Visualization of HTLV-1-specific cytotoxic T lymphocytes in the spinal cords of patients with HTLV-1-associated myelopathy/tropical spastic paraparesis

Novel insights into human T-lymphotropic virus type-1 (HTLV-1) pathogenesis-host interactions in the manifestation of HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus type-1 (HTLV-1) was the first discovered human oncogenic retrovirus, the etiological agent of two serious diseases have been identified as adult T-cell leukaemia/lymphoma malignancy and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a debilitating chronic neuro-myelopathy. Despite more than 40 years of molecular, histopathological and immunological studies on HTLV-1-associated diseases, the virulence and pathogenicity of this virus are yet to be clarified. The reason why the majority of HTLV-1-infected individuals (∼95%) remain asymptomatic carriers is still unclear. The deterioration of the immune system towards oncogenicity and autoimmunity makes HTLV-1 a natural probe for the study of malignancy and neuro-inflammatory diseases. Additionally, its slow worldwide spreading has prompted public health authorities and researchers, as urged by the WHO, to focus on eradicating HTLV-1. In contrast, neither an effective therapy nor a protective vaccine has been introduced. This comprehensive review focused on the most relevant studies of the neuro-inflammatory propensity of HTLV-1-induced HAM/TSP. Such an emphasis on the virus-host interactions in the HAM/TSP pathogenesis will be critically discussed epigenetically. The findings may shed light on future research venues in designing and developing proper HTLV-1 therapeutics.

HTLV-1 induces an inflammatory CD4+CD8+ T cell population in HTLV-1-associated myelopathy

Human T cell leukemia virus type 1 (HTLV-1) is a retrovirus with preferential CD4+ T cell tropism that causes a range of conditions spanning from asymptomatic infection to adult T cell leukemia and HTLV-1-associated myelopathy (HAM), an inflammatory disease of the CNS. The mechanisms by which HTLV-1 induces HAM are poorly understood. By directly examining the ex vivo phenotype and function of T cells from asymptomatic carriers and patients with HAM, we show that patients with HAM have a higher frequency of CD4+CD8+ double-positive (DP) T cells, which are infected with HTLV-1 at higher rates than CD4+ T cells. Displaying both helper and cytotoxic phenotypes, these DP T cells are highly proinflammatory and contain high frequencies of HTLV-1-specific cells. Mechanistically, we demonstrate that DP T cells arise by direct HTLV-1 infection of CD4+ and CD8+ T cells. High levels of CD49d and CXCR3 expression suggest that DP T cells possess the ability to migrate to the CNS, and when cocultured with astrocytes, DP T cells induce proinflammatory astrocytes that express high levels of CXCL10, IFN-γ, and IL-6. These results demonstrate the potential of DP T cells to directly contribute to CNS pathology.

Differential modulation of IL-4, IL-10, IL-17, and IFN-γ production mediated by IgG from Human T-lymphotropic virus-1 (HTLV-1) infected patients on healthy peripheral T (CD4+, CD8+, and γδ) and B cells

Human T-lymphotropic virus 1 (HTLV-1) infected individuals remain as asymptomatic carriers (ACs) or can develop the chronic neurological disorder HTLV-1-associated myelopathy/Tropical Spastic Paraparesis (HAM/TSP) or the adult T-cell leukemia/lymphoma (ATLL), and the immunological mechanisms involved in this pathologies need to be elucidated. Recently, it has been demonstrated that induced or naturally developed IgG repertoires obtained from different groups of donors, grouped by immune status, can modulate human T and B cell functions. Here we aimed to evaluate if the IgG obtained from HTLV-1-infected ACs, HAM/TSP, and ATLL patients can differentially modulate the production of cytokines by human T and B cells. With this purpose, we cultured PBMCs with IgG purified from ACs, HAM/TSP, or ATLL donors and evaluated the frequency and intracellular cytokine production by flow cytometry. Our results indicate that IgG from HAM/TSP patients could induce an augment of IL-17-producing CD4+ T cells, reduce the frequency of IL-4-producing CD4+ T cells, increase IFN-γ-producing CD8+ T cells, and reduce IL-4-producing CD8+ T cells. IgG from ATLL could reduce the frequency of IL-4-producing CD4+ T cells, similarly to IgG from HAM/TSP /TSP, and could reduce the frequency of IFN-γ-producing γδT cells without influence on IL-17- and IL4-producing γδT and could reduce the frequency of IL-10- producing B cells. Finally, IgG from both HAM/TSP and ATLL patients could reduce the frequency of IFN-γ producing B cells. In conclusion, these results suggest that these preparations are active, partly overlapping in their effects, and able to elicit distinct effects on target populations.

EZH1/2 dual inhibitors suppress HTLV-1-infected cell proliferation and hyperimmune response in HTLV-1-associated myelopathy

Background

Human T-cell leukemia virus type 1 (HTLV-1) causes HTLV-1-associated myelopathy (HAM), adult T-cell leukemia/lymphoma (ATL), HTLV-1-associated uveitis, and pulmonary diseases. Although both HAM and ATL show proliferation of infected cells, their pathogeneses are quite different. In particular, the pathogenesis of HAM is characterized by hyperimmune responses to HTLV-1-infected cells. Recently, we demonstrated the overexpression of histone methyltransferase EZH2 in ATL cells and the cytotoxic effects of EZH2 inhibitors and EZH1/2 dual inhibitors on these cells. However, these phenomena have never been studied in HAM. Furthermore, what effect these agents have on the hyperimmune response seen in HAM is completely unknown.

Methods

In this study, we investigated histone methyltransferase expression levels in infected cell populations (CD4⁺ and CD4⁺CCR4⁺ cells) from patients with HAM using microarray and RT-qPCR analyses. Next, using an assay system that utilizes the spontaneous proliferation characteristic of peripheral blood mononuclear cells derived from patients with HAM (HAM-PBMCs), we investigated the effects of EZH2 selective inhibitors (GSK126 and tazemetostat) and EZH1/2 dual inhibitors (OR-S1 and valemetostat, also known as DS-3201), particularly on cell proliferation rate, cytokine production, and HTLV-1 proviral load. We also examined the effect of EZH1/2 inhibitors on the proliferation of HTLV-1-infected cell lines (HCT-4 and HCT-5) derived from patients with HAM.

