Unravelling the pathogenic role of Helicobacter pylori in peptic ulcer: potential new therapies and vaccines

The recognition that peptic ulcer is an infectious disease caused by the bacterium Helicobacter pylori has revolutionized the approach to diagnosis and therapy of this condition. Treatment of the symptoms of peptic ulcer with drugs that block acid secretion is already being replaced by antibiotic eradication of the causative agent. Studies of the molecular events that lead to H. pylori pathogenesis have shown that clinical isolates can be divided into two groups, only one of which produces a cytotoxin and is associated with severe disease. The cloning of the genes coding for molecules specific for disease-associated strains of H. pylori, and the development of animal models that mimic the human pathology, will provide the basis for better strategies to treat and prevent peptic-ulcer disease.

Gene structure of the Helicobacter pylori cytotoxin and evidence of its key role in gastric disease

The gram negative, microaerophilic bacterium Helicobacter pylori colonizes the human gastric mucosa and establishes a chronic infection that is tightly associated with atrophic gastritis, peptic ulcer, and gastric carcinoma. Cloning of the H. pylori cytotoxin gene shows that the protein is synthesized as a 140-kD precursor that is processed to a 94-kD fully active toxin. Oral administration to mice of the purified 94-kD protein caused ulceration and gastric lesions that bear some similarities to the pathology observed in humans. The cloning of the cytotoxin gene and the development of a mouse model of human gastric disease will provide the basis for the understanding of H. pylori pathogenesis and the development of therapeutics and vaccines.

Depression of liver metabolism and induction of cytokine release by diphtheria and tetanus toxoids and pertussis vaccines: role of Bordetella pertussis cells in toxicity

A 24-h pretreatment of mice with diphtheria and tetanus toxoids and whole-cell pertussis vaccines depressed liver cytochrome P-450 and therefore prolonged hexobarbital-induced sleeping time in mice. The depression of liver drug metabolism by a cellular vaccine containing a mutated pertussis toxin was less marked than that induced by the wild-type vaccines, indicating that the mutated vaccine might have lower toxicity in this regard. The wild-type vaccines decreased microsomal P-450 levels by 50%, while the mutated whole-cell vaccine had a less marked effect (a decrease of 30%), paralleling the results obtained in sleeping time experiments. Furthermore, an acellular mutated vaccine did not affect liver drug metabolism, indicating a role of the whole bacterial cell in this side effect. All the cellular vaccines studied induced high serum interleukin-6 levels; on the other hand, the acellular mutated vaccine induced very low interleukin-6 levels, indicating that the whole bacterial cell is also important for interleukin-6 induction. All vaccines studied were very poor tumor necrosis factor inducers.

Importance of brain IL-1 type II receptors in fever and thermogenesis in the rat

Interleukin-1 (IL-1) acts centrally to induce fever and thermogenesis in rodents. The central actions of IL-1 alpha and IL-1 beta apparently involve different mechanisms, and the effects of IL-1 beta are not consistent with interaction with a type I (IL-1RI) 80-kDa receptor. In the present study the involvement of the type II IL-1 receptor (IL-1RII) was tested in the rat by examining the effects of central injection of a monoclonal antibody (ALVA-42), which blocks the IL-1RII. Pretreatment of rats with ALVA-42 (6 micrograms icv) inhibited the thermogenic and pyrogenic responses to intracerebroventricular injection of 5 ng (but not 50 ng) of IL-1 beta in conscious rats but did not significantly modify responses to IL-1 alpha. ALVA-42 also failed to modify the responses to peripherally administered IL-1 beta (1 microgram) but significantly attenuated the pyrogenic and thermogenic responses to peripheral (125 micrograms) or central (1 microgram) injection of endotoxin. These data indicate that IL-1RII mediates the central effects of a low dose of IL-1 beta, but not IL-1 alpha, on fever and thermogenesis in the rat. They also imply that responses to endotoxin are due, at least in part, to the activation of IL-1RII by IL-1 beta released within the brain and that effects of peripherally injected IL-1 beta involve different mechanisms, probably associated with IL-1RI.

