Human T-cell Lymphotropic Virus Type 1 Proviral Load Research Articles

In Memoriam – Hugh A. Smythe, 1927–2012

<h3>Objective</h3> To test the hypothesis that teriflunomide can reduce ex vivo spontaneous proliferation of peripheral blood mononuclear cells (PBMCs) from patients with human T-cell lymphotropic virus type 1 (HTLV-1)–associated myelopathy/tropical spastic paraparesis (HAM/TSP). <h3>Methods</h3> PBMCs from patients with HAM/TSP were cultured in the presence and absence of teriflunomide and assessed for cell viability, lymphocyte proliferation, activation markers, HTLV-1 <i>tax</i> and HTLV-1 <i>hbz</i> messenger ribonucleic acid (mRNA) expression, and HTLV-1 Tax protein expression. <h3>Results</h3> In culture, teriflunomide did not affect cell viability. A concentration-dependent reduction in spontaneous proliferation of PBMCs was observed with 25 μM (38.3% inhibition), 50 μM (65.8% inhibition), and 100 μM (90.7% inhibition) teriflunomide. The inhibitory effects of teriflunomide were detected in both CD8⁺ and CD4⁺ T-cell subsets, which are involved in the immune response to HTLV-1 infection and the pathogenesis of HAM/TSP. There was no significant change in HTLV-1 proviral load (PVL) or <i>tax</i> mRNA/Tax protein expression in these short-term cultures, but there was a significant reduction of HTLV-1 PVL due to inhibition of proliferation of CD4⁺ T cells obtained from a subset of patients with HAM/TSP. <h3>Conclusions</h3> These results suggest that teriflunomide inhibits abnormal T-cell proliferation associated with HTLV-1 infection and may have potential as a therapeutic option in patients with HAM/TSP.

Dengue fever and human T-cell lymphotropic virus type 1 infection

Globalization has increased both the number of emergent diseases and the diversity of co-infections, which could in turn mutually influence the pathogenesis of well-known infectious diseases. Here, we report the first series of chronic human T-cell lymphotropic virus type 1 (HTLV-1) patients co-infected with the dengue fever virus. As both of these diseases are immuno-mediated, we anticipated interference in the development of both diseases, with atypical clinical and laboratory parameter results. All the patients had classic dengue fever, and the main outstanding abnormality was leukopenia associated with lymphopenia. Although a mutual influence was expected, dengue fever did not affect the clinical course of HTLV-1 infection, and HTLV-1 proviral loads revealed unpredictable patterns of change.

Antiretroviral therapy promotes an inflammatory-like pattern of human T-cell lymphotropic virus type 1 (HTLV-1) replication in human immunodeficiency virus type 1/HTLV-1 co-infected individuals

Upon antiretroviral therapy (ART) human immunodeficiency virus (HIV)/human T-cell lymphotropic virus type 1 (HTLV-1) co-infected individuals frequently develop neurological disorders through hitherto unknown mechanisms. Here, we show that effective anti-HIV ART increases HTLV-1 proviral load through a polyclonal integration pattern of HTLV-1 in both CD4(+) and CD8(+) T-cell subsets that is reminiscent of that typically associated with HTLV-1-related inflammatory conditions. These data indicate that preventing ART-triggered clonal expansion of HTLV-1-infected cells in co-infected individuals deserves investigation.

Human T Cell Lymphotropic Virus Type 1 Viral Load Variability and Long-Term Trends in Asymptomatic Carriers and in Patients with Human T Cell Lymphotropic Virus Type 1-Related Diseases

