A new Helicobacter pylori vacuolating cytotoxin determinant, the intermediate region, is associated with gastric cancer

Helicobacter pylori cagE, cagG, and cagM can be a prognostic marker for intestinal and diffuse gastric cancer

It is known that Helicobacter pylori is the main cause of peptic ulceration and gastric cancer. However, there is a lack of information on whether H. pylori strains may differ in gastric cancer histological subtypes. This study aimed to investigate different H. pylori strains considering six cag Pathogenicity Island - cagPAI genes (cagA, cagE, cagG, cagM, cagT, and virb11), and vacuolating cytotoxin - vacA alleles, and their relation to gastric cancer histologic subtypes. For this purpose, tumor samples from 285 patients with gastric carcinoma were used. H. pylori infection and genotypes were determined by polymerase chain reaction (PCR). H. pylori was detected in 93.9% of gastric tumors. For comparative analyzes between histopathological subtypes considering H. pylori cagPAI genes the strains were grouped according to the vacA s1/s2 alleles. In the vacAs1 group, the strains cagA(-)cagE(+), cagA(+)cagE(+)cagG(+), cagA(+)cagM(+), or only cagE(+) strains were more frequent in the intestinal subtype (P = .009; P = .024; P = .046, respectively). In contrast, cagM(+)cagG(+)cagA(-) and cagE(-) were associated with diffuse tumors (P = .036), highlighting the presence of cagE in the development of intestinal tumors, and the presence of cagG and absence of cagE in diffuse tumors. Furthermore, WEKA software and Decision Tree (CART) analyses confirmed these findings, in which cagE presence was associated with intestinal tumors, and cagE absence and cagG(+) with diffuse tumors. In conclusion our results showed that vacAs1 (cagG + cagM) strains, mainly cagG positive with cagE absence, were relevant in the studied population for the diffuse outcome, while the presence of cagE was relevant for the intestinal outcome. These findings suggest the relevance of these H. pylori genes as potential markers for gastric cancer histological outcomes.

Is there a relationship between Helicobacter pylori vacA i1 or i2 alleles and development into peptic ulcer and gastric cancer? A meta-analysis study on an Iranian population

Helicobacter pylori has several virulance factor i.e. VacA, CagA, BabA, SabA, AlpA, AlpB and etc. VacA has several polymorphic region in the nucleotide sequence such as s,m,i,d and, c. It has been suggested that each variation in these polymorphic region has been influenced the toxicity of VacA toxin. We performed a comprehensive meta-analysis to determine the main role of VacAi1/i2 in development into peptic ulcer and gastric cancer in an Iranian 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.

Functional Properties of Helicobacter pylori VacA Toxin m1 and m2 Variants

Helicobacter pylori colonizes the gastric mucosa and secretes a pore-forming toxin (VacA). Two main types of VacA, m1 and m2, can be distinguished by phylogenetic analysis. Type m1 forms of VacA have been extensively studied, but there has been relatively little study of m2 forms. In this study, we generated H. pylori strains producing chimeric proteins in which VacA m1 segments of a parental strain were replaced by corresponding m2 sequences. In comparison to the parental m1 VacA protein, a chimeric protein (designated m2/m1) containing m2 sequences in the N-terminal portion of the m region was less potent in causing vacuolation of HeLa cells, AGS gastric cells, and AZ-521 duodenal cells and had reduced capacity to cause membrane depolarization or death of AZ-521 cells. Consistent with the observed differences in activity, the chimeric m2/m1 VacA protein bound to cells at reduced levels compared to the binding levels of the parental m1 protein. The presence of two strain-specific insertions or deletions within or adjacent to the m region did not influence toxin activity. Experiments with human gastric organoids grown as monolayers indicated that m1 and m2/m1 forms of VacA had similar cell-vacuolating activities. Interestingly, both forms of VacA bound preferentially to the basolateral surface of organoid monolayers and caused increased cell vacuolation when interacting with the basolateral surface compared to the apical surface. These data provide insights into functional correlates of sequence variation in the VacA midregion (m region).

Helicobacter pylori-related risk predictors of gastric cancer: The latest models, challenges, and future prospects

Helicobacter pylori is known as an important determinant of preneoplastic lesions or gastric cancer (GC) risk. The bacterial genotypes may determine the clinical outcomes. However, the evidence for these associations has varied between and within continents, and the actual effect of each gene and corresponding allelic variants are still debatable. In recent years, two new models have been proposed to predict the risk of GC; the phylogeographic origin of H. pylori strains and a disrupted co-evolution between H. pylori and its human host, which potentially explain the geographic differences in the risk of H. pylori-related cancer. However, these models and earlier ones based on putative virulence factors of the bacterium may not fully justify differences in the incidence of GC, reflecting that new theories should be developed and examined. Notably, the new findings also support the role of ancestry-specific germline alteration in contributing to the ethnic/population differences in cancer risk. Moreover the high and low incidence areas of GC have shown differences in transmission ecology, largely affecting the composition of H. pylori populations. As a new hypothesis, it is proposed that any high-risk population may have its own specific risk loci (or variants) as well as new H. pylori strains with national/maybe regional gene pools that should be considered. The latter is seen in the Americas where the rapid evolution of distinct H. pylori subpopulations has been occurred. It is therefore proposed that the deep sequencing of both H. pylori and its human host is simultaneously performed in GC patients and age-sex-matched controls from high-risk areas. The expression and functional activities of the identified new determinants of GC must then be assessed and matched with human and pathogen ancestry, because some of risk loci are ancestry-specific. In addition, potential study-level covariates and moderator variables (eg physical conditions, life styles, gastric microbiome, etc) linked to causal relationships, and their impact, should be recognized and controlled.

Immunological markers and Helicobacter pylori in patients with stomach cancer: Expression and correlation

Programmed death-ligand 1 (PD-L1) and ICOS-L (also referred to as B7 homolog 1 and 2, respectively) modulate the immune inflammatory response. The aim of the present study was to examine the expression levels of these inflammatory mediators in two groups of patients with an Helicobacter pylori (H. pylori) infection; patients with and without gastric cancer. The association between bacterial virulence factors, CagA and VacA, was also examined, as well as their correlation with the inflammatory profile. Endoscopy analysis indicated that 18 patients suffered from cancer and 28 patients suffered from other gastric pathologies. PCR and reverse transcription-quantitative PCR were used to analyze gastric biopsies and determine the expression levels of the inflammatory modulators PD-L1 and ICOS-L, transcription factors, cytokines and other genes associated with inflammation and pathogenicity. All 46 patients were determined positive for markers of H. pylori. Patients with stomach cancer had lower levels of ICOS-L (P<0.05) and GATA3 (P<0.01), a negative correlation between CagA and IL-17 (P<0.05), a positive correlation between CagA and IL-10 (P<0.05), a negative correlation between vacA-m1 and retinoid orphan receptor γt (RORγt) (P<0.001), and a positive correlation between RORγt and ICOS-L (P<0.001). The reduced levels of ICOS-L and GATA3 along with the negative correlation between CagA and IL-17, and between vacA-m1 and RORγt were all associated with an increased risk of gastric cancer in the present cohort.

