Association of CagA-positive infection with Helicobacter pylori antibodies of IgA class

Helicobacter pylori infection in patients with selective immunoglobulin a deficiency

Selective immunoglobulin A (IgA) deficiency (IgAD) is the most common primary immunodeficiency in the western world. The aim of the study was to investigate the prevalence and clinical characteristics of Helicobacter pylori-infected dyspeptic patients with IgAD. Case samples were drawn from all subjects ≥ 12 years of age (n = 104729) who had undergone serum total IgA measurements during 2004-14 for any reason at Leumit Healthcare Services (Israel) and had serum total IgA < 0·07 g/l. The control group was comprised of a random sample of remaining patients with a case-control ratio of 10 controls for each case. The dyspeptic diseases were identified and retrieved from Leumit Health Care Services electronic database using specific ICD-9-CM diagnostic codes. The case group included 347 subjects and the control group 3470 subjects. There were no significant differences in the prevalence of patients with dyspepsia [84 (24·2%) versus 821 (23·6%) for cases and controls, respectively]. Additionally, there was no difference in a proportion of dyspeptic H. pylori-positive subjects [59 (17·1%) versus 524 (15·1%)] between the case and control groups. Only 59 (17%) among the 347 IgAD patients underwent gastroscopy. A significantly larger proportion of case subjects experienced several forms of gastritis [13 (61·9%) versus 38 (21·6%), P < 0·001), duodenal ulcers [seven (33·3%) versus 19 (10·8%); P = 0·01] and nodular lymphoid hyperplasia (NLH) [two (9·5%) versus none; P = 0·011]. IgAD is not associated with increased prevalence of H. pylori-associated dyspepsia; nevertheless, H. pylori-infected dyspeptic IgAD subjects experience more EGD-proved gastritis, duodenal ulcers and NLH.

CagA, a major virulence factor of Helicobacter pylori, promotes the production and underglycosylation of IgA1 in DAKIKI cells

While Helicobacter pylori (Hp) infection is closely associated with IgA nephropathy (IgAN), the underlying molecular mechanisms remain to be elucidated. This study was to investigate the effect of cytotoxin associated gene A protein (CagA), a major virulence factor of Hp, on the production and underglycosylation of IgA1 in the B cell line DAKIKI cells. Cells were cultured and treated with recombinant CagA protein. We found that CagA stimulated cell proliferation and the production of IgA1 in a dose-dependent and time-dependent manner. Moreover, CagA promoted the underglycosylation of IgA1, which at least partly attributed to the downregulation of β1,3-galactosyltransferase (C1GALT1) and its chaperone Cosmc. In conclusion, we demonstrated that Hp infection, at least via CagA, may participate in the pathogenesis of IgAN by influencing the production and glycosylation of IgA1 in B cells.

Immune responses against Helicobacter pylori in gastric cancer patients and in risk groups for gastric cancer

BACKGROUND

It has previously been reported that weak serum IgG but elevated IgA antibody responses against H. pylori may be associated with risk of gastric cancer (GC) development. To search for potential immunologic markers for GC, we analyzed antibody responses against H. pylori in risk groups of cancer development.

MATERIAL AND METHODS

Sera and stomach biopsies collected from H. pylori-infected GC patients as well as from patients with gastric ulcer (GU), atrophic gastritis, intestinal metaplasia (IM) and duodenal ulcer and from H. pylori-infected control subjects without atrophy or IM, and in addition from H. pylori-negative subjects were analyzed for IgG and IgA antibodies against three different H. pylori antigen preparations, that is, membrane protein (MP), urease, and CagA.

RESULTS

We observed an increased serum IgA/IgG titer ratio against H. pylori anti-MP in GC and GU patients, and against CagA in Hp-infected GC patients and risk groups. Female patients with GC had a higher serum anti-MP IgA/IgG titer ratio and a higher proportion of poorly differentiated cancer compared with male patients. As earlier observed, the non-tumorous mucosa of H. pylori-infected GC patients contained considerably lower levels of total IgA and H. pylori-specific IgA compared with H. pylori-infected controls. Similarly, we observed decreased specific mucosal anti-MP IgA response in patients with IM.

CONCLUSION

We observed several differences in local and systemic immunologic responses against H. pylori in H. pylori-infected GC patients and putative GC risk group patients compared with H. pylori-infected controls. These findings may be of importance in efforts to identify risk groups of GC or early stages of GC.

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.

