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Journal of Virology, December 1999, p. 10289-10295, Vol. 73, No. 12
Department of Genito-Urinary Medicine and Communicable
Diseases,
Received 22 March 1999/Accepted 4 September 1999
Patients with human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP)
typically have a high HTLV-1 proviral load in peripheral blood
mononuclear cells and abundant, activated HTLV-1-specific cytotoxic T
lymphocytes (CTLs). No effective treatment for HAM/TSP has been
described so far. We report a 10-fold reduction in viral DNA for five
patients with HAM/TSP during treatment with the reverse transcriptase
inhibitor lamivudine. In one patient with recent-onset HAM/TSP, the
reduction in viral DNA was associated with a fall in the frequency of
CTLs specific to two peptides in the immunodominant viral antigen Tax. The half-life of peripheral blood mononuclear cell populations was
estimated from changes in viral DNA copy number, CTL frequency, reduction in CD25 expression, and the loss of dicentric chromosomes following radiation-induced damage. Each of these four different techniques indicated a cellular half-life of approximately 3 days consistent with continuous lymphocyte replication and destruction. These results indicate that viral replication through reverse transcription significantly contributes to the maintenance of HTLV-1
viral DNA load. The relative contribution of proliferation versus
replication may vary between infected people.
The human T-cell leukemia virus type
1 (HTLV-1), an endemic retrovirus, causes lifelong infection. The
majority of persons infected are asymptomatic carriers. In a minority,
HTLV-1 infection causes inflammatory diseases characterized by
lymphocytic infiltration, of which HTLV-1-associated
myelopathy/tropical spastic paraparesis (HAM/TSP) is the most notable
and causes significant morbidity (7, 20). HTLV-1 also causes
adult T-cell leukemia/lymphoma, an aggressive condition resistant to
chemotherapy (9, 30). The proviral load of HTLV-1 in
peripheral blood mononuclear cells (PBMCs) has been estimated by
diverse techniques: mean proviral load is approximately 10 copies/100
PBMCs in patients with HAM/TSP and 10-fold less in asymptomatic
carriers (16). HTLV-1 proviral load might be maintained
either by lymphocyte proliferation, with duplication of the HTLV-1
genome at every cell division, or by classical retroviral replication
via reverse transcription. The relative contribution of these two
replication pathways to the total proviral load has not been
determined. However, multiple clonal expansions of HTLV-1-infected
lymphocytes have been demonstrated for patients with HAM/TSP and for
asymptomatic carriers (2). Consequently, Wattel et al. have
hypothesized that lymphocyte proliferation maintains HTLV-1 proviral
load and that the absence of reverse transcription after a few initial
rounds of replication might explain the relative conservation of the
HTLV-1 genome compared to the other human retroviruses (32).
However, a number of observations suggest that viral antigen expression
is continuous and that ongoing viral replication occurs in at least a
subpopulation of infected cells. HTLV-1-infected subjects have high
titers of antibody to structural gene products throughout the course of
the infection (5). HTLV-1 mRNA is detected in peripheral
blood lymphocytes especially in patients with a high proviral load
(19). A persistent active cytotoxic T-cell response has been
demonstrated for patients with HAM/TSP (11) and for
asymptomatic carriers (4). Despite an interisolate diversity
of only 4 to 8% between the major HTLV-1 subtypes (12), within-isolate sequence variation and a high dN/dS ratio in the tax gene have been demonstrated, particularly for
asymptomatic carriers (17).
If proviral load were maintained by reverse transcription, sustained
inhibition of reverse transcriptase (RT) may be expected to reduce
proviral load, by analogy with human immunodeficiency virus (HIV)
infection (1). In addition to its proven in vitro and in
vivo efficacy against HIV, zidovudine has been shown previously to be
effective against murine (21) (Rauscher murine leukemia virus) and feline (26) (feline leukemia virus) retroviruses in vitro and in vivo.
Matsushita et al. (14) found a profound suppression of
HTLV-1 Gag protein production and a reduction in proviral DNA when primary CD4+ T lymphocytes were exposed to HTLV-1 and
cultured in the presence of zidovudine. Nusinoff-Lehrman et al.
