Primary and acquired Helicobacter pylori resistance to clarithromycin, metronidazole, and amoxicillin--influence on treatment outcome.

OBJECTIVE: The aim of this study was to evaluate the primary and acquired resistance of H. pylori against clarithromycin, metronidazole, and amoxicillin, and to elucidate the consequential influence on H. pylori eradication. METHODS: A total of 195 patients with positive H. pylori status were consecutively included. In 172 patients, H. pylori could be cultured for evaluation of primary antibiotic resistance. Fifty patients received a 2-wk dual therapy with an acid inhibitor and amoxicillin 2,000 mg daily (A), the other 122 patients a 1-wk modified triple therapy with the acid inhibitor clarithromycin 500-1,000 mg daily, and metronidazole 1,000-1,500 mg daily (B: n = 78), or amoxicillin 2,000 mg daily and metronidazole 1,000 mg daily (C: n = 44), respectively. Acid inhibition was conducted with pantoprazole 40 mg b.i.d. (n = 62), omeprazole 20 mg b.i.d. (n = 50), lansoprazole 30 mg b.i.d. (n = 10), or ranitidine 150 mg t.i.d. (n = 50). After therapy, 36 patients remained H. pylori-positive, 20 after dual therapy (A) and 16 after modified triple therapy (B: n = 7, C: n = 9). In 32 of these patients, H. pylori could be recultured for evaluation of acquired resistance (A: n = 18, B: n = 7, C: n = 7). RESULTS: Primary H. pylori resistance to metronidazole was observed in 36 of 172 patients (21%) and to clarithromycin in three of 172 (2%). Acquired resistance was found in six of 14 (43%) and in two of seven (29%), respectively, whereas neither primary nor acquired H. pylori resistance to amoxicillin was noted. Patients infected with metronidazole resistant H. pylori strains were successfully treated in combination with clarithromycin (eight of nine vs 63 of 67 with sensitive strains, NS), but not with amoxicillin (one of eight vs 32 of 34 with sensitive strains, p < 0.0001). In two patients with acquired combined clarithromycin and metronidazole resistance, modified triple therapy failed. CONCLUSION: The value of modified triple therapy with amoxicillin and metronidazole is significantly limited by metronidazole resistance. However, metronidazole resistance does not negatively influence treatment outcome in modified triple therapy including clarithromycin. H. pylori resistance to amoxicillin still is not present.

Partial characterization of a cell proliferation-inhibiting protein produced by Helicobacter pylori.

Despite the induction of an immunological reaction, Helicobacter pylori-associated gastritis is a chronic disease, suggesting that this microbe can evade the host immune defense. Previous studies by our group showed that H. pylori suppresses the in vitro proliferative response of human mononuclear cells to mitogens and antigens. Here we demonstrate that the antiproliferative activity of H. pylori also affects the proliferation of various mammalian cell lines (U937, Jurkat, AGS, Kato-3, HEP-2, and P388D1). This effect is detectable in the first 16 h of incubation and maximal between 24 and 48 h. In addition, the presence of H. pylori significantly diminished the protein synthesis of cells in the first 6 h of incubation, comparable to the results with cycloheximide and diphtheria toxin. The urease enzyme, the cagA gene product, and the vacuolizing cytotoxin of H. pylori were excluded as causative agents of the antiproliferative effect by using isogenic knockout mutant strains. The inhibitory effect was not due to a lytic activity of this bacterium. The results reported here indicate that the responsible factor is a protein with an apparent native molecular mass of 100 +/- 10 kDa. Our work implicates the presence of a protein factor in H. pylori (termed PIP [for proliferation-inhibiting protein]) with antiproliferative activity for mammalian cells, including immunocompetent and epithelial cells. Thus, it is reasonable to presume that this property may contribute to the pathogenesis of H. pylori-induced diseases. It may be involved on the one hand in immune response evasion and on the other hand in the suppression of epithelial repair mechanisms.

The influence of sulbactam on the in vitro activity of mezlocillin, piperacillin and cefotaxime.

