Acupuncture in the treatment of HTLV-I-associated myelopathy / tropical spastic Paraparesis.

We investigate the possible effects of acupuncture on the improvement of neurological problems in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP)disease. Twenty patients with HAM/TSP were studied in this pre and post-test clinical trial. Urinary incontinence, global motor disability, spasticity, and pain severity were evaluated before, one month, and three-month after the intervention. Analyses demonstrated a significant reduction of urinary symptoms one month after acupuncture (P = 0.023). A significant improvement was observed in patients' pain and the spasticity at the upper extremity joints, one and three-month after the intervention (P < 0.05). This study suggests that body acupuncture can be used as a complementary treatment to improve HAM/TSP neurological symptoms.

Effectiveness of virtual reality games for falls, postural oscillations, pain and quality of life of individual HAM/TSP: a randomized, controlled, clinical trial.

People with HTLV-1 associated myelopathy or tropical spastic paraparesis (HAM/TSP) have sensorimotor losses and postural instability, resulting in frequent falls. These findings stimulate the use of exercise protocols associated with postural control. This study investigated the effectiveness of a balance training exercise protocol through a virtual game. This is a randomized crossover clinical trial performed in subjects with imbalance disorders (HAM/TSP). To evaluate postural oscillations by baropodometry (total area, anterior, posterior and lateral projection), the Footwork® system was used and by cinemetry (angle of the body, hip and ankle alignment in the lateral view), the CVMob system. In addition, the Brief Pain Inventory and the WHOQoL Bref were used to measure pain intensity and quality of life. Comparison tests of the averages (intra and inter groups) and correlations were applied considering an alpha of 5% and power of 80%. The study was approved by the Ethics Committee of the Catholic University of Salvador and registered in the Clinical Trials database (NCT02877030). The final sample consisted of 26, predominantly female subjects. An increase in the postural oscillations of the control subjects (p < 0.05), a reduction in the occurrence of falls (p = 0.039) and an improvement in the quality of life of the control-test group (p < 0.05) were observed. Virtual game training did not improve the static balance, promoting an increase in postural oscillations. Immediately after the application of the protocol, there was a reduction in fall occurrence and improvement in the quality of life.

Impact of host immunity on HTLV-1 pathogenesis: potential of Tax-targeted immunotherapy against ATL.

Human T-cell leukemia virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATL), HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and other inflammatory diseases. There is no disease-specific difference in viral strains, and it is unclear how HTLV-1 causes such different diseases manifesting as lymphoproliferation or inflammation. Although some progress has been made in therapies for these diseases, the prognosis for ATL is still dismal and HAM/TSP remains an intractable disease. So far, two regulatory proteins of HTLV-1, Tax and HBZ, have been well studied and shown to have pleiotropic functions implicated in viral pathogenesis. Tax in particular can strongly activate NFκB, which is constitutively activated in HTLV-1-infected cells and considered to contribute to both oncogenesis and inflammation. However, the expression level of Tax is very low in vivo, leading to confusion in understanding its role in viral pathogenesis. A series of studies using IL-2-dependent HTLV-1-infected cells indicated that IL-10, an anti-inflammatory/immune suppressive cytokine, could induce a proliferative phenotype in HTLV-1-infected cells. In addition, type I interferon (IFN) suppresses HTLV-1 expression in a reversible manner. These findings suggest involvement of host innate immunity in the switch between lymphoproliferative and inflammatory diseases as well as the regulation of HTLV-1 expression. Innate immune responses also affect another important host determinant, Tax-specific cytotoxic T lymphocytes (CTLs), which are impaired in ATL patients, while activated in HAM/TSP patients. Activation of Tax-specific CTLs in ATL patients after hematopoietic stem cell transplantation indicates Tax expression and its fluctuation in vivo. A recently developed anti-ATL therapeutic vaccine, consisting of Tax peptide-pulsed dendritic cells, induced Tax-specific CTL responses in ATL patients and exhibited favorable clinical outcomes, unless Tax-defective ATL clones emerged. These findings support the significance of Tax in HTLV-1 pathogenesis, at least in part, and encourage Tax-targeted immunotherapy in ATL. Host innate and acquired immune responses induce host microenvironments that modify HTLV-1-encoded pathogenesis and establish a complicated network for development of diseases in HTLV-1 infection. Both host and viral factors should be taken into consideration in development of therapeutic and prophylactic strategies in HTLV-1 infection.

