Role of Peyer's patches in the induction of Helicobacter pylori-induced gastritis

Helicobacter pylori infection and risk of multiple sclerosis: an updated meta-analysis

Numerous studies have proposed that Helicobacter pylori infection may possess a protective effect in terms of future risk of multiple sclerosis (MS), however is poorly evidenced. We performed a systematic review and meta-analysis to obtain the pooled results regarding the prevalence of H. pylori infection in persons with multiple sclerosis (pwMS) and healthy controls. A comprehensive database search was performed in PubMed, Embase, and medRxiv for all relevant literature published from the inception of the databases until the August 1, 2022. The retrieved articles were first screened by title and abstract, followed by full-text screening based on the pre-established eligibility criteria. The risk of bias was assessed using the ROBINS-I tool. Data on the seroprevalence of H. pylori in pwMS and healthy controls was extracted, and a meta-analysis was performed in Review Manager Version 5.4.1. Sub-group analysis was performed in accordance with the geographical distribution (Eastern and Western countries) and the method of detection of H. pylori infection enzyme-linked-immunoassay (ELISA), Immunofluorescence, Immunochromatography). Furthermore, sensitivity analyses and publication bias were determined. The preliminary database search retrieved a total of 822 studies. Seventeen case-control studies with a total of 2721 pwMS and 2245 controls were included as a final sample size for the meta-analysis. The overall risk of bias was moderate. Overall, the rate of H. pylori infection in pwMS was not significantly different than in healthy controls (OR: 0.79 (95% CI = 0.58-1.08); I2 = 79%, p = 0.14). Subgroup analysis revealed that the rate of H. pylori infection among PwMS was not significant in both Eastern and Western countries (OR: 0.75 (95% CI = 0.52-1.08); I2 = 81%, p = 0.12). In contrast, data revealed that the prevalence of H. pylori infection in pwMS was significantly lower than that of control based on studies utilizing ELISA assays detection (OR: 0.71 (95% CI = 0.50-1.00); I2 = 81%, p = 0.05), while no significant difference was seen on studies using other assays than ELISA (OR: 1.19 (95% CI = 0.81-1.77); I2 = 0%, p = 0.38). Our findings of statistically indifferent prevalence of H. pylori infection as compared between pwMS and healthy controls suggested the absence of protective effect for risk of MS following H. pylori infection.

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

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

The inhibitory effect of oral administration of lentinan on DSS-induced inflammation is exerted by the migration of T cells activated in the ileum to the colon

Oral administration of lentinan ameliorated dextran sulfate sodium (DSS)-induced colitis through Dectin-1 receptor on intestinal epithelial cells. However, it is unclear where lentinan affects in the intestine to prevent the inflammation. We found that the administration of lentinan has induced migration of CD4+ cells from the ileum to the colon by using Kikume Green-Red (KikGR) mice in this study. This result suggests that the oral lentinan treatment could accelerate the migration of Th cells in lymphocyte from ileum into the colon during lentinan intake. Then, C57BL/6 mice were administered 2% DSS to induce colitis. The mice were administered lentinan daily via oral or rectal route before DSS administration. Its rectal administration also suppressed DSS-induced colitis, but its suppressive effects were lower compared to when orally administered, indicating that the biological responses to lentinan in the small intestine contributed to the anti-inflammatory effects. In normal mice (without DSS treatment), the expression of Il12b was significantly increased in the ileum by the oral administration of lentinan, but not by rectal one. On the other hand, no change was observed in the colon by either administration method. In addition, Tbx21 was significantly increased in the ileum. These suggested that IL-12 was increased in the ileum and Th1 cells differentiated in dependence on it. Therefore, Th1 predominant condition in the ileum could influence immunity in the colon and improve the colitis.

Helicobacter pylori promotes colorectal carcinogenesis by deregulating intestinal immunity and inducing a mucus-degrading microbiota signature

OBJECTIVE

Helicobacter pylori infection is the most prevalent bacterial infection worldwide. Besides being the most important risk factor for gastric cancer development, epidemiological data show that infected individuals harbour a nearly twofold increased risk to develop colorectal cancer (CRC). However, a direct causal and functional connection between H. pylori infection and colon cancer is lacking.

DESIGN

We infected two Apc-mutant mouse models and C57BL/6 mice with H. pylori and conducted a comprehensive analysis of H. pylori-induced changes in intestinal immune responses and epithelial signatures via flow cytometry, chip cytometry, immunohistochemistry and single cell RNA sequencing. Microbial signatures were characterised and evaluated in germ-free mice and via stool transfer experiments.

RESULTS

H. pylori infection accelerated tumour development in Apc-mutant mice. We identified a unique H. pylori-driven immune alteration signature characterised by a reduction in regulatory T cells and pro-inflammatory T cells. Furthermore, in the intestinal and colonic epithelium, H. pylori induced pro-carcinogenic STAT3 signalling and a loss of goblet cells, changes that have been shown to contribute-in combination with pro-inflammatory and mucus degrading microbial signatures-to tumour development. Similar immune and epithelial alterations were found in human colon biopsies from H. pylori-infected patients. Housing of Apc-mutant mice under germ-free conditions ameliorated, and early antibiotic eradication of H. pylori infection normalised the tumour incidence to the level of uninfected controls.

CONCLUSIONS

Our studies provide evidence that H. pylori infection is a strong causal promoter of colorectal carcinogenesis. Therefore, implementation of H. pylori status into preventive measures of CRC should be considered.

