Search PubMed⌕ Search

Biomedical subjects

G A Levy

Publications and source records attributed to G A Levy.

At least 37 records · Page 2Linked to original sources
PubMed1999

Outcome of long-term ribavirin therapy for recurrent hepatitis C after liver transplantation.

Ribavirin therapy was initiated at a median of 181 days after liver transplantation in 18 patients with persistent elevation of alanine aminotransferase values and biopsy-proven hepatitis, and continued for 23 months (12-44 months). All patients had a prompt biochemical response, with alanine aminotransferase decreasing by 69%; complete normalization occurred in 5 (28%). Serum hepatitis C virus RNA levels did not change during therapy. Liver biopsies obtained after 17 months (9-38 months) of therapy showed no improvement in necroinflammation. However, worsening of fibrosis occurred in 12 patients; and cirrhosis developed in 5 patients (28%), with 3 patients progressing to graft failure. Biopsies from 27 untreated patients who did not fulfill treatment criteria (median follow-up, 38 months) and 4 patients who received 3 months of ribavirin (44 months) showed cirrhosis in 11 and 75%, respectively. Patient and graft survival rates for treated and untreated patients were similar. Although ribavirin improves alanine aminotransferase, it does not prevent the development or progression of fibrosis in patients with recurrent hepatitis C virus.

Adult↗
PubMed1999

Neoral/cyclosporine-based immunosuppression.

The introduction of cyclosporine (CsA) has been a major advance. Its use paved the way for successful programs in heart, lung, liver, kidney, and kidney-pancreas transplantation. The recent introduction of Neoral has overcome many of the problems associated with the use of Sandimmune (Novartis, Basel, Switzerland), including poor bioavailability, dependence on bile for absorption, and need for intravenous CsA early in the postoperative period. The use of Neoral has resulted in (1) a marked reduction in the incidence of acute cellular rejection, (2) ability to discontinue steroid therapy in the early posttransplantation period, and (3) low toxicity profiles. In direct comparison with tacrolimus, Neoral was equally efficacious and less toxic. This is even more impressive when one now realizes the monitoring of Neoral has been inadequate, and with more sensitive monitoring tools, including peak CsA level; a surrogate marker for C(max), CsA blood concentrations 2 hours after drug intake; or area under the CsA time-concentration curve, rejection rates may be improved, with improvement in toxicity profiles.

Adult↗
PubMed1999

The emerging role of immunoregulation of fibrinogen-related procoagulant Fgl2 in the success or spontaneous abortion of early pregnancy in mice and humans.

PROBLEM: Abortion of chromosomally normal embryos in the CBA X DBA/2 mating combination is triggered by release of Th1 cytokines (tumor necrosis factor [TNF]-alpha, interferon [IFN]-gamma, and interleukin [IL]-1), which cause abortion via a novel prothrombinase, Fgl2, and polymorphonuclear leukocytes. The site of activation may be maternal vascular endothelium on arteries and veins nourishing the placenta. Activation of coagulation is also prominent in spontaneous abortion of chromosomally normal human embryos. We asked where is Fgl2 up-regulated in the uterus in murine abortions, and if similar Fgl2 expression occurs in human pregnancy failure. METHODS: Control CBA X DBA/2 pregnant mice, or from mice injected with TNF-alpha + IFN-gamma on day 7.5 of gestation, were removed on day 8.5, fixed, sectioned, and subject to in situ hybridization for Fgl2. Sections were also stained for fibrin. Elective first trimester termination samples or biopsies taken early in the course of a recurrent miscarriage were similarly fixed, sectioned, and analyzed by in situ hybridization. Control and cytokine-treated mice were anticoagulated with heparin, an activator of antithrombin III, and/or the direct anti-thrombin inhibitor hirudin. RESULTS: Low level Fgl2 expression localized to basal decidua remote from the embryo was noted in control mice; cytokine treatment, which causes greater than 80% of abortions, produced a striking up-regulation in this area as well as in a band at the junction of decidua and myometrium. Trophoblast also became strikingly positive. Fgl2 expression was associated with increased fibrin staining. Anticoagulation significantly protected against abortions, but doses were limited by the complication of retroplacental hemorrhage. In tissue from normal first trimester pregnancy, minimal Fgl2 positivity was seen in some villous syncytiotrophoblast, in villous stroma, cytotrophoblast, and in some cells in decidua. In spontaneous abortion of normal embryo, striking Fgl2 positivity was seen in syncytiotrophoblast and extravillous cytotrophoblast, in association with areas of thrombus formation. CONCLUSIONS: Fgl2 appears to be physiologically expressed and may protect against the internal danger of maternal and/or fetal bleeding during pregnancy and at parturition; a role in inhibiting transplacental traffic is also possible. External dangers in the form of stress, endotoxin, and antigens eliciting Th1 cytokine responses upregulate Fgl2 prothrombinase in trophoblast as well as in decidua, which results in spontaneous abortion of immunogenetically "weaker" embryos.