(18) also found that at zidovudine concentrations of 2.4 µg/ml or above, HTLV-1-specific DNA could not be detected by Southern
blot analysis when infected lymphocytes were cocultured with
susceptible target cells. Macchi et al. (13) have shown that
low concentrations (as low as 0.1 µM) of zidovudine inhibit
transmission of HTLV-1 to adult PBMCs in vitro, inhibiting the
production of viral DNA and RNA. Zidovudine decreased CD25 expression
on T lymphocytes in culture exposed to HTLV-1 as well as in uninfected
PBMCs, but down-regulation of HLA-DR expression was more marked in
HTLV-1-infected cells. Zidovudine had no antiretroviral effect on PBMCs
already infected with HTLV-1 (13). In rabbits, the
administration of zidovudine inhibited HTLV-1 replication following
inoculation of an HTLV-1-transformed cell line (10). The
cytosine analogue 2',3'-dideoxycytidine (zalcitabine) also inhibited
the synthesis of HTLV-1 viral DNA in CD4+ lymphocytes in
vitro (14). Two groups who had previously used zidovudine to
treat patients with HAM/TSP did not report HTLV-1 proviral load
(8, 24).
In order to elucidate the extent of HTLV-1 replication in vivo, we
studied the effect of nucleoside analogue RT inhibitors on the quantity
of HTLV-1 viral DNA in PBMCs, T-lymphocyte phenotype, anti-Tax
cytotoxic T-lymphocyte (CTL) precursor frequency, and clinical status,
first in a patient with early, progressing HAM/TSP and subsequently in
four other patients with HAM/TSP and high HTLV-1 viral DNA copy number.
Subjects.
The subjects were five patients with
HAM/TSP, whose demographic and clinical characteristics are shown in
Table 1; all cases satisfied the
international criteria for diagnosis of HAM/TSP (34). Four
patients were ambulant with aid, and one was wheelchair bound.
Four had stable disease for more than 3 years, while one, patient TAN,
developed HAM/TSP while participating in a prospective study of
initially asymptomatic HTLV-1 carriers (28). Following a
period of assessment with multiple baseline measurements, treatment with a nucleoside analogue RT inhibitor was initiated. Patient TAN was
treated first with zidovudine (200 mg) three times daily for 3 months
and subsequently with lamivudine (150 mg) twice daily; the other four
patients were treated only with lamivudine (150 mg) twice daily. The
mean period of treatment with lamivudine was 10.2 months (range, 5.6 to
17.2 months). No other treatment was taken concurrently, with the
single exception of patient TAF, who was undergoing treatment with
alpha interferon for hepatitis C virus-related chronic active
hepatitis. The study was approved by the local ethical review board,
and all study participants gave written informed consent.
Quantification of HTLV-1 viral DNA in PBMCs.
To quantify
HTLV-1 DNA in PBMCs, DNA was extracted from 2 × 106
PBMCs by the proteinase K method. Replicate serial dilutions of the DNA
were amplified by a nested-PCR technique that reliably detected a
single copy of HTLV-1 tax DNA in genomic DNA from
105 cells (29). The viral DNA copy number was
calculated from the Poisson distribution of negative samples at the
cutoff dilution. Interassay variability (0.3 log10) was
determined by repeated testing of a random selection of patient samples
(29).
Quantification of CTL frequency.
CTL effector frequency was
determined in a limiting dilution assay (LDA) (4).
CD8+ lymphocytes, separated from fresh PBMCs with M-450
anti-CD8-coated Dynabeads, were plated out at known cell numbers per
well in 96-well plates. The CD8+ cells were stimulated with
phytohemagglutinin (1 µg/ml) in culture medium (RPMI 1640 medium,
10% fetal calf serum, and 10% Lymphocult-T [Biotest UK Ltd.,
Solihull, United Kingdom]) on day 3. On day 7, the cells were divided
into three duplicate 96-well plates and were made up to 200 µl/well
with the same culture medium. LDAs were performed on day 10 with 3,000 51Cr-labelled, peptide-pulsed autologous Epstein-Barr
virus-transformed B cells (target cells) per well. Target cells were
pulsed for 1 h with 50 µM peptide X1 (MEPTLGQHLPTLSFPD) or X6
(VIFCHPGQLGAFLTN), which contained the immunodominant Tax epitopes
recognized by patient TAN's CTLs (data not shown). Target cells pulsed
with medium alone were used as controls to measure nonspecific lysis. Lysis in each well was considered positive if the 51Cr
release exceeded the mean + 3 standard deviations of the
nonspecific lysis. The effector frequencies for both X1 and X6 were
added at each time point and represent the minimum number of
Tax-specific CTLs in each sample. The frequency of activated CTLs
measured in the LDA correlated closely with the activity of CTLs in the bulk CTL assay (data not shown) and was independent of the background lysis.
