Mechanism of action of glatiramer acetate in treatment of multiple sclerosis

Glatiramer acetate (GA) (Copolymer-1, Copaxone, Teva, Israel, YEAK) is a polypeptide-based therapy approved for the treatment of relapsing-remitting multiple sclerosis. Most investigations have attributed the immunomodulatory effect of GAs to its capability to alter T-cell differentiation. Specifically, GA treatment is believed to promote development of Th2-polarized GA-reactive CD4⁺ T-cells, which may dampen neighboring inflammation within the central nervous system. Recent reports indicate that the deficiency in CD4⁺CD25⁺FoxP3⁺ regulatory T-cells in multiple sclerosis is restored by GA treatment. GA also exerts immunomodulatory activity on antigen presenting cells, which participate in innate immune responses. These new findings represent a plausible explanation for GA-mediated T-cell immune modulation and may provide useful insight for the development of new and more effective treatment options for multiple sclerosis.     

Cell Therapy for Multiple Sclerosis

The spontaneous recovery observed in the early stages of multiple sclerosis (MS) is substituted with a later progressive course and failure of endogenous processes of repair and remyelination. Although this is the basic rationale for cell therapy, it is not clear yet to what degree the MS brain is amenable for repair and whether cell therapy has an advantage in comparison to other strategies to enhance endogenous remyelination. Central to the promise of stem cell therapy is the therapeutic plasticity, by which neural precursors can replace damaged oligodendrocytes and myelin, and also effectively attenuate the autoimmune process in a local, nonsystemic manner to protect brain cells from further injury, as well as facilitate the intrinsic capacity of the brain for recovery. These fundamental immunomodulatory and neurotrophic properties are shared by stem cells of different sources. By using different routes of delivery, cells may target both affected white matter tracts and the perivascular niche where the trafficking of immune cells occur. It is unclear yet whether the therapeutic properties of transplanted cells are maintained with the duration of time. The application of neural stem cell therapy (derived from fetal brain or from human embryonic stem cells) will be realized once their purification, mass generation, and safety are guaranteed. However, previous clinical experience with bone marrow stromal (mesenchymal) stem cells and the relative easy expansion of autologous cells have opened the way to their experimental application in MS. An initial clinical trial has established the probable safety of their intravenous and intrathecal delivery. Short-term follow-up observed immunomodulatory effects and clinical benefit justifying further clinical trials.     

Time limited immunomodulatory functions of transplanted neural precursor cells

Fetal neural stem/precursor cells (NPCs) possess powerful immunomodulatory properties which enable them to protect the brain from immune‐mediated injury. A major issue in developing neural stem/precursor cell (NPC) therapy for chronic neuroinflammatory disorders such as multiple sclerosis is whether cells maintain their immune‐regulatory properties for prolonged periods of time. Therefore, we studied time‐associated changes in NPC immunomodulatory properties. We examined whether intracerebrally‐transplanted NPCs are able to inhibit early versus delayed induction of autoimmune brain inflammation and whether allogeneic NPC grafts continuously inhibit host rejection responses. In two experimental designs, intraventricular fetal NPC grafts attenuated clinically and pathologically brain inflammation during early EAE relapse but failed to inhibit the disease relapse if induced at a delayed time point. In correlation, long‐term cultured neural precursors lost their capacity to inhibit immune cell proliferation in vitro. Loss of NPC immune functions was associated with transition into a quiescent undifferentiated state. Also, allogeneic fetal NPC grafts elicited a strong immune reaction of T cell and microglial infiltration and were rejected from the host brain. We conclude that long‐term functional changes in transplanted neural precursor cells lead to loss of their therapeutic immune‐regulatory properties, and render allogeneic grafts vulnerable to immunologic rejection. Thus, the immunomodulatory effects of neural precursor cell transplantation are limited in time. © 2012 Wiley Periodicals, Inc.     