Helicobacter pylori IgA and IgG antibodies, serum pepsinogen I and the risk of gastric cancer: changes in the risk with extended follow-up period

The prediction of Helicobacter pylori antibodies immunoglobulin A (IgA) and immunoglobulin G (IgG) and serum pepsinogen I (PG I) on gastric cancer occurrence was studied in a nested case-control study, based on 225 incident cancer cases and 435 matched controls from a Finnish cohort followed from 1966-1991. The odds ratio of noncardia gastric cancer between infected and noninfected persons was 3.12 (95% confidence interval (CI)=1.97-4.95) for elevated IgA and 2.88 (CI: 1.63-5.07) for elevated IgG antibodies. The odds ratio between low and high PG I was 2.24 (CI: 1.43-3.49). The strength of association was significant for IgA antibodies during the total follow-up, but for IgG antibodies this was only true for follow-up periods of 15 years or more. IgA antibodies were significantly associated with all registered histological subtypes apart from intestinal type adenocarcinoma. The highest gastric cancer risk was found among individuals with simultaneously elevated IgA and IgG antibodies and low PG I with an odds ratio of 10.9 (CI: 4.31-27.7) in comparison with those who were negative for both antibodies and had normal PG I. Elevated IgA and IgG antibodies and low PG I were not associated with cancers of the gastric cardia. The findings support the hypothesis that H. pylori infection is a cause of noncardia gastric cancer. Although elevated H. pylori IgA and IgG antibodies and low PG I independently could predict the occurrence of noncardia gastric cancer, their power to do so varied with the stage and length of the follow-up period and it increased when they were applied in combination.

IgA antibodies in persisting Helicobacter pylori infection in Finnish adults

Most individuals infected with Helicobacter pylori have elevated levels of specific IgG antibodies, but only in about two-thirds of cases does the IgA titre exceed the cut-off level. The aim of this study was to determine whether H. pylori-infected subjects with elevated IgG levels would subsequently produce IgA antibodies, and whether elevated IgA levels increased during infection. Paired sera were available from 336 adults who took part in a large population-based health survey in 1977-1980 and a follow-up study on asthma and atopic diseases in 1997-1998 (series A). Data on paired sera from 224 adults who participated in a population-based health survey in Vammala, Finland in 1973 and who gave a follow-up blood sample in 1994 (series B) were also re-analysed. H. pylori IgG and IgA levels were determined with commercially available (series A) and in-house (series B) enzyme immunoassays. Twenty-one (35%) of the 60 subjects who initially had elevated levels of IgG antibodies only were found to be IgA-positive at follow-up. In those subjects whose baseline and follow-up samples were IgG- and IgA-positive, the median IgA levels increased by 48% and 22% in series A and B (p < 0.0001 and p 0.0241), respectively, whereas the median IgG levels did not change significantly in either series. During H. pylori infection, an increase in specific IgA was reflected by the increase in the number of responders and by the rise in titres.

Association of Helicobacter pylori IgA antibodies with the risk of peptic ulcer disease and gastric cancer

AIM

To compare the prevalence of Helicobacter pylori (H pylori) IgG and IgA antibodies between adult subjects, with defined gastric diseases, non-defined gastric disorders and those representing the population.

METHODS

Data on H pylori IgG and IgA antibodies, determined by enzyme immunoassay, were analyzed in 3,252 subjects with DGD including 482 patients with gastric ulcer, 882 patients with duodenal ulcer, 1,525 patients with chronic gastritis only and 363 subjects with subsequent gastric cancer, 19,145 patients with NoDg and 4,854 POPUL subjects. The age-adjusted prevalences were calculated for 1- and 20-year age cohorts.

RESULTS

The prevalences of IgG antibodies were equally high (89-96%) in all 20-year age cohorts of the DGD groups, whereas the prevalences of IgG antibodies were lower and increased by age in the POPUL and NoDg groups. The prevalences of IgA antibodies were also higher in the DGD groups; among them CA (84-89%) and GU groups (78-91%) showed significantly higher prevalences than DU (68-77%) and CG patients (59-74%) (OR 2.49, 95%CI 1.86-3.34 between the GU and DU groups). In the CA, GU, and DU groups, the IgA prevalences showed only minor variation according to age, while they increased by age in the CG, POPUL, and NoDg groups (P<=0.0001). The IgA response, but not the IgG response, was associated with an increased risk of CA (OR 2.41, 95%CI 1.79-3.53) and GU (OR 2.57, 95%CI 1.95-3.39) in comparison with CG patients.

CONCLUSION

An IgA antibody response during H pylori infection is significantly more common in CA and GU patients as compared with CG patients.