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)

Mutagenic treatments resulted in occasional, not systematic, human immunodeficiency virus type 1 (HIV-1) extinction. To study the possibility that a combination of an antiretroviral inhibitor, to reduce the viral replicative load, and a mutagenic agent could be more effective in producing viral extinction than a mutagenic agent alone, we have compared the efficiency of extinction of HIV-1 by the mutagenic deoxyribonucleoside analogue 5-hydroxydeoxycytidine (5-OHdC) alone and in combination with the HIV-1 nucleoside reverse transcriptase (RT) inhibitor AZT. Serial passages in peripheral mononuclear cells (PBMC) or MT-4 cells of primary HIV-1 isolates or HIV-1 NL4-3 in the presence of a single drug (AZT 0.01 microM or 5-OHdC 2 mM) failed to systematically extinguish high fitness HIV-1 replication after 16 serial transfers. However, systematic extinction of HIV-1 was observed when a combination of the mutagenic agent 5-OHdC and AZT was used. These results demonstrate that combinations of mutagenic agents and antiretroviral inhibitors have the potential to drive HIV-1 into extinction.
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PMID:Combination of a mutagenic agent with a reverse transcriptase inhibitor results in systematic inhibition of HIV-1 infection. 1593 49

We analyzed the subtypes and genotypic and phenotypic drug susceptibility profiles of 18 HIV-1 isolates from treatment-naive patients in Nigeria. A modified gp41-based heteroduplex mobility assay was used to determine the clade designation based on the envelope gene. The protease and most of the reverse transcriptase regions were cloned into a retroviral expression vector and sequenced. Samples were also analyzed phenotypically using a rapid phenotypic assay (PhenoSense HIV, ViroLogic, Inc.). According to the modified gp41-based heteroduplex mobility assay, the patients were infected with either clade G (17 specimens) or clade A (one specimen) isolates. From phylogenetic analyses of 1212 nucleotides of the polymerase gene, 14 of the 18 isolates were strongly grouped with subtype G reference strains. The remaining four isolates were grouped with the CRF_02_AG clade. Within the protease region, all 18 isolates had mutations/polymorphic substitutions at six locations compared to the HIV-1 NL4-3 reference sequence, two of which have been associated with resistance to protease inhibitors (K20I and M36I). At least half of the isolates had mutations/polymorphic substitutions at an additional five positions in the protease region. Within the reverse transcriptase (RT) region, all 18 isolates showed an E291D mutation/polymorphic substitution. Mutations/polymorphic substitutions were also found in at least half of the isolates at 21 positions. The phenotypic profiles of the viruses correlated well with the observed genotypes. Two isolates showed slightly reduced susceptibility to one or two of the five PIs assessed (ritonavir and ritonavir/nelfinavir) and all 18 viruses were susceptible to all NRTIs and NNRTIs analyzed.
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PMID:Genotypic and phenotypic analyses of human immunodeficiency virus type 1 in antiretroviral drug-naive Nigerian patients. 1643 41

Capravirine (CPV; formerly AG1549 and S-1153) is a novel, nonnucleoside reverse transcriptase inhibitor (NNRTI) of human immunodeficiency virus type 1 (HIV-1) that has demonstrated potent in vitro antiviral activity against several HIV-1 laboratory strains and clinical isolates with EC50 values ranging from 0.7 to 10.3 nM. In this study, we evaluated the resistance and cross-resistance profiles of CPV through selection of resistant HIV-1 variants from in vitro serial passage of HIV-1 NL4-3 and HIV-1 IIIB and by performing susceptibility assays on HIV-1 variants constructed to contain CPV-specific amino acid substitutions in reverse transcriptase (RT). Results demonstrate that HIV-1 variants selected at increasing CPV concentrations contained multiple substitutions in diverse patterns including L100I, Y181C, G190E and/or L234I in various combinations with K101R/E, K103T, V106A/I, V108I, E138K, T139K, A158T, V179D/I/G, Y188D, V189I, G190A, F227C, W229R, L234F, M230I/L and P236H/T. Interestingly, HIV-1 variants constructed to contain the T215Y zidovudine (AZT)-resistance associated substitution with CPV-resistance associated substitutions V106A, Y181C, F227C, F227L, L234I or V106A/F227L demonstrated 2.4-5.4-fold increased susceptibility to CPV. Results also demonstrate that the CPV-resistance associated substitutions Y181C, F227C, F227L and L234I reverse the phenotypic resistance to AZT conferred by the T215Y substitution.
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PMID:In vitro selection of mutations in human immunodeficiency virus type 1 reverse transcriptase that confer resistance to capravirine, a novel nonnucleoside reverse transcriptase inhibitor. 1647 77

