Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Expression of the human immunodeficiency virus (HIV) structural proteins in mammalian cells is regulated posttranscriptionally by the viral Rev protein. Rev has been shown to trans-activate expression by relieving the nuclear sequestration of RNAs containing viral gag or env coding regions. We have studied the effects of Rev on expression of the HIV type 1 env gene in Drosophila melanogaster cells. We demonstrated that synthesis of the gp160 envelope protein was fully Rev dependent; that is, gp160 was produced only when Rev function was coexpressed in the cell. Analysis of total cellular RNA indicated that Rev did not significantly affect the overall levels of gp160 RNA production. Instead, mRNA encoding gp160 was found in the cytoplasm only in cells expressing Rev, whereas in cells lacking Rev, this RNA was present only in the nucleus. Furthermore, comparison of these results with the previously demonstrated Rev-independent expression of gp120 envelope protein with this system indicated that information contained in the gp41 coding region appears to be critical to the selective nuclear retention of gp160 transcripts in the absence of Rev. Our results clearly demonstrate that the mechanism of Rev action is conserved in the insect cell system, and, thus, Rev must function via cellular machinery common to most, if not all, higher cell systems.
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PMID:Rev-dependent expression of human immunodeficiency virus type 1 gp160 in Drosophila melanogaster cells. 212 89

The envelope protein of the human T-cell leukemia virus type I (HTLV-I) is highly conserved among the isolates sequenced so far, as opposed to what is observed for the human immunodeficiency virus (HIV) envelope. By linker insertion scanning, we have produced 33 random mutations along the HTLV-I envelope gene, cloned into a eukaryotic expression vector. The resulting envelope products were analysed by immunoprecipitation and syncytia formation after transfection into COS-1 cells. We show here that 25 out of 33 mutations result in a non-functional envelope product as assessed by the lack of ability to form syncytia. In the majority of these mutants, the processing of the envelope gp61 precursor into the mature gp45 and gp20 proteins was affected. We propose that conformational constraints for processing and fusion abilities tend to limit the variability of the HTLV-I envelope. In three mutants, processing was observed but no syncytia were formed. These mutations might affect regions important for HTLV-I envelope functions, such as the receptor binding region.
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PMID:Mutations introduced along the HTLV-I envelope gene result in a non-functional protein: a basis for envelope conservation? 212 68

Visna virus is an ungulate lentivirus that is distantly related to the primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1). Replication of HIV-1 and of other complex primate retroviruses, including human T-cell leukemia virus type I (HTLV-I), requires the expression in trans of a virally encoded post-transcriptional activator of viral structural gene expression termed Rev (HIV-1) or Rex (HTLV-I). We demonstrate that the previously defined L open reading frame of visna virus encodes a protein, here termed Rev-V, that is required for the cytoplasmic expression of the incompletely spliced RNA that encodes the viral envelope protein. Transactivation by Rev-V was shown to require a cis-acting target sequence that coincides with a predicted RNA secondary structure located within the visna virus env gene. However, Rev-V was unable to function by using the structurally similar RNA target sequences previously defined for Rev or Rex and, therefore, displays a distinct sequence specificity. Remarkably, substitution of this visna virus target sequence in place of the HIV-1 Rev response element permitted the Rev-V protein to efficiently rescue the expression of HIV-1 structural proteins, including Gag, from a Rev- proviral clone. These results suggest that the post-transcriptional regulation of viral structural gene expression may be a characteristic feature of complex retroviruses.
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PMID:Visna virus encodes a post-transcriptional regulator of viral structural gene expression. 217 Sep 81

The study of monocyte/macrophage functions after human immunodeficiency virus type 1 (HIV-1) infection may help in understanding the pathogenesis of AIDS. The production of four cytokines, tumor necrosis factor alpha (TNF alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and granulocyte-macrophage colony-stimulating factor (GM-CSF), by peripheral blood monocytes/macrophages was evaluated after in vitro infection with HIV-1. HIV-1 infection of these monocytes/macrophages did not result in release of any of these cytokines. Similarly, treatment of uninfected cells with purified recombinant HIV-1 envelope protein did not result in cytokine production. After stimulation with endotoxin or endotoxin plus interferon-gamma, HIV-1-infected monocytes/macrophages produced amounts of TNF alpha, IL-6, GM-CSF, and IL-1 beta comparable to that of uninfected cells. HIV-1 infection does not appear to induce or alter cytokine production by mononuclear phagocytes, which retain the capacity to produce these cytokines after endotoxin stimulation.
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PMID:Production of cytokines by peripheral blood monocytes/macrophages infected with human immunodeficiency virus type 1 (HIV-1). 218 29

