Therapeutic potential of carbon monoxide in multiple sclerosis

Carbon monoxide (CO) is produced during the catabolism of free haem, catalyzed by haem oxygenase (HO) enzymes, and its physiological roles include vasodilation, neurotransmission, inhibition of platelet aggregation and anti-proliferative effects on smooth muscle. In vivo preclinical studies have shown that exogenously administered quantities of CO may represent an effective treatment for conditions characterized by a dysregulated immune response. The carbon monoxide-releasing molecules (CORMs) represent a group of compounds capable of carrying and liberating controlled quantities of CO in the cellular systems. This review covers the physiological and anti-inflammatory properties of the HO/CO pathway in the central nervous system. It also discusses the effects of CORMs in preclinical models of inflammation. The accumulating data discussed herein support the possibility that CORMs may represent a novel class of drugs with disease-modifying properties in multiple sclerosis.

HCG hastens both the development of mammary carcinoma and the metastatization of HCG/LH and ERBB-2 receptor-positive cells in mice

Breast cancer is more frequent in human nulliparae, whereas its incidence is reduced by early fullterm pregnancy. Rodent studies suggest that chorionic gonadotropin secretion during pregnancy affords protection by inducing breast structure differentiation. Opposite effects, however, have been observed in cancer prone transgenic mice overexpressing the β subunit of chorionic gonadotropin or pituitary luteinic hormone (LH). Here we assessed the effect of administration of human chorionic gonadotropin (hCG) for 21 days (corresponding to the duration of a mouse pregnancy) in virgin female mice transgenic for the activated rat (r-) ERBB-2 oncogene (BALB-neuT). In these mice, the onset of atypical mammary duct hyperplasia and its progression towards multiple mammary carcinomas is accelerated by hCG. hCG enhances the in vitro proliferation and in vivo metastatization of tumor cells from a BALB-neuT mammary tumor expressing the hCG/LH as well as the ERBB-2 receptors. These findings suggest that hCG favours the growth and progression of hCG/LH and ERBB-2 receptor-positive breast tumors.

The new and less toxic protease inhibitor saquinavir-NO maintains anti-HIV-1 properties in vitro indistinguishable from those of the parental compound saquinavir

Although, the antiviral activity, tolerability and convenience of protease inhibitors have improved significantly in recent years, toxicity-associated adverse events including diarrhea, lipid alterations, disturbance of glucose homeostasis and liver enzyme elevations still remain a major concern during treatment of HIV-1 patients. We have recently shown that the covalent attachment of the NO moiety to the HIV-1 protease inhibitor saquinavir (Saq-NO) reduces its toxicity. In this study, we evaluated in vitro the anti-HIV activity of Saq-NO vs. its parental compound Saq. Site directed mutants with the most frequently identified Saq associated resistance mutations and their combinations were generated on proviral AD8-based backbones. Phenotypic assays were conducted using wild type clinical isolates and fully replicating recombinant viruses with Saq and Saq-NO in parallel on purified CD4+ T cells. The following recombinant viruses were generated and tested: L33F, M46I, G48V, I54V, I84V + L90M, M46I + L90M, G48V + L90M, M46I + I54V + L90M, L33F + M46I + L90M. The fold change resistance compared to the wild type viruses was between 1.3 and 7 for all single mutants, between 3.4 and 20 for double mutants and between 16.7 and 28.5 for viruses carrying three mutations for both compounds. The results clearly demonstrate that Saq-NO maintains an anti-HIV-1 profile very similar to that of Saq. The possibility to reduce Saq associated side effects and to increase the concentration of the drug in vivo may allow a higher and possibly more effective dosage of Saq-NO in HIV-1-infected patients and to increase the genetic barrier of this PI thus impairing the selection of resistant clones.

Generation of potent neutralizing human monoclonal antibodies against cytomegalovirus infection from immune B cells

Background

Human monoclonal antibodies (mAbs) generated as a result of the immune response are likely to be the most effective therapeutic antibodies, particularly in the case of infectious diseases against which the immune response is protective.

Human cytomegalovirus (HCMV) is an ubiquitous opportunistic virus that is the most serious pathogenic agent in transplant patients. The available therapeutic armamentarium (e.g. HCMV hyperimmune globulins or antivirals) is associated with severe side effects and the emergence of drug-resistant strains; therefore, neutralizing human mAb may be a decisive alternative in the prevention of primary and re-activated HCMV infections in these patients.

Results

The purpose of this study was to generate neutralizing mAb against HCMV from the immunological repertoire of immune donors. To this aim, we designed an efficient technology relying on two discrete and sequential steps: first, human B-lymphocytes are stimulated with TLR9-agonists and IL-2; second, after both additives are removed, the cells are infected with EBV. Using this strategy we obtained 29 clones secreting IgG neutralizing the HCMV infectivity; four among these were further characterized. All of the mAbs neutralize the infection in different combinations of HCMV strains and target cells, with a potency ~20 fold higher than that of the HCMV hyperimmune globulins, currently used in transplant recipients. Recombinant human monoclonal IgG1 suitable as a prophylactic or therapeutic tool in clinical applications has been generated.

Conclusion

The technology described has proven to be more reproducible, efficient and rapid than previously reported techniques, and can be adopted at low overall costs by any cell biology laboratory for the development of fully human mAbs for immunotherapeutic uses.

Anticancer properties of the novel nitric oxide-donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide in vitro and in vivo

Preclinical studies have shown that nitric oxide (NO)-donating nonsteroidal anti-inflammatory drugs possess anticancer activities. Here, we report in vitro and in vivo studies showing the antitumor effect of the NO-donating isoxazole derivative (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid (GIT-27NO). GIT-27NO, but not the NO-deprived parental compound VGX-1027, significantly affected viability of both rodent (L929, B16, and C6) and human (U251, BT20, HeLa, and LS174) tumor cell lines. GIT-27NO triggered either apoptotic cell death (e.g., L929 cells) or autophagic cell death (C6 and B16 cells). Moreover, GIT-27NO hampered the viability of cisplatin-resistant B16 cells. NO scavenger hemoglobin completely prevented GIT-27NO-induced death, indicating that NO release mediated the tumoricidal effect of the compound. Increase in intracellular NO upon on the treatment was associated with intensified production of reactive oxygen species, whereas their neutralization by antioxidant N-acetylcysteine resulted in partial recovery of cell viability. The antitumor activity of the drug was mediated by the selective activation of mitogen-activated protein kinases in a cell-specific manner and was neutralized by their specific inhibitors. In vivo treatment with GIT-27NO significantly reduced the B16 melanoma growth in syngeneic C57BL/6 mice. The therapeutic effect occurred at dose (0.5 mg/mouse) up to 160 times lower than those needed to induce acute lethality (80 mg/mouse). In addition, a dose of GIT-27NO five times higher than that found effective in the melanoma model was well tolerated by the mice when administered for 4 consecutive weeks. These data warrant additional studies to evaluate the possible translation of these findings to the clinical setting.

IL-6 Promotes compensatory liver regeneration in cirrhotic rat after partial hepatectomy

Major hepatic resection in cirrhotic patients is associated with impaired liver regeneration and failure, leading to high peri-operative mortality. In this work, the causes of defective regeneration in cirrhotic liver and the utility of IL-6 treatment were investigated in an experimental model combining cirrhosis and partial hepatectomy in the rat. Relative to normal controls, decompensated cirrhotic animals showed decreased survival, while compensated cirrhotic animals showed similar survival but reduced hepatic DNA synthesis and newly regenerated liver mass amount. Defective liver regeneration was associated with a decrease in STAT3 and NF-kB activation, consistent with an increased accumulation of their respective inhibitors PIAS3 and IkBalpha, and with a decreased induction of Bcl-xL. Treatment with recombinant IL-6 enhanced survival of decompensated cirrhotic animals, while it did not affect survival of compensated cirrhotic animals but sustained liver regeneration, by restoring STAT3 and NF-kB activation and Bcl-xL induction to the levels found in normal controls. The pro-growth effects exerted by IL-6 treatment in cirrhotic liver were attained also at low, pharmacologically acceptable doses. In conclusion, our results suggest that IL-6 treatment may be therapeutic in major resection of cirrhotic liver.