Lymphocyte half-life.
To determine the lymphocyte half-life,
10 ml of peripheral blood at each time point was taken into
preservative-free sodium heparin (20 IU/ml; Monoparin; CP
Pharmaceuticals, Barnstable, United Kingdom) before and after
computerized tomography of patient TAN's thorax, which was performed
(for a clinical indication) during the 6th week of therapy with
lamivudine (week 186), which coincided with the nadir in HTLV-1 DNA
copies and anti-HTLV-1 Tax CTL frequency. The lymphocytes were
separated as described above and then cultured for 48 h in RPMI
1640 medium with 15% bovine serum (Serum Supreme; BioWhittaker,
Walkersville, Md.) and 10 µg of lectin (Sigma Chemical Co., St.
Louis, Mo.) per ml in a conical flask. After disaggregation by
pipetting, the cells were incubated with 0.05 µg of
N-deacetyl-N-methylcolchicine (Demecolcine; Sigma-Aldrich Co. Ltd., Poole, United Kingdom) per ml at 37°C for 30 to 180 min, pelleted (1,000 × g for 5 min), and
resuspended in 10 ml of 0.075 M KCl for 0 to 15 min at room
temperature. Cells were again centrifuged (1,000 × g
for 5 min), resuspended gently in 10 ml of freshly prepared 3:1
methanol-glacial acetic acid, and stored at 4°C. Chromosome
preparations were made by dropping the fragile cells onto chilled glass
slides and staining them with 3% Giemsa stain for 4 min. Cells
(n = 200) were examined for dicentric chromosomes by a
blinded observer (C.A.M.).
Lymphocyte phenotyping.
The phenotype of freshly isolated
PBMCs was determined by flow cytometry (FACScan; Becton Dickinson,
Oxford, United Kingdom) in the lymphocyte gate with a panel of
monoclonal antibodies (MAbs) specific to CD3, CD4, CD8, CD25, CD38, and
HLA-DR (Becton Dickinson). A fluorescein isothiocyanate-conjugated
anti-mouse immunoglobulin F(ab)2 fragment was used as the
second layer. In some assays, directly conjugated phycoerythrin- and
fluorescein isothiocyanate-conjugated MAbs were used. To avoid
nonspecific binding, the Fc receptor was blocked with human AB serum in
all washes and incubations. Control preparations included omission of
the first-layer MAb and its replacement by a mouse immunoglobulin of a
matched isotype. Results were evaluated on a FACScan flow cytometer
with a lymphocyte gate.
RT gene sequencing.
To search for mutations in the HTLV-1
pol gene that might confer resistance to lamivudine, we
determined the sequence of a 2,843-bp region of HTLV-1 viral DNA
encompassing the full coding region of RT and the initial 909 bp of
INT. DNA was extracted from patient TAN's PBMCs before
treatment, during rebound of viral DNA while the patient was on
lamivudine treatment, and when the viral DNA load had returned to
baseline levels after 24 weeks of lamivudine therapy. The sequence of
PCR-amplified DNA was determined, by using an ABI 377 automated DNA
sequencer, in forward and reverse directions, by direct sequencing
without cloning; Taq polymerase errors should therefore make
a negligible contribution to the sequence obtained.
The change in HTLV-1 DNA copies per 100 PBMCs in all five
patients, in relation to duration of therapy with lamivudine, is shown
in Fig. 1A. The median pretreatment load
was 2.2 HTLV-1 DNA copies/100 PBMCs. The median reduction in viral DNA
copy number of all five patients was 1.1 log10. The median
nadir in viral DNA load from pretreatment levels was 2.35 log10 but the time to reach the nadir varied between
patients from 4 to 24 weeks (Fig. 1B).
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Effect of Lamivudine on Human T-Cell Leukemia Virus
Type 1 (HTLV-1) DNA Copy Number, T-Cell Phenotype, and Anti-Tax
Cytotoxic T-Cell Frequency in Patients with HTLV-1-Associated
Myelopathy
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
MATERIALS AND METHODS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
TABLE 1.
Characteristics of subjectsa
RESULTS
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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FIG. 1.
All patients. (A) Median changes in HTLV-1 DNA copy
number for five HTLV-1-infected subjects treated with lamivudine over
24 weeks. (B) Maximum reduction (nadir) in viral DNA copy number during
lamivudine therapy in five patients with HAM/TSP: TAD (solid line with
solid squares), TAL (short-dashed line with open squares), TAK
(long-dashed line with open squares), TAF (dashed line with open
circles), and TAN (shaded line with open triangle).
