Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019693 (HIV)
 170,526 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CCR5-using (R5) human immunodeficiency virus type 1 (HIV-1) is a major viral population that is transmitted by sexual intercourse and that replicates in infected individuals during the asymptomatic stage of HIV-1 infection, suggesting that agents effective against R5 HIV-1 can be expected to prevent viral transmission and delay disease progression. However, R5 HIV-1 is unable to replicate in human T-cell lines, which is an apparent obstacle to efficient and reliable susceptibility tests of compounds for their activities against R5 HIV-1. To establish a simple and rapid assay system for the monitoring of R5 HIV-1 replication and drug susceptibility, we have established a novel reporter T-cell line, MOCHA (which represents MOLT-4 cells stably expressing CCR5 and carrying the HIV-1 long terminal repeat-driven secretory alkaline phosphatase). Cells of this cell line express CD4, CXCR4, and CCR5 on their surfaces and secrete human placental alkaline phosphatase into the culture supernatants during HIV-1 infection. MOCHA cells proved to be highly permissive for the replication of R5 HIV-1 as well as CXCR4-using (X4) HIV-1, and the alkaline phosphatase activity increased in parallel with increasing HIV-1 p24 antigen levels in the culture supernatants. When HIV-1 reverse transcriptase inhibitors, protease inhibitors, and entry inhibitors, including the CCR5 antagonist TAK-779 and the CXCR4 antagonist AMD3100, were examined for their inhibitory effects on R5 and X4 HIV-1 replication in MOCHA cells, the antiviral activities of these compounds were found to be almost identical to those previously reported in peripheral blood mononuclear cells. Thus, MOCHA cells are an extremely useful tool for detection of R5 and X4 HIV-1 replication and drug susceptibility tests.
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PMID:Novel reporter T-cell line highly susceptible to both CCR5- and CXCR4-using human immunodeficiency virus type 1 and its application to drug susceptibility tests. 1279 75

Propagation of R5 strains of HIV-1 on CD4 lymphocytes and macrophages requires expression of the CCR5 coreceptor on the cell surface. Individuals lacking CCR5 (CCR5 Delta 32 homozygous genotype) are phenotypically normal and resistant to infection with HIV-1. CCR5 expression on lymphocytes depends on signaling through the IL-2 receptor. By FACS analysis we demonstrate that rapamycin (RAPA), a drug that disrupts IL-2 receptor signaling, reduces CCR5 surface expression on T cells at concentrations as low as 1 nM. In addition, lower concentrations of RAPA (0.01 nM) were sufficient to reduce CCR5 surface expression on maturing monocytes. PCR analysis on peripheral blood mononuclear cells (PBMCs) showed that RAPA interfered with CCR5 expression at the transcriptional level. Reduced expression of CCR5 on PBMCs cultured in the presence of RAPA was associated with increased extracellular levels of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta. In infectivity assays, RAPA suppressed the replication of R5 strains of HIV-1 both in PBMC and macrophage cultures. In total PBMC cultures, RAPA-mediated inhibition of CCR5-using strains of HIV-1 occurred at 0.01 nM, a concentration of drug that is approximately 103 times lower than therapeutic through levels of drug in renal transplant recipients. In addition, RAPA enhanced the antiviral activity of the CCR5 antagonist TAK-779. These results suggest that low concentrations of RAPA may have a role in both the treatment and prevention of HIV-1 infection.
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PMID:Rapamycin causes down-regulation of CCR5 and accumulation of anti-HIV beta-chemokines: an approach to suppress R5 strains of HIV-1. 1291 36

