|
|||||||||
|
|
|
|
|
|
|
|
|
|
|
CLINICAL OBSERVATIONS, INTERVENTIONS, AND THERAPEUTIC TRIALS
From the Viral Immunology Section, Neuroimmunology
Branch, National Institute of Neurological Disorders and Stroke,
National Institutes of Health, Bethesda, MD; Center for Chronic Viral
Diseases, Faculty of Medicine, Kagoshima University, Japan; and Third
Department of Internal Medicine, Faculty of Medicine, Kagoshima
University, Japan.
To investigate the role of viral expression in individuals infected
with human T-cell lymphotropic virus type 1 (HTLV-1), a real-time
quantitative reverse transcription-polymerase chain reaction (RT-PCR)
of HTLV-1 tax messenger RNA (mRNA) using ABI Prism 7700 Sequence Detection System was developed. Using this system, the HTLV-1
tax mRNA load was compared with HTLV-1 proviral DNA load,
HTLV-1 Tax protein expression, HTLV-1 Tax-specific CD8+
T-cell frequency, and disease severity of HTLV-1-associated
myelopathy/tropical spastic paraparesis (HAM/TSP). This approach was a
sensitive and specific technique for the precise quantification of
HTLV-1 tax mRNA. The total amount of HTLV-1 tax
mRNA and mRNA expression level in HTLV-1-infected cells (mRNA/DNA
ratio) were higher in HAM/TSP patients than in asymptomatic HTLV-1
carriers. The HTLV-1 tax mRNA load correlated with the
HTLV-1 proviral DNA load ex vivo, the Tax protein expression in vitro,
and the Tax-specific CD8+ T-cell frequency ex vivo. The
HTLV-1 tax mRNA load also correlated with disease severity
in HAM/TSP patients. These data suggest that increased HTLV-1
expression plays an important role in the pathogenesis of HAM/TSP, and
the HTLV-1 tax mRNA level could be a useful predictor of
disease progression in patients with HAM/TSP.
(Blood. 2002;99:88-94) Human T-cell lymphotropic virus type 1 (HTLV-1) is
a human retrovirus that infects approximately 10 million people
worldwide.1 The majority of infected individuals remain
healthy lifelong asymptomatic carriers (ACs), approximately 0.25% to
3% develop an inflammatory disease of the central nervous system
termed HTLV-1-associated myelopathy/tropical spastic paraparesis
(HAM/TSP),2-5 and another 2% to 3% develop an aggressive
mature T-cell malignancy termed adult T-cell leukemia
(ATL).6,7 Patients with HAM/TSP generally harbor a much
larger population of HTLV-1-infected T cells in peripheral blood
mononuclear cells (PBMCs)8-10 and a higher immune response
against HTLV-1 antigens than ACs.11-13 These findings indicate that an abundant viral load plays an important role in the
pathogenesis of HAM/TSP, suggesting that high viral expression may be
associated with the high immune response against the virus.
Even though a high proviral DNA load is characteristic of
patients with HAM/TSP, the expression of HTLV-1 in PBMCs appears to be
very low,14-18 which suggests that HTLV-1 may be latent in peripheral blood. However, this suggestion is difficult to reconcile with the observation of high activated immune responses in patients with HAM/TSP.11-13 Moreover, it has been reported that a
significant proportion of PBMCs infected with HTLV-1 are capable of
expressing HTLV-1 proteins after short-term cultivation in
vitro,17,19 supporting the hypothesis that HTLV-1 is not
inherently latent. Recently, a correlation between the HTLV-1 proviral
DNA load and the frequency of HTLV-1 Tax-specific CD8+ T
cells20,21 has been described in patients with HAM/TSP. Collectively, these data suggest HTLV-1 antigens continuously restimulate the cellular immune system in vivo. However, no reports have characterized the HTLV-1 tax messenger RNA (mRNA)
expression in the relationship between the HTLV-1 proviral DNA load and
the virus-specific T-cell immune response in individuals infected with
HTLV-1. In this study, to determine the importance of HTLV-1 tax mRNA expression in that relationship and in the
pathogenesis of HAM/TSP, a rapid, sensitive, and precise quantification
of HTLV-1 tax mRNA expression was developed by a real-time
reverse transcription-polymerase chain reaction (RT-PCR) method using the ABI Prism 7700 Sequence Detection System. Because the level of
human immunodeficiency virus type 1 (HIV-1) RNA has been found to be a
valid predictor of the clinical progression of HIV-1-related disease
and efficacy of anti-HIV therapy,22,23 it was also of
interest to determine if the HTLV-1 tax mRNA load as
quantified by this novel method might be a marker of disease activity
and of relative prognostic value in HAM/TSP.
