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)

Serum thymidine kinase (TK), measured using Prolifigen TK-REA, from AB Sangtec Medical, was investigated in 24 HIV seropositive patients without immunological alterations, 26 seropositives with immunological alterations, 125 LAS, 25 ARC, and 20 AIDS. Subjects with serological markers of prior EBV, HBV, and CMV infection were included but none with acute infectious mononucleosis or acute viral hepatitis. Serum TK was elevated from the beginning of the HIV infection, the seropositive stage, and more markedly afterwards during the course of the infection, with a close correlation with the stage. TK also increased during AZT treatment, due to bone-marrow toxicity. On lowering the dosage or discontinuing the drug TK returned to basal levels. Although the rise in serum may well not be correlated only with the HIV infection, it does add to the picture given by other clinical and/or laboratory methods. Serum TK can be a helpful laboratory test in the follow-up of patients with HIV infection, especially when serum levels are disproportionate to the stage, opportunistic infections, lymphoproliferative malignancies. In such cases bone-marrow toxicity due to treatment can be suspected.
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PMID:Serum thymidine kinase (TK) evaluation in HIV infection. 274 46

Plasmids were constructed whereby the expression of a reporter gene, either the cDNA corresponding to the secreted form of human alkaline phosphatase (SEAP) or the herpes simplex virus type 1 (HSV1) thymidine kinase (tk) gene, was rendered dependent upon the expression of the human immunodeficiency virus type 1 (HIV1) tat and rev proteins. The SEAP or tk genes were placed between HIV1 splice donor and acceptor sites. One SEAP construct carried a series of alternating splice donor and acceptor sites. In all cases, the rev response element mapped within an intron. Despite such mimicry of the HIV1 genome, residual expression of the reporter gene in the absence of tat and rev was observed. These results, as well as non-specific T-cell recruitment, suggest limits to the specificity of using HIV-activated toxic gene expression to kill HIV-infected cells.
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PMID:Residual expression of reporter genes in constructs mimicking HIV genome organization. 748 Oct 89

L-beta-Deoxythymidine (L-dT), the optical enantiomer of D-beta-deoxythymidine (D-dT), and L-enantiomers of nucleoside analogs, such as 5-iodo-2'-deoxy-L-uridine (L-IdU) and E-5-(2-bromovinyl)-2'-deoxy-L-uridine (L-BVdU), are not recognized in vitro by human cytosolic thymidine kinase (TK), but are phosphorylated by herpes simplex virus type 1 (HSV-1) TK and inhibit HSV-1 proliferation in infected cells. Here we report that: (i) L-dT is selectively phosphorylated in vivo to L-dTMP by HSV-1 TK and L-dTMP is further phosphorylated to the di- and triphosphate forms by non-stereospecific cellular kinases; (ii) L-dTTP not only inhibits HSV-1 DNA polymerase in vitro, but also human DNA polymerase alpha, gamma, delta and epsilon, human immunodeficiency virus reverse transcriptase (HIV-1 RT), Escherichia coli DNA polymerase 1 and calf thymus terminal transferase, although DNA polymerase beta was resistant; (iii) whereas DNA polymerase beta, gamma, delta and epsilon are unable to utilize L-dTTP as a substrate, the other DNA polymerases clearly incorporate at least one L-dTMP residue, with DNA polymerase alpha and HIV-1 RT able to further elongate the DNA chain by catalyzing the formation of the phosphodiester bond between the incorporated L-dTMP and an incoming L-dTTP; (iv) incorporated L-nucleotides at the 3'-OH terminus make DNA more resistant to 3'-->5' exonucleases. In conclusion, our results suggest a possible mechanism for the inhibition of viral proliferation by L-nucleosides.
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PMID:Stereospecificity of human DNA polymerases alpha, beta, gamma, delta and epsilon, HIV-reverse transcriptase, HSV-1 DNA polymerase, calf thymus terminal transferase and Escherichia coli DNA polymerase I in recognizing D- and L-thymidine 5'-triphosphate as substrate. 754 86

