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Journal of Virology, December 2000, p. 10958-10964, Vol. 74, No. 23
Laboratory of Molecular Retrovirology,
Clinical Services Program, SAIC-Frederick, Frederick Cancer Research
and Development Center, Frederick,1 and
Laboratory of Immunoregulation, National Institute of Allergy
and Infectious Diseases, Bethesda,3 Maryland,
and Hospital General Gregorio Maranon, Madrid,
Spain2
Received 13 June 2000/Accepted 28 August 2000
The combination of an amino acid deletion at codon 67 (
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Relative Replication Fitness of a High-Level
3'-Azido-3'-Deoxythymidine-Resistant Variant of Human Immunodeficiency
Virus Type 1 Possessing an Amino Acid Deletion at Codon 67 and a Novel
Substitution (Thr
Gly) at Codon 69
67) and
Thr-to-Gly change at codon 69 (T69G) in the reverse transcriptase (RT)
of human immunodeficiency virus type 1 (HIV-1) is associated with
high-level resistance to multiple RT inhibitors. To determine the
relative contributions of the
67 and T69G mutations on viral fitness, we performed a series of studies of HIV replication using recombinant variants. A high-level 3'-azido-3'-deoxythymidine (AZT)-resistant variant containing
67 plus
T69G/K70R/L74I/K103N/T215F/K219Q in RT replicated as efficiently as
wild-type virus (Wt). In contrast, the construct without
67
exhibited impaired replication (23% of growth of Wt). A competitive
fitness study failed to reveal any differences in replication rates
between the
67+T69G/K70R/L74I/K103N/T215F/K219Q mutant and Wt.
Evaluation of proviral DNA sequences over a 3-year period in a patient
harboring the multiresistant HIV revealed that the T69G mutation
emerged in the context of a D67N/K70R/T215F/K219Q mutant backbone prior
to appearance of the
67 deletion. To assess the impact of this
stepwise accumulation of mutations on viral replication, a series of
recombinant variants was constructed and analyzed for replication
competence. The T69G mutation was found to confer 2',3'-dideoxyinosine
resistance at the expense of fitness. Subsequently, the development of
the
67 deletion led to a virus with improved replication and
high-level AZT resistance.
*
Corresponding author. Mailing address: Building 550, Room 126, SAIC-Frederick, NCI-FCRDC, P.O. Box B, Frederick, MD 21702. Phone: (301) 846-5450. Fax: (301) 846-6762. E-mail:
timamichi{at}nih.gov.
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