Isolation and biochemical and molecular analyses of a species-specific protein antigen from the gastric pathogen Helicobacter pylori

Large-Scale Evaluation of ureC (glmM) and SSA Conventional PCR for Rapid Direct Detection of Helicobacter pylori in Gastric Biopsies as Compared to rpoB-based Quantitative Real-Time PCR

Background:

Conventional polymerase chain reaction (PCR)-based methods play a major role in the direct detection of H. pylori in clinical specimens, with time-saving as compared to culture-based methods. However, specificity and sensitivity vary among different varieties of these PCRs, which consequently could affect the accuracy of diagnosis of H. pylori infection. The study aimed to evaluate the utility of ureC (glmM) and SSA conventional PCR methods for rapid direct detection of H. pylori by comparing them with rpoB-based quantitative real-time PCR.

Methods:

A total of 402 non-repeated gastric biopsy specimens were subjected to DNA extraction followed by conventional ureC (glmM) and SSA PCR, and rpoB-based quantitative real-time PCR, which was used as the gold standard.

Results:

H. pylori was detected in 119 (29.6%), 126 (31.34%), and 187 (46.5%) of the tested specimens using ureC (glmM) PCR, SSA PCR, and real-time quantitative PCR, respectively. The specificity of the SSA PCR was higher than that of ureC (glmM) PCR (99.5% and 98.6%, respectively). The SSA PCR was more sensitive than the ureC (glmM), (66.8% and 62%, respectively). The diagnostic accuracy of SSA PCR (84.33%) was higher than that of ureC (glmM) PCR (81.59%).

Conclusion:

Overall, SSA PCR is more specific, sensitive, and diagnostically accurate than ureC (glmM) PCR, giving the SSA PCR assay superiority as a simple, rapid, and accurate diagnostic tool for direct detection of H. pylori in gastric tissue specimens.

Differential proteomics of Helicobacter pylori associated with autoimmune atrophic gastritis

Atrophic autoimmune gastritis (AAG) is a condition of chronic inflammation and atrophy of stomach mucosa, for which development can be partially triggered by the bacterial pathogen Helicobacter pylori (HP). HP can cause a variety of gastric diseases, such as duodenal ulcer (DU) or gastric cancer (GC). In this study, a comparative proteomic approach was used by two-dimensional fluorescence difference gel electrophoresis (DIGE) to identify differentially expressed proteins of HP strains isolated from patients with AAG, to identify markers of HP strain associated with AAG. Proteome profiles of HP isolated from GC or DU were used as a reference to compare proteomic levels. Proteomics analyses revealed 27 differentially expressed spots in AAG-associated HP in comparison with GC, whereas only 9 differential spots were found in AAG-associated HP profiles compared with DU. Proteins were identified after matrix-assisted laser desorption ionization (MALDI)-TOF and peptide mass fingerprinting. Some AAG-HP differential proteins were common between DU- and GC-HP (peroxiredoxin, heat shock protein 70 [HSP70], adenosine 5'-triphosphate [ATP] synthase subunit α, flagellin A). Our results presented here may suggest that comparative proteomes of HP isolated from AAG and DU share more common protein expression than GC and provide subsets of putative AAG-specific upregulated or downregulated proteins that could be proposed as putative markers of AAG-associated HP. Other comparative studies by two-dimensional maps integrated with functional genomics of candidate proteins will undoubtedly contribute to better decipher the biology of AAG-associated HP strains.

Helicobacter species infection may be associated with cholangiocarcinoma: a meta-analysis

OBJECTIVE

Since the discovery of Helicobacter species in human biliary system, the association between Helicobacter species infection and cholangiocarcinoma is under debate. This meta-analysis aims to explore this issue.

METHODS

Literature search was carried out to identify all eligible articles. We performed overall meta-analysis of all included studies and subgroup analysis based on regional distribution. Subgroup analysis in the light of detection methods and specimens was also conducted.

RESULTS

Ten case-control studies were included. Overall meta-analysis favoured a significant association between Helicobacter species infection and cholangiocarcinoma (cumulative OR 8.88, 95% CI 3.67-21.49). Subgroup analysis based on geographic distribution indicated that Helicobacter species infection may serve as a risk factor not only in a region with high cholangiocarcinoma incidence (Asia, OR 6.68, 95% CI 2.29-19.49) but also in low incidence region (Europe, OR 14.90, 95% CI 4.79-46.35). The other subgroup analysis showed that PCR was the most effective and efficient method to detect Helicobacter species in surgically resected tissue and bile. There was significant heterogeneity among studies and obvious publication bias.

CONCLUSION

Our meta-analysis supports the possible association between Helicobacter species infection and cholangiocarcinoma. Further investigations are required to clarify the role of Helicobacter species in this malignancy.

Immunodot blot assay to detect Helicobacter pylori using monoclonal antibodies against the 26 kDa protein

Development of a specific immunoassay to detect Helicobacter pylori infection in stool samples requires monoclonal antibody against the specific antigen. The aims of this study were to establish monoclonal antibodies against the 26 kDa protein of H. pylori and develop an immunodot blot for their application to recognize H. pylori infection using stool samples. Mice were immunized intraperitoneally with homogenized gel containing the 26 kDa band of cell surface proteins of H. pylori in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The monoclonal antibodies were produced using the hybridoma technique. Reactivity of monoclonal antibodies was tested with the purified 26 kDa antigen and cell surface proteins from cultured H. pylori by ELISA. Furthermore reactivity of monoclonal antibodies was tested on negative and positive stool samples for H. pylori and suspensions of several major bacteria in stool by immunodot blot assay. Five stable hybridoma monoclones were obtained. The concordant reactivity of the monoclonal antibodies with H. pylori present in the stool samples, which had been tested previously using an ACON ELISA kit for H. pylori stool antigen testing, and unreactivity with several different major fecal bacteria in immunodot blotting indicates high specificity of the immunodot blot based on the reaction of produced monoclonal antibodies with the H. pylori antigen in stools. The findings indicate that the novel immunodot blot developed based on new monoclonal antibodies for stool antigens would be useful as a noninvasive method of diagnosing H. pylori infection.

Construction and use of a prokaryotic expression system for Helicobacter pylori AhpC

Background

Helicobacter pylori is an important pathogen responsible for human gastric problems like inflammation, ulcers and cancer. It is widely prevalent in developing countries with low socioeconomic status. Since the infection remains asymptomatic in most individuals, efforts for efficient diagnostic markers to identify high risk patients are warranted. In this study, we constructed an expression vector that overexpresses the H. pylori AhpC protein as a glutathione S-transferase fusion protein. We furthermore examined whether this recombinant fusion protein retained immunogenicity and thus would be useful as a diagnostic marker.

Findings

The full-length tsaA gene from H. pylori strain G27, which encodes AhpC, was cloned in plasmid vector pGEX-6P-2 to create the recombinant plasmid vector pGEX-tsaA. The nucleotide sequence of the clone showed 100% homology with corresponding published sequence of original gene. Over-expression of the target protein GST-AhpC was achieved in E. coli BL21 (DE3) cells by induction with isopropyl-beta-D-thiogalactoside (IPTG). GST-AhpC was extracted and identified using SDS-PAGE as a 52 kDa protein. Western blotting results using commercial antibodies against whole cell H. pylori showed that the fusion protein retained immunogenecity.

Conclusion

A recombinant prokaryotic expression system was successfully established with high expression efficiency for target fusion gene pGEX-tsaA. The expressed GST-AhpC protein showed immunoreactivity against commercial anti-H. pylori antibodies. This recombinant fusion protein can be developed as a diagnostic marker for screening patients with chronic H. pylori infections.