In this study, the HTLV-1 tax mRNA load in PBMCs from
patients with HAM/TSP and ACs was measured and compared with HTLV-1 proviral DNA load, HTLV-1 Tax protein expression, HTLV-1 Tax-specific CD8+ T-cell frequency, and disease severity in patients
with HAM/TSP. The data presented demonstrate that increased HTLV-1
expression plays an important role in the pathogenesis of HAM/TSP, and
HTLV-1 tax mRNA level could be a useful predictor of disease
progression in HAM/TSP patients.
Subjects and cells
Real-time RT-PCR of complementary DNA
Primers used for the amplification of HTLV-1 tax cDNA were slightly modified from the sequence previously reported18 to be suitable for this system. The forward primer RPX-3 (5096-5115; 5'-ATCCCGTGGAGACTCCTCAA-3') and the reverse primer RPX-4 + 3 (7360-7338; 5'-CCAAACACGTAGACTGGGTATCC-3') were located upstream and downstream of the second splice junction site of HTLV-1 pX (tax/rex) mRNA. The amplified DNA was 147 base pairs (bp). The probe (5172-5183, 7302-7312; 5'-TCCAACACCATG-GCCCACTTCCC-3') surrounded the second splice junction site of HTLV-1 pX (tax/rex) mRNA. We used the human housekeeping gene hypoxanthine ribosyl transferase (HPRT) primers and probe set (Applied Biosystems) for internal calibration. This internal control appeared to be most stable within PBMCs from HDs, ACs, HAM/TSP patients, and ATL patients by using the TaqMan Human Endogenous Control Plate (Applied Biosystems). PCR conditions were as follows: 10 µL cDNA solution synthesized from 300 ng RNA was added to 40 µL reaction mixture containing10 mM Tris-HCl (pH 8.3), 50 mM KCl, 10 mM EDTA, 60 nM ROX (passive reference dye to normalize receptor signal), 5.5 mM MgCl2, 0.3 µM each primer, 0.2 µM TaqMan probe, 200 µM each of dATP, dGTP, and dCTP, 400 µM dUTP, 0.5 U AmpErase uracil-N-glycosylase (UNG), and 0.25 U AmpliTaq Gold DNA polymerase (AmpliTaq Gold; Applied Biosystems). The thermal cycler conditions were 2 minutes at 50°C to activate AmpErase UNG enzyme, 10 minutes at 95°C to inactivate UNG and activate AmpliTaq Gold DNA polymerase, and then 45 cycles of 15 seconds at 95°C (denaturation) followed by 1 minute at 60°C (annealing and extension). Standard curves for the value of HTLV-1 tax mRNA and
HPRT mRNA were generated using cDNA from MT-2 cells. MT-2 cDNA was
serially diluted 10-fold with diethyl pyrocarbonate (DEPC)
H2O down to a 10 The relative HTLV-1 tax mRNA load was calculated by the following formula: HTLV-1 tax mRNA load = (value of tax)/(value of HPRT) × 10 000. Real-time PCR of DNA The HTLV-1 proviral DNA load was measured using this same TaqMan system as previously described.10,21 DNA was extracted from 1 × 106 cells using Puregene DNA Isolation Kit (Gentra, Minneapolis, MN) and 100 ng of the sample DNA solution per well was analyzed by this system. The HTLV-1 proviral DNA load was calculated by the following formula: copy number of HTLV-1 (pX) per 100 cells = (copy number of pX)/(copy number of -actin/2) × 100.
HTLV-1 Tax protein expression in PBMCs The PBMCs (5 × 105) were placed on a culture well (round bottom 96-well plate) in 200 µL RPMI 1640 supplemented with L-glutamine, penicillin, streptomycin, and 5% human AB serum. Harvested cells were washed with phosphate-buffered saline (PBS) containing 1% fetal calf serum (FCS) and 0.1% NaN3 and incubated with antihuman CD4-PE (Caltag Laboratories, Burlingame, CA) and antihuman CD8-Tricolor monoclonal antibodies (mAbs; Caltag Laboratories) for 20 minutes at 4°C. Following washing with PBS containing 1% FCS and 0.1% NaN3, cells were fixed and permeabilized with 4% formaldehyde and 0.1% saponin (CytoFix/Cytoperm kits, Pharmingen, SanDiego, CA) for 20 minutes at 4°C. After washing with 0.1% saponin buffer (Perm/Wash solution, Pharmingen), cells were incubated with anti-HTLV-1 Tax mAb (obtained through the AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: HTLV-1 Tax hybridoma 168A51-42 from Dr Beatrice Langton) for 30 minutes at 4°C. Followed by washing unbound antibody with 0.1% saponin buffer, fluorescein isothiocyanate (FITC)-conjugated goat F(ab')2 antimouse IgG2a was used as second antibody for labeling anti-HTLV-1 Tax mAb. After a 20-minute incubation, cells underwent a final wash. Flow cytometric analyses were performed using a FACS Calibur (Becton Dickinson, Mountain View, CA).Identification of HTLV-1 Tax-specific CD8+ T cells The HTLV-1 Tax 11-19 peptide is a dominant epitope recognized by HLA-A2-restricted CD8+ T cells in HAM/TSP patients.13,28 HTLV-1 Tax11-19/HLA A*0201-specific CD8+ T cells were analyzed