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Antimicrobial Agents and Chemotherapy, August 1999, p. 2077-2080, Vol. 43, No. 8
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
A New Point Mutation (P157S) in the Reverse
Transcriptase of Human Immunodeficiency Virus Type 1 Confers Low-Level
Resistance to (
)-
-2',3'-Dideoxy-3'-Thiacytidine
Robert A.
Smith,1
George J.
Klarmann,1
Kirsten M.
Stray,1
Uta K.
von
Schwedler,1
Raymond F.
Schinazi,2,3
Bradley D.
Preston,1,* and
Thomas W.
North4
Eccles Institute of Human Genetics,
University of Utah, Salt Lake City, Utah 841121;
Georgia VA Research Center for AIDS and HIV
Infections2 and Department of
Pediatrics, Emory University School of
Medicine,3 Decatur, Georgia 30033; and
Center for Comparative Medicine, University of California,
Davis, California 956164
Received 18 November 1998/Returned for modification 8 March
1999/Accepted 13 May 1999
 |
ABSTRACT |
A P157S mutation in the reverse transcriptase (RT) of human
immunodeficiency virus type 1 conferred fivefold resistance to (
)-
-2',3'-dideoxy-3'-thiacytidine in cell culture. Interestingly, the P157S mutation resulted in increased sensitivity (two- to threefold) to 3'-azido-3'-deoxythymidine (AZT) and to
(R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA). A similar
increase in susceptibility to AZT and to PMPA was also conferred by the
M184V mutation in RT.
| |
TEXT |
The drugs 3TC
[()--2',3'-dideoxy-3'-thiacytidine, also known as lamivudine]
and AZT (3'-azido-3'-deoxythymidine, also known as zidovudine) are
nucleoside analogs commonly used in the treatment of patients infected
with human immunodeficiency virus type 1 (HIV-1). The efficacy of these
drugs in both monotherapy and combination therapy is limited by the
emergence of drug-resistant variants (7, 17, 23, 32).
Resistance to 3TC or AZT alone has been shown to result from specific
mutations in the reverse transcriptase (RT)-encoding region of the
pol gene (19, 33). However, the mechanism of
resistance to the combination of 3TC plus AZT has remained somewhat
elusive. Dual drug resistance in virus isolates derived from patients
receiving 3TC plus AZT combination chemotherapy has recently been
reported (23, 25). In one study, dual resistance was
attributed to the combined presence of M184V (which alone confers
>100-fold resistance to 3TC [2, 9, 20, 34, 42]), the
mutations commonly associated with AZT resistance, and several additional mutations in the N-terminal portion of RT (25).
Passage of virus in culture in the presence of 3TC and AZT has also
provided HIV-1 isolates resistant to both inhibitors (14).
In this case, dual resistance is attributed to the presence of a
previously undocumented mutation at codon 333 in genomes containing
other AZT and 3TC resistance mutations. In addition, virus isolates containing either the Q151M V75I F77L F116Y mutation series or a
threonine-to-serine mutation followed by an insertion of two amino
acids at codon 69 of RT are resistant to AZT and dideoxynucleosides and
possess 5- to 40-fold-decreased susceptibility to 3TC in vitro (12, 46).
Our investigation of dual AZT-3TC resistance stems from previous work
with the feline immunodeficiency virus (FIV). We recently reported the
selection of 3TC-resistant mutants of FIV that contained a novel P156S
mutation in RT (35). In addition to conferring 3TC
resistance, the P156S mutation conferred low-level resistance to AZT
alone and eightfold resistance to the combination of 3TC plus AZT
(35). P156 is highly conserved in RTs from retroviruses and
retroelements (8) and is located in a region which has 87%
amino acid similarity with HIV-1 RT (35). The corresponding amino acid in HIV-1, P157, is predicted to reside in the "template grip" region of the enzyme and is proximal to M184, which is located in the active site of RT (10, 13, 15).