Haemophilus influenzae and oxidative stress

Haemophilus influenzae is a commensal of the human upper respiratory tract. H. influenzae can, however, move out of its commensal niche and cause multiple respiratory tract diseases. Such diseases include otitis media in young children, as well as exacerbations of chronic obstructive pulmonary disease (COPD), sinusitis, conjunctivitis, and bronchitis. During the course of colonization and infection, H. influenzae must withstand oxidative stress generated by multiple reactive oxygen species produced endogenously, by other co-pathogens and by host cells. H. influenzae has, therefore, evolved multiple mechanisms that protect the cell against oxygen-generated stresses. In this review, we will describe these systems relative to the well-described systems in Escherichia coli. Moreover, we will compare how H. influenzae combats the effect of oxidative stress as a necessary phenotype for its roles as both a successful commensal and pathogen.

Detection of the glmM gene in Helicobacter pylori isolates with a novel primer by PCR

A novel reverse primer (GLM MR1) was designed for detection of the glmM gene in Helicobacter pylori by PCR. The percentage of amplification in clinical isolates using GLM MR1 was 100% for detection of the glmM gene and 86.36% for the ureA gene. The primer designed is useful for the identification of H. pylori.

Evaluation of a new antigen for diagnosis of Helicobacter pylori infection in stool of adult and children

BACKGROUND

Nowadays, there is an increasing interest in noninvasive methods to diagnose Helicobacter pylori infection. Indeed, they can profitably replace endoscopy in predicting the diagnosis. The stool antigen test for H. pylori is a noninvasive immunoassay to diagnose active infection with this bacterium in human fecal samples. The aim of this study was detection of alkyl hydroperoxide reductase protein (AhpC) antigen by immunoblotting in stool samples for diagnosis of H. pylori.

MATERIALS AND METHODS

Chromosomal DNA from H. pylori was isolated. AhpC gene was amplified by PCR, These amplicons were cloned into pTZ57R/T cloning vector then subcloned into pQE30 expression vector and overexpressed using isopropyl-beta-D-thiogalactopyranoside in E. coli M15. AhpC protein was purified by affinity chromatography. Rabbits were immunized with the purified AhpC protein for the production of antibodies. To determine the accuracy of the test for diagnosing H. pylori infection from stool, we evaluated 84 patients (6-81 years old) using Western blot analysis by rabbit anti-AhpC antibody. Positive rapid urease test on biopsy samples was considered as the gold standard.

RESULTS

AhpC gene was overexpressed, and AhpC protein was purified. Rabbit anti-AhpC antibody produced after immunization with the purified AhpC protein. By immunoblotting, we detected AhpC protein in the positive stool samples. The test showed a 83.3% sensitivity (95% CI: 69.8-92.5%) and a 91.7% specificity (95% CI: 77.5-98.2). Among the children, the sensitivity was 88.2% (95% CI: 63.6-98.5) and the specificity was 100% (95% CI: 69.2-100); in adults, the sensitivity and specificity were 80.6% (95% CI: 62.5-92.5) and 88.5% (95% CI: 69.8-97.6), respectively.

CONCLUSIONS

Using of AhpC antigen for diagnosis of H. pylori infection is a useful noninvasive method, accurate in adolescents and children, and can be used for the development of a stool antigen detection kit for H. pylori.

Structural and biochemical characterization of peroxiredoxin Qbeta from Xylella fastidiosa: catalytic mechanism and high reactivity

The phytopathogenic bacterium Xylella fastidiosa is the etiological agent of various plant diseases. To survive under oxidative stress imposed by the host, microorganisms express antioxidant proteins, including cysteine-based peroxidases named peroxiredoxins. This work is a comprehensive analysis of the catalysis performed by PrxQ from X. fastidiosa (XfPrxQ) that belongs to a peroxiredoxin class still poorly characterized and previously considered as moderately reactive toward hydroperoxides. Contrary to these assumptions, our competitive kinetics studies have shown that the second-order rate constants of the peroxidase reactions of XfPrxQ with hydrogen peroxide and peroxynitrite are in the order of 10(7) and 10(6) M(-1) S(-1), respectively, which are as fast as the most efficient peroxidases. The XfPrxQ disulfides were only slightly reducible by dithiothreitol; therefore, the identification of a thioredoxin system as the probable biological reductant of XfPrxQ was a relevant finding. We also showed by site-specific mutagenesis and mass spectrometry that an intramolecular disulfide bond between Cys-47 and Cys-83 is generated during the catalytic cycle. Furthermore, we elucidated the crystal structure of XfPrxQ C47S in which Ser-47 and Cys-83 lie approximately 12.3 A apart. Therefore, significant conformational changes are required for disulfide bond formation. In fact, circular dichroism data indicated that there was a significant redox-dependent unfolding of alpha-helices, which is probably triggered by the peroxidatic cysteine oxidation. Finally, we proposed a model that takes data from this work as well data as from the literature into account.

Preparative SDS-PAGE Electroelution for Rapid Purification of Alkyl Hydroperoxide Reductase from Helicobacter pylori

BACKGROUND

Alkyl hydroperoxide reductase (AhpC) of Helicobacter pylori is considered as a diagnostic antigen. Therefore, this antigen can be used to detect H. pylori infection by stool immunoassays such as ELISA. The aim of this study was to simplify the AhpC protein purification procedures.

METHODS

For whole cell protein extraction, the bacterial cells were ruptured by octly-β-D glucopyranoside. The isolation and purification of AhpC protein were attempted by various techniques including ammonium sulfate precipitation, dialysis, preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and electroelution.

RESULTS

A simple method was used for protein purification AhpC protein. One-dimensional preparative gel electrophoresis allows a single and short purification step; the high resolution capacity of this technique leads to a high level of purity of the protein. Moreover, it avoids contamination by other non-specific proteins which often appear during protein purification by column chromatography.

CONCLUSION

The present method is simple, rapid and makes it possible to preparate AhpC from H. pylori.

Comparative genomics and proteomics of Helicobacter mustelae, an ulcerogenic and carcinogenic gastric pathogen

Background

Helicobacter mustelae causes gastritis, ulcers and gastric cancer in ferrets and other mustelids. H. mustelae remains the only helicobacter other than H. pylori that causes gastric ulceration and cancer in its natural host. To improve understanding of H. mustelae pathogenesis, and the ulcerogenic and carcinogenic potential of helicobacters in general, we sequenced the H. mustelae genome, and identified 425 expressed proteins in the envelope and cytosolic proteome.

Results

The H. mustelae genome lacks orthologs of major H. pylori virulence factors including CagA, VacA, BabA, SabA and OipA. However, it encodes ten autotransporter surface proteins, seven of which were detected in the expressed proteome, and which, except for the Hsr protein, are of unknown function. There are 26 putative outer membrane proteins in H. mustelae, some of which are most similar to the Hof proteins of H. pylori. Although homologs of putative virulence determinants of H. pylori (NapA, plasminogen adhesin, collagenase) and Campylobacter jejuni (CiaB, Peb4a) are present in the H. mustelae genome, it also includes a distinct complement of virulence-related genes including a haemagglutinin/haemolysin protein, and a glycosyl transferase for producing blood group A/B on its lipopolysaccharide. The most highly expressed 264 proteins in the cytosolic proteome included many corresponding proteins from H. pylori, but the rank profile in H. mustelae was distinctive. Of 27 genes shown to be essential for H. pylori colonization of the gerbil, all but three had orthologs in H. mustelae, identifying a shared set of core proteins for gastric persistence.

Conclusions

The determination of the genome sequence and expressed proteome of the ulcerogenic species H mustelae provides a comparative model for H. pylori to investigate bacterial gastric carcinogenesis in mammals, and to suggest ways whereby cag minus H. pylori strains might cause ulceration and cancer.

The genome sequence was deposited in EMBL/GenBank/DDBJ under accession number FN555004.