Results

We found elevated expression of EZH2 in CD4⁺ and CD4⁺CCR4⁺ cells from patients with HAM. EZH2 selective inhibitors and EZH1/2 inhibitors significantly inhibited spontaneous proliferation of HAM-PBMC in a concentration-dependent manner. The effect was greater with EZH1/2 inhibitors. EZH1/2 inhibitors also reduced the frequencies of Ki67⁺ CD4⁺ T cells and Ki67⁺ CD8⁺ T cells. Furthermore, they reduced HTLV-1 proviral loads and increased IL-10 levels in culture supernatants but did not alter IFN-γ and TNF-α levels. These agents also caused a concentration-dependent inhibition of the proliferation of HTLV-1-infected cell lines derived from patients with HAM and increased annexin-V(+)7-aminoactinomycin D(-) early apoptotic cells.

Conclusion

This study showed that EZH1/2 inhibitors suppress HTLV-1-infected cell proliferation through apoptosis and the hyperimmune response in HAM. This indicates that EZH1/2 inhibitors may be effective in treating HAM.

Identification and tracking of HTLV-1-infected T cell clones in virus-associated neurologic disease

Human T lymphotropic virus type 1-assoicated (HTLV-1-associated) myelopathy/tropical spastic paraparesis (HAM/TSP) is a neuroinflammatory disease caused by the persistent proliferation of HTLV-1-infected T cells. Here, we performed a T cell receptor (TCR) repertoire analysis focused on HTLV-1-infected cells to identify and track the infected T cell clones that are preserved in patients with HAM/TSP and migrate to the CNS. TCRβ repertoire analysis revealed higher clonal expansion in HTLV-1-infected cells compared with noninfected cells from patients with HAM/TSP and asymptomatic carriers (ACs). TCR clonality in HTLV-1-infected cells was similar in patients with HAM/TSP and ACs. Longitudinal analysis showed that the TCR repertoire signature in HTLV-1-infected cells remained stable, and highly expanded infected clones were preserved within each patient with HAM/TSP over years. Expanded HTLV-1-infected clones revealed different distributions between cerebrospinal fluid (CSF) and peripheral blood and were enriched in the CSF of patients with HAM/TSP. Cluster analysis showed similarity in TCRβ sequences in HTLV-1-infected cells, suggesting that they proliferate after common antigen stimulation. Our results indicate that exploring TCR repertoires of HTLV-1-infected cells can elucidate individual clonal dynamics and identify potential pathogenic clones expanded in the CNS.

STLV-1 Commonly Targets Neurons in the Brain of Asymptomatic Non-Human Primates

The human T-cell leukemia virus (HTLV)-1 is responsible for an aggressive neurodegenerative disease (HAM/TSP) and multiple neurological alterations. The capacity of HTLV-1 to infect central nervous system (CNS) resident cells, together with the neuroimmune-driven response, has not been well-established. Here, we combined the use of human induced pluripotent stem cells (hiPSC) and of naturally STLV-1-infected nonhuman primates (NHP) as models with which to investigate HTLV-1 neurotropism. Hence, neuronal cells obtained after hiPSC differentiation in neural polycultures were the main cell population infected by HTLV-1. Further, we report the infection of neurons with STLV-1 in spinal cord regions as well as in brain cortical and cerebellar sections of postmortem NHP. Additionally, reactive microglial cells were found in infected areas, suggesting an immune antiviral response. These results emphasize the need to develop new efficient models by which to understand HTLV-1 neuroinfection and suggest an alternative mechanism that leads to HAM/TSP.

Viral-induced neuroinflammation: Different mechanisms converging to similar exacerbated glial responses

There is increasing evidence that viral infections are the source/origin of various types of encephalitis, encephalomyelitis, and other neurological and cognitive disorders. While the involvement of certain viruses, such as the Nipah virus and measles virus, is known, the mechanisms of neural invasion and the factors that trigger intense immune reactions are not fully understood. Based on recent publications, this review discusses the role of the immune response, interactions between viruses and glial cells, and cytokine mediators in the development of inflammatory diseases in the central nervous system. It also highlights the significant gaps in knowledge regarding these mechanisms.

Efficacy of l-Arginine treatment in patients with HTLV-1-associated neurological disease

OBJECTIVE

HTLV-1 infection causes HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), resulting in loss of motor function. In this Phase 2 trial, we assessed the efficacy and safety of l-arginine in patients with HAM/TSP.

METHODS

This open-label, single-arm, Phase 2 study enrolled patients diagnosed with HAM/TSP. Patients received l-arginine at a dose of 20 g orally for 1 week and were followed-up for 3 weeks. The primary endpoint was change in walking speed in the 10-m walk test (10MWT). The main secondary endpoints were change in Timed Up and Go Test (TUGT) time, improvement in inflammatory markers in cerebrospinal fluid (CSF), safety, and tolerability.

RESULTS

The study enrolled 20 patients (13 [65%] female) with a mean age of 67.8 years (95% CI 62.3 to 73.3). Although the primary endpoint, the changes in 10MWT time between baseline (Day 0) and Day 7, did not reach statistical significance (mean percent change in time -3.5%, 95% CI -10.8% to 3.7%; P = 0.32), a significant improvement was detected between baseline and Day 14 (-9.4%, 95% CI -16.6% to -2.2%; P = 0.01). Significant improvements were also observed in selected secondary endpoints, including in TUGT time (-9.1%, 95% CI -15.5% to -2.7%; P < 0.01), and in neopterin concentration in CSF (-2.1 pmol/mL, 95% CI -3.8 to -0.5; P = 0.01). Adverse events were infrequent, mild, and resolved rapidly.

INTERPRETATION

l-arginine therapy improved motor function and decreased CSF inflammatory markers. l-arginine thus represents a promising therapeutic option for patients with HAM/TSP.

TRIAL REGISTRATION NUMBER

UMIN000023854.

Human T Lymphotropic Virus 1-Associated Myelopathy: Overview of Human T Cell Lymphotropic Virus-1/2 Tests and Potential Biomarkers

Human T cell lymphotropic virus (HTLV)-1-associated myelopathy is a chronic, disabling inflammatory disorder of the spinal cord caused by HTLV-1 infection. The diagnosis of HTLV-1-associated myelopathy (HAM) is based on clinical and laboratorial findings. The disease is characterized by the presence of spastic paraparesis associated with detection of anti-HTLV-1 antibodies or HTLV-1 genomes in blood and cerebrospinal fluid (CSF). New inflammatory markers have been proposed for the diagnosis and assessment of the prognosis of HAM. We reviewed the laboratory diagnostic and potential surrogate markers for HAM. The serological screening tests for detection of anti-HTLV-1/2 antibodies are highly sensitive and specific, but confirmation and typing of HTLV-1 or HTLV-2 infection by other serological or molecular methods are essential. Detection of intrathecal anti-HTLV-1 antibodies and quantification of the HTLV-1 provirus in CSF provide additional evidence for diagnosis especially in atypical cases or where alternative causes of neuroinflammation cannot be excluded. The CXC motif chemokine ligand 10 and neopterin in serum and CSF are now emerging as inflammatory markers with prognostic value and for HAM monitoring and management. In addition, measures of neurodegeneration, such as neurofilament light chain in the CSF and blood, may also contribute to the HAM prognosis. This review is useful for clinicians and researchers evaluating potential benefits and limitations of each biomarker in clinical practice. The advent of new markers makes it necessary to update the criteria for the best evidence-based approach and for worldwide consensus regarding the use of diagnostic and surrogate markers for HAM.

