High production of interferon gamma but not interleukin-2 by human T-lymphotropic virus type I-infected peripheral blood mononuclear cells

Th17/IL-17 Axis in HTLV-1-Associated Myelopathy Tropical Spastic Paraparesis and Multiple Sclerosis: Novel Insights into the Immunity During HAMTSP

Human T lymphotropic virus-associated myelopathy/tropical spastic paraparesis (HTLV/TSP), also known as HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and multiple sclerosis (MS) are chronic debilitating diseases of the central nervous system; although the etiology of which is different, similarities have been observed between these two demyelinating diseases, especially in clinical manifestation and immunopathogenesis. Exorbitant response of the immune system to the virus and neurons in CNS is the causative agent of HAM/TSP and MS, respectively. Helper T lymphocyte-17 cells (Th17s), a component of the immune system, which have a proven role in immunity and autoimmunity, mediate protection against bacterial/fungal infections. The role of these cells has been reviewed in several CNS diseases. A pivotal role for Th17s is presented in demyelination, even more axial than Th1s, during MS. The effect of Th17s is not well determined in HTLV-1-associated infections; however, the evidence that we have supplied in this review illustrates the attendance, also the role of Th17 cells during HAM/TSP. Furthermore, for better conception concerning the trace of these cells in HAM/TSP, a comparative characterization with MS, the resembling disease, has been applied here.

Dietary Intake and Serum Selenium Levels Influence the Outcome of HTLV-1 Infection

Human T cell leukemia virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), as the most common neurological emersion related to HTLV-1, is a debilitating and lifelong treating disease with no definitive treatment. Furthermore, it has been determined that dietary compositions (inflammatory and anti-inflammatory) and some micronutrients (such as vitamin D and selenium) have an effect on inflammatory and immune processes and with this background; the study was done to compare the nutritional status between age- and sex-matched with infected and non-infected HTLV-1. In a multi-center setting, 70 healthy controls (HCs), 35 asymptomatic carriers (ACs), and 35 HAM/TSP patients were recruited in the HTLV-1 Foundation, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran. Nutritional status including anthropometric indices, dietary (micro- and macronutrient) intake, and serum vitamin D, vitamin B12, zinc, and selenium were measured. In anthropometric indices, mean waist circumference (WC) in the carrier group was significantly higher than the patient and the control groups (p = 0.008). In the dietary intake, the patient group received less energy, protein, mono-unsaturated fatty acids (MUFA), and oleic, but more fat than the HTLV-1 carrier and control groups, and these differences were remarkable in three groups (p = 0.002, 0.005, 0.001, 0.01, and 0.001, respectively), whereas the carrier group received more saturated fatty acid and less poly-unsaturated fatty acids (PUFA), linoleic, and linolenic than patient and control groups with a different significant (p = 0.01, 0.007, 0.005, and 0.006, respectively) in three groups. In micronutrient intake, although selenium, zinc, and vitamins B12 and D were lower in the patient group than the carrier and control group, however, no significant differences were observed. In comparison with micronutrient serum concentrations, vitamins B12 and D and selenium in the patient group were lower than the carrier and control groups, but statistically, the considerable difference was found only in the selenium concentration (p = 0.001). The study showed that there were differences in dietary intake (including energy, macronutrients, and fatty acids), WC, and selenium serum levels between HAM/TSP patients and HTLV-1 carriers, suggesting that nutritional statues influence the inflammatory immune response in HTLV-1 infection.

Impact of HIV co-infection on immunological biomarker profile of HTLV-1 infected patients

The impact of HIV co-infection on the plasma immunological biomarker profile of HTLV-1 infected patients was evaluated. The plasma levels of leukotrienes and chemokines/cytokines were quantified by ELISA and Cytometric Bead Array. A total of 138 volunteers were enrolled and divided into two subgroups ("HTLV-1(+)HIV(-)" and "HTLV-1(+)(HIV(+)"), which were categorized according to the HTLV-1-associated neurological disease (AS, pHAM and HAM). Reference controls were BD and HIV mono-infected patients. HAM(+) exhibited higher CD4⁺ T-cell counts as compared to HIV+ mono-infected patients and lower HTLV-1 proviral load as compared to mono-infected HAM(-) patients. AS(+) exhibited higher levels of CysLT, CXCL8/IL-8 and lower levels of CCL5/RANTES as compared to AS(-). Increased levels of IL-6 and TNF with reduced levels of CXCL10/IP10 and CCL5/RANTES were observed in co-infected pHAM(+) as compared to mono-infected pHAM(-). HAM(+) patients revealed an increase in CXCL8/IL-8, CCL2/MCP-1, CXCL-10/IP-10, TNF and a decrease in IL-2 as compared to HAM(-) subgroup.

EOS, an Ikaros family zinc finger transcription factor, interacts with the HTLV-1 oncoprotein Tax and is downregulated in peripheral blood mononuclear cells of HTLV-1-infected individuals, irrespective of clinical statuses

BACKGROUND

EOS plays an important role in maintaining the suppressive function of regulatory T cells (Tregs), and induces a regulated transformation of Tregs into T helper-like cells, which are capable of secreting proinflammatory cytokines in response to specific inflammatory signals. Meanwhile, significant reduction in Treg activity along with production of proinflammatory cytokines has been reported in patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP).

METHODS

In this study, to examine whether there is an alteration in EOS expression in peripheral blood mononuclear cells (PBMCs) derived from HTLV-1-infected individuals especially HAM/TSP, we investigated the expression of HTLV-1 tax genotype, proviral load (PVL), and the mRNA expression of tax, HBZ and EOS in HTLV-1 infected individuals including adult T-cell leukemia/lymphoma (ATL), HAM/TSP, or asymptomatic carriers. The expression levels of EOS mRNA and protein in various HTLV-1-infected or uninfected human T-cell lines were also investigated.

RESULTS

EOS was highly expressed at the protein level in most HTLV-1 infected T-cell lines, and was augmented after the HTLV-1 regulatory factor Tax was induced in a Tax-inducible JPX-9 cell line. Immunoprecipitation experiments demonstrated a physical interaction between EOS and the viral regulatory protein Tax, but not HBZ. Meanwhile, there was a significant decrease in EOS mRNA levels in PBMCs of HTLV-1 infected individuals irrespective of their clinical statuses. We found an inverse correlation between EOS mRNA levels and HTLV-1 PVL in ATL patients, and positive correlations between both EOS mRNA load and PVL, and EOS and HBZ mRNA load in HAM/TSP patients, whereas this correlation was not observed in other clinical statuses.

CONCLUSIONS

These findings suggest that both Tax and HBZ can alter the expression of EOS through undetermined mechanisms, and dysregulated expression of EOS in PBMCs of HTLV-1 infected individuals may contribute to the pathological progression of HTLV-1-associated diseases, such as ATL and HAM/TSP.

Role of HTLV-1 orf-I encoded proteins in viral transmission and persistence

The human T cell leukemia virus type 1 (HTVL-1), first reported in 1980 by Robert Gallo's group, is the etiologic agent of both cancer and inflammatory diseases. Despite approximately 40 years of investigation, the prognosis for afflicted patients remains poor with no effective treatments. The virus persists in the infected host by evading the host immune response and inducing proliferation of infected CD4⁺ T-cells. Here, we will review the role that viral orf-I protein products play in altering intracellular signaling, protein expression and cell-cell communication in order to escape immune recognition and promote T-cell proliferation. We will also review studies of orf-I mutations found in infected patients and their potential impact on viral load, transmission and persistence. Finally, we will compare the orf-I gene in HTLV-1 subtypes as well as related STLV-1.

