Helicobacter pylori infection induces gastric cancer in mongolian gerbils

Development of gastric carcinoma from intestinal metaplasia in Cdx2-transgenic mice

In the progression of chronic gastritis, gastric mucosal cells deviate from the normal pathway of gastric differentiation to an intestinal phenotype. Many epidemiologic studies have found an association between the formation of intestinal metaplasia and the development of gastric carcinoma. However, there is no direct evidence that shows intestinal metaplasia is a precursor lesion of gastric carcinoma, to date. We periodically examined the intestinal metaplastic mucosa of Cdx2-transgenic mice we have previously generated. Gastric polyps developed from intestinal metaplastic mucosa in all stomachs of Cdx2-transgenic mice examined. These gastric polyps consisted of intestinal-type adenocarcinoma that invaded the submucosa and muscularis propria and occasionally spread into the subserosa. p53 and APC gene mutations were recognized in the adenocarcinomas. The participation of APC and p53 gene mutations in gastric carcinogenesis from the intestinal metaplasia was verified by the Cdx2-transgenic mice, carrying Apc(Min) mutation or p53 deficiency, that developed gastric polyps much earlier than Cdx2 alone. We successfully showed that long-term intestinal metaplasia induces invasive gastric carcinoma. These results indicate that intestinal metaplasia itself plays a significant role in the genesis and progression of gastric carcinoma.

A new subtype of 3’ region of cagA gene in Helicobacter pylori strains isolated from Zhejiang Province in China

AIM: To isolate the subtypes of 3’ region of cagA gene in Helicobacter pylori (H pylori) strains from Zhejiang Province in China and to investigate their relations to H pylori-associated gastroduodenal diseases.

METHODS: One hundred and thirty-seven H pylori clinical strains were isolated from the gastric mucosa specimens of 74 patients with chronic gastritis, 61 with peptic ulceration, and 2 with gastric cancer. Bacterial genomic DNA was extracted and 3’ region of cagA gene was amplified by polymerase chain reaction (PCR). Subtypes of 3’ region of cagA gene were determined by the size of PCR amplified segments. The sequences of the subtypes were analyzed by PCR-based sequencing.

RESULTS: Of the 137 H pylori isolates from Zhejiang Province, 132 (96.4%) yielded PCR products that could be classified into three groups of subtypes, named as subtypes I, II, and III according to their sizes. The sizes of subtypes I, II, and III were 648-650 bp, 705-707 bp, and 815 bp, respectively. Among the 132 cagA-positive H pylori strains, 123 (93.2%) belonged to the group of subtype I, 6 (4.5%) presented subtype II, 1 (0.8%) was subtype III, and 2 (1.5%) presented subtypes I and III both. The primary structure of subtype I was composed of 3 repeats of R1, 1 repeat of R2 and 1 repeat of R3. Subtype II possessing 4 repeats of R1, 2 repeats of R2 and 1 repeat of R3 was a newly found type of 3’ region of cagA gene which had not been reported before. The primary structure of subtype III consisted of 4 repeats of R1, 1 repeat of R2 and 2 repeats of R3. Comparison of the sequences of subtype I strains with the corresponding sequences deposited in GenBank, showed a similarity of 95.0% (94.0%-96.1%) for nucleotide sequences and 95.9% (94.9%-97.4%) for deduced amino acid sequences. Comparison of the sequences of subtype III strains with the corresponding sequences deposited in GenBank, showed a similarity of 93.9% (90.8%-96.9%) for nucleotide sequences and 93.2% (90.2%-96.2%) for deduced amino acid sequences. Among subtype II strains, the nucleotide and deduced amino acid sequences showed a similarity of 95.2% (94.1%-96.5%) and 96.4% (93.8%-97.9%), respectively. There were no statistical differences in the distribution of subtypes of 3’ region of cagA gene among different H pylori-associated gastroduodenal diseases (χ² = 11.544, P > 0.05).

CONCLUSION: There are three subtypes (I, II, and III) of 3’ region of cagA gene in H pylori strains isolated from Zhejiang Province, and subtypeIis predominant. Subtype II is a newly found subtype of 3’ region of cagA gene. The result of this study does not support the view that the subtypes of 3’ region of cagA gene in H pylori isolated from Zhejiang Province are correlated with the clinical outcomes of H pylori infection.

Development of gastric adenocarcinoma in Mongolian gerbils after long-term infection with Helicobacter pylori

BACKGROUND AND AIM

The experimental evidence that long-term colonization of Helicobacter pylori results in the development of gastric cancer in Mongolian gerbils has been reported only by two Japanese groups to date. This study aimed to investigate the carcinogenicity of H. pylori infection in a Mongolian gerbil model.

METHODS

Thirty-six Mongolian gerbils (inner Mongolian origin) were divided into two groups (male to female ratio, 1:1) and orally inoculated with a standard H. pylori strain (ATCC43504) or H. pylori161 (isolated from a Chinese patient with gastric adenocarcinoma), respectively, once a week for 5 weeks. Another 10 control gerbils were given phosphate-buffered saline. The animals were killed 8, 20, 28 and 84 weeks after inoculation for bacterial and histological examination.

RESULTS

Seven inoculated gerbils died at the week 42. Overall, H. pylori colonization was detected in 24 (83%) of the 29 available inoculated gerbils. The gastric lesions were aggravated gradually over time. At week 84, moderate to severe gastritis, characterized by diffuse infiltration of mononuclear cells and formation of multiple lymphoid follicles in mucosa and submucosa, and even the lymphoepithelial lesions, were observed. Epithelial hyperplasia were dominant in almost all gerbils. Four (24%) of the 17 animals had hyperplastic polyps. Intestinal metaplasia were rarely seen (in three gerbils). Well-differentiated gastric adenocarcinomas developed in three (18%) of the 17 gerbils after 84 weeks. Of the three gerbils, one female gerbil was infected with H. pylori161 and the others (one male and one female) were infected with ATCC43504.

CONCLUSIONS

The present study reconfirms that H. pylori infection alone can induce gastric adenocarcinoma in Mongolian gerbils and suggests that different species of gerbil and both standard and clinically isolated H. pylori strains can be used for investigating the carcinogenesis of H. pylori. This is the first report of the development of gastric cancer in female gerbils, which highlights the importance of using both sexes to investigate the pathogenesis of H. pylori and whether host susceptibility is influenced by sex.

Helicobacter pylori infection of human and murine primary gastric cells

The effect of Helicobacter pylori infection on human and murine primary gastric cells was determined. CagA was phosphorylated following adherence of H. pylori to primary human gastric cells. However, it did not adhere to human primary duodenal cells or murine gastric cells, and CagA could not be detected in cell lysates. Identification of an easily available animal model of infection in which the organism adheres to gastric mucosal cells would enhance studies of the virulence of H. pylori.

Heightened susceptibility to chronic gastritis, hyperplasia and metaplasia in Kcnq1 mutant mice

Increased susceptibility to gastric cancer has been associated with a wide range of host genetic and environmental factors, including Helicobacter pylori infection. Helicobacter pylori infection is postulated to initiate a progression through atrophic gastritis, metaplasia and dysplasia to cancer, and has been associated with reduction of acid output and dysregulation of stomach mucins. Here, we present the characterization of two mouse lines carrying mutant alleles of the gene encoding the Kcnq1 potassium channel, which very rapidly establish chronic gastritis in a pathogen-exposed environment. These mice develop gastric hyperplasia, hypochlorhydria and mucin dysregulation independent of infection. Metaplasia, dysplasia and pre-malignant adenomatous hyperplasia of the stomach have been observed in these Kcnq1 mutant mice, also independent of infection. The data presented here suggest that Kcnq1 mutant mice can be used both as an efficient model for the development of atrophic gastritis after infection and to determine the processes during the later stages of progression to gastric cancer independent of infection. Thus, Kcnq1 mutant mice are a powerful new tool for investigating the connection between acid balance, Helicobacter infection and mucin disruption in the progression to gastric cancer.

Construction of prokaryotic expression system of ltB-ureB fusion gene and identification of the recombinant protein immunity and adjuvanticity

AIM: To construct ltB-ureB fusion gene and its prokaryotic expression system and identify immunity and adjuvanticity of the expressed recombinant protein.

