Biomedical subjects
Robert Clancy
Publications and source records attributed to Robert Clancy.
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.
Autoantibodies against the serotoninergic 5-HT4 receptor and congenital heart block: a reassessment.
The specificity of autoantibodies against the serotoninergic 5-HT4 receptor in congenital heart block has led to conflicting observations. In order to clarify the situation, a collaborative effort was undertaken to discover the reasons for these discrepancies and to reassess the importance of such autoantibodies by making use of the Research Registry for Neonatal Lupus. Sera from 128 patients (101 anti-SSA/Ro52 positive mothers among which 74 have children with congenital heart block (CHB), 9 anti-SSA/Ro52 negative patients of which 1 had a child with heart block and 18 healthy donors) were assessed in a single blind test using an ELISA coated with a 5-HT4 receptor-derived peptide. Discrepancies between previous observations in our two groups could be ascribed to small differences in the set up of the assay. Of the 75 sera from mothers of children with CHB, 12 were reactive with the 5-HT4 peptide. Four sera among which three were from 35 Ro52 negative mothers without affected children as well as 2 in the 18 controls were positive. Interestingly, in 1 mother with an isolated child with CHB but who had no detectable anti-SSA/Ro52 antibodies and 1 mother with a child with a structural heart block and no detectable antibodies to any component of SSA/Ro, reactivity with the 5-HT4 receptor was noted. While 5-HT4 receptor autoantibodies do not have the predictive value of anti-Ro52 autoantibodies, the presence of these antibodies in a minor subset of mothers whose children have CHB suggests an additional risk factor which may contribute to the pathogenesis of disease.
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.
Probiotics under the regulatory microscope.
This review examines current knowledge regarding the safety of probiotic bacteria in man. Tighter and more comprehensive standards and regulations will be developed as probiotic therapy moves from a limited number of products used in the food industry, into more defined therapeutic categories and more complex organisms. A new framework considering probiotics as nonspecific promoters of mucosal immunity, defines probiotic characteristics and the clinical circumstances in which it is used. For example, those with immune deficiency taking a high dose of viable bacteria may have an increased risk. A wider range of bacteria is now being used, sometimes in territories other than the gut mucosa. The question of competition with multiple isolates must be addressed, as does the use of nonselected faecal isolates. Transfer of antibiotic resistance with probiotics acting as a 'shuttle' needs clarification. These issues are addressed and reviewed as probiotics evolve into a new therapeutic arena.
Regulation of metalloproteinases and NF-kappaB activation in rabbit synovial fibroblasts via E prostaglandins and Erk: contrasting effects of nabumetone and 6MNA.
1 Nabumetone is a prodrug that is converted in vivo into 6-methoxy-2-naphthylacetic acid (6MNA), a cyclooxygenase inhibitor with anti-inflammatory properties. We tested the effects of nabumetone and 6MNA on the inflammatory responses of synovial fibroblasts (SFs). 2 Brief exposures to 6MNA (50-150 microm) had no effect on IL-1beta/TNF-alpha (each 20 ng ml(-1))-stimulated Erk activation. Longer exposures depleted prostaglandin E1 (PGE1) as much as 70%, and stimulated Erk as much as 300%. Nabumetone (150 microm) inhibited Erk activation by 60-80%. 6MNA (50-150 microm) stimulated (approximately 200%) and nabumetone (150 microm) inhibited (approximately 50%) matrix metalloproteinase (MMP)-1, but not MMP-13 secretion from SFs. 3 6MNA stimulation of MMP-1 secretion was inhibited approximately 30% by PGE1 (1 microm) and approximately 80% by the Erk pathway inhibitor UO126 (10 microm), confirming that PGE depletion and Erk activation mediate MMP-1 secretion by 6MNA. 4 Consistent with its role as an Erk inhibitor, nabumetone (150 microm) abrogated 6MNA enhancement of MMP-1 secretion. 5 UO126 (10 microm) and nabumetone (150 microm) inhibited (approximately 70 and 40%, respectively), but 6MNA (150 microm) enhanced (approximately 40%), NF-kappaB activation. 6 Our data indicate that 6MNA shares with other COX inhibitors several proinflammatory effects on synovial fibroblasts. In contrast, nabumetone demonstrates anti-inflammatory and potentially arthroprotective effects that have not been previously appreciated.