Abortion, Spontaneous↗
PubMed1999

Xenotransplantation: A potential solution to the critical organ donor shortage.

The success of allotransplantation as a treatment for end-stage organ failure has resulted in the need for an increasing number of organ donors. Attempts to meet this need include the use of organs from living related and unrelated donors, financial or other incentives for the donor family, and even the reuse of transplanted organs. Despite these initiatives, the supply of organs for transplantation still falls far short of the demand, as evidenced by longer waiting times for transplantation and decreasing transplantation rates. Even if Canada were able to increase its organ donor rate to that of Spain (40 to 50/million), where organ donation is governed by 'presumed consent' legislation, this would not alleviate the problem of donor shortage. Interest in xenotransplantation stems from the need to overcome this increasingly severe shortage of human organs. Indeed, some argue that xenotransplantation is the only potential way of addressing this shortage. As immunological barriers to xenotransplantation are better understood, those hurdles are being addressed through genetic engineering of donor animals and the development of new drug therapies. However, before xenotransplantation can be fully implemented, both the scientific/medical communities and the general public must seriously consider and attempt to resolve the many complex ethical, social and economic issues that it presents.

Animals↗
PubMed1999

Identification of a unique glomerular factor X activator in murine lupus nephritis.

The role of glomerular procoagulant activity (PCA) was studied in mice (MRL/lpr, NZBxWF,, and BXSB) that are known to develop lupus nephritis. In young mice (6 to 8 wk) without renal disease, there was no increase in spontaneous glomerular PCA. In contrast, older (5 to 8 mo) autoimmune mice had significant augmentation in glomerular PCA, coinciding with the histologic appearance of severe glomerulonephritis and renal fibrin deposition. The PCA was characterized as a serine protease that directly activated factor X. This factor X activator is not tissue factor because (1) expression of PCA was not dependent on factor VII; (2) a monoclonal antibody against the factor X activator inhibited glomerular PCA, but not tissue factor; (3) the molecular weight (66 kD) of the activator was different from that of tissue factor; and (4) concanavalin A inhibited tissue factor but not glomerular PCA. Immunohistochemical studies localized the factor X activator to the glomerular mesangium and capillary wall of 4- to 6-mo-old diseased MRL/lpr mice. Immunogold-labeled antibody bound to the dense deposits, macrophages, and endothelial cells of diseased glomeruli. These studies define the role of a unique glomerular factor X activator in murine lupus nephritis.

Animals↗
PubMed1998

Coronavirus MHV-3-induced apoptosis in macrophages.