Human T cell lymphotropic virus type 1 (HTLV-1) proviral load (PVL) in peripheral blood mononuclear cells (PBMCs) is high in patients with adult T cell leukemia/lymphoma or HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and in some asymptomatic carriers, but fluctuates. Our objectives were to document ranges of HTLV PVL across a broader spectrum of diseases and tissues, to quantify the normal range of intrapatient PVL variability, and to identify which PVL values and changes deserve further investigation. PVL was measured in 191 patients with HTLV-1-associated diseases and in 211 asymptomatic carriers, using real-time quantitative PCR. The intraassay variability increases as viral load decreases: 8% at high load, 17% at medium load, and 33% at low load. The interassay variability is not different from the intraassay. Mean intrapatient CV is 65% (SD 21) in asymptomatic carriers and 59% (SD 22) in HAM/TSP. PVL values varied widely between individuals, but were relatively constant within individuals. High PVL in cerebrospinal fluid (CSF) and lymph nodes (LN) was associated with disease but 57% of asymptomatic carriers had a PVL greater than 1% in PBMCs. Our results suggest that (1) PVL changes falling outside a coefficient of variation of 100% require more detailed assessment, (2) asymptomatic carriers with PVL higher than 10% should undergo more frequent clinical and laboratory monitoring, and (3) HTLV-1 PVL in blood and tissue is helpful in the diagnosis and monitoring of HTLV-1 infection.

Evolution of HTLV-1 proviral load in patients from Salvador, Brazil

IntroductionVariations in human T cell lymphotropic virus type 1 (HTLV-1) proviral load (PVL) in infected individuals over time are not well understood. ObjectiveTo evaluate the evolution of proviral load in asymptomatic individuals and HAM/TSP patients in order to help determine periodicity for measuring proviral load. MethodsA group of 104 HTLV-1 infected patients, followed at the HTLV reference center in Salvador, Brazil, were included in the study (70 asymptomatic and 34 HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients). HTLV-1 PVL was measured using real-time polymerase chain reaction (PCR) at baseline and again at another point, either ≤ 12 months, between 12-24 months, or ≥ 24 months. ResultsHAM/TSP patients had higher PVL (ranging from 11,041 to 317,009 copies/106 PBMC) when compared to asymptomatic individuals (ranging from 0 to 68,228 copies/106 PBMC). No statistically significant differences were observed in the medians of PVL in HAM/TSP patients or asymptomatic individuals over time. However, in asymptomatic individuals with a PVL below 50,000 copies/106 PBMC, a statistically significant two-fold increase was observed over time. ConclusionHTLV-1-PVL remained stable in both asymptomatic individuals and HAM/TSP patients over time. Frequent monitoring of asymptomatic individuals with low PVLs is recommended and further studies should be conducted to assess the course of PVL in these patients over extended periods of time.

Maternal Proviral Load and Vertical Transmission of Human T Cell Lymphotropic Virus Type 1 in Guinea-Bissau

The relative importance of routes of transmission of human T cell lymphotropic virus type 1 (HTLV-1) in Guinea-Bissau is largely unknown; vertical transmission is thought to be important, but there are very few existing data. We aimed to examine factors associated with transmission in mothers and children in Guinea-Bissau, where HTLV-1 is endemic (prevalence of 5% in the adult population). A cross-sectional survey was performed among mothers and their children (aged <15 years) in a rural community in Guinea-Bissau. A questionnaire to identify risk factors for infection and a blood sample were obtained. HTLV-1 proviral load in peripheral blood was determined and PCR was performed to compare long terminal repeat (LTR) sequences in mother-child pairs. Fourteen out of 55 children (25%) of 31 HTLV-1-infected mothers were infected versus none of 70 children of 30 uninfected mothers. The only factor significantly associated with HTLV-1 infection in the child was the proviral load of the mother; the risk of infection increased significantly with the log(10) proviral load in the mother's peripheral blood (OR 5.5, 95% CI 2.1-14.6, per quartile), adjusted for weaning age and maternal income. HTLV-1 sequences of the LTR region obtained from mother-child pairs were identical within pairs but differed between the pairs. Vertical transmission plays an important role in HTLV-1 transmission in this community in Guinea-Bissau. The risk of transmission increases with the mother's proviral load in the peripheral blood. Identical sequences in mother-child pairs give additional support to the maternal source of the children's infection.

Interferon Beta-1a Improves Urinary Symptoms, Reduces Proviral Load, and Modifies the Immune Response in a Patient with HAM/TSP

The human T-cell lymphotropic virus type 1 (HTLV-1) is the known causative agent of a chronic neurologic condition known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Although several therapies have been evaluated for HAM/TSP, none have been approved for use in humans. In this paper, we describe a 55-year-old female patient with HAM/TSP who was treated with interferon beta-1a. This patient, in comparison to 20 female patients with HAM/TSP who were not treated, showed improvement in urinary symptoms over four years of therapy, as well as a reduction in HTLV-1 proviral load and serum cytokine levels typically observed in HAM/TSP. This improved outcome merits further controlled studies on the use and efficacy of interferon beta-1a as a therapy for HAM/TSP.

