Helicobacter pylori glycan biosynthesis modulates host immune cell recognition and response.

Introduction: The pathogenic bacterium Helicobacter pylori has evolved glycan-mediated mechanisms to evade host immune defenses. This study tests the hypothesis that genetic disruption of H. pylori glycan biosynthesis alters immune recognition and response by human gastric epithelial cells and monocyte-derived dendritic cells. Methods: To test this hypothesis, human cell lines were challenged with wildtype H. pylori alongside an array of H. pylori glycosylation mutants. The relative levels of immune response were measured via immature dendritic cell maturation and cytokine secretion. Results: Our findings indicate that disruption of lipopolysaccharide biosynthesis diminishes gastric cytokine production, without disrupting dendritic cell recognition and activation. In contrast, variable immune responses were observed in protein glycosylation mutants which prompted us to test the hypothesis that phase variation plays a role in regulating bacterial cell surface glycosylation and subsequent immune recognition. Lewis antigen presentation does not correlate with extent of immune response, while the extent of lipopolysaccharide O-antigen elaboration does. Discussion: The outcomes of this study demonstrate that H. pylori glycans modulate the host immune response. This work provides a foundation to pursue immune-based tailoring of bacterial glycans towards modulating immunogenicity of microbial pathogens.

History of chronic gastritis: How our perceptions have changed.

Currently, the diagnostic strategy for chronic gastritis (CG) is aimed not just at fixing the presence of gastric mucosal inflammation, but also at gastric cancer (GC) risk stratification in a particular patient. Modern classification approach with the definition of the stage of gastritis determines the need, activities and frequency of dynamic monitoring of a patient. However, this attitude to the patient suffering from CG was far from always. The present publication is a literature review describing the key milestones in the history of CG research, from the description of the first observations of inflammation of the gastric mucosa, assessment of gastritis as a predominantly functional disease, to the advent of endoscopy of the upper digestive tract and diagnostic gastric biopsy, assessment of the role of Helicobacter pylori infection in progression of inflammatory changes to atrophy, intestinal metaplasia, dysplasia and GC.

Gastric digestion of the sweet-tasting plant protein thaumatin releases bitter peptides that reduce H. pylori induced pro-inflammatory IL-17A release via the TAS2R16 bitter taste receptor.

About half of the world's population is infected with the bacterium Helicobacter pylori. For colonization, the bacterium neutralizes the low gastric pH and recruits immune cells to the stomach. The immune cells secrete cytokines, i.e., the pro-inflammatory IL-17A, which directly or indirectly damage surface epithelial cells. Since (I) dietary proteins are known to be digested into bitter tasting peptides in the gastric lumen, and (II) bitter tasting compounds have been demonstrated to reduce the release of pro-inflammatory cytokines through functional involvement of bitter taste receptors (TAS2Rs), we hypothesized that the sweet-tasting plant protein thaumatin would be cleaved into anti-inflammatory bitter peptides during gastric digestion. Using immortalized human parietal cells (HGT-1 cells), we demonstrated a bitter taste receptor TAS2R16-dependent reduction of a H. pylori-evoked IL-17A release by up to 89.7 ± 21.9% (p ≤ 0.01). Functional involvement of TAS2R16 was demonstrated by the study of specific antagonists and siRNA knock-down experiments.

Intracellular presence of Helicobacter pylori antigen and genes within gastric and vaginal Candida.

BACKGROUND: Helicobacter pylori infections are generally acquired during childhood and affect half of the global population, but its transmission route remains unclear. It is reported that H. pylori can be internalized into Candida, but more evidence is needed for the internalization of H. pylori in human gastrointestinal Candida and vaginal Candida. METHODS: Candida was isolated from vaginal discharge and gastric mucosa biopsies. We PCR-amplified and sequenced H. pylori-specific genes from Candida genomic DNA. Using optical and immunofluorescence microscopy, we identified and observed bacteria-like bodies (BLBs) in Candida isolates and subcultures. Intracellular H. pylori antigen were detected by immunofluorescence using Fluorescein isothiocyanate (FITC)-labeled anti-H. pylori IgG antibodies. Urease activity in H. pylori internalized by Candida was detected by inoculating with urea-based Sabouraud dextrose agar, which changed the agar color from yellow to pink, indicating urease activity. RESULTS: A total of 59 vaginal Candida and two gastric Candida strains were isolated from vaginal discharge and gastric mucosa. Twenty-three isolates were positive for H. pylori 16S rDNA, 12 were positive for cagA and 21 were positive for ureA. The BLBs could be observed in Candida cells, which were positive for H. pylori 16S rDNA, and were viable determined by the LIVE/DEAD BacLight Bacterial Viability kit. Fluorescein isothiocyanate (FITC)-conjugated antibodies could be reacted specifically with H. pylori antigen inside Candida cells by immunofluorescence. Finally, H. pylori-positive Candida remained positive for H. pylori 16S rDNA even after ten subcultures. Urease activity of H. pylori internalized by Candida was positive. CONCLUSION: In the form of BLBs, H. pylori can internalize into gastric Candida and even vaginal Candida, which might have great significance in its transmission and pathogenicity.

