Helicobacter pylori immune escape is mediated by dendritic cell-induced Treg skewing and Th17 suppression in mice

Mechanisms of persistence, innate immune activation and immunomodulation by the gastric pathogen Helicobacter pylori

The gastric bacterium Helicobacter pylori efficiently evades innate immune detection and persistently colonizes its human host. Understanding the genetic determinants that H. pylori uses to establish and maintain persistence, along with their cellular targets, is key to our understanding of the pathogenesis of this extraordinarily successful bacterial colonizer of the human stomach. This review highlights recent advances in elucidating innate immune recognition of H. pylori, its interactions with myeloid cells and the consequences that this very local infection has for immune responses at extragastric sites in models of allergy, autoimmunity and parasitic infection. The human-specific, gram-negative gastric colonizer and carcinogen H. pylori represents the prototype of a persistent bacterial pathogen. It is transmitted during early childhood, typically from mother to infant, and is believed to persist in its human host from the cradle to the grave. The tremendous success of H. pylori in infecting and colonizing half of the world's population, and in continuously accompanying humans since they migrated out of Africa over 60000 years ago, can largely be attributed to its ability to manipulate the host immune system to its own advantage, and to thereby ensure its own persistence and chronicity. In his final years as an active PI, Stanley Falkow increasingly recognized the need to understand bacterial persistence strategies as a prerequisite of understanding the pathogenesis of chronic bacterial infections, and, inspired in large part by Denise Monack's work on Salmonella persistence, many of our discussions at the time revolved around this topic. Multiple labs have since made important contributions to our understanding of innate immune detection of H. pylori, the types and polarization of adaptive immune responses that ensue, the ability of H. pylori to skew such immune responses to its advantage, and its ability to manipulate the host immune system with far-reaching, even systemic consequences. This review attempts to cover some of these topics, with a particular focus on the most recent contributions by researchers in the field.

Helicobacter pylori Reactivates Human Immunodeficiency Virus-1 in Latently Infected Monocytes with Increased Expression of IL-1β and CXCL8

Background

Helicobacter pylori are gram-negative bacteria, which colonize the human stomach. More than 50% of the world's population is infected by H. pylori. Based on the high prevalence of H. pylori, it is very likely that HIV and H. pylori infection may coexist. However, the molecular events that occur during HIV-H. pylori co-infection remain unclear. Latent HIV reservoirs are the major obstacle in HIV cure despite effective therapy. Here, we explored the effect of H. pylori stimulation on latently HIV-infected monocytic cell line U1.

Methods

High throughput RNA-Seq using Illumina platform was performed to analyse the change in transcriptome between unstimulated and H. pylori-stimulated latently HIV-infected U1 cells. Transcriptome analysis identified potential genes and pathways involved in the reversal of HIV latency using bioinformatic tools that were validated by real-time PCR.

Results

H. pylori stimulation increased the expression of HIV-1 Gag, both at transcription (p<0.001) and protein level. H. pylori stimulation also increased the expression of proinflammatory cytokines IL-1β, CXCL8 and CXCL10 (p<0.0001). Heat-killed H. pylori retained their ability to induce HIV transcription. RNA-Seq analysis revealed 197 significantly upregulated and 101 significantly downregulated genes in H. pylori-stimulated U1 cells. IL-1β and CXCL8 were found to be significantly upregulated using transcriptome analysis, which was consistent with real-time PCR data.

Conclusion

H. pylori reactivate HIV-1 in latently infected monocytes with the upregulation of IL-1β and CXCL8, which are prominent cytokines involved in the majority of inflammatory pathways. Our results warrant future in vivo studies elucidating the effect of H. pylori in HIV latency and pathogenesis.

The Binary Classification Of Chronic Diseases

Acute diseases start with an insult and end when insult disappears. If the trauma induces an immune reaction (which happens in most cases), this reaction must be terminated with some type of resolution mechanism, when the cause of the trauma ceases. Chronicity develops if insult is permanent or if the resolution mechanism is defective. Another way to reach disease chronicity is a positive feedback loop, whereby the immune reaction activates an internal, insult-like reaction. A distinction between chronic states characterized by a persistent, low suppressive effect and those characterized by a persistent, high suppressive effect of regulatory T cells (Treg), is proposed. This two-class division represents two ways to reach chronicity: (a) by maintaining inflammatory reaction long after insult disappears ("low Treg"), or (b) by suppressing inflammatory reaction prior to the disappearance of insult ("high Treg"). This two-class division may explain the strong association between certain pathogens and cancer, on one hand, and between several other pathogens and autoimmunity, on the other hand. The weak association between autoimmune diseases and HIV infection and the relatively weak association between autoimmune diseases and cancer may be elucidated as well. In addition, the model rationalizes why immune-modulating drugs, which are effective in cancer, are also effective in "high Treg" viral infections, while corticosteroids, which are generally effective in autoimmune diseases, are also effective in other "low Treg" diseases (such as asthma, atopic dermatitis, and "low Treg" infections) but are not effective in solid malignancies and "high Treg" infections. Moreover, the model expounds why certain bacteria inhibit tumor growth and why these very bacteria induce autoimmune diseases.

Selected commensal bacteria change profiles of Helicobacter pylori-induced T cells via dendritic cell modulation

BACKGROUND

The mechanisms of downregulation of protective immunity against Helicobacter pylori (Hp) infection strongly depend on dendritic cell (DC)-induced T-lymphocyte differentiation pattern. Lactic acid bacteria (LAB) strains can modulate Hp-induced immunoresponse by changes in DC activation profiles. Here, we want to find out if the LAB-pulsed DCs will change Hp-induced T-cell responsiveness patterns.

MATERIALS AND METHODS

The naive peripheral CD4⁺ T cells were co-cultured with Hp CagA + pulsed monocyte-derived DCs (DC/CD4⁺ T cell) in the presence/absence of the feces-derived probiotics: antagonistic or non-antagonistic to Hp (Lactobacillus rhamnosus 900, Lr, Lactobacillus paracasei 915, Lp, respectively), as assessed by the agar slab method. The regulatory T-cell (Treg) population was assessed by flow cytometry, and IFN-γ, IL-12p70, IL-10, and IL-17A levels were evaluated by ELISA method.

RESULTS

The Hp-pulsed DC/CD4⁺ T-cell co-cultures were characterized by high IL-10, decreased IL-12p70 and IFN-γ levels, and elevated Treg population. In contrast, Lr-pulsed DC/CD4⁺ T-cell co-cultures expressed low IL-10, high IL-12p70 and IFN-γ levels and declined Treg population; this responsiveness pattern was not changed by Hp. The responsiveness pattern of the Lp/Hp-pulsed DC/CD4⁺ T-cell co-cultures did not differ from those pulsed with Hp alone.

CONCLUSION

In contrast to Lp, Lr probiotic strain overcomes Hp-mediated immune profile in the DC/T-cell co-cultures toward Th1 pattern and limited generation of Tregs in vitro. Lr may therefore be used as a component of anti-Hp treatment.

Immunity and Vaccine Development Against Helicobacter pylori

Helicobacter pylori is a highly-adapted gastrointestinal pathogen of humans and the immunology of this chronic infection is extremely complex. Despite the availability of antibiotic therapy, the global incidence of H. pylori infection remains high, particularly in low to middle-income nations. Failure of therapy and the spread of antibiotic resistance among the bacteria are significant problems and provide impetus for the development of new therapies and vaccines to treat or prevent gastric ulcer, and gastric carcinoma. The expansion of knowledge on gastric conventional and regulatory T cell responses, and the role of T_H17 in chronic gastritis from studies in mouse models and patients have provided valuable insights into how gastritis is initiated and maintained. The development of human challenge models for testing candidate vaccines has meant a unique opportunity to study acute infection, but the field of vaccine development has not progressed as rapidly as anticipated. One clear lesson learned from previous studies is that we need a better understanding of the immune suppressive mechanisms in vivo to be able to design vaccine strategies. There is still an urgent need to identify practical surrogate markers of protection that could be deployed in future field vaccine trials. Important developments in our understanding of the chronic inflammatory response, progress and problems arising from human studies, and an outlook for the future of clinical vaccine trials will be discussed.

