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)

The AC133 is a novel antigen selectively expressed on primitive CD34bright stem cells and is a valuable marker for the selection of long-term culture-initiating cells (LTC-ICs) and severe combined immunodeficiency (SCID)-repopulating cells. Human placental cord blood (HPCB) is a rich source of CD34+AC133+ cells. Since AC133 antibody is likely to be used as an alternative to CD34 for the selection of stem cells in transplant and gene therapy situations, we examined the susceptibility of HPCB-isolated CD34+AC133+ stem cells to infection with free and cell-associated HIV-1 in vitro. Freshly isolated HPCB CD34+AC133+ stem cells were not susceptible to HIV-1 infection as determined by PCR and reverse transcriptase assays. Inoculation with HIV-1 did not affect the viability and clonogenic ability of HPCB CD34+AC133+ cells. Although the highly purified HPCB CD34+AC133+ stem cells contained mRNA for CD4 and CXCR4 receptors, CD4 and CXCR4 proteins were not expressed on these cells. Similarly, CCR5 protein, the major macrophage-tropic HIV-1 coreceptor, was not expressed in freshly isolated HPCB CD34+AC133+ stem cells, although the transcript for CCR5 was identified in these cells. Expression of CD4, CXCR4, and CCR5 receptor proteins on the progeny derived from HPCB CD34+AC133+ stem cells was detected and correlated with susceptibility to HIV-1 infection in vitro. These findings suggest that freshly isolated HPCB CD34+AC133+ stem cells are not susceptible to HIV-1 infection and may not be a viral reservoir. These data have important implications for the use of AC133 antibody as a means of enriching for primitive hematopoietic stem cells from placental cord blood and in the design of stem cell or progenitor cell-based gene therapeutic strategies for perinatal HIV-1 infection.
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PMID:Human immunodeficiency virus infection of human placental cord blood CD34+AC133+ stem cells and their progeny. 1058 Apr 5

We examined CD4 and major HIV-1 co-receptor expression by trophoblast cells (TC) from early placentas, and the permissiveness of TC for infection by several natural HIV-1 isolates in vitro. Ten early placentas (4-6 weeks of gestation) from HIV- women were obtained after elective abortion. CD4 and HIV-1 co-receptor expression by TC was examined in terms of both mRNA and protein. The same TC were then challenged with three clinical HIV isolates of known phenotype, two originating from mothers who transmitted the virus to their child and one from a vertically infected newborn. TC infection was detected by polymerase chain reaction. CD4 expression was detected in five of the 10 placentas, while membrane protein expression of CCR3, CXCR4 and CCR5 was detected in every case, despite quantitative differences among individuals. Bonzo, GPR1 and ChemR23 mRNAs were detected in all TC preparations. TC from seven out of eight placentas were permissive to HIV entry, but no productive viral replication was detected (reverse transcriptase activity in culture supernatants). Interestingly, the addition of chemokine(s) or a CD4-blocking antibody to the cultures failed to inhibit TC virus entry. These data point to marked interindividual variability in HIV co-receptor expression by trophoblast cells and show that TC from early placentas can be infected in vitro by clinical HIV-1 isolates. They also suggest that viral entry in vitro might occur through a mechanism independent of both CD4 and chemokine receptors.
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PMID:HIV-1 co-receptor expression on trophoblastic cells from early placentas and permissivity to infection by several HIV-1 primary isolates. 1069 21

Phenotypic drug susceptibility assays of human immunodeficiency virus type 1 (HIV-1) isolates generally use time-consuming, expensive assays with peripheral blood mononuclear cells. A new HIV-1 indicator cell line, MAGI-CCR5, has been developed and applied for this purpose. This cell line expresses human CD4, the two major HIV-1 coreceptors, CCR5 and CXCR4, the reporter gene beta-galactosidase driven by the HIV-1 LTR, and quantitates infection within 48 h. A panel of reference strains and primary HIV-1 isolates were all found to infect this cell line. Susceptibility assays with a nucleoside (zidovudine, ZDV) and a non-nucleoside reverse transcriptase inhibitor (nevirapine, NVP) were performed with reference and primary isolates. The assay was modified into two steps for protease inhibitor (indivinavir, IDV and ritonavir, RTV) susceptibility assays. Primary isolates derived from drug naive patients displayed mean baseline 50% effective concentrations (EC50) of 0.14 microM for ZDV, 0.33 microM for NVP, and 0.02 microM for IDV. Isolates derived from patients under treatment displayed increased EC50 concentrations. The MAGI-CCR5 cell line offers a rapid, efficient, and reproducible method of testing a wide range of HIV-1 isolates for drug susceptibility.
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PMID:Rapid phenotypic drug susceptibility assay for HIV-1 with a CCR5 expressing indicator cell line. 1071 48