Immunovirological markers in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Human T cell lymphotropic virus 1 (HTLV-1) is a human retrovirus and infects approximately 10–20 million people worldwide. While the majority of infected people are asymptomatic carriers of HTLV-1, only 4% of infected people develop HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is a chronic, progressive, neurological disease which usually progresses slowly without remission, and is characterized by perivascular inflammatory infiltrates in chronic inflammatory lesions of the central nervous system (CNS), primarily affecting the spinal cord. A high HTLV-1 proviral load, high levels of antibodies against HTLV-1 antigens, and elevated concentration of proteins are detected in cerebrospinal fluid (CSF) of HAM/TSP patients. These chronically activated immune responses against HTLV-1 and infiltration of inflammatory cells including HTLV-1 infected cells into the CNS contribute to clinical disability and underlie the pathogenesis of HAM/TSP. Since the disease development of HAM/TSP mainly occurs in adults, with a mean age at onset of 40–50 years, it is important for HTLV-1-infected carriers and HAM/TSP patients to be monitored throughout the disease process. Recent advances in technologies and findings provide new insights to virological and immunological aspects in both the CNS as well as in peripheral blood. In this review, we focus on understanding the inflammatory milieu in the CNS and discuss the immunopathogenic process in HTLV-1-associated neurologic diseases.

40 years of the human T-cell leukemia virus: past, present, and future

It has been nearly 40 years since human T-cell leukemia virus-1 (HTLV-1), the first oncogenic retrovirus in humans and the first demonstrable cause of cancer by an infectious agent, was discovered. Studies indicate that HTLV-1 is arguably one of the most carcinogenic agents to humans. In addition, HTLV-1 causes a diverse array of diseases, including myelopathy and immunodeficiency, which cause morbidity and mortality to many people in the world, including the indigenous population in Australia, a fact that was emphasized only recently. HTLV-1 can be transmitted by infected lymphocytes, from mother to child via breast feeding, by sex, by blood transfusion, and by organ transplant. Therefore, the prevention of HTLV-1 infection is possible but such action has been taken in only a limited part of the world. However, until now it has not been listed by the World Health Organization as a sexually transmitted organism nor, oddly, recognized as an oncogenic virus by the recent list of the National Cancer Institute/National Institutes of Health. Such underestimation of HTLV-1 by health agencies has led to a remarkable lack of funding supporting research and development of treatments and vaccines, causing HTLV-1 to remain a global threat. Nonetheless, there are emerging novel therapeutic and prevention strategies which will help people who have diseases caused by HTLV-1. In this review, we present a brief historic overview of the key events in HTLV-1 research, including its pivotal role in generating ideas of a retrovirus cause of AIDS and in several essential technologies applicable to the discovery of HIV and the unraveling of its genes and their function. This is followed by the status of HTLV-1 research and the preventive and therapeutic developments of today. We also discuss pending issues and remaining challenges to enable the eradication of HTLV-1 in the future.

Diversity of cell phenotypes among MT-2 cell lines affects the growth of U937 cells and cytokine production

We previously reported the diversity of structure and integration sites of human T-cell leukemia virus type 1 (HTLV-1) provirus among different MT-2 cell lines. This raised the question as to whether cell phenotypes also differed among MT-2 cell lines. The influence of two different MT-2 cell lines (MT-2J and MT-2B) on the growth of the promonocytic leukemia cell line, U937, was investigated. Protein levels and mRNA expression of cytokines were also investigated. In addition, Western blot analysis of HTLV-1 regulatory proteins, Tax and HBZ, was also performed. Culture supernatant from MT-2B, but not MT-2J, cells showed marked suppressive effects on U937 cell growth. MT-2B showed high tumor necrosis factor (TNF)-α, TNF-β, and interferon (IFN)-γ both in protein levels of the culture supernatant and mRNA levels of the cells. Analysis using recombinant cytokines indicated that the suppressive effects of MT-2B were due, at least in part, to high levels of TNF-β and its synergic effects with IFN-γ in the culture supernatant. Protein levels of HTLV-1 Tax and HBZ were higher in MT-2B than those in MT-2J cells. These molecules have been reported to affect the cytokine production of HTLV-1 infected cells; therefore, the difference in these molecules may have accounted for the differences in cytokine production between MT-2J and MT-2B cells. Furthermore, because MT-2 cells showed a large variation of integrated HTLV-1 proviruses as well as cell phenotypes, it is important to exercise caution in the assessment and interpretation of experimental data from MT-2 cells.

Human T-cell leukaemia virus type 1: parasitism and pathogenesis

Human T-cell leukaemia virus type 1 (HTLV-1) causes not only adult T-cell leukaemia-lymphoma (ATL), but also inflammatory diseases including HTLV-1-associated myelopathy/tropical spastic paraparesis. HTLV-1 transmits primarily through cell-to-cell contact, and generates abundant infected cells in the host in order to survive and transmit to a new host. The resulting high proviral load is closely associated with the development of ATL and inflammatory diseases. To increase the number of infected cells, HTLV-1 changes the immunophenotype of infected cells, induces proliferation and inhibits apoptosis through the cooperative actions of two viral genes, tax and HTLV-1 bZIP factor (HBZ). As a result, infected cells survive, proliferate and infiltrate into the tissues, which is critical for transmission of the virus. Thus, the strategy of this virus is indivisibly linked with its pathogenesis, providing a clue for prevention and treatment of HTLV-1-induced diseases.

This article is part of the themed issue ‘Human oncogenic viruses’.

Role of HTLV-1 Tax and HBZ in the Pathogenesis of HAM/TSP

Human T cell lymphotropic virus type 1 (HTLV-1) infection can lead to development of adult T cell leukemia/lymphoma (ATL) or HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in a subset of infected subjects. Understanding the interaction between host and HTLV-1 and the molecular mechanisms associated with disease pathogenesis is critical for development efficient therapies. Two HTLV-1 genes, tax and HTLV-1 basic leucine zipper factor (HBZ), have been demonstrated to play important roles in HTLV-1 infectivity and the growth and survival of leukemic cells. Increased HTLV-1 Tax expression induces the expression of various cellular genes such as IL-2 and IL-15, which directly contributes to lymphocyte activation and immunopathogenesis in HAM/TSP patients. However, little is known about the molecular and cellular mechanism of HBZ in development of HAM/TSP. It has been reported that HBZ mRNA expression was detected in HAM/TSP patients higher than in asymptomatic carriers and correlated with proviral load and disease severity. Unlike HTLV-1 tax, HBZ escapes efficient anti-viral immune responses and therefore these reactivities are difficult to detect. Thus, it is important to focus on understanding the function and the role of HTLV-1 tax and HBZ in disease development of HAM/TSP and discuss the potential use of these HTLV-1 viral gene products as biomarkers and therapeutic targets for HAM/TSP.

Human T Cell Leukemia Virus Type 1: Persistence and Pathogenesis

Human T cell leukemia virus type 1 (HTLV-1), also known as human T lymphotropic virus type 1, was the first exogenous human retrovirus discovered. Unlike the distantly related lentivirus HIV-1, HTLV-1 causes disease in only 5-10% of infected people, depending on their ethnic origin. But whereas HIV-1 infection and the consequent diseases can be efficiently contained in most cases by antiretroviral drug treatment, there is no satisfactory treatment for the malignant or inflammatory diseases caused by HTLV-1. The purpose of the present article is to review recent advances in the understanding of the mechanisms by which the virus persists in vivo and causes disabling or fatal diseases.

Mediators Go Together: High Production of CXCL9, CXCL10, IFN-γ, and TNF-α in HTLV-1-Associated Myelopathy/Tropical Spastic Paraparesis

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic demyelinating and disabling syndrome caused by human T lymphotropic virus 1 (HTLV-1). Although the pathogenic mechanisms that lead to HAM/TSP outcome have not been elucidated, genetic and immunological factors may be involved in the myelopathy occurrence. This study aimed to compare cytokines, chemokines, and nitric oxide (NO) levels in asymptomatic and HAM/TSP HTLV-1-infected patients. The study group consisted of 21 HAM/TSP and 48 asymptomatic HTLV-1 patients. Chemokines (CCL5, CCL2, CXCL8, CXCL9, and CXCL10) and cytokines [IL-2, interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), IL-4, IL-6, and IL-10] were measured using cytometric bead array, whereas NO production was measured after reaction of supernatants with nitrate reduction solution. CXCL9 and CXCL10 chemokines levels were found to be higher in the HAM/TSP group. CXCL9 was also strongly correlated with CXCL10 and both CXCL9 and CXCL10 were moderately correlated with CCL2 and CCL5 levels, in both HAM/TSP and asymptomatic groups. There was no significant difference related to NO, IL-4, IL-6, and IL-10 levels between the clinical groups but TNF-α and IFN-γ levels were increased in HAM/TSP patients. Thus, factors such as CXCL9, CXCL10, TNF-α, and IFN-γ could be good prognostic biomarker candidates, and further studies may help to clarify their association with HAM/TSP immunopathogenesis.