Myelopathy due to human T-cell leukemia virus type-1 from the donor after ABO-incompatible liver transplantation.

We report the case of a 53-year-old-man who developed human T-cell leukemia virus type-1-associated myelopathy (HAM) after ABO-incompatible liver transplantation for alcoholic liver cirrhosis. The living donor was seropositive for human T-cell leukemia virus type-1 (HTLV-1) and the recipient was seronegative for HTLV-1 before transplantation. After transplantation, the recipient developed steroid-resistant acute cellular rejection, which was successfully treated using anti-thymocyte globulin, and he was eventually discharged. He underwent spinal surgery twice after the transplantation for the treatment of cervical spondylosis that had been present for a period of 9 months before the transplantation. The surgery improved his gait impairment temporarily. However, his gait impairment progressed, and magnetic resonance imaging revealed multiple sites of myelopathy. He was diagnosed with HAM 16 months after the transplantation. Pulse steroid therapy (1000mg) was administered over a period of 3 days, and his limb paresis improved. Presently, steroid therapy is being continued, with a plan to eventually taper the dose, and he is being carefully followed up at our institution. Our case suggests that liver transplantation involving an HTLV-1-positive living donor carries the risk of virus transmission and short-term development of HAM after transplantation.

Mogamulizumab, an anti-CCR4 antibody, targets human T-lymphotropic virus type 1-infected CD8+ and CD4+ T cells to treat associated myelopathy.

BACKGROUND: Human T-lymphotropic virus type 1 (HTLV-1) can cause chronic spinal cord inflammation, known as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Since CD4(+)CCR4(+) T cells are the main HTLV-1 reservoir, we evaluated the defucosylated humanized anti-CCR4 antibody mogamulizumab as a treatment for HAM/TSP. METHODS: We assessed the effects of mogamulizumab on peripheral blood mononuclear cells from 11 patients with HAM/TSP. We also studied how CD8(+) T cells, namely CD8(+) CCR4(+) T cells and cytotoxic T lymphocytes, are involved in HTLV-1 infection and HAM/TSP pathogenesis and how they would be affected by mogamulizumab. RESULTS: Mogamulizumab effectively reduced the HTLV-1 proviral load (56.4% mean reduction at a minimum effective concentration of 0.01 µg/mL), spontaneous proliferation, and production of proinflammatory cytokines, including interferon γ (IFN-γ). Like CD4(+)CCR4(+) T cells, CD8(+)CCR4(+) T cells from patients with HAM/TSP exhibited high proviral loads and spontaneous IFN-γ production, unlike their CCR4(-) counterparts. CD8(+)CCR4(+) T cells from patients with HAM/TSP contained more IFN-γ-expressing cells and fewer interleukin 4-expressing cells than those from healthy donors. Notably, Tax-specific cytotoxic T lymphocytes that may help control the HTLV-1 infection were overwhelmingly CCR4(-). CONCLUSIONS: We determined that CD8(+)CCR4(+) T cells and CD4(+)CCR4(+) T cells are prime therapeutic targets for treating HAM/TSP and propose mogamulizumab as a new treatment.

HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP): Case based discussion of risk factors, clinical, and therapeutic considerations.

HTLV-1 is a retrovirus virus that infects CD4+ T cells. Most people with HTLV-1 infection remain asymptomatic but some may develop conditions such as HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or adult T-cell leukemia/lymphoma. HAM/TSP is characterized by progressive spasticity and weakness of the lower extremities, as well as loss of bladder control and sensory disturbances. The risk of developing HAM/TSP is associated with the duration of infection and the proviral load. There is currently no cure for the disease but medications can help manage symptoms and slow the progression of the disease. This is the case of a 66-year-old female who presented with nonspecific symptoms of weakness and spasticity in a hospital in Connecticut and was subsequently diagnosed with HAM/TSP. The patient's diagnosis highlights the importance of considering diseases previously confined to specific endemic regions in a globalized world where increased emigration and population mixing can occur. Early identification and management of such cases is essential for optimizing patient outcomes and quality of life.

