Helicobacter pylori actively suppresses innate immune nucleic acid receptors.

Chronic mucosal pathogens have evolved multiple strategies to manipulate the host immune response; consequently, microbes contribute to the development of >2 million cases of cancer/year. Gastric adenocarcinoma is the fourth leading cause of cancer-related death and Helicobacter pylori confers the highest risk for this disease. Gastric innate immune effectors can either eliminate bacteria or mobilize adaptive immune responses including Toll-like receptors (TLRs), and cytosolic DNA sensor/adaptor proteins (e.g., stimulator of interferon genes, STING). The H. pylori strain-specific cag type IV secretion system (T4SS) augments gastric cancer risk and translocates DNA into epithelial cells where it activates the microbial DNA sensor TLR9 and suppresses injury in vivo; however, the ability of H. pylori to suppress additional nucleic acid PRRs within the context of chronic gastric inflammation and injury remains undefined. In this study, in vitro and ex vivo experiments identified a novel mechanism through which H. pylori actively suppresses STING and RIG-I signaling via downregulation of IRF3 activation. In vivo, the use of genetically deficient mice revealed that Th17 inflammatory responses are heightened following H. pylori infection within the context of Sting deficiency in conjunction with increased expression of a known host immune regulator, Trim30a. This novel mechanism of immune suppression by H. pylori is likely a critical component of a finely tuned rheostat that not only regulates the initial innate immune response, but also drives chronic gastric inflammation and injury.

Helicobacter pylori-Induced TLR9 Activation and Injury Are Associated With the Virulence-Associated Adhesin HopQ.

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma. The H. pylori cancer-associated cag pathogenicity island (cag-PAI) encodes a type IV secretion system (T4SS), which translocates microbial DNA and activates TLR9; however, most cag-PAI+-infected persons do not develop cancer and cag-PAI-independent regulators of pathogenesis, including strain-specific adhesins, remain understudied. We defined the relationships between H. pylori HopQ adhesin allelic type, gastric injury, and TLR9 activation. Type I hopQ alleles were significantly associated with magnitude of injury, cag-T4SS function, and TLR9 activation. Genetic deletion of hopQ significantly decreased H. pylori-induced TLR9 activation, implicating this adhesin in H. pylori-mediated disease.

Helicobacter pylori diversification during chronic infection within a single host generates sub-populations with distinct phenotypes.

Helicobacter pylori chronically infects the stomach of approximately half of the world's population. Manifestation of clinical diseases associated with H. pylori infection, including cancer, is driven by strain properties and host responses; and as chronic infection persists, both are subject to change. Previous studies have documented frequent and extensive within-host bacterial genetic variation. To define how within-host diversity contributes to phenotypes related to H. pylori pathogenesis, this project leverages a collection of 39 clinical isolates acquired prospectively from a single subject at two time points and from multiple gastric sites. During the six years separating collection of these isolates, this individual, initially harboring a duodenal ulcer, progressed to gastric atrophy and concomitant loss of acid secretion. Whole genome sequence analysis identified 1,767 unique single nucleotide polymorphisms (SNPs) across isolates and a nucleotide substitution rate of 1.3x10-4 substitutions/site/year. Gene ontology analysis identified cell envelope genes among the genes with excess accumulation of nonsynonymous SNPs (nSNPs). A maximum likelihood tree based on genetic similarity clusters isolates from each time point separately. Within time points, there is segregation of subgroups with phenotypic differences in bacterial morphology, ability to induce inflammatory cytokines, and mouse colonization. Higher inflammatory cytokine induction in recent isolates maps to shared polymorphisms in the Cag PAI protein, CagY, while rod morphology in a subgroup of recent isolates mapped to eight mutations in three distinct helical cell shape determining (csd) genes. The presence of subgroups with unique genetic and phenotypic properties suggest complex selective forces and multiple niches within the stomach during chronic infection.

Helicobacter pylori antimicrobial resistance and antibiotic consumption in the low-resource Central America setting.

