Modes of Helicobacter colonization and gastric epithelial damage

Evaluation of Immunohistochemical Expression of Heparanase in Helicobacter pylori-Associated Chronic Gastritis

Background

Chronic gastritis (CG) is a very common disease. More than half of the worldwide population suffers from symptoms of CG. This disease has received great attention since the discovery of H. pylori as the most important cause of CG. Symptoms experienced by patients with CG are attributed to H. pylori-induced inflammatory reactions. Heparanase (HPSE) is a mammalian β-endoglucoronidase. In inflammation; HPSE degrades and remodels the extracellular matrix's heparan sulfate polysaccharide chains liberating heparan sulfate-bound cytokines and chemokines, HPSE also facilitates movement of inflammatory cells.

Aims

This study aimed to detect the function of HPSE in CG by correlating levels of HPSE expression with histopathological features of CG, including H. pylori infection, acute and chronic inflammatory cells, mucosal atrophic and/or metaplastic features.

Methods

Ninety-five upper endoscopic-guided gastric punch biopsies were enrolled in this study. From each specimen, formalin-fixed and paraffin-embedded tissue blocks were prepared. Tissue sections were stained by Hematoxylin and eosin, Giemsa, and anti-heparanase antibody.

Results

HPSE expression was statistically associated with H. pylori infection (P-value < .000), and intensity of chronic lymphocytic inflammatory infiltrate in the gastric mucosal tissues (P = .004). High levels of HPSE expression were also related to the presence of neutrophils in the gastric surface epithelium and lamina propria (P-value < .009).

Conclusions

HPSE expression was upregulated in H. pylori-associated chronic gastritis. Thus, future therapeutic agents that could specifically inhibit HPSE enzyme activity, may aid in the reduction of sequelae of H. pylori infection.

Rumen epithelial transcriptome and microbiome profiles of rumen epithelium and contents of beef cattle with and without liver abscesses

Abscess is the highest cause of liver condemnation and is estimated to cost the beef industry US$64 million annually. Fusobacterium necrophorum, commonly found in the bovine rumen, is the primary bacteria associated with liver abscess in cattle. Theoretically, damage to the rumen wall allows F. necrophorum to invade the bloodstream and colonize the liver. The objective of this study was to determine the changes in gene expression in the rumen epithelium and microbial populations adherent to the rumen epithelium and in the rumen contents of beef cattle with liver abscesses compared with those with no liver abscesses. Rumen epithelial tissue and rumen content were collected from 31 steers and heifers with liver abscesses and 30 animals with no liver abscesses. Ribonucleic acid (RNA) sequencing was performed on the rumen epithelium, and a total of 221 genes were identified as differentially expressed in the animals with liver abscesses compared with animals with no abscesses, after removal of genes that were identified as a result of interaction with sex. The nuclear factor kappa-light-chain enhancer of activated B cells signaling and interferon signaling pathways were significantly enriched in the differentially expressed gene (DEG) set. The majority of the genes in these pathways were downregulated in animals with liver abscesses. In addition, RNA translation and protein processing genes were also downregulated, suggesting that protein synthesis may be compromised in animals with liver abscesses. The rumen content bacterial communities were significantly different from the rumen wall epimural bacterial communities. Permutational multivariate analysis of variance (PERMANOVA) analysis did not identify global differences in the microbiome of the rumen contents but did identify differences in the epimural bacterial communities on the rumen wall of animals without and with liver abscesses. In addition, associations between DEG and specific bacterial amplicon sequence variants of epimural bacteria were observed. The DEG and bacterial profile on the rumen papillae identified in this study may serve as a method to monitor animals with existing liver abscesses or to predict those that are more likely to develop liver abscesses.

Clinicopathological characteristics of invasive gastric Helicobacter pylori

Helicobacter pylori organisms have been observed deep within the stomach mucosa with an "intracellular" appearance, although the clinicopathological characteristics of such cases remain poorly understood. We analyzed 18 cases of deep mucosal H pylori and associated clinical (sex, age, history of H pylori infection, or proton pump inhibitor [PPI] use, medications, smoking, alcohol use, comorbidities, treatment response) and pathological (presence of lymphoid aggregates, intestinal metaplasia, PPI effect, active and/or chronic inflammation, quantity of invasive versus surface H pylori) characteristics. Electron microscopy was performed on 6 cases with the highest burden of invasive H pylori. Within our sample, 3 of 16 had a history of H pylori infection, 10 of 15 were receiving PPIs at the time of biopsy, and 12 of 13 had a negative posttreatment follow-up. Histology revealed that invasive H pylori were more commonly associated with chronic inflammation, in both the antrum (15/15 chronic, 8/15 acute) and fundus (17/18 chronic, 8/18 acute). Electron microscopy showed organisms within intercellular and luminal spaces, but no intracellular organisms. Deep mucosal H pylori often have an intracellular appearance but are contained within intercellular and luminal spaces and are responsive to standard therapy.