Interleukin-6 sustains hepatic regeneration in cirrhotic rat

BACKGROUND/AIMS

In the liver IL-6 displays growth-inducing and pro-survival activities. We studied the pro-proliferative and protective mechanisms of IL-6 treatment in a model of liver cirrhosis in wild type rat, investigating the theoretical basis for a potential pharmacologic role of IL-6 in cirrhosis.

METHODOLOGY

We analyzed IL-6 receptors levels in cirrhotic liver. We also studied the activation of signaling pathways downstream IL-6 receptors by analyzing the DNA-binding activity of transcription factors STAT3, AP-1, HNF-1 and NF-kappaB and the phosphorylation status of AKT and eNOS. We also analyzed hepato-cell proliferation, by determining BrdU incorporation into DNA, and liver mass expansion.

RESULTS

We show that liver cells from cirrhotic animals have increased expression of the IL-6 receptor alpha/gp80. In addition, we show that in cirrhosis the main molecular pathways downstream the receptors are intact and that IL-6 activates STAT3, AP-1 and NF-kappaB transcription factors, induces AKT and eNOS phosphorylation and increases hepato-cell proliferation and liver mass expansion in a dose-dependent manner.

CONCLUSIONS

Our data demonstrate that the theoretical basis exists for the therapeutic employment of IL-6 in liver cirrhosis.

Mechanisms of interleukin-6 protection against ischemia-reperfusion injury in rat liver

Numerous animal studies simulating liver injury have demonstrated that interleukin-6 (IL-6) exerts a protective effect. This study was designed to further analyze the molecular mechanisms underlying the protective role of IL-6 in a rat model of liver ischemia/reperfusion injury. We show that IL-6: (i) at high doses reduces cell damage which occurs in ischemic-reperfused liver, while at low doses displays only a limited protective capacity, (ii) anticipates and enhances hepatocyte compensatory proliferation seen in ischemic-reperfused liver also at a low, more pharmacologically acceptable dose, (iii) sustains the acute phase response which is dampened in ischemic-reperfused liver, (iv) strengthens the heat shock-stress response shown by ischemic-reperfused liver and (v) overcomes the dysfunctions of the unfolding protein response found in ischemic-reperfused liver. We also show that IL-6-enhanced STAT3 activation probably plays a crucial role in the potentiation of the different protective pathways activated in ischemic-reperfused liver. Our data confirm that IL-6 is a potential therapeutic in liver injury of different etiologies and reveal novel mechanisms by which IL-6 sustains liver function after ischemia/reperfusion injury.

Interleukin-6 attenuates the development of experimental diabetes-related neuropathy

Neuropathy is the most severe and the least understood complication of diabetes. We investigated the potential neuroprotective effect of IL-6 therapy in an experimental model of diabetic neuropathy. A single i.v. injection of streptozotocin (STZ, 55 mg/kg) was used to induce experimental diabetes in adult males. IL-6 (1, 10 or 30 microg/kg) was administrated either intraperitoneally on a daily basis or subcutaneously (s.c.) on a daily, on a three times or one time per week basis, starting at day 10 post-STZ. A decrease in sensory nerve conduction velocity (SNCV), indicative of neuropathy, is seen in STZ rats as early as day 10 post-STZ, a time at which blood glycaemia is already maximal. At later time points, this electrophysiological impairment became severe and clinically apparent by affecting tail flick latency. Motor dysfunction defined by a significant increase in compound muscle action potential (CMAP) latency was also recorded. At the completion of the study (day 40 post-STZ), histological examination revealed significant axonopathy and myelin loss, along with an increase in the proportion of fibers with abnormal appearance in sciatic nerves of STZ rats. These changes were not observed in non-diabetic rats and were significantly prevented by IL-6 treatment. The optimal dose appeared to be 10 microg/kg s.c. three injections per week, which showed a better effect in most of the parameters studied than 4-methylcatechol, a NGF-like neuroprotective compound. Once weekly and three times weekly administrations of IL-6 were as effective as daily treatment. Taken together, these results support the potential neuroprotective actions of IL-6. The fact that the half-life of IL-6 is only approximately 5 h while weekly dosing was neuroprotective strongly suggests activation by IL-6 of effector molecule(s) with longer duration of action.

Acute haemodynamic effects of IL-6 treatment in vivo: involvement of vagus nerve in NO-mediated negative inotropism

Interleukin-6 (IL-6) reduces myocardial haemodynamics. However, the intrinsic mechanisms of IL-6 effects are not known. We hypothesized that nitric oxide (NO) synthesised by neuronal synthase (nNOS) can be the molecular mediator of IL-6-mediated cardiac effects. Thus, we investigated in vivo after IL-6 acute administration: (1) the role of NO pathway; (2) the importance of NO derived from nNOS located in intracardiac vagal ganglion in the anterior surface of the left ventricle. Sprague-Dawley (SD) rats (225-250 g) were anaesthetized (sodium pentobarbital 30 mg/kg intraperitoneally administered) and ventilated. The effects of a single IL-6 bolus (100 microg/kg intravenously administered) were studied in four experimental groups: (a) IL-6 (n=6), (b) IL-6 plus 30 mg/kg of L-NAME (an eNOS and nNOS inhibitor; n=6), (c) IL-6 plus 25mg/kg of 7-NI (a specific nNOS inhibitor; n=6), (d) IL-6 plus vagal resection (n=6). We evaluated the following parameters: mean aortic pressure (MAP), left ventricular end systolic pressure (LVESP), left ventricular positive peak dP/dt (PP dP/dt). Data are expressed as mean+/-sem. IL-6 caused a transient but significant reduction of MAP (-21.8% of basal: p<0.05), LVESP (from 130+/-4.2 to 1056.5 mmHg: p<0.05) and PP dP/dt (from 5390+/-158 to 4400+/-223 mmHg/s, p<0.02). Concomitant treatment with L-NAME or 7-NI totally abolished IL-6 effects. Vagal resection significantly reduced the haemodynamic effects (MAP: -10% of basal: p=ns; LVEDS: from 125+/-7.3 to 117+/-6.8 mmHg, p<0.05; PP dP/dt from 5500+/-150 to 5000+/-143 mmHg/s, p<0.05). We conclude that acute administration of IL-6 caused transient but significant cardiac negative inotropism. IL-6 haemodynamic effects are partly due to NO synthesised by nNOS located in vagal left ventricular ganglia.

Prevention of neuron and oligodendrocyte degeneration by interleukin-6 (IL-6) and IL-6 receptor/IL-6 fusion protein in organotypic hippocampal slices

We investigated the effects of IL-6 and a chimeric derivative of IL-6 and soluble IL-6 receptor (IL6RIL6 chimera) on excitotoxic injury in rat organotypic hippocampal slices. Brief application of N-methyl-d-aspartate (NMDA) induced astrocyte reactivity, neuron cell death, and oligodendrocyte degeneration, the latter caused by secondary activation of AMPA/kainate receptors. Both these cytokines rescued neurons and oligodendrocytes, albeit the chimeric compound was much more potent and efficient than IL-6. No change was produced on reactive astrocytosis. The cytokines preserved myelin basic protein (MBP) production in slices exposed to excitotoxic insult, and when applied singularly for a week, they also enhanced both MBP and proteolipid protein expression. These effects occurred through activating the signal transducer gp130 and were associated with stimulation of transcription factors STAT1 and STAT3. Our results suggest that IL-6 and IL6RIL6 may prove to be valuable in treating neurodegenerative and demyelinating diseases.

