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)

Several dideoxynucleosides, including 3'-azido-2',3'-dideoxythymidine (zidovudine, azidothymidine, AZT), 2',3'-dideoxycytidine (ddC), and 2',3'-dideoxyinosine (ddI), have been shown to be potent inhibitors of human immunodeficiency virus (HIV) replication in human T cells and macrophages. These compounds undergo anabolic phosphorylation within target cells to a 3'-triphosphate moiety; as triphosphates, they act at the level of HIV DNA polymerase (reverse transcriptase). AZT has been shown to reduce the morbidity and mortality of patients with severe HIV infection and to at least temporarily ameliorate certain cases of HIV-induced dementia. In phase 1 studies, ddC and ddI have been shown to induce immunologic and virologic improvements in patients with AIDS or related disorders; phase 2 studies of ddC and ddI are underway. The use of these drugs can be associated with toxicity. AZT can cause bone marrow toxicity or myositis with prolonged use, ddC can cause peripheral neuropathy at high doses, and ddI can cause sporadic pancreatitis and peripheral neuropathy at high doses. For each compound, however, a therapeutic window exists in which an anti-HIV effect can be attained without short-term toxicity in most patients. Dose-intensity appears to be an important determinant of the toxicity of dideoxynucleosides. Studies are underway to explore how the therapeutic profiles of these compounds may be enhanced by attention to scheduling or through the use of combination therapy.
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PMID:Initial clinical experience with dideoxynucleosides as single agents and in combination therapy. 207 27

Although the detection of antibodies to a specific pathogen is used initially as the assay of choice, direct detection of human retroviruses is difficult. First, only a small fraction of cells are infected in the peripheral blood and lymphatic tissue may serve as a reservoir for infection. Second, infected cells may harbor only a small number of copies of the viral sequences. Third, a latent infection marked by transcriptional dormancy is often established thereby obviating the use of proteins or RNA to detect the viruses. Fourth, closely related but distinct members of the onco-and lenti-virus families may complicate specific detection of a particular virus. An additional hurdle is viral heterogeneity. HIV variants, for example, have been identified within and among individuals harboring this virus. Accordingly, sensitive and specific detection of the human retroviruses seemingly requires specific amplification of viral DNA sequences prior to detection. In this regard, an in vitro DNA amplification procedure using DNA polymerase and termed the polymerase chain reaction (PCR) initially applied to human genetic diseases has been successfully applied to human retroviruses. A PCR-based assay has demonstrated utility for detecting infection: (1) prior to the generation of detectable antibodies, (2) in individuals with ambiguous or indeterminate serological status, (3) for neonatal screening, (4) by a specific type or multiple viruses, and (5) in therapeutic trials to allow the monitoring of infected cell load and viremia. It is also unlikely that the viruses identified to date represent all of the retroviruses responsible for human disease. Lymphatic disorders, in general, and immunodeficiencies, in particular, merit closer scrutiny for a retroviral etiologic agent.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The polymerase chain reaction (PCR): a valuable method for retroviral detection. 217 Jul 79

The development of potent anti-retroviral drugs is central to the control of human immunodeficiency virus (HIV) infection and the prevention of disease. Despite the benefit (albeit limited) shown by the early trials of zidovudine in patients with acquired immune deficiency syndrome (AIDS), there is general agreement that the best prospects for therapeutic intervention lie in the use of agents early in the infectious process. There is a definite possibility that this can be achieved if compounds acting specifically against virus encoded events can be found or developed. Although relatively simple in its structure, HIV is highly sophisticated in its mode of replication. The unique nature of the replication cycle of the retroviridae and the specific controlling mechanisms operative in HIV offer a number of possible targets for chemotherapeutic agents. The details of the structure and replication cycle of HIV will be briefly reviewed with comments on the possible virus specific and non-specific sites for potential antiviral drug development. The first specific target to be recognised was the unique, virus-associated enzyme, the reverse transcriptase (RNA directed DNA polymerase). Several inhibitors of reverse transcriptase were identified during the 1970s (e.g. suramin, HPA23, phosphonoformate). These have been found, in early trials, to be either insufficiently potent or too toxic to consider for development as anti-retroviral drugs. Indeed, knowledge of the pathogenesis of HIV infection led to the realisation that any putative drug would need to satisfy several important criteria; namely potency, low toxicity, easy administration, penetration of the blood-brain barrier and hopefully, low production costs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Targets for antiviral therapy of human immunodeficiency virus infection. 246 49