Immune Cell Signaling by Helicobacter pylori: Impact on Gastric Pathology

Helicobacter pylori represents a highly successful colonizer of the human stomach. Infections with this Gram-negative bacterium can persist lifelong, and although in the majority of cases colonization is asymptomatic, it can trigger pathologies ranging from chronic gastritis and peptic ulceration to gastric cancer. The interaction of the bacteria with the human host modulates immune responses in different ways to enable bacterial survival and persistence. H. pylori uses various pathogenicity-associated factors such as VacA, NapA, CGT, GGT, lipopolysaccharide, peptidoglycan, heptose 1,7-bisphosphate, ADP-heptose, cholesterol glucosides, urease and a type IV secretion system for controlling immune signaling and cellular functions. It appears that H. pylori manipulates multiple extracellular immune receptors such as integrin-β₂ (CD18), EGFR, CD74, CD300E, DC-SIGN, MINCLE, TRPM2, T-cell and Toll-like receptors as well as a number of intracellular receptors including NLRP3, NOD1, NOD2, TIFA and ALPK1. Consequently, downstream signaling pathways are hijacked, inducing tolerogenic dendritic cells, inhibiting effector T cell responses and changing the gastrointestinal microbiota. Here, we discuss in detail the interplay of bacterial factors with multiple immuno-regulatory cells and summarize the main immune evasion and persistence strategies employed by H. pylori.

Th17 Cells in Helicobacter pylori Infection: a Dichotomy of Help and Harm

Helicobacter pylori is a Gram-negative bacterium that infects the gastric epithelia of its human host. Everyone who is colonized with these pathogenic bacteria can develop gastric inflammation, termed gastritis. Additionally, a small proportion of colonized people develop more adverse outcomes, including gastric ulcer disease, gastric adenocarcinoma, or gastric mucosa-associated lymphoid tissue lymphoma. The development of these adverse outcomes is dependent on the establishment of a chronic inflammatory response. The development and control of this chronic inflammatory response are significantly impacted by CD4⁺ T helper cell activity. Noteworthy, T helper 17 (Th17) cells, a proinflammatory subset of CD4⁺ T cells, produce several proinflammatory cytokines that activate innate immune cell antimicrobial activity, drive a pathogenic immune response, regulate B cell responses, and participate in wound healing. Therefore, this review was written to take an intricate look at the involvement of Th17 cells and their affiliated cytokines (interleukin-17A [IL-17A], IL-17F, IL-21, IL-22, and IL-26) in regulating the immune response to H. pylori colonization and carcinogenesis.

Interleukin-21 (IL-21) Downregulates Dendritic Cell Cytokine Responses to Helicobacter pylori and Modulates T Lymphocyte IL-17A Expression in Peyer's Patches during Infection

Interleukin-21 (IL-21), a cytokine produced by many subsets of activated immune cells, is critical for driving inflammation in several models. Using Helicobacter pylori infection as a model for chronic mucosal infection, we previously published that IL-21 is required for the development of gastritis in response to infection. Concomitant with protection from chronic inflammation, H. pylori-infected IL-21^-/- mice exhibited limited Th1 and Th17 responses in their gastric mucosa. Here we report that H. pylori-infected IL-21^-/- mice express significantly higher levels of IL-17A than H. pylori-infected wild-type (WT) mice in the Peyer's patches and mesenteric lymph nodes. This led us to hypothesize that IL-21 may indirectly regulate H. pylori-specific T cell responses by controlling dendritic cell (DC) functions in mucosa-associated lymphoid tissue. It was found that IL-21 treatment reduced the ability of dendritic cells to produce proinflammatory cytokines in response to H. pylori While H. pylori increased the expression of costimulatory proteins on DCs, IL-21 reduced the expression of CD40 in the presence of H. pylori Also, Th17 recall responses were intact when DCs were used as antigen-presenting cells in the presence of IL-21, but IL-21 did impact the ability of DCs to induce antigen-specific proliferation. These data suggest that IL-21, while proinflammatory in most settings, downregulates the proinflammatory cytokine microenvironment through modulating the cytokine expression of DCs, indirectly modifying IL-17A expression. Understanding how these proinflammatory cytokines are regulated will advance our understanding of how and why H. pylori infection may be tolerated in some individuals while it causes gastritis, ulcers, or cancer in others.

Synbiotic supplementation to decrease Salmonella colonization in the intestine and carcass contamination in broiler birds

In vitro and in vivo experiments were conducted to study the effects of synbiotic supplementation on Salmonella enterica ser. Enteritidis (SE) proliferation, cecal content load, and broiler carcass contamination. Lactobacillus reuteri, Enterococcus faecium, Bifidobacterium animalis, and Pediococcus acidilactici culture supernatants decreased (P < 0.05) the in vitro proliferation of SE at 1:1 supernatant: pathogen dilution. A total of 240 Cobb-500 broiler chicks were randomly allotted to three treatment groups (8 replicates/group with 10 birds/replicate): control (basal diet), antibiotic (Virginiamycin at 20 mg/kg feed), synbiotic (PoultryStar® ME at 0.5 g/kg feed containing L. reuteri, E. faecium, B. animalis, P. acidilactici and a Fructooligosaccharide) from day of hatch. At 21 d of age, all birds in experimental groups were orally inoculated with 250 μl of 1 X 109 CFU SE. Antibiotic supplementation increased (P < 0.05) body weight and feed consumption, compared to the control group. Birds in the synbiotic supplementation had intermediate body weight and feed consumption that were not significantly different from both the control and antibiotic group at 42 d of age in SE infected birds. No significant effects were observed in feed efficiency at 42 d of age among the groups. Antibiotic and synbiotic supplementation decreased (P < 0.05) SE load in cecal contents by 0.90 and 0.85 log units/ g and carcass SE load by 1.4 and 1.5 log units/mL of rinsate compared to the control group at 42 d of age (21 dpi). The relative abundance of IL-10, IL-1, TLR-4, and IFNγ mRNA was decreased (P < 0.05) in the antibiotic and synbiotic supplementation groups compared to the control birds at 42 d of age (21 dpi). It can be concluded that synbiotic supplementation decreased SE proliferation in vitro and decreased SE load in the cecal contents and broiler carcass.

Gastric Cancer in the Era of Immune Checkpoint Blockade

Gastric cancer (GC) is one of the most important malignancies worldwide because of its high incidence and mortality. The very low survival rates are mainly related to late diagnosis and limited treatment options. GC is the final clinical outcome of a stepwise process that starts with a chronic and sustained inflammatory reaction mounted in response to Helicobacter pylori infection. The bacterium modulates innate and adaptive immunity presumably as part of the strategies to survive, which favors the creation of an immunosuppressive microenvironment that ultimately facilitates GC progression. T-cell exhaustion, which is characterized by elevated expression of immune checkpoint (IC) proteins, is one of the most salient manifestations of immunosuppressive microenvironments. It has been consistently demonstrated that the tumor-immune microenvironment(TIME)‐exhausted phenotype can be reverted by blocking ICs with monoclonal antibodies. Although these therapies are associated with long-lasting response rates, only a subset of patients derive clinical benefit, which varies according to tumor site. The search for biomarkers to predict the response to IC inhibition is a matter of intense investigation as this may contribute to maximize disease control, reduce side effects, and minimize cost. The approval of pembrolizumab for its use in GC has rocketed immuno-oncology research in this cancer type. In this review, we summarize the current knowledge centered around the immune contexture and recent findings in connection with IC inhibition in GC.