Patient TAN had been monitored prospectively over a period of 3 years prior to and during the development of HAM/TSP; the HTLV-1 DNA copy number in PBMCs was consistently high over this period, with a median of 14 (range, 7 to 28) copies of viral DNA per 100 PBMCs, compared with other asymptomatic carriers (median viral DNA, 0.28 copies per 100 PBMCs) (28), and this was not significantly reduced during 3 months' treatment with the RT inhibitor zidovudine (median, 10.5 copies/100 PBMCs; range, 3 to 14 copies) (Fig. 2A). During the first 3 weeks of therapy with lamivudine (weeks 180 to 183), HTLV-1 viral DNA copy number fell from 3 to 0.03 per 100 PBMCs (Fig. 2A). While patient TAN was on continuous therapy with lamivudine, viral DNA load rose to baseline levels after 8 weeks and then fluctuated between baseline and nadir over 3 orders of magnitude for the full 24-week duration of therapy. After cessation of lamivudine, the fluctuations became smaller and the viral DNA load remained consistently above 1 copy per 100 PBMCs for a further 70 weeks (Fig. 2A). The rate of HTLV-1 viral DNA decline after the initiation of lamivudine indicated a viral DNA half-life of about 3.2 days. The estimated total number of HTLV-1-infected PBMCs prior to lamivudine treatment was 3 × 107. The observed half-life suggests that approximately 6 × 106 new cells become infected every day.
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The consensus sequence of RT after 14 weeks of lamivudine therapy (week
201) did not differ from the pre-lamivudine (pre-zidovudine and during
zidovudine) treatment sequences. However, the consensus RT sequence
after 36 weeks of lamivudine therapy (week 224) differed at 11 nucleotide positions from the pretreatment sequences (Table 2). Of these 11 sequences, only one
(A3982T) changed the predicted amino acid sequence of RT (Q488H); the
new amino acid residue (H488) is present in seven of nine HTLV-1
sequences in the GenBank-EMBL database and is therefore unlikely to
have been selected in patient TAN because it conferred resistance to
lamivudine. In particular, no YMDD substitution was found. One further
silent nucleotide substitution was found in the integrase coding region
(T4588C); again, this substitution appeared for the first time after 24 weeks of lamivudine therapy.
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Prior to treatment, a high frequency of activated anti-Tax
CD8+ lymphocytes recognizing several Tax epitopes
simultaneously was present in the peripheral circulation of patient
TAN. During treatment with lamivudine, the anti-Tax CTL frequency
declined with the fall in viral DNA load and then rose again as the
viral DNA copy number increased (Fig. 2B). The frequency of anti-Tax
CTLs prior to lamivudine treatment was 7.9 × 10
4
CD8+ cells, declining to 1.6 × 106
CD8+ cells after 5 weeks of therapy. This is consistent
with a CTL half-life of 3.9 days. Since the LDA is conducted over a
period equal to 2.5 in vivo half-lives of the CTLs, the results may
underestimate the frequency of Tax-specific CTLs; however, in vitro
their half-life may be prolonged by the exogenous interleukin-2 support.
Prospective quantification of T-lymphocyte phenotypic markers was undertaken with patient TAN. There was no trend in the absolute counts or percentage of CD4+ or CD8+ T-lymphocyte counts or in the absolute number of circulating lymphocytes over time and no change in relation to lamivudine therapy. However, the proportion of CD25+ lymphocytes, which was elevated before and after lamivudine therapy, fell from 15 to 2%, coincident with the reduction in viral DNA copies on the initiation of lamivudine therapy and fluctuated in a manner parallel to that of the viral DNA copy number and anti-Tax CTL precursor frequency changes during therapy (Fig. 2C). The estimated half-life of CD25+ lymphocytes was 6.1 days.
The presence of both abundant anti-Tax CTLs and the high viral DNA load suggested the possibility that there might be frequent CTL-mediated killing of infected CD4+ T lymphocytes in vivo. Lymphocyte half-lives can be estimated by measuring the rate of disappearance from the circulation of lymphocytes with stable, radiation-induced chromosome damage (15). We therefore counted the proportion of PBMCs that contained dicentric chromosomes, after patient TAN had undergone computerized tomography of the thorax, and their rate of disappearance from the blood (Fig. 3). The estimated half-life of 2.5 days reflects the rate at which the PBMCs were dividing or dying and is consistent with the observed rapid reduction in HTLV-1 viral DNA (estimated half-life, 3.2 days) and CTL frequency (estimated half-life, 3.9 days).