Antiviral effect of raltegravir on HTLV-1 carriers

In vitro studies support that integrase inhibitors, such as raltegravir, may inhibit human T cell lymphotropic virus type 1 (HTLV-1) replication. However, this hypothesis has not been tested in vivo. HTLV-1-infected individuals were invited to participate in a pilot, open study that examined whether 400 mg of raltegravir twice daily could exhibit any recognizable virological effect over 12 months. Proviral DNA was measured by a real-time PCR targeting the pol region. HTLV-1 integrase sequences were obtained from peripheral blood mononuclear cells (PBMCs) at baseline and during follow-up. A total of five HTLV-1-infected individuals entered the study. All were infected with HTLV-1 subtype a. Two patients had HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), the rest being asymptomatic. The HTLV-1 proviral load was high in all cases (median 758 HTLV-1 DNA copies/10(4) PBMCs). Following the initiation of raltegravir therapy and for up to 6 months, both of the HAM/TSP patients experienced a transient decline in the HTLV-1 proviral load (2248 to 519 and 1033 to 861 copies/10(4) PBMCs, respectively), returning to baseline levels on subsequent determinations. No significant changes in the HTLV-1 proviral load were noticed in the three asymptomatic individuals (median proviral load of 755 copies/10(4) PBMCs over time). A total of 20 integrase sequences could be obtained from the five patients, and no genotypic substitutions were recognized comparing baseline and follow-up specimens under raltegravir. Treatment with raltegravir in HTLV-1-infected individuals does not result in a significant reduction of proviral load beyond 6 months of therapy. The lack of continuous viral replication cycles in chronic HTLV-1 carriers most likely explains our findings.

Keratoconjunctivitis sicca of human T cell lymphotropic virus type 1 (HTLV-1) infected individuals is associated with high levels of HTLV-1 proviral load

Background A high HTLV-1 proviral load is found in HTLV-1-associated diseases, mainly HAM/TSP. However, the association between proviral load and keratoconjunctivitis sicca (KCS) has not been well established. Aim To verify the association between KCS and HTLV-1 proviral load. Study design 104 HTLV-1 infected patients (51 asymptomatic and 52 with HAM/TSP) from the HTLV reference center in Salvador, Brazil were followed from June 2008 to May 2010. Evaluation of tear secretion was performed by BUT (break-up time), Rose Bengal and Schirmer I tests. The diagnosis of KCS was based upon the presence of symptoms and when at least two of three tests were positive. HTLV-1 proviral load was determined using real-time PCR. Results The prevalence of KCS was 44.2%. KCS was more frequent among HAM/TSP patients ( p = 0.022). Patients with KCS had higher proviral load (mean 134,672 ± 150,393 copies/10 6 PBMC) than patients without the disease (mean 66,880 ± 109,525 copies/10 6 PBMC) ( p = 0.001). HTLV-1 proviral load > 100,000 copies/10 6 PBMC increased significantly the risk of developing KCS (OR = 4.05 and 95% CI = 1.40–11.76). After age > 45 years and HAM/TSP status were excluded in stepway reward analysis, the variables PVL > 100,000 (OR = 4.77 and 95% CI = 1.83–12.44) still remained statistically significant. Conclusion HTLV-1 proviral loads are higher in patients with KCS and may represent a relevant biological marker of disease.

Maternal proviral load and vertical transmission of Human T cell Lymphotropic Virus type 1 in Guinea-Bissau

Abstract The relative importance of routes of transmission of human T cell lymphotropic virus type 1 (HTLV-1) in Guinea-Bissau is largely unknown; vertical transmission is thought to be important, but there are very few existing data. We aimed to examine factors associated with transmission in mothers and children in Guinea-Bissau, where HTLV-1 is endemic (prevalence of 5% in the adult population). A cross-sectional survey was performed among mothers and their children (aged <15 years) in a rural community in Guinea-Bissau. A questionnaire to identify risk factors for infection and a blood sample were obtained. HTLV-1 proviral load in peripheral blood was determined and PCR was performed to compare long terminal repeat (LTR) sequences in mother–child pairs. Fourteen out of 55 children (25%) of 31 HTLV-1-infected mothers were infected versus none of 70 children of 30 uninfected mothers. The only factor significantly associated with HTLV-1 infection in the child was the proviral load of the mother; the risk...

