased risk for the development of chronic gastritis. CagA positivity may be a risk factor for development of gastritis.

Helicobacter pylori and gastric cancer

Infection with Helicobacter pylori is established as the major risk factor for gastric cancer development. Damage of the mucosal barrier due to H. pylori-induced inflammation enhances the carcinogenic effect of other risk factors such as salt intake or tobacco smoking. The genetic disposition of both the bacterial strain and the host can increase the potential towards gastric cancer formation. Genetic variance of the bacterial proteins CagA and VacA is associated with a higher gastric cancer risk, as are polymorphisms and epigenetic changes in host gene coding for interleukins (IL1β, IL8), transcription factors (CDX2, RUNX3) and DNA repair enzymes. Application of high-throughput assays for genome-wide assessment of either genetic structural variance or gene expression patterns may lead to a better understanding of the pathobiological background of these processes, including the underlying signaling pathways. Understanding of the stepwise alterations that take place in the transition from chronic atrophic gastritis, via metaplastic changes, to invasive neoplasia is vital to define the 'point of no return' before which eradication of H. pylori has the potential to prevent gastric cancer. Currently, eradication as preventive strategy is only recommended for high-incidence regions in Asia; large population studies with an adequate follow-up are required to demonstrate the effectiveness of such an approach in Western populations.

H. pylori virulence factors: influence on immune system and pathology

Helicobacter pylori is the most widespread chronic bacterial agent in humans and is well recognized for its association with ulcer disease and gastric cancer, with both representing major global health and socioeconomic issues. Given the high level of adaptation and the coevolution of this bacterium with its human host, a thorough and multidirectional view of the specific microbiological characteristics of this infection as well as the host physiology is needed in order to develop novel means of prevention of therapy. This review aims to pinpoint some of these potentially important angles, which have to be considered mutually when studying H. pylori's pathogenicity. The host's biological changes due to the virulence factors are a valuable pillar of H. pylori research as are the mechanisms by which bacteria provoke these changes. In this context, necessary adhesion molecules and significant virulence factors of H. pylori are discussed. Moreover, metabolism of the bacteria, one of the most important aspects for a better understanding of bacterial physiology and consequently possible therapeutic and prophylactic strategies, is addressed. On the other hand, we discuss the recent experimental proofs of the "hygiene hypothesis" in correlation with Helicobacter's infection, which adds another aspect of complexity to this infection.

Host genetic factors respond to pathogenic step-specific virulence factors of Helicobacter pylori in gastric carcinogenesis

The interindividual differences in risk of Helicobacter pylori (H. pylori)-associated gastric cancer involve significant heterogeneities of both host genetics and H. pylori strains. Several recent studies proposed a distinct sequence for H. pylori exerting its virulence in the host stomach: (i) adhering to and colonizing the surface of gastric epithelial cells, (ii) evading and attenuating the host defense, and (iii) invading and damaging the gastric mucosa. This review focuses on several key issues that still need to be clarified, such as which virulence factors of H. pylori are involved in the three pathogenic steps, which host genes respond to the step-specific virulence factors, and whether and/or how the corresponding host genetic variations influence the risk of gastric carcinogenesis. Urease, BabA and SabA in the adhesion-step, PGN and LPS in the immune evasion-step, and CagA, VacA and Tipα in the mucosal damage-step were documented to play an important role in step-specific pathogenicity of H. pylori infection. There is evidence further supporting a role of potentially functional polymorphisms of host genes directly responding to these pathogenic step-specific virulence factors in the susceptibility of gastric carcinogenesis, especially for urease-interacting HLA class II genes, BabA-interacting MUC1, PGN-interacting NOD1, LPS-interacting TLR4, and CagA-interacting PTPN11 and CDH1. With the continuous improvement of understanding the genetic profile of H. pylori-associated gastric carcinogenesis, a person at increased risk for gastric cancer may benefit from several aspects of efforts: (i) prevent H. pylori infection with a vaccine targeting certain step-specific virulence factor; (ii) eradicate H. pylori infection by blocking step-specific psychopathological characteristics of virulence factors; and (iii) adjust host physiological function to resist the carcinogenic role of step-specific virulence factors or interrupt the cellular signal transduction of the interplay between H. pylori and host in each pathogenic step, especially for the subjects with precancerous lesions in the stomach.