Immunobiotics and the probiotic evolution.
The term 'probiotic' was coined by the food industry to describe microbes beneficial to health. Scientific criticism based on poorly characterised isolates, soft clinical targets, and an absence of a mechanistic framework limited value of this concept. Current clinical and animal model studies support a role for certain 'probiotics', activating the common mucosal system through the stimulation of gut antigen-presenting cells to both promote protection and to switch regulatory mechanisms. It is concluded that a new term is required to identify bacteria that promote health through driving mucosal immune mechanisms, compared to those with strictly local effects. The term 'immunobiotics' is suggested as appropriate to fulfil this need.
Development of surrogate markers for oral immunisation against Candida albicans.
We have developed an oral vaccine using the blastococcoid form of Candida albicans with a murine model of oral candidiasis with infection-resistant (BALB/c) and infection-prone (DBA/2) mice. Previous studies had demonstrated that enhanced clearance was linked to increased production of both Th1 and Th2 cytokines (IFN-gamma and IL-4, respectively) in regional lymph nodes, and increased secretion of IFN-gamma and NO in saliva. Subsequent study using oral Lactobacillus acidophilus (LAVRI-A1) induced a local cytokine pattern and enhanced clearance of intra-oral C. albicans similar to that noted in animals given killed candida vaccine. Thus, the experiment was repeated with a 2 month gap between completion of a vaccine course and challenge with live C. albicans. Compared to control mice, those given the oral vaccine had a 4 log reduction in colonisation on day 2, associated with twice the levels of secretion of IFN-gamma and IL-4 from the regional node cells, five times the level of nitric oxide in saliva, and suppression of NO production with MMLA induced a 2 log increase in oral colonisation. Thus while both IFN-gamma and IL-4 appear to contribute to clearance of oral C. albicans, IL-4 appears to act through a paracrine enhancement of NO production. Studies in man are in progress to define similar surrogate markers of immune protection, prior to oral vaccine trial.
Can the response to eradication therapy in Helicobacter pylori infection be predicted?
The failure to eradicate Helicobacter pylori infection with antibiotic therapy has become a major clinical problem, not entirely accounted for by either poor compliance or antibiotic resistance. Recognition that failed eradication is one outcome of the host-parasite relationship focuses attention on impaired host protection as a determinant of nonresponse to antibiotics. A secreted interleukin (IL)-4 whole blood assay was developed to determine whether persistent infection was contributed to by impaired cytokine responses. The blood assay was shown to correlate well with mucosal organ cultures. Significantly lower levels of IL-4 were detected in the whole blood assays in 11 subjects with failed eradication compared with subjects with successful eradication (P<0.05). This latter group underwent a Th1 to Th0 "switch", which appears to be important to successful eradication. Detection of subjects at risk for failing to eradicate infection with standard combination therapy, by virtue of low secreted IL-4 in whole blood cultures, may have clinical value.
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.
Cardiac 5-HT(4) serotoninergic receptors, 52kD SSA/Ro and autoimmune-associated congenital heart block.
It was recently reported that sera from patients with systemic lupus erythematosus contain antibodies reactive with the second extracellular loop of the serotoninergic 5-HT(4) receptor expressed in the human heart. This antibody response was associated with antibodies to 52kD SSA/Ro, a reactivity prevalent in mothers of children with congenital heart block (CHB). The current study was undertaken to determine whether the 5-HT(4) receptor is a target of the immune response in these mothers. Initial experiments demonstrated mRNA expression of the 5-HT(4) receptor in the human foetal atrium. Electrophysiologic studies established that human foetal atrial cells express functional 5-HT(4) receptors. Sera from 116 mothers enrolled in the Research Registry for Neonatal Lupus, whose children have CHB, were evaluated. Ninety-nine (85%) of these maternal sera contained antibodies to SSA/Ro, 84% of which were reactive with the 52kD SSA/Ro component by immunoblot. None of the 116 sera were reactive with the peptide spanning aa165-185 of the serotoninergic receptor. Rabbit antisera which recognized this peptide did not react with 52kD SSA/Ro or peptide aa365-382 in the C terminus. Although 5-HT(4) receptors are present and functional in the human foetal heart, maternal antibodies to the 5-HT(4) receptor are not associated with the development of CHB.