Production of polyclonal antibody against alkyl hydroperoxide reductase of Helicobacter pylori and its antigenicity

Stool-antigen detection kits for diagnosis of Helicobacter pylori infection have been widely used because of their full non-invasive nature. Because Helicobacter pylori strains show a distinctive genetic diversity, it is important to find a protein that is a common antigen of various strains and shows a strong immunogenicity for the development of a stool- antigen detection kit. Alkyl hydroperoxide reductase (AhpC) of Helicobacter pylori strongly reacts with the sera of patients with gastritis and peptic ulcer. Therefore, AhpC seems to be an excellent candidate as a target protein for this study. Accordingly, polyclonal antiserum against AhpC was produced in adult New Zealand white rabbits by using AhpC in the gel bands without adding Freund's adjuvant. In addition, isolation and purification of AhpC were perfomed by preparative sodium dodecyl sulfate polyacrylamide gel electrophoresis and electroelution. In this study, a simple method was used for rapid production of polyclonal antibody against AhpC of H. pylori, which avoids both the long-term AhpC purification and the addition of Freund's adjuvant. One-dimensional preparative gel electrophoresis allows a single and short purification step; the high-resolution capacity of this technique leads to a high level of purity of the protein and consequently to a very high specificity of the antibody. Moreover, this method avoids contamination by other non-specific proteins, which often appear during the purification process by column chromatographic techniques, which may also decrease the purity of the immunogen. The present method is simple, rapid and cost-effective, and also makes it possible to produce antibody for stool-antigen enzyme immunoassay in a short time and at low cost.

Evaluation of nested PCR in detection of Helicobacter pylori targeting a highly conserved gene: HSP60

OBJECTIVE

To comparatively evaluate a new nested set of primers designed for the detection of Helicobacter pylori targeting a highly conserved heat shock protein gene (Hsp60).

METHODS

A total of 60 subjects having peptic ulcer diseases were tested for the detection of H. pylori using rapid urease test (RUT), histology, culture, and polymerase chain reaction (PCR) in their antral biopsy specimens. A newly designed Hsp60 gene-based primer set was evaluated against commonly used PCR primers for detection of H. pylori.

RESULTS

Forty-six of the 60 study subjects were found positive for culture isolation and all the 46 culture-positive specimens were also positive with Hsp60 gene PCR. Of the 46 culture-positive specimens, 44 were positive for 16S rRNA gene, ureC gene, RUT, and histology whereas only 29 were positive with ureA gene PCR. Of the 14 culture-negative subjects, 10 were positive with 16S rRNA gene, 4 were positive with ureC (glmM) gene PCR, and 2 were positive with RUT and 1 was positive on histology.

CONCLUSION

This study shows that nested amplification targeting Hsp60 gene is the most sensitive and specific with LR+ and LR- values of proportional, variant and 0, respectively, when compared with the other three PCR methods. Also, HSP60 gene-specific nested protocol was the most appropriate for detection of H. pylori in clinical specimens. This is particularly valuable because it can be used as a noninvasive method for detecting H. pylori infection in young children and also, in follow-up studies with peptic ulcer patients, on samples like feces and saliva.

Relationship among oxidative DNA damage, gastric mucosal density and the relevance of cagA, vacA and iceA genotypes of Helicobacter pylori

The aim of this study was to evaluate the relationship among oxidative DNA damage, density of Helicobacter pylori and the relevance of cagA, vacA and iceA genotypes of H. pylori. Gastric epithelial cells were isolated from 24 uninfected patients, 42 H. pylori infected patients with gastritis, and 61 patients with gastric cancer. Oxidative DNA damage was analyzed by the Comet assay, the density of H. pylori was measured by real-time polymerase chain reaction (PCR), and allelic variants of cagA, vacA and iceA were identified using the PCR. Infected patients by Helicobacter pylori cagA(+), vacAs1 m1 and iceA1 genotype showed higher levels of oxidative DNA damage than infected patients with H. pylori cagA(-), vacAs2 m2 and iceA2 genotypes and uninfected patients. Density of H. pylori did not influence oxidative DNA damage. Our results indicate that H. pylori genotype is more relevant than density for oxidative DNA damage.

Increased rate of Helicobacter pylori infection detected by PCR in biopsies with chronic gastritis

Histology is considered a sensitive method for detection of Helicobacter pylori, in gastric biopsies. We investigated the diagnostic potential of qualitative nested (nPCR) and quantitative PCR (qPCR) for detection of H. pylori using different primers on 126 archived gastric biopsies with inflammation and correlated the inflammatory changes with the presence and density of bacteria. H. pylori was detected in 42.8% biopsies by histology and PCR, an additional 15 samples were positive exclusively by PCR: nPCR was positive in all histologically positive samples, but qPCR failed to detect H. pylori in 10 biopsies. The inflammatory score was significantly higher in biopsies positive for H. pylori only by PCR showed a significant higher inflammatory score compared with negative biopsies (mean of neutrophils score, 1.60 vs. 0.90, P < 0.01; mean of mononuclear cells score, 2.27 vs. 1.67, P < 0.01), whereas the inflammatory score was similar compared with biopsies positive for H. pylori by histology (mean of neutrophils score, 1.60 vs. 1.56, not significant; mean of mononuclear cells score, 2.27 vs. 2.20, not significant). A weak correlation between inflammatory score and the density of H. pylori detected by histology was observed. The mean values of H. pylori DNA were significantly higher in histologic-positive than in histologic negative biopsies. We have shown that PCR can detect H. pylori in about 20% of histologic-negative gastric biopsies, indicating the clinical relevance of H. pylori detection by PCR in biopsies with characteristic inflammatory changes.

Hydrogen peroxide scavenging is not a virulence determinant in the pathogenesis of Haemophilus influenzae type b strain Eagan

BACKGROUND

A potentially lethal flux of hydrogen peroxide (H2O2) is continuously generated during aerobic metabolism. It follows that aerobic organisms have equipped themselves with specific H2O2 dismutases and H2O2 reductases, of which catalase and the alkyl hydroperoxide reductase (AhpR) are the best-studied prokaryotic members. The sequenced Haemophilus influenzae Rd genome reveals one catalase, designated HktE, and no AhpR. However, Haemophilus influenzae type b strain Eagan (Hib), a causative agent of bacterial sepsis and meningitis in young children, disrupted in its hktE gene is not attenuated in virulence, and retains the ability to rapidly scavenge H2O2. This redundancy in H2O2-scavenging is accounted for by peroxidatic activity which specifically uses glutathione as the reducing substrate.

RESULTS

We show here that inside acatalasaemic H. influenzae all of the residual peroxidatic activity is catalyzed by PGdx, a hybrid peroxiredoxin-glutaredoxin glutathione-dependent peroxidase. In vitro kinetic assays on crude hktE- pgdx- H. influenzae Rd extracts revealed the presence of NAD(P)H:peroxide oxidoreductase activity, which, however, appears to be physiologically insignificant because of its low affinity for H2O2 (Km = 1.1 mM). Hydroperoxidase-deficient hktE- pgdx- H. influenzae Rd showed a slightly affected aerobic growth phenotype in rich broth, while, in chemically defined medium, growth was completely inhibited by aerobic conditions, unless the medium contained an amino acid/vitamin supplement. To study the role of PGdx in virulence and to assess the requirement of H2O2-scavenging during the course of infection, both a pgdx single mutant and a pgdx/hktE double mutant of Hib were assayed for virulence in an infant rat model. The ability of both mutant strains to cause bacteremia was unaffected.

CONCLUSION

Catalase (HktE) and a sole peroxidase (PGdx) account for the majority of scavenging of metabolically generated H2O2 in the H. influenzae cytoplasm. Growth experiments with hydroperoxidase-deficient hktE- pgdx- H. influenzae Rd suggest that the cytotoxicity inflicted by the continuous accumulation of H2O2 during aerobic growth brings about bacteriostasis rather than bacterial killing. Finally, H2O2-scavenging is not a determinant of Hib virulence in the infant rat model of infection.