Increasing the immunogenicity of protein antigens through the genetic insertion of VQGEESNDK sequence of human IL-1 beta into their sequence

The immunogenicity of two recombinant protein Ag containing the immunostimulatory sequence of human IL-1 beta 163-171 (VQGEESNDK) genetically engineered into their structure has been evaluated. The IL-1 beta sequence was inserted into the loop between alpha helices D and E of recombinant human ferritin H chain and into the hypervariable region of recombinant flagellin from Salmonella muenchen. The chimeric proteins were injected into mice and the level of humoral immune response developed against the native proteins was assessed by measuring the number of Ag-specific plaque forming cells/spleen or as the level of serum IgG response. The response was compared to that of mice receiving injections with wild-type protein Ag not containing the VQGEESNDK sequence or with hybrid constructs containing unrelated foreign peptide sequences of the same length. A significantly higher immune response was observed in mice immunized with chimeric constructs containing the human IL-1 beta 163-171 sequence. These data suggest that the insertion of the VQGEESNDK sequence may prove useful to increase the immune response against poorly immunogenic recombinant proteins.

Increasing the immunogenicity of protein antigens through the genetic insertion of VQGEESNDK sequence of human IL-1 beta into their sequence

The immunogenicity of two recombinant protein Ag containing the immunostimulatory sequence of human IL-1 beta 163-171 (VQGEESNDK) genetically engineered into their structure has been evaluated. The IL-1 beta sequence was inserted into the loop between alpha helices D and E of recombinant human ferritin H chain and into the hypervariable region of recombinant flagellin from Salmonella muenchen. The chimeric proteins were injected into mice and the level of humoral immune response developed against the native proteins was assessed by measuring the number of Ag-specific plaque forming cells/spleen or as the level of serum IgG response. The response was compared to that of mice receiving injections with wild-type protein Ag not containing the VQGEESNDK sequence or with hybrid constructs containing unrelated foreign peptide sequences of the same length. A significantly higher immune response was observed in mice immunized with chimeric constructs containing the human IL-1 beta 163-171 sequence. These data suggest that the insertion of the VQGEESNDK sequence may prove useful to increase the immune response against poorly immunogenic recombinant proteins.

A chimeric type II/type I interleukin-1 receptor can mediate interleukin-1 induction of gene expression in T cells

The type I interleukin-1 receptor (IL-1R) is capable of transducing a signal resulting in promoter activation in T cells. This signal transduction is dependent on the cytoplasmic domain, which consists of 213 amino acids. In contrast to the type I receptor, the type II IL-1R has a small cytoplasmic tail, and it is not clear whether this receptor is a signal-transducing or a regulatory molecule. Here we report that the type II IL-1R does not mediate gene activation in Jurkat cells. However, a hybrid receptor composed of the extracellular and transmembrane regions of the human type II interleukin-1 fused to the cytoplasmic domain of the human type I IL-1R was capable of transducing a signal across the membrane resulting in a pattern of gene activation identical to that mediated by the type I IL-1R. Our results indicated that the extracellular domain of the type II IL-1R was capable of functionally interacting with interleukin-1 and transmitting the resulting signal to a heterologous cytoplasmic domain.

[Interleukin-1 beta in the gingival tissues of patients with periodontitis: immunohistochemical data]

Interleukin-1 beta (Il-1 beta) is a cytokine which is considered to play a role in inducing the inflammatory reaction and the bone resorption that takes place in periodontal disease. With the aim of studying the presence and location of Il-1 beta positive cells in this disease, human gingival tissues from 12 patients with periodontitis and from 4 healthy control subjects were examined by immunohistochemical analysis. The cytokine was detected in all the patients having untreated periodontitis, although its content in gingival tissues revealed considerable variations among subjects. Il-1 beta was mainly localized within macrophage-like cells. Il-1 beta positive cells were not present in normal gingival tissue; however in 2 of the subjects considered normal there were few Il-1 beta positive cells in small areas of inflammation present in proximity of the dento-gingival junction.