Helicobacter pylori antigen HP0986 (TieA) interacts with cultured gastric epithelial cells and induces IL8 secretion via NF-κB mediated pathway

BACKGROUND

The envisaged roles and partly understood functional properties of Helicobacter pylori protein HP0986 are significant in the context of proinflammatory and or proapoptotic activities, the two important facilitators of pathogen survival and persistence. In addition, sequence analysis of this gene predicts a restriction endonuclease function which remained unknown thus far. To evaluate the role of HP0986 in gastric inflammation, we studied its expression profile using a large number of clinical isolates but a limited number of biopsies and patient sera. Also, we studied antigenic role of HP0986 in altering cytokine responses of human gastric epithelial (AGS) cells including its interaction with and localization within the AGS cells.

MATERIALS AND METHODS

For in vitro expression study of HP0986, 110 H. pylori clinical isolates were cultured from patients with functional dyspepsia. For expression analysis by qRT PCR of HP0986, 10 gastric biopsy specimens were studied. HP0986 was also used to detect antibodies in patient sera. AGS cells were incubated with recombinant HP0986 to determine cytokine response and NF-κB activation. Transient transfection with HP0986 cloned in pEGFPN1 was used to study its subcellular localization or homing in AGS cells.

RESULTS

Out of 110 cultured H. pylori strains, 34 (31%) were positive for HP0986 and this observation was correlated with in vitro expression profiles. HP0986 mRNA was detected in 7 of the 10 biopsy specimens. Further, HP0986 induced IL-8 secretion in gastric epithelial cells in a dose and time-dependent manner via NF-κB pathway. Serum antibodies against HP0986 were positively associated with H. pylori positive patients. Transient transfection of AGS cells revealed both cytoplasmic and nuclear localization of HP0986.

CONCLUSION

HP0986 was moderately prevalent in clinical isolates and its expression profile in cultures and gastric biopsies points to its being naturally expressed. Collective observations including the induction of IL-8 via TNFR1 and NF-κB, subcellular localization, and seropositivity data point to a significant role of HP0986 in gastroduodenal inflammation. We propose to name the HP0986 gene/protein as 'TNFR1 interacting endonuclease A (TieA or tieA)'.

Disease manifestations of Helicobacter pylori infection in Arctic Canada: using epidemiology to address community concerns

OBJECTIVES

Helicobacter pylori infection, linked to gastric cancer, is responsible for a large worldwide disease burden. H pylori prevalence and gastric cancer rates are elevated among indigenous Arctic communities, but implementation of prevention strategies is hampered by insufficient information. Some communities in northern Canada have advocated for H pylori prevention research. As a first step, community-driven research was undertaken to describe the H pylori-associated disease burden in concerned communities.

DESIGN

Participants in this cross-sectional study completed a clinical interview and gastroscopy with gastric biopsies taken for histopathological examination in February 2008.

SETTING

Study procedures were carried out at the health centre in Aklavik, Northwest Territories, Canada (population ∼600).

PARTICIPANTS

All residents of Aklavik were invited to complete a clinical interview and gastroscopy; 194 (58% female participants; 91% Aboriginal; age range 10-80 years) completed gastroscopy and had gastric biopsies taken.

PRIMARY AND SECONDARY OUTCOME MEASURES

This analysis estimates the prevalence of gastric abnormalities detected by endoscopy and histopathology, and associations of demographic and clinical variables with H pylori prevalence.

RESULTS

Among 194 participants with evaluable gastric biopsies, 66% were H pylori-positive on histology. Among H pylori-positive participants, prevalence was 94% for acute gastritis, 100% for chronic gastritis, 21% for gastric atrophy and 11% for intestinal metaplasia of the gastric mucosa, while chronic inflammation severity was mild in 9%, moderate in 47% and severe in 43%. In a multivariable model, H pylori prevalence was inversely associated with previous gastroscopy, previous H pylori therapy and aspirin use, and was positively associated with alcohol consumption.

CONCLUSIONS

In this population, H pylori-associated gastric histopathology shows a pattern compatible with elevated risk of gastric cancer. These findings demonstrate that local concern about health risks from H pylori is warranted and provide an example of how epidemiological research can address health priorities identified by communities.

Gastric exocrine and endocrine cell morphology under prolonged acid inhibition therapy: results of a 5-year follow-up in the LOTUS trial

BACKGROUND

Sustained acid inhibition with PPI stimulates gastrin secretion, exerting a proliferative drive on enterochromaffin-like cells (ECL cells) of the oxyntic mucosa. It may also accelerate development of gastric gland atrophy in Helicobacter pylori-infected individuals.

AIMS

To evaluate gastric exocrine and endocrine cell changes in GERD patients randomised to laparoscopic antireflux surgery (LARS, n = 288) or long-term (5 years) esomeprazole (ESO) treatment (n = 266).