Synthetic Lipopeptide Enhances Protective Immunity Against Helicobacter pylori Infection

Over fifty percent of the people around the world is infected with Helicobacter pylori (H. pylori), which is the main cause of gastric diseases such as chronic gastritis and stomach cancer. H. pylori adhesin A (HpaA), which is a surface-located lipoprotein, is essential for bacterial colonization in the gastric mucosa. HpaA had been proposed to be a promising vaccine candidate against H. pylori infection. However, the effect of non-lipidated recombinant HpaA (rHpaA) to stimulate immune response was not very ideal, and the protective effect against H. pylori infection was also limited. Here, we hypothesized that low immunogenicity of rHpaA may attribute to lacking the immunostimulatory properties endowed by the lipid moiety. In this study, two novel lipopeptides, LP1 and LP2, which mimic the terminal structure of the native HpaA (nHpaA), were synthesized and TLR2 activation activity was confirmed in vitro. To investigate whether two novel lipopeptides could improve the protective effect of rHpaA against the infection of H. pylori, groups of mice were immunized either intramuscularly or intranasally with rHpaA together with LP1 or LP2. Compared with rHpaA alone, the bacterial colonization of the mice immunized with rHpaA plus LP2 via intranasal route was significantly decreased and the expression levels of serum IgG2a, IFN-γ, and IL-17 cytokines in spleen lymphocyte culture supernatant increased obviously, indicating that the enhanced protection of LP2 may be associated with elevated specific Th1 and Th17 responses. In conclusion, LP2 has been shown to improve the protective effect of rHpaA against H. pylori infection, which may be closely related to its ability in activating TLR2 by mimicking the terminal structure of nHpaA.

BATF3-dependent dendritic cells drive both effector and regulatory T-cell responses in bacterially infected tissues

The gastric lamina propria of mice that have been experimentally infected with the pathobiont Helicobacter pylori hosts a dense network of myeloid cells that includes BATF3-dependent CD103⁺ dendritic cells (DCs). We show here that CD103⁺ DCs are strictly required for gastric Th1 responses to H. pylori and for H. pylori infection control. A similar dependence of type 1 immunity on CD103⁺ DCs is observed in a Mycobacterium bovis BCG infection model, and in a syngeneic colon cancer model. Strikingly, we find that not only the expansion and/or recruitment of Th1 cells, but also of peripherally induced, neuropilin-negative regulatory T-cells to sites of infection requires BATF3-dependent DCs. A shared feature of the examined models is the strongly reduced production of the chemokines and CXCR3 ligands CXCL9, 10 and 11 in BATF3-deficient mice. The results implicate BATF3-dependent DCs in the recruitment of CXCR3⁺ effector and regulatory T-cells to target tissues and in their local expansion.

In this work, Arnold & Zhang et al report that CD103⁺ DCs are required for protective Th1 responses, infection control of mucosal and systemic bacterial pathogens, and anti-tumor immunity driven by CD4⁺ Th1 cells and CD8⁺ T cells. CD103⁺ DCs further specifically promote the recruitment of Tbet⁺ peripherally induced Tregs to sites of infection. The results implicate CD103⁺ DCs in the trafficking of CXCR3⁺ Tbet⁺ T-cells to sites of infection and tumorigenesis.

Regulatory T lymphocytes are associated with increased nasopharyngeal colonization in children

OBJECTIVES

Regulatory T lymphocytes (T_reg) have been linked to survival of commensal bacteria at mucosal sites, but their presence and role in chronic otitis media (COM) and their response to otopathogens has not been evaluated previously. We investigated the association between T_reg lymphocytes and otopathogens in COM prone and non-COM prone children.

METHODS

Forty children, 2-7 years of age, scheduled for adenoidectomy were enrolled into COM (n = 20) or non-COM (n = 20) groups. Adenoid biopsy and nasopharyngeal aspirate bacteriology were assessed by conventional culture techniques. Peripheral blood and adenoid lymphocytes were stained with viability stain, monoclonal anti-CD19, anti-CD3, anti-CD4, anti-CD8, anti-CD25 and anti-CD127. Cells were stained intracellularly with monoclonal anti-FoxP3 and then quantified by flow cytometry.

RESULTS

Children with nasopharyngeal otopathogen-positive culture had significantly more circulating CD3⁺CD4⁺FoxP3⁺CD25^hi+CD127^lo+ lymphocytes (M = 4.4%) compared to culture-negative children (M = 3.1%, p = 0.005). Circulating CD19⁺ lymphocytes were significantly increased in children with positive Moraxella catarrhalis nasopharyngeal culture (M = 12.4%) compared to culture-negative children (M = 8.6%, p = 0.006). Adenoid-derived lymphocytes were not significantly different in children with any positive nasopharyngeal culture compared to negative culture. Lymphocyte subsets were not significantly different between COM and non-COM prone children.

CONCLUSION

Clinically-detectable otopathogen nasopharyngeal culture is positively associated with T_reg lymphocytes, potentially inducing suppressive effector responses to promote colonization and infection chronicity. This finding supports further investigation of T_reg lymphocyte activity and influence on upper airway colonization of young children.

Immunologic balance of regulatory T cell/T helper 17 responses in gastrointestinal infectious diseases: Role of miRNAs

Gastrointestinal Infectious diseases (GIDs) are the second cause of death worldwide. T helper17 cells (Th17) play an important role in GIDs through production of IL-17A, IL-17F, and IL-22 cytokines. Because of their increased activities in GID, Th17 and its inflammatory cytokines can inhibit the progression and eliminate the infection. Actually, although Th17 have the best performance in the acute phase, regulatory T cells (Treg cells) are enhanced in the chronic phase and infection progress through its suppressive function. In addition, Treg cells prevent undesirable inflammatory damages developed by immune system components. On the other hand, miRNAs have important roles in the regulation of immune responses to eliminate bacterial infections and protect host organisms from harmful effects. Actually, miRNAs can reinforce innate and adaptive immunity to remove infections. Of note, miRNAs can develop a regulatory network with the immune system. Additionally, miRNAs can also serve in favor of bacteria to reduce immune responses. Therefore, balance of immune responses in Treg and Th17 cells can influence outcome of many infectious diseases. In conclusion, there is an imbalance in the Treg/Th17 ratio in GIDs; importantly, sets of miRNAs, particularly miR155 and miR146, were determined to be involved clearly in GIDs.

Helicobacter pylori VacA Targets Myeloid Cells in the Gastric Lamina Propria To Promote Peripherally Induced Regulatory T-Cell Differentiation and Persistent Infection

Helicobacter pylori has coexisted with humans for at least 60.000 years and has evolved persistence strategies that allow it to evade host immunity and colonize its host for life. The VacA protein is expressed by all H. pylori strains and is required for high-level persistent infection in experimental mouse models. Here, we show that VacA targets myeloid cells in the gastric mucosa to create a tolerogenic environment that facilitates regulatory T-cell differentiation, while suppressing effector T-cell priming and functionality. Tregs that are induced in the periphery during H. pylori infection can be found not only in the stomach but also in the lungs of infected mice, where they are likely to affect immune responses to allergens.

The gastric bacterium Helicobacter pylori causes a persistent infection that is directly responsible for gastric ulcers and gastric cancer in some patients and protective against allergic and other immunological disorders in others. The two outcomes of the Helicobacter-host interaction can be modeled in mice that are infected as immunocompetent adults and as neonates, respectively. Here, we have investigated the contribution of the Helicobacter immunomodulator VacA to H. pylori-specific local and systemic immune responses in both models. We found that neonatally infected mice are colonized at higher levels than mice infected as adults and fail to generate effector T-cell responses to the bacteria; rather, T-cell responses in neonatally infected mice are skewed toward Foxp3-positive (Foxp3⁺) regulatory T cells that are neuropilin negative and express RORγt. We found these peripherally induced regulatory T cells (pTregs) to be enriched, in a VacA-dependent manner, not only in the gastric mucosa but also in the lungs of infected mice. Pulmonary pTreg accumulation was observed in mice that have been infected neonatally with wild-type H. pylori but not in mice that have been infected as adults or mice infected with a VacA null mutant. Finally, we traced VacA to gastric lamina propria myeloid cells and show that it suppressed interleukin-23 (IL-23) expression by dendritic cells and induced IL-10 and TGF-β expression in macrophages. Taken together, the results are consistent with the idea that H. pylori creates a tolerogenic environment through its immunomodulator VacA, which skews T-cell responses toward Tregs, favors H. pylori persistence, and affects immunity at distant sites.

A Novel Gastric Spheroid Co-culture Model Reveals Chemokine-Dependent Recruitment of Human Dendritic Cells to the Gastric Epithelium

BACKGROUND & AIMS

Gastric dendritic cells (DCs) control the adaptive response to infection with Helicobacter pylori, a major risk factor for peptic ulcer disease and gastric cancer. We hypothesize that DC interactions with the gastric epithelium position gastric DCs for uptake of luminal H pylori and promote DC responses to epithelial-derived mediators. The aim of this study was to determine whether the gastric epithelium actively recruits DCs using a novel co-culture model of human gastric epithelial spheroids and monocyte-derived DCs.