using a phycoerythrin (PE)-conjugated HLA-A*0201 tetramer (provided by NIAID MHC Tetramer Core Facility, Atlanta, GA, and NIH AIDS Research and Reference Reagent Program) for HLA A*0201 subjects. The tetramer was loaded with HTLV-1 Tax 11-19 peptide (LLFGYPVYV; single-letter amino acid codes), which was synthesized and 95% purified by high-performance liquid chromatography (HPLC; New England Peptide, Fitchburg, MA). Tetramer loaded with HIV Gag 77-85 peptide (SLYNTVATL) was used as a negative control. PBMCs from HLA-A*0201 subjects were washed and incubated with PE-conjugated HLA-A*0201 tetramer, antihuman CD4-FITC (Caltag Laboratories), and antihuman CD8-Tricolor mAbs (Caltag Laboratories) for 30 minutes at 4°C, and then analyzed by flow cytometry. The frequencies of HTLV-1 Tax-specific CD8+ T cells were expressed as a percentage of total CD8+ T cells.Statistical analysis The Mann-Whitney U test was used to compare the data between patients with HAM/TSP and ACs. Simple regression analysis was used to test the correlation between HTLV-1 proviral DNA load, HTLV-1 tax mRNA load, mRNA/DNA ratio, and HTLV-1 Tax-specific CD8+ T-cell frequency. To test the correlation of EDSS with HTLV-1 proviral DNA load, HTLV-1 tax mRNA load and mRNA/DNA ratio, the Spearman rank correlation was used.
Accuracy of real-time RT-PCR To determine the interassay coefficient of variance of this real-time HTLV-1 tax RT-PCR system, cDNA from the HTLV-1-infected MT-2 cell was diluted serially with cDNA from the HTLV-1-noninfected Jurkat cell, and HTLV-1 tax mRNA load of each dilution was measured 5 times (Figure 1A). In this study, the HTLV-1 tax mRNA load was calculated as the value of HTLV-1 tax mRNA divided by the value of HPRT as described in "Patients, materials, and methods." To estimate the accuracy of this system, we calculated the intercoefficient of variance (CV%) in each amount. The mean interassay CV% was 19.3%, which is consistent with the CV% measuring HTLV-1 proviral DNA using real-time PCR methods.10,29
To test the intra-assay coefficient of variance of this real-time HTLV-1 tax RT-PCR system, PBMCs from 3 patients with HAM/TSP were separated into 5 samples per individual. RNA was extracted from each sample, cDNA was synthesized, and HTLV-1 tax mRNA load for each sample was determined (Figure 1B). The CV% was calculated for each patient. The mean value of intra-assay CV% was 19.2%, which is consistent with the CV% measuring HIV-1 RNA.30 These data demonstrate that this real-time HTLV-1 tax RT-PCR assay is accurate and reliable for quantitation of HTLV-1 tax mRNA. Sensitivity and specificity of real-time RT-PCR To determine the sensitivity of this real-time RT-PCR assay, the HTLV-1 tax mRNA load was determined from MT-2 cells diluted serially with PBMCs from a healthy donor not infected with HTLV-1. As shown in Figure 2A, the HTLV-1 tax mRNA signal could be detected in a dose-dependent manner with a sensitivity limit as low as one MT-2 cell in 106 PBMCs.
To test the specificity of this assay, cDNA from HTLV-1-noninfected
Jurkat cells and PBMCs from HTLV-1-noninfected HDs (n = 5) were
analyzed. No signal was observed from any of these HTLV-1 HTLV-1 tax mRNA load in HAM/TSP patients and ACs Using this novel method, HTLV-1 tax mRNA load was analyzed in PBMCs from HAM/TSP patients and ACs. As demonstrated in Table 1 and Figure 3, the HTLV-1 tax mRNA load ranged from 0.06 to 187.90 in HAM/TSP patients and 0.00 to 5.58 in ACs. The HTLV-1 tax mRNA load in HAM/TSP patients was significantly higher than that in ACs (P = .0014, Mann Whitney U test) as reported previously.34 The absolute amount of HTLV-1 tax mRNA before adjusting by the HPRT value in HTLV-1-infected individuals was 103 to 106 times less than that in MT-2 cells, which is consistent with previous reports.18,34
Comparison of HTLV-1 tax mRNA load with HTLV-1 proviral DNA load ex vivo To determine if there was a correlation between the HTLV-1 proviral DNA load and the HTLV-1 tax mRNA load in HTLV-1-infected individuals, a real-time quantitative HTLV-1 DNA PCR assay21 was used to measure the HTLV-1 proviral DNA load in PBMCs from HAM/TSP patients and ACs. As previously reported,10,21 the HTLV-1 proviral DNA load, which represented a population of infected cells in PBMCs, was greater in HAM/TSP patients than ACs (P = .0003, Mann Whitney U test, Table 1). Furthermore, the HTLV-1 proviral DNA load was correlated significantly with the HTLV-1 tax mRNA load in HAM/TSP patients (P < .0001, r2 = 0.812, simple regression analysis, Figure 4).
