Multicenter, randomized, double-blind, placebo-controlled phase 3 study of mogamulizumab with open-label extension study in a minimum number of patients with human T-cell leukemia virus type-1-associated myelopathy.

Human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic neurodegenerative disease. This multicenter, randomized phase 3 study evaluated the efficacy and safety of 0.3 mg/kg intravenous mogamulizumab, a monoclonal antibody targeting-CC chemokine receptor 4, every 12 weeks in HAM/TSP patients. This study comprised a 24-week double-blind, placebo-controlled period, 24-week open-label period, and extension treatment period. The primary endpoint was the proportion of patients with a ≥ 1-grade improvement in the Osame motor disability score (OMDS). Secondary endpoints were changes in HTLV-1 proviral load, 10-m timed walk, cerebrospinal fluid (CSF) neopterin levels, and safety. The exploratory endpoint was CSF chemokine C-X-C motif ligand 10 (CXCL10) levels. Thirty-four and 33 patients were randomized to mogamulizumab and placebo arms, respectively. At the end of the double-blind period, no significant difference was found in the OMDS improvement rate or other secondary efficacy endpoints assessing motor activities. However, the mogamulizumab arm showed a significant decrease in HTLV-1 proviral load (- 59.39 ± 29.91% vs. placebo 2.32 ± 36.31%) and CSF neopterin (p < 0.001)/CXCL10 levels (p = 0.004). The baseline OMDS pattern and the 60-80% HTLV-1 proviral load reduction were sustained through the open-label and extension treatment periods. Although a higher incidence of rash (69.2%) was reported, the safety profile was similar compared with a previous phase 1/2a study. We found no significant difference in clinical benefit; however, mogamulizumab may provide long-term clinical benefit by preventing disease progression, as CSF neopterin/CXCL10 levels are associated with long-term prognosis in HAM/TSP.Clinical Trial Registration Number: NCT03191526 (registered date: 6-June-2017).

Quantitative and Morphological Assessment of Computed Tomography-depicted Gynecomastia in Spinal and Bulbar Muscular Atrophy.

RATIONALE AND OBJECTIVES: To evaluate the prevalence, size, and characteristics of gynecomastia on thoracic computed tomography (CT) in patients with spinal and bulbar muscular atrophy (SBMA) or amyotrophic lateral sclerosis (ALS), compared to those of patients with myasthenia gravis (as controls). MATERIALS AND METHODS: A total of 189 male patients (SBMA [n = 15]; ALS [n = 76]; control [n = 98]) who underwent thoracic computed tomography were included. The size of breast glandular tissue diameters, and characteristic of CT-depicted gynecomastia were compared. RESULTS: On multivariate logistic regression analysis, mean breast glandular tissue diameter (adjusted odds ratio [aOR] 1.13, 95% confidence interval [CI] 1.08-1.19), maximum breast glandular tissue diameter (aOR 1.14, 95% CI 1.08-1.20), prevalence of CT-depicted gynecomastia (aOR 21.71, 95% CI 5.39-87.38), dendritic or diffuse pattern of gynecomastia (aOR 35.30, 95% CI 8.02-155.40), and bilateral gynecomastia (aOR 41.96, 95% CI 10.20-172.69) were positively associated with SBMA, but not ALS. On receiver operating characteristic (ROC) analysis, the area under the curve of the mean breast tissue diameter for predicting SBMA was 0.92 with the optimal cutoff value of 16.5 mm. The ROC analysis showed that a maximum breast tissue diameter of 18.6 mm can also effectively distinguish SBMA from controls. CONCLUSION: These findings suggest that the evaluation of breast glandular tissue on thoracic CT could be a screening examination to distinguish SBMA patients and assist in its differential diagnosis.

Zonisamide attenuates the severity of levodopa-induced dyskinesia via modulation of the striatal serotonergic system in a rat model of Parkinson's disease.