METHODS

Antral and corpus biopsies were taken at endoscopy and serum gastrin and chromogranin A levels were assayed, at baseline and after 1, 3 and 5 years' therapy.

RESULTS

Biopsies were available at each time point for 158 LARS patients and 180 ESO patients. In H. pylori-infected subjects, antral mucosal inflammation and activity improved significantly (P < 0.001) and stabilised after 3 years on esomeprazole while no change in inflammation was observed after LARS. Oxyntic mucosal inflammation and activity remained stable on esomeprazole but decreased slightly over time after LARS. Neither intestinal metaplasia nor atrophy developed in the oxyntic mucosa. ECL cell density increased significantly after ESO (P < 0.001), corresponding with an increase in circulating gastrin and chromogranin A. After LARS, there was a significant decrease in ECL cell density (P < 0.05), accompanied by a marginal decrease in gastrin and chromogranin.

CONCLUSIONS

Antral gastritis improved in H. pylori-infected GERD patients after 5 years on esomeprazole, with little change in laparoscopic antireflux surgery patients, who acted as a control. Despite a continued proliferative drive on enterochromaffin-like cells during esomeprazole treatment, no dysplastic or neoplastic lesions were found and no safety concerns were raised. NCT 00251927.

Human lactoferrin increases Helicobacter pylori internalisation into AGS cells

Helicobacter pylori has high global infection rates and can cause other undesirable clinical manifestations such as duodenal ulcer (DU) and gastric cancer (GC). Frequencies of re-infection after therapeutic clearance and rates of DU versus GC vary geographically and differ markedly between developed and developing countries, which suggests additional factors may be involved. The possibility that, in vivo, lactoferrin (Lf) may play a subtle role in modulating micronutrient availability or bacterial internalisation with implications for disease etiology is considered. Lf is an iron binding protein produced in mammals that has antimicrobial and immunomodulatory properties. Some bacteria that regularly colonise mammalian hosts have adapted to living in high Lf environments and we investigated if this included the gastric pathogen H. pylori. We found that H. pylori was able to use iron from fully iron-saturated human Lf (hLf) whereas partially iron-saturated hLf (apo) did not increase H. pylori growth. Instead, apo-hLf increased adherence to and internalisation of bacteria into cultured epithelial cells. By increasing internalisation, we speculate that apo-human lactoferrin may contribute to H. pylori's ability to persistence in the human stomach, an observation that potentially has implications for the risk of H. pylori-associated disease.

In vivo accumulation of Helicobacter pylori products, NOD1, ubiquitinated proteins and proteasome in a novel cytoplasmic structure

Cell internalization and intracellular fate of H. pylori products/virulence factors in vivo by human gastric epithelium, the main target of H. pylori-induced pathologies (i.e., peptic ulcer and cancer), are still largely unknown. Investigating gastric endoscopic biopsies from dyspeptic patients by means of ultrastructural immunocytochemistry, here we show that, in human superficial-foveolar epithelium and its metaplastic or dysplastic foci, H. pylori virulence factors accumulated in a discrete cytoplasmic structure characterized by 13-nm-thick cylindrical particles of regular punctate-linear substructure resembling the proteasome complex in size and structure. Inside this particle-rich cytoplasmic structure (PaCS) we observed colocalization of VacA, CagA, urease and outer membrane proteins with NOD1 receptor, ubiquitin-activating enzyme E1, polyubiquitinated proteins, proteasome components and potentially oncogenic proteins like SHP2 and ERKs in human gastric epithelium. By means of electron and confocal microscopy, we demonstrate that the in vivo findings were reproduced in vitro by incubating human epithelial cell lines with H. pylori products/virulence factors. PaCSs differed from VacA-induced vacuoles, phagosomes, aggresomes or related bodies. Our data suggest that PaCS is a novel, proteasome-enriched structure arising in ribosome-rich cytoplasm at sites of H. pylori products accumulation. As a site of selective concentration of bacterial virulence factors, the ubiquitin-proteasome system and interactive proteins, PaCS is likely to modulate immune-inflammatory and proliferative responses of the gastric epithelium of potential pathologic relevance.

Indistinguishable cellular changes in gastric mucosa between Helicobacter pylori infected asymptomatic tribal and duodenal ulcer patients

AIM

To investigate the changing pattern of different histological parameters occurring in the stomach tissue of Helicobacter pylori (H pylori) infected tribal populations and duodenal ulcer patients among ethnic Bengalis and correlation of the genotypes of H pylori with different histological parameters.

METHODS

One hundred and twelve adult individuals were enrolled into this study between 2002 and 2004. Among them, 72 had clinical features of duodenal ulcer (DU) from ethnic Bengali population and 40 were asymptomatic ethnic tribals. Endoscopic gastric biopsy samples were processed for histology, genotyping and rapid urease test. Histologically, haematoxylin and eosin staining was applied to assess the pathomorphological changes and a modified Giemsa staining was used for better detection of H pylori. For intestinal metaplasia, special stainings, i.e. Alcian blue periodic acid-Schiff and high iron diamine-Alcian blue staining, were performed. PCR was performed on bacterial DNA to characterize the presence or absence of virulence-associated genes, like cagA, and distribution of different alleles of vacA and iceA.