METHODS: The ureB gene from a clinical Helicobacter pylori (H pylori) strain Y06 and the ltB gene from Escherichia coli (E. coli) strain 44851 were linked into ltB-ureB fusion gene by PCR. The fusion gene sequence was analyzed after T-A cloning. A prokaryotic recombinant expression vector pET32a inserted with ltB-ureB fusion gene (pET32a-ltB-ureB) was constructed. Expression of the recombinant LTB-UreB protein (rLTB-UreB) in E. coli BL21DE3 induced by isopropylthio-β-D-galactoside (IPTG) at different concentrations was detected by SDS-PAGE. Western blot assays were used to examine the immunoreaction of rLTB-UreB by a commercial antibody against whole cell of H pylori and a self-prepared rabbit anti-rUreB serum, respectively, and determine the antigenicity of the recombinant protein on inducing specific antibody in rabbits. GM₁-ELISA was used to demonstrate the adjuvanticity of rLTB-UreB. Immunoreaction of rLTB-UreB to the UreB antibody positive sera from 125 gastric patients was determined by using ELISA.

RESULTS: In comparison with the corresponding sequences of original genes, the nucleotide sequence homologies of the cloned ltB-ureB fusion gene were 100%. IPTG with different dosages of 0.1-1.0 mmol/L could efficiently induce pET32a-ltB-ureB-E. coli BL21DE3 to express the rLTB-UreB. The output of the target recombinant protein expressed by pET32a-ureB-E. coli BL21DE3 was approximately 35% of the total bacterial proteins. rLTB-UreB mainly presented in the form of inclusion body. Western blotting results demonstrated that rLTB-UreB could combine with the commercial antibody against whole cell of H pylori and anti-rUreB serum as well as induce rabbit to produce specific antibody. The strong ability of rLTB-UreB binding bovine GM₁ indicated the existence of adjuvanticity of the recombinant protein. All the UreB antibody positive sera from the patients (125/125) were positive for rLTB-UreB.

CONCLUSION: A recombinant prokaryotic expression system with high expression efficiency of the target fusion gene ltB-ureB was successfully established. The expressed rLTB-UreB showed qualified immunogenicity, antigenicity and adjuvanticity. All the results mentioned above laid a firm foundation for further development of H pylori genetically engineered vaccine.

Risks of interleukin-1 genetic polymorphisms and Helicobacter pylori infection in the development of gastric cancer

BACKGROUND

The host genetic factors that determine the clinical outcomes of Helicobacter pylori-infected individuals remain unclear.

AIM

To elucidate the risks of host interleukin-1 (IL-1) genetic polymorphisms and H. pylori infection in the development of gastric cancer.

METHODS

In a case-control study of 164 controls and 142 patients with gastric cancer, the IL-1B-511 biallelic polymorphisms and the IL-1RN penta-allelic variable number of tandem repeats were genotyped.

RESULTS

The carriage of IL-1RN*2, male gender, old age and H. pylori infection independently increased the risk of gastric cancer, with odds ratios of 3.3 [95% confidence interval (CI), 1.4-7.7], 2.1 (95% CI, 1.2-3.8), 5.3 (95% CI, 3.1-9.0) and 2.2 (95% CI, 1.3-3.8), respectively. H. pylori-infected individuals who were carriers of IL-1RN*2 showed increased risks of both intestinal and diffuse types of gastric cancer, with odds ratios of 11.0 and 8.7, respectively. In addition, these individuals also had a higher score of intestinal metaplasia in the corpus than did uninfected non-carriers.

CONCLUSIONS

This study is the first to verify IL-1RN*2 as an independent factor governing the development of gastric cancer in Asian individuals. A combination of H. pylori testing and host genotyping may target the eradication of H. pylori to high-risk individuals.

Hypoacidity combined with high gastric juice nitrite induced by Helicobacter pylori infection is associated with gastric cancer

BACKGROUND

In patients with Helicobacter pylori infection, the concentration of nitrite in gastric juice is elevated. The degree of elevation correlates with that of inflammation and H. pylori density.

AIM

The aim of this study was to examine hypoacidity and high nitrite levels related to H. pylori infection in patients with gastric cancer.

METHODS

We studied 88 patients with more than one history of endoscopic mucosal resection (EMR) for early gastric cancer and 88 age-matched controls. Concentration of nitrite in gastric juice was measured by Griess reaction, and serum pepsinogen levels were measured by RIA.

RESULTS

Multiple malignant lesions were found in 20 of the 88 patients. Serum gastrin, gastric juice pH and nitrite levels in patients with gastric cancer were significantly higher and pepsinogen I and pepsinogen I/II significantly lower than in control subjects. Pepsinogen I level and I/II ratio were lower and gastric juice pH was higher in the protruded-type group than in the depressed-type group. Pepsinogen I and pepsinogen I/II were lower and gastric juice pH was higher in multiple than in single cases.

CONCLUSIONS

Hypoacidity combined with high gastric juice nitrite induced by H. pylori infection is associated with the intestinal type of gastric cancer, especially protruded lesions.

Relationship between Helicobacter pylori infection and the prevalence, site and histological type of gastric cancer

AIM

To evaluate the relationship between Helicobacter pylori infection and gastric cancer in Japan.

METHODS

This was a multicentre study conducted in various regions in Japan. A total of 6578 individuals as controls and 2503 with histologically confirmed gastric cancer were enrolled. H. pylori status was determined by enzyme-linked immunosorbent assay (ELISA) for anti-H. pylori immunoglobulin G (IgG).

RESULTS

The prevalence of H. pylori infection in gastric cancer patients was markedly high in all age groups. In contrast, the rate increased with age among control subjects. The overall prevalence of H. pylori infection in control subjects was 50.2% (3300/6578) vs. 82.8% in gastric cancer patients (2072/2503) (OR = 2.47; 95% CI: 2.19-2.79). The prevalence of H. pylori in early gastric cancer was significantly higher than that in advanced gastric cancer (86.5% vs. 75.7%; OR = 2.06; 95% CI: 1.66-2.55). There were no significant differences in the prevalence of H. pylori between the intestinal and diffuse types of gastric cancer or among gastric cancer in antrum, body and cardia.

CONCLUSION

H. pylori infection is strongly associated with the development of gastric cancer. The difference in odds ratios among younger and older persons with gastric cancer likely reflects the decrease in prevalence of H. pylori in the population, and is more reflective of the actual risks associated with the infection.

Therapeutic vaccination against Helicobacter pylori in the beagle dog experimental model: safety, immunogenicity, and efficacy

Helicobacter pylori is a gram-negative bacterium that colonizes the human gastric mucosa causing gastritis and peptic ulcer and increasing the risk of gastric cancer. The efficacy of current antibiotic-based therapies can be limited by problems of patient compliance and increasing antibiotic resistance; the vaccine approach can overcome these limits. The present study describes the therapeutic vaccination of experimentally H. pylori-infected beagle dogs, an animal model that reproduces several aspects of the human infection with H. pylori. The vaccine consisted of three recombinant H. pylori antigens, CagA, VacA, and NAP, formulated at different doses (10, 25, or 50 microg each) with alum and administered intramuscularly either weekly or monthly. No adverse effects were observed after vaccination and a good immunoglobulin G response was generated against each of the three antigens. Bacterial colonization and gastritis were decreased after the completion of the vaccination cycle, especially in the case of the monthly immunization schedule. In conclusion, therapeutic vaccination in the beagle dog model was safe and immunogenic and was able to limit H. pylori colonization and the related gastric pathology.

Amelioration of oxidative stress with ensuing inflammation contributes to chemoprevention of H. pylori-associated gastric carcinogenesis

The gastric inflammatory response provoked by Helicobacter pylori (H. pylori) consists of infiltrations by neutrophils, lymphocytes, and macrophages, resulting in varying degrees of epithelial cell damage. H. pylori-associated inflammation not only activates various oxidant-producing enzymes such as NADPH oxidase and inducible nitric oxide synthase, but also lowers the antioxidant ascorbic acid in the stomach. Reactive oxygen metabolites and nitrogen metabolites generated by these enzymes react with each other to generate new or more potent reactive species. The specific types of cellular damage resulting from reactive oxygen metabolites include lipid peroxidation, protein oxidation, and oxidative DNA damage. All of these oxidative products can result in biochemical changes leading to cancer. A positive association has been demonstrated between H. pylori infection and gastric adenocarcinoma with increased oxidative stress. Therefore, appropriate treatment to reduce oxidative stress would be expected to prevent subsequent gastric carcinogenesis through lessening of H. pylori-associated inflammation. This review will provide evidence that antiinflammatory regimens can decrease the development of tumors and the amelioration of gastric inflammation might lead to chemoprevention strategies by the attenuation of oxidative stress.