In the present study, we examined changes in drug susceptibility
resulting from the P157S mutation in HIV-1 RT. Virus containing the
M184V mutation, which is commonly found in 3TC-resistant HIV-1 (33), was also constructed and used as a reference strain in these experiments. Drug susceptibilities were examined in cell culture,
and inhibition constants for drug triphosphates were determined in
kinetic assays with purified recombinant RTs.
Infectivity of the P157S mutant.
To determine if HIV-1
containing the P157S mutation in RT is replication competent, molecular
clones containing P157S, M184V, or wild-type RT were assayed for the
ability to produce infectious virions in a single round of replication.
Mutations were constructed in the R9
Apa proviral clone
(37) by using oligonucleotide-mediated mutagenesis
(Muta-Gene phagemid mutagenesis kit; Bio-Rad) and the subcloning
strategy of Iversen et al. (12). The presence of the desired
mutations and the absence of additional changes were confirmed by
automated DNA sequencing of the RT-encoding region of the
pol gene. The R9Apa clone contains the
gag, pol, and env genes from
HIV-1NL4-3, with 5' and 3' long terminal repeats derived
from HIV-1HXB2. Molecular clones were transfected into 293tsA1609neo (293T) cells for the production of virus
(28). Genetic heterogeneity in the resulting stocks was
minimal (<10
4 mutations per nucleotide
[27]), as the 293T cultures do not express the CD4
receptor and therefore cannot be reinfected by progeny virions.
Viral titers were quantitated by plating supernatants from 293T
cultures onto P4 (HeLa-CD4-LTR--galactosidase) indicator cells and
staining with
5-bromo-4-chloro-3-indolyl--D-galactopyranoside (X-Gal)
to develop blue foci (4). Titers from the focal assay were
normalized against the p24 concentration (DuPont HIV-1 p24 enzyme-linked immunosorbent assay) to determine the infectivity of the
mutants relative to wild-type virus (Table
1). In this single-cycle assay, P157S did
not substantially differ from M184V or wild-type clones with respect to
p24 production and infectivity of the resulting particles. Studies of
the M184V mutant in spreading infections show that replication fitness
is cell type dependent. Thus, M184V virus exhibits reduced fitness
relative to wild-type HIV-1 in peripheral blood mononuclear cells but
not in a T-cell line (1). Our data indicate that both the
M184V and P157S mutants replicate at near wild-type levels in
CD4+ HeLa cells. However, subtle differences in replication
capacity that are magnified over multiple rounds of replication in a
spreading infection (5, 30) would not be detected in our
single-cycle assay.
Drug susceptibility in culture.
To examine the potential role
of the P157S mutation in dual AZT-3TC resistance, we first determined
the relative susceptibility of P157S virus to inhibition by 3TC (Fig.
1A). Drug susceptibility was determined
by measuring the dose-dependent reduction of focus formation in
CD4+ HeLa indicator cell cultures. Concentrations of drug
required to inhibit focus formation by 50% (50% effective
concentrations [EC50s]) are summarized in Table
2. P157S conferred fivefold resistance to
3TC, compared to the >100-fold resistance resulting from the M184V
mutation. The low-level 3TC resistance conferred by P157S in HIV-1 is
comparable to that observed in P156S mutants of FIV (eightfold)
(35).
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FIG. 1.
Susceptibility of a wild-type strain ( ) and M184V
( ) and P157S ( ) mutants of HIV-1 to inhibition by 3TC (A) and AZT
(B) in CD4+ HeLa cells. Foci were detected as described in
the text. Data are plotted as the percentage of control foci (no drug)
versus inhibitor concentration. Results are from two or more assays,
with four determinations per assay. Bars represent standard errors of
the means.
|
|
We also determined the susceptibility of P157S, M184V, and wild-type
virus to AZT (Fig.
