Mass eradication of Helicobacter pylori: feasible and advisable?

Validation of a Blood Biomarker for Identification of Individuals at High Risk for Gastric Cancer

BACKGROUND

Helicobacter pylori is the leading cause of gastric cancer, yet the majority of infected individuals will not develop neoplasia. Previously, we developed and replicated serologic H. pylori biomarkers for gastric cancer risk among prospective cohorts in East Asia and now seek to validate the performance of these biomarkers in identifying individuals with premalignant lesions.

METHODS

This cross-sectional study included 1,402 individuals from Linqu County screened by upper endoscopy. H. pylori protein-specific antibody levels were assessed using multiplex serology. Multivariable-adjusted logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for prevalent intestinal metaplasia, indefinite dysplasia, or dysplasia, compared with superficial or mild atrophic gastritis.

RESULTS

Compared with individuals seronegative to Omp and HP0305, individuals seropositive to both were seven times more likely to have precancerous lesions (OR, 7.43; 95% CI, 5.59-9.88). A classification model for precancerous lesions that includes age, smoking, and seropositivity to H. pylori, Omp, and HP0305 resulted in an area under the curve (AUC) of 0.751 (95% CI, 0.725-0.777), which is significantly better than the same model, including the established gastric cancer risk factor CagA (AUC, 0.718; 95% CI, 0.691-0.746, P _difference = 0.0002).

CONCLUSIONS

The present study of prevalent precancerous gastric lesions provides support for two new serum biomarkers of gastric cancer risk, Omp and HP 0305.

IMPACT

Our results support further research into the serological biomarkers Omp and HP0305 as possible improvements over the established virulence marker CagA for identifying individuals with precancerous lesions in East Asia.

A CagA-independent cluster of antigens related to the risk of noncardia gastric cancer: associations between Helicobacter pylori antibodies and gastric adenocarcinoma explored by multiplex serology

Because of the differences in bacterial epitopes and host characteristics, infections with Helicobacter pylori (H. pylori) induce different immune responses. We explored the possibility that certain antibody response patterns are more closely linked to gastric adenocarcinoma (GAC) than others. In a Swedish population-based case-control study, serum samples were obtained from 268 cases and 222 controls, aged 40-79 years and frequency-matched according to age and sex. We measured antibodies against 17 H. pylori proteins using multiplex serology. Associations were estimated with multivariably adjusted logistic regression models, using odds ratio (OR) with 95% confidence interval (CI) as measures of relative risk. Associations were essentially confined to non-cardia GAC but did not differ significantly between intestinal and diffuse subtypes. Point estimates for all antibodies were above unity, 15 significant with top three being CagA (OR = 9.2), GroEL (6.6), HyuA (3.6). ORs were substantially attenuated in individuals with chronic atrophic gastritis. Principal component analysis identified two significant factors: a CagA-dominant factor (antibodies against CagA, VacA and Omp as prominent markers), and a non-CagA factor (antibodies against NapA and Catalase as prominent markers). Both factors showed dose-dependent associations with non-cardia GAC risk (CagA-dominant factor, highest vs. lowest quartiles, OR = 16.2 [95% CI 4.8-54.9]; non-CagA factor OR = 5.3 [95% CI 2.1-13.3]). Overall, our results confirm that serum antibodies against different H. pylori proteins are associated with the presence of non-cardia GAC. Although strongest association is detected by antibodies against CagA and covarying proteins, a pattern of antibodies unrelated to CagA is also significantly linked to the risk of non-cardia GAC.

Follow-up of Helicobacter pylori infection in children over two decades (1988-2007): persistence, relapse and acquisition rates. Epidemiol Infect. 2014;142:767-775. [PMID: 23809783 DOI: 10.1017/S0950268813001428]