Peroxiredoxins: a historical overview and speculative preview of novel mechanisms and emerging concepts in cell signaling

The observation that purified yeast glutamine synthetase is rapidly inactivated in a thiol-containing buffer yet retains activity in crude extracts containing the same thiol led to our discovery of an enzyme that protects against oxidation in a thiol-containing system. This novel antioxidant enzyme was shown to reduce hydroperoxides and, more recently, peroxynitrite with the use of electrons provided by a physiological thiol like thioredoxin. It defined a family of proteins, present in organisms from all kingdoms, that was named peroxiredoxin (Prx). All Prx enzymes contain a conserved Cys residue that undergoes a cycle of peroxide-dependent oxidation and thiol-dependent reduction during catalysis. Mammalian cells express six isoforms of Prx (Prx I to VI), which are classified into three subgroups (2-Cys, atypical 2-Cys, and 1-Cys) based on the number and position of Cys residues that participate in catalysis. The relative abundance of Prx enzymes in mammalian cells appears to protect cellular components by removing the low levels of peroxides produced as a result of normal cellular metabolism. During catalysis, the active site cysteine is occasionally overoxidized to cysteine sulfinic acid. Contrary to the general belief that oxidation to the sulfinic state is an irreversible process in cells, studies on the fate of the overoxidized Prx species revealed a mechanism by which the catalytically active thiol form is recovered. This sulfinic reduction is a slow, ATP-dependent process that is specific to 2-Cys Prx isoforms. This reversible overoxidation may represent an adaptation unique to eukaryotic cells that accommodates the intracellular messenger function of H(2)O(2), but experimental validation of such speculation is yet to come.

Helicobacter pylori induces transendothelial migration of activated memory T cells

Helicobacter pylori infection is associated with pronounced infiltration of granulocytes and lymphocytes into the gastric mucosa, resulting in active chronic gastritis that may develop into duodenal ulcer disease or gastric adenocarcinoma. Infiltrating T cells play a major role in the pathology of these diseases, but the signals involved in recruitment of T cells from blood to H. pylori-infected tissues are not well understood. We therefore examined H. pylori-induced T-cell transendothelial migration (TEM). The Transwell system, employing a monolayer of human umbilical vein endothelial cells, was used as a model to study TEM. H. pylori induced a significant T-cell migration, compared to spontaneous migration. CD4+ and CD8+ T cells migrated to the same extent in response to H. pylori, whereas there was significantly larger transmigration of memory T cells compared to naive T cells. Both H. pylori culture filtrate and urease induced migration, and the presence of the H. pylori cag pathogenicity island increased TEM. T-cell TEM was mediated by LFA-1-ICAM-1 interactions in accordance with an increased ICAM-1 expression on the endothelial cells after contact with H. pylori. Migrating T cells had increased expression of activation marker CD69 and chemokine receptors CXCR3, CCR4, and CCR9. Furthermore, T cells migrating in response to H. pylori secreted Th1 but not Th2 cytokines upon stimulation. In conclusion, our data indicate that live H. pylori and its secreted products contribute to T-cell recruitment to the gastric mucosa and that the responding T cells have an activated memory Th1 phenotype.

Topographical localisation of cagA positive and cagA negative Helicobacter pylori strains in the gastric mucosa; an in situ hybridisation study

BACKGROUND

The cagA gene is a marker for the presence of the cag pathogenicity island, and the presence of cagA positive strains of Helicobacter pylori can identify individuals with a higher risk of developing gastrointestinal diseases.

AIMS

To study the interaction between H. pylori cagA(+) and cagA(-) strains and the gastric mucosa.

METHODS

Patients with H. pylori associated gastritis and peptic ulcers were studied. Biopsies were obtained from the antrum, corpus, fundus, and incisura for H pylori culture, and for in situ hybridisation studies. From each biopsy, multiple single H. pylori colonies were isolated and propagated for DNA isolation, and cagA was detected by the polymerase chain reaction (PCR). For in situ detection of H. pylori an oligonucleotide specific for an H. pylori common antigen and an oligonucleotide specific for cagA were used as probes. Biotinylated probes were incubated with biopsy sections, developed with streptavidin-horseradish peroxidase, and amplified with the tyramide system.

RESULTS

PCR results for cagA in isolated colonies confirmed the in situ hydridisation studies. In situ hybridisation identified cagA(+) bacteria in patients with cagA(+) isolates; cagA(-) bacteria in patients with cagA(-) isolates, and cagA(+) and cagA (-) bacteria in patients with both cagA(+) and cagA(-) isolates. CagA(-) bacteria usually colonised the mucous gel or the apical epithelial surface, whereas cagA(+) bacteria colonised the immediate vicinity of epithelial cells or the intercellular spaces.

CONCLUSIONS

These results document a different in vivo interaction between H. pylori cagA(+) or cagA(-) strains and the gastric mucosa.

Simultaneous detection and differentiation of anti-Helicobacter pylori antibodies by flow microparticle immunofluorescence assay

Helicobacter pylori is the key pathogen for gastroduodenal diseases. The clinical outcome of H. pylori infection is influenced by the presence of strain-specific virulence factors that are usually detected by the presence of specific anti-H. pylori antibodies in serum. Apart from the detection of these antibodies by enzyme-linked immunosorbent assay (ELISA), it is desirable to obtain additional information concerning the presence of certain virulence factors of H. pylori that are currently detected by immunoblot analysis. At present, the immunodiagnosis of an H. pylori infection includes two separate methods: ELISA and immunoblot analysis. Here, we report the development and evaluation of a new rapid flow microparticle immunofluorescence assay (FMIA) for detection of anti-H. pylori antibodies in human serum. The assay allows rapid qualitative and quantitative detection of anti-H. pylori antibodies by using crude antigen preparations as well as single recombinant antigens (urease A, urease B, CagA, and alkylhydroxy peroxide reductase) in the same sample with one measurement, and thus it combines the advantages of enzyme immunoassay and Western blot analysis. Seventy-five patient samples were analyzed by FMIA, ELISA, and Western blotting with respect to their immunoreactivity against crude H. pylori extracts and individual H. pylori antigens. Statistical analyses revealed an overall similarity of more than 90% among the results for FMIA, ELISA, and Western blot. Therefore, we conclude that FMIA is a powerful and time- and cost-saving assay system for the detection of antimicrobial antibodies, with higher sensitivity and a larger measurement range than ELISA.

Immunoblotting for the serodiagnosis of Helicobacter pylori infection in Brazilian patients with and without gastric carcinoma

We evaluated the performance of a commercial immunoblotting in the serodiagnosis of Helicobacter pylori infection in Brazilian patients. The presence of anti-H. pylori antibodies was also investigated in a group of 20 duodenal ulcer patients after successful treatment. One hundred and ninety one patients were studied. Among the 164 infected patients, 46 had gastric carcinoma. The duodenal ulcer patients were treated with antimicrobial drugs and the eradication of the microorganism was confirmed in all of them one month after the end of the treatment by the 13C-urea breath test. Sera were assayed for H. pylori antibodies using the Helicoblot 2.0 (Genelabs Diagnostics, Singapore). The sensitivity, specificity, positive, and negative predictive values of the test were 93.9%, 92.6%, 98.7%, and 71.4%, respectively. The sensitivity of the test was similar in patients with (93.5%) and without (95.7%) gastric carcinoma. Twenty-four months after the end of the treatment, the band of 116 kDa was still detected in one of the patients. In conclusion, the Helicoblot 2.0 is an accurate test to diagnose H. pylori infection and although it can not be employed to monitor the bacterium eradication, it may be useful for diagnosing past infection, especially in gastric carcinoma patients.

Global regulation of virulence and the stress response by CsrA in the highly adapted human gastric pathogen Helicobacter pylori

Although successful and persistent colonization of the gastric mucosa depends on the ability to respond to changing environmental conditions and co-ordinate the expression of virulence factors during the course of infection, Helicobacter pylori possesses relatively few transcriptional regulators. We therefore investigated the contribution of the regulatory protein CsrA to global gene regulation in this important human pathogen. CsrA was necessary for full motility and survival of H. pylori under conditions of oxidative stress. Loss of csrA expression deregulated the oxidant-induced transcriptional responses of napA and ahpC, the acid induction of napA, cagA, vacA, the urease operon, and fur, as well as the heat shock responses of napA, groESL and hspR. Although the level of napA transcript was higher in the csrA mutant, its stability was similar in the wild-type and mutant strains, and less NapA protein was produced in the mutant strain. Finally, H. pylori strains deficient in the production of CsrA were significantly attenuated for virulence in a mouse model of infection. This work provides evidence that CsrA has a broad role in regulating the physiology of H. pylori in response to environmental stimuli, and may be important in facilitating adaptation to the different environments encountered during colonization of the gastric mucosa. Furthermore, CsrA appears to mediate its effects in H. pylori at the post-transcriptional level by influencing the processing and translation of target transcripts, with minimal effect on the stability of the target mRNAs.

