A M(r) 34,000 proinflammatory outer membrane protein (oipA) of Helicobacter pylori

Helicobacter pylori-dependent NF-kappa B activation in newly established Mongolian gerbil gastric cancer cell lines

Mongolian gerbils are an ideal animal model to explore the role of H. pylori on cancer development. However, there have been no established adenocarcinoma cell lines from this model animal. In the present study, we have established cancer cell lines from a primary gastric cancer tissue of a Mongolian gerbil. The derived cells could be stably attached with H. pylori, revealed under a scanning electron microscope, and easily transplanted to the nude mice. Rapid phosphorylation of IkappaB, Erk1/2, and AKT of these cells was observed by Interleukin-1 beta stimulation, and luciferase reporter gene assay on transcriptional activation of Nuclear Factor kappa B after challenging with either H. pylori NCTC11637 or its isogenic cagE-knockout mutant, H. pylori revealed the cagE-dependent NF-kappaB transcriptional activation. The newly established cancer cell lines from the in vivo gastric carcinogenesis model animal, the Mongolian gerbil, can be used to develop effective therapeutic strategies against gastric cancer, especially in exploring the effect of H. pylori, and thus might greatly contribute to gastric cancer prevention and treatment in humans.

Phase variation mediated niche adaptation during prolonged experimental murine infection with Helicobacter pylori

Changes in the repeats associated with the recently redefined repertoire of 31 phase-variable genes in Helicobacter pylori were investigated following murine gastric colonization for up to one year in three unrelated H. pylori strains. Between the beginning and end of the experimental period, changes were seen in ten genes (32 %), which would alter gene expression in one or more of the three strains studied. For those genes that showed repeat length changes at the longest time points, intermediate time points showed differences between the rates of change for different functional groups of genes. Genes most likely to be associated with immediate niche fitting changed most rapidly, including phospholipase A (pldA) and LPS biosynthetic genes. Other surface proteins, which may be under adaptive immune selection, changed more slowly. Restriction-modification genes showed no particular temporal pattern. The number of genes that phase varied during adaptation to the murine gastric environment correlated inversely with their relative fitness as previously determined in this murine model of colonization. This suggests a role for these genes in determining initial fitness for colonization as well as in subsequent niche adaptation. In addition, a coding tandem repeat within a phase-variable gene which does not control actual gene expression was also investigated. This repeat was found to vary in copy number during colonization. This suggests that changes in the structures encoded by tandem repeats may also play a role in altered protein functions and/or immune evasion during H. pylori colonization.

Responsiveness to acidity via metal ion regulators mediates virulence in the gastric pathogen Helicobacter pylori

The virulence of pathogenic bacteria is dependent on their adaptation to and survival in the stressful conditions encountered in their hosts. Helicobacter pylori exclusively colonizes the acid stomach of primates, making it an ideal study model. Little is known about how H. pylori responds to the moderately acidic conditions encountered at its colonization site, the gastric mucus layer. Thus, we compared gene expression profiles of H. pylori 26695 grown at neutral and acidic pH, and validated the data for a selection of genes by real-time polymerase chain reaction, dot-blots or enzymatic assays. During growth in acidic conditions, 56 genes were upregulated and 45 genes downregulated. We found that acidity is a signal modulating the expression of several virulence factors. Regulation of genes related to metal ion homeostasis suggests protective mechanisms involving diminished transport and enhanced storage. Genes encoding subunits of the F0F1 ATPase and of a newly identified Na+/H+ antiporter (NhaC-HP0946) were downregulated, revealing that this bacterium uses original mechanisms to control proton entry. Five of the upregulated genes encoded proteins controlling intracellular ammonia synthesis, including urease, amidase and formamidase, underlining the major role of this buffering compound in the protection against acidity in H. pylori. Regulatory networks and transcriptome analysis as well as enzymatic assays implicated two metal-responsive transcriptional regulators (NikR and Fur) and an essential two-component response regulator (HP0166, OmpR-like) as effectors of the H. pylori acid response. Finally, a nikR-fur mutant is attenuated in the mouse model, emphasizing the link between response to acidity, metal metabolism and virulence in this gastric pathogen.

H. pylori infection: bacterial virulence factors and cytokine gene polymorphisms as determinants of infection outcome

The gram negative bacterium H. pylori infects the human stomach worldwide, invariably causing mucosal inflammation. In the majority of cases, H. pylori-associated gastritis remains the only clinical manifestation of the infection, which might cause, otherwise, peptic ulcer, gastric adenocarcinoma. or MALToma. The balance between the bacterial virulence machinery and the host response to the infection determines the different clinical outcomes. The main bacterial virulence factors comprise adhesins (BabA, SabA), the vacuolating cytotoxin VacA, and the products of cag pathogenicity island. The pattern of cytokine production in response to the infection is one of the main host determinants involved in limiting the infection outcome to gastritis or in favoring peptic ulcer or cancer onset. The polymorphisms of some cytokine genes (IL-1beta IL-1RN, TNF-alpha, IFN-gamma) have been correlated with H. pylori-associated gastric adenocarcinoma or peptic ulcer, possibly because they influence the amount of cytokine production in response to H. pylori infection. This review focuses on the role of H. pylori virulence genes and on host cytokines' genes polymorphisms in determining clinical outcome to H. pylori infection.

Cloning and sequence analysis of gene oipA encoding an outer membrane protein of human Helicobacter pylori

AIM: To construct a recombinant E. coli strain that would highly express the proinflammatory outer membrane protein of human Helicobacter pylori (H pylori).

METHODS: The oipA DNA was amplified by PCR, inserted into pET-32a, and transformed into Top10 E. coli strain. This recombinant plasmid of Top10 was sent out for nucleotide sequence analysis. Finally this sequence AF479754 was compared with HP0638 and JHP0581.

RESULTS: The sequence of the aim gene was obtained. It had 924 base pairs. The identity was 95.32% against HP0638, 95.02% against JHP0581, which was higher than the identity between HP0638 and JHP0581.

CONCLUSION: Although the aim gene was obtained, but it was different from the published sequence of GenBank. It is not clear what makes this difference. Maybe it is because different strain was used or because there were some variations. So more researches are required to prove it.

Alanine-threonine polymorphism of Helicobacter pylori RpoB is correlated with differential induction of interleukin-8 in MKN45 cells

Geographical differences in the genetic diversity of Helicobacter pylori isolates were examined by analyzing rpoB sequences. An extremely high level of allelic diversity among H. pylori strains was found. The rpoB sequences of Asian and non-Asian (North and South American, European, and South African) strains were found to differ. An amino acid polymorphism (alanine and threonine RpoB types) was found at the 497th residue by deduced amino acid analysis. RpoB with a threonine residue (RpoB(Thr)) was uniquely present in East Asian countries, and two-thirds of the H. pylori isolate population in this region was RpoB(Thr); however, this type was rare or absent in Western countries, where RpoB(Ala) predominated. RpoB(Thr) strains induced a much larger amount of interleukin-8, a chemokine that plays an important role in chronic inflammation, than RpoB(Ala) strains in cultured MKN45 cells.

Correlation between Helicobacter pylori OipA protein expression and oipA gene switch status

Polyclonal antisera to either a synthetic OipA peptide or a recombinant OipA protein detected OipA expression in Helicobacter pylori and correlated with functional oipA status determined by PCR sequence (sensitivity and specificity of >94%). Immunoblotting is a simple and accurate method for detecting expression of the important virulence factor OipA.

The Helicobacter pylori restriction endonuclease-replacing gene, hrgA, and clinical outcome: comparison of East Asia and Western countries

It has been suggested that the putative Helicobacter pylori virulence factor hrgA is the first disease-specific marker for an H. pylori-related disease, (i.e., development of gastric cancer in East Asia). Our aim was to test the hypothesis that the presence of hrgA has disease specificity. We examined 458 H. pylori isolates including 289 from East Asia and 169 from Western countries whose cagA and vacA genotypes had previously been characterized. hrgA/hpyIIIR status and iceA genotypes were determined by polymerase chain reaction using DNA expanded from a single colony. hrgA was present in 29% of gastric cancers, 29% of ulcers, and 31% of gastritis cases among H. pylori from East Asia (P > 0.9). Overall, there was no significant relationship between the presence of the hrgA gene and disease presentation (cancer, ulcer, or neither) or between its presence and the cag pathogenicity island, vacA s1 , babA2, and oipA, "on" genotypes. The prevalence of the hrgA gene was significantly lower in H. pylori from East Asia (29%) vs. those from the West (49%) (P < 0.001). The prevalence of the hrgA gene was not related to clinical outcome or to other important putative virulence factors.