Novel approaches for HTLV-1 therapy: innovative applications of CRISPR-Cas9.

The human T-cell lymphotropic virus type 1 (HTLV-1) is a single-stranded positive-sense RNA virus that belongs to the Retroviridae family, genus Deltaretro, and infects approximately five to 10 million people worldwide. Although a significant number of individuals living with HTLV-1 remain asymptomatic throughout their lives, some develop one or more severe clinical conditions, such as HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a progressive and debilitating disease, and/or a subtype of non-Hodgkin's lymphoma with a more threatening course known as adult T-cell leukemia/lymphoma (ATLL). Moreover, current therapeutic options are limited and focus primarily on treating symptoms and controlling viral latency. CRISPR-Cas9 gene editing is proposed as a promising tool to address the intricate links associated with HTLV-1. By targeting or silencing key genes during initial infection and dysregulating immune signaling pathways, CRISPR-Cas9 offers potential intervention opportunities. In this review, we address the therapeutic potential of CRISPR-Cas9 gene editing, as well as examine the primary mechanisms involved in editing potential target genes and discuss the existing evidence in the current scientific literature.

[Pathophysiology, treatment and biomarkers for HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)].

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a rare neurodegenerative disease of the central nervous system caused by infection with human T-lymphotropic virus type-1 (HTLV-1). HAM/TSP is characterized by chronic inflammation in spinal cord, leading to neurodegeneration and consequently the patients with HAM/TSP suffer from unremitting myelopathic symptoms such as spastic paraparesis, lower limb sensory disturbance, and bladder/bowel dysfunction. In the past quarter century since the discovery of this disease, significant advances have been made in the field of HAM/TSP research. Here we summarize current clinical and pathophysiological knowledge on HAM/TSP and discusses future focus areas for research on this disease.

[National Questionnaire Survey on the Actual Use and Content Evaluation of the human T-cell leukemia virus type I (HTLV-1) -associated Myelopathy (HAM) Practice Guidelines 2019].

It is not enough to just create medical practice guidelines; they are also required to be implemented into practice. Therefore, we surveyed specialists to determine the extent of the dissemination of the "HAM Practice Guidelines 2019," to quantify gaps, identify challenges, and understand needs in daily practice. The survey also revealed that the 25% of the specialists were unaware of the tests required for confirming human T-cell leukemia virus type I (HTLV-1) infection. Additionally, they had insufficient knowledge of the HTLV-1 infection. About 90.7% of the specialists agreed with the policy of determining treatment intensity based on disease activity. However, the implementation rate of cerebrospinal fluid marker measurement, which is useful for this assessment, was as low as 27%. Hence, it is important to use the findings of this study to further promote awareness about this issue.

Advances in the treatment of human T-cell lymphotropic virus type-I associated myelopathy.

INTRODUCTION: Nearly 2-3% of those 10 to 20 million individuals infected with the Human T-cell lymphotropic virus type-1 (HTLV-1); are predisposed to developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is a neuro-inflammatory disease; differentiated from multiple sclerosis based on the presence of typical neurologic symptoms, confirmation of HTLV-1 infection, and other molecular biomarkers. AREAS COVERED: A brief review of the epidemiology, host immune responses, and molecular pathogenesis of HAM/TSP is followed by detailed discussions about the host-related risk factors for developing HAM/TSP and success/failure stories of the attempted management strategies. EXPERT OPINION: Currently, there is no effective treatment for HAM/TSP. Anti-retroviral therapy, peculiar cytokines (IFN-α), some anti-oxidants, and allograft bone marrow transplantation have been used for treating these patients with limited success. Under current conditions, asymptomatic carriers should be examined periodically by a neurologist for early signs of spinal cord injury. Then it is crucial to determine the progress rate to adapt the best management plan for each patient. Corticosteroid therapy is most beneficial in those with acute myelitis. However, slow-progressing patients are best managed using a combination of symptomatic and physical therapy. Additionally, preventive measures should be taken to decrease further spread of HTLV-1 infection.

Tropical spastic paraparesis and HTLV-1 associated myelopathy: clinical, epidemiological, virological and therapeutic aspects.