Efavirenz resistance during HIV-1 treatment failure is usually associated with the reverse transcriptase mutation K103N. L100I, V108I, or P225H can emerge after K103N and increase its level of efavirenz resistance. K103N + L100I is the most drug-resistant of the double mutants but is the least common clinically. We hypothesized that differences in replication efficiency, or fitness, influence the relative frequencies of these secondary efavirenz resistance mutations in clinical isolates. We measured fitness of each secondary mutant introduced into HIV(NL4-3), alone and in combination with K103N, using growth competition assays in H9 cells. In the absence of efavirenz, the fitness of V108I was indistinguishable from wild type. K103N, L100I, and P225H were minimally, but consistently, less fit than wild type. K103N + L100I had a greater reduction in fitness and was less fit than K103N + V108I and K103N + P225H. The fitness defect of K103N + L100I relative to K103N was completely compensated for by the addition of the nucleoside resistance mutation L74V. In the presence of efavirenz, L100I was less fit than K103N, and K103N + L100I was more fit than K103N + V108I. Our studies suggest the primary driving force behind the selection of secondary efavirenz resistance mutations is the acquisition of higher levels of drug resistance, but the specific secondary mutations to emerge are those with the least cost in terms of replication efficiency. In addition, nucleoside and NNRTI resistance mutations can interact to affect HIV replication efficiency; these interactions may influence which mutations emerge during treatment failure. These studies have important implications for the design of more durable NNRTI-nucleoside combination regimens.
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PMID:Relative replication fitness of efavirenz-resistant mutants of HIV-1: correlation with frequency during clinical therapy and evidence of compensation for the reduced fitness of K103N + L100I by the nucleoside resistance mutation L74V. 1679 50

We examined the intracytoplasmic anabolism and kinetics of antiviral activity against human immunodeficiency virus type 1 (HIV-1) of a nucleoside reverse transcriptase inhibitor, 4'-ethynyl-2-fluoro-2'-deoxyadenosine (EFdA), which has potent activity against wild-type and multidrug-resistant HIV-1 strains. When CEM cells were exposed to 0.1 microM [(3)H]EFdA or [(3)H]3'-azido-2',3'-dideoxythymidine (AZT) for 6 h, the intracellular EFdA-triphosphate (TP) level was 91.6 pmol/10(9) cells, while that of AZT was 396.5 pmol/10(9) cells. When CEM cells were exposed to 10 microM [(3)H]EFdA, the amount of EFdA-TP increased by 22-fold (2,090 pmol/10(9) cells), while the amount of [(3)H]AZT-TP increased only moderately by 2.4-fold (970 pmol/10(9) cells). The intracellular half-life values of EFdA-TP and AZT-TP were approximately 17 and approximately 3 h, respectively. When MT-4 cells were cultured with 0.01 microM EFdA for 24 h, thoroughly washed to remove EFdA, further cultured without EFdA for various periods of time, exposed to HIV-1(NL4-3), and cultured for an additional 5 days, the protection values were 75 and 47%, respectively, after 24 and 48 h with no drug incubation, while those with 1 microM AZT were 55 and 9.2%, respectively. The 50% inhibitory concentration values of EFdA-TP against human polymerases alpha, beta, and gamma were >100 microM, >100 microM, and 10 microM, respectively, while those of ddA-TP were >100 microM, 0.2 microM, and 0.2 microM, respectively. These data warrant further development of EFdA as a potential therapeutic agent for those patients who harbor wild-type HIV-1 and/or multidrug-resistant variants.
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PMID:Activity against human immunodeficiency virus type 1, intracellular metabolism, and effects on human DNA polymerases of 4'-ethynyl-2-fluoro-2'-deoxyadenosine. 1754 98