Evaluation of HTLV-1 HBZ and proviral load, together with host IFN λ3, in pathogenesis of HAM/TSP

Human T-cell lymphotropic virus 1 (HTLV-1) is associated with two progressive diseases: HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia/lymphoma (ATLL). Although HTLV-1 proviral load (PVL) has been introduced as a risk factor for these diseases' progression, it is not sufficient on its own to yield an accurate estimation of the outcome of the infection. In the present study, PVL and HTLV-1 basic leucine zipper factor (HBZ) expression level as viral factors, and IFN λ3 as a host factor, were evaluated in HAM/TSP patients and HTLV-1 asymptomatic carriers (ACs). During 2014-2015, 12 HAM/TSP patients and 18 ACs who had been referred to the HTLV-1 Clinic, Ghaem Hospital, Mashhad University of Medical Sciences (MUMS), Mashhad, Iran, were enrolled in this study. Peripheral blood mononuclear cells (PBMCs) were isolated and the DNA and mRNA were extracted for quantification of HBZ, IFN λ3 expression, and PVL using real-time PCR (TaqMan method). Although the PVL was higher in the HAM/TSP group, with a 94% confidence interval, there were no considerable differences in terms of HBZ mRNA and PVL between ACs and HAM patients. IFN λ3 expression in the HAM/TSP group was significantly higher than in the ACs (P = 0.02). To the best of our knowledge, no study has evaluated the expression level of IFN λ3 in HTLV-1 positive patients. The immune response against HTLV-1 viral antigens and virulent factors will therefore further refine our knowledge of interactions between the virus and host in the pathogenesis of HTLV-1-related disorders. The virus PVL and the host IFN λ3 can be used as pathogenic factors of HTLV-1 infected patients at risk of HAM/TSP manifestation. J. Med. Virol. 89:1102-1107, 2017. © 2016 Wiley Periodicals, Inc.

IL17A Polymorphism Is Not Associated with Human T-Lymphotropic Virus 1-Associated Myelopathy/Tropical Spastic Paraparesis

The human T-lymphotropic virus 1 (HTLV-1) is the causative agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The present study investigated the association between the rs2275913 polymorphism in the IL17A gene and the development of HAM/TSP. Peripheral blood samples were collected from 116 patients (29 symptomatic patients with HAM/TSP and 87 asymptomatic) with a positive diagnosis of HTLV-1. The single nucleotide polymorphism genotyping was carried out by real time PCR using TaqMan probes. In addition, serum levels of IL-2, IFN-γ, TNF-α, IL-4, IL-6, IL-10, and IL-17 were measured in 64 infected individuals from the study (47 asymptomatic and 17 HAM/TSP), using cytometric bead array technique. No significant differences were found in genotypic and allelic frequencies between the groups. Analysis of cytokine levels showed highest concentrations of IFN-γ and TNF-α in HAM/TSP patients. The results of the present study, therefore, suggest a lack of association between the rs2275913 polymorphism in the IL17A gene and the presence of HAM/TSP.

Downregulation of proinflammatory cytokines in HTLV-1-infected T cells by Resveratrol

BACKGROUND

Human T-cell leukemia virus (HTLV-1) is a lymphotropic retrovirus associated to adult T cell leukemia (ATL) and to non-neoplastic inflammatory conditions affecting the central nervous system, lung or skin. The inflammatory disorders associated to HTLV-1 are mediated by different proinflammatory cytokines as IL-1α, IL-6, TNF-α. The release and the role of IL-17 is still debated. Aims of this study were to analyze IL-17 induction by HTLV-1 infection and to determine whether resveratrol (RES) is able to down regulate the pathway of cytokines production either in HTLV-1 chronically infected MT-2 cell line or in human CD4+ cells infected in vitro with HTLV-1.

METHODS

MT-2 and HTLV-1 infected CD4+ cells were analyzed for proinflammatory cytokine production before or after RES treatment. The concentrations of IL-17, IL-1α, IL-6, and TNF-α were measured in cell culture supernatants by ELISA and SearchLight™ technology. The IL-17 mRNA expression was evaluated by RT-PCR. NF-kB activation was detected by non-radioactive, Electro Mobility Shift Assay (EMSA). HTLV-1 RNA expression was detected by Real-time-PCR (RQ-PCR).

RESULTS

We found that RES is capable of inducing a dose-dependent inhibition of IL-1α, IL-6 and TNF-α production in vitro and can down regulate the expression of IL-17 at both mRNA and protein levels in HTLV-1 infected cells. This effect was associated with a dose-dependent inhibition of the of the nuclear factor kappa-B (NF-kB) activity. Conversely, RES did not apparently affect HTLV-1 proliferation.

CONCLUSIONS

These results support the anti-inflammatory properties of RES, suggesting that it might be a useful therapeutic agent for the treatment of HTLV-1 related inflammatory diseases.

Human T Cell Leukemia Virus Type 1 Infection of the Three Monocyte Subsets Contributes to Viral Burden in Humans

Because the viral DNA burden correlates with disease development, we investigated the contribution of monocyte subsets (classical, intermediate, and nonclassical monocytes) to the total viral burden in 22 human T cell leukemia virus type 1 (HTLV-1)-infected individuals by assessing their infectivity status, frequency, as well as chemotactic and phagocytic functions. All three monocyte subsets sorted from HTLV-1-infected individuals were positive for viral DNA, and the frequency of classical monocytes was lower in the blood of HTLV-1-infected individuals than in that of uninfected individuals, while the expression levels of the chemokine receptors CCR5, CXCR3, and CX3CR1 in classical monocytes were higher in HTLV-1-infected individuals than uninfected individuals; the percentage of intermediate monocytes and their levels of chemokine receptor expression did not differ between HTLV-1-infected and uninfected individuals. However, the capacity of intermediate monocytes to migrate to CCL5, the ligand for CCR5, was higher, and a higher proportion of nonclassical monocytes expressed CCR1, CXCR3, and CX3CR1. The level of viral DNA in the monocyte subsets correlated with the capacity to migrate to CCL2, CCL5, and CX3CL1 for classical monocytes, with lower levels of phagocytosis for intermediate monocytes, and with the level of viral DNA in CD8(+) and CD4(+) T cells for nonclassical monocytes. These data suggest a model whereby HTLV-1 infection augments the number of classical monocytes that migrate to tissues and become infected and the number of infected nonclassical monocytes that transmit virus to CD4(+) and CD8(+) T cells. These results, together with prior findings in a macaque model of HTLV-1 infection, support the notion that infection of monocytes by HTLV-1 is likely a requisite for viral persistence in humans.

IMPORTANCE

Monocytes have been implicated in immune regulation and disease progression in patients with HTLV-1-associated inflammatory diseases. We detected HTLV-1 DNA in all three monocyte subsets and found that infection impacts surface receptor expression, migratory function, and subset frequency. The frequency of nonclassical patrolling monocytes is increased in HTLV-1-infected individuals, and they have increased expression of CCR1, CXCR3, and CX3CR1. The viral DNA level in nonclassical monocytes correlated with the viral DNA level in CD4(+) and CD8(+) T cells. Altogether, these data suggest an increased recruitment of classical monocytes to inflammation sites that may result in virus acquisition and, in turn, facilitate virus dissemination and viral persistence. Our findings thus provide new insight into the importance of monocyte infection in viral spread and suggest targeting of monocytes for therapeutic intervention.

How does HTLV-1 cause adult T-cell leukaemia/lymphoma (ATL)?

A typical person infected with the retrovirus human T-lymphotropic virus type 1 (HTLV-1) carries tens of thousands of clones of HTLV-1-infected T lymphocytes, each clone distinguished by a unique integration site of the provirus in the host genome. However, only 5% of infected people develop the malignant disease adult T cell leukaemia/lymphoma, usually more than 50 years after becoming infected. We review the host and viral factors that cause this aggressive disease.

HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a progressive disease of the CNS that causes weakness or paralysis of the legs, lower back pain and urinary symptoms. HAM/TSP was first described in Jamaica in the nineteenth century, but the aetiology of the condition, infection with the retrovirus HTLV-1, was only identified in the 1980s. HAM/TSP causes chronic disability and, accordingly, imposes a substantial health burden in areas where HTLV-1 infection is endemic. Since the discovery of the cause of HAM/TSP, considerable advances have been made in the understanding of the virology, immunology, cell biology and pathology of HTLV-1 infection and its associated diseases. However, progress has been limited by the lack of accurate animal models of the disease. Moreover, the treatment of HAM/TSP remains highly unsatisfactory: antiretroviral drugs have little impact on the infection and, although potential disease-modifying therapies are widely used, their value is unproved. At present, clinical management is focused on symptomatic treatment and counselling. Here, we summarize current knowledge on the epidemiology, pathogenesis and treatment of HAM/TSP and identify areas in which further research is needed. For an illustrated summary of this Primer, visit: http://go.nature.com/tjZCFM.

HTLV-1 induces a Th1-like state in CD4+CCR4+ T cells

Human T-lymphotropic virus type 1 (HTLV-1) is linked to multiple diseases, including the neuroinflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and adult T cell leukemia/lymphoma. Evidence suggests that HTLV-1, via the viral protein Tax, exploits CD4+ T cell plasticity and induces transcriptional changes in infected T cells that cause suppressive CD4+CD25+CCR4+ Tregs to lose expression of the transcription factor FOXP3 and produce IFN-γ, thus promoting inflammation. We hypothesized that transformation of HTLV-1-infected CCR4+ T cells into Th1-like cells plays a key role in the pathogenesis of HAM/TSP. Here, using patient cells and cell lines, we demonstrated that Tax, in cooperation with specificity protein 1 (Sp1), boosts expression of the Th1 master regulator T box transcription factor (T-bet) and consequently promotes production of IFN-γ. Evaluation of CSF and spinal cord lesions of HAM/TSP patients revealed the presence of abundant CD4+CCR4+ T cells that coexpressed the Th1 marker CXCR3 and produced T-bet and IFN-γ. Finally, treatment of isolated PBMCs and CNS cells from HAM/TSP patients with an antibody that targets CCR4+ T cells and induces cytotoxicity in these cells reduced both viral load and IFN-γ production, which suggests that targeting CCR4+ T cells may be a viable treatment option for HAM/TSP.

Positive feedback loop via astrocytes causes chronic inflammation in virus-associated myelopathy

Human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a rare neurodegenerative disease characterized by chronic inflammation in the spinal cord. We hypothesized that a positive feedback loop driven by chemokines may be responsible for the chronic inflammation in HAM/TSP. We aimed to determine the identity of these chemokines, where they are produced, and how they drive chronic inflammation in HAM/TSP. We found that patients with HAM/TSP have extraordinarily high levels of the chemokine CXCL10 (also known as IP-10) and an abundance of cells expressing the CXCL10-binding receptor CXCR3 in the cerebrospinal fluid. Histological analysis revealed that astrocytes are the main producers of CXCL10 in the spinal cords of patients with HAM/TSP. Co-culture of human astrocytoma cells with CD4+ T cells from patients with HAM/TSP revealed that astrocytes produce CXCL10 in response to IFN-γ secreted by CD4+ T cells. Chemotaxis assays results suggest that CXCL10 induces migration of peripheral blood mononuclear cells to the central nervous system and that anti-CXCL10 neutralizing antibody can disrupt this migration. In short, we inferred that human T-lymphotropic virus type 1-infected cells in the central nervous system produce IFN-γ that induces astrocytes to secrete CXCL10, which recruits more infected cells to the area via CXCR3, constituting a T helper type 1-centric positive feedback loop that results in chronic inflammation.

Human T-lymphotropic virus type 1 non-structural proteins: Requirements for latent infection

It has been more than 30 years since the discovery of human T-lymphotropic virus type 1 (HTLV-1), the first human retrovirus identified. Human T-lymphotropic virus type 1 infects 15-20 million people worldwide causing two major diseases: adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis. Human T-lymphotropic virus type 1 establishes several decades of latent infection, during which viral-host interaction determines disease segregation. This review highlights non-structural proteins that are encoded on the viral genome and manage latent infection. Latent infection is a key in HTLV pathology, so that effective inhibition of these proteins might lead to successful disease management.

Increased osteopontin expression in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patient cells is associated with IL-17 expression

BACKGROUND

HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurological inflammatory disease associated with a predominant infiltration of CD4+ T lymphocytes, which are the main subset of HTLV-1-infected cells. It has been demonstrated that in cell line the viral Tax protein transcriptionnally regulate expression of osteopontin, an inflammatory cytokine associated with Th17-related pathologies.

OBJECTIVES

The aim of the study was to explore osteopontin expression in HTLV-1 asymptomatic carriers and in HAM/TSP patients and consequences on IL17 expression.

STUDY DESIGN

We quantified Tax, osteopontin, RORγ, IL17 and IL22 mRNA expressions in cells from 10 HAM/TSP patients, 6 asymptomatic HTLV-1 carriers (ASY) and 4 HTLV-1-negative healthy donors during ex vivo culture.

RESULTS

We observed that the expression of osteopontin was higher in HAM/TSP patients and correlated with Tax expression levels. Positive regulation of RORγ, IL17 and IL22 were also observed during cell culture.

CONCLUSIONS

Our results propose a new mechanism which could contribute to HAM/TSP pathogenesis.

Expansion in CD39⁺ CD4⁺ immunoregulatory t cells and rarity of Th17 cells in HTLV-1 infected patients is associated with neurological complications

HTLV-1 infection is associated with several inflammatory disorders, including the neurodegenerative condition HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is unclear why a minority of infected subjects develops HAM/TSP. CD4⁺ T cells are the main target of infection and play a pivotal role in regulating immunity to HTLV and are hypothesized to participate in the pathogenesis of HAM/TSP. The CD39 ectonucleotidase receptor is expressed on CD4⁺ T cells and based on co-expression with CD25, marks T cells with distinct regulatory (CD39⁺CD25⁺) and effector (CD39⁺CD25⁻) function. Here, we investigated the expression of CD39 on CD4⁺ T cells from a cohort of HAM/TSP patients, HTLV-1 asymptomatic carriers (AC), and matched uninfected controls. The frequency of CD39⁺ CD4⁺ T cells was increased in HTLV-1 infected patients, regardless of clinical status. More importantly, the proportion of the immunostimulatory CD39⁺CD25⁻ CD4⁺ T-cell subset was significantly elevated in HAM/TSP patients as compared to AC and phenotypically had lower levels of the immunoinhibitory receptor, PD-1. We saw no difference in the frequency of CD39⁺CD25⁺ regulatory (Treg) cells between AC and HAM/TSP patients. However, these cells transition from being anergic to displaying a polyfunctional cytokine response following HTLV-1 infection. CD39⁻CD25⁺ T cell subsets predominantly secreted the inflammatory cytokine IL-17. We found that HAM/TSP patients had significantly fewer numbers of IL-17 secreting CD4⁺ T cells compared to uninfected controls. Taken together, we show that the expression of CD39 is upregulated on CD4⁺ T cells HAM/TSP patients. This upregulation may play a role in the development of the proinflammatory milieu through pathways both distinct and separate among the different CD39 T cell subsets. CD39 upregulation may therefore serve as a surrogate diagnostic marker of progression and could potentially be a target for interventions to reduce the development of HAM/TSP.

Human endogenous retrovirus K(HML-2) Gag and Env specific T-cell responses are not detected in HTLV-I-infected subjects using standard peptide screening methods

BACKGROUND

An estimated 10-20 million individuals are infected with the retrovirus human T-cell leukemia virus type 1 (HTLV-1). While the majority of these individuals remain asymptomatic, 0.3-4% develop a neurodegenerative inflammatory disease, termed HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP results in the progressive demyelination of the central nervous system and is a differential diagnosis of multiple sclerosis (MS). The etiology of HAM/TSP is unclear, but evidence points to a role for CNS-inflitrating T-cells in pathogenesis. Recently, the HTLV-1-Tax protein has been shown to induce transcription of the human endogenous retrovirus (HERV) families W, H and K. Intriguingly, numerous studies have implicated these same HERV families in MS, though this association remains controversial.