Glutamate, GABA, acetylcholine, dopamine, and serotonin interact with each other to regulate the flow of neural information in the striatum. Serotonin type 1A receptor (5HT1A) is primarily expressed on glutamatergic nerve terminals, and 5HT1B is expressed on GABAergic medium spiny neurons (MSNs). Zonisamide (ZNS) reportedly improves the off period without worsening levodopa-induced dyskinesia (LID) in patients with advanced Parkinson's disease. In this study, LID model rats were prepared by administrating levodopa to unilaterally 6-OHDA-lesioned rats. We analyzed changes in serotonergic neurotransmission of LID model rats to elucidate the relationship between LID and the serotonergic system and pathomechanism of the anti-dyskinetic effects of ZNS. Abnormal involuntary movements (AIMs) were most severe in intermittently levodopa-treated rats but milder in rats intermittently medicated with levodopa and ZNS. Continuously levodopa-infused rats or intermittently ZNS-injected rats did not develop AIMs, and no differences in the expression of brain-derived neurotrophic factor, 5-HT transporter, 5HT1A, and 5HT1B mRNA between the lesioned striatum and normal side were observed. Expression of 5HT1B mRNA was elevated in the lesioned striatum of intermittently levodopa-treated rats, but this elevation was normalized by concomitant use of ZNS. The severity of AIMs was correlated with the ratio of 5HT1B to 5HT1A mRNA expression in the lesioned striatum, indicating that the anti-LID effect of ZNS is based on inhibition via 5HT1B receptors to direct pathway MSNs sensitized by intermittent levodopa treatment. Selectively acting serotonergic drugs, especially those that lower the 5HT1B to 5HT1A ratio, are promising new therapeutic agents to attenuate LID development.

Efficacy and safety of tacrolimus as long-term monotherapy for myasthenia gravis.

The objective was to evaluate the long-term efficacy and safety of tacrolimus monotherapy in myasthenia gravis (MG) patients. Immunosuppressive drug-naïve MG patients were administered tacrolimus, followed by thymectomy in some of the cases according to the clinical guideline for MG. Additional aggressive immunosuppressive therapies were allowed if the patients without thymectomy did not achieve minimal manifestation (MM) or better status after 3 weeks of tacrolimus administration or in the thymectomized patients by 1-2 weeks after the operation (i.e., 1st evaluation). Of all 14 patients included in this study, 8 of them (57%) achieved MM or better status at the 1st evaluation, and the remaining 6 (43%), who had failed to gain MM or better status at the 1st evaluation, also achieved MM or better status with 1 course of aggressive immunosuppressive therapy. The quantitative MG (QMG) scores, MG-Activities of Daily Living (ADL) scales, and anti-acetylcholine receptor (AchR) antibody levels were significantly decreased at 6 months and maintained thereafter. At the end of the follow-up period (41-70 months), all patients were in MM or better status. None of the patients experienced severe adverse effects. Our small preliminary study indicates that long-term tacrolimus monotherapy is possibly effective and safe for MG patients.

Genome wide association study of HTLV-1-associated myelopathy/tropical spastic paraparesis in the Japanese population.