Human T cell lymphotropic virus type 1 (HTLV‐1) proviral load of HTLV‐associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients according to new diagnostic criteria of HAM/TSP

A high human T-cell lymphotropic virus type 1 (HTLV-1) proviral load is described in HTLV-1-associated diseases, especially HAM/TSP. However, the cut-off value to define high levels of HTLV-1 proviral load is not well established. 281 HTLV-1-infected patients from the HTLV reference center in Salvador, Brazil, were followed from 2005 to 2008. Patients were classified as asymptomatic, possible-, probable-, and definite-HAM/TSP, in accordance with diagnostic criteria proposed by De Castro-Costa et al. (2006): AIDS Res Hum Retroviruses 22:931-935. HTLV-1 proviral load was determined using real-time PCR. A receiver operator characteristic (ROC) curve was constructed using only asymptomatic individuals and definite-HAM/TSP patients. The ROC curve was used to predict the proviral load level that differentiates these two groups. Out of 281 patients, 189 were asymptomatic and 92 were diagnosed with HAM/TSP (22 possible, 23 probable, 47 definite). The mean HTLV-1 proviral load was higher in possible- (89,104 ± 93,006 copies/106 PBMC), -probable (175,854 ± 128,083 copies/106 PBMC), and definite-HAM/TSP patients (150,667 ± 122,320 copies/106 PBMC),when compared to asymptomatic individuals (27,178 ± 41,155 copies/106 PBMC) (P < 0.0001). A comparison of all HAM/TSP groups showed the highest proviral loads in probable-HAM/TSP patients, yet the differences in mean values were not statistically significant. The ROC curve suggested a value of 49,865 copies/106 PBMC, with 87% sensitivity (95% CI ¼ 74-95) and 81% specificity (95% CI ¼ 75-86), as the best proviral load cut-off point to differentiate definite HAM/TSP patients from asymptomatic individuals. HTLV-1 proviral loads are higher in groups of infected patients with eurological symptoms and may represent a relevant biological marker of disease progression.

New entity, definition and diagnostic criteria of cutaneous adult T‐cell leukemia/lymphoma: Human T‐lymphotropic virus type 1 proviral DNA load can distinguish between cutaneous and smoldering types

Adult T-cell leukemia/lymphoma (ATLL) has been divided into four subtypes up to now: (i) acute; (ii) lymphoma; (iii) chronic; and (iv) smoldering. Skin lesion(s) may be present and the cases showing less than 5% abnormal T-lymphocytes in peripheral blood without involvement of other organs, have been classified as smoldering ATLL. However, this type of ATLL with skin manifestations had a worse prognosis than that without skin lesions. This study aimed to define and distinguish cutaneous ATLL lacking nodal lymphoma and leukemic change from smoldering ATLL. We propose an entity of cutaneous ATLL, which has less than 5% abnormal T lymphocyte in peripheral blood, a normal lymphocyte count (i.e. <4 x 10(9)/L), no hypercalcemia and lactate dehydrogenase values of up to 1.5 times the normal upper limit. At least one of the histologically proven skin lesions should be present accompanying monoclonal integration of human T-cell lymphotropic virus type 1 (HTLV-1) proviral DNA in the skin lesion. Blood samples were collected from 41 HTLV-1-infected patients, 21 asymptomatic carriers, 16 patients with cutaneous ATLL and four patients with smoldering ATLL. HTLV-1 proviral loads, soluble interleukin-2 receptors and other parameters were examined in each case. HTLV-1 proviral DNA loads in smoldering ATLL group are significantly higher than those in asymptomatic carrier and cutaneous ATLL group. Cutaneous ATLL may be a distinct entity that should be separated from smoldering ATLL clinically and virologically.

The Frequency, Diversity, and Function of Human T-Cell Leukemia Virus Type 1-Specific CD8+ T-Cell Is Reduced in Adult T-Cell Leukemia Patients.

