Use of standardized SCID-hu Thy/Liv mouse model for preclinical efficacy testing of anti-human immunodeficiency virus type 1 compounds (original) (raw)
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Antimicrobial Agents and Chemotherapy, 1999
The racemic nucleoside analogue 2-deoxy-3-oxa-4-thiocytidine (dOTC) is in clinical development for the treatment of human immunodeficiency virus (HIV) type 1 (HIV-1) infection. dOTC is structurally related to lamivudine (3TC), but the oxygen and sulfur in the furanosyl ring are transposed. Intracellular metabolism studies showed that dOTC is phosphorylated within cells via the deoxycytidine kinase pathway and that approximately 2 to 5% of dOTC is converted into the racemic triphosphate derivatives, which had measurable half-lives (2 to 3 hours) within cells. Both 5-triphosphate (TP) derivatives of dOTC were more potent than 3TC-TP at inhibiting HIV-1 reverse transcriptase (RT) in vitro. The K i values for dOTC-TP obtained against human DNA polymerases ␣, , and ␥ were 5,000-, 78-, and 571-fold greater, respectively, than those for HIV RT (28 nM), indicating a good selectivity for the viral enzyme. In culture experiments, dOTC is a potent inhibitor of primary isolates of HIV-1, which were obtained from antiretroviral drug-naive patients as well as from nucleoside therapy-experienced (3TC-and/or zidovudine [AZT]-treated) patients. The mean 50% inhibitory concentration of dOTC for drug-naive isolates was 1.76 M, rising to only 2.53 and 2.5 M for viruses resistant to 3TC and viruses resistant to 3TC and AZT, respectively. This minimal change in activity is in contrast to the more dramatic changes observed when 3TC or AZT was evaluated against these same viral isolates. In tissue culture studies, the 50% toxicity levels for dOTC, which were determined by using [ 3 H]thymidine uptake as a measure of logarithmic-phase cell proliferation, was greater than 100 M for all cell lines tested. In addition, after 14 days of continuous culture, at concentrations up to 10 M, no measurable toxic effect on HepG2 cells or mitochondrial DNA replication within these cells was observed. When administered orally to rats, dOTC was well absorbed, with a bioavailability of approximately 77%, with a high proportion (approximately 16.5% of the levels in serum) found in the cerebrospinal fluid.
Validation of the SCID-hu Thy/Liv Mouse Model with Four Classes of Licensed Antiretrovirals
PLOS One, 2007
Background. The SCID-hu Thy/Liv mouse model of HIV-1 infection is a useful platform for the preclinical evaluation of antiviral efficacy in vivo. We performed this study to validate the model with representatives of all four classes of licensed antiretrovirals. Methodology/Principal Findings. Endpoint analyses for quantification of Thy/Liv implant viral load included ELISA for cell-associated p24, branched DNA assay for HIV-1 RNA, and detection of infected thymocytes by intracellular staining for Gag-p24. Antiviral protection from HIV-1-mediated thymocyte depletion was assessed by multicolor flow cytometric analysis of thymocyte subpopulations based on surface expression of CD3, CD4, and CD8. These mice can be productively infected with molecular clones of HIV-1 (e.g., the X4 clone NL4-3) as well as with primary R5 and R5X4 isolates. To determine whether results in this model are concordant with those found in humans, we performed direct comparisons of two drugs in the same class, each of which has known potency and dosing levels in humans. Here we show that second-generation antiretrovirals were, as expected, more potent than their first-generation predecessors: emtricitabine was more potent than lamivudine, efavirenz was more potent than nevirapine, and atazanavir was more potent than indinavir. After interspecies pharmacodynamic scaling, the dose ranges found to inhibit viral replication in the SCID-hu Thy/Liv mouse were similar to those used in humans. Moreover, HIV-1 replication in these mice was genetically stable; treatment of the mice with lamivudine did not result in the M184V substitution in reverse transcriptase, and the multidrug-resistant NY index case HIV-1 retained its drugresistance substitutions. Conclusion. Given the fidelity of such comparisons, we conclude that this highly reproducible mouse model is likely to predict clinical antiviral efficacy in humans. Citation: Stoddart CA, Bales CA, Bare JC, Chkhenkeli G, Galkina SA, et al (2007) Validation of the SCID-hu Thy/Liv Mouse Model with Four Classes of Licensed Antiretrovirals. PLoS ONE 2(8): e655.