HTLV-1-associated myelopathy (HAM/TSP) is a chronic and progressive inflammatory disease of the central nervous system. The aim of our study was to identify genetic determinants related to the onset of HAM/TSP in the Japanese population. We conducted a genome-wide association study comprising 753 HAM/TSP patients and 899 asymptomatic HTLV-1 carriers. We also performed comprehensive genotyping of HLA-A, -B, -C, -DPB1, -DQB1, and -DRB1 genes using next-generation sequencing technology for 651 HAM/TSP patients and 804 carriers. A strong association was observed in HLA class I (P = 1.54 × 10-9) and class II (P = 1.21 × 10-8) loci with HAM/TSP. Association analysis using HLA genotyping results showed that HLA-C*07:02 (P = 2.61 × 10-5), HLA-B*07:02 (P = 4.97 × 10-10), HLA-DRB1*01:01 (P = 1.15 × 10-9) and HLA-DQB1*05:01 (P = 2.30 × 10-9) were associated with disease risk, while HLA-B*40:06 (P = 3.03 × 10-5), HLA-DRB1*15:01 (P = 1.06 × 10-5) and HLA-DQB1*06:02 (P = 1.78 × 10-6) worked protectively. Logistic regression analysis identified amino acid position 7 in the G-BETA domain of HLA-DRB1 as strongly associated with HAM/TSP (P = 9.52 × 10-10); individuals homozygous for leucine had an associated increased risk of HAM/TSP (odds ratio, 9.57), and proline was protective (odds ratio, 0.65). Both associations were independent of the known risk associated with proviral load. DRB1-GB-7-Leu was not significantly associated with proviral load. We have identified DRB1-GB-7-Leu as a genetic risk factor for HAM/TSP development independent of proviral load. This suggests that the amino acid residue may serve as a specific marker to identify the risk of HAM/TSP even without knowledge of proviral load. In light of its allele frequency worldwide, this biomarker will likely prove useful in HTLV-1 endemic areas across the globe.

Expression of TSLC1 in patients with HAM/TSP.

Human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is chronic myelopathy characterized by slowly progressive spastic paraparesis and urinary dysfunction. A few biomarkers in the cerebrospinal fluid are known to be related to disease activity, but no biomarker has been reported in peripheral blood. This study aims to explore the expression level of the adhesion molecule during the expression level of the adhesion molecule among HAM/TSP disease activity. In lymphocyte function-associated antigen 1 and DNAX accessory molecule 1, no variation in expression levels specific to HTLV-1 infection was observed in CD4-positive T cells; however, TSLC1 expression was higher in HAM patients than in asymptomatic carriers and non-infected persons. TSLC1 tended to be higher in patients whose symptoms were worsening. On the contrary, the expression level of TSLC1 in CD8-positive T cells was lower in HAM patients than in asymptomatic carriers, and this tendency was stronger in patients whose symptoms had deteriorated. No significant correlation was found between TSLC1 and either of the transcription factors Tax or HBZ in any T cell group. Therefore, TSLC1 expression in CD4-positive T cells might be a useful biomarker of HAM/TSP disease activity.

Conflicting effects of poly(ADP-ribose) polymerase inhibitor on cell-mediated and virion-mediated HTLV-1 infection.

Adult T-cell leukemia and human T-cell leukemia virus type 1 (HTLV-1) - associated myelopathy/tropical spastic paraparesis, which develop after HTLV-1 infection, are difficult to cure. In particular, the mode of HTLV-1 propagation is not well understood. Poly (ADP-ribose) polymerase-1 is reported to be a co-activator of HTLV-1 Tax protein; however, the effects of polyADP-ribosylation on infectivity of HTLV-1 have not been fully clarified. We studied the effects of a PARP inhibitor on two modes of HTLV-1 transmission: through cell adhesion between MT-2 cells (an HTLV-1-infected cell line) and uninfected cells and through virus particles produced by HTLV-1-producing c77 cells. Although the PARP inhibitor decreased HTLV-1 infection through cell adhesion, it increased HTLV-1 infection through virion production and caused apoptosis of HTLV-1-infected cells. Thus, careful consideration is required for clinical application of PARP inhibitors in HTLV-1 patients.

Effects of radiation based on whole-body irradiation in HTLV-1-infected mice.