1B). Surprisingly, both P157S and
M184V were
slightly hypersensitive to AZT, with EC
50s two- to
threefold lower than that for wild-type virus (Table
2). Initial
reports describe little or no change in AZT sensitivity for M184V
relative to wild-type virus (
2,
9,
20,
34,
42), with
one
exception: a virus isolate selected with
(
)-
-2',3'-dideoxy-5-fluoro-3'-thiacytidine
and containing a
mixture of M184I and M184V variants displayed
a fivefold increase in
susceptibility to AZT when assayed in MT-2
cells (
34). In
addition, recent studies demonstrate that two-
to fivefold AZT
hypersensitivity is conferred by M184V both in
the HXB2D clonal
background (
44) and in recombinant constructs
containing
patient-derived RTs (
22,
24,
41). Variability
in reports of
the AZT susceptibility of M184V HIV-1 may reflect
differences in the
genetic backgrounds used to select or construct
the mutant or
differences in the sensitivities of the particular
assays used to
quantitate drug
susceptibility.
Cell culture assays with
(
R)-9-(2-phosphonylmethoxypropyl)adenine (PMPA) revealed
that the M184V and P157S mutations also
confer a twofold increase in
sensitivity to PMPA (Table
2). This
result is consistent with recent
reports that virus isolates containing
the M184V mutation display
increased susceptibility to PMPA (
22,
44). Taken together,
these data suggest that P157S and M184V
mutants may be more effectively
suppressed than wild-type virus
by PMPA and AZT in vivo. AZT
hypersensitivity may in part account
for the observed delay in the
appearance of AZT resistance mutations
in viruses containing M184V
(
41).
A comparison of HIV-1 P157S and FIV P156S drug susceptibility reveals
important similarities and differences between these
two closely
related lentiviruses. The resistance of both variants
to 3TC
demonstrates the utility of the FIV model for discovering
candidate
drug-resistant mutants of HIV-1 which otherwise may
not have been
identified. However, the P157S variant of HIV-1
does not share the
AZT-resistant phenotype of the FIV mutant and
is instead slightly
hypersensitive to the drug. This result should
be considered in future
experiments when FIV is used for studying
resistance to the combination
of 3TC plus
AZT.
Inhibitor susceptibilities of purified RTs.
Changes in drug
susceptibility resulting from the P157S mutation were further
characterized in cell-free RT assays. P157S, M184V, and wild-type RTs
were expressed in Escherichia coli and purified as p66-p51
heterodimers (36). The resulting enzyme preparations
contained equal ratios of each subunit and were approximately 95% pure
as judged by Coomassie-stained sodium dodecyl sulfate-polyacrylamide gels (data not shown). Sensitivities of the RTs to the 5'-triphosphate forms of 3TC (3TCTP) and AZT (AZTTP) were compared in kinetic assays
(Table 3). Wild-type and mutant RTs
exhibited similar apparent Km values for dCTP
and dTTP, ranging from 13 to 25 µM. Based on
Ki/Km ratios (45), the
P157S and M184V RTs had 5- and 200-fold-increased resistance to 3TCTP,
respectively. These results parallel the trend in 3TC sensitivity
observed with cultured virus (wild-type > P157S 
M184V) (Fig.
1A and Table 2).
Although the M184V and P157S viruses showed increased sensitivity to
AZT in culture (Fig.
1B and Table
2), the purified RTs
containing these
mutations both showed modest AZTTP resistance
(two- and threefold,
respectively) (Table
3). Similar discrepancies
between virus
susceptibility to AZT and inhibition of purified
RTs by AZTTP have been
noted in other studies (
18,
31). The
biochemical basis of
this discordance is not fully understood,
but it is clear that
conventional assays used to measure AZTTP
susceptibilities of purified
RTs do not accurately reflect the
susceptibilities of virus isolates to
AZT.
Existence of low-level 3TC-resistant variants in vivo.
