Enzyme-linked immunosorbent assay for Campylobacter pyloridis: correlation with presence of C. pyloridis in the gastric mucosa

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.

Helicobacter species in the human colon

OBJECTIVE

To determine the prevalence, frequency and colonization patterns of Helicobacter species throughout the colon.

METHOD

Patients having initial colonoscopy for nonspecific gastrointestinal disturbance had colonic biopsies taken from up to four sites during colonoscopy and examined for evidence of the Helicobacteraceae family using a group-specific PCR. Serum was also collected and examined for IgG reactivity to Helicobacter pylori.

RESULTS

100 patients had colonoscopy of whom 35 were found to have DNA evidence of Helicobacter species throughout the colon, with 22 having H. pylori. Fifteen patients had a demonstrable serum IgG response to H. pylori that was not always associated with molecular evidence of H. pylori DNA in colon biopsies and vice versa. No specific association with colon disease was found in patients with H. pylori infection.

CONCLUSION

We found evidence of Helicobacter infection in a significant number of patients presenting for colonoscopy but no specific association between the presence of these bacteria and colon disease. Our finding of disparity between molecular and serological techniques to detect Helicobacter species suggests that future studies should not rely on serology alone to detect these bacteria in the human colon.

A better method for confirming Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Our aim was to evaluate the accuracy of the stool antigen test and the optimal time point for detecting Helicobacter pylori infection in a Mongolian gerbil model.

METHODS

We inoculated 8-week-old Mongolian gerbils with H. pylori (Vac A (+)/CagA(+)). The gerbil-infected model was developed as follows: H. pylori was put into broth (about 10(9) CFU/ml), and 50 gerbils were then fed with 1 ml intragastrically twice within a 3-day interval. Another ten gerbils were fed broth only. Twenty-six weeks after the inoculation, the gerbils were killed. The gastric mucosa was sampled for a series of examinations including culture, histology, rapid urease test, and polymerase chain reaction. Stool samples for a stool antigen test, H. pylori-specific stool antigen assay (HpSA), were collected during weeks 4, 6, 8, 12, and 26 after inoculation. Of the 50 gerbils inoculated with H. pylori, the inoculation was successful in 88%. Severe active gastritis, ulceration, and intestinal metaplasia were obvious.

RESULTS

The HpSA test results were sensitivity, 88.6%; specificity, 100%; positive predictive value (PPV), 100%; negative predictive value (NPV), 54.5%, and accuracy, 90%. The HpSA test began to be more sensitive and accurate (P < 0.05) beginning during week 6 after inoculation. We also found that H. pylori could be detected earlier and more easily in the group with high H. pylori density.

CONCLUSIONS

HpSA seems to be suitable for confirming colonization of gerbils with H. pylori. The optimal testing time point is around 6 weeks after inoculation. This test is a good choice for long-term observation of H. pylori infection in Mongolian gerbils.

Chronic Chlamydia pneumoniae infection may promote coronary artery disease in humans through enhancing secretion of interleukin-4

Atherosclerosis is an inflammatory response, probably to a range of initiating causes. Chronic infection with Chlamydia pneumoniae (C.pn) has been suggested as one cause, but the nature of the association is controversial, in large part due to lack of an identified mechanism to link infection with the atherosclerotic process in man. This study examined 139 consecutive subjects with stable chest pain, with the aim of correlating the serological status of C.pn infection with the pattern of secretion of cytokines from CD4(+) T lymphocytes. C.pn seropositive subjects secreted significantly more interleukin (IL)-4 than did those who were C.pn seronegative (P = 0.02). No significant difference was noted for secreted interferon (IFN)-gamma. The amount of secreted IL-4, but not of secreted IFN-gamma, correlated positively with the extent of coronary artery disease (P = 0.006). A similar correlation with secreted IL-4 was not identified with Helicobacter pylori infection. These results support the hypothesis that C.pn infection contributes to the inflammatory process responsible for coronary artery atherosclerosis. The method used to detect cytokine secretion involves ligation of CD40L on blood CD4(+) T cells, which may have relevance to tissue events.

Selective reduction of anti-Helicobacter pylori IgG subclass antibody in gastric carcinoma

BACKGROUND

Epidemiological studies have demonstrated strong links between Helicobacter pylori infection and gastric adenocarcinoma. Recent studies suggest that cell-mediated immunity influences the outcome of infection, including the development of gastric adenocarcinoma. The T-cell response can be characterized in terms of the secreted cytokine profile, which in turn influences the B-cell response including the balance of IgG subclass antibody.

METHODS

Serum anti-H. pylori IgG, IgG1 and IgG2 antibodies were studied by ELISA in subjects with benign gastric diseases, gastric dysplasia and gastric adenocarcinoma.

RESULTS

The distribution patterns of IgG subclass anti-H. pylori antibody varies significantly between H. pylori-linked benign and malignant disease in subjects infected with H. pylori. Significantly lower IgG2 levels were found in subjects with gastric adenocarcinoma compared with those with reflux esophagitis, chronic gastritis, gastric ulcer, and peptic ulcer, while IgG1 antibody remained at similar levels in both benign and malignant disease. A limited study of seropositive subjects with premalignant change was consistent with the fall in IgG2 antibody pre-dating malignant change, although pre-eradication results are needed to validate these data.

CONCLUSIONS

These studies indicate that subjects with low levels of IgG2 anti-H. pylori antibody are at risk of gastric adenocarcinoma, and that the previously described linkage between gastric adenocarcinoma and low total IgG antibody does not simply reflect reduced gastric colonization. The diagnostic value of this assay for pre-endoscopy screening is attractive.

Impaired host immunity contributes to Helicobacter pylori eradication failure

OBJECTIVES

Effective eradication of Helicobacter pylori (H. pylori) infection has often proved more difficult than expected. Antimicrobial resistance incompletely explains eradication failure. This study tests the hypothesis that an impaired immune response may contribute to failed eradication after standard antibiotic therapy.

METHODS

Parameters of host immunity were assessed as blood T lymphocyte production of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) being surrogate markers of mucosal Th1 and Th2 responses, respectively. The validity of using circulating T cell cytokines as surrogate markers of mucosal immunity was established (unstimulated lymphocyte IL-4 level correlation r2 = 0.549, p < 0.001; antigen-stimulated lymphocyte correlation r2 = 0.62, p < 0.001).

RESULTS

A total of 52 dyspeptic patients and 11 patients with previous H. pylori eradication failure were recruited into the study. There was no significant difference in secretion of IFN-gamma from peripheral blood T cells, in either unstimulated or antigen-stimulated cultures, between clinical groups. There was, however, a significant reduction in secretion of IL-4 from blood T cells in subjects failing to eradicate H. pylori compared with those who successfully eradicated the infection in both unstimulated and stimulated cultures. A significant difference in IL-4 secretion was also detected in antigen-stimulated cultures compared with that in H. pylori-positive subjects (p < 0.05). Low levels of IL-4 secretion were detected irrespective of the number of courses of antibiotic therapy. Lower levels of IgG anti-H. pylori antibody were detected in both serum and saliva of subjects with persistent H. pylori infection after use of antibiotics compared with untreated H. pylori-positive subjects (difference not statistically significant).

