Expression and purification of epitope vaccine against four virulence proteins from Helicobacter pylori and construction of label-free electrochemical immunosensor

The epitope vaccine against four virulence proteins (FVpE) from Helicobacter pylori (H. pylori) was expressed and purified. Western blot and Enzyme-linked Immunosorbent Assays (ELISA) were used to identify and investigate the immunoreactivity of FVpE protein. The immune-sensing platform based on titanium carbide/colloidal gold nanoparticles@carbon nanofiber/ionic liquid composites electrode was constructed for immobilizing FVpE. Electrochemical impedance spectroscopy (EIS) was used to study the electrochemical properties of the modified electrodes. The relevant influenced factors were optimized including pH value, antigen concentration, and incubating time. The prepared H. pylori label-free electrochemical immunosensor was used for antibody detection using differential pulse voltammetry (DPV). Under the optimal experimental conditions, the linear ranges of H. pylori antibodies, including anti-H. pylori, cytotoxin-associated gene A (CagA), vacuolating cytotoxin-associated gene A (VacA), and urease A (UreA), were all 0.1-5 ng mL-1, except urease B (UreB, 0.1-4.5 ng mL-1). The selectivity study showed that other antibodies had little influence on the detection of H. pylori antibodies. The immunosensor could be used to detect serum samples, and the recoveries were in the range of 68.5%-100.5%.

A novel role for Helicobacter pylori cytotoxin-associated gene A in negative regulation of autophagy in human gastric cells

BACKGROUND

Autophagy plays an important role in carcinogenesis and tumor progression in many cancers, including gastric cancer. Cytotoxin-associated gene A (CagA) is a well-known virulent factor in Helicobacter pylori (H. pylori) infection that plays a critical role in gastric inflammation and gastric cancer development. However, its role in autophagy during these processes remains unclear. Therefore, we aimed to clarify the role of CagA in autophagy in CagA-related inflammation.

METHODS

We evaluated the autophagic index of AGS cells infected with wild-type cagA-positive H. pylori (Hp-WT) and cagA-knockout H. pylori (Hp-ΔcagA) and rat gastric mucosal (RGM1) cells transfected with CagA genes. To identify the mechanisms underlying the down regulation of autophagy in AGS cells infected with H. pylori, we evaluated protein and mRNA expression levels of autophagy core proteins using western blotting and quantitative reverse transcription-polymerase chain reaction (RT-PCR). To determine whether autophagy induced the expression of the pro-inflammatory mediator, cyclooxygenase-2 (COX-2), we evaluated COX-2 expression in AGS cells treated with an autophagy inducer and inhibitor and infected with H. pylori. In addition, we evaluated whether COX-2 protein expression in AGS cells influenced beclin-1 (BECN1) expression with si-RNA transfection when infected with H. pylori.

RESULTS

Autophagic flux assay using chloroquine showed that autophagy in AGS cells was significantly suppressed after H. pylori infection. The autophagic index of AGS cells infected with Hp-WT was decreased significantly when compared with that in AGS cells infected with Hp-ΔcagA. The autophagic index of RGM1 cells transfected with CagA was lower, suggesting that CagA inhibits autophagy. In addition, BECN1 expression levels in AGS cells infected with Hp-WT were reduced compared to those in AGS cells infected with Hp-ΔcagA. Furthermore, COX-2 expression in AGS cells infected with H. pylori was controlled in an autophagy-dependent manner. When AGS cells were transfected with small interfering RNA specific for BECN1 and infected with Hp-WT and Hp-ΔcagA, COX-2 was upregulated significantly in cells infected with Hp-ΔcagA.

CONCLUSIONS

In conclusion, the H. pylori CagA protein negatively regulated autophagy by downregulating BECN1. CagA-induced autophagy inhibition may be a causative factor in promoting pro-inflammatory mediator production in human gastric epithelial cells.

Polymorphism in autophagy-related genes LRP1 and CAPZA1 may promote gastric mucosal atrophy

BACKGROUND

Helicobacter pylori secretes cytotoxin-associated gene A (CagA) into the gastric epithelium, causing gastric mucosal atrophy (GMA) and gastric cancer. In contrast, host cells degrade CagA via autophagy. However, the association between polymorphisms in autophagy-related genes and GMA must be fully elucidated.