Certain chemokines inhibit HIV replication through binding to cell surface receptors which also act as viral coreceptors. Based on our previous observations that HIV-1 Tat can interact with alpha- and beta-chemokine receptors, we investigated the potential effect of extracellular Tat (ecTat) on infection and replication of CCR5-dependent (R5) and CXCR4-using (X4) HIV-1 strains in primary activated peripheral blood mononuclear cells (PBMC) of uninfected donors. Receptor desensitization and binding competition studies were used to determine chemokine receptor binding by ecTat. Standard HIV replication assays based on reverse transcriptase (RT) activity determination in culture supernatants of PBMC and real time PCR for HIV-1 gag DNA were used to determine potential effects on early (entry or RT) steps of infection. ecTat bound to CXCR4 expressing monocytes and mitogen-activated PBMC, and competed with the natural ligand of CXCR4, SDF-1alpha (stromal cell-derived factor-1alpha) in calcium mobilization assays. EcTat inhibited replication of the X4 HIV-1 (LAI/IIIB strain) in activated PBMC at concentrations close to those of SDF-1alpha, whereas it only modestly interfered with R5 HIV-1 (BaL) replication in PBMC. Both SDF-1alpha and ecTat inhibited accumulation of X4 HIV-1 gag DNA, indicating interference with viral entry and/or RT. Our data show the surprising and counter-intuitive observation that ecTat selectively represses X4 HIV replication. This could favour spreading of R5 viruses, a condition observed in vivo immediately after transmission and in the early asymptomatic phase of infection.
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PMID:Inhibition of CXCR4-dependent HIV-1 infection by extracellular HIV-1 Tat. 1077 39

All HIV-1 strains studied to date use CCR5, CXCR4, or both receptors to enter cells. Simian immunodeficiency virus (SIV) infection of non-human primates has served as a useful model for understanding AIDS pathogenesis in humans. Research on several genetically divergent SIV isolates has revealed that SIV uses CCR5, and not CXCR4, for entry. CEM x174, a human lymphoid cell line, has been routinely used to cultivate and maintain various SIV strains. However, questions have arisen about how CEM x174, which reportedly was unable to express detectable amounts of CCR5 transcripts, efficiently supports the growth of SIV. In searching for an answer, we resorted to a sensitive competitive reverse transcriptase-polymerase chain reaction procedure in an attempt to detect as well as quantify the amount of CCR5 expression. Here we present our findings, which indicate that CEM x174 indeed expresses CCR5 and that the amount of CCR5 is increased in cells pretreated with morphine. These results correlate well with our previous observations that morphine treatment causes CEM x174 cells to be more susceptible to SIV infection. Similar morphine effect was not observed on CEM x174 cells infected with simian retroviruses, which do not depend on CCR5 for entry. These findings suggest a plausible mechanism whereby opiate drug users render themselves more susceptible to HIV infection, thereby explaining the vast prevalence of HIV infection among endemic drug use populations.
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PMID:Morphine induces gene expression of CCR5 in human CEMx174 lymphocytes. 1088 75