METHODS

Spheroid cultures of primary gastric epithelial cells were infected with H pylori by microinjection. Co-cultures were established by adding human monocyte-derived DCs to the spheroid cultures and were analyzed for DC recruitment and antigen uptake by confocal microscopy. Protein array, gene expression polymerase chain reaction array, and chemotaxis assays were used to identify epithelial-derived chemotactic factors that attract DCs. Data from the co-culture model were confirmed using human gastric tissue samples.

RESULTS

Human monocyte-derived DCs co-cultured with gastric spheroids spontaneously migrated to the gastric epithelium, established tight interactions with the epithelial cells, and phagocytosed luminally applied H pylori. DC recruitment was increased upon H pylori infection of the spheroids and involved the activity of multiple chemokines including CXCL1, CXCL16, CXCL17, and CCL20. Enhanced chemokine expression and DC recruitment to the gastric epithelium also was observed in H pylori-infected human gastric tissue samples.

CONCLUSIONS

Our results indicate that the gastric epithelium actively recruits DCs for immunosurveillance and pathogen sampling through chemokine-dependent mechanisms, with increased recruitment upon active H pylori infection.

Review of antimicrobial peptides with anti-Helicobacter pylori activity

BACKGROUND

The emergence of antibiotic-resistant Helicobacter pylori strains in recent years has increased the need for finding an alternative in the post-antibiotic era. One of the fields being considered for this purpose is antimicrobial peptides. The aim of this review was to provide an obvious scheme from the studied anti-H. pylori peptides and to investigate their common features.

METHOD

First, all of the antimicrobial peptides with their anti-H. pylori effects have been proved up to September 2018 were selected and their information including structure, mechanism of action, and function was reviewed. To achieve this, three databases of PubMed, Scopus, and Web of science were used.

RESULTS

A total of 9 groups containing 22 antimicrobial peptides were found with demonstrated anti-H. pylori effects. The nine groups included pexiganan, tilapia piscidins, epinecidin-1, cathelicidins, defensins, bicarinalin, odorranain-HP, PGLa-AM1, and bacteriocins. Most of the antimicrobial peptides, not all, had common features such as the ability to kill antibiotic-resistant strains, having α-helical structure, being cationic, with high positive charge and isoelectric point.

CONCLUSION

Antimicrobial peptides with anti-H. pylori effects have the potential to replace the antibiotics, especially in the post-antibiotic era, if a rapid and low-cost production method would be found.

Helicobacter pylori Deregulates T and B Cell Signaling to Trigger Immune Evasion

Helicobacter pylori is a prevalent human pathogen that successfully establishes chronic infection, which leads to clinically significant gastric diseases including chronic gastritis, peptic ulcer disease (PUD), and gastric cancer (GC). H. pylori is able to produce a persistent infection due in large part to its ability to hijack the host immune response. The host adaptive immune response is activated to strategically and specifically attack pathogens and normally clears them from the infected host. Since B and T lymphocytes are central mediators of adaptive immunity, in this chapter we review their development and the fundamental mechanisms regulating their activation in order to understand how some of the normal processes are subverted by H. pylori. In this review, we place particular emphasis on the CD4⁺ T cell responses, their subtypes, and regulatory mechanisms because of the expanding literature in this area related to H. pylori. T lymphocyte differentiation and function are finely orchestrated through a series of cell-cell interactions, which include immune checkpoint receptors. Among the immune checkpoint receptor family, there are some with inhibitory properties that are exploited by tumor cells to facilitate their immune evasion. Gastric epithelial cells (GECs), which act as antigen-presenting cells (APCs) in the gastric mucosa, are induced by H. pylori to express immune checkpoint receptors known to sway T lymphocyte function and thus circumvent effective T effector lymphocyte responses. This chapter reviews these and other mechanisms used by H. pylori to interfere with host immunity in order to persist.

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.

Yersinia Pseudotuberculosis Modulates Regulatory T Cell Stability via Injection of Yersinia Outer Proteins in a Type III Secretion System-Dependent Manner

Adaptive immunity is essentially required to control acute infection with enteropathogenic Yersinia pseudotuberculosis (Yptb). We have recently demonstrated that Yptb can directly modulate naïve CD4⁺ T cell differentiation. However, whether fully differentiated forkhead box protein P3 (Foxp3⁺) regulatory T cells (Tregs), fundamental key players to maintain immune homeostasis, are targeted by Yptb remains elusive. Here, we demonstrate that within the CD4⁺ T cell compartment Yptb preferentially targets Tregs and injects Yersinia outer proteins (Yops) in a process that depends on the type III secretion system and invasins. Remarkably, Yop-translocation into ex vivo isolated Foxp3⁺ Tregs resulted in a substantial downregulation of Foxp3 expression and a decreased capacity to express the immunosuppressive cytokine interleukin-10 (IL-10). Together, these findings highlight that invasins are critically required to mediate Yptb attachment to Foxp3⁺ Tregs, which allows efficient Yop-translocation and finally enables the modulation of the Foxp3⁺ Tregs' suppressive phenotype.

CD103 (αE Integrin) Undergoes Endosomal Trafficking in Human Dendritic Cells, but Does Not Mediate Epithelial Adhesion

Dendritic cell (DC) expression of CD103, the α subunit of αEβ7 integrin, is thought to enable DC interactions with E-cadherin-expressing gastrointestinal epithelia for improved mucosal immunosurveillance. In the stomach, efficient DC surveillance of the epithelial barrier is crucial for the induction of immune responses to H. pylori, the causative agent of peptic ulcers and gastric cancer. However, gastric DCs express only low levels of surface CD103, as we previously showed. We here tested the hypothesis that intracellular pools of CD103 in human gastric DCs can be redistributed to the cell surface for engagement of epithelial cell-expressed E-cadherin to promote DC-epithelial cell adhesion. In support of our hypothesis, immunofluorescence analysis of tissue sections showed that CD103+ gastric DCs were preferentially localized within the gastric epithelial layer. Flow cytometry and imaging cytometry revealed that human gastric DCs expressed intracellular CD103, corroborating our previous findings in monocyte-derived DCs (MoDCs). Using confocal microscopy, we show that CD103 was present in endosomal compartments, where CD103 partially co-localized with clathrin, early endosome antigen-1 and Rab11, suggesting that CD103 undergoes endosomal trafficking similar to β1 integrins. Dynamic expression of CD103 on human MoDCs was confirmed by internalization assay. To analyze whether DC-expressed CD103 promotes adhesion to E-cadherin, we performed adhesion and spreading assays on E-cadherin-coated glass slides. In MoDCs generated in the presence of retinoic acid, which express increased CD103, intracellular CD103 significantly redistributed toward the E-cadherin-coated glass surface. However, DCs spreading and adhesion did not differ between E-cadherin-coated slides and slides coated with serum alone. In adhesion assays using E-cadherin-positive HT-29 cells, DC binding was significantly improved by addition of Mn2+ and decreased in the presence of EGTA, consistent with the dependence of integrin-based interactions on divalent cations. However, retinoic acid failed to increase DC adhesion, and a CD103 neutralizing antibody was unable to inhibit DC binding to the E-cadherin positive cells. In contrast, a blocking antibody to DC-expressed E-cadherin significantly reduced DC binding to the epithelium. Overall, these data indicate that CD103 engages in DC-epithelial cell interactions upon contact with epithelial E-cadherin, but is not a major driver of DC adhesion to gastrointestinal epithelia.

