CagA seropositivity associated with development of gastric cancer in a Japanese population

cDNA array analysis of cag pathogenicity island-associated Helicobacter pylori epithelial cell response genes

Helicobacter pylori strains containing the cag pathogenicity island (PAI) induce NF-kappaB activation and interleukin-8 secretion in gastric epithelial cells. The aim of this study was to investigate changes in epithelial gene expression induced by cag PAI-positive and -negative strains of H. pylori using high-density cDNA array hybridization technology. Radio-labeled cDNA prepared from H. pylori-infected Kato 3 gastric epithelial cells was hybridized to high-density cDNA arrays to identify changes in epithelial gene expression compared to noninfected controls. In vivo expression of selected, differentially expressed genes was examined by reverse transcription-PCR analysis of H. pylori-positive and -negative gastric mucosa. Screening of ca. 57,800 cDNAs identified 208 known genes and 48 novel genes and/or expressed sequence tags of unknown function to be differentially expressed in Kato 3 cells following H. pylori infection. Marked differences in gene expression profiles were observed following cag PAI-positive and cag PAI-negative infection with 15 novel cDNAs and 92 known genes being differentially expressed. H. pylori was found to change the expression of genes encoding growth factors and cytokine/chemokines and their receptors, apoptosis proteins, transcription factors and metalloprotease-disintegrin proteins (ADAMs), and tissue inhibitors of metalloproteinases. Gastric differential expression of selected known genes (amphiregulin and ADAM 10) and a novel gene (HPYR1) was confirmed in vivo in patients with H. pylori infection. Confirmation of the in vivo expression of selected genes demonstrates the usefulness of this approach for investigating pathogen-induced changes in host gene expression.

pathogenesis of Helicobacter pylori-induced gastric inflammation

Helicobacter pylori causes persistent inflammation in the human stomach, yet only a minority of persons harbouring this organism develop peptic ulcer disease or gastric malignancy. An important question is why such variation exists among colonized individuals. Recent evidence has demonstrated that H. pylori isolates possess substantial phenotypic and genotypic diversity, which may engender differential host inflammatory responses that influence clinical outcome. For example, H. pylori strains that possess the cag pathogenicity island induce more severe gastritis and augment the risk for developing peptic ulcer disease and distal gastric cancer. An alternative, but not exclusive, hypothesis is that enhanced inflammation and injury is a consequence of an inappropriate host immune response to the chronic presence of H. pylori within the gastric niche. Investigations that precisely delineate the mechanisms responsible for induction of gastritis will ultimately help to define which H. pylori-colonized persons bear the highest risk for subsequent development of clinical disease, and thus, enable physicians to focus eradication therapy.

Assessment of Helicobacter pylori vacA and cagA genotypes and host serological response

Helicobacter pylori strains can be distinguished by genotyping of virulence-associated genes, such as vacA and cagA. Because serological discrimination between strain types would reduce the need for endoscopy, 61 patients carrying H. pylori were studied by vacA and cagA genotyping of H. pylori in gastric biopsy specimens and by detection of specific serum antibodies. Serological responses to H. pylori were determined by Helicoblot (versions 2.0 and 2.1). Antibodies to CagA also were determined by a rapid anti-CagA assay (Pyloriset screen CagA) as well as by two noncommercially developed enzyme immunoassays, each using a recombinant CagA protein. Assessment of performance of the Helicoblot assays indicated substantial interobserver variation, with kappa values between 0.20 and 0.93. There was no relationship between the serological profiles on the Helicoblot and the genotypes from the same patients, except for strong associations between the presence of anti-CagA and the cagA-positive and vacA s1 H. pylori genotypes. Detection of anti-CagA by the five different assays varied considerably, with kappa values ranging from 0.21 to 0.78. Using the cagA genotype as the "gold standard," the sensitivity and specificity of the anti-CagA assays varied from 71.4 to 85.7% and from 54.2 to 100%, respectively. Thus, serological profiles of antibodies to H. pylori are heterogeneous and, with the exception of anti-CagA antibodies, show no relation to the H. pylori vacA and cagA genotypes. Detection of anti-CagA antibodies is strongly dependent on the test used.

Dyspepsia is associated with CagA-positive Helicobacter pylori

OBJECTIVE

The role of Helicobacter pylori in nonulcer dyspepsia is controversial. Speculation has arisen that only strains of H. pylori carrying the CagA virulence factor are important in the development of dyspepsia. The objective of this study was to determine whether nonulcer dyspepsia correlated with CagA-positive H. pylori infection.

METHODS

A total of 435 healthy blood donors and 102 general medicine clinic respondents completed the Bowel Disease Questionnaire and the PRIME-MD survey, a validated screen for common psychiatric disorders. Subjects were classified as cases of nonulcer dyspepsia if they reported pain in the upper abdomen more than six times in the previous year and denied a past or current history of peptic ulcer disease. Study participants were tested for IgG antibodies to H. pylori and the CagA protein.