CONCLUSIONS

These results support the hypothesis that impaired mucosal immunity, particularly involving the secretion of IL-4, may contribute to H. pylori eradication failure. Measurement of whole blood secretion of IL-4 may predict which patients are more likely to fail standard antibiotic therapy.

Identification of an antigenic epitope in Helicobacter pylori urease that induces neutralizing antibody production

We previously reported a mouse monoclonal antibody (MAb), termed L2, specific for Helicobacter pylori urease strongly inhibited its enzymatic activity. Here, to gain insight into how this antibody affects urease activity, the epitope that was recognized by the antibody was determined. By screening a panel of overlapping synthetic peptides covering the entire sequence of the two subunits (UreA and UreB), we identified a stretch of UreB-derived 19 amino acid (aa) residues (UB-33; aa 321 to 339, CHHLDKSIKEDVQFADSRI) that was specifically recognized by the L2 antibody. Further sequential amino acid deletion of the 19-mer peptide from either end allowed us to determine the minimal epitope as 8 amino acid residues (F8; SIKEDVQF) for L2 reactivity. This epitope appears to lie exactly on a short sequence which formed a flap over the active site of urease, suggesting that binding of the L2 antibody sterically inhibits access of urea, the substrate of urease. Finally, immunization of rabbits with either the 19-mer peptide or the 8-mer minimal epitope resulted in generation of antiurease antibodies that were capable of inhibiting the enzymatic activity. Since urease is critical for virulence of H. pylori, antigenic peptides that induce production of antibodies to inhibit its enzymatic activity may potentially be a useful tool as a vaccine for prevention and treatment of H. pylori infection.

Two-thirds of atrophic body gastritis patients have evidence of Helicobacter pylori infection

BACKGROUND

Helicobacter pylori is involved in the induction of atrophic body gastritis (ABG). During the progression of atrophic gastritis the disappearance of H. pylori has been documented and in time serology is the only sign that indicates a previous infection. It has been shown that a positive serology, in ABG patients without histological evidence of infection, indicates an active H. pylori infection.

AIM

To investigate in a population of patients with ABG the prevalence of H. pylori infection on the basis of histology and serology.

PATIENTS

A total of 150 consecutive outpatients with atrophic body gastritis were diagnosed on the basis of a screening system.

METHODS

All patients had a detailed assessment including measurement of specific anti-H. pylori antibodies, parietal cell antibodies, and fasting gastrin, gastroscopy with biopsies from gastric antrum and body.

RESULTS

24.6% of patients were histologically and serologically negative (Group A). 52.7% H. pylori was not detected on histology but IgG to H. pylori were in all these patients elevated (Group B). 22.6% of patients were found to be positive at histology in the corpus mucosa; all but one of these patients had elevated circulating IgG to H. pylori (Group C). Mean corporal atrophy score in Group B patients was statistically lower than in Group A patients (2.43 +/- 0.08 vs. 2.75 +/- 0.09; p <.05), but was statistically higher than in Group C patients (1.79 +/- 0.11; p <.001). Thus, in corporal mucosa a gradient of atrophy was shown: Group C < Group B < Group A. A similar gradient was observed for the presence of pernicious anemia being lowest in Group C 11.8% increasing to 45.6% in Group B and being highest in Group C 75.6%. A statistical correlation was obtained (r =.04791, p <.05) between the histological score of corporal atrophy and the titer of antibodies to parietal cells and an inverse correlation was obtained (r = -.2322, p <.0001) between the histological score of corporal atrophy and IgG to H. pylori.

CONCLUSION

This study shows that two-thirds of ABG patients have evidence of H. pylori infection. This suggests that atrophic gastritis of the corpus is a spectrum of damage where H. pylori is a key agent able to induce gastric atrophic damage and also gastric autoimmunity.

Shift of the gastric T-cell response in gastric carcinoma

BACKGROUND AND AIMS

The etiology and pathophysiology of stomach carcinoma is complex, and the mechanism whereby H. pylori directly or indirectly induces carcinoma remains unclear. In this study, interleukin (IL)-8, IL-4 and interferon (IFN)-gamma were measured in the tissue culture supernatant of gastric organ cultures from subjects with chronic gastritis with or without H. pylori infection, and with or without gastric cancer and gastric dysplasia.

RESULTS

Interleukin-8 levels were higher in cancer- and H. pylori-infected gastritis subjects than in H. pylori-negative subjects (12.95 +/- 3.16, 10.48 +/- 1.55 and 4.49 +/- 1.28 ng/mL, respectively). Elevated levels of IFN-gamma were detected in both H. pylori-infected and non-infected subjects with uncomplicated gastritis (72.23 +/- 19.0 and 34.61 +/- 5.30 pg/mL) and in non-infected dysplasia subjects (88 +/- 20.5 pg/mL). Background levels of IL-4 (< or = 9.4 pg/mL) in uncomplicated gastritis subjects and relatively high levels of IL-4 in dysplasia subjects (25.8 +/- 7.3 pg/mL) were detected. In contrast, trace amounts of IFN-gamma (16.01 +/- 0.35 pg/mL) and high levels of IL-4 (42.81 +/- 8.49 pg/mL) in gastric biopsy culture supernatants were found in cancer subjects. Mucosal IL-4 levels (but not IL-8 levels) correlated with infection and mucosal anti-H. pylori immunoglobulin G antibody.

CONCLUSIONS

The significant differences between gastritis with and without cancer and dysplasia indicated a shift from a Th1 to a Th2 helper cell pattern of cytokine secretion. This study has identified a local mucosal defect in gastric cancer. The near absence of IFN-gamma production from the mucosa at the margins of the tumor may be a critical factor in promoting growth of neoplastic cells.

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

cagA gene, the best known virulence factor of Helicobacter pylori, codes for an immunodominant CagA protein. In this study, CagA antibodies of the IgG class were measured by immunoblot or enzyme immunoassay in subjects with positive H. pylori serology, and the presence of CagA antibodies was compared with that of H. pylori antibodies of IgA and IgG classes. Serum samples were available for a total of 1,481 subjects, including gastroscopied patients with biopsy-verified H. pylori infection, smoking men with a normal or low serum pepsinogen I level indicating atrophic corpus gastritis, and subjects who later developed gastric cancer and their matched controls. CagA antibodies were significantly more prevalent among individuals with elevated H. pylori antibody titres of the IgA class than in those with IgG antibodies only, with the exception of a small subgroup of individuals who later developed gastric cancer. CagA-positive H. pylori strains seem to induce an immune response with a markedly higher frequency of IgA than what is found in inflammation caused by CagA-negative strains. The presence of serum IgA antibodies to H. pylori seems to indicate a higher risk for CagA-positive H. pylori infection and possibly more severe late sequelae of the disease.

