A novel diagnostic monoclonal antibody specific for Helicobacter pylori CagA of East Asian type

The validation of the Helicobacter pylori CagA typing by immunohistochemistry: nationwide application in Indonesia

We aimed to validate 2 types of antibodies, anti-CagA antibody and anti-East Asian CagA specific antibody (α-EAS antibody) for the determination of CagA status in Indonesia. We also confirmed the performance of α-EAS antibody for the detection of East Asian-type CagA H. pylori. Immunohistochemistry was performed using anti-CagA antibody and α-EAS antibody on gastric biopsy specimens from a total of 967 Indonesian patients. Diagnostic values of immunohistochemistry were evaluated with PCR-based sequencing as gold standard. Anti-CagA antibody had high sensitivity, specificity, and accuracy (87.0 %, 100 %, and 98.8 %, respectively) for determining CagA status. The α-EAS antibody was not suitable for the purpose of CagA status determination, as it had a low sensitivity (23.9 %). High specificity (97.6 %) but low sensitivity (41.2 %) and accuracy (66.3 %) was observed in α-EAS antibody to detect East Asian-type CagA. Patients with positive result of immunohistochemistry using anti-CagA antibody had significantly higher monocyte infiltration score in antrum (P < 0.001) and corpus (P = 0.009). In conclusion, the anti-CagA antibody is still suitable to be used in Indonesia for determining the CagA status, whilst the α-EAS antibody was not appropriate to discriminate between East Asian-type and non-East Asian-type CagA in Indonesia.

Detection of Anti-CagA Antibodies in Sera of Helicobacter pylori-Infected Patients Using an Immunochromatographic Test Strip

The cagA gene of Helicobacter pylori that encodes an immunodominant CagA protein provokes severe mucosal damage and acts as a risk factor for the development of peptic ulcer disease and gastric cancer. Our aim is to develop an immunochromatographic test strip (ICTS) using our previously developed recombinant CagA (rCagA) protein and anti-rCagA monoclonal antibody (Mab) for the detection of anti-CagA antibodies in sera of infected patients. The rCagA was firstly conjugated to gold nanoparticle and placed into the conjugate pad. A nonconjugated rCagA and anti-rCagA Mab (CK-02) were immobilized on the test line and control line, respectively. Biopsy and serum samples from 30 H. pylori-infected patients were used. The presence of cagA gene in biopsy samples was first detected by PCR (Polymerase Chain Reaction), and 22 patients were found positive while 8 were negative. When serum samples were tested by our developed ICTS, 21 were positive for anti-CagA antibodies while 9 were negative. The serum samples were also tested by a commercial ELISA (Enzyme Linked Immunosorbent Assay), and when compared to the ICTS a sensitivity of 95% and a specificity of 100% were obtained. The ICTS can be used for rapid detection of CagA-positive H. pylori infection instead of expensive, time consuming and laborious invasive approaches.

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Autophagy-related genes in Helicobacter pylori infection

BACKGROUND

In vitro studies have shown that Helicobacter pylori (H. pylori) infection induces autophagy in gastric epithelial cells. However, prolonged exposure to H. pylori reduces autophagy by preventing maturation of the autolysosome. The alterations of the autophagy-related genes in H. pylori infection are not yet fully understood.

MATERIALS AND METHODS

We analyzed autophagy-related gene expression in H. pylori-infected gastric mucosa compared with uninfected gastric mucosa obtained from 136 Bhutanese volunteers with mild dyspeptic symptoms. We also studied single nucleotide polymorphisms (SNPs) of autophagy-related gene in 283 Bhutanese participants to identify the influence on susceptibility to H. pylori infection.

RESULTS

Microarray analysis of 226 autophagy-related genes showed that 16 genes were upregulated (7%) and nine were downregulated (4%). We used quantitative reverse transcriptase polymerase chain reaction to measure mRNA levels of the downregulated genes (ATG16L1, ATG5, ATG4D, and ATG9A) that were core molecules of autophagy. ATG16L1 and ATG5 mRNA levels in H. pylori-positive specimens (n=86) were significantly less than those in H. pylori-negative specimens (n=50). ATG16L1 mRNA levels were inversely related to H. pylori density. We also compared SNPs of ATG16L1 (rs2241880) among 206 H. pylori-positive and 77 H. pylori-negative subjects. The odds ratio for the presence of H. pylori in the GG genotype was 0.40 (95% CI: 0.18-0.91) relative to the AA/AG genotypes.

CONCLUSIONS

Autophagy-related gene expression profiling using high-throughput microarray analysis indicated that downregulation of core autophagy machinery genes may depress autophagy functions and possibly provide a better intracellular habit for H. pylori in gastric epithelial cells.

Prostate stem cell antigen gene TT genotype and development of intestinal metaplasia in Helicobacter pylori infection

OBJECTIVES

Gastric cancer is etiologically related to interactions between Helicobacter pylori (H. pylori) infection, environmental and host factors. Gastric carcinoma is associated with a cascade of increasing atrophic gastric mucosal damage. Prostate stem cell antigen (PSCA) polymorphisms have been associated with an increased risk of gastric cancer. We aimed to examine the interaction between PSCA polymorphisms and H. pylori in the progression of H. pylori-related gastritis.