Long-standing gastric mucosal barrier dysfunction in Helicobacter pylori-induced gastritis in mongolian gerbils

BACKGROUND AND AIMS

Helicobacter pylori infection causes chronic gastritis and leads to peptic ulcer and gastric adenocarcinoma. An impaired gastric mucosal barrier could be involved in these processes. Our aim was to investigate gastric barrier function in H. pylori-induced gastritis.

METHODS

Stripped gastric mucosal tissues of H. pylori-infected Mongolian gerbils (4 weeks and 70 weeks after inoculation, respectively) and controls were mounted in Ussing chambers. (51)Cr-EDTA (paracellular probe) and horseradish peroxidase (HRP, protein antigen) were used to assess mucosal barrier function. The electrophysiological parameters of the mucosa (transepithelial potential, short circuit current, and transepithelial resistance) were monitored as measurements of barrier integrity and viability. Tissue histology was performed to assess inflammation.

RESULTS

In the antrum, both short-term gastritis [4.68 (3.88-5.74) x 10(-6) vs. control 2.86 (2.34-3.77) x 10(-6) cm/s, p <.001] and gastritis of long-standing [5.72 (3.88-10.94) x 10(-6) cm/s, p <.001 vs. control] showed increased permeability to (51)Cr-EDTA. In long-standing antral gastritis there was also an increased HRP flux [9.01 (2.98-45.02) vs. control 0.52 (0.06-1.20) pmol/h/cm(2), p <.001]. In the corpus, permeability to (51)Cr-EDTA was increased only in long-standing gastritis [4.63 (3.64-7.45) x 10(-6) vs. control 2.86 (2.12-3.98) x 10(-6) cm/s, p <.01]. Gastric mucosal permeability to (51)Cr-EDTA was correlated to histological inflammation and inflammatory activity. The levels of serum anti-H. pylori immunoglobulin G were positively correlated to HRP flux and (51)Cr-EDTA permeation.

CONCLUSIONS

Helicobacter pylori-induced gastritis in Mongolian gerbils was associated with a long-standing gastric mucosal barrier dysfunction. The barrier defect extended from the antrum into the corpus over time. This impaired barrier function may contribute to perpetuation of chronic inflammation and may be involved in H. pylori-associated carcinogenesis.

ECL-Cell Derived Gastric Cancer in Male Cotton Rats Dosed with the H2-Blocker Loxtidine

Spontaneously hypergastrinemic cotton rats (Sigmodon hispidus) develop tumors that have the phenotype of an adenocarcinoma but most likely originate from the enterochromaffin-like (ECL) cells. Among inbred animals approximately 50% of the females, but <1% of males develop spontaneous gastric carcinomas. Gastrin is the principle carcinogen in this model, as >4 months of hypergastrinemia results in carcinoma, but a gastrin receptor antagonist prevents carcinomas. Carcinomas can also be induced by partial corpectomy. In the present study, the insurmountable H2-receptor antagonist loxtidine (200 mg/kg/day) was given to male cotton rats for 6 months. The loxtidine-dosed animals developed hypergastrinemia, whereas control animals remained normogastrinemic. At termination, 4 of 5 cotton rats had cancer located to the oxyntic mucosa, whereas 1 animal had dysplasia. The gastric mucosa of all of the control animals was normal. In the dysplastic mucosa of loxtidine-dosed animals there was a marked increase in chromogranin A-positive cells, where numerous groups of cells also stained positive with the Sevier-Munger technique. In areas of high proliferation and cancer there were also histidine decarboxylase, chromogranin A, and Sevier-Munger-positive cells, altogether indicating an ECL cell origin of the tumors. This represents an interesting animal model where ECL cell-derived gastric cancer can be induced by pharmacological acid inhibition in 6 months.

Dynamic changes of gastric mucosal pathology after clearance of Helico-bacter pylori infection

AIM: To investigate the characteristics of pathological changes in the gastric mucosa after anti-Helicobacter pylori (H. pylori ) therapy.

METHODS: The samples were obtained through electronic gastroscope or operation and divided into two groups: therapy group (n = 32) in which the patients received standard anti-H. pylori therapy; and control group (n = 25) without anti-H. pylori therapy. Histological examinations were carried out after gastroscopic inspection or operation, half a year and one year later.

RESULTS: H. pylori in the mucous membrane of the stomach in all 32 cases in therapy group diminished or disappeared and pathological changes (inflammation, intestinal metaplasia and dysplasia) attenuated to some extent. There were significant differences between samples at different time points of examination (P < 0.05). In all 25 cases in group control, changes of H. pylori and pathology of the mucous membrane were not apparent. There was not a stalistical significance between samples at different time points of examination (P > 0.05). There was significant difference between samples of therapy and control groups (P < 0.05).

CONCLUSION: Anti-H. pylori therapy has active significance for the improvement of pathological changes in the mucous membrane of the stomach.

Effectiveness and pharmaceutical cost of sequential treatment for Helicobacter pylori in patients with non-ulcer dyspepsia

BACKGROUND

A novel 10-day sequential treatment regimen recently achieved a significantly higher eradication rate than standard 7-day therapy in both peptic ulcer disease and non-ulcer dyspepsia. Its higher performance has recently been confirmed using a halved clarithromycin dose in peptic ulcer disease.

AIMS

To evaluate whether an acceptable eradication rate could also be obtained by halving the clarithromycin dose in dyspeptic patients and to assess the role of possible factors affecting the outcome of therapy.

METHODS

In a prospective, open-label study, 162 patients with non-ulcer dyspepsia and Helicobacter pylori infection, assessed by rapid urease test and histology, were enrolled. Patients were randomized to receive either 10-day sequential therapy, comprising rabeprazole 20 mg b.d. plus amoxicillin 1 g b.d. for the first 5 days, followed by rabeprazole 20 mg b.d., clarithromycin 250 mg b.d. and tinidazole 500 mg b.d. for the remaining 5 days (low-dose therapy), or a similar schedule with clarithromycin 500 mg b.d. (high-dose therapy). Four to six weeks after therapy, H. pylori eradication was assessed by endoscopy/histology.

RESULTS

A similar H. pylori eradication rate was observed following low- and high-dose regimens for both per protocol (94% vs. 95%; P = N.S.) and intention-to-treat (93% vs. 94%; P = N.S.) analyses. No major side-effects were reported. Halving the clarithromycin dose leads to a per patient saving in pharmaceutical costs of 24.6 euros. None of the variables examined affected the effectiveness of eradication of the sequential regimen.

CONCLUSION

A reduction of the clarithromycin dose does not affect H. pylori eradication with the sequential regimen in non-ulcer dyspepsia and affords lower costs.

Review article: How useful are the rodent animal models of gastric adenocarcinoma?

Gastric cancer is the second most common cause of cancer-related mortality world-wide. In most cases, it develops via the pre-malignant stages of atrophic gastritis, intestinal metaplasia and dysplasia, following Helicobacter pylori infection of susceptible individuals. A number of rodent models have recently provided valuable insights into the host, bacterial and environmental factors involved in gastric carcinogenesis. Wild-type rodents do not develop gastric adenocarcinoma, but early studies showed that the disease could be induced in several rodent species by chemical carcinogens. More recently, it has been demonstrated that gastric adenocarcinoma can be induced in Mongolian gerbils by H. pylori infection and in C57BL/6 mice by long-term H. felis infection. These models have allowed the importance of Helicobacter virulence genes, host factors, such as gender, strain and immune response, and environmental factors, such as dietary salt, to be explored. A number of transgenic mice with alterations in various pathways, including the immune response, gastrin biosynthesis, parietal cell development, growth factors and tumour suppressors, have also provided models of various stages of gastric carcinogenesis. One model that has proved to be particularly valuable is the hypergastrinaemic INS-GAS mouse, in which gastric carcinoma develops spontaneously in old animals, but the process is greatly accelerated by Helicobacter infection.

Construction of prokaryotic expression system of ureB gene from a clinical Helicobacter pylori strain and identification of the recombinant protein immunity

AIM: To clone ureB gene from a clinical isolate of Helicobacter pylori and construct a prokaryotic expression system of the gene and identify immunity of the expressed recombinant protein.