Accurate diagnosis of Helicobacter pylori. Serologic testing

Serologic testing is a useful noninvasive testing strategy for H. pylori. It is particularly useful in areas where the prevalence of H. pylori is high and inexpensive point-of-contact fingerprick tests are used. Sensitive tests are valuable ways of excluding H. pylori infection and can be used in conjunction with a direct test (urease histology culture or breath test) to confirm absence of H. pylori if the two methods are concordant. Serologic testing is more definitive and differentiating if the antigenic epitopes of H. pylori can be differentiated based on the antigenic epitopes that specifically associate with gastric cancer, peptic ulcer, and nonulcer dyspepsia. A study by Kawahara's group reported that Hsp 60 may be involved in the development of mucosa-associated lymphoid tissue based on ELISA. The idea of differentiating antigens for H. pylori may open a new area for use of serologic testing in the diagnostic approach of H. pylori infections.

Non-urease producing Helicobacter pylori in chronic gastritis

BACKGROUND

Helicobacter pylori infection is the commonest cause of gastritis. Different patterns of immune response to H. pylori infection and characteristics of bacteria are considered to contribute to clinical outcomes.

AIM

To determine characteristics of the host H. pylori relationship in subjects with non-ulcer dyspepsia and a histological diagnosis of gastritis.

METHODS

Thirty-five subjects with chronic gastritis undergoing endoscopy (mean age 53 years, range 24-82, 14 male and 21 female) were studied, none of whom was on nonsteroidal anti-inflammatory drugs or antibiotics. H. pylori infection was determined by rapid urease test (CLOtest), culture, antibody and RT-PCR for Ure C, Cag A and 26 kDa gene and histology. Cytokine production of mucosal IL-6 and IL-8 were measured by ELISA.

RESULTS

Fifteen subjects were positive by CLOtest and/or bacterial culture. In these subjects histology showed numerous helical forms of H. pylori (Group I). Nine subjects were negative by CLOtest, bacterial culture, and mRNA for urease C fragment, but positive by PCR for the 26 kDa protein encoding gene. Histology in these subjects showed the presence of either coccoid forms (four), or scant helical forms (two), or mixed coccoid/helical forms (three) (Group II). Eleven subjects were negative by all methods of detection (Group III). IgG and IgA antibody levels in serum (p<0.05) and gastric tissue culture supernatant (p<0.001) were significantly higher in Group I than those in Group II or III. There were significant differences in the IgG serum and IgA supernatant antibody levels (p<0.01 and p<0.05) when Group II was compared to Group III. Supernatant IL-6 levels were significantly higher in Group I (p<0.01) than those from Groups II and III. IL-8 levels were higher in Group I (p<0.01) and Group II (p<0.05) when compared to Group III.

CONCLUSIONS

'H. pylori-negative' gastritis can be associated with a non-urease producing form of H. pylori, with a reduction in both local and systemic antibody levels and mucosal pro-inflammatory cytokines.

Concordance between noninvasive tests in detecting Helicobacter pylori and potential use of serology for monitoring eradication in gastric ulcer

Our aim was to determine concordance between 13C-urea breath test and serology in detecting Helicobacter pylori and to study their potential use for monitoring eradication in patients with gastric ulcer. We prospectively studied 73 gastric ulcer patients. On endoscopy, biopsies were taken for hematoxylineosin staining and rapid urease testing. Blood samples were drawn for immunoglobulin G antibody determination by enzyme-linked immunosorbent assay (ELISA). A 13C-urea breath test was performed as well. Histology, serology, and urea breath tests were all repeated 1, 6, and 12 months after therapy completion in 56 infected patients. A proportion of positive agreement between serology and breath test results as high as 0.95 was found. McNemar statistic was 3 (p = 0.08), whereas kappa statistic was 0.83 (p < 0.0001). At month 6, significant differences in patients successfully treated relative to baseline serologic values were observed (chi2 = 11.7; p < 0.001). The area under the receiver operating characteristic (ROC) curve for diagnostic efficiency was 0.76, sensitivity was 74%, and specificity was 90% (for H. pylori eradication) when the fall of at least one category in serologic levels was considered as cut-off point. No further decreases in serologic levels were noted over the next 6 months, and 48.8% of patients remained seropositive 1 year after completion of successful treatment. A high concordance between serology and 13C-urea breath test results is observed when the two procedures are used for H. pylori infection diagnosis in patients with gastric ulcer. Also, serology can be successfully used for monitoring H. pylori eradication 6 months after therapy completion.

Circulating T-cell response to Helicobacter pylori infection in chronic gastritis

BACKGROUND

Helicobacter pylori elicits a specific humoral and cellular immune response. There is increasing evidence that the type of T-cell response contributes to clinical outcome in H. pylori infection.

MATERIALS AND METHODS

The host response to H. pylori infection in 34 subjects with chronic gastritis was examined in terms of T-cell proliferation and cytokine production in whole-blood cultures stimulated or unstimulated with H. pylori acid-glycine extract antigens (AGE).

RESULTS

The proliferative response in whole-blood cultures was similar for both H. pylori-positive and -negative subjects stimulated with H. pylori AGE. While an increase in interferon-gamma (IFN-gamma) production was observed from both H. pylori-positive and -negative subjects with gastritis, significantly higher levels of IFN-gamma were detected in the former when stimulated with H. pylori AGE. In contrast, interleukin 4 (IL-4) was undetectable regardless of antigen stimulation. However, if an in situ IL-4 antibody capture assay was used, antigen-independent production of IL-4 was detected, but there was no difference between H. pylori-positive and -negative subjects with gastritis. After eradication of H. pylori, antigen-induced production of IL-4 was increased, with no decrease in the levels of secretion of IFN-gamma. IL-4 production was dependent on CD4+ T cells, as addition of anti-CD4 but not anti-CD8 mouse monoclonal antibody or matched IgG isotype to the whole-blood culture inhibited the production of IL-4.

CONCLUSION

The results suggest that a shift toward a balanced Th1-Th2 response due to an increase in antigen-induced IL-4 production from CD4+ T cells follows eradication. We suggest that the downregulation of mucosal inflammation consequent on reduction in antigen levels or removal of downregulation after eradication of H. pylori contributes to this shift in cytokine balance.