Challenge model for Helicobacter pylori infection in human volunteers

BACKGROUND

A reliable challenge model is needed to evaluate Helicobacter pylori vaccine candidates.

METHODS

A cag pathogenicity island negative, OipA positive, multiple antibiotic susceptible strain of H pylori obtained from an individual with mild gastritis (Baylor strain 100) was used to challenge volunteers. Volunteers received 40 mg of famotidine at bedtime and 10(4)-10(10) cfu of H pylori in beef broth the next morning. Infection was confirmed by (13)C urea breath test ((13)C-UBT), culture, and histology. Eradication therapy was given four or 12 weeks post challenge and eradication was confirmed by at least two separate UBTs, as well as culture and histology.

RESULTS

Twenty subjects (nine women and 11 men; aged 23-33 years) received a H pylori challenge. Eighteen (90%) became infected. Mild to moderate dyspeptic symptoms occurred, peaked between days 9 and 12, and resolved. Vomitus from one subject contained >10(3) viable/ml H pylori. By two weeks post challenge gastric histology showed typical chronic H pylori gastritis with intense acute and chronic inflammation. The density of H pylori (as assessed by cfu/biopsy) was similarly independent of the challenge dose. A minimal infectious dose was not found. Gastric mucosal interleukin 8 levels increased more than 20-fold by two weeks after the challenge.

CONCLUSION

Challenge reliably resulted in H pylori infection. Infection was associated with typical H pylori gastritis with intense polymorphonuclear cell infiltration and interleukin 8 induction in gastric mucosa, despite absence of the cag pathogenicity island. Experimental H pylori infection is one of the viable approaches to evaluate vaccine candidates.

The diversity within an expanded and redefined repertoire of phase-variable genes in Helicobacter pylori

Phase variation is a common mechanism used by pathogenic bacteria to generate intra-strain diversity that is important in niche adaptation and is strongly associated with virulence determinants. Previous analyses of the complete sequences of the Helicobacter pylori strains 26695 and J99 have identified 36 putative phase-variable genes among the two genomes through their association with homopolymeric tracts and dinucleotide repeats. Here a comparative analysis of the two genomes is reported and an updated and expanded list of 46 candidate phase-variable genes in H. pylori is described. These have been systematically investigated by PCR and sequencing for the presence of the genes, and the presence and variability in length of the repeats in strains 26695 and J99 and in a collection of unrelated H. pylori strains representative of the main global subdivisions recently suggested. This provides supportive evidence for the phase variability of 30 of the 46 candidates. Other differences in this subset of genes were observed (i) in the repeats, which can be present or absent among the strains, or stabilized in different strains and (ii) in the gene-complements of the strains. Differences between genes were not consistently correlated with the geographic population distribution of the strains. This study extends and provides new evidence for variation of this type in H. pylori, and of the high degree of diversity of the repertoire of genes which display phase-variable switching within individual strains.

Heterogeneity among Helicobacter pylori strains in expression of the outer membrane protein BabA

The BabA adhesin of Helicobacter pylori is an outer membrane protein that binds to the fucosylated Lewis b histo-blood group antigen on the surface of gastric epithelial cells. We screened a phage-displayed ScFv (single-chain fragment variable) recombinant antibody library for antibodies reactive with a recombinant BabA fragment and identified two such antibodies. Each antibody recognized an approximately 75-kDa protein present in wild-type H. pylori strain J99 but absent from an isogenic babA mutant strain. An immunoreactive BabA protein was detected by at least one of the antibodies in 18 (46%) of 39 different wild-type H. pylori strains and was detected more commonly in cagA-positive strains than in cagA-negative strains. Numerous amino acid polymorphisms were detected among BabA proteins expressed by different strains, with the greatest diversity occurring in the middle region of the proteins. Among the 18 strains that expressed a detectable BabA protein, there was considerable variation in the level of binding to Lewis b in vitro. Heterogeneity among H. pylori strains in expression of the BabA protein may be a factor that contributes to differing clinical outcomes among H. pylori-infected humans.

The functional status of the Helicobacter pylori sabB adhesin gene as a putative marker for disease outcome

BACKGROUND

Helicobacter pylori factors that contribute to disease outcome are largely unknown, but intimate contact with host cells mediated by outer membrane proteins is thought to play an important role. Expression of the outer membrane proteins OipA, HopZ, SabA, and SabB is regulated by phase-variable dinucleotide repeats in the coding regions of the respective genes. We have evaluated the correlation between the expression status of these four genes and disease outcome of H. pylori infection in a Dutch patient population.

MATERIALS AND METHODS

H. pylori strains, isolated from 96 Dutch patients with gastritis (n = 29), duodenal ulcer (n = 28), gastric ulcer (n = 21), gastric carcinoma (n = 9), and lymphoma (n = 9), were analyzed for the 'on/off' expression status of the H. pylori genes oipA, hopZ, sabA, and sabB by direct DNA sequence analysis of amplified fragments.

RESULTS

The off-status of sabB was significantly associated with duodenal ulcer (p =.036), but not with gastric ulcer. In contrast, the expression status of oipA, hopZ, and sabA did not correlate with disease outcome. Furthermore, lymphoma strains appeared to express a significantly smaller amount of putative adhesins when compared to gastritis, gastric ulcer, duodenal ulcer and gastric carcinoma strains (p <.02 for all groups tested).

CONCLUSIONS

The off-status of sabB was found to be associated with duodenal ulcer disease, and thus represents a putative marker for disease outcome. Assuming that SabB is involved in bacterial adhesion, this association suggests that adherent H. pylori are more prone to elimination by the host immune system.

Evaluation of the association of nine Helicobacter pylori virulence factors with strains involved in low-grade gastric mucosa-associated lymphoid tissue lymphoma

Helicobacter pylori has been associated with the development of two malignant diseases: gastric adenocarcinoma and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Although the cag pathogenicity island, especially the cagA gene, has been linked with adenocarcinoma, few data concerning H. pylori pathogenic factors involved in low-grade gastric MALT lymphoma are available. The goal of this study was to analyze the prevalence of and correlation between genes coding for seven H. pylori virulence factors (cagA, cagE, vacA, iceA, babA, hopQ, and oipA) and two novel adhesins (sabA and hopZ) by comparing a collection of 43 H. pylori strains isolated from patients with low-grade gastric MALT lymphoma to 39 strains isolated from age-matched patients with gastritis only. Our results show that taken individually, none of the nine genes tested can be considered associated with MALT strains and allow us to conclude that MALT pathogenesis is not linked with more proinflammatory H. pylori strains. We demonstrated that in patients infected with strains harboring the iceA1 allele, sabA functional status, and hopZ "off" status, the odds of developing a MALT lymphoma were 10 times higher. However, the low prevalence of such strains (10 of 43 MALT strains) renders this triple association a low-sensitivity marker for MALT strains. Our data confirmed that H. pylori virulence factors are correlated with one another. If the involvement of H. pylori in MALT lymphoma is well established, the pathomechanism by which gastric lymphoma occurs remains to be identified.

Persistent infection with Helicobacter pylori and the development of gastric cancer

Gastric malignancies have been closely linked to infection of the gastric mucosa with Helicobacter pylori, but the individual factors involved in the multistage process of tumor development are still poorly understood. H. pylori evades the host defense system and causes persistent infection and chronic inflammation. Immune activation leads to DNA damage by the release of oxygen and nitrogen radicals. Ongoing tissue repair mechanisms and the secretion of cytokines and growth factors, as well as bacterial effector molecules, cause disturbances in the balance between epithelial cell proliferation and apoptosis, promote the accumulation of potential oncogenic mutations, and support neovascularization and tumor growth. In addition, H. pylori might hamper the development of an efficient antitumor immunity and provoke immune-mediated pathology. This review summarizes the recent progress in the understanding of the intimate bacteria-host relationship and the mechanisms by which H. pylori may promote the process of tumor development.

