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

Zidovudine triphosphate inhibits the hepatitis B virus (HBV) DNA polymerase (DNAp) in vitro. Serial measurements of serum HBV DNAp activity and HBV DNA were made in 14 consecutive male homosexual patients starting zidovudine for symptomatic HIV-1 infection. Median duration of treatment was 15 weeks (range 2-72). In the 13 patients with detectable DNAp/DNA pre-treatment, no significant change in either measure of viral replication was observed during the first 16 weeks of treatment compared with the 13 weeks prior to treatment. The lack of response may be due to the opposing effect of immunosuppression, or to a failure of in vivo activity.
 ...
PMID:No effect of zidovudine on hepatitis B virus replication in homosexual men with symptomatic HIV-1 infection. 203 94

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.
 ...
PMID:Initial clinical experience with dideoxynucleosides as single agents and in combination therapy. 207 27

In a previous paper, we determined that treatment of lymphocytes with nonviable preparations of human immunodeficiency virus type 1 (HIV-1) results in an impairment of the phosphatidylinositol/protein kinase C pathway, most likely due to an inhibition of the cleavage of phosphatidylinositol bisphosphate into inositol trisphosphate and diacylglycerol, mediated by phospholipase C. Here we show that one consequence of these changes is a reduced phosphorylation of nuclear matrix-associated DNA topoisomerase II, resulting in an inhibition of the activity of this enzyme. Antibodies to the viral proteins suppressed the inhibitory effects caused by the HIV-1 preparation. Furthermore, the phytohemagglutinin A-caused augmentation of nuclear matrix-associated DNA polymerase alpha and beta activities was found to be abolished by coincubation with the HIV preparation or with the HIV-1 gp120. The phytohemagglutinin A-enhanced matrix association and processivity of DNA polymerase alpha was determined to be reduced if the lymphocytes were in contact with HIV-1 preparation. These results suggest that the reduced proliferative response of lymphocytes to phytohemagglutinin A in the presence of disrupted HIV-1 preparation is due to inhibition of at least two, perhaps separate, pathways, one involving protein kinase C resulting in a reduced phosphorylation of DNA topoisomerase II and the other changing the state of matrix association of DNA polymerase alpha and beta.
 ...
PMID:Effect of nonviable preparations from human immunodeficiency virus type 1 on nuclear matrix-associated DNA polymerase alpha and DNA topoisomerase II activities. 215 2

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)
 ...
PMID:The polymerase chain reaction (PCR): a valuable method for retroviral detection. 217 Jul 79

Two alkylation products implicated in initiation of carcinogenesis are O6-alkylguanine (m6G) and O4-alkylthymine (m4T). We have used site-specific insertion of these derivatives into oligonucleotides and measured the kinetic constants of various pairings, using both prokaryotic and eukaryotic polymerases for replication. Preliminary data are also reported for another carcinogen product, N2,3-ethenodeoxyguanosine ( epsilon G). The immediate neighbor bases play an important role in determining the frequency of specific changed basepairing and subsequent elongation of the annealed primer. However, both m4T and m6G prefer to form a type of G.T pairing which would lead to the transitions: G.C----A.T or T.A----C.G. The enzymes were the Klenow fragment of E. coli DNA polymerase I (Kf), engineered 3'----5' exonuclease-free Kf (exo-free Kf), polymerase alpha-primase complex from Drosophila melanogaster or calf thymus, and human immunodeficient virus-I reverse transcriptase (HIV-I RT). All enzymes led to approximately the same frequency of transitions. It is postulated that the mutation frequency at a given site is primarily a function of the structure of the sequence around the target site.
 ...
PMID:Site-directed mutagenesis for quantitation of base-base interactions at defined sites. 223 12

Four flavonoids (i.e., baicalein, quercetin, quercetagetin, and myricetin), known to be inhibitors of HIV-reverse transcriptase, have been shown to be more or less inhibitory to the activities of various cellular DNA and RNA polymerases. The degree of the inhibition varied depending on the combination of the flavonoid and the enzyme species: baicalein was moderately inhibitory to DNA polymerase gamma and E. coli DNA polymerase I; quercetin was strongly inhibitory to DNA polymerase beta and E. coli RNA polymerase and moderately inhibitory to DNA polymerase I; quercetagetin was a potent inhibitor for all of DNA polymerases alpha, beta, gamma, and I and RNA polymerase; myricetin was a strong inhibitor of DNA polymerases alpha and I and RNA polymerase. However, terminal deoxynucleotidyltransferase was virtually insensitive to inhibition by these flavonoids. The inhibition by the flavonoids was due to competition with the template.primer in the case of the DNA polymerases, whereas the inhibition was due to competition with the triphosphate substrate (GTP) in the case of RNA polymerase. The Ki values of these flavonoid inhibitors for DNA and RNA polymerases was determined.
 ...
PMID:Mechanisms of inhibition of various cellular DNA and RNA polymerases by several flavonoids. 229 90

The sugar-modified dTTP analogues 2',3'-didehydro-2',3'-dideoxy-thymidine 5'-triphosphate (ddeTTP), 2',3'-dideoxythymidine 5'-triphosphate (ddTTP), 3'-fluorothymidine 5'-triphosphate (FdTTP), and 3'-azidothymidine 5'-triphosphate (N3dTTP) are demonstrated to be very effective and selective inhibitors of the HIV-associated reverse transcriptase (HIV-RT). This conclusion is based on a comparison of the ID50 values of the compounds for the HIV-RT (ranging from 0.03 microM for ddeTTP to 0.1 microM for ddTTP) and the cellular DNA polymerase alpha (greater than 200 microM). DNA polymerase beta is partially affected by N3dTTP (ID50 = 31 microM) and by the other analogues (ID50 = 1-2.2 microM). FdTTP has proved as effective as N3dTTP (ID50 = 0.05 microM) in suppressing the HIV-RT activity. Kinetic analysis revealed for both dTTP analogues a competitive type of inhibition and the same K1 values (about 0.05 microM).
 ...
PMID:Inhibition of HIV-associated reverse transcriptase by sugar-modified derivatives of thymidine 5'-triphosphate in comparison to cellular DNA polymerases alpha and beta. 244 44

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)
 ...
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.
 ...
PMID:Fidelity of human immunodeficiency virus type I reverse transcriptase in copying natural DNA. 246 38

Carbocylic 2',3'-didehydro-2',3'-dideoxyguanosine (Carbovir; NSC 614846) is an antiretroviral agent which may be useful in the treatment of AIDS. We have synthesized the 5'-triphosphate of Carbovir and examined its ability to inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (EC 2.7.7.49) and other retroviral reverse transcriptases, as well as human DNA polymerases alpha, beta, gamma (EC 2.7.7.7) and DNA primase (EC 2.7.7.6). Carbovir triphosphate emerges as a highly selective inhibitor of reverse transcriptases with little, if any, effect on the cellular enzymes. 3'-Azido-2',3'-dideoxythymidine (AZT) triphosphate and the two dideoxynucleoside triphosphates, ddTTP and ddGTP, inhibited HIV-1 reverse transcriptase to the same degree as Carbovir triphosphate, but were less selective in that they also inhibited DNA polymerases beta and gamma. We conclude that Carbovir is a highly selective antiretroviral agent.
 ...
PMID:Comparison of the effect of Carbovir, AZT, and dideoxynucleoside triphosphates on the activity of human immunodeficiency virus reverse transcriptase and selected human polymerases. 247 36


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>