RESULTS

Clinic respondents were more likely than healthy blood donors to meet the case definition for nonulcer dyspepsia (34% vs 13%, p < 0.001), to be seropositive for H. pylori (54% vs 18%, p < 0.001), and to be CagA seropositive (41% vs 10%, p = 0.01). Logistic regression identified CagA seropositivity (p = 0.03), race (p = 0.001), and positive screens for depression (p = 0.007) or somatization (p < 0.001) as variables independently associated with nonulcer dyspepsia.

CONCLUSION

Infection with a CagA-positive strain of H. pylori is associated with a clinical diagnosis of nonulcer dyspepsia. However, nonulcer dyspepsia was also strongly and independently associated with positive screens for depression or somatization disorder as well as with ethnicity. These potential sources of variance should be considered in the design of future studies evaluating nonulcer dyspepsia.

Antibody response of patients with Helicobacter pylori-related gastric adenocarcinoma: significance of anti-cagA antibodies

The aim of this study was to search for a specific antibody pattern in sera from patients suffering from Helicobacter pylori-related gastric adenocarcinoma (GAC). The serological response of 22 patients suffering from GAC, 31 patients with gastroduodenal ulcer, and 39 asymptomatic subjects was analyzed using immunoblotting performed with three H. pylori strains: strain ATCC 43579; strain B110, isolated from a patient with ulcers; and strain B225, isolated from a patient with GAC. In addition, the latex agglutination test Pyloriset Dry was used to analyze ambiguous sera. H. pylori seropositivity was 75% in the GAC group, 61.3% in the ulcer group, and 56.4% in the asymptomatic group. Anti-CagA antibodies were found more often in the GAC group (48.8%) and in the ulcer group (47.3%) than in the asymptomatic group (21.2%). These percentages depended on the strain used as an antigen: in the GAC group, the anti-CagA frequencies were 93.3, 40, and 13.3% with strains B225, B110, and ATCC 43579, respectively. Thus the presence of anti-CagA antibodies was increased in patients suffering from H. pylori-related GAC, in particular when the CagA antigen was from a GAC strain. These data suggest the existence of a CagA protein specifically expressed by H. pylori strains isolated from GAC patients.

Infection with virulent strains of Helicobacter pylori is not associated with ischaemic heart disease: evidence from a population-based case-control study of myocardial infarction

BACKGROUND

Although the majority of evidence does not support association between Helicobacter pylori infection and ischaemic heart disease, the nature of this relationship may differ when virulence of the infecting strains are examined.

METHODS AND RESULTS

The prevalence of IgG antibody evidence of infection with CagA positive stains of H. pylori was investigated in stored plasma samples from 259 cases of myocardial infarction (aged 25-70 years, 74 males) and 259 population based controls from the same area in Northern Ireland. Two-hundred and seventy (52.1%) subjects were seropositive for anti-CagA IgG. CagA seropositivity was more common in cases than in controls: 56.4 vs 47.9%, odds ratio for seropositivity in cases (95% CI) 1.41 (1.00, 1.99). Substantial attenuation of this relationship occurred on adjustment for age, sex, number of siblings, smoking and measures of socio-economic status: odds ratio (95% CI) 1.16 (0.79, 1.70). A similar pattern was seen for seropositivity for all H. pylori strains.

CONCLUSION

Infection with the more virulent strains of H. pylori, as with all strains, is not associated with myocardial infarction.

Individual and joint contribution of family history and Helicobacter pylori infection to the risk of gastric carcinoma

BACKGROUND

Helicobacter pylori infection and a positive family history of gastric carcinoma have been identified as risk factors for the disease. It is unclear, however, to what degree their impact on the risk of gastric carcinoma is independent, because H. pylori also clusters within families.

METHODS

The authors carried out a population-based, statewide case-control study in Saarland, Germany, to assess the individual and joint contributions of family history and H. pylori infection to the risk of gastric carcinoma. Cases included 68 patients with histologically verified gastric carcinoma. Controls included 239 patients with colorectal carcinoma who were matched to the cases by age and gender. Information on family history (defined as gastric carcinoma in at least one first-degree relative) and potential confounders was collected by standardized interviews. Immunoglobulin G antibodies against H. pylori were measured by enzyme-linked immunosorbent assay. In addition, antibodies against the CagA antigen were determined by Western blot analysis.