In 1980, Human T cell leukemia/lymphoma virus type 1 (HTLV-1) was the first oncogenic human retrovirus to be discovered. HTLV-1 belongs to the Retroviridae family, the Orthoretrovirinae subfamily and to the deltaretrovirus genus. HTLV-1 preferentially infects CD4(+) lymphoid cells in vivo. Three molecules have been identified for binding and/or entry of HTLV-1: heparan sulfate proteoglycans, neuropilin-1, and glucose transporter 1. An efficient transfer of the virus from an infected cell to a target cell can occur through the formation of a viral synapse and/or by virofilm structure. As for all retroviruses, HTLV-1 genome possesses three major ORFs (gag, pol and env) encoding the structural and enzymatic proteins. HTLV-1 encodes also some regulatory and auxillary proteins including the tax protein with transforming activities and the HBZ protein which plays a role in the proliferation and maintenance of the leukemic cells. HTLV-1 is present throughout the world with clusters of high endemicity including mainly Southern Japan, the Caribbean region, areas in South America and in intertropical Africa. The worldwide HTLV-1 infected population is estimated to be around 10-20 million. HTLV-1 has three modes of transmission: (1): mother to child, mainly linked to prolonged breast-feeding; (2): sexual, mainly occurring from male to female and (3): contaminated blood products. HTLV-1 possesses a remarkable genetic stability. HTLV-1 is the etiological agent of mainly two severe diseases: a malignant T CD4(+) cell lymphoproliferation, of very poor prognosis, named Adult T cell Leukemia/Lymphoma (ATLL), and a chronic neuro-myelopathy named Tropical spastic paraparesis/HTLV-1 Associated Myelopathy (TSP/HAM). The lifetime risk among HTLV-1 carriers is estimated to be around 0.25 to 3%. TSP/HAM mainly occurs in adults, with a mean age at onset of 40-50 years and it is more common in women than in men. Blood transfusion is a major risk factor for TSP/HAM development. Clinically, TSP/HAM is mainly defined as a chronic spastic paraparesis and minor sensory signs. The onset is insidious with often gait disturbance and urinary symptoms. In more than 90% of the cases, the neurological features involve: spasticity and/or hyperreflexia of the lower extremities, urinary bladder disturbance, lower extremity muscle weakness, and in around 50% of the cases, sensory disturbances with low back pain. Central functions and cranial nerves are usually spared. The clinical course is generally progressive without remission. High levels of antibodies titers directed against HTLV-1 antigens are present in blood and cerebrospinal fluid (CSF). A high HTLV-1 proviral load is frequently observed in the blood. Mild to moderate increase of proteins may be present in the CSF. However, intrathecal production of specific HTLV-1 antibody index provides additional data to support the diagnosis. Brain white matter lesions on magnetic resonance imaging are frequent. A mild atrophy of the thoracic spinal cord can also be observed. Pathologically, it is characterized by a chronic inflammation with perivascular lymphocytic cuffing and mild parenchymal lymphocytic infiltrates. The cells are mostly CD4(+) in early disease and mostly CD8(+) in latter disease. Pyramidal tract damage with myelin and axonal loss, mainly in the lower thoracic spinal cord are observed. TSP/HAM pathogenesis is still poorly understood and viral and host factors as the proviral load and the cellular immune response play a major role in disease progression. TSP/HAM can be associated with other HTLV-1 associated symptoms (uveitis, myositis, infective dermatitis). Therapy of TSP/HAM remains disappointing and symptomatic treatment remains still the mainstay of therapy.

[HTLV-1-associated myelopathy/tropical spastic paraparesis: a differential diagnosis in multiple sclerosis]. / HTLV-1-assoziierte Myelopathie/tropische spastische Paraparese : Eine Differenzialdiagnose der Multiplen Sklerose.

Human T-cell lymphotropic virus 1 (HTLV-1) associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurological disease caused by infection with HTLV-1. The disorder is very rare in Europe but endemic in many parts of the world. The pathogenesis is not clearly characterized but is based on a possibly immune-mediated injury of the cervicothoracic spinal cord. Clinically, HAM/TSP constitutes a slowly progressive spastic paraparesis associated with bladder dysfunction and often mimics the course of autoimmune and neurodegenerative diseases. The diagnosis is based on typical symptoms as well as detection of HTLV-1 specific antibodies and proviral HTLV-1 DNA or HTLV-1 RNA. The therapy is limited to symptomatic treatment. Transmission of HTLV-1 can occur vertically by breast feeding, through sexual contact or via infected blood products. Based on a clinical case report, we present here a current review on the pathophysiology, epidemiology, clinical manifestations, diagnosis and treatment of HAM/TSP.