RESULTS

Intraglandular neutrophil infiltration, a hallmark of activity of gastritis, was present in 34 (94%) of tribals (TRs) and 42 (84%) of DU individuals infected with H pylori. Lymphoid follicles and aggregates, which are important landmarks in H pylori infection, were positive amongst 15 (41%) of TRs and 20 (40%) of DU subjects. Atrophic changes were observed in 60% and 27.7%, respectively, among DU cases and tribals (P > 0.003). Metaplastic changes were detected in low numbers in both groups. Moderate to severe density distribution of H pylori in the gastric mucosa was 63% among TRs, whereas it was 62% in DU subjects. There were no significant differences in the distribution of virulence-associated genes like cagA, vacA and iceA of H pylori strains carried by these two populations.

CONCLUSION

Our study showed almost similar distribution of inflammatory cells among asymptomatic tribals and DU Bengali patients. Interestingly, the tribal population are free from any clinical symptoms despite evidence of active histologic gastritis and infection with H pylori strains carrying similar virulence markers as of strains isolated from patients with DU. There was an increased cellular response, especially in terms of neutrophil infiltration, but much lower risk of developing atrophy and metaplastic changes among the tribal population.

Prevalence of Helicobacter pylori infection, chronic gastritis, and intestinal metaplasia in Mozambican dyspeptic patients

We estimated the prevalence of Helicobacter pylori infection, chronic gastritis, atrophy, and intestinal metaplasia in dyspeptic patients from Maputo Central Hospital, Mozambique and evaluated the relationship between infection and histopathological features of chronic gastritis. Biopsies from 109 consecutive patients observed in 2005-2006 were collected from antrum, incisura angularis, and corpus for histopathological study according to the Modified Sydney system. H. pylori infection was assessed by histology and polymerase chain reaction. H. pylori prevalence was 94.5%. Chronic gastritis was the most frequent diagnosis (90.8%). Degenerative surface epithelial damage was associated with higher H. pylori density. Glandular atrophy (8.3%) and intestinal metaplasia (8.3%) were infrequent. Our results confirm previous observations in African countries with high prevalence of H. pylori infection and low rates of gastric cancer: high frequency of chronic H. pylori-associated gastritis with very low frequency of gastric atrophy and intestinal metaplasia.

Helicobacter pylori is invasive and it may be a facultative intracellular organism

The pathogenicity of many bacteria colonizing the gastrointestinal tract often depends on their ability to gain access to cells that are normally non-phagocytic. Helicobacter pylori colonizes the stomach of over half the world population and is the main cause of peptic ulcer disease and gastric cancer. It is generally considered to be a non-invasive pathogen present only in the lumen of the stomach and attached to gastric epithelial cells although a number of in vivo and in vitro studies have demonstrated that H. pylori is in fact invasive. In addition, H. pylori can repopulate the extracellular environment after complete elimination of extracellular bacteria with gentamicin, suggesting it may be considered a facultative intracellular bacterium. This review examines the validity of these observations and describes the evidence suggesting that the intracellular presence of H. pylori plays a role in the induction of diseases, in immune evasion, and in life-long persistence of the bacterium in the stomach of a majority of humans.

Intracellular, intercellular, and stromal invasion of gastric mucosa, preneoplastic lesions, and cancer by Helicobacter pylori

BACKGROUND AND AIMS

It is not clear how Helicobacter pylori, an apparently extracellular pathogen colonizing the luminal side of the gastric epithelium, invariably causes an immune-inflammatory response on the stromal side of the mucosa. Penetration of H pylori into epithelial cell lines and its interaction with immune-inflammatory cells have been documented in vitro. Several investigations also showed in vivo bacterial penetration into the epithelium up to the lamina propria; however, the identification as H pylori of the bacteria-like bodies observed in unchanged, metaplastic, or neoplastic mucosa remained sometimes questionable.

METHODS

To search for bacteria-like organisms, we used transmission electron microscopy on endoscopic biopsy specimens from 20 dyspeptic subjects and surgical specimens of neoplastic and nonneoplastic mucosa from 20 cancerous stomachs. To ascertain the H pylori nature of the organisms found, we used 6 different antibodies directed against bacterial lysates, purified vacuolating cytotoxin A, or purified cytotoxin-associated antigen A in immunogold tests. The results were compared with those of H pylori strains cultivated in vitro.

RESULTS

In nonmetaplastic gastric epithelium, cytochemically proven H pylori were detected, in the majority of cases, inside cytoplasm of epithelial cells, in intraepithelial intercellular spaces, and in underlying lamina propria, often in direct contact with immune-inflammatory cells and sometimes inside small blood vessels. Cytochemically proven H pylori were also observed inside 6 of 8 intestinal metaplasias and 9 of 20 cancers.