METHODS: ureB gene from a clinical H pylori strain Y06 was amplified by the high fidelity polymerase chain reaction technique. The target DNA fragment amplified from ureB gene was sequenced after T-A cloning. Prokaryotic recombinant expression vector pET32a inserted with ureB gene (pET32a-ureB) was constructed. The expression of recombinant UreB protein (rUreB) in E. coli BL21DE3 induced by isopropylthio-β-D-galactoside (IPTG) at different concentrations was examined by SDS-PAGE. Western blot using commercial antibodies against whole cell of H pylori and an immunodiffusion assay using a self-prepared rabbit anti-rUreB antibody were applied to determine immunity of the target recombinant protein. ELISA was used to detect the antibody against rUreB in sera of 125 H pylori infected patients and to examine rUreB expression in 109 H pylori isolates.

RESULTS: In comparison with the reported corresponding sequences, the nucleotide sequence homology of the cloned ureB gene was from 96.88-97.82% while the homology of its putative amino acid sequence was as high as 99.65-99.82%. The rUreB output expressed by pET32a-ureB-BL21DE3 was approximate 30% of the total bacterial proteins. rUreB specifically combined with the commercial antibodies against whole cell of H pylori and strongly induced rabbits to produce antibody with a 1:8 immunodiffusion titer after the animals were immunized with the recombinant protein. Serum samples from all H pylori infected patients were positive for UreB antibody and UreB expression were detectable in all tested H pylori isolates.

CONCLUSION: A prokaryotic expression system with high expression efficiency of H pylori ureB gene was successfully established. The expressed rUreB showed qualified immunoreactivity and antigenicity. High frequencies of UreB expression in different H pylori isolates and specific antibody against UreB in sera of H pylori infected patients indicate that UreB is an excellent antigen candidate for developing H pylori vaccine.

Low prevalence of Helicobacter pylori but high prevalence of cytomegalovirus-associated peptic ulcer disease in AIDS patients: Comparative study of symptomatic subjects evaluated by endoscopy and CD4 counts

BACKGROUND AND AIMS

The role of Helicobacter pylori infection in gastroduodenal lesions might be different between the general population and AIDS patients. The aim of the present study was to compare the prevalence of H. pylori and cytomegalovirus (CMV) infection in AIDS patients and HIV-negative controls. The impact of CD4 lymphocyte counts on H. pylori and CMV infection in the same subjects was also assessed.

METHODS

One hundred and fifty-six patients (52 HIV-positive, 104 HIV-negative) with gastrointestinal symptoms were evaluated with upper gastrointestinal endoscopy and biopsy. Comparison of the prevalence of H. pylori and CMV infection was made by dividing AIDS patients into two groups: those with CD4 counts >100/mm3 and those with CD4 counts <100/mm3, and ulcer and non-ulcer patients.

RESULTS

In comparison with HIV-negative controls, AIDS patients had a lower prevalence of H. pylori infection (P < 0.0001) but a higher prevalence of CMV infection (P < 0.0001). Cytomegalovirus infection was frequently found in AIDS patients with CD4 count <100/mm3, in comparison with those with a CD4 count >100/mm3. In AIDS patients, CMV was more frequently detected in subjects with peptic ulcers (P = 0.0125). Conversely, the prevalence of H. pylori infection in AIDS patients was not different between those with and without peptic ulcers.

CONCLUSIONS

The low prevalence of H. pylori infection and peptic ulcer in AIDS patients suggests a different role of H. pylori infection in peptic ulcer or even a different mechanism of peptic ulcerogenesis in HIV-positive subjects. Cytomegalovirus, rather than H. pylori, may be the main causative pathogen of peptic ulcers in AIDS patients.

Immunogenetic analysis of gastric MALT lymphoma-like lesions induced by Helicobacter pylori infection in neonatally thymectomized mice

Most gastric mucosa-associated lymphoid tissue (MALT) lymphomas are caused by Helicobacter pylori (H. pylori) infection. We previously reported that acquired lymphoid follicles with germinal centers were induced by H. pylori infection in neonatally thymectomized (nTx) mice. In the present study, we developed gastric MALT lymphoma-like lesions in nTx mice by long-term H. pylori infection, and performed immunogenetic analyses. BALB/c mice were thymectomized on the 3rd day after birth. At 6 weeks of age, mice were orally infected with 10(8) H. pylori and serially killed 2, 4, 6, and 12 months later. Normal BALB/c and noninfected nTx mice served as controls. Follicle formation occurred after 2 months of H. pylori infection in the nTx mice. Follicle formation and infiltration of intraepithelial lymphocytes progressed in a time-dependent manner. Lymphoepithelial lesions, a characteristic feature of MALT lymphoma, also occurred in a time-dependent manner (100% at 12 months). Serum immunoelectrophoresis revealed a monoclonal band (M-protein) in 30% (3/10) of mice 6 months after infection. M-protein-positive mice had amplification of one or two IgM and/or IgG heavy-chain genes in the gastric B lymphocytes, as determined with polymerase chain reaction, suggesting mono- or oligoclonality. Overexpression of Bcl-X(L) protein was immunohistologically observed in the infiltrating B lymphocytes and in some follicular B lymphocytes in 80% (8/10) of the cases at 12 months. Thus, H. pylori infection is involved in the development of gastric MALT lymphoma-like lesions in nTx mice. Our mouse model is useful for clarifying the pathogenetic mechanism of gastric MALT lymphoma by H. pylori infection.

Gastric mucosal cytokine and epithelial cell responses to Helicobacter pylori infection in Mongolian gerbils

Experimental infection with Helicobacter pylori in Mongolian gerbils results in chronic gastritis and gastric cancer. To investigate epithelial cell proliferation, apoptosis, and mucosal cytokine responses in gastritis, Mongolian gerbils were infected with the H pylori SS1 strain. At 4 weeks post-infection, gastritis was predominantly within the antrum, but extended to the corpus in approximately 50% of gerbils by 36 weeks. Epithelial cell proliferation and apoptosis in glandular epithelial cells were increased with infection. Antral cell proliferation, but not apoptosis, correlated significantly with gastric inflammation. In female gerbils, H pylori significantly increased expression of transcripts for IFN-gamma and IL-12p40, but not TGF-beta or IL-10, in the gastric mucosa. Significantly reduced IFN-gamma and IL-12p40 responses were observed in male gerbils infected with H pylori, but epithelial proliferative and apoptotic responses were comparable to those of females. These studies demonstrate that the female gerbil cytokine response to H pylori has a Th1 profile and that there are gender differences in the magnitude of the gastric cytokine responses to H pylori. The absence of a down-regulatory cytokine response may account for the more severe gastritis observed with H pylori infection in gerbils than in mice.

Helicobacter pylori CagA induces Ras-independent morphogenetic response through SHP-2 recruitment and activation

The CagA protein of Helicobacter pylori, which is injected from the bacteria into bacteria-attached gastric epithelial cells, is associated with gastric carcinoma. CagA is tyrosine-phosphorylated by Src family kinases, binds the SH2 domain-containing SHP-2 phosphatase in a tyrosine phosphorylation-dependent manner, and deregulates its enzymatic activity. We established AGS human gastric epithelial cells that inducibly express wild-type or a phosphorylation-resistant CagA, in which tyrosine residues constituting the EPIYA motifs were substituted with alanines. Upon induction, wild-type CagA, but not the mutant CagA, elicited strong elongation of cell shape, termed the "hummingbird" phenotype. Time-lapse video microscopic analysis revealed that the CagA-expressing cells exhibited a marked increase in cell motility with successive rounds of elongation-contraction processes. Inhibition of CagA phosphorylation by an Src kinase inhibitor, PP2, or knockdown of SHP-2 expression by small interference RNA (siRNA) abolished the CagA-mediated hummingbird phenotype. The morphogenetic activity of CagA also required Erk MAPK but was independent of Ras or Grb2. In AGS cells, CagA prolonged duration of Erk activation in response to serum stimulation. Conversely, inhibition of SHP-2 expression by siRNA abolished the sustained Erk activation. Thus, SHP-2 acts as a positive regulator of Erk activity in AGS cells. These results indicate that SHP-2 is involved in the Ras-independent modification of Erk signals that is necessary for the morphogenetic activity of CagA. Our work therefore suggests a key role of SHP-2 in the pathological activity of H. pylori virulence factor CagA.

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 is a fragile bacteria when stored at low and ultra-low temperatures

BACKGROUND AND AIM

Usually, bacteria are cryopreserved for short-term storage at low and ultra-low temperatures. There are no reports as to whether Helicobacter pylori is a fragile bacteria when stored at low and ultra-low temperatures as compared with other intestinal bacteria. A study was done on seven H. pylori strains and other intestinal bacteria to compare different temperatures for storage of organisms in saline solution.

