Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A majority of human immunodeficiency virus type I (HIV-1)-infected-individuals manifest a plethora of central nervous system (CNS) diseases unrelated to opportunistic infections, including acquired immune deficiency syndrome (AIDS)-dementia complex (ADC), encephalitis, and various other disorders of the CNS. A series of devastating clinical conditions in the CNS of certain HIV-1-infected-individuals may be caused by infection of cells in the brain parenchyma. ADC is characterized by cognitive dysfunction, motor difficulties, coordination abnormalities and other neurological signs and symptoms, which develop in many HIV-1-infected-individuals. The precise molecular mechanisms leading to AIDS dementia remain incompletely explained. Various mechanisms including cytokine dysregulation, toxic effects of viral proteins and release of certain toxic substances from macrophages, especially nitric oxide, have been implicated as pathogenic mediators in the development of ADC. We have examined post mortem CNS tissues collected from 22 patients, previously diagnosed with AIDS, to explore if nitric oxide is responsible for the observed pathology in ADC. As controls, we utilized tissues collected from the brains of patients who expired without AIDS or other CNS pathologies. In addition, we also utilized post-mortem brain tissues from eight patients who were diagnosed with multiple sclerosis (MS) and were found to express inducible nitric oxide synthase (iNOS) in our previous studies, as positive controls. Highly sensitive in situ reverse transcriptase-initiated polymerase chain reaction (RT-IS-PCR) studies demonstrated that iNOS mRNA was present in the CNS tissues from all the positive MS controls, but were absent in all 22 specimens from AIDS patients, as well as in the brain tissues from normal controls. We have also analyzed the tissues for the presence of the NO reaction product, nitrotyrosine, to evaluate the presence of a protein nitrosalation adduct. Nitrotyrosine was not demonstrable in any of the AIDS brains. These findings indicate that iNOS may not play a significant role in the neuropathogenesis of most cases of ADC.
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PMID:Absence of the inducible form of nitric oxide synthase in the brains of patients with the acquired immunodeficiency syndrome. 911 Nov 78

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease of the central nervous system (CNS), and the most commonly used experimental model for multiple sclerosis. It is mediated by autoreactive T cell clones exhibiting a T helper cell (Th) 1 cytokine profile. Nonencephalitogenic T lymphocytes specific for self or exogenous antigens have been found to suppress encephalitogenic T cell responses and to protect against autoimmune disease. The mechanisms by which exogenous antigens modulate autoimmunity are not fully understood. In this study, we tested the hypothesis that a Th2-type immune response against an exogenous, nonself antigen, keyhole limpet hemocyanin (KLH), by releasing IL-4 in the microenvironment, could shift the cytokine profile of encephalitogenic T cells from an inflammatory Th1 to a protective Th2 type. SJL/J mice were preimmunized with the KLH in incomplete Freund's adjuvant to induce a population of Th2 memory cells that would be expected to release Th2 cytokines when activated by the specific antigen at the time of EAE induction. Four weeks later, mice received an encephalitogenic challenge containing guinea pig myelin in complete Freund's adjuvant with or without KLH. All KLH primed animals not receiving the exogenous antigen at the time of EAE induction developed a severe clinical disease indistinguishable from control mice not KLH primed. In contrast, animals preimmunized and challenged with the encephalitogenic inoculum containing KLH showed either no, or markedly reduced, clinical signs. Enzyme-linked immunospot analysis demonstrated that KLH-specific T cells in the primed mice were producing IL-4 characteristic of Th2 cells. In the KLH-primed and restimulated mice, the cytokine profile of the autoreactive, myelin basic protein-specific T cells was shifted from an inflammatory Th1 towards a protective Th2 type. We infer that the presence of IL-4 secreted by KLH-specific memory Th2 cells in the lymphoid system microenvironment in which the autoreactive T cells were engaged by the encephalitogenic stimulus were able to bias their cytokine profile towards a protective Th2 phenotype. This interpretation is supported by the observation that the protective effect of preimmunization with KLH was overcome by rm-IL-12, which inhibited the production of IL-4 by the Th1 cells and biased the autoimmune response to a predominantly Th1 type. Since IL-4 mRNA could not be detected by reverse transcriptase PCR in the CNS, the protective effect was inferred to be mediated by Th2 cells in the lymphoid system, and not the target organ. We conclude that exogenous, nonself antigens that can induce Th2 responses, can modify the cytokine environment sufficiently to alter the cytokine phenotype of inflammatory, autoreactive T cell clones, and ultimately, to provide significant protection against EAE and possibly other T cell-mediated autoimmune diseases.
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PMID:A T helper cell 2 (Th2) immune response against non-self antigens modifies the cytokine profile of autoimmune T cells and protects against experimental allergic encephalomyelitis. 912 Mar 96