In a multicentre study, the in-vitro activity of mezlocillin (MEZ, Chemical Abstract Service [CAS] 51481-65-3), piperacillin (PIP, CAS 61477-96-1) and cefotaxime (CTX, CAS 63527-52-6) against mezlocillin-resistant organisms was determined alone and in combination with the beta-lactamase inhibitor sulbactam (SBT, CAS 68373-14-8). A total of 870 strains were investigated (481 Enterobacteriaceae, 57 Pseudomonas aeruginosa, 41 Acinetobacter spp., 194 Bacteroides fragilis and 97 Staphylococcus spp.). MIC values were determined using the agar dilution test (aerobic organisms) or the microbroth dilution test (Bacteroides spp.) in accordance with Deutsche Industrie für Normung 58 940. SBT was added in fixed concentrations of 5 mg/l and 10 mg/l. For all combinations with SBT investigated, the geometric mean of the MIC and the MIC(50) and MIC(90) values were reduced as compared with the antibiotic alone (without SBT). Consequently, the proportion of sensitive strains was appreciably increased, for example in the Enterobacteriaceae: MEZ 1%, MEZ + 10 mg/l SBT 53%; PIP 4%, PIP + 10 mg/l SBT 54%; CTX 52%, CTX + 10 mg/l SBT 68%. The effect of SBT was especially pronounced on Bacteroides spp. For this organism, the proportion of sensitive strain rose from 2% to 97% (MEZ), 6% to 95% (PIP) and from 7% to 98% (CTX). The results show that adding SBT appreciably enhances the activity of MEZ, PIP and CTX against resistant strains of microorganism, and extends the activity spectrum to include anaerobic organisms. Thus the availability of SBT as a single-agent preparation for use in combination with various beta-lacta antibiotics represents a worthwhile enlargement of the therapeutic armamentarium for treating bacterial infections.

Cure of Helicobacter pylori infection: role of duration of treatment with omeprazole and amoxicillin.

OBJECTIVES: To date, some studies have suggested that short-term therapy may be a promising therapeutic concept for the eradication of Helicobacter pylori. The primary objective of the present study was to elucidate the role of the duration of treatment in the cure of H. pylori infection. METHODS: Forty consecutive patients with H. pylori-positive peptic ulcer disease were randomly allocated to four study groups. The groups were treated with a 14-day course of 20 mg omeprazole b.i.d. orally combined with 2 g amoxicillin t.i.d. intravenously for 1 day (n = 10; six women, age range 40-84 yr), for 3 days (n = 10; five women, age range 29-74 yr), for 5 days (n = 10; five women, age range 21-82 yr), for 7 days (n = 10); five women, age 42-82 yr), respectively. Initially, a standardized clinical evaluation of symptoms and and upper GI tract endoscopy were performed for assessment of H. pylori infection of the gastric mucosa (biopsy urease test, specific culture, and histology). At least 4 wk after cessation of omeprazole medication, H. pylori eradication was evaluated either as described or with the help of the 13C-urea breath test. RESULTS: H. pylori eradication, defined as negative bacterial findings in urease test, culture, and histology or 13C-urea breath test at least 4 wk after discontinuation of omeprazole therapy, was achieved in one of 10 patients (10%) in the one-day group, none of 10 patients (0%) in the 3- and 5-day groups and six of 10 patients (60%) in the 7-day group. CONCLUSION: We conclude that short-term therapies with the proton pump inhibitor omeprazole and the antibiotic amoxicillin must be considered completely ineffective if performed as a short-term therapy for up to 5 days. A therapy duration of 7 days seems to mark a turning point in antibiotic effectiveness, with a rapid increase in eradication rates.

[Short-term triple therapy with pantoprazole, clarithromycin and metronidazole for the healing of Helicobacter pylori infection]. / Kurzzeit-Tripel-Therapie mit Pantoprazol, Clarithromycin und Metronidazol zur Heilung der Helicobacter-pylori-Infektion.