Human T-cell lymphotropic virus type 1 (HTLV-1)-specific CTL are thought to be immune effectors that reduce the risk of adult T-cell leukemia (ATL). However, in vivo conditions of anti-HTLV-1 CTL before and after ATL development have yet to be determined. To characterize anti-HTLV-1 CTL in asymptomatic HTLV-1 carriers (AC) and ATL patients, we analyzed the frequency and diversity of HTLV-1-specific CD8+ T cells in PBMC of 35 AC and 32 ATL patients using 16 distinct epitopes of HTLV-1 Tax or Env/HLA tetramers along with intracellular cytolytic effector molecules (IFN-γ , perforin, and granzyme B). Overall frequency of subjects possessing Tax-specific CD8+ T cells was significantly lower in ATL than AC (53% vs. 90%, p < 0.001) whereas the difference in Env-specific CD8+ T cells was not statistically significant. AC possessed Tax11-19/HLA-A*0201-specific tetramer+ cells by 90% and Tax301-309/HLA-A*2402-specific tetramer+ cells by 92%. Some AC recognized more than one epitope. In contrast, ATL recognized only Tax 11-19 with HLA-A*0201 and Tax301-309 with HLA-A*2402 at frequencies of 30% and 55%. There were also significant differences in percentage of cells binding Tax11-19/HLA-A*0201, Tax301-309/HLA-A*2402, and CMV/HLA tetramers between AC and ATL. Anti-HTLV-1 Tax CD8+ T cells in AC and ATL produced IFN-γ in response to Tax. Contrarily, perforin and granzyme B expression in anti-HTLV-1 CD8+ T cells of ATL was significant lower than that of AC, but no differences in anti-CMV CD8+ T cells. In addition, expression of perforin and granzyme B in HTLV-1 Tax tetramer+/CD8+ T lymphocytes were diminished in comparison to those in CMV tetramer+/CD8+ T lymphocytes in both AC and ATL. Frequency of Tax-specific CD8+ T cells in AC were related with proviral load in HLA-A*0201. These results suggest that our HTLV-1/HLA tetramer assay enabled analysis of anti-HTLV-1 CD8+ T cells in PBMC of AC and ATL patients and demonstrated deletion of anti-Tax CD8+ T cells in ATL patients. Intracellular cytokine expression in anti-HTLV-1 CD8+ T cells had significant difference between AC and ATL, but not in anti-CMV CD8+ T cells. The reduced frequency, diversity, and function of anti-HTLV-1 Tax CD8+ T cell clones may be related to the development of ATL. This HLA tetramer assay can be used for monitoring the in vivo status of CTL and it may be possible to identify the high risk group in AC of developing to ATL.Summary of HTLV-1-specific tetramer and HTLV-1 proviral load in AC and ATL patientsACATLSubjects positive for Tax tetramer†28 (n = 31)15 (n = 28) *Subjects positive for Env tetramer†4 (n = 31)0 (n = 28)Tax11-19 tetramer+ CD8+ T cells†9 (n = 10)3 (n = 10) **Tax301-309 tetramer+ CD8+ T cells†22 (n = 24)12 (n = 22) *HTLV-1 proviral load††65.4 ± 7.4 (n = 35)1095.4 ± 194.1 (n = 29) *†The number of subject positive for tetramers; the percentage of HTLV-1/HLA tetramer+/CD8+ T cells in the CD8+/CD45+ T lymphocytes > 0.1% are counted as subject positives for tetramer. ††The HTLV-1 proviral load is the ± S.E., copies/1000 PBMC.*p < 0.001; **p < 0.05, Significant differences between AC and ATL.