T cell receptor repertoire analysis in HTLV-1-associated diseases

Human T lymphotropic virus 1 (HTLV-1) is a human retrovirus identified as the causative agent in adult T-cell leukemia/lymphoma (ATL) and chronic-progressive neuroinflammatory disorder HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 is estimated to infect between 5-20 million people worldwide, although most infected individuals remain asymptomatic. HTLV-1 infected persons carry an estimated lifetime risk of approximately 5% of developing ATL, and between 0.25% and 1.8% of developing HAM/TSP. Most HTLV-1 infection is detected in CD4⁺ T cells in vivo which causes the aggressive malignancy in ATL. In HAM/TSP, the increase of HTLV-1 provirus induces immune dysregulation to alter inflammatory milieu, such as expansion of HTLV-1-specific CD8⁺ T cells, in the central nervous system of the infected subjects, which have been suggested to underlie the pathogenesis of HAM/TSP. Factors contributing to the conversion from asymptomatic carrier to disease state remain poorly understood. As such, the identification and tracking of HTLV-1-specific T cell biomarkers that may be used to monitor the progression from primary infection to immune dysfunction and disease are of great interest. T cell receptor (TCR) repertoires have been extensively investigated as a mechanism of monitoring adaptive T cell immune response to viruses and tumors. Breakthrough technologies such as single-cell RNA sequencing have increased the specificity with which T cell clones may be characterized and continue to improve our understanding of TCR signatures in viral infection, cancer, and associated treatments. In HTLV-1-associated disease, sequencing of TCR repertoires has been used to reveal repertoire patterns, diversity, and clonal expansions of HTLV-1-specific T cells capable of immune evasion and dysregulation in ATL as well as in HAM/TSP. Conserved sequence analysis has further been used to identify CDR3 motif sequences and exploit disease- or patient-specificity and commonality in HTLV-1-associated disease. In this article we review current research on TCR repertoires and HTLV-1-specific clonotypes in HTLV-1-associated diseases ATL and HAM/TSP and discuss the implications of TCR clonal expansions on HTLV-1-associated disease course and treatments.

Potential role of HTLV-1 Tax-specific cytotoxic t lymphocytes expressing a unique t-cell receptor to promote inflammation of the central nervous system in myelopathy associated with HTLV-1

Human T-lymphotropic virus 1 (HTLV-1) infection causes two serious diseases: adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy (HAM). Immunological studies have revealed that HTLV-1 Tax-specific CD8⁺ cytotoxic T-cells (Tax-CTLs) in asymptomatic carriers (ACs) and ATL patients play an important role in the elimination of HTLV-1-infected host cells, whereas Tax-CTLs in HAM patients trigger an excessive immune response against HTLV-1-infected host cells infiltrating the central nervous system (CNS), leading to local inflammation. Our previous evaluation of HTLV-1 Tax_301-309 (SFHSLHLLF)-specific Tax-CTLs (Tax_301-309-CTLs) revealed that a unique T-cell receptor (TCR) containing amino acid (AA)-sequence motif PDR, was shared among HLA-A*24:02⁺ ACs and ATL patients and behaved as an eliminator by strong activity against HTLV-1. However, it remains unclear whether PDR⁺Tax_301-309-CTLs also exist in HLA-A*24:02⁺ HAM patients and are involved in the pathogenesis of HAM. In the present study, by high-throughput TCR repertoire analysis technology, we revealed TCR repertoires of Tax_301-309-CTLs in peripheral blood (PB) of HLA-A*24:02⁺ HAM patients were skewed, and a unique TCR-motif PDR was conserved in HAM patients (10 of 11 cases). The remaining case dominantly expressed (-DR, P-R, and PD-), which differed by one AA from PDR. Overall, TCRs with unique AA-sequence motifs PDR, or (-DR, P-R, and PD-) accounted for a total of 0.3-98.1% of Tax_301-309-CTLs repertoires of HLA-A*24:02⁺ HAM patients. Moreover, TCR repertoire analysis of T-cells in the cerebrospinal fluid (CSF) from four HAM patients demonstrated the possibility that PDR⁺Tax_301-309-CTLs and (-DR, P-R, and PD-)⁺Tax_301-309-CTLs efficiently migrated and accumulated in the CSF of HAM patients fostering increased inflammation, although we observed no clear significant correlation between the frequencies of them in PB and the levels of CSF neopterin, a known disease activity biomarker of HAM. Furthermore, to better understand the potential function of PDR⁺Tax_301-309-CTLs, we performed immune profiling by single-cell RNA-sequencing of Tax_301-309-CTLs, and the result showed that PDR⁺Tax_301-309-CTLs up-regulated the gene expression of natural killer cell marker KLRB1 (CD161), which may be associated with T-cell activation and highly cytotoxic potential of memory T-cells. These findings indicated that unique and shared PDR⁺Tax_301-309-CTLs have a potential role in promoting local inflammation within the CNS of HAM patients.

Magnetic resonance imaging evaluation of spinal cord lesions: what can we find? - Part 2. Inflammatory and infectious injuries

Diseases involving the spinal cord include a heterogeneous group of abnormalities, including those of inflammatory, infectious, neoplastic, vascular, metabolic, and traumatic origin. Making the clinical differentiation between different entities is often difficult, magnetic resonance imaging being the diagnostic method of choice. Although the neuroimaging findings are not pathognomonic, many are quite suggestive, and the radiologist can assist in the diagnosis and, consequently, in the therapeutic guidance. In this second part of our article, the objective is to review the magnetic resonance imaging findings of the main inflammatory and infectious spinal cord injuries.