CONCLUSIONS

H pylori penetrates normal, metaplastic, and neoplastic gastric epithelium in vivo, intracellularly, or interstitially to cause a strong immune-inflammatory response and promote gastric carcinogenesis.

Urease activity does not reflect the degree of colonization by Helicobacter pylori in children

BACKGROUND

Urea breath test is an accurate method for the diagnosis of Helicobacter pylori infection in children. This test could estimate the bacterial load by measuring the urease activity in gastric mucosa. The aim of the study was to correlate the result of 13C-urea breath test (13C-UBT) and histological estimative for bacterial colonization and severity of inflammatory infiltrate.

METHODS

Forty-four patients (mean age 8.54 +/- 3.9 years) with dyspeptic symptoms were evaluated. Patients were evaluated through endoscopy and 13C-UBT. Helicobacter pylori infection was defined by histology, rapid urease test and 13C-UBT. Breath test results were expressed by delta over baseline (DOB) and urea hydrolysis rate (UHR). Test results were treated logarithmically for statistical analysis.

RESULTS

There was a significant inverse correlation between age and Log DOB (-0.501, P= 0.0005), but there was no relationship between Log UHR and age (-0.148, P= 0.336). The study did not find correlation between the breath test result and histological grades for mononuclear infiltrate, neutrophilic infiltrate and bacterial density.

CONCLUSION

The 13C-UBT does not estimate the severity of histological findings in children with Helicobacter pylori infection. The results of the breath test should be interpreted in a qualitative way.

Changes of gastric mucosal architecture during long-term omeprazole therapy: results of a randomized clinical trial

BACKGROUND

The impact of long-term acid suppression on the gastric mucosa remains controversial.

AIM

To report further observations on an established cohort of patients with gastro-oesophageal reflux disease, after 7 years of follow-up.

METHODS

Of the original cohort randomized to either antireflux surgery or omeprazole, 117 and 98 patients remained in the medical and surgical arms, respectively. Gastric biopsies were taken at baseline and throughout the study.

RESULTS

Fifty-three antireflux surgery and 39 omeprazole-treated patients had Helicobacter pylori infection at randomization. Eighty-three omeprazole-treated and 60 antireflux surgery patients remained H. pylori negative over the 7 years, and no change was observed in mucosal morphology except for a change in endocrine cell population (linear and diffuse hyperplasia, P = 0.03). During the 7-year study many patients, who were initially H. pylori infected, had the infection eradicated leaving only 13 omeprazole and 12 antireflux surgery patients still infected. In these patients, omeprazole induced a deterioration of the mucosal inflammation scores (P = 0.01) with a numerical increase of glandular atrophy.

CONCLUSIONS

Long-term omeprazole therapy does not alter the exocrine oxyntic mucosal morphology in H. pylori-negative patients, but mucosal endocrine cells appear to be under proliferative stimulation; in H. pylori-positive patients there are changes in mucosal inflammation and atrophy.

Concentrations of gastric mucosal cytokines in children with food allergy and Helicobacter pylori infection

AIM: To measure the concentrations of chosen cytokines in the antrum mucosa depending on the kind of harmful pathogenic factors and to compare the concentrations with the values of controls without allergy and coexisting Helicobacter pylori (H pylori) infection.

METHODS: The patients (97 children) were divided into three groups according to the data obtained from the case history, to the main cause of the disease and to the dominant clinical symptoms. Group I: children with food allergy (Fa); group II: children infected with H pylori; group III (control group): children with functional disorders of the alimentary tract (without Fa and Hp infection). H pylori infection was determined by the presence of anti-Hp antibodies in serum (ELISA method) and urease test performed during endoscopic examination. Cytokine concentration in homogenates of gastric mucosa was detected by ELISA method.

RESULTS: The IL-2 concentration in gastric mucosa bioptates was the highest in children with Hp infection (116.5±179.5 pg/mg of the protein) and Fa and Hp infection (98.1±101.0 pg/mg), while decreased in children with Fa (44.8±50.3 pg/mg) and controls (45.7±23.5 pg/mg). The lowest mean concentration of IFN-γ was observed in children with Hp infection (18.9±16.4 pg/mg), with Fa and Hp infection (25.5±27.7 pg/mg), with Fa (40.6±39.7 pg/mg) and controls (49.9±33.4 pg/mg). The highest IL-4 concentrations were observed in children with Hp infection (35.3±52.8 pg/mg) and in children with Fa and Hp infection (37.2±51.7 pg/mg), while lower IL-4 concentration (23.6±35.8 pg/mg) was found in children with Fa compared to the controls (22.7±13.8 pg/mg). The analysis of IL-4 concentrations in children with Hp infection regarding the intensity of gastritis showed the highest value (62.2±61.2 pg/mg) in mild and moderate gastritis. The concentrations of IL-5 in the gastric mucosa of children with or without Fa did not differ significantly and were comparable to the control group. The highest mean IL-8 value was observed in Hp-infected children with or without Fa. The highest concentration of mucosal IL-10 was detected in children with Hp infection (79.3±41.2 pg/mg) and decreased in children with Fa and Hp infection (50.1±18.8 pg/mg) and in children with Fa (39.9±35.5 pg/mg). The intensity and activity of the inflammation did not affect IL-10 concentrations in the gastric mucosa. In children with Hp infection, TNF-α concentration was the highest (45.9±49.3 pg/mg) and in children with Fa and Hp infection was low (45.3±32.6 pg/mg), whereas decreased in children with Fa (21.7±34.2 pg/mg) and in controls (31.6±14.5 pg/mg).