Dermatological Findings in 3 Generations of a Family with a High Prevalence of Human T Cell Lymphotropic Virus Type 1 Infection in Brazil

Dermatologic manifestations are quite common in patients with adult T cell leukemia and lymphoma and patients with myelopathy and/or tropical spastic paraparesis associated with human T cell lymphotropic virus type 1 (HTLV-1). The aim of this study was to investigate dermatological findings presented by 30 members of a Brazilian family, half of whom are infected with HTLV-1 (as confirmed by enzyme-linked immunosorbent assay and Western blot). The subjects underwent dermatologic examination and laboratory assessment, which included the search for the HTLV-1 genome in peripheral blood mononuclear cells (PBMCs) by qualitative and semiquantitative polymerase chain reaction (PCR) and in skin samples by nested qualitative PCR and immunofluorescence assay. We found that cases of xerotic dermatological alterations, including 3 cases of acquired ichthyosis, were more frequent among the infected patients (7 cases vs. none among the uninfected individuals; P=.0063). Other lesions observed in this group included impetigo, scabies, epidermal nevus, herpes zoster scar, rosacea, and juvenile acne. One HTLV-1-infected individual presented with concurrently acquired ichthyosis, impetigo, scabies, dermatophytosis, and seborrheic dermatitis. The PCR performed on PBMCs and skin samples from 24 patients confirmed the serological results in all cases. Additionally, the HTLV-1 proviral load was higher in patients with >1 skin lesion. Finally, HTLV-1 could be identified in the skin by immunofluorescence assay, which, by use of PCR as the gold standard, showed a sensitivity and specificity of 61.5% and 100%, respectively. Altogether, these clinical and laboratory findings point to an HTLV-1 tropism toward the skin, even in HTLV-1 carriers without adult T cell leukemia/lymphoma or HTLV-1-associated myelopathy and/or tropical spastic paraparesis.

The efficacy of combined therapy of arsenic trioxide and alpha interferon in human T-cell leukemia virus type-1-infected squirrel monkeys ( Saimiri sciureus)

Human T-cell lymphotropic virus type 1 (HTLV-1)-associated adult T-cell leukemia/lymphoma (ATLL) has a poor prognosis owing to its intrinsic resistance to chemotherapy. Although zidovudine (AZT) and alpha interferon (IFN-α) give rise to some response and improve the prognosis of ATLL, alternative therapies are needed. Arsenic trioxide (As 2O 3) has been shown to synergize with IFN-α in arresting cell growth and inducing apoptosis of ATLL cells in vitro. In this study, we evaluated the toxicity and the efficacy of this combined treatment in HTLV-1-infected squirrel monkeys ( Saimiri sciureus) and HTLV-1 infected cell lines derived therefrom. We first show that treatment with As 2O 3 and IFN-α can induce growth arrest in HTLV-1-transformed monkey T-cell lines in vitro. We then show that treatment of squirrel monkeys with As 2O 3 in vivo is highly toxic at 0.9 or 0.3 mg/day but not at 0.14 mg/day for up to 2 weeks. Although the combination of As 2O 3 and IFN-α did not affect significantly the HTLV-1 proviral load in infected monkeys, it reduced the absolute numbers of CD3 +, CD4 + and CD8 + cells during treatment, with a significant reduction in the total number of circulating HTLV-1 flower cells in the infected monkeys with chronic ATLL-like disease.

HTLV-1 proviral load in peripheral blood mononuclear cells quantified in 100 HAM/TSP patients: A marker of disease progression

A high proviral load of human T cell lymphotropic virus type 1 (HTLV-1) in peripheral blood mononuclear cells (PBMCs) has been reported in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The aim of the present study was to investigate the role of HTLV-1 proviral load in PBMCs (expressed as the number of copies per 10 6 PBMCs) in HAM/TSP disease course. One hundred consecutive HAM/TSP patients were recruited and assigned on the basis of the disability score and disease duration to either a rapid ( n = 38) or a slow ( n = 62) progression group. Thirty-four asymptomatic HTLV-1 carriers were also included. HTLV-1 proviral load was quantified in all HAM/TSP patients and asymptomatic subjects. The mean HTLV-1 proviral load was 6-fold lower in asymptomatic carriers than in HAM/TSP patients (18,224 ± 24,811 vs. 107,905 ± 96,651, p < 0.0001) and significantly higher in rapid progression patients than in slow progression patients (146,469 ± 98,943 vs. 84,270 ± 87,912, p = 0.0002). HTLV-1 proviral load in HAM/TSP patients was independent of age at the time of study, age at onset, and disease duration, and was not related to ophthalmological-associated disease or Chisholm grade. A high level of pulmonary lymphocytosis correlated with high HTLV-1 proviral load level ( p = 0.01). Our results suggest that the level of HTLV-1 proviral load in PBMCs parallels the course of HTLV-1 infection, being low in asymptomatic carriers and high and very high, respectively, in slow and rapid progression HAM/TSP patients. The magnitude of the HTLV-1 proviral load in PBMCs can be used as a biological marker of disease progression and could be a useful marker of disease activity in the monitoring of therapeutic trials.

