Impaired expression of DICER and some microRNAs in HBZ expressing cells from acute adult T-cell leukemia patients.

Global dysregulation of microRNAs (miRNAs), a class of non-coding RNAs that regulate genes expression, is a common feature of human tumors. Profiling of cellular miRNAs on Adult T cell Leukemia (ATL) cells by Yamagishi et al. showed a strong decrease in expression for 96.7% of cellular miRNAs in ATL cells. However, the mechanisms that regulate the expression of miRNAs in ATL cells are still largely unknown. In this study, we compared the expression of 12 miRs previously described for being overexpress by Tax and the expression of several key components of the miRNAs biogenesis pathways in different HBZ expressing cell lines as well as in primary CD4 (+) cells from acute ATL patients. We showed that the expression of miRNAs and Dicer1 were downregulated in cells lines expressing HBZ as well as in fresh CD4 (+) cells from acute ATL patients. Using qRT-PCR, western blotting analysis and Chromatin Immunoprecipitation, we showed that dicer transcription was regulated by c-Jun and JunD, two AP-1 transcription factors. We also demonstrated that HBZ affects the expression of Dicer by removing JunD from the proximal promoter. Furthermore, we showed that at therapeutic concentration of 1mM, Valproate (VPA) an HDAC inhibitors often used in cancer treatment, rescue Dicer expression and miRNAs maturation. These results might offer a rationale for clinical studies of new combined therapy in an effort to improve the outcome of patients with acute ATL.

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.

Safety of long-term treatment of HAM/TSP patients with valproic acid.

HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurodegenerative disease of the central nervous system induced by human T-lymphotropic virus type 1. As a potential therapeutic approach, we previously suggested reducing the proviral load by modulating lysine deacetylase activity using valproic acid (VPA) and exposing virus-positive cells to the host immune response. We conducted a single-center, 2-year, open-label trial, with 19 HAM/TSP volunteers treated with oral VPA. Proviral load, CD38/HLA-DR expression, and CD8(+) lysis efficiency were not significantly affected by VPA. Mean scores of HAM/TSP disability did not differ between baseline and final visit. Walking Time Test increased significantly (> 20%) in 3 patients and was in keeping with minor VPA side effects (drowsiness and tremor). Walking Time Test improved rapidly after VPA discontinuation. We conclude that long-term treatment with VPA is safe in HAM/TSP.

Effects of valproate on Tax and HBZ expression in HTLV-1 and HAM/TSP T lymphocytes.

A determinant of human T-lymphotropic virus-1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) development is the HTLV-1-infected cell burden. Viral proteins Tax and HBZ, encoded by the sense and antisense strands of the pX region, respectively, play key roles in HTLV-1 persistence. Tax drives CD4(+)-T cell clonal expansion and is the immunodominant viral antigen recognized by the immune response. Valproate (2-n-propylpentanoic acid, VPA), a histone deacetylase inhibitor, was thought to trigger Tax expression, thereby exposing the latent HTLV-1 reservoir to immune destruction. We evaluated the impact of VPA on Tax, Gag, and HBZ expressions in cultured lymphocytes from HTLV-1 asymptomatic carriers and HAM/TSP patients. Approximately one-fifth of provirus-positive CD4(+) T cells spontaneously became Tax-positive, but this fraction rose to two-thirds of Tax-positive-infected cells when cultured with VPA. Valproate enhanced Gag-p19 release. Tax- and Gag-mRNA levels peaked spontaneously, before declining concomitantly to HBZ-mRNA increase. VPA enhanced and prolonged Tax-mRNA expression, whereas it blocked HBZ expression. Our findings suggest that, in addition to modulating Tax expression, another mechanism involving HBZ repression might determine the outcome of VPA treatment on HTLV-1-infected-cell proliferation and survival.

Gene activation therapy: from the BLV model to HAM/TSP patients.

HTLV-1 (human T-lymphotropic virus type 1) and BLV (bovine leukemia virus) are two related retroviruses infecting CD4+ and B lymphocytes in humans and ruminants, respectively. During infection, the host-pathogen interplay is characterized by very dynamic kinetics resulting in equilibrium between the virus, which attempts to proliferate, and the immune response, which seeks to exert tight control of the virus. A major determinant of disease induction by both viruses is the accumulation of provirus in peripheral blood. In the absence of viral proteins, virus infected cells escape recognition and destruction by the host immune response. We propose a novel therapeutic strategy based on transient activation of viral expression using epigenetic modulators; this exposes infected cells to the immune response and results in significant reductions in proviral loads. In the absence of satisfactory therapies, this viral gene-activation strategy might delay progression, or even be curative, for HTLV-1 induced myelopathy / tropical spastic paraparesis (HAM/TSP).

Histone deacetylase mediated transcriptional activation reduces proviral loads in HTLV-1 associated myelopathy/tropical spastic paraparesis patients.

Epigenetic modifications of chromatin may play a role in maintaining viral latency and thus persistence of the human T-lymphotropic virus type 1 (HTLV-1), which is responsible for HTLV-associated myelopathy/tropical spastic paraparesis (HAM/TSP). A major determinant of disease progression is increased peripheral blood proviral load (PVL), possibly via the accumulation of infected cells in the central nervous system (CNS) creating a damaging inflammatory response. Current therapeutic approaches that focus on reducing either cell proliferation, viral replication, or tissue invasion are still unsatisfactory. Contrasting with these inhibitory strategies, we evaluated the efficacy of a novel approach aimed, paradoxically, at activating viral gene expression to expose virus-positive cells to the host immune response. We used valproate (VPA), a histone deacetylase inhibitor that has been used for decades as a chronic, safe treatment for epileptic disorders. Based on in vitro and in vivo data, we provide evidence that transient activation of the latent viral reservoir causes its collapse, a process that may alleviate the condition of HAM/TSP. This represents the first such approach to treating HAM/TSP, using gene activation therapy to tilt the host-pathogen balance in favor of an existing antiviral response. This trial is registered at http://clinicaltrials.gov/as no. NCT00519181.