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)

In the present report, we have studied the in vitro transition of normal blood monocytes to macrophages by changes in cell morphology, and the expression of surface antigens with a panel of monoclonal antibodies. The maturation process was accompanied by notable changes in cell-surface markers in a time-dependent manner. The percentage of cells expressing CD11c, ICAM-1, HLA-DR, and Fc receptor class III increased while the CD4 and CD35 expression was markedly decreased. After demonstrating that in vitro monocytes mature to macrophages in a recognizable manner, we studied the susceptibility to HIV-1 infection at time points representing different stages of cell maturation. The results show that monocyte/macrophages are susceptible to HIV-1 infection at all stages of differentiation. However, the kinetics of virus replication depends on the degree of maturation at the time of infection. Two major patterns of replication were observed: Infection of monocytes resulted in efficient virus production measurable by reverse transcriptase activity in culture supernatant, whereas infection of fully differentiated macrophages yielded low but sustained virus release only demonstrable by p24 antigen assay. We were not able to detect differences in the capacity of the virus to infect and replicate in monocyte/macrophages with respect to cellular origin of the virus isolate and whether the viruses were laboratory-adapted strains or low-passaged patient isolates.
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PMID:In vitro maturation of mononuclear phagocytes and susceptibility to HIV-1 infection. 185 87

A variant of simian immunodeficiency virus from sooty mangabey monkeys (SIVsmm), termed SIVsmmPBj14, was previously identified and shown to induce acute disease and death within 1 to 2 weeks of inoculation of pig-tailed macaques and mangabey monkeys (P. N. Fultz, H. M. McClure, D. C. Anderson, and W. M. Switzer, AIDS Res. Hum. Retroviruses 5:397-409, 1989). SIVsmmPBj14 differed from its parent virus, SIVsmm9, not only in pathogenicity but also in multiple in vitro properties. As a first approach to understanding the biological and molecular mechanisms responsible for the acute disease and death induced by this variant, virus-host cell interactions of SIVsmmPBj14 and SIVsmm9 were studied. Initial rates of replication of the two viruses were identical in primary peripheral blood mononuclear cells (PBMC) from normal pig-tailed macaques and mangabey monkeys, but SIVsmmPBj14 infection always resulted in higher yields of virus than did SIVsmm9 infection, as assessed by levels of reverse transcriptase activity in culture supernatants. Surprisingly, despite its cytopathicity for macaque and mangabey CD4+ cells, replication of SIVsmmPBj14 was accompanied by up to 10-fold increases in number of viable cells compared with cell numbers in uninfected or SIVsmm9-infected cultures. Furthermore, SIVsmmPBj14 was shown to infect and replicate in resting PBMC just as efficiently as in mitogen-stimulated PBMC, irrespective of whether exogenous interleukin-2 (IL-2) or antibodies that neutralized IL-2 were added to culture media. Accumulation of virus in culture supernatants of resting PBMC preceded by several days the appearance of activated cells which expressed the IL-2 receptor alpha subunit (CD25), suggesting that activation of cells was not essential for replication. The ability to activate and to induce simian PBMC to proliferate appeared specific for the acutely lethal variant because incorporation of [3H]thymidine by PBMC from naive animals was observed only upon incubation with concentrated, heat-inactivated SIVsmmPBj14 and not with other viruses. Both CD4(+)- and CD8(+)-enriched cell populations proliferated in response to SIVsmmPBj14. These results are consistent with in vivo observations and suggest that the abilities both to replicate in resting cells and to induce lymphocytes to proliferate may contribute to the extreme virulence of SIVsmmPBj14.
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PMID:Replication of an acutely lethal simian immunodeficiency virus activates and induces proliferation of lymphocytes. 187 Feb 5

The role of placental cells in transplacental transmission of human immunodeficiency virus type 1 (HIV 1) was investigated. Placental macrophages and trophoblasts, which together represent the main cell components of the placenta, were cultivated separately and then compared to foetal monocyte-derived macrophages for susceptibility to HIV 1 infection. Placental macrophages treated with granulocyte-macrophage colony-stimulating factor (GM-CSF) were less easily infected with HIV 1 than were GM-CSF-treated foetal monocyte-derived macrophages. HIV 1 replication in cocultures consisting of infected placental macrophages together with a highly HIV 1-permissive cell line (CEM) was detected persistently for at least 6 weeks by reverse transcriptase assay, even though placental macrophages expressed no detectable CD4 receptor, as indicated by indirect immunofluorescence. HIV 1-specific DNA sequences were also detected in infected placental macrophages. Trophoblasts exhibited no detectable CD4 expression and did not support the replication of HIV 1, although low levels of HIV 1-specific DNA sequences could be detected in infected trophoblasts. Placental macrophages or trophoblasts (or both) may thus play an important role in transplacental HIV 1 transmission.
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PMID:Replication of human immunodeficiency virus type 1 in primary cultured placental cells. 189 50