BACKGROUND: Antimicrobial resistance is a global public health problem, particularly in low- and middle-income countries (LMICs), where antibiotics are often obtained without a prescription. H. pylori antimicrobial resistance patterns are informative for patient care and gastric cancer prevention programs, have been shown to correlate with general antimicrobial consumption, and may guide antimicrobial stewardship programs in LMICs. We report H. pylori resistance and antimicrobial utilization patterns for western Honduras, representative of rural Central America. METHODS: In the context of the western Honduras gastric cancer epidemiology initiative, gastric biopsies from 189 patients were studied for culture and resistance patterns. Antimicrobial utilization was investigated for common H. pylori treatment regimens from regional public (7 antimicrobials) and national private (4 antimicrobials) data, analyzed in accordance with WHO anatomical therapeutic chemical defined daily doses (DDD) method and expressed as DDD/1000 inhabitants per day (DID) and per year (DIY). RESULTS: H. pylori was successfully cultured from 116 patients (56% males, mean age: 54), and nearly all strains were cagA+ and vacAs1m1+ positive (99% and 90.4%, respectively). Unexpectedly, high resistance was noted for levofloxacin (20.9%) and amoxicillin (10.7%), while metronidazole (67.9%) and clarithromycin (11.2%) were similar to data from Latin America. Significant associations with age, gender, or histology were not noted, with the exception of levofloxacin (28%, P = 0.01) in those with histology limited to non-atrophic gastritis. Total antimicrobial usage in western Honduras of amoxicillin (17.3 DID) and the quinolones had the highest relative utilizations compared with other representative nations. CONCLUSIONS: We observed significant H. pylori resistance to amoxicillin and levofloxacin in the context of high community antimicrobial utilization. This has implications in Central America for H. pylori treatment guidelines as well as antimicrobial stewardship programs.

Genetic Manipulation of Helicobacter pylori Virulence Function by Host Carcinogenic Phenotypes.

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, yet only a minority of infected persons ever develop this malignancy. One cancer-linked locus is the cag type 4 secretion system (cagT4SS), which translocates an oncoprotein into host cells. A structural component of the cagT4SS is CagY, which becomes rapidly altered during in vivo adaptation in mice and rhesus monkeys, rendering the cagT4SS nonfunctional; however, these models rarely develop gastric cancer. We previously demonstrated that the H. pylori cag+ strain 7.13 rapidly induces gastric cancer in Mongolian gerbils. We now use this model, in conjunction with samples from patients with premalignant lesions, to define the effects of a carcinogenic host environment on the virulence phenotype of H. pylori to understand how only a subset of infected individuals develop cancer. H. pylori cagY sequence differences and cagT4SS function were directly related to the severity of inflammation in human gastric mucosa in either a synchronous or metachronous manner. Serial infections of Mongolian gerbils with H. pylori strain 7.13 identified an oscillating pattern of cagT4SS function. The development of dysplasia or cancer selected for attenuated virulence phenotypes, but robust cagT4SS function could be restored upon infection of new hosts. Changes in the genetic composition of cagY mirrored cagT4SS function, although the mechanisms of cagY alterations differed in human isolates (mutations) versus gerbil isolates (addition/deletion of motifs). These results indicate that host carcinogenic phenotypes modify cagT4SS function via altering cagY, allowing the bacteria to persist and induce carcinogenic consequences in the gastric niche. Cancer Res; 77(9); 2401-12. ©2017 AACR.

Helicobacter pylori-induced cell death is counteracted by NF-κB-mediated transcription of DARPP-32.