RESULTS

Here, we explore the hypothesis that HTLV-1-infection results in the induction of HERV antigen expression and the elicitation of HERV-specific T-cells responses which, in turn, may be reactive against neurons and other tissues. PBMC from 15 HTLV-1-infected subjects, 5 of whom presented with HAM/TSP, were comprehensively screened for T-cell responses to overlapping peptides spanning HERV-K(HML-2) Gag and Env. In addition, we screened for responses to peptides derived from diverse HERV families, selected based on predicted binding to predicted optimal epitopes. We observed a lack of responses to each of these peptide sets.

CONCLUSIONS

Thus, although the limited scope of our screening prevents us from conclusively disproving our hypothesis, the current study does not provide data supporting a role for HERV-specific T-cell responses in HTLV-1 associated immunopathology.

Proviral load and the balance of serum cytokines in HTLV-1-asymptomatic infection and in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

This study compared the proviral load and the plasma cytokine profiles (interleukin-IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ) in 87 HTLV-1-infected individuals, including 28 with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), 32 with possible pHAM/TSP and 27 asymptomatic carriers (AC). The control group was composed by 21 HTLV-1-seronegative individuals. Our finding demonstrated that HAM/TSP group presented higher proviral load as compared to all other HTLV-1 groups (p<0.0001). The HAM/TSP group showed higher serum concentration of IL-6 (p=0.0009) as compared to all other groups. Moreover, higher serum concentration of IFN-γ (p=0.0118) and IL-4 (p=0.0166) were observed in HAM/TSP group as compared to the healthy controls. Additionally, the HAM/TSP group also showed higher serum concentration of TNF-α (p=0.0239) and IFN-γ (p=0.0118) as compared to AC. No differences in the serum concentration of IL-2 and IL-10 were observed among the groups. The analysis of cytokine balance demonstrated that HAM/TSP presented higher pro-inflammatory profile with enhanced IFN-γ/IL-10 and IFN-γ/IL-4 ratio as compared to AC and pHAM/TSP. Further analysis pointed out to a positive correlation between the IFN-γ response and the proviral load in AC. Conversely, a negative association between TNF-α and IL-2 with the proviral load was the hallmark of HAM/TSP group. These findings suggested that the proviral load and the pro-inflammatory cytokine profile may be independent events in the peripheral blood of HAM/TSP individuals. The knowledge about the existence of individual virological/immunological behavior upon HTLV-1 infection, may guide to the establishment of more effective therapeutic interventions.

Clinical pathophysiology of human T-lymphotropic virus-type 1-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus type 1 (HTLV-1), a human retrovirus, is the causative agent of a progressive neurological disease termed HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is a chronic inflammatory disease of the central nervous system and is characterized by unremitting myelopathic symptoms such as spastic paraparesis, lower limb sensory disturbance, and bladder/bowel dysfunction. Approximately 0.25-3.8% of HTLV-1-infected individuals develop HAM/TSP, which is more common in women than in men. Since the discovery of HAM/TSP, significant advances have been made with respect to elucidating the virological, molecular, and immunopathological mechanisms underlying this disease. These findings suggest that spinal cord invasion by HTLV-1-infected T cells triggers a strong virus-specific immune response and increases proinflammatory cytokine and chemokine production, leading to chronic lymphocytic inflammation and tissue damage in spinal cord lesions. However, little progress has been made in the development of an optimal treatment for HAM/TSP, more specifically in the identification of biomarkers for predicting disease progression and of molecular targets for novel therapeutic strategies targeting the underlying pathological mechanisms. This review summarizes current clinical and pathophysiological knowledge on HAM/TSP and discusses future focus areas for research on this disease.

Minocycline modulates antigen-specific CTL activity through inactivation of mononuclear phagocytes in patients with HTLV-I associated neurologic disease

BACKGROUND

The activation of mononuclear phagocytes (MPs), including monocytes, macrophages and dendritic cells, contributes to central nervous system inflammation in various neurological diseases. In HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), MPs are reservoirs of HTLV-I, and induce proinflammatory cytokines and excess T cell responses. The virus-infected or activated MPs may play a role in immuneregulation and disease progression in patients with HTLV-I-associated neurological diseases.

RESULTS

Phenotypic analysis of CD14⁺ monocytes in HAM/TSP patients demonstrated high expression of CX3CR1 and HLA-DR in CD14lowCD16⁺ monocytes, compared to healthy normal donors (NDs) and asymptomatic carriers (ACs), and the production of TNF-α and IL-1β in cultured CD14⁺ cells of HAM/TSP patients. CD14⁺ cells of HAM/TSP patients also showed acceleration of HTLV-I Tax expression in CD4⁺ T cells. Minocycline, an inhibitor of activated MPs, decreased TNF-α expression in CD14⁺ cells and IL-1β release in PBMCs of HAM/TSP patients. Minocycline significantly inhibited spontaneous lymphoproliferation and degranulation/IFN-γ expression in CD8⁺ T cells of HAM/TSP patients. Treatment of minocycline also inhibited IFN-γ expression in CD8⁺ T cells of HAM/TSP patients after Tax11-19 stimulation and downregulated MHC class I expression in CD14⁺ cells.

CONCLUSION

These results demonstrate that minocycline directly inhibits the activated MPs and that the downregulation of MP function can modulate CD8⁺ T cells function in HAM/TSP patients. It is suggested that activated MPs may be a therapeutic target for clinical intervention in HAM/TSP.

Quantitative differences in HTLV-I antibody responses: classification and relative risk assessment for asymptomatic carriers and ATL and HAM/TSP patients from Jamaica

Adult T-cell leukemia (ATL) and human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) are known to be caused by HTLV-I infection. However, current methods used to determine HTLV-I infection do not differentiate between HTLV-I asymptomatic carriers (ACs) and ATL and HAM/TSP patients. Using the luciferase immunoprecipitation system, a highly sensitive, quantitative technology that can efficiently detect HTLV-I Ab responses, we examined Ab responses for HTLV-I in serum/plasma samples from 439 subjects in Jamaica, including HTLV-I-seronegative donors, ACs, and ATL and HAM/TSP patients. The Ab responses of HTLV-I-infected subjects differed significantly from those of seronegative donors for all 3 immunodominant proteins, Gag, Env, and Tax. HAM/TSP patients had significantly higher Ab responses for Gag and Env compared with ACs, and Ab responses for all 3 Ags were higher in HAM/TSP patients than in ATL patients. Moreover, immunoreactivities for HTLV-I Ags as determined by the luciferase immunoprecipitation system could distinguish HAM/TSP patients from ACs at a true-positive rate of 85.42% and from ATL patients at a true-positive rate of 75.00%, and modeled in conjunction with subject information to distinguish HAM/TSP patients from ACs (odds ratio = 14.12) and from ATL patients (odds ratio = 7.00). The relative risk assessment resulting from these significant differences between Ab responses in HTLV-I-infected groups may be a useful diagnostic tool in the future.

Human T-lymphotropic virus type 1 (HTLV-1) and regulatory T cells in HTLV-1-associated neuroinflammatory disease

Human T-lymphotropic virus type 1 (HTLV-1) is a retrovirus that is the causative agent of adult T cell leukemia/lymphoma (ATL) and associated with multiorgan inflammatory disorders, including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and uveitis. HTLV-1-infected T cells have been hypothesized to contribute to the development of these disorders, although the precise mechanisms are not well understood. HTLV-1 primarily infects CD4(+) T helper (Th) cells that play a central role in adaptive immune responses. Based on their functions, patterns of cytokine secretion, and expression of specific transcription factors and chemokine receptors, Th cells that are differentiated from naïve CD4(+) T cells are classified into four major lineages: Th1, Th2, Th17, and T regulatory (Treg) cells. The CD4(+)CD25(+)CCR4(+) T cell population, which consists primarily of suppressive T cell subsets, such as the Treg and Th2 subsets in healthy individuals, is the predominant viral reservoir of HTLV-1 in both ATL and HAM/TSP patients. Interestingly, CD4(+)CD25(+)CCR4(+) T cells become Th1-like cells in HAM/TSP patients, as evidenced by their overproduction of IFN-γ, suggesting that HTLV-1 may intracellularly induce T cell plasticity from Treg to IFN-γ(+) T cells. This review examines the recent research into the association between HTLV-1 and Treg cells that has greatly enhanced understanding of the pathogenic mechanisms underlying immune dysregulation in HTLV-1-associated neuroinflammatory disease.