METHODS

The genotypes (TT, TC and CC) of PSCA single nucleotide polymorphism rs2294008 among H. pylori infected and uninfected Bhutanese were compared with the severity of H. pylori-related gastritis [neutrophils, monocytes, atrophy scores, H. pylori density, and the presence and extent of intestinal metaplasia (IM)] using the updated Sydney system.

RESULTS

Biopsies from 339 participants were included. The proportion of biopsies with IM was significantly (P < 0.05) greater in those with the TT genotype than in either those with the CT or CC genotype. Although no significant differences were found in inflammation or H. pylori density scores, the scores for IM at both gastric corpus and antrum among participants infected by H. pylori with the TT genotype was significantly (P < 0.05) greater than in the C allele carriers.

CONCLUSION

PSCA TT genotype is associated with a more than a threefold increase in the prevalence and the extent of gastric mucosal IM compared to C allele carriers among H. pylori-infected Bhutanese.

Biomarkers for Helicobacter pylori infection and gastroduodenal diseases

Helicobacter pylori infection is a major cause of gastric cancer. Although identifying H. pylori infected subjects is the first approach for delineating the high-risk population for gastric cancer, the presence of H. pylori antibodies is not sufficient for gastric cancer screening. Among H. pylori infected subjects, only a minority of infected individuals develop gastric cancer. Serologic markers of H. pylori infection can serve as potential predictors for the development of gastric cancer. Serum or urinary H. pylori antibodies, cytotoxin-associated gene A antibodies, pepsinogen and microRNAs were reported to be associated with precancerous lesions or gastric cancer. In this review, we summarized the utilities and limitations of each strategy.

Differences in interleukin 8 expression in Helicobacter pylori-infected gastric mucosa tissues from patients in Bhutan and the Dominican Republic

The outcomes of Helicobacter pylori infection vary geographically. H pylori strains, disease presentation, and environments differ markedly in Bhutan and Dominican Republic. The aims were to compare the strains, histology, and expression of interleukin (IL) 8 and IL-10 from gastric mucosa from the 2 countries. H pylori status was assessed by the combination of rapid urease test, culture, and histology. Histology was evaluated using the updated Sydney System, and cytokines in gastric biopsies were measured using real-time polymerase chain reaction (PCR). There were 138 subjects from Bhutan and 155 from Dominican Republic. The prevalence of H pylori infection was 65% and 59%, respectively. The genotype of cagA was predominantly East Asian type in Bhutan versus Western type in Dominican Republic. Gastritis severity was significantly higher in H pylori-infected subjects from Bhutan than those from Dominican Republic. IL-8 expression by H pylori infection was 5.5-fold increased in Bhutan versus 3-fold in Dominican Republic (P < .001); IL-10 expression was similar. IL-8 expression levels among H pylori-infected cases tended to be positively correlated with polymorphonuclear leucocyte and monocyte infiltration scores in both countries. IL-8 expression among those with grade 2 and 3 polymorphonuclear leucocyte and monocyte infiltration was significantly higher in Bhutan than in Dominican Republic. The difference in IL-8 expression in the 2 countries is reflected in the different disease pattern between them. Whether the dominant factor is differences in H pylori virulence, in host-H pylori-environmental interactions, genetic factors or all remains unclear. However, severity of inflammation appears to be a critical factor in disease pathogenesis. We compared IL-8 messenger RNA levels between the high gastric cancer risk country, Bhutan (mainly East Asian-type H pylori), and the lower gastric cancer risk country, Dominican Republic (mainly Western-type H pylori).

Serum Helicobacter pylori CagA antibody titer as a useful marker for advanced inflammation in the stomach in Japan

BACKGROUND AND AIM

Subjects infected with Helicobacter pylori containing cagA do not always induce serum CagA antibody. Our previous meta-analysis showed that serum CagA seropositivity was associated with gastric cancer even in East Asian countries. However, it remains unclear why serum CagA-positive status is associated with gastric cancer. In this study, we aimed to examine the relationship between anti-CagA antibody titer and the levels of pepsinogen (PG), and histological score.

METHODS

Eighty-eight H. pylori-positive Japanese patients with gastritis were included. Serum CagA antibody titer, PG I, and PG II were evaluated by ELISA. Histological scores were evaluated according to Update Sydney System. CagA expression was examined by immunoblot.

RESULTS

Seroprevalence of CagA antibody was found in 75.0%. Interestingly, serum CagA antibody titer was significantly correlated with PG I and PG II levels (P = 0.003 and 0.004, respectively). Serum CagA antibody titer was also significantly correlated with mucosal inflammation in the corpus (P = 0.04). On the other hand, bacterial density was not related with CagA antibody titer. CagA expression level of the strains was irrespective of the status of PG and serum CagA antibody.

CONCLUSIONS

Subjects with higher serum CagA antibody titer can be considered as high-risk population for the development of gastric cancer from the point of strong gastric inflammatory response even in Japan. Host recognition rather than bacterial colonization might be associated with the difference of serum CagA antibody titer.