OBJECTIVE: DARPP-32 is a frequently amplified and overexpressed gene that promotes several oncogenic functions in gastric cancer. Herein, we investigated the relationship between Helicobacter pylori infection, proinflammatory NF-κB activation and regulation of DARPP-32. DESIGN: The study used in vivo and in vitro experiments. Luciferase reporter, quantitative real-time PCR, immunoblot, chromatin immunoprecipitation (ChIP), cell viability, H. pylori infection, tissue microarrays and immunohistochemical assays were used. RESULTS: Our results indicated that H. pylori infection increased the DARPP-32 mRNA and protein levels in gastric cancer cell lines and gastric mucosa of mice. H. pylori infection increased the activity of NF-κB reporter and p-NF-κB (S536) protein level in vitro and in vivo. To investigate the transcriptional regulation of DARPP-32, we cloned a 3019 bp of the DARPP-32 promoter into the luciferase reporter (pGL3-Luc). Both H. pylori infection and tumour necrosis factor-α treatment induced DARPP-32 reporter activity (p<0.01). Using deletion constructs of DARPP-32 promoter and ChIP assay, we demonstrated that the sequence -996 to -1008 bp containing putative NF-κB-binding sites is the most active region. The induction of DARPP-32 expression by H. pylori infection counteracted H. pylori-induced cell death through activation of serine/threonine-specific protein kinase (AKT), as determined by ATP-Glo and clonogenic survival assays. Immunohistochemistry analysis demonstrated a significant positive correlation between NF-κB and DARPP-32 expression levels in gastric cancer tissues (r2=0.43, p<0.01). CONCLUSIONS: Given the high frequency of DARPP-32 overexpression and its prosurvival oncogenic functions, the induction of DARPP-32 expression following H. pylori infection and activation of NF-κB provides a link between infection, inflammation and gastric tumourigenesis.

TLR9 activation suppresses inflammation in response to Helicobacter pylori infection.

Helicobacter pylori (H. pylori) induces chronic gastritis in humans, and infection can persist for decades. One H. pylori strain-specific constituent that augments disease risk is the cag pathogenicity island. The cag island encodes a type IV secretion system (T4SS) that translocates DNA into host cells. Toll-like receptor 9 (TLR9) is an innate immune receptor that detects hypo-methylated CpG DNA motifs. In this study, we sought to define the role of the H. pylori cag T4SS on TLR9-mediated responses in vivo. H. pylori strain PMSS1 or its cagE- mutant, which fails to assemble a T4SS, were used to infect wild-type or Tlr9-/- C57BL/6 mice. PMSS1-infected Tlr9-/- mice developed significantly higher levels of inflammation, despite similar levels of colonization density, compared with PMSS1-infected wild-type mice. These changes were cag dependent, as both mouse genotypes infected with the cagE- mutant only developed minimal inflammation. Tlr9-/- genotypes did not alter the microbial phenotypes of in vivo-adapted H. pylori strains; therefore, we examined host immunological responses. There were no differences in levels of TH1 or TH2 cytokines in infected mice when stratified by host genotype. However, gastric mucosal levels of IL-17 were significantly increased in infected Tlr9-/- mice compared with infected wild-type mice, and H. pylori infection of IL-17A-/- mice concordantly led to significantly decreased levels of gastritis. Thus loss of Tlr9 selectively augments the intensity of IL-17-driven immune responses to H. pylori in a cag T4SS-dependent manner. These results suggest that H. pylori utilizes the cag T4SS to manipulate the intensity of the host immune response.

Genetic Evolution of a Helicobacter pylori Acid-Sensing Histidine Kinase and Gastric Disease.

Helicobacter pylori is the strongest risk factor for gastric adenocarcinoma, which develops within a hypochlorhydric environment. We sequentially isolated H. pylori (strain J99) from a patient who developed corpus-predominant gastritis and hypochlorhydia over a 6-year interval. Archival J99 survived significantly better under acidic conditions than recent J99 strains. H. pylori arsRS encodes a 2-component system critical for stress responses; recent J99 isolates harbored 2 nonsynonymous arsS mutations, and arsS inactivation abolished acid survival. In vivo, acid-resistant archival, but not recent J99, successfully colonized high-acid-secreting rodents. Thus, genetic evolution of arsS may influence progression to hypochlorhydia and gastric cancer.

Trefoil factor 1 expression suppresses Helicobacter pylori-induced inflammation in gastric carcinogenesis.