To adjust the HTLV-1 tax mRNA expression level in HTLV-1-infected PBMCs, we calculated the mRNA/DNA ratio by dividing the HTLV-1 tax mRNA load by HTLV-1 proviral DNA load. The mean value of the mRNA/DNA ratio was 109.82 for HAM/TSP patients and 45.93 for ACs. The mRNA/DNA ratio of HAM/TSP patients was statistically higher than that of AC (P = .0433, Mann Whitney U test, Table 1). Comparison of HTLV-1 tax mRNA load with HTLV-1 Tax protein expression in vitro Because increased levels of mRNA may be associated with increased protein production, it was important to determine if there was a correlation between the HTLV-1 tax mRNA load and the amount of HTLV-1 Tax protein expression. PBMCs from 4 HAM/TSP patients (HAM-1, -11, -14, -15) were cultured for 48 hours in culture medium without mitogenic stimuli. PBMC samples were taken after 0, 12, 24, and 48 hours, respectively, and the HTLV-1 tax mRNA load and HTLV-1 Tax protein expression level as measured by FACS analysis using monoclonal anti-Tax antibodies were determined. As shown in Figure 5, a close correlation was found between the HTLV-1 tax mRNA load and the percentage of cells expressing HTLV-1 Tax protein. The detection of HTLV-1 tax mRNA and the expression of HTLV-1 Tax protein were coincident and peaked at approximately 12 to 24 hours of in vitro culture (Figure 5).
Comparison of HTLV-1 tax mRNA load with HTLV-1 Tax-specific CD8+ T-cell frequency ex vivo The high levels of HTLV-1 proviral DNA load detected in PBMCs from HAM/TSP patients have been shown previously to correlate with high frequencies of virus-specific CD8+ T cells.20,21 It was therefore of interest to determine if HTLV-1 tax mRNA load also correlated with the frequency of HTLV-1 Tax-specific CD8+ T cells. The frequency of HTLV-1 Tax 11-19/HLA A*0201-specific CD8+ T cells was analyzed using a PE-conjugated HLA-A*0201 tetramer for HLA-A*0201 subjects (HAM-2-5, -11, -13, -16 and AC-4, -6, -7). The percentages of HTLV-1 Tax 11-19/HLA A*0201-specific CD8+ T cells in the total amount of CD8+ T cells are summarized in Table 1. As reported previously,20,21 the HTLV-1 proviral DNA load significantly correlated with the frequency of HTLV-1 Tax-specific CD8+ T cells in HAM/TSP patients (P = .0191, r2 = 0.699, simple regression analysis, Table 1). Furthermore, the HTLV-1 tax mRNA load was also significantly correlated with the frequency of HTLV-1 Tax-specific CD8+ T cells in HAM/TSP patients (P = .0013, r2 = 0.893, simple regression analysis; Table 1 and Figure 6). HTLV-1 Tax 11-19/HLA A*0201-specific CD8+ T cells have also been reported in PBMCs of ACs35 and although in this study the sample size of HLA A*0201+ ACs was too small to compare statistically, increased mRNA load in this group was associated with a higher frequency of HTLV-1 Tax-specific CD8+ T cells (Table 1).
Comparison of disease severity with HTLV-1 proviral DNA load, HTLV-1 tax mRNA load, and mRNA/DNA ratio in HAM/TSP patients Clinical features of HAM/TSP patients included in this study are shown in Table 1. Because HAM/TSP is a chronic progressive disease, patients with a long duration of illness are usually severely affected.36 However, there were 3 patients (HAM-3, -4, -5) who showed relatively mild progression and had a long duration of illness as reflected by relatively low scores on the EDSS (Table 1). The EDSS index is a neurologic measure of disability that is weighted toward ambulation.25 Of interest is the observation that the HTLV-1 tax mRNA loads of all 3 of these patients were low, even though 2 of the 3 patients (HAM-3, -4) harbored average levels of HTLV-1 proviral DNA load. Furthermore, patients with high HTLV-1 tax mRNA load and a long duration of illness (HAM-11, -13, -15, -16) had more severe disease with EDSS scores above 7 (patients essentially restricted to a wheelchair).To examine the possibility that quantitative real-time PCR for HTLV-1 DNA and RNA determinations might have prognostic value in HAM/TSP disease progression, the EDSS values of these patients were statistically compared with HTLV-1 proviral DNA load, HTLV-1 tax mRNA load, and mRNA/DNA ratio by Spearman rank correlation analysis (Table 1). The EDSS score significantly correlated with both HTLV-1 tax mRNA load and mRNA/DNA ratio (P = .0109 and .0089, respectively), but not with HTLV-1 proviral DNA load (P = .5236). Thus, HTLV-1 tax mRNA load and mRNA/DNA ratio may have relative prognostic value for the assessment of disease progression in HAM/TSP.
