Chemokine receptor 5 expression in gastric mucosa of Helicobacter pylori-infected and noninfected children

The important role played by chemokines influence the clinical outcome of Helicobacter pylori infection

The extended infection with Helicobacter pylori (H. pylori), one of the most frequent infectious agents in humans, may cause gastritis, peptic ulcers, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer. During H. pylori infection, different kinds of inflammatory cells such as dendritic cells, macrophages, neutrophils, mast cells, eosinophils, T cells and B cells are accumulated into the stomach. The interactions between chemokines and their respective receptors recruit particular types of the leukocytes that ultimately determine the nature of immune response and therefore, have a main influence on the consequence of infection. The suitable production of chemokines especially in the early stages of H. pylori infection shapes appropriate immune responses that contribute to the H. pylori elimination. The unbalanced expression of the chemokines can contribute in the induction of inappropriate responses that result in the tissue damage or malignancy. Thus, chemokines and their receptors may be promising potential targets for designing the therapeutic strategies against various types H. pylori-related gastrointestinal disorders. In this review, a comprehensive explanation regarding the roles played by chemokines in H. pylori-mediated peptic ulcer, gastritis and gastric malignancies was provided while presenting the potential utilization of these chemoattractants as therapeutic elements.

Mechanisms of Inflammasome Signaling, microRNA Induction and Resolution of Inflammation by Helicobacter pylori

Inflammasome-controlled transcription and subsequent cleavage-mediated activation of mature IL-1β and IL-18 cytokines exemplify a crucial innate immune mechanism to combat intruding pathogens. Helicobacter pylori represents a predominant persistent infection in humans, affecting approximately half of the population worldwide, and is associated with the development of chronic gastritis, peptic ulcer disease, and gastric cancer. Studies in knockout mice have demonstrated that the pro-inflammatory cytokine IL-1β plays a central role in gastric tumorigenesis. Infection by H. pylori was recently reported to stimulate the inflammasome both in cells of the mouse and human immune systems. Using mouse models and in vitro cultured cell systems, the bacterial pathogenicity factors and molecular mechanisms of inflammasome activation have been analyzed. On the one hand, it appears that H. pylori-stimulated IL-1β production is triggered by engagement of the immune receptors TLR2 and NLRP3, and caspase-1. On the other hand, microRNA hsa-miR-223-3p is induced by the bacteria, which controls the expression of NLRP3. This regulating effect by H. pylori on microRNA expression was also described for more than 60 additionally identified microRNAs, indicating a prominent role for inflammatory and other responses. Besides TLR2, TLR9 becomes activated by H. pylori DNA and further TLR10 stimulated by the bacteria induce the secretion of IL-8 and TNF, respectively. Interestingly, TLR-dependent pathways can accelerate both pro- and anti-inflammatory responses during H. pylori infection. Balancing from a pro-inflammation to anti-inflammation phenotype results in a reduction in immune attack, allowing H. pylori to persistently colonize and to survive in the gastric niche. In this chapter, we will pinpoint the role of H. pylori in TLR- and NLRP3 inflammasome-dependent signaling together with the differential functions of pro- and anti-inflammatory cytokines. Moreover, the impact of microRNAs on H. pylori-host interaction will be discussed, and its role in resolution of infection versus chronic infection, as well as in gastric disease development.

Importance of the CCR5-CCL5 axis for mucosal Trypanosoma cruzi protection and B cell activation

Trypanosoma cruzi is an intracellular parasite and the causative agent of Chagas disease. Previous work has shown that the chemokine receptor CCR5 plays a role in systemic T. cruzi protection. We evaluated the importance of CCR5 and CCL5 for mucosal protection against natural oral and conjunctival T. cruzi challenges. T. cruzi-immune CCR5(-/-) and wild-type C57BL/6 mice were generated by repeated infectious challenges with T. cruzi. CCR5(-/-) and wild-type mice developed equivalent levels of cellular, humoral, and protective mucosal responses. However, CCR5(-/-)-immune mice produced increased levels of CCL5 in protected gastric tissues, suggesting compensatory signaling through additional receptors. Neutralization of CCL5 in CCR5(-/-)-immune mice resulted in decreased mucosal inflammatory responses, reduced T. cruzi-specific Ab-secreting cells, and significantly less mucosal T. cruzi protection, confirming an important role for CCL5 in optimal immune control of T. cruzi replication at the point of initial mucosal invasion. To investigate further the mechanism responsible for mucosal protection mediated by CCL5-CCR5 signaling, we evaluated the effects of CCL5 on B cells. CCL5 enhanced proliferation and IgM secretion in highly purified B cells triggered by suboptimal doses of LPS. In addition, neutralization of endogenous CCL5 inhibited B cell proliferation and IgM secretion during stimulation of highly purified B cells, indicating that B cell production of CCL5 has important autocrine effects. These findings demonstrate direct effects of CCL5 on B cells, with significant implications for the development of mucosal adjuvants, and further suggest that CCL5 may be important as a general B cell coactivator.