Quantitative detection for low levels of Helicobacter pylori infection in experimentally infected mice by real-time PCR

Accurate diagnosis of Helicobacter pylori infection is important in both clinical practice and clinical research. Molecular methods are highly specific and sensitive, and various PCR-based tests have been developed to detect H. pylori in gastric biopsy specimens. We optimized a sensitive and specific quantitative SYBR Green I real-time PCR assay for detection of H. pylori based on amplification of the fragment of a 26-kDa Helicobacter species-specific antigen gene that allows for detection of 5 bacterial cells per PCR sample. Under the assay conditions, SYBR Green I real-time PCR is highly reproducible with a precise log-linear relation in the range of six orders of magnitude of bacterial DNA concentrations. For accurate comparison of H. pylori infection in different tissue samples, the amount of total host DNA in each sample is normalized by TaqMan real-time PCR of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) pseudogenes. The developed method was validated in prophilactically immunized and experimentally infected mice and revealed a level of H. pylori gastric colonisation that was below the limit of detection for a rapid urease test. This new method established for a quantitative analysis of H. pylori in the host's stomach may be useful in experimental studies evaluating new anti-H. pylori drugs and vaccines.

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.

Immune response to a 26-kDa protein, alkyl hydroperoxide reductase, in Helicobacter pylori-infected Mongolian gerbil model

BACKGROUND

The host immune response is thought to play an important role in the outcome of Helicobacter pylori infection. The successful development of the H. pylori-infected Mongolian gerbil model that mimics human disease has enabled study of the antibody response against H. pylori antigens.

MATERIALS AND METHODS

Serum samples from ulcer and carcinogenesis models of H. pylori-infected gerbils were used to screen for H. pylori antigens that cause a humoral immune response in the infected hosts. H. pylori alkyl hydroperoxide reductase (AhpC) is one such antigen on which we report here. The tsaA gene encoding AhpC was amplified by PCR from H. pylori ATCC 43504 strain, cloned into pMAL(TM)-c2 expression vector and expressed in Escherichia coli. Maltose-binding protein fusion protein (MBP-AhpC) was purified by a MBP affinity column. Using purified recombinant AhpC protein as an antigen, the antibody response and changes of antibody levels against AhpC in the gerbil models were studied by Western blotting and ELISA.

RESULTS

Antibody against AhpC was negative in the early stages of infection, and became positive in the gerbils with the emergence of gastric diseases such as chronic active gastritis, gastric ulcer and gastric cancer. The antibody levels (ELISA) increased gradually over time and were higher in gerbils with gastric ulcer than that in gerbils without ulcers.

CONCLUSIONS

Use of the gerbil model that mimics human H. pylori infection is likely to provide insights into the role of H. pylori-specific antigens possibly related to the subsequent development of gastric diseases.

HpaA shows variable surface localization but the gene expression is similar in different Helicobacter pylori strains

Due to earlier contradictory results regarding the localization of the putative Helicobacter pylori adhesin A (HpaA), we aimed to compare the gene and protein expression and surface localization of HpaA in different H. pylori strains. Five H. pylori strains were cultivated for 11 days and analysed by Northern blot analysis, flow cytometry (FCM), semi-quantitative dot blot, colony blot, immuno-electron microscopy (IEM), and phase-contrast microscopy. The highest transcriptional activity of the hapA gene as observed after 3-4 days of cultivation and two mRNA transcripts of 1600 and 3100 nucleotides, respectively, were detected in all five strains with the hpaA probe. We also showed by reverse transcription-polymerase chain reaction (RT-PCR) that the hpaA gene is co-transcribed with the downstream omp18 gene. The highest total HpaA protein production in bacteria occurred between day 3 and 7, as determined by semi-quantitative dot blot, and was similar in the different strains. The maximal proportion of cells with HpaA on the bacterial surface, detected by FCM, was for strain SS1, 90%; Hel 344, 60%; CCUG 17875, 61%; CCUG 17874, 86% and for strain AH 244 only 35%. By IEM HpaA was detected in all strains both on the bacterial surface and on the flagellar sheath.

Nickel-responsive induction of urease expression in Helicobacter pylori is mediated at the transcriptional level

The nickel-containing enzyme urease is an essential colonization factor of the gastric pathogen Helicobacter pylori, as it allows the bacterium to survive the acidic conditions in the gastric mucosa. Although urease can represents up to 10% of the total protein content of H. pylori, expression of urease genes is thought to be constitutive. Here it is demonstrated that H. pylori regulates the expression and activity of its urease enzyme as a function of the availability of the cofactor nickel. Supplementation of brucella growth medium with 1 or 100 microM NiCl(2) resulted in up to 3.5-fold-increased expression of the urease subunit proteins UreA and UreB and up to 12-fold-increased urease enzyme activity. The induction was specific for nickel, since the addition of cadmium, cobalt, copper, iron, manganese, or zinc did not affect the expression of urease. Both Northern hybridization studies and a transcriptional ureA::lacZ fusion demonstrated that the observed nickel-responsive regulation of urease is mediated at the transcriptional level. Mutation of the HP1027 gene, encoding the ferric uptake regulator (Fur), did not affect the expression of urease in unsupplemented medium but reduced the nickel induction of urease expression to only twofold. This indicates that Fur is involved in the modulation of urease expression in response to nickel. These data demonstrate nickel-responsive regulation of H. pylori urease, a phenomenon likely to be of importance during the colonization and persistence of H. pylori in the gastric mucosa.

Serum immunoglobulin G immune response to Helicobacter pylori antigens in Mongolian gerbils

The Mongolian gerbil model for Helicobacter pylori infection is an animal model that mimics human disease. We examined the serum immune response to H. pylori infection in gerbils by enzyme-linked immunosorbent assay (ELISA) and Western blotting, both with whole-cell (H. pylori) extracts. A total of 66 7-week-old specific-pathogen-free male gerbils were inoculated orogastrically with H. pylori strain ATCC 43504. Sera were collected 1, 2, 4, 8, 12, 26, 38, and 52 weeks after H. pylori inoculation. Sixty-nine noninfected gerbils and their sera were used as controls. The specificity of the ELISA was 95.7%. The frequency of seropositivity increased over time: 2 of 10 (20%), 7 of 10 (70%), and 7 of 7 (100%) samples of sera from inoculated gerbils were positive for H. pylori at 2, 4, and 8 weeks postinoculation, respectively. Western blot assays showed that the primary immunoglobulin G (IgG) response against low-molecular-mass (25-, 30-, and 20-kDa) proteins appeared after a lag period of 2 to 8 weeks after inoculation. Antibodies against 160-, 150-, 110-, 120-, 80-, 66-, and 63-kDa proteins were observed 12 weeks after inoculation. The early reactive 30-kDa protein was identified as a urease alpha subunit by N-terminal amino acid sequencing. After 26 weeks, two groups of animals could be distinguished: one group developed ulcers (n = 5), and the other developed hyperplastic polyps without ulcers (n = 19). Gerbils in the gastric ulcer group showed significantly higher serum anti-H. pylori IgG levels than did gerbils in the hyperplastic group (P = 0.001) as measured by ELISA. Furthermore, a higher proportion of animals developed antibodies to H. pylori proteins of 26, 25, and 20 kDa in the ulcer group than those animals with hyperplastic polyps (75 to 100% versus 17 to 50%) in Western blot assays. These results highlight the importance of the immune response of the host in the development of H. pylori-related gastric lesions.