RESULTS

H. pylori infection and family history were positively related, and both risk factors were more common among cases than among controls. Although the association between family history and gastric carcinoma was somewhat reduced by control for H. pylori infection, both risk factors still showed strong independent relations with gastric carcinoma after control for each other. Compared with uninfected subjects who had no family history, subjects with both a positive family history and infection with a CagA positive H. pylori strain had a more than 8-fold total risk of gastric carcinoma (adjusted odds ratio [OR], 8.2; 95% confidence interval [CI], 2.2-30.4) and a 16-fold risk of noncardia gastric carcinoma (OR, 16.0; 95% CI, 3.9-66.4).

CONCLUSIONS

Infection with CagA positive H. pylori strains and a positive family history appear to be strong independent risk factors for gastric carcinoma. They may be useful markers for identifying subjects at high risk for the disease and for targeting efforts of prevention and early detection.

Helicobacter pylori infection among offspring of patients with stomach cancer

BACKGROUND & AIMS

A positive family history is associated with an increased risk of stomach cancer. We compared the prevalence of Helicobacter pylori infection, a known risk factor for stomach cancer, between subjects with and without parental history of stomach cancer to evaluate a potential role of H. pylori infection in familial aggregation of stomach cancer.

METHODS

A total of 1351 men and women aged 30-74 years who participated in the German Health and Nutrition Survey conducted in the western part of Germany in 1987-1988 were included in the study. Detailed information on sociodemographic factors, nutritional factors, and parental history of cancer was obtained by standardized interviews. Serum samples were analyzed for immunoglobulin G antibodies against H. pylori by enzyme-linked immunosorbent assay.

RESULTS

The prevalence of H. pylori infection was much higher (69%) among subjects with a parental history of stomach cancer than among other subjects (44%). This association persisted after control for potential confounders by multiple logistic regression (adjusted odds ratio, 2.7; 95% confidence interval, 1.3-5.9), and was particularly strong among subjects below age 55 (adjusted odds ratio, 5.1; 95% confidence interval, 1.6-16.1).

CONCLUSIONS

These results suggest that familial aggregation of stomach cancer may be explained at least partly by familial clustering of H. pylori infection.

Association between infections with CagA-positive or -negative strains of Helicobacter pylori and risk for gastric cancer in young adults. Research Group on Prevention of Gastric Carcinoma Among Young Adults

OBJECTIVE

We assessed the association between infection with CagA-positive and -negative Helicobacter pylori and the risk of gastric cancer in young adults.

METHODS

CagA IgG antibodies were measured in sera of subjects participating in a case-control study in Japan. The study subjects were 103 gastric cancer patients <40 yr of age, 100 inpatients with benign diseases, and 101 screenees younger than age 43 yr.

RESULTS

Compared with the H. pylori-negative/CagA-negative (H. pylori-/CagA-) group, both the H. pylori-positive/CagA-negative (H. pylori+/CagA-) group and the H. pylori-positive/CagA-positive (H. pylori+/CagA+) groups showed elevated odds ratios for intestinal-type, diffuse-type, early, advanced, proximal, and distal gastric cancers. All the relationships were significant except for the H. pylori+/CagA- group in relation to proximal cancer. The overall odds ratios (95% confidence intervals) for gastric cancer in the H. pylori+/CagA- and the H. pylori+/CagA+ groups were 15.0 (6.4, 35.2) and 14.6 (6.7, 31.9), respectively. Between these two groups, no significant difference was observed in risks for intestinal-type, diffuse-type, early, advanced, proximal, or distal gastric cancer.

CONCLUSIONS

In those <40 yr of age, it is concluded that both CagA-positive and CagA-negative H. pylori infections are related to risks of intestinal-type, diffuse-type, early, advanced, and distal gastric cancers.

Association of Helicobacter pylori infection with gastric carcinoma: a meta-analysis

OBJECTIVE

As conflicting studies have recently been published, we aimed to determine if Helicobacter pylori (H. pylori) infection is associated with gastric adenocarcinoma.

METHODS

This was a meta-analysis of observational epidemiological studies.

RESULTS

A total of 42 studies met the selection criteria and were categorized by the type of study design: eight cohort and 34 case-control studies. The pooled odds ratio for H. pylori in relation to gastric carcinoma was 2.04 (95% CI: 1.69-2.45). Both patient age (OR 0.77, 95% CI: 0.68-0.89) and intestinal type cancers (OR 1.14, 95% CI: 1.05-1.25) were independent effect modifiers. Analysis of other effect modifiers showed no relationship with female gender (OR 0.76, 95% CI: 0.64-0.89), stage of cancer (advanced %) (OR 1.12, 95% CI: 0.88-1.43), anatomical location (cardia %) (OR 1.54, 95% CI: 0.32-7.39) or cohort (nested case-control) studies (OR 1.72, 95% CI: 0.32-9.17). There was significant heterogeneity among the studies (tau2 = 149; p < 0.001). The quality of the studies varied considerably, with the majority of excellent studies producing positive results and the very poor to moderate studies producing mixed results.