Helicobacter pylori antigens as immunomodulators of immune system.

Helicobacter pylori (H. pylori) is one of the most prevalent human pathogens and the leading cause of chronic infection in almost half of the population in the world (~59%). The bacterium is a major leading cause of chronic gastritis, gastric and duodenal ulcers, and two type of malignancies, gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. Despite the immune responses mounted by the host, the bacteria are not cleared from the body resulting in a chronic infection accompanied by a chronic inflammation. Herein, a review of the literature discussing H. pylori antigens modulating the immune responses is presented. The mechanisms that are involved in the modulation of innate immune response, include modulation of recognition by pattern recognition receptors (PRRs) such as modulation of recognition by toll like receptors (TLR)4 and TLR5, modulation of phagocytic function, and modulation of phagocytic killing mediated by reactive oxygen species (ROS) and nitric oxide (NO). On the other hands, H. pylori modulates acquired immune response by the induction of tolerogenic dendritic cells (DCs), modulation of apoptosis, induction of regulatory T cells, modulation of T helper (Th)1 response, and modulation of Th17 response.

Gastric microbiota in patients with gastric MALT lymphoma according to Helicobacter pylori infection.

BACKGROUND: Gastric Mucosa Associated Lymphoid Tissue lymphoma (GML) development is triggered by Helicobacter pylori (H. pylori) infection. Little is known about the impact of H. pylori infection on gastric microbiota. METHODS: The gastric microbiota was retrospectively investigated using 16S rRNA gene sequencing in 32 patients with untreated GML (10 H. pylori-positive and 22 H. pylori-negative), 23 with remitted and 18 refractory GML and 35 controls. Differences in microbial diversity, bacterial composition and taxonomic repartition were assessed. RESULTS: There was no change in diversity and bacterial composition between GML and control patients taking into account H. pylori status. Differential taxa analysis identified specific changes associated with H. pylori-negative GML: the abundances of Actinobacillus, Lactobacillus and Chryseobacterium were increased while the abundances of Veillonella, Atopobium, Leptotrichia, Catonella, Filifactor and Escherichia_Shigella were increased in control patients. In patients with remitted GML, the genera Haemophilus and Moraxella were significantly more abundant than in refractory patients, while Atopobium and Actinomyces were significantly more abundant in refractory patients. CONCLUSION: Detailed analysis of the gastric microbiota revealed significant changes in the bacterial composition of the gastric mucosa in patients with GML that may have a role in gastric lymphomagenesis but not any new pathobionts.

Reactive oxygen species and gastric carcinogenesis: The complex interaction between Helicobacter pylori and host.

Helicobacter pylori (H. pylori) is a highly successful human pathogen that colonizes stomach in around 50% of the global population. The colonization of bacterium induces an inflammatory response and a substantial rise in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), mostly derived from host neutrophils and gastric epithelial cells, which play a crucial role in combating bacterial infections. However, H. pylori has developed various strategies to quench the deleterious effects of ROS, including the production of antioxidant enzymes, antioxidant proteins as well as blocking the generation of oxidants. The host's inability to eliminate H. pylori infection results in persistent ROS production. Notably, excessive ROS can disrupt the intracellular signal transduction and biological processes of the host, incurring chronic inflammation and cellular damage, such as DNA damage, lipid peroxidation, and protein oxidation. Markedly, the sustained inflammatory response and oxidative stress during H. pylori infection are major risk factor for gastric carcinogenesis. In this context, we summarize the literature on H. pylori infection-induced ROS production, the strategies used by H. pylori to counteract the host response, and subsequent host damage and gastric carcinogenesis.

