babA2- and cagA-positive Helicobacter pylori strains are associated with duodenal ulcer and gastric carcinoma in Brazil

Prevalence of Helicobacter pylori cagA, iceA and babA2 alleles in Brazilian patients with upper gastrointestinal diseases

Helicobacter pylori is an important human pathogen associated with gastrointestinal diseases such as gastritis, gastric and duodenal ulcer (peptic ulcer disease, PUD), and gastric cancer. A number of pathogenic factors have been described for this bacterium, and some of them have been proposed as markers for the prediction of the clinical outcome. However, with the exception of the cag and vacA status, there is no universal consensus regarding the importance of the other virulence factors. Therefore, the aim of this study was to investigate the status of H. pylori strains regarding the babA and iceA alleles, as well as the cagA genotype, to reveal any association between these genotypes and clinical outcomes in Brazilian patients. The great majority (92.6%) of the strains were typed as iceA1, while 40.4% were found to possess the babA2 allele. The cagA gene was detected in 73.4% of the strains. The iceA2 and cagA genotypes were associated with PUD, while iceA1 was negatively correlated with PUD. However, considering the high percentage of strains typed as iceA1, these associations must be treated with caution. No clinical entity was associated with the babA2 allele. These results suggest that iceA1 is not a good marker for the diseases associated with H. pylori infection in Brazil. Further studies are needed in order to elucidate the relevance of the babA status, because other studies performed in Brazil have associated the babA2 allele with clinical outcomes. These results also indicate the existence of regional differences in the H. pylori genotypes and their association with clinical outcomes.

Progressive proliferative and dysplastic typhlocolitis in aging syrian hamsters naturally infected with Helicobacter spp.: a spontaneous model of inflammatory bowel disease

Helicobacter spp. have been implicated in a variety of gastrointestinal tract diseases, including peptic ulcer disease, gastric cancer, and inflammatory bowel disease (IBD), in humans and animals. Although most models of IBD are experimentally induced, spontaneous or natural models of IBD are rare. Herein, we describe a long-term study of chronic, progressive lesions that develop in the distal portion of the large bowel of unmanipulated Syrian hamsters naturally infected with Helicobacter spp. Twenty-four Syrian hamsters of three age groups (group A, 1 month [n = 4], group B, 7-12 months [n = 12], group C, 18-24 months [n = 12]), underwent complete postmortem examination. Results of microbial isolation and polymerase chain reaction and restriction fragment length polymorphism analyses confirmed the presence of Helicobacter spp. infection in the distal portion of the large bowel of all animals. Additionally, confounding pathogens, such as Clostridium difficile, Lawsonia intracellularis, and Giardia spp. that can cause proliferative enteritis, were absent in the hamsters of this study. Histopathologic scores for inflammation (P < 0.01), hyperplasia (P < 0.01), and dysplasia (P < 0.05) were significantly higher in the ileocecocolic (ICC) junction of animals in group C, relative to group A. Dysplastic lesions of various grades were detected in 5 of 11 hamsters in group C. Interestingly, the segment of the bowel that is usually colonized by Helicobacter spp. in hamsters had the most severe lesions. One hamster of group C developed a malignant fibrous histiocytoma, whereas another hamster developed a round cell sarcoma originating from the ICC junction. Thus, lesions in the distal portion of the large bowel of aging hamsters naturally colonized with Helicobacter spp. warrants developing the hamster as an animal model of IBD and potentially IBD-related cancer.

No correlation of babA2 with vacA and cagA genotypes of Helicobacter pylori and grading of gastritis from peptic ulcer disease patients in Brazil

BACKGROUND

The babA2 gene, which encodes a blood-group antigen-binding adhesin that mediates attachment of Helicobacter pylori to human Lewis(b) antigens on gastric epithelial cells, has been associated with a higher risk of peptic ulcer and gastric cancer. The purpose of this study was to ascertain the frequency of babA2 genotype in H. pylori strains of patients with peptic ulcer and to correlate with other virulence factors.

MATERIALS AND METHODS

vacA, cagA, and babA2 genotypes of H. pylori were determined by using polymerase chain reaction (PCR). DNA was extracted from positive urease test gastric samples of 150 patients with peptic ulcer. Antrum and corpus biopsies were taken for histologic examination according to the updated Sydney system classification.