The 26-kilodalton, AhpC homologue, of Helicobacter pylori is also produced by other Helicobacter species

BACKGROUND

The 26 kDa protein, which is an alkyl hydroperoxide reductase (AhpC) homologue, has earlier been described as specific for Helicobacter pylori. The aims of this study were to analyse whether this protein, or the corresponding gene, could be identified in other Helicobacter species.

MATERIALS AND METHODS

Two different monoclonal antibodies (Mabs), which recognise the 26 kDa protein in H. pylori, were used in immunoblots to determine the presence of the protein in 10 Helicobacter species. PCR was performed in order to analyse whether the gene was detectable and the PCR products were sequenced. Southern and Northern blot analyses were done on chromosomal DNA and total RNA, respectively, isolated from some selected Helicobacter species in order to compare the genes and mRNA transcripts to H. pylori.

RESULTS

The 26 kDa protein was identified in H. nemestrinae (primate), H. acinonychis (cheetah), H. bilis (mouse), H. felis (cat) and H. salomonis (dog) but not in H. mustelae (ferret), H. cinaedi (human), H. canis (dog), H. fennelliae (human) or H. pullorum (poultry). By PCR the gene was also recognised in H. mustelae, H. cinaedi and H. pullorum. The PCR products showed high sequence homology (66-98%) compared to H. pylori. The gene was also highly conserved in four H. pylori strains (94-99% homology). Southern blot showed that the H. nemestrinae and H. acinonychis chromosomal DNA contained a single copy of the gene and the Northern blot analyses indicated mono-cistronic transcription of the gene in these two species, as has been found in H. pylori.

CONCLUSIONS

A gene similar to ahpC was found in eight out of 10 Helicobacter species analysed.

Essential thioredoxin-dependent peroxiredoxin system from Helicobacter pylori: genetic and kinetic characterization

Helicobacter pylori, an oxygen-sensitive microaerophile, contains an alkyl hydroperoxide reductase homologue (AhpC, HP1563) that is more closely related to 2-Cys peroxiredoxins of higher organisms than to most other eubacterial AhpC proteins. Allelic replacement mutagenesis revealed ahpC to be essential, suggesting a critical role for AhpC in defending H. pylori against oxygen toxicity. Characterization of the ahpC promoter region divulged two putative regulatory elements and identified the transcription initiation site, which was mapped to 96 and 94 bp upstream of the initiation codon. No homologue of ahpF, which encodes the dedicated AhpC reductase in most eubacteria, was found in the H. pylori genome. Instead, homologues of Escherichia coli thioredoxin (Trx) reductase (TrxR, HP0825) and Trx (Trx1, HP0824) formed a reductase system for H. pylori AhpC. A second Trx homologue (Trx2, HP1458) was identified but was incapable of AhpC reduction, although Trx2 exhibited disulfide reductase activity with other substrates [insulin and 5,5'-dithiobis(2-nitrobenzoic acid)]. AhpC interactions with each substrate, Trx1 and hydroperoxide, were bimolecular and nonsaturable (infinite V(max) and K(m) values) but rapid enough (at 1 x 10(5) to 2 x 10(5) M(-1) s(-1)) to suggest an important role for AhpC in cellular peroxide metabolism. AhpC also exhibited a wide specificity for hydroperoxide substrates, which, taken together with the above results, suggests a minimal binding site for hydroperoxides composed of little more than the cysteinyl (Cys49) active site. H. pylori AhpC was not reduced by Salmonella typhimurium AhpF and was slightly more active with E. coli TrxR and Trx1 than was S. typhimurium AhpC, demonstrating the specialized catalytic properties of this peroxiredoxin.

pH-dependent protein profiles of Helicobacter pylori analyzed by two-dimensional gels

BACKGROUND

Helicobacter pylori survives transient exposure to extreme acid prior to adherence and growth on the gastric epithelium at neutral pH.

MATERIALS AND METHODS

The effect of pH stress on protein profiles of H. pylori was observed using two-dimensional gel electrophoresis (2-D gels). H. pylori 26695 was grown microaerobically in tryptone-yeast extract broth, 3% fetal bovine serum. Growth in acid alkalinized the medium, whereas growth in base caused acidification. For 2-D gel analysis of protein profiles, cultures were grown in media buffered at pH 5.7 and at pH 7.5.

RESULTS

Under all pH conditions, the most abundant proteins observed were the urease structural subunit UreB and the chaperonin GroEL. Growth in acid significantly increased the abundance of UreB. Thus, urease expression is not completely constitutive, as reported previously, but shows regulation by pH. Another protein observed only at low pH was identified as mammalian apolipoprotein A-I, possibly taken up by H. pylori from bovine serum in the growth medium. This finding, if confirmed, suggests that uptake of high-density lipoprotein from the human host may facilitate acquisition of cholesterol, required for formation of the unique cholesteryl glucosides in the membrane of H. pylori. In growth above pH 7, three stress proteins were induced: GroES (HspA), GroEL (HspB), and the antioxidant AhpC homolog TsaA. In addition, N-terminal sequence analysis identified five additional proteins that had not previously been reported on 2-D gels of H. pylori (FMN, SodB, TrxB, TsaA, and Tsr).

CONCLUSIONS

In summary, our 2-D gel study reveals expression of several proteins dependent on growth pH.

Application of genomics and proteomics for identification of bacterial gene products as potential vaccine candidates

The ability of bioinformatics to characterize genomic sequences from pathogenic bacteria for prediction of genes that may encode vaccine candidates, e.g. surface localized proteins, has been evaluated. By applying appropriate tools for genomic mining to the published sequence of Haemophilus influenzae Rd genome, it was possible to identify a putative vaccine candidate, the outer membrane lipoprotein, P6. Proteomics complements genomics by offering abilities to rapidly identify the products of predicted genes, e.g. proteins in outer membrane preparations. The ability to identify the P6 protein uniquely from entries in a sequence database from the expected peptide-mass fingerprint of P6 demonstrates the power of proteomics. The application of proteomics for identification of vaccine candidates for another pathogenic bacterium, Helicobacter pylori using two different approaches is described. The first involves rapid identification of a series of monoclonal antibody reactive proteins from N-terminal sequence tags. The other approach involves identification of proteins in outer membrane preparations by 2-D electrophoresis followed by trypsin digestion and peptide mass map analysis. Our combined studies demonstrate that utilization of genome sequences by application of bioinformatics through genomics and proteomics can expedite the vaccine discovery process by rapidly providing a set of potential candidates for further testing.

A 26 kDa protein of helicobacter pylori shows alkyl hydroperoxide reductase (AhpC) activity and the mono-cistronic transcription of the gene is affected by pH

The 26 kDa protein of Helicobacter pylori, with 67% amino acid identity to alkyl hydroperoxide reductase (AhpC) of Campylobacter jejuni, was studied. We wanted to evaluate it the protein has AhpC activity. Therefore, an Escherichia coli mutant defective for alkyl hydroperoxide reductase and a plasmid expressing the 26 kDa protein from H. pylori were used in complementation studies. The complemented E. coli mutant showed a decreased sensitivity to cumene hydroperoxide indicating that the 26 kDa protein of H. pylori has AhpC activity and could be of importance in the defence against oxidative stress. Furthermore, Northern blot analysis detected one mRNA transcript of approximately 700 bp which is in agreement with the gene being transcribed as a single gene with its own promoter. This promoter region was further characterized by primer extension experiments. Additional studies on how environmental factors, such as long term growth and pH, can affect the transcription of the gene were performed on two H. pylori strains. We found that low pH and long term growth repressed transcription of the gene. Attempts to construct a mutant deficient for the gene in H. pylori were unsuccessful.

Non-urease producing Helicobacter pylori in chronic gastritis

BACKGROUND

Helicobacter pylori infection is the commonest cause of gastritis. Different patterns of immune response to H. pylori infection and characteristics of bacteria are considered to contribute to clinical outcomes.