Identification of dysregulated pathways underlying HTLV-1-associated myelopathy/tropical spastic paraparesis through co-expression network analysis

Human T cell lymphotropic virus-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a pathogen-caused disease which is associated with the progressive neurological disorder. HAM/TSP affects the expression level of several proteins and dysregulates some biological pathways. To identify the interaction patterns among expressed genes in HAM/TSP patients, weighted gene co-expression network analysis (WGCNA) was applied. Three microarray datasets regarding HAM/TSP were merged, and the co-expression network was constructed among genes. A total of 38 modules were identified. Three preserved modules in HAM/TSP in comparison to the healthy subjects which also had the most connected proteins and enriched in the biological pathways were selected. These modules were enriched in pathways related to immune systems, cell cycle, viral infection, and neuronal systems. Moreover, the involvement of novel immunological-related proteins including C1QB, GBP5, PSME1, SERPING1, and UBE2C; neurological-related proteins including TUBA4A, TUBB8, and TP63; and also proteins including TRPC6, PRKG2, OPRD1, PRKACA, and TUBB4A involved in the cGMP-PKG signaling pathway, thyroid hormone synthesis, and recruitment of mitotic centrosome proteins and complexes were found. Therefore, tracing these proteins and the identified modules can shed light on the pathogenesis mechanism of HAM/TSP and help to find potential therapeutic targets. However, further experimental validation should be performed to confirm the proposed functional players.

The CD8 T Cell-Epstein-Barr Virus-B Cell Trialogue: A Central Issue in Multiple Sclerosis Pathogenesis

The cause and the pathogenic mechanisms leading to multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), are still under scrutiny. During the last decade, awareness has increased that multiple genetic and environmental factors act in concert to modulate MS risk. Likewise, the landscape of cells of the adaptive immune system that are believed to play a role in MS immunopathogenesis has expanded by including not only CD4 T helper cells but also cytotoxic CD8 T cells and B cells. Once the key cellular players are identified, the main challenge is to define precisely how they act and interact to induce neuroinflammation and the neurodegenerative cascade in MS. CD8 T cells have been implicated in MS pathogenesis since the 80's when it was shown that CD8 T cells predominate in MS brain lesions. Interest in the role of CD8 T cells in MS was revived in 2000 and the years thereafter by studies showing that CNS-recruited CD8 T cells are clonally expanded and have a memory effector phenotype indicating in situ antigen-driven reactivation. The association of certain MHC class I alleles with MS genetic risk implicates CD8 T cells in disease pathogenesis. Moreover, experimental studies have highlighted the detrimental effects of CD8 T cell activation on neural cells. While the antigens responsible for T cell recruitment and activation in the CNS remain elusive, the high efficacy of B-cell depleting drugs in MS and a growing number of studies implicate B cells and Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus that is strongly associated with MS, in the activation of pathogenic T cells. This article reviews the results of human studies that have contributed to elucidate the role of CD8 T cells in MS immunopathogenesis, and discusses them in light of current understanding of autoreactivity, B-cell and EBV involvement in MS, and mechanism of action of different MS treatments. Based on the available evidences, an immunopathological model of MS is proposed that entails a persistent EBV infection of CNS-infiltrating B cells as the target of a dysregulated cytotoxic CD8 T cell response causing CNS tissue damage.

Effect of Teriflunomide on Cells From Patients With Human T-cell Lymphotropic Virus Type 1-Associated Neurologic Disease

Objective

To test the hypothesis that teriflunomide can reduce ex vivo spontaneous proliferation of peripheral blood mononuclear cells (PBMCs) from patients with human T-cell lymphotropic virus type 1 (HTLV-1)–associated myelopathy/tropical spastic paraparesis (HAM/TSP).

Methods

PBMCs from patients with HAM/TSP were cultured in the presence and absence of teriflunomide and assessed for cell viability, lymphocyte proliferation, activation markers, HTLV-1 tax and HTLV-1 hbz messenger ribonucleic acid (mRNA) expression, and HTLV-1 Tax protein expression.

Results

In culture, teriflunomide did not affect cell viability. A concentration-dependent reduction in spontaneous proliferation of PBMCs was observed with 25 μM (38.3% inhibition), 50 μM (65.8% inhibition), and 100 μM (90.7% inhibition) teriflunomide. The inhibitory effects of teriflunomide were detected in both CD8⁺ and CD4⁺ T-cell subsets, which are involved in the immune response to HTLV-1 infection and the pathogenesis of HAM/TSP. There was no significant change in HTLV-1 proviral load (PVL) or tax mRNA/Tax protein expression in these short-term cultures, but there was a significant reduction of HTLV-1 PVL due to inhibition of proliferation of CD4⁺ T cells obtained from a subset of patients with HAM/TSP.

Conclusions

These results suggest that teriflunomide inhibits abnormal T-cell proliferation associated with HTLV-1 infection and may have potential as a therapeutic option in patients with HAM/TSP.

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.

Effective Treatment with Tocilizumab in a Rheumatoid Arthritis Patient Complicated with Human T-cell Leukemia Virus Type 1-associated Myelopathy

A 61-year-old woman with human T-cell leukemia virus type 1 (HTLV-1)-associated myelopathy (HAM)/tropical spastic paraparesis (TSP) and interstitial pneumonia (IP) was admitted to our hospital. She complained of sicca symptoms, polyarthralgia, and swollen joints. She was diagnosed with rheumatoid arthritis (RA) and Sjögren's syndrome. Methotrexate and anti-tumor necrosis factor therapy were not utilized because of the inclusion of severe respiratory disorders among the complications and the neurological symptoms of HAM/TSP. Tocilizumab monotherapy improved the RA disease activity without exacerbating HAM/TSP. The present case suggests that tocilizumab might be a suitable treatment option in patients with RA and HAM/TSP.

Human T-lymphotropic virus type 1 (HTLV-1) and cellular immune response in HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus type 1 (HTLV-1) is associated with adult T cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is an inflammatory disease of the spinal cord and clinically characterized by progressive spastic paraparesis, urinary incontinence, and mild sensory disturbance. The interaction between the host immune response and HTLV-1-infected cells regulates the development of HAM/TSP. HTLV-1 preferentially infects CD4⁺ T cells and is maintained by proliferation of the infected T cells. HTLV-1-infected cells rarely express viral antigens in vivo; however, they easily express the antigens after short-term culture. Therefore, such virus-expressing cells may lead to activation and expansion of antigen-specific T cell responses. Infected T cells with HTLV-1 and HTLV-1-specific CD8⁺ cytotoxic T lymphocytes invade the central nervous system and produce various proinflammatory cytokines and chemokines, leading to neuronal damage and degeneration. Therefore, cellular immune responses to HTLV-1 have been considered to play important roles in disease development of HAM/TSP. Recent studies have clarified the viral strategy for persistence in the host through genetic and epigenetic changes by HTLV-1 and host immune responses including T cell function and differentiation. Newly developed animal models could provide the opportunity to uncover the precise pathogenesis and development of clinically effective treatment. Several molecular target drugs are undergoing clinical trials with promising efficacy. In this review, we summarize recent advances in the immunopathogenesis of HAM/TSP and discuss the perspectives of the research on this disease.