The contribution of IL-17A-dependent low LCN2 levels to Helicobacter pylori infection: Insights from clinical and experimental studies.

BACKGROUND: Helicobacter pylori (H. pylori) infection is a common bacterial infection that is widespread globally. It is crucial to comprehend the molecular mechanisms that underlie the infection caused by H. pylori in order to devise successful therapeutic approaches. The objective of this study was to examine the involvement of Lipocalin-2 (LCN2) in the development of H. pylori infection. METHODS: LCN2 expression levels in human gastric mucosa and H. pylori-infected mouse models were analyzed using quantitative PCR and immunohistochemistry methods. The effects of LCN2 on the attachment of H. pylori to gastric mucosa cells were assessed using bacterial culture and fluorescence intensity tests. To investigate the correlation between LCN2, CCL20, and IL-17A, we performed gene expression analysis and measured serum levels. RESULTS: The findings indicated an increase in LCN2 levels in the gastric mucosa of both patients and mice infected with H. pylori. Blocking the natural LCN2 resulted in an increased attachment of H. pylori to cells in the gastric mucosa. In addition, we noticed that reduced levels of LCN2 promoted the attachment of H. pylori to cells in the gastric mucosa. Furthermore, H. pylori-infected patients exhibited increased expression of both LCN2 and CCL20, and there was a positive correlation between serum levels of CCL20 and LCN2. LCN2 expression was found to depend on the presence of IL-17A, and inhibiting IL-17A led to a higher H. pylori colonization. CONCLUSION: The persistence of H. pylori infection is facilitated by the presence of low levels of LCN2, which is dependent on IL-17A. This finding offers valuable perspectives for the development of novel therapeutic approaches for H. pylori infection.

Urolithin B alleviates Helicobacter pylori-induced inflammation and oxidative stress in mice.

BACKGROUND: Helicobacter pylori is one of the most common chronic bacterial infections. Active eradication of H. pylori infection is rare due to the fact that most infected patients are asymptomatic and the use of large amounts of antibiotics in eradication therapy leads to severe side effects. Urolithin B (UB) is an additional major intestinal metabolite of ellagic acid (EA), which has been shown to possess anti-inflammatory, antioxidant, and antiapoptotic biological activities. Preventing the incidence of H. pylori-related gastric disease and reducing the damage to the host by H. pylori is a current approach to control H. pylori infection. In this study, we explored the effect of UB on H. pylori infection. MATERIALS AND METHODS: The effects of UB on inflammation and oxidative stress induced by H. pylori in vivo and in vitro were investigated by qPCR, ELISA, HE staining, IHC staining, etc. RESULTS: UB reduced the adhesion and colonization of H. pylori and improved H. pylori-induced inflammation and oxidative stress in vivo and in vitro. Moreover, UB had better anti-inflammatory and antioxidant effects than clarithromycin (CLR) and metronidazole (MET). In addition to inhibiting the secretion of CagA, UB reduced tissue damage by H. pylori infection. CONCLUSIONS: UB was effective in improving damage caused by H. pylori.

Isotope tracing reveals bacterial catabolism of host-derived glutathione during Helicobacter pylori infection.

Mammalian cells synthesize the antioxidant glutathione (GSH) to shield cellular biomolecules from oxidative damage. Certain bacteria, including the gastric pathogen Helicobacter pylori, can perturb host GSH homeostasis. H. pylori infection significantly decreases GSH levels in host tissues, which has been attributed to the accumulation of reactive oxygen species in infected cells. However, the precise mechanism of H. pylori-induced GSH depletion remains unknown, and tools for studying this process during infection are limited. We developed an isotope-tracing approach to quantitatively monitor host-derived GSH in H. pylori-infected cells by mass spectrometry. Using this method, we determined that H. pylori catabolizes reduced GSH from gastric cells using γ-glutamyl transpeptidase (gGT), an enzyme that hydrolyzes GSH to glutamate and cysteinylglycine (Cys-Gly). gGT is an established virulence factor with immunomodulatory properties that is required for H. pylori colonization in vivo. We found that H. pylori internalizes Cys-Gly in a gGT-dependent manner and that Cys-Gly production during H. pylori infection is coupled to the depletion of intracellular GSH from infected cells. Consistent with bacterial catabolism of host GSH, levels of oxidized GSH did not increase during H. pylori infection, and exogenous antioxidants were unable to restore the GSH content of infected cells. Altogether, our results indicate that H. pylori-induced GSH depletion proceeds via an oxidation-independent mechanism driven by the bacterial enzyme gGT, which fortifies bacterial acquisition of nutrients from the host. Additionally, our work establishes a method for tracking the metabolic fate of host-derived GSH during infection.