Sonicated diagnostic immunoblot for bartonellosis

Two simple Bartonella bacilliformis immunoblot preparation methods were developed. Antigen was prepared by two different methods: sonication of whole organisms or glycine extraction. Both methods were then tested for sensitivity and specificity. Well-defined control sera were utilized in the development of these diagnostic immunoblots, and possible cross-reactions were thoroughly examined. Sera investigated for cross-reaction with these diagnostic antigens were drawn from patients with brucellosis, chlamydiosis, Q fever, and cat scratch disease, all of whom were from regions where bartonellosis is not endemic. While both immunoblots yielded reasonable sensitivity and high specificity, we recommend the use of the sonicated immunoblot, which has a higher sensitivity when used to detect acute disease and produces fewer cross-reactions. The sonicated immunoblot reported here is 94% sensitive to chronic bartonellosis and 70% sensitive to acute bartonellosis. In a healthy group, it is 100% specific. This immunoblot preparation requires a simple sonication protocol for the harvesting of B. bacilliformis antigens and is well suited for use in regions of endemicity.

Does quantitative serologic testing for Helicobacter pylori predict peptic ulcer disease in cirrhosis?

BACKGROUND

Helicobacter Pylori is strongly associated with peptic ulcer disease. A correlation between high IgG serum antibody concentrations and a clinical diagnosis has been reported. It has been recognized that peptic ulcer disease occurs with increased frequency in cirrhosis. In this study, we attempted to establish a relation between the magnitude of serum IgG antibody to H pylori and the endoscopic diagnoses in H pylori-infected cirrhotic patients.

METHODS

All cirrhotic patients who had undergone esophagogastroduodenoscopy with a positive H pylori IgG serology and who did not receive anti-H pylori treatment or take medications noxious to the gastroduodenal mucosa were included in the study. H pylori IgG serology was determined by an enzyme-linked immunosorbent assay with values of greater than 50 units/mL being seropositive. The functional reserve of cirrhosis was classified by modified Pugh-Child criteria.

RESULTS

One hundred four seropositive cirrhotic patients were recruited. The serum IgG titers ranged from 51 to 1200 units/mL with a peak frequency at 50 to 99 units/mL (35. 6%). Statistical analysis did not reveal any relation between the quantitative H pylori IgG values and the endoscopic diagnoses, which included gastric ulcers, duodenal ulcers, gastroduodenal erosions, and normal findings.

CONCLUSIONS

In cirrhosis, the magnitude of H pylori IgG serology cannot be used to predict the presence or absence of peptic ulcer disease.

Correlation of kinin generating activity with Helicobacter pylori-associated gastric infection

The kallikrein-kinin system involves a biologically complex set of interactive proteases that signal the first-line onset of inflammation and associated cellular processes. The basic enzymatic cleavage of kininogen substrate by the serine protease tissue kallikrein to liberate kinins is regulated by a number of factors. These may include the recently discovered bacterial involvement in the causation of gastritis. The gram-negative Helicobacter pylori organism, colonises the human gastric epithelium and initiates ulcerogenesis and may induce, in the longer term, tumour formation. The aim of this study was to investigate the role of kinins in H. pylori-induced gastric dyspepsia. During endoscopic examination, lavage aspirates of 23 patients were collected, and the tissue kallikrein content measured by a kinin-generating assay and an enzyme-linked immunosorbent assay. Gastric antral and pyloric biopsy tissue was histologically examined for degrees of inflammation and H. pylori infection, and then immunolabelled for tissue kallikrein and kinin receptors. Results show that labelled tissue kallikrein in the fundic glands and parietal cells of the diseased antrum was elevated with increasing severity of gastritis. Further, kinin-generating potential of the lavage fluid appeared to be greater with increasing evidence of infection. Tissue kallikrein immunosorbent assay levels were significantly raised in patients showing mild to moderate H. pylori infection. One outcome of this study may be the inclusion of kinin antagonists in management of gastric dyspepsia.

Gastric inflammation is enhanced in children with CagA-positive Helicobacter pylori infection

BACKGROUND

Helicobacter pylori infection is likely to be acquired at an early age. The factors leading to active inflammation in childhood, however, are largely unknown.

SUBJECTS AND METHODS

We determined the CagA status, the best characterized virulence factor of H. pylori, and serum antibodies of IgG and IgA classes to H. pylori in 39 infected children.

RESULTS

Mononuclear cell infiltration in the antrum but not in the gastric body was more intense in CagA-positive children than in CagA-negative children. The degree of polymorphonuclear cell infiltration on the other hand was independent of the CagA status. The antibody titers of IgG and IgA classes to H. pylori were higher in CagA-positive than in CagA-negative infections (P<0.001 and P<0.01, respectively). IgG antibody titers to H. pylori correlated directly with the density of mononuclear and polymorphonuclear cell infiltration in the gastric antrum but not in the gastric body.

CONCLUSION

H. pylori-infected children with CagA antibodies seem to have a more severe inflammation in the gastric antrum than CagA-negative children as shown by an increase in the density of antral mononuclear cells. A finding of higher serum antibody titers to H. pylori in CagA-positive children may be related to this enhancement of inflammation.

Evaluation of enzyme-linked immunosorbent assay for the diagnosis of Helicobacter pylori infection in children from different age groups with and without duodenal ulcer

BACKGROUND

Although enzyme-linked immunosorbent assay (ELISA) is highly sensitive and specific for the diagnosis of Helicobacter pylori infection in adults, their performance in children is still controversial.

METHODS

A second-generation ELISA was used to evaluate the IgG response to H. pylori in the serum of 130 consecutive children who underwent upper gastrointestinal endoscopy. The presence of H. pylori was determined in antral biopsy specimens by culture, urease test, and histologic analysis.

RESULTS

Sixty-eight children (all of the 20 who had duodenal ulcer) were H. pylori positive by microbiologic test. Immunoglobulin G antibodies to H. pylori were detected in 79.4% of the infected children and in 8.1% of the noninfected ones. The sensitivity of the test was higher in patients with duodenal ulcer (100%) than in those without (70.8%). When used in children of different ages the test also presented differences in sensitivity: 44.4% in children 2 to 6 years old; 76.7% in children 7 to 11 years old, and 93.1% in children 12 to 16 years old (p = 0.006). The serum immunoglobulin G concentration was significantly higher (p = 0.0003) in children with duodenal ulcer than in those without and was higher in older children than in younger ones without duodenal ulcer (p = 0.05).

CONCLUSIONS

The accuracy of the test in children with duodenal ulcer and in children more than 12 years old was good; however, in children up to 12 years of age without duodenal ulcer, the sensitivity of the test was too low to be used for screening purposes or to rule out the presence of infection.

Coexistence of Helicobacter pylori spiral and coccoid forms in experimental mice

AIM: To infect mice with Helicobacter pylori and detect immune response against two form of H. pylori.