Using a newly established real-time RT-PCR assay to quantitate HTLV-1 tax mRNA load, this study demonstrated a significant difference in the HTLV-1 tax mRNA load between patients with HAM/TSP and ACs. Furthermore, HTLV-1 tax mRNA load significantly correlated with the HTLV-1 proviral DNA load, the HTLV-1 Tax protein expression, and the frequency of HTLV-1 Tax 11-19/HLA A*0201-specific CD8+ T cells. Collectively, these results support previous studies demonstrating a relationship between the HTLV-1 proviral DNA load and the frequency of HTLV-1 Tax-specific CD8+ T cells in HAM/TSP patients,20 the existence of chronically activated HTLV-1 Tax-specific CD8+ T cells,21 and the existence of high anti-HTLV-1 IgM antibodies suggesting continuous immune stimulation in vivo.37 These results indicate that HAM/TSP patients have more HTLV-1 proviral DNA load than ACs, which may be associated with higher mRNA expression resulting in heightened virus-specific immune responses. This profile does not characterize all retroviruses. For example, in individuals infected with HIV-1, the plasma viral RNA load, which is known to be significantly correlated with HIV-1 RNA load in PBMCs,38,39 is inversely proportional to the frequency of HIV-1-specific CD8+ T cells,40,41 which suggests an effective immunologic elimination of HIV-1 antigens. However, in HTLV-1 infection, as the virus antigen expression increases, HTLV-1-specific CD8+ T cells are generated, which appear to be unable to eliminate infected cells. Therefore, these results support the hypothesis that expansion of HTLV-1 can occur in the presence of an activated immune system that is trying to control the infection. This novel assay is also useful to define the role of HTLV-1 viral expression in patients with ATL. In preliminary data, HTLV-1 tax mRNA load was generally low in patients with ATL even in individuals with a high proviral DNA load (data not shown). Quantitative measurements of HTLV-1 tax mRNA load in PBMCs from HAM/TSP patients and ACs continue to highlight differences between these 2 groups. This study demonstrated that adjusting the HTLV-1 tax mRNA load with HTLV-1 proviral DNA load (mRNA/DNA ratio) was higher in HAM/TSP patients than in ACs. These results indicate that in HAM/TSP patients a higher proportion of HTLV-1-infected cells express HTLV-1 tax mRNA at higher levels than in ACs. These observations support and extend previous reports describing a number of host genetic and virologic differences between HAM/TSP patients and ACs including differences in human leukocyte antigen haplotypes,35,42 differences in the amount of soluble suppressive factors16,43 and CD8+ T-cell responses,19-21,44 and differences in HTLV-1 tax genomic sequences.45 Many of these observations distinguishing HAM/TSP patients from carriers may also be related to higher proviral DNA load, higher mRNA load (as demonstrated in this study), and higher immune response against HTLV-1.10-13 The mRNA/DNA ratios as determined by quantitative DNA and RNA PCR assays presented here differed from a previous report34 that showed that the mRNA/DNA ratio was similar in both HAM/TSP patients and ACs although the total HTLV-1 tax mRNA load was higher in HAM/TSP patients than in ACs (also demonstrated in the present study). This may be due to differences in the technology and accuracy of the assays used. Therefore, it is important to extend the observations on differences in the mRNA/DNA ratio between HAM/TSP patients and ACs to larger groups of individuals infected with HTLV-1. Because HAM/TSP is a chronic progressive disorder,36 clinical end points are cumbersome when evaluating disease activity. Thus, a clinical and laboratory goal is to define surrogate markers of HTLV-1 infection that can be used to monitor HAM/TSP disease activity. Surrogate markers of HAM/TSP disease activity have been reported. Neopterin levels in cerebrospinal fluid (CSF), a marker of cell-mediated immune activation,46,47 have been used as an immunologic marker for monitoring disease activity and treatment efficacy.48 Monitoring of ex vivo spontaneous lymphoproliferation and the frequency of HTLV-1 Tax-specific CD8+ T cells, which have reported to be associated with the pathogenesis of HAM/TSP,12,20,21 have also been used as potential surrogate immunologic markers of disease progression.49 In this present report, HTLV-1 tax mRNA load was correlated with HTLV-1 Tax-specific CD8+ T-cell frequencies in HAM/TSP patients, suggesting that the quantitative analysis of HTLV-1 tax mRNA might also be used to monitor HAM/TSP disease activity. In this study, the