The
P157S mutation described here was detected in a significant proportion
of cloned RT sequences from a patient (C0034b) after 2 years of
AZT-plus-3TC combination chemotherapy (25); M184V, five AZT
resistance mutations (at amino acid positions 41, 67, 70, 215, and
219), and other mutations were also present in the sequences from this
individual. A search of 912 viral sequences deposited in the Los Alamos
HIV database also revealed the presence of the P157S mutation in the
pol gene sequence from a German isolate of HIV-1 (clone
NH51, accession no. LO7423) submitted in 1992 (16). Other
point mutations conferring low-level resistance to 3TC (e.g., K70E,
K65R, and V75T) are also occasionally observed in isolates from
patients receiving nucleoside analog therapy (33). The
clinical significance of these rare variants is not known. It is likely
that such mutations exist in viral populations at low frequencies prior
to and/or during the course of therapy (5) and may
contribute to the development of high-level drug resistance in
3TC-treated individuals (5, 30).
Contribution of RT template grip to drug susceptibility.
Cocrystal structures of HIV-1 RT bound to template-primer show that
P157 is located near the N terminus of helix 
E, which contributes to
the "template grip" functionality of the enzyme (10,
13). P157 interacts with the minor groove of the template strand,
making van der Waals contacts with both the sugar and base moieties of
the nucleotide located two residues from the catalytic active site.
P157 does not directly interact with the incoming deoxynucleoside
triphosphate. Thus, the altered drug susceptibility conferred by P157S
must be due to an indirect effect on drug triphosphate recognition at
the active site. This idea is supported by the observation that other
mutations in the template grip region of RT resulted in resistance to
phosphonoformic acid (a pyrophosphate analog) and altered
susceptibility to a variety of nucleoside analogs (11, 21, 29,
38-40, 43). Boyer et al. (3) propose that the
template grip mutant E89G confers drug resistance by repositioning the
template-primer at the active site, thereby perturbing the precise
relative position of protein and nucleic acid required for normal
substrate recognition. This mechanism might also explain the
alterations in drug susceptibility resulting from P157S and other
mutations in the template grip of RT. Additional biochemical,
biophysical, and structural studies are required to directly test this model.
| |
ACKNOWLEDGMENTS |
This work was supported by Public Health Service grants R01
AI34834, R01 AI38755, and P30 CA42014 to B.P., R01 AI28189 to T.N., and
F32 AI10139 to R.A.S. from the National Institutes of Health and by the
Department of Veterans Affairs and the Georgia Research Center on AIDS
and HIV Infection (R.F.S.).
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Eccles Institute
of Human Genetics, University of Utah, Salt Lake City, UT 84112. Phone: (801) 585-6342. Fax: (801) 585-3501. E-mail:
bpreston{at}hci.utah.edu.
| |
REFERENCES |
| 1.
|
Back, N. K.,
M. Nijhuis,
W. Keulen,
C. A. Boucher,
B. O. Oude Essink,
A. B. van Kuilenburg,
A. H. van Gennip, and B. Berkhout.
1996.
Reduced replication of 3TC-resistant HIV-1 variants in primary cells due to a processivity defect of the reverse transcriptase enzyme.
EMBO J.
15:4040-4049[Medline].
|
| 2.
|
Boucher, C. A. B.,
N. Cammack,
P. Schipper,
R. Schuurman,
P. Rouse,
M. A. Wainberg, and J. M. Cameron.
1993.
High-level resistance to () enantiomeric 2'-deoxy-3'-thiacytidine in vitro is due to one amino acid substitution in the catalytic site of human immunodeficiency virus type 1 reverse transcriptase.
Antimicrob. Agents Chemother.
37:2231-2234[Abstract/Free Full Text].
|
| 3.
|
Boyer, P. L.,
C. Tantillo,
A. Jacobo-Molina,
R. G. Nanni,
J. Ding,
E. Arnold, and S. H. Hughes.
1994.
Sensitivity of wild type human immunodeficiency virus type 1 reverse transcriptase to dideoxynucleotides depends on template length; the sensitivity of drug resistant mutants does not.
Proc. Natl. Acad. Sci. USA
91:4882-4886[Abstract/Free Full Text].
|
| 4.
|
Charneau, P.,
G. Mirambeau,
P. Roux,
S. Paulous,
H. Buc, and F. Clavel.
1994.