RESULTS

We evaluated the association between single nucleotide polymorphisms (SNPs) in autophagy-related genes (low-density lipoprotein receptor-related protein 1, LRP1; capping actin protein of muscle Z-line alpha subunit 1, CAPAZ1; and lysosomal-associated membrane protein 1, LAMP1) and GMA in 200 H. pylori-positive individuals. The frequency of the T/T genotype at rs1800137 in LRP1 was significantly lower in the GMA group than in the non-GMA group (p = 0.018, odds ratio [OR] = 0.188). The frequencies of the G/A or A/A genotype at rs4423118 and T/A or A/A genotype at rs58618380 of CAPAZ1 in the GMA group were significantly higher than those in the non-GMA group (p = 0.029 and p = 0.027, respectively). Multivariate analysis revealed that C/C or C/T genotype at rs1800137, T/A or A/A genotype at rs58618380, and age were independent risk factors for GMA (p = 0.038, p = 0.023, and p = 0.006, respectively). Furthermore, individuals with the rs1800137 C/C or C/T genotype of LRP1 had a 5.3-fold higher susceptibility to GMA. These genetic tests may provide future directions for precision medicine for individuals more likely to develop GMA.

CONCLUSION

LRP1 and CAPZA1 polymorphisms may be associated with the development of GMA.

Impact of Helicobacter pylori virulence markers on clinical outcomes in adult populations

BACKGROUND

In recent years, associations between specific virulence markers of Helicobacter pylori (H. pylori) and gastrointestinal disorders have been suggested.

AIM

To investigate the presence of virulence factors including vacuolating cytotoxin A genotypes (s1m1, s1m2, s2m1, and s2m2), cytotoxin-associated gene A (CagA), and urease activity in H. pylori strains isolated from Arab and Jewish populations in northern Israel and to assess associations between these factors and patients’ demographics and clinical outcomes.

METHODS

Patients (n = 108) who underwent gastroscopy at the Baruch Padeh Medical Center, Poriya due to symptomatic gastroduodenal pathologies as part of H. pylori diagnosis were enrolled in the study. Gastric biopsy specimens were collected from the antrum of the stomach. Clinical condition was assessed by clinical pathology tests. Bacteria were isolated on modified BD Helicobacter Agar (BD Diagnostics, Sparks, MD, United States). Bacterial DNA was extracted, and PCR was performed to detect CagA and vacuolating cytotoxin A genes. Urease activity was assessed using a rapid urease test.

RESULTS

A significant correlation was found between disease severity and patient ethnicity (P = 0.002). A significant correlation was found between CagA presence and the s1m1 genotype (P = 0.02), which is considered the most virulent genotype. Further, a higher level of urease activity was associated with isolates originating from the Jewish population. Moreover, higher urease activity levels were measured among CagA-/s1m1 and CagA-/s2m2 isolates.

CONCLUSION

Our study highlights the importance of incorporating molecular methods for detection of virulence markers of H. pylori in order to tailor optimal treatments for each patient. Further investigation should be performed regarding associations between H. pylori virulence factors and ethnicity.

Helicobacters and cancer, not only gastric cancer?

The Helicobacter genus actually comprises 46 validly published species divided into two main clades: gastric and enterohepatic Helicobacters. These bacteria colonize alternative sites of the digestive system in animals and humans, and contribute to inflammation and cancers. In humans, Helicobacter infection is mainly related to H. pylori, a gastric pathogen infecting more than half of the world's population, leading to chronic inflammation of the gastric mucosa that can evolve into two types of gastric cancers: gastric adenocarcinomas and gastric MALT lymphoma. In addition, H. pylori but also non-H. pylori Helicobacter infection has been associated with many extra-gastric malignancies. This review focuses on H. pylori and its role in gastric cancers and extra-gastric diseases, as well as malignancies induced by non-H. pylori Helicobacters. Their different virulence factors and their involvement in carcinogenesis is discussed. This review highlights the importance of both gastric and enterohepatic Helicobacters in gastrointestinal and liver cancers.

Molecular Mechanism of Helicobacter pylori-Induced Gastric Cancer

Introduction

Various types of cancers threaten human life. The role of bacteria in causing cancer is controversial, but it has been determined that the Helicobacter pylori infection is one of the identified risk factors for gastric cancer. Helicobacter pylori infection is highly prevalent, and about half of the world^,s population is infected with it.

Objective

The aim of this study was the role of Helicobacter pylori in the development of gastric cancer.

Method

We obtained information from previously published articles.

Results and Conclusion

The bacterium has various virulence factors, including cytotoxin- associated gene A, vacuolating cytotoxin A, and the different outer membrane proteins that cause cancer by different mechanisms. These virulence factors activate cell signaling pathways such as PI3-kinase/Akt, JAK/STAT and Ras, Raf, and ERK signaling that control cell proliferation. Uncontrolled proliferation can lead to cancer.