Adult T-cell leukemia is one of the life-threatening diseases that occur in individuals infected with human T-cell leukemia virus type 1 (HTLV-1). Clinical trials of hematopoietic stem cell transplantation therapy are being performed in addition to chemotherapy; however, neither is satisfactory. As a pretreatment for transplantation, anticancer drugs or whole-body irradiation is used to decrease the number of HTLV-1-infected cells, but there are numerous side effects. Therefore, in the present study, using a mouse model of HTLV-1 infection, the long-term survival and number of infected cells in the reservoir organ were investigated in order to determine the effect of γ-irradiation on HTLV-1-infected mice in vivo. There was no improvement in the survival period following γ-irradiation in the γ-irradiated group after HTLV-1 infection when compared with the HTLV-1-infected group. It was also found that the incidence of splenomegaly was ≥80% in the HTLV-1-infected and γ-irradiated group, which was significantly higher than that in the HTLV-1-infected mice. The tissue morphology in the spleen became non-uniform because of γ-rays. Importantly, the number of infected cells in the spleen was increased 4.1-fold in the HTLV-1-infected and γ-irradiated mice compared with that in the HTLV-1-infected mice. Careful consideration might be necessary when using whole-body irradiation in patients with HTLV-1 infection.

Induction of APOBEC3B cytidine deaminase in HTLV-1-infected humanized mice.

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATL). Following viral infection with HTLV-1, certain infected cells exhibit clonal proliferation. Additional genetic and epigenetic changes in these clonally proliferating cells provide them with the selective advantage of growth, which eventually results in ATL. The precise mechanism, however, has yet to be completely elucidated. It has previously been established that APOBEC3 enzymes are potent host-antiviral restriction factors. Conversely, previous studies have reported that the A3B level is increased in tumor virus infections, such as those caused by HBV and HPV, suggesting that A3B exerts a function as a mutagen. Therefore, the present study analyzed the expression of APOBEC3 family members in various HTLV-1 infection states. No significant differences were observed in the expression between healthy donors and patients with HTLV-1-associated myelopathy. Although no significant changes in the expressions of A3C, A3D, A3F and A3G between uninfected and HTLV-1-infected mice were observed, an increased A3B expression was observed in a short-term humanized mouse model following HTLV-1 infection. In a long-term humanized mouse model following HTLV-1 infection, the gene expression array data exhibited an apparent increase in A3B and CADM1, which are indicators of ATL. Collectively, the results of the present study suggest that A3B is likely involved in the development of ATL in HTLV-1-infected humanized mice.

Human T-cell leukemia virus type 1 infects multiple lineage hematopoietic cells in vivo.

Human T-cell leukemia virus type 1 (HTLV-1) infects mainly CD4+CCR4+ effector/memory T cells in vivo. However, it remains unknown whether HTLV-1 preferentially infects these T cells or this virus converts infected precursor cells to specialized T cells. Expression of viral genes in vivo is critical to study viral replication and proliferation of infected cells. Therefore, we first analyzed viral gene expression in non-human primates naturally infected with simian T-cell leukemia virus type 1 (STLV-1), whose virological attributes closely resemble those of HTLV-1. Although the tax transcript was detected only in certain tissues, Tax expression was much higher in the bone marrow, indicating the possibility of de novo infection. Furthermore, Tax expression of non-T cells was suspected in bone marrow. These data suggest that HTLV-1 infects hematopoietic cells in the bone marrow. To explore the possibility that HTLV-1 infects hematopoietic stem cells (HSCs), we analyzed integration sites of HTLV-1 provirus in various lineages of hematopoietic cells in patients with HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) and a HTLV-1 carrier using the high-throughput sequencing method. Identical integration sites were detected in neutrophils, monocytes, B cells, CD8+ T cells and CD4+ T cells, indicating that HTLV-1 infects HSCs in vivo. We also detected Tax protein in myeloperoxidase positive neutrophils. Furthermore, dendritic cells differentiated from HTLV-1 infected monocytes caused de novo infection to T cells, indicating that infected monocytes are implicated in viral spreading in vivo. Certain integration sites were re-detected in neutrophils from HAM/TSP patients at different time points, indicating that infected HSCs persist and differentiate in vivo. This study demonstrates that HTLV-1 infects HSCs, and infected stem cells differentiate into diverse cell lineages. These data indicate that infection of HSCs can contribute to the persistence and spread of HTLV-1 in vivo.

Zonisamide ameliorates levodopa-induced dyskinesia and reduces expression of striatal genes in Parkinson model rats.