The functional interplay of Helicobacter pylori factors with gastric epithelial cells induces a multi-step process in pathogenesis

Infections with the human pathogen Helicobacter pylori (H. pylori) can lead to severe gastric diseases ranging from chronic gastritis and ulceration to neoplastic changes in the stomach. Development and progress of H. pylori-associated disorders are determined by multifarious bacterial factors. Many of them interact directly with host cells or require specific receptors, while others enter the host cytoplasm to derail cellular functions. Several adhesins (e.g. BabA, SabA, AlpA/B, or OipA) establish close contact with the gastric epithelium as an important first step in persistent colonization. Soluble H. pylori factors (e.g. urease, VacA, or HtrA) have been suggested to alter cell survival and intercellular adhesions. Via a type IV secretion system (T4SS), H. pylori also translocates the effector cytotoxin-associated gene A (CagA) and peptidoglycan directly into the host cytoplasm, where cancer- and inflammation-associated signal transduction pathways can be deregulated. Through these manifold possibilities of interaction with host cells, H. pylori interferes with the complex signal transduction networks in its host and mediates a multi-step pathogenesis.

The Role of Helicobacter pylori Outer Membrane Proteins in Adherence and Pathogenesis

Helicobacter pylori is one of the most successful human pathogens, which colonizes the mucus layer of the gastric epithelium of more than 50% of the world’s population. This curved, microaerophilic, Gram-negative bacterium induces a chronic active gastritis, often asymptomatic, in all infected individuals. In some cases, this gastritis evolves to more severe diseases such as peptic ulcer disease, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue lymphoma. H. pylori has developed a unique set of factors, actively supporting its successful survival and persistence in its natural hostile ecological niche, the human stomach, throughout the individual’s life, unless treated. In the human stomach, the vast majority of H. pylori cells are motile in the mucus layer lining, but a small percentage adheres to the epithelial cell surfaces. Adherence to the gastric epithelium is important for the ability of H. pylori to cause disease because this intimate attachment facilitates: (1) colonization and persistence, by preventing the bacteria from being eliminated from the stomach, by mucus turnover and gastric peristalsis; (2) evasion from the human immune system and (3) efficient delivery of proteins into the gastric cell, such as the CagA oncoprotein. Therefore, bacteria with better adherence properties colonize the host at higher densities. H. pylori is one of the most genetically diverse bacterial species known and is equipped with an extraordinarily large set of outer membrane proteins, whose role in the infection and persistence process will be discussed in this review, as well as the different receptor structures that have been so far described for mucosal adherence.

Infection with Helicobacter pylori strains carrying babA2 and cagA is associated with an increased risk of peptic ulcer disease development in Iraq

BACKGROUND AND STUDY AIM

Several genes of Helicobacter pylori, such as vacA, cagA, iceA and babA, have been reported to significantly increase the risk of gastrointestinal diseases. The aim of this study was to study the relationship between H. pylori virulence factors and clinical outcomes and identify the independent markers of peptic ulcer disease in Iraq.

PATIENTS AND METHODS

DNA was extracted from specimens taken from 154 unselected H. Pylori positive Iraqi patients. Genotyping was performed by the polymerase chain reaction (PCR), using specific primers for cagA, vacA (s, m), iceA and babA2 genes.

RESULTS

A total of 56 (82%) peptic ulcer disease (PUD) patients carried cagA+ strains, significantly more than the 56 (65%) non-ulcer disease (NUD) patients (p=0.017). The difference in the prevalence of babA2 positivity was significant between patients with NUD (33.7%) and PUD (58.8%) (p=0.002). In addition, babA2 was associated as an independent factor, with PUD (p=0.005; odds ratio (OR)=0.4; confidence interval (CI)=0.18-0.68) followed by cagA (p=0.05; OR=0.4; CI=0.18-0.85). Forty-five isolates (29%) were typed as 'triple positive' strains, and their presence was significantly associated with PUD (p=0.001).

CONCLUSION

The cagA and babA2 genotypes might be considered as useful markers for PUD patients. However, iceA1 and iceA2 seem not to be good markers for the disease. The presence of H. pylori strains with triple-positive status is of high clinical relevance to H. pylori-associated diseases.

Pathogen-driven gastrointestinal cancers: Time for a change in treatment paradigm?

