1st International Workshop on HIV Drug Resistance & Treatment Strategies


25-28 June 1997, St. Petersburg, Florida, USA


LIMITING DNTP CONCENTRATIONS EMPHASIZE THE PROCESSIVITY DEFECT OF LAMIVUDINE-RESISTANT VARIANTS OF HIV-1 REVERSE TRANSCRIPTASE

Antiviral Therapy 1997;2 (Suppl 5):13 (abstract no. 20)

Nicole KT Back and Ben Berkhout
Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

The nucleoside drug lamivudine triggers the selection of resistant forms of HIV-1 reverse transcriptase (RT) with a substitution of amino acid 184Met. The lamivudine-resistant RT enzymes 184Val and 184Ile exhibit a processivity defect in in vitro assays that correlates with reduced replication of the corresponding virus variants in primary cells. However, no replication defect is apparent for these two mutants in the transformed T cell line SupT1. One obvious difference between the two cell types is the intracellular dNTP level. Primary cells have a much smaller dNTP pool, and this cellular condition may emphasize the processivity defect of the codon 184 RT variants. Alternatively, cell-specific co-factors may exist that influence the process of reverse transcription. Such accessory factors may be packaged into the virion to exert an effect on the RT enzyme. To discriminate between these possibilities we performed additional assays with the wild-type and mutant RT enzymes. The RT proteins were either isolated from virions produced by primary and transformed cell types or expressed as recombinant protein. We also performed infection assays in cells treated with a drug that reduces the intracellular dNTP pool. Furthermore, reverse transcription was studied within virus particles in the endogenous assay, which allows manipulation of the dNTP level. The combined results indicate that the enzymatic defect of the lamivudine-resistant HIV-1 variants is stressed at low dNTP concentrations.

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1997-06-25
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