Dipyridamole (DP) is a widely used coronary vasodilator and antithrombotic drug. The presented experiments demonstrate that DP inhibits the replication of HIV-1 and markedly potentiates the anti-HIV activity of azidothymidine (AZT) and dideoxycytidine in CD4-positive cells (monocyte-macrophages and T-lymphocytes). At the same time DP does not potentiate the bone marrow toxicity of AZT, and, in CEM-ss lymphoblastoid cells, it significantly suppresses the cytotoxicity of AZT. Studies on the mechanism of these effects suggest that DP inhibits the intracellular phosphorylation of physiological nucleosides, whereas it does not affect phosphorylation of AZT and other antiviral dideoxynucleoside drugs. This may lead to relative enhancement of the metabolic activation of dideoxynucleoside drugs and the inhibitory action of their active, triphosphate form on HIV reverse transcriptase. Studies comparing the binding of DP to proteins in tissue culture media and in human plasma suggest that in order to achieve significant antiviral potentiation in vivo, high doses of DP will be required.
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PMID:[A new drug in a new role: dipyridamole in the treatment of HIV-1 infections?]. 192 62

Interferon alpha was one of the first drugs tested for the treatment of patients with AIDS-related Kaposi's sarcoma based on its known antiviral properties and its abilities to modulate immune function and inhibit neoplastic cell proliferation. In vitro studies demonstrated defective production of interferon by blood cells of HIV-infected individuals and suppression of HIV replication by interferons alpha and beta. Interferons have also been shown to inhibit angiogenesis induced by tumour cells or by allogeneic lymphocytes in mice. The efficacy of recombinant interferon alpha for the treatment of AIDS-related Kaposi's sarcoma has been well documented with antitumour responses seen in approximately 30% of all patients treated in single agent efficacy trials with doses of at least 20 MU/m2. In several uncontrolled studies, response of Kaposi's sarcoma to treatment with interferon alpha was associated with longer survival and few opportunistic infections. Tumour response appears to be correlated with an absence of opportunistic infection and with CD4 cell numbers. Several studies using high interferon alpha doses have demonstrated decreases in serum HIV P24 core antigens which appear to be confined to patients whose tumours also regressed. The use of interferon alpha in HIV-infected patients with or without Kaposi's sarcoma have demonstrated in vivo anti-HIV activity. Studies have recently evaluated the tolerance and therapeutic potential of interferon alpha in combination with the reverse transcriptase inhibitor, zidovudine (azidothymidine AZT). Synergistic suppression of HIV replication in vitro has been demonstrated with the combination of interferon alpha and zidovudine. The description of HIV isolates with reduced sensitivity to zidovudine following prolonged treatment, and the finding that interferon alpha, but not zidovudine, prevents HIV expression in chronically infected cell lines, suggests that this combination might be useful in long-term treatment of patients with HIV infection.
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PMID:Interferon alpha in the treatment of AIDS-related Kaposi's sarcoma. 193 14

Human immunodeficiency type 1 isolates from 18 initially symptom-free men who were treated with zidovudine for 2 years were investigated for drug sensitivity. At the start all the men had persistent core antigenaemia; the acquired immunodeficiency syndrome developed in 6 during the study. The polymerase chain reaction was used to detect mutations at residue 215 of reverse transcriptase, a mutation associated with reduced drug sensitivity. After 2 years 16/18 isolates were mutant. However, after about 6 months of treatment the mutation was detected in only 7 isolates, 4 from individuals who subsequently had AIDS. Limited direct virus sensitivity data correlated with the genetic data. The rate of appearance of the 215 mutation seemed to correlate with CD4 counts and viral virulence.
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PMID:Zidovudine sensitivity of human immunodeficiency viruses from high-risk, symptom-free individuals during therapy. 197 78

Antiretroviral therapy for children is still at an early stage, although progress is being made slowly. Zidovudine administered at 180 mg/m2/dose every 6 hours is the current standard therapy for symptomatic children and those with low CD4 counts. This standard is likely to evolve as further testing clarifies the optimal dosage for ZDV in different populations. Children on ZDV need to be monitored very closely (at least monthly) for hematologic side effects, which are most common in the more seriously ill children. The role of some of the newer antiretrovirals, like ddI and ddC, which are likely to be licensed, has yet to be established. They have a different toxicity profile than ZDV and thus may work well in combination with it. The issue of peripheral neuropathy and the lack of an easy test to measure it makes using ddC or ddI in young, preverbal children a daunting proposition. As with ZDV, the optimum dosage and timing have yet to be fixed for ddC or ddI alone, and even less available are regimens for combination therapy. Antiretroviral drugs other than the dideoxynucleosides are less well developed. Some, like high-titer antiviral immunoglobulin, involve technology that is already available and thus will be relatively easy to study. Others, like the antisense oligomers, are such a new technology that there are many hurdles to be overcome as the agents move from the laboratory to the clinic. The goal of agents that work on sites other than reverse transcriptase is a reasonable one, but the work in perfecting such new categories of drug is difficult and slow. In the meantime, children with HIV should be symptomatically supported and offered the most effective antiretroviral regimens available.
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PMID:Antiviral therapy for human immunodeficiency virus infection in children. 198 14