Polymorphisms in chemokine and receptor genes and gastric cancer risk and survival in a high risk Polish population

OBJECTIVE

To examine if genetic variations in chemokine receptor and ligand genes are associated with gastric cancer risk and survival.

METHODS

The study included 298 cases and 417 controls from a population-based study of gastric cancer conducted in Warsaw, Poland in 1994-1996. We investigated seven single nucleotide polymorphisms in a chemokine ligand (CXCL12) and chemokine receptor (CCR2, CCR5, CX3CR1) genes and one frameshift deletion (CCR5) in blood leukocyte DNA in relation to gastric cancer risk and survival. Genotyping was conducted at the NCI Core Genotyping Facility. Odds ratios and 95% confidence intervals were computed using univariate and multivariate logistic regression models. Survival analysis was performed using Cox proportional hazards models.

RESULTS

Gastric cancer risk was not associated with single chemokine polymorphisms. A CCR5 haplotype that contained the common alleles of IVS1+151 G>T (rs2734648), IVS2+80 C>T (rs1800024) and minor allele of IVS1+246 A>G (rs1799987) was associated with a borderline significantly increased risk (OR = 1.5, 95% CI: 1.0?2.2). For gastric cancer cases, there was a greater risk of death for carriers of the minor alleles of CCR2 Ex2+241 G>A (rs1799864) (HR = 1.5, 95% CI: 1.1-2.1) and CCR5 IVS2+80 C>T (rs1800024) (HR = 1.5, 95% CI: 1.1-2.1). Carriers of the CCR5 minor allele of IVS1+151 G>T (rs2734648) had a decreased risk of death compared to homozygote carriers of the common allele (HR = 0.8, 95% CI: 0.6-1.0).

CONCLUSIONS

Our findings do not support an association between gastric cancer risk and single chemokine genetic variation. The observed associations between cancer risk and a CCR5 haplotype and between survival and polymorphisms in CCR2 and CCR5 need replication in future studies.

Pediatric Helicobacter pylori infection and circulating T-lymphocyte activation and differentiation

BACKGROUND

In this study, H. pylori-infected and noninfected children with gastritis were compared to a control group with respect to circulating CD4(+) and CD8(+) T lymphocytes expressing activation and differentiation markers. Additionally, the lymphocyte phenotypes of children with gastritis were correlated with the gastric inflammation scores.

MATERIALS AND METHODS

H. pylori infection status was assessed based on [¹³C]urea breath test, rapid urease test, and histology. Analysis of the lymphocyte surface molecule expression was carried out by triple-color flow cytometry.

RESULTS

The group of H. pylori-infected children showed an elevated proportion of peripheral B cells with CD19(low) , along with a twofold increase in the percentage of memory (CD45RO(+)) CD4(+) and CD8(+) T-cell subsets (p < .05). Moreover, a positive correlation between the age and the percentage of these subsets was seen (r = .38, p = .04 and r = .56, p < .01, respectively). Children with gastritis but without infection had a slightly increased percentage of CD8(+) T cells and CD56(+) NK cells, CD3(high) T cells and CD45RO(high) CD4(+) T-cell subsets (p < .05). Both H. pylori-infected and noninfected children with gastritis were characterized by an increased percentage of memory/effector CD4(+) T cells, the presence of NK cells with CD56(high), memory T-cell subset with CD4(high), and naive, memory, memory/effector, and effector T-cell subsets with CD8(high) (p < .05). Gastric inflammation scores correlated positively with the percentage of CD4(+) T lymphocytes in H. pylori-infected children (r = .42, p = .03). In noninfected children, gastric inflammation scores correlated positively with the percentage of B cells (r = .45, p = .04).

CONCLUSION

In H. pylori-negative children, gastritis was associated with an increased percentage of activated NK and T cells, and intermediate-differentiated peripheral blood CD4(+) T cells, which was more pronounced in H. pylori-positive children who also showed an increased B-cell response. However, increased inflammation was only associated with the elevation of CD4(+) T-cell percentage in H. pylori-positive children as well as B-cell percentage in H. pylori-negative children with gastritis.