Synthesis, Biological Activity, and Three-Dimensional Quantitative Structure−Activity Relationship Model for a Series of Benzo[c]quinolizin-3-ones, Nonsteroidal Inhibitors of Human Steroid 5α-Reductase 1

New 5alpha-reductase 1 (5alphaR-1) inhibitors were designed to complete a consistent set of analogues suitable for a 3D QSAR study. These compounds were synthesized by a modification of the aza-Robinson annulation, further functionalized by Pd-catalyzed cross-coupling processes, and were tested with human 5alphaR-1 expressed in Chinese hamster ovary 1827 cells. It turned out that the potency of the resulting inhibitors was strongly dependent on the type of substitution at the 8 position, with the IC(50) values ranging from 8.1 to 1050 nM. The construction of this homogeneous set of molecules allowed a 3D QSAR study. In particular, comparative molecular field analysis (CoMFA) was used to correlate the potency of the inhibitors with their physicochemical features. Highly accurate evaluations of the atomic point charges were carried out by means of quantum chemical calculations at the DFT/B3LYP level of theory followed by the RESP fitting procedure. It turned out that increasing the reliability of electrostatic parameters greatly affected the statistical results of the QSAR analysis. The 3D QSAR model proposed could be very useful in the further development of 5alphaR-1 inhibitors, which are suitable candidates to be evaluated as drugs in the treatment of 5alphaR-1 related diseases such as acne and alopecia in men and hirsutism in women.

Human cytomegalovirus stimulates cellular IKK2 activity and requires the enzyme for productive replication

Human cytomegalovirus (HCMV) exploits the host transcription factor NF-kappaB to enhance its own replication, dissemination, and reactivation from latency. Here we report that HCMV infection activates the upstream IkappaB kinase (IKK) complex and that its catalytic IKK2 subunit is required for HCMV-induced NF-kappaB activation, as well as the replication of different HCMV strains. These results indicate that IKK2 is essential for HCMV replication and emphasize the feasibility of blocking NF-kappaB activation as a way of inhibiting infection.

Age- and irradiation-associated loss of bone marrow hematopoietic function in mice is reversed by recombinant human growth hormone

OBJECTIVE

The aim of this story was to evaluate the activity of recombinant human (rh) growth hormone (GH) in restoring bone marrow progenitor cell growth as well as cytokine-elicited stem cell mobilization in aged BALB/c mice with impaired marrow hematopoietic function and reduced stem cell mobilizing capacity.

MATERIALS AND METHODS

BALB/c mice included in this study were either naturally aged (group I) or aged after having been used for radioprotective assays (group II). Mice were treated for 5 weeks with either rhGH [2.5 mg/kg/day intraperitoneally (IP)] or phosphate-buffered saline (PBS). Subsequently, colony-forming cells (CFCs) and long-term culture-initiating cells (LTC-ICs) were evaluated. In addition, progenitor cell mobilization elicited by granulocyte colony-stimulating factor (rhG-CSF) was analyzed.

RESULTS

Compared with young controls, the growth of marrow CFCs and LTC-ICs was significantly reduced (P < or = 0.05) in group I and II mice. Treatment with rhGH significantly enhanced marrow hematopoiesis in mice of both groups, as demonstrated by a complete restoration of marrow cellularity, and CFC and LTC-IC growth. To further evaluate the hematopoietic potential of rhGH, aged mice treated with rhGH or PBS were mobilized with rhG-CSF (10 microg/day IP for 5 days). Compared with PBS-injected mice, rhGH-treated mice showed a significant improvement of rhG/CSF-elicited stem cell mobilization, with significant increases of white blood cell counts (5633 vs 8133, P < or = 0.05), frequency of circulating CFCs per 10(5) mononuclear cells (36 vs 67, P < or = 0.009), as well as absolute numbers per mL of blood of circulating CFCs (783 vs 2288, P < or = 0.001) and LTC-IC (21 vs 64, P < or = 0.001).

CONCLUSION

Our data demonstrate in mice that a 5-week treatment with rhGH restores age- and irradiation-associated loss of marrow primitive and committed progenitors.

Functional, structural, and distribution analysis of the chorionic gonadotropin receptor using murine monoclonal antibodies

LH and human chorionic gonadotropin (hCG) control steroid production and gametogenesis. They also function as growth factors through interaction with a specific receptor that is a member of the seven-transmembrane receptor family coupled via G proteins to signal pathways involving cAMP and phospholipase C/inositol 3 phosphate. For this study, monoclonal antibodies (mAbs) were raised against the human LH receptor (LHR)/hCG receptor (hCGR), using Chinese hamster ovary LHR-transfected cells as the immunogen. Two reagents were then selected on the basis of their ability to recognize the full-length transmembrane receptor expressed both by Chinese hamster ovary LHR-transfected cells and by a limited number of tumor cell lines. One of these mAbs reacts with the LHR/hCGR in tissue sections of both frozen and paraffin-embedded specimens. This unique feature allowed us to map the cytological distribution of LHR/hCGR in human breast tissues at different stages of development in physiological and benign pathological conditions. The same mAb proved to be agonistic: receptor ligation elicits signals that modulate the growth of selected breast tumor cell lines. This observation suggests that the mAb recognizes an epitope that is included in the domain of the receptor involved in the interaction with the natural ligand.

Soluble interleukin-6 (IL-6) receptor/IL-6 fusion protein enhances in vitro differentiation of purified rat oligodendroglial lineage cells

We investigated the effects of a chimeric protein (IL6RIL6 chimera) containing interleukin-6 (IL-6) fused to its soluble receptor (sIL-6R) on the proliferation and/or differentiation of rat oligodendrocyte progenitor cells (OPCs) and on oligodendrocyte survival. Exposure of OPCs to IL6RIL6 chimera for 48 h induced a dose-dependent decrease of bromodeoxyuridine (BrdU) incorporation. IL6RIL6 chimera treatment for 48 h also strongly increased the reduction of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) by mitochondrial enzymes and enhanced oligodendrocyte staining with a mitochondrial fluorescent dye. A strong, dose-dependent increase in the number and length of processes immunostained for early (galactocerebroside) or late (myelin basic protein) oligodendrocyte differentiation markers was revealed after OPC treatment with IL6RIL6 chimera for 2-7 days, respectively. Moreover, treatment with IL6RIL6 chimera improved oligodendrocyte survival. The chimera-induced increase of oligodendrocyte arborization was mimicked, although with lower efficacy, by ciliary neurotrophic factor (CNTF) but not by IL-6 and was reduced in the presence of a gp130 soluble peptide which is able to inhibit the gp130-mediated signals of the IL-6/sIL-6R complex. Oligodendrocyte treatment with IL6RIL6 chimera for 30 min induced both signal transducer and the activator of transcription-1 (STAT-1) and STAT-3 phosphorylation and nuclear translocation. We conclude that, by interacting with membrane gp130 and possibly by activating Janus kinase/STAT pathways, IL6RIL6 chimera induces OPCs to differentiate into mature oligodendrocytes, promotes their survival, and could deserve investigation as a therapeutic strategy for enhancing remyelination.

Analysis of eosinophils and myeloid progenitor responses to modified forms of MPIF-2

Myeloid progenitor inhibitory factor (MPIF)-2 is a beta-chemokine with select and potent activities on eosinophils and myeloid progenitors. In the beta-chemokine family, biological activity is modulated by differential processing of the amino-terminus. Here, for MPIF-2, we describe the biological activities of NH(2)-terminal deletion mutants and compare regions necessary for eosinophil and myeloid progenitor activities. Five MPIF-2 proteins with deletions at the amino-terminus were produced in Escherichia coli and assayed for calcium mobilization, chemotaxis and receptor binding activities on eosinophils, and for their ability to inhibit colony formation of human myeloid bone marrow progenitors. For eosinophils, deletion of the first two amino acids did not markedly alter activity, while subsequent truncations result in a complete loss of activity. One of the MPIF-2 mutants, MPIF-2 (P30-R99) was converted from an agonist to an antagonist of eotaxin, MPIF-2 and MCP-4 functional responses in eosinophil calcium flux and chemotaxis assays. Surprisingly, while displaying a complete loss of agonist activity toward eosinophils, MPIF-2 (P30-R99) retains ability to inhibit human bone marrow myeloid progenitor cell colony formation. In addition, processing at the amino terminus of MPIF-2 in vivo, may result in a chemokine with altered biological activities.