HIV 1 reverse transcription. A termination step at the center of the genome.
J. Mol. Biol.
241:651-662[Medline].
|
| 5.
|
Coffin, J. M.
1995.
HIV population dynamics in vivo: implications for genetic variation, pathogenesis, and therapy.
Science
267:483-489.
|
| 6.
|
Cronn, R. C.,
K. M. Remington,
B. D. Preston, and T. W. North.
1992.
Inhibition of reverse transcriptase from feline immunodeficiency virus by analogs of 2'-deoxyadenosine-5'-triphosphate.
Biochem. Pharmacol.
44:1375-1381[Medline].
|
| 7.
|
D'Aquila, R. T.,
V. A. Johnson,
S. L. Welles,
A. J. Japour,
D. R. Kuritzkes,
V. DeGruttola,
P. S. Reichelderfer,
R. W. Coombs,
C. S. Crumpacker,
J. O. Kahn, and D. D. Richman.
1995.
Zidovudine resistance and HIV-1 disease progression during antiretroviral therapy. AIDS Clinical Trials Group Protocol 116B/117 Team and the Virology Committee Resistance Working Group.
Ann. Intern. Med.
122:401-408[Abstract/Free Full Text].
|
| 8.
|
Doolittle, R. F.,
D. F. Feng,
M. S. Johnson, and M. A. McClure.
1989.
Origins and evolutionary relationships of retroviruses.
Q. Rev. Biol.
64:1-30[Medline].
|
| 9.
|
Gao, Q.,
Z. Gu,
M. A. Parniak,
J. Cameron,
N. Cammack,
C. Boucher, and M. A. Wainberg.
1993.
The same mutation that encodes low-level human immunodeficiency virus type 1 resistance to 2',3'-dideoxyinosine and 2',3'-dideoxycytidine confers high-level resistance to the () enantiomer of 2',3'-dideoxy-3'-thiacytidine.
Antimicrob. Agents Chemother.
37:1390-1392[Abstract/Free Full Text].
|
| 10.
|
Huang, H.,
R. Chopra,
G. L. Verdine, and S. C. Harrison.
1998.
Structure of a covalently trapped catalytic complex of HIV 1 reverse transcriptase: implications for drug resistance.
Science
282:1669-1675[Abstract/Free Full Text].
|
| 11.
|
Im, G. J.,
E. Tramontano,
C. J. Gonzalez, and Y. C. Cheng.
1993.
Identification of the amino acid in the human immunodeficiency virus type 1 reverse transcriptase involved in the pyrophosphate binding of antiviral nucleoside triphosphate analogs and phosphonoformate. Implications for multiple drug resistance.
Biochem. Pharmacol.
46:2307-2313[Medline].
|
| 12.
|
Iversen, A. K. N.,
R. W. Shafer,
K. Wehrly,
M. A. Winters,
J. I. Mullins,
B. Chesebro, and T. C. Merigan.
1996.
Multidrug-resistant human immunodeficiency virus type 1 strains resulting from combination antiretroviral therapy.
J. Virol.
70:1086-1090[Abstract].
|
| 13.
|
Jacobo-Molina, A.,
J. Ding,
R. G. Nanni,
A. D. Clark, Jr.,
X. Lu,
C. Tantillo,
R. L. Williams,
G. Kamer,
A. L. Ferris,
P. Clark,
A. Hizi,
S. H. Hughes, and E. Arnold.
1993.
Crystal structure of human immunodeficiency virus type 1 reverse transcriptase complexed with double-stranded DNA at 3.0 Å resolution shows bent DNA.
Proc. Natl. Acad. Sci. USA
90:6320-6324[Abstract/Free Full Text].
|
| 14.
|
Kemp, S. D.,
C. Shi,
S. Bloor,
P. R. Harrigan,
J. W. Mellors, and B. A. Larder.
1998.