C-type lectin Mincle-dependent and -independent activation of invariant NKT cells by exposure to Helicobacter pylori α-cholesteryl glucosides

Helicobacter pylori extracts cholesterol from the host and converts it to its glycosides. We found that cholesteryl 6'-O-acyl α-glucoside (ChAcαG) produced by H. pylori is recognised by both invariant Vα14⁺ NKT (iNKT) cells and a C-type lectin receptor Mincle (Clec4e). However, it is unclear how these duplicated recognitions cooperate and contribute to host defence against H. pylori. Among T cell populations in the liver, iNKT cells predominantly expressed the T cell activation marker CD69 just after stimulation with ChAcαG. The production of IFN-γ and IL-4 was strictly dependent on both CD1d and Jα18 expressions, indicating the necessity of iNKT cell activation for the initiation of immune responses. Production of IFN-γ by iNKT cells was markedly reduced by the Mincle deficiency on antigen-presenting cells (APCs), while IL-4 production was not significantly influenced. IL-2 production by iNKT cell hybridomas was also diminished by the Mincle deficiency upon stimulation with APCs previously loaded with ChAcαG. Here, the immune responses of iNKT cell hybridomas stimulated with wild-type APCs were reduced by the addition of anti-IL-12 blocking antibody to the level stimulated with Mincle-deficient APCs. Collectively, these results suggest that iNKT cells can be activated with the cholesteryl glycosides via a Mincle-dependent, IL-12 signal-dependent pathway and a Mincle-independent, invariant TCR signal-dominant pathway. iNKT cells activated via the Mincle-dependent pathway produce IFN-γ-dominant cytokines; hence, they may contribute to enhancing proinflammatory responses against H. pylori infection.

Recombinant Helicobacter pylori Vaccine Delivery Vehicle: A Promising Tool to Treat Infections and Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) has become a global public health threat. Experts agree that unless proper actions are taken, the number of deaths due to AMR will increase. Many strategies are being pursued to tackle AMR, one of the most important being the development of efficient vaccines. Similar to other bacterial pathogens, AMR in Helicobacter pylori (Hp) is rising worldwide. Hp infects half of the human population and its prevalence ranges from <10% in developed countries to up to 90% in low-income countries. Currently, there is no vaccine available for Hp. This review provides a brief summary of the use of antibiotic-based treatment for Hp infection and its related AMR problems together with a brief description of the status of vaccine development for Hp. It is mainly dedicated to genetic tools and strategies that can be used to develop an oral recombinant Hp vaccine delivery platform that is (i) completely attenuated, (ii) can survive, synthesize in situ and deliver antigens, DNA vaccines, and adjuvants to antigen-presenting cells at the gastric mucosa, and (iii) possibly activate desired compartments of the gut-associated mucosal immune system. Recombinant Hp vaccine delivery vehicles can be used for therapeutic or prophylactic vaccination for Hp and other microbial pathogens.

Intestinal single-cell atlas reveals novel lymphocytes in pigs with similarities to human cells

Single-cell RNA sequencing of porcine ileal lymphocytes reveals similarities to human cells and discovery of porcine intestinal innate lymphoid cells.

Lymphocytes can heavily influence intestinal health, but resolving intestinal lymphocyte function is challenging as the intestine contains a vastly heterogeneous mixture of cells. Pigs are an advantageous biomedical model, but deeper understanding of intestinal lymphocytes is warranted to improve model utility. Twenty-six cell types were identified in the porcine ileum by single-cell RNA sequencing and further compared with cells in human and murine ileum. Though general consensus of cell subsets across species was revealed, some porcine-specific lymphocyte subsets were identified. Differential tissue dissection and in situ analyses conferred spatial context, revealing similar locations of lymphocyte subsets in Peyer’s patches and epithelium in pig-to-human comparisons. Like humans, activated and effector lymphocytes were abundant in the ileum but not periphery of pigs, suggesting tissue-specific and/or activation-associated gene expression. Gene signatures for peripheral and ileal innate lymphoid cells newly discovered in pigs were defined and highlighted similarities to human innate lymphoid cells. Overall, we reveal novel lymphocyte subsets in pigs and highlight utility of pigs for intestinal research applications.

The porcine large intestine contains developmentally distinct submucosal lymphoid clusters and mucosal isolated lymphoid follicles

Gut-associated lymphoid tissues (GALT) serve as key priming sites for intestinal adaptive immune responses. Most of our understanding of GALT function and development arises from studies in mice. However, the diversity, structure and cellular composition of GALT differs markedly between mammalian species and the developmental window in which distinct GALT structures develop in large mammals remains poorly understood. Given the importance of pigs as models of human disease, as well as their role in livestock production, we adapted a recently developed protocol for the isolation of human GALT to assess the diversity, development and immune composition of large intestinal GALT in neonatal and adult pigs. We demonstrate that the large intestine of adult pigs contains two major GALT types; multifollicular submucosal GALT that we term submucosal lymphoid clusters (SLC) which develop prenatally, and as yet undescribed mucosal isolated lymphoid follicles (M-ILF), which arise after birth. Using confocal laser microscopy and flow cytometry, we additionally assess the microanatomy and lymphocyte composition of SLC and M-ILF, compare them to jejunal Peyer's patches (PP), and describe the maturation of these structures. Collectively, our results provide a deeper understanding of the diversity and development of GALT within the porcine large intestine.

Efficacy and Safety of Zuojin Pill for the Treatment of Chronic Nonatrophic Gastritis: A Randomized Active-Controlled Clinical Trial

Objective

Zuojin pill (ZJP) is used as the classical prescription for a wide variety of digestive diseases. However, there is a lack of direct evidence for its use in the treatment of chronic nonatrophic gastritis (CNG). In particular, there is a lack of rigorous trials of randomized controlled designs. In this study, a randomized active-controlled clinical trial was performed to verify the efficacy and safety of ZJP in detail.