METHODS: An isolate of H. pylori obtained from a patient with gastric cancer was used to infect mice. Fifty mice were divided into eight groups. Two groups served as negative control without any inoculation and internal negative control with 0.5 M NaHCO₃ and brain heart infusion (HBI), respectively. Mice in each experimental group were first inoculated with 0.5 M NaHCO₃ and then H. pylori suspension for 3 times at a 2-d interval. Mice from controls and infectious groups were sacrificed at a weekly interval postinfection. Gastric samples were trimmed, inoculated onto chocolate blood agar and then incujbated in microaerophilic atmosphere at 37¡æ for 14 d. Sera were examined for immunoglobulins against H. pylori spiral and coccoid antigens by ELISA.

RESULTS: After inoculation H. pylori was isolated in one mouse from one week postinfection. No H. pylori was detected in control mice. However, urease test was positive in 50% (5/10) control mice, 70% (7/10) mice inoculated with NaHCO₃ and BHI and 77% (23/30) mice infected with H. pylori. The systemic immune responses of the mice to H. pylori strain were determined by ELISA. The mice showed immune responses to both H. pylori spiral and coccoid antigens one week after infection with H. pylori. The peak mean absorbances of antibodies against spiral and coccoid forms were four weeks postinfection which showed 6 and 18 times higher than that of negative control group respectively (P < 0.01).

CONCLUSION: Spiral and coccoid forms of H. pylori coexist in experimental mice studied.

Serodiagnosis of Helicobacter pylori infection in Korean patients using enzyme-linked immunosorbent assay

Helicobacter pylori (H. pylori) is a gram-negative spiral bacteria that are associated with gastritis, peptic ulcer and gastric cancer. We have developed enzyme-linked immunosorbent assay (ELISA) that detects serum anti-H. pylori immunoglobulin G antibodies using H. pylori strains isolated from Korean patients. To assess the sensitivity and specificity of our assay system with different commercial kits, serum samples from 249 Korean patients with a variety of gastrointestinal diseases were tested. Among 249 Korean patients, 178 (71.5%) were positive in culture and/or urease test. The sensitivity and specificity between our assay system and four other commercial kits (Bio-Rad, DAKO, ROCHE, and IPR) were as follows: 97.8% and 92%, 94.3% and 53%, 56.5% and 92%, 83.3% and 96%, 58.2% and 92%, respectively. All sera showing discordant immunoassay results between different ELISA kits were confirmed by immunoblot analysis. These results indicate that our assay system showed a highly accurate and reliable results in diagnosis of H. pylori infection in Korean patients.

Serum IgG response to differentiated antigens of Helicobacter pylori

AIM: To detect antibodies against Helicobacter pylori spiral and coccoid antigens in human sera.

METHODS: Blood samples were collected from 278 patients with gastric diseases. A 3-day-old culture of H. pylori on chocolate blood agar was used to providespiral form. ‘Synchronous’ coccoids were cultured in (BHY) (brain heart infusion supplemented with 10% horse serum and 0.4% yeast extract) medium in a chemostat. Antigens from spiral and coccoid form were prepared using acid glycine extraction. Enzyme-linked immunosorbent assay (ELISA) was performed to detect serum IgG antibodies against spiral and coccoid forms of H. pylori.

RESULTS: Seroprevalence of H. pylori infection was higher in patients with gastric ulcer (79%) and gastric cancer (83%) than those with non-ulcer dyspepsia (NUD) (44%) and other diseases (45%) (P < 0.05). IgG antibodies against spiral and coccoid antigens were detected in 50.7% (141/278) and 49.6% (138/278), respectively.

CONCLUSION: The spiral and coccoid forms of H. pylori coexist in patients infected with the bacterium.

Gastric ulcer, atrophic gastritis, and intestinal metaplasia caused by Helicobacter pylori infection in Mongolian gerbils

BACKGROUND

Helicobacter pylori infection is associated with gastroduodenal disease in humans. In this study we aimed to show this relationship directly in Mongolian gerbils.

METHODS

The animals were challenged orally with H. pylori and killed 1, 2, 3, and 6 months after inoculation for histologic and anti-H. pylori antibody titer examination.

RESULTS

The spiral bacteria were observed in the mucus and gastric pits of all infected animals. A severe infiltration of the lamina propria by polymorphonuclear and mononuclear cells was seen 1 month after H. pylori inoculation. The submucosa was infiltrated by mainly mononuclear cells with formation of lymphoid follicles. Erosion of the gastric mucosa appeared soon after inoculation, whereas gastric ulcers, gastritis cystica profunda, and atrophy with goblet cell metaplasia occurred between 3 and 6 months after inoculation. In the duodenal mucosa a mild inflammatory cell infiltration with ballooning and diminished number of duodenal glands was seen. The IgG anti-H. pylori antibody titer increased gradually after 2 months of inoculation.

CONCLUSIONS

Since the gastritis, gastric ulcers, atrophic gastritis, and intestinal metaplasia that developed in Mongolian gerbils were similar to those observed in humans, this model may be useful to study the therapy of gastric ulcer and, with a longer observation period, to confirm a possible relationship between H. pylori and malignancy.

Heterogeneity of immunoglobulin G response to Helicobacter pylori measured by the unweighted pair group method with averages

The heterogeneity of the immune response to Helicobacter pylori has always been noticed but has never been evaluated by obtaining a quantitative measure. For this purpose, sera were tested by enzyme-linked immunosorbent assay, and 207 positive serum specimens were subsequently tested by immunoblotting. The presence or absence of six specific bands was noted. The homology of the different profiles of bands was measured by calculating the Dice coefficient, and a dendrogram was constructed. Thirty-four profiles were found, with each profile containing from 1 to 43 serum specimens. At a level of 72% similarity, 115 of the serum specimens studied fell into eight profiles. At a level of 48% similarity, 186 of the serum specimens studied fell into 22 profiles. The difference in immunoblot profiles was probably linked to the host immune response, but infection with strains carrying different antigens cannot be ruled out.

Relationship between local immune response to Helicobacter pylori and the diversity of disease: investigation of H. pylori-specific IgA in gastric juice

In order to evaluate the relationship between local immune response to Helicobacter pylori and the diversity of disease, 77 asymptomatic subjects who underwent a health examination were studied. Helicobacter pylori-specific IgG in serum and H. pylori-specific IgA in gastric juice were measured by ELISA, and the measured IgA titre was classified into two grades, low or high. Histological classification of gastritis was performed according to the Sydney system. Cytokines in gastric juice were also measured, and the cytotoxin-associated gene A (cagA) status of H. pylori was tested by PCR. Of the 65 subjects who were positive for H. pylori-specific IgG in serum, 38 (58.5%) were classified as H. pylori-specific IgA low titre in gastric juice and 27 (41.5%) had high titres. In the IgG-positive, IgA-low group, the rate of peptic ulcers (especially duodenal ulcers) in endoscopic findings was higher (P < 0.05); the score of activity and the density of H. pylori were higher (P < 0.001 and P < 0.05, respectively); the score of metaplasia was lower (P < 0.05); and the level of interleukin-1 beta was lower (P < 0.05) than in the IgG-positive, IgA-high group. The positive rate of the cagA gene was 84.4% and there was no significant difference between the two groups. There were differences in endoscopic and histological findings between the IgG-positive, IgA-low and the IgG-positive, IgA-high groups. It is suggested that persons infected with H. pylori can be divided into two different states of disease according to local immune response.