Emtricitabine (FTC) and lamivudine (3TC) are cytosine nucleoside analogues approved for use in HIV-1 infection. Both compounds select for the M184V/I mutation resulting in high-level resistance. This study compared the phenotypic resistance profiles of FTC and 3TC. Both compounds were tested against clinical samples submitted for routine resistance testing (PhenoSense HIV assay). We evaluated 306 viruses with nucleoside reverse transcriptase inhibitor mutations (NRTI-R) and 100 viruses without resistance mutations (WT). Seventy-two percent had > or = 1 thymidine analogue mutation (TAM), 21% had mixtures at M184, 14% had L74V and 7.5% had K65R. Results were expressed as fold change (FC) in 50% effective concentration compared with the NL4-3 reference. Concordance of FC was evaluated based on biological (99th percentile of the distribution of WT virus population) and clinical cutoffs (FC above which an optimal virological response declines). Against the WT viruses, FTC and 3TC had identical mean FC values relative to the NL4-3 reference of 0.9-fold +/- 0.2 and identical biological cutoffs of 1.4-fold against WT viruses. For NRTI-R isolates, there was a strong linear correlation between FTC and 3TC FC values (r2 = 0.94). Moreover, there was > 90% concordance in resistance calls based on either the biological (1.4-fold) or proposed clinical (3.5-fold) cutoffs among all NRTI-R isolates or isolates with M184V/I mixtures. In the absence of M184V/I, the majority of samples with resistance (> 3.5 FC) exhibited TAMs with a trend toward increased levels of cross-resistance with increasing numbers of TAMs. FTC and 3TC demonstrate nearly identical phenotypic resistance profiles and have the same biological cutoff in this panel of NRTI-R and WT clinical HIV-1 isolates.
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PMID:A comparison of the phenotypic susceptibility profiles of emtricitabine and lamivudine. 1804 62

We have identified 1H-benzylindole analogues as a novel series of human immunodeficiency virus (HIV) integrase inhibitors with antiretroviral activities against different strains of HIV type 1 (HIV-1), HIV-2, and simian immunodeficiency virus strain MAC(251) [SIV(MAC(251))]. Molecular modeling and structure-activity relationship-based optimization resulted in the identification of CHI/1043 as the most potent congener. CHI/1043 inhibited the replication of HIV-1(III(B)) in MT-4 cells at a 50% effective concentration (EC(50)) of 0.60 microM, 70-fold below its cytotoxic concentration. Equal activities against HIV-1(NL4.3), HIV-2(ROD), HIV-2(EHO), and SIV(MAC(251)) were observed. CHI/1043 was equally active against virus strains resistant against inhibitors of reverse transcriptase or protease. Replication of both X4 and R5 strains in peripheral blood mononuclear cells was sensitive to the inhibitory effect of CHI/1043 (EC(50), 0.30 to 0.38 microM). CHI/1043 inhibited integrase strand transfer activity in oligonucleotide-based enzymatic assays at low micromolar concentrations. Time-of-addition experiments confirmed CHI/1043 to interfere with the viral replication cycle at the time of retroviral integration. Quantitative Alu PCR corroborated that the anti-HIV activity is based upon the inhibition of proviral DNA integration. An HIV-1 strain selected for 70 passages in the presence of CHI/1043 was evaluated genotypically and phenotypically. The mutations T66I and Q146K were present in integrase. Cross-resistance to other integrase strand transfer inhibitors, such as L-708,906, the naphthyridine analogue L-870,810, and the clinical drugs GS/9137 and MK-0518, was observed. In adsorption, distribution, metabolism, excretion, and toxicity studies, antiviral activity was strongly reduced by protein binding, and metabolization in human liver microsomes was observed. Transport studies with Caco cells suggest a low oral bioavailability.
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PMID:Preclinical evaluation of 1H-benzylindole derivatives as novel human immunodeficiency virus integrase strand transfer inhibitors. 1854 26

The genetic diversity of HIV-1 has required its classification into types and subtypes. There is controversy as to how and to what extent genetic diversity may affect the emergence of antiretroviral drug resistance in HIV-1 subtypes other than B. To better understand the impact of genetic diversity (represented by different HIV-1 subtypes) on resistance to reverse transcriptase and protease inhibitor drugs, a systematic review was conducted on virologic and biochemical evidence obtained from work with non-B HIV-1 subtypes. We searched 11 databases and retrieved 3,486 citations on all aspects of non-B subtype-related resistance research. Twenty-seven studies with virologic and/or biochemical data met the eligibility criteria for our systematic review. Nineteen studies were found that reported phenotypes in non-B subtypes (304 from naive isolates and 242 from drug-exposed isolates) and 11 studies that used molecular biology techniques to study non-B resistance to antiretroviral drugs. Compared to the NL4-3 laboratory strain, lower baseline susceptibilities of recombinant A/G subtype virus to protease inhibitors were observed and a substantial proportion of subtype C isolates displayed higher IC50 at baseline for atazanavir. Some A/G isolates were found to have reduced susceptibility to abacavir. Mutations not typical of B subtypes include the reverse transcriptase mutation V106M and the protease mutations M89I/V and N83T. Virologic and biochemical data suggest that K65R is more likely to emerge in subtype C HIV-1. There is evidence to suggest differential effects of other mutations according to subtype, e.g. the protease inhibitor mutations I93L and M89I/V. Importantly, the most widely used commercial phenotyping systems do not take into account gag variations among natural isolates, which could limit the accuracy of measured susceptibility. Enzymatic and virologic data support the concept that naturally occurring polymorphisms in different non-B subtypes can affect the susceptibility of HIV-1 to different antiretroviral drugs, the magnitude of resistance conferred by major mutations, and the propensity to acquire some resistance mutations. Tools may need to be optimized to accurately measure drug susceptibility of non-B subtypes, especially for protease inhibitors.
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PMID:Role of genetic diversity amongst HIV-1 non-B subtypes in drug resistance: a systematic review of virologic and biochemical evidence. 1909 77