Methods

Patients with CNG were divided into the ZJP group and the Marzulene-S granule group. Patients were enrolled from September 2019 to February 2021 (ChiCTR2000040549). Endoscopy and histology scores were evaluated as the primary outcome measure. The Helicobacter pylori positive rate and the disappearance rate of symptoms were also measured to reflect the outcomes. Finally, adverse events were also calculated as the index of safety.

Results

A total of 68 eligible patients were enrolled in this trial and randomly divided into two groups with baseline comparability. ZJP was able to improve the red plaques as well as bile reflux scores compared with Marzulene-S granule (P=0.043 and P=0.019, respectively). Moreover, it also remarkably alleviated the active chronic inflammation score (P=0.043). However, there was no difference between the Helicobacter pylori positivity rate (P=0.752). The symptom scores of abdominal distension (P=0.004), belching (P=0.010), and loss of appetite (P=0.019) were alleviated by ZJP, but nausea and vomiting were not (P=0.616). ZJP can also be considered safe with no obvious adverse effects.

Conclusion

ZJP might decrease mucosal injury and alleviate symptoms in CNG. In addition, more large-scale clinical trials should be carried out to further confirm its clinical efficacy and safety.

Helicobacter Pylori and Autoimmune Diseases: Involving Multiple Systems

The modern Gastroenterology have witnessed an essential stride since Helicobacter pylori was first found in the stomach and then its pathogenic effect was discovered. According to the researches conducted during the nearly 40 years, it has been found that this bacterium is associated with a natural history of many upper gastrointestinal diseases. Epidemiological data show an increased incidence of autoimmune disorders with or after infection with specific microorganisms. The researches have revealed that H. pylori is a potential trigger of gastric autoimmunity, and it may be associated with other autoimmune diseases, both innate and acquired. This paper reviews the current support or opposition about H. pylori as the role of potential triggers of autoimmune diseases, including inflammatory bowel disease, autoimmune thyroiditis, type 1 diabetes mellitus, autoimmune liver diseases, rheumatoid arthritis, idiopathic thrombocytopenic purpura, systemic lupus erythematosus, as well as Sjogren’s syndrome, chronic urticaria and psoriasis, and tried to explain the possible mechanisms.

Progress in elucidating the relationship between Helicobacter pylori infection and intestinal diseases

Helicobacter pylori (H. pylori) infection causes changes to the intestinal flora, such as small intestinal bacterial overgrowth, and increases gastric acid secretion-stimulating gastrointestinal hormones, mainly gastrin, due to a decrease in gastric acid caused by atrophic gastritis. In addition, the cellular components of H. pylori travel through the intestinal tract, so the bacterial infection affects the immune system. Therefore, the effects of H. pylori infection are observed not only in the stomach and the proximal duodenum but also in the small and large intestines. In particular, meta-analyses reported that H. pylori-infected individuals had an increased risk of colorectal adenoma and colorectal cancer. Moreover, a recent study reported that the risk of developing colorectal cancer was increased in subjects carrying H. pylori vacuolating cytotoxin A antibody. In addition, it has been reported that H. pylori infection exacerbates the symptoms of Fabry’s disease and familial Mediterranean fever attack and is involved in irritable bowel syndrome and small intestinal ulcers. On the other hand, some studies have reported that the frequency of ulcerative colitis, Crohn’s disease, and celiac disease is low in H. pylori-infected individuals. Thus, H. pylori infection is considered to have various effects on the small and large intestines. However, few studies have reported on these issues, and the details of their effects have not been well elucidated. Therefore, additional studies are needed.

Recent strategies driving oral biologic administration

INTRODUCTION

High patient compliance, noninvasiveness, and self-administration are the leading features of vaccine delivery through the oral route. The implementation of swift mass vaccination campaigns in pandemic outbreaks fascinates the use of oral vaccination. This approach can elicit both mucosal and systemic immune responses to protect against infection at the surface of the mucosa.

AREA COVERED

As pathogen entry and spread mainly occurs through the gastrointestinal tract (GIT) mucosal surfaces, oral vaccination may protect and limit disease spread. Oral vaccines target various potential mucosal inductive sites in the GIT, such as the oral cavity, gastric area, and small intestine. Orally delivered vaccines having subunit and nucleic acid pass through various GIT-associated risks, such as the biodegradation of biologics and their reduced absorption. This article presents a summarized review of the existing technologies and prospects for oral vaccination.

EXPERT OPINION

The intestinal mucosa focuses on current approaches, while future strategies target new mucosal sites, i.e. oral cavity and stomach. Recent developments in biologic delivery through the oral route and their potential use in future oral vaccination are mainly considered.

Helicobacter pylori metabolites exacerbate gastritis through C-type lectin receptors

Helicobacter pylori causes gastritis, which has been attributed to the development of H. pylori-specific T cells during infection. However, the mechanism underlying innate immune detection leading to the priming of T cells is not fully understood, as H. pylori evades TLR detection. Here, we report that H. pylori metabolites modified from host cholesterol exacerbate gastritis through the interaction with C-type lectin receptors. Cholesteryl acyl α-glucoside (αCAG) and cholesteryl phosphatidyl α-glucoside (αCPG) were identified as noncanonical ligands for Mincle (Clec4e) and DCAR (Clec4b1). During chronic infection, H. pylori-specific T cell responses and gastritis were ameliorated in Mincle-deficient mice, although bacterial burdens remained unchanged. Furthermore, a mutant H. pylori strain lacking αCAG and αCPG exhibited an impaired ability to cause gastritis. Thus H. pylori-specific modification of host cholesterol plays a pathophysiological role that exacerbates gastric inflammation by triggering C-type lectin receptors.