A novel polymorphism at codon 333 of human immunodeficiency virus type 1 reverse transcriptase can facilitate dual resistance to zidovudine and L-2',3'-dideoxy-3'-thiacytidine.
J. Virol.
72:5093-5098[Abstract/Free Full Text].
|
| 15.
|
Kohlstaedt, L. A.,
J. Wang,
J. M. Friedman,
P. A. Rice, and T. A. Steitz.
1992.
Crystal structure at 3.5 Å resolution of HIV-1 reverse transcriptase complexed with an inhibitor.
Science
256:1783-1790[Abstract/Free Full Text].
|
| 16.
| Korber, B., B. Hahn, B. Foley, J. W. Mellors, T. Leitner, G. Myers, F. McCutchan, and F. Kuiken (ed.). December
1998, revision date. Human retroviruses and AIDS 1998: a compilation
and analysis of nucleic acid and amino acid sequences. [Online.]
Theoretical Biology and Biophysics Group, Los Alamos, N. Mex.
http://hiv-web.lanl.gov. [11 March 1999, last date accessed.]
|
| 17.
|
Kuritzkes, D. R.,
J. B. Quinn,
S. L. Benoit,
D. L. Shugarts,
A. Griffin,
M. Bakhtiari,
D. Poticha,
J. J. Eron,
M. A. Fallon, and M. Rubin.
1996.
Drug resistance and virologic response in NUCA 3001, a randomized trial of lamivudine (3TC) versus zidovudine (ZDV) versus ZDV plus 3TC in previously untreated patients.
AIDS
10:975-981[Medline].
|
| 18.
|
Lacey, S. F.,
J. E. Reardon,
E. S. Furfine,
T. A. Kunkel,
K. Bebenek,
K. A. Eckert,
S. D. Kemp, and B. A. Larder.
1992.
Biochemical studies on the reverse transcriptase and RNase H activities from human immunodeficiency virus strains resistant to 3'-azido-3'-deoxythymidine.
J. Biol. Chem.
267:15789-15794[Abstract/Free Full Text].
|
| 19.
|
Larder, B. A.
1994.
Interactions between drug resistance mutations in human immunodeficiency virus type 1 reverse transcriptase.
J. Gen. Virol.
75:951-957[Abstract/Free Full Text].
|
| 20.
|
Larder, B. A.,
S. D. Kemp, and P. R. Harrigan.
1995.
Potential mechanism for sustained antiretroviral efficacy of AZT-3TC combination therapy.
Science
269:696-699[Abstract/Free Full Text].
|
| 21.
|
Mellors, J. W.,
H. Z. Bazmi,
R. F. Schinazi,
B. M. Roy,
Y. Hsiou,
E. Arnold,
J. Weir, and D. L. Mayers.
1995.
Novel mutations in reverse transcriptase of human immunodeficiency virus type 1 reduce susceptibility to foscarnet in laboratory and clinical isolates.
Antimicrob. Agents Chemother.
39:1087-1092[Abstract].
|
| 22.
|
Miller, M. D.,
K. E. Anton,
A. S. Mulato,
P. D. Lamy, and J. M. Cherrington.
1999.
Human immunodeficiency virus type 1 expressing the lamivudine associated M184V mutation in reverse transcriptase shows increased susceptibility to adefovir and decreased replication capability in vitro.
J. Infect. Dis.
179:92-100[Medline].
|
| 23.
|
Miller, V.,
A. Phillips,
C. Rottmann,
S. Staszewski,
R. Pauwels,
K. Hertogs,
M. P. de Bethune,
S. D. Kemp,
S. Bloor,
P. R. Harrigan, and B. A. Larder.
1998.
Dual resistance to zidovudine and lamivudine in patients treated with zidovudine-lamivudine combination therapy: association with therapy failure.
J. Infect. Dis.
177:1521-1532[Medline].
|
| 24.
|
Miller, V.,
M. Sturmer,
S. Staszewski,
B. Groschel,
K. Hertogs,
M. P. de Bethune,
R. Pauwels,
P. R. Harrigan,
S. Bloor,
S. D. Kemp, and B. A. Larder.
1998.