Observation of an unexpected third receptor molecule in the crystal structure of human interferon-gamma receptor complex

BACKGROUND

Molecular interactions among cytokines and cytokine receptors form the basis of many cell-signaling pathways relevant to immune function. Interferon-gamma (IFN-gamma) signals through a multimeric receptor complex consisting of two different but structurally related transmembrane chains: the high-affinity receptor-binding subunit (IFN-gammaRalpha) and a species-specific accessory factor (AF-1 or IFN-gammaRbeta). In the signaling complex, the two receptors probably interact with one another through their extracellular domains. Understanding the atomic interactions of signaling complexes enhances the ability to control and alter cell signaling and also provides a greater understanding of basic biochemical processes.

RESULTS

The crystal structure of the complex of human IFN-gamma with the soluble, glycosylated extracellular part of IFN-gammaRalpha has been determined at 2.9 A resolution using multiwavelength anomalous diffraction methods. In addition to the expected 2:1 complex, the crystal structure reveals the presence of a third receptor molecule not directly associated with the IFN-gamma dimer. Two distinct intermolecular contacts, involving the edge strands of the C-terminal domains, are observed between this extra receptor and the 2:1 receptor-ligand complex thereby forming a 3:1 complex.

CONCLUSIONS

The observed interactions in the 2:1 complex of the high-affinity cell-surface receptor with the IFN-gamma cytokine are similar to those seen in a previously reported structure where the receptor chains were not glycosylated. The formation of beta-sheet packing interactions between pairs of IFN-gammaRalpha receptors in these crystals suggests a possible model for receptor oligomerization of Ralpha and the structurally homologous Rbeta receptors in the fully active IFN-gamma signaling complex.

Essential pathogenetic role for interferon (IFN-)gamma in concanavalin A-induced T cell-dependent hepatitis: exacerbation by exogenous IFN-gamma and prevention by IFN-gamma receptor-immunoglobulin fusion protein

We have studied the effects of either exogenously-administered interferon (IFN-)gamma or of a nonimmunogenic mouse IFN-gamma receptor-Immunoglobulin (IFN-gamma R-Ig) fusion protein on the development of Concanavalin (Con)A-induced hepatitis in NMRI mice. PBS-treated control mice injected with 20 mg/kg ConA developed classical serological and histological signs of hepatitis with elevation of transaminases in the blood and infiltration of the liver by mononuclear cells and neutrophils. Treating the mice with rat IFN-gamma 24 h prior to and 1 h after ConA-challenge markedly exacerbated these signs of hepatitis in a dose-dependent fashion. Moreover, mice injected with lower, non hepatitogenic, doses of ConA (10, 5 mg/kg) became fully susceptible to develop hepatitis upon similar treatment with IFN-gamma. Concordantly, ConA-induced hepatitis was abrogated by either IFN-gamma R-Ig fusion protein or anti-IFN-gamma mAb. These data provide further evidence for the central pathogenetic role of endogenous IFN-gamma in ConA-induced hepatitis and demonstrate the feasibility to prevent disease development by means of a non immunogenic IFN-gamma R-Ig fusion protein.

Tumor rejection and immune memory elicited by locally released LEC chemokine are associated with an impressive recruitment of APCs, lymphocytes, and granulocytes

The human beta chemokine known as LEC (also called NCC-4, HCC-4, or LMC) displays chemotactic activity for monocytes and dendritic cells. The possibility that its local presence increases tumor immunogenicity is addressed in this paper. TSA parental cells (TSA-pc) are poorly immunogenic adenocarcinoma cells that grow progressively, kill both nu/nu and syngeneic BALB/c mice, and give rise to lung metastases. TSA cells engineered to release LEC (TSA-LEC) are still able to grow in nu/nu mice, but are promptly rejected and display a marginal metastatic phenotype in BALB/c mice. Rejection is associated with a marked T lymphocyte and granulocyte infiltration, along with extensive macrophage and dendritic cell recruitment. NK cells and CD4+ T lymphocytes are uninfluential in TSA-LEC cell rejection, whereas both CD8+ lymphocytes and polymorphonuclear leukocytes play a major role. An antitumor immune memory is established very quickly after rejection, since 6 days later 75% of BALB/c mice were already resistant to a TSA-pc challenge. Spleen cells from rejecting mice display specific cytotoxic activity against TSA-pc and secrete IFN-gamma and IL-2 when restimulated by TSA-pc. The ability of LEC to markedly improve recognition of poorly immunogenic cells by promoting APC-T cell cross-talk suggests that it could be an effective component of antitumor vaccines.

Dichotomic effects of IFN-gamma on the development of systemic lupus erythematosus-like syndrome in MRL-lpr / lpr mice

Systemic lupus erythematosus (SLE)-prone female MRL-lpr / lpr (MRL-lpr) mice were treated with mouse or rat IFN-gamma under different experimental conditions, both prophylactically in 6- to 8 week-old animals and therapeutically in 12- to 18-week-old SLE-affected mice. It was found that IFN-gamma heterogeneously modulated the course of the disease in MRL-lpr mice. When administered prophylactically, IFN-gamma favorably modulated the histological, serological and clinical signs of the disease. Relative to untreated or PBS-treated control animals, the MRL-lpr mice which received IFN gamma were virtually free of inflammatory infiltration of the kidneys and the lungs, had lower levels of azotemia with reduction of both circulating IgG1, IgG2a and IgG3 and anti-double strand (ds) and single strand (ss) DNA antibodies, milder skin vasculitis, significantly reduced enlargement of their lymph nodes and lower weight of the spleens. IFN-gamma also lowered the rate of mortality of MRL-lpr mice. In contrast to these findings, therapeutically administered IFN-gamma worsened the course of the disease in MRL-lpr mice, which exhibited increased proteinuria, higher levels of IgG2a and IgG3 and anti-ds and -ss DNA antibodies, more aggressive nephritis and died at an earlier age than PBS-treated control mice. The dichotomic effect of IFN-gamma on disease manifestation in MRL-lpr mice offers new insights into the complex role of this cytokine in the regulation of systemic autoimmunity such as SLE.

Baculovirus stimulates antiviral effects in mammalian cells

Herein, we report that Autographa californica nucleopolyhedrovirus, a member of the Baculoviridae family, is capable of stimulating antiviral activity in mammalian cells. Baculoviruses are not pathogenic to mammalian cells. Nevertheless, live baculovirus is shown here to induce interferons (IFN) from murine and human cell lines and induces in vivo protection of mice from encephalomyocarditis virus infection. Monoclonal antibodies specific for the baculovirus envelope gp67 neutralize baculovirus-dependent IFN production. Moreover, UV treatment of baculovirus eliminates both infectivity and IFN-inducing activity. In contrast, the IFN-inducing activity of the baculovirus was unaffected by DNase or RNase treatment. These data demonstrate that IFN production can be induced in mammalian cells by baculovirus even though the cells fail to serve as a natural host for an active viral infection. Baculoviruses, therefore, provide a novel model in which to study at least one alternative mechanism for IFN induction in mammalian cells.