Human gut-associated lymphoid tissues (GALT); diversity, structure, and function

Gut-associated lymphoid tissues (GALT) are the key antigen sampling and adaptive immune inductive sites within the intestinal wall. Human GALT includes the multi-follicular Peyer's patches of the ileum, the vermiform appendix, and the numerous isolated lymphoid follicles (ILF) which are distributed along the length of the intestine. Our current understanding of GALT diversity and function derives primarily from studies in mice, and the relevance of many of these findings to human GALT remains unclear. Here we review our current understanding of human GALT diversity, structure, and composition as well as their potential for regulating intestinal immune responses during homeostasis and inflammatory bowel disease (IBD). Finally, we outline some key remaining questions regarding human GALT, the answers to which will advance our understanding of intestinal immune responses and provide potential opportunities to improve the treatment of intestinal diseases.

Structure, metabolism and biological functions of steryl glycosides in mammals

Steryl glycosides (SGs) are sterols glycosylated at their 3β-hydroxy group. They are widely distributed in plants, algae, and fungi, but are relatively rare in bacteria and animals. Glycosylation of sterols, resulting in important components of the cell membrane SGs, alters their biophysical properties and confers resistance against stress by freezing or heat shock to cells. Besides, many biological functions in animals have been suggested from the observations of SG administration. Recently, cholesteryl glucosides synthesized via the transglycosidation by glucocerebrosidases (GBAs) were found in the central nervous system of animals. Identification of patients with congenital mutations in GBA genes or availability of respective animal models will enable investigation of the function of such endogenously synthesized cholesteryl glycosides by genetic approaches. In addition, mechanisms of the host immune responses against pathogenic bacterial SGs have partially been resolved. This review is focused on the biological functions of SGs in mammals taking into consideration their therapeutic applications in the future.

Regional heterogeneity in rat Peyer's patches through whole transcriptome analysis

Peyer's patches are gut-associated lymphoid tissue located throughout the intestinal wall. Peyer's patches consist of highly organized ovoid-shaped follicles, classified as non-encapsulated lymphatic tissues, populated with B cells, T cells, macrophages, and dendritic cells and function as an organism's intestinal surveillance. Limited work compares the gene profiles of Peyer's patches derived from different intestinal regions. In the current study, we first performed whole transcriptome analysis using RNAseq to compare duodenal and ileal Peyer's patches obtained from the small intestine of Long Evans rats. Of the 12,300 genes that were highly expressed, 18.5% were significantly different between the duodenum and ileum. Using samples obtained from additional subjects (n = 10), we validated the novel gene expression patterns in Peyer's patches obtained from the three regions of the small intestine. Rats had a significantly reduced number of Peyer's patches in the duodenum in comparison to either the jejunum or ileum. Regional differences in structural, metabolic, and immune-related genes were validated. Genes such as alcohol dehydrogenase 1, gap junction protein beta 2, and serine peptidase inhibitor clade b, member 1a were significantly reduced in the ileum in comparison to other regions. On the other hand, genes such as complement C3d receptor type, lymphocyte cytosolic protein 1, and lysozyme C2 precursor were significantly lower in the duodenum. In summary, the gene expression pattern of Peyer's patches is influenced by intestinal location and may contribute to its role in that segment.

Oral Biologic Delivery: Advances Toward Oral Subunit, DNA, and mRNA Vaccines and the Potential for Mass Vaccination During Pandemics

Oral vaccination enables pain-free and self-administrable vaccine delivery for rapid mass vaccination during pandemic outbreaks. Furthermore, it elicits systemic and mucosal immune responses. This protects against infection at mucosal surfaces, which may further enhance protection and minimize the spread of disease. The gastrointestinal (GI) tract presents a number of prospective mucosal inductive sites for vaccine targeting, including the oral cavity, stomach, and small intestine. However, currently available oral vaccines are effectively limited to live-attenuated and inactivated vaccines against enteric diseases. The GI tract poses a number of challenges,including degradative processes that digest biologics and mucosal barriers that limit their absorption. This review summarizes the approaches currently under development and future opportunities for oral vaccine delivery to established (intestinal) and relatively new (oral cavity, stomach) mucosal targets. Special consideration is given to recent advances in oral biologic delivery that offer promise as future platforms for the administration of oral vaccines.

Ileo-colonic lymphoma: presentation, diagnosis, and management

PURPOSE OF REVIEW

The gut-associated lymphoid tissue (GALT), the bulk of which is located in the ileo-colonic region comprises the lymphoid cells of the gastrointestinal tract and confers specific immunological responses. Repetitive antigenic stimulation of these cells predispose to a monoclonal proliferation of this tissue and the eventual development of lymphoma. The gastrointestinal tract is the most commonly involved site of extranodal lymphomas. This review will focus primarily on lymphomas of the ileo-colonic region (defined as the terminal ileum, the colon, and the rectum). We will discuss the epidemiology, pathogenesis, and presentation as well as current practices in diagnosis and management.

RECENT FINDINGS

Despite the majority of the GALT to be located in the ileo-colonic region of the gut, the lymphomas in this location are relatively rare. However, the overall annual incidence of ileo-colonic lymphomas is steadily increasing. This entity has a varied spectrum of clinical presentations. Ileo-colonoscopy with adequate targeted biopsies can serve as a gold standard for definitive diagnosis. Ileo-colonic lymphomas may be managed with chemotherapy alone while surgery is reserved for highly aggressive tumors or clinical emergencies. Radiation is not a preferred adjuvant treatment for lymphomas in this location of the gut. Adequate endoscopic surveillance measures and tools to potentially prevent recurrence and improve the overall prognosis of this disease are lacking.