2',3'-Didehydro-3'-deoxy-4'-ethynylthymidine (4'-Ed4T), a derivative of stavudine (d4T), has potent activity against human immunodeficiency virus and is much less inhibitory to mitochondrial DNA synthesis and cell growth than its progenitor, d4T. 4'-Ed4T triphosphate was a better reverse transcriptase (RT) inhibitor than d4T triphosphate, due to the additional binding of the 4'-ethynyl group at a presumed hydrophobic pocket in the RT active site. Previous in vitro selection for 4'-Ed4T-resistant viral strains revealed M184V and P119S/T165A/M184V mutations on days 26 and 81, respectively; M184V and P119S/T165A/M184V conferred 3- and 130-fold resistance to 4'-Ed4T, respectively. We investigated the relative contributions of these mutations, engineered into the strain NL4-3 background, to drug resistance, RT activity, and viral growth. Viral variants with single RT mutations (P119S or T165A) did not show resistance to 4'-Ed4T; however, M184V and P119S/T165A/M184V conferred three- and fivefold resistance, respectively, compared with that of the wild-type virus. The P119S/M184V and T165A/M184V variants showed about fourfold resistance to 4'-Ed4T. The differences in the growth kinetics of the variants were not more than threefold. The purified RT of mutants with the P119S/M184V and T165A/M184V mutations were inhibited by 4'-Ed4TTP with 8- to 13-fold less efficiency than wild-type RT. M184V may be the primary resistance-associated mutation of 4'-Ed4T, and P119S and T165A are secondary mutations. On the basis of our findings and the results of structural modeling, a virus with a high degree of resistance to 4'-Ed4T (e.g., more than 50-fold resistance) will be difficult to develop. The previously observed 130-fold resistance of the virus with P119S/T165A/M184V to 4'-Ed4T may be partly due to mutations both in the RT sequence and outside the RT sequence.
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PMID:Impact of novel human immunodeficiency virus type 1 reverse transcriptase mutations P119S and T165A on 4'-ethynylthymidine analog resistance profile. 1970 31

Retroviruses rely on host RNA-binding proteins to modulate various steps in their replication. Previously several animal retroviruses were determined to mediate Dhx9/RNA helicase A (RHA) interaction with a 5' terminal post-transcriptional control element (PCE) for efficient translation. Herein PCE reporter assays determined HTLV-1 and HIV-1 RU5 confer orientation-dependent PCE activity. The effect of Dhx9/RHA down-regulation and rescue with siRNA-resistant RHA on expression of HIV-1(NL4-3) provirus determined that RHA is necessary for efficient HIV-1 RNA translation and requires ATPase-dependent helicase function. Quantitative analysis determined HIV-1 RNA steady-state and cytoplasmic accumulation were not reduced; rather the translational activity of viral RNA was reduced. Western blotting determined that RHA-deficient virions assemble with Lys-tRNA synthetase, exhibit processed reverse transcriptase and contain similar level of viral RNA, but they are poorly infectious on primary lymphocytes and HeLa cells. The results demonstrate RHA is an important host factor within the virus-producer cell and within the viral particle. The identification of RHA-dependent PCE activity in cellular junD RNA and in six of seven genera of Retroviridae suggests conservation of this translational control mechanism among vertebrates, and convergent evolution of Retroviridae to utilize this host mechanism.
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PMID:RNA helicase A modulates translation of HIV-1 and infectivity of progeny virions. 2000 98


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