METHODS

Seven H. pylori strains, specifically American Type Culture Collection (ATCC) strains 43504 and TN2GF4, and five strains isolated from the present patients were grown on a modified Skirrow's agar for H. pylori. Escherichia coli and Bacteroides distasonis, both representing isolates from the present patients, were grown on trypticase soy blood agar for E. coli, and EG agar for B. distasonis. Culture was for 4-5 days under microaerobic, aerobic and anaerobic conditions at 37 degrees C. Cells were harvested by scraping growth from the solid medium and into sterile saline. The cells were adjusted to concentrations of 109 viable cells/mL in saline and preserved at 4 degrees C, -20 degrees C, or -80 degrees C for 3 weeks before reculture under microaerobic, aerobic and anaerobic conditions at 37 degrees C for 7 days. After incubation, morphologically distinct colonies were counted, isolated, and identified by standard bacteriologic techniques. The H. pylori were morphologically analyzed by electronic microscopy before and after preservation. Mongolian gerbils were inoculated with the cryopreserved H. pylori to evaluate the bacterial infectivity.

RESULTS

Six of the seven H. pylori strains failed to culture after being preserved at 4 degrees C, -20 degrees C, or -80 degrees C. Only ATCC 43504 could be cultured after freezing at -80 degrees C. The number of H. pylori ATCC 43504 before preservation was 9.0 +/- 0.5 (log10 no. organisms/mL) and decreased to 5.7 +/- 0.6 after preservation. Morphologically, all H. pylori except ATCC 43504 strains transformed from a bacillary to a coccoid form after preservation. In addition, none of the H. pylori strains could infect Mongolian gerbils after preservation. Escherichia coli and B. distasonis were recovered. Titers before and after 4 degrees C, -20 degrees C, and -80 degrees C, respectively, were 9.1 +/- 0.2, 8.9 +/- 0.5, 8.6 +/- 0.3, and 8.7 +/- 0.3 for E. coli and 9.1 +/- 0.4, 8.7 +/- 0.6, 8.6 +/- 0.5, and 8.8 +/- 0.3 for B. distasonis.

CONCLUSIONS

Helicobacter pylori is a fragile bacteria for storage at low and ultra-low temperatures in comparison with other intestinal bacteria.

Helicobacter pylori and molecular mechanisms of gastric carcinogenesis: targets for prevention and therapy

Gastric cancer is still a leading cause of cancer death worldwide. It is frequently diagnosed in an advanced stage and the overall prognosis is dismal. A major improvement will only be reached with a better understanding of the genetic changes underlying gastric cancer, which may provide us with effective prevention and treatment strategies. This review will highlight the present knowledge on the role of Helicobacter pylori in gastric carcinogenesis and the molecular pathogenesis of gastric cancer, as well as provide a brief overview of possible future targets for more specific and successful treatment options.

Helicobacter pylori and gastric cancer prevention is possible

Epidemiological data gathered during the past few years have shown an association between Helicobacter pylori infection and gastric carcinoma. This association is considered to be causal because of its biological plausibility and the existence of an animal model, even though the positive consequences of eradication on cancer prevention have not yet been definitely proven. The limited proportion of H. pylori infected subjects who develop a gastric cancer can be explained by host factors (certain alleles of IL-1beta) and bacterial factors (cag positive strains), and to a lesser extent by environmental factors (diet). Arguments in favor of the prevention of gastric carcinoma by eradicating H. pylori are now stronger than before, given the availability of simple and accurate diagnostic tests (serology) and treatment follow-up (urea breath test), as well as a 7-day treatment which is usually sufficient for eradication.

Prevalence of gastric precancerous lesions in Ardabil, a high incidence province for gastric adenocarcinoma in the northwest of Iran

BACKGROUND/AIMS

Ardabil Province, in northwestern Iran, has the highest rate of gastric (predominantly cardia) adenocarcinoma in Iran. This study aimed to investigate the feasibility of endoscopic screening and to look for associated Helicobacter pylori infection and gastric precancerous lesions.

METHODS

One thousand one hundred and five adult volunteers, residents of Ardabil and Meshkinshahr, districts, 40 years old and above were selected and invited by a simple random household canvass in rural and urban locations. Informed consents were obtained and upper gastrointestinal video endoscopy was performed to biopsy all visible lesions and standard sites in the antrum, corpus, and cardia.

RESULTS

One thousand and eleven of the invited individuals agreed to participate, including 494 men and 517 women, with a mean (SD) age of 53.32 (10.39) years. Endoscopy was well tolerated by all subjects; 96.7% of antral and 80.7% of cardia mucosal biopsies were satisfactory. The urease test or histology for H pylori was positive in at least 89.2% of subjects. Histological evidence of mucosal atrophy was seen in 39.3% of antral and 21.9% of cardia samples. Chronic gastritis with or without activity, reactive atypia of glandular epithelium, intestinal metaplasia, dysplasia, and cancer were found in 95.1%, 38.0%, 8.7%, 0.2%, and 0.3% of antral and 85.3%, 22.9%, 3.8%, 0.3%, and 0.1% of cardiac biopsies, respectively.

CONCLUSION

Endoscopic screening for upper gastrointestinal diseases was feasible and well tolerated in Ardabil, Iran. Most subjects showed H pylori infection. Atrophic gastritis, reactive atypia, and intestinal metaplasia were common in antrum, corpus, and cardia subsites.

Case of early gastric cancer with nodular gastritis

A case of depressed early gastric cancer with nodular gastritis is described. A 47‐year‐old Japanese man was referred to our hospital and admitted for surgical treatment of gastric cancer. Barium upper gastrointestinal study and endoscopy examination showed a 4.5 × 3.0 cm depressed lesion with a deep central ulceration in the anterior wall of the lower corpus. An unusual miliary pattern resembling ‘goose flesh’ was observed endoscopically in the antrum. Biopsy specimens from the tumor showed poorly differentiated adenocarcinoma, and specimens from the antrum showed many lymphoid follicles with a germinal center. Immunoglobulin G antibody and histological tests (Giemsa stain) for Helicobacter pylori were both positive. Early gastric cancer with nodular gastritis was diagnosed and a subtotal gastrectomy was performed. Histological examination of the resected specimen showed a stage I tumor infiltrating a poorly differentiated adenocarcinoma with a depressed lesion in the corpus (type 0 IIc + III) and nodular gastritis in the antrum. The patient is doing well 1 year after surgery.

Animal models for the study of Helicobacter-induced gastric carcinoma

Helicobacter pylori is considered to have a close association with gastric cancer. Many epidemiological studies have shown a strong association between chronic H. pylori infection and subsequent development of gastric carcinoma in humans. To clarify this link more clearly, it is necessary to use this bacterium in experimental studies to develop gastric carcinoma in suitable experimental animals. Persistent H. pylori infection was seen in the Japanese monkey model, and has recently been achieved in the Mongolian gerbil model. In these models, the sequential histopathological changes in the gastric mucosa are very similar to those in humans. The Japanese monkey model showed advances in atrophic change and p53 point mutations in the gastric mucosa during long-term observation. The Mongolian gerbil model demonstrated that H. pylori infection enhances gastric carcinogenesis in combination with known carcinogens such as N-methyl-N-nitrosourea (MNU) and N-methyl-N-nitro-N'-nitrosoguanidine (MNNG), and also showed that H. pylori infection alone can result in the development of gastric carcinoma. These important results provide a starting point for further studies to clarify the mechanism of gastric carcinogenesis as a result of H. pylori infection and assist in the planning of eradication therapy to prevent gastric carcinoma.

Gastric cancer: who is at risk?

Gastric cancer is a multifactorial disease. Helicobacter pylori infection, host genetic factors and dietetic factors play an important role in the development of gastric cancer. Individuals with a positive family history of gastric cancer and/or pro-inflammatory polymorphisms of the interleukin-1 and tumor necrosis factor A genes infected by H. pylori virulent strains (cagA-, vacA s1-, vacA m1- and babA2-positive) have the highest risk of gastric cancer development. Diets rich in salted and smoked food and poor in fresh fruit and vegetables favor gastric carcinogenesis. Genetic combined with bacterial and host genotyping may allow for the identification of patients at high risk of gastric cancer who can benefit from preventive eradication therapy.