BACKGROUND: Infection with Helicobacter pylori, a high-risk factor for gastric cancer, is frequently associated with chronic inflammation through activation of nuclear factor κB (NF-κB). Trefoil factor 1 (TFF1) is a constitutively expressed protein in the stomach that has tumor-suppressor functions and plays a critical role in maintaining mucosal integrity. This study investigated the role of TFF1 in regulating the proinflammatory response to H. pylori infections. METHODS: For in vitro studies, immunofluorescence, luciferase reporter assays, Western blots, and quantitative real-time polymerase chain reaction were performed to investigate the activation of NF-κB and its target genes in response to infections with H. pylori strains J166 and 7.13. In addition, Tff1-knockout (KO) and Tff1-wild-type mice were used for infections with the H. pylori strain called premouse Sydney strain 1. RESULTS: The reconstitution of TFF1 expression in gastric cancer cells significantly suppressed H. pylori-mediated increases in NF-κB-p65 nuclear staining, transcriptional activity, and expression of proinflammatory cytokine genes (tumor necrosis factor α, interleukin 1ß, chemokine [C-X-C motif] ligand 5, and interleukin 4 receptor) that were associated with reductions in the expression and phosphorylation of NF-κB-p65 and IκB kinase α/ß proteins. The in vivo studies using the Tff1-KO mouse model of gastric neoplasia confirmed the in vitro findings. Furthermore, they demonstrated increases in chronic inflammation scores and in the frequency of invasive gastric adenocarcinoma in the Tff1-KO mice infected with H. pylori versus the uninfected Tff1-KO mice. CONCLUSIONS: These findings underscore an important protective role of TFF1 in abrogating H. pylori-mediated inflammation, a crucial hallmark of gastric tumorigenesis. Therefore, loss of TFF1 expression could be an important step in H. pylori-mediated gastric carcinogenesis.

Draft Genome Sequence of Gerbil-Adapted Carcinogenic Helicobacter pylori Strain 7.13.

We report here the draft genome sequence of Helicobacter pylori strain 7.13, a gerbil-adapted strain that causes gastric cancer in gerbils. Strain 7.13 is derived from clinical strain B128, isolated from a patient with a duodenal ulcer. This study reveals genes associated with the virulence of the strain.

Loss of TFF1 promotes Helicobacter pylori-induced ß-catenin activation and gastric tumorigenesis.

Using in vitro and in vivo models, we investigated the role of TFF1 in suppressing H. pylori-mediated activation of oncogenic ß-catenin in gastric tumorigenesis. A reconstitution of TFF1 expression in gastric cancer cells decreased H. pylori-induced ß-catenin nuclear translocation, as compared to control (p < 0.001). These cells exhibited significantly lower ß-catenin transcriptional activity, measured by pTopFlash reporter, and induction of its target genes (CCND1 and c-MYC), as compared to control. Because of the role of AKT in regulating ß-catenin, we performed Western blot analysis and demonstrated that TFF1 reconstitution abrogates H. pylori-induced p-AKT (Ser473), p-ß-catenin (Ser552), c-MYC, and CCND1 protein levels. For in vivo validation, we utilized the Tff1-KO gastric neoplasm mouse model. Following infection with PMSS1 H. pylori strain, we detected an increase in the nuclear staining for ß-catenin and Ki-67 with a significant induction in the levels of Ccnd1 and c-Myc in the stomach of the Tff1-KO, as compared to Tff1-WT mice (p < 0.05). Only 10% of uninfected Tff1-KO mice, as opposed to one-third of H. pylori-infected Tff1-KO mice, developed invasive adenocarcinoma (p = 0.03). These findings suggest that loss of TFF1 could be a critical step in promoting the H. pylori-mediated oncogenic activation of ß-catenin and gastric tumorigenesis.

Helicobacter pylori promotes the expression of Krüppel-like factor 5, a mediator of carcinogenesis, in vitro and in vivo.