A "stealth effect": adenocarcinoma cells engineered to express TRAIL elude tumor-specific and allogeneic T cell reactions

BALB/c mammary adenocarcinoma cells engineered to express TNF-related apoptosis-inducing ligand (TRAIL)/APO-2 ligand (APO-2L) on their membrane (TSA-TRAIL) grow with kinetics similar to that of parental cells (TSA-pc) in vitro and in nu/nu mice. In contrast, TSA-TRAIL cells grow faster than TSA-pc in normal BALB/c mice. In DBA/2 mice, which differ from BALB/c mice at minor histocompatibility Ags, they also grow faster and display a higher percentage of tumor takes than TSA-pc. In fully histoincompatible C57BL/6 (B6) mice, TSA-TRAIL cells form evident tumors that are slowly rejected by most mice, but outgrow in a few. In contrast, TSA-pc cells are rejected at once by B6 mice. Since TRAIL/APO-2L induces apoptosis by interacting with a variety of specific receptors, this rapid growth in both syngeneic and allogeneic mice may be the result of an immunosuppressive mechanism. The following evidence supports this hypothesis: 1) TSA-TRAIL cells overcome the strong immunity against TSA-pc cells elicited in BALB/c mice by preimmunization with TSA cells engineered to release IL-4; 2) their rejection by B6 mice does not prime a CTL-mediated memory; 3) thymidine uptake by T lymphocytes unstimulated or stimulated by allogeneic cells is inhibited when TSA-TRAIL cells are added as third party cells; 4) CTL kill TSA-pc but not TSA-TRAIL cells in 48-h assays; and 5) activated lymphocytes interacting with TSA-TRAIL cells in vivo and in vitro undergo apoptosis.

A “Stealth Effect”: Adenocarcinoma Cells Engineered to Express TRAIL Elude Tumor-Specific and Allogeneic T Cell Reactions

BALB/c mammary adenocarcinoma cells engineered to express TNF-related apoptosis-inducing ligand (TRAIL)/APO-2 ligand (APO-2L) on their membrane (TSA-TRAIL) grow with kinetics similar to that of parental cells (TSA-pc) in vitro and in nu/nu mice. In contrast, TSA-TRAIL cells grow faster than TSA-pc in normal BALB/c mice. In DBA/2 mice, which differ from BALB/c mice at minor histocompatibility Ags, they also grow faster and display a higher percentage of tumor takes than TSA-pc. In fully histoincompatible C57BL/6 (B6) mice, TSA-TRAIL cells form evident tumors that are slowly rejected by most mice, but outgrow in a few. In contrast, TSA-pc cells are rejected at once by B6 mice. Since TRAIL/APO-2L induces apoptosis by interacting with a variety of specific receptors, this rapid growth in both syngeneic and allogeneic mice may be the result of an immunosuppressive mechanism. The following evidence supports this hypothesis: 1) TSA-TRAIL cells overcome the strong immunity against TSA-pc cells elicited in BALB/c mice by preimmunization with TSA cells engineered to release IL-4; 2) their rejection by B6 mice does not prime a CTL-mediated memory; 3) thymidine uptake by T lymphocytes unstimulated or stimulated by allogeneic cells is inhibited when TSA-TRAIL cells are added as third party cells; 4) CTL kill TSA-pc but not TSA-TRAIL cells in 48-h assays; and 5) activated lymphocytes interacting with TSA-TRAIL cells in vivo and in vitro undergo apoptosis.

Failure of exogenously administered interferon-gamma or blockage of endogenous interleukin-4 with specific inhibitors to augment the incidence of autoimmune diabetes in male NOD mice

Interferon (IFN)-gamma and interleukin (IL)-4 are prototypic type 1 and type 2 cytokines which are known to play pathogenetic and protective roles, respectively, in NOD mouse IDDM. The capacity of male NOD mice to produce more IL-4 and less IFN-gamma within the insulitic lesions than females has been suggested to contribute to their lower incidence of diabetes. In this study we have tested the effects of prolonged prophylactic treatment of male NOD mice with rat IFN-gamma, mouse IFN-gamma, anti-IL-4 monoclonal antibody (mAb) and recombinant murine soluble IL-4 receptor (smIL-4R) on the diabetogenic events leading to insulitis and diabetes. None of these treatments influenced spontaneous and/or cyclophosphamide-induced autoimmune diabetogenesis in male NOD mice. Control mice exhibited comparable histological signs of insulitis and incidence of diabetes to those treated with either mouse/rat IFN-gamma or specific IL-4 inhibitors. On the contrary, both clinical and histological signs of diabetes were suppressed by prophylactic treatment with anti-IFN-gamma mAb. These findings indicate that the autoimmune diathesis of male NOD mice towards IDDM cannot be augmented by manipulation of endogenous IFN-gamma or IL-4.

Dendritic cells and MPIF-1: chemotactic activity and inhibition of endogenous chemokine production by IFN-gamma and CD40 ligation

We have examined the biological activity of the CC chemokine myeloid progenitor inhibitory factor 1 (MPIF-1) on human dendritic cells. MPIF-1 has chemotactic activity on dendritic cells derived from either peripheral blood monocytes or cord blood CD34+ progenitors. However, chemokine treatment did not induce further cell activation or maturation. In addition, MPIF-1 is constitutively released by monocyte-derived dendritic cells but not macrophages or monocytes (resting or stimulated). The proinflammatory stimuli lipopolysaccharide and tumor necrosis factor alpha, which induced the release of monocyte chemotactic protein-1, macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-1beta, and interleukin-8, did not affect MPIF-1 release. In contrast, CD40 ligation and interferon-gamma treatment, while stimulating the production of the other chemokines, caused a pronounced reduction of MPIF-1 transcript and protein release. Thus, in dendritic cells the regulation of the production and release of MPIF-1 is distinct in comparison to other CC and CXC chemokines.

Paradoxical antidiabetogenic effect of gamma-interferon in DP-BB rats

Previous studies have shown that anti-gamma-interferon (IFN-gamma) antibody reduces the frequency of autoimmune IDDM in the DP-BB rat. We tested the effects of systemically administered recombinant rat IFN-gamma in both DP-BB and DR-BB rats. Unexpectedly, IFN-gamma markedly reduced the incidence of IDDM as compared with control rats when administered six times per week at a dosage of 280,000 U between ages 30-35 to 105 days or ages 60-64 to 105 days. A lower dosage (28,000 U on alternate days) was also protective when administered to DP-BB rats between birth and age 60 days. However, long-lasting protection against IDDM development over the 1-year study period was achieved only by the highest dosage of IFN-gamma administered from age 30 to 105 days. Ex vivo production of tumor necrosis factor-alpha from splenic lymphoid cells (SLCs) and peritoneal macrophages of the rats treated with IFN-gamma was comparable with that of controls; however, SLCs from the IFN-gamma-treated animals secreted lower amounts of IFN-gamma after stimulation with concanavalin A. IFN-gamma treatment also markedly reduced the frequency of phenotypically activated SLC-expressing class II antigens and interleukin-2 receptor. Finally, in agreement with the observed antidiabetogenic effects, exogenously administered IFN-gamma induced neither insulitis nor IDDM development in DR-BB rats, a subline of DP-BB rats in which autoimmune diabetes rarely occurs spontaneously but can be induced by administration of polyinosinic-polycytidilic acid.

The interferon gamma (IFN-gamma) receptor: a paradigm for the multichain cytokine receptor

With the purification and cloning of the interferon gamma (IFN-gamma) receptor chains the mechanism of IFN-gamma action and the resultant signal transduction events were delineated in remarkable detail. The interferon gamma (IFN-gamma) receptor complex consists of two chains: IFN-gammaR1, the ligand-binding chain, and IFN-gammaR2, the accessory chain. Binding of IFN-gamma causes oligomerization of the two IFN-gamma receptor subunits, IFN-gammaR1 and IFN-gammaR2, which initiates the signal transduction events: activation of Jak1 and Jak2 receptor associated protein tyrosine kinases, phosphorylation of the IFN-gammaR1 intracellular domain on Tyr440 followed by phosphorylation and activation of Stat1alpha, the latent transcriptional factor. With all these steps established, the IFN-gamma receptor complex has provided the basic model for understanding the receptors for other members of the family of class II cytokine receptors.