The regulation of cancerous tumor development is converged upon by multiple pathways and factors. Besides environmental factors, gastrointestinal (GI) tract cancer can be caused by chronic inflammation, which is generally induced by bacteria, viruses, and parasites. The role of these inducers in cancer development, cell differentiation and transformation, cell cycle deregulation, and in the expression of tumor-associated genes cannot be ignored. Although Helicobacter pylori activates many oncogenic pathways, particularly those in gastric and colorectal cancers, the role of viruses in tumor development is also significant. Viruses possess significant oncogenic potential to interfere with normal cell cycle control and genome stability, stimulating the growth of deregulated cells. An increasing amount of recent data also implies the association of GI cancers with bacterial colonization and viruses. This review focuses on host-cell interactions that facilitate primary mechanisms of tumorigenesis and provides new insights into novel GI cancer treatments.

Redefinition of the carbohydrate binding specificity of Helicobacter pylori BabA adhesin

Certain Helicobacter pylori strains adhere to the human gastric epithelium using the blood group antigen-binding adhesin (BabA). All BabA-expressing H. pylori strains bind to the blood group O determinants on type 1 core chains, i.e. to the Lewis b antigen (Fucα2Galβ3(Fucα4)GlcNAc; Le^b) and the H type 1 determinant (Fucα2Galβ3GlcNAc). Recently, BabA strains have been categorized into those recognizing only Le^b and H type 1 determinants (designated specialist strains) and those that also bind to A and B type 1 determinants (designated generalist strains). Here, the structural requirements for carbohydrate recognition by generalist and specialist BabA were further explored by binding of these types of strains to a panel of different glycosphingolipids. Three glycosphingolipids recognized by both specialist and generalist BabA were isolated from the small intestine of a blood group O pig and characterized by mass spectrometry and proton NMR as H type 1 pentaglycosylceramide (Fucα2Galβ3GlcNAcβ3Galβ4Glcβ1Cer), Globo H hexaglycosylceramide (Fucα2Galβ3GalNAcβ3Galα4Galβ4Glcβ1Cer), and a mixture of three complex glycosphingolipids (Fucα2Galβ4GlcNAcβ6(Fucα2Galβ3GlcNAcβ3)Galβ3GlcNAcβ3Galβ4Glcβ1Cer, Fucα2Galβ3GlcNAcβ6(Fucα2Galβ3GlcNAcβ3)Galβ3GlcNAcβ3Galβ4Glcβ1Cer, and Fucα2Galβ4(Fucα3)GlcNAcβ6(Fucα2Galβ3GlcNAcβ3)Galβ3GlcNAcβ3Galβ4Glcβ1Cer). In addition to the binding of both strains to the Globo H hexaglycosylceramide, i.e. a blood group O determinant on a type 4 core chain, the generalist strain bound to the Globo A heptaglycosylceramide (GalNAcα3(Fucα2)Galβ3GalNAcβ3Galα4Galβ4Glcβ1Cer), i.e. a blood group A determinant on a type 4 core chain. The binding of BabA to the two sets of isoreceptors is due to conformational similarities of the terminal disaccharides of H type 1 and Globo H and of the terminal trisaccharides of A type 1 and Globo A.

Gastric carcinogenesis

INTRODUCTION

In most patients, gastric cancer is diagnosed in advanced stage. Curative treatment options are limited and the mortality is high. The process of gastric carcinogenesis is triggered by Helicobacter pylori-driven gastritis and is further characterized by its complexity of interaction with other risk factors. Health care systems are challenged for the improvement of prevention, early diagnosis, and effective treatments.

METHODS

An extensive literature research has been performed to elucidate the interplay between etiological factors involved in gastric carcinogenesis.

RESULTS

H. pylori is the most important carcinogen for gastric adenocarcinoma. Evidence is provided by experiments including animal studies as well as clinical observational and interventional studies in humans. Eradication has the potential to prevent gastric cancer and offers the greatest benefit if performed before premalignant changes of the gastric mucosa have occurred. Bacterial virulence factors are essential players in modulating the immune response involved in the initiation of the carcinogenesis in the stomach. Host genetic factors contribute to the regulation of the inflammatory response and in the aggravation of mucosal damage. The harmful role of environmental factors is restricted to salt intake and smoking of tobacco. The ingestion of fruit and vegetables has some protective effect.

CONCLUSION

Infection with H. pylori is the major risk factor for gastric cancer development, and thus, eradication of the Helicobacter offers a promising best option for prevention of the disease. Bacterial virulence, host genetic factors, and environmental influences are interacting in the multifactorial process of gastric carcinogenesis.