Presence of cagPAI genes and characterization of vacA s, i and m regions in Helicobacter pylori isolated from Alaskans and their association with clinical pathologies

Introduction. Gastric cancer is a health disparity in the Alaska Native people. The incidence of Helicobacter pylori infection, a risk factor for non-cardia gastric adenocarcinoma, is also high. Gastric cancer is partially associated with the virulence of the infecting strain.Aim. To genotype the vacA s, m and i and cag pathogenicity island (cagPAI) genes in H. pylori from Alaskans and investigate associations with gastropathy.Methodology. We enrolled patients with gastritis, peptic ulcer disease (PUD) and intestinal metaplasia (IM) in 1998-2005 and patients with gastric cancer in 2011-2013. Gastric biopsies were collected and cultured and PCR was performed to detect the presence of the right and left ends of the cagPAI, the cagA, cagE, cagT and virD4 genes and to genotype the vacA s, m and i regions.Results. We recruited 263 people; 22 (8 %) had no/mild gastritis, 121 (46 %) had moderate gastritis, 40 (15%) had severe gastritis, 38 (14 %) had PUD, 30 (11 %) had IM and 12 (5 %) had gastric cancer. H. pylori isolates from 150 (57%) people had an intact cagPAI; those were associated with a more severe gastropathy (P≤0.02 for all comparisons). H. pylori isolates from 77 % of people had either the vacA s1/i1/m1 (40 %; 94/234) or s2/i2/m2 (37 %; 86/234) genotype. vacA s1/i1/m1 was associated with a more severe gastropathy (P≤0.03 for all comparisons).Conclusions. In this population with high rates of gastric cancer, we found that just over half of the H. pylori contained an intact cagPAI and 40 % had the vacA s1/i1/m1 genotype. Infection with these strains was associated with a more severe gastropathy.

Unique constellations of five polymorphic sites of Helicobacter pylori vacA and cagA status associated with risk of gastric cancer

Helicobacter pylori possesses virulence genes that are involved in the pathogenesis of the bacterium. There are little data regarding all constellations of five polymorphic sites of H. pylori vacA and cagA status. We therefore aimed to i) find any associations between H. pylori vacA alleles (s1/s2, m1/m2, i1/i2, d1/d2, and c1/c2) and cagA status and ii) determine the frequency of all five-genotype combinations of the vacA alleles with and without cagA gene, and their associations with risk of gastric cancer (GC). A total of 290 Iranian H. pylori isolates from gastrointestinal patients were obtained successfully by the cultivation of biopsies and genotyped. The patients included 144/290 with non-atrophic gastritis (NAG), 57/290 with peptic ulcer disease (PUD), and 89/290 with GC. We found that each of the vacA m1-, i1-, d1-, and c1-genotypes was significantly associated with cagA⁺ status. The odds ratio(OR) and 95% confidence interval (95% CI) was 2.316 (1.241-4.301) for cagA⁺/vacA m1, 2.764 (1.540-4.960) for cagA⁺/vacA i1, 4.288 (2.305-7.977) for cagA⁺/vacA d1, and 2.639 (1.488-4.680) for cagA⁺/vacA c1, respectively. In this study, 43 five- and six-genotype combinations were found among 224 strains. The highest frequencies were observed for vacA s1m2i2d2c2 (85/224, 37.9%), s1m2i2d2c2/cagA (48/222, 21.6%), s1m1i1d1c1 (40/224, 17.9%) and s1m1i1d1c1/cagA (35/222, 15.8%). Logistic regression analysis showed that vacA s1m1i1d1c1, s1m2i1d2c1, s1m2i2d2c1, and s1m2i2d2c1/cagA had a high prevalence in GC patients compared to non-atrophic gastritis patients (p < .05). The ORs and 95% CI were 2.433 (1.070-5.531), 11.524 (1.253-106.023), 4.200 (1.261-13.993), and 6.263 (1.494-26.256), respectively. These results were also confirmed when the controls were non-tumors (NAG/PUD). We found novel five- and six-genotype combinations associated with the risk of GC. These associations seem to be strongly dependent on the presence of c1-type of vacA. Therefore, analysis of all combined genotypes of the vacA alleles and cagA status may play a significant role in determining H. pylori-related clinical outcomes.

Genetic diversity and virulence characteristics of Helicobacter pylori isolates in different human ethnic groups

Helicobacter pylori is the most predominant bacterium in almost 50% of the world's population and colonization causes a persistent inflammatory response leading to chronic gastritis. It shows high genetic diversity and individuals generally harbour a distinct bacterial population. With the advancement of whole-genome sequencing technology, new H. pylori subpopulations have been identified that show admixture between various H. pylori strains. Genotypic variation of H. pylori may be related to the presence of virulence factors among strains and is associated with different outcomes of infection in different individuals. This review summarizes the genetic diversity in H. pylori strain populations and its virulence characteristics responsible for variable outcomes in different ethnic groups.

Helicobacter pylori Infection, Virulence Genes' Distribution and Accompanying Clinical Outcomes: The West Africa Situation

Data on Helicobacter pylori (H. pylori) infection and virulence factors in countries across West Africa are scattered. This systematic review seeks to present an update on the status of H. pylori infection focusing on prevalence rate, distribution of virulent genes, and their link to clinical outcomes across countries in the western part of Africa. This information is expected to broaden the knowledge base of clinicians and researchers regarding H. pylori infection and associated virulence factors in West African countries. Search Method. A comprehensive search of the scientific literature in PubMed and ScienceDirect was conducted using the search terms including “Helicobacter pylori infection in West Africa”. Databases were sourced from January 1988 to December 2018. Results. Data on the incidence of H. pylori infection and related pathological factors were found for some countries, whereas others had no information on it. Smoking, alcohol, exposure to high levels of carcinogens and diet were reported to be involved in the pathogenesis of gastroduodenal diseases and gastric cancer. Besides the environmental factors and genetic characteristics, there are important characteristics of H. pylori such as the ability to infect, replicate, and persist in a host that have been associated with the pathogenesis of various gastroduodenal diseases. Concluding Remarks. This systematic search has provided information so far available on H. pylori virulence factors and clinical outcomes in West Africa. Accordingly, this piece has identified gaps in the body of knowledge highlighting the need for more studies to clarify the role of H. pylori virulence factors and associated clinical outcomes in the burden of this bacterial infection in West Africa, as data from these countries do not give the needed direct relation.

Helicobacter pylori and Epstein-Barr Virus Infection in Gastric Diseases: Correlation with IL-10 and IL1RN Polymorphism

Introduction

Helicobacter pylori and Epstein–Barr virus (EBV) infection have recently been shown to be associated with gastric diseases. Polymorphisms in genes encoding cytokines such as interleukin 10 (IL-10) and interleukin 1 Receptor (IL-1RN) influence cytokine secretion levels and appear to contribute to the risk of developing gastroduodenal diseases. To our knowledge, this is the first preliminary study to address the association of coinfection with H. pylori and EBV and their correlation with genetic predisposition in the development of gastric diseases.