Interferon immunogenicity: preclinical evaluation of interferon-alpha 2a

A preclinical evaluation of the immunogenicity of various preparations of interferon-alpha (IFN-alpha) was performed with in vitro and in vivo animal models. The distribution of genes for IFN-alpha 2a, IFN-alpha 2b, and IFN-alpha 2c in various cell populations and the response of human T cell clones to IFN-alpha peptides were investigated. The immunogenicity of IFN-alpha in IFN-alpha 2b transgenic mice and factors that influence the immunogenicity of IFN-alpha in normal mice were also studied. The genes for IFN-alpha 2a and IFN-alpha 2b were found in KG-1 cells, whereas IFN-alpha 2b and IFN-alpha 2c genes were present in Namalwa cells. No difference in proliferation of human T cells, T cell lines, or T cell clones could be obtained with IFN-alpha peptides. In transgenic mice bearing the human IFN-alpha 2b gene, no antibody response was obtained following immunization with either IFN-alpha 2a or IFN-alpha 2b. Normal mice immunized with either IFN-alpha 2a or IFN-alpha 2b produced equivalent titers of antibodies, which cross-reacted with both IFNs. Studies evaluating the relative immunogenicity of IFN-alpha in normal mice demonstrated that a number of treatment and host variables can modulate immunogenicity of IFN-alpha preparations.

Genetic differences in immune reactivity to mercuric chloride (HgCl2): immunosuppression of H-2d mice is mediated by interferon-gamma (IFN-gamma)

Upon treatment with HgCl2, H-2s mice, such as B10.S, develop an activation of B lymphocytes that depends, at least partially, on activation of T helper type 2 (Th2) cells and results in increased serum levels of IgG1 and IgE, appearance of IgG autoantibodies, and development of immune glomerulonephritis and vasculitis. Results of previous studies and of experiments presented here indicate that the B cell activation and systemic autoimmune disease fail to develop in MHC-congenic B10.D2 (H-2d) and B10.BR (H-2k) mice treated with HgCl2, although B10.D2 T cells showed signs of activation by and specificity for HgCl2 comparable to those seen in strain B10.S. Here, we report that following HgCl2 injections the antibody response to sheep erythrocytes is normal in B10.S, but suppressed in B10.D2 mice. This suppression was prevented by MoAb to mouse IFN-gamma. Conversely, treatment of B10.D2 mice with murine recombinant IFN-gamma (rIFN-gamma) was able to reproduce the immunosuppression seen after HgCl2 treatment. In B10.S mice, it took administration of both rIFN-gamma and HgCl2 to suppress the anti-sheep erythrocyte response. Although rIFN-gamma diminished the increase in IgE serum levels of HgCl2-treated B10.S mice, it failed to prevent their autoantibody production and immune glomerulonephritis. These findings further strengthen the concept that B10.S mice react to HgCl2 by preferential activation of their Th2 cells producing IL-4, whereas B10.D2 mice react to HgCl2 by preferential activation of their Th1 cells, which produce IFN-gamma and thus suppress antibody responses.

Differential cytokine production in stimulated blood cultures from intensive care patients with bacterial infections

Mice infected with bacteria develop an interferon-gamma (IFN-gamma) dependent hypersensitivity to lipopolysaccharide (LPS) and other bacterial components. The broader aim of this study is to find out whether such hypersensitivity also occurs in patients suffering from bacterial infections. The capacity of stimulated peripheral blood cells from infected, intensive-care patients to produce cytokines (IFN-gamma, tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6)) was compared to that of healthy donors. Culturing of the cells was carried out preferentially in whole blood diluted 1:3. Whole blood cultures (WBC) were stimulated with lipopolysaccharide (LPS), whole killed Salmonella typhimurium and Staphylococcus aureus and concanavalin A (ConA), and the cytokine production was determined. Two main findings emerged from this study: The IFN-gamma production by WBC of patients was, compared to healthy donors, markedly suppressed, regardless of stimulus used. Further, patients' WBC exhibited a suppressed TNF-alpha production after stimulation with LPS. Surprisingly, following stimulation with bacteria (S. typhimurium and S. aureus) an elevated TNF-alpha and IL-6 response was obtained. Thus, in severely infected patients the cytokine responses of peripheral blood cells to LPS may be suppressed, while the response to other bacterial components is enhanced.

CKbeta8, a novel CC chemokine that predominantly acts on monocytes

We have studied the biological properties of a new human CC chemokine, CKbeta8, consisting of 99 amino acids including six cysteines. CKbeta8 mRNA transcripts were induced in monocytes by IL-1beta and, to a lesser extent, by IFNgamma, and were detected in RNA extracted from normal human liver and gastrointestinal tract. CKbeta8 is chemotactic for monocytes, but is inactive on IL-2 conditioned T lymphocytes, eosinophils and neutrophils. Desensitization experiments indicate that CKbeta8 and MIP-1beta completely share receptors on monocytes and that the CKbeta8 receptor, which appears to differ from the known ones, is also recognized by MCP-1, MCP-2, MCP-3, MCP-4, MIP-1alpha and RANTES.

Molecular and functional characterization of two novel human C-C chemokines as inhibitors of two distinct classes of myeloid progenitors

Two novel human beta-chemokines, Ck beta-8 or myeloid progenitor inhibitory factor 1 (MPIF-1), and Ck beta-6 or MPIF-2, were discovered as part of a large scale cDNA sequencing effort. The MPIF-1 and MPIF-2 cDNAs were isolated from aortic endothelium and activated monocyte libraries, respectively. Both of the cDNAs were cloned into a baculovirus vector and expressed in insect cells. The mature recombinant MPIF-1 protein consists of 99 amino acids and is most homologous to macrophage inflammatory protein (MIP)-1alpha, showing 51% identity. It displays chemotactic activity on resting T lymphocytes and monocytes, a minimal but significant activity on neutrophils, and is negative on activated T lymphocytes. MPIF-1 is also a potent suppressor of bone marrow low proliferative potential colony-forming cells, a committed progenitor that gives rise to granulocyte and monocyte lineages. The mature recombinant MPIF-2 has 93 amino acid residues and shows 39 and 42% identity with monocyte chemoattractant protein (MCP)-3 and MIP-1alpha, respectively. It displays chemotactic activity on resting T lymphocytes, a minimal activity on neutrophils, and is negative on monocytes and activated T lymphocytes. On eosinophils, MPIF-2 produces a transient rise of cytosolic Ca2+ and uses the receptor for eotaxin and MCP-4. In hematopoietic assays, MPIF-2 strongly suppressed the colony formation by the high proliferative potential colony-forming cell (HPP-CFC), which represents a multipotential hematopoietic progenitor.

Prevention of spontaneous autoimmune diabetes in diabetes-prone BB rats by prophylactic treatment with antirat interferon-gamma antibody

The role of endogenous interferon-gamma (IFN gamma) in the development of insulin-dependent diabetes mellitus (IDDM) in diabetes-prone BB rats was evaluated. Several groups of these animals were treated under different, experimental conditions with a purified polyclonal antibody (Ab), antirat IFN gamma. The results show that when administered at doses of 100 or 200 micrograms/week from the 30/33th until the 105th day of age, the anti-IFN gamma Ab reversibly reduced the incidence of IDDM compared to that in control rats treated with either irrelevant rabbit IgG or PBS. Moreover, when given up to the 105th day of age, these doses of anti-IFN gamma Abs exerted comparable preventive effects regardless of whether application started as early as within 24 h after birth or at the end of the prediabetic period (e.g. 70/75 days). In contrast, under none of the above experimental conditions did larger doses of anti-IFN gamma Ab (500 micrograms or 1 mg/week) exert antidiabetogenic effects in the BB rats. Apparently, this was due to the exuberant production of neutralizing Abs elicited by the large amount of the xenogeneic Ab injected. At histoimmunological analyses, the BB rats treated with 200 micrograms/ week anti-IFN gamma Abs from 30-80 days of age exhibited a milder insulitic process along with diminished spleen frequency of activated lymphoid cells (MHC class II and interleukin-2 receptor positive). Taken together, these results provide further in vivo evidence for the central pathogenic role of IFN gamma in BB rat IDDM and anticipate the usefulness of specific IFN gamma inhibitors in the prevention of the disease in the clinical setting. Defining novel and less immunogenic forms of specific IFN gamma inhibitors than xenogeneic Abs is important for improving the efficiency of anti-IFN gamma-oriented approaches.