Reverse transcriptase from the human immunodeficiency virus type I (HIV-1) was expressed in E. coli and purified to near homogeneity. The enzyme was shown to contain reverse transcriptase, DNA polymerase and ribonuclease H activities. The DNA polymerase activity converted singly-primed phi X174 (+) DNA into the double-stranded form. Two third of the replication product is ligatable to covalently closed circular DNA (RFIV-form DNA) indicating that DNA synthesis by HIV reverse transcriptase can proceed until the enzyme matches the 5'-end of a pre-existing primer molecule. The in vitro accuracy of HIV reverse transcriptase was measured with the phi X174am16 reversion assay to be 1/7,400. Reversion rates for the individual mispairs were determined from pool bias studies to be 1/8,000 for the dGMP:T template mismatch, 1/35,000 for the dGMP:A template mismatch, 1/45,000 for the dAMP:G template mismatch, 1/73,000 for the dCMP:T template mispair, 1/140,000 for the dCMP:A template mispair, and 1/180,000 for the dGMP:G template mismatch. The dTMP:T template mispair was below the detection limit of the assay indicating a reversion rate of less than 1/300,000 for this particular mispair.
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PMID:Fidelity of human immunodeficiency virus type I reverse transcriptase in copying natural DNA. 246 38

Direct recognition of viral gene sequences can be used to detect human immunodeficiency virus (HIV-1) in clinical specimens. A modification of the polymerase chain reaction (PCR) for amplification of gene sequences was used for detection of HIV-1-specific RNA prepared from peripheral blood mononuclear cells (PBMC). The RNA served as a template for reverse transcriptase using primers derived from both the 3'ORF and the LTR regions of HIV-1, as well as from the control cellular sequences encoding beta-actin and T cell receptor. The resultant DNA was amplified with DNA polymerase. A transcriptional step using the bacteriophage T7 promoter recognition sequences, incorporated into the primers, was used to enhance the efficiency of the amplification process. This assay detects as few as 100 RNA copies of cloned HIV-1 genome. Starting with 1 microgram RNA isolated from PBMC, we were able to detect HIV-1 sequences in patients with symptomatic and asymptomatic HIV-1 infection. The inclusion of T cell-specific primers permitted simultaneous evaluation of an immunologic parameter. The PCR can be applied to RNA samples for detection of viral and cellular sequences and is a rapid and efficient means for detection of HIV-1 sequences as well as potentially informative cellular sequences.
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PMID:Confirmation of HIV infection using gene amplification. 252 May 45

Combinations of 3'-azido-3'-deoxythymidine and phosphonoformate produced a moderate synergistic inhibitory effect against human immunodeficiency virus type 1 in vitro at concentrations that are easily achieved in humans. The synergistic effect was more pronounced with increasing concentrations and was not secondary to toxic effects of the drugs. 3'-Azido-3'-deoxythymidine neither inhibited the replication of human cytomegalovirus in human embryonic lung fibroblasts nor interfered with the anticytomegalovirus effect of phosphonoformate. By using partially purified reverse transcriptase of human immunodeficiency virus type 1 and human cytomegalovirus DNA polymerase, various combinations of 3'-azido-3'-deoxythymidine-5'-triphosphate and phosphonoformate produced strong indications of additive interactions. The synergistic interactions in infected cells and the additive effects observed at the reverse transcriptase level indicate that mechanisms other than the reverse transcriptase may be of importance for the inhibition of human immunodeficiency virus replication by these two compounds. A concomitant treatment of cytomegalovirus infections, such as cytomegalovirus retinitis, with phosphonoformate in patients with acquired immunodeficiency syndrome receiving 3'-azido-3'-deoxythymidine may be appropriate, and this combination may also be useful in controlling human immunodeficiency virus infection.
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PMID:Combinations of 3'-azido-3'-deoxythymidine (zidovudine) and phosphonoformate (foscarnet) against human immunodeficiency virus type 1 and cytomegalovirus replication in vitro. 254 87

Thirty-five patients with active chronic hepatitis B (ACH-B) were evaluated. They were in stable replicative phase (HBeAg +; DNA polymerase and ALT stable in two determinations at least one month apart) and had not been infected by delta virus or HIV-1. Thirty-four patients were heterosexual and no patient was a drug abuser except one. The 23 initial cases were followed up for 15 months without therapy. The subsequent 12 cases were treated with maximal doses of 2.5 megaunits/m2 of lymphoblastoid alpha interferon (IFN-L) daily for two weeks and three times a week during 10 more weeks. While in the controls only two cases (8.69%) lost the DNA-polymerase activity and HBeAg, 5 treated patients (41.66%; p less than 0.05) developed seroconversion to nonreplicative phase. No patient from the control series lost the HBsAg; however, this happened in 2 treated patients (16.66%). These results show that IFN-L is effective in heterosexual patients with ACH-B in replicative phase without delta virus or HIV-I co-infection.
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PMID:[Treatment of chronic hepatitis B with lymphoblastoid alpha interferon]. 261 34