Growth in infancy, infant feeding, childhood living conditions, and Helicobacter pylori infection at age 70

AIM

To examine childhood correlates of Helicobacter pylori infection in adults.

DESIGN

Follow up study of men and women whose birth weight, weight at age 1 year, and feeding in infancy were recorded by health visitors. Data on childhood housing conditions were obtained by recall.

SUBJECTS

631 men and 389 women born in Hertfordshire during 1920-30 and still living in the east or northwest districts of the county.

MAIN OUTCOME MEASURES

Serum H pylori IgG antibodies measured by enzyme linked immunosorbent assay.

RESULTS

Independent of their current social class, subjects were more likely to be H pylori seropositive if they had large numbers of siblings (p < 0.0001), and if they had lived in a crowded house (p = 0.001), or shared a bedroom or bed in childhood (p = 0.02). Low weight at 1 year was associated with increased seropositivity rates in men (p = 0.0002), but not women (p = 0.8). Men and women who were breast fed in infancy were less likely to be seropositive than those who were bottle fed (p = 0.08).

CONCLUSIONS

The findings support the current view that H pylori infection is often acquired in childhood by close person to person contact, and persists into adult life. H pylori infection may be a cause of failure to thrive in infancy, especially in boys. Alternatively, small infants may be more susceptible to infection. Breast feeding may prevent early infection.

Antigenic characterization of Helicobacter pylori strains from different parts of the world

Although Helicobacter pylori is considered to be relatively homogeneous at the phenotypic level, our aim was to describe its antigenic heterogeneity and to examine differences in host response. Whole-cell lysates of H. pylori strains originally isolated from persons from Africa, the People's Republic of China, Japan, Peru, Thailand, or the United States or from monkeys were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoblots were performed by using sera from H. pylori-infected persons from different areas of the world and rabbit immune sera against H. pylori antigens. Specific H. pylori antibody responses in persons from the United States and the People's Republic of China were analyzed by enzyme-linked immunosorbent assay with antigens prepared from U.S. or Chinese strains. Despite diverse origins, the strains showed conserved major bands of 84, 60, 56, 31, and 25 kDa. Although there were clear differences in minor bands, there was no obvious geographic pattern. The anti-CagA serum recognized 120- to 140-kDa bands in cagA+ strains from around the world. Although antigenic preparations from individual U.S. or Chinese strains were not optimally sensitive for serologic detection of infection in the heterologous country, use of pools of strains largely overcame this phenomenon. We conclude that conserved H. pylori antigens exist and are recognized by sera from persons from many parts of the world. The heterogeneity of H. pylori antigens and the serological responses of infected hosts is not fully explained by geographic differences. Use of pools may allow development of antigens for serologic testing in any country.

Normal gastric histology in Helicobacter pylori-infected children

BACKGROUND

In adults, Helicobacter pylori infection is always associated with gastritis or ulcer. However, very active gastritis and ulcers are rarely seen in children. The aim of the present work was to study the relationships between H. pylori and gastric mucosa in children.

METHODS

Eighty infected children and adolescents including 48 (60%) neurologically impaired institutionalized patients, aged 2 months-22 years (mean 11.7 +/- 5.2 years) were studied retrospectively. All the patients underwent gastroscopy, and three antral and two fundic biopsy specimens were taken for histology and bacteriology.

RESULTS

A normal gastric mucosa was found in 22 of 80 patients (27.5%), whereas the others had gastritis (n = 58, 72.5%). There were no statistical differences between patients with normal histology and those presenting with gastritis for age, sex, ethnic background, symptoms, and the degree of bacterial colonization. The macroscopic aspect of gastritis was less frequently found in children with a normal histology compared with those with histological gastritis (p < 0.001).

CONCLUSIONS

These data show that H. pylori infection can be associated with a normal gastric histology in children.

The evaluation of tissue kallikrein in Helicobacter pylori-associated gastric ulcer disease

Helicobacter pylori (Hp) associated ulcer disease is a common form of gastric disorder involving mucosal damage and invasion of the mucosa by polymorphic inflammatory cells with concomitant changes in the epithelial cell structure. The bacteria are thought to adhere by specific junction zones to the epithelial cell surface resulting in the degeneration of the mucosal layer. Our study was undertaken to examine the relative status of tissue kallikrein (TK) in antral and fundic biopsies, endoscopically obtained from 10 patients suspected of having gastric disorders. For histological evidence of inflammation the tissue was stained with hematoxylin and eosin and classified as mild, active, chronic and chronic active gastritis. Hp infection was determined by Giemsa staining. For localisation of TK, slide-mounted tissue sections were subjected to PAP and immunofluorescent staining using a goat anti-human TK IgG antibody. The results revealed that in the antral control tissue, removed during partial antractomy, TK was immunovisualised along the luminal border of the deep pyloric glands. The surface epithelia and superficial glands showed no labelling. The fundic control tissue revealed an absence of TK in the superficial and surface epithelial glands, but was positive in the parietal cells. The fundic biopsy specimens showed similar immunoreactivity in these areas. By contrast, in the inflammed pyloric mucosa, there was a shift of TK localisation to the basal part of the glandular cells and there was also expression of TK in the superficial glands that showed histological evidence of regeneration. In the fundic biopsies there was no change observed in the sites of TK localisation (similar to control tissue). It was observed, that even though 8 of the 10 subjects exhibited Hp infection, the inflamed mucosa showed no discernable difference in the staining patterns between the infected and non-infected tissue sections. Our findings suggest an important role for a B1/B2 kinin antagonist in patients with gastritis.

Evaluation of a rapid, new method for detecting serum IgG antibodies to Helicobacter pylori

There is an increased need for rapid, inexpensive tests to diagnose Helicobacter pylori infection. Our objective was to determine the performance characteristics of an immunochromatographic test (ICT) for detection of anti-H. pylori IgG antibodies. A commercially available ICT kit (FlexSure® HP) was tested with a well-characterized cohort of banked sera as well as with fresh serum from randomly selected symptomatic patients. The ICT was evaluated with 107 stored sera and 96 prospective patients. The test correctly identified 65 of 68 H. pylori-infected and 37 of 39 noninfected stored sera and 54 of 57 infected and 30 of 39 noninfected patients. Sensitivity, specificity, and positive and negative predictive values were 96%, 95%, 97%, and 93% in stored serum and 95%, 77%, 86%, and 91% in fresh serum, respectively. We concluded that the ICT, reported at 4 min, is highly sensitive for detecting anti-H. pylori IgG antibodies in human serum. With a high negative predictive value, the test may be used to exclude H. pylori infection in symptomatic patients.