The role of CTLs in persistent viral infection: cytolytic gene expression in CD8+ lymphocytes distinguishes between individuals with a high or low proviral load of human T cell lymphotropic virus type 1.

The proviral load in human T cell lymphotropic virus type 1 (HTLV-1) infection is typically constant in each infected host, but varies by >1000-fold between hosts and is strongly correlated with the risk of HTLV-1-associated inflammatory disease. However, the factors that determine an individual's HTLV-1 proviral load remain uncertain. Experimental evidence from studies of host genetics, viral genetics, and lymphocyte function and theoretical considerations suggest that a major determinant of the equilibrium proviral load is the CD8+ T cell response to HTLV-1. In this study, we tested the hypothesis that the gene expression profile in circulating CD8+ and CD4+ lymphocytes distinguishes between individuals with a low proviral load of HTLV-1 and those with a high proviral load. We show that circulating CD8+ lymphocytes from individuals with a low HTLV-1 proviral load overexpressed a core group of nine genes with strong functional coherence: eight of the nine genes encode granzymes or other proteins involved in cell-mediated lysis or Ag recognition. We conclude that successful suppression of the HTLV-1 proviral load is associated with strong cytotoxic CD8+ lymphocyte activity in the peripheral blood.

Genetic Evidence of Transmission of Human T Cell Lymphotropic Virus Type 1 between Spouses

Sexual transmission of human T cell lymphotropic virus type 1 (HTLV-1) is considered to be an important route of infection in adults. However, no direct evidence has been reported that supports this observation. To address this issue, sequence variations of the gp46 (envelope)-coding region of HTLV-1 were determined in 13 patients infected with HTLV-1 who experienced seroconversion and in their spouses. Twenty-two nucleotide changes that were different from the reference sequence of lambdaATK-1 were identified. However, the gp46 sequences found were identical within each married couple. HTLV-1 proviral DNA loads measured in 11 of these couples varied from 10 to 3430 copies per 10(5) PBMC, and the proviral DNA loads of spouses often differed. This study provides the first genetic confirmation of the transmission of HTLV-1 from a carrier spouse to his/her partner. The findings also suggest that host-related factors play a more important role than do virus-specific factors in determining HTLV-1 proviral DNA load.

Correlation of human T-cell lymphotropic virus type 1 (HTLV-1) mRNA with proviral DNA load, virus-specific CD8+ T cells, and disease severity in HTLV-1–associated myelopathy (HAM/TSP)

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.

Quantification of human T-cell lymphotropic virus type 1 proviral load by quantitative competitive polymerase chain reaction

The polymerase chain reaction (PCR) has been established as a highly sensitive technique for detection of viral DNA or RNA. However, due to inherent limitations of PCR the amount of amplified product often does not correlate with the initial amount of template DNA. This is particularly true for PCR detection of viral infections that are characterized by low in vivo viral copy numbers in certain stages of the infection, such as human T-cell lymphotropic virus type 1 (HTLV-1) and simian T-cell lymphotropic virus type 1 (STLV-1). Therefore, we developed a quantitative competitive polymerase chain reaction (qcPCR) for detection of HTLV-1 and STLV-1 proviral DNA. The assay was optimized using an infectious HTLV-1 clone, ACH, HTLV-1 infected cell lines, MT-2.6 and HUT-102 and STLV-1 infected lines Kia and Matsu. Applicability of this system was demonstrated by determining HTLV-1 proviral load in peripheral blood mononuclear cells (PBMC) of human subjects with HTLV-1 associated diseases and an asymptomatic carrier as well as rabbits infected experimentally. This qcPCR method, the first designed specifically for HTLV-1 and STLV-1, will provide an important tool for pathogenesis studies of HTLV-1 and for evaluating the efficacy of antiviral drugs and vaccines against the viral infection using animal models.