Helicobacter pylori and gastric cardia cancer: What do we know about their relationship?

The incidence of gastric cardia cancer is increasing around the world. Since the discovery of Helicobacter pylori (H. pylori), numerous studies have proved that it is a causative factor for many kinds of digestive system tumors. Although the literature on gastric cardia cancer and H. pylori is not scarce, there are still many controversies on the relationship between gastric cardia cancer and H. pylori. Many Western research results showed that there was a negative or no correlation between H. pylori infection and gastric cardia cancer, but in several studies in Asian countries, such as China, H. pylori was demonstrated to be a risk factor for gastric cardia cancer. Therefore, we intended to analyze the related studies to find out the relationship between H. pylori and gastric cardia cancer and find out the causes of the above controversies. We also conducted a meta-analysis of the relationship between cagA positive expression of H. pylori and gastric cardia cancer, to find out whether there is an effect between those two. The primary purpose of this paper was to explore the relationship between gastric cardia cancer and H. pylori. Through analysis, the study showed the reasons for the controversies mentioned above: (1) Geographical factors could affect the relationship between H. pylori and gastric cardia cancer; (2) The definition of gastric cardia cancer in various studies is inconsistent. The result of a meta-analysis about the relationship between H. pylori virulence factor cagA and gastric cardia cancer showed that there was no relationship between these two.

Relationship between Helicobacter pylori cagA Genotypes Infection and IL-10 and TGFβ1 Genes' Expression in Gastric Epithelial Cells

Background

The correlation of Helicobacter pylori infection with gastritis, peptic ulcer, and gastric cancer has been proven. The aim of this study was to determine the effects of cagA ⁺ and cagA ^- genotypes of H. pylori on genes expression of interleukin (IL) -10 and tumor growth factor (TGF) β1 in gastric epithelial cells of patients with gastritis and H. pylori infection.

Methods

In all, 45 gastric biopsy samples were collected from patients with gastritis and H. pylori infection admitted to Tohid Hospital in Sanandaj city. Status of urease and cagA genes of H. pylori were directly determined from the biopsy samples using polymerase chain reaction (PCR) method. Expression of IL-10 and TGF-β1 genes in gastric epithelial cells of patients with gastritis and cagA ⁺ and cagA^- genotypes of H. pylori infection was serveyed using real-time PCR method.

Results

Overall, 25 samples had infection with H. pylori cagA ⁺ and 20 with cagA ^- genotypes. This study showed that there is a positive correlation between cagA ^- genotypes of H. pylori and increasing of IL-10 gene expression in gastric epithelial cells of patients with gastritis (P = 0.001).

Conclusions

Level of gene expression of IL-10 as an anti-inflammatory cytokine in gastric epithelial cells of patients with H. pylori infection is connected to cagA- genotypes.

Helicobacter pylori CagA induced interleukin-8 secretion in gastric epithelial cells

AIM

Since, contradictory data have been reported about the effect of diverse variants of H. pylori virulence factors on IL-8 induction, we aimed to analyze the effect of this diversity on levels of IL-8 secretion in AGS cell line.

BACKGROUND

Helicobacter pylori colonizes the human stomach and induces the activation of inflammatory cytokines, including interleukin (IL)-8, in the gastric mucosa. This induction promotes neutrophil and monocyte recruitment that causes gastric tissue damage.

METHODS

To determine whether different strains of H. pylori and their CagA variants have possible roles on IL-8 induction, polarized AGS cell line was infected with CagA+ H. pylori strains carrying different EPIYA motifs (ABCCC and ABC) and CagA- strain for 24 hours. Difference in stimulation of IL-8 was measured by ELISA.

RESULTS

IL-8 secretion was elevated in the treated cells with CagA encoding strains compared with the negative one. Furthermore, a noticeably increased level of IL-8 induction was measured by the CagA-EPIYA type ABCCC encoding strain in compare to that carried EPIYA type ABC.

CONCLUSION

Results of this study provide new evidence about different effects of H. pylori strains and possible roles of their CagA variants on IL-8 induction. It seems that not only carriage of cagA and its expression, but also diversity in EPIYA motif be involved in IL-8 induction in the gastric epithelial cells.

Association of endothelial dysfunction and cytotoxin-associated gene A-positive Helicobacter pylori in patients with cardiac syndrome X

Background

Existence of coronary endothelial dysfunction has been demonstrated in patients with cardiac syndrome X (CSX). In addition, Helicobacter pylorus (H. pylori) has been associated with CSX. We aimed to assess the possible association of endothelial dysfunction and cytotoxin-associated gene A-positive H. pylori (CagA+) infection in CSX patients.