Helicobacter pylori is the strongest known risk factor for the development of gastric adenocarcinoma. H. pylori expresses a repertoire of virulence factors that increase gastric cancer risk, including the cag pathogenicity island and the vacuolating cytotoxin (VacA). One host element that promotes carcinogenesis within the gastrointestinal tract is Krüppel-like factor 5 (KLF5), a transcription factor that mediates key cellular functions. To define the role of KLF5 within the context of H. pylori-induced inflammation and injury, human gastric epithelial cells were co-cultured with the wild-type cag(+) H. pylori strain 60190. KLF5 expression was significantly upregulated following co-culture with H. pylori, but increased expression was independent of the cag island or VacA. To translate these findings into an in vivo model, C57BL/6 mice were challenged with the wild-type rodent-adapted cag(+) H. pylori strain PMSS1 or a PMSS1 cagE(-) isogenic mutant. Similar to findings in vitro, KLF5 staining was significantly enhanced in gastric epithelium of H. pylori-infected compared to uninfected mice and this was independent of the cag island. Flow cytometry revealed that the majority of KLF5(+) cells also stained positively for the stem cell marker, Lrig1, and KLF5(+)/Lrig1(+) cells were significantly increased in H. pylori-infected versus uninfected tissue. To extend these results into the natural niche of this pathogen, levels of KLF5 expression were assessed in human gastric biopsies isolated from patients with or without premalignant lesions. Levels of KLF5 expression increased in parallel with advancing stages of neoplastic progression, being significantly elevated in gastritis, intestinal metaplasia, and dysplasia compared to normal gastric tissue. These results indicate that H. pylori induces expression of KLF5 in gastric epithelial cells in vitro and in vivo, and that the degree of KLF5 expression parallels the severity of premalignant lesions in human gastric carcinogenesis.

An evaluation of serial blood lactate measurement as an early predictor of shock and its outcome in patients of trauma or sepsis.

CONTEXT: Attainment of hemodynamic parameters to within a normal range may leave patients in compensatory shock. In such patients, serial blood lactate evaluation can be useful in predicting shock. AIMS: To ascertain the role of serum lactate as a predictor of shock and its outcome in patients of trauma and sepsis. SETTINGS AND DESIGN: A prospective, non-interventional study. MATERIALS AND METHODS: The study included 50 patients (5 to 60 years old) of trauma admitted within 12 hours of injury and patients of suspected or proven sepsis. Those with chronic medical illnesses, alcohol intoxication, or poisoning were excluded. Blood lactate levels were analyzed at admission and 12, 24, and 36 hours of inclusion with records of corresponding hemodynamic variables, investigations, and interventions. The outcome was recorded as survival or non-survival. STATISTICAL ANALYSIS USED: Statistical analysis was done with a student's t test and repeated measure ANOVA (Analysis of Variance). RESULTS: An analysis revealed higher mean lactate levels in non-survivors as compared with survivors. Mean lactate levels in non-survivors did not attain normal levels, while that of survivors reached normal levels by 24 hrs in trauma patients and 36 hrs in sepsis patients. The predicted mortality rates by a lactate level> 40 mg/dl at admission, 12, 24, and 36 hours were 52.6%, 61.5%, 83.3%, and 100%, respectively for both the subgroups combined. Non-survivors had a higher incidence of MODS (Multi Organ Dysfunction Syndrome). CONCLUSIONS: Serial lactate values followed over a period of time can be used to predict impending complications or grave outcome in patients of trauma or sepsis. Interventions that decrease lactate values to normal early may improve chances of survival and can be considered effective therapy. Lactate values need to be followed for a longer period of time in critical patients.

Delineation of a carcinogenic Helicobacter pylori proteome.

Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, yet only a fraction of infected persons ever develop cancer. The extensive genetic diversity inherent to this pathogen has precluded comprehensive analyses of constituents that mediate carcinogenesis. We previously reported that in vivo adaptation of a non-carcinogenic H. pylori strain endowed the output derivative with the ability to induce adenocarcinoma, providing a unique opportunity to identify proteins selectively expressed by an oncogenic H. pylori strain. Using a global proteomics DIGE/MS approach, a novel missense mutation of the flagellar protein FlaA was identified that affects structure and function of this virulence-related organelle. Among 25 additional differentially abundant proteins, this approach also identified new proteins previously unassociated with gastric cancer, generating a profile of H. pylori proteins to use in vaccine development and for screening persons infected with strains most likely to induce severe disease.

Role of Helicobacter pylori CagA molecular variations in induction of host phenotypes with carcinogenic potential.

Helicobacter pylori cagA-positive strains exert population-specific risks for gastric cancer. We determined whether variations in CagA phosphorylation motifs were associated with carcinogenic or proinflammatory epithelial phenotypes induced by strains from regions with divergent cancer risks (Colombia and Nashville, TN). Motif number was significantly related to levels of CagA phosphorylation and cytoskeletal abnormalities. Precancerous isolates possessed a higher number of motifs, and precancerous strains from Nashville induced higher levels of IL-8 than Colombian strains. These results indicate that CagA variants are linked with premalignant lesions in distinct populations and that epithelial responses to these strains are selective based upon locale.