Control of Treg cell homeostasis and immune equilibrium by Lkb1 in dendritic cells

To balance immunity and tolerance, the endogenous pool of Foxp3⁺ regulatory T (T_reg) cells is tightly controlled, but the underlying mechanisms of this control remain poorly understood. Here we show that the number of T_reg cells is negatively regulated by the kinase Lkb1 in dendritic cells (DCs). Conditional knockout of the Lkb1 gene in DCs leads to excessive T_reg cell expansion in multiple organs and dampens antigen-specific T cell immunity. Lkb1-deficient DCs are capable of enhancing, compared with wild-type DCs, T_reg cell proliferation via cell-cell contact involving the IKK/IKBα-independent activation of the NF-κB/OX40L pathway. Intriguingly, treating wild-type mice with lipopolysaccharide selectively depletes Lkb1 protein in DCs, resulting in T_reg cell expansion and suppressed inflammatory injury upon subsequent challenge. Loss of Lkb1 does not obviously upregulate proinflammatory molecules expression on DCs. We thus identify Lkb1 as a regulatory switch in DCs for controlling T_reg cell homeostasis, immune response and tolerance.

Regulatory T (Treg) cells are important for maintaining immune homeostasis by suppressing immune cell activation, but how the Treg cell pool is maintained is still unclear. Here the authors show that a kinase, Lkb1, operates in dendritic cells (DC) to inhibit Treg cell expansion and immunosuppression via mechanisms involving NF-kB/OX40L signalling.

Immune response and immune escape mechanism in Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a Gram-negative bacterium which is parasitic on the surface of the gastric mucosa, and it is a causative agent in the development of chronic gastritis, gastric and duodenal peptic ulcer, gastric adenocarcinoma, and lymphoid tissue lymphoma associated with the gastric mucosa. After H. pylori infection, the bacterium is first recognized by the pattern recognition receptors of immune cells, which in turn causes the innate immune and adaptive immune responses, but these responses are usually insufficient to eliminate bacterial infections. H. pylori can evade the identification and clearance by the immune system by modifying and attenuating the immunogenicity of its pathogen-associated molecular patterns, regulating the immune responses of innate immune cells and T cells, and leading to persistent infection. A thorough understanding of the immune response and immune escape mechanism in H. pylori infection is of great significance for eliminating H. pylori infection and controlling the occurrence of H. pylori infection-related diseases.

Downregulation of Interleukin- (IL-) 17 through Enhanced Indoleamine 2,3-Dioxygenase (IDO) Induction by Curcumin: A Potential Mechanism of Tolerance towards Helicobacter pylori

The anti-inflammatory and antimicrobial properties of curcumin suggest its use as an anti-Helicobacter pylori (H. pylori) agent, but mechanisms underlying its helpful activity are still not clear. Indoleamine 2,3-dioxygenase (IDO) promotes the effector T cell apoptosis by catalyzing the rate-limiting first step in tryptophan catabolism, and its high expression in H. pylori-infected human gastric mucosa attenuates Th1 and Th17 immune response. The aim of this study was to investigate the role of curcumin in modulating the expression of IL-17 and IDO in H. pylori-infected human gastric mucosa. In an organ culture chamber, gastric biopsies from 35 patients were treated with and without 200 μM curcumin. In H. pylori-infected patients (n = 21), IL-17 was significantly lower, both in gastric biopsies (p = 0.0003) and culture supernatant (p = 0.0001) while IDO significantly increased (p < 0.00001) in curcumin-treated sample compared with untreated samples. In a subgroup of H. pylori-infected patients (n = 15), samples treated with curcumin in addition to IDO inhibitor 1-methyl-L-tryptophan (1-MT) showed a higher expression of IL-17 compared with untreated samples and curcumin-treated alone (p < 0.00001). Curcumin downregulates IL-17 production through the induction of IDO in H. pylori-infected human gastric mucosa, suggesting its role in dampening H. pylori-induced immune-mediated inflammatory changes.

Helicobacter pylori infection and inflammatory bowel disease: a crosstalk between upper and lower digestive tract

Helicobacter pylori has coexisted with humans for approximately 60,000 years and greater than 50% of the global population is infected with H. pylori. H. pylori was successfully cultured in vitro in 1983 and studies of H. pylori have achieved substantial advances over the last 35 years. Since then, H. pylori has been characterized as the primary pathogenic factor for chronic gastritis, peptic ulcer, and gastric malignancy. Numerous patients have received H. pylori eradication treatment, but only 1-2% of H. pylori-infected individuals ultimately develop gastric cancer. Recently, numerous epidemiological and basic experimental studies suggested a role for chronic H. pylori infection in protecting against inflammatory bowel disease (IBD) by inducing systematic immune tolerance and suppressing inflammatory responses. Here we summarize the current research progress on the association between H. pylori and IBD, and further describe the detailed molecular mechanism underlying H. pylori-induced dendritic cells (DCs) with the tolerogenic phenotype and immunosuppressive regulatory T cells (Tregs). Based on the potential protective role of H. pylori infection on IBD, we suggest that the interaction between H. pylori and the host is complicated, and H. pylori eradication treatment should be administered with caution, especially for children and young adults.

Helicobacter pylori in human health and disease: Mechanisms for local gastric and systemic effects

Helicobacter pylori (H. pylori) is present in roughly 50% of the human population worldwide and infection levels reach over 70% in developing countries. The infection has classically been associated with different gastro-intestinal diseases, but also with extra gastric diseases. Despite such associations, the bacterium frequently persists in the human host without inducing disease, and it has been suggested that H. pylori may also play a beneficial role in health. To understand how H. pylori can produce such diverse effects in the human host, several studies have focused on understanding the local and systemic effects triggered by this bacterium. One of the main mechanisms by which H. pylori is thought to damage the host is by inducing local and systemic inflammation. However, more recently, studies are beginning to focus on the effects of H. pylori and its metabolism on the gastric and intestinal microbiome. The objective of this review is to discuss how H. pylori has co-evolved with humans, how H. pylori presence is associated with positive and negative effects in human health and how inflammation and/or changes in the microbiome are associated with the observed outcomes.

Stimulator of Interferon Genes in Classical Dendritic Cells Controls Mucosal Th17 Responses to Cyclic Dinucleotides for Host Defenses Against Microbial Infections in Gut

Cyclic dinucleotides are bacterial signal transducers that bind to host intracellular protein, stimulator of interferon genes (STING) encoded by Tmem173. In this study, we demonstrate that STING triggers adaptive immune responses that control Th17 differentiation. Cyclic dinucleotides recognition enables classical dendritic cells (cDCs) that predominantly express CD103 to induce Th17 lymphocytes in an IL-6/IL-1β-dependent manner in gut. STING expression in human lamina propria is associated with the severity of mucosal inflammation and clinical disease activity in patients with Crohn’s disease. Mice deficient in Tmem173 fail to mount Th17 responses to cyclic dinucleotides or prevent immune evasion of enteroinvasive pathogens. In summary, STING in mucosal cDCs controls Th17 subspecification that is essential for host defenses against microbial infection in gut-associated immune system.

Up-regulated Th17 cell function is associated with increased peptic ulcer disease in Helicobacter pylori-infection

BACKGROUND

During Helicobacter pylori (H. pylori) infection CD4⁺ T cells in the gastric lamina propria are hyporesponsive and polarized by Th1/Th17 cell responses controlled by Treg cells. The objective of this study was to determine the number of Th17 cells in gastric mucosa of patients with gastritis and peptic ulcer and determined the relationship between main virulence factor of H. pylori and Th17 cells.

METHODS AND MATERIALS

A total of 89 H. pylori-infected gastritis patients, 63 H. pylori-infected peptic ulcer patients and 48 H. pylori-negative non-ulcer dysplasia patients were enrolled in this study. The number of Th17 was determined by immunohistochemistry. IL-8 and IL-17A expressions were determined by real-time polymerase chain reaction (qPCR). Also, the grade of chronic and active inflammation was investigated for involvement according to the density of neutrophils and mononuclear in gastric mucosal crypts, from one to all crypts.

RESULTS

The number of Th17 cells and the expression of IL-8 and IL-17A in infected patients were significantly higher than uninfected subjects. The number of Th17 cells and the expression of IL-8 and IL-17A in infected patients with peptic ulcer were significantly higher than patients with gastritis. Additionally, the numbers of Th17 cells as well as the expression of IL-8 and IL-17A were positively correlated with the degree of H. pylori density in infected patients with peptic ulcer, while this correlation was negative in infected patients with gastritis. The numbers of Th17 cells as well as the expression of IL-8 and IL-17A were positively correlated with the degree of chronic inflammation.

CONCLUSION

The predominant Th17 cell responses may play a role in the pathogenesis of peptic ulcers disease in infected patients.