Human T-lymphotropic virus type 1-induced CC chemokine ligand 22 maintains a high frequency of functional FoxP3+ regulatory T cells

We recently reported that human T-lymphotropic virus type 1 (HTLV-1) infection is accompanied by a high frequency of CD4(+)FoxP3(+) cells in the circulation. In asymptomatic carriers of HTLV-1 and in patients with HTLV-1-associated inflammatory and malignant diseases, a high FoxP3(+) cell frequency correlated with inefficient cytotoxic T cell-mediated killing of HTLV-1-infected cells. In adult T cell leukemia/lymphoma (ATLL), the FoxP3(+) population was distinct from the leukemic T cell clones. However, the cause of the increase in FoxP3(+) cell frequency in HTLV-1 infection was unknown. In this study, we report that the plasma concentration of the chemokine CCL22 is abnormally high in HTLV-1-infected subjects and that the concentration is strongly correlated with the frequency of FoxP3(+) cells, which express the CCL22 receptor CCR4. Further, we show that CCL22 is produced by cells that express the HTLV-1 transactivator protein Tax, and that the increased CCL22 enhances the migration and survival of FoxP3(+) cells in vitro. Finally, we show that FoxP3(+) cells inhibit the proliferation of ex vivo, autologous leukemic clones from patients with ATLL. We conclude that HTLV-1-induced CCL22 causes the high frequency of FoxP3(+) cells observed in HTLV-1 infection; these FoxP3(+) cells may both retard the progression of ATLL and HTLV-1-associated inflammatory diseases and contribute to the immune suppression seen in HTLV-1 infection, especially in ATLL.

Neuroimmunity of HTLV-I Infection

Human T-lymphotrophic virus type I (HTLV-I) is an oncogenic retrovirus and its infection is associated with a variety of human diseases including HTLV-I-associated myelopathy/tropic spastic paraparesis (HAM/TSP). Large numbers of epidemiological, virological, immunological, and clinical studies on HTLV-I- and HTLV-I-associated diseases have been published, although the pathogenesis of HAM/TSP remains to be fully understood. In the last several years, researchers have shown that several key factors are important in HTLV-I-associated neurologic disease including high HTLV-I proviral load and a strong immune response to HTLV-I. Here, we review pathophysiological findings on HAM/TSP and focus on viral-host immune responses to the virus in HTLV-I infected individuals. In particular, the role of HTLV-I-specific CD8+ T cell response is highlighted.

High expression of CD244 and SAP regulated CD8 T cell responses of patients with HTLV-I associated neurologic disease

HTLV-I-specific CD8⁺ T cells have been characterized with high frequencies in peripheral blood and cerebrospinal fluid and production of proinflammatory cytokines, which contribute to central nervous system inflammation in HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). However, little is known about the differences in CD8⁺ T cell activation status between asymptomatic carrier (ACs) and patients with HAM/TSP. The expression of CD244, a signaling lymphocyte activation molecule (SLAM) family receptor, was significantly higher on CD8⁺ T cells in HTLV-I-infected patients, both ACs and patients with HAM/TSP, than those on healthy normal donors (NDs). Blockade of CD244 inhibited degranulation and IFN-γ production in CD8⁺ T cells of patients with HAM/TSP, suggesting that CD244 is associated with effector functions of CD8⁺ T cells in patients with HAM/TSP. Moreover, SLAM-associated protein (SAP) was overexpressed in patients with HAM/TSP compared to ACs and NDs. SAP expression in Tax-specific CTLs was correlated in the HTLV-I proviral DNA loads and the frequency of the cells in HTLV-I-infected patients. SAP knockdown by siRNA also inhibited IFN-γ production in CD8⁺ T cells of patients with HAM/TSP. Thus, the CD244/SAP pathway was involved in the active regulation of CD8⁺ T cells of patients with HAM/TSP, and may play roles in promoting inflammatory neurological disease.

Human T-lymphotropic virus type I (HTLV-I) is a retrovirus that persistently infects 20 million people worldwide. The majority of infected individuals are asymptomatic carriers of the virus, but 5–10% of infected people develop either adult T cell leukemia/lymphoma (ATL) or a chronic, progressive neurological disease termed HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is characterized by central nervous system (CNS) inflammation including HTLV-I-specific CD8⁺ T cells where disease progression and pathogenesis is associated with a dysregulation of antigen-specific CD8⁺ T cells, although the mechanism of this dysregulation remains to be defined. Here we demonstrate that a signaling lymphocyte activation molecule (SLAM) family of receptors, CD244, was overexpressed on CD8⁺ T cells of HTLV-I-infected patients than those of healthy normal donors, and that the upregulation of the adaptor protein, SAP, in CD8⁺ T cells distinguished HTLV-I infected individuals with and without neurologic disease. Both CD244 and SAP were associated with effector functions (high expression of IFN-γ) of CD8⁺ T cells in patients with HAM/TSP. This finding has important implication for T cell-mediated pathogenesis in human chronic viral infection associated with imbalance of immune function.

The elevated interferon gamma production is an important immunological marker in HAM/TSP pathogenesis

Human T-lymphotropic virus type 1 (HTLV-1) is the agent of the HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), which may occur in >5% of patients during their lifetime. HTLV-1-infection causes disturbances in the immune system, and the viral load may also play an important role in the pathogenesis of HAM/TSP. Some cytokines are involved in the pathogenesis of this disorder. We have determined IL-2, IL-4, IL-10, IL-12 p70, IFN-gamma and TNF-alpha production among HTLV-1-infected subjects from our HTLV-out Clinic in Institute of Infectious 'Emílio Ribas' in Sao Paulo city, Brazil. PBMC obtained from healthy controls (n = 32), asymptomatic HTLV-1 carriers (n = 68) and HAM/TSP patients (n = 44) were grown in the absence and in the presence of phytohaemagglutinin (PHA), and the supernatants' fluids were measured for cytokines production. IL-2 levels were increased in the asymptomatic HTLV-1 carriers, and IFN-gamma was increased in both groups of patients (asymptomatic HTLV-1 carriers and more significantly among HAM/TSP patients). IL-4, IL-10, TNF-alpha and IL-12 p70 levels were not significantly increased on both groups of patients, as compared with controls. The major finding of this study is that IFN-gamma was an important cytokine for the HAM/TSP pathogenesis. Therefore, immune modulation of IFN-gamma may be critical to treat of HAM/TSP patients.

Abnormally high levels of virus-infected IFN-gamma+ CCR4+ CD4+ CD25+ T cells in a retrovirus-associated neuroinflammatory disorder

BACKGROUND

Human T-lymphotropic virus type 1 (HTLV-1) is a human retrovirus associated with both HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), which is a chronic neuroinflammatory disease, and adult T-cell leukemia (ATL). The pathogenesis of HAM/TSP is known to be as follows: HTLV-1-infected T cells trigger a hyperimmune response leading to neuroinflammation. However, the HTLV-1-infected T cell subset that plays a major role in the accelerated immune response has not yet been identified.

PRINCIPAL FINDINGS

Here, we demonstrate that CD4(+)CD25(+)CCR4(+) T cells are the predominant viral reservoir, and their levels are increased in HAM/TSP patients. While CCR4 is known to be selectively expressed on T helper type 2 (Th2), Th17, and regulatory T (Treg) cells in healthy individuals, we demonstrate that IFN-gamma production is extraordinarily increased and IL-4, IL-10, IL-17, and Foxp3 expression is decreased in the CD4(+)CD25(+)CCR4(+) T cells of HAM/TSP patients as compared to those in healthy individuals, and the alteration in function is specific to this cell subtype. Notably, the frequency of IFN-gamma-producing CD4(+)CD25(+)CCR4(+)Foxp3(-) T cells is dramatically increased in HAM/TSP patients, and this was found to be correlated with disease activity and severity.