In a prospective study 27 patients (13 women, 14 men; mean age 62 [45-83] years) with Helicobacter (H.) pylori associated disease received over 7 days pantoprazole (40 mg twice daily), clarithromycin (500 mg twice daily) and metronidazole (500 mg twice daily). Six patients had gastric ulcer, 4 duodenal ulcer, 4 erosive gastritis, 6 erosive duodenitis and 7 had H. pylori-positive functional dyspepsia. Pre-treatment oesophago-gastro-duodenoscopy was combined in 4 patients with antral and in 4 others with body-of-stomach biopsies to demonstrate H, pylori (urease test, specific culture and histology). The H. pylori status was checked with the 13C-urea breath test 4 weeks after the end of treatment. In addition, 9 patients with peptic ulcer were examined endoscopically at least 2 weeks after onset of the treatment to check for any healing of the ulcers, 25 of the patients completed the study according to the protocol. The H. pylori eradication rate was 100% (25 of 25 patients), while the "intention to treat" analysis gave a rate of 92.6% (25 of the 27 patients). The peptic ulcers were found to be healed in all 9 patients who had been endoscoped. One woman developed a reversible stomatitis, but the drug treatment did not have to be stopped. -These findings indicate that short-term triple treatment in the described manner is efficacious in curing H. pylori infection and any peptic ulcer. It is thus a highly promising treatment of H. pylori-associated diseases.

Synthesis, Characterization and Molecular Structures of some Bismuth(III) Complexes with Thiosemicarbazones and Dithiocarbazonic Acid Methylester Derivatives with Activity against Helicobacter Pylori.

The reactions of bismuth(III) nitrate pentahydrate and bismuth(III) chloride with heterocyclic thiosemicarbazones and derivatives of dithiocarbazonic acid methylester were used to synthesize the respective bismuth(III) complexes, which could be divided into five groups D-H because of their stoichiometrical properties and their molecular structures. The molecular structure and the near coordination sphere of the bismuth(III) central atom of four representative compounds were determined by single-crystal X-ray studies. Bis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N',N(3),S]bismuth(III) nitrate (5) belongs to group D. The two tridentate ligands and the nitrate ion surround the bismuth atom. The best description of the coordination sphere appears to be that of a distorted trigonal dodecahedron with one position occupied by the lone pair of the bismuth atom. Bis[1-azepanyl-4-(2-thienyl)-2,3-diazapenta-1,3-diene-1-thiolato-N(3),S]bismuth(III) nitrate (9) is assigned to complex type E. Here, two deprotonated ligand molecules are coordinated to the bismuth(III) central atom as bidentate ligands. The structure of this complex can best be described as a distorted trigonal antiprism with a five-coordinated central atom. The two triangular faces are formed by the atoms S(4), N(6), O(11) and S(3), N(4) and the lone pair of the central atom. The two chelate rings are almost perpendicular to each other. Complex molecules of group F form dimeric units with bichloro-bridged bismuth atoms. The structure of di-mu-chlorobis[1-azepanyl-4-(2-pyridyl)-2,3-diazapenta-1,3-diene-1-thiolato-N',N(3),S-chloro]dibismuth(III) (15) can be described as two six-coordinated bismuth atoms, which are bound together via two bridging chlorine atoms. The two bismuth atoms Bi(1) and Bi(1a) and the two bridging chlorine atoms Cl(2) and Cl(2a) form the Bi(2)Cl(2) plane. The two tridentate ligand molecules coordinate via the same atoms as shown in complex 5. In addition, they form two parallel planes, which are perpendicular to the Bi(2)Cl(2) plane. With regard to the center of the Bi(1)-Bi(2) axis they are central point symmetrical, i.e. one pyridine ring lies above and the other beneath the Bi(2)Cl(2) plane. Bismuth(III) chloride and pyridine-2-carboxaldehydethiosemicarbazone 1 b or 2-acetylpyridine-thiosemicarbazone 1 c form complexes of group G. Three chlorine atoms and a bidentate ligand are coordinated to the bismuth(III) central atom. The bidentate ligand bound to the central atom through the N(3) atom and the sulfur atom of the thioketo group. The structure of 18 is completely different from the structures of the bismuth(III) complexes discussed so far and was therefore assigned to group H. The bismuth central atom is coordinated with two ligands, which are bound in different ways. One of them is deprotonated. This ligand is bound to the central atom via the sulfur atom S(3) of the thiolate group and the N(5) atom. An interaction between the sulfur atom of the thiophene ring and the bismuth atom is not possible.The other ligand molecule is not deprotonated. This ligand is bound to the bismuth(III) cation merely via the sulfur atom S(1) of the thioketo group. The best description of the coordination sphere of the bismuth atom is that of a distorted square bipyramidal polyhedron. The square face is formed by the atoms S(3), N(5), Cl(1), the lone pair and the bismuth atom within. The axial positions are occupied by the atoms S(1) and Cl(2). The bond angle between S(1), Bi(1) and Cl(2) differs by about eight degrees from the value determined for a regular square bipyramidal polyhedron of 180 degrees.Some of the newly synthesized bismuth complexes and three ligands have been tested against several strains of Helicobacter pylori bacteria in an agar dilution test. Almost all of the listed bismuth complexes show excellent inhibitory properties with regard to growth of H. pylori already at low concentrations.