CONCLUSION: The morphological changes of the gastric mucosa in children with Hp infection are comparable to those in children with Fa and coexisting Hp infection. Cytokine concentration in children with Fa and Hp infection is significantly different in IFN-γ, IL-2, IL-8, and TNF-α.

Helicobacter pylori: an invading microorganism? A review

In this review we evaluate the pros and cons of Helicobacter pylori invasion of epithelial cells as part of the natural history of H. pylori infection. H. pylori is generally considered an extracellular microorganism. However, a growing body of evidence supports the controversial hypothesis that at least a subset of H. pylori microorganisms has an intracellular (intraepithelial) location. Most significant is the fact that H. pylori invades cultured epithelial cells with invasion frequencies similar to Yersinia enterocolitica and better than Shigella flexneri; furthermore, studies of invasion mechanisms suggest that H. pylori invasion of and survival within epithelial cells is not merely a passive event, but requires active participation of the microorganism. Although many studies of human gastric biopsy specimens have failed to demonstrate any intracellular H. pylori, some studies have revealed a minor fraction of H. pylori inside gastric epithelial cells, with possible linkage to peptic ulceration and epithelial cell damage. In conclusion, these data encourage further research to establish whether intracellular H. pylori does play a role in H. pylori colonization of the human stomach and in peptic ulcer pathogenesis.

Helicobacter pylori enter and survive within multivesicular vacuoles of epithelial cells

Although intracellular Helicobacter pylori have been described in biopsy specimens and in cultured epithelial cells, the fate of these bacteria is unknown. Using differential interference contrast (DIC) video and immunofluorescence microscopy, we document that a proportion of cell-associated H. pylori enter large cytoplasmic vacuoles, where they remain viable and motile and can survive lethal concentrations of extracellular gentamicin. Entry into vacuoles occurs in multiple epithelial cell lines including AGS gastric adenocarcinoma, Caco-2 colon adenocarcinoma and MDCK kidney cell line, and depends on the actin cytoskeleton. Time-lapse microscopy over several hours was used to follow the movement of live H. pylori within vacuoles of a single cell. Pulsed, extracellular gentamicin treatments show that the half-life of intravacuolar bacteria is on the order of 24 h. Viable H. pylori repopulate the extracellular environment in parallel with the disappearance of intravacuolar bacteria, suggesting release from the intravacuolar niche. Using electron microscopy and live fluorescent staining with endosomal dyes, we observe that H. pylori-containing vacuoles are similar in morphology to late endosomal multivesicular bodies. VacA is not required for these events, as isogenic vacA- mutants still enter and survive within the intravacuolar niche. The exploitation of an intravacuolar niche is a new aspect of the biological life cycle of H. pylori that could explain the difficulties in eradicating this infection.

Phenotypic and genotypic characterization of Helicobacter pylori from patients with and without peptic ulcer disease

BACKGROUND

Helicobacter pylori plays an important role in peptic ulcer disease, although not all H. pylori-infected persons will develop a peptic ulcer. Currently, H. pylori strains cannot be divided into commensals and pathogens.

METHODS

Fifty H. pylori strains were cultured from patients divided into five groups on the basis of upper endoscopic findings: gastric ulcer, duodenal ulcer, gastritis, esophagitis, or normal. The ultrastructural adherence pattern in vivo, autoagglutination, hemagglutination, adhesion to human gastric adenocarcinoma (AGS) cells, and the lipopolysaccharide (LPS) profile of H. pylori strains were recorded; randomly amplified polymorphic DNA (RAPD) and urease gene typing were performed and correlated with diagnostic groups.

RESULTS

Electron micrographs showed that H. pylori strains from patients with gastric ulcers adhered more frequently through filamentous strands and were less frequently found free in mucus than any other diagnostic group (P < 0.0001). Neither median hemagglutination titer nor median adhesion capacity to a human gastric adenocarcinoma cell line was related to endoscopic findings. Nevertheless, H. pylori strains from patients with gastric ulcers were more prone to autoagglutinate than were strains from the other diagnostic groups (P = 0.03). H. pylori strains from gastric ulcer patients were found to be more homogeneous, as determined by RAPD and urease gene typing, than strains from the other diagnostic groups (P < 0.01). In addition, a positive correlation was found between a patient's age and the adhesion to AGS cells of the patient's H. pylori strain (P = 0.006).

