Synergistic anti-human immunodeficiency virus type 1 effect of hydroxamate compounds with 2',3'-dideoxyinosine in infected resting human lymphocytes.

Abstract

The cellular models generally used in the in vitro evaluation of anti-human immunodeficiency virus compounds are dividing cells. A model constituted by resting lymphocytes may more accurately reflect a drug's future efficacy in humans, since viral DNA synthesis is known to take place in quiescent cells, creating a reservoir of infected cells awaiting activation to complete their viral replication cycle and to produce infectious virions. We report here the activity of 3'-azido-3'-deoxythymidine, 2',3'-dideoxyinosine, 2',3'-dideoxycytidine, and two hydroxamates, D-aspartic acid jhydroxamate and hydroxycarbamide (hydroxyurea), alone and in various comnbinations, in an in vitro model based on resting lymphocytes. In our model, resting peripheral blood lymphocytes were infected with human immunodeficiency virus type 1 and treated with drugs for 7 days, at which time drugs were removed and the cells were activated by phytohemagglutinin.We show that under these conditions 3-azido-3'-deoxythymidine, 2',3'-dideoxyinosine, and 2',3'-dideoxycytidine, alone or in combination, neither fully inhibit viral production nor protect lymphocytes from the cytopathic effect of viral replication, at concentrations corresponding to the peak plasma levels observed in a typical treatment schedule in humans. In contrast, we report the synergistic effect of treatment by each hydroxamate with 2',3'-dideoxyinosine of infected resting lymphocytes, resulting in the total suppression of viral production, total protection against the cytopathic effect induced by viral replication, and no effect on the ability of the cells to replicate in this cell culture system.

Inhibition of Human Immunodeficiency Virus Type 1 Transcription by Chemical Cyclin-Dependent Kinase Inhibitors

“…A number of studies have demonstrated that hydroxyurea can inhibit HIV-1 replication by reducing the intracellular pool of deoxynucleotides, which is essential for successful reverse transcription of HIV-1 RNA in both activated and resting PBMC (12,28,29,30). However, in this study we examined the postintegrative events related to HIV-1 transcription and the subsequent steps prior to progeny formation.…”

In Vivo and In Vitro Comparison of the Short‐Term Hematopoietic Toxicity Between Hydroxyurea and Trimidox or Didox, Novel Ribonucleotide Reductase Inhibitors with Potential Anti‐HIV‐1 Activity

“…The rationale for this approach is that inhibition of ribonucleotide reductase depletes the cellular pool of deoxynucleotide triphosphates (dNTPs) required for proviral DNA synthesis by viral reverse transcriptase (RT) [13,14,46]. In addition, depletion of the endogenous dNTP pool increases the anti-HIV activity of dideoxynucleotide drugs (e.g., ddI/AZT) by decreasing competition for their incorporation into the active site of RT, thereby enhancing termination of the nascent proviral DNA chain [14][15][16][17][18]. An added advantage of including HU in HIV-1 combination therapy is the ability to overcome the development of nucleoside analog drug resistance [47].…”

“…HU has also been shown to potentiate the activity of dideoxynucleoside drugs in vitro, particularly 2′,3′-dideoxyinosine (ddI) [15][16][17][18][19]. In addition, several clinical trials have shown that the combination of HU with ddI can substantially reduce viral load in patients infected with HIV-1 much more effectively than ddI monotherapy can, with efficacy approaching that of protease-inhibitor-containing regimens [20][21][22].…”

Disparate actions of hydroxyurea in potentiation of purine and pyrimidine 2',3'-dideoxynucleoside activities against replication of human immunodeficiency virus.

“…Thus, restriction of host dNTP synthesis may represent a strategy not only for inhibiting the rate of HIV-1 replication but also for slowing the development of drugresistant mutants. We (5) and others (6,7) have reported that the ribonucleotide reductase inhibitor hydroxyurea increases the anti-HIV-1 activities of the 2',3'-dideoxynucleosides 3'-azido-3'-deoxythymidine (AZT), 2',3'-dideoxycytidine (ddCyd), and particularly 2',3'-dideoxyinosine (ddIno) in primary cultured human peripheral blood mononuclear (PBM) cells, and the combination of hydroxyurea and ddlno is presently in early clinical trials (6).…”