Effect of Helicobacter pylori on dbc-AMP stimulated acid secretion by human parietal cells.

This study examines the effect of different H.p. strains (A-D) on dbc-AMP stimulated acid secretion by human parietal cells in vitro. H.p. strains A and D reduced acid secretion dose-dependently between 20 and 80%. In contrast, H.p. strains B and C had little or no effect. We conclude that H.p. strains vary in their ability to suppress acid secretion, and that the site of inhibition lies beyond the c-AMP level, possibly involving the K+H(+)-ATPase of the parietal cell. Interference with acid secretion may facilitate H.p. colonization of the stomach and may prove to be an important pathogenetic factor.

[The modified 13C-urea breath test in the diagnosis of Helicobacter pylori colonization of the gastric mucosa]. / Modifizierter 13C-Harnstoff-Atemtest in der Diagnostik der Helicobacter-pylori-Besiedlung der gastralen Mucosa.

The value of a modified 13C-urea breath test for the detection of Helicobacter pylori was analysed in a prospective study of 50 consecutive patients (28 women, 22 men, aged 20-90 years) with unknown Helicobacter pylori status about to undergo upper intestinal endoscopy. Four biopsies each were obtained in each patient from the antrum and the body of the stomach and examined for Helicobacter pylori infection of the gastric mucosa histologically (haematoxylin-eosin and Giemsa stain), with the rapid urease test and by culture. The patients then underwent a modified 13C-urea breath test. Results were positive histologically and(or) by culture in 29 patients, while the breath test was positive in 28 (sensitivity 96.3%). The breath test was falsely positive in two (specificity 91.3%). The biopsy urease test had a sensitivity of 96.3% with a 100% specificity. These results demonstrate that the modified 13C-urea breath test is a simple and accurate way of demonstrating Helicobacter pylori infection, equal in diagnostic value to the biopsy urease test.

Intravenous omeprazole/amoxicillin and omeprazole pretreatment in Helicobacter pylori-positive acute peptide ulcer bleeding. A pilot study.

