IgG subclass antibodies againstHelicobacter pyloriheat-stabile antigens in normal persons and in dyspeptic patients

Response of IgG1 and IgG2 subclasses to Helicobacter pylori in subjects with chronic inflammation of the gastric mucosa, atrophy and gastric cancer in a country with high Helicobacter pylori infection prevalence

Polarized immune response to Helicobacter pylori and induction of chronic inflammation may increase the risk of gastric atrophy and adenocarcinoma. We studied the association of the response of IgG1 and IgG2 antibodies to H. pylori with grade of gastric chronic inflammation and atrophy in a population with a high prevalence of H. pylori, and compared these data with the data obtained from the study of gastric cancer patients, as well as with the data for CagA positivity. Altogether, 114 persons from two adult population samples from Estonia and 45 consecutive gastric cancer patients were studied. All patients were positive for the H. pylori antibody determined by ELISA. Adenocarcinoma was classified histologically according to the Laurén's system. The response of the IgG subclasses to H. pylori (acid glycine-extracted whole cell proteins) was determined by ELISA and the results were compared with the ELISA results for the recombinant fragment of the CagA protein. Helicobacter pylori IgG level was lower in atrophic gastritis compared with nonatrophic gastritis (chronic inflammation) (p=0.001). In the group of cancer patients, the response of IgG and IgG1 was lower compared with both gastritis groups (p=0.01 and p=0.0002 for IgG, and p=0.001 and p=0.0005 for IgG1). IgG2 was lower for gastric cancer localized in the corpus (p=0.03). In conclusion, atrophic gastritis and gastric cancer were associated with a significant decline in IgG and IgG1 response to H. pylori compared with nonatrophic gastritis. Higher value of CagA antibodies was seen in gastric cancer and in gastric atrophy compared with nonatrophic gastritis; in gastric cancer patients, IgG1 response to H. pylori was correlated with CagA status.

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IgG subclass response to Helicobacter pylori and CagA antigens in children

Specific serum IgG subclass antibodies against Helicobacter pylori antigens and recombinant CagA were analysed in 75 symptomatic children with histologically confirmed H. pylori infection. H. pylori stimulated an IgG1 predominant response, and IgG3 titres showed a positive association with peptic ulcer disease, chronicity of antral inflammation and density of H. pylori colonization. Two methods used for assessing serum IgG CagA antibody status, i.e. Western blotting and enzyme-linked immunosorbent assay (ELISA), were concordant. CagA stimulated an IgG1 and IgG3 predominant humoral response. Total CagA IgG titres were higher in children with active and more severe chronic antral inflammation. These findings suggest that in children the systemic humoral immune response to H. pylori infection may reflect gastroduodenal pathology.

Helicobacter pylori resists phagocytosis by macrophages: quantitative assessment by confocal microscopy and fluorescence-activated cell sorting

Helicobacter pylori infection of the stomach epithelium is characterized by an infiltration of polymorphonuclear and mononuclear cells. These immune cells contribute to mucosal damage which may eventually lead to gastritis, peptic ulcer, gastric cancer, and/or MALT-associated gastric lymphoma. Here we show that H. pylori inhibits its own uptake, as well as in trans the phagocytosis of Neisseria gonorrhoeae, by human and murine macrophages. This antiphagocytic activity is dependent on the presence of the cag pathogenicity island in the H. pylori genome. We demonstrate that H. pylori also expresses its antiphagocytic activity towards the myelomonocytic cell line JOSKM, thus providing a potent model for the study of the interaction between H. pylori and phagocytes. Our data were obtained using laser confocal microscopy and flow cytometry after quenching the fluorescence of labeled extracellular bacteria. The antiphagocytic activity of H. pylori may explain the persistence of H. pylori and its pathological consequences. The use of cell lines and flow cytometry will hopefully facilitate progress in our understanding of the immune escape of these persistent bacteria.