Increased expression and cellular localization of lipocalin-type prostaglandin D synthase in Helicobacter pylori-induced gastritis

Immunological responses in the host can result in different disease outcomes of Helicobacter pylori-induced gastritis. Prostaglandin E2 derived from cyclooxygenase (COX) and prostaglandin E synthase contribute to gastric protection. Recently, prostaglandin D2 was shown to be involved in host immunity by chemotactic activity through chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), but its role in H. pylori-induced gastritis has not been clarified. We determined the expression levels of mRNAs for haematopoietic PGD synthase (H-PGDS) and lipocalin-type PGDS (L-PGDS), MIP-1 alpha, IFN-gamma, IL-4, and CDX2 in H. pylori-induced gastritis mucosa by quantitative RT-PCR. We found that L-PGDS was constitutively expressed in the epithelium of the glandular base. L-PGDS, but not H-PGDS, was induced on fibroblasts close to infiltrating cells in the H. pylori-infected gastric mucosa. These fibroblasts co-expressed COX-2. The level of L-PGDS mRNA expression decreased as gastritis became more severe. In most of the H. pylori-infected gastric mucosa, CCR5(+) cells had more actively infiltrated than had CRTH2(+) cells. However, the expression level of IFN-gamma was lower in the mucosa of the CRTH2(+) cells-dominantly infiltrating group than that of the less CRTH2-infiltrating group. Exogenously added PGD2 decreased the H. pylori-induced expression of IFN-gamma in peripheral blood mononuclear cells in vitro. The data suggest that PGD2 derived from the gastric mucosa and fibroblasts plays protective roles against inflammatory changes in H. pylori-induced gastritis.

Eradication of Helicobacter pylori can facilitate immune reconstitution in HIV-1-infected immunological non-responders

OBJECTIVE

A significant number of HIV-1 patients experience poor immune reconstitution despite long-term viral suppression with highly active antiretroviral therapy (immunological non-responders). The aims of the present study were to determine whether eradication of Helicobacter pylori could facilitate a better immune reconstitution in these patients.

METHODS

Forty-nine immunological non-responder HIV-1 patients were evaluated by (13)C-urea breath test (UBT) for the presence of active H. pylori infection. They were all asymptomatic. The UBT was positive in 26 (53%) of them. Eleven patients (group 1) were treated with a combination of omeprazole 20mg bid, amoxicillin 1g bid and clarithromycin 500mg bid for 14 consecutive days. Eight weeks later, successful eradication was proven by a repeat negative UBT in all 11 patients. The remaining 15 (group 2) refused the H. pylori eradication treatment. All 26 patients were followed for 24 months and evaluated for blood CD4 and CD8 cell counts and percentages and for plasma HIV-1 viral load.

RESULTS

At the time of H. pylori diagnosis and eradication (baseline), CD4 and CD8 cell counts were similar in both study groups. All 11 H. pylori eradicated patients (group 1) had a significant increase in CD4 cell count starting 3 months and peaking 12-18 months after H. pylori eradication. Thereafter, CD4 levels gradually declined. Nevertheless, 24 months after triple therapy it was significantly higher than prior to H. pylori eradication. Parallel reciprocal changes were observed in CD8 cell counts. There were no significant changes in either CD4 or CD8 cell counts in group 2 patients. None of the patients of group 1 demonstrated virological failure, while four (26.7%) group 2 patients experienced virological failure requiring change of highly active antiretroviral therapy (HAART) regimen.

CONCLUSION

Triple therapy for H. pylori eradication is associated with a significant, although possibly transient immune reconstitution in HAART-treated HIV-1 patients with viral suppression without immunological response.

Global analysis of the human gastric epithelial transcriptome altered by Helicobacter pylori eradication in vivo

OBJECTIVE

The transcriptional profile of gastric epithelial cell lines cocultured with Helicobacter pylori and the global gene expression of whole gastric mucosa has been described previously. We aimed to overcome limitations of previous studies by determining the effects of H pylori eradication on the transcriptome of purified human gastric epithelium using each patient as their own control.

DESIGN

Laser capture microdissection (LCM) was used to extract mRNA from paraffin-embedded antral epithelium from 10 patients with peptic ulcer disease, before and after H pylori eradication. mRNA was reverse transcribed and applied on to Affymetrix cDNA microarray chips customised for formalin-fixed tissue. Differentially expressed genes were identified and a subset validated by real-time polymerase chain reaction (PCR).

RESULTS

A total of 13 817 transcripts decreased and 9680 increased after H pylori eradication. Applying cut-off criteria (p<0.02, fold-change threshold 2.5) reduced the sample to 98 differentially expressed genes. Genes detected included those previously implicated in H pylori pathophysiology such as interleukin 8, chemokine ligand 3, beta defensin and somatostatin, as well as novel genes such as GDDR (TFIZ1), chemokine receptors 7 and 8, and gastrokine.

CONCLUSIONS

LCM of archival specimens has enabled the identification of gastric epithelial genes whose expression is considerably altered after H pylori eradication. This study has confirmed the presence of genes previously implicated in the pathogenesis of H pylori, as well as highlighted novel candidates for further investigation.