Methods

Gastric biopsy samples of 96 patients with different gastric diseases were used.

Results

Our results showed that the rate of coinfection was higher in patients with gastric cancer than in patients with normal gastric mucosa, active chronic gastritis, and MALT lymphoma. As regards the characterization of H. pilory strains, the polymorphism s1m1i1 of vacA gene was more frequent in patients with MALT Lymphoma in comparison to others, while the polymorphism s2m2i2 was most frequent in patients with normal gastric mucosa. In addition, patients who tested positive for the cagA gene were more frequently those affected with gastric cancer than those with inactive chronic gastritis. Similarly, the patients with oipA gene ON were more frequently those with gastric cancer than those with inactive chronic gastritis.

Conclusion

According to our analysis, there was no correlation between coinfection and polymorphisms in genes encoding IL-10 and IL-1RN. We conclude that various factors can be involved in the development of gastric diseases.

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.

Activity and Functional Importance of Helicobacter pylori Virulence Factors

Helicobacter pylori is a very successful Gram-negative pathogen colonizing the stomach of humans worldwide. Infections with this bacterium can generate pathologies ranging from chronic gastritis and peptic ulceration to gastric cancer. The best characterized H. pylori virulence factors that cause direct cell damage include an effector protein encoded by the cytotoxin-associated gene A (CagA), a type IV secretion system (T4SS) encoded in the cag-pathogenicity island (cag PAI), vacuolating cytotoxin A (VacA), γ-glutamyl transpeptidase (GGT), high temperature requirement A (HtrA, a serine protease) and cholesterol glycosyl-transferase (CGT). Since these H. pylori factors are either surface-exposed, secreted or translocated, they can directly interact with host cell molecules and are able to hijack cellular functions. Studies on these bacterial factors have progressed substantially in recent years. Here, we review the current status in the characterization of signaling cascades by these factors in vivo and in vitro, which comprise the disruption of cell-to-cell junctions, induction of membrane rearrangements, cytoskeletal dynamics, proliferative, pro-inflammatory, as well as, pro-apoptotic and anti-apoptotic responses or immune evasion. The impact of these signal transduction modules in the pathogenesis of H. pylori infections is discussed.

How does Helicobacter pylori cause gastric cancer through connexins: An opinion review

Helicobacter pylori (H. pylori) is a Gram-negative bacterium with a number of virulence factors, such as cytotoxin-associated gene A, vacuolating cytotoxin A, its pathogenicity island, and lipopolysaccharide, which cause gastrointestinal diseases. Connexins function in gap junctional homeostasis, and their downregulation is closely related to gastric carcinogenesis. Investigations into H. pylori infection and the fine-tuning of connexins in cells or tissues have been reported in previous studies. Therefore, in this review, the potential mechanisms of H. pylori-induced gastric cancer through connexins are summarized in detail.

Association between the relative abundance of gastric microbiota and the risk of gastric cancer: a case-control study

The human gut hosts a diverse community of bacteria referred to as the gut microbiome. We investigated the association between the relative abundance of gastric microbiota and gastric cancer (GC) risk in a Korean population. The study participants included 268 GC patients and 288 controls. DNA was extracted from gastric biopsies, and 16S rRNA gene analysis was performed. Unconditional logistic regression models were used to observe the associations. Of the participants, those who had the highest level (highest tertile) of relative Helicobacter pylori and Propionibacterium acnes abundances showed a significantly higher risk for GC after adjusting for potential confounding variables (odds ratio (OR) = 1.86, 95% confidence interval (CI) = 1.17–2.97, p for trend = 0.017 and OR = 4.77, 95% CI = 2.94–7.74, p for trend <0.001, respectively). Subjects who carried Prevotella copri had a significantly higher risk of GC than noncarriers (OR = 2.54, 95% CI = 1.42–4.55, p for trend = 0.002). There was a lower risk of GC in subjects carrying Lactococcus lactis than in noncarriers (OR = 0.21, 95% CI = 0.10–0.44, p for trend <0.001). H. pylori, P. acnes and P. copri are strong risk factors, whereas L. lactis is a protective factor, for GC development in Koreans. Further microbiome studies are warranted to verify the findings of the current study.

The analysis of virulence factors and antibiotic resistance between Helicobacter pylori strains isolated from gastric antrum and body

Background

Individuals can be infected with multiple strains of Helicobacter pylori. However, the differences among co-infecting strains have not been well analyzed yet. This study aimed to investigate whether the virulence factors and antibiotic resistance patterns of H. pylori differ between strains isolated from different locations of the stomach in the same patient.

Methods

H. pylori isolates were obtained from the antrum and body of the stomach. Genetic differences were examined by random amplified polymorphic DNA (RAPD) fingerprinting. Antibiotic resistance was assessed using the agar dilution method. Virulence factors were identified by polymerase chain reaction and DNA sequencing.

Results

Among 80 patients, co-infection by two H. pylori strains was detected in 10 patients. Among the 10 pairs of H. pylori strains, differences in antibiotic resistance patterns were detected in 7 pairs (clarithromycin, 1 patient; quinolone, 3 patients; metronidazole, 4 patients) and differences in virulence factors were detected in 5 pairs. The cagA virulence gene was detected in all 10 patients, and 2 patients had H. pylori strains with different EPIYA motifs. Differences in vacA genotypes were detected in 4 patients.

Conclusions

Co-infection by two H. pylori strains was confirmed by RAPD fingerprinting. Frequently, two H. pylori strains obtained from a single host differed in their virulence factors and antibiotic resistance patterns. Co-infection by multiple H. pylori strains could undermine the success of eradication therapy and should be considered when interpreting the results of antimicrobial susceptibility tests.

Electronic supplementary material

The online version of this article (10.1186/s12876-019-1062-5) contains supplementary material, which is available to authorized users.

Differential Helicobacter pylori Plasticity in the Gastric Niche of Subjects at Increased Gastric Cancer Risk

Helicobacter pylori (H. pylori) represents an independent risk factor for Gastric Cancer (GC). First Degree Relatives (FDR) of GC subjects and Autoimmune Gastritis (AG) patients are both at increased risk for GC. H. pylori genetic heterogeneity within the gastric niche of FDR and AG individuals has been little explored. To understand whether they exploit an increased H. pylori stability and virulence, 14 AG, 25 FDR, 39 GC and 13 dyspeptic patients (D) were investigated by a cultural PCR-based approach characterizing single colonies-forming-units. We chose three loci within the Cytotoxin-associated gene-A Pathogenicity Island (CagPAI) (cagA,cagE,virB11), vacA, homA and homB as markers of virulence with reported association to GC. Inflammatory/precancerous lesions were staged according to Sydney System. When compared to D, FDR, similarly to GC patients, were associated to higher atrophy (OR = 6.29; 95% CI:1.23-31.96 in FDR; OR = 7.50; 95% CI:1.67-33.72 in GC) and a lower frequency of mixed infections (OR = 0.16; 95% CI:0.03-0.81 in FDR; OR = 0.10; 95% CI:0.02-0.48 in GC). FDR presented also an increased neutrophil infiltration (OR = 7.19; 95% CI:1.16-44.65). Both FDR and GC carried a higher proportion of CagPAI⁺vacAs1i1mx⁺homB⁺ profiles (OR = 2.71; 95% CI: 1.66-4.41 and OR = 3.43; 95% CI: 2.16-5.44, respectively). Conversely, AG patients presented a lower frequency of subtypes carrying a stable CagPAI and vacAs1i1mx. These results underline different H. pylori plasticity in FDR and AG individuals, and thus, a different host-bacterium interaction capacity that should be considered in the context of eradication therapies.