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The only clinical improvement was seen in the patient with recent-onset HAM/TSP, an improvement which persisted only during the period when lamivudine appeared to have reduced the viral burden. The patients with severe, long-standing, and stable disability showed no symptomatic improvement despite reduced HTLV-1 DNA load (27).
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DISCUSSION |
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Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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In this study, zidovudine treatment of patient TAN led to no change in HTLV-1 viral DNA copy number, CTL precursor frequency, or T-lymphocyte phenotype. Treatment was therefore changed to lamivudine, a cytosine analogue which has been found to be safe and effective with patients infected with HIV-1 (31) or hepatitis B virus (6). Other licensed nucleoside analogues, didanosine, stavudine, and zalcitabine, are associated with peripheral neuropathy during prolonged therapy (25). In cell proliferation assays (Glaxo Research and Development Ltd.) (12a), lamivudine does not affect the uptake of [3H]thymidine by uninfected and HTLV-1-infected PBMCs. The 50% infective dose of lamivudine in PBMCs was 2,533 µM (compared to 90 µM for zidovudine). Similar results were obtained for lymphocyte cell lines including HTLV-1 provirus-bearing C8166 cells. The administration of lamivudine orally, in the dose used in this study, results in a maximum concentration of lamivudine in serum which is 6 log10 below the antiproliferative concentration.
Initiation of lamivudine therapy was followed by an immediate reduction in viral DNA copy number. Subsequently, the viral DNA copy number oscillated, with the troughs gradually rising toward the baseline. CTL precursor frequency and CD25+ T lymphocytes also showed periodic oscillations during lamivudine therapy, which appeared to coincide with the changes in viral DNA load. Mathematical analysis shows that such oscillations in the quantity of viral DNA may result from the production of HTLV-1-infected cells from both cell division (not affected by lamivudine) and reverse transcription and from the interplay of viral production with CTL-mediated killing of infected cells (33). This model suggests that the high viral DNA load of HTLV-1 is indeed maintained by proviral expansion but that this is consistent with, and indeed may require, a high rate of HTLV-1 virion production (33). The subsequent return to pretreatment viral DNA levels in a compliant patient could be due to cellular resistance (a reduction in the uptake or phosphorylation of lamivudine) or the emergence of viral variants with decreased susceptibility to lamivudine. Lamivudine resistance in HIV-1 infection is often accompanied by a mutation in the active site of the HIV-1 RT (22). However, the corresponding region in the HTLV-1 RT gene was unchanged for patient TAN. The only coding change that appears in the RT gene following lamivudine treatment is commonly found in naturally occurring isolates of HTLV-1 and is therefore unlikely to have been selected because it confers resistance to lamivudine. However, the de novo appearance of 11 nucleotide substitutions in the consensus sequence of a 2,843-bp region of the HTLV-1 genome strongly suggests that the virus is replicating, causing the introduction of polymerase errors, and that the viral population passed through a bottleneck. The newly emergent consensus sequence represents a clone that (by chance) survived the genetic bottleneck and grew to replace the preexisting dominant sequence. Although we cannot exclude the possibility of drug resistance mutations in a minority of viruses, any such viruses cannot have made a major contribution to the recrudescence of HTLV-1 viral DNA in PBMCs.
Our previous finding of abundant activated anti-Tax CTLs in HTLV-1-infected patients (4) already suggested that there is persistent expression of the tax gene in the infected host. However, it was not clear whether expression was confined to the tax gene or whether it represented persistent replication of HTLV-1. The rapid fall in viral DNA for three patients during treatment with lamivudine suggests that the high pretreatment viral DNA copy number was maintained chiefly by active viral replication. Proliferation of infected lymphocytes, which has been suggested by others to be the main cause of high proviral load in HTLV-1 infection, is not sufficient to maintain the high viral DNA load in these patients. These results are in keeping with the recent observation that HTLV-1 mRNA was more frequently detected in patients with a high proviral load (19). However, for two patients a much more gradual decline in the amount of viral DNA was noted, suggesting that the relative importance of reverse transcription in the maintenance of viral DNA load differs between subjects.