Methods

Fifty-six patients with CSX (23 male/33 female; age: 51.25 ± 8.86 years) who were anti-H. pylori IgG-positive [H. pylori(+)] and 24 CSX patients (7 male/17 female; age: 52.79 ± 9.88 years) who were H. pylori(−) were included. Also, anti-H. pylori IgG-positive patients were determined by the presence of IgG antibody to CagA. Levels of endothelin-1 (ET-1), E-selectin and intercellular adhesion molecule-1 (ICAM-1) were measured.

Results

Endothelial dysfunction biomarkers were higher in H. pylori(+) than in H. pylori(−) patients (ET-1: 54.60 ± 25.39 vs. 42.59 ± 18.37 pg/ml, p = 0.04; E-selectin: 42.68 ± 14.26 vs. 31.72 ± 8.26 ng/ml, p = 0.001; ICAM-1: 339.68 ± 135.8 vs. 266.51 ± 125.1 ng/ml, p = 0.02). Among H. pylori(+) subjects, 28 cases were CagA(+) and 28 cases were CagA(−). There were significant differences in measured levels of E-selectin between CagA(+) and CagA(−) groups (48.00 ± 16.37 vs. 37.37 ± 9.37 ng/ml, p = 0.004). For ET-1 and ICAM-1 levels, the difference between CagA(+) and CagA(−) was insignificant (p = 0.174 and p = 0.07, respectively).

Conclusion

High levels of endothelial dysfunction biomarkers are found in CSX patients with anti-CagA(+). These findings suggest the infection with CagA(+) H. pylori strain may play a role as a risk factor in development of CSX through provocation of endothelial dysfunction. Therefore, a long term follow up to investigate the outcomes of these patients is proposed.

Tight junction disruption: Helicobacter pylori and dysregulation of the gastric mucosal barrier

Long-term chronic infection with Helicobacter pylori (H. pylori) is a risk factor for gastric cancer development. In the multi-step process that leads to gastric cancer, tight junction dysfunction is thought to occur and serve as a risk factor by permitting the permeation of luminal contents across an otherwise tight mucosa. Mechanisms that regulate tight junction function and structure in the normal stomach, or dysfunction in the infected stomach, however, are largely unknown. Although conventional tight junction components are expressed in gastric epithelial cells, claudins regulate paracellular permeability and are likely the target of inflammation or H. pylori itself. There are 27 different claudin molecules, each with unique properties that render the mucosa an intact barrier that is permselective in a way that is consistent with cell physiology. Understanding the architecture of tight junctions in the normal stomach and then changes that occur during infection is important but challenging, because most of the reports that catalog claudin expression in gastric cancer pathogenesis are contradictory. Furthermore, the role of H. pylori virulence factors, such as cytotoxin-associated gene A and vacoulating cytotoxin, in regulating tight junction dysfunction during infection is inconsistent in different gastric cell lines and in vivo, likely because non-gastric epithelial cell cultures were initially used to unravel the details of their effects on the stomach. Hampering further study, as well, is the relative lack of cultured cell models that have tight junction claudins that are consistent with native tissues. This summary will review the current state of knowledge about gastric tight junctions, normally and in H. pylori infection, and make predictions about the consequences of claudin reorganization during H. pylori infection.

Repressed TGF-β signaling through CagA-Smad3 interaction as pathogenic mechanisms of Helicobacter pylori-associated gastritis

Helicobacter pylori (H. pylori) infection causes chronic gastric inflammation, peptic ulceration, and gastric carcinogenesis, in which H. pylori cytotoxin-associated gene A (CagA) plays major pathogenic action. Since transforming growth factor-β (TGF-β) and its signaling also are principally implicated in either modulating gastric mucosal inflammatory responses or causing carcinogenesis and are attenuated after H. pylori infection, we hypothesized that dysregulated Smad signaling and repressed TGF-β might be core pathogenic mechanism for H. pylori-associated gastritis or carcinogenesis. Until now, no precise underlying mechanism how deranged TGF-β signaling developed after H. pylori infection relevant to various clinical manifestations remains unclear. In this study, we examined the molecular mechanism about the inhibition of TGF-β signaling by H. pylori CagA protein. H. pylori CagA significantly suppressed TGF-β/Smad transcriptional responses through critical inhibition of Smad3, though CagA interacted constitutively with Smad2, Smad3, and Smad4. CagA inhibited TGF-β-induced suppression of proinflammatory chemokines, such as IL-8, CXCL1 and CXCL3, as well as TGF-β-induced transcription of target genes. In conclusion, repressed TGF-β signaling associated with CagA-positive H. pylori infection could be an important determinant for the outcome of H. pylori infection. Therefore, TGF-β signaling is one of the important determinants to avoid from H. pylori CagA pathogenicity.