CONCLUSIONS

H. pylori infection is associated with a 2-fold increased risk of developing gastric adenocarcinoma.

Modulation of Helicobacter pylori induced interleukin-8 synthesis in gastric epithelial cells mediated by cag PAI encoded VirD4 homologue

BACKGROUND

Strains of Helicobacter pylori carrying the virulence associated cag pathogenicity island (PAI) induce gastric epithelial synthesis of the chemokine interleukin-8 (IL-8), a neutrophil chemoattractant, and thereby a strong inflammatory response during chronic infection of the human gastric mucosa. Previous mutational analyses have shown that many genes in the cag PAI are needed to elicit IL-8 synthesis in gastric epithelial cells, and also that some genes are not involved.

AIM

To test the possibility that certain genes in the cag PAI also downregulate (modulate) the inflammatory response elicited by cag+ H pylori infection.

METHODS

Cells of L5F11, a derivative of the Kato-3 gastric epithelial cell line that carries an engineered IL-8 promoter-luciferase reporter gene fusion, were cocultured with H pylori strain 26695 or with an isogenic mutant in which most of the cag PAI ORF 10 gene, an Agrobacterium virD4 homologue, was deleted. Luciferase activity was measured to assess IL-8 gene transcription and secreted IL-8 was measured by enzyme linked immunosorbent assay to assess synthesis and release of IL-8 protein from gastric epithelial cells.

RESULTS

Inactivation of ORF10 led to a 2.8-fold increase in IL-8 gene transcription and a 3.6-fold increase in IL-8 synthesis and secretion.

CONCLUSIONS

The results suggest that this VirD4 homologue participates in the control of inflammation that H pylori infection elicits by downregulating (modulating) the strong induction of IL-8 synthesis mediated by other cag encoded proteins.

Multiple genes in the left half of the cag pathogenicity island of Helicobacter pylori are required for tyrosine kinase-dependent transcription of interleukin-8 in gastric epithelial cells

Helicobacter pylori strains that contain the cag pathogenicity island (PAI) elicit increased synthesis of gastric C-X-C chemokines, promote neutrophilic infiltration into the gastric epithelium, and stimulate the synthesis of interleukin-8 (IL-8) in cultured gastric epithelial cells. To investigate the effects of cag PAI genes on the transcription of the IL-8 gene, the Kato-3 gastric epithelial cell line was stably transfected with plasmid DNA containing the IL-8 gene promoter fused to a luciferase reporter gene. The resulting reporter cell line, L5F11, was used to monitor the effects of infection in cell culture by H. pylori 26695 and isogenic derivatives with null mutations in genes in the cag PAI on transcription of the IL-8 gene. We found that null mutations in eight open reading frames, including homologs of the Agrobacterium virB9, virB10, and virB11 genes, in the left half of the cag PAI abrogated the induction of IL-8 gene transcription. Further studies with the L5F11 cell line showed that IL-8 gene transcription induced by H. pylori was blocked by the protein tyrosine kinase inhibitor herbimycin A but not by the protein kinase C inhibitor calphostin C or by the protein kinase G inhibitor KT5823. IL-8 gene transcription in L5F11 cells could also be induced by the cytokine tumor necrosis factor alpha (TNF-alpha) without exposure to H. pylori. This TNF-alpha-induced IL-8 transcription was inhibited by the protein kinase A inhibitor H7, which had no significant effect on H. pylori-induced IL-8 transcription. These studies show that multiple genes in the left half of the cag PAI are essential for the transcription of the IL-8 gene in gastric epithelial cells and that this depends on protein tyrosine kinase activation.

Gastric cancer, cytotoxin-associated gene A-positive Helicobacter pylori, and serum pepsinogens: an international study. The Eurogst Study Group

BACKGROUND & AIMS

CagA-positive Helicobacter pylori infection has been more closely associated with gastric disease than CagA-negative infection. This study evaluated whether geographic variation in the prevalence of CagA could explain variation in gastric cancer rates.

METHODS

The Eurogast study was conducted in 17 centers in 13 countries. Gastric cancer rates were calculated for each center, and serum samples from approximately 2850 subjects were assayed for immunoglobulin G antibodies to H. pylori and CagA and for pepsinogens A and C.

RESULTS

The proportion of CagA-positive H. pylori infections varied across the centers, but this variation did not explain any more of the variation in gastric cancer rates than H. pylori alone. Subjects with CagA-positive infection had, however, significantly higher pepsinogen levels and a lower pepsinogen A/C ratio than subjects with CagA-negative infection; this pattern was observed consistently across the study centers.

CONCLUSIONS

Variation in the seroprevalence of CagA did not explain geographic variation in gastric cancer rates any better than H. pylori alone. However, the consistent variation in pepsinogen levels with CagA status across the study centers supports the importance of the role of CagA in the development of gastric disease.