In this study we provide further evidence associating activated cells of the monocyte lineage with the lesions of multiple sclerosis (MS). Using a combination of immunohistochemistry and reverse transcriptase-dependent in situ polymerase chain reaction analysis, we have identified monocytes expressing inducible nitric oxide synthase (iNOS) to be prevalent in the plaque areas of post mortem brain tissue from patients with MS. In addition, we have obtained evidence of the nitration of tyrosine residues in brain areas local to accumulations of iNOS-positive cells. In parallel studies we have assessed the effects of inhibitors of iNOS induction, as well as scavengers of nitric oxide and peroxynitrite in the experimental allergic encephalomyelitis model. Significant therapeutic effects were seen with the inhibitor of iNOS induction, tricyclodecan-9-xyl-xanthogenate, a nitric oxide scavenger, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and a peroxynitrite scavenger, uric acid. In particular, treatment with high doses of uric acid virtually prevented clinical symptoms of the disease. Together with our demonstration of the presence of activated macrophages expressing high levels of iNOS and evidence of peroxynitrite formation in brain tissue from patients with MS, these findings are of importance in the development of approaches to treat this disease.
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PMID:Prevention of experimental allergic encephalomyelitis by targeting nitric oxide and peroxynitrite: implications for the treatment of multiple sclerosis. 912 29

CD30 is a member of the tumor necrosis factor (TNF) receptor family, originally described as a marker for Hodgkin and Reed-Sternberg cells in Hodgkin's disease, which has been found to be preferentially expressed by T cells producing Th2-type cytokines. The presence of CD30 expression was assessed by both immunohistochemistry and reverse transcriptase-polymerase chain reaction in the target organs of patients with Th1- or Th2-dominated disorders. CD30 expression was found in neither the gut of patients with Crohn's disease nor in the gastric antrum of Helicobacter pylori-infected patients, where there was high interferon-gamma (IFN-gamma) expression. In contrast, high CD30 expression in the apparent absence of IFN-gamma expression was observed in the skin of patients with systemic sclerosis or chronic graft versus host disease (GVHD), which can be considered Th2-dominated disorders. Moreover, high levels of soluble CD30 were found in the serum of both systemic sclerosis and GVHD patients but not in the serum of patients suffering from multiple sclerosis, a Th1-dominated disorder. Thus, CD30 expression appears to be preferentially associated with Th2-type responses not only in vitro but also in vivo.
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PMID:In vivo CD30 expression in human diseases with predominant activation of Th2-like T cells. 912 1

These studies were performed to characterize retroviruses found in cell lines spontaneously developed from peripheral blood mononuclear cells (PBMNC) from 6 multiple sclerosis patients, a patient with progressive myelopathy and a healthy control. The cell lines are B-lymphoblastoid and produce Epstein-Barr virus (EBV) particles or express EBV proteins. The B-lymphoblastoid cell lines are also characterized by production of low, fluctuating amounts of retrovirus. The low productivity complicates purification and characterization, but implementation of product-enhanced reverse transcriptase (PERT) assays has provided a highly useful tool for monitoring retrovirus production. By electron microscopy, the retroviral particles appear type-C-like. Functional assays indicate the presence of Pol, Gag and Env. Indirect ELISA demonstrates a significant relation between disease activity and reactivity towards retroviral peptides. Molecular characterization is primarily based on RT-PCR, cloning, sequencing and Northern- or Southern analyses. Molecular characterization is continuing.
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PMID:Characterization of retroviruses from patients with multiple sclerosis. 917 40

The partial molecular characterization of multiple sclerosis (MS)-associated retrovirus (MSRV), a novel retrovirus previously called LM7, is reported. MSRV has been isolated repeatedly from leptomeningeal, choroid plexus and from Epstein-Barr virus-immortalized B cells of MS patients. A strategy based on reverse transcriptase PCR with RNA-purified extracellular virions yielded an initial pol fragment from which other regions of the retroviral genome were subsequently obtained by sequence extension. MSRV-specific PCR primers amplified a pol region from RNA present at the peak of reverse transcriptase activity, coinciding with extracellular viral particles in sucrose density gradients. The same sequence was detected in noncellular RNA from MS patient plasma and in cerebrospinal fluid from untreated MS patients. MSRV is related to, but distinct from, the endogenous retroviral sequence ERV9. Whether MSRV represents an exogenous retrovirus with closely related endogenous elements or a replication-competent, virion-producing, endogenous provirus is as yet unknown. Further molecular epidemiological studies are required to determine precisely the apparent association of virions containing MSRV RNA with MS.
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PMID:Molecular identification of a novel retrovirus repeatedly isolated from patients with multiple sclerosis. The Collaborative Research Group on Multiple Sclerosis. 920 35