T cell subsets play an important role in the determination of the clinical outcome of Helicobacter pylori infection

Helicobacter pylori (H. pylori) is one of the most prevalent human pathogen and a persistent infection with this bacterium causes common pathologies, such as gastritis or peptic ulcers, and also less common but more serious pathologies, such as gastric cancer or gastric mucosa-associated lymphoid tissue (MALT) lymphoma. The clinical outcome of gastrointestinal infection sustained by H. pylori is determined by the reciprocal interactions between virulence factors of the bacterium and host factors, including immune response genes. Although H. pylori induces a strong immune response, the bacterium is not eliminated. The eradication failure could be attributed to the bacterial capability to regulate helper T (Th) cell-related responses. H. pylori specific CD4⁺ T cells play a fundamental role in regulating host immunity and immunopathologic events. It has been documented that Th1, Th2, Th9, Th17, Th22 and T regulatory (Treg) cells, separately or in coordination with each other, can affect the outcome of the infection sustained by of H. pylori. Some studies indicated that both Th1 and Th17 cells may be protective or pathogenic, whereas Treg and Th2 cells perform anti-inflammatory impacts during H. pylori infection. This review gathers recent information regarding the association of the CD4⁺ T cells-mediated immunological responses and the clinical consequence of H. pylori infection.

Modulatory Influence of Segmented Filamentous Bacteria on Transcriptomic Response of Gnotobiotic Mice Exposed to TCDD

Environmental toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR), are known to induce host toxicity and structural shifts in the gut microbiota. Key bacterial populations with similar or opposing functional responses to AhR ligand exposure may potentially help regulate expression of genes associated with immune dysfunction. To examine this question and the mechanisms for AhR ligand-induced bacterial shifts, C57BL/6 gnotobiotic mice were colonized with and without segmented filamentous bacteria (SFB) – an immune activator. Mice were also colonized with polysaccharide A producing Bacteroides fragilis – an immune suppressor to serve as a commensal background. Following colonization, mice were administered TCDD (30 μg/kg) every 4 days for 28 days by oral gavage. Quantified with the nCounter^® mouse immunology panel, opposing responses in ileal gene expression (e.g., genes associated with T-cell differentiation via the class II major histocompatibility complex) as a result of TCDD dosing and SFB colonization were observed. Genes that responded to TCDD in the presence of SFB did not show a significant response in the absence of SFB, and vice versa. Regulatory T-cells examined in the mesenteric lymph-nodes, spleen, and blood were also less impacted by TCDD in mice colonized with SFB. TCDD-induced shifts in abundance of SFB and B. fragilis compared with previous studies in mice with a traditional gut microbiome. With regard to the mouse model colonized with individual populations, results indicate that TCDD-induced host response was significantly modulated by the presence of SFB in the gut microbiome, providing insight into therapeutic potential between AhR ligands and key commensals.

Is There a Link Between H. Pylori and the Epidemiology of Crohn's Disease?

INTRODUCTION

Case control studies suggest an inverse association between Helicobacter pylori (H. pylori) and Crohn's disease (CD). It is possible this could be accounted for by confounders such as antibiotic therapy. Analyzing the geographic distribution of H. pylori and the links with the incidence and prevalence of CD would be an alternative approach to circumvent these confounders.

METHODS

The literature was searched for studies published between 1990 and 2016 that reported incidence or prevalence data for CD in random population samples in developed countries (GDP per capita >20,000 USD/year). Corresponding prevalence studies for H. pylori in these same regions were then sought matched to the same time period (±6 years). The association between the incidence and prevalence of CD and H. pylori prevalence rates were assessed before and after adjusting for GDP and life expectancy.

RESULTS

A total of 19 CD prevalence and 22 CD incidence studies from 10 European countries, Japan, USA, and Australia with date-matched H. pylori prevalence data were identified. The mean H. pylori prevalence rate was 43.4% (range 15.5-85%), and the mean rates for incidence and prevalence for CD were 6.9 and 91.0/100,000 respectively. The incidence (r = -0.469, p < 0.03) and prevalence (r = -0.527, p = 0.02) of CD was inversely and significantly associated with prevalence of H. pylori infection.

CONCLUSIONS

Our data demonstrate a significant inverse association between geographic distribution of H. pylori and CD. Thus, it is highly unlikely that the findings of previous case control studies were simply due to confounding factors such as concomitant antibiotic use in CD patients.

TIFA Signaling in Gastric Epithelial Cells Initiates the cag Type 4 Secretion System-Dependent Innate Immune Response to Helicobacter pylori Infection

Helicobacter pylori is a bacterial pathogen that colonizes the human stomach, causing inflammation which, in some cases, leads to gastric ulcers and cancer. The clinical outcome of infection depends on a complex interplay of bacterial, host genetic, and environmental factors. Although H. pylori is recognized by both the innate and adaptive immune systems, this rarely results in bacterial clearance. Gastric epithelial cells are the first line of defense against H. pylori and alert the immune system to bacterial presence. Cytosolic delivery of proinflammatory bacterial factors through the cag type 4 secretion system (cag-T4SS) has long been appreciated as the major mechanism by which gastric epithelial cells detect H. pylori Classically attributed to the peptidoglycan sensor NOD1, recent work has highlighted the role of NOD1-independent pathways in detecting H. pylori; however, the bacterial and host factors involved have remained unknown. Here, we show that bacterially derived heptose-1,7-bisphosphate (HBP), a metabolic precursor in lipopolysaccharide (LPS) biosynthesis, is delivered to the host cytosol through the cag-T4SS, where it activates the host tumor necrosis factor receptor-associated factor (TRAF)-interacting protein with forkhead-associated domain (TIFA)-dependent cytosolic surveillance pathway. This response, which is independent of NOD1, drives robust NF-κB-dependent inflammation within hours of infection and precedes NOD1 activation. We also found that the CagA toxin contributes to the NF-κB-driven response subsequent to TIFA and NOD1 activation. Taken together, our results indicate that the sequential activation of TIFA, NOD1, and CagA delivery drives the initial inflammatory response in gastric epithelial cells, orchestrating the subsequent recruitment of immune cells and leading to chronic gastritis.IMPORTANCEH. pylori is a globally prevalent cause of gastric and duodenal ulcers and cancer. H. pylori antibiotic resistance is rapidly increasing, and a vaccine remains elusive. The earliest immune response to H. pylori is initiated by gastric epithelial cells and sets the stage for the subsequent immunopathogenesis. This study revealed that host TIFA and H. pylori-derived HBP are critical effectors of innate immune signaling that account for much of the inflammatory response to H. pylori in gastric epithelial cells. HBP is delivered to the host cell via the cag-T4SS at a time point that precedes activation of the previously described NOD1 and CagA inflammatory pathways. Manipulation of the TIFA-driven immune response in the host and/or targeting of ADP-heptose biosynthesis enzymes in H. pylori may therefore provide novel strategies that may be therapeutically harnessed to achieve bacterial clearance.

Downregulated regulatory T cell function is associated with increased peptic ulcer in Helicobacter pylori-infection

BACKGROUND

Helicobacter pylori (H. pylori) chronically colonizes gastric/duodenal mucosa and induces gastroduodenal disease such as gastritis and peptic ulcer and induces vigorous innate and specific immune responses; however, the infection is not removed, a state of chronic active gastritis persists for life if untreated. The objective of this study was to determine the number of regulatory T cells (Tregs) in gastric mucosa of patients with gastritis and peptic ulcer and determined the relationship between main virulence factor of H. pylori and Tregs.

METHODS AND MATERIALS

A total of 89 patients with gastritis, 63 patients with peptic ulcer and 40 healthy, H. pylori-negative subjects were enrolled in this study. Expression of CD4 and Foxp3 was determined by immunohistochemistry. Antrum biopsy was obtained for detection of H. pylori, bacterial virulence factors and histopathological assessments. TGF-β1, IL-10 and FOXP3 expressions were determined by real-time polymerase chain reaction (qPCR).

