cagA-positive Strains Research Articles

Real-time PCR detection of Helicobacter pylori and virulence-associated cagA in nasal polyps and laryngeal disorders

Objective To identify Helicobacter pylori and major virulance factor, cagA, in patients with laryngeal diseases and nasal polyps. Study Design Cross-sectional study with planned data collection. Setting The study was performed on fresh tissue samples from patients with 32 nasal polyps, 29 normal nasal mucosa, and 27 laryngeal diseases presenting to the Otolaryngology–Head and Neck Surgery department of a major military hospital in Istanbul, Turkey. Subjects and Methods Tissue specimens were evaluated by in-house polymerase chain reaction (PCR) and real-time PCR for bacterial DNA and by real-time PCR for cagA. The impact of commercial and in-house DNA extraction methods was also evaluated. Results H pylori DNA was detected only by real-time PCR in 59.4 percent of nasal polyps, 70.4 percent of nasal mucosa samples, and 58.6 percent of larynx samples. cagA was identified in 78.9, 89.5, and 82.4 percent of positive polyp, nasal mucosa, and larynx samples, respectively. No statistically significant differences were observed between groups. DNA purification methods were equally effective. Conclusion H pylori DNA is present in nasal polyp and larynx tissues as well as normal nasal mucosa, as detected by a sensitive real-time PCR assay. cagA-positive strains dominate in all groups.

T1650 CagA-Positive Strains of H. pylori Cross React with Trophoblast Cells: A Role for Pre-Eclampsia and Poliabortivity?

T1650 CagA-Positive Strains of H. pylori Cross React with Trophoblast Cells: A Role for Pre-Eclampsia and Poliabortivity?

Role ofHelicobacter pyloriCagA Molecular Variations in Induction of Host Phenotypes with Carcinogenic Potential

Helicobacter pylori cagA-positive strains exert population-specific risks for gastric cancer. We determined whether variations in CagA phosphorylation motifs were associated with carcinogenic or proinflammatory epithelial phenotypes induced by strains from regions with divergent cancer risks (Colombia and Nashville, TN). Motif number was significantly related to levels of CagA phosphorylation and cytoskeletal abnormalities. Precancerous isolates possessed a higher number of motifs, and precancerous strains from Nashville induced higher levels of IL-8 than Colombian strains. These results indicate that CagA variants are linked with premalignant lesions in distinct populations and that epithelial responses to these strains are selective based upon locale.

Infection by CagA-Positive Helicobacter pylori Strains may Contribute to Alter the Sperm Quality of Men with Fertility Disorders and Increase the Systemic Levels of TNF-α

This study was aimed to address the possibility that Helicobacter pylori infection may play a detrimental role in semen quality of men with idiopathic infertility. Infection by H. pylori and by strains expressing CagA was determined in 80 male infertile patients by Western blotting and ELISA. Semen analysis was performed by light microscopy and transmission electron microscopy quantitatively elaborated (fertility index, immaturity, necrosis, and apoptosis percentages). Systemic levels of IL-6 and TNF-alpha were evaluated. Infertile patients infected with H. pylori showed a low sperm quality respective to uninfected patients. Particularly, in CagA-positive patients we observed a significant reduction in sperm motility and in the fertility index, while apoptosis and necrosis were increased. In these patients, the means of systemic TNF-alpha levels were higher than those of uninfected patients. The negative influence of CagA-positive H. pylori infection on sperm quality may help to understand the role of chronic infections in reproductive disorders.