Epidermal growth factor receptor activation protects gastric epithelial cells from Helicobacter pylori-induced apoptosis.

BACKGROUND & AIMS: Helicobacter pylori infection disrupts the balance between gastric epithelial cell proliferation and apoptosis, which is likely to lower the threshold for the development of gastric adenocarcinoma. H pylori infection is associated with epidermal growth factor (EGF) receptor (EGFR) activation through metalloproteinase-dependent release of EGFR ligands in gastric epithelial cells. Because EGFR signaling regulates cell survival, we investigated whether activation of EGFR following H pylori infection promotes gastric epithelial survival. METHODS: Mouse conditionally immortalized stomach epithelial cells (ImSt) and a human gastric epithelial cell line, AGS cells, as well as wild-type and kinase-defective EGFR (EGFRwa2) mice, were infected with the H pylori cag+ strain 7.13. Apoptosis, caspase activity, EGFR activation (phosphorylation), and EGFR downstream targets were analyzed. RESULTS: Inhibiting EGFR kinase activity or decreasing EGFR expression significantly increased H pylori-induced apoptosis in ImSt. Blocking H pylori-induced EGFR activation with a heparin-binding (HB)-EGF neutralizing antibody or abrogating a disintegrin and matrix metalloproteinase-17 (ADAM-17) expression increased apoptosis of H pylori-infected AGS and ImSt, respectively. Conversely, pretreatment of ImSt with HB-EGF completely blocked H pylori-induced apoptosis. H pylori infection stimulated gastric epithelial cell apoptosis in EGFRwa2 but not in wild-type mice. Furthermore, H pylori-induced EGFR phosphorylation stimulated phosphotidylinositol-3'-kinase-dependent activation of the antiapoptotic factor Akt, increased expression of the antiapoptotic factor Bcl-2, and decreased expression of the proapoptotic factor Bax. CONCLUSIONS: EGFR activation by H pylori infection has an antiapoptotic effect in gastric epithelial cells that appears to involve Akt signaling and Bcl family members. These findings provide important insights into the mechanisms of H pylori-associated tumorigenesis.

p120 and Kaiso regulate Helicobacter pylori-induced expression of matrix metalloproteinase-7.

Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, yet only a fraction of infected persons develop cancer. One H. pylori constituent that augments disease risk is the cytotoxin-associated gene (cag) pathogenicity island, which encodes a secretion system that translocates bacterial effector molecules into host cells. Matrix metalloproteinase (MMP)-7, a member of a family of enzymes with tumor-initiating properties, is overexpressed in premalignant and malignant gastric lesions, and H. pylori cag(+) strains selectively increase MMP-7 protein levels in gastric epithelial cells in vitro and in vivo. We now report that H. pylori-mediated mmp-7 induction is transcriptionally regulated via aberrant activation of p120-catenin (p120), a component of adherens junctions. H. pylori increases mmp-7 mRNA levels in a cag- and p120-dependent manner and induces translocation of p120 to the nucleus in vitro and in a novel ex vivo gastric gland culture system. Nuclear translocation of p120 in response to H. pylori relieves Kaiso-mediated transcriptional repression of mmp-7, which is implicated in tumorigenesis. These results indicate that selective and coordinated induction of mmp-7 expression by H. pylori cag(+) isolates may explain in part the augmentation in gastric cancer risk associated with these strains.

Regulation of the Helicobacter pylori cellular receptor decay-accelerating factor.