Helicobacter pylori infection influences expression of genes related to angiogenesis and invasion in human gastric carcinoma cells

Infection with Helicobacter pylori (H. pylori) is considered a risk factor for gastric carcinoma. The purpose of this study was to clarify whether H. pylori infection plays a role in progression of gastric carcinoma. We examined the expression of genes encoding angiogenic factors and proteases by human gastric carcinoma cell lines (MKN-1 and TMK-1) co-cultured with or without H. pylori by cDNA microarray analysis. Co-culture with H. pylori increased expression of mRNAs encoding interleukin (IL)-8, vascular endothelial growth factor (VEGF), angiogenin, urokinase-type plasminogen activator (uPA), and metalloproteinase (MMP)-9 by gastric carcinoma cells. Up-regulation of these genes at the mRNA and protein levels was confirmed by Northern blot analysis, semi-quantitative RT-PCR analysis, and ELISA. In vitro angiogenic and collagenase activities of conditioned medium from the gastric carcinoma cells were also stimulated by co-culture with H. pylori. These results indicate that H. pylori infection may regulate angiogenesis and invasion of human gastric carcinoma.

Construction of expression systems for flaA and flaB genes of Helicobacter pylori and determination of immunoreactivity and antigenicity of recombinant proteins

AIM: To clone flagellin genes A (flaA) and B (flaB) from a clinical strain of Helicobacter pylori (H pylori) and to construct prokaryotic expression systems of the genes and identify immunity of the fusion proteins.

METHODS: The flaA and flaB genes from a clinical H pylori isolate Y06 were amplified by high fidelity PCR. The nucleotide sequences of target DNA amplification fragments from the two genes were sequenced after T-A cloning. The recombinant expression vector pET32a inserted with flaA and flaB genes was constructed, respectively. The expressions of FlaA and FlaB fusion proteins in E. coli BL21DE3 induced by isopropylthio-β-D-galactoside (IPTG) at different concentrations were examined by SDS-PAGE. Western blot using commercial antibodies against whole cell of H pylori and immunodiffusion assay using self-prepared rabbit antiserum against FlaA (rFlaA) or FlaB (rFlaB) recombinant proteins were applied to the determination of the fusion proteins immunity. ELISA was used to detect the antibodies against rFlaA and rFlaB in sera of 125 H pylori infected patients and to examine rFlaA and rFlaB expression in 98 clinical isolates of H pylori, respectively.

RESULTS: In comparison with the reported corresponding sequences, the nucleotide sequence homologies of the cloned flaA and flaB genes were from 96.28%-97.13% and 96.31%-97.73%, and their putative amino acid sequence homologies were 99.61%-99.80% and 99.41%-100% for the two genes, respectively. The output of rFlaA and rFlaB expressed by pET32a-flaA-BL21DE3 and pET32a-flaB-BL21DE3 systems was as high as 40%-50% of the total bacterial proteins. Both rFlaA and rFlaB were able to combine with the commercial antibodies against whole cell of H pylori and to induce rabbits to produce specific antibodies with the same 1:2 immunodiffusion titers after the animals were immunized with the two recombinant proteins. Ninety-eight and zero point 4 and 92.80% of the serum samples from 125 patients infected with H pylori were positive for rFlaA and rFlaB antibodies, respectively. One hundred percent and 98.98% of the 98 tested isolates of H pylori were detectable for rFlaA and rFlaB epitopes, respectively.

CONCLUSION: Two prokaryotic expression systems with high efficiency of H pylori flaA and flaB genes were successfully established. The expressed rFlaA and rFlaB showed satisfactory immunoreactivity and antigenicity. High frequencies of FlaA and FlaB expression in different H pylori clinical strains and the general existence of specific antibodies against FlaA and FlaB in H pylori infected patients strongly indicate that FlaA and FlaB are excellent antigen candidates for developing H pylori vaccine.

Childhood Helicobacter pylori infection in a murine model: maternal transmission and eradication by systemic immunization using bacterial antigen-aluminium hydroxide

In humans, transmission of Helicobacter pylori is thought to occur largely during childhood. Infected mothers are generally considered to be the main source of the pathogen. However, little is known about when and how often maternal transmission of H. pylori occurs during childhood. In the present study, we examined these issues in an experimental murine model. Pregnant C57BL/6 mice, infected experimentally with H. pylori, delivered and nursed their litters. The stomachs of the infants were isolated and assessed for transmission of H. pylori. We also investigated the effect of systemic immunization using H. pylori antigen-aluminium hydroxide (AlOH) with regard to providing anti-H. pylori immunity and eradicating the maternally transmitted bacteria in infants. Polymerase chain reaction (PCR) was used to examine the presence of transmitted bacteria and their eradication. Maternal transmission of H. pylori varied widely during the nursing period, but almost all litters showed bacterial transmission at 2 weeks postpartum. Systemic immunization with bacterial antigen-AlOH eradicated the bacteria in most litters; this immunization induced a local decrease of Th2 cytokines and a local increase of Th1 cytokines in the gastric tissue, as determined by ELISA. Our results indicate that our H. pylori vaccine provides not only protection, but also eradication of the already transmitted H. pylori.

Effect of bacterial flora on postimmunization gastritis following oral vaccination of mice with Helicobacter pylori heat shock protein 60

In order to assess the efficacy of oral Helicobacter pylori heat shock protein 60 (HSP60) as a vaccine, protection against H. pylori infection in specific-pathogen-free (SPF) C57BL/6 and germfree (GF) IQI mice was examined. Prophylactic oral vaccination of these two strains of mice with either H. pylori HSP60 or Escherichia coli GroEL inhibited H. pylori colonization by 90 to 95% at 3 weeks postinfection (p.i.). However, these mice were only partially protected because bacterial loads increased in all animals at 10 weeks p.i. Anti-H. pylori HSP60 immunoglobulin G was detected in serum at 3 weeks p.i. in mice vaccinated with either H. pylori HSP60 or GroEL. Significant increases in the gastritis scores were observed only in SPF mice immunized with H. pylori HSP60. These results indicate that oral vaccination with H. pylori HSP60 has partial protective effects on subsequent H. pylori infection but also induces postimmunization gastritis. However, GF mice immunized with H. pylori HSP60 did not suffer from severe gastritis. Therefore, the presence of bacterial flora appears to contribute to the induction of postimmunization gastritis.

Construction and characterization of bivalent vaccine candidate expressing HspA and Mr18000 OMP from Helicobacter pylori

AIM: To construct a recombinant vector which can express outer membrane protein (OMP) with M_r18000 and heat shock protein A (HspA) from Helicobacter pylori (H. pylori) in E. coli BL21, and to exploit the possibility for obtaining the vaccine conferring protection from H. pylori infection.

METHODS: The target gene of HspA was amplified from H. pylori chromosome by PCR, and then inserted into the prokaryotic expression vector pET32a (+) by restrictive endonuclease enzyme kpn I, BamH I simultaneously. The recombinant vector was used to sequence, and then together with pET32a (+)/Omp₁₈, digested by restrictive endonuclease enzyme Hind III and BamH I simultaneously. pET32a(+)/ HspA and Omp₁₈ were recovered from 1% agarose gel by gel kit, and ligated with T₄ ligase by BamH I digested viscidity end. The recombinant plasmid of pET32a(+)/HspA/Omp₁₈ was transformed and expressed in E. coli BL21 (DE3) under induction of IPTG. After purification, its antigenicity of the fusion protein was detected by Western blot.

RESULTS: Enzyme digestion analysis and sequencing showed that the target genes were inserted into the recombinant vector, composed of 891 base pairs, encoded objective polypeptides of 297 amino acid residues. Compared with GenBank reported by Tomb et al there were 1.3% and 1.4% differences in obtained H. pylori nucleotide sequence and amino acid residues, respectively. SDS-PAGE analysis showed that relative molecule mass (M_r) of the expressed product was M_r 51000, M_r of protein expressed by pET32a (+) was about M_r 20000, and soluble expression product accounted for 18.96% of total bacterial protein. After purification with Ni⁺²-NTA agarose resins, the purification of recombinant fusion protein was about 95%. Western blot showed that recombinant fusion protein could be recognized by the patients’ serum infected with H. pylori and anti-Omp₁₈ monoclone, suggesting that this protein had good antigenicity.

CONCLUSION: The gene coding for H. pylori M_r18000 OMP and HspA was cloned and expressed successfully. The results obtained lay the foundation for development of H. pylori protein vaccine and a quick diagnostic kit.

Intragastric ascorbic but not uric acid is depleted in relation with the increased pH in patients with atrophic body gastritis and H. pylori gastritis

BACKGROUND

Helicobacter pylori gastritis induces reversible lowering of Ascorbic Acid (AA) intragastric concentrations. No studies have been aimed at determining the gastric juice AA concentration of atrophic body gastritis (ABG) patients. Uric Acid (UA), is another potent hydro-soluble scavenger of ROS and its possible modification in the gastric juice of patients with H. pylori gastritis have never been investigated. This study was aimed at investigating the levels of AA and UA in the plasma and gastric juice of ABG patients, compared with H. pylori positive patients without corporal atrophy, and with healthy individuals.