[The current and future approaches to the treatment of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)].

Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus that is the causative agent of a progressive neurological disease termed HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is a chronic neuroinflammatory disease characterized by spastic paraparesis, lower limb sensory disturbance and bladder/bowel dysfunction. Over the twenty-five years since the discovery of this disease, significant advancements have been made in the pathogenic mechanisms associated with HAM/TSP, however, little progress has been made in the treatment of this disorder. This review highlights the natural history of HAM/TSP, informative results of clinical trials, and discusses the current and future approaches to the treatment of HAM/TSP within the context of our understanding of the underlying pathogenic mechanisms.

Severe loss of invariant NKT cells exhibiting anti-HTLV-1 activity in patients with HTLV-1-associated disorders.

Invariant natural killer T (iNKT) cells are unique T cells that regulate the immune response to microbes, cancers, and autoimmunity. We assessed the characteristics of iNKT cells from persons infected with human T-lymphotropic virus type 1 (HTLV-1). Whereas most infected persons remain asymptomatic carriers (ACs) throughout their lives, a small proportion, usually with high equilibrium proviral loads,develop 2 diseases: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia (ATL). We demonstrated that the frequency of iNKT, NK, and dendritic cells in the peripheral blood of HAM/TSP and ATL patients is decreased. We also observed an inverse correlation between the iNKT cell frequency and the HTLV-1 proviral load in the peripheral blood of infected persons. Notably, in vitro stimulation of peripheral blood cells with alpha-galactosylceramide led to an increase in the iNKT cell number and a subsequent decrease in the HTLV-1-infected T-cell number in samples from ACs but not HAM/TSP or ATL patients. Our results suggest that iNKT cells contribute to the immune defense against HTLV-1, and iNKT-cell depletion plays an important role in the pathogenesis of HAM/TSP and ATL. Therefore, iNKT cell-based immunotherapy may be an effective strategy for preventing these HTLV-1-associated disorders.

Therapeutic effects of virtual reality video gaming on functional mobility, balance, and gait speed in individuals with tropical spastic paraparesis: A randomized crossover clinical trial.

INTRODUCTION: Individuals with human T-cell lymphotropic virus 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) experience sensorimotor alterations, which can affect functional performance. Virtual reality (VR) videogaming is a therapeutic option, though there is scarce evidence for its use in this population. We aimed to investigate the therapeutic effects of a VR video game on functional mobility, balance, and gait speed in individuals with HAM/TSP. METHODS: We conducted a blinded, crossover clinical trial comprising 29 individuals with HAM/TSP and randomized them into two groups: (1) early therapy: rehabilitative protocol started immediately after the initial evaluation and (2) late therapy: rehabilitative protocol started 10 weeks later. We assessed all participants for balance using the Berg Balance Scale (BBS) scores, functional mobility using the Timed Up and Go (TUG) test, and gait speed using video camera and CvMob software. Differences were considered significant if p<0.05. RESULTS: The early therapy group individuals presented with higher BBS scores (p=0.415), less TUG times (p=0.290), and greater gait speed (p=0.296) than the late therapy group individuals. CONCLUSIONS: VR videogaming is a useful option for rehabilitative therapy in individuals with HAM/TSP; it positively affects balance, functional mobility, and gait speed.

Pilates exercise improves the clinical and immunological profiles of patients with human T-cell lymphotropic virus 1 associated myelopathy: A pilot study.