CONCLUSION

A combination of an H. pylori autoagglutination test, RAPD, and urease gene typing may be useful in separating gastric ulcer-related strains from duodenal ulcer-related and non-ulcer dyspepsia-related strains.

Serum IgG response to differentiated antigens of Helicobacter pylori

AIM: To detect antibodies against Helicobacter pylori spiral and coccoid antigens in human sera.

METHODS: Blood samples were collected from 278 patients with gastric diseases. A 3-day-old culture of H. pylori on chocolate blood agar was used to providespiral form. ‘Synchronous’ coccoids were cultured in (BHY) (brain heart infusion supplemented with 10% horse serum and 0.4% yeast extract) medium in a chemostat. Antigens from spiral and coccoid form were prepared using acid glycine extraction. Enzyme-linked immunosorbent assay (ELISA) was performed to detect serum IgG antibodies against spiral and coccoid forms of H. pylori.

RESULTS: Seroprevalence of H. pylori infection was higher in patients with gastric ulcer (79%) and gastric cancer (83%) than those with non-ulcer dyspepsia (NUD) (44%) and other diseases (45%) (P < 0.05). IgG antibodies against spiral and coccoid antigens were detected in 50.7% (141/278) and 49.6% (138/278), respectively.

CONCLUSION: The spiral and coccoid forms of H. pylori coexist in patients infected with the bacterium.

Helicobacter pylori (H. pylori) in gastric mucosa of children with abdominal complaints: immunohistochemistry detects antigen-reactive corpus mucosa cells

BACKGROUND

Previous morphological and serological studies of gastric Helicobacter pylori (H. pylori) colonization among Estonian children with abdominal complaints, as well as among populations of schoolchildren, have shown a high prevalence of H. pylori (49-60%). Based on published data concerning the high specificity and sensitivity of immunohistochemical detection of H. pylori, we examined the prevalence of H. pylori in gastric biopsy specimens of Estonian children by different localization and morphological type of gastritis comparing Giemsa staining with immunohistochemistry.

MATERIAL AND METHODS

Formalin-fixed biopsies (107 antral, 108 corpus mucosa) of 112 children (41 boys, 71 girls, age range 1-16 years, median age 12 years) with abdominal complaints were stained with hematoxylin & eosin and Giemsa stains, as well as examined using the peroxidase antiperoxidase (PAP) method with polyclonal antibodies to H. pylori.

RESULTS

Gastritis of any degree and localization was found in 84/112 (75%) children. Using Giemsa staining H. pylori were detected in 83/112 (74%) of all children, and by use of the PAP method in 55/112 (49%) (p = .001). Concordance of the results of immunohistochemical and Giemsa methods in antrum biopsies was 70%, in corpus biopsies 73%. In 12 out of 108 (11%) corpus mucosa specimens a positive staining with anti-H. pylori IgG was localized in the cytoplasma of corpus mucosal cells in the neck part of the glands.

CONCLUSIONS

The prevalence of H. pylori was higher when employing the Giemsa stain in comparison with immunohistochemistry. Antibody reactivity of cells in the neck part of the corpus glands may either be due to cross-reactivity of anti-H. pylori IgG with epithelial cell epitopes, or to internalization of H. pylori by these cells, suggesting a pathogenic role of neck cells in an anti-H. pylori immune response.

A novel flow cytometric assay for quantitating adherence of Helicobacter pylori to gastric epithelial cells

Adherence may be an important virulence factor for Helicobacter pylori. Current methods available for quantitation of adherence are time consuming and liable to observer error. A new direct technique for fluorescent labelling of bacteria has been developed to quantitate adherence of H. pylori to epithelial cells by fluorescence activated cell sorting (FACS). Type strains of H. pylori, H. mustelae, H. cinaedi and H. fennelliae were grown microaerobically in broth culture for 24 h and fluorescently labelled by incubation with carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) at 37 degrees C. After washing to remove excess CFDA-SE, bacteria were co-incubated (ratio 10:1) with gastric epithelial cells at 37 degrees C for up to 24 h. After washing to remove non-adherent bacteria, epithelial cells were detached with EDTA (2 mM) and fixed with formaldehyde for flow cytometry. Adherence was quantitated both in terms of the proportion of cells with adherent H. pylori and as the mean number of adherent bacteria per cell. All H. pylori strains adhered to gastric-type epithelial cells. The proportion of cells with bound bacteria varied from 40-99% and the number of bacteria per cell from 1-50, both of which correlated with microscopy (r = 0.6, and r = 0.8 respectively, n = 35). Time course studies demonstrated saturation of binding by H. pylori within 90 min. For H. mustelae, H. cinaedi and H. fennelliae the proportion of cells with bound bacteria varied from 5-15% and the mean number of bacteria per cell was < 4. Binding of H. pylori to epithelial cells could be partly blocked by pre-incubation with polyclonal anti-sera or using oligosaccharides against potential binding epitopes of gastric mucus. Fluorescent labelling of H. pylori with CFDA-SE in combination with flow cytometry provides a quick, specific, and sensitive method to quantitate in vitro the adherence of H. pylori.