Inhibition of ABL1 tyrosine kinase reduces HTLV-1 proviral loads in peripheral blood mononuclear cells from patients with HTLV-1-associated myelopathy/tropical spastic paraparesis

Human T-cell leukemia virus type 1 (HTLV-1) causes incurable adult T-cell leukemia and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP have increased levels of HTLV-1-infected cells compared with asymptomatic HTLV-1 carriers. However, the roles of cellular genes in HTLV-1-infected CD4+ T cells await discovery. We performed microarray analysis of CD4+ T cells from HAM/TSP patients and found that the ABL1 is an important gene in HAM/TSP. ABL1 is a known survival factor for T- and B-lymphocytes and is part of the fused gene (BCR-ABL) known to be responsible for chronic myelogenous leukemia (CML). ABL1 tyrosine kinase inhibitors (TKIs), including imatinib, nilotinib, and dasatinib, are used clinically for treating CML. To evaluate whether ABL1 is indeed important for HAM/TSP, we investigated the effect of TKIs on HTLV-1-infected cells. We developed a propidium monoazide-HTLV-1 viability quantitative PCR assay, which distinguishes DNA from live cells and dead cells. Using this method, we were able to measure the HTLV-1 proviral load (PVL) in live cells alone when peripheral blood mononuclear cells (PBMCs) from HAM/TSP cases were treated with TKIs. Treating the PBMCs with nilotinib or dasatinib induced significant reductions in PVL (21.0% and 17.5%, respectively) in live cells. Furthermore, ABL1 siRNA transfection reduced cell viability in HTLV-1-infected cell lines, but not in uninfected cell lines. A retrospective survey based on our clinical records found a rare case of HAM/TSP who also suffered from CML. The patient showed an 84.2% PVL reduction after CML treatment with imatinib. We conclude that inhibiting the ABL1 tyrosine kinase specifically reduced the PVL in PBMCs from patients with HAM/TSP, suggesting that ABL1 is an important gene for the survival of HTLV-1-infected cells and that TKIs may be potential therapeutic agents for HAM/TSP.

Prognosis Markers for Monitoring HTLV-1 Neurologic Disease

Background

Human T-cell lymphotropic virus type 1 (HTLV-1) infection is associated not only with some severe manifestations, such as HTLV-1-associated myelopathy (HAM) and ATLL, but also with other, less severe conditions. Some studies have reported neurologic manifestations that did not meet all the criteria for the diagnosis of HAM in individuals infected with HTLV-1; these conditions may later progress to HAM or constitute an intermediate clinical form, between asymptomatic HTLV-1 carriers and those with full myelopathy. This study evaluated the prognostic value and looked for a possible association of those parameters with the intermediate syndrome (IS) status and HAM status.

Methods

Proviral load (PVL), spontaneous lymphoproliferation, interferon (IFN)-γ spontaneous production was quantified in samples of asymptomatic and HAM patients, as well as patients with IS.

Results

The critical age range was 50-60 years for IS outcome and more of 60 years for HAM outcome, with an increased risk of 2.5-fold for IS and 6.8-fold for HAM. IFN-γ was increased in patients with IS compared with asymptomatic carriers (ACs) (p = 0.007) and in patients with HAM compared with ACs (p = 0.03). Lymphoproliferation was increased in patients with HAM vs ACs (p = 0.0001) and patients with IS (p = 0.0001). PVL was similar between groups.

Conclusion

IFN-γ has high specificity of prediction of subject remain asymptomatic compared with PVL and lymphoproliferation assay tests. IFN-γ has been shown to be a biomarker of progression to intermediate stage and to HAM. The association of other markers with manifestations associated with HTLV-1 infection that does not meet the HAM criteria should be verified.

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.

Influence of Immunogenetic Biomarkers in the Clinical Outcome of HTLV-1 Infected Persons

Human T-lymphotropic virus 1, a member of the Retroviridae family, causes a neglected, silent, persistent infection affecting circa 5 to 10 million people around the world, with biology, immune pathology, clinical diseases, epidemiology, and laboratory issues still unsolved. Most of the infected subjects are asymptomatic, but severe clinical disorders appear as a neurodegenerative disease (HTLV-1 associated myelopathy—HAM) or a lymphoprolipherative disorder (Adult T Leukemia/Lymphoma—ATLL) and in other target organs of the human body. HTLV-1 infections are frequently asymptomatic, but there is a large spectrum of diseases that have been described along the years. The mechanisms by which the virus interacts with the host, the different modes of response of the host to the infection, and the immunogenic characteristics of the host are some of the interesting and unanswered questions that may direct the outcome of the disease. The most relevant published results dealing with the genetic variations of the host, the immune response to HTLV-1 infection, and the outcome of the infection are presented herein, including Human Leucocyte Antigen (HLA), Killer Immunoglobulin-like Receptors (KIR), interleukin 6, 10, 28, Fas and Fas ligand, IFN-gamma, TNF-A, and Mannose-binding lectin. In summary, there are still several unmet research needs in the field of useful biomarkers on HTLV-1 pathogenesis.

Pentosan Polysulfate Demonstrates Anti-human T-Cell Leukemia Virus Type 1 Activities In Vitro and In Vivo

Human T-cell leukemia virus type 1 (HTLV-1) infection causes T-cell leukemia and inflammatory diseases, most notably including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The underlying mechanism for the pathogenesis of HAM/TSP remains unclear. According to a recent clinical trial, a humanized antibody that targets CCR4⁺ cells ameliorates inflammation by reducing the number of infected cells in the central nervous system; this result suggests that the transmigration of HTLV-1-infected cells plays a crucial role in HAM/TSP. Partly due to the blood-brain barrier, current treatments for HAM/TSP are mostly palliative. Pentosan polysulfate (PPS), a semisynthetic glycosaminoglycan, has recently been used to treat HAM/TSP and was found to alleviate the symptoms. In this study, we investigated the effect of PPS on HTLV-1-infected cells and provide evidence for its efficacy in HAM/TSP. PPS was cytotoxic to certain HTLV-1-infected cells and significantly suppressed HTLV-1 virion production. PPS also efficiently inhibited HTLV-1 cell-cell transmission in T cells. In addition, PPS blocked HTLV-1 infection of primary endothelial cells (human umbilical vascular endothelial cells) and suppressed the subsequent induction of proinflammatory cytokine expression. Furthermore, PPS was found to inhibit the adhesion and transmigration of HTLV-1-infected cells. We also confirmed the anti-HTLV-1 effect of PPS in vivo using two mouse models. PPS blocked HTLV-1 infection in a mouse model with peripheral blood mononuclear cell (PBMC)-humanized NOD-scid IL2Rgamma^null (huPBMC NSG) mice. PPS was also found to suppress the development of dermatitis and lung damage in HTLV-1 bZIP factor (HBZ)-transgenic (HBZ-Tg) mice, an HTLV-1 transgenic mouse model in which the mice develop systemic inflammation.IMPORTANCE HTLV-1 is the first human retrovirus to have been identified and is endemic in certain areas worldwide. HTLV-1 infection leads to the development of an inflammatory disease called HAM/TSP, a myelopathy characterized by slowly progressive spastic paraparesis. There have been no effective therapeutics available for HAM/TSP, but recently, a semisynthetic glycosaminoglycan, named pentosan polysulfate (PPS), has been found to alleviate the symptoms of HAM/TSP. Here we conducted a comprehensive study on the effect of PPS both in vitro and in vivo PPS demonstrated anti-HTLV-1 potential in infected cell lines, as shown by its suppressive effects on HTLV-1 replication and transmission and on the transmigration of infected T cells. Moreover, results obtained from two HTLV-1 mouse models demonstrate that PPS inhibits HTLV-1 infection and inflammation development in vivo Our work offers insights into the treatment of HAM/TSP by PPS and also suggests its possible use for treating other HTLV-1-induced inflammatory diseases.