Azidothymidine (zidovudine, AZT) used for treatment of HIV infection blocks the viral reverse transcriptase after phosphorylation by cellular enzymes. The first step in this reaction is the formation of AZT monophosphate, primarily catalyzed by host cytoplasmatic thymidine kinase (TK1). The activity of TK1 was determined in extracts of PHA-stimulated peripheral blood mononuclear cells (PBMCs) from 20 healthy volunteers and 49 HIV-infected patients at different stages of disease. In both groups we found a large intra- and interindividual variation of TK activity. Because TK1 expression is cell cycle regulated the proportion of stimulated cells was determined in the samples and the median thymidine kinase activity calculated. It was 3.0 pmol/mg/min x % S phase in the HIV-seronegative group and 1.1 pmol/mg/min x % S phase in HIV-infected individuals. The difference in thymidine kinase activity is statistically significant (p = 0.0001). The concentration of TK1 protein in the same extracts was also determined by immunoblotting. A positive correlation (r = 0.74) was observed between TK activity and amount of TK1 protein. The reason for this downregulation of TK is still unknown but may be related to the anergy observed in lymphocytes from HIV-infected persons. The reduced capacity for intracellular phosphorylation of AZT in HIV-infected individuals may be an important factor in the emergence of clinical AZT resistance and should also be accounted for in testing AZT resistance in vitro with PBMCs from healthy blood donors.
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PMID:Decreased thymidine kinase levels in peripheral blood cells from HIV-seropositive individuals: implications for zidovudine metabolism. 754 7

The synthesis, in vitro anti-HIV-1 activity, and decomposition pathways of several mononucleoside phosphotriester derivatives of 3'-azido-2',3'-dideoxythymidine (AZT) incorporating a new kind of carboxylate esterase-labile transient phosphate-protecting group, namely, S-acyl-2-thioethyl, are reported. All the described compounds showed marked antiviral activity in thymidine kinase-deficient CEM cells in which AZT was virtually inactive. The results strongly support the hypothesis that such pronucleotides exert their biological effects via intracellular delivery of the 5'-mononucleotide of AZT. This point was corroborated by decomposition studies in cell extracts and culture medium.
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PMID:Mononucleoside phosphotriester derivatives with S-acyl-2-thioethyl bioreversible phosphate-protecting groups: intracellular delivery of 3'-azido-2',3'-dideoxythymidine 5'-monophosphate. 756 27

3'-Azido-2',3'-dideoxy-5-iodouridine (AzIdUrd) and 3'-azido-2',3'-dideoxy-5-bromouridine (AzBdUrd), previously shown to be potent and selective inhibitors of human immunodeficiency virus replication in vitro were minimally toxic to the uninfected human lymphoid cell line H9 (IC50 = 197 and 590 microM, respectively). Both compounds strongly inhibited the incorporation of [3H]thymidine but not [3H]deoxyadenosine into DNA, and we observed no significant inhibition of [3H]uridine incorporation into RNA or [3H]amino acid incorporation into protein. Exposure of H9 cells to AzIdUrd or AzBdUrd (100 microM, 24 hr) and pulse-labeling with [3H]thymidine resulted in approximately 80% reduction in levels of tritiated dTMP, dTDP, and dTTP relative to control. [125I]AzIdUrd was phosphorylated rapidly in H9 cells with the monophosphate accounting for over 90% of total soluble radioactivity. A relatively low but stable level of AzIdUTP was maintained over a 12-hr period. [125I]AzIdUrd was phosphorylated by a cell free extract of H9 cells at a rate approximately three times that of thymidine and its phosphorylation was inhibited by excess thymidine. AzIdUrd was found to be a competitive inhibitor of cytosolic thymidine kinase with a Ki of 2.63 microM and AzIdUMP a weak competitive inhibitor of thymidylate kinase with a Ki of 55.3 microM. Both AzIdUTP and AzBdUTP were potent competitive inhibitors of HIV-1 reverse transcriptase (Ki = 0.028 and 0.043 microM, respectively) and relatively poor inhibitors of H9 cell DNA polymerase alpha (Ki = 42.0 and 42.7 microM, respectively). Thus, the high therapeutic index of these compounds is due to the sensitivity of the viral reverse transcriptase, coupled with the relative insensitivity of the host cell DNA polymerase alpha.
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PMID:Metabolism and mode of selective inhibition of human immunodeficiency virus replication by 3'-azido-2',3'-dideoxy-5-iodouridine and 3'-azido-2',3'-dideoxy-5-bromouridine. 767 40