Cytotoxin‐Associated Gene‐A – Positive Helicobacter pylori Strains Infection Increases the Risk of Recurrent Atherosclerotic Stroke

CagA-positive Helicobacter pylori infection has been found to be associated with a first-ever atherosclerotic stroke. The aim of this study was to investigate whether these strains represent an independent risk factor for recurrent atherosclerotic stroke. We performed a longitudinal study of patients with a first-ever large vessels stroke and resulted positive at H. pylori serology. Patients had clinical examination 1 month after the acute event, and were subsequently visited or contacted by telephone up to 3 years at 6-month intervals. Sera obtained at the time of enrollment were frozen and analyzed for the presence of anti-CagA antibodies at the end of the study. The primary outcome event was any fatal or nonfatal stroke after the index stroke. One hundred seventy H. pylori-positive patients were included (n = 68 CagA positive and n = 102 CagA negative). No significant difference regarding age and other stroke risk factors was detected. According to Kaplan-Meier survival analysis, CagA-positive patients showed a significantly higher risk for stroke recurrence than CagA-negative ones (45.6% vs 17.6%; p < .001). Difference in the rate of recurrent stroke between the two groups persisted after Cox regression analysis taking into account possible confounding factors (hazard ratio = 3.5; 95% CI = 1.9-6.4; p < .001). Infection with H. pylori CagA-positive strains increases the risk of recurrent atherosclerotic stroke. Seropositivity determination should be performed in order to identify high-risk patients requiring a strict clinical surveillance, and the possible beneficial effect of eradication therapy should be evaluated.

Helicobacter pylori and esophageal cancer risk: a meta-analysis.

We conducted this meta-analysis to examine the association between Helicobacter pylori and esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma. We searched the PubMed database, the ISI database, and the references of the selected articles. Case-control or nested case-control studies were selected if they used serology or endoscopic methods to detect H. pylori in the stomach and if control subjects were not restricted to upper gastrointestinal tract cancer or peptic ulcer disease patients. A total of 19 studies were used for this analysis. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were calculated using the DerSimonian-Laird method. Q statistics and I(2) statistics were calculated to examine heterogeneity. Subgroup analyses were conducted by CagA status. For EAC, the summary OR (95% CI) was 0.56 (0.46-0.68). There was little heterogeneity among studies (I(2) = 15%). Further analysis showed that colonization with CagA-positive strains was inversely associated with EAC risk (OR, 0.41; 95% CI, 0.28-0.62) but colonization with CagA-negative strains was not (OR, 1.08; 95% CI, 0.76-1.53). For esophageal squamous cell carcinoma, the summary OR (95% CI) was 1.10 (0.78-1.55). However, there was substantial heterogeneity among studies (I(2) = 73%), with statistically significant associations in both directions. Our results suggest an inverse association between CagA-positive H. pylori colonization and risk of EAC. The prominent decline of H. pylori colonization in the past few decades may be partly responsible for the recent increase in EAC incidence in Western countries.

Structural and functional diversity in the PAR1b/MARK2‐binding region of Helicobacter pylori CagA

Helicobacter pylori (H. pylori) cagA-positive strains are associated with gastritis, peptic ulcerations, and gastric adenocarcinoma. Upon delivery into gastric epithelial cells, the cagA-encoded CagA protein specifically binds and aberrantly activates SHP-2 oncoprotein in a manner that is dependent on CagA tyrosine phosphorylation. CagA-deregulated SHP-2 then elicits aberrant Erk activation while causing an elongated cell shape known as the hummingbird phenotype. In polarized epithelial cells, CagA also binds to PAR1b/MARK2 and inhibits the PAR1b kinase activity, thereby disrupting tight junctions and epithelial cell polarity independent of CagA tyrosine phosphorylation. We show here that the CagA-multimerization (CM) sequence that mediates interaction of CagA with PAR1b is not only essential for the CagA-triggered junctional defects but also plays an important role in induction of the hummingbird phenotype by potentiating CagA-SHP-2 complex formation. We also show that the CM sequence of CagA isolated from East Asian H. pylori (referred to as the E-CM sequence) binds PAR1b more strongly than that of CagA isolated from Western H. pylori (referred to as the W-CM sequence). Within Western CagA species, the ability to bind PAR1b is proportional to the number of W-CM sequences. Furthermore, the level of PAR1b-binding activity of CagA correlates with the magnitude of junctional defects and the degree of hummingbird phenotype induction. Our findings reveal that structural diversity in the CM sequence is an important determinant for the degree of virulence of CagA, a bacterial oncoprotein that is associated with gastric carcinogenesis.