Phenotypic and functional changes in gamma delta T lymphocytes from HTLV-1 carriers

Human T-cell lymphotropic virus type-1 (HTLV-1) is the etiologic agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), which is a chronic inflammatory disease that leads to gradual loss of motor movement as a result of the death of spinal cord cells through immune mediated mechanisms. The risk to develop HAM/TSP disease positively correlates with the magnitude of HTLV-1 proviral load. Gamma-delta T lymphocytes have been recognized as important players in a variety of infectious diseases. Therefore, we have investigated interactions between HTLV-1 infection and γδ T lymphocytes during HAM/TSP. Similar frequencies of total γδ T lymphocytes and their Vγ9δ2⁺ and Vγ9δ2^neg subpopulations were observed in HAM/TSP patients. However, T lymphocytes obtained from HTLV-1 carriers displayed significantly higher rates of spontaneous proliferation and NKp30 expression when compared to cells from uninfected donors. In addition, an important decrease in the frequency of granzyme B⁺ γδ T lymphocytes (approximately 50%) was observed in HAM/TSP patients. Higher proportion of IFN-γ⁺ γδ T lymphocytes was found in HTLV-1-infected patients, which positively correlated with the HTLV-1 proviral load in peripheral blood mononuclear cells. Collectively, our data indicates that HTLV-1 infection leads to phenotypic and functional changes in the population of γδ T lymphocyte population, suggesting that HTLV-1 infection modulates functions associated to these cells, which might be involved in controlling the infection or in the development of HTLV-1-associated diseases.

Clinical trial of a humanized anti-IL-2/IL-15 receptor β 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‐Mikβ1, a humanized monoclonal antibody directed toward the IL‐2/IL‐15 receptor β‐chain (IL‐2/IL‐15Rβ: CD122), to saturate CD122 and regulate abnormal immune responses in patients with HAM/TSP by inhibition of IL‐15 action.

Methods

Hu‐Mikβ1 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‐Mikβ1 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‐Mikβ1 administration in HAM/TSP patients. Saturation of CD122 by Hu‐Mikβ1 was achieved in five out of nine HAM/TSP patients. Administration of Hu‐Mikβ1 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‐Mikβ1 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.

Neuroimmunology of Human T-Lymphotropic Virus Type 1-Associated Myelopathy/Tropical Spastic Paraparesis

Human T-lymphotropic virus type 1 (HTLV-1) is the etiologic agent of both adult T-cell leukemia/lymphoma and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HAM/TSP is clinically characterized by chronic progressive spastic paraparesis, urinary incontinence, and mild sensory disturbance. Given its well-characterized clinical presentation and pathophysiology, which is similar to the progressive forms of multiple sclerosis (MS), HAM/TSP is an ideal system to better understand other neuroimmunological disorders such as MS. Since the discovery of HAM/TSP, large numbers of clinical, virological, molecular, and immunological studies have been published. The host-virus interaction and host immune response play an important role for the development with HAM/TSP. HTLV-1-infected circulating T-cells invade the central nervous system (CNS) and cause an immunopathogenic response against virus and possibly components of the CNS. Neural damage and subsequent degeneration can cause severe disability in patients with HAM/TSP. Little progress has been made in the discovery of objective biomarkers for grading stages and predicting progression of disease and the development of molecular targeted therapy based on the underlying pathological mechanisms. We review the recent understanding of immunopathological mechanism of HAM/TSP and discuss the unmet need for research on this disease.

HTLV-1-host interactions on the development of adult T cell leukemia/lymphoma: virus and host gene expressions

Background

Adult T-cell leukemia/lymphoma (ATLL) is a lymphoproliferative disorder of HTLV-1-host interactions in infected TCD4+ cells. In this study, the HTLV-1 proviral load (PVL) and HBZ as viral elements and AKT1, BAD, FOXP3, RORγt and IFNλ3 as the host factors were investigated.

Methods

The study was conducted in ATLLs, HTLV-1-associated myelopathy/tropical spastic paraparesis patients (HAM/TSPs) and HTLV-1-asympthomatic carriers (ACs). The DNA and mRNA from peripheral blood mononuclear cells were extracted for gene expression assessments via qRT-PCR, TaqMan assay, and then confirmed by western blotting.

Results

As it was expected, the HTLV-1-PVL were higher in ATLLs than ACs (P = 0.002) and HAM/TSP (P = 0.041). The HBZ expression in ATLL (101.76 ± 61.3) was radically higher than in ACs (0.12 ± 0.05) and HAM/TSP (0.01 ± 0.1) (P = 0.001). Furthermore, the AKT1 expression in ATLLs (13.52 ± 4.78) was higher than ACs (1.17 ± 0.27) (P = 0.05) and HAM/TSPs (0.72 ± 0.49) (P = 0.008). However, BAD expression in ATLL was slightly higher than ACs and HAM/TSPs and not significant. The FOXP3 in ATLLs (41.02 ± 24.2) was more than ACs (1.44 ± 1) (P = 0.007) and HAM/TSP (0.45 ± 0.15) (P = 0.01). However, RORγt in ATLLs (27.43 ± 14.8) was higher than ACs (1.05 ± 0.32) (P = 0.02) but not HAM/TSPs. Finally, the IFNλ3 expression between ATLLs (31.92 ± 26.02) and ACs (1.46 ± 0.63) (P = 0.01) and ACs and HAM/TSPs (680.62 ± 674.6) (P = 0.02) were statistically different, but not between ATLLs and HAM/TSPs.