Human peritoneal mesothelial cells produce many cytokines (granulocyte colony-stimulating factor [CSF], granulocyte-monocyte-CSF, macrophage-CSF, interleukin-1 [IL-1], and IL-6) and are activated and stimulated to grow by IL-1

To investigate the role of peritoneal mesothelial cells in regulating hematopoiesis, as well as inflammation, healing, and tissue regeneration processes, long-term cultures of peritoneal mesothelial cells from human endocavitarian fluids were established. The purity of the cell population was assessed by morphologic and immunocytochemical criteria. Five peritoneal mesothelial cell cultures were analyzed for cytokine expression. Macrophage colony-stimulating factor (M-CSF), granulocyte-CSF (G-CSF), interleukin-1 alpha (IL-1 alpha), IL-1 beta, and IL-6 transcripts were constantly but variably detected throughout the culture period, while granulocyte-monocyte-CSF (GM-CSF) expression started as the cell culture aged. No IL-2, IL-3, IL-4, IL-5, or IL-7 transcripts were detected in the same samples. Corresponding cytokine activities were detected in the supernatants of the cultures. Peritoneal mesothelial cells proliferated after the addition of exogenous IL-1 beta or IL-1 alpha, whereas the addition of recombinant GM-CSF, G-CSF, M-CSF, or IL-6 failed to trigger proliferation. IL-1 receptor type I transcripts were detected in peritoneal mesothelial cells. Moreover, IL-1 was able to upregulate the expression of the genes that code for G-CSF, GM-CSF, IL-1 alpha, and IL-1 beta in these cells. These data indicate that peritoneal mesothelial cells produce many cytokines and suggest that IL-1 is a regulatory molecule for peritoneal mesothelial cells.

Binding and internalization of the 163-171 fragment of human IL-1 beta

The mechanisms of cell association of the human interleukin (IL-1 beta) immunostimulatory fragment 163-171 have been studied. The fragment was able to associate abundantly to both IL-1R- and IL-1R+ cells. Binding was strictly temperature dependent, was not saturable and could be inhibited by excess amounts of unlabelled 163-171 peptide but not by IL-1 beta, suggesting that the 163-171 fragment is not an IL-1R-binding domain of IL-1 beta. The fragment is readily internalized by cells by a cytochalasin-insensitive mechanism and it localizes mainly in the cytoplasm. It is concluded that the active domain 163-171 of IL-1 beta can be taken up by cells through a receptor-independent, temperature-dependent mechanisms and that its ability to activate cellular functions is based on IL-1R-independent intracellular pathways.

Differential inhibition of IL-1 beta activities and receptor binding by monoclonal antibodies mapping within a discrete region of the protein

The importance of the region in position 148-192 for the biological activities and receptor-binding capacity of the human IL-1 beta protein has been assessed by the use of mAbs. Four mAbs have been used, which recognize different epitopes within the 148-192 region. None of the mAbs could inhibit binding of IL-1 beta to IL-1RI (expressed on T cells and fibroblasts), suggesting that the 148-192 region does not contain IL-1RI binding sites. Conversely, mAbs Vhp20 (recognizing the fragment 166-169) and BRhD2 (directed to an epitope in the sequence 177-186) recognize sites partially involved in binding to IL-1RII (expressed on B cells, macrophages, and PMN). Only mAbs BRhD2 and FIB 1 (which recognizes an epitope in the sequence 174-186) can inhibit IL-1 beta-induced thymocyte proliferation, whereas all four can inhibit the adjuvant capacity of IL-1 beta in vivo. It is concluded that the region 148-192 encompasses domains important for T cell activation but not for binding to the IL-1RI on T cells, others involved in immunostimulation in vivo, and others important for binding to IL-1RII, although not directly involved in it.

Endothelial cells express the interleukin-1 receptor type I

Interleukin-1 (IL-1) profoundly affects a number of functions of vascular cells. Two distinct IL-1 receptors (IL-1R) are expressed on different cell types: the 80 Kd IL-1RI on T cells and fibroblasts, and the 68 Kd IL-1RII on B cells and myelomonocytic cells. The presence and functionality of IL-1R on vascular cells has been investigated by using polyomatransformed mouse endothelial cell (EC) lines (sEnd.1 and tEnd.1). These cells expressed specific and saturable binding sites for IL-1 (1,273 sites per cell with kd 9.5 x 10(-11) mol/L for sEnd.1, and 771 sites per cell with kd 8.5 x 10(-11) mol/L for tEnd.1, with radioiodinated IL-1 alpha as ligand). Binding of IL-1 was also evident at single cell level by autoradiography. By cross-linking studies, the molecular weight of the IL-1 binding protein on EC was approximately 80 Kd. This was confirmed by the presence in EC of mRNA for the 80 Kd IL-1RI. The IL-1RI on EC was apparently functional, since EC responded to IL-1 with IL-6 mRNA expression and IL-6 bioactivity production. These results were extended to human EC and vascular smooth muscle cells, which were also found to express mRNA for IL-1RI.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Binding of IL-1 beta to IL-1R type II at single cell level