BACKGROUND: The aims of this study were to evaluate a Helicobacter pylori eradication schedule for H. pylori-positive gastroduodenal ulcer bleeding, which could be commenced intravenously after endoscopic diagnosis, and to assess the effect of omeprazole pretreatment on bacterial eradication. METHODS: In a prospective study 20 consecutive patients with H. pylori-positive acute peptide ulcer bleeding, who were managed conservatively including endoscopic injection therapy, were treated with a 2-week regimen consisting of either 40 mg omeprazole three times daily (with the exception of the loading dose of 80 mg) and 2 g amoxicillin three times daily intravenously for 3 days and 20 mg omeprazole twice daily and 1 g amoxicillin twice daily orally for 11 days (n = 10) or only with 40 mg omeprazole three times daily (with the exception of the loading dose of 80 mg) intravenously for 3 days and 20 mg omeprazole twice daily and 1 g amoxicillin twice daily orally for 11 days (n = 10). Subsequently, both groups received 20 mg omeprazole twice daily orally for 4 weeks. RESULTS: H. pylori eradication, defined as negative bacterial findings in urease test, culture and histology, or 13C-urea breath test at least 4 weeks after cessation of omeprazole medication, was achieved in 100% (10/10) of patients in the first group but only in 30% (3/10) of patients in the second group (p < 0.01). Ulcer healing was endoscopically confirmed in all but one patient in the second group. CONCLUSIONS: For the first time a promising concept for H. pylori eradication in H. pylori-positive ulcer bleeding is available by using a combined intravenous and oral omeprazole/amoxicillin therapy, which can be started intravenously immediately after an emergency upper GI endoscopy. In addition, these data imply that omeprazole pretreatment may not be wise when H. pylori eradication is attempted.

Expression of capsular polysaccharide determines serum resistance in Escherichia coli K92.

The amount of capsular polysaccharide expression has been shown to be the major determinant of serum resistance in Escherichia coli K1. E. coli K92, like K1, is a polymer of sialic acid molecules. It differs from K1 by containing both alpha (2.8) and alpha (2.9) linkages. Four strains of E. coli K92 were tested for serum resistance. Three strains were serum-resistant (50% normal human serum), one strain was moderately serum-sensitive. The serum-resistant strains expressed significantly more capsular polysaccharide than did the serum-sensitive strain. For each of the serum-resistant strains, six mutants were isolated by selection for resistance against infection with a K92-specific bacteriophage. All of the mutants expressed less capsular polysaccharide than the respective wild-type strains. All mutants were more sensitive to serum killing than the wild-type strains. In all groups, the mutants with lowest expression of capsular polysaccharide were highly serum-sensitive. Changes of outer membrane proteins or lipopolysaccharide patterns that were present in some mutants did not correlate with serum resistance properties of the mutants. Furthermore, it was investigated whether the presence of active serum had an influence on capsule expression. In the serum-sensitive strain, the presence of serum induced a significant and concentration-dependent increase of capsule expression. Serum had no effect on capsule expression by the serum-resistant strains. We conclude from the data that the expression of K92 capsular polysaccharide determines serum resistance in the strains examined.

Fumarate reductase of Helicobacter pylori--an immunogenic protein.

An immunogenic protein with an apparent mol. wt of 80 kDa that was recognised by 55% of sera from patients infected with Helicobacter pylori in Western blots was found in butanol extracts of H. pylori membranes. The N-terminal amino-acid sequence of the 80-kDa protein showed 80% identity with the N-terminal sequence of subunit A of the fumarate reductase of Wolinella succinogenes, suggesting the existence of a fumarate reductase in H. pylori. The membrane fraction of H. pylori catalysed succinate oxidation with methylene blue at a specific enzyme activity of 0.06 U/mg of protein. The enzyme was purified by Triton X100 extraction followed by ion-exchange chromatography. The purified enzyme contained an 80-kDa protein which was recognised by rabbit serum raised against subunit A of fumarate reductase of W. succinogenes. A second protein band with a mol. wt of 31 kDa was recognised by rabbit serum raised against subunit B of fumarate reductase of W. succinogenes. Two-dimensional gel electrophoresis demonstrated that the 80- and 31-kDa proteins were subunits of one protein complex. These results indicate that H. pylori contains an enzyme that is very similar to W. succinogenes fumarate reductase. The 80-kDa subunit was recognised in sonicates of all 32 H. pylori strains tested by rabbit antibodies raised against subunit A of fumarate reductase of W. succinogenes, indicating that fumarate reductase is a common protein in H. pylori. The fumarate reductase of H. pylori might enable the bacterium to perform anaerobic respiration in a similar fashion to other anaerobic or facultative bacteria.

Effects of Helicobacter pylori on histamine and carbachol stimulated acid secretion by human parietal cells.

