The significance of cagA and vacA subtypes of Helicobacter pylori in the pathogenesis of inflammation and peptic ulceration. (1/6695)

AIMS: To assess the significance of cagA and vacA subtypes of Helicobacter pylori in relation to inflammation and density of bacterial colonisation in vivo within a dyspeptic UK population. METHODS: Dyspeptic patients who were Helicobacter pylori positive had antral samples taken for histology and culture. Gastroduodenal pathology was noted. The grade of bacterial density and inflammation was assessed using the Sydney system. Bacterial DNA was extracted and the vacA alleles and the cagA/gene typed using PCR. RESULTS: 120 patients were studied. There was high rate of cagA positive strains in this population. Bacterial density did not correlate with the presence of peptic ulceration. There was a significant association between cagA positive strains and increased inflammation and bacterial density. The vacA s1 type independently correlated with extensive chronic inflammation but there was no association with bacterial density. The vacA m type did not correlate with extent of inflammation or bacterial density. CONCLUSIONS: The results suggest that cagA is important in the pathogenesis of inflammation and peptic ulceration. These findings are in keeping with the hypothesis that cagA acts as a marker for a cag pathogenicity island which encodes several genes involved in inflammation. The vacA s1 allele correlates with inflammation independently of cagA, possibly through its enhanced ability to produce the vacuolating cytotoxin.  (+info)

Chemokine mRNA expression in gastric mucosa is associated with Helicobacter pylori cagA positivity and severity of gastritis. (2/6695)

AIM: To investigate the association between the quantity of gastric chemokine mRNA expression, severity of gastritis, and cagA positivity in Helicobacter pylori associated gastritis. METHODS: In 83 dyspeptic patients, antral and corpus biopsies were taken for semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and histological grading of gastritis. Gastritis was evaluated by visual analogue scales. Quantities of chemokine (IL-8, GRO alpha, ENA-78, RANTES, MCP-1) RT-PCR products were compared with G3PDH products. Each sample was also evaluated for the presence of cagA and ureA mRNA by RT-PCR. RESULTS: mRNA expression of all five chemokines was significantly greater in H pylori positive than in H pylori negative mucosa. In H pylori positive patients, in the antrum C-X-C chemokine mRNA expression was significantly greater in cagA positive patients than in cagA negative patients, but there were no significant differences in C-C chemokine mRNA expression. In H pylori positive patients, chemokine mRNA expression in the corpus was less than in the antrum. In contrast to the antrum, only GRO alpha mRNA expression was significantly greater in cagA positive infection. Polymorphonuclear cell infiltration was correlated with C-X-C chemokine mRNA expression. Significant correlations were also found between bacterial density and C-X-C chemokine mRNA expression. CONCLUSIONS: In H pylori infection, C-X-C chemokines may play a primary role in active gastritis. Infection with cagA positive H pylori induces greater gastric chemokine mRNA expression in the antral mucosa, which may be relevant to the increased mucosal damage associated with cagA positive H pylori infection.  (+info)

Helicobacter pylori infection, garlic intake and precancerous lesions in a Chinese population at low risk of gastric cancer. (3/6695)

BACKGROUND: Cangshan County of Shandong Province has one of the lowest rates of gastric cancer (GC) in China. While intestinal metaplasia (IM) and dysplasia (DYS) are less common in Cangshan than in areas of Shandong at high risk of GC, these precursor lesions nevertheless affect about 20% of adults age > or = 55. SUBJECTS AND SETTING: In order to evaluate determinants of IM and DYS in Cangshan County, a low risk area of GC a survey was conducted among 214 adults who participated in a gastroscopic screening survey in Cangshan County in 1994. METHOD: A dietary interview and measurement of serum Helicobacter pylori antibodies were performed. RESULTS: The prevalence of H. pylori was lowest (19%) among those with normal gastric mucosa, rising steadily to 35% for superficial gastritis (SG), 56% for chronic atrophic gastritis (CAG), 80% for IM, and 100% for DYS. The prevalence odds of precancerous lesions were compared with the odds of normal histology or SG. The odds ratio (OR) or CAG associated with H. pylori positivity was 4.2 (95% confidence interval [CI] : 1.7-10.0), while the OR of IM/DYS associated with H. pylori positivity was 31.5 (95% CI: 5.2-187). After adjusting for H. pylori infection, drinking alcohol was a risk factor for CAG (OR = 3.2, 95% CI: 1.1-9.2) and IM/DYS (OR = 7.8, 95% CI: 1.3-47.7). On the other hand, consumption of garlic showed non-significant protective effects and an inverse association with H. pylori infection. CONCLUSIONS: The findings of this study suggest that infection with H. pylori is a risk factor and garlic may be protective, in the development and progression of advanced precancerous gastric lesions in an area of China at relatively low risk of GC.  (+info)

Structure of cag pathogenicity island in Japanese Helicobacter pylori isolates. (4/6695)