Role of Helicobacter pylori virulence factor cytotoxin-associated gene A in gastric mucosa-associated lymphoid tissue lymphoma

Helicobacter pylori (H. pylori) infection might initiate and contribute to the progression of lymphoma from gastric mucosa-associated lymphoid tissue (MALT). Increasing evidence shows that eradication of H. pylori with antibiotic therapy can lead to regression of gastric MALT lymphoma and can result in a 10-year sustained remission. The eradication of H. pylori is the standard care for patients with gastric MALT lymphoma. Cytotoxin-associated gene A (CagA) protein, one of the most extensively studied H. pylori virulence factors, is strongly associated with the gastric MALT lymphoma. CagA possesses polymorphisms according to its C-terminal structure and displays different functions among areas and races. After being translocated into B lymphocytes via type IV secretion system, CagA deregulates intracellular signaling pathways in both tyrosine phosphorylation-dependent and -independent manners and/or some other pathways, and thereby promotes lymphomagenesis. A variety of proteins including p53 and protein tyrosine phosphatases-2 are involved in the malignant transformation induced by CagA. Mucosal inflammation is the foundational mechanism underlying the occurrence and development of gastric MALT lymphoma.

In silico experiment with an-antigen-toll like receptor-5 agonist fusion construct for immunogenic application to Helicobacter pylori

BACKGROUNDS

Helicobacter pylori colonize the gastric mucosa of half of the world's population. Although it is classified as a definitive type I carcinogen by World Health Organization, there is no effective vaccine against this bacterium. H. pylori evade the host immune response by avoiding toll-like detection, such as detection via toll-like receptor-5 (TLR-5). Thus, a chimeric construct consisting of selected epitopes from virulence factors that is incorporated into a TLR-5 ligand (Pseudomonas flagellin) could result in more potent innate and adaptive immune responses.

MATERIALS AND METHODS

Based on the histocompatibility antigens of BALB/c mice, in silico techniques were used to select several fragments from H. pylori virulence factors with a high density of B- and T-cell epitopes.

RESULTS

These segments consist of cytotoxin-associated geneA (residue 162-283), neutrophil activating protein (residue 30-135) and outer inflammatory protein A (residue 155-268). The secondary and tertiary structure of the chimeric constructs and other bioinformatics analyses such as stability, solubility, and antigenicity were performed. The chimeric construct containing antigenic segments of H. pylori proteins was fused with the D3 domain of Pseudomonas flagellin. This recombinant chimeric gene was optimized for expression in Escherichia coli. The in silico results showed that the conserved C- and N-terminal domains of flagellin and the antigenicity of selected fragments were retained.

DISCUSSION

In silico analysis showed that Pseudomonas flagellin is a suitable platform for incorporation of an antigenic construct from H. pylori. This strategy may be an effective tool for the control of H. pylori and other persistent infections.

Diversity of cagA gene 3' terminal variable region and its corresponding protein in Helicobacter pylori

AIM: To study the diversity and structural characteristics of cagA (cytotoxin-associated gene A) gene 3' terminal variable region in Helicobacter pylori as well as their correlations with the outcome of H. pylori-related diseases.

METHODS: PCR products with positive H. pylori cagA were obtained from 20 cases and then sequenced by ExPASy-Translation software. Meanwhile, 3 to 6 cases of H. pylori 3' terminal variable region and amino acid sequence, collected from NCBI database in different countries, were comparatively analyzed.

RESULTS: The amino acid sequences were found with obvious regional characteristics, and could be classified into eastern-asian type and western type. Western-type aberrations occurred in some eastern-asian strains. Totally, 87.4% H. pylori stains contained 3 EPIYA motifs in series, and 8.2% strains had 4 or more EPIYA motifs. A new sequence containing 3 amino acids was found. There was no correlation between the numbers of EPIYA motifs in the amino acid sequences of cagA protein and the clinical outcomes.

CONCLUSION: There exists marked diversity in cagA gene and protein of H. pylori, which can be distinguished by the main sequences of H. pylori cagA 3' terminal variable region. The number of EPIYA motifs in cagA 3' terminal variable region is not correlated with the clinical outcomes of diseases.