Cellular expression of the herpes simplex virus type 1 thymidine kinase (HSV1-TK) gene promotes cell death in the presence of specific nucleoside analog substrates such as acyclovir (ACV). We have reported that lymphoid CD4+ cells harboring an HSV1-TK gene, under the transcriptional control of the HIV-1 long terminal repeat (HUT-TK), are completely protected from HIV-1 spread in the presence of 10 microM ACV. In this report we clarify the efficiency, generality, and mechanism of this protective effect. We show that the protection from HIV-1 spread in HUT-TK cells obtains from both an inhibition of HIV reverse transcription by ACV metabolites and an HIV-induced and ACV-dependent cell killing. We also demonstrate that monocytic cells harboring the HIV-1-inducible HSV1-TK gene are protected from HIV spread in the presence of ACV. These observations facilitate the design of therapeutic strategies to limit HIV replication based on HSV1-TK expression.
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PMID:Expression of a Tat-inducible herpes simplex virus-thymidine kinase gene protects acyclovir-treated CD4 cells from HIV-1 spread by conditional suicide and inhibition of reverse transcription. 783 5

Human immunodeficiency virus (HIV) resistance to the nonnucleoside reverse transcriptase inhibitors emerges very rapidly under selection in culture and in patients. In contrast, zidovudine (3'-azido-3'-deoxythymidine [AZT])-resistant HIV generally emerges in patients only after more-prolonged therapy. Although HIV can be cultured from many patients shortly after the initiation of AZT treatment, characterization of the virus that is cultured generally indicates that it is sensitive to AZT. To initiate an evaluation of the mechanisms contributing to early HIV breakthrough in the presence of AZT and other nucleoside analogs, we have utilized replication-defective HIV encoding reporter genes. These recombinant HIV allow a quantitative analysis of a single cycle of infection. Results with these defective HIV indicate that early infection in the presence of AZT often results from the infection of a cell which is refractory to the antiretroviral effects of AZT. Characterization of a cell line derived from one such cell has demonstrated decreased accumulation of AZT triphosphate, increased phosphorylation of thymidine to thymidine triphosphate, and increased levels of thymidine kinase activity. In addition, AZT inhibition of replication-competent HIV infection is also significantly impaired in this cell line. Attempts to detect and characterize the mechanisms responsible for early viral infection after initiation of AZT therapy may result in the development of new strategies for prolonged suppression of viral infection prior to the emergence of drug-resistant virus.
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PMID:Sanctuary growth of human immunodeficiency virus in the presence of 3'-azido-3'-deoxythymidine. 785 95

AZT is an inhibitor of HIV reverse transcriptase which active form is AZT-triphosphate. Its clinical efficacy is limited by its toxicity and the emergence of mutant resistant viruses. This might be due to an unfficient cellular metabolism of AZT which leads to the intracellular accumulation of AZT monophosphate. We tested a possible enhancement of this metabolism with the HSV1 thymidine kinase, an enzyme that also possesses a good thymidilate kinase activity. We show that, compared to parental cells, the proportion of AZT triphosphate is increased 3 fold in HSV1-TK expressing cells, and that inhibition of HIV replication in these cells requires 3 to 10 fold less AZT. This observation forms the basis for a new gene therapy strategy named genetically controlled pharmacomodulation.
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PMID:[Genetically controlled pharmacomodulation: application to the treatment of HIV infection]. 788 39

Moloney murine leukemia virua (MoMuLV)-derived retroviral vectors were engineered to express human immunodeficiency virus type 1 (HIV-1) packaging (psi) signal and Rev response element (RRE) sequences in either sense or antisense orientation. The RRE sequences were expressed under the control of the herpes simplex virus (HSV) thymidine kinase (tk) promoter fused to the HIV-1 trans-activation-responsive (TAR) element, while the psi signal sequences were expressed under control of the HSV tk promoter. Both RRE and psi signal sequences were expressed as part of the 3' untranslated region of the neomycin phosphotransferase (neo) mRNA. The constructs were used to transfect/infect packaging cell lines and the retroviral vector particles released were used to infect a human CD4+ lymphocyte-derived MT4 cell line. The stable MT4 transformants, harboring proviral vector DNA expressing one to two copies of HIV-1 RRE and psi signal in either antisense or sense orientation, were each tested for their susceptibility to HIV-1 infection. Compared to the results obtained with the control cells lacking any of the test DNA sequences, the rate of HIV-1 production remained unaltered in RRE1+ (sense RNA containing a single copy of RRE) RNA-containing cells, whereas it was delayed in cells expressing both RRE2+ (sense RNA containing two copies of RRE) and RRE1- (antisense RNA containing a single copy of RRE) RNA-expressing cells. In cells expressing HIV-1 psi signal, HIV-1 production remained unaltered in psi + RNA-expressing cells, whereas it was delayed by up to 30 days in psi - RNA-expressing cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of HIV-1 multiplication in a human CD4+ lymphocytic cell line expressing antisense and sense RNA molecules containing HIV-1 packaging signal and Rev response element(s). 791 62


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