Although the envelope gene of human immunodeficiency virus type 1 shows considerable strain variability, cysteine residues of the envelope protein are strongly conserved, suggesting that they are important to the envelope structure. We constructed and analyzed mutants of a biologically active molecular clone of human immunodeficiency virus type 1 in which different cysteines were replaced by other amino acids in order to determine their functional importance. Substitution of cysteines 296 and 331, on either side of a region recognized by type-specific neutralizing antibodies, or on either side (residues 418 and 445) of a region important for CD4 binding, resulted in noninfectious mutants. These mutants were blocked early in the viral life cycle. Their gp160 envelope precursor polypeptides were poorly cleaved, and CD4 binding was also strongly impaired. Similar substitutions in the first variable region (residue 131) or between the first and second variable regions (residue 196) also gave noninfectious mutant virus, but here the block was late in the virus life cycle; these mutants were defective for syncytium formation. Substitution of cys386, between the neutralization and CD4 binding regions, resulted in a virus which retained infectivity but which spread much more slowly than the wild type. As with the cys131 and cys196 mutants, the cys386 mutant appeared to be defective in syncytium formation. These results show that all seven of the tested cysteines are vital for envelope function and suggest that this is likely true for all envelope cysteines. The results further show that regions important for CD4 binding, proteolytic cleavage recognition, and syncytium formation are all multiple and distributed over a relatively large part of the gp120 and therefore are likely dependent on protein tertiary structure.
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PMID:Functional contribution of cysteine residues to the human immunodeficiency virus type 1 envelope. 218 10

The infectivity of the human immunodeficiency virus (HIV) is related to the structure of its envelope protein, gp160, which is responsible for viral entry. We considered the possibility that a structural homology between gp160 and major histocompatibility complex (MHC) molecules might be associated with the extraordinary affinity that gp120 has for its receptor, CD4. Amino acid sequence comparisons revealed five regions of structural similarity between the HLA-DR beta molecule and gp160. The DR2 beta synthetic peptides containing these regions were examined for their ability to block HIV-induced syncytia formation using a 51Cr release assay. The peptide beta 141-155 inhibited the formation of syncytia whereas the other four DR beta peptides with gp160 similarity did not. Our results indicate that this region in gp120, which is similar to an HLA-DR region, is crucial to T cell-gp120 interactions, and should be considered in the design of future vaccines.
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PMID:HLA-DR peptide inhibits HIV-induced syncytia. 219 18

Twenty patients with chronic purulent rhinosinusitis were treated with TP-1 (Serono; 1 mg/kg body weight), in a double-blind cross-over trial. TP-1 was administered by daily i.m. injections for the first 14 days followed by two injections/week for 6 further weeks. The patients were immunologically special in that they had defects in their cell-mediated immune system. Fourteen showed a decreased chemotactic responsiveness of their peripheral blood monocytes as measured in the polarization assay. This defective function can probably be ascribed to the presence in serum of low molecular weight factors (LMWFs; less than 25 kD). As reported earlier, this factor shows a structural homology to the envelope protein of murine and feline leukaemia virus (P15E). Thirteen patients showed a defective delayed-type hypersensitivity (DTH) skin test reactivity towards candidin and/or streptokinase-streptodornase (Sk/Sd) antigen, 14 had a defective MIF production from their peripheral blood lymphocytes towards candidin, Sk/Sd and/or Haemophilus influenzae antigen. Eighteen patients completed the TP-1 trial and showed clinical improvements: 12 out of 15 were feeling better during TP-1 therapy and the nasal mucosa showed on inspection absent mucopurulent secretion in 13 patients. Positive bacterial culture rates for the nose decreased from 14 out of 16 to five out of 15. Placebo treatment had no significant effects. The clinical improvements were accompanied by a better performance of the cell-mediated immune system; the most significant effects were recorded in the monocyte polarization assay. The suppressive P15E-like LMWFs in serum clearly decreased during TP-1 treatment. In vitro TP-1 neutralized the immunosuppressive effect of the LMWFs. The restoring effects of TP-1 on monocyte polarization and its neutralizing activity of P15E-like LMWFs could explain the beneficial effects of thymic hormone treatment reported in adults with clinical signs of immunodeficiency in the presence of a full T cell repertoire.
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PMID:Beneficial effects of the thymic hormone preparation thymostimulin in patients with defects in cell-mediated immunity and chronic purulent rhinosinusitis. A double-blind cross-over trial on improvements in monocyte polarization and clinical effects. 219 46