HIV replication occurs principally in activated CD4+ T cells and macrophages. The HIV-1 Tat protein is essential for HIV replication and requires a cellular protein kinase activity termed TAK/P-TEFb, composed of CDK9 and cyclin T1, for its transactivation function. This article reviews recent work indicating that under some circumstances TAK/P-TEFb is likely to be limiting for HIV replication in CD4+ T cells and macrophages, and discusses mechanisms of regulation of the TAK/P-TEFb subunits in these cell types. In resting CD4+ T lymphocytes, TAK/P-TEFb function is low. Following lymphocyte activation, even under conditions of minimal activation in which activation markers and cellular proliferation are not induced, both CDK9 and cyclin T1 mRNA and protein levels are increased, leading to an induction of TAK/P-TEFb kinase activity that correlates with increased viral replication. In macrophages, regulation of TAK/P-TEFb involves mechanisms distinct from those in lymphocytes. In freshly isolated monocytes, CDK9 protein levels are high, while cyclin T1 protein levels are low to undetectable. Cyclin T1 protein expression is up-regulated during early macrophage differentiation by a mechanism that involves post-transcriptional regulation. Later during differentiation, cyclin T1 expression becomes shut off by a post-transcriptional mechanism, and this correlates with a decrease in Tat transactivation. Interestingly, cyclin T1 can be re-induced with lipopolysaccharide (LPS). These findings suggest that changes in cyclin T1 expression can influence HIV-1 replication levels in monocytes and macrophages. Important areas for future research on Tat and TAK/P-TEFb function are discussed.
Curr HIV Res 2003 Oct
PMID:Regulation of TAK/P-TEFb in CD4+ T lymphocytes and macrophages. 1504 26

The chemokine receptors CXCR4 and CCR5 are used as the main co-receptors by the T-cell-tropic (CXCR4-dependent, X4) and macrophage-tropic (CCR5-dependent, R5) HIV-1 strains, respectively, for entering their target cells. The natural ligands for CXCR4, the CXC-chemokine SDF-1 and CCR5, the CC-chemokines RANTES, MIP-1alpha and MIP-1beta are described to inhibit viral entry. In this review we focus on chemokine receptor/HIV co-receptor inhibitors. Modified chemokines such as Met-RANTES and AOP-RANTES showed antiviral activity against R5 viruses. Several low-molecular weight CCR5 antagonists have been described (such as TAK-779 and SCH-C) with potent antiviral activity. The latter compound is also orally available and is able to decrease R5 viral load levels in HIV-infected subjects. Several peptidic compounds, such as T22 (an 18-mer), T134 (a 14-mer), ALX40-4C (a 9-mer) and CGP 64222 (also a 9-mer) have anti-HIV activity and have been identified as CXCR4 antagonists. Also, the HIV-1 Tat protein has been described as a "natural" CXCR4 antagonist with anti-HIV-1 activity. The most potent and specific CXCR4 antagonists are the bicyclam derivatives, which also potently inhibit X4 HIV replication. AMD3100 has proved to be a highly specific CXCR4 antagonist, which consistently blocks X4 viral replication in any target cell-type evaluated so far. AMD3100 was selected as the clinical drug candidate, which, after initial phase I (safety) studies, had proceeded to phase II (efficacy) trials. The compound dose-dependently inhibited X4 viruses after 10 days of continuous infusion of the drug. Recently, the orally bioavailable CXCR4 antagonist, AMD070, is presented as a candidate HIV drug. We believe that chemokine receptor antagonists will become important new antiviral drugs to combat AIDS. Both (CXCR4 and CCR5) chemokine receptor inhibitors will be needed in combination to inhibit viral replication and even in combinations of antiviral drugs that also target other aspects of the HIV replication cycle, such as reverse transcriptase and protease, to obtain optimum therapeutic effects.
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PMID:HIV co-receptors as targets for antiviral therapy. 1513 47