frequency of CD8+ T cells specific only to the HTLV-1 Tax region was analyzed; however, other HTLV-1 regions have also been shown to be important as targets for CD8+ T-cell immune responses.50,51 In the assessment of any new HTLV-1-associated immunologic assay, it is of interest to determine if it can be used as a prognostic indicator of disease progression in HAM/TSP. For example, it has been reported that the anti-HTLV-1 antibody titers and the neopterin levels in CSF are high in patients with acute progressive HAM/TSP and low in those with slowly progressive disease.36 The HTLV-1 tax mRNA load measured by this novel real-time RT-PCR method was demonstrated to generate a quantitative prognostic index of clinical progression in a limited cohort of HAM/TSP patients. The EDSS value is a commonly used neurologic measure of disability25 and significantly correlated with both HTLV-1 tax mRNA load and mRNA/DNA ratio (P = .0109 and .0089, respectively), but interestingly not with HTLV-1 proviral DNA load (P = .5236). This tendency has been also observed in HIV-1 infection.22,23 These findings suggest that the amounts of expressed antigen and induced immune response may be more sensitive than proviral DNA load as a prognostic indicator in virus-associated diseases. As with any chronic, progressive neurologic disease, it is difficult to predict clinical progression. However, the HTLV-1 tax mRNA load was demonstrated to reflect viral activity and could be an important marker to be used to predict long-term outcome in HAM/TSP patients. We are currently evaluating virologic and immunologic markers described here over time in HAM/TSP patients with or without treatment. HTLV-1 proviral DNA load, HTLV-1 tax mRNA load, and HTLV-1 Tax-specific CD8+ T-cell frequency are generally stable over time in untreated patients (data not shown). Further longitudinal and controlled studies enrolling a large number of patients must be conducted. In summary, a real-time quantitative RT-PCR of HTLV-1 tax mRNA has been developed. This approach proved to be a sensitive and specific technique for precise quantification of HTLV-1 tax mRNA. The novel assay demonstrated a significant correlation between HTLV-1 DNA, RNA, protein, and HTLV-1-specific T-cell immune response. Additionally, HTLV-1 expression levels in virus-infected cells (mRNA/DNA ratio) were higher in HAM/TSP patients than in ACs, suggesting the existence of genetic or virologic differences. Furthermore, comparison of molecular results with clinical features suggested that HTLV-1 tax mRNA load and mRNA/DNA ratio may be valid predictors of disease progression. These data support the hypothesis that higher HTLV-1 expression plays an important role in the pathogenesis of HAM/TSP.
We thank Nazli Azimi, National Cancer Institute, for her kind help and James M. Dambrosia, Biostatistics Branch, National Institute of Neurological Disorders and Stroke, for his support in statistical analysis.
Submitted July 24, 2001; accepted September 6, 2001.
The publication costs of this article were defrayed in part by page charge payment. Therefore, and solely to indicate this fact, this article is hereby marked "advertisement" in accordance with 18 U.S.C. section 1734.
Reprints: Steven Jacobson, NIH/NINDS/NIB Bldg 10, Rm 5B-16, Bethesda, MD 20892; e-mail: jacobsons{at}ninds.nih.gov.
1. de The G, Bomford R. An HTLV-I vaccine: why, how, for whom? AIDS Res Hum Retroviruses. 1993;9:381-386[Medline] [Order article via Infotrieve]. 2. Osame M, Usuku K, Izumo S, et al. HTLV-I associated myelopathy, a new clinical entity [letter]. Lancet. 1986;1:1031-1032[Medline] [Order article via Infotrieve]. 3. Gessain A, Barin F, Vernant JC, et al. Antibodies to human T-lymphotropic virus type-I in patients with tropical spastic paraparesis. Lancet. 1985;2:407-410[CrossRef][Medline] [Order article via Infotrieve]. 4. Kaplan JE, Osame M, Kubota H, et al. The risk of development of HTLV-I-associated myelopathy/tropical spastic paraparesis among persons infected with HTLV-I. J Acquir Immune Defic Syndr. 1990;3:1096-1101. 5. Trujillo JM, Concha M, Munoz A, et al. Seroprevalence and cofactors of HTLV-I infection in Tumaco, Colombia. AIDS Res Hum Retroviruses. 1992;8:651-657[Medline] [Order article via Infotrieve].
6.
Uchiyama T, Yodoi J, Sagawa K, Takatsuki K, Uchino H.
Adult T-cell leukemia: clinical and hematologic features of 16 cases.
Blood.
1977;50:481-492 7. Uchiyama T. Human T cell leukemia virus type I (HTLV-I) and human diseases. Annu Rev Immunol. 1997;15:15-37[CrossRef][Medline] [Order article via Infotrieve].
8.
Gessain A, Saal F, Gout O, et al.