Increase of antigen-presenting cells in the gastric mucosa of Helicobacter pylori-infected children

BACKGROUND

Infection with Helicobacter pylori leads to an increase of T cells in the gastric mucosa of children. In contrast to peripheral blood, where monocytes are the most abundant antigen-presenting cells, CD14+ macrophages are very rare in infected gastric mucosa. We postulated that other types of antigen-presenting cells must be present in infected gastric mucosa.

MATERIAL AND METHODS

Antral biopsies were obtained from 56 children. The cellular expression of major histocompatibility complex (MHC) class II molecules, CD1a/b, and CD23, which are involved in antigen presentation were analyzed by immunohistochemistry. In addition, T cells (CD4, CD8, CD25, and gamma/delta-TCR), B cells (anti-IgM), macrophages (CD14) and granulocytes (CD15) were quantified.

RESULTS

Twenty-eight children were H. pylori-infected. Thirteen children were healthy, 15 had other gastric pathologies. T cells (p<.0001), B cells (p<.0001), CD23+ (p<.0001), and CD1a/b+ (p<.005) cells were significantly increased in the lamina propria of H. pylori-infected children, whereas macrophages were rare without significant differences among the groups. Within the epithelium, CD8+ T lymphocytes predominated clearly over CD4+ cells. H. pylori-negative children had only few MHC class II-positive cells within the gastric epithelium, whereas MHC class II antigens were strongly expressed on epithelial cells (p<.0001) of all H. pylori-infected children.

CONCLUSION

Helicobacter pylori infection leads to an enhanced expression of antigen-presenting molecules together with a parallel rise of T cells in the lamina propria. This may represent an effort of the immune system to optimize local immune responses against H. pylori. We speculate that the epithelium participates in the initiation of a local immune response against H. pylori.

Inhibition of primary human T cell proliferation by Helicobacter pylori vacuolating toxin (VacA) is independent of VacA effects on IL-2 secretion

Recent evidence indicates that the secreted Helicobacter pylori vacuolating toxin (VacA) inhibits the activation of T cells. VacA blocks IL-2 secretion in transformed T cell lines by suppressing the activation of nuclear factor of activated T cells (NFAT). In this study, we investigated the effects of VacA on primary human CD4(+) T cells. VacA inhibited the proliferation of primary human T cells activated through the T cell receptor (TCR) and CD28. VacA-treated Jurkat T cells secreted markedly diminished levels of IL-2 compared with untreated cells, whereas VacA-treated primary human T cells continued to secrete high levels of IL-2. Further experiments indicated that the VacA-induced inhibition of primary human T cell proliferation was not attributable to VacA effects on NFAT activation or IL-2 secretion. We show here that VacA suppresses IL-2-induced cell-cycle progression and proliferation of primary human T cells without affecting IL-2-dependent survival. Through the analysis of a panel of mutant VacA proteins, we demonstrate that VacA-mediated inhibition of T cell proliferation requires an intact N-terminal hydrophobic region necessary for the formation of anion-selective membrane channels. Remarkably, we demonstrate that one of these mutant VacA proteins [VacA-Delta(6-27)] abrogates the immunosuppressive actions of wild-type VacA in a dominant-negative fashion. We suggest that VacA may inhibit the clonal expansion of T cells that have already been activated by H. pylori antigens, thereby allowing H. pylori to evade the adaptive immune response and establish chronic infection.

Intensity of inflammation, density of colonization and interleukin-8 response in the gastric mucosa of children infected with Helicobacter pylori

BACKGROUND

Few reports exist on inflammation and interleukin (IL)-8 response in H. pylori-infected children. The aim of this study was to determine the intensity of inflammation, density of colonization and magnitude of IL-8 response in children with and without H. pylori infection.

MATERIALS AND METHODS

We studied 45 children with dyspeptic symptoms, 21 infected with H. pylori and 24 without infection. Antrum and corpus gastric biopsies were obtained and studied for H. pylori infection with an immunofluorescence technique and for IL-8 with an immunohistochemical assay. Biopsy specimens were stained with hematoxilin and eosin and gastritis was graded according to the Sydney system. The magnitudes of the IL-8 response and H. pylori colonization were estimated microscopically with image analyzer software.

RESULTS

In H. pylori-infected children, mild mono-nuclear cell infiltration was found in 50%, and no neutrophils in 40% of cases. In the antrum but not in the corpus, the intensity of colonization correlated with neutrophil and mononuclear cell infiltration. The IL-8 response was significantly higher in the antrum (p <.05) and corpus (p <.02) of infected children, and was localized mainly in the surface and crypts of the epithelium. No correlation was found between the magnitude of the IL-8 response and the infiltration of either neutrophil or mononuclear cells.

CONCLUSIONS

In H. pylori-infected children, poor mononuclear and neutrophil infiltration was observed. Infection was associated with a higher IL-8 response by gastric epithelial cells. The density of colonization but not the IL-8 response correlated with neutrophil cell infiltration.