The transcription factor REST silences neuronal gene expression in non-neuronal cells. In neurons, the protein is sequestered in the cytoplasm in part through binding to huntingtin. Polyglutamine expansions in huntingtin, which causes Huntington’s disease (HD), abrogates REST-huntingtin binding. Consequently, REST translocates to the nucleus, occupies RE1 repressor sequences and decreases neuronal gene expression. In this work, we found that levels of several microRNAs (miRNAs) with upstream RE1 sites are decreased in HD patient cortices relative to healthy controls. Interestingly, one of these, the bi-functional brain enriched miR-9/miR-9*, targets two components of the REST complex: miR-9 targets REST and miR-9* targets CoREST. These data provide evidence for a double negative feedback loop between the REST silencing complex and the miRNAs it regulates.

Administration of daclizumab, a humanized mAb directed against the IL-2R␣ chain, strongly reduces brain inflammation in multiple sclerosis patients. Here we show that daclizumab treatment leads to only a mild functional blockade of CD4 ؉ T cells, the major candidate in multiple sclerosis pathogenesis. Instead, daclizumab therapy was associated with a gradual decline in circulating CD4 ؉ and CD8 ؉ T cells and significant expansion of CD56 bright natural killer (NK) cells in vivo, and this effect correlated highly with the treatment response. In vitro studies showed that NK cells inhibited T cell survival in activated peripheral blood mononuclear cell cultures by a contact-dependent mechanism. Positive correlations between expansion of CD56 bright NK cells and contraction of CD4 ؉ and CD8 ؉ T cell numbers in individual patients in vivo provides supporting evidence for NK cell-mediated negative immunoregulation of activated T cells during daclizumab therapy. Our data support the existence of an immunoregulatory pathway wherein activated CD56 bright NK cells inhibit T cell survival. This immunoregulation has potential importance for the treatment of autoimmune diseases and transplant rejection and toward modification of tumor immunity.CD25 ͉ IL-2 ͉ immunoregulatory natural killer cells M ultiple sclerosis (MS) is an inflammatory͞demyelinating disease of the CNS that is one of the leading causes of neurological disability in young adults (1). It is believed that MS is a T cell-mediated autoimmune disease, and therefore the search for new therapies focuses on agents that affect lymphocyte function. Daclizumab (Zenapax), a humanized mAb that blocks the IL-2 binding site on the IL-2R␣ chain, CD25 (i.e., Tac epitope), is among these novel agents (2). The IL-2R complex is comprised of three subunits: IL-2R␣ (CD25), IL-2R␤ (CD122), and IL-2R␥ (CD132). CD122 and CD132 have intracellular signaling motifs and together form the intermediate-affinity (K dis Ϸ 0.1-1 nM) IL-2R. CD25 binds IL-2 with low (K dis Ϸ 10 nM) affinity, but when it associates with CD122͞CD132 it stabilizes the complex to form the highaffinity (K dis Ϸ 10 pM) receptor (3). CD25 is present at low levels in resting human T cells (with the exception of T regulatory cells) but is significantly up-regulated on activated T cells, enabling them to receive a high-affinity IL-2 signal (4). Therefore, it is believed that the blockade of CD25 will result in selective functional inhibition of activated T cells (5). Although it has been demonstrated that daclizumab (or the original murine anti-Tac mAb) inhibits early IL-2R signal transduction events (6, 7) and blocks T cell activation and expansion in vitro (8), a comprehensive characterization of its in vivo effects is still lacking.We recently concluded a phase II, open-label, baseline-versustreatment crossover trial of daclizumab in 10 MS patients with incomplete therapeutic response to IFN-␤. Daclizumab showed a profound inhibitory effect on brain inflammatory activity (78% reduction) and subsequent stabilization o...

Clinical trials have indicated that autologous hematopoietic stem cell transplantation (HSCT) can persistently suppress inflammatory disease activity in a subset of patients with severe multiple sclerosis (MS), but the mechanism has remained unclear. To understand whether the beneficial effects on the course of disease are mediated by lympho-depletive effects alone or are sustained by a regeneration of the immune repertoire, we examined the long-term immune reconstitution in patients with MS who received HSCT. After numeric recovery of leukocytes, at 2-yr follow-up there was on average a doubling of the frequency of naive CD4+ T cells at the expense of memory T cells. Phenotypic and T cell receptor excision circle (TREC) analysis confirmed a recent thymic origin of the expanded naive T cell subset. Analysis of the T cell receptor repertoire showed the reconstitution of an overall broader clonal diversity and an extensive renewal of clonal specificities compared with pretherapy. These data are the first to demonstrate that long-term suppression of inflammatory activity in MS patients who received HSCT does not depend on persisting lymphopenia and is associated with profound qualitative immunological changes that demonstrate a de novo regeneration of the T cell compartment.

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Rolipram, a prototypic phosphodiesterase-4 inhibitor is highly effective in suppressing Th1 autoimmunity in multiple animal models, including experimental autoimmune encephalomyelitis (EAE). Additionally, Rolipram has been extensively studied as a potential neuroprotective agent. Based on its anti-inflammatory activity, we tested the efficacy of Rolipram in suppressing inflammatory disease activity in MS in a proof-of-principle phase I/II open label clinical trial. Enrolled MS patients were evaluated by monthly MRI and clinical examinations during three months (four MRIs) of pre-treatment baseline and eight months of Rolipram therapy. The primary outcome was the change in contrast-enhancing lesions (CEL) between baseline and last four months of Rolipram therapy. Previously defined biomarkers of Rolipram-mediated immunomodulation were evaluated during study. The trial was stopped prematurely because the drug was poorly tolerated and because of safety concerns: we observed an increase, rather than decrease in the brain inflammatory activity measured by contrast-enhancing lesions (CEL) on brain MRI. At the administered doses Rolipram was active in vivo as documented by immunological assays. We conclude that the reasons underlying the discrepancy between the therapeutic efficacy of Rolipram in EAE versus MS are at present not clear.

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