Toll-like receptor (TLR2, TLR4 and TLR5) gene polymorphisms and Helicobacter pylori infection in children with and without duodenal ulcer

Helicobacter pylori infection is mainly acquired in childhood, and polymorphisms in the host genes coding for Toll-like receptors (TLRs) may influence the innate and adaptive immune response to the infection, affecting the susceptibility to H. pylori or the disease outcomes. Our aim was to investigate whether TLR4, TLR2, and TLR5 polymorphisms were associated with H. pylori susceptibility and risk for duodenal ulcer in children. Gastric biopsy specimens were obtained at endoscopy for evaluation of H. pylori status, TLR4, TLR2 and TLR5 polymorphisms from 486 children (254 H. pylori-negative and 232 H. pylori-positive: 72 with and 160 without duodenal ulcer). cagA status of H. pylori infection was investigated by PCR. The levels of gastric cytokines were detected by ELISA. H. pylori-positivity or duodenal ulcer were not associated with TLR2, TLR4 or TLR5 polymorphisms. Otherwise, the presence of TLR4 polymorphic allele was associated with infection by cagA-positive strains and with increased gastric levels of interleukin-8 and interleukin-10. TLR4 polymorphism might ultimately contribute to more severe consequences of the infection in adulthood since it was associated with susceptibility to cagA-positive H. pylori infection early in life.

Helicobacter pylori cagA Status and Peptic Ulcer Disease in Iran

Helicobacter pylori contributes to the development of peptic ulcers and atrophic gastritis. Furthermore, H. pylori strains carrying the cagA gene are more virulent than cagA -negative strains and are associated with the development of gastric adenocarcinoma. The cagA gene is a putative H. pylori virulence factor of unknown function. The aim of this study was to determine the prevalence of the cagA gene among H. pylori isolates and its relationship with peptic ulcer disease in 128 Iranian patients. A total of 107 (83.6%) samples were positive, including 40 (95%) of the 42 patients with duodenal ulcer, 43 (86%) of the 50 patients with gastric ulcer, and 24 (66.6%) of the 36 patients with gastritis. cagA was present in 32 (80%) of 40 strains from duodenal ulcer patients, 33 (77%) of 43 strains from gastric ulcer patients, and 11 (46%) of 24 from gastritis patients. We also attempted to investigate the subtypes of 3' region of cagA gene in H. pylori strains isolated from Iranian patients and their relation to H. pylori-associated gastroduodenal diseases. The PCR product of cagA positive strains obtained with primer set CAG1/CAG2 differed in size, varying from 642 to 651 bp (subtype A) in 33 isolates to 756 bp (subtype B/D) in 13 isolates. This does not support the view that subtypes of the 3' region of cagA gene in H. pylori isolated from Iran correlate with the clinical outcomes of H. pylori, but colonization with cagA positive strains was significantly higher among duodenal ulcer than gastritis patients in Iran.

High Prevalence of Cag‐A Positive H. pylori Strains in Ischemic Stroke: A Primary Care Multicenter Study

Previous studies suggested an association between CagA-positive H. pylori strains and ischemic stroke. The aim of the present study was to assess the prevalence of Helicobacter pylori infection and CagA status in patients with atherosclerotic stroke in the primary care setting. A total of 106 consecutive patients (age 76.6 +/- 8 years; males 52%) with well-documented history of atherosclerotic stroke and 106 sex-age- (age 76.5 +/- 9 years; males 52%) and social background-matched controls without relevant vascular diseases. Risk factors for ischemic stroke were recorded in all subjects. H. pylori infection was assessed by[13]C-urea breath test. A serologic assay for specific IgG against CagA was performed in infected subjects. A trend toward a higher prevalence of H. pylori was observed in cases (63%) with respect to controls (54%) without reaching a statistical significance. CagA positivity was associated to a higher risk of atherosclerotic stroke (adjusted odds ratio 2.69, 95% confidence interval 1.37-5.30). Our findings suggest that CagA-positive strains of H. pylori are significantly associated to atherosclerotic stroke. This is not a merely confirmative study since it has been performed for the first time in the primary care setting and included only subjects with an active infection.