RESULTS

babA2 genotype was present in 104 (69.3%) and cagA in 113 (75.3%) gastric samples. No significant correlation was observed between babA2 and vacAs1 genotype or between babA2 and cagA status. The correlation of vacAs1 genotype with positive cagA was statistically significant ( p < .001). The babA2-positive strain was more frequently found from the gastric samples of men, than of women (p = .01). Strains harboring cagA, vacAs1, and babA2 genotypes had no association to the grading of gastritis, presence of glandular atrophy, or intestinal metaplasia. The simultaneous presence of cagA, vacAs1, and babA2 was found in 32.6% of the H. pylori strains.

CONCLUSIONS

babA2 genotype is frequently found in H. pylori strains from peptic ulcer disease in Brazil, although it has no significant correlation to the worsening of the gastritis and to other virulence markers such as vacAs1 and cagA.

A candidate gene approach of immune mediators effecting the susceptibility to and severity of upper gastrointestinal tract diseases in relation to Helicobacter pylori and Epstein-Barr virus infections

This review focuses on immunogenetic aspects of diseases of the upper gastrointestinal tract in which infectious agents may play a role in the aetiopathogenesis, such as Helicobacter pylori, Epstein-Barr virus (EBV) and HIV. Gastric adenocarcinoma is a common cancer all around the world, with declining incidences in Europe and high incidences in Asia and central and south America. Together with gastric atrophy and peptic ulcer disease, gastric adenocarcinoma belongs to the commonest upper gastrointestinal tract diseases. These diseases are multifactorial and factors such as smoking and dietary habits contribute to the pathogenesis. More recently, scientists have turned their eyes on the host. Functional polymorphisms in the genes regulating the host immune system may contribute to the susceptibility to and progression of disease. In multifactorial and polygenetic diseases, candidate gene studies of single nucleotide polymorphisms (SNPs) detect small to moderate relative risks. Unfortunately, only a few functional SNPs have been identified. The candidate gene approach can be seen as a useful first step in exploring causal pathways between genetic determinants and complex diseases such as those mentioned above. To date, little is known about the immunogenetics of upper gastrointestinal tract diseases. We review the literature on H. pylori, EBV and gene polymorphisms that affect key immune mediators influencing the pathogenesis of the inflammatory response, such as the genes that code for the IL-1 family, TNF-alpha, lymphotoxin alpha, and IL-10. IL-1, IL-10, lymphotoxin alpha and TNF-alpha polymorphisms increase the risk of upper gastrointestinal pathogenesis in H. pylori-infected patients, whereas IL-1 and TNF-alpha polymorphisms confer risk in EBV-infected patients.

Use of Comet assay to assess DNA damage in patients infected by Helicobacter pylori: comparisons between visual and image analyses

Studies of DNA damage in gastric epithelial cells of Helicobacter pylori (H. pylori)-infected patients are conflicting, possibly due to different methods used for scoring DNA damage by Comet assay. Therefore, we compared the sensitivity of visual microscopic analysis (arbitrary units-scores and comets%) and image analysis system (tail moment), in the gastric epithelial cells from the antrum and corpus of 122 H. pylori-infected and 32 non-infected patients. The feasibility of cryopreserved peripheral blood lymphocytes and whole-blood cells for DNA damage biomonitoring was also investigated. In the antrum, the levels of DNA damage were significantly higher in H. pylori-infected patients with gastritis than in non-infected patients with normal mucosa, when evaluated by image analysis system, arbitrary units and comets%. In the corpus, the comets% was not sufficiently sensitive to detect the difference between H. pylori-infected patients with gastritis and non-infected patients with normal mucosa. The image analysis system was sensitive enough to detect differences between non-infected patients and H. pylori-infected patients with mild gastritis and between infected patients with moderate and severe gastritis, in both antrum and corpus, while arbitrary units and comets% were unable to detect these differences. In cryopreserved peripheral blood lymphocytes, the levels of DNA damage (tail moment) were significantly higher in H. pylori-infected patients with moderate and severe gastritis than in non-infected patients. Overall, our results indicate that the image analysis system is more sensitive and adequate to measure the levels of DNA damage in gastric epithelial cells than the other methods assayed.

cagA vacA alelles and babA2 genotypes of Helicobacter pylori associated with gastric disease in Brazilian adult patients