MATERIALS AND METHODS

Thirteen ABG patients (Group 1); 32 Chronic non-atrophic H. pylori gastritis patients (Group 2); and 13 healthy stomach controls (Group 3) attending gastroscopy with gastric biopsies (antrum=3, corpus=3) had plasma and intragastric levels of AA and UA measured.

RESULTS

Intragastric AA concentration was significantly lower in group 1 (median 0.21 microg/ml, range 0.1-24) compared both with groups 2 (median 5.5 microg/ml, range 0.1-33.2) (p=0.043) and 3 (median 14.9 microg/ml, range 0.34-44.8) (p=0.0028). Intragastric UA was not different between the three groups. Intragastric AA concentration resulted negatively correlated with the intragastric pH (Spearman r=-0.47, p=0.0003). In patients with gastritis (groups 1 and 2) there was a significant negative correlation between the sum of the Sydney Score variables in the body mucosa, and AA in the gastric juice (Spearman r=-0.55; p=0.0001).

CONCLUSION

The study shows that intragastric pH is the key factor for the depletion of gastric juice AA observed in patients with corporal atrophy and to a lower extent with nonatrophic H. pylori gastritis.

Construction of hpaA gene from a clinical isolate of Helicobacter pylori and identification of fusion protein

AIM: To clone hpaA gene from a clinical strain of Helicobacter pylori and to construct the expression vector of the gene and to identify immunity of the fusion protein.

METHODS: The hpaA gene from a clinical isolate Y06 of H. pylori was amplified by high fidelity PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The recombinant expression vector inserted with hpaA gene was constructed. The expression of HpaA fusion protein in E.coli BL21(DE3) induced by IPTG at different dosages was examined by SDS-PAGE. Western blot with commercial antibody against whole cell of H. pylori as well as immunodiffusion assay with self-prepared rabbit antiserum against HpaA fusion protein were applied to determine immunity of the fusion protein. ELISA was used to detect the antibody against HpaA in sera of 125 patients infected with H. pylori and to examine HpaA expression of 109 clinical isolates of H. pylori.

RESULTS: In comparison with the reported corresponding sequences, the homologies of nucleotide and putative amino acid sequences of the cloned hpaA gene were from 94.25%-97.32% and 95.38%-98.46%, respectively. The output of HpaA fusion protein in its expression system of pET32a-hpaA-BL21(DE3) was approximately 40% of the total bacterial proteins. HpaA fusion protein was able to combine with the commercial antibody against whole cell of H. pylori and to induce rabbit producing specific antiserum with 1:4 immunodiffusion titer after the animal was immunized with the fusion protein. 81.6% of the serum samples from 125 patients infected with H. pylori (102/125) were positive for HpaA antibody and all of the tested isolates of H. pylori (109/109) were detectable for HpaA.

CONCLUSION: A prokaryotic expression system with high efficiency of H. pylorihpaA gene was successfully established. The HpaA expressing fusion protein showed satisfactory immunoreactivity and antigenicity. High frequencies of HpaA expression in different H. pylori clinical strains and specific antibody production in H. pylori infected patients indicate that HpaA is an excellent and ideal antigen for developing H. pylori vaccine.

The effects of cure of Helicobacter pylori infection on the signal transduction of gastric epithelial cells

BACKGROUND

The CagA protein of Helicobacter pylori is directly injected from the bacteria into cells via the bacterial type IV secretion system and undergoes tyrosine phosphorylation in the gastric epithelial cells. Translocated CagA forms a physical complex with the SRC homology 2 domain (SH2)-containing tyrosine phosphatase SHP-2, which plays an important role in mitogenic signal transduction in the host cells.

AIM

We examined the effect of eradication therapy on the signal transduction pathway of gastric epithelial cells induced by the CagA protein of H. pylori.

METHODS

Gastric biopsy samples were obtained from 20 H. pylori-positive atrophic gastritis patients before, and 3 months after, H. pylori infection eradication therapy, and subjected to immunoblot analysis to detect tyrosine phosphorylated CagA protein and CagA co-immunoprecipitated endogenous SHP-2.

RESULTS

Tyrosine phosphorylated CagA protein and CagA co-immunoprecipitated endogenous SHP-2 were detected in the gastric mucosa from H. pylori-positive atrophic gastritis patients. All H. pylori strains from these patients were cagA-positive type I strains. After curing H. pylori infection, the tyrosine phosphorylated CagA protein and CagA co-immunoprecipitated endogenous SHP-2 disappeared from the gastric mucosa.

CONCLUSION

The cure of infection reduces the stimulated signal transduction of gastric epithelial cells by the translocated CagA protein of H. pylori, and may confer a beneficial effect on the reduction of cancer risk.

Animal models of Helicobacter pylori infection and disease

The acceptance of Helicobacter pylori as a major human pathogen has necessitated the development of animal models to help elucidate the pathogenic mechanisms of this bacterium and aid in the development of improved strategies for the treatment of gastric disease. Appropriate models, utilising a range of animal species, have been developed to examine factors such as the influence of host responses and bacterial factors in disease development and the success of new therapeutic regimens, including vaccination, to cure infection.

Functional and morphological aspects of Helicobacter pylori-induced gastric cancer in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection of Mongolian gerbils is an established model of gastric carcinogenesis, but gastric secretory aspects of this carcinogenesis have not been studied.

METHODS

The effects of single intragastric inoculation of gerbils with H. pylori strain (cagA+ vacA+, 5 x 10(6) CFU/ml) or vehicle (saline) were examined at 1, 2, 4, 6, 9, 12 and 30 weeks from inoculation. Gastric morphology, the presence of H. pylori using the rapid urease test, the density of H. pylori and 16S rRNA and the plasma gastrin and somatostatin were determined.

RESULTS

H. pylori was detected in gastric mucosa in all infected animals. Basal gastric acid in gerbils was reduced by about 50% after H. pylori inoculation. Early lesions seen at 4 weeks after H. pylori inoculation consisted of chronic gastritis with thickened mucosal folds, oedema, congestion and mucosal lymphocytic infiltration. Adenomatous hyperplasia with cellular atypia with increased mitotic activity and the formation of apoptotic bodies and visible erosions and ulcerations were observed at 12-30 weeks after inoculation. The atypical gastric glands were situated 'back-to-back', suggesting gastric pre-cancer. The gastric blood flow in H. pylori-infected gerbils was significantly lower than that in the controls. Six- to seven-fold increase in plasma gastrin levels combined with significant fall in gastric somatostatin contents and the intraepithelial neoplasia were noticed in gerbils at all tested periods.

CONCLUSION

H. pylori-infection in gerbils resulted in gastric pre-cancer associated with functional changes, such as suppression of gastric secretion and impairment of both gastric mucosal microcirculation and the gastrin-somatostatin link.

Suppressed apoptosis in the inflamed gastric mucosa of Helicobacter pylori-colonized iNOS-knockout mice

Deregulated cell turnover in Helicobacter pylori (H. pylori)-colonized gastric mucosa has been suggested to be linked to the gastric carcinogenesis pathway. We previously reported attenuation of apoptosis and enhancement of cellular proliferation in the H. pylori-colonized gastric mucosa of Mongolian gerbils as compared to that in mice, which might reflect a specific link between H. pylori colonization and carcinogenesis in the Mongolian gerbils; the difference between the two strains could be attributable to differences in the host genetic background. Inducible-type nitric oxide synthase (iNOS) is thought to participate in not only the inflammatory response, but also in the regulation of gastric mucosal cell turnover in H. pylori-colonized gastric mucosa. Thus, the present study was designed to examine gastric leukocyte activation and epithelial cell apoptosis in the gastric mucosa following H. pylori inoculation in iNOS-knockout mice.

METHODS

iNOS-knockout mice (iNOS(-/-)) and their iNOS(+/+) littermates were orally inoculated with the Sydney strain of H. pylori (SS1, 10(8) colony-forming units [CFU]). H. pylori infection was confirmed by microaerobic bacterial culture. The stomach of each mouse was evaluated 14 weeks and 30 weeks after the inoculation. Gastric mucosal accumulation of polymorphonuclear leukocytes (PMN) was assessed by determining the myeloperoxidase (MPO) activity and histological score based on the updated Sydney system. The level of apoptosis was determined by estimation of the cytoplasmic levels of mono- and oligonucleosomes and by the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method.