High human T-cell lymphotropic virus type I proviral DNA load with polyclonal integration in peripheral blood mononuclear cells of French West Indian, Guyanese, and African patients with tropical spastic paraparesis.
Blood.
1990;75:428-433 9. Kira J, Koyanagi Y, Yamada T, et al. Increased HTLV-I proviral DNA in HTLV-I-associated myelopathy: a quantitative polymerase chain reaction study [published erratum appears in Ann Neurol 1991;29:363]. Ann Neurol. 1991;29:194-201[CrossRef][Medline] [Order article via Infotrieve]. 10. Nagai M, Usuku K, Matsumoto W, et al. 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. 1998;4:586-593[Medline] [Order article via Infotrieve]. 11. Jacobson S, Zaninovic V, Mora C, et al. Immunological findings in neurological diseases associated with antibodies to HTLV-I: activated lymphocytes in tropical spastic paraparesis. Ann Neurol. 1988;23:S196-200. 12. Jacobson S, Gupta A, Mattson D, Mingioli E, McFarlin DE. Immunological studies in tropical spastic paraparesis. Ann Neurol. 1990;27:149-156[CrossRef][Medline] [Order article via Infotrieve]. 13. Parker CE, Daenke S, Nightingale S, Bangham CR. Activated, HTLV-1-specific cytotoxic T-lymphocytes are found in healthy seropositives as well as in patients with tropical spastic paraparesis. Virology. 1992;188:628-636[CrossRef][Medline] [Order article via Infotrieve]. 14. Shimoyama M, Minato K, Tobinai K, et al. Atypical adult T-cell leukemia-lymphoma: diverse clinical manifestations of adult T-cell leukemia-lymphoma. Jpn J Clin Oncol. 1983;13:165-187. 15. Sugamura K, Fujii M, Kannagi M, et al. Cell surface phenotypes and expression of viral antigens of various human cell lines carrying human T-cell leukemia virus. Int J Cancer. 1984;34:221-228[Medline] [Order article via Infotrieve]. 16. Tochikura T, Iwahashi M, Matsumoto T, et al. Effect of human serum anti-HTLV antibodies on viral antigen induction in vitro cultured peripheral lymphocytes from adult T-cell leukemia patients and healthy virus carriers. Int J Cancer. 1985;36:1-7[Medline] [Order article via Infotrieve].
17.
Gessain A, Saal F, Giron M, et al.
Cell surface phenotype and human T lymphotropic virus type 1 antigen expression in 12 T cell lines derived from peripheral blood and cerebrospinal fluid of West Indian, Guyanese and African patients with tropical spastic paraparesis.
J Gen Virol.
1990;71:333-341
18.
Kinoshita T, Shimoyama M, Tobinai K, et al.
Detection of mRNA for the tax1/rex1 gene of human T-cell leukemia virus type I in fresh peripheral blood mononuclear cells of adult T-cell leukemia patients and viral carriers by using the polymerase chain reaction.
Proc Natl Acad Sci U S A.
1989;86:5620-5624
19.
Hanon E, Hall S, Taylor GP, et al.
Abundant tax protein expression in CD4+ T cells infected with human T-cell lymphotropic virus type I (HTLV-I) is prevented by cytotoxic T lymphocytes.
Blood.
2000;95:1386-1392 20. Kubota R, Kawanishi T, Matsubara H, Manns A, Jacobson S. HTLV-I specific IFN-gamma+ CD8+ lymphocytes correlate with the proviral load in peripheral blood of infected individuals. J Neuroimmunol. 2000;102:208-215[CrossRef][Medline] [Order article via Infotrieve]. 21. Nagai M, Kubota R, Greten T, et al. Increased activated human T cell lymphotropic virus type I (HTLV-I) Tax11-19-specific memory and effector CD8+ cells in patients with HTLV-I-associated myelopathy/tropical spastic paraparesis: correlation with HTLV-I provirus load. J Infect Dis. 2001;183:197-205[CrossRef][Medline] [Order article via Infotrieve].
22.
O'Brien W, Hartigan P, Martin D, et al.
Changes in plasma HIV-1 RNA and CD4+ lymphocyte counts and the risk of progression to AIDS. Veterans Affairs Cooperative Study Group on AIDS.
N Engl J Med.
1996;334:426-431
23.
Mellors JW, Munoz A, Giorgi JV, et al.
Plasma viral load and CD4+ lymphocytes as prognostic markers of HIV-1 infection.
Ann Intern Med.
1997;126:946-954 24. Osame M. Reveiw of WHO Kagoshima meeting and diagnostic guidelines for HAM/TSP. In: Blattner W, ed. Human Retrovirology HTLV. New York, NY: Raven Press; 1990:191-197.
25.
Kurtzke J.
Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS).
Neurology.