Helicobacter pylori is an important human pathogen that causes chronic gastritis and is associated with development of peptic ulcer disease and gastric malignancies. The vacuolating cytotoxin (vacA), cagA gene, and babA2 gene are important virulence factor involving gastric diseases. Eighty-nine Helicobacter pylori-positive gastric biopsies were analyzed by polymerase chain reaction and Southern blotting for H. pylori detection and genotyping with primer pairs from each virulence gene. Fifty-three strains (59%) were common vacA genotype s1/m1, and only 14 (16%) were s2/m2, 12% of strains was found to have multiple infection. The cagA presence was detected in 48% (43 strains) and babA2 gene was detected in 44% of our H. pylori strains. We observed high percentage of s1/m1 strains with chronic gastritis and peptic ulcer and a significant correlation between cagA presence with the s1 allele and babA2 gene with chronic gastritis.

Clinical relevance of iceA and babA2 genotypes of Helicobacter pylori in a Shanghai population

OBJECTIVE

To determine the distribution of the iceA and babA2 genotypes of Helicobacter pylori in patients with various gastroduodenal diseases in Shanghai, and to explore the association between genotype and the clinical outcome of infection.

METHODS

One hundred and forty-one strains of H. pylori were isolated from gastric biopsies of 43 patients with chronic gastritis, 47 with duodenal ulcer (DU), 30 with gastric ulcer (GU) and 21 with non-cardia gastric carcinoma. The iceA, babA2, cagA and vacA genotypes were determined by polymerase chain reaction (PCR).

RESULTS

The iceA1, iceA2 and babA2 genotypes were detected in 74.5% (105/141), 15.6% (22/141) and 63.8% (90/141), respectively, of the H. pylori strains studied. Two H. pylori isolates (1.4%) were positive for both iceA alleles and 16 (11.3%) were negative for both. The prevalence of babA2 and its combination with cagA (cagA(+)/babA2(+)) in DU patients was significantly higher than that in GU patients (74.5%vs 50.0% for babA2, P = 0.028; 70.2%vs 46.7% for cagA(+)/babA2(+), P = 0.039). There was no significant difference in the prevalence of babA2 among the other disease groups, and no significant association of the iceA genotypes with the different clinical diseases (P > 0.05).

CONCLUSIONS

The most predominant genotype of the H. pylori strains isolated from patients in Shanghai are iceA1(+)/babA2(+), and the babA2 genotype may play a different role in the pathogenesis of DU and GU. An association between iceA status and clinical outcome of H. pylori infection could not be confirmed in the present study.

Epidemiology of Helicobacter pylori infection

This review summarizes key results of epidemiologic studies published in peer-reviewed journals between April 2003 and March 2004. The prevalence of H. pylori infection continues to vary strongly between developing countries and developed countries, and according to ethnicity, place of birth and socioeconomic factors among people living in the same country. Intrafamilial spread appears to play a central role in transmission of the infection in both developing and developed countries. The role of H. pylori infection in development of noncardia gastric cancer appears to be even much stronger than previously assumed, whereas the lack of an association with cardia cancer and an inverse association with adenocarcinoma of the esophagus could be confirmed. Suggestions for an inverse association of the infection with atopic diseases have recently received further support, whereas evidence concerning the role of the infection (or its eradication) in GERD and a large variety of other extragastric diseases, including cardiovascular disease, remains inconclusive.

Determinants and consequences of different levels of CagA phosphorylation for clinical isolates of Helicobacter pylori

BACKGROUND & AIMS

The Helicobacter pylori cag pathogenicity island encodes a secretory system that translocates CagA into epithelial cells, where it becomes tyrosine phosphorylated and induces cytoskeletal rearrangements. Strains with more CagA tyrosine phosphorylation motifs are most closely associated with gastric cancer. Here we assess whether clinical strains can deliver CagA, whether strains with different numbers of CagA phosphorylation motifs have CagA phosphorylated to different degrees, and whether this induces different amounts of epithelial cytoskeletal change.

METHODS

Forty-four H. pylori strains from South African patients, all cagA gene positive, were cocultured with the gastric adenocarcinoma cell line AGS. CagA expression and phosphorylation were determined by Western blot and interleukin-8 secretion by enzyme-linked immunosorbent assay. The cagA 3' variable regions of 22 strains were sequenced and shown to possess 3-6 phosphorylation motifs. These strains were used to quantify CagA phosphorylation and cytoskeletal rearrangements.