BACKGROUND: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an infectious chronic-inflammatory disease, which can lead to lower limb motions. METHODS: The study evaluated the effects of serial Pilates exercises on the clinical and immunological profiles of patients with HAM/TSP. Eight patients with ages ranging from 39 to 70 years old (2 males and 6 females), 2 wheelchair users and 6 with compromised gait, were evaluated. The patients were submitted to 20 Pilates sessions for 10 weeks. Data were collected at 3 time points (beginning of the study, after Pilates sessions and after 10 weeks without Pilates) and consisted of evaluations of the pain level, spasticity, motor strength, balance, mobility, functional capacity, quality of life and quantification of IFN-γ, IL-10 and IL-9 cytokines levels. RESULTS: After the Pilates sessions, significant improvements in pain level, static and dynamic balance, trunk control, mobility and quality of life were observed, with simultaneous and significant reductions in the serum levels of the cytokines IFN-γ and IL-10. However, after 10 weeks without Pilates, there were significant changes in terms of increasing pain and regression of mobility, with no changes in strength, spasticity, functional capacity in any of the periods of the study. CONCLUSIONS: The results suggest that Pilates may be a promising auxiliary physical therapy for patients with HAM/TSP.

HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP): the role of HTLV-I-infected Th1 cells in the pathogenesis, and therapeutic strategy.

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive myelopathy characterized by bilateral pyramidal tract involvement with sphincteric disturbances. The primary neuropathological feature of HAM/TSP is chronic myelitis characterized by perivascular cuffing and parenchymal infiltration of lymphocytes. Although the exact cellular and molecular events underlying the induction of chronic inflammation in the spinal cord by HTLV-I are still unclear, a long-standing bystander mechanism, such as the destruction of surrounding nervous tissue by the interaction between HTLV-I-infected CD4+ T cells and HTLV-I-specific cytotoxic T cells in the spinal cord, is probably critical in the immunopathogenesis of HAM/TSP. In this review, the role of HTLV-I-infected CD4+ T cells as activated Th1 cells in the peripheral blood will be discussed as the first responders of this mechanism in the immunopathogenesis of HAM/TSP. Since the discovery of HAM/TSP, various therapeutic approaches, such as immunomodulatory or anti-viral drugs, have been used for HAM/TSP patients. However, an effective therapeutic strategy against HAM/TSP is still unavailable. As HTLV-I-infected CD4+ T cells are the first responders in the immunopathogenesis of HAM/TSP, the ideal treatment is the elimination of HTLV-I-infected cells from the peripheral blood. In this review, the focus will be on therapeutic strategies aimed at targeting HTLV-I-infected CD4+ T cells in HAM/TSP patients.

Clinical trial of a humanized anti-IL-2/IL-15 receptor ß chain in HAM/TSP.

OBJECTIVE: Human T cell lymphotropic virus 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive, neurological disease. Chronic activation of CD8+ T cells, as evidenced by increased spontaneous lymphoproliferation and HTLV-1-specific cytotoxic T cells, has been demonstrated in HAM/TSP patients. Since IL-2 and IL-15 stimulate memory CD8+ T cell activity, these cytokines have been implicated in the immunopathogenesis of HAM/TSP. In this phase I trial, we evaluated the safety, pharmacokinetics, and ability of Hu-Mikß1, a humanized monoclonal antibody directed toward the IL-2/IL-15 receptor ß-chain (IL-2/IL-15Rß: CD122), to saturate CD122 and regulate abnormal immune responses in patients with HAM/TSP by inhibition of IL-15 action. METHODS: Hu-Mikß1 was administered intravenously at doses of 0.5 mg/kg, 1.0 mg/kg, or 1.5 mg/kg in a total of nine HAM/TSP patients. Five doses of Hu-Mikß1 were administered at 3-week intervals. The clinical response was evaluated using standardized scales. Viral and immunologic outcome measures were examined including HTLV-1 proviral load, T cell phenotypic analysis and spontaneous lymphoproliferation in HAM/TSP patients. RESULTS: There was no significant toxicity associated with Hu-Mikß1 administration in HAM/TSP patients. Saturation of CD122 by Hu-Mikß1 was achieved in five out of nine HAM/TSP patients. Administration of Hu-Mikß1 was associated with inhibition of aberrant CD8+ T cell function including spontaneous lymphoproliferation and degranulation and IFN-γ expression, especially in HAM/TSP patients that achieved CD122 saturation. INTERPRETATION: The treatment with Hu-Mikß1 had a number of immunological effects on HAM/TSP patients although no clinical efficacy was observed. We also did not see any dose-related toxicity.