Mouse macrophages carrying both subunits of the human interferon-gamma (IFN-gamma) receptor respond to human IFN-gamma but do not acquire full protection against viral cytopathic effect

Studies of hamster-human and mouse-human somatic fibroblast hybrids and transfected mouse fibroblasts have demonstrated that signaling through the human interferon-gamma receptor (hu-IFN-gammaR) requires the formation of a complex consisting of ligand (IFN-gamma), a ligand binding receptor chain (IFN-gammaR1), and a signal transducing receptor chain (IFN-gammaR2). To date, the ability of this receptor complex to transduce the full repertoire of biological signals has been difficult to assess due to the limited number of activities that IFN-gamma can exert on fibroblasts. The current report assesses the ability of hu-IFN-gammaR chains to transduce signals in the absence of background human gene products by expressing hu-IFN-gammaR2 in a transformed macrophage cell line (F10/96) derived from a hu-IFN-gammaR1 transgenic mouse. Our results indicate that F10/96 clones expressing both human receptor proteins bind hu-IFN-gamma with an affinity comparable to that of human cells. Binding of either human or mouse IFN-gamma to its respective receptor elicits classic IFN-gamma responses such as up-regulation of major histocompatibility complex antigens, enhanced expression of IRF-1, and increased production of NO2- radicals, interleukin-6, tumor necrosis factor-alpha, and granulocyte macrophage-colony stimulating factor. However, hu-IFN-gamma could not fully protect the clones from cytopathic effects of encephalomyocarditis virus and vesicular stomatitis virus while mo-IFN-gamma could. These results demonstrate that while co-expression of hu-IFN-gammaR1 and hu-IFN-gammaR2 is necessary and sufficient for most IFN-gamma-induced responses, it is not sufficient to confer a generalized antiviral state. These findings further suggest that additional species-specific accessory factor(s) are necessary for full signaling potential through the IFN-gamma receptor complex. The nature and potential role of such factors in IFN-gammaR signaling is discussed.

The intracellular domain of the second chain of the interferon-gamma receptor is interchangeable between species

In this report we show that the mouse interferon (IFN)-gamma R1 and IFN-gamma R2 subunits expressed in hamster cells are capable of rendering the cells sensitive to mouse IFN-gamma as measured by induction of class I MHC antigens and the activation of the transcription factor Stat1 alpha. However, these cells showed no antiviral protection in response to IFN-gamma when challenged with vesicular stomatitis virus (VSV) but limited protection when challenged with encephalomyocarditis virus (EMCV). Furthermore, the cytoplasmic domains of the IFN-gamma R2 subunits, like the cytoplasmic domains of the IFN-gamma R1 chains, can be interchanged between species with no loss of biologic activity, demonstrating that the species-specific interaction of the IFN-gamma R1 and IFN-gamma R2 chains involves only the extracellular domains of the two proteins.

The effects of a nonimmunogenic form of murine soluble interferon-gamma receptor on the development of autoimmune diabetes in the NOD mouse

Previous studies have shown that in vivo treatment with antiinterferon-gamma (anti-IFNgamma) monoclonal antibodies (mAbs) prevents the development of autoimmune diabetes in NOD mice. Although these findings anticipate that specific anti-IFNgamma therapies may be useful for the prevention/treatment of human insulin-dependent diabetes mellitus, there are several reasons why the use of anti-IFNgamma mAb may be difficult in the clinical setting. With the aim to develop alternative forms of specific anti-IFNgamma therapies, we recently produced a nonimmunogenic form of the soluble IFNgamma receptor (sIFNgammaR) that binds and neutralizes murine IFNgamma with an affinity higher than that of anti-IFNgamma mAb. In this study we compared the efficacy of sIFNgammaR to that of two anti-IFNgamma mAbs (XMG 1.2 and AN-18) in the prevention of spontaneous and accelerated (cyclophosphamide-induced) forms of autoimmune diabetes in NOD mice. The results show that in the spontaneous model, sIFNgammaR could prevent histological and clinical signs of autoimmune diabetes as efficiently as the two mAbs. Under ex vivo conditions, sIFNgammaR exhibited a more powerful modulatory effect than XMG 1.2 mAb on cytokine secretion from splenic lymphoid cells, which resulted in a significant reduction of Concanavalin A-induced IL-2 secretion and an augmented release of both unstimulated and lipopolysaccharide-induced IL-6. Moreover, although both mAbs were immunogenic and elicited formation of high titers of anti-rat IgG, sIFNgammaR did not induce antibody formation. Unexpectedly, in the cyclophosphamide-induced model, sIFNgammaR turned out to be less effective than either of the two anti-IFNgamma mAbs. Taken together, these data support the role of IFNgamma in the pathogenesis of NOD mice, but, more importantly, suggest that a nonimmunogenic approach is possible to the diminution of the effects of IFNgamma in this model.

Switching on of the proliferation or apoptosis of activated human T lymphocytes by IFN-gamma is correlated with the differential expression of the alpha- and beta-chains of its receptor

To find out how physiologically secreted IFN-gamma controls either the proliferation or the apoptosis of human T lymphocytes, the kinetics of expression of the alpha- and beta-chains of its receptor (IFN-gamma R) were sequentially followed on T lymphocytes first activated with PHA and then cultured in the presence of IL-2, and related to the kinetics of expression of Fas, Bcl-2, and IL-2R p55 chain. Both IFN-gamma R chains were poorly expressed on the membrane of resting T lymphocytes. Following their stimulation with PHA, IFN-gamma R alpha but not IFN gamma R beta-chain up-modulated before T lymphocyte entry into the S phase, and then IFN-gamma R alpha down-modulated when they passed through the S and G2/M. The ensuing proliferative response was inhibited by an anti-IFN-gamma R alpha mAb that impeded the binding of IFN-gamma. When PHA-activated T lymphoblasts were cultured for 16 days with IL-2, IFN-gamma R alpha expression increased, whereas that of the beta-chain remained barely detectable. Fas and Bcl-2 were both highly expressed. When these T lymphoblasts were restimulated by PHA, OKT3, or Staphylococcus enterotoxin beta-pokeweed mitogen, both chains up-modulated and most cells underwent apoptosis in a way apparently independent of Bcl-2, but not of Fas. This apoptosis, too, was prevented by the anti-IFN-gamma R alpha mAb. Physiologically secreted IFN-gamma is thus involved in the activation of resting T lymphocytes and in the apoptosis of reactivated lymphoblasts. However, high expression of IFN-gamma R beta took place when IFN-gamma induced apoptosis, but not when it induced proliferation. In conclusion, a correlation exists between differential expression of the IFN-gamma R beta-chain and the delivery by IFN-gamma of proliferative or apoptotic signals.