Infection with mouse hepatitis virus strain 3 (MHV-3) results in lethal fulminant hepatic necrosis in fully susceptible BALB/c mice compared to the minimal disease observed in resistant strain A/J mice. Macrophages play a central role in the pathogenesis of MHV-3-induced hepatitis. In the present study we have shown that MHV-3 infection of macrophages induces these cells to undergo apoptosis. Three methods to detect apoptosis were applied: flow cytometry analysis of nuclear DNA content, fluorescence microscopic visualization of apoptotic cells labeled by the TUNEL assay, and gel electrophoresis to detect DNA laddering. Apoptosis in A/J and BALB/c macrophages was first detected at 8 h postinfection (p.i.) and reached a maximum by 12 h p.i. The degree of MHV-3-induced apoptosis was much greater in A/J-derived macrophages than in BALB/c-derived cells. Apoptosis was inversely correlated with the development of typical MHV cytopathology, namely syncytia formation. Infected macrophages from A/J mice did not form synctia in contrast to the extensive synctia formation observed in BALB/c-derived macrophages. In MHV-3-infected BALB/c macrophage cultures, apoptotic cells were not incorporated into syncytia. Apoptosis was also inversely correlated with the expression of MHV-3-induced fgl2 prothrombinase in macrophages. These results add the murine coronavirus MHV-3 to the list of RNA-containing viruses capable of inducing apoptosis.

Animals↗
PubMed1998

Cytokine-dependent abortion in CBA x DBA/2 mice is mediated by the procoagulant fgl2 prothrombinase [correction of prothombinase].

Spontaneous resorption in the CBA x DBA/2 model is attributed to NK cells, macrophages, and Th1-type cytokines. In vivo depletion of NK cells by anti-asialoGM1 Ab or macrophage depletion by silicon dioxide treatment reduced abortion rates, which could no longer be boosted by injecting TNF-alpha (which activates NK cells) or IFN-gamma (which activates macrophages). TNF-alpha + gamma-IFN coadministration aborted >80% of the embryos whether or not NK cells or macrophages had been depleted or estradiol + progesterone was injected to correct potential reduction in ovarian function by cytokines. The cytokines also aborted IRF1+/+ C57BL/6 but not IRF1-/- females pregnant by IRF1+/+ DBA/2. Both spontaneous and cytokine-boosted abortions in CBA x DBA/2 were blocked by Ab to fgl2 prothrombinase [corrected] expressed by cytokine-stimulated vascular endothelial cells and monocytes; in vivo Ab depletion of granulocytes also prevented TNF-alpha + IFN-gamma-induced abortions. Cytokine-triggered thrombotic/inflammatory processes in maternal uteroplacental blood vessels causes abortion.

Abortion, Spontaneous↗
PubMed1998

Domino liver transplantation for familial amyloid polyneuropathy.

Familial amyloid polyneuropathy is an autosomal dominant disorder in which the liver produces a variant prealbumin that is deposited along nerves, leading to a progressive and fatal polyneuropathy that begins in the third decade of life. Liver transplantation has been the only successful treatment to date. Apart from the production of the variant protein, there are no other abnormalities in these amyloid livers. We describe two cases in which, at the time of transplantation, the amyloid livers were subsequently used for transplantation in another patient, and we discuss the implications.

Adult↗
PubMed1998

Resistance of naive mice to murine hepatitis virus strain 3 requires development of a Th1, but not a Th2, response, whereas pre-existing antibody partially protects against primary infection.

Murine hepatitis virus strain 3 (MHV-3) produces a host-strain-dependent spectrum of disease. The development of liver necrosis has been shown to be related to production of a unique macrophage procoagulant activity (PCA), encoded by the gene fgl-2, in susceptible mice. These studies were designed to examine the influence of Th1/Th2 cells on resistance/susceptibility and production of macrophage procoagulant activity (PCA) in resistant (A/J) and susceptible (Balb/cJ) strains of mice following infection with MHV-3. Immunization of A/J mice with MHV-3 induced a Th1 cellular immune response and one Th1 cell line (3F9.1) protected susceptible mice and inhibited production of PCA by macrophages both in vitro and in vivo. In contrast, immunization of Balb/cJ mice with an attenuated variant of MHV-3 derived from passaging MHV-3 in YAC-1 cells resulted in a Th2 response. Transfer of spleen cells and T cell lines from immunized Balb/cJ mice failed to protect naive susceptible syngeneic mice from infection with MHV-3 and augmented production of IL-1 beta, TNF-alpha and PCA by macrophages to MHV-3 in vitro. Serum from immunized Balb/cJ mice contained high titered neutralizing antibody which protected naive Balb/cJ animals from lethal primary MHV-3 infection. These results demonstrate that susceptible Balb/cJ mice generate a Th2 response following MHV-3 infection and that these Th2 cells neither inhibit MHV-3-induced macrophage PCA production nor protect naive mice from MHV-3 infection. The results suggest that antibody protects against primary infection, but could not eradicate ongoing infection. Ribavirin, a synthetic guanosine analogue prolonged survival to MHV-3 infection, inhibited production and transcription of the macrophage pro-inflammatory cytokines IL-1 beta and TNF-alpha and Th2 cytokines while preserving Th1 cytokine production. Thus, this data defines the differential role of Th1/Th2 lymphocytes in primary and secondary MHV-3 infection and further defines the importance of macrophage inflammatory mediators in the pathogenesis of MHV-3 infection.