Helicobacter pylori (H pylori) infection is associated with hypo, normal, and hypersecretory disorders of the gastric mucosa. Pathophysiological pathways by which H pylori interacts with acid secretion are still unclear. The effects of H pylori on (14C) aminopyrine uptake by human parietal cells were examined as an indirect assay for acid secretion. Isolated oxyntic glands were stimulated with submaximal concentrations of histamine or carbachol and incubated with sonicates of different H pylori strains. Omeprazole and sonicates of Campylobacter jejuni served as positive and negative controls, respectively. Two of four H pylori strains reduced hydrochloric acid sequestration within the parietal cells significantly and in a dose dependent manner in up to 80%. Interaction with acid secretion may therefore constitute a factor contributing to a distinct pathogenicity of H pylori strains.

[Omeprazole modified antibiotic therapy of Helicobacter pylori infection: can clarithromycin be replaced by roxithromycin?]. / Omeprazol modifizierte antibiotische Therapie der Helicobacter pylori-Infektion: Kann Clarithromycin durch Roxithromycin ersetzt werden?

Thirty-five consecutive patients (median age: 50 years, 17 men and 18 women) suffering from Helicobacter pylori associated peptic ulcer disease (duodenal ulcer: n = 15, gastric ulcer: n = 13) or severe functional dyspepsia (n = 7) were enrolled in a two-center clinical trial and treated with omeprazole 20 mg bid preprandially and roxithromycin 300 mg bid postprandially over two weeks. After cessation of the study medication, ulcer patients received a full dose H2-blocker treatment up to the final examination four weeks later. All patients completed the trial without contravening the protocol. Side effects were not recorded. The overall proportion of cure of Helicobacter pylori-infection was 29% (10 out of 35 patients) without statistically significant difference between the two participating centers (center I: 7 out of 20 patients [35%], center II: 3 out of 15 patients [20%]; p = 0.33). We conclude from our results that omeprazole plus roxithromycin is an ineffective treatment schedule with regard to cure of H.pylori-infection in patients with peptic ulcer disease or dyspepsia.

Suppression of human mononuclear cell response by Helicobacter pylori: effects on isolated monocytes and lymphocytes.

Helicobacter pylori colonization of the human gastric mucosa causes a long-term, not self-limiting inflammation, suggesting that the microbe has properties to protect itself against the host immune defence system. Recently we were able to demonstrate that H. pylori suppresses the in vitro proliferative response of human peripheral blood mononuclear cells to antigens as well as to mitogens without affecting cell viability. The purpose of this study was to clarify which cell subsets of mononuclear cells are influenced by H. pylori. The use of monocytes which had been pretreated with a soluble cytoplasmic fraction of H. pylori (30 micrograms ml-1) led to a suppressed proliferation of T cells after PHA-activation. Activation of isolated T cells with PHA and PMA revealed that the proliferative response of lymphocytes could also be inhibited independently of monocytes. The anti-proliferative effect was associated with a reduction of IL-2 receptor (CD25) expression as well as an inhibition of blastogenesis. Furthermore, the spontaneous proliferation of EBV-transformed B cell lines was suppressed in a dose-dependent manner. FACS-analysis of HLA-DR, ICAM-1 and CD14 expression on the surface of monocytes revealed an influence of H. pylori on CD14 expression at a concentration of 30 micrograms ml-1, while the expression of HLA-DR and ICAM-1 was not affected at this concentration.

Medium-term results of oral and intravenous omeprazole/amoxicillin Helicobacter pylori eradication therapy.