Helicobacter pylori inhibits phagocytosis by professional phagocytes involving type IV secretion components

Gastric infections by Helicobacter pylori are characteristically associated with an intense inflammation and infiltration of mainly polymorphonuclear lymphocytes (PMNs) and monocytes. The inflammatory response by infiltrated immune cells appears to be a primary cause of the damage to surface epithelial layers and may eventually result in gastritis, peptic ulcer, gastric cancer and/or MALT-associated gastric lymphoma. Our analysis of the interaction between H. pylori and PMNs and monocytes revealed that H. pylori inhibits its own uptake by these professional phagocytes. To some degree, this effect resembles antiphagocytosis by Yersinia enterocolitica. Increasing numbers of bacteria associated per cell are more efficient at blocking their own engulfment. In H. pylori, bacterial protein synthesis is necessary to block phagocytic uptake, as shown by the time and concentration dependence of the bacteriostatic protein synthesis inhibitor chloramphenicol. Furthermore, H. pylori appears broadly to inhibit the phagocytic function of monocytes and PMNs, as infection with H. pylori abrogates the phagocytes' ability to engulf latex beads or adherent Neisseria gonorrhoeae cells. This antiphagocytic phenotype depends on distinct virulence (vir) genes, such as virB7 and virB11, encoding core components of a putative type IV secretion apparatus. Our data indicate that H. pylori exhibits an antiphagocytic activity that may play an essential role in the immune escape of this persistent pathogen.

Cephalic phase of lipolysis is impaired in pancreatic insufficiency: role of gastric lipase

BACKGROUND

Gastric lipase contributes significantly to overall lipolysis and is regulated by interacting neuro-hormonal mechanisms. Patients with alcoholic chronic pancreatitis (ACP) have low, or even absent, activity of pancreatic lipases. In that state the secretion of gastric lipase could be essential and compensate for the pancreatic defect. However, conflicting studies have not resolved the order of magnitude of gastric lipase secretion in these patients. This could be explained by differences in regulatory mechanisms, gastric mucosal changes, and abdominal vagal tone.

METHODS

Nasogastric intubation with modified sham feeding and upper endoscopy including biopsies for histologic classification and Helicobacter pylori infection status were performed in eight ACP patients, and eight healthy volunteers were studied on separate occasions. Vagal nerve function was assessed by calculation of heart rate variability in ACP patients. Gastric lipase was measured in aspirates by means of enzyme-linked immunosorbent assay and an enzyme kinetic assay. Plasma concentrations of gastrin, secretin, cholecystokinin, and pancreatic polypeptide were measured throughout the study.

RESULTS

Sham feeding rapidly and significantly increased gastric lipase secretion in healthy volunteers, whereas ACP patients did not respond to sham feeding. Two of eight patients were infected with H. pylori and had mucosal changes accordingly. The lack of lipase response could not be ascribed to dysfunction of the abdominal vagus.

CONCLUSIONS

The cephalic phase of gastric lipase secretion is impaired in ACP patients. Although their fundic cells continue to secrete gastric lipase, they are not subject to normal neuro-hormonal regulation.

Serodiagnosis of Helicobacter pylori infection by Cobas Core ELISA in adults from Minas Gerais, Brazil

We evaluated the accuracy of a 2nd generation ELISA to detect Helicobacter pylori infection in adults from a developing country in view of variations in sensitivity and specificity reported for different populations. We studied 97 non-consecutive patients who underwent endoscopy for evaluation of dispeptic symptoms. The presence of H. pylori was determined in antral biopsy specimens by culture, by the preformed urease test and in carbolfuchsin-stained smears. Patients were considered to be H. pylori positive if at least two of the three tests presented a positive result or if the culture was positive, and negative if the three tests were negative. Sixty-five adults (31 with peptic ulcer) were H. pylori positive and 32 adults were H. pylori negative. Antibodies were detected by Cobas Core anti-H. pylori EIA in 62 of 65 H. pylori-positive adults and in none of the negative adults. The sensitivity, specificity and positive and negative predictive values of the test were 95.4, 100, 100 and 91.4%, respectively. The Cobas Core anti-H. pylori EIA presented high sensitivity and specificity when employed for a population in Brazil, permitting the use of the test both to confirm the clinical diagnosis and to perform epidemiologic surveys.

Effect of sham feeding and acute suppression of acid secretion on human gastric lipase secretion

OBJECTIVE

Gastric lipase and gastric acid are secreted simultaneously. The aim of this study was to investigate whether the acid interferes with the lipase secretion. The secretion of human gastric lipase was studied during blockade of gastric acid secretion and modified sham feeding to estimate the impact of these conditions on both gastric lipase enzyme activity and immunoreactivity.