We identified a novel spirodiketopiperazine (SDP) derivative, AK602/ONO4128/GW873140, which specifically blocked the binding of macrophage inflammatory protein 1alpha (MIP-1alpha) to CCR5 with a high affinity (K(d) of approximately 3 nM), potently blocked human immunodeficiency virus type 1 (HIV-1) gp120/CCR5 binding and exerted potent activity against a wide spectrum of laboratory and primary R5 HIV-1 isolates, including multidrug-resistant HIV-1 (HIV-1(MDR)) (50% inhibitory concentration values of 0.1 to 0.6 nM) in vitro. AK602 competitively blocked the binding to CCR5 expressed on Chinese hamster ovary cells of two monoclonal antibodies, 45523, directed against multidomain epitopes of CCR5, and 45531, specific against the C-terminal half of the second extracellular loop (ECL2B) of CCR5. AK602, despite its much greater anti-HIV-1 activity than other previously published CCR5 inhibitors, including TAK-779 and SCH-C, preserved RANTES (regulated on activation normal T-cell expressed and secreted) and MIP-1beta binding to CCR5(+) cells and their functions, including CC-chemokine-induced chemotaxis and CCR5 internalization, while TAK-779 and SCH-C fully blocked the CC-chemokine/CCR5 interactions. Pharmacokinetic studies revealed favorable oral bioavailability in rodents. These data warrant further development of AK602 as a potential therapeutic for HIV-1 infection.
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PMID:Spirodiketopiperazine-based CCR5 inhibitor which preserves CC-chemokine/CCR5 interactions and exerts potent activity against R5 human immunodeficiency virus type 1 in vitro. 1528 Apr 74

HIV-1 infection is initiated by the interaction of the envelope glycoprotein gp120 with the cellular receptor CD4 that triggers conformational changes in gp120 necessary for subsequent interaction with a coreceptor CCR5 (or CXCR4). The CD4-induced (CD4i) conformation of gp120 can be mimicked by a full-length single chain (FLSC) protein consisting of gp120 linked with the D1D2 domains of CD4 by a 20-amino-acid linker. We have used this protein to establish a flow cytometry-based assay and an ELISA-based assay to identify inhibitors that block the binding of gp120 to CCR5. Both assays are specific for detecting the known CCR5 antagonist TAK-779, but the ELISA-based assay was more sensitive, simple, inexpensive, and rapid; thus, it can be adapted to high throughput screening (HTS). The ELISA-based method was validated with a diverse set of known antagonists, for example, TAK-779, AOP-RANTES, PSC-RANTES, and several mAbs.
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PMID:A novel assay to identify entry inhibitors that block binding of HIV-1 gp120 to CCR5. 1532 3

Cdk9, a member of the cyclin-dependent kinase family, is the catalytic subunit of P-TEFb, a protein kinase complex that stimulates transcriptional elongation. Cdk9, complexed with its regulatory partner cyclin T1, serves as the cellular mediator of the transactivation function of the HIV Tat protein. There are two known isoforms of Cdk9: a 42 kDa protein (42k, originally identified as PITALRE) and a more recently identified 55 kDa form (55k). To investigate possible functional differences between the two isoforms, we examined their kinase activities, their subcellular distributions, and their expression levels in primary cells relevant to HIV infection. Both isoforms were found to hyper-phosphorylate the carboxyl-terminal domain of the largest subunit of RNA polymerase II and displayed identical phosphorylation patterns with 144 peptide substrates. Epitope-tagged transiently-expressed Cdk9 42k localized diffusely in the nucleoplasm, while Cdk9 55k accumulated in the nucleolus. In primary undifferentiated monocytes, Cdk9 55k expression was not detected although 42k was present at high levels; however, 55k expression was induced upon macrophage differentiation. In primary lymphocytes, the levels of 55k decreased or remained steady following activation, while the levels of 42k increased. The promoter for 42k was significantly stronger than that of 55k in HeLa cells, and only the 42k promoter was responsive to activation signals in primary lymphocytes. These results indicate that expression of the 42k and 55k isoforms is differentially regulated and suggest that functional differences between the 42k and 55k isoforms of Cdk9 are likely to depend on access to substrates based on their differential subcellular localization and expression patterns.
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PMID:Differential localization and expression of the Cdk9 42k and 55k isoforms. 1545 30