Cryo-EM Analysis Reveals Structural Basis of Helicobacter pylori VacA Toxin Oligomerization

Helicobacter pylori colonizes the human stomach and contributes to the development of gastric cancer and peptic ulcer disease. H. pylori secretes a pore-forming toxin called vacuolating cytotoxin A (VacA), which contains two domains (p33 and p55) and assembles into oligomeric structures. Using single-particle cryo-electron microscopy, we have determined low-resolution structures of a VacA dodecamer and heptamer, as well as a 3.8-Å structure of the VacA hexamer. These analyses show that VacA p88 consists predominantly of a right-handed beta-helix that extends from the p55 domain into the p33 domain. We map the regions of p33 and p55 involved in hexamer assembly, model how interactions between protomers support heptamer formation, and identify surfaces of VacA that likely contact membrane. This work provides structural insights into the process of VacA oligomerization and identifies regions of VacA protomers that are predicted to contact the host cell surface during channel formation.

Helicobacter pylori VacA, a distinct toxin exerts diverse functionalities in numerous cells: An overview

BACKGROUND

Helicobacter pylori, gastric cancer-causing bacteria, survive in their gastric environment of more than 50% of the world population. The presence of H. pylori in the gastric vicinity promotes the development of various diseases including peptic ulcer and gastric carcinoma. H. pylori produce and secret Vacuolating cytotoxin A (VacA), a major toxin facilitating the bacteria against the host defense system. The toxin causes multiple effects in epithelial cells and immune cells, especially T cells, B cells, and Macrophages.

METHODS

This review describes the diverse functionalities of protein toxin VacA. The specific objective of this review is to address the overall structure, mechanism, and functions of VacA in various cell types. The recent advancements are summarized and discussed and thus conclusion is drawn based on the overall reported evidences.

RESULTS

The searched articles on H. pylori VacA were evaluated and limited up to 66 articles for this review. The articles were divided into four major categories including articles on vacA gene, VacA toxin, distinct effects of VacA toxin, and their effects on various cells. Based on these studies, the review article was prepared.

CONCLUSIONS

This review describes an overview of how VacA is secreted by H. pylori and contributes to colonization and virulence in multiple ways by affecting epithelial cells, T cells, Dendritic cells, B cells, and Macrophages. The reported evidence suggests that the comprehensive outlook need to be developed for understanding distinctive functionalities of VacA.

Genetic Polymorphisms in Inflammatory and Other Regulators in Gastric Cancer: Risks and Clinical Consequences

Helicobacter pylori infection is associated with the development of a chronic inflammatory response, which may induce peptic ulcers, gastric cancer (GC), and mucosa-associated lymphoid tissue (MALT) lymphoma. Chronic H. pylori infection promotes the genetic instability of gastric epithelial cells and interferes with the DNA repair systems in host cells. Colonization of the stomach with H. pylori is an important cause of non-cardia GC and gastric MALT lymphoma. The reduction of GC development in patients who underwent anti-H. pylori eradication schemes has also been well described. Individual susceptibility to GC development depends on the host's genetic predisposition, H. pylori virulence factors, environmental conditions, and geographical determinants. Biological determinants are urgently sought to predict the clinical course of infection in individuals with confirmed H. pylori infection. Possible candidates for such biomarkers include genetic aberrations such as single-nucleotide polymorphisms (SNPs) found in various cytokines/growth factors (e.g., IL-1β, IL-2, IL-6, IL-8, IL-10, IL-13, IL-17A/B, IFN-γ, TNF, TGF-β) and their receptors (IL-RN, TGFR), innate immunity receptors (TLR2, TLR4, CD14, NOD1, NOD2), enzymes involved in signal transduction cascades (PLCE1, PKLR, PRKAA1) as well as glycoproteins (MUC1, PSCA), and DNA repair enzymes (ERCC2, XRCC1, XRCC3). Bacterial determinants related to GC development include infection with CagA-positive (particularly with a high number of EPIYA-C phosphorylation motifs) and VacA-positive isolates (in particular s1/m1 allele strains). The combined genotyping of bacterial and host determinants suggests that the accumulation of polymorphisms favoring host and bacterial features increases the risk for precancerous and cancerous lesions in patients.

Impact of Helicobacter pylori Virulence Factors on the Host Immune Response and Gastric Pathology

Helicobacter pylori chronically infects nearly half the world's population, yet most of those infected remain asymptomatic throughout their lifetime. The outcome of infection-peptic ulcer disease or gastric cancer versus asymptomatic colonization-is a product of host genetics, environmental influences, and differences in bacterial virulence factors. Here, we review the current understanding of the cag pathogenicity island (cagPAI), the vacuolating cytotoxin (VacA), and a large family of outer membrane proteins (OMPs), which are among the best understood H. pylori virulence determinants that contribute to disease. Each of these virulence factors is characterized by allelic and phenotypic diversity that is apparent within and across individuals, as well as over time, and modulates inflammation. From the bacterial perspective, inflammation is probably a necessary evil because it promotes nutrient acquisition, but at the cost of reduction in bacterial load and therefore decreases the chance of transmission to a new host. The general picture that emerges is one of a chronic bacterial infection that is dependent on both inducing and carefully regulating the host inflammatory response. A better understanding of these regulatory mechanisms may have implications for the control of chronic inflammatory diseases that are increasingly common causes of human morbidity and mortality.

Intensive formation of coccoid forms as a feature strongly associated with highly pathogenic Helicobacter pylori strains

The variability of Helicobacter pylori morphology and the heterogeneity of virulence factors expressed by these bacteria play a key role as a driving force for adaptation to the hostile stomach environment. The aim of the study was to determine the relationship between the presence of certain genes encoding virulence factors and H. pylori morphology. One reference and 13 clinical H. pylori strains with a known virulence profile (vacA, cagA, babA2, dupA, and iceA) were used in this study. Bacteria were cultured for 1 h and 24 h in stressogenic culture conditions, i.e., serum-free BHI broths at suboptimal conditions (room temperature and atmosphere, without shaking). H. pylori cell morphology was observed by light and scanning electron microscopy. The vacA polymorphism and the cagA and babA2 presence were positively correlated with the reduction in cell size. Exposure to short-time stressogenic conditions caused more intense transformation to coccoid forms in highly pathogenic H. pylori type I strains (35.83% and 47.5% for type I s1m2 and I s1m1, respectively) than in intermediate-pathogenic type III (8.17%) and low pathogenic type II (9.92%) strains. The inverse relationship was observed for the number of rods, which were more common in type III (46.83%) and II (48.42%) strains than in type I s1m2 (19.25%) or I s1m1 (6.58%) strains. Our results suggest that there is a close relationship between the presence of virulence genes of H. pylori strains and their adaptive morphological features.