Chronic gastritis induced by Helicobacter pylori is the strongest known risk factor for peptic ulceration and distal gastric cancer, and adherence of H. pylori to gastric epithelial cells is critical for induction of inflammation. One H. pylori constituent that increases disease risk is the cag pathogenicity island, which encodes a secretion system that translocates bacterial effector molecules into host cells. Decay-accelerating factor (DAF) is a cellular receptor for H. pylori and a mediator of the inflammatory response to this pathogen. H. pylori induces DAF expression in human gastric epithelial cells; therefore, we sought to define the mechanism by which H. pylori up-regulates DAF and to extend these findings into a murine model of H. pylori-induced injury. Co-culture of MKN28 gastric epithelial cells with the wild-type H. pylori cag(+) strain J166 induced transcriptional expression of DAF, which was attenuated by disruption of a structural component of the cag secretion system (cagE). H. pylori-induced expression of DAF was dependent upon activation of the p38 mitogen-activated protein kinase pathway but not NF-kappaB. Hypergastrinemic INS-GAS mice infected with wild-type H. pylori demonstrated significantly increased DAF expression in gastric epithelium versus uninfected controls or mice infected with an H. pylori cagE(-) isogenic mutant strain. These results indicate that H. pylori cag(+) strains induce up-regulation of a cognate cellular receptor in vitro and in vivo in a cag-dependent manner, representing the first evidence of regulation of an H. pylori host receptor by the cag pathogenicity island.

Regulation of gastric carcinogenesis by Helicobacter pylori virulence factors.

Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, and strains that possess the cag secretion system, which translocates the bacterial effector CagA into host cells, augment cancer risk. H. pylori strains that express the vacuolating cytotoxin or the outer membrane protein OipA are similarly associated with severe pathologic outcomes. We previously reported that an in vivo adapted H. pylori strain, 7.13, induces gastric adenocarcinoma in rodent models of gastritis. In the current study, we used carcinogenic strain 7.13 as a prototype to define the role of virulence constituents in H. pylori-mediated carcinogenesis. Mongolian gerbils were infected with wild-type strain 7.13 or cagA(-), vacA(-), or oipA(-) mutants for 12 to 52 weeks. All infected gerbils developed gastritis; however, inflammation was significantly attenuated in animals infected with the cagA(-) but not the vacA(-) or oipA(-) strains. Gastric dysplasia and cancer developed in >50% of gerbils infected with either the wild-type or vacA(-) strain but in none of the animals infected with the cagA(-) strain. Inactivation of oipA decreased beta-catenin nuclear localization in vitro and reduced the incidence of cancer in gerbils. OipA expression was detected significantly more frequently among H. pylori strains isolated from human subjects with gastric cancer precursor lesions versus persons with gastritis alone. These results indicate that loss of CagA prevents the development of cancer in this model. Inactivation of oipA attenuates beta-catenin nuclear translocation and also decreases the incidence of carcinoma. In addition to defining factors that mediate H. pylori-induced cancer, these results provide insight into mechanisms that may regulate the development of other malignancies arising within the context of inflammatory states.

Effect of Helicobacter pylori eradication on gastric carcinogenesis.

Chronic gastritis induced by Helicobacter pylori is the strongest known risk factor for gastric adenocarcinoma, yet the effects of bacterial eradication on carcinogenesis remain unclear. Animal models provide important insights into factors that are involved in gastric carcinogenesis, and we previously utilized such a model to demonstrate that an in vivo-adapted H. pylori strain, 7.13, rapidly and reproducibly induces inflammation-mediated gastric carcinoma. In the current study, we used this bacterial strain as a prototype to define the role of targeted antimicrobial therapy in gastric carcinogenesis. Mongolian gerbils were infected with H. pylori for 4 or 8 weeks, treated with antimicrobial agents or vehicle, and then euthanized at 8 weeks after the completion of therapy. All infected gerbils developed gastritis; however, inflammation was significantly attenuated in animals receiving antimicrobial therapy. Gastric dysplasia or cancer developed in >60% of the gerbils that remained persistently colonized with H. pylori, but in none of the animals treated with antibiotics following 4 weeks of infection. Infection with H. pylori for 8 weeks prior to therapy resulted in an attenuation, but not complete prevention, of pre-malignant and malignant lesions. Similarly, antibiotic therapy initiated at 4, but not 8, weeks after H. pylori challenge significantly reduced expression of the Th1 pro-inflammatory cytokine interferon-gamma within colonized gastric mucosa. These results indicate that treatment of H. pylori in this model decreases the incidence and severity of lesions with carcinogenic potential. The effectiveness of eradication is dependent upon the timing of intervention, providing insights into mechanisms that may regulate the development of malignancies arising within the context of inflammatory states.