The human immunodeficiency virus type 1 (HIV-1) Tat protein recruits positive transcription elongation factor b (P-TEFb) to the transactivation response (TAR) RNA structure to facilitate formation of processive transcription elongation complexes (TECs). Here we examine the role of the Tat/TAR-specified cyclin-dependent kinase 9 (CDK9) kinase activity in regulation of HIV-1 transcription elongation and histone methylation. In HIV-1 TECs, P-TEFb phosphorylates the RNA polymerase II (RNAP II) carboxyl-terminal domain (CTD) and the transcription elongation factors SPT5 and Tat-SF1 in a Tat/TAR-dependent manner. Using in vivo chromatin immunoprecipitation analysis, we demonstrate the following distinct properties of the HIV-1 transcription complexes. First, the RNAP II CTD is phosphorylated at Ser 2 and Ser 5 near the promoter and at downstream coding regions. Second, the stable association of SPT5 with the TECs is dependent upon P-TEFb kinase activity. Third, P-TEFb kinase activity is critical for the induction of methylation of histone H3 at lysine 4 and lysine 36 on HIV-1 genes. Flavopiridol, a potent P-TEFb kinase inhibitor, inhibits CTD phosphorylation, stable SPT5 binding, and histone methylation, suggesting that its potent antiviral activity is due to its ability to inhibit several critical and unique steps in HIV-1 transcription elongation.
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PMID:Coordination of transcription factor phosphorylation and histone methylation by the P-TEFb kinase during human immunodeficiency virus type 1 transcription. 1556 63

Considerable advances have been made in the last years in the design of derivatives acting as inhibitors of HIV entry and fusion. The discovery of chemokines focused the attention on cellular coreceptors used by the virus for entering within cells, and consequently the various steps of such processes have been characterized in detail. Intense research led to a wide range of effective compounds that are able to inhibit the initial steps of HIV life cycle. All steps in the process of HIV entry into the cell may be targeted by specific compounds that may be developed as novel types of antiretrovirals. Thus, several inhibitors of the gp120-CD4 interaction have been detected so far (zintevir, FP-21399 and BMS-378806 in clinical trials). Small molecule chemokine receptor antagonists acting as HIV entry inhibitors also were described in the last period, which interact both with the CXCR4 coreceptor (such as AMD3100; AMD3465; ALX40-4C; T22, T134 and T140), or which are antagonist of the CCR5 coreceptor (TAK-779, TAK-220, SCH-C, SCH-D, E913, AK-602, UK-427857 and NSC 651016 in clinical trials), together with new types of fusion inhibitors possessing the same mechanism of action as enfuvirtide (such as T1249). Recently, a third family of antivirals started to be used clinically (in addition to the reverse transcriptase and protease inhibitors), with the advent of enfuvirtide (T20), the first fusion inhibitor to be approved as an anti-HIV agent. Some of these compounds demonstrated in vitro synergism with other classes of antivirals, offering thus the rationale for their combination in therapies for HIV-infected individuals. Many HIV entry and fusion inhibitors are currently being investigated in controlled clinical trials, and a number of them is bioavailable as oral formulations. This is an essential feature for an extended use of these compounds with the purpose of ameliorating adherence of patients to these medications and preventing the development of drug resistance.
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PMID:New advances in HIV entry inhibitors development. 1557 75

The cellular positive transcription elongation factor b (P-TEFb), containing cyclin T1 and cyclin-dependent kinase 9 (CDK9), interacts with the human immunodeficiency virus, type 1 (HIV-1) regulatory protein Tat to enable viral transcription and replication. Cyclin T1 is an unusually long cyclin and is engaged by cellular regulatory proteins. Previous studies showed that the granulin/epithelin precursor (GEP) binds the histidine-rich region of cyclin T1 and inhibits P-TEFb function. GEP is composed of repeats that vary in sequence and properties. GEP also binds directly to Tat. Here we show that GEP and some of its constituent granulin repeats can inhibit HIV-1 transcription via Tat without directly binding to cyclin T1. The interactions of granulins with Tat and cyclin T1 differ with respect to their binding sites and divalent cation requirements, and we identified granulin repeats that bind differentially to Tat and cyclin T1. Granulins DE and E bind Tat but do not interact directly with cyclin T1. These granulins are present in complexes with Tat and P-TEFb in which Tat forms a bridge between the cellular proteins. Granulins DE and E repress transcription from the HIV-1 LTR and gene expression from the viral genome, raising the possibility of developing granulin-based inhibitors of viral infection.
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PMID:Granulin and granulin repeats interact with the Tat.P-TEFb complex and inhibit Tat transactivation. 1565 95


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