CONCLUSIONS

We have defined a unique T cell subset--IFN-gamma(+)CCR4(+)CD4(+)CD25(+) T cells--that is abnormally increased and functionally altered in this retrovirus-associated inflammatory disorder of the central nervous system.

Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease

Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.

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.

Significantly increased antibody response to heterogeneous nuclear ribonucleoproteins in cerebrospinal fluid of multiple sclerosis patients but not in patients with human T-lymphotropic virus type I-associated myelopathy/tropical spastic paraparesis

It has been reported that antibodies (Abs) against heterogeneous nuclear ribonucleoproteins (hnRNPs) are associated with human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and multiple sclerosis (MS). However, these studies were done under nonmasked conditions. In order to determine whether Abs against hnRNPs associate with HAM/TSP and MS, the authors assayed Abs against two major hnRNPs, hnRNP A1 and A2/B1, in 105 cerebrospinal fluid (CSF) samples under fully masked conditions. Samples included 40 cases of HAM/TSP, 28 of MS, and 37 of other neurological diseases. Anti-hnRNP A1 Abs, and especially anti-hnRNP A2/B1 Abs, were found significantly more often in the CSF of MS patients than in other groups. However, there was no difference in the incidence of anti-hnRNP A1 Abs between HAM/TSP and other disease groups.

Retrovirally induced CTL degranulation mediated by IL-15 expression and infection of mononuclear phagocytes in patients with HTLV-I-associated neurologic disease

CD8(+) T cells contribute to central nervous system inflammation in human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP). We analyzed CD8(+) T-cell dysfunction (degranulation and IFN-gamma production) and have demonstrated that CD8(+) T cells of patients with HAM/TSP (HAM/TSP patients) spontaneously degranulate and express IFN-gamma in ex vivo unstimulated culture. CD8(+) T cells of HTLV-I asymptomatic carriers and healthy donors did not. Spontaneous degranulation was detected in Tax11-19/HLA-A*201 tetramer(+) cells, but not in CMV pp65 tetramer(+) cells. Interestingly, degranulation and IFN-gamma production in CD8(+) T cells was induced by coculture with autologous CD14(+) cells, but not CD4(+) T cells, of HAM/TSP patients, which correlated with proviral DNA load in CD14(+) cells of infected patients. Moreover, the expression of IL-15, which induced degranulation and IFN-gamma production in infected patients, was enhanced on surface of CD14(+) cells in HAM/TSP patients. Blockade of MHC class I and IL-15 confirmed these results. Thus, CD8(+) T-cell dysregulation was mediated by both virus infection and enhanced IL-15 on CD14(+) cells in HAM/TSP patients. Despite lower viral expression than in CD4(+) T cells, HTLV-I-infected or -activated CD14(+) cells may be a heretofore important but under recognized reservoir particularly in HAM/TSP patients.

High frequency of CD4+FoxP3+ cells in HTLV-1 infection: inverse correlation with HTLV-1-specific CTL response

Evidence from population genetics, gene expression microarrays, and assays of ex vivo T-cell function indicates that the cytotoxic T lymphocyte (CTL) response to human T-lymphotropic virus type 1 (HTLV-1) controls the level of HTLV-1 expression and the proviral load. The rate at which CTLs kill autologous HTLV-1–infected lymphocytes differs significantly among infected people, but the reasons for such variation are unknown. Here, we demonstrate a strong negative cor-relation between the frequency of CD4⁺FoxP3⁺ Tax⁻ regulatory T cells (T_regs) in the circulation and the rate of CTL-mediated lysis of autologous HTLV-1–infected cells ex vivo. We propose that the frequency of CD4⁺FoxP3⁺ Tax⁻ T_regs is one of the chief determinants of the efficiency of T cell–mediated immune control of HTLV-1.

Immunological changes and cytokine gene expression during primary infection with human T-cell leukaemia virus type 1 in squirrel monkeys (Saimiri sciureus)

We have developed an animal model of experimental HTLV-1 infection in Saimiri sciureus monkeys in order to study both the immunological and the virological aspects of the infection. As cytokines expressed by immune cells play an essential role during viral infection, we have studied the correlation between the expression of some Th1/Th2 cytokines, including IL-2, IL-5, IL-6, IL-10, and IFN-gamma, and immunological dynamics during primary and chronic HTLV-1 infection in this model. We first demonstrated that, during primary infection, IFN-gamma, IL-2 and IL-10 are expressed at different times and levels. The expression of these cytokines is concomitant with the increase in the numbers of CD4(+), CD8(+) and CD16(+) cells and with the presence of tax/rex viral mRNA. These data indicate the involvement of various cell types in the antiviral immune response. Subsequently, we showed that peripheral blood mononuclear cells freshly isolated from chronically infected monkeys express IFN-gamma and IL-6 at higher levels than those from uninfected animals. IFN-gamma expression is quantitatively correlated to the proviral load and to the presence of circulating effector T-cells against Tax peptide, as detected by Elispot. Further studies will be needed to determine the effective role of these cytokines and other immune system modulators in the control of viral replication during primary HTLV-1 infection or latency.

Zidovudine plus lamivudine in Human T-Lymphotropic Virus type-I-associated myelopathy: a randomised trial

BACKGROUND

No therapies have been proven to persistently improve the outcome of HTLV-I-associated myelopathy. Clinical benefit has been reported with zidovudine and with lamivudine in observational studies. We therefore conducted a randomised, double blind, placebo controlled study of six months combination therapy with these nucleoside analogues in sixteen patients.

RESULTS

Primary outcomes were change in HTLV-I proviral load in PBMCs and clinical measures. Secondary endpoints were changes in T-cell subsets and markers of activation and proliferation. Six patients discontinued zidovudine. No significant changes in pain, bladder function, disability score, gait, proviral load or markers of T-cell activation or proliferation were seen between the two arms. Active therapy was associated with an unexplained decrease in CD8 and non-T lymphocyte counts.

CONCLUSION

Failure to detect clinical improvement may have been due irreversible nerve damage in these patients with a long clinical history and future studies should target patients presenting earlier. The lack of virological effect but may reflect a lack of activity of these nucleoside analogues against HTLV-I RT in vivo, inadequate intracellular concentrations of the active moiety or the contribution of new cell infection to maintaining proviral load at this stage of infection may be relatively small masking the effects of RT inhibition.

Association of cytokines, neurological disability, and disease duration in HAM/TSP patients

OBJECTIVE

To identify clinical and immunological markers associated with HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP).

METHOD

237 HTLV-I infected individuals were clinically assessed. They were classified according to the Expanded Disability Status Scale (EDSS) and Osames Motor Disability Score (OMDS). Cytokine levels were determined in HTLV-I seropositive individuals.

RESULTS

37 patients had HAM/TSP. There was a correlation between the degrees of disability assessed by both scales. There was also a correlation between the duration of HAM/TSP and the severity of disability assessed by either EDSS or OMDS. Higher levels of IFN-gamma were detected in unstimulated peripheral blood mononuclear cells (PBMC) from HAM/TSP patients as compared with HTLV-I carriers.

CONCLUSION

This study shows the validity of the neurological scales to classify the degree of neurological disability in HTLV-I carriers and suggests a progressive behavior of HAM/TSP. This study also shows that IFN-gamma in PBMC supernatants are markers of HAM/TSP.

