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.
D and L isomers of aspartic acid beta-hydroxamate (respectively DAH and LAH) were compared for their in vitro and in vivo activity against the murine leukemia L5178Y and their tolerance in vivo in DBA/2 mice. DAH and LAH displayed comparable cytotoxic activity against L5178Y leukemia in vitro. Death of leukemia cells was observed at concentrations above 1.2 mM for both DAH and LAH. High concentrations of L-asparagine partially reversed the growth-inhibitory effects of DAH and LAH on L5178Y cells for concentrations of DAH and LAH lower than 0.6 mM. Intraperitoneal administration of DAH and LAH to mice showed that the LD10, LD50 and LD90 of DAH was 3- to 4-fold greater for DAH than for LAH. DAH was able to eradicate L5178Y tumors in mice without inducing toxic deaths, whereas LAH at comparable doses killed all the animals treated.
D-aspartic acid beta-hydroxamate (DAH), an aspartic acid analogue, exerts anti-tumoral activity against murine leukemia L5178Y both in vitro and in vivo. We show here that DAH displays activity against Friend leukemia cells (FLC) in vitro: a concentration of 2 mM results in a total inhibition of cell growth. DAH is also active in vivo against Friend virus (FV-P)-induced erythroleukemia. Treatment with DAH, given for 95 days as a single daily i.p. injection to DBA/2 mice 3 days following FV-P inoculation, induced a marked increase of 212% in the mean survival time (MST) of treated animals. Since FV-P-induced erythroleukemia is characterized by the proliferation of mature erythroid precursors, we examined the effect of DAH treatment on erythroid colony-forming cells (CFU-E) and observed that the number of CFU-E per spleen was 30 times lower in DAH-treated mice than in the controls. To gain further insight into the early effects of DAH treatment on the early phase of Friend disease, we examined the effects of short DAH treatment on spleen size, hematocrit and viremia in FV-P-infected mice. DAH treatment initiated 3 days post infection (p.i.) inhibited splenomegaly, prevented virus-induced polycythemia, and reduced serum viremia. Late DAH treatment (18 days p.i.) induced regression of FVP-induced disease as evidenced by reduction of spleen weight.
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