To gain information on the possible biologic role of IL-1R type II (IL-1RII), expression of the 68-kDa IL-1 binding protein on human lymphoblastoid B cells was investigated at single cell level. Binding of iodinated IL-1 beta was evaluated by autoradiography on cytosmears of IL-1RII positive B cell lines RAJI, the RAJI clone 1H7, and STS 25. Results obtained suggest an heterogeneity of IL-1RII expression within the B cell population, with only 5 to 16% of the cells able to bind IL-1 beta. Up-regulation of IL-1RII expression by dexamethasone, evident in conventional binding assays, was achieved through both increase in the number of IL-1 binding cells (14-30%) and augmentation of receptor density on positive cells, By combining autoradiography with immunocytochemical staining, it could be shown that about 80% of IL-1RII + cells were negative for Ki67, a nuclear antigen expressed from late G1 to M phase. Cell cycle dependent expression of IL-1RII was confirmed on cells enriched in different phases of the cell cycle by counterflow centrifugal elutriation. It is thus proposed that IL-1RII is associated to the cell cycle.

Alpha-melanocyte-stimulating hormone reduces interleukin-1 beta effects on rat stomach preparations possibly through interference with a type I receptor

Contractions elicited by CaCl2 on isolated rat stomach strip preparations have been reported to be potentiated by interleukin-1 beta (IL-1 beta). We have investigated whether this effect can be reduced by the putative IL-1 beta antagonist, alpha-melanocyte-stimulating hormone (alpha MSH). Additionally, the effects of alpha MSH on the specific binding of IL-1 beta to B- and T-cells have been investigated to further clarify its inhibitory activities. Both alpha MSH and its carboxyl terminal tripeptide concentration dependently reduced the potentiation of CaCl2-induced contractions caused by IL-1 beta but not those caused by leukotriene D4, the parent molecule being approximately 250 times more active. Additionally, both peptides potently and selectively reduced 125I-IL-1 beta binding to the T-cell sub-clone EL4-6.1 but not to the B-cell sub-clone 1H7. The results indicate that IL-1 beta effects on rat stomach may be mediated through a type-I (80 kDa) IL-1 beta receptor.

Quantitation of biologically active IL-1 by a sensitive assay based on immobilized human IL-1 receptor type II (IL-1RII)

A rapid and sensitive solid-phase radioassay is described for the quantitative detection of human interleukin-1 (IL-1) based on its capability to bind the nitrocellulose-immobilized IL-1 receptor solubilized from plasma membranes of a subclone of the human B cell lymphoma Raji. The assay can detect human IL-1 beta levels as low as 1 X 10(-11) M, both in physiological buffers and in human plasma. Much lower sensitivity was observed for human IL-1 alpha (3.7 X 10(-9) M) and murine IL-1 beta (2 X 10(-9) M). This assay has the advantage to specifically detect only the correctly folded biologically active IL-1. Simple pretreatment procedure that selectively removes IL-1 beta from samples has been devised so that the ratio of the two IL-1s isoforms in the sample can be precisely determined. This assay represents a fast method for the simultaneous-testing of large numbers of biological samples.