Four independent techniques (limiting dilution analysis of CTL frequency, HTLV-1 viral DNA quantification, fluorescence-activated cell sorting analysis of lymphocyte phenotypes, and the clearance of cells containing dicentric chromosomes) during antiretroviral therapy each produced estimates of the average life expectancy of patient TAN's PBMCs of 3 to 6 days. CTL-mediated killing of HTLV-1-infected cells may account for part of this rapid cell turnover. However, other factors must also have been involved, as even rapid killing of a minority population of PBMCs expressing Tax protein (at most, 14% of PBMCs) and high turnover of CD8+ HTLV-specific CTLs (which may constitute up to 10% of CD8+ PBMCs [16a]) would not reduce the average life expectancy of all PBMCs so far below the normal value of approximately 150 days (memory lymphocytes) or 3.5 years (naive lymphocytes) (15). Vigorous cell activation and proliferation, driven by HTLV-1 Tax protein, may have predisposed PBMCs to apoptosis (3).
In conclusion, lamivudine reduced the amount of HTLV-1 DNA in five of five patients with HAM/TSP. This reduction and the subsequent increase in the amount of viral DNA during treatment are consistent with active viral replication through reverse transcription. The viral kinetics indicate that the importance of viral replication in maintaining viral DNA load varies between patients. The results have important implications for our understanding of HTLV-1 pathogenesis and might open the way to specific therapy for HTLV-1-associated inflammatory disease.
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ACKNOWLEDGMENTS |
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S.E.H. and C.R.M.B. are supported by The Wellcome Trust. G.P.T. was supported by the Jefferiss Trust. The HTLV European Research Network supported by the European Community Biomed Programme (BMH4 CT98-3781) provided a forum for critical appraisal of this work.
Jennifer Tosswill of the Central Public Health Laboratory, Colindale, London, United Kingdom, assisted with the HTLV-1 DNA measurements.
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FOOTNOTES |
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* Corresponding author. Mailing address: Department of Genito-Urinary Medicine and Communicable Diseases, Imperial College School of Medicine, Norfolk Place, London W2 1PG, United Kingdom. Phone and fax: 44 171 886 6738. E-mail: g.p.taylor{at}ic.ac.uk.
Present address: Institute for Advanced Study, Princeton, NJ 08540.
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REFERENCES |
|---|
|
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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|---|
| 1. | Brun-Vezinet, F., C. Boucher, C. Loveday, D. Descamps, V. Fauveau, J. Izopet, D. Jeffries, S. Kaye, C. Krzyanowski, A. Nunn, R. Schuurman, J. M. Seigneurin, C. Tamalet, R. Tedder, J. Weber, and G. J. Weverling. 1997. HIV-1 viral load, phenotype, and resistance in a subset of drug-naive participants from the Delta trial. The National Virology Groups. Delta Virology Working Group and Coordinating Committee. Lancet 350:983-990[Medline]. |
| 2. | Cavrois, M., A. Gessain, S. Wain-Hobson, and E. Wattel. 1996. Proliferation of HTLV-1 infected circulating cells in vivo in all asymptomatic carriers and patients with TSP/HAM. Oncogene 12:2419-2423[Medline]. |
| 3. | Chlichlia, K., G. Moldenhauer, P. T. Daniel, M. Busslinger, L. Gazzolo, V. Schirrmacher, and K. Khazaie. 1995. Immediate effects of reversible HTLV-I tax function: T-cell activation and apoptosis. Oncogene 10:269-277[Medline]. |
| 4. | Daenke, S., A. Kermonde, S. E. Hall, G. Taylor, J. Weber, S. Nightingale, and C. R. M. Bangham. 1996. High activated and memory cytotoxic T-cell responses to HTLV-1 in healthy carriers and patients with tropical spastic paraparesis. Virology 217:139-146[Medline]. |
| 5. | Dalgleish, A., J. Richardson, E. Matutes, K. Cruickshank, A. Newell, A. Sinclair, R. Thorpe, M. Brasher, J. Weber, D. Catovsky, et al. 1989. HTLV-I infection in tropical spastic paraparesis: lymphocyte culture and serological response. AIDS Res. Hum. Retroviruses 4:475-485. |
| 6. |
Dienstag, J. L.,
R. P. Perrillo,
E. R. Schiff,
M. Bartholomew,
C. Vicary, and M. Rubin.
1995.
Preliminary trial of lamivudine for chronic hepatitis B infection.