Spotlight on statins

Statins are among the most widely prescribed drugs to prevent cardiovascular morbidity. Over recent years, statins have also been shown to exert pleiotropic immunomodulatory effects that might be of therapeutic benefit in autoimmune disorders. Interestingly, the primary mechanism by which statins alter immune function appears to be largely independent of lipidlowering and mediated primarily through inhibition of post-translational prenylation of regulatory proteins. In experimental autoimmune encephalomyelitis, the mouse model for multiple sclerosis (MS), statins prevent and even reverse established paralysis. Furthermore, statins were recently shown to exert synergistic benefit in combination with some agents already approved for MS therapy. Based upon these encouraging results obtained in the animal model, statins are now being evaluated in clinical trials as potential therapy for MS.     

Mesenchymal stem cells for the treatment of multiple sclerosis and other neurological diseases

The rationale for use of adult stem cells as a treatment for neurological diseases such as multiple sclerosis arose from the hope that they had the capacity to foster repair of the CNS through tissue integration and differentiation into neural cells. Evidence from preclinical studies suggested that mesenchymal stem cells (MSCs), a subset of adult progenitor cells, are an effective therapy in preclinical animal models of neurological diseases such as experimental autoimmune encephalomyelitis, a model for multiple sclerosis, and stroke. In experimental autoimmune encephalomyelitis, intravenous injection of MSCs ameliorates clinical course and decreases demyelination, immune infiltrates, and axonal loss. Surprisingly, these effects do not require full CNS engraftment by MSCs, but rely on the capacity of MSCs to inhibit pathogenic immune responses and release neuroprotective and pro-oligodendrogenic molecules favouring tissue repair. These results led to the conclusion that therapeutic use of MSCs should initially focus on individuals with multiple sclerosis and persistent inflammation. Small clinical studies in different neurological diseases have suggested that MSCs are safe, paving the road for larger phase 2 studies addressing the effect of MSCs on clinical outcomes and markers of disease activity.     

Activation and control of CNS innate immune responses in health and diseases: a balancing act finely tuned by neuroimmune regulators (NIReg)

Innate immunity is an arsenal of molecules and receptors expressed by professional phagocytes, glial cells and neurons and involved in host defence and clearance of toxic and dangerous cell debris. However, any uncontrolled innate immune responses within the central nervous system (CNS) are widely recognized as playing a major role in the development of autoimmune disorders and neurodegeneration, with multiple sclerosis (MS) and Alzheimer's diseases (AD) being primary examples. Critically, neuroimmune regulatory proteins (NIReg) may control the adverse immune responses in health and diseases. NIRegs are found mainly on neurons, glia, endothelia and ependymal cells and include GPI-anchored molecules (CD24, CD90, complement regulators CD55 and CD59), molecules of the immunoglobulin superfamily (siglec CD22, Siglec 10, CD200, ICAM-5) and others (CD47, fractalkine, TAM receptor tyrosine kinase and complement C3a and factor H). These regulators modulate the innate immune response in the CNS and for instance critically control the level of phagocytosis and inflammation engaged by resident microglia and infiltrating immune cells. Others will sequester and neutralize proinflammatory molecules such as HMGB1 and DNA. Moreover, some NIRegs can instigate the recruitment of stem cells to mediate tissue repair. In the absence of these regulators, when neurons die by apoptosis, become infected or damaged, microglia and infiltrating immune cells are free to cause injury and an adverse inflammatory response in acute and chronic settings. The therapeutic applications of NIRegs should be exploited given their natural and selective healing properties.     

Immune Mechanisms Underlying the Beneficial Effects of Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis

A recent phase I/II clinical trial drew serious attention to the therapeutic potential of autologous hematopoietic stem cell transplantation (AHSCT) in multiple sclerosis. However, questions were raised as to whether these beneficial effects should be attributed to the newly reconstituted immune system per se, or to the lymphoablative conditioning regimen-induced immunosuppression, given that T-cell depleting combinational drug therapies were used in the study. We discuss here the possibility that both AHSCT and T-cell depleting therapies may re-program alternatively the immune system, and why transplantation of CD34⁺ hematopoietic stem cells may offer AHSCT a possible advantage regarding long-term remission.     