Clinical significance of serum Th1-, Th2- and regulatory T cells-associated cytokines in adult T-cell leukemia/lymphoma: high interleukin-5 and -10 levels are significant unfavorable prognostic factors

Patients with adult T-cell leukemia/lymphoma (ATLL) are in a severely immunocompromised state. Therefore, it is assumed that ATLL cells either express particular cytokines or induce their expression in host immune cells, disrupting the balanced production of cytokines and causing the host's immune system to break down. We examined the levels of serum cytokines including T helper type 1- (Th1-) associated cytokines [IFN-gamma, TNF-alpha, and interleukin (IL)-2], Th2-associated cytokines (IL-4, -5 and -6) and regulatory T cell-associated cytokines (IL-10 and TGF-beta1) in 94 ATLL patients, 39 asymptomatic human T-cell lymphotropic virus type-1 (HTLV-1) carriers and 50 healthy adult volunteers, to clarify whether elevated levels of particular cytokines are associated with the prognosis of ATLL patients. On multivariate analysis, high IL-5 and IL-10 levels were independent and significant unfavorable prognostic factors among the ATLL patients. The IL-10 level significantly increased with disease progression at each step from asymptomatic HTLV-1 carrier to ATLL of the indolent variant (chronic and smoldering subtypes) to ATLL of the aggressive variant (acute and lymphoma subtypes). Furthermore, high IL-10 was significantly associated with high lactate dehydrogenase (LDH), indicating that the IL-10 level reflects the tumor burden. The IL-5 level was not associated with disease progression nor LDH. Among ATLL patients with the aggressive variant, high IL-5, but not high IL-10, was an independent and significant unfavorable prognostic factor on multivariate analysis. Measurement of serum IL-5 and IL-10 levels is useful for predicting the prognosis and for determining a suitable treatment strategy for ATLL patients.

Targeting mutated tyrosine kinases in the therapy of myeloid leukaemias

Myeloid leukaemias are frequently associated with translocations and mutations of tyrosine kinase genes. The products of these oncogenes, including BCR-ABL, TEL-PDGFR, Flt3 and c-Kit, have elevated tyrosine kinase activity and transform haematopoietic cells, mainly by augmentation of proliferation and enhanced viability. Activated ABL kinases are associated with chronic myeloid leukaemia. Mutations in platelet-derived growth factor receptor beta are associated with chronic myelomonocytic leukaemia. Flt3 or c-Kit cooperate with other types of oncogenes to create fully transformed acute leukaemias. Elevated activity of these tyrosine kinases is crucial for transformation, thus making the kinase domain an ideal target for therapeutic intervention. Tyrosine kinase inhibitors for various kinases are currently being evaluated in clinical trials and are potentially useful therapeutic agents in myeloid leukaemias. Here, the authors review the signalling activities, mechanism of transformation and therapeutic targeting of several tyrosine kinase oncogenes important in myeloid leukaemias.

Heparan sulfate proteoglycans mediate attachment and entry of human T-cell leukemia virus type 1 virions into CD4+ T cells

Heparan sulfate proteoglycans (HSPGs) are used by a number of viruses to facilitate entry into host cells. For the retrovirus human T-cell leukemia virus type 1 (HTLV-1), it has recently been reported that HSPGs are critical for efficient binding of soluble HTLV-1 SU and the entry of HTLV pseudotyped viruses into non-T cells. However, the primary in vivo targets of HTLV-1, CD4(+) T cells, have been reported to express low or undetectable levels of HSPGs. For this study, we reexamined the expression of HSPGs in CD4(+) T cells and examined their role in HTLV-1 attachment and entry. We observed that while quiescent primary CD4(+) T cells do not express detectable levels of HSPGs, HSPGs are expressed on primary CD4(+) T cells following immune activation. Enzymatic modification of HSPGs on the surfaces of either established CD4(+) T-cell lines or primary CD4(+) T cells dramatically reduced the binding of both soluble HTLV-1 SU and HTLV-1 virions. HSPGs also affected the efficiency of HTLV-1 entry, since blocking the interaction with HSPGs markedly reduced both the internalization of HTLV-1 virions and the titer of HTLV-1 pseudotyped viral infection in CD4(+) T cells. Thus, HSPGs play a critical role in the binding and entry of HTLV-1 into CD4(+) T cells.

Tumor necrosis factor-alpha up-regulation in spontaneously proliferating cells derived from bovine leukemia virus-infected cattle

We previously reported that tumor necrosis factor alpha (TNF-alpha) was one of the cytokines that contributed to the leukemogenesis caused by bovine leukemia virus (BLV). To determine if the spontaneous cell proliferation observed in the late disease stages, such as persistent lymphocytosis and lymphosarcoma, correlated with the expression level of TNF-alpha, we analyzed the mRNA expression levels for TNF-alpha in spontaneously proliferating PBMCs derived from BLV-infected cattle. The mean mRNA expression level for TNF-alpha was higher in the spontaneously proliferating PBMCs derived from BLV-infected cattle than in non-spontaneously proliferating PBMCs from normal cattle. The TNF-alpha protein level in the PBMCs was determined by flow cytometric analysis, and it was noted that most of the cells expressing membrane-bound TNF-alpha in the spontaneously proliferating cells were CD5+ or sIgM+-cells. Additionally, in order to determine if this spontaneous proliferation can be blocked by anti-bovine TNF-alpha MAb, the spontaneously proliferating PBMCs from a BLV-infected cattle were cultured in the presence of the MAb. The addition of this MAb at the beginning of the 72 h-cultivation clearly inhibited spontaneous proliferation of cells in a dose-dependent manner, indicating the direct involvement of TNF-alpha in the spontaneous proliferation of PBMCs during the late disease stage. These data suggest that an aberrant expression of TNF-alpha might contribute to the progression of bovine leukosis in animals which develop persistent lymphocytosis of B-cells or B-cell lymphosarcoma.

Increased mRNA expression of Th1-cytokine signaling molecules in patients with HTLV-I-associated myelopathy/tropical spastic paraparesis

Expression of inflammatory cytokines derived from Th1 cell population is increased in patients with human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It has been shown that cytokine signaling molecules, including transcription factors T-bet and GATA-3, interleukin-12 receptor beta 2 (IL-12R beta 2) and suppressors of cytokine signaling (SOCS), such as SOCS1, are important in differentiation of naive T cells into Th1 helper T cells. To assess the immunological status from the stand-point of cytokine signaling in patients with HAM/TSP, we analyzed mRNA expression of these cytokine signaling molecules in peripheral blood mononuclear cells using quantitative RT-PCR. Twenty-eight HAM/TSP patients, nine HTLV-I-infected individuals without HAM/TSP and twenty-two HTLV-I-uninfected individuals were included in this study. Expression of T-bet, GATA-3, IL-12R beta 2 and SOCS1 was significantly increased in HAM/TSP patients in comparison with HTLV-I-uninfected individuals. In contrast, expression of SOCS3, a marker for Th2 cells, was significantly decreased in HTLV-I-infected individuals. These results indicate that HAM/TSP patients are associated with increased Th1 and decreased Th2 cytokine signaling activities.

Human leukocyte antigen-class II-negative long-term cultured human T-cell leukemia virus type-I-infected T-cell lines with progressed cytological properties significantly induce superantigen-dependent normal T-cell proliferation

While most human T-cell leukemia virus type-I (HTLV-I)-infected T cells express abundant class II antigens, some aggressive-type adult T-cell leukemia (ATL) cells lose their expression. To investigate the significance of the class II antigen of HTLV-I infected cells, the progressiveness of HTLV-I-infected long-term cultured T-cell lines was evaluated, and then their antigen-presenting capacity was examined using a superantigen, staphylococcus enterotoxin B (SEB). Among the cell lines derived from peripheral blood, HPB-ATL-T (ATL-T), HPB-ATL-2 (ATL-2) and HPB-ATL-O were more progressed than Tax exclusively expressing HPB-CTL-I (CTL-I), because the former deleted p16 gene (polymerase chain reaction (PCR)) and strongly transcribed survivin (reverse transcriptase-PCR). Notably, interferon gamma-independent loss of class II expression of ATL-T and ATL-2 was found. In antigen-presenting experiments, however, both cell lines induced SEB-dependent significant T-cell proliferation estimated by [(3)H] thymidine uptake. No class II-re-expressed ATL-2 cells were observed in the SEB-presenting cultures by indirect immunofluorescence, and only minimum inhibition of SEB-dependent T-cell response by anti-human leukocyte antigen (HLA)-DR monoclonal antibody was observed. These findings suggest that both ATL-T and ATL-2 very effectively present SEB to T cells less dependently on class II molecules. These less immunogenic leukemic cells of aggressive ATL may contribute to disease aggression.