To investigate the difference in results according to the mode of levodopa administration and the effect of zonisamide (ZNS), we analyzed the mRNA expression of dopaminergic and non-dopaminergic receptors in the striatum of Parkinson model rats in relation to the development of levodopa-induced dyskinesia (LID). Unilateral Parkinson model rats were subdivided into 4 groups and treated as follows: no medication (group N), continuous levodopa infusion (group C), intermittent levodopa injection (group I), and intermittent levodopa and ZNS injection (group Z). Two weeks after the treatment, LID was observed in group I and Z, but less severe in group Z. The level of both D1 and D2 receptor mRNAs was elevated in groups I and Z, but only D2 receptor mRNA expression was elevated in group C. Adenosine A2A receptor mRNA showed increased expression only in group I. The level of endocannabinoid CB1 receptor mRNA was elevated in groups N, C, and I, but not in group Z. Intermittent injection of levodopa caused LID, in association with elevated expression of D1 and A2A receptors. ZNS ameliorated the development of LID and inhibited up-regulation of A2A and CB1 receptors. Modulation of these receptors may lead to therapeutic approaches for dyskinesia.

Effectiveness of Daily Prednisolone to Slow Progression of Human T-Lymphotropic Virus Type 1-Associated Myelopathy/Tropical Spastic Paraparesis: A Multicenter Retrospective Cohort Study.

Millions of people are infected with human T-lymphotropic virus type 1 (HTLV-1) worldwide; notable endemic areas include Brazil, the Caribbean islands, Iran, and Japan. A small number of those infected develop the progressive neurodegenerative disease HTLV-1-associated myelopathy (HAM), also known as tropical spastic paraparesis (TSP), which is characterized by chronic spinal cord inflammation and accompanying myelopathic symptoms. The corticosteroid prednisolone (PSL) is a classic treatment for HAM/TSP, yet its effectiveness remains controversial owing to insufficient and conflicting studies. We conducted a multicenter retrospective study using data collected by physicians monitoring patients with HAM/TSP at 7 hospitals throughout Japan. The Osame Motor Disability Score (OMDS) was used to evaluate 57 patients treated with low-dose PSL (mean 4.8 mg/day) versus 29 untreated patients. Roughly half of the evaluations spanned < 3 years (Short-Term) and half > 3 years (Long-Term), with a mean of 3.4 years. While the OMDS of most untreated patients remained unchanged in the Short-Term (87%) and worsened in the Long-Term (79%), most treated patients improved in the Short-Term (52%) and remained unchanged or improved in the Long-Term (68%). Overall, the mean change in OMDS per year was -0.13 in the Steroids group and +0.12 in the Untreated group (p < 0.01). This study addressed the effectiveness of PSL for HAM/TSP in 3 novel ways: 1) continuous low-dose administration; 2) comparison with an untreated group; and 3) Long-Term evaluation. These findings provide robust evidence supporting PSL maintenance therapy for HAM/TSP.

Weight loss in the early stage of progressive supranuclear palsy.

OBJECTIVES: To clarify whether weight change in patients with Parkinson's disease (PD) or progressive supranuclear palsy (PSP) is caused by the disease itself or secondarily by other factors. MATERIALS AND METHODS: We conducted a retrospective analysis of 51 patients with PD and 14 patients with PSP, especially during the early stage of their diseases. All patients were independent in terms of their activities of daily living and did not have any feeding difficulty. RESULTS: The body mass index measured within 3 years after the disease onset did not show a significant difference between the two diseases. However, the subsequent weight was stable in patients with PD and significantly decreased in patients with PSP. CONCLUSIONS: Weight loss begins in the early stage of PSP, whereas dopaminergic treatment may contribute to keep weight in the early stage of PD through reduction of energy expenditure and/or improvement in appetite.

HTLV-1 bZIP Factor Impairs Anti-viral Immunity by Inducing Co-inhibitory Molecule, T Cell Immunoglobulin and ITIM Domain (TIGIT).