Occurrence of cagA+ vacA s1a m1 i1 Helicobacter pylori in farm animals in Egypt and ability to survive in experimentally contaminated UHT milk

Cases of human gastric cancer due to Helicobacter pylori have been reported worldwide and animals might act as a reservoir of infection in certain circumstances. The recent few decades showed a rapid decline in the incidence of gastric cancer, which was mainly due to the decrease in H. pylori infection. The aims of the present study were to determine the prevalence of H. pylori among livestock and investigate whether the animal isolates can be transmitted through contaminated milk causing gastric infection. Feces and milk samples were collected from apparently healthy cows, buffaloes, and sheep, and were examined by nested PCR and genotyping. The PCR positive samples were further subjected to bacterial culture followed by partial 16s sequencing of the isolates. Twenty-nine percent of the animals showed the presence of H. pylori, mainly the virulent cagA+vacA+s1a m1 i1 genotype, which is known to be associated with serious diseases in humans. The spiral viable culturable form (SVCF) of this strain was inoculated into UHT (ultra-high temperature) milk and remained viable for up to 10 days at 4 °C. Increasing period of storage and or temperature led to a decrease in the number of the SVCF and occurrence of the coccoid viable non-culturable form (CVNCF). The infectivity of the survived forms was determined by feeding healthy groups of laboratory mice with the contaminated UHT milk containing SVCF or CVNCF for 40 days. The gastric mucosa of the two mice groups showed similar levels of H. pylori load. This highlights that H. pylori can persist in contaminated milk by entering a non-culturable state, which can induce gastric infection.

Priming the seed: Helicobacter pylori alters epithelial cell invasiveness in early gastric carcinogenesis

Helicobacter pylori (H. pylori) infection is a well-established risk factor for the development of gastric cancer (GC), one of the most common and deadliest neoplasms worldwide. H. pylori infection induces chronic inflammation in the gastric mucosa that, in the absence of treatment, may progress through a series of steps to GC. GC is only one of several clinical outcomes associated with this bacterial infection, which may be at least partially attributed to the high genetic variability of H. pylori. The biological mechanisms underlying how and under what circumstances H. pylori alters normal physiological processes remain enigmatic. A key aspect of carcinogenesis is the acquisition of traits that equip preneoplastic cells with the ability to invade. Accumulating evidence implicates H. pylori in the manipulation of cellular and molecular programs that are crucial for conferring cells with invasive capabilities. We present here an overview of the main findings about the involvement of H. pylori in the acquisition of cell invasive behavior, specifically focusing on the epithelial-to-mesenchymal transition, changes in cell polarity, and deregulation of molecules that control extracellular matrix remodeling.

The impacts of H. pylori virulence factors on the development of gastroduodenal diseases

Although most H. pylori infectors are asymptomatic, some may develop serious disease, such as gastric adenocarcinoma, gastric high-grade B cell lymphoma and peptic ulcer disease. Epidemiological and basic studies have provided evidence that infection with H. pylori carrying specific virulence factors can lead to more severe outcome. The virulence factors that are associated with gastric adenocarcinoma development include the presence, expression intensity and types of cytotoxin-associated gene A (CagA, especially EPIYA-D type and multiple copies of EPIYA-C) and type IV secretion system (CagL polymorphism) responsible for its translocation into the host cells, the genotypes of vacuolating cytotoxin A (vacA, s1/i1/m1 type), and expression intensity of blood group antigen binding adhesin (BabA, low-producer or chimeric with BabB). The presence of CagA is also related to gastric high-grade B cell lymphoma occurrence. Peptic ulcer disease is closely associated with cagA-genopositive, vacA s1/m1 genotype, babA2-genopositive (encodes BabA protein), presence of duodenal ulcer promoting gene cluster (dupA cluster) and induced by contact with epithelium gene A1 (iceA1), and expression status of outer inflammatory protein (OipA). The prevalence of these virulence factors is diverse among H. pylori isolated from different geographic areas and ethnic groups, which may explain the differences in disease incidences. For example, in East Asia where gastric cancer incidence is highest worldwide, almost all H. pylori isolates were cagA genopositive, vacA s1/i1/m1 and BabA-expressing. Therefore, selection of appropriate virulence markers and testing methods are important when using them to determine risk of diseases. This review summarizes the evidences of H. pylori virulence factors in relation with gastroduodenal diseases and discusses the geographic differences and appropriate methods of analyzing these virulence markers.

Are Helicobacter pylori highly cytotoxic genotypes and cardia gastric adenocarcinoma linked? Lessons from Iran

BACKGROUND

Although the most extensive studies revealed the role of H. pylori VacA and CagA toxins in the development of gastric adenocarcinoma, the magnitude of this association and the correlations of vacA mosaicism and cagA status with cardia gastric adenocarcinoma (CGA) still remain controversial.

OBJECTIVE

We aimed to examine the linkage of H. pylori highly cytotoxic genotypes to CGA in Iranian populations as a model.

METHODS

A total of 601 Iranian patients were enrolled. Biopsies were cultured, genotyped, and anatomically and histologically classified.

RESULTS

The vacA c1 genotype, but not cagA status, showed a strong association with the risk of both CGA and non-cardia adenocarcinoma (NCGA), whether the controls were non-tumors, as those with either non-atrophic gastritis or peptic ulcerations, (the OR (95%CI) was 14.11 (4.91-40.52) and 9.59 (4.06-22.65), respectively) or those with NAG (the OR (95%CI) was 10.71 (3.49-32.82) and 8.11 (3.26-20.16), respectively). The vacA c1/cagA+ genotype was significantly associated with an increased risk of NCGA, whether the controls were non-tumors or those with NAG; the adjusted risk was 4.706 (1.41-15.67) and 4.85 (1.42-16.51), respectively.

CONCLUSIONS

The H. pylori vacA c1 genotype, but not cagA status, might be the first important bacterial biomarker for predicting the cardia adenocarcinoma risk in male patients aged ⩾ 55 in Iran.

The role of T helper 1-cell response in Helicobacter pylori-infection

Helicobacter pylori (H. pylori) is a human pathogen affecting over 50% of the world population. This pathogen is usually associated with chronic inflammation of the gastric mucosa that can lead to peptic ulcer disease (PUD) and gastric cancer (GC), especially in susceptible individuals. These outcomes have been attributed to the interaction of several factors, including host genetic susceptibility, local innate and adaptive immune responses, virulence factors of H. pylori, and environmental factors. T helper (Th) cell subsets and their signature cytokines especially IFN-γ, contribute to anti-bacterial response, but at the mean time sustaining chronic inflammatory responses in the site of infection. It has been acknowledged that H. pylori-infection results in a Th1-dominant response and that inflammation of the gastric mucosa depends mainly on Th1 cell responses. But, the mechanism of the role of Th1 cell responses in H. pylori-infection has not yet been clearly explained. In this review, we will focus on the role of Th1 involved in H. pylori-infection, its interaction with Th17/Treg cells and its association with the clinical consequences of the infection.