The M184V mutation in HIV 1 reverse transcriptase (RT) conferring lamivudine resistance does not result in broad cross resistance to nucleoside analogue RT inhibitors.
AIDS
12:705-712[Medline].
|
| 25.
|
Nijhuis, M.,
R. Schuurman,
D. de Jong,
R. van Leeuwen,
J. Lange,
S. Danner,
W. Keulen,
T. de Groot, and C. A. Boucher.
1997.
Lamivudine-resistant human immunodeficiency virus type 1 variants (184V) require multiple amino acid changes to become co-resistant to zidovudine in vivo.
J. Infect. Dis.
176:398-405[Medline].
|
| 26.
|
North, T. W.,
R. C. Cronn,
K. M. Remington, and R. T. Tandberg.
1990.
Direct comparisons of inhibitor sensitivities of reverse transcriptases from feline and human immunodeficiency viruses.
Antimicrob. Agents Chemother.
34:1505-1507[Abstract/Free Full Text].
|
| 27.
| O'Neil, P. K., G. Sun, H. Yu, J. P. Dougherty, and B. D. Preston. Unpublished results.
|
| 28.
|
Pear, W. S.,
G. P. Nolan,
M. L. Scott, and D. Baltimore.
1993.
Production of high titer helper free retroviruses by transient transfection.
Proc. Natl. Acad. Sci. USA
90:8392-8396[Abstract/Free Full Text].
|
| 29.
|
Prasad, V. R.,
I. Lowy,
T. de los Santos,
L. Chiang, and S. P. Goff.
1991.
Isolation and characterization of a dideoxyguanosine triphosphate resistant mutant of human immunodeficiency virus reverse transcriptase.
Proc. Natl. Acad. Sci. USA
88:11363-11367[Abstract/Free Full Text].
|
| 30.
|
Preston, B. D.
1997.
Reverse transcriptase fidelity and HIV 1 variation.
Science
275:228-229[Medline].
|
| 31.
|
Remington, K. M.,
Y.-Q. Zhu,
T. R. Phillips, and T. W. North.
1994.
Rapid phenotypic reversion of zidovudine-resistant feline immunodeficiency virus without loss of drug-resistant reverse transcriptase.
J. Virol.
68:632-637[Abstract/Free Full Text].
|
| 32.
|
Richman, D. D.
1994.
Resistance, drug failure, and disease progression.
AIDS Res. Hum. Retroviruses
10:901-905[Medline].
|
| 33.
|
Schinazi, R. F.,
B. A. Larder, and J. W. Mellors.
1999.
Resistance table: mutations in retroviral genes associated with drug resistance. 1999-2000 update.
Int. Antivir. News
7:46-69.
|
| 34.
|
Schinazi, R. F.,
R. M. Lloyd, Jr.,
M.-H. Nguyen,
D. L. Cannon,
A. McMillan,
N. Ilksoy,
C. K. Chu,
D. C. Liotta,
H. Z. Bazmi, and J. W. Mellors.
1993.
Characterization of human immunodeficiency viruses resistant to oxathiolane-cytosine nucleosides.
Antimicrob. Agents Chemother.
37:875-881[Abstract/Free Full Text].
|
| 35.
|
Smith, R. A.,
K. M. Remington,
B. D. Preston,
R. F. Schinazi, and T. W. North.
1998.
A novel point mutation at position 156 of reverse transcriptase from feline immunodeficiency virus confers resistance to the combination of ()--2',3'-dideoxy-3'-thiacytidine and 3'-azido-3'-deoxythymidine.
J. Virol.
72:2335-2340[Abstract/Free Full Text].
|
| 36.
|
Stahlhut, M. W., and D. B. Olsen.
1996.
Expression and purification of retroviral HIV 1 reverse transcriptase.
Methods Enzymol.
275:122-133[Medline].
|
| 37.
|
Swingler, S.,
P. Gallay,
D. Camaur,
J. Song,
A. Abo, and D. Trono.
1997.