RESULTS

The SS1-inoculated mice showed persistent H. pylori colonization for 12 weeks. While gastric mucosal PMN infiltration increased following SS1 inoculation in both iNOS(+/+) and iNOS(-/-)strains, enhanced DNA fragmentation was observed in only SS1-colonized iNOS(+/+) mice, and not in the iNOS(-/-) mice. In conclusion, although the recruitment of PMN in response to H. pylori was evoked even in the gastric mucosa of iNOS(-/-) mice, epithelial cell apoptosis induced by H. pylori was attenuated in this strain. These data suggest that iNOS may play an important role in promoting apoptosis in the H. pylori-infected inflamed gastric mucosa, and that persistent inflammation without apoptosis in iNOS(-/-) mice with H. pylori infection may be linked to preneoplastic transformation.

CagA tyrosine phosphorylation in gastric epithelial cells caused by Helicobacter pylori in patients with gastric adenocarcinoma

BACKGROUND

Tyrosine phosphorylation of Helicobacter pylori cytotoxin-associated protein of in gastric epithelial cells is reported. The goals of this study are first to examine the occurrence of CagA tyrosine phosphorylation in H. pylori strains isolated from patients with gastric adenocarcinoma and gastritis, and second to clarify the relationship between the diversity of tyrosine phosphorylation motifs and the presence of CagA tyrosine phosphorylation.

METHODS

Fifty-eight clinical isolates of H. pylori from patients with gastric adenocarcinoma (29 cases) and gastritis (29 cases) were studied for CagA tyrosine phosphorylation by Western blotting. Sequence diversity of tyrosine phosphorylation motifs was analysed among positive- or negative-CagA tyrosine phosphorylation isolates.

RESULTS

Positive CagA tyrosine phosphorylation was found in 93.1% (27 of 29) of strains from gastric adenocarcinoma patients and 51.7% (15 of 29) of strains from gastritis patients (p < 0.001). Intact motifs were found in H. pylori isolates with CagA tyrosine phosphorylation. Of the 16 negative CagA tyrosine phosphorylation isolates, intact tyrosine phosphorylation motifs were found in 15 isolates.

CONCLUSIONS

CagA tyrosine phosphorylation, which is significantly greater in strains from gastric adenocarcinoma patients, may play a role in gastric carcinogenesis, and could be a better marker of more virulent strains than the cag pathogenicity island in Asia, where the cag pathogenicity island is present in nearly all H. pylori strains. Sequence diversity of tyrosine phosphorylation motifs on CagA was not related to the presence of tyrosine phosphorylation. The absence of tyrosine phosphorylation motif might result in negative tyrosine phosphorylation phenotypes, but such motifs are not the sole factors associated with CagA tyrosine phosphorylation.

In vitro and in vivo anti- Helicobacter pylori activity of Y-904, a new fluoroquinolone

Y-904 is a new fluoroquinolone with a broad antimicrobial spectrum. In particular, it has anti- Helicobacter pylori activity superior to that of existing fluoroquinolones. In the present study it was examined for its in vitro antibacterial activity against 51 clinical isolates of H. pylori, including clarithromycin- and metronidazole-resistant strains. The minimum inhibitory concentration of Y-904 at which 90% of isolates were inhibited was close to that of amoxicillin and clarithromycin and lower than that of levofloxacin and metronidazole (0.1, 0.1, 0.2, 3.13, and 12.5 micrograms/ml, respectively). Y-904 showed equally strong activity at pH 5.5 as at pH 7.0. At 10 times the minimum inhibitory concentration, Y-904 decreased the viable count of H. pylori to below 10(-5) within 2 h after exposure. No significant change in the minimum inhibitory concentration was observed when H. pylori, Staphylococcus aureus, and Escherichia coli were successively subcultured in medium containing subinhibitory concentrations of Y-904. Y-904 also strongly inhibited the supercoiling activity of DNA gyrase from H. pylori ATCC43504 (IC(50), 1.48 micrograms/ml). A study of Y-904 treatment in H. pylori-infected Mongolian gerbils using twice-daily oral administration for 7 days demonstrated that the complete clearance dose of Y-904 was 1 mg/kg and that its potency was around 10, 30, and 30 times that of amoxicillin, clarithromycin, and levofloxacin, respectively. These results indicate that Y-904 is a promising candidate for the eradication of H. pylori infection.

Review article: molecular basis of gastric carcinogenesis

Gastric cancer is constituted by two histomorphological entities 'intestinal' and 'diffuse', however lesions with similar morphologies may differ in biological aggressiveness and response to therapy. Two distinct molecular pathways have been identified in gastric carcinogenesis: the microsatellite mutator phenotype and a phenotype associated with chromosomal and intrachromosomal instability. Mounting evidence suggests that microsatellite mutator phenotype alterations and expression of the products of cancer-related genes are early markers of cell transformation, and may serve to identify the gastric carcinoma histotypes. The lack of a clear genetic basis, lends weight to the notion that gastric cancer is not a monomorphic entity but may be affected by environmental factors. Helicobacter pylori is the most important environmental risk factor associated with sporadic gastric cancer. Exposure of gastric epithelial cells to bacterium results in the generation of reactive oxygen species and inducible nitric oxide synthase that in turn may cause genetic alterations leading to cancer in a subset of subjects. Thus, gastric cancer may be considered the result of an interplay between host genetic profile and environmental toxic agents. The new technologies of molecular analysis will help to establish an individual's risk of developing gastric cancer and will lead to novel biological therapeutic strategies.

Host and microbial constituents influence Helicobacter pylori-induced cancer in a murine model of hypergastrinemia

BACKGROUND & AIMS

Helicobacter pylori cag(+) strains and high-expression host interleukin 1beta (IL-1beta) polymorphisms augment the risk for intestinal-type gastric adenocarcinoma, a malignancy that predominates in males. We examined the effects of an H. pylori cancer-associated determinant (cagE), IL-1beta, and host gender in a transgenic hypergastrinemic (INS-GAS) murine model of gastric carcinogenesis.

METHODS

Male and female INS-GAS mice infected with wild-type H. pylori, an H. pylori cagE(-) mutant, or H. felis were killed 2-24 weeks postchallenge. Gastric injury was scored from 0 to 4, and mucosal IL-1beta levels were quantified by ELISA.

RESULTS

Male INS-GAS mice infected with H. pylori uniformly developed atrophy, intestinal metaplasia, and dysplasia by 6 weeks and carcinoma by 24 weeks. Mucosal IL-1beta concentrations increased 12 weeks following Helicobacter challenge, but levels then decreased by 24 weeks. Inactivation of cagE delayed the progression to carcinoma, but neoplasia ultimately developed in all males infected with the H. pylori mutant. In contrast, none of the H. pylori-infected female mice developed cancer, and injury scores, but not IL-1beta levels, were significantly higher in males compared with females.

CONCLUSIONS

H. pylori infection induces gastric adenocarcinoma in an experimental mouse model of disease. Cancer is restricted to males and loss of cagE temporally retards but does not abrogate pathologic progression. Mucosal levels of IL-1beta increase prior to the development of gastric cancer but are not related to gender. The INS-GAS model is effective for investigating discrete host-microbial interactions that culminate in gastric cancer within the context of biologic conditions induced by H. pylori.

Five month persistence of Helicobacter pylori infection in guinea pigs

Seven Dunkin-Hartley guinea pigs were infected with the Sydney strain of H. pylori (SS1). Gastric histopathology was evaluated and serum antibody response to H. pylori cell-surface proteins was analysed by enzyme immunoassay (EIA) and immunoblot. Tissue and faecal samples from five control animals were analysed for the presence of naturally occurring Helicobacter spp. infection by culture and Helicobacter genus-specific PCR. The H. pylori infection persisted for 5 months, in most animals accompanied by a histologically severe antral gastritis, exhibiting focal degeneration and necrosis of gastric crypt epithelium. Increased numbers of mitotic figures were observed in the gastric epithelium, indicating a regenerative process. Infected animals displayed specific antibodies towards H. pylori cell-surface proteins in immunoblot, whereas EIA was of dubious value creating false-positive results. Serum complement C3 and cholesterol levels appeared to be elevated in infected animals. Helicobacter spp. infection was not detected in the control animals. The persistent infection, accompanied by severe gastritis and a prominent serum antibody response, and the apparent absence of a natural Helicobacter spp. infection makes the guinea pig model useful in H. pylori research.