Animals↗
PubMed1998

Expression of the fgl2 and its protein product (prothrombinase) in tissues during murine hepatitis virus strain-3 (MHV-3) infection.

Murine Hepatitis Virus Strain 3 (MHV-3) produces fulminant hepatitis with 80-90% mortality in Balb/cJ mice. Previous studies in our laboratory have shown that peritoneal macrophages from MHV-3 infected mice produce a procoagulant (PCA) which has the ability to cleave prothrombin to thrombin (prothrombinase) encoded by the gene fgl2 located on chromosome 5. PCA accounts for sinusoidal thrombosis and hepatic necrosis and the necrosis and mortality can be prevented by treatment of animals with a monoclonal antibody to PCA. These present studies were designed to examine the expression of this gene (mRNA by Northern analysis and in situ hybridization) and the gene product PCA (immunochemistry) in tissues recovered from MHV-3 infected Balb/cJ mice in an attempt to explain the liver specific nature of MHV-3 disease. Fgl2 gene expression was detected as early as 8 hours after MHV-3 infection which persisted to 48 hours in the liver, spleen and lungs whereas no gene expression was seen in the brain or kidneys despite the fact that equivalent viral titers were detected in all tissues at all times. In the liver, fgl2 gene expression was confined to endothelial and Kupffer cells with no expression in hepatocytes. Immunochemistry localized the PCA protein to Kupffer cells and endothelial cells and necrotic foci within the liver. No PCA protein was detected by immunochemistry in any other tissues at any time during the course of MHV-3 infection. These results explain the liver specific nature (fulminant hepatitis) of MHV-3 infection and provides further evidence for the role of PCA in the pathogenesis of fulminant hepatitis. MHV-3 induces selective transcription of the gene fgl2 and only hepatic reticuloendothelial cells produce functional protein (PCA) which is known to account for fulminant hepatic failure produced by MHV-3.

Animals↗
PubMed1998

The pattern of induction of apoptosis during infection with MHV-3 correlates with strain variation in resistance and susceptibility to lethal hepatitis.

In the present study we have investigated the possibility that strain specific differences in the induction of apoptosis in macrophages could play a role in the resistance of strain A/J mice to MHV-3 induced hepatitis. MHV-3 infected macrophages from Balb/c and A/J mice were analyzed at various time points after infection. Apoptosis in A/J macrophages could be detected at 8 h post infection and increased significantly by 12 h, when almost 50-70% of the infected cells were undergoing apoptosis. In Balb/c macrophages, apoptotic changes were less pronounced and were observed in only 5-10% of the cells. MHV-3 induced apoptosis was inversely correlated with the ability of this virus to induce expression of fgl-2 prothrombinase protein and syncytia formation. Infected macrophages from A/J mice did not express fgl-2 protein and did not form syncytia. In contrast, infection of Balb/c derived macrophages resulted in fgl-2 expression and extensive syncytia formation. These data fit a model in which apoptosis of virally infected cells is a protective response which eliminates cells whose survival might be harmful for the whole organism.

Animals↗
PubMed1998

Strategies to prevent thrombosis in xenotransplants.