Helicobacter pylori disrupts STAT1-mediated gamma interferon-induced signal transduction in epithelial cells

Infection with Helicobacter pylori is chronic despite a vigorous mucosal immune response characterized by gastric T-helper type 1 cell expansion and gamma interferon (IFN-gamma) production. IFN-gamma signals by activation and nuclear translocation of signal transducer and activator of transcription 1 (STAT1); however, the effect of H. pylori infection on IFN-gamma-STAT1 signaling is unknown. We infected human gastric (MKN45 and AGS) and laryngeal (HEp-2) epithelial cell lines with type 1 and type 2 H. pylori strains and then stimulated them with IFN-gamma. Western blotting of whole-cell protein extracts revealed that infection with live, but not heat-killed, H. pylori time-dependently decreased IFN-gamma-induced STAT1 tyrosine phosphorylation. Electrophoretic mobility shift assay of nuclear protein extracts demonstrated that H. pylori infection reduced IFN-gamma-induced STAT1 DNA binding. STAT1 was unable to translocate from the cytoplasm to the nucleus in H. pylori-infected HEp-2 cells examined by immunofluorescence, and reverse transcription-PCR showed that IFN-gamma-induced interferon regulatory factor 1 expression was inhibited. These effects were independent of the cagA, cagE, and VacA status of the infecting H. pylori strain. Furthermore, neither H. pylori culture supernatants nor conditioned medium from H. pylori-infected MKN45 cells inhibited IFN-gamma-induced STAT1 tyrosine phosphorylation, suggesting that inhibition is independent of a soluble epithelial or bacterial factor but is dependent on bacterial contact with epithelial cells. H. pylori disruption of IFN-gamma-STAT1 signaling in epithelial cells may represent a mechanism by which the bacterium modifies mucosal immune responses to promote its survival in the human host.

Functional analysis of the cag pathogenicity island in Helicobacter pylori isolates from patients with gastritis, peptic ulcer, and gastric cancer

Helicobacter pylori is the causative agent of a variety of gastric diseases, but the clinical relevance of bacterial virulence factors is still controversial. Virulent strains carrying the cag pathogenicity island (cagPAI) are thought to be key players in disease development. Here, we have compared cagPAI-dependent in vitro responses in H. pylori isolates obtained from 75 patients with gastritis, peptic ulcer, and gastric cancer (n = 25 in each group). AGS gastric epithelial cells were infected with each strain and assayed for (i) CagA expression, (ii) translocation and tyrosine phosphorylation of CagA, (iii) c-Src inactivation, (iv) cortactin dephosphorylation, (v) induction of actin cytoskeletal rearrangements associated with cell elongation, (vi) induction of cellular motility, and (vii) secretion of interleukin-8. Interestingly, we found high but similar prevalences of all of these cagPAI-dependent host cell responses (ranging from 56 to 80%) among the various groups of patients. This study revealed CagA proteins with unique features, CagA subspecies of various sizes, and new functional properties for the phenotypic outcomes. We further showed that induction of AGS cell motility and elongation are two independent processes. Our data corroborate epidemiological studies, which indicate a significant association of cagPAI presence and functionality with histopathological findings in gastritis, peptic ulcer, and gastric cancer patients, thus emphasizing the importance of the cagPAI for the pathogenicity of H. pylori. Nevertheless, we found no significant association of the specific H. pylori-induced responses with any particular patient group. This may indicate that the determination of disease development is highly complex and involves multiple bacterial and/or host factors.

Helicobacter pylori outer membrane vesicles modulate proliferation and interleukin-8 production by gastric epithelial cells

Helicobacter pylori infection, which is always associated with gastritis, can progress to ulceration or malignancy. The diversity in clinical outcomes is partly attributed to the expression of virulence factors and adhesins by H. pylori. However, H. pylori may not have to adhere to the epithelium to cause gastritis. We hypothesize that outer membrane vesicles (OMV), which are constantly shed from the surface of H. pylori, play a role as independent activators of host cell responses. In this study, we found that low doses of OMV from cag PAI+ toxigenic and cag PAI- nontoxigenic strains increased proliferation of AGS gastric epithelial cells. At higher doses, we detected growth arrest, increased toxicity, and interleukin-8 (IL-8) production. The only strain differences detected were vacuolation with the toxigenic strain and higher levels of IL-8 production with OMV from the cag PAI- nontoxigenic strain. In summary, we suggest that constitutively shed OMV play a role in promoting the low-grade gastritis associated with H. pylori infection.

Cyclooxygenase expression during Helicobacter pylori infection in Mongolian gerbils

We investigated the expression of cyclooxygenase-2 (COX-2) and COX-1 mRNAs during longterm Helicobacter pylori infection of the Mongolian gerbil (18 months) as well as the effect of eradication therapy and the cag pathogenicity island on COX mRNA expression. COX mRNA levels were determined by reverse transcription-polymerase chain reaction. Pyloric channel ulcers were noted in one of 10 gerbils (10%) at 3 months, 33% at 6 months, 50% at 9 months, 17% at 10 months, 40% at 12 months and 25% at 18 months after inoculation of parental strains. Nineteen of 21 gerbils had successful H. pylori eradication and showed significant reduction of inflammation and no ulcerations. There were no significant differences in COX-1 mRNA expression between the groups. COX-2 mRNA expression was significantly increased 1 and 3 months after inoculation and then decreased to basal levels. In control animals, COX-2 mRNA expression was significantly higher at 12 and 18 months compared to younger animals. cagE knockout mutants did not induce gastric inflammation and induced significantly lower COX-2 mRNA expression compared to parental strains. COX-2 mRNA was induced early in H. pylori infection and then declined. COX-2 mRNA expression was also induced with aging.

Helicobacter pylori infection interferes with epithelial Stat6-mediated interleukin-4 signal transduction independent of cagA, cagE, or VacA

Helicobacter pylori is a bacterial pathogen evolved to chronically colonize the gastric epithelium, evade immune clearance by the host, and cause gastritis, peptic ulcers, and even gastric malignancies in some infected humans. In view of the known ability of this bacterium to manipulate gastric epithelial cell signal transduction cascades, we determined the effects of H. pylori infection on epithelial IL-4-Stat6 signal transduction. HEp-2 and MKN45 epithelial cells were infected with H. pylori strains LC11 or 8823 (type 1; cagA(+)/cagE(+)/VacA(+)), LC20 (type 2; cagA(-), cagE(-), VacA(-)), and cagA, cagE, and vacA isogenic mutants of strain 8823, with some cells receiving subsequent treatment with the Th2 cytokine IL-4, a known Stat6 activator. Immunofluorescence showed a disruption of Stat6-induced nuclear translocation by IL-4 in LC11-infected HEp-2 cells. IL-4-inducible Stat6 DNA binding in HEp-2 and MKN45 cells was abrogated by infection, but MKN45 cell viability was unaffected. A decrease in IL-4-mediated Stat6 tyrosine phosphorylation in nuclear and whole cell lysates was also observed following infection with strains LC11 and LC20, while neither strain altered IL-4 receptor chain alpha or Janus kinase 1 protein expression. Furthermore, parental strain 8823 and its isogenic cagA, cagE, and vacA mutants also suppressed IL-4-induced Stat6 tyrosine phosphorylation to comparable degrees. Thus, H. pylori did not directly activate Stat6, but blocked the IL-4-induced activation of epithelial Stat6. This may represent an evolutionarily conserved strategy to disrupt a Th2 response and evade the host immune system, allowing for successful chronic infection.