Conclusions

The present and our previous study demonstrated that HTLV-1-PVL and HBZ and host AKT1 and Rad 51 are novel candidates for molecular targeting therapy of ATLL. However, high level of RORγt may inhibit Th1 response and complicated in ATLL progressions.

Cytokine Networks Dysregulation during HTLV-1 Infection and Associated Diseases

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of a neural chronic inflammation, called HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and of a malignant lymphoproliferation, called the adult T-cell leukemia/lymphoma (ATLL). The mechanisms through which the HTLV-1 induces these diseases are still unclear, but they might rely on immune alterations. HAM/TSP is associated with an impaired production of pro-inflammatory cytokines and chemokines, such as IFN-γ, TNF-α, CXCL9, or CXCL10. ATLL is associated with high levels of IL-10 and TGF-β. These immunosuppressive cytokines could promote a protumoral micro-environment. Moreover, HTLV-1 infection impairs the IFN-I production and signaling, and favors the IL-2, IL-4, and IL-6 expression. This contributes both to immune escape and to infected cells proliferation. Here, we review the landscape of cytokine dysregulations induced by HTLV-1 infection and the role of these cytokines in the HTLV-1-associated diseases progression.

Different roles of CXCR1 and CXCR2 in HTLV-1 carriers and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients

One of the prominent features of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is the excessive recruitment of leukocytes to the central nervous system (CNS), which leads to an inflammatory response-with chemokines and their receptors playing the main role in this recruitment. The aim of the study was to examine the relation of CXCR1 and CXCR2, both of which are involved in the trafficking of lymphocytes into the CNS, with the outcome of HTLV-1 infection. The mRNA levels of CXCR1 and CXCR2 were examined in peripheral blood mononuclear cells (PBMCs) of HAM/TSP patients, HTLV-1 asymptomatic carriers (ACs), and healthy controls (HCs). Furthermore, the frequency of CD4⁺ and CD8⁺ T cells expressing CXCR1 and CXCR2 was evaluated in the studied groups. The results of the present study showed a substantial increase in the mean mRNA expression of CXCR2 in the HAM/TSP patients compared to the HCs and ACs (p < 0.001). A positive correlation was also found between PVL and CXCR2 mRNA expression in the total population of HTLV-1-infected subjects (R = 0.526, p < 0.001). Moreover, the percentage of CD8⁺ CXCR2-expressing cells was higher in HAM/TSP patients compared to ACs and HCs (p < 0.05, p < 0.01, respectively). Although the percentage of CD4⁺ CXCR2-expressing cells was higher in HAM/TSP patients than in ACs and HCs, a significant difference was only found between HAM/TSP patients and HCs (p < 0.05). No significant difference in the CXCR1 mRNA expression was observed in the studied groups. The frequency of the CD8⁺ CXCR1- and CD4⁺ CXCR1-expressing cells was significantly lower in HAM/TSP patients than in ACs and HCs (p < 0.001 and p < 0.01, respectively). In conclusion, the high frequency of CXCR2 CD8⁺ T cells and the high levels of CXCR2 mRNA expression in HAM/TSP patients are associated with disease pathogenesis, while the high frequencies of CXCR1 T cells in ACs might suggest that these cells act as effector CD8 T cells and are involved in controlling the viral spread and modulation of the immune response.

Viral antigens detectable in CSF exosomes from patients with retrovirus associated neurologic disease: functional role of exosomes

BACKGROUND

HTLV-1 infects over 20 million people worldwide and causes a progressive neuroinflammatory disorder in a subset of infected individuals called HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). The detection of HTLV-1 specific T cells in the cerebrospinal fluid (CSF) suggests this disease is immunopathologically mediated and that it may be driven by viral antigens. Exosomes are microvesicles originating from the endosomal compartment that are shed into the extracellular space by various cell types. It is now understood that several viruses take advantage of this mode of intercellular communication for packaging of viral components as well. We sought to understand if this is the case in HTLV-1 infection, and specifically if HTLV-1 proteins can be found in the CSF of HAM/TSP patients where we know free virus is absent, and furthermore, if exosomes containing HTLV-1 Tax have functional consequences.

RESULTS

Exosomes that were positive for HTLV-1 Tax by Western blot were isolated from HAM/TSP patient PBMCs (25/36) in ex vivo cultures by trapping exosomes from culture supernatants. HTLV-1 seronegative PBMCs did not have exosomes with Tax (0/12), (Fisher exact test, p = 0.0001). We were able to observe HAM/TSP patient CSF (12/20) containing Tax⁺ exosomes but not in HTLV-1 seronegative MS donors (0/5), despite the absence of viral detection in the CSF supernatant (Fisher exact test p = 0.0391). Furthermore, exosomes cultivated from HAM/TSP PBMCs were capable of sensitizing target cells for HTLV-1 specific CTL lysis.

CONCLUSION

Cumulatively, these results show that there are HTLV-1 proteins present in exosomes found in virus-free CSF. HAM/TSP PBMCs, particularly CD4⁺CD25⁺ T cells, can excrete these exosomes containing HTLV-1 Tax and may be a source of the exosomes found in patient CSF. Importantly, these exosomes are capable of sensitizing an HTLV-1 specific immune response, suggesting that they may play a role in the immunopathology observed in HAM/TSP. Given the infiltration of HTLV-1 Tax-specific CTLs into the CNS of HAM/TSP patients, it is likely that exosomes may also contribute to the continuous activation and inflammation observed in HAM/TSP, and may suggest future targeted therapies in this disorder.

Multiple spotty lesions of the spinal cord in a Chinese patient with human T-lymphotropic virus type 1-associated myelopathy/tropical spastic paraparesis

The case of a Chinese patient with human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), who showed typical neurological symptoms of the disease, is reported here. Since the presence of anti-HTLV-1 antibody was not investigated, this patient's diagnosis of HAM/TSP was delayed for 4 years. Magnetic resonance imaging revealed multiple spotty lesions in the cervical spinal cord, probably reflecting pathological changes known as perivascular lymphocytic infiltrations of the spinal cord. As this is the first case report of a HAM/TSP patient in China, it is suggested that serological testing for HTLV-1 should be considered in patients with spastic paraparesis even in areas that are non-endemic for HTLV-1.

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.