SUMMARY

Ileo-colonic lymphomas are rare and can present with varied symptoms and signs. Endoscopy with adequate sampling can aid in making a definitive diagnosis. Chemotherapy can be highly effective in management while surgery is indicated for emergency presentations. Adequate endoscopic surveillance tools are lacking, yet imperative to prevent recurrence and improve prognosis.

Male-Dependent Promotion of Colitis in 129 Rag2-/- Mice Co-Infected with Helicobacter pylori and Helicobacter hepaticus

The prevalence of gastric Helicobacter pylori (Hp) infection is ~50% of the world population. However, how Hp infection influences inflammatory bowel disease in humans is not fully defined. In this study, we examined whether co-infection with Hp influenced Helicobacter hepaticus (Hh)–induced intestinal pathology in Rag2^−/− mice. Rag2^−/− mice of both sexes were infected with Hh, of which a subgroup was followed by infection with Hp two weeks later. Co-infected males, but not females, had significantly higher total colitis index scores in the colon at both 10 and 21 weeks post-Hh infection (WPI) and developed more severe dysplasia at 21 WPI compared with mono-Hh males. There were no significant differences in colonization levels of gastric Hp and colonic Hh between sexes or time-points. In addition, mRNA levels of colonic Il-1β, Ifnγ, Tnfα, Il-17A, Il-17F, Il-18, and Il-23, which play important roles in the development and function of proinflammatory innate lymphoid cell groups 1 and 3, were significantly up-regulated in the dually infected males compared with mono-Hh males at 21 WPI. These data suggest that concomitant Hp infection enhances the inflammatory responses in the colon of-Hh-infected Rag2^−/− males, which results in more severe colitis and dysplasia.

A peptide of a type I toxin-antitoxin system induces Helicobacter pylori morphological transformation from spiral shape to coccoids

Toxin-antitoxin systems are found in many bacterial chromosomes and plasmids with roles ranging from plasmid stabilization to biofilm formation and persistence. In these systems, the expression/activity of the toxin is counteracted by an antitoxin, which, in type I systems, is an antisense RNA. While the regulatory mechanisms of these systems are mostly well defined, the toxins' biological activity and expression conditions are less understood. Here, these questions were investigated for a type I toxin-antitoxin system (AapA1-IsoA1) expressed from the chromosome of the human pathogen Helicobacter pylori We show that expression of the AapA1 toxin in H. pylori causes growth arrest associated with rapid morphological transformation from spiral-shaped bacteria to round coccoid cells. Coccoids are observed in patients and during in vitro growth as a response to different stress conditions. The AapA1 toxin, first molecular effector of coccoids to be identified, targets H. pylori inner membrane without disrupting it, as visualized by cryoelectron microscopy. The peptidoglycan composition of coccoids is modified with respect to spiral bacteria. No major changes in membrane potential or adenosine 5'-triphosphate (ATP) concentration result from AapA1 expression, suggesting coccoid viability. Single-cell live microscopy tracking the shape conversion suggests a possible association of this process with cell elongation/division interference. Oxidative stress induces coccoid formation and is associated with repression of the antitoxin promoter and enhanced processing of its transcript, leading to an imbalance in favor of AapA1 toxin expression. Our data support the hypothesis of viable coccoids with characteristics of dormant bacteria that might be important in H. pylori infections refractory to treatment.

H.pylori Infection Alleviates Acute and Chronic Colitis with the Expansion of Regulatory B Cells in Mice

Epidemiological studies showed that there was an inverse relationship between Helicobacter pylori (H. pylori) infection and the incidence of inflammatory bowel diseases (IBD). Our previous research indicated that the regulatory immune responses induced by H. pylori infection were not limited to gastric mucosa, and the balance of intestinal mucosal immunity was influenced. In this study, mice were infected with H. pylori SS1, and then colitis was induced by 3% dextran sulphate sodium (DSS), to investigate the role of the regulatory B cells in the effects of H. pylori infection on acute and chronic colitis. In acute and chronic colitis groups, DAI and colonic histological scores reduced significantly and colon length shorted less, the proinflammatory cytokines mRNA expression downregulated in colonic mucosa, and the percentages of CD19⁺IL-10⁺Breg cells were higher in the H. pylori/DSS co-treated groups compared with the DSS-treated groups. Our study suggests that H. pylori infection can alleviate the acute and chronic colitis induced by DSS, and CD19⁺IL-10⁺Breg cells may play a critical role in the alleviation of acute and chronic colitis following H. pylori infection.

Epitope peptides of Helicobacter pylori CagA antibodies from sera by whole-peptide mapping

BACKGROUND

Helicobacter pylori CagA has been found to be immuno-dominant protein and utilized for the diagnosis of the infection with cagA-positive strains. It is important to characterize the peptide epitopes capable of detecting serum anti-CagA antibodies to understand CagA immunogenicity.

METHODS

Sera from 171 Japanese patients were subjected for the epitope mapping study. Eighty seven peptides were designed from the CagA consensus sequence and were used for ELISA protocol to test the serum samples. The reacting anti-CagA IgG amounts to specific peptides were measured and compared.

RESULTS

The study revealed a strong reactivity of two peptides (c7-NNTEPIYAQVNKKKAGQAT and c8-AGQATSPEEPIYAQVAKKV) in H. pylori-infected group. Interestingly, these two peptides contained the well-known EPIYA-A and EPIYA-B region, respectively, which are two out of three CagA phosphorylation domains. Tyrosine-phosphorylation of these peptides reduced their reactivity in most sera. Moreover, additional peptides' mapping and chimeric-peptides' experiments indicated that the amino acids (QV and KK) accommodated in right-side flanking regions of both EPIYA-motifs were essential for their strong reactivity, whereas the third EPIYA-motif containing peptide (c12-GRSASPEPIYATIDFDEA) with differing flanking amino acids was not reactive in most cases.