Mechanism of acute toxicity of IL-1 beta in mice

Human recombinant IL-1 beta was able to kill C3H/HeJ mice only when inoculated intravenously at very high doses. IL-1 beta, inoculated at 100 mg/kg i.v. as a bolus, induced a shock-like state characterized by anorexia, severe hypothermia and hypoglycemia and persistent neutrophilia, leading to death in 55% of animals generally between 24 and 48 h. In contrast, the noninflammatory adjuvant IL-1 beta peptide VQGEESNDK (position 163-171) did not induce any toxic effect in vivo, when administered following the same schedule. At variance with what was previously observed in endotoxin induced shock, IL-1 beta induced death was not preceded by appearance of circulating TNF. On the other hand, very high and persistent levels of circulating IL-6 could be detected after lethal IL-1 beta administration. Treatment of mice with ibuprofen or with chlorpromazine, both known to counteract some of the toxic effects of IL-1 in vivo, could protect from IL-1 beta induced mortality. Both drugs, at doses protecting from IL-1 beta induced death, were able to abolish IL-1 beta-induced rise of circulating phospholipase A2 (PLA2) activity, and the subsequent generation of toxic PLA2-derived metabolites.

Defining the structural requirements of a biologically active domain of human IL-1 beta

The immunostimulatory activity in vivo of the pleiotropic cytokine IL-1 beta can be retained by its nonapeptide VQGEESNDK, in position 163-171. A series of shorter and longer peptides around this position has been assayed for IL-1-like biological activity, in order to identify the structural requirements for full expression of adjuvant capacity. Elongated peptides, comprising the loop region 165-169 and up to six amino acids in the preceding beta strand or up to seven amino acids in the following beta strand, showed activity comparable or lower than that of the nonapeptide 163-171. This would indicate that the beta strand sequences are not required for optimizing the active conformation of the immunostimulatory IL-1 beta moiety. Accordingly, stabilization of the 163-171 peptide conformation by cyclization did not increase its biological activity. In contrast, the pentapeptide GEESN, corresponding the exposed loop 165-169 between two beta strands, had biological activity higher than that of the 163-171 nonapeptide and fully comparable to that of the entire IL-1 beta protein. Thus, the highly exposed fragment 165-169 within the IL-1 beta molecule may be the structure selectively responsible for the IL-1 beta immunostimulatory capacity in vivo.

Differential activity of interleukin 1 alpha and interleukin 1 beta in the stimulation of the immune response in vivo

The biological activities of human recombinant interleukin (IL) 1 alpha and IL 1 beta were compared in different biological systems. The two IL 1 forms were equally active in vitro in inducing proliferation of murine thymocytes and of the murine T helper clone D10.G4.1, and in triggering release of prostaglandin E2 from human skin fibroblasts. In vivo, IL 1 alpha and IL 1 beta were similarly pyrogenic both in rabbits and mice, and could equally increase the circulating levels of the acute phase protein serum amyloid A in mice. However, only IL 1 beta showed immunostimulatory activity in vivo, as it could enhance the number of specific antibody-producing cells in the spleen of mice immunized with either a T-dependent or a T-independent antigen. Although devoid of immunostimulatory activity, IL 1 alpha could efficiently compete immunostimulation induced by IL 1 beta, suggesting an effective interaction with the IL 1 receptor. Thus, IL 1 beta appears to have an important role in the positive regulation of immune responses, while IL 1 alpha may act as down-regulator of the IL 1 beta effect.

Differential binding of IL-1 alpha and IL-1 beta to receptors on B and T cells

The interleukin 1 receptors (IL-1R) on the human B lymphoma RAJI and on the murine thymoma EL4-6.1 have been characterized. Equilibrium binding analysis using both 125I-labeled IL-1 alpha and IL-1 beta showed that RAJI cells have a higher number of binding sites/cell for IL-1 beta (2400, Kd 2.2 nM) than for IL-1 alpha (316, Kd 0.13 nM). On the other hand, EL4-6.1 cells have more receptors/cell for IL-1 alpha (22 656, Kd 1 nM) than for IL-1 beta (2988, Kd 0.36 nM). Dexamethasone (DXM) induced on RAJI cells a time-dependent increase in binding sites for both IL-1 beta and IL-1 alpha without affecting their binding affinities. However, while receptor-bound 125I-IL-1 alpha was displaced with equal efficiency by both IL-1 forms, only unlabeled IL-1 beta could effectively displace 125I-IL-1 beta. Cross-linking experiments indicated that RAJI cells have a predominant IL-1R of about 68 kDa, while EL4-6.1 cells have an IL-1-binding polypeptide of 80 kDa. These results suggest that B and T cells possess structurally different IL-1R with distinct binding properties for IL-1 alpha and IL-1 beta.