Virtually all the compounds that are currently used, or under advanced clinical trial, for the treatment of HIV infections, belong to one of the following classes: (i) nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs), (ii) non-nucleoside reverse transcriptase inhibitors (NNRTIs) and (iii) protease inhibitors (PIs). In addition to the reverse transcriptase and protease step, various other events in the HIV replicative cycle are potential targets for chemotherapeutic intervention: (i) viral adsorption, through binding to the viral envelope glycoprotein gp120 (polysulphates, polysulphonates, polyoxometalates, zintevir, negatively charged albumins); (ii) viral entry, through blockade of the viral coreceptors CXCR4 and CCR5 [bicyclams (AMD3100), polyphemusins (T22), TAK-779]; (iii) virus-cell fusion, through binding to the viral glycoprotein gp41 [T-20 (DP-178), siamycins, betulinic acid derivatives]; (iv) viral assembly and disassembly, through NCp7 zinc finger-targeted agents [2,2'-dithiobisbenzamides (DIBAs), azadicarbonamide (ADA)]; (v) proviral DNA integration, through integrase inhibitors such as L-chicoric acid; (vi) viral mRNA transcription, through inhibitors of the transcription (transactivation) process (peptoid CGP64222, fluoroquinolone K-12, Streptomyces product EM2487). Also, in recent years new NRTIs, NNRTIs and PIs have been developed that possess, respectively, improved metabolic characteristics (i.e. phosphoramidate and cyclosaligenyl pronucleotides of d4T), or increased activity against NNRTI-resistant HIV strains, or, in the case of PIs, a different, non-peptidic scaffold. Given the multitude of molecular targets with which anti-HIV agents can interact, one should be cautious in extrapolating from cell-free enzymatic assays to the mode of action of these agents in intact cells. A number of compounds (i.e. zintevir and L-chicoric acid, on the one hand; and CGP64222 on the other hand) have recently been found to interact with virus-cell binding and viral entry in contrast to their proposed modes of action targeted at the integrase and transactivation process, respectively.
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PMID:Novel compounds in preclinical/early clinical development for the treatment of HIV infections. 1089 72

A large variety of natural products have been described as anti-HIV agents, and for a portion thereof the target of interaction has been identified. Cyanovirin-N, a 11-kDa protein from Cyanobacterium (blue-green alga) irreversibly inactivates HIV and also aborts cell-to-cell fusion and transmission of HIV, due to its high-affinity interaction with gp120. Various sulfated polysaccharides extracted from seaweeds (i.e., Nothogenia fastigiata, Aghardhiella tenera) inhibit the virus adsorption process. Ingenol derivatives may inhibit virus adsorption at least in part through down-regulation of CD4 molecules on the host cells. Inhibition of virus adsorption by flavanoids such as (-)epicatechin and its 3-O-gallate has been attributed to an irreversible interaction with gp120 (although these compounds are also known as reverse transcriptase inhibitors). For the triterpene glycyrrhizin (extracted from the licorice root Glycyrrhiza radix) the mode of anti-HIV action may at least in part be attributed to interference with virus-cell binding. The mannose-specific plant lectins from Galanthus, Hippeastrum, Narcissus, Epipac tis helleborine, and Listera ovata, and the N-acetylgl ucosamine-specific lectin from Urtica dioica would primarily be targeted at the virus-cell fusion process. Various other natural products seem to qualify as HIV-cell fusion inhibitors: the siamycins [siamycin I (BMY-29304), siamycin II (RP 71955, BMY 29303), and NP-06 (FR901724)] which are tricyclic 21-amino-acid peptides isolated from Streptomyces spp that differ from one another only at position 4 or 17 (valine or isoleucine in each case); the betulinic acid derivative RPR 103611, and the peptides tachyplesin and polyphemusin which are highly abundant in hemocyte debris of the horseshoe crabs Tachypleus tridentatus and Limulus polyphemus, i.e., the 18-amino-acid peptide T22 from which T134 has been derived. Both T22 and T134 have been shown to block T-tropic X4 HIV-1 strains through a specific antagonism with the HIV corecept or CXCR4. A number of natural products have been reported to interact with the reverse transcriptase, i.e., baicalin, avarol, avarone, psychotrine, phloroglucinol derivatives, and, in particular, calanolides (from the tropical rainforest tree, Calophyllum lanigerum) and inophyllums (from the Malaysian tree, Calophyllum inophyllum). The natural marine substance illimaquinone would be targeted at the RNase H function of the reverse transcriptase. Curcumin (diferuloylmethane, from turmeric, the roots/rhizomes of Curcuma spp), dicaffeoylquinic and dicaffeoylt artaric acids, L-chicoric acid, and a number of fungal metabolites (equisetin, phomasetin, oteromycin, and integric acid) have all been proposed as HIV-1 integrase inhibitors. Yet, we have recently shown that L-c hicoric acid owes its anti-HIV activity to a specific interaction with the viral envelope gp120 rather than integrase. A number of compounds would be able to inhibit HIV-1 gene expression at the transcription level: the flavonoid chrysin (through inhibition of casein kinase II, the antibacter ial peptides melittin (from bee venom) and cecropin, and EM2487, a novel substance produced by Streptomyces. (ABSTRACT TRUNCATED)
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PMID:Current lead natural products for the chemotherapy of human immunodeficiency virus (HIV) infection. 1093 47