Chemokine network in multiple sclerosis: role in pathogenesis and targeting for future treatments

Multiple sclerosis is the most common inflammatory disorder of the CNS. Evidence suggests that an immunomediated mechanism plays a crucial role during the development of the disease. Currently, two classes of immunomodulatory agents -- interferon-beta and glatiramer acetate (Copaxone, Teva Pharmaceutical Industries), have been approved for the long-term treatment of multiple sclerosis. New drugs which effectively target the immunological processes occurring in multiple sclerosis have been proposed. This review summarizes the immunological background that occurs during the pathogenesis of multiple sclerosis focusing on chemokines and related receptors. The effects of standard treatments on the immune system are analyzed along with the current knowledge of potential new immunomodulatory molecules, such as antiadhesion molecules, statins, estriol, cannabinoids, neurotrophic factors and chemokine antagonists.     

A Belgian consensus protocol for autologous hematopoietic stem cell transplantation in multiple sclerosis

Multiple sclerosis is considered to be an immune mediated inflammatory disorder of the central nervous system. It mainly affects young, socioeconomic active patients. Although our armamentarium for this disease has significantly evolved in recent years some patients remain refractory to conventional therapies. In these cases, autologous hematopoietic stem cell transplantation can be considered as a therapeutic option. Decreasing morbidity, mortality, and increasing patient awareness have led to rising inquiry by our patients about this treatment option. With the aim of a standardized protocol and data registration, a Belgian working party on stem cell therapy in multiple sclerosis was established. In this paper, we report the consensus protocol of this working party on autologous hematopoietic stem cell transplantation in multiple sclerosis.     

Promising treatments of tomorrow for multiple sclerosis

The therapeutic options for multiple sclerosis are rapidly expanding. What was once seen as a disease with little hope for treatment is now a target of rapid drug development. Current therapies have demonstrated efficacy in limiting the impact of the disease, but none is fully effective in all patients. However, promising new treatments are on the horizon. In this review we will discuss potential novel immunomodulating drugs that are in advanced stages of investigation; these drugs include monoclonal antibodies, chimeric molecules, and oral therapies. The use of hematopoietic stem cells will also be discussed and, in addition, we will look farther ahead at possible novel targets for the development of new immunomodulatory or neuroprotective pharmaceuticals.     

Therapeutic effect of ghrelin in experimental autoimmune encephalomyelitis by inhibiting antigen-specific Th1/Th17 responses and inducing regulatory T cells

Ghrelin is an important gastrointestinal hormone that regulates feeding and metabolism. Moreover, ghrelin is produced by immune cells and shows potent anti-inflammatory activities. Here, we investigated its effect in two models of experimental autoimmune encephalomyelitis (EAE) that mirror chronic and relapsing-remitting multiple sclerosis. A short systemic treatment with ghrelin after the disease onset reduced clinical severity and incidence of both forms of EAE, which was associated with a decrease in inflammatory infiltrates in spinal cord and in the subsequent demyelination. This therapeutic effect was exerted through the reduction of the autoimmune and inflammatory components of the disease. Ghrelin decreased the presence/activation of encephalitogenic Th1 and Th17 cells in periphery and nervous system, down-regulated various inflammatory mediators, and induced regulatory T cells. In summary, our findings provide a powerful rationale for the assessment of the efficacy of ghrelin as a novel therapeutic approach for treating multiple sclerosis through distinct immunomodulatory mechanisms and further support the concept that the neuroendocrine and immune systems crosstalk to finely tune the final immune response of our body.     

Metabolic pathways as possible therapeutic targets for progressive multiple sclerosis