N. Engl. J. Med.
333:1657-1661 |
| 7. | Gessain, A., J. C. Vernant, L. Maurs, F. Barin, O. Gout, A. Calender, and G. de Thé. 1985. Antibodies to human T-lymphotropic virus type-I in patients with tropical spastic paraparesis. Lancet ii:407-409. |
| 8. | Gout, O., A. Gessain, M. Iba-Zizen, S. Kouzan, F. Bolgert, G. de Thé, and O. Lyon-Caen. 1991. The effect of zidovudine on chronic myelopathy associated with HTLV-I. J. Neurol. 238:108-109[Medline]. |
| 9. | International Agency for Research on Cancer. 1996. IARC monographs on the evaluation of carcinogenic risks to humans, vol. 67. Human immunodeficiency viruses and human T-cell lymphotrophic viruses. International Agency for Research on Cancer, Lyon, France |
| 10. | Isono, T., K. Ogawa, and A. Seto. 1990. Antiviral effect of zidovudine in the experimental model of adult T-cell leukaemia in rabbits. Leuk. Res. 14:841-847[Medline]. |
| 11. | Jacobson, S., H. Shida, D. E. McFarlin, A. S. Fauci, and S. Koenig. 1990. Circulating CD8+ cytotoxic T lymphocytes specific for HTLV-I pX in patients with HTLV-I associated neurological disease. Nature 348:245-248[Medline]. |
| 12. |
Koralnik, I. J.,
E. Boeri,
W. C. Saxinger,
A. Lo Monico,
J. Fullen,
A. Gessain,
H.-G. Guo,
R. C. Gallo,
P. Markham,
V. Kalyanaraman,
V. Hirsch,
J. Allen,
K. Murthy,
P. Alford,
J. P. Slattery,
S. J. O'Brien, and G. Franchini.
1994.
Phylogenetic associations of human and simian T-cell leukemia/lymphotropic virus type I strains: evidence for interspecies transmission.
J. Virol.
68:2693-2707 |
| 12a. | Macchi, B. Personal communication. |
| 13. | Macchi, B., I. Faraoni, J. Zhang, S. Grelli, C. Favalli, A. Mastino, and E. Bonmassar. 1997. AZT inhibits the transmission of human T cell leukaemia/lymphoma virus type I to adult peripheral blood mononuclear cells in vitro. J. Gen. Virol. 78:1007-1016[Abstract]. |
| 14. | Matsushita, S., H. Mitsuya, M. S. Reitz, and S. Broder. 1987. Pharmacological inhibition of in vitro infectivity of human T lymphotropic virus type I. J. Clin. Investig. 80:394-400. |
| 15. |
McLean, A. R., and C. A. Michie.
1995.
In vivo estimates of division and death rates of human T lymphocytes.
Proc. Natl. Acad. Sci. USA
92:3707-3711 |
| 16. | Nagai, M., K. Usuku, W. Matsumoto, D. Kodama, N. Takenouchi, T. Moritoyo, S. Hashiguchi, M. Ichinose, C. R. M. Bangham, S. Izumo, and M. Osame. 1998. Analysis of HTLV-I proviral load in 202 HAM/TSP patients and 243 asymptomatic HTLV-I carriers: high proviral load strongly predisposes to HAM/TSP. J. Neurovirol. 4:586-593[Medline]. |
| 16a. | Navarrete, S., S. E. Hall, and C. R. M. Bangham. Unpublished data. |
| 17. |
Niewiesk, S.,
S. Daenke,
C. E. Parker,
G. P. Taylor,
J. N. Weber,
S. Nightingale, and C. R. M. Bangham.
1994.
The transactivator gene of human T-cell leukemia virus type I is more variable within and between healthy carriers than patients with tropical spastic paraparesis.
J. Virol.
68:6778-6781 |
| 18. | Nusinoff-Lehrman, S., M. St. Clair, R. L. Miller, S. Broder, H. R. Wilson, M. Bushby, et al. 1986. Azidothymidine: spectrum of in vitro antimicrobial activity, abstr. 556, p. 66. In Proceedings of the Second International Conference on AIDS, Paris, France, 23 to 25 June 1986 |
| 19. | Okayama, A., N. Tachibana, S. Ishihara, Y. Nagatomo, K. Murai, M. Okamoto, T. Shima, K. Sagawa, H. Tsubouchi, S. Stuver, and N. Mueller. 1997. Increased expression of interleukin-2 receptor alpha on peripheral blood mononuclear cells in HTLV-I tax/rex mRNA-positive asymptomatic carriers. J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. 15:70-75[Medline]. |
| 20. | Osame, M., K. Usuku, S. Izumo, N. Ijichi, H. Amitani, A. Igata, M. Matsumoto, and M. Tara. 1986. HTLV-I associated myelopathy, a new clinical entity. Lancet i:1031-1032. (Letter.) |
| 21. | Ruprecht, R. M., L. G. O'Brien, L. D. Rossoni, and S. Nusinoff-Lehrman. 1986. Suppression of mouse viraemia and retroviral disease by 3'-azido-3'-deoxythymidine. Nature 323:467-469[Medline]. |
| 22. | Schuurman, R., M. Nijhuis, L. M. van-Leeuwen, P. Schipper, D. de-Jong, P. Collis, S. A. Danner, J. Mulder, C. Loveday, C. Christopherson, et al. 1995. Rapid changes in human immunodeficiency virus type 1 RNA load and appearance of drug resistant virus populations in persons treated with lamivudine (3TC). J. Infect. Dis. 171:1411-1419[Medline]. |