In investigating a possible link between a novel retroviral agent (provisionally called MSRV), recently characterised in multiple sclerosis (MS), and the neuropathology of MS, it was found that there was a significant correlation between gliotoxicity and reverse transcriptase activity in monocyte/macrophage culture supernatants (MMCS) unique to MS patients. MMCS from healthy controls and patients with other neurological diseases did not display either gliotoxicity or reverse transcriptase activity. The observed gliotoxic effect was an initial, intermediate filament network disorganization and subsequent cell death which was specific to astrocytes and oligodendrocytes. The reverse transcriptase activity and MSRV-specific RNA were observed during the first 2 weeks of culture in MMCS from patients with active MS. The further elucidation of the molecular form(s) of this gliotoxic factor and its original source may be crucial in elucidating important etiopathogenic mechanisms in MS.
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PMID:Gliotoxicity, reverse transcriptase activity and retroviral RNA in monocyte/macrophage culture supernatants from patients with multiple sclerosis. 930 59

A novel retrovirus, provisionally called Multiple Sclerosis RetroVirus (MSRV), was recently described in multiple sclerosis (MS). We report here that monocyte/macrophage culture supernatants from MS patients containing reverse transcriptase activity secrete a cytotoxin which induces death of primary mouse cortical glial cells. This cytotoxin, which was also found in MS cerebrospinal fluid, specifically causes death of mouse immortalized astrocytes and oligodendrocytes in vitro and seems to be associated to MSRV-specific RNA. This toxic factor, called gliotoxin, is present only in active cases of MS and is a stable glycosylated protein of 17 kDa, in CSF as well as in monocyte/macrophage culture supernatants. Since this gliotoxin is highly toxic for glial cells, it may represent an initial pathogenic factor, leading to the neuropathological features of MS, like blood brain barrier disruption and demyelination.
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PMID:A cytotoxic factor for glial cells: a new avenue of research for multiple sclerosis? 935 36

The complement anaphylatoxins C5a and C3a are released at the inflammatory site, where they contribute to the recruitment and activation of leukocytes and the activation of resident cells. The distribution of the receptor for C5a (C5aR) has been well studied; however, the receptor for C3a (C3aR) has only recently been cloned, and its distribution is uncharacterized. Using a specific affinity-purified anti-C3aR peptide Ab and oligonucleotides for reverse transcriptase-PCR analysis, C3aR expression was characterized in vitro on myeloid and nonmyeloid cells and in vivo in the brain. C3aR was expressed by adult astrocytes, astrocyte cell lines, monocyte lines THP1 and U937, neutrophils, and monocytes, but not by K562 or Ramos. C3aR staining was confirmed by flow cytometry, confocal imaging, and electron microscopy analysis. A 65-kDa protein was immunoprecipitated by the anti-C3aR from astrocyte and monocyte cell lysates. Our results at the protein level were confirmed at the mRNA level. Using reverse transcriptase-PCR, Southern blot, and sequencing we found that C3aR mRNA was expressed by fetal astrocytes, astrocyte cell lines, and THP1, but not by K562 or Ramos. The astrocyte C3aR cDNA was identical with the reported C3aR cDNA. C3aR expression was not detected in normal brain sections. However, a strong C3aR staining was evident in areas of inflammation in multiple sclerosis and bacterial meningitis. In meningitis, C3aR was abundantly expressed by reactive astrocytes, microglia, and infiltrating cells (macrophages and neutrophils). In multiple sclerosis, infiltrating lymphocytes did not express C3aR, but a strong staining was detected on smooth muscle cells (pericytes) surrounding blood vessels.
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PMID:The receptor for complement anaphylatoxin C3a is expressed by myeloid cells and nonmyeloid cells in inflamed human central nervous system: analysis in multiple sclerosis and bacterial meningitis. 953 17

The Fas and FasL apoptotic pathway was investigated by protein immunohistochemistry, flow cytometry, and reverse transcriptase-PCR analysis to assess whether it is involved in the elimination of target and/or effector cells from the central nervous system (CNS) during adoptively transferred chronic relapsing experimental autoimmune encephalomyelitis (EAE), a model for multiple sclerosis. In addition to Fas and FasL, we studied Bax, an intracellular protein of the apoptotic cascade, the Bax antagonist and anti-apoptotic molecule Bcl-2, and DNA fragmentation, the final step in the apoptotic pathway. Infiltrating CD4+ T cells and parenchymal microglia expressed Fas, FasL, and Bax, and about half of these cells showed DNA fragmentation, a combination indicative of ongoing apoptosis. Using flow cytometry and reverse transcriptase-PCR, a positive correlation was seen between disease activity and up-regulation of the Fas system; in fact, Fas and FasL were expressed at low levels at the onset of EAE and increased at the height of disease to involve about one-third of all infiltrating lymphocytes. In the normal CNS, Fas immunoreactivity was constitutively present at low levels on oligodendrocytes and was up-regulated in the CNS during the course of EAE. However, oligodendrocytes showed no Bax reactivity or DNA fragmentation and expressed high levels of Bcl-2, as did the majority of infiltrating CD3+ cells, a pattern inconsistent with apoptosis. Thus, while molecules of the apoptotic cascade are well represented in the CNS during EAE, their expression correlates with elimination of infiltrating cells and microglia, not the myelinating cell, the oligodendrocyte.
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PMID:Cell death during autoimmune demyelination: effector but not target cells are eliminated by apoptosis. 954 18


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