Consequences of attachment of Helicobacter pylori to gastric cells

Helicobacter pylori, a human pathogen and type 1 carcinogen, causes gastritis, gastric ulcers and gastric cancer. In vivo, H pylori colonizes only gastric surface cells from the antral and fundal regions of the stomach, and heterotopic or metaplastic gastric epithelium present within the esophagus and duodenum. This review summarizes what is known about the association and consequences of attachment between H pylori and gastric cells in vitro, and compares this to the findings demonstrated in vivo. It has been shown that attachment of H pylori to gastric cells results in cup and pedestal formation and cytoskeleton rearrangement similar to that described for enteropathogenic Escherichia coli. Attachment of H pylori induces additional cellular changes in the host cell, including cytokine responses and induction of signal transduction pathways.

Is the study of human cancer-associated factors, the best or the only model for human carcinogenesis research? I. The question of Helicobacter pylori infection as an accused human gastric carcinogen

Experimental carcinogenesis has discovered and analyzed the inductive effect for one type of cancer, of single factors in given animal strains. Human carcinogenesis analyses the effect of associated factors on one cancer type incidence. It does not find any direct correlation and finds a lot of intermediary effects and mechanism between the factor and established carcinogenesis. Regarding Helicobacter pylori (HP), one realizes there is no statistical correlation between gastric infection and carcinoma. The only data which sustain its role is its possible effect in promoting atrophic gastritis with intestinal metaplasia, via the serum pepsinogen 1 reduction due to anti-HP immunoglobulin A (IgA) antibody. Intestinal metaplasia of the stomach is a condition increasing cell proliferation.

Helicobacter pylori in children

Helicobacter pylori is the major cause of antral gastritis in children, however, it is not always associated with symptoms. The exception to this occurs in duodenal ulcer disease with which H. pylori is linked in children albeit less strongly than in adults. Duodenal ulcers do not recur in older children following eradication of H. pylori. The importance of asymptomatic carriage of H. pylori in children, particularly in relation to the duration of this infection and the subsequent development of gastric cancer, remain to be established. Helicobacter pylori is associated with both hypochlorhydria and persistent diarrhoea in children in developing countries, but the significance of this association is still unknown. Although there is no consensus on the optimal regimen for treating H. pylori infection in children, dual therapy with amoxycillin and bismuth subcitrate for 2 weeks followed by monotherapy with bismuth subcitrate for a further 6 weeks will eradicate H. pylori infection in the majority of children. Those who relapse may be treated with a repeat course plus metronidazole for 4 weeks. Compliance with such regimens is a problem and shorter treatment courses that are equally effective in children need to be defined. Similarly, studies are required on the influence of the intrafamilial reservoir of H. pylori infection on relapse after treatment and the need for whole family eradication therapy.

Future research in peptic ulcer disease

For the past 10 years, research into peptic ulcer disease has focused on the surprising suggestion that gastritis and peptic ulcers may be caused by the bacterium Helicobacter pylori. However, the time has now come to reappraise research directions, as a causal link has been established, and even the most ardent sceptics now accept that H. pylori infection is the major factor in most cases of peptic ulcer disease. As with any established microbial disease, we need to understand the epidemiology and mechanisms of pathogenesis, but the major focus should be towards improving therapies and defining the long-term outcome of H. pylori eradication. To devise novel therapeutic agents effectively, we must increase our knowledge of the basic physiology of H. pylori and its ecology in the stomach. This has been a surprisingly neglected area of research and major questions remain. Why does the organism flourish in different areas of the gastric mucosa when gastric pH is increased? Is a change in pH the reason for the potentiating effects of acid-inhibitory agents on anti-H. pylori activity? Will knowledge of the host and bacterial factors that initiate ulcerogenesis allow us to better predict H. pylori-associated ulcers by using non-invasive methods? As H. pylori is a major gastroduodenal pathogen, can we eliminate the infection from selected populations? What are the criteria that will allow therapeutic intervention? The first steps have been taken in the development of an effective vaccine, but who should be immunized?(ABSTRACT TRUNCATED AT 250 WORDS)

Helicobacter pylori: microbiology of a 'slow' bacterial infection

The bacterium Helicobacter pylori lives in the gastric mucus layer of humans and induces a chronic inflammatory response that can result in both peptic ulceration and gastric neoplasms. Helicobacter pylori infection can be considered as a 'slow', adaptive and autoregulating process. The mechanisms by which this slow bacterial pathogen survives and interacts with the host immune system may provide a model for other persistent mucosal pathogens.