Some colonic and neuronal cells which are CD4- but galactosyl ceramide-positive are susceptible to infection with HIV-1. We have previously shown that the T-cell tropic V3 loop of HIV-1 gp120 serves as a primary viral determinant for infectivity of CD4- neuronal cells. However, the nature of the V3 loop of HIV-1 needed for infection and the V3 loop's interaction with coreceptors on colonic epithelial cells have not been fully analyzed. By using HIV-1 molecular clones, we show that the T-cell tropic V3 domain is critical for HIV-1 infection of colonic HT-29 epithelial cells. Because T-cell tropic HIV-1 can use CXCR4 as a coreceptor in T cells, we set out to determine the role of CXCR4 during infection of HT-29 cells. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and immunostaining, we show that these epithelial cells of colonic origin express the chemokine receptor CXCR4. Importantly, antibody against CXCR4 or a neutralizing antibody against HIV-1 gp120 V3 loop blocks T-cell tropic HIV-1 entry into HT-29 cells. These data indicate that the V3 loop of HIV-1 and the chemokine receptor CXCR4 are both critical for HIV-1 infection of colonic HT-29 epithelial cells. An HIV-1 T-tropic virus may be responsible for the infection of human colonic epithelial cells in vivo.
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PMID:T-tropic sequence of the V3 loop is critical for HIV-1 infection of CXCR4-positive colonic HT-29 epithelial cells. 1106 98

The role of placenta in vertical transmission is not yet fully understood. A protective role of the placenta during gestation is suggested by the finding that caesarian sections reduce the risk of transmission of human immunodeficiency virus (HIV)-1 from mother to child three- to fourfold. Here we investigated whether the immunological milieu of the placenta might be important in HIV-1 transmission. In situ imaging of immunohistochemically stained placenta sections and reverse transcriptase-polymerase chain reaction demonstrated a fourfold increase in CCR5:CXCR4 expression ratio in placentae from transmitting women compared to placentae from nontransmitting women. This chemokine receptor repertoire was consistent with an up-regulation of interleukin-4 and interleukin-10 expression in placentae from nontransmitting placentae compared to transmitting placentae. In situ imaging demonstrated that CCR5 and CXCR4 were expressed on placental macrophages and lymphocytes but not in trophoblasts. Simultaneous immunofluorescence/ultrasensitive in situ hybridization for HIV-1 gag-pol mRNA revealed that HIV-1 infects primarily CXCR4-expressing cells in placentae from nontransmitting women whereas predominantly CCR5-expressing cells were infected in placentae from transmitting women. These data are consistent with transmission of a homogeneous population of nonsyncytium-inducing HIV-1 isolates that use CCR5 as co-receptor.
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PMID:Up-regulation of CCR5 expression in the placenta is associated with human immunodeficiency virus-1 vertical transmission. 1110 53

The lung represents a potential target during HIV infection, and the onset of AIDS is associated with severe pulmonary complications in many patients. T-lymphocytes and alveolar macrophages form the majority of HIV-infected cells in the lung. However, other cell types in the lung could participate in HIV-mediated lung pathology and their role has not been investigated. The aims of this study were to determine if human lung microvascular endothelial cells (HLMEC) express HIV receptor and coreceptors, and if HIV can directly infect HLMEC. Specifically, we wished to determine if these cells constitute a viral reservoir in the lung, and if HIV-1 envelope proteins induce cytotoxic effects on HLMEC. Our results showed that by flow cytometry, HLMEC failed to express any CXCR4 or CCR5 on their surface. In contrast, RT-PCR revealed the presence of CXCR4 and CCR5 mRNA, but not CD4 in HLMEC. Two dual-tropic HIV-1 isolates failed to infect HLMEC in vitro, as determined by (1) p24 antigen capture ELISA, (2) reverse transcriptase assay, RT-PCR, and (3) DNA PCR. However, a recombinant HIV-1 gp120 preparation induced apoptotic cell death of HLMEC. These data support the hypothesis that no productive HIV-1 infection of HLMEC occurs in vitro. This suggests that in vivo, HLMEC may not be a major reservoir of HIV in the lung and the primary route for HIV invasion of the lung. Thus, while other mechanisms must play a role in HIV invasion and subsequent dissemination in the lung, lung endothelial cells do represent potential targets for the lethal effects of HIV viral proteins.
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PMID:Analysis of human lung endothelial cells for susceptibility to HIV type 1 infection, coreceptor expression, and cytotoxicity of gp120 protein. 1117 82


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