Human T-cell leukemia virus type 1 (HTLV-1) infects CD4+ T cells and induces proliferation of infected cells in vivo, which leads to the onset of adult T-cell leukemia (ATL) in some infected individuals. The HTLV-1 bZIP factor (HBZ) gene, which is encoded in the minus strand of HTLV-1, plays critical roles in pathogenesis. In this study, RNA-seq and ChIP-seq analyses using HBZ transduced T cells revealed that HBZ upregulates the expression and promoter acetylation levels of a co-inhibitory molecule, T cell immunoglobulin and ITIM domain (TIGIT), in addition to those of regulatory T cells related genes, Foxp3 and Ccr4. TIGIT was expressed on CD4+ T cells from HBZ-transgenic (HBZ-Tg) mice, and on ATL cells and HTLV-1 infected CD4+ T cells of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in vivo. Expression of Blimp1 and IL-10 was upregulated in TIGIT+CD4+ cells of HBZ-Tg mice compared with TIGIT-CD4+ T cells, suggesting the correlation between TIGIT expression and IL-10 production. When CD4+ T cells from HBZ-Tg mice were stimulated with TIGIT's ligand, CD155, their production of the inhibitory cytokine IL-10 was enhanced. Furthermore, dendritic cells from HBZ-Tg mice produced high levels of IL-10 after stimulation. These data suggest that HBZ alters immune system to suppressive state via TIGIT and IL-10. Importantly, TIGIT suppressed T-cell responses to another HTLV-1 virus protein, Tax, in vitro. Blocking of TIGIT and PD-1 slightly increased anti-Tax T-cell activity in some HAM/TSP patients. These results suggest that HBZ-induced TIGIT on HTLV-1 infected cells impairs T-cell responses to viral antigens. This study shows that HBZ-induced TIGIT plays a pivotal role in attenuating host immune responses and shaping a microenvironment favorable to HTLV-1.

An animal model of adult T-cell leukemia: humanized mice with HTLV-1-specific immunity.

Human T-cell leukemia virus type 1 (HTLV-1) is causally associated with adult T-cell leukemia (ATL), an aggressive T-cell malignancy with a poor prognosis. To elucidate ATL pathogenesis in vivo, a variety of animal models have been established; however, the mechanisms driving this disorder remain poorly understood due to deficiencies in each of these animal models. Here, we report a novel HTLV-1-infected humanized mouse model generated by intra-bone marrow injection of human CD133(+) stem cells into NOD/Shi-scid/IL-2Rγc null (NOG) mice (IBMI-huNOG mice). Upon infection, the number of CD4(+) human T cells in the periphery increased rapidly, and atypical lymphocytes with lobulated nuclei resembling ATL-specific flower cells were observed 4 to 5 months after infection. Proliferation was seen in both CD25(-) and CD25(+) CD4 T cells with identical proviral integration sites; however, a limited number of CD25(+)-infected T-cell clones eventually dominated, indicating an association between clonal selection of infected T cells and expression of CD25. Additionally, HTLV-1-specific adaptive immune responses were induced in infected mice and might be involved in the control of HTLV-1-infected cells. Thus, the HTLV-1-infected IBMI-huNOG mouse model successfully recapitulated the development of ATL and may serve as an important tool for investigating in vivo mechanisms of ATL leukemogenesis and evaluating anti-ATL drug and vaccine candidates.

Accumulation of human T-lymphotropic virus type I (HTLV-I)-infected cells in the cerebrospinal fluid during the exacerbation of HTLV-I-associated myelopathy.