The Nef protein of human immunodeficiency virus type 1 enhances serine phosphorylation of the viral matrix.
J. Virol.
71:4372-4377[Abstract].
|
| 38.
|
Tachedjian, G.,
D. J. Hooker,
A. D. Gurusinghe,
H. Bazmi,
N. J. Deacon,
J. Mellors,
C. Birch, and J. Mills.
1995.
Characterisation of foscarnet resistant strains of human immunodeficiency virus type 1.
Virology
212:58-68[Medline].
|
| 39.
|
Tachedjian, G.,
J. Mellors,
H. Bazmi,
C. Birch, and J. Mills.
1996.
Zidovudine resistance is suppressed by mutations conferring resistance of human immunodeficiency virus type 1 to foscarnet.
J. Virol.
70:7171-7181[Abstract/Free Full Text].
|
| 40.
|
Tachedjian, G.,
J. W. Mellors,
H. Bazmi, and J. Mills.
1998.
Impaired fitness of foscarnet resistant strains of human immunodeficiency virus type 1.
AIDS Res. Hum. Retroviruses
14:1059-1064[Medline].
|
| 41.
|
Tian, H.,
J. Whitcomb,
K. Limoli,
T. Wrin,
G. Winslow,
N. Parkin,
D. Smith,
Y. Lie,
M. Bakthiari,
D. Shugarts,
R. Schooley,
D. Kuritzkes, and C. Petropoulos.
1998.
Zidovudine/lamivudine co-resistance is preceded by a transient period of zidovudine hypersensitivity, abstr. 30, p. 22-23.
In
Programme and abstracts of the 2nd International Workshop on HIV Drug Resistance and Treatment Strategies. International Medical Press, London, United Kingdom.
|
| 42.
|
Tisdale, M.,
S. D. Kemp,
N. R. Parry, and B. A. Larder.
1993.
Rapid in vitro selection of human immunodeficiency virus type 1 resistant to 3'-thiacytidine inhibitors due to a mutation in the YMDD region of reverse transcriptase.
Proc. Natl. Acad. Sci. USA
90:5653-5656[Abstract/Free Full Text].
|
| 43.
|
Tramontano, E.,
G. Piras,
J. W. Mellors,
M. Putzolu,
H. Z. Bazmi, and P. La Colla.
1998.
Biochemical characterization of HIV 1 reverse transcriptases encoding mutations at amino acid residues 161 and 208 involved in resistance to phosphonoformate.
Biochem. Pharmacol.
56:1583-1589[Medline].
|
| 44.
| Wainberg, M. A., M. D. Miller, Y. Quan, H. Solomon, A. S. Mulato, P. D. Lamy, N. A. Margot, K. E. Anton, and J. M. Cherrington. In vitro selection and
characterization of HIV-1 with reduced susceptibility to PMPA. Antivir.
Ther., in press.
|
| 45.
|
Wilson, J. E.,
A. Aulabaugh,
B. Caligan,
S. McPherson,
J. K. Wakefield,
S. Jablonski,
C. D. Morrow,
J. E. Reardon, and P. A. Furman.
1996.
Human immunodeficiency virus type-1 reverse transcriptase. Contribution of Met-184 to binding of nucleoside 5'-triphosphate.
J. Biol. Chem.
271:13656-13662[Abstract/Free Full Text].
|
| 46.
|
Winters, M. A.,
K. L. Coolley,
Y. A. Girard,
D. J. Levee,
H. Hamdan,
R. W. Shafer,
D. A. Katzenstein, and T. C. Merigan.
1998.
A 6-basepair insert in the reverse transcriptase gene of human immunodeficiency virus type 1 confers resistance to multiple nucleoside inhibitors.
J. Clin. Investig.
102:1769-1775[Medline].
|
Antimicrobial Agents and Chemotherapy, August 1999, p. 2077-2080, Vol. 43, No. 8
0066-4804/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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