Evaluation of experimental therapeutics in a new mouse model of Helicobacter felis utilizing 16S rRNA polymerase chain reaction for detection

BACKGROUND

A new mouse model of Helicobacter felis infection, which mimics the human infection observed with H. pylori, has recently been developed utilizing polymerase chain reaction (PCR) based on the 16S rRNA gene sequence for detection of infection.

METHODS

We tested several therapeutic regimens in this model, including some currently utilized in the clinic and some shown ineffective in the clinic.

RESULTS

The therapeutic results obtained by PCR with this model are consistent with results observed in the published human H. pylori clinical trials and also with results obtained in another H. felis mouse model utilizing culture and histology.

CONCLUSIONS

These results support further use of this new model in screening for new therapeutic regimens for the management of Helicobacter disease.

Association between Helicobacter pylori infection and serum pepsinogen concentrations in gastroduodenal disease

AIM

To investigate the association between Helicobacter pylori infection and serum pepsinogen (PG) 1 and 2 concentrations in various gastroduodenal diseases.

METHODS

Serum PG1 and 2 concentrations and antibodies to H pylori were measured by enzyme linked immunosorbent assay (ELISA); gastric mucosal pH was assessed and urease activity in biopsy tissue was determined. A comparison of the ELISA and urease test results permitted division of the cases into positive, false positive, false negative and negative categories for control, gastritis, and ulcer groups.

RESULTS

The gastric mucosal pH and serum PG2 in cases positive for H pylori were significantly increased in ulcer and gastritis cases compared with H pylori negative cases. Similar tendencies were observed for the false positive and false negative categories.

CONCLUSIONS

A positive ELISA reaction for antibodies and an increased serum PG2 concentration are reliable indicators of H pylori infection.

Is saliva serology useful for the diagnosis of Helicobacter pylori?

BACKGROUND

The Cortecs Diagnostics Helisal Assay test is a quantitative immunoassay for salivary IgG antibodies against Helicobacter pylori. Saliva can be obtained simply with the kit in the general practitioners surgery.

AIMS

To compare the new saliva serological test for H pylori with 'gold standard' evidence of H pylori infection (antral biopsy specimens for histology, culture, and urease test) and a new serum serological test.

PATIENTS

Eighty six unselected dyspeptic patients undergoing endoscopy.

METHODS

Each patient provided saliva and serum before endoscopy for H pylori serology, which was compared against 'gold standard' evidence of infection.

RESULTS

Thirty two patients were H pylori positive by the 'gold standard' tests. At a cut off value of 0.15 EU/ml the saliva test had a sensitivity of 88% and a specificity of 71%, with a negative predictive value of 90%. If patients who were taking omeprazole or had recent antibiotics are excluded, the sensitivity is unchanged but the specificity increases to 79%. The serum test had a similar sensitivity of 85% but better specificity of 78%.

CONCLUSION

Serum testing remains the best serological test for H pylori in the hospital setting. Saliva testing may have a role in epidemiological studies and in screening dyspeptic patients in general practice, especially in children in whom venesection is more difficult.

Helicobacter Pylori Infection in Patients with Gastric Adenocarcinoma

We examined the biologic tumor behavior in Helicobacter pylori-seropositive patients with gastric adenocarcinoma. A total of 214 consecutive patients with pathologically confirmed adenocarcinoma of the stomach who underwent gastric resection were studied. The stored serum samples were tested for serum antibody to H. pylori by using a highly sensitive and specific IgG enzyme-linked immunosorbent assay. The difference in H. pylori-seropositive and seronegative patients with gastric adenocarcinoma was evaluated in terms of various clinicopathologic parameters. A multivariate logistic regression analysis was used to adjust for potential confounding variables. Antibodies to H. pylori were detected in 65.9% of patients with gastric adenocarcinoma. H. pylori-seropositive patients were younger than seronegative patients and had infiltrative tumor according to Ming's criteria. When adjusted for age, infiltrative tumor come out stronger. These findings suggest that H. pylori infection may be related to infiltrative type gastric adenocarcinoma; further study is necessary.

A sensitive and specific PCR method to detect Helicobacter felis in a conventional mouse model

Although many detection methods have been used to determine Helicobacter colonization in small animal models, the sensitivity and specificity of these detection methods are limited. To improve the Helicobacter felis conventional mouse model for accurate evaluation of therapeutic regimens, we developed a PCR for detection of, and a competitive PCR for quantitation of, H. felis in viral antibody-free (VAF) mice. The PCR was based on the H. felis 16S rRNA gene. An internal control DNA was used for competitive quantitation of the PCR. VAF conventional Swiss-Webster mice were infected with an H. felis culture by oral gavage. At various times after H. felis challenge and therapy, stomach mucosa was collected and evaluated by PCR. PCR detected approximately 50 to 100 H. felis cells per mouse stomach and showed no cross-reaction with other bacteria commonly found in mouse stomachs. Colonization of H. felis in the mouse stomach was confirmed by culture isolation from germfree mice and histological examination of VAF mice. Response to therapy in this H. felis model correlated well with results seen in human clinical trials with H. pylori. A model utilizing PCR detection which may be useful for discovering new antibiotics and/or vaccines against Helicobacter ulcer disease has been developed.

PCR detection of colonization by Helicobacter pylori in conventional, euthymic mice based on the 16S ribosomal gene sequence

Many animal models of Helicobacter infection have been described, including infection in rhesus monkeys, ferrets, gnotobiotic piglets, and mice. These animal models utilize a combination of detection methods, including culture, urease testing, and histopathology, all of which may be unreliable, insensitive, or labor-intensive. Development of new animal models of Helicobacter pylori requires new methods of detection with increased sensitivity and specificity. We have developed sensitive and specific PCR primers based on the 16S ribosomal gene sequence of H. pylori. The primers detected single-copy 16S DNA representing 0.2 cell of pure H. pylori (2 cells in the presence of mouse stomach mucosal DNA) and did not cross-react with closely related bacteria. We were able to detect colonization by H. pylori in conventional, euthymic, outbred mice up to 4 weeks postinoculation with a high percentage of isolates tested. One isolate of H. pylori was detected by PCR in 100% of the mice at 6 months and 60% of the mice 1 year after inoculation. Approximately 10(3) to 10(4) H. pylori cells per stomach were detected by utilizing this PCR methodology semiquantitatively. These primers and PCR methodology have facilitated detection of H. pylori colonization in conventional, euthymic mice, colonization which may not have been detectable by other methods.