Recombinant full-length CD4 expressed in Spodoptera frugiperda 9 cells with the baculovirus system was electroinserted in erythrocyte (RBC) membranes. Of the inserted CD4, 70% was "correctly" oriented as shown by fluorescence quenching experiments with fluorescein-labeled CD4. The inserted CD4 displayed the same epitopes as the naturally occurring CD4 in human T4 cells. Double-labeling experiments (125I-CD4 and 51Cr-RBC) showed that the half-life of CD4 electroinserted in RBC membrane in rabbits was approximately 7 days. Using the fluorescence dequenching technique with octadecylrhodamine B-labeled human immunodeficiency virus (HIV)-1, we showed fusion of the HIV envelope with the plasma membrane of RBC-CD4, whereas no such fusion could be detected with RBC. The dequenching efficiency of RBC-CD4 is the same as that of CEM cells. Exposure to anti-CD4 monoclonal antibody OKT4A, which binds to the CD4 region that attaches to envelope glycoprotein gp120, caused a significant decrease in the dequenching of fluorescence. In vitro infectivity studies showed that preincubation of HIV-1 with RBC-CD4 reduced by 80-90% the appearance of HIV antigens in target cells, the amount of viral reverse transcriptase, and the amount of p24 core antigen produced by the target cells. RBC-CD4, but not RBCs, aggregated with chronically HIV-1-infected T cells and caused formation of giant cells. These data show that the RBC-CD4 reagent is relatively long lived in circulation and efficient in attaching to HIV-1 and HIV-infected cells, and thus it may have value as a therapeutic agent against AIDS.
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PMID:Full-length CD4 electroinserted in the erythrocyte membrane as a long-lived inhibitor of infection by human immunodeficiency virus. 203 80

Viral isolates were recovered by cocultivation on macrophage colony-stimulatingfactor (MCSF)-treated monocyte target cells from peripheral blood mononuclear cells (PBMCs) in 25 out of 27 patients seropositive or at risk for HIV infection. Frequency of virus recovery was independent of the patient's age, sex, numbers of CD4+ T cells, clinical stage or zidovudine (azidothymidine) therapy. Sixteen out of 19 HIV isolates were serially passaged in MCSF- treated monocytes. Five out of five virus isolates were also passaged in phytohemagglutinin/interleukin-2 (PHA/IL-2)-treated lymphoblasts. In lymphoblasts, no qualitative or quantitative differences were observed between these isolates and human T-cell leukemia virus IIIB (HTLV-IIIB) for (1) release of p24 antigen reverse transcriptase, and infectious virus, (2) induction of typical cytopathic effects (cell syncytia in 3-10% of cells) and cell lysis, (3) frequency of infected cells (5-20% of PBMC) as detected by in situ hybridization for HIV RNA, (4) down-modulation of T cell plasma membrane CD4, and (5) site of progeny virion assembly and budding (plasma membrane only with no intracytoplasmic accumulation of virus). Progeny virus recovered from infected lymphoblasts was fully infectious for other lymphoblasts, but failed to infect MCSF-treated monocytes. Detailed analysis of target cell tropism among HIV isolates showed that HIV isolated in monocytes infected both monocytes and lymphoblasts; progeny virus isolated in lymphoblasts infected only T cells. HIV interacts differently with monocytes and T cells. Understanding this interaction may more clearly define both the pathogenesis of HIV disease and strategies for therapeutic intervention.
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PMID:Macrophage-HIV interaction: viral isolation and target cell tropism. 211 97

Although knowledge has accumulated about GP110-CD4 interaction, viral penetration into human CD4+ lymphocytes remains unclear, in spite of the fact that all studies on HIV infection were performed on cell-transformed lineages, or on human polyclonal CD4+ cells. In order to investigate this viral entrance into susceptible cells, we studied the permissivity of 13 human monoclonal CD4+ lymphocytes by means of reverse transcriptase (RT) assay and immunocapture. We demonstrated a differential susceptibility to HIV of these CD4+ clones. In a second experiment, HIV infection was studied: (1) sequentially by RT assay and P24 immunocapture on several clones; (2) by cocultivation of infected clones with umbilical cord lymphocytes. These experiments suggested existence of permissive and "nonpermissive" CD4+ monoclonal lymphocytes. Slot blot, then PCR, revealed that proviral DNA sequences were detectable in all clones, but were present at lower levels in nonpermissive clones.
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PMID:Lack of permissivity of human monoclonal CD4+ lymphocytes to HIV. 212 40


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