Human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive, inflammatory disease of the central nervous system (CNS). We report a patient with transverse myelitis, who exhibited acute onset and rapid progression of the disease and whose symptoms resembled those observed in multiple sclerosis with spinal cord presentation. During neurological exacerbation of the condition, the HTLV-I proviral load in the cerebrospinal fluid (CSF) increased to 10 times that in the peripheral blood. This suggests that the accumulation of HTLV-I-infected cells in the CNS contributes to neurological exacerbation. Based on the increased proviral load in the CSF, we diagnosed the disease as acute progressive HAM/TSP. The measurement of the HTLV-I proviral load in the CSF is useful for the diagnosis of HAM/TSP and for monitoring its progression.

Reduced Foxp3 expression with increased cytomegalovirus-specific CTL in HTLV-I-associated myelopathy.

Human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients show high immune responses to HTLV-I. However, it is unclear whether the cytotoxic T lymphocyte (CTL) responses to other chronic viruses also increase. We investigated the responses in the peripheral blood by using HLA-A*0201/peptide pentamers. The frequency of cytomegalovirus (CMV)-specific CTL tended to be higher in HAM/TSP patients than in healthy controls (HCs). The frequency of CMV-specific CTL positively correlated with that of HTLV-I Tax-specific CTL. The frequency of Foxp3+ cells in CD4+ lymphocytes tended to be higher in HAM/TSP patients than in ACs and HCs. The expression level of Foxp3 was lower in HAM/TSP patients than in HCs and was inversely correlated with the CMV-specific CTL frequency. A percentage of Foxp3+ cells showed a positive correlation with the HTLV-I proviral load. These results suggest that a decrease in the Foxp3 expression may contribute to the high immune response to CMV and that the Foxp3+ regulatory T cells may play a role in the immune surveillance of HTLV-I.

GLUT1 is not the primary binding receptor but is associated with cell-to-cell transmission of human T-cell leukemia virus type 1.

GLUT1 has recently been suggested to be a binding receptor for human T-cell leukemia virus type 1 (HTLV-1). We used a novel, short-term assay to define the role of GLUT1 in cell-to-cell transmission. Although increasing cell surface levels of GLUT1 enhanced HTLV-I transfer, efficient virus spread correlated largely with heparan sulfate proteoglycan (HSPG) expression on target cells. Moreover, since activated CD4+ T cells and cord blood lymphocytes that are susceptible to HTLV-1 infection expressed undetectable levels of surface GLUT1, these results indicate that GLUT1 and HSPGs are important for efficient cell-to-cell transmission of HTLV-1 but raise concerns on the role of GLUT1 as the HTLV-1 primary binding receptor.

Foxp3 represses retroviral transcription by targeting both NF-kappaB and CREB pathways.

Forkhead box (Fox)/winged-helix transcription factors regulate multiple aspects of immune responsiveness and Foxp3 is recognized as an essential functional marker of regulatory T cells. Herein we describe downstream signaling pathways targeted by Foxp3 that may negatively impact retroviral pathogenesis. Overexpression of Foxp3 in HEK 293T and purified CD4+ T cells resulted in a dose-dependent and time-dependent decrease in basal levels of nuclear factor-kappaB (NF-kappaB) activation. Deletion of the carboxyl-terminal forkhead (FKH) domain, critical for nuclear localization and DNA-binding activity, abrogated the ability of Foxp3 to suppress NF-kappaB activity in HEK 293T cells, but not in Jurkat or primary human CD4+ T cells. We further demonstrate that Foxp3 suppressed the transcription of two human retroviral promoters (HIV-1 and human T cell lymphotropic virus type I [HTLV-I]) utilizing NF-kappaB-dependent and NF-kappaB-independent mechanisms. Examination of the latter identified the cAMP-responsive element binding protein (CREB) pathway as a target of Foxp3. Finally, comparison of the percent Foxp3+CD4+CD25+ T cells to the HTLV-I proviral load in HTLV-I-infected asymptomatic carriers and patients with HTLV-I-associated myelopathy/tropical spastic paraparesis suggested that high Foxp3 expression is associated with low proviral load and absence of disease. These results suggest an expanded role for Foxp3 in regulating NF-kappaB- and CREB-dependent cellular and viral gene expression.