RESULTS

The numbers of CD4⁺ and Foxp3⁺ T cells as well as the expression of IL-10, TGF-β1, FOXP3, INF-γ and IL-17A in infected patients were significantly higher than the ones in uninfected patients. Also, the number of CD4⁺ T cells was independent on the vacuolating cytotoxin A (vacA) and outer inflammatory protein A (oipA), but it was positively correlated with cytotoxin-associated gene A (cagA). Instead, the number of Foxp3⁺ T cells was dependent on the vacA and oipA, but it was independent on cagA. The number of Foxp3⁺ T cells and the expression of IL-10, TGF-β1 and FOXP3 in infected patients with gastritis were significantly higher than the ones in infected patients with peptic ulcer. Moreover, the number of CD4⁺ T cells and the expression of IL-17A and INF-γ was the lowest in the gastritis patients, however, increased progressively in the peptic ulcer patients. Additionally, the numbers of CD4⁺ and Foxp3⁺ T cells as well as the expression of IL-10, TGF-β1, FOXP3 and INF-γ were positively correlated with the degree of H. pylori density and chronic inflammation.

CONCLUSION

Tregs are positively associated with vacA alleles and oipA status of H. pylori and histological grade but negatively associated with peptic ulcer disease.

Helicobacter suis induces changes in gastric inflammation and acid secretion markers in pigs of different ages

Gastric mRNA expression of markers for acid secretion and inflammation and presence of gastric ulceration was studied in naturally Helicobacter suis-infected and non-infected 2–3 months old, 6–8 months old and adult pigs. In H. suis-infected 2–3 months old pigs, IL-8 and IL-1β transcript levels were upregulated in the pyloric gland zone, indicating an innate immune response. A similar response was demonstrated in the fundic gland zone of adult pigs, potentially due to a shift of H. suis colonization from the pyloric to the fundic gland zone. A Treg response in combination with decreased expressions of IL-8, IL-17A and IFN-γ was indicated to be present in the H. suis-infected 6–8 months old pigs, which may have contributed to persistence of H. suis. In H. suis-infected adult pigs, a Treg response accompanied by a Th17 response was indicated, which may have played a role in the decreased number of H. suis bacteria in the stomach of this age group. The decreased G-cell mass and upregulated expression of somatostatin indicated decreased acid secretion in H. suis-infected 6–8 months old pigs. In H. suis-infected adult pigs, upregulation of most markers for gastric acid secretion and increased G-cell mass was detected. Presence of severe hyperkeratosis and erosions in the non-glandular part of the stomach were mainly seen in the H. suis-positive groups. These results show that H. suis infection affects the expression of markers for acid secretion and inflammation and indicate that these effects differ depending on the infection phase.

Species-specific immunity to Helicobacter suis

BACKGROUND

Helicobacter (H.) suis is mainly associated with pigs, but is also the most prevalent gastric non-H. pylori Helicobacter species found in humans. Both H. pylori and H. suis may cause persistent infection of the stomach. Several immune evasion mechanisms have been proposed for H. pylori, which focus to a great extent on its major virulence factors, which are absent in H. suis. The aim of this study was to gain more knowledge on immune evasion by H. suis.

MATERIALS AND METHODS

Cytokine expression kinetics were monitored in the stomach of BALB/c mice experimentally infected with H. suis. The cytokine expression profile in the stomach of naturally H. suis-infected pigs was also determined. Subsequently, the effect of H. suis on murine and porcine dendritic cell (DC) maturation and their ability to elicit T-cell effector responses was analyzed.

RESULTS

Despite a Th17/Th2 response in the murine stomach, the inflammatory cell influx was unable to clear H. suis infection. H. suis-stimulated murine bone marrow-derived dendritic cells induced IL-17 secretion by CD4⁺ cells in vitro. Natural H. suis infection in pigs evoked increased expression levels of IL-17 mRNA in the antrum and IL-10 mRNA in the fundus. In contrast to mice, H. suis-stimulated porcine monocyte-derived dendritic cells were unable to express MHCII molecules on their cell surface. These semimature DCs induced proliferation of T-cells, which showed an increased expression of TGF-β and FoxP3 mRNA levels.

CONCLUSIONS

Helicobacter suis might evade host immune responses by skewing toward a Treg-biased response.

From inflammation to gastric cancer - the importance of Hedgehog/GLI signaling in Helicobacter pylori-induced chronic inflammatory and neoplastic diseases

Infections with the human pathogen Helicobacter pylori (H. pylori) are closely associated with the development of inflammatory disorders and neoplastic transformation of the gastric epithelium. Drastic changes in the micromilieu involve a complex network of H. pylori-regulated signal transduction pathways leading to the release of proinflammatory cytokines, gut hormones and a wide range of signaling molecules. Besides controlling embryonic development, the Hedgehog/GLI signaling pathway also plays important roles in epithelial proliferation, differentiation, and regeneration of the gastric physiology, but also in the induction and progression of inflammation and neoplastic transformation in H. pylori infections. Here, we summarize recent findings of H. pylori-associated Hedgehog/GLI signaling in gastric homeostasis, malignant development and the modulation of the gastric tumor microenvironment.

Cooperation of Gastric Mononuclear Phagocytes with Helicobacter pylori during Colonization

Helicobacter pylori, the dominant member of the human gastric microbiota, elicits immunoregulatory responses implicated in protective versus pathological outcomes. To evaluate the role of macrophages during infection, we employed a system with a shifted proinflammatory macrophage phenotype by deleting PPARγ in myeloid cells and found a 5- to 10-fold decrease in gastric bacterial loads. Higher levels of colonization in wild-type mice were associated with increased presence of mononuclear phagocytes and in particular with the accumulation of CD11b+F4/80hiCD64+CX3CR1+ macrophages in the gastric lamina propria. Depletion of phagocytic cells by clodronate liposomes in wild-type mice resulted in a reduction of gastric H. pylori colonization compared with nontreated mice. PPARγ-deficient and macrophage-depleted mice presented decreased IL-10-mediated myeloid and T cell regulatory responses soon after infection. IL-10 neutralization during H. pylori infection led to increased IL-17-mediated responses and increased neutrophil accumulation at the gastric mucosa. In conclusion, we report the induction of IL-10-driven regulatory responses mediated by CD11b+F4/80hiCD64+CX3CR1+ mononuclear phagocytes that contribute to maintaining high levels of H. pylori loads in the stomach by modulating effector T cell responses at the gastric mucosa.

CCR2 mediates Helicobacter pylori-induced immune tolerance and contributes to mucosal homeostasis

BACKGROUND

We previously demonstrated that H. pylori infection leads to increased induction of regulatory T cells in local and systemic immune compartments. Here, we investigate the role of CCR2 in the tolerogenic programing of dendritic cells in a mouse model of H. pylori infection.

MATERIALS AND METHODS

CCR2 deficient (CCR2KO) mice and wild-type (Wt) mice infected with H. pylori SS1 strain were analyzed by qPCR and FACS analysis. In vitro, bone marrow-derived DC on day 6 from CCR2KO and Wt mice cocultured with or without H. pylori were examined to determine the impact of CCR2 signaling on dendritic cells function by qPCR, ELISA, and FACS analyses.

RESULTS

Acute H. pylori infection was associated with a threefold increase in CCR2 mRNA expression in the gastric mucosa. H. pylori-infected CCR2KO mice exhibited a higher degree of mucosal inflammation, that is, increased gastritis scores and pro-inflammatory cytokine mRNA levels, but lower degree of H. pylori gastric colonization compared to infected Wt mice. Peripheral H. pylori-specific immune response measured in the CCR2KO spleen was characterized by a higher Th17 response and a lower Treg response. In vitro, CCR2KO bone marrow-derived DC was less mature and shown a lower Treg/Th17 ratio. Moreover, blockade of CCR2 signaling by MCP-1 neutralizing antibody inhibited H. pylori-stimulated bone marrow-derived DC maturation.

CONCLUSIONS

Our results indicate that CCR2 plays an essential role in H. pylori-induced immune tolerance and shed light on a novel mechanism of CCR2-dependent DC Treg induction, which appears to be important in maintaining mucosal homeostasis during H. pylori infection.