CONCLUSIONS

Our results suggest that the amino acid sequences constituted in the two reactive peptides are the important immunogenic regions of CagA which would be useful to develop next-generation peptide-based diagnostic assays.

Relationship between Helicobacter pylori Infection and Plasmacytoid and Myeloid Dendritic Cells in Peripheral Blood and Gastric Mucosa of Children

PURPOSE

To investigate the frequency and activation status of peripheral plasmacytoid DCs (pDCs) and myeloid DCs (mDCs) as well as gastric mucosa DC subset distribution in Helicobacter pylori- (H. pylori-) infected and noninfected children.

MATERIALS AND METHODS

Thirty-six children were studied; twenty-one had H. pylori. The frequencies of circulating pDCs (lineage-HLA-DR+CD123+) and mDCs (lineage-HLA-DR+CD11c+) and their activation status (CD83, CD86, and HLA-DR expression) were assessed by flow cytometry. Additionally, the densities of CD11c+, CD123+, CD83+, CD86+, and LAMP3+ cells in the gastric mucosa were determined by immunohistochemistry.

RESULTS

The frequency of circulating CD83+ mDCs was higher in H. pylori-infected children than in the noninfected controls. The pDCs demonstrated upregulated HLA-DR surface expression, but no change in CD86 expression. Additionally, the densities of gastric lamina propria CD11c+ cells and epithelial pDCs were increased. There was a significant association between frequency of circulating CD83+ mDCs and gastric lamina propria mDC infiltration.

CONCLUSION

This study shows that although H. pylori-infected children had an increased population of mature mDCs bearing CD83 in the peripheral blood, they lack mature CD83+ mDCs in the gastric mucosa, which may promote tolerance to local antigens rather than immunity. In addition, this may reduce excessive inflammatory activity as reported for children compared to adults.

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.

Gastrointestinal lymphoma: the new mimic

Background

Gastrointestinal (GI) lymphomas comprise a group of distinct clinicopathological entities of B- or T- cell type, with primary gastrointestinal Hodgkin lymphoma being extremely uncommon. The GI tract is the predominant site of extranodal non-Hodgkin lymphoma accounting for 30–40% of all extranodal lymphomas. In the Western world, the stomach is the most commonly involved site followed by the small bowel. Several chronic inflammatory and immune-mediated disorders which predispose to accelerated cell turnover may lead to the malignant transformation of gut lymphocytes and ultimately manifest as GI lymphoma. The challenge for the clinical gastroenterologist is that these tumors may have varied presentations, ranging from nonspecific symptoms such as dyspepsia or bloating to abdominal pain, nausea, vomiting, GI bleeding, diarrhea, weight loss or bowel obstruction.

Objective

We illustrate the range of presentations of GI lymphoma with examples based on consecutive cases evaluated at our institution over a 6-month period. These cases demonstrate how appropriately directed endoscopic evaluation with biopsies has the potential to provide a definitive diagnosis and allow the patient to proceed to definitive therapy.

Conclusions

The GI tract is the most commonly involved site for extranodal lymphoma with the stomach being most frequently involved organ. Chronic Helicobacter pylori infection, celiac disease, inflammatory bowel disease and autoimmune disorders may predispose to GI lymphoma. This heterogenous group of diseases has varied presentations that may mimic several other GI clinico-pathologic entities. GI lymphomas may be diagnosed with appropriately directed endoscopic evaluation coupled with generous tissue sampling and expert pathologic assessment. Management may range from antibiotic therapy, in the case of Helicobacter pylori-associated gastric MALT lymphoma, to chemotherapy with or without radiation and, in rare instances, surgery. There are presently no guidelines to direct endoscopic surveillance of GI lymphomas following treatment.

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.

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.

Characterization of morphological conversion of Helicobacter pylori under anaerobic conditions

Helicobacter pylori (H. pylori), a gram-negative microaerophilic bacterial pathogen that colonizes the stomachs of more than half of all humans, is linked to chronic gastritis, peptic ulcers and gastric cancer. Spiral-shaped H. pylori undergo morphologic conversion to a viable but not culturable coccoid form when they transit from the microaerobic stomach into the anaerobic intestinal tract. However, little is known about the morphological and pathogenic characteristics of H. pylori under prolonged anaerobic conditions. In this study, scanning electron microscopy was used to document anaerobiosis-induced morphological changes of H. pylori, from helical to coccoid to a newly defined fragmented form. Western blot analysis indicated that all three forms express certain pathogenic proteins, including the bacterial cytotoxin-associated gene A (CagA), components of the cag-Type IV secretion system (TFSS), the blood group antigen-binding adhesin BabA, and UreA (an apoenzyme of urease), almost equally. Similar urease activities were also detected in all three forms of H. pylori. However, in contrast to the helical form, bacterial motility and TFSS activity were found to have been abrogated in the anaerobiosis-induced coccoid and fragmented forms of H. pylori. Notably, it was demonstrated that some of the anaerobiosis-induced fragmented state cells could be converted to proliferation-competent helical bacteria in vitro. These results indicate that prolonged exposure to the anaerobic intestine may not eliminate the potential for H. pylori to revert to the helical pathogenic state.