RESULTS

cagA genotype and typing of cag pathogenicity island genes were poorly predictive of phenotype. Thirty-four of 44 strains expressed CagA protein that could be delivered to and phosphorylated within AGS cells. Only these 34 strains induced interleukin-8 secretion from AGS cells. Among those strains, the number of CagA tyrosine phosphorylation motifs determined the degree of CagA phosphorylation and the level of biologic activity in terms of degree and extent of AGS cell elongation.

CONCLUSIONS

H. pylori strains that deliver CagA with more phosphorylation motifs induce higher levels of CagA phosphorylation in epithelial cells, induce more cytoskeletal changes, and are more likely to be associated with gastric cancer.

Helicobacter pylori infection: anything new should we know?

Over the past year, 2003-4, there have been a number of studies consolidating previous work in relation to pathogenesis of disease, diagnosis and management of Helicobacter pylori. Studies into the pathogenesis of disease have identified the main adhesin of H. pylori as an important virulence marker and as a potential target for therapy. Molecular investigations of both the strain and host variations have identified the action of several of the virulence factors, e.g. cagA, vacA, on disrupting host cell signalling and the consequences in respect of the release of chemokines from the damaged gastric epithelium and the effect on apoptosis. Over the past year, there have been further diagnostic kits developed based on modifications of current technology. Two promising areas of research for diagnosis are the use of host/strain genome polymorphisms as a means of identifying high-risk patients who may develop severe disease and the use of proteomics to identify potential antigens of diagnostic (or therapeutic) use. The three main antibiotics that are used in first-line eradication regimens are clarithromycin, metronidazole and amoxycillin. Of these, metronidazole has the highest prevalence of resistance, followed by clarithromycin; amoxycillin resistance is only rarely reported. The decreasing success of current first-line therapy is the driving force for the development of new antibiotic combinations and a search for novel sources for chemotherapeutic agents and novel therapeutic targets.

cagA genotype and variants in Chinese Helicobacter pylori strains and relationship to gastroduodenal diseases

Previous studies have implicated CagA [encoded by cytotoxin-associated gene A (cagA)] in Helicobacter pylori-associated gastroduodenal pathology and distinct subgenotypes of cagA may circulate in different pathological manifestations of cagA-positive H. pylori infection. To investigate cagA genotype and variants in Chinese H. pylori strains and explore their relationship with gastroduodenal diseases, the cagA status of 82 Chinese H. pylori strains was examined and variation in size of the 3' region of cagA in 71 of these strains was analysed by PCR. cagA was detected in 28 (100%) of 28 strains from peptic ulcer patients, two (100%) of two strains from gastric cancer patients, 32 (94.1%) of 34 strains from chronic gastritis patients and 17 (94.4%) of 18 strains from healthy volunteers. PCR products of the cagA 3' variable region were obtained from 71 (92.2%) of 77 Chinese H. pylori strains and could be classified into subgenotypes I, II and III, which gave PCR products of around 825, 900 and 950 bp, respectively. Subgenotype I cagA predominated in Chinese H. pylori strains (67/71), whereas subgenotype II cagA presented in two isolates from patients with chronic gastritis and subgenotype III presented in two isolates from healthy volunteers. Therefore, neither cagA nor its 3' region variants can be used as a sole marker for the presence of particular H. pylori-related gastroduodenal diseases in the Chinese population.

Helicobacter pylori: current status and future prospects

Helicobacter pylori is a global pathogen that causes severe gastrointestinal diseases leading to a significant morbidity and mortality. There is an effective treatment for peptic ulcer disease, however, this is being compromised by an increase in the prevalence of antibiotic resistance. Although alternative rescue regimens have been advocated, the best strategy would be to prevent disease, especially in the case of gastric cancer for which there is still no treatment. One approach is to inhibit the first step in the pathogenic process - adhesion of the organism to the host tissue. Another and probably a better approach is vaccination, but clinical trials have so far been unsuccessful. There is still a large uncertainty in relation to how H. pylori causes disease. Knowledge from genomics, proteomics, and the relationship between polymorphism of the bacterium and the host, as well as the continuing investigation of the role played by important virulence factors in the outcome of the disease, will help both in understanding pathogenesis of disease and in the design of the best vaccine.