Helicobacter pylori culture on gastric biopsy was performed on 4964 subjects aged <18 years from 1988 to 2007 at a central laboratory in Brussels. The total number of biopsies increased markedly from 941 in 1988-1993 to 1608 in 2004-2007. Biopsies were repeated at least once for 922 subjects (603 initially negative and 319 initially positive for H. pylori). Persistence rate of H. pylori at 1 year after initial positive biopsy was greater in the 1998-2007 cohort than in the 1988-1997 cohort (72.7% vs. 45.8%, P = 0.002), suggesting a tailored selection of candidates for biopsy with non-invasive tests (13C urea breath test). Of 68 subjects initially positive and re-examined subsequently after a documented cure, re-infection/relapse rate was 48.6% within 5 years post-elimination of H. pylori. Acquisition rate over 10 years follow-up in the initially negative cohort (603 patients) was 38.7% (re-infection/relapse vs. acquisition: P < 0.001). Multivariate analysis showed a fourfold greater risk of H. pylori acquisition in children of non-European origin vs. European origin (P < 0.001). Clarithromycin and metronidazole susceptibility were determined in 226 and 223 paired positive cultures in cases of re-infection/relapse or persistence. An initial non-susceptibility profile was highly predictive of a subsequent non-susceptibility profile, and the non-susceptible proportion increased markedly from 13.3% to 21.2% for clarithromycin (P < 0.001) and from 27.3% to 35.0% for metronidazole (P = 0.014), with no difference regarding European or non-European origin.

Haem oxygenase-1 inhibits phosphorylation of the Helicobacter pylori oncoprotein CagA in gastric epithelial cells

The cytotoxin-associated gene A protein (CagA) plays a pivotal role in the aetiology of Helicobacter pylori-associated gastric diseases. CagA is injected into the cytoplasm of host cells by a type IV secretion system, and is phosphorylated on tyrosine residues by the host enzyme c-Src. We previously reported that the enzyme haem oxygenase-1 (HO-1) inhibits IL-8 secretion by H. pylori-infected cells. However, the cellular mechanism by which HO-1 regulates the innate immune function of infected cells remains unknown. We now show that nitric oxide and haemin, two inducers of HO-1, decrease the level of phosphorylated CagA (p-CagA) in H. pylori-infected gastric epithelial cells and this is blocked by either pharmacological inhibition of HO-1 or siRNA knockdown of hmox-1. Moreover, forced expression of HO-1 by transfection of a plasmid expressing hmox-1 also results in a strong attenuation of CagA phosphorylation. This occurs through the inhibition of H. pylori-induced c-Src phosphorylation/activation by HO-1. Consequently, H. pylori-induced cytoskeletal rearrangements and activation of the pro-inflammatory response mediated by p-CagA are inhibited in HO-1-expressing cells. These data highlight a mechanism by which the innate immune response of the host can restrict the pathogenicity of H. pylori by attenuating CagA phosphorylation in gastric epithelial cells.

Performance of a one-step fecal sample-based test for diagnosis of Helicobacter pylori infection in primary care and mass screening settings

BACKGROUND/PURPOSE

An alternative screening test is needed to efficiently eradicate Helicobacter pylori from a population with prevalent upper gastrointestinal lesions. We evaluated the performance of a new one-step fecal test for H. pylori for diagnosis of H. pylori infection in Taiwan.

METHODS

We developed a fecal test to detect H. pylori based on the immunochronomatographic assay and a mixture of monoclonal antibodies. We first recruited symptomatic patients from the primary care setting to evaluate fecal test performance using a reference standard consisting of (13)C urea breath test, rapid urease test, and histology. We also compared the performance of the fecal test with that of others. Next, we recruited asymptomatic participants from the mass screening setting to evaluate population attendance for the fecal test and compared its performance with that of (13)C urea breath test.

RESULTS

In the primary care setting, 117 patients were recruited; H. pylori infection was confirmed in 58 (49.6%). Fecal test sensitivity, specificity, positive and negative predictive values, and accuracy were 88.0% [95% confidence interval (CI): 79.6-96.4%], 100%, 100%, 89.4% (95% CI, 82.0-96.8%), and 94% (95% CI, 89.7-98.3%), respectively. Fecal test specificity and positive predictive value were significantly higher than those of the serological test, whereas the sensitivity and negative predictive value were lower than those of the (13)C urea breath test (p < 0.05). In the mass screening setting, 2720 of 3520 invited individuals participated (77.3%; 95% CI, 76-78.7%); 649 (23.9%) showed positive results. Concordance rate and kappa statistic between the fecal test and (13)C urea breath test were 91.7% (563/614; 95% CI, 89.9-94.1%) and 0.78 (95% CI, 0.73-0.84), respectively.

CONCLUSION

Given the acceptable sensitivity, excellent specificity, and high participation rate to screening, the one-step H. pylori stool antigen test is feasible for wide application in the community.