METHODS

Eight healthy volunteers were intubated with a nasogastric tube. We examined gastric aspirates for the amount and activity of lipase secretion during basal conditions, after blockade of acid secretion with a proton pump inhibitor (omeprazole iv. infusion), and in response to sham feeding (chewing gum) during the blockade.

RESULTS

The amount of secreted gastric lipase was unaffected by blockade of acid secretion and increased significantly after sham feeding (169.9+/-35.7 microg/15 min to 348.1+/-79.2 microg/15 min; p < 0.01). Likewise, the output of enzyme activity increased after sham feeding (0.63+/-0.09 kU/15 min to 1.52+/-0.36 kU/15 min; p < 0.03). The concentration of enzyme activity remained unchanged by blockade of acid secretion, whereas the output of enzyme activity was decreased, probably because of reduced volume secretion or denaturation and conformational changes of the enzyme. Plasma concentrations of gastrin increased in response to blockade of acid secretion (basal 9.6+/-1.4 pmol/L to 13.3+/-2.9 pmol/L; p < 0.02).

CONCLUSIONS

Gastric acid secretion is not a prerequisite for gastric lipase secretion. Lipase enzyme activity, though, is sensitive to anacidic conditions.

Cross-reactive antigens shared by Pseudomonas aeruginosa, Helicobacter pylori, Campylobacter jejuni, and Haemophilus influenzae may cause false-positive titers of antibody to H. pylori

Cystic fibrosis (CF) patients suffer from many of the gastrointestinal conditions which occur in non-CF individuals, e.g., dyspepsia and peptic ulceration. These symptoms may be caused by Helicobacter pylori but could also be due to either pancreatic insufficiency or the intensive antibiotic treatment used in CF patients. Since CF patients chronically infected with Pseudomonas aeruginosa produce antibodies against a wide range of antigens, including antigens common to many other bacteria, e.g., GroEL and lipopolysaccharide, we studied, by the Western blot (immunoblot) technique, the specificity of immunoglobulin G antibodies to H. pylori in Danish CF patients chronically infected with P. aeruginosa, CF patients without P. aeruginosa infection but with Haemophilus influenzae infection, patients with dyspeptic ulcers associated with H. pylori, and patients recovering from acute Campylobacter jejuni or Campylobacter coli infection. Sera from CF patients with chronic P. aeruginosa or H. influenzae infection and patients recovering from acute C. jejuni infection cross-reacted with H. pylori antigens. A strong cross-reacting protein antigen at approximately 14 kDa and minor cross-reactive antigens at approximately 27, 30, and 60 kDa (the heat shock protein GroEL is equivalent to the common antigen of P. aeruginosa) could be demonstrated. The results of this study show that high immunoglobulin G antibody titers against H. pylori in CF patients cannot be regarded as indicating present or past H. pylori infection unless their specificity is proven by absorption studies.

Interaction of cells of Helicobacter pylori with human polymorphonuclear leucocytes: possible role of haemagglutinins

The interaction of fluorescein isothiocyanate (FITC)-labelled cells of Helicobacter pylori with human polymorphonuclear leucocytes (PMNs) was studied. Two strains with surface haemagglutinins expressing different receptor specificity were used in order to decide if cell surface haemagglutinins of H. pylori may play a role in lectin-mediated binding to/uptake by phagocytes: (1) strain 17874 (NCTC 11637) which expresses sialic acid-specific haemagglutinin; and (2) strain 17875 (NCTC 11638) which expresses a sialic acid-independent haemagglutinin. Cells of strain 17874 were poorly attached to/ingested by PMNs compared to cells of strain 17875. Pre-treatment of bacteria with fetuin or rabbit antibodies against partly purified sialic acid-specific haemagglutinin enhanced interaction of cells of strain 17874 with PMNs. The enhancement did not occur in the case of strain 17875. Phagocytosis of H. pylori 17874 bacteria was slightly increased by fresh human sera positive for anti-H. pylori antibodies. The results suggest that the sialic acid-specific haemagglutinin complex of 17874 bacteria might disturb their uptake by human PMNs.