DEC205 mediates local and systemic immune responses to Helicobacter pylori infection in humans

Helicobacter pylori infections cause gastritis and affect systemic immune responses; however, no direct association between immune cells and stomach bacteria has yet been reported. The present study investigated DEC205-mediated phagocytosis of H. pylori and the role of DEC205-positive macrophages in the human gastric mucosa. DEC205 mediated phagocytosis of H. pylori was detected immunocytochemically in PMA-stimulated macrophages differentiated from NOMO1 cells. Expression of DEC205 mRNA in peripheral blood mononuclear cells (PBMCs) from H. pylori-infected patients was analyzed following stimulation with H. pylori cell lysate. We found that anti-DEC205 antibodies inhibited phagocytosis of H. pylori. The number of cells double-positive for DEC205 and CD14 in human gastric mucosa was higher in H. pylori-infected patients. DEC205-positive macrophages invaded the extracellular space between epithelial cells within gastric pits. In addition, DEC205 mRNA expression was upregulated in human PBMCs stimulated with H. pylori lysate. These findings suggest DEC205-expressing macrophages are important for recognition of H. pylori in human gastric mucosa, which affects systemic immunity.

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.

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.

Interferon-γ-producing B cells induce the formation of gastric lymphoid follicles after Helicobacter suis infection

Helicobacter (H.) suis is capable of infecting various animals including humans, and H. suis infections can lead to gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Recently, we reported that interferon-γ (IFN-γ) was highly expressed in the stomachs of H. suis-infected mice, but the direct relationship between the upregulation of IFN-γ expression and the formation of gastric lymphoid follicles after H. suis infection remains unclear. Here, we demonstrated that the IFN-γ produced by B cells plays an important role in the formation of gastric lymphoid follicles after H. suis infection. In addition, IFN-γ-producing B cells evoked gastric lymphoid follicle formation independent of T-cell help, suggesting that they are crucial for the development of gastric MALT induced by Helicobacter infection.

Helicobacter pylori and gastric cancer: a state of the art review

Gastric cancer is the third most common cause of cancer-related death in the world. It is now well- established that Helicobacter pylori infection predispose individuals toward gastric adenocarcinoma later in life. It has since been classified as a class I carcinogen by the World Health Organization. Research suggests that the oncogenic effects of Helicobacter pylori can occur through a variety of mechanisms, including the indirect inflammatory effects of Helicobacter pylori on the gastric mucosa and the direct epigenetic effects of Helicobacter pylori on individual cells. Whilst infected with Helicobacter pylori, a combination of environmental and host-dependent factors determines the likelihood of developing gastric cancer. Controversy remains regarding the effects of eradication of Helicobacter pylori on the prevention of further progression of gastric lesions and the possibility for regression of atrophic gastritis. The aim of this review is to synthesis different elements that contribute to the step-wise progression of normal gastric mucosa to gastric adenocarcinoma. This review helps clinicians to better identify those infected individuals who are at high risk of developing gastric cancer and implement the necessary investigations and treatment.

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

BACKGROUND

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

RESULTS

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

CONCLUSION

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

Genetic determinants and clinico-pathological outcomes of helicobacter pylori infection

Helicobacter pylori is a spiral Gram-negative bacterium with a relatively small genome and is known to be the most common human bacterial infection worldwide, infecting about half of the world's population. The bacterium represents one of the most successful human pathogens, inducing severe clinical symptoms only in a small subset of individuals, thus signifying a highly balanced degree of co-evolution of H. pylori and humans. The prevalence of Helicobacter pylori infection varies greatly among countries and among population groups within the same country, but is falling in most developed countries. The clinical course of H. pylori infection is highly variable and is influenced by both microbial and host factors including genetic susceptibility while the pattern and distribution of inflammation correlate strongly with the risk of clinical sequelae, namely duodenal or gastric ulcers, mucosal atrophy, gastric carcinoma, or gastric lymphoma. Cytokine gene polymorphisms directly influence inter-individual variation in the magnitude of cytokine response, and this clearly contributes to an individual's ultimate clinical outcome. Polymorphisms in genes coding for innate immune factors have also been incriminated in the pathogenesis of H. pylori related disease, while promoter hypermethylation of tumor suppressor genes is considered an important factor in carcinogenesis and known to be present in H. pylori associated gastric tumors. Functional genomics may fill many of the gaps in our understanding of the pathogenesis of H. pylori infection and accelerate the development of novel therapies, including H. pylori specific antimicrobial agents.

Helicobacter pylori infection in gastric mucosa-associated lymphoid tissue lymphoma

Gastrointestinal lymphoma is the most common type of extranodal lymphoma, and most commonly affects the stomach. Marginal zone B-cell lymphoma of the mucosa-associated lymphoid tissue (MALT) and diffuse large B-cell lymphoma are the most common histologic types of gastric lymphoma. Despite its increasing incidence, diagnosis of gastric lymphoma is difficult at an earlier stage due to its nonspecific symptoms and endoscopic findings, and, thus, a high index of suspicion, and multiple, deep, repeated biopsies at abnormally and normally appearing sites in the stomach are needed. In addition, testing for Helicobacter pylori (H. pylori) infection and endoscopic ultrasonography to determine the depth of tumor invasion and involvement of regional lymph nodes is essential for predicting response to H. pylori eradication and for assessment of disease progression. In addition, H. pylori infection and MALT lymphoma development are associated, and complete regression of low-grade MALT lymphomas after H. pylori eradication has been demonstrated. Radiotherapy and/or chemotherapy can be used in cases that show poor response to H. pylori eradication, negativity for H. pylori infection, or high-grade lymphoma.

A screening trial of Helicobacter pylori-specific antigen tests in saliva to identify an oral infection

OBJECTIVE

Helicobacter pylori infection places a heavy burden on medical and economic resources. Standard diagnosis requires the presence of established H. pylori gastric disease.