Switching on of the proliferation or apoptosis of activated human T lymphocytes by IFN-gamma is correlated with the differential expression of the alpha- and beta-chains of its receptor

To find out how physiologically secreted IFN-gamma controls either the proliferation or the apoptosis of human T lymphocytes, the kinetics of expression of the alpha- and beta-chains of its receptor (IFN-gamma R) were sequentially followed on T lymphocytes first activated with PHA and then cultured in the presence of IL-2, and related to the kinetics of expression of Fas, Bcl-2, and IL-2R p55 chain. Both IFN-gamma R chains were poorly expressed on the membrane of resting T lymphocytes. Following their stimulation with PHA, IFN-gamma R alpha but not IFN gamma R beta-chain up-modulated before T lymphocyte entry into the S phase, and then IFN-gamma R alpha down-modulated when they passed through the S and G2/M. The ensuing proliferative response was inhibited by an anti-IFN-gamma R alpha mAb that impeded the binding of IFN-gamma. When PHA-activated T lymphoblasts were cultured for 16 days with IL-2, IFN-gamma R alpha expression increased, whereas that of the beta-chain remained barely detectable. Fas and Bcl-2 were both highly expressed. When these T lymphoblasts were restimulated by PHA, OKT3, or Staphylococcus enterotoxin beta-pokeweed mitogen, both chains up-modulated and most cells underwent apoptosis in a way apparently independent of Bcl-2, but not of Fas. This apoptosis, too, was prevented by the anti-IFN-gamma R alpha mAb. Physiologically secreted IFN-gamma is thus involved in the activation of resting T lymphocytes and in the apoptosis of reactivated lymphoblasts. However, high expression of IFN-gamma R beta took place when IFN-gamma induced apoptosis, but not when it induced proliferation. In conclusion, a correlation exists between differential expression of the IFN-gamma R beta-chain and the delivery by IFN-gamma of proliferative or apoptotic signals.

Monocyte chemotactic protein 4 (MCP-4), a novel structural and functional analogue of MCP-3 and eotaxin

A novel human CC chemokine complementary DNA was identified in a library constructed from human fetal RNA, cloned into a baculovirus vector, and expressed in Sf9 insect cells. The mature recombinant protein that was released had the NH2-terminal sequence pyro-QPDALNVPSTC...and consisted of 75 amino acids. Minor amounts of two variants of 77 and 82 residues (NH2 termini: LAQPDA...and FNPQGLAQPDA...) were released as well. The novel chemokine was designated monocyte chemotactic protein 4 (MCP-4) and the variants were designated (LA)MCP-4 and (FNPQGLA)MCP-4. MCP-4 shares the pyroglutamic acidproline NH2-terminal motif and 56-61% sequence identity with the three known monocyte chemotactic proteins and is 60% identical to eotaxin. It has marked functional similarities to MCP-3 and eotaxin. Like MCP-3, MCP-4 is a chemoattractant of high efficacy for monocytes and T lymphocytes. On these cells, it binds to receptors that recognize MCP-1, MCP-3, and RANTES. On eosinophils, MCP-4 has similar efficacy and potency as MCP-3, RANTES, and cotaxin. It shares receptors with eotaxin and shows full cross-desensitization with this cosinophil-selective chemokine. Of the two variants, only (LA)MCP-4 could be purified in sufficient quantities for testing and was found to be at least 30-fold less potent than MCP-4 itself. This suggests that the 75-residue form with the characteristic NH2 terminus of an MCP is the biologically relevant species.

IFN-gamma restores HIV- and non-HIV-specific cell mediated immune response in vitro and its activity is neutralized by antibodies from patients with AIDS

The addition of IFN-gamma to cultures of peripheral blood mononuclear cells (PBMCs) obtained from asymptomatic HIV-infected patients increased cell proliferation in response to HIV envelope synthetic peptides (Env), influenza A virus (VIRUS), and allogeneic lymphocytes (ALLO) but not to phytohaemagglutinin (PHA) stimulation. F(Ab)2 fragments of IgG purified from the sera of HIV-seropositive patients specifically interfered with IFN-gamma-induced cell proliferation in response to recall antigens. Neutralization of the lymphokine activity was found to be sustained by specific IFN-gamma antibodies. Data obtained demonstrate that IFN-gamma can restore the cell-mediated immunity of a number of asymptomatic HIV+ individuals in vitro, while IFN-gamma antibodies present in sera of patients with AIDS interfere with the activity of the lymphokine.

Aspects of molecular interaction between HIV p17 and human gamma interferon

We describe the specific interaction between high-purity recombinant human immunodeficiency virus (HIV) type 1 p17 and human gamma interferon (hIFN-gamma) proteins. This interaction was found to be dose dependent and to involve conformational epitopes on both sides. Specificity was confirmed by competition ELISA, using monoclonal antibodies (MAbs) to hIFN-gamma as specific reagents. By competition experiments we also identified the epitope(s) on the hIFN-gamma molecule involved in p17 binding, very close to the receptor binding site. The kinetic constants were determined by surface plasmon resonance (SPR) analysis. The affinity constant (KA) of the complex was 2.78 x 10(8) M-1, that is, the ratio between a low dissociation rate constant (Koff)(1 x 10(-5)sec-1) and a high association rate constant (Kon) (3 x 10(3) M-1sec-1). However, p17 did not displace the binding of hIFN-gamma to its cellular receptor, nor did it interfere with the capability of the lymphokine to induce de novo expression of HLA-DR antigens on human monocytic cells or to inhibit the proliferation of tumor cells.

CD4+ and CD8+ lymphocytes of patients with AIDS synthesize increased amounts of interferon-gamma

Individual cells capable of interferon-gamma (IFN-gamma) synthesis are easily detected by immunofluorescence and flow cytometric analysis using an anti-IFN-gamma monoclonal antibody as specific reagent. By IFN-gamma flow cytometry assay, we demonstrated that HIV-seropositive patients, starting at the early stage of viral infection, generally have an increased percentage of lymphocytes potentially able to produce IFN-gamma, compared with healthy blood donors. IFN-gamma expression in patient lymphocytes was observed to increase with the progressive stages of HIV infection, with the highest figures occurring in stage C patients. Such increased IFN-gamma expression involved both CD4+ and CD8+ T cell subsets. Most interestingly, we found patients at the same stage of HIV infection who had similar numbers of total and CD4+ lymphocytes but highly different percentages of lymphocytes potentially capable of producing IFN-gamma.

Variable region cDNA sequences and characterization of murine anti-human interferon gamma receptor monoclonal antibodies that inhibit receptor binding by interferon gamma

Murine monoclonal antibodies (mAbs) are described that recognize the extracellular human interferon gamma receptor alpha-chain (IFN gamma R) and inhibit the binding to it of interferon gamma. The inhibitory activities (IC50s) of these mAbs, quantified by radioimmunoassay using native receptor on human Raji cells, lie in the range 0.5-24 nM, whereas their relative affinities for the immobilised recombinant extracellular receptor, determined using surface plasmon resonance technology, are in the range 0.6-40.9 nM. Nine mAbs derived from one immunization, were shown by variable region cDNA sequencing to be clonally related, with mAb A6 from this group showing the highest affinity for the receptor. Another two mAbs, gamma R38 and gamma R99, derived from a separate immunization, are clonally unrelated to each other and to those in the A6 family. From the V-region sequences, the L-chains of mAbs A6, gamma R38 and gamma R99 were shown to belong to the V kappa 34C, V kappa 34C and V kappa 1 families, whereas the H-chains belong to the 3069, J606 and J558 families, respectively. The mAbs A6 and gamma R38 recognize overlapping epitopes on the N-terminal Ig-like domain of the IFN gamma R, whereas the gamma R99 epitope is located largely in the membrane proximal Ig-like domain. Sequence comparisons with Ig structures solved by X-ray diffraction allowed deductions concerning likely CDR canonical conformations. These studies provide essential information for crystallographic and mutagenesis experiments aimed at understanding the molecular basis of the interactions of these mAbs with the extracellular IFN gamma R.

The in vivo antiviral activity of interleukin-12 is mediated by gamma interferon

The injection of 20 ng of mouse interleukin-12 (IL-12) protects mice from a lethal infection with encephalomyocarditis virus. In vitro, an anti-gamma interferon (anti-IFN-gamma) monoclonal antibody but not an anti-IL-12 monoclonal antibody neutralizes the antiviral activity present in the supernatants of splenocytes stimulated with IL-12. Finally, IL-12 fails to protect 129 Sv/Ev IFN-gamma R0/0 mice against encephalomyocarditis virus infection. These results demonstrate that IL-12 exerts its antiviral activity through the induction of endogenous IFN-gamma.