Th-17 response and antimicrobial peptide expression are uniformly expressed in gastric mucosa of Helicobacter pylori-infected patients independently of their clinical outcomes

BACKGROUND

The pathological determinism of H. pylori infection is explained by complex interplay between bacterial virulence and host inflammatory response. In a large prospective multicenter clinical study, Th17 response, expression of antimicrobial peptides (AMPs), cagA and vacA status, and bacterial density were investigated in the gastric mucosa of H. pylori -infected patients.

MATERIALS AND METHODS

Gastric inflammatory response was analyzed by RT-qPCR for quantification of Th17 cytokines (IL-17A, IL-22), CXCL-8, and AMPs (BD2 and S100A9) mRNA levels in gastric biopsies. Detection and genotyping of H. pylori strains were achieved by bacterial culture and PCR.

RESULTS

Among 787 patients screened for H. pylori, 269 were analyzed (147 H. pylori -infected and 122 uninfected patients). In H. pylori -infected patients, distribution was 83 gastritis, 12 duodenal ulcers, 5 gastric ulcers, and 47 precancerous and cancerous lesions. CXCL-8, IL-17A, BD2, and S100A9 mRNA levels were significantly increased in H. pylori -infected patients but, surprisingly, IL-22 was not, and no difference was shown between H. pylori -related diseases. A positive correlation was identified between S100A9 expression and bacterial density. Although expression of the virulence genes cagA and vacA did not impact inflammatory response, patients infected with a cagA-positive strain were associated with severe H. pylori -related diseases.

CONCLUSION

This study showed that CXCL-8, IL-17A, and AMPs are not differently expressed according to the various H. pylori -related diseases. The clinical outcome determinism of H. pylori infection is most likely not driven by gastric inflammation but rather tends to mainly influenced by bacterial virulence factors.

New insights of Helicobacter pylori host-pathogen interactions: The triangle of virulence factors, epigenetic modifications and non-coding RNAs

Helicobacter pylori (H. pylori) is a model organism for understanding host-pathogen interactions and infection-mediated carcinogenesis. Gastric cancer and H. pylori colonization indicates the strong correlation. The progression and exacerbation of H. pylori infection are influenced by some factors of pathogen and host. Several virulence factors involved in the proper adherence and attenuation of immune defense to contribute the risk of emerging gastric cancer, therefore analysis of them is very important. H. pylori also modulates inflammatory and autophagy process to intensify its pathogenicity. From the host regard, different genetic factors particularly affect the development of gastric cancer. Indeed, epigenetic modifications, MicroRNA and long non-coding RNA received more attention. Generally, various factors related to pathogen and host that modulate gastric cancer development in response to H. pylori need more attention due to develop an efficacious therapeutic intervention. Therefore, this paper will present a brief overview of host-pathogen interaction especially emphases on bacterial virulence factors, interruption of host cellular signaling, the role of epigenetic modifications and non-coding RNAs.

Association of oral Helicobacter pylori with gastric complications

AIM

This study was aimed to identify the presence of Helicobacter pylori (H. pylori) genes in oral mucosa and find out their relationship between oral H. pylori infection and gastric complications.

METHODS

This study is a case control study consists of 567 subjects with periodontal infection (278 gastric complication cases and 289 controls normal gastric intestinal mucosa) with age range of 20-80 years. Oral health status was recorded by calculating oral hygiene index (OHI), probing depths (PD) and clinical attachment loss (CAL). Each participant provided gastric biopsy and plaque samples which were subjected to H. pylori detection. Polymerase chain reaction (PCR) with different primers specifically β globulin, 16SrRNA, babA, cagA, ureA, ureC and vacA gene was performed which were then analyzed using gel electrophoresis.

RESULTS

No significant differences (χ² = 11.873, p value > 0.05) were observed between oral H. pylori and gastric infections/complications. However, H. pylori increase the risk of developing gastro-esophageal reflux grade II (OR = 1.458, 95%CI = 0.659-3.226), normal upper GIT mucosa with lax esophageal sphincters (OR = 1.215, 95%CI = 0.285-5.181) and duodenal ulcer/duodenitis (OR = 2.187, 95%CI = 0.225-21.278). This study also showed a significant increased risk of gastritis with babA gene.

CONCLUSION

Oral pathogenic H. pylori genes may enhance the severity of the gastric infection.

Can bacterial virulence factors predict antibiotic resistant Helicobacter pylori infection?

AIM

To evaluate the association between virulence factor status and antibiotic resistance in Helicobacter pylori (H. pylori)-infected patients in Ireland.

METHODS

DNA was extracted from antral and corpus biopsies obtained from 165 H. pylori-infected patients. Genotyping for clarithromycin and fluoroquinolone-mediating mutations was performed using the Genotype HelicoDR assay. cagA and vacA genotypes were investigated using PCR.

RESULTS

Primary, secondary and overall resistance rates for clarithromycin were 50.5% (n = 53/105), 78.3% (n = 47/60) and 60.6% (n = 100/165), respectively. Primary, secondary and overall resistance rates for fluoroquinolones were 15.2% (n = 16/105) and 28.3% (n = 17/60) and 20% (n = 33/165), respectively. Resistance to both antibiotics was 12.4% (n = 13/105) in treatment-naïve patients, 25% (n = 15/60) in those previously treated and 17% (n = 28/165) overall. A cagA-positive genotype was detected in 22.4% (n = 37/165) of patient samples. The dominant vacA genotype was S1/M2 at 44.8% (n = 74/165), followed by S2/M2 at 26.7% (n = 44/165), S1/M1 at 23.6% (n = 39/165) and S2/M1 at 4.8% (n = 8/165). Primary clarithromycin resistance was significantly lower in cagA-positive strains than in cagA-negative strains [32% (n = 8/25) vs 56.3% (n = 45/80) P = 0.03]. Similarly, in patients infected with more virulent H. pylori strains bearing the vacA s1 genotype, primary clarithromycin resistance was significantly lower than in those infected with less virulent strains bearing the vacA s2 genotype, [41% (n = 32/78) vs 77.8% (n = 21/27) P = 0.0001]. No statistically significant association was found between primary fluoroquinolone resistance and virulence factor status.

CONCLUSION

Genotypic H. pylori clarithromycin resistance is high and cagA-negative strains are dominant in our population. Less virulent (cagA-negative and vacA S2-containing) strains of H. pylori are associated with primary clarithromycin resistance.

Status of Helicobacter pylori cag pathogenicity island (cagPAI) integrity and significance of its individual genes

One of the most important virulence factors of H. pylori is the intact cagPAI. The aim of the present study is to investigate cagPAI intactness among Bulgarian H. pylori isolates, its associations with clinical outcomes and vacA alleles, and to evaluate the significance of individual cagPAI genes.

