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Antimicrob. Agents Chemother., 11 1997, 2484-2491, Vol 41, No. 11
NK Back and B Berkhout
The nucleoside drug lamivudine (3TC) triggers the selection of resistant
forms of the human immunodeficiency virus type 1 (HIV-1) reverse
transcriptase (RT) with a substitution of amino acid 184Met. The
3TC-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 deoxynucleoside triphosphate (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 cofactors that influence the process of reverse transcription
may exist. 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 with 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 for the
manipulation of the dNTP level. The combined results indicate that the
enzymatic defect of the 3TC-resistant HIV-1 variants is stressed at low
dNTP concentrations.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Limiting deoxynucleoside triphosphate concentrations emphasize the processivity defect of lamivudine-resistant variants of human immunodeficiency virus type 1 reverse transcriptase
Department of Human Retrovirology, Academic Medical Center, University of Amsterdam, The Netherlands.
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