Serum Helicobacter pylori CagA antibody as a biomarker for gastric cancer in east-Asian countries

AIMS

In east-Asian countries, while almost all Helicobacter pylori strains possess the cytotokine-associated gene A (CagA) gene, serum CagA antibody is not detected in some infected subjects. We aimed to clarify the association between anti-CagA antibody and gastric cancer in east-Asian countries.

MATERIALS AND METHODS

We performed a meta-analysis of case-control studies with age- and sex-matched controls, which provided raw data in east-Asian countries.

RESULTS

Ten studies with a total of 4325 patients were identified in the search. Some reports from Japan, Korea and China showed a positive association between the presence of anti-CagA antibody and gastric cancer; however, the results differed in their various backgrounds. The disparate findings appeared to result from the use of different methods or from variations in the antigens used to detect the anti-CagA antibody. CagA seropositivity was associated with an increased risk of developing gastric cancer.

CONCLUSION

Anti-CagA antibody can be used as a biomarker for gastric cancer even in east-Asian countries.

Impact of Helicobacter pylori CagA diversity on gastric mucosal damage: an immunohistochemical study of East-Asian-type CagA

BACKGROUND AND AIMS

Recently, we successfully produced an anti-East-Asian-type CagA-specific antibody called α-EAS Ab, which is specifically immunoreactive only with East-Asian-type CagA but not Western-type CagA. In this study, the correlations between Helicobacter pylori CagA protein diversity and gastric mucosal condition was investigated using immunohistochemical staining with α-EAS Ab in Japan.

METHODS

There were 254 H. pylori-positive patients enrolled in this study. α-EAS Ab was used to determine the CagA phenotype instead of cagA sequencing, and, moreover, the histological findings and endoscopic gastric mucosal condition were evaluated according to the updated Sydney System and the Kimura-Takemoto classification system, respectively.

RESULTS

A total of 224 (88.2%) of the patients were immunoreactive for α-EAS Ab. The remaining 30 (11.8%) were negative for α-EAS Ab, suggesting that they were infected with either Western-type CagA or CagA-negative strains (i.e. non-East-Asian-type CagA strains). The grades of activity of gastritis, mucosal atrophy and intestinal metaplasia according to the updated Sydney System were significantly higher in patients infected with East-Asian-type CagA strains than those infected with non-East-Asian-type CagA strains. The grade of endoscopic gastric mucosal atrophy evaluated using the Kimura-Takemoto classification system was similar. All 28 strains isolated from patients with gastric cancer possessed the East-Asian-type CagA.

CONCLUSIONS

  Infection with East-Asian-type CagA H. pylori was more closely associated with gastric mucosal atrophy and gastric cancer than infection with non-East-Asian-type CagA H. pylori. The efficiency of immunohistochemical analysis for CagA should be equivalent to that of cagA sequencing.

Diagnosis of Helicobacter pylori infection

If we had to give a general view of the articles published in the year 2010, we should conclude that the evidence in the year 2010 suggests that, also in Helicobacter pylori diagnosis, "the devil is in the details". In this sense, different studies suggested that skipping citric acid pretreatment or local validation or reducing the (13) C-urea dose markedly decreases the accuracy of the urea breath test. The studies also implied that, even between monoclonal stool tests, there are large differences between the marketed tests. Finally, even histology does not work adequately in patients with gastric cancer or extensive areas of intestinal metaplasia. In these cases, specific gastric sites should be biopsied to improve the reliability of histology.

Development of immunoreagents for diagnostics of CagA-positive Helicobacter pylori infections

BACKGROUND

Helicobacter pylori strains expressing cytotoxic CagA protein are more likely to provoke severe gastric mucosal pathology and cause adenocarcinoma development than that lacking CagA. Determination of the CagA-status of a pathogen, therefore, is regarded as informative approach in H. pylori infection diagnostics and disease risk prediction.

MATERIALS AND METHODS

Molecular cloning, recombinant protein expression in Escherichia coli, affinity chromatography, electrophoresis and commonly used techniques of hybridoma production and screening were used as well as different immunosorbent assays and Western blot procedures.

RESULTS

Four overlapping N-terminally His(6)-tagged recombinant fragments of CagA that covered the entire CagA sequence were produced and purified. An ELISA for specific anti-CagA serum antibodies detection was developed and evaluated. Utilizing recombinant fragments, the first set of monoclonal antibodies against CagA-antigen was produced and characterized. Three antibodies recognized distinct linear epitopes inside conserved regions of the cytotoxin whereas the epitope of the forth antibody was mapped in the variable area of CagA. The monoclonal antibodies allowed discriminating CagA-positive and CagA-negative H. pylori strains by means of Western blot and immunosorbent assays.

CONCLUSIONS

The use of recombinant protein technology allowed obtaining pure CagA antigen, thus providing new perspectives for development of immunodiagnostic reagents. The set of monoclonal antibodies is a valuable tool for determination of CagA-status of H. pylori infection and for the investigation of cytotoxin molecule as well.