Viral Commensalism in Humans?

Viral Commensalism in Humans?

The Relationship Between Virulence Factors of Helicobacter pylori and Severity of Gastritis in Infected Patients

The outcome of Helicobacter pylori infection has been related to specific virulence-associated bacterial genotypes. The best known genotypic virulence factors of H. pylori are cytotoxin-associated gene A (cagA) and vacuolating cytotoxin gene A (vacA). The objective of this study was to assess the relationship between H. pylori cagA and vacA status and histopathological findings. Esophagogastrodoedonoscopy was performed in 80 dyspeptic patients. Antrum and corpus biopsies were obtained for isolation of H. pylori and for histopathological assessment. The polymerase chain reaction was used to detect cagA and vacA genes of H. pylori using specific primers. Biopsy samples were stained with hematoxylin and eosin, and histopathological findings were graded using the "updated Sydney system". H. pylori from 57 of the 80 patients was incubated. Of the 57 patients, 44 were cagA positive. In the corpus biopsy specimens there was a significant relationship between the density of H. pylori colonization (P = 0.02) and chronic inflammation (P = 0.02) and cagA-positive genotypes. In the antrum specimens there was a significant relationship between cagA positivity and neutrophil activity (P = 0.003) and glandular atrophy (P = 0.002), but not with H. pylori density, chronic inflammation, and intestinal metaplasia. The odds ratio of cagA-positive vs. cagA-negative strains for the presence of glandular atrophy, irrespective of grading and of gastric localization, was 4.62 (95% CI, 1.18-18.08, P = 0.041). No significant relationships were observed between vacA s1 and s2 genotypes and histopathological parameters. Corpus neutrophil infiltration was found to be more severe in the m1 group than in the m2 group (P = 0.004). Other histopathological features showed no difference between m1 and m2 genotypes. In conclusion H. pylori strains showing cagA positivity are associated with more severe gastritis in some histological features but virulence factors of H. pylori do not appear to determine the overall pattern of gastritis.

Cholesterol Depletion ReducesHelicobacter pyloriCagA Translocation and CagA-Induced Responses in AGS Cells

Infection with Helicobacter pylori cagA-positive strains is associated with gastritis, ulcerations, and gastric cancer. CagA is translocated into infected epithelial cells by a type IV secretion system and can be tyrosine phosphorylated, inducing signal transduction and motogenic responses in epithelial cells. Cellular cholesterol, a vital component of the membrane, contributes to membrane dynamics and functions and is important in VacA intoxication and phagocyte evasion during H. pylori infection. In this investigation, we showed that cholesterol extraction by methyl-beta-cyclodextrin reduced the level of CagA translocation and phosphorylation. Confocal microscope visualization revealed that a significant portion of translocated CagA was colocalized with the raft marker GM1 and c-Src during infection. Moreover, GM1 was rapidly recruited into sites of bacterial attachment by live-cell imaging analysis. CagA and VacA were cofractionated with detergent-resistant membranes (DRMs), suggesting that the distribution of CagA and VacA is associated with rafts in infected cells. Upon cholesterol depletion, the distribution shifted to non-DRMs. Accordingly, the CagA-induced hummingbird phenotype and interleukin-8 induction were blocked by cholesterol depletion. Raft-disrupting agents did not influence bacterial adherence but did significantly reduce internalization activity in AGS cells. Together, these results suggest that delivery of CagA into epithelial cells by the bacterial type IV secretion system is mediated in a cholesterol-dependent manner.