OBJECTIVES: The aim of the present study was to examine the effect of the application route of the antibiotic amoxicillin in Helicobacter pylori eradication, using omeprazole/amoxicillin. METHODS: In a prospective medium-term study, 31 patients with H. pylori-positive gastroduodenal ulcer disease were treated with a 14-day course of 20 mg omeprazole bid orally, combined with either 1 g amoxicillin tid intravenously (n = 15) or 500 mg amoxicillin six times daily orally (n = 16). RESULTS: H. pylori eradication, defined as negative bacterial findings in urease test, culture, and histology at least 4 wk after cessation of study medication, was achieved in 93% (14/15) of the patients in the first group and in 91% (11/12) of the patients in the second group. To obtain medium-term results, patients in whom H. pylori had been successfully eradicated were investigated with a 13C-urea breath test at least 6 months later. Medium-term eradication rates of 91% (10/11 patients) in the first and 100% (10/10 patients) in the second group were observed. CONCLUSIONS: In view of the equally high eradication rates obtained by a 14-day course of intravenously administered amoxicillin and an oral therapy of the same length and dosage, during the necessary induction of luminal hypoacidity by the proton pump inhibitor omeprazole, we conclude that the route of administration of amoxicillin does not play a decisive role in bacterial eradication.

Stimulatory effects of Helicobacter pylori on human peripheral blood mononuclear cells of H. pylori infected patients and healthy blood donors.

The ability of 23 different strains of Helicobacter pylori to induce proliferative response of human peripheral blood mononuclear cells (PBMC) was investigated. All tested strains stimulated the DNA synthesis of PBMC from both healthy and H. pylori infected blood donors, but with lower stimulation of PBMC of infected donors. Using different bacterial antigen preparations, such as crude membranes, cytoplasmic proteins, and urease, a significantly lower induction of the proliferative response of PBMC from H. pylori infected than from healthy blood donors could also be demonstrated. In contrast to this result the reaction to phytohemagglutinin and purified protein derivative of tuberculin was similar in both groups. The stimulation pathway was interleukin 2 (IL-2) dependent as proved by inhibition of the proliferative response with an alpha-IL-2-receptor antibody. Using an antibody against HLA-DR the lymphoproliferation could also be blocked showing the importance of the major histocompatibility class II (MHCII) complex. Only coincubation of T cells with monocytes plus antigen or with antigen-preincubated monocytes led to a proliferative response showing the necessity of antigen-presenting cells. At least a part of the lymphoproliferative response is MHCII restricted as could be shown with H. pylori specific T-cell lines. These results and the kinetics of the proliferative response with a maximum at day 7 suggest that the proliferative response of human PBMC was mainly induced by antigens than by a mitogen.

Immune suppressive effects of Helicobacter pylori on human peripheral blood mononuclear cells.

Helicobacter pylori, the causative agent of type-B gastritis and duodenal ulcer in man is described as a bacterium able to stimulate the human immune system. This study demonstrates that H. pylori besides this property possesses an immune suppressive activity. The in vitro proliferation of human peripheral blood mononuclear cells to purified protein derivative of tuberculin (PPD), phytohemagglutinin, and concanavalin A was reduced in a dose-dependent manner by bacteria which had been inactivated by incubation at 56 degrees C as well as by a soluble cytoplasmic fraction of H. pylori. The immune suppressive effect on the mitogen-induced proliferation could be increased by preincubation of the mononuclear cells with H. pylori. The observed effect does not seem to be a specific phenomenon depending on prior exposure of the blood donors to H. pylori, since suppression occurred with mononuclear cells of H. pylori-infected patients as well as of antibody-negative healthy control individuals. The suppressive activity was non-dialyzable, heat-labile (100 degrees C, 30 min) and sensitive to trypsin. Furthermore, the treatment at 100 degrees C caused an increase in the capability of H. pylori to induce lymphoproliferation. This fact indicates that the suppressive factor is also effective on H. pylori antigens. While exogenous interleukin-2, could to a certain extent, restore the responsiveness of the lymphocytes after PPD-stimulation in the presence of H. pylori, the addition of interleukin-1 had no effect on the suppressed lymphoproliferation. Cell-separation and cell-mixing experiments indicated that an influence on monocytes rather than on T cells is the major cause of the observed suppressive effect. Although the immunological mechanisms involved in H. pylori-associated gastritis are not clearly defined, it is reasonable to presume that suppression of host defense mechanisms may contribute to the pathogenesis of this disease.