Helicobacter pylori expresses a complex surface carbohydrate, Lewis X

Monoclonal antibodies (MAbs) specific for Lewis X (Lex) reacted with whole cells of Helicobacter pylori NCTC11637, UA799, UA802, UA825, UA861, UA1182, and UA1206 in immunoelectron microscopy and enzyme-linked immunosorbent assay (ELISA) experiments. These MAbs have documented specificity to Lex, whereas MAbs for Lea and Leb were negative in both immunoelectron microscopy and ELISA. H. pylori coccoid forms also reacted with the MAbs, whereas the flagellum lacking the sheath showed no reactivity. The Lex structures were associated with membrane fractions in the ELISA experiments, and silver-stained sodium dodecyl sulfate-polyacrylamide gels confirmed the presence of lipopolysaccharides which reacted with the MAbs in immunoblots. Serum from an H. pylori-infected individual contained immunoglobulins which blocked the binding of the Lex MAbs, indicating that part of the host immune response to H. pylori is to the Lex structure. The ability of this gastric pathogen to mimic an oncofetal antigen (self) could explain the down regulation of anti-H. pylori T-cell response seen in H. pylori-infected individuals.

Lack of association of Helicobacter pylori seroprevalence and gastric cancer in a population with low gastric cancer incidence

BACKGROUND

Previous studies have suggested that infection with Helicobacter pylori is associated with an increased risk of gastric adenocarcinoma.

METHODS

We examined the sera of 111 Caucasian patients with histologically confirmed gastric cancer (36 with cancer of the cardia, 70 with cancer of the body or antrum, and 5 with stump carcinomas after Billroth-II procedures) and 111 age-matched controls with colorectal carcinomas for the presence of H. pylori IgG antibodies by enzyme-linked immunoassay.

RESULTS

The overall prevalence of H. pylori infection was 58.6% (65 of 111) in gastric cancer patients as compared with 50.5% (56 of 111) in matched control subjects (odds ratio, 1.39; 95% confidence interval, 0.82 to 2.36). Carcinomas of the cardia were not linked to H. pylori infection (odds ratio, 1.25; 95% confidence interval, 0.65 to 2.46), nor diffuse or intestinal-type carcinomas (odds ratios, 1.79 and 1.0; 95% confidence intervals, 0.69 to 4.67 and 0.34 to 2.91, respectively). Age, sex, and height of the IgG immune response did not affect risk.

CONCLUSIONS

In contrast to previous results, these data do not provide evidence that the contribution of H. pylori infection to the carcinogenesis of gastric cancer is of major significance in a population with low gastric cancer rates and with high socioeconomic status.

Serum antibody against Helicobacter pylori assayed by a new capture ELISA

We developed a highly specific detection technique for serum antibody, using a monoclonal antibody to a specific antigen of Helicobacter pylori. A monoclonal antibody preparation that reacted with the 54-kDa molecule of H. pylori antigens was obtained. Using this preparation, an antigen-capture enzyme-linked immunosorbent assay (ELISA) was established by fixation of the monoclonal antibody, followed by reaction with sonicated whole cell antigens. The serum antibody titers of patients with gastritis and peptic ulcers were significantly higher than control titers, and the antibody titer correlated with the histological severity of gastritis. Patients positive for H. pylori by bacterial culture had higher titers than H. pylori-negative patients. Our new ELISA may be useful for the diagnosis of H. pylori infections and for evaluation of the severity of gastric inflammation.

Significance of rapid urease test for identification of Helicobacter pylori in comparison with histological and culture studies

Helicobacter pylori in the stomach is an etiological factor of gastritis and peptic ulcer. It is now considered that gastric cancer can be, at least in some cases, a late complication of H. pylori infection. In 123 consecutive endoscopic antral biopsies obtained from patients with the Okamoto Hospital, the specimens were subjected to the rapid urease test (RUT), histology (H&E stain), and culture, for the identification of H. pylori. The results of these methods were compared semi-quantitatively in order to evaluate these detection methods for identifying H. pylori. The results of these methods were found to agree well, with the Spearman's rank correlation coefficient between RUT and culture being 0.90 (P < 0.01) and that between histology and culture being 0.80 (P < 0.01). RUT is considered to be a very simple, sensitive, and highly specific test which enables the endoscopist to diagnose H. pylori infection.

Helicobacter pylori colonization in children with peptic ulcer disease. III. Diagnostic value of the 13C-urea breath test to detect gastric H. pylori colonization

The efficiency of the 13C-Urea Breath Test (13C-UBT) for the detection of Helicobacter pylori colonization in gastric mucosa was evaluated. The 13C-UBT was performed in five pediatric and six adult subjects who had had upper gastrointestinal endoscopy within 2 weeks. H. pylori colonization was confirmed in two pediatric and three adult subjects with peptic ulcer combined with antral gastritis, by histological examination of antral biopsy specimens. When an individual with H. pylori colonization ingested a solution containing 13C-urea, a significant amount of 13CO2 appeared in the respiratory CO2 within 10 min. The mean cumulative percentage dose of 13C recovered in the breath over 30 min in the cases with H. pylori colonization was significantly higher than that in those who were not colonized (4.91 vs 0.41, P < 0.001). In addition, the effect of antibiotic on the eradication of H. pylori from gastric mucosa was monitored by 13C-UBT in two cases. The values of cumulative percentage dose of 13C over 30 min fell to the same levels as those observed in H. pylori negative subjects after just 2 weeks treatment with amoxicillin; however, positive results were obtained again 1 month after the withdrawal of amoxicillin. In summary, 13C-UBT is a simple, reliable, non-invasive method in the diagnosis of gastric H. pylori colonization especially for pediatric patients.

Correlation between serological and mucosal inflammatory responses to Helicobacter pylori

In 82 patients who underwent gastroduodenoscopy, acute and chronic gastric mucosal inflammation was scored for severity, and systemic humoral immune responses to Helicobacter pylori antigens were assessed by enzyme-linked immunosorbent assays. On the basis of culture, gastric histology, and serologic evaluation, 33 patients were classified as H. pylori infected and 36 were classified as uninfected. Thirteen patients had negative cultures and stains but were seropositive and were analyzed separately from the other two groups. Specific serum immunoglobulin G (IgG) subclass responses to H. pylori whole-cell antigens and specific IgG responses to the 54-kDa heat shock protein homolog (Hp54K) and vacuolating cytotoxin were significantly greater in infected than in uninfected patients as were specific IgA responses to whole-cell antigens and cytotoxin (P < 0.001). Among the H. pylori-infected persons, serum IgG responses to Hp54K and to the vacuolating cytotoxin were correlated with acute mucosal inflammatory scores. In contrast, serum IgA responses to whole-cell sonicate and to vacuolating cytotoxin were inversely related to chronic inflammatory scores. By multivariant regression analysis, only specific serum IgG responses to Hp54K correlated with severity of inflammation (both acute and chronic; P < 0.001); these responses may be markers of inflammation or these antibodies could play a direct role in the pathogenesis of H. pylori-induced inflammation.