No Association Between Helicobacter pylori Infection or CagA-bearing Strains and Glaucoma

Accumulating evidence indicates that a variety of infections contribute to the pathogenesis of glaucoma. The role of Helicobacter pylori infection in glaucoma is controversial. Prospective, population-based study. Patients with various types of glaucoma and a control group of patients with cataract. We evaluated seropositivity to H. pylori and to its cytotoxin-associated gene A (CagA) product in patients with various types of glaucoma and compared the findings to those of a control group of patients with cataract. H. pylori infection and CagA seropositivity were detected in 31/51 (60.8%) and 26/51 (51%) glaucoma patients compared with 22/36 (61.1%) and 19/36 (52%) control patients, respectively (P=0.88, 0.67, not significant). Similar rates of H. pylori infection and CagA-positive strain were found in all glaucoma subgroups, and none of them was statistically different from those of controls. Neither H. pylori infection nor seropositivity for virulent CagA-bearing H. pylori strains have significant association with the occurrence of glaucoma of any type.

T1812 CagA-Positive Strains of H. pylori Affect Trophoblast Cells Invasiveness: Do They Play a Role in Pre-Eclampsia and Poliabortivity?

T1812 CagA-Positive Strains of H. pylori Affect Trophoblast Cells Invasiveness: Do They Play a Role in Pre-Eclampsia and Poliabortivity?

Helicobacter pylori Genotyping and Sequencing Using Paraffin‐Embedded Biopsies from Residents of Colombian Areas with Contrasting Gastric Cancer Risks

cagA-positive and vacA s1 and m1 genotypes of Helicobacter pylori are associated with an elevated risk of gastric cancer (GC). We determined these genotypes using paraffin-embedded gastric biopsy specimens harvested from infected individuals and compared genotype distributions in two Colombian populations residing in geographic regions with a high and low incidence of GC. DNA from paraffin-embedded gastric biopsies from 107 adults was amplified using primers specific for cagA, for the cag'empty site', for the s and m alleles of vacA, and for H. pylori 16S rRNA. H. pylori infection was detected by molecular assays in 97 (90.7%) biopsies. Complete genotyping of cagA and vacA was achieved in 94 (96.9%) cases. The presence of cagA was detected in 78 of 97 cases (80.4%); when considered separately, cagA and vacA s regions were not significantly associated with a particular geographic area. The vacA m1 allele and s1m1 genotypes were more common in the area of high risk for GC (p = .037 and p = .044, respectively), while the vacA m2 allele and s2m2 genotypes were more prevalent in the low-risk area. The prevalence of the combination of cagA-positive, vacA s1m1 genotypes was 84.3% and 60.5% for high and low risk areas, respectively (p = .011). H. pylori cagA and vacA genotyping from paraffin-embedded gastric biopsies permitted reliable typability and discrimination. The more virulent cagA-positive s1m1 strains, as well as vacA m1 genotype, were more prevalent in high risk than in low risk areas, which may contribute to the difference in GC risk between those two regions.

Abdominal aortic aneurysm and infection with CagA positive strains of Helicobacter pylori

The aim of the present study was to investigate whether virulent CagA positive Helicobacter pylori strains are those preferentially related to abdominal aortic aneurysm (AAA) rupture. Several microorganisms have been linked to aneurysm development. Chronic Chlamydophila pneumoniae infection has been suggested as a possible contributing factor for the development and expansion of AAA. Previous studies have shown increased risk of carotid atherosclerosis and coronary heart disease in subjects harbouring CagA positive strains of H. pylori. The relevance of CagA positive H. pylori involved in the processes underlying aneurysmal development, expansion, and rupture is unknown. In a case-control study, 119 patients with AAA and 36 matched controls were prospectively investigated with H. pylori serology. Patients with ruptured AAA have similar levels of IgG antibodies against H. pylori to patients with electively operated AAA, small AAA, and controls. In conclusion, this study fails to demonstrate a connection between H. pylori CagA seropositivity and abdominal aortic aneurysm rupture.