MATERIAL AND METHODS

Totally, 156 isolates from 156 patients with endoscopic findings for duodenal or gastric ulcer (33 subjects), non-ulcer disease (121) and other diseases, such as Crohn's disease and hepatitis (2) were tested. Polymerase chain reaction (PCR) was used to detect 14 essential cagPAI genes, including cagA, as well as vacA s, i and m alleles.

RESULTS

CagA positive were 81.4% of all H. pylori isolates. Intact cagPAI was found in 64.1% of the all isolates, 16.7% and 19.2% showed complete and partial cagPAI absence, respectively. The prevalence of all cagPAI genes and intact cagPAI was significantly higher in isolates from ulcer patients compared with those from non-ulcer patients (p = 0.001). The most frequently missing genes among the isolates with partially deleted cagPAIs were cagE or/and cagY (28 of 30 isolates). Overall prevalence of vacA s1a allele was 80.1% and that of vacA i1 was 64.1%. The vacA s1a, m1 and i1 alleles were more prevalent in H. pylori isolates from ulcer patients (p = 0.03, p = 0.009, and p = 0.0003, respectively) and were associated with isolates with intact cagPAI.

CONCLUSIONS

In Bulgaria the prevalence of intact cagPAI was high. cagE or/and cagY absence was the most important predictor of cagPAI status.

Biological characteristics and virulence of Helicobacter pylori

This review summarizes the most recent data on the biological characteristics of Helicobacter pylori (morphological, cultural, biochemical). H. pylori pathogenicity factors promoting colonization, adhesion, biofilm formation, aggression, and cytotoxicity, their contribution to the pathogenesis of diseases as well as the possible relationships with various clinical outcomes are described in detail. The genetic heterogeneity of H. pylori strains which can determine different clinical manifestations and have significance for conducting epidemiological studies is also considered.

Prevalence, risk factors, and virulence genes of Helicobacter pylori among dyspeptic patients in two different gastric cancer risk regions of Thailand

Gastric cancer risk is varied among different regions of Thailand. We examined the characteristics of Helicobacter pylori infection in two regions of Thailand. The H. pylori status of 273 dyspeptic patients (136 from the South and 137 from the North; a low and high incidence of gastric cancer region, respectively) was evaluated, and virulence genotypes (cagA, vacA, hrgA and jhp0562-positive/β-(1,3)galT) were determined. The overall H. pylori infection rate was 34.1% (93/273). The prevalence was higher in the North than in the South (50.4% vs. 17.6%, P <0.001) and was significantly higher among individuals with the following characteristics: low income, birthplace in the Northeast or North regions, agricultural employment, or consumption of alcohol or unboiling water. Among these socio-demographic determinants, region was an independent risk factor for H. pylori infection (odds ratio = 6.37). Patients including both H. pylori infected and uninfected cases who lived in the North had significantly more severe histological scores than those in the South. In contrast, among H. pylori-positive cases, patients in the South had significantly more severe histological scores than those in the North. Of the 74 strains cultured, 56.8% carried Western-type cagA, with a higher proportion in the South than in the North (76.2% vs. 49.1%, P = 0.05). In disagreement with the current consensus, patients infected with the Western-type cagA strains had more severe inflammation scores in the antrum than those infected with the East Asian-type cagA strains (P = 0.027). Moreover, Western-type cagA strains induced more severe histological scores in patients from the South than those of either genotype from the North. Other virulence genes had no influence on histological scores. The incidence of gastric cancer in Thailand was different among regions and corresponded to differences in the prevalence of H. pylori infection. More careful follow-up for patients in the South will be required, even if they are infected with H. pylori carrying Western-type cagA.

Helicobacter pylori Vacuolating Toxin and Gastric Cancer

Helicobacter pylori VacA is a channel-forming toxin unrelated to other known bacterial toxins. Most H. pylori strains contain a vacA gene, but there is marked variation among strains in VacA toxin activity. This variation is attributable to strain-specific variations in VacA amino acid sequences, as well as variations in the levels of VacA transcription and secretion. In this review, we discuss epidemiologic studies showing an association between specific vacA allelic types and gastric cancer, as well as studies that have used animal models to investigate VacA activities relevant to gastric cancer. We also discuss the mechanisms by which VacA-induced cellular alterations may contribute to the pathogenesis of gastric cancer.

Helicobacter pylori virulence genes of minor ethnic groups in North Thailand

Background

There are few studies analyzed concurrently the prevalence and genotypes of Helicobacter pylori infection with the ancestor origins from different ethnics, especially with including minority groups. We recruited a total of 289 patients in MaeSot, Thailand (154 Thai, 14 Thai-Chinese, 29 Karen and 92 Hmong ethnics). The virulence genes and genealogy of the strains were determined by PCR-based sequencing.

Results

Based on culture and histology/immunohistochemistry, the prevalence of H. pylori infection was 54.5% (158/289). Among 152 isolates cultured, the East-Asian-type cagA was predominant genotype among strains from Hmong, Thai-Chinese and Thai (96.0% [48/50], 85.7% [6/7] and 62.7% [47/75], respectively), whilst majority of strains from Karen had Western-type cagA (73.3% [11/15]). Patients infected with the East-Asian-type cagA strains had significantly higher activity and intestinal metaplasia in the antrum and activity in the corpus than those with Western-type cagA (P = 0.024, 0.006 and 0.005, respectively). The multilocus sequencing typing analysis discriminated that most strains from Hmong and Thai-Chinese belonged to hspEAsia (92.0 and 85.7%, respectively), whereas strains from Karen predominantly possessed hpAsia2 (86.7%) and strains from Thai were classified into hspEAsia (45.2%) and hpAsia2 (31.1%).

Conclusions

Helicobacter pylori genotypes were relatively different among ethnic groups in Thailand and were associated with the source of ancestor even living in a small rural town. Caution and careful check-up are required especially on Hmong ethnic associated with high prevalence of virulence genotypes of H. pylori.

Electronic supplementary material

The online version of this article (doi:10.1186/s13099-017-0205-x) contains supplementary material, which is available to authorized users.

Insulin-like growth factor binding protein-1 (IGFBP-1) upregulated by Helicobacter pylori and is associated with gastric cancer cells migration

Insulin-like growth factor binding protein-1 (IGFBP-1), a secreted protein, implicated of various cells in mediating the proliferation, migration, invasion, adhesion, survival and so on. In this study, we assessed the expression and release of IGFBP-1 from gastric cancer cells with H. pylori 26695 infection and the biological functions of IGFBP-1 in gastric cancer cells. The results showed that the expression and release of IGFBP-1 were increased in gastric cancer cells (MGC-803, BGC-823, SGC-7901) infected with H. pylori 26695. In addition, the upregulation of IGFBP-1 was dose-dependent in BGC-823 cells infected with H. pylori 26695 but not time-dependent. The upregulation of IGFBP-1 got to peak at 12h after H. pylori 26695 infection and then decreased over time. Subsequently, we measured its functions by silencing and overexpressing IGFBP1 which suggested that overexpression of IGFBP-1 could inhibit the migration of BGC-823 and SGC-7901 cells. However, knocking down the IGFBP-1 could increase the migration of BGC-823 and SGC-7901 cells. Functional findings illustrated that IGFBP-1 was implicated in H. pylori 26695-induced MMP-9 expression in BGC-823 cells. In addition, overexpressing IGFBP1 reduce the promoting effect of MMP-9 on the BGC-823 cells migration. In summary, we demonstrated that IGFBP-1 suppress the migration of BGC-823 cells and play a protective role in the process of H. pylori-induced gastric cancer.