Picomolar concentrations of native or recombinant coat protein gp120, from the human immunodeficiency virus type 1 (HIV-1), injured rat retinal ganglion cell neurons in culture. This form of neurotoxicity could be completely abrogated by anti-gp120 but not by control preimmune serum, suggesting that the lethal effects of the purified preparations of the envelope protein were due to gp120 and not to a contaminant. Entry of HIV-1 is mediated by gp120 binding to a surface protein, designated "CD4," which is located, for example, on T lymphocytes. However, in the present study, specific anti-CD4 antibodies, at concentrations known to block effects mediated by high-affinity binding to CD4 on the surface of rat T cells, did not prevent neuronal injury induced by gp120. These findings suggest that injury of central neurons engendered by gp120 may be responsible, at least in part, for the neurologic manifestations observed in as many as 2/3 of the patients with acquired immunodeficiency syndrome, such as dementia, myelopathy, and visual loss, even in the absence of superinfection. In contrast with previous studies, however, this report suggests that the deleterious effects of gp120 on neurons may not be mediated via binding to the CD4 molecule.
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PMID:Neuronal injury due to HIV-1 envelope protein is blocked by anti-gp120 antibodies but not by anti-CD4 antibodies. 223 33

The CD4 antigen, which serves as the receptor for human immunodeficiency virus type 1 (HIV-1) on T cells, has been detected on human megakaryocytes. Recent evidence of impaired thrombopoiesis in HIV-1-related thrombocytopenia suggested that these cells could be directly infected by the virus and prompted a search for a receptor on megakaryocytes of normal subjects that could permit entry of HIV-1. Bone marrow specimens from uninfected normal control subjects were centrifuged over Ficoll-Hypaque (1.077 g/ml) and analyzed by three-color analysis with a flow cytometer utilizing monoclonal antibodies against CD4 and a glycoprotein present on the surface of megakaryocytes and platelets (GPIIb/IIIa; CD41), as well as 7-aminoactinomycin D, a stain for DNA. Cells presumed to be megakaryocytes were identified by having a DNA content greater than tetraploid and staining brightly with anti-CD41. Approximately 0.4% of the nucleated cells of the marrow met these criteria. Twenty-five percent of these megakaryocytes stained as brightly as CD4+ T cells. Several clones of antibody recognizing different epitopes of the CD4 molecule gave similar results. Platelets were CD4-. Staining of megakaryocytes with anti-CD4 was confirmed by direct microscopic examination of Percoll-gradient-enriched megakaryocytes employing two-color (CD4-phycoerythrin and CD41-fluorescein) immunofluorescence analysis and phase-contrast microscopy. The proportion of double-labeled cells among 112 phase-contrast-identifiable megakaryocytes from five bone marrow specimens varied between 20% and 26% with a mean and SD of 22% +/- 2.5%. Thus some human megakaryocytes express CD4 on their surface that should be capable of binding the HIV-1 gp120 envelope protein. This could serve as a portal of entry for HIV-1.
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PMID:Expression of CD4 by human megakaryocytes. 223 21

The envelope glycoprotein of human immunodeficiency virus consists of two subunits, designated gp120 and gp41, derived from the cleavage of a precursor polypeptide gp160. When expressed from a recombinant vaccinia virus and analyzed by velocity gradient sedimentation and polyacrylamide gel electrophoresis, a significant proportion of gp160 molecules formed oligomers that were stabilized by intermolecular disulfide bonds. Oligomeric forms of both gp120 and gp41 were also observed, but these oligomers were noncovalently associated. Both the intermolecularly linked oligomers of gp160 and the unlinked oligomeric envelope protein subunits were found to accumulate with time. These results indicate that there are two populations of gp160 precursors, one that is folded and processed correctly into gp120 and gp41 and another that is intermolecularly disulfide bonded and remains uncleaved. We propose that the formation of intermolecular disulfide bonds is not an intermediate step in the maturation of the envelope glycoprotein, but rather a result of misfolding of the gp160 precursor which prevents it from being properly processed.
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PMID:The human immunodeficiency virus type 1 envelope glycoprotein precursor acquires aberrant intermolecular disulfide bonds that may prevent normal proteolytic processing. 223 72


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