The regulation roles of miRNAs in Helicobacter pylori infection

Helicobacter pylori is a kind of Gram-negative bacteria that parasitizes on human gastric mucosa. Helicobacter pylori infection is very common in human beings, which often causes gastrointestinal diseases, including chronic gastritis, duodenal ulcer and gastric cancer. MicroRNAs are a group of endogenous non-coding single stranded RNAs, which play an important role in cell proliferation, differentiation, autophagy, apoptosis and inflammation. In recent years, relevant studies have found that the expression of microRNA is changed after Helicobacter pylori infection, and then regulate the biological process of host cells. This paper reviews the regulation role of microRNAs on cell biological behavior through different signal pathways after Helicobacter pylori infection (AU)

BanXiaXieXin decoction treating gastritis mice with drug-resistant Helicobacter pylori and its mechanism.

BACKGROUND: Helicobacter pylori (H. pylori) is the main pathogen that causes a variety of upper digestive diseases. The drug resistance rate of H. pylori is increasingly higher, and the eradication rate is increasingly lower. The antimicrobial resistance of H. pylori is an urgent global problem. It has been confirmed that Banxia Xiexin decoction (BXXXT) demonstrates the effects of treating gastrointestinal diseases, inhibiting H. pylori and protecting gastric mucosa. The purpose of the present study is to further explore the therapeutic effects of BXXXT on drug-resistant H. pylori. AIM: To confirm that BXXXT demonstrates therapeutical effects in vivo and in vitro on gastritis mice with drug-resistant H. pylori and explain its mechanism to provide an experimental basis for promoting the application of BXXXT. METHODS: The aqueous extract of BXXXT was gained by water decocting method. The inhibitory effect of the aqueous extract on H. pylori was detected by dilution in vitro; drug-resistant H. pylori cells were used to build an acute gastritis model in vivo. Thereafter, the model mice were treated with the aqueous extract of BXXXT. The amount of H. pylori colonization, the repair of gastric mucosal damage, changes of inflammatory factors, apoptosis, etc., were assessed. In terms of mechanism exploration, the main medicinal compositions of BXXXT aqueous extract and the synergistic bacteriostatic effects they had demonstrated were analyzed using mass spectrometry; the immune function of peripheral blood cells such as CD3+ T and CD4+ T of mice with gastritis before and after treatment with BXXXT aqueous extract was detected using a flow cytometry; the H. pylori transcriptome and proteome after treatment with BXXXT aqueous extract were detected. Differently expressed genes were screened and verification was performed thereon with knockout expression. RESULTS: The minimum inhibitory concentration of BXXXT aqueous extract against H. pylori was 256-512 µg/mL. A dose of 28 mg/kg BXXXT aqueous extract treatment produced better therapeutical effects than the standard triple therapy did; the BXXXT aqueous extract have at least 11 ingredients inhibiting H. pylori, including berberine, quercetin, baicalin, luteolin, gallic acid, rosmarinic acid, aloe emodin, etc., of which berberine, aloe emodin, luteolin and gallic acid have a synergistic effect; BXXXT aqueous extract was found to stimulate the expressions of CD3+ T and CD4+ T and increase the number of CD4+ T/CD8+ T in gastritis mice; the detection of transcriptome and proteome, quantitative polymerase chain reaction, Western blotting and knockout verification revealed that the main targets of BXXXT aqueous extract are CFAs related to urea enzymes, and CagA, VacA, etc. CONCLUSION: BXXXT aqueous extract could demonstrate good therapeutic effects on drug-resistance H. pylori in vitro and in vivo and its mechanism comes down to the synergistic or additional antibacterial effects of berberine, emodin and luteolin, the main components of the extract; the extract could activate the immune function and enhance bactericidal effects; BXXXT aqueous extract, with main targets of BXXXT aqueous extract related to urease, virulence factors, etc., could reduce the urease and virulence of H. pylori, weaken its colonization, and reduce its inflammatory damage to the gastric mucosa.

Induction of MMP-3 and MMP-9 expression during Helicobacter pylori infection via MAPK signaling pathways.