Helicobacter pylori and cagA seroprevalence in sub-Saharan inmigrants recently arrived to Gran Canaria (Spain)

Non-ulcerous dyspepsia is common among sub-Saharan people migrating into Spain. Given the high prevalence of H. pylori (HP) infection in their countries of origin, we studied the prevalence of infection in this population, and specifically the prevalence of infection by the more virulent, cagA-positive strains (CAP). 140 sub-Saharan immigrants recently arrived to Gran Canaria (Canary Islands, Spain) were studied. 80.7% were male, with a mean age of 24.2 y. 90.7% tested seropositive for HP and 72.2% of them carried antibodies against the 'pathogenicity island' cagA. We did not find any relationship between the presence of these antibodies and the clinical variables studied. We can conclude that HP infection is virtually universal in this population, with a high percentage of infection by CAP strains.

Relationship Between Helicobacter pylori Infection and Esophageal Neoplasia: A Meta-analysis

Helicobacter pylori is an important causative factor in gastric carcinogenesis. However, its role in extragastric gastrointestinal malignancies, such as esophageal cancer, is controversial. The aim of this study was to explore the relationship of H. pylori infection and H. pylori cagA-positive strain with this malignancy by performing meta-analysis of all relevant studies. Extensive MEDLINE English language medical literature searches for human studies were performed through February 2007 with suitable keywords. Pooled estimates were obtained by using fixed or random-effects model as appropriate. Heterogeneity between studies was evaluated with the Cochran Q test, whereas the likelihood of publication bias was assessed by constructing funnel plots. Their symmetry was estimated by the Begg and Mazumdar adjusted rank correlation test. In adenocarcinoma patients there were inverse significant relationships with both the H. pylori prevalence (pooled odds ratio [OR], 0.52; 95% confidence interval [CI], 0.37-0.73; P < .001) and the prevalence of H. pylori cagA-positive strain (pooled OR, 0.51; 95% CI, 0.31-0.82; P = .006). Similarly in patients with Barrett's esophagus there were inverse significant relationships (pooled OR, 0.64; 95% CI, 0.43-0.94; P = .025 and pooled OR, 0.39; 95% CI, 0.21-0.76; P = .005, respectively). In patients with squamous cell carcinoma there were no significant relationships with both H. pylori prevalence (pooled OR, 0.85; 95% CI, 0.55-1.33; P = .48) and the prevalence of H. pylori cagA-positive strains (pooled OR, 1.22; 95% CI, 0.7-2.13; P = .48). The results showed an inverse statistically significant relationship of H. pylori infection with both esophageal adenocarcinoma and Barrett's esophagus, which might suggest a protective role of the infection in these entities. On the contrary, no statistically significant relationship with squamous cell carcinoma was found.

Deregulation of β‐catenin signal by Helicobacter pylori CagA requires the CagA‐multimerization sequence

Infection with Helicobacter pylori cagA-positive strains causes gastritis and peptic ulceration and is associated with gastric adenocarcinoma. The cagA gene product CagA is delivered into gastric epithelial cells, where it undergoes tyrosine phosphorylation by Src family kinases at the C-terminal EPIYA-repeat region. Tyrosine-phosphorylated CagA specifically binds and activates SHP-2 tyrosine phosphatase, causing cell morphological transformation known as the hummingbird phenotype. CagA also destabilizes the E-cadherin/beta-catenin complex to elicit aberrant activation of the beta-catenin signal that underlies intestinal metaplasia. Here we show that translocalization of membranous beta-catenin and subsequent activation of the beta-catenin signal by CagA requires the EPIYA-repeat region, which is characterized by structural variation between CagA of H. pylori isolated in Western countries (Western CagA) and that of East Asian H. pylori isolates (East Asian CagA), but is independent of CagA tyrosine phosphorylation. Detailed analysis using a series of Western and East Asian CagA mutants revealed that deregulation of beta-catenin requires residues 1009-1086 and residues 908-1012 of ABCCC Western CagA and ABD East Asian CagA, respectively, and is mediated by the 16-amino-acid CagA multimerization sequence that is conserved between the 2 geographically distinct H. pylori CagA species. Our results indicate that aberrant activation of the beta-catenin signal, which promotes precancerous intestinal metaplasia, is an inherent and fundamental CagA activity that is independent of the structural polymorphism of CagA.