STUDY DESIGN AND SETTING

A multicenter screening trial assessing 2 immunochromatographic H. pylori antigen oral tests was carried out with 201 participants. The analysis also included a urea breath test (UBT), a Campylobacter-like organism test, silver stain, culture, serology, and stool tests.

RESULTS

The participants were grouped into UBT positive (UBT+) and UBT negative (UBT-) people, using conventional methods with congruent clusters based on p values from McNemar's paired χ2 analysis and 95% CI estimates. Both oral tests were also positive in 82% of the seropositive UBT- people. However, oral antigen and seroprevalence divided UBT- people into 2 statistically separate CI subgroups: the UBT- symptomatic (highly positive) group and the UBT- asymptomatic (mostly negative) group. 90.5% of all people whose oral tests were both negative were also UBT-.

CONCLUSIONS

Saliva H. pylori antigen is an important indicator in UBT- asymptomatic patients. Currently, its clinical significance remains uncertain, but saliva may be a reservoir from where H. pylori is transmitted to the stomach. In symptomatic patients, it is strongly associated with stomach infection.

Role of childhood infection in the sequelae of H. pylori disease

The persistence of Helicobacter pylori infection plays a fundamental role in the development of H. pylori-associated complications. Since the majority of infected persons acquire the bacteria during early childhood, an examination of the immunobiology of H. pylori infection in children compared with that of adults may help identify host factors that contribute to persistent infection. Therefore, we begin our review of the role of persistence in H. pylori disease with an assessment of the clinical features of H. pylori infection in children. We next review the bacterial factors that promote colonization and evasion of host defense mechanisms. We then focus our attention on the early host immunological factors that promote persistence of the infection and its complications in humans and mouse models. We also highlight topics in which further research is needed. An examination of how immunological factors cause divergent manifestations of H. pylori infection in children compared with adults may provide new insight for therapeutic modification or prevention of persistent H. pylori infection and its complications.

Why can't we make an effective vaccine against Helicobacter pylori?

Helicobacter pylori is a major human pathogen that colonizes the stomach and is the lead etiological agent for several pathologies. An effective vaccine against these bacteria would be invaluable for protecting against gastric adenocarcinoma. However, the development of such a vaccine has stalled and the field has progressed little in the last decade. In this review, the authors provide an opinion on key problems that are preventing the development of a H. pylori vaccine. Primarily, this involves the inability to produce a completely protective immune response. The knock-on effects of this include a loss of industry investment. Overcoming these problems will likely involve defeating the immune-evasion defenses of H. pylori, in particular the mechanism(s) by which it evades antibody-mediated attack.

Predictive computational modeling of the mucosal immune responses during Helicobacter pylori infection

T helper (Th) cells play a major role in the immune response and pathology at the gastric mucosa during Helicobacter pylori infection. There is a limited mechanistic understanding regarding the contributions of CD4+ T cell subsets to gastritis development during H. pylori colonization. We used two computational approaches: ordinary differential equation (ODE)-based and agent-based modeling (ABM) to study the mechanisms underlying cellular immune responses to H. pylori and how CD4+ T cell subsets influenced initiation, progression and outcome of disease. To calibrate the model, in vivo experimentation was performed by infecting C57BL/6 mice intragastrically with H. pylori and assaying immune cell subsets in the stomach and gastric lymph nodes (GLN) on days 0, 7, 14, 30 and 60 post-infection. Our computational model reproduced the dynamics of effector and regulatory pathways in the gastric lamina propria (LP) in silico. Simulation results show the induction of a Th17 response and a dominant Th1 response, together with a regulatory response characterized by high levels of mucosal Treg) cells. We also investigated the potential role of peroxisome proliferator-activated receptor γ (PPARγ) activation on the modulation of host responses to H. pylori by using loss-of-function approaches. Specifically, in silico results showed a predominance of Th1 and Th17 cells in the stomach of the cell-specific PPARγ knockout system when compared to the wild-type simulation. Spatio-temporal, object-oriented ABM approaches suggested similar dynamics in induction of host responses showing analogous T cell distributions to ODE modeling and facilitated tracking lesion formation. In addition, sensitivity analysis predicted a crucial contribution of Th1 and Th17 effector responses as mediators of histopathological changes in the gastric mucosa during chronic stages of infection, which were experimentally validated in mice. These integrated immunoinformatics approaches characterized the induction of mucosal effector and regulatory pathways controlled by PPARγ during H. pylori infection affecting disease outcomes.

Dendritic cell function in the host response to Helicobacter pylori infection of the gastric mucosa

Dendritic cells (DCs) play an important role as antigen-presenting cells that direct the nature of the adaptive immune response. Subtypes are differentiated by lineage, tissue, marker expression and function. Their function in promoting regulatory T cells in the gut to maintain immunologic homeostasis is well documented, but their role in the Helicobacter pylori-infected stomach is less clear. Some analyses of bone marrow-derived DCs stimulated with H. pylori have demonstrated proinflammatory potential based on secretion of IL-12 or IL-23 or activation of Th1 and Th17 cells. Other analyses indicate that H. pylori-activated DCs are less responsive compared with other gastrointestinal bacteria and activate DCs to promote Treg development. DC depletion in mice supports a role for DCs in down-regulating H. pylori-induced gastritis. These data indicate that gastric DCs recognize H. pylori much like DCs in the gut that recognize commensal organisms and promote a regulatory T-cell response. This is consistent with a growing body of literature documenting the prevalence and function of Treg cells in the host response to H. pylori. Research is now focused on characterizing how H. pylori induces such activity in DCs and identifying the mechanisms by which H. pylori-activated DCs activate Treg cells.