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Journal of Virology, July 1999, p. 5803-5813, Vol. 73, No. 7
Departments of
Medicine,1 Microbiology and
Immunology,2 and Biochemistry and
Biophysics3 and Cancer
Center,4 University of Rochester School of
Medicine and Dentistry, Rochester, New York 14642
Received 28 December 1998/Accepted 19 April 1999
The nonnucleoside reverse transcriptase (RT) inhibitor (NNRTI)
delavirdine (DLV) selects in vitro for the human immunodeficiency virus
type 1 (HIV-1) RT mutation P236L, which confers high-level resistance
to DLV but not other NNRTIs. Unexpectedly, P236L has developed
infrequently in HIV-1 isolates obtained from patients receiving DLV;
K103N is the predominant resistance mutation observed in that setting.
We characterized the replication fitness of viruses derived from pNL4-3
containing P236L or K103N in both H9 and primary human peripheral blood
mononuclear cell cultures infected in parallel with the two mutants. In
the absence of DLV, p24 production by wild-type virus occurred more
rapidly and to higher levels than with either mutant; P236L
consistently demonstrated a two- to threefold decrease in p24 relative
to K103N. At low levels of DLV, growth of wild-type virus was severely
inhibited, and K103N replicated two- to threefold more efficiently than
P236L. At high concentrations of DLV, P236L replication and K103N
replication were both inhibited. Recombinant RTs containing K103N or
P236L were analyzed for DNA polymerization on heteropolymeric RNA
templates and RNase H degradation of RNA-DNA hybrids. Neither mutant
demonstrated defects in polymerization. K103N demonstrated normal RNA
5'-end-directed RNase H cleavage and slowed DNA 3'-end-directed RNase H
cleavage compared to wild-type RT. P236L demonstrated slowing of both
DNA 3'-end- and RNA 5'-end-directed RNase H cleavage, consistent with its reduced replication efficiency relative to K103N. These data suggest that NNRTI resistance mutations can lead to reductions in the
efficiency of RNase H cleavage, which may contribute to a reduction in
the replication fitness of HIV-1.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The P236L Delavirdine-Resistant Human
Immunodeficiency Virus Type 1 Mutant Is Replication Defective and
Demonstrates Alterations in both RNA 5'-End- and DNA
3'-End-Directed RNase H Activities

*
Corresponding author. Mailing address: University of
Rochester Medical Center, Infectious Diseases Unit, Box 689, 601 Elmwood Ave., Rochester, NY 14642. Phone: (716) 275-4764. Fax: (716)
442-9328. E-mail: Lisa_Demeter{at}urmc.rochester.edu.
Present address: Amersham Pharmacia Biotech, Inc., Cleveland,
OH 44128.
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