| 23. |
Seiki, M.,
S. Hattori,
Y. Hirayama, and M. Yoshida.
1983.
Human adult T-cell leukemia virus: complete nucleotide sequence of the provirus genome integrated in leukemia cell DNA.
Proc. Natl. Acad. Sci. USA
80:3618-3622 |
| 24. |
Sheremata, W. A.,
D. Benedict,
D. C. Squilacote,
A. Sazant, and S. DeFreitas.
1993.
High-dose zidovudine induction in HTLV-I-associated myelopathy: safety and possible efficacy.
Neurology
43:2125-2129 |
| 25. | Simpson, D. M., and M. Tagliati. 1995. Nucleoside analogue-associated peripheral neuropathy in human immunodeficiency virus infection. J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. 9:153-161[Medline]. |
| 26. |
Tavares, L.,
C. Roneker,
K. Johnston,
S. N. Lehrman, and F. de Noronha.
1987.
3'-Azido-3'-deoxythymidine in feline leukemia virus-infected cats: a model for therapy and prophylaxis of AIDS.
Cancer Res.
47:3190-3194 |
| 27. | Taylor, G. P., S. Hall, M. Nowak, C. Michie, M. Rossor, R. Davis, C. R. M. Bangham, and J. N. Weber. 1998. Reduction of HTLV-I proviral load in patients with HTLV-I associated myelopathy through lamivudine monotherapy, abstr. 508, p. 175. In Abstracts of the 5th Conference on Retroviruses and Opportunistic Infections, Chicago, Ill., 1 to 5 February 1998 |
| 28. | Taylor, G. P., J. H. C. Tosswill, E. Matutes, S. Daenke, S. Hall, B. Bain, M. Rossor, D. Thomas, C. R. M. Bangham, and J. N. Weber. 1999. Inflammatory consequences of HTLV-I infection in an initially asymptomatic UK cohort. J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. 22:92-100. |
| 29. | Tosswill, J. H. C., G. P. Taylor, J. P. Clewley, and J. N. Weber. 1998. Quantification of proviral DNA load in human T-cell leukaemia virus type-I infections. J. Virol. Methods 75:21-26[Medline]. |
| 30. |
Uchiyama, T.,
J. Yodoi,
K. Sagawa,
K. Takatsuki, and H. Uchino.
1977.
Adult T-cell leukaemia: clinical and haematological features of 16 cases.
Blood
50:481-492 |
| 31. | van-Leeuwen, R., C. Katlam, V. Kitchen, C. A. Boucher, R. Tubiana, M. McBride, D. Ingrand, J. Weber, A. Hill, H. McDade, et al. 1995. Evaluation of safety and efficacy of 3TC (lamivudine) in patients with asymptomatic or mildly symptomatic human immunodeficiency virus infection: a phase I/II study. J. Infect. Dis. 171:1166-1171[Medline]. |
| 32. | Wattel, E., M. Cavrois, A. Gessain, and S. Wain-Hobson. 1996. Clonal expansion of infected cells. A way of life for HTLV-I. J. Acquir. Immune Defic. Syndr. Hum. Retrovirol. 13(Suppl. 1):S92-S99. |
| 33. | Wodarz, D., M. A. Nowak, and C. R. M. Bangham. 1999. The dynamics of HTLV-I and the CTL response. Immunol. Today 20:220-227[Medline]. |
| 34. | World Health Organization. 1989. WHO diagnostic guidelines of HAM. Virus diseases. Human T-lymphotropic virus type I, HTLV-I. Weekly Epidemiol. Rec. 49:382-383. |
Journal of Virology, December 1999, p. 10289-10295, Vol. 73, No. 12
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