TRAF6 regulates the effects of polarized maturation of tolerability: Marrow-derived dendritic cells on collagen-induced arthritis in mice

The study aimed to investigate the relationship between tumor necrosis factor receptor-associated factor 6 (TRAF6) and a differentially mature dendritic cell (mDC) in collagen-induced arthritis (CIA) mice and to determine whether or not TRAF6 regulates the activation of an immature dendritic cell (iDC) and inhibits iDC maturation to induce immune tolerance. The mouse bone marrow stem cells were induced with recombinant granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and recombinant interleukin-4 (rmIL-4) to differentiate immature dendritic cells (DCs), which were divided into four groups with different maturation states: rmGM-CSF, rmIL-4; TNF-α; LPS; and FK506 group. The levels of the cell surfaces of CD80, CD86, and MHI-II were analyzed by flow cytometry to prove DCs at different levels of maturity. The expression of IL-12 in DCs at different maturation states was detected by enzyme-linked immunosorbent assay (ELISA). The expression of TRAF6 mRNA and protein in each group of DCs was detected by a reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis. The results revealed that the differentiation of bone marrow cells into iDCs was significantly induced by cytokines (rmGM-CSF, IL-4). CD80, CD86, MHC-II were expressed in the four groups, and the difference between them was statistically significant (P<0.05). A higher degree of DC differentiation led to a gradual increase of IL-12 secretion in the four groups. The difference was statistically significant (P<0.05) for this secretion (group D, 10,620.73±276.73 pg/ml). The expression levels of TRAF6 mRNA were significantly higher in group D than those in the other three groups (P<0.01). Although there was no significant difference in the expression levels of TRAF6 mRNA between groups B and C, the expression levels of TRAF6 mRNA between groups B and C were higher than those of the control group. The TRAF6 protein expression was higher in group D than that in the other three groups (P<0.01), and the difference was statistically significant. There was a statistically significant difference in the TRAF6 protein expression between group A and groups B and C, but the expression in group C was higher than that in group B (P<0.01). In conclusion, the expression of co-stimulatory molecules gradually increased in the DCs of different maturation states, and the expression of IL-12, TRAF6 mRNA, and TRAF6 protein positively correlated with the degree of DC maturation. TRAF6 is important in iDC polarity and maturation.

Host pathogen interactions in Helicobacter pylori related gastric cancer

Helicobacter pylori (H. pylori), discovered in 1982, is a microaerophilic, spiral-shaped gram-negative bacterium that is able to colonize the human stomach. Nearly half of the world's population is infected by this pathogen. Its ability to induce gastritis, peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma has been confirmed. The susceptibility of an individual to these clinical outcomes is multifactorial and depends on H. pylori virulence, environmental factors, the genetic susceptibility of the host and the reactivity of the host immune system. Despite the host immune response, H. pylori infection can be difficult to eradicate. H. pylori is categorized as a group I carcinogen since this bacterium is responsible for the highest rate of cancer-related deaths worldwide. Early detection of cancer can be lifesaving. The 5-year survival rate for gastric cancer patients diagnosed in the early stages is nearly 90%. Gastric cancer is asymptomatic in the early stages but always progresses over time and begins to cause symptoms when untreated. In 97% of stomach cancer cases, cancer cells metastasize to other organs. H. pylori infection is responsible for nearly 60% of the intestinal-type gastric cancer cases but also influences the development of diffuse gastric cancer. The host genetic susceptibility depends on polymorphisms of genes involved in H. pylori-related inflammation and the cytokine response of gastric epithelial and immune cells. H. pylori strains differ in their ability to induce a deleterious inflammatory response. H. pylori-driven cytokines accelerate the inflammatory response and promote malignancy. Chronic H. pylori infection induces genetic instability in gastric epithelial cells and affects the DNA damage repair systems. Therefore, H. pylori infection should always be considered a pro-cancerous factor.

Inflammation, DNA Damage, Helicobacter pylori and Gastric Tumorigenesis

Helicobacter pylori (H. pylori) is a Gram negative bacterium that colonizes the stomach of almost half human population. It has evolved to escape immune surveillance, establishes lifelong inflammation, predisposing to genomic instability and DNA damage, notably double strand breaks. The epithelial host cell responds by activation of DNA damage repair (DDR) machinery that seems to be compromised by the infection. It is therefore now accepted that genetic damage is a major mechanism operating in cases of H. pylori induced carcinogenesis. Here, we review the data on the molecular pathways involved in DNA damage and DDR activation during H. pylori infection.

Regulation of Gastric Metaplasia, Dysplasia, and Neoplasia by Bone Morphogenetic Protein Signaling

The bone morphogenetic proteins, (BMP)s are regulatory peptides that have significant effects on the growth and differentiation of gastrointestinal tissues. In addition, the BMPs have been shown to exert anti-inflammatory actions in the gut and to negatively regulate the growth of gastric neoplasms. The role of BMP signaling in the regulation of gastric metaplasia, dysplasia and neoplasia has been poorly characterized. Transgenic expression in the mouse stomach of the BMP inhibitor noggin leads to decreased parietal cell number, increased epithelial cell proliferation, and to the emergence of SPEM. Moreover, expression of noggin increases Helicobacter-induced inflammation and epithelial cell proliferation, accelerates the development of dysplasia, and it increases the expression of signal transducer and activator of transcription 3 (STAT3) and of activation-induced cytidine deaminase (AID). These findings provide new clues for a better understanding of the pathophysiological mechanisms that regulate gastric inflammation and the development of both dysplastic and neoplastic lesions of the stomach.

Il-10 deficient mice express IFN-γ mRNA and clear Leptospira interrogans from their kidneys more rapidly than normal C57BL/6 mice

Leptospira interrogans (L. interrogans), the causative agent of leptospirosis, is a widespread zoonotic spirochete that lives a dual lifestyle. L. interrogans infects mice, rats, and wildlife in a persistent and asymptomatic fashion, while also causing productive and acute infections in other mammals such as humans and hamsters. Infections in humans can be fatal, accompanied by a cytokine storm and shock-like symptoms. Production of IL-10 has been noted in both rodent and human infections which has led a number of investigators to hypothesize that IL-10 plays a role in the pathogenesis of this disease. To test this hypothesis we have compared bacteremia and the cytokine response of normal and IL-10 deficient C57Bl/6 mice following ip infection with L. interrogans. In normal mice bacterial 16s mRNA was detected in both lung and kidney tissues within a day after infection. Levels of 16s mRNA then dropped in both organs with complete elimination from the lung by day 3 but persistence in the kidney for 7days after infection. In contrast, in IL-10 deficient mice, the organism was eliminated more rapidly from the kidney. We found that infection of both control and IL-10 deficient mice produced similar levels of a number of pro-inflammatory cytokine mRNAs. On the other hand, IFN-γ mRNA was only induced in IL-10 deficient mice. These results support the hypothesis that L. interrogans ability to induce IL-10, which in turn prevents production of IFN-γ and inhibits T cell immunity, may contribute to the persistent growth of this microorganism in the murine kidney.

IL-22-induced antimicrobial peptides are key determinants of mucosal vaccine-induced protection against H. pylori in mice

Despite the recent description of the mucosal vaccine-induced reduction of Helicobacter pylori natural infection in a phase 3 clinical trial, the absence of immune correlates of protection slows the final development of the vaccine. In this study, we evaluated the role of interleukin (IL)-22 in mucosal vaccine-induced protection. Gastric IL-22 levels were increased in mice intranasally immunized with urease+cholera toxin and challenged with H. felis, as compared with controls. Flow cytometry analysis showed that a peak of CD4+IL-22+IL-17+ T cells infiltrating the gastric mucosa occurred in immunized mice in contrast to control mice. The inhibition of the IL-22 biological activity prevented the vaccine-induced reduction of H. pylori infection. Remarkably, anti-microbial peptides (AMPs) extracted from the stomachs of vaccinated mice, but not from the stomachs of non-immunized or immunized mice, injected with anti-IL-22 antibodies efficiently killed H. pylori in vitro. Finally, H. pylori infection in vaccinated RegIIIβ-deficient mice was not reduced as efficiently as in wild-type mice. These results demonstrate that IL-22 has a critical role in vaccine-induced protection, by promoting the expression of AMPs, such as RegIIIβ, capable of killing Helicobacter. Therefore, it can be concluded that urease-specific memory Th17/Th22 cells could constitute immune correlates of vaccine protection in humans.