Zoster is the clinical manifestation of the endogenous reactivation of the varicella-zoster virus. Current observations of viral reactivation emphasize the role of cellular immunity and show an inverse correlation between the specific cellular immune response of the host and the incidence of zoster. Thus, immunocompromised persons like patients with immune deficiency syndrome, lymphoproliferative cancer, or immunosuppressive therapy are at a high risk for the development of disseminated zoster, which may either involve the skin only, or affect more than one organ. During the last few years zoster has been proved a prognostic marker for HIV-positive persons. The incidence of zoster and post-zoster neuralgia increases with advancing age. In young children, immunosuppressive therapy and varicella in utero or during the first year of life are the only risk factors for zoster infection. Prevention of dissemination has been one of the major goals in antiviral chemotherapy of zoster in immunocompromised patients. Among the antiviral drugs available at present, aciclovir has proved especially useful, acting as an inhibitor of viral DNA polymerase. It is well-tolerated and can be applied together with corticoids, analgetics, and retrovir. It is most effective in reducing complications of zoster.
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PMID:[New knowledge regarding herpes zoster]. 266 Apr 44

The 2',3'-dideoxynucleosides (ddNs) are currently undergoing clinical evaluation as antiretroviral agents in HIV-infected individuals. When phosphorylated, the ddNs (ddNTPs) function as chain-terminating substrate analogues with reverse transcriptase, thereby inhibiting HIV replication. These nucleoside analogues can also inhibit, by chain-terminating additions, the primitive lymphoid DNA polymerase, terminal deoxynucleotidyl transferase (TdT). To determine the effect of possible intracellular chain-terminating additions of ddNMPs by TdT, we exposed a series of TdT-positive and TdT-negative cell lines to 2',3'-dideoxyadenosine (ddA), a representative ddN. At ddA concentrations 25-fold higher than required for inhibition of HIV replication, progressive dose-related cytotoxicity was observed in the TdT-positive cell lines. This was accentuated by the adenosine deaminase inhibitor Coformycin (CF), presumably by enhancing the intracellular generation of ddATP from ddA. A central role of TdT in mediating the ddA/CF cytotoxicity was suggested by studies in a pre-B-cell line rendered TdT positive by infection with a TdT cDNA-containing retroviral vector. After a 48-hour continuous exposure period to 250 mumol/L ddA and 30 mumol/L CF, 30% cell death was observed in the TdT-negative parental line, whereas 90% cell death was observed in the TdT-positive daughter line. Exposure of fresh TdT-positive leukemic cells to ddA/CF for 72 hours ex vivo resulted in cytotoxicity (six cases of acute lymphocytic leukemia [ALL]) while not affecting TdT-negative acute leukemic cells (six cases). We conclude that ddA/CF selectively damages TdT-positive cells, presumably by chain-terminating additions of ddAMP, and that this may have therapeutic relevance in TdT-positive malignant disease.
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PMID:2',3'-Dideoxyadenosine is selectively toxic for TdT-positive cells. 283 1

The accuracy of DNA synthesis catalyzed by the Thermus aquaticus DNA polymerase and the 3'-->5' exonuclease-deficient Klenow fragment of Escherichia coli DNA polymerase I varies as a function of reaction pH (Eckert, K.A. and Kunkel, T.A. (1990) Nucleic Acids Res. 18, 3739-3744; Eckert, K.A. and Kunkel, T.A. (1993) J. Biol. Chem. 268, 13462-13471). In the current study, we demonstrate that the fidelity of human DNA polymerase alpha increases 10-fold when the pH of the in vitro synthesis reaction is lowered from pH 8.6 to pH 6.1 (37 degrees C), as determined using a base substitution reversion assay to score polymerase errors within the lacZ alpha gene of bacteriophage M13mp2. Similarly, the base substitution fidelity of DNA-dependent DNA synthesis by the human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT) was improved nine-fold at pH 6.5 relative to pH 8.0 (37 degrees C). A detailed comparison of HIV-1 RT error specificity at neutral and low pH in a lacZ alpha forward mutation assay revealed that low pH suppresses both mispairing-mediated and misalignment-mediated mutations; however, the characteristic HIV-1 RT pattern of mutational hotspots at homopolymeric sequences is retained at the lower pH. Consistent with the presumption that these mutations result, in part, from increased termination of DNA synthesis within the hotspot sequences relative to other homopolymeric sequences, the HIV-1 RT termination pattern during processive DNA synthesis is not altered by low pH. The HIV-1 RT results are in agreement with our previous hypothesis that the observed increase in polymerase fidelity at low pH results from a decreased efficiency of continuing DNA synthesis from premutational DNA intermediates.
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PMID:Fidelity of DNA synthesis catalyzed by human DNA polymerase alpha and HIV-1 reverse transcriptase: effect of reaction pH. 750 13


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