BACKGROUND AND AIMS: Helicobacter pylori (H. pylori)-induced gastric pathology involves remodeling of extracellular matrix mediated by aberrant activity of matrix metalloproteinases (MMPs). We have previously shown that in vitro H. pylori infection leads to MMP-3 and MMP-9 overexpression, associated with phosphorylation of bacterial oncoprotein CagA. We extended these findings in an in vivo model of H. pylori infection and further assessed the involvement of MAPK pathways in MMP expression. MATERIALS AND METHODS: C57BL/6 mice were infected with H. pylori strains HPARE, HPARE ΔCagA, and SS1, for 6 and 9 months. Transcriptional expression of Mmp-3 and Mmp-9 was evaluated via qPCR while respective protein levels in the gastric mucosa were determined immunohistochemically. Epithelial cell lines AGS and GES-1 were infected with H. pylori strain P12 in the presence of chemical inhibitors of JNK, ERK1/2, and p38 pathways, for 24 h. mRNA and protein expression of MMP-3 and MMP-9 were determined via qPCR and Western blot, respectively. RESULTS: We observed transcriptional activation of Mmp-3 and Mmp-9 as well as aberrant MMP-3 and MMP-9 protein expression in murine gastric tissue following H. pylori infection. CagA expression was associated with MMP upregulation, particularly during the early time points of infection. We found that inhibition of ERK1/2 resulted in reduced mRNA and protein expression of MMP-3 and MMP-9 during H. pylori infection, in both cell lines. Expressed protein levels of both MMPs were also found reduced in the presence of JNK pathway inhibitors in both cell lines. However, p38 inhibition resulted in a more complex effect, probably attributed to the accumulation of phospho-p38 and increased phospho-ERK1/2 activity due to crosstalk between MAPK pathways. CONCLUSIONS: H. pylori colonization leads to the upregulation of MMP-3 and MMP-9 in vivo, which primarily involves ERK1/2 and JNK pathways. Therefore, their inhibition may potentially offer a protective effect against gastric carcinogenesis and metastasis.

Metabolic alterations in patients with Helicobacter pylori-related gastritis: The H. pylori-gut microbiota-metabolism axis in progression of the chronic inflammation in the gastric mucosa.

PURPOSE: To characterize the serum metabolism in patients with Helicobacter pylori-positive and H. pylori-negative gastritis. METHODS: Clinical data and serum gastric function parameters, PGI (pepsinogen I), PGII, PGR (PGI/II), and G-17 (gastrin-17) of 117 patients with chronic gastritis were collected, including 57 H. pylori positive and 60 H. pylori negative subjects. Twenty cases in each group were randomly selected to collect intestinal mucosa specimens and serum samples. The gut microbiota profiles were generated by 16S rRNA gene sequencing, and the serum metabolites were analyzed by a targeted metabolomics approach based on liquid chromatography-mass spectrometry (LC-MS) technology. RESULTS: Altered expression of 20 metabolites, including isovaleric acid, was detected in patients with HPAG. Some taxa of Bacteroides, Fusobacterium, and Prevotella in the gut microbiota showed significant correlations with differentially expressed metabolites between H. pylori positive and H. pylori negative individuals. As a result, an H. pylori-gut microbiota-metabolism (HGM) axis was proposed. CONCLUSION: Helicobacter pylori infection may influence the progression of mucosal diseases and the emergence of other complications in the host by altering the gut microbiota, and thus affecting the host serum metabolism.

Gastric mucosal swab as an alternative to biopsy for Helicobacter pylori detection.

BACKGROUND AND AIMS: Gastric mucosal swab may be a more sensitive sampling method than a biopsy since Helicobacter pylori (H. pylori) resides within the mucus layer. We compared the diagnostic performance of the rapid urease test (RUT) and bacterial load of H. pylori between swabs and tissue biopsy. METHODS: Overall, 276 RUTs (138 swab-RUTs (S-RUT) and 138 tissue-RUTs (T-RUT)) were performed. To diagnose H. pylori infection, RUT, H. pylori PCR, and 16S ribosomal RNA gene sequencing of tissue and swab were used, and its infection was defined as at least two positives of the six test results. The diagnostic performances of RUTs and the H. pylori bacterial load using qPCR were compared between swab and biopsy. RESULTS: The positivity rates of S-RUT and T-RUT were 35.5% (49/138) and 25.4% (35/138), respectively. The sensitivity, specificity, and accuracy of S-RUT were 98.0%, 100.0%, and 99.2%, while those of T-RUT were 70.0%, 100%, and 89.1%, respectively. The sensitivity and accuracy were significantly higher for S-RUT than for T-RUT (p < 0.05). In the patients with atrophic gastritis and intestinal metaplasia, S-RUT showed significantly higher sensitivity than T-RUT. qPCR showed that the swab contained a significantly higher H. pylori bacterial load than tissue biopsy (22.92-fold and 31.61-fold in the antrum and body (p < 0.05), respectively). CONCLUSIONS: Gastric mucosal swabs showed higher RUT accuracy and H. pylori bacterial load than a tissue biopsy. This may be an alternative to a biopsy when diagnosing H. pylori infection during endoscopy is necessary. (ClinicalTrials.gov, NCT05349578).