Antimicrobial Agents and Chemotherapy, 2003
The emergence of human immunodeficiency virus type 1 (HIV-1) strains resistant to highly active antiretroviral therapy necessitates continued drug discovery for the treatment of HIV-1 infection. Most current drug discovery strategies focus upon a single aspect of HIV-1 replication. A virus-cell-based assay, which can be adapted to high-throughput screening, would allow the screening of multiple targets simultaneously. HIV-1based vector systems mimic the HIV-1 life cycle without yielding replication-competent virus, making them potentially important tools for the development of safe, wide-ranging, rapid, and cost-effective assays amenable to high-throughput screening. Since replication of vector virus is typically restricted to a single cycle, a crucial question is whether such an assay provides the needed sensitivity to detect potential HIV-1 inhibitors. With a stable, inducible vector virus-producing cell line, the inhibitory effects of four reverse transcriptase inhibitors (zidovudine, stavudine, lamivudine, and didanosine) and one protease inhibitor (indinavir) were assessed. It was found that HIV-1 vector virus titer was inhibited in a single cycle of replication up to 300-fold without affecting cell viability, indicating that the assay provides the necessary sensitivity for identifying antiviral molecules. Thus, it seems likely that HIV-1-derived vector systems can be utilized in a novel fashion to facilitate the development of a safe, efficient method for screening compound libraries for anti-HIV-1 activity.
Antimicrobial Agents and Chemotherapy, 1990
Three analogs of thymidine, D4T [2',3'-didehydro-2',3'-dideoxythymidine; 1-(2,3-dideoxy-beta-D-glyceropent-2-enofuranosyl)thymine], FddT (3'-fluoro-3'-deoxythymidine), and AZT (3'-azido-3'-deoxythymidine), were compared in biological tests designed to assess their potential utility as anti-human immunodeficiency virus (HIV) agents. The in vitro potencies of these compounds against HIV infection in CEM cells were measured, with FddT and AZT being more potent than D4T. The cytotoxicities of D4T, FddT, and AZT for CEM cells were comparable. The triphosphates of these three derivatives inhibited purified HIV reverse transcriptase, and their affinities for this polymerase were found to be 1 or 2 orders of magnitude greater than that for the normal substrate, dTTP. D4T was less toxic than FddT or AZT for cultured human and mouse bone marrow cells (granulocyte-macrophage CFU). The three compounds had similar toxicities for human progenitor erythrocyte burst-...
Antimicrobial Agents and Chemotherapy, 1987
It is generally accepted that human immunodeficiency virus (HIV) is the etiologic agent of the acquired immunodeficiency syndrome and related diseases. In this report, we demonstrate the antiviral effect of nucleoside analogs 2',3'-didehydro-2',3'-dideoxythymidine (DHT) and 2',3'-didehydro-2',3'-dideoxycytidine (DHC) by using human T-cell lymphotropic virus type I-carrying MT-4 cells, which are extremely susceptible to HIV infection. These agents efficiently inhibited the cytopathic effects and expression of HIV-specific antigens in MT-4 cells after infection of the virus. Both DHT and DHC also strongly blocked viral replication as determined by our quantitative bioassay system using a plaque-forming assay. These antiviral effects were obtained at concentrations at which the drugs produced little or no toxicity and were comparable to those with 3'-azido-3'-deoxythymidine and 2',3'-dideoxynucleosides. These findings warrant further inve...