BACKGROUND: cag pathogenicity island (PAI) is reported to be a major virulence factor of Helicobacter pylori. AIM: To characterise cagA and the cag PAI in Japanese H pylori strains. METHODS: H pylori isolates from Japanese patients were evaluated for CagA by immunoblot, for cagA transcription by northern blot, and for cagA and 13 other cag PAI genes by Southern blot. cagA negative strains from Western countries were also studied. Induction of interleukin-8 secretion from gastric epithelial cells was also investigated. RESULTS: All Japanese strains retained cagA. Fifty nine of 63 (94%) strains had all the cag PAI genes. In the remaining four, cag PAI was partially deleted, lacking cagA transcripts and not producing CagA protein. Details of the PAI of these strains were checked; three lacked cagB to cagQ (cagI) and continuously cagS to cag13 (cagII), and the remaining one lacked cagB to cag8. Western cagA negative strains completely lacked cag PAI including cagA. Nucleotide sequence analysis in one strain in which the cag PAI was partially deleted showed that the partial deletion contained 25 kb of cag PAI and the cagA promoter. Interleukin-8 induction was lower with the cag PAI partial deletion strains than with the intact ones. All Japanese cag PAI deleted strains were derived from patients with non-ulcer dyspepsia, whereas 41 of 59 (70%) CagA-producing strains were from patients with peptic ulcers or gastric cancer (p<0.05). CONCLUSIONS: Most Japanese H pylori strains had the intact cag PAI. However, some lacked most of the cag PAI in spite of the presence of cagA. Thus the presence of the cagA gene is not an invariable marker of cag PAI related virulence in Japanese strains.  (+info)

Chronic infection with Helicobacter pylori, Chlamydia pneumoniae, or cytomegalovirus: population based study of coronary heart disease. (5/6695)

OBJECTIVE: To study possible associations between coronary heart disease and serological evidence of persistent infection with Helicobacter pylori, Chlamydia pneumoniae, or cytomegalovirus. DESIGN: Population based, case-control study, nested within a randomised trial. SETTING: Five general practices in Bedfordshire, UK. INDIVIDUALS: 288 patients with incident or prevalent coronary heart disease and 704 age and sex matched controls. RESULTS: High concentrations of serum IgG antibodies to H pylori were present in 54% of cases v 46% of controls, with corresponding results for C pneumoniae seropositivity (33% v 33%), and cytomegalovirus seropositivity (40% v 31%). After adjustments for age, sex, smoking, indicators of socioeconomic status, and standard risk factors, the odds ratios (95% confidence intervals) for coronary heart disease of seropositivity to these agents were: 1.28 (0.93 to 1.75) for H pylori, 0.95 (0.66 to 1.36) for C pneumoniae, and 1.40 (0.96 to 2. 05) for cytomegalovirus. CONCLUSIONS: There is no good evidence of strong associations between coronary heart disease and serological markers of persistent infection with H pylori, C pneumoniae, or cytomegalovirus. To determine the existence of moderate associations between these agents and disease, however, larger scale studies will be needed that can keep residual confounders to a minimum.  (+info)

Multiplex sequence analysis demonstrates the competitive growth advantage of the A-to-G mutants of clarithromycin-resistant Helicobacter pylori. (6/6695)

Clarithromycin resistance in Helicobacter pylori is due to point mutation within the 23S rRNA. We examined the growth rates of different types of site-directed mutants and demonstrated quantitatively the competitive growth advantage of A-to-G mutants over other types of mutants by a multiplex sequencing assay. The results provide a rational explanation of why A-to-G mutants are predominantly observed among clarithromycin-resistant clinical isolates.  (+info)

Helicobacter pylori vacuolating toxin forms anion-selective channels in planar lipid bilayers: possible implications for the mechanism of cellular vacuolation. (7/6695)

The Helicobacter pylori VacA toxin plays a major role in the gastric pathologies associated with this bacterium. When added to cultured cells, VacA induces vacuolation, an effect potentiated by preexposure of the toxin to low pH. Its mechanism of action is unknown. We report here that VacA forms anion-selective, voltage-dependent pores in artificial membranes. Channel formation was greatly potentiated by acidic conditions or by pretreatment of VacA at low pH. No requirement for particular lipid(s) was identified. Selectivity studies showed that anion selectivity was maintained over the pH range 4.8-12, with the following permeability sequence: Cl- approximately HCO3- > pyruvate > gluconate > K+ approximately Li+ approximately Ba2+ > NH4+. Membrane permeabilization was due to the incorporation of channels with a voltage-dependent conductance in the 10-30 pS range (2 M KCl), displaying a voltage-independent high open probability. Deletion of the NH2 terminus domain (p37) or chemical modification of VacA by diethylpyrocarbonate inhibited both channel activity and vacuolation of HeLa cells without affecting toxin internalization by the cells. Collectively, these observations strongly suggest that VacA channel formation is needed to induce cellular vacuolation, possibly by inducing an osmotic imbalance of intracellular acidic compartments.  (+info)

The vacuolating toxin from Helicobacter pylori forms hexameric pores in lipid bilayers at low pH. (8/6695)

Pathogenic strains of Helicobacter pylori secrete a cytotoxin, VacA, that in the presence of weak bases, causes osmotic swelling of acidic intracellular compartments enriched in markers for late endosomes and lysosomes. The molecular mechanisms by which VacA causes this vacuolation remain largely unknown. At neutral pH, VacA is predominantly a water-soluble dodecamer formed by two apposing hexamers. In this report, we show by using atomic force microscopy that below pH approximately 5, VacA associates with anionic lipid bilayers to form hexameric membrane-associated complexes. We propose that water-soluble dodecameric VacA proteins disassemble at low pH and reassemble into membrane-spanning hexamers. The surface contour of the membrane-bound hexamer is strikingly similar to the outer surface of the soluble dodecamer, suggesting that the VacA surface in contact with the membrane is buried within the dodecamer before protonation. In addition, electrophysiological measurements indicate that, under the conditions determined by atomic force microscopy for membrane association, VacA forms pores across planar lipid bilayers. This low pH-triggered pore formation is likely a critical step in VacA activity.  (+info)