The first 5 years of Helicobacter pylori research-With an emphasis on the United Kingdom.

In the 1970s, 1% of the UK population consulted with dyspepsia; fiberoptic gastroscopy allowed biopsy specimens under direct vision enabling systematic histopathology. Steer et al described clusters of flagellated bacteria closely apposed to the gastric epithelium associated with chronic active gastritis. The first UK series of Helicobacter pylori following Marshall's 1983 visit to Worcester confirmed the association of H. pylori with gastritis. UK researchers completed much early helicobacter research as there were many UK campylobacteriologists. Steer and Newell proved the Campylobacter-like organisms grown on culture were the same as those seen in the gastric mucosa using antiserum raised by inoculating rabbits with H. pylori from cultures. Wyatt, Rathbone, and others showed a strong correlation between the number of organisms, type and severity of acute gastritis, immunological response, and bacterial adhesion similar to enteropathogenic E coli. Seroprevalence studies indicated H. pylori increased with age. Histopathologists also showed peptic duodenitis was in effect "gastritis in the duodenum" caused by H. pylori, unifying its role in the pathogenesis of both gastritis and duodenal ulceration. These bacteria were initially called Campylobacter pyloridis and then C. pylori. However, electron microscopy suggested that the bacteria were not campylobacters, and this was supported by differences in fatty acid and polyacrylamide electrophoresis profiles. In-vitro tests indicated that H. pylori was susceptible to penicillins, erythromycin, and quinolones, but not trimethoprim or cefsulodin allowing development of selective media for culture. Monotherapy with erythromycin ethylsuccinate was ineffective, and patients treated with bismuth subsalicylate initially responded with clearance of H. pylori and the associated gastritis, but then many relapsed. Thus, pharmacokinetic and treatment studies were important to direct suitable dual and triple treatments. Work optimized serology, and the rapid biopsy urease and urea breath tests. The link between H.pylori and gastric cancer was established in large seroprevalence studies, and H. pylori test and treat for dyspepsia became routine.

Microbial composition of tumorous and adjacent gastric tissue is associated with prognosis of gastric cancer.

Helicobacter pylori (H. pylori) infection has been considered as the main causal factor in gastric carcinogenesis, but other bacterial species may also play an important role in pathophysiology of gastric cancer. The aim of the study was to explore the link between gastric cancer prognosis and the mucosal microbial community in tumorous and adjacent gastric tissue. The bacterial profile was analysed using 16S sequencing (V1-V2 region). Microbial differences were mostly characterized by lower relative abundances of H. pylori in tumorous gastric tissues. Bacterial community and outcome data analysis revealed the genus Fusobacterium and Prevotella significantly associated with worse overall survival in gastric cancer patients. In particular, Fusobacterium was associated with significant increase in hazard ratio in both univariable and multivariable analysis and independently validated using TCMA data. Phylogenetic biodiversity of Fusobacterium species in the stomach revealed F. periodonticum as the most prevalent in healthy subjects, while F. nucleatum was most abundant in patients with gastric cancer. Bacterial community network analysis in gastric cancer suggests substantial complexity and a strong interplay between F. nucleatum and Prevotella. In summary, mucosal microbial community in the stomach was associated with worse overall survival in gastric cancer patients. Strongest negative impact on prognosis was linked to the abundance of F. nucleatum in tumorous specimens, suggesting its translational relevance in management of gastric cancer patients.

Helicobacter pylori initiates successful gastric colonization by utilizing L-lactate to promote complement resistance.