Spinal cord anteroposterior atrophy in HAM/TSP: Magnetic resonance imaging and neuropathological analyses

To evaluate the spinal cord atrophy that occurs in HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), we conducted magnetic resonance imaging (MRI) and pathological analyses. In the MRI study, 15 patients with HAM/TSP and 20 age-matched normal control subjects were enrolled. Anteroposterior and transverse distances and cross-sectional areas were measured and calculated at the C2, C4, C6, T2, and T6 vertebral levels. In the pathological study, spinal cord autopsy specimens were compared between a HAM/TSP case and an adult T cell leukemia/lymphoma case. In both the MRI and pathological studies, HAM/TSP spinal cords demonstrated more severe atrophy in the anteroposterior direction than those of controls. The spinal cord atrophy and pathological changes in HAM/TSP occurred predominantly in the white matter, especially in the lateral columns. This is the first report indicating spinal cord atrophy in the anteroposterior direction using MRI. In pathological analysis, atrophy and pathological changes were prominent in areas of the spinal cord with slow blood flow. Hemodynamic and anatomical factors are speculated to be among the main mechanisms of atrophy in the anteroposterior direction.

Effects of host restriction factors and the HTLV-1 subtype on susceptibility to HTLV-1-associated myelopathy/tropical spastic paraparesis

BACKGROUND

Although human T-lymphotropic virus type 1 (HTLV-1) infection is a prerequisite for the development of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), specific provirus mutations in HAM/TSP have not yet been reported. In this study, we examined whether HAM/TSP patients had the disease-specific genomic variants of HTLV-1 by analyzing entire sequences of HTLV-1 proviruses in these patients, including familial cases. In addition, we investigated the genetic variants of host restriction factors conferring antiretroviral activity to determine which mutations may be related to resistance or susceptibility to HAM/TSP.

RESULTS

The subjects included 30 patients with familial HAM/TSP (f-HAM/TSP), 92 patients with sporadic HAM/TSP (s-HAM/TSP), and 89 asymptomatic HTLV-1 carriers (ACs). In all 211 samples, 37 samples (18%) were classified into transcontinental subtype and 174 samples (82%) were classified as Japanese subtype. Among three groups, the percentage of transcontinental subtype in f-HAM/TSP, s-HAM/TSP and ACs was 33, 23 and 7%, respectively. The frequency of transcontinental subtype was significantly higher in both f-HAM/TSP (p < 0.001) and s-HAM/TSP (p < 0.001) than in ACs. Fifty mutations in HTLV-1 sequences were significantly more frequent in HAM/TSP patients than in ACs, however, they were common only in transcontinental subtype. Among these mutations, ten common mutations causing amino acid changes in the HTLV-1 sequences were specific to the transcontinental subtype. We examined host restriction factors, and detected a rare variant in TRIM5α in HAM/TSP patients. The patients with TRIM5α 136Q showed lower proviral loads (PVLs) than those with 136R (354 vs. 654 copies/10⁴ PBMC, p = 0.003). The patients with the 304L variant of TRIM5α had significantly higher PVLs than those with 304H (1669 vs. 595 copies/10⁴ PBMC, p = 0.025). We could not find any HAM/TSP-specific mutations of host restriction factors.

CONCLUSIONS

Transcontinental subtype is susceptible to HAM/TSP, especially in familial cases. Ten common mutations causing amino acid changes in the HTLV-1 gene were specific to the transcontinental subtype. TRIM5α polymorphisms were associated with PVLs, indicating that TRIM5α could be implicated in HTLV-1 replication.

Role of IL-21 in HTLV-1 infections with emphasis on HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP)

Interleukin-21 (IL-21) enhances the survival and cytotoxic properties of cytotoxic T cells (CTLs) and exhibits essential roles in controlling chronic viral infections. HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic progressive inflammatory disease of the nervous system. The main determinant of disease progression is efficiency of the CTL response to Human T lymphotropic virus types I (HTLV-1). In this study, the expression of host IL-21 and HTLV-I Tax and proviral load (PVL) was evaluated to understand the role and mechanism of IL-21 in HTLV-1 infections and the subsequent development of HAM/TSP. A cross-sectional study was carried out on 20 HAM/TSP patients, 20 asymptomatic HTLV-1 carriers (ACs) and 20 healthy controls (HCs) to evaluate the expression of IL-21 and Tax and PVL in non-activated and phorbol myristate acetate (PMA)-ionomycin-activated peripheral blood mononuclear cells (PBMCs). The mean mRNA expression of IL-21 in the non-activated and activated PBMCs was higher (by 5-13 times) in the HAM/TSP patients than in ACs and HCs (p < 0.05); however, there was no significant difference between ACs and HCs. In contrast to the IL-21 mRNA expression, the serum level of the IL-21 protein was significantly lower in the HAM/TSP patients than in ACs and HCs (p < 0.05). Furthermore, higher expression of Tax and PVL was observed in the HAM/TSP subjects than ACs (p < 0.05). In addition, Tax gene expression was positively correlated with PVL (R = 0.595, p = 0.000) and IL-21 gene expression (R = 0.395, p = 0.021) in the HTLV-1-infected subjects. In conclusion, the increase in IL-21 mRNA expression may reflect the attempt of infected T cells to induce an appropriate antiviral response, and the decrease in IL-21 protein expression may reflect the inhibition of IL-21 mRNA translation by viral factors in favour of virus evasion and dissemination.

Dynamic acquisition of HTLV-1 tax protein by mononuclear phagocytes: Role in neurologic disease

Pathology of HTLV-1 associated myelopathy/Tropical spastic paraparesis (HAM/TSP) is believed to be the result of "bystander damage" involving effector CD8 (+) T lymphocytes (CTLs) killing of virus infected cells. But the specific cellular events leading up to tissue injury are still unclear. Here, we developed the Microscopy Imaging of Cytotoxic T lymphocyte assay with Fluorescence emission (MI-CaFé), an optimized visualization analysis to explore the interactions between CTLs and virus infected or viral antigen presenting target cells. Various cell-to-cell formations can be observed and our results demonstrate elevated frequencies of CTL-target cell conjugates in HAM/TSP patient PBMCs compared to control PBMCs. Furthermore, HTLV-1 Tax protein expression can be localized at the cell-cell junctions and also tracked moving from an infected cell to a CD14 (+) mononuclear phagocyte (MP). Activation of CD14 (+) MPs in HAM/TSP patient PBMCs and antigenic presentation of HTLV-1 Tax by MPs can be inferred by their spontaneous cytotoxicity after 18h of in vitro culture. Given that CD4 (+) T lymphocytes are the primary reservoirs of HTLV-1 and MPs are scavenger cells responsible for pathogen clearance, spontaneous cytotoxicity against MPs in HAM/TSP PBMCs suggests a mechanism of chronic inflammation, secondary to low level of persistent virus infection within the central nervous system.