Experimentally revised repertoire of putative contingency loci in Neisseria meningitidis strain MC58: evidence for a novel mechanism of phase variation

Analysis of the genome sequence of Neisseria meningitidis strain MC58 revealed 65 genes associated with simple sequence repeats. Experimental evidence of phase variation exists for only 14 of these 65 putatively phase variable genes. We investigated the phase variable potential of the remaining 51 genes. The repeat tract associated with 20 of these 51 genes was sequenced in 26 genetically distinct strains. This analysis provided circumstantial evidence for or against the phase variability of the candidate genes, based on the sequence and the length of the repeated motif. These predictions of phase variability were substantiated for three of these candidate genes using colony immunoblotting or beta-galactosidase as a reporter. This investigation identified a novel phase variable gene (NMB1994 or nadA) associated with a repeat tract (TAAA) not previously reported to be associated with phase variable genes in N. meningitidis. Analysis of the nadA transcript revealed that the repeat tract was located upstream of the putative -35 element of the nadA promoter. Semiquantitative RT-PCR showed that variation in the number of repeats was associated with changes in the level of expression of nadA, findings consistent with a model whereby the variable number of (TAAA) repeats modulates the promoter strength.

Host gastric Lewis expression determines the bacterial density of Helicobacter pylori in babA2 genopositive infection

BACKGROUND AND AIMS

We tested if host gastric Lewis antigens and the babA2 genotype of Helicobacter pylori correlated with clinicohistological outcome.

METHODS

We enrolled 188 dyspeptic patients (45 with duodenal ulcer, 45 with gastric ulcer, and 98 with chronic gastritis) with H pylori infection, proved by culture and gastric histology, reviewed by the updated Sydney system. Gastric expression of Lewis (Le) antigens Le(a), Le(b), Le(x), and Le(y) was determined immunochemically to determine intensity (range 0-3). The corresponding 188 H pylori isolates were screened for babA2 genotype by polymerase chain reaction.

RESULTS

All H pylori isolates had a positive babA2 genotype. We identified Le(a) in 33.5%, Le(b) in 72.9%, Le(x) in 86.2%, and Le(y) in 97.4% of biopsies from these 188 patients. Patients who expressed Le(b) had a higher H pylori density than those who did not express Le(b) (p<0.001). Among 139 patients who expressed Le(b), H pylori density increased with a higher Le(b) intensity (p<0.05). Gastric atrophy decreased with Le(b) intensity and thus resulted in lower H pylori density in the antrum (p<0.05). For the 49 patients without gastric Le(b) expression, H pylori density was positively related with Le(x) and Le(a) expression (p<0.05).

CONCLUSIONS

Taiwanese H pylori isolates are 100% babA2 genopositive. Gastric Le(b) as well as Le(x) intensity may be major determinants of H pylori density. While lacking gastric Le(b) expression, Le(x) and Le(a) were closely related to H pylori colonisation.

Investigation of the biological relevance of Helicobacter pylori cagE locus diversity, presence of CagA tyrosine phosphorylation motifs and vacuolating cytotoxin genotype on IL-8 induction in gastric epithelial cells

Isolates of Helicobacter pylori from dyspeptic patients in England and South Africa were tested for ability to induce interleukin-8 (IL-8) in gastric cells. All isolates were cagA-positive, which was used as a marker for the presence of the cag pathogenicity island. The aims were to determine if activities were related to diversity within cagE (HP0544), a locus encoding a key component in the Type IV secretion system, and if disease severity might be linked to a combination of strain features. We found that isolates were heterogeneous in ability to induce IL-8 activity with the 23 positive isolates (59%) showing activities ranging from 260 to 3200 pg ml(-1). The cagE locus was detected in most isolates and RFLP analysis of a 1.52-kb internal fragment showed interstrain diversity with 12 combined (MboI/NlaIII) types. Most cagE genotypes were not associated with IL-8 induction, however two genotypes were found only in IL-8-inducing strains and one genotype was associated with lack of IL-8 induction. IL-8 activity was not associated with either the number or composition of cagA tyrosine phosphorylation motifs and vacA m-type. Although we found a weak association between cagE type and the ability to induce IL-8, our results imply that gastric cell factors or bacterial factors other than vacA, cagA and cagE are involved in the induction of IL-8 and the development of severe gastric disease.

DNA-level characterization of Helicobacter pylori strains from patients with overt disease and with benign infections in Bangladesh

The complex relation between the genotype of Helicobacter pylori and its association with clinical outcome is not well understood. Studies in the West have showed that strains expressing certain virulence factors (vacAs1, vacAm1, and cagA) are associated with duodenal ulcer disease. However, the H. pylori genotype is known to vary with geographic region. In the present study, we compared several virulence markers (cagA, vacA, and iceA) and neutral markers (IS605, IS606, and IS608) in H. pylori strains isolated from 65 adult patients with peptic ulcer (PU) and 50 patients with nonulcer dyspepsia (NUD). PCR tests indicated that cagA is present in 75% of the strains from patients with PU compared to 55% in patients with NUD, and 80% of the isolates from patients with PU carried potentially toxigenic vacAs1 alleles of the vacuolating cytotoxin gene (vacA) compared to 60% in isolates from patients with NUD. However, no significant difference in any other virulence marker was observed in isolates from both groups. Phylogenetic analysis of the vacA middle region and the 5' end of the cagA gene indicates that Bangladeshi isolates are more closely related to H. pylori isolates from India and are different from isolates from East Asia.

Quantitative evaluation of inflammatory and immune responses in the early stages of chronic Helicobacter pylori infection

The early consequences of Helicobacter pylori infection and the role of bacterial virulence determinants in disease outcome remain to be established. The present study sought to measure the development of host inflammatory and immune responses and their relationship to the putative bacterial virulence factors cag pathogenicity island (cagPAI), vacA allele, and oipA in combination with bacterial colonization density in a feline model of the early stages of H. pylori infection. Gastric tissues obtained from infected and uninfected cats were evaluated for H. pylori ureB, cagPAI, vacA allele, and oipA and colonization density (urease, histology, and real-time PCR). Inflammation was assessed by measuring mRNA upregulation of gamma interferon (IFN-gamma), interleukin (IL)-1 alpha, IL-1 beta, IL-4, IL-6, IL-8, IL-10, and IL-12 p40 and histopathology. The mucosal immune response was characterized by morphometric analysis of lymphoid follicles and by differentiating lymphocyte populations with antibodies against surface markers. Infecting H. pylori strains were positive for vacAs1 but lacked cagPAI and an active oipA gene. Colonization density was uniform throughout the stomach. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and increased severity of inflammatory infiltrates and fibrosis were observed in infected cats. The median number and total area of lymphoid aggregates were 5 and 10 times greater, respectively, in the stomachs of infected than uninfected cats. Secondary lymphoid follicles in uninfected cats were rare and positive for BLA.36 and B220 but negative for CD3 and CD79 alpha, whereas in infected cats they were frequent and positive for BLA.36, CD79 alpha, and CD3 but negative for B220. Upregulation of IFN-gamma, IL-1 alpha, IL-1 beta, and IL-8 and marked hyperplasia of secondary lymphoid follicles are early consequences of H. pylori infection in cats. The response appears to be similar to that of infected people, particularly children, can develop independently of the pathogenicity factors cagPAI and oipA, and is not correlated with the degree of colonization density or urease activity.

Helicobacter pylori babA2, cagA, and s1 vacA genes work synergistically in causing intestinal metaplasia

AIMS

To determine any associations between the Helicobacter pylori genes babA2, oipA, cagA and the s and m alleles of vacA. In addition, to verify whether these genes work synergistically or independently in causing gastritis, peptic ulcer, and intestinal metaplasia.

METHODS

One hundred and sixty seven H pylori positive patients were studied (52 antral gastritis, 41 diffuse gastritis, 41 peptic ulcer, and 33 duodenitis). Helicobacter pylori virulence genes were amplified by means of the polymerase chain reaction.

RESULTS

Significant associations were found between babA2 and the other H pylori genes studied. When considered singly, all the genes were associated with disease diagnosis, inflammation, and intestinal metaplasia. Four H pylori groups were defined. Group A: cagA-, s2m2, babA2-; group B: cagA+, s1m1, babA2+; group C: cagA+, s1m2, babA2+; group D: cagA+, s1m2, babA2-. Group A infecting strains were associated with less severe endoscopic and inflammatory conditions, whereas group B strains were associated with the worst endoscopic and inflammatory findings. Intestinal metaplasia was a rare finding in group A infected patients (< 10%), whereas it was frequent in those infected with group B strains (48%).