1983;33:1444-1452 26. Miyoshi I, Kubonishi I, Yoshimoto S, et al. Type C virus particles in a cord T-cell line derived by co-cultivating normal human cord leukocytes and human leukaemic T cells. Nature. 1981;294:770-771[CrossRef][Medline] [Order article via Infotrieve].
27.
Poiesz BJ, Ruscetti FW, Gazdar AF, et al.
Detection and isolation of type C retrovirus particles from fresh and cultured lymphocytes of a patient with cutaneous T-cell lymphoma.
Proc Natl Acad Sci U S A.
1980;77:7415-7419 28. Koenig S, Woods RM, Brewah YA, et al. Characterization of MHC class I restricted cytotoxic T cell responses to tax in HTLV-1 infected patients with neurologic disease. J Immunol. 1993;151:3874-3883[Abstract]. 29. Kamihira S, Dateki N, Sugahara K, et al. Real-time polymerase chain reaction for quantification of HTLV-1 proviral load: application for analyzing aberrant integration of the proviral DNA in adult T-cell leukemia. Int J Hematol. 2000;72:79-84[Medline] [Order article via Infotrieve].
30.
Sun R, Ku J, Jayakar H, et al.
Ultrasensitive reverse transcription-PCR assay for quantitation of human immunodeficiency virus type 1 RNA in plasma.
J Clin Microbiol.
1998;36:2964-2969 31. Kobayashi NK, Sabe H, Shigesada H, Noma K, Honjo T, Hatanaka M. Genomic structure of HTLV (human T-cell leukemia virus): detection of defective genome and its amplification in MT-2 cells. EMBO J. 1984;3:1339-1343[Medline] [Order article via Infotrieve]. 32. Cimarelli A, Duclos CA, Gessain A, et al. Quantification of HTLV-II proviral copies by competitive polymerase chain reaction in peripheral blood mononuclear cells of Italian injecting drug users, central Africans, and Amerindians. J Acquir Immune Defic Syndr Hum Retrovirol. 1995;10:198-204[Medline] [Order article via Infotrieve]. 33. Albrecht B, Collins ND, Newbound GC, Ratner L, Lairmore MD. Quantification of human T-cell lymphotropic virus type 1 proviral load by quantitative competitive polymerase chain reaction. J Virol Methods. 1998;75:123-140[CrossRef][Medline] [Order article via Infotrieve]. 34. Furukawa Y, Osame M, Kubota R, Tara M, Yoshida M. Human T-cell leukemia virus type-1 (HTLV-1) Tax is expressed at the same level in infected cells of HTLV-1-associated myelopathy or tropical spastic paraparesis patients as in asymptomatic carriers but at a lower level in adult T-cell leukemia cells. Blood. 1995;1:1865-1870.
35.
Jeffery KJ, Usuku K, Hall SE, et al.
HLA alleles determine human T-lymphotropic virus-I (HTLV-I) proviral load and the risk of HTLV-I-associated myelopathy.
Proc Natl Acad Sci U S A.
1999;96:3848-3853 36. Nakagawa M, Izumo S, Ijichi S, et al. HTLV-I-associated myelopathy: analysis of 213 patients based on clinical features and laboratory findings. J Neurovirol. 1995;1:50-61[Medline] [Order article via Infotrieve]. 37. Nagasato K, Nakamura T, Ohishi K, et al. Active production of anti-human T-lymphotropic virus type I (HTLV-I) IgM antibody in HTLV-I-associated myelopathy. J Neuroimmunol. 1991;32:105-109[CrossRef][Medline] [Order article via Infotrieve]. 38. Sei S, Kleiner DE, Kopp JB, et al. Quantitative analysis of viral burden in tissues from adults and children with symptomatic human immunodeficiency virus type 1 infection assessed by polymerase chain reaction. J Infect Dis. 1994;170:325-333[Medline] [Order article via Infotrieve]. 39. Meylan PR, Burgisser P, Weyrich SC, Spertini F. Viral load and immunophenotype of cells obtained from lymph nodes by fine needle aspiration as compared with peripheral blood cells in HIV-infected patients. J Acquir Immune Defic Syndr Hum Retrovirol. 1996;13:39-47[CrossRef][Medline] [Order article via Infotrieve]. 40. Greenough T, Brettler D, Somasundaran M, Panicali D, Sullivan J. Human immunodeficiency virus type 1-specific cytotoxic T lymphocytes (CTL), virus load, and CD4 T cell loss: evidence supporting a protective role for CTL in vivo. J Infect Dis. 1997;176:118-125[Medline] [Orde |
Top
Abstract
Introduction
4 dilution, and sample cDNA
from 300 ng RNA per well was applied and analyzed by this system. The
amplification of standard cDNA and sample cDNA was carried out in a
96-well reaction plate. All standards and samples were assayed in
triplicate. Each plate always contained the same standard. When a
serial dilution of 100 to 10