Coagulation remains a major barrier to successful xenotransplantation. Identification of the role of complement activation in HAR and prevention of complement activation by high expression of DAF and CD59 has largely overcome HAR. Understanding the molecular basis of DXR and identification of novel strategies to prevent activation of endothelial cells using monoclonal antibodies, soluble inhibitors of coagulation, vaccination, antisense constructs, and recombinant DNA technology offers the promise of overcoming the thrombosis associated with xenotransplantation.

Acute Disease↗
PubMed1998

Resistance to murine hepatitis virus strain 3 is dependent on production of nitric oxide.

The strain-specific spectrum of liver disease following murine hepatitis virus type 3 (MHV-3) infection is dependent on inflammatory mediators released by macrophages. Production of nitric oxide (NO) by macrophages has been implicated in resistance to a number of viruses, including ectromelia virus, vaccinia virus, and herpes simplex virus type 1. This study was undertaken to define the role of NO in MHV-3 infection. Gamma interferon-induced production of NO inhibited growth of MHV-3 in a murine macrophage cell line (RAW 264.7). Viral inhibitory activity was reproduced by the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP), whereas N-acetyl-DL-pencillamine (NAP), an inactive analog of SNAP, had no effect. Electron microscopy studies confirmed the inhibitory effects of NO on viral replication. Peritoneal macrophages isolated from A/J mice known to be resistant to MHV-3 produced a fivefold-higher level of NO and higher levels of mRNA transcripts of inducible NO synthase in response to gamma interferon than macrophages from susceptible BALB/cJ mice. SNAP inhibited growth of MHV-3 in macrophages from both strains of mice to similar degrees. In vivo inhibition of NO by N-monomethyl-L-arginine resulted in loss of resistance to MHV-3 in A/J mice. These results collectively demonstrate a defect in the production of NO in macrophages from susceptible BALB/cJ mice and define the importance of endogenous NO in resistance to MHV-3 infection in resistant A/J mice.

Animals↗
PubMed1998

Pretreatment of donor stimulator cells by 16,16 dimethyl prostaglandin E2 influences the recipient immune response.

BACKGROUND: Immunosuppressive strategies have largely ignored donor-derived stimulatory cells as a target. This study examined whether lipopolysaccharide (LPS) or 16,16 dimethyl prostaglandin E2 (dmPGE2) pretreatment of stimulator cells from B10.BR mice influences effector function of responder T lymphocytes from C3H/HeJ mice in vitro or in vivo. METHODS: B10.BR spleen cells were incubated in vitro in the presence or absence of dmPGE2 or or LPS before the cells were used as stimulators in a mixed lymphocyte culture (MLC) with T cells from C3H/HeJ mice. In parallel studies, B10.BR mice were treated in vivo with dmPGE2 or LPS; spleen cells from these animals were used as stimulators in an MLC and skin was harvested for skin grafts. Cells from untreated or pretreated mice were examined for expression of intercellular adhesion molecule-1 (ICAM-1), B7-1, and B7-2 by fluorescence-activated cell sorter analysis. ICAM-1 mRNA transcripts were determined by reverse transcriptase-polymerase chain reaction. RESULTS: Stimulation of B10.BR-derived spleen cells with LPS before their use as stimulator cells in a MLC resulted in an increase in responder T-cell proliferation compared with use of unstimulated spleen cells (P < 0.05). In contrast, pretreatment of stimulator spleen cells with dmPGE2 resulted in dose-dependent inhibition of the responder T-cell proliferation, with maximum effect seen using a concentration of dmPGE2 of 10(-5) mol/L. The decreased expression of interleukin-1, tumor necrosis factor, leukotriene B4 procoagulant activity, and ICAM-1 by the dmPGE2 pretreated spleen cells correlated with their inefficient in stimulating T-cell proliferation. Spleen cells harvested from B10.BR mice previously injected with dmPGE2 similarly were inefficient as stimulator cells. Skin graft survival was delayed, but not prevented, by in vivo pretreatment of donor mice with dmPGE2. CONCLUSIONS: These data demonstrate the effect of immunomodulation of allogeneic stimulator spleen cells on subsequent responder T-lymphocyte function and allograft survival.

16,16-Dimethylprostaglandin E2↗