AIM

To determine characteristics of the host H. pylori relationship in subjects with non-ulcer dyspepsia and a histological diagnosis of gastritis.

METHODS

Thirty-five subjects with chronic gastritis undergoing endoscopy (mean age 53 years, range 24-82, 14 male and 21 female) were studied, none of whom was on nonsteroidal anti-inflammatory drugs or antibiotics. H. pylori infection was determined by rapid urease test (CLOtest), culture, antibody and RT-PCR for Ure C, Cag A and 26 kDa gene and histology. Cytokine production of mucosal IL-6 and IL-8 were measured by ELISA.

RESULTS

Fifteen subjects were positive by CLOtest and/or bacterial culture. In these subjects histology showed numerous helical forms of H. pylori (Group I). Nine subjects were negative by CLOtest, bacterial culture, and mRNA for urease C fragment, but positive by PCR for the 26 kDa protein encoding gene. Histology in these subjects showed the presence of either coccoid forms (four), or scant helical forms (two), or mixed coccoid/helical forms (three) (Group II). Eleven subjects were negative by all methods of detection (Group III). IgG and IgA antibody levels in serum (p<0.05) and gastric tissue culture supernatant (p<0.001) were significantly higher in Group I than those in Group II or III. There were significant differences in the IgG serum and IgA supernatant antibody levels (p<0.01 and p<0.05) when Group II was compared to Group III. Supernatant IL-6 levels were significantly higher in Group I (p<0.01) than those from Groups II and III. IL-8 levels were higher in Group I (p<0.01) and Group II (p<0.05) when compared to Group III.

CONCLUSIONS

'H. pylori-negative' gastritis can be associated with a non-urease producing form of H. pylori, with a reduction in both local and systemic antibody levels and mucosal pro-inflammatory cytokines.

Evaluation of a PCR primer based on the isocitrate dehydrogenase gene for detection of Helicobacter pylori in feces

In order to improve detection and identification of Helicobacter pylori in highly contaminated samples, we evaluated new specific primers based on the DNA base sequence within the isocitrate dehydrogenase (icd) gene to amplify a 1,200-bp DNA segment. The specificity of the icd primer was tested against DNA derived from various bacteria, including 7 Helicobacter species and a panel of 1 gram-variable, 2 gram-positive, and 16 gram-negative bacteria, as well as DNA from houseflies and feces from H. pylori-negative patients. The primers permitted the detection of all clinical H. pylori isolates tested, but no reactions were observed with negative controls. Several procedures for DNA extraction from feces were evaluated using PCR with icd primers. The lower limits of detection of H. pylori DNA from two different sources containing the same number of H. pylori organisms, a pure culture and feces spiked with H. pylori, were established for each extraction method tested. The results were 8.0 x 10(3) CFU/ml for cultures of pure H. pylori, and 8.0 x 10(6) CFU/ml for H. pylori from feces, using the phenol-chloroform method; 8.0 x 10(2) and 7.0 x 10(3) CFU/ml, respectively, for a glass matrix and chaotropic solution protocol; 8.0 x 10(2) and 7.0 x 10(3) CFU/ml, respectively, for the QIAamp tissue kit; and 5.0 x 10(2) and 5.0 x 10(3) CFU/ml, respectively, for the XTRAX DNA extraction kit. We conclude that the use of the icd gene as a primer for PCR represents a specific and sensitive assay for detection of H. pylori in highly contaminated samples.

Peroxynitrite reductase activity of bacterial peroxiredoxins

Nitric oxide (NO) is present in soil and air, and is produced by bacteria, animals and plants. Superoxide (O2-) arises in all organisms inhabiting aerobic environments. Thus, many organisms are likely to encounter peroxynitrite (OONO-), a product of NO and O2- that forms at near diffusion-limited rates, and rapidly decomposes upon protonation through isomerization to nitrate (NO3-; ref. 1) while generating hydroxyl radical (*OH) and nitrogen dioxide radical (*NO2) (refs 2, 3), both more reactive than peroxynitrite's precursors. The oxidative, inflammatory, mutagenic and cytotoxic potential (ref. 4) of peroxynitrite contrasts with the antioxidant, anti-inflammatory and tissue-protective properties ascribed to NO itself. Thus, the ability of cells to cope with peroxynitrite is central in determining the biological consequences of NO production. We considered whether cells might be equipped with enzymes to detoxify peroxynitrite. Peroxiredoxins have been identified in most genomes sequenced, but their functions are only partly understood. Here we show that the peroxiredoxin alkylhydroperoxide reductase subunit C (AhpC) from Salmonella typhimurium catalytically detoxifies peroxynitrite to nitrite fast enough to forestall the oxidation of bystander molecules such as DNA. Results are similar with peroxiredoxins from Mycobacterium tuberculosis and Helicobacter pylori. Thus, peroxynitrite reductase activity may be widespread among bacterial genera.

Differences in surface-exposed antigen expression between Helicobacter pylori strains isolated from duodenal ulcer patients and from asymptomatic subjects

We have analyzed possible qualitative and quantitative differences in antigen expression between Helicobacter pylori strains isolated from the antrum and different locations in the duodenum of 21 duodenal ulcer (DU) patients and 20 asymptomatic subjects (AS) by enzyme-linked immunosorbent assay (ELISA) and inhibition ELISA. Almost all antral and duodenal strains grown in vitro expressed the N-acetyl-neuroaminyllactose-binding hemagglutinin, flagellins (subunits FlaA and FlaB), urease, a 26-kDa protein, and a neutrophil-activating protein. In 75% of both the DU patients and the AS, antral H. pylori strains expressed either the blood group antigen Lewis y (Le(y)) alone or together with the Le(x) antigen. However, duodenal H. pylori strains of DU patients expressed Le(y) antigen more frequently than corresponding strains of AS (P < 0.05). Presence of Le(y) on H. pylori was related to the degree of active duodenitis (P < 0.05). Duodenal H. pylori strains isolated from AS were significantly more often Lewis nontypeable than duodenal strains of DU patients (P < 0.01). Presence of H. pylori blood group antigen-binding adhesin (BabA) was significantly higher on both antral and duodenal strains isolated from DU patients than on corresponding strains isolated from AS (P < 0.05). BabA-positive duodenal H. pylori strains isolated from DU patients were associated with active duodenitis more frequently than corresponding strains isolated from AS (P < 0.01). Infection with H. pylori strains positive for Le(y) and BabA in the duodenum is associated with development of duodenal ulcer formation.

Detection of Helicobacter pylori DNA in human biliary tree and its association with hepatolithiasis

Recently, several authors have reported that Helicobacter pylori DNA has been found in human bile. The aim of this study is to investigate the presence of H. pylori in the biliary tree of Koreans, including the bile, biliary epithelium, and gallstones. This study analyzed intrahepatic bile, bile duct tissue, and gallstones from 43 patients with hepatobiliary disease (PTCS group), gallbladder bile and tissue from 23 patients with gallbladder disease (CCT group), and eight patients without hepatobiliary disease (control group). H. pylori was examined by PCR with two different primers. PCR was positive in 4/43 (9.3%) by 26 kDa protein antigen primer and in 5/43 (11.6%) by urease A gene primer in bile from the PTCS group. However, in intrahepatic duct tissue, PCR was positive in only one case. PCR of gallbladder bile, tissue, and intrahepatic duct stones was negative. Upon intrahepatic bile analysis, the pH was significantly lower in PCR-positive than in negative cases (P < 0.05). In conclusion, H. pylori DNA may be present in the bile when there are certain environmental changes, such as lowered pH; however, H. pylori does not colonize the bile duct epithelium. We could find no pathogenetic role for H. pylori in the formation of hepatolithiasis.