The complement system has long been appreciated for its role in bloodborne infections, but its activities in other places, including the gastrointestinal tract, remain elusive. Here, we report that complement restricts gastric infection by the pathogen Helicobacter pylori. This bacterium colonized complement-deficient mice to higher levels than wild-type counterparts, particularly in the gastric corpus region. H. pylori uses uptake of the host molecule L-lactate to create a complement-resistant state that relies on blocking the deposition of the active complement C4b component on H. pylori's surface. H. pylori mutants unable to achieve this complement-resistant state have a significant mouse colonization defect that is largely corrected by mutational removal of complement. This work highlights a previously unknown role for complement in the stomach, and has revealed an unrecognized mechanism for microbial-derived complement resistance.

Helicobacter pylori infection induces abnormal expression of pro-angiogenic gene ANGPT2 and miR-203a in AGS gastric cell line.

Helicobacter pylori colonizes the stomach and induces an inflammatory response that can develop into gastric pathologies including cancer. The infection can alter the gastric vasculature by the deregulation of angiogenic factors and microRNAs. In this study, we investigate the expression level of pro-angiogenic genes (ANGPT2, ANGPT1, receptor TEK), and microRNAs (miR-135a, miR-200a, miR-203a) predicted to regulate those genes, using H. pylori co-cultures with gastric cancer cell lines. In vitro infections of different gastric cancer cell lines with H. pylori strains were performed, and the expression of ANGPT1, ANGPT2, and TEK genes, and miR-135a, miR-200a, and miR-203a, was quantified after 24 h of infection (h.p.i.). We performed a time course experiment of H. pylori 26695 infections in AGS cells at 6 different time points (3, 6, 12, 28, 24, and 36 h.p.i.). The angiogenic response induced by supernatants of non-infected and infected cells at 24 h.p.i. was evaluated in vivo, using the chicken chorioallantoic membrane (CAM) assay. In response to infection, ANGPT2 mRNA was upregulated at 24 h.p.i, and miR-203a was downregulated in AGS cells co-cultured with different H. pylori strains. The time course of H. pylori 26695 infection in AGS cells showed a gradual decrease of miR-203a expression concomitant with an increase of ANGPT2 mRNA and protein expression. Expression of ANGPT1 and TEK mRNA or protein could not be detected in any of the infected or non-infected cells. CAM assays showed that the supernatants of AGS-infected cells with 26695 strain induced a significantly higher angiogenic and inflammatory response. Our results suggest that H. pylori could contribute to the process of carcinogenesis by downregulating miR-203a, which further promotes angiogenesis in gastric mucosa by increasing ANGPT2 expression. Further investigation is needed to elucidate the underlying molecular mechanisms.

Helicobacter pylori Chronic Infection Selects for Effective Colonizers of Metaplastic Glands.

Chronic gastric infection with Helicobacter pylori can lead to progressive tissue changes that culminate in cancer, but how H. pylori adapts to the changing tissue environment during disease development is not fully understood. In a transgenic mouse gastric metaplasia model, we found that strains from unrelated individuals differed in their ability to infect the stomach, to colonize metaplastic glands, and to alter the expression of the metaplasia-associated protein TFF3. H. pylori isolates from different stages of disease from a single individual had differential ability to colonize healthy and metaplastic gastric glands. Exposure to the metaplastic environment selected for high gastric colonization by one of these strains. Complete genome sequencing revealed a unique alteration in the frequency of a variant allele of the putative adhesin sabB, arising from a recombination event with the related sialic acid binding adhesin (SabA) gene. Mutation of sabB in multiple H. pylori strain backgrounds strongly reduced adherence to both normal and metaplastic gastric tissue, and highly attenuated stomach colonization in mice. Thus, the changing gastric environment during disease development promotes bacterial adhesin gene variation associated with enhanced gastric colonization. IMPORTANCE Chronic infection with Helicobacter pylori is the primary risk factor for developing stomach cancer. As disease progresses H. pylori must adapt to a changing host tissue environment that includes induction of new cell fates in the cells that line the stomach. We tested representative H. pylori isolates collected from the same patient during early and later stages of disease in a mouse model where we can rapidly induce disease-associated tissue changes. Only the later-stage H. pylori strains could robustly colonize the diseased stomach environment. We also found that the ability to colonize the diseased stomach was associated with genetic variation in a putative cell surface adhesin gene called sabB. Additional experiments revealed that SabB promotes binding to stomach tissue and is critical for stomach colonization by the late-stage strains. Thus, H. pylori diversifies its genome during disease progression and these genomic changes highlight critical factors for bacterial persistence.