Helicobacter pylori outer inflammatory protein A (OipA) suppresses apoptosis of AGS gastric cells in vitro

Outer inflammatory protein A (OipA) is an important virulence factor associated with gastric cancer and ulcer development; however, the results have not been well established and turned out to be controversial. This study aims to elucidate the role of OipA in Helicobacter pylori infection using clinical strains harbouring oipA "on" and "off" motifs. Proteomics analysis was performed on AGS cell pre-infection and postinfection with H. pylori oipA "on" and "off" strains, using liquid chromatography/mass spectrometry. AGS apoptosis and cell cycle assays were performed. Moreover, expression of vacuolating cytotoxin A (VacA) was screened using Western blotting. AGS proteins that have been suggested previously to play a role or associated with gastric disease were down-regulated postinfection with oipA "off" strains comparing to oipA "on" strains. Furthermore, oipA "off" and ΔoipA cause higher level of AGS cells apoptosis and G0/G1 cell-cycle arrest than oipA "on" strains. Interestingly, deletion of oipA increased bacterial VacA production. The capability of H. pylori to induce apoptosis and suppress expression of proteins having roles in human disease in the absence of oipA suggests that strains not expressing OipA may be less virulent or may even be protective against carcinogenesis compared those expressing OipA. This potentially explains the higher incidence of gastric cancer in East Asia where oipA "on" strains predominates.

Two populations of less-virulent Helicobacter pylori genotypes in Bangladesh

Bangladesh has a population with a low gastric cancer risk but high prevalence of Helicobacter pylori infection. Several studies have examined virulence genes in H. pylori from Bangladesh. We analyzed cagA and vacA subtypes and their association with severe histology phenotypes, and analyzed population types among Bangladeshi strains. We included patients who underwent endoscopy in Dhaka. Sequences of virulence genes and seven housekeeping genes were obtained by next generation sequencing and confirmed by Sanger sequencing. We isolated 56 H. pylori strains from 133 patients, of which 73.2% carried cagA, and all were considered Western-type. Patients infected with cagA-positive strains had more severe histological scores than patients infected with cagA-negative strains. Among vacA s1 and m1 genotypes, the s1a (97.8%, 43/44) and m1c (28/30, 93.3%) genotypes were predominant. All strains containing s1 and m1 (30/56, 53.6%) also had i1, d1, and c1. In contrast, all strains containing the less-virulent genotypes s2 and m2 (12/56, 21.4%) also possessed i2, d2, and c2. Multivariate analysis indicated that subjects infected with vacA m1-genotype strains only had a significantly higher risk of antrum atrophy than patients infected with m2-genotype strains. Of the two main H. pylori populations in this study, hpAsia2 strains were associated with higher activity and inflammation in the antrum compared to hpEurope strains; however, only vacA s1m1i1d1c1 strains, independent of population type, were significantly associated with inflammation in the antrum, unlike the s2m2i2d2c2 genotype. In conclusion, Bangladeshi strains were divided into two main populations of different genotypes. The low incidence of gastric cancer in Bangladesh might be attributable to the high proportion of less-virulent genotypes, which may be a better predictor of gastric cancer risk than the ancestral origin of the H. pylori strains. Finally, the vacA m region may be a better virulence marker than other regions.

Helicobacter pylori vacA genotype is a predominant determinant of immune response to Helicobacter pylori CagA

AIM

To evaluate the frequency of Helicobacter pylori (H. pylori) CagA antibodies in H. pylori infected subjects and to identify potential histopathological and bacterial factors related to H. pylori CagA-immune response.

METHODS

Systematic data to H. pylori isolates, blood samples, gastric biopsies for histological and molecular analyses were available from 99 prospectively recruited subjects. Serological profile (anti-H. pylori, anti-CagA) was correlated with H. pylori isolates (cagA, EPIYA, vacA s/m genotype), histology (Sydney classification) and mucosal interleukin-8 (IL-8) mRNA and protein expression. Selected H. pylori strains were assessed for H. pylori CagA protein expression and IL-8 induction in co-cultivation model with AGS cells.

RESULTS

Thirty point three percent of microbiologically confirmed H. pylori infected patients were seropositive for CagA. Majority of H. pylori isolates were cagA gene positive (93.9%) with following vacA polymorphisms: 42.4% vacA s1m1, 23.2% s1m2 and 34.3% s2m2. Anti-CagA-IgG seropositivity was strongly associated with atrophic gastritis, increased mucosal inflammation according to the Sydney score, IL-8 and cagA mRNA expression. VacA s and m polymorphisms were the major determinants for positive (vacA s1m1) or negative (vacA s2m2) anti-CagA serological immune response, which also correlated with the in vitro inflammatory potential in AGS cells. In vitro co-cultivation of representative H. pylori strains with AGS cells confirmed functional CagA translocation, which showed only partial correlation with CagA seropositivity in patients, supporting vacA as major co-determinant of the immune response.

CONCLUSION

Serological immune response to H. pylori cagA+ strain in H. pylori infected patients is strongly associated with vacA polymorphism, suggesting the crucial role of bacterial factors in immune and clinical phenotype of the infection.

The Human Stomach in Health and Disease: Infection Strategies by Helicobacter pylori

Helicobacter pylori is a bacterial pathogen which commonly colonizes the human gastric mucosa from early childhood and persists throughout life. In the vast majority of cases, the infection is asymptomatic. H. pylori is the leading cause of peptic ulcer disease and gastric cancer, however, and these outcomes occur in 10-15% of those infected. Gastric adenocarcinoma is the third most common cause of cancer-associated death, and peptic ulcer disease is a significant cause of morbidity. Disease risk is related to the interplay of numerous bacterial host and environmental factors, many of which influence chronic inflammation and damage to the gastric mucosa. This chapter summarizes what is known about health and disease in H. pylori infection, and highlights the need for additional research in this area.

Helicobacter pylori Strains and Gastric MALT Lymphoma

This article summarizes the main findings concerning Helicobacter pylori associated with gastric MALT lymphoma (GML). Considered together, GML strains based on their virulence factor profile appear to be less virulent than those associated with peptic ulcers or gastric adenocarcinoma. A particular Lewis antigen profile has been identified in GML strains and could represent an alternative adaptive mechanism to escape the host immune response thereby allowing continuous antigenic stimulation of infiltrating lymphocytes.