Detection of Helicobacter pylori DNA in human biliary tree and its association with hepatolithiasis

Recently, several authors have reported that Helicobacter pylori DNA has been found in human bile. The aim of this study is to investigate the presence of H. pylori in the biliary tree of Koreans, including the bile, biliary epithelium, and gallstones. This study analyzed intrahepatic bile, bile duct tissue, and gallstones from 43 patients with hepatobiliary disease (PTCS group), gallbladder bile and tissue from 23 patients with gallbladder disease (CCT group), and eight patients without hepatobiliary disease (control group). H. pylori was examined by PCR with two different primers. PCR was positive in 4/43 (9.3%) by 26 kDa protein antigen primer and in 5/43 (11.6%) by urease A gene primer in bile from the PTCS group. However, in intrahepatic duct tissue, PCR was positive in only one case. PCR of gallbladder bile, tissue, and intrahepatic duct stones was negative. Upon intrahepatic bile analysis, the pH was significantly lower in PCR-positive than in negative cases (P < 0.05). In conclusion, H. pylori DNA may be present in the bile when there are certain environmental changes, such as lowered pH; however, H. pylori does not colonize the bile duct epithelium. We could find no pathogenetic role for H. pylori in the formation of hepatolithiasis.

Identification of Helicobacter pylori and other Helicobacter species by PCR, hybridization, and partial DNA sequencing in human liver samples from patients with primary sclerosing cholangitis or primary biliary cirrhosis

Helicobacter pylori was identified in human liver tissue by PCR, hybridization, and partial DNA sequencing. Liver biopsies were obtained from patients with primary sclerosing cholangitis (n = 12), primary biliary cirrhosis (n = 12), and noncholestatic liver cirrhosis (n = 13) and (as controls) normal livers (n = 10). PCR analyses were carried out using primers for the Helicobacter genus, Helicobacter pylori (the gene encoding a species-specific 26-kDa protein and the 16S rRNA), Helicobacter bilis, Helicobacter pullorum, and Helicobacter hepaticus. Samples from patients with primary biliary cirrhosis and primary sclerosing cholangitis (11 and 9 samples, respectively) were positive by PCR with Helicobacter genus-specific primers. Of these 20 samples, 8 were positive with the 16S rRNA primer and 9 were positive with the 26-kDa protein primer of H. pylori. These nine latter samples were also positive by Southern blot hybridization for the amplified 26-kDa fragment, and four of those were verified to be H. pylori by partial 16S rDNA sequencing. None of the samples reacted with primers for H. bilis, H. pullorum, or H. hepaticus. None of the normal livers had positive results in the Helicobacter genus PCR assay, and only one patient in the noncholestatic liver cirrhosis group, a young boy who at reexamination showed histological features suggesting primary sclerosing cholangitis, had a positive result in the same assay. Helicobacter positivity was thus significantly more common in patients with cholestatic diseases (20 of 24) than in patients with noncholestatic diseases and normal controls (1 of 23) (P = <0.00001). Patients positive for Helicobacter genus had significantly higher values of alkaline phosphatases and prothrombin complex than Helicobacter-negative patients (P = 0.0001 and P = 0.0003, respectively). Among primary sclerosing cholangitis patients, Helicobacter genus PCR positivity was weakly associated with ulcerative colitis (P = 0.05). Significant differences related to blood group or HLA status were not found.

An iron-regulated alkyl hydroperoxide reductase (AhpC) confers aerotolerance and oxidative stress resistance to the microaerophilic pathogen Campylobacter jejuni

Microaerophiles like Campylobacter jejuni must resist oxidative stresses during transmission or infection. Growth of C. jejuni 81116 under iron limitation greatly increased the expression of two polypeptides of 26 and 55 kDa. The identification of these proteins by N-terminal amino acid sequencing showed both to be involved in the defense against oxidative stress. The 55-kDa polypeptide was identical to C. jejuni catalase (KatA), whereas the N terminus of the 26-kDa polypeptide was homologous to a 26-kDa Helicobacter pylori protein. The gene encoding the C. jejuni 26-kDa protein was cloned, and the encoded protein showed significant homology to the small subunit of alkyl hydroperoxide reductase (AhpC). The upstream region of ahpC encoded a divergent ferredoxin (fdxA) homolog, whereas downstream sequences contained flhB and motB homologs, which are involved in flagellar motility. There was no evidence for an adjacent homolog of ahpF, encoding the large subunit of alkyl hydroperoxide reductase. Reporter gene studies showed that iron regulation of ahpC and katA is achieved at the transcriptional level. Insertional mutagenesis of the ahpC gene resulted in an increased sensitivity to oxidative stresses caused by cumene hydroperoxide and exposure to atmospheric oxygen, while resistance to hydrogen peroxide was not affected. The C. jejuni AhpC protein is an important determinant of the ability of this microaerophilic pathogen to survive oxidative and aerobic stress.

Molecular characterization of a flagellar export locus of Helicobacter pylori

Motility of Helicobacter species has been shown to be essential for successful colonization of the host. We have investigated the organization of a flagellar export locus in Helicobacter pylori. A 7-kb fragment of the H. pylori CCUG 17874 genome was cloned and sequenced, revealing an operon comprising an open reading frame of unknown function (ORF03), essential housekeeping genes (ileS and murB), flagellar export genes (fliI and fliQ), and a homolog to a gene implicated in virulence factor transport in other pathogens (virB11). A promoter for this operon, showing similarity to the Escherichia coli sigma70 consensus, was identified by primer extension. Cotranscription of the genes in the operon was demonstrated by reverse transcription-PCR, and transcription of virB11, fliI, fliQ, and murB was detected in human or mouse biopsies obtained from infected hosts. The genetic organization of this locus was conserved in a panel of H. pylori clinical isolates. Engineered fliI and fliQ mutant strains were completely aflagellate and nonmotile, whereas a virB11 mutant still produced flagella. The fliI and fliQ mutant strains produced reduced levels of flagellin and the hook protein FlgE. Production of OMP4, a member of the outer membrane protein family identified in H. pylori 26695, was reduced in both the virB11 mutant and the fliI mutant, suggesting related functions of the virulence factor export protein (VirB11) and the flagellar export component (FliI).

Seroprevalence of Helicobacter pylori, incidence of gastric cancer, and peptic ulcer-associated hospitalizations in a Canadian Indian population

The living conditions of many aboriginal communities in Canada may place their residents at risk for H. pylori infection. Our aims were to determine: (1) the seroprevalence of H. pylori in a traditional Indian community, (2) the clinical relevance of H. pylori infection in this population, and (3) if H. pylori could be identified by polymerase chain reaction from the local water. A demographic questionnaire was administered, and blood was collected from subjects in an Indian community in northwestern Manitoba. The serum was analyzed by ELISA for IgG to H. pylori and to CagA. ABO and Lewis antigens were tested. Age-adjusted incidence of gastric cancer and of hospitalizations associated with diagnoses of peptic ulcer were determined for the Indian and non-Indian Manitoba population in the years 1989-1993. Nested PCR was performed on lake water using H. pylori-specific primers and the amplicons probed with an internal Dig-labeled probe. Three hundred six (59%) of approximately 518 individuals who were resident in the community at the time of the study were enrolled. The ELISA for H. pylori was positive in 291 (95%). There was no association between H. pylori seropositivity and age, sex, gastrointestinal complaints, medications, housing characteristics, and ABO or Lewis antigen status. CagA was positive in 84.5% of infected subjects. The average annual age-adjusted incidence of hospitalizations associated with diagnoses of peptic ulcer disease in Manitoba was higher for treaty-status Indians (394.3/100,000) than for non-Indians (203.8/100,000), but gastric cancer rates were similar (11.2/100,000 vs 11.6/100,000). No H. pylori DNA was detected in the lake water. In conclusion, the seroprevalence of CagA-positive H. pylori is high in this representative Manitoban Indian community. This may be associated with an increased risk for peptic ulcer disease but is not associated with an increased risk for gastric cancer.

Comparison of five PCR methods for detection of Helicobacter pylori DNA in gastric tissues

Five different PCR methods for the detection of Helicobacter pylori were evaluated. The results of this study indicate that of the five PCR methods examined, the ureC (glmM) gene PCR is the most sensitive and specific for the detection of H. pylori in gastric biopsy specimens.