CONCLUSIONS

The H pylori genes cagA, oipA "on", s1 and m1 vacA, and babA2 are associated with each other, possibly as a result of shared selective pressure. When coexpressed by the same H pylori strain, cagA, s1 and m1 vacA, and babA2 work synergistically in worsening inflammation. Infections caused by strains coexpressing cagA, s1m1 vacA, and babA2 are those at higher risk for intestinal metaplasia.

Helicobacter pylori infection in children and adults: a single pathogen but a different pathology

BACKGROUND

The aims of this retrospective study were to ascertain in large series of children and adults: the relationship of the infecting strain to gastric mucosal lesions; and the relationship of the infecting strain to its duodenal localization.

MATERIALS AND METHODS

We studied 307 and 604 consecutive children and adults. In gastric mucosal samples H. pylori was cultured, genotyped and histologically assessed, while inflammation, activity and intestinal metaplasia were graded. In a subset of 171 patients H. pylori ureaseA (ureA) and cagA genes were amplified (PCR) using mucosal biopsies from the duodenum.

RESULTS

H. pylori infection was diagnosed in 40 children and 308 adults. cagA was identified in 50% and 65.5% of infected children and adults. Antral activity was associated with the density of infecting bacteria (p <.001) and with cagA (p <.01). Intestinal metaplasia was correlated with cagA (p <.001). The ureA gene was found in 56 duodenal samples from 82 H. pylori positive patients. Duodenal H. pylori ureA was significantly more frequent in patients with duodenal diseases than in those without (p <.01), cagA positive strains being mainly involved in the infection of this anatomical area (p <.01).

CONCLUSIONS

A severe H. pylori-associated gastritis is more prevalent when the density of infecting bacteria is high and when cagA positive strains cause the infection. The most virulent cagA positive H. pylori colonizes not only the gastric, but also the duodenal mucosa, which can be directly damaged by the bacteria itself or by its products.

Current trends in the treatment of upper gastrointestinal disease

The past 25 years have seen an amazing improvement in the treatment and understanding of acid-related disorders. In particular, the introduction of selective histamine receptor antagonists and proton pump inhibitors has made the medical control of acid secretion an effective means of therapy. The demonstration that infection with Helicobacter pylori is responsible for most cases of peptic ulcer disease resulted in another major improvement in therapy in these areas as a result of the eradication of the organism. Research continues in an attempt to find improved means of acid control and better methods for the eradication of H. pylori based on unique proteins expressed by the organism to resist gastric acidity.

Transcriptional phase variation of a type III restriction-modification system in Helicobacter pylori

Phase variation is important in bacterial pathogenesis, since it generates antigenic variation for the evasion of immune responses and provides a strategy for quick adaptation to environmental changes. In this study, a Helicobacter pylori clone, designated MOD525, was identified that displayed phase-variable lacZ expression. The clone contained a transcriptional lacZ fusion in a putative type III DNA methyltransferase gene (mod, a homolog of the gene JHP1296 of strain J99), organized in an operon-like structure with a putative type III restriction endonuclease gene (res, a homolog of the gene JHP1297), located directly upstream of it. This putative type III restriction-modification system was common in H. pylori, as it was present in 15 out of 16 clinical isolates. Phase variation of the mod gene occurred at the transcriptional level both in clone MOD525 and in the parental H. pylori strain 1061. Further analysis showed that the res gene also displayed transcriptional phase variation and that it was cotranscribed with the mod gene. A homopolymeric cytosine tract (C tract) was present in the 5' coding region of the res gene. Length variation of this C tract caused the res open reading frame (ORF) to shift in and out of frame, switching the res gene on and off at the translational level. Surprisingly, the presence of an intact res ORF was positively correlated with active transcription of the downstream mod gene. Moreover, the C tract was required for the occurrence of transcriptional phase variation. Our finding that translation and transcription are linked during phase variation through slipped-strand mispairing is new for H. pylori.

Two different families of hopQ alleles in Helicobacter pylori

Helicobacter pylori genomes contain about 30 different hop genes, which encode outer membrane proteins. In this study, we analyzed genetic diversity in the H. pylori hopQ (omp27) locus, which corresponds to HP1177 in the genome of H. pylori reference strain 26,695. hopQ and its flanking genes were PCR amplified from multiple H. pylori strains, and the nucleotide sequences were determined. This analysis revealed the existence of two different families of hopQ alleles. Type I hopQ alleles are present in the genomes of two fully sequenced H. pylori strains, whereas the existence of type II hopQ alleles has not previously been recognized. Type I and type II hopQ alleles are 75 to 80% identical in nucleotide sequences and encode predicted outer membrane proteins that are 68 to 72% identical in amino acid sequences. PCR-based methods were developed to enable rapid differentiation between type I and type II hopQ alleles. Type I hopQ alleles were found significantly more commonly in cag(+)/type s1-vacA strains from patients with peptic ulcer disease than in cag-negative/s2-vacA strains from patients without ulcer disease (P < 0.001). Determination of hopQ allelic types provides a new method for classification of H. pylori strains. Further studies in multiple populations of patients are indicated to evaluate the usefulness of this approach for distinguishing potentially ulcerogenic H. pylori strains from less virulent strains.

Helicobacter pylori infection in mice: Role of outer membrane proteins in colonization and inflammation

BACKGROUND & AIMS

Mouse models of Helicobacter pylori infection have yielded variable results with respect to colonization and inflammation. We examined whether outer membrane proteins (OMPs) or the cag pathogenicity island (PAI) was responsible for some of this variability.

METHODS

C57BL/6 mice received clinical H. pylori isolates with different genotypes for the cag PAI and OMP gene switch status, as well as isogenic gene knockout mutants for cagE, oipA, babA2, hopZ, cagE/oipA, or oipA/hopZ. Bacterial density, histology, and mucosal cytokine/chemokine levels were measured after 4 and 12 weeks.

RESULTS

oipA, hopZ, hopO, and hopP switch status influenced both H. pylori density and colonization ability in mice. When 2 or more of the genes were "off," colonization rates were markedly reduced compared with those for strains with all genes "on" (from 58% to 0% after 12 weeks). oipA knockout mutants caused reduced inflammation and decreased mucosal interleukin 6 messenger RNA and KC messenger RNA and protein levels. H. pylori density and colonization ability were reduced if hopO or hopP switch status was changed from "on" to "off." There was a close relationship (r > 0.7) between the H. pylori density of the gastric mucosa of humans and mice when using the same H. pylori strains.

CONCLUSIONS

Many of the differences reported with mouse models may reflect subtle unrecognized differences (e.g., switch status of an OMP gene), emphasizing the necessity of characterizing isolates before and after experiments. The mouse model may be suitable for investigating factors related to colonization ability, H. pylori density, and gastric mucosal inflammation.

New serological assay for detection of putative Helicobacter pylori virulence factors

We evaluated a new immunoblot assay (Helicoblot 2.1) for Helicobacter pylori infection and CagA and VacA status by using serum samples from 222 patients. The test accurately detected H. pylori infection and VacA status, but improvements in the interpretation criteria are required before it can be recommended for determination of CagA status.

Transcriptional phase variation of a type III restriction-modification system in Helicobacter pylori

Phase variation is important in bacterial pathogenesis, since it generates antigenic variation for the evasion of immune responses and provides a strategy for quick adaptation to environmental changes. In this study, a Helicobacter pylori clone, designated MOD525, was identified that displayed phase-variable lacZ expression. The clone contained a transcriptional lacZ fusion in a putative type III DNA methyltransferase gene (mod, a homolog of the gene JHP1296 of strain J99), organized in an operon-like structure with a putative type III restriction endonuclease gene (res, a homolog of the gene JHP1297), located directly upstream of it. This putative type III restriction-modification system was common in H. pylori, as it was present in 15 out of 16 clinical isolates. Phase variation of the mod gene occurred at the transcriptional level both in clone MOD525 and in the parental H. pylori strain 1061. Further analysis showed that the res gene also displayed transcriptional phase variation and that it was cotranscribed with the mod gene. A homopolymeric cytosine tract (C tract) was present in the 5' coding region of the res gene. Length variation of this C tract caused the res open reading frame (ORF) to shift in and out of frame, switching the res gene on and off at the translational level. Surprisingly, the presence of an intact res ORF was positively correlated with active transcription of the downstream mod gene. Moreover, the C tract was required for the occurrence of transcriptional phase variation. Our finding that translation and transcription are linked during phase variation through slipped-strand mispairing is new for H. pylori.

East Asian genotypes of Helicobacter pylori strains in Amerindians provide evidence for its ancient human carriage

Phylogenies of indigenous microbes have been used as surrogates for the origins of the hosts that carry them. Conversely, polymorphisms may be used to date the spread of a microbial species when information about their host populations is available. Therefore, we examined polymorphisms in Helicobacter pylori, which persistently colonize the human stomach, to test the hypothesis that they have been ancient inhabitants of humans. Three H. pylori loci that previously have been shown to have phylogeographic affinity have been analyzed for two populations with different ethnic origins from Venezuela. In a group of Amerindian subjects from Amazonia, East Asian H. pylori genotypes were present for each of the loci examined but were absent in a mestizo population from Caracas. These findings provide evidence that H. pylori has been present in humans at least since ancestors of Amerindians migrated from Asia more than 11,000 years ago.

Pathogenesis and therapy of gastric and duodenal ulcer disease

Despite the decreasing frequency of Helicobacter pylori-induced peptic ulcers, peptic ulcer disease remains a major clinical problem partly because nonsteroidal anti-inflammatory drug ulcers have increased in frequency. The reduction in nonsteroidal anti-inflammatory drug ulcers by use of selective cyclooxygenase-2 inhibitors will not eliminate the problem because of increased use of aspirin for cardiovascular prophylaxis. This article reviews current concepts of peptic ulcer pathogenesis and therapy according to ulcer etiology; discusses potential interactions between etiologies; and considers the therapy for H pylori infection including the effects of antimicrobial resistance, and the role of bismuth quadruple therapy or furazolidone salvage therapy.

CagA tyrosine phosphorylation and interleukin-8 induction by Helicobacter pylori are independent from alpAB, HopZ and bab group outer membrane proteins

In several studies Helicobacter pylori type I strains (cag-positive strains) have been described to translocate their CagA protein into epithelial cells, where it is tyrosine-phosphorylated. The intimate contact allows a Cag-dependent bacteria-to-cell signaling inducing the secretion of the chemokine interleukin-8. Although a contact between the bacterial and the eukaryotic cell is known to be necessary for these signal transduction events the bacterial adhesin and the cellular receptor are unknown, so far. In this study, we investigated the influence of several outer membrane proteins associated with adherence on CagA translocation and IL-8 induction. The quantitative assessment of a cag deletion mutant strain binding to epithelial cells revealed that the Cag secretion apparatus is not primarily necessary for attachment. In contrast, the knockout mutation of the adherence-associated alpAB locus significantly reduced the binding capacity in two independent strains. Despite this partial adherence defect, the alpAB mutation did not affect CagA translocation and IL-8 induction. The mutagenesis of the bab group genes hp317, hp896 and hp1243 in H. pylori 26695 did not influence the Cag-dependent signaling either. No causative linkage could be found between the production of the outer membrane proteins HopZ, OipA or seven additional outer membrane proteins and CagA translocation or IL-8 induction.

Clinical presentation in relation to diversity within the Helicobacter pylori cag pathogenicity island

OBJECTIVE

This study investigated the genetic diversity of the cag pathogenicity island (PAI) in Helicobacter pylori (H. pylori) in relation to clinical outcome and interleukin (IL)-8 production.

METHODS

Seven genes in the cag PAI (cagA, cagE, cagG, cagM, cagT, open reading frame 13 and 10) were examined by polymerase chain reaction and Southern blot hybridization using H. pylori from 120 patients with different presentations (duodenal ulcer, gastric cancer, gastritis alone). IL-8 production from AGS cells (gastric cancer cell line) cocultured with H. pylori was measured by ELISA.

RESULTS

An intact cag PAI was present in 104 (87%) isolates, and five (4%) had deletions within the cag PAI; 11 (9%) lacked the entire cag PAI. Clinical isolates containing the complete cag PAI induced a greater secretion of IL-8 as compared with those without the cag PAI (3048 +/- 263 vs 480 +/- 28 pg/ml, p < 0.001). Deletion of only cagG reduced IL-8 secretion by two thirds. Deletions of more than one locus reduced IL-8 secretion to background. A similar proportion of H. pylori from patients with gastritis, duodenal ulcer, or gastric cancer had intact cag PAI (88%, 88%, and 85%, respectively). Although the presence of cagG was a better predictor of the presence of an intact cag PAI than cagA or cagE, the presence or absence of any of these genes had no association with clinical presentation.

CONCLUSION

Although the cag PAI plays an important role in IL-8 production, clinical presentation cannot be predicted by the presence of an intact cag PAI or any of these seven cag PAI genes.

Molecular and cellular mechanisms involved in Helicobacter pylori-induced inflammation and oxidative stress

Helicobacter pylori (H. pylori)-infection leads to different clinical and pathological outcomes in humans, including chronic gastritis, peptic ulcer disease, and gastric neoplasia. The key determinants of these outcomes are the severity and distribution of the H. pylori-induced inflammation. Antral-type gastritis is associated with excessive acid secretion and a high risk of duodenal ulcer. In contrast, gastritis that involves the acid-secreting corpus region leads to hypochlorhydria, progressive gastric atrophy, and an increased risk of gastric cancer. The key pathophysiological event in H. pylori infection is initiation and continuance of an inflammatory response. Bacteria or their products trigger this inflammatory process and the main mediators are cytokines. Identification of both host- and bacterial-factors that mediate is an intense area of interest in current researches. Recent data indicates that the cag pathogenicity island plays a crucial role in H. pylori-induced gastric inflammation via the activation of gene transcription. It has been demonstrated that oxidative and nitrosative stress associated with inflammation plays an important role in gastric carcinogenesis as a mediator of carcinogenic compound formation, DNA damage, and cell proliferation. Genetic information regulating such stress would be one of the host factors determining the outcome--particularly when the outcome is gastric cancer--of H. pylori infection, and the compound that attenuates such stress may be a candidate for use in chemoprevention. This review highlights recent advances in understanding of the mechanisms underlying chronic inflammation following infection with H. pylori.

Helicobacter pylori: consensus and controversy

Helicobacter pylori is uniquely adapted to colonize the human stomach. Infection leads to a range of subclinical and clinical outcomes that depend on properties of the infecting strain, the host, and the environment. Eradication therapy is indicated for infected persons who develop peptic ulcer disease or gastric lymphoma or who are beginning long-term treatment with nonsteroidal anti-inflammatory drugs. However, treatment may worsen gastroesophageal reflux disease and increase the risk of esophageal cancer. H. pylori infections can be diagnosed noninvasively and can be eradicated with approximately 85% success by a variety of multidrug, 7-14-day regimens. Unfortunately, antibiotic resistance is affecting treatment effectiveness in the United States and abroad. A more complete understanding of the variation in H. pylori pathogenesis should lead to clearer recommendations about treatment for infected persons who have neither peptic ulcer disease nor gastric lymphoma.

cag pathogenicity island of Helicobacter pylori in Korean children

BACKGROUND

cag pathogenicity island is reported to be a major virulence factor of Helicobacter pylori. The aim of this study was to investigate the status of cag pathogenicity island genes and gastric histology in Korean children with H. pylori gastritis.

METHODS

Helicobacter pylori DNA was extracted from antral biopsy specimens from 25 children with H. pylori gastritis. Specific polymerase chain reaction assays were used for four genes of cag pathogenicity island. The features of gastritis were scored in accordance with the updated Sydney System.

RESULTS

cagA was present in 23 (92%) of 25 children, and cagE in 24 (96%). Twenty-two (88%) children were cagT positive and 19 (76%) virD4 positive. All of the selected genes of the cag pathogenicity island were present in 17 (68%) children and completely deleted in one child. There were no differences in neutrophil activity and chronic inflammation between children infected with intact cag pathogenicity island strains and those with partially or totally deleted-cag pathogenicity island strains.

CONCLUSION

cag pathogenicity island is not a uniform, conserved entity in Korea. Completeness of cag pathogenicity island may not be the major factor to determine the severity of H. pylori gastritis in children.

Importance of Helicobacter pylori oipA in clinical presentation, gastric inflammation, and mucosal interleukin 8 production

BACKGROUND & AIMS

Disease-associated virulence factors of Helicobacter pylori may not be independent of one another. The aim was to determine which H. pylori virulence factor(s) was the most important predictor of severity of gastric inflammation or clinical outcome.

METHODS

cag Pathogenicity island (PAI), vacA babA2, and iceA status were determined by polymerase chain reaction (PCR). oipA functionality was based on switch status determined by PCR-based sequencing. A backward stepwise multiple regression analysis was performed to determine which factor(s) was the most discriminating for clinical outcome as well as the relationship to mucosal histology (H. pylori density, neutrophil infiltration, intestinal metaplasia, and gastric atrophy) and mucosal interleukin 8 (IL-8) production.

RESULTS

H. pylori were obtained from 247 patients (86 with gastritis, 86 with duodenal ulcer, and 75 with gastric carcinoma). Although oipA status was closely linked to specific cag PAI, vacA, and babA2 genotypes, only oipA status remained in the final model to discriminate duodenal ulcer from gastritis (adjusted odds ratio [OR] = 5 and 95% confidence interval [CI] = 2.1-11.9). Among the factors, only a functional oipA was significantly associated with high H. pylori density, severe neutrophil infiltration, and high mucosal IL-8 levels (P < 0.001). oipA status had no relationship to gastric atrophic changes.

CONCLUSIONS

oipA functional status was related to clinical presentation, H. pylori density, and gastric inflammation. cag PAI, babA2, or vacA status appear important only as surrogate markers for a functional oipA gene.

Helicobacter pylori virulence genes and host IL-1RN and IL-1beta genes interplay in favouring the development of peptic ulcer and intestinal metaplasia

Helicobacter pylori infection outcome might depend on genotypic polymorphisms of both the bacterium and the host. We ascertained: (1) the functionality of H. pylori oipA gene; (2) the polymorphism of the hostinterleukin (IL-1beta) gene (-31 C/T) and of the IL-1RN gene (intron 2 VNTR); (3) the association between the above genes and the histological and pathological outcome of H. pylori infection. One hundred and sixty-five H. pylori positive and 137 H. pylori negative subjects (23 gastric adenocarcinoma, 58 peptic ulcer, 221 gastritis) were studied. oipA was sequenced, IL-1beta was RFLP analysed. Antral and body mucosal biopsies were histologically evaluated. Functional oipA genes were correlated with cagA gene; both genes were significantly associated with gastritis activity, peptic ulcer and gastric adenocarcinoma. In these patients heterozygousIL-1RN 1/2 and IL-1beta C/T genotypes were more frequent than in gastritis patients. Intestinal metaplasia was associated with cagA, functional oipA and IL-1RN 2 allele. In conclusion, peptic ulcer and the preneoplastic intestinal metaplasia are associated with H. pylori virulence genes and with IL-1RN 2 host allele. An interplay between bacterial virulence factors and cytokines genotypes, is probably the main route causing H. pylori infection to lead to benign mild disease, benign severe disease or preneoplastic lesions.

The Helicobacter pylori blood group antigen-binding adhesin facilitates bacterial colonization and augments a nonspecific immune response

Presence of the Helicobacter pylori adherence factor blood group Ag-binding adhesin (BabA; binding to Lewis(b) (Le(b))) is associated with ulcer disease, adenocarcinoma, and precancerous lesions. The importance of BabA for bacterial colonization and the inflammatory response is unknown. A total of 141 antral biopsies from H. pylori-infected patients were assessed in regard to the degree of granulocytic (G0 degrees--G3 degrees) and lymphocytic (L1 degrees--L3 degrees) infiltration. DNA genotypes of babA2 (the transcriptionally active gene of BabA), cagA, and vacAs1/2 were determined by PCR. Colonization density and Le(b) status on gastric epithelial cells were determined by immunohistochemistry. Real-time quantitative (TaqMan) RT-PCR determined mRNA expression of IL-8, TNF -alpha, and the Th1 markers IFN-gamma and the IL-12R beta2 chain. A total of 91% of infected patients were Le(b) positive. The vacAs1(+)/cagA(+) strains harboring babA2 showed significantly higher levels of granulocytic infiltration, bacterial colonization, and IL-8 mRNA than vacAs1(+)/cagA(+) strains lacking babA2. IL-8 mRNA and protein production by KATO III cells in vitro increased dose dependently with addition of different numbers of type 1 strains (G27 and 2808 strains, 0.1--20 bacteria/cell). The mRNA expression of TNF-alpha, IFN-gamma, and IL-12R beta2 was higher in H. pylori-positive patients than in controls, but it did not differ significantly between patients infected with different strain types. These data suggest that BabA facilitates colonization of H. pylori and thereby increases IL-8 response, resulting in enhanced mucosal inflammation. Infection with strains harboring BabA thereby augment a nonspecific immune response, whereas the Th1 response toward H. pylori appears to be independent of BabA, cytotoxin-associated gene A, or vacuolating cytotoxin.

Specific identification of three low molecular weight membrane-associated antigens of Helicobacter pylori

BACKGROUND

A large number of Helicobacter pylori proteins are antigenic, but antibodies to these proteins persist in spite of the eradication of the infection.

METHODS AND RESULTS

The analysis of sera from H. pylori-infected and non-infected patients, before and 3 and 5 months after eradication, showed that the antibody response against unknown H. pylori antigens at 32, 30, 22 and 14 kDa in sodium dodecylsulphate polyacrylamide gel electrophoresis decreased by > or = 60% at 3 months and > or = 70% at 5 months after treatment. Two-dimensional gel electrophoresis and mass spectrometry allowed the identification of eight proteins at these positions: neuraminyl-lactose-binding haemagglutinin precursor, 3-oxoadipate CoA-transferase subunit A, elongation factor P, peptidoglycan-associated lipoprotein precursor, hypothetical protein HP0596, adhesin-thiol peroxidase, 50S ribosomal protein L7/L12 and subunit b' of the F(0) ATP synthase. Three of these eight, expressed as recombinant proteins (32 kDa neuraminyl-lactose-binding haemagglutinin precursor, 30 kDa peptidoglycan-associated lipoprotein precursor and 22 kDa hypothetical protein HP0596), reacted specifically with sera from infected patients, while the 14 kDa 50S ribosomal protein L7/L12 cross-reacted with one out of five sera from H. pylori-negative patients. The other recombinant proteins did not show significant immunoreactivity.

CONCLUSIONS

Four low molecular weight antigens were identified by these methods, three of which were specific. Immunoreaction with these three proteins (neuraminyl-lactose-binding haemagglutinin precursor, peptidoglycan-associated lipoprotein precursor and hypothetical protein HP0596) could provide a serological assessment not only of H. pylori infection, but also of eradication.

Decreased adherence of cagG-deleted Helicobacter pylori to gastric epithelial cells in Japanese clinical isolates

BACKGROUND

The cag pathogenicity island (cag PAI) is a major virulence factor. The ability of Helicobacter pylori to adhere to gastric epithelial cells is an important initial step for virulence. The aim of this study was to evaluate the relationship between genetic variations of cag PAI in Japanese clinical isolates and the ability of H. pylori to adhere to gastric epithelial cells.

MATERIALS AND METHODS

The polymerase chain reaction and Southern blot analysis were used to verify the presence or absence of cagA, cagE, cagG, cagI and cagM in the cag PAI in 236 Japanese clinical isolates. The ability of H. pylori to adhere to KATOIII cells was examined by flow cytometry.

RESULTS

Seven (3.0%) cag PAI partial-deleted strains were found in 236 clinical isolates, and these strains showed three patterns in the deleted region within the cag PAI. All of the cagG-deleted strains showed decreased adherence to KATOIII cells, in comparison with cagG-positive strains. These strains had abolished IL-8 induction despite the presence of cagE, which is essential for IL-8 induction.

CONCLUSIONS

Our results suggest that cagG or surrounding genes in the cag PAI has a function related to adhesion to epithelial cells.

Host cell responses to genotypically similar Helicobacter pylori isolates from United States and Japan

Associations of Helicobacter pylori genotypes with disease differ between Western countries and Asia. Therefore, we directly compared histopathological and in vitro responses to clinical isolates with similar genotypes. Sixty-three cagA(+) vacAs1/m1 H. pylori isolates (United States, n = 24; Japan, n = 39) and eight cagA-negative vacAs2/m2 strains were incubated with AGS cells, and supernatants were assayed for interleukin-8 (IL-8) and for DNA fragmentation. CagA tyrosine phosphorylation in AGS cells and the sequence of the putative HP0638 (oipA) signal sequence region were determined for 22 representative strains. HP0638 and/or cag island mutant strains were created and examined in IL-8 and CagA tyrosine phosphorylation assays. Levels of IL-8 induction and DNA fragmentation were similar in the U.S. and Japanese cagA(+) vacAs1/m1 isolates. All 10 of the isolates with the highest IL-8 induction and 8 of the 10 isolates with the lowest IL-8 induction had an in-frame oipA open reading frame, and all 10 of the isolates with the highest IL-8 induction and 7 of the 10 isolates with the lowest IL-8 induction induced CagA tyrosine phosphorylation in AGS cells. Eight isolates from gastric ulcer patients induced significantly more apoptosis in vitro, and more severe gastritis and atrophy in vivo, than other Japanese isolates. Disruption of HP0638 did not affect IL-8 induction or CagA tyrosine phosphorylation. Thus, H. pylori cagA(+) vacAs1/m1 isolates from the United States and Japan induce similar IL-8 and apoptosis levels. Inactivation of HP0638 does not alter epithelial responses mediated by the cag island in vitro. Assessment of apoptosis in vitro identified a group of H. pylori isolates that induce more severe gastric inflammation and atrophy.

Polymorphisms of Helicobacter pylori HP0638 reflect geographic origin and correlate with cagA status

Since the associations between Helicobacter pylori genotype and disease differ in Asia and the West, we investigated the correlation between HP0638, encoding an outer membrane protein, and potential markers of virulence (cagA, vacA, and iceA). For 109 strains from nine countries, the status of cagA, vacA, and iceA was determined by PCR and/or a line probe assay. We also studied 18 strains from 8 patients (parents and 6 daughters) from a Dutch family and paired strains collected on average 8 years apart from 11 patients. When the HP0638 signal sequences were amplified by PCR and DNA sequence determinations were performed, 89 (96%) of 93 cagA-positive strains had HP0638 in frame, versus none (0%) of 16 cagA-negative strains (P < 0.001). Among strains in which HP0638 was in frame, a six-CT dinucleotide repeat pattern was dominant in Western countries (23 of 33 strains [70%]), while a pattern of three CT repeats with another CT after four T's (3 + 1-CT-repeat pattern) was dominant in East Asia (31 of 46 strains [67%]); however, specific CT repeat patterns did not correlate with clinical outcome. HP0638 phylogenetic trees also showed geographic characters. The HP0638 frame status and CT dinucleotide repeat patterns were identical for 9 of 11 pairs of strains obtained on average 8 years apart from individuals and the 15 strains obtained from the mother and all six daughters. Thus, HP0638 frame status and cagA status are strongly correlated. The CT dinucleotide repeat pattern in the putative HP0638 signal sequence has geographic characters and appears stable in particular patients and families over a period of years. Analysis of HP0638 CT polymorphisms may serve as a new typing system to discriminate H. pylori isolates for epidemiological purposes.

Atrophic gastritis and intestinal metaplasia in Japan: results of a large multicenter study

BACKGROUND

This study evaluated the relationship between Helicobacter pylori infection, atrophic gastritis and intestinal metaplasia in Japan.

MATERIALS AND METHODS

This was a multicenter study performed in 21 centers in Japan. A total of 2455 individuals were enrolled. H. pylori status was determined by validated ELISAs. Atrophic gastritis was diagnosed by histology, endoscopy with Congo Red dye scattering or the Kimura-Takemoto endoscopic classification.

RESULTS

Atrophic gastritis increased from 9.4% in those less than 20 years of age to > 70% in those aged 60 or older and was strongly associated with H. pylori infection. The overall prevalence of atrophic gastritis in H. pylori infection was 82.9% (1272/1534) compared with 9.8% (90/921) among uninfected (OR = 44.8; 95% CI = 34.7-57.8). Intestinal metaplasia was present in 43.1% (542/1258) of H. pylori positive persons compared with 6.2% (51/823) among the uninfected (OR = 11.5; 95% CI = 8.5-15.5). Atrophic gastritis in H. pylori positive Japanese was very high in the younger generation (38.5% in those aged 20 or less and 58.5% in those 21-30).

CONCLUSIONS

Atrophic gastritis and intestinal metaplasia were strongly associated with H. pylori and not with aging. The fall in prevalence of H. pylori in Japan has not been associated with a corresponding fall in the prevalence of atrophic gastritis among those with H. pylori infection. The high prevalence of the precursor lesion, atrophic gastritis with intestinal metaplasia, among those with H. pylori infection suggests that the risk of development of early gastric cancer will continue to remain high in Japan.

Phosphorylation of tyrosine 972 of the Helicobacter pylori CagA protein is essential for induction of a scattering phenotype in gastric epithelial cells

Helicobacter pylori colonizes the human stomach and is the causative agent of a variety of gastric diseases. After bacterial attachment, the H. pylori CagA protein is translocated into gastric epithelial cells and tyrosine phosphorylated. This process is associated with characteristic cytoskeletal rearrangements, resulting in a scatter factor-like ('hummingbird') phenotype. In this study, using a cagA mutant complemented with wild-type cagA and transiently expressing CagA in AGS cells, we have demonstrated that translocated CagA is necessary for rearrangements of the actin cytoskeleton to occur. Anti-phosphotyrosine immunoblotting studies and treatment of infected cells with phosphotyrosine kinase inhibitors suggested that not only translocation but also phosphorylation of CagA is important in this process. Transient expression of CagA-green fluorescent protein (GFP) fusion proteins and two-dimensional gel electrophoresis of CagA protein species demonstrated tyrosine phosphorylation in the C-terminus. Site-directed mutagenesis of CagA revealed that tyrosine residue 972 is essential for induction of the cellular phenotype. We have also demonstrated that translocation and phosphorylation of CagA is necessary but not sufficient for induction of the hummingbird phenotype in AGS cells, indicating the involvement of as yet unidentified bacterial factor(s).

pathogenesis of Helicobacter pylori-induced gastric inflammation

Helicobacter pylori causes persistent inflammation in the human stomach, yet only a minority of persons harbouring this organism develop peptic ulcer disease or gastric malignancy. An important question is why such variation exists among colonized individuals. Recent evidence has demonstrated that H. pylori isolates possess substantial phenotypic and genotypic diversity, which may engender differential host inflammatory responses that influence clinical outcome. For example, H. pylori strains that possess the cag pathogenicity island induce more severe gastritis and augment the risk for developing peptic ulcer disease and distal gastric cancer. An alternative, but not exclusive, hypothesis is that enhanced inflammation and injury is a consequence of an inappropriate host immune response to the chronic presence of H. pylori within the gastric niche. Investigations that precisely delineate the mechanisms responsible for induction of gastritis will ultimately help to define which H. pylori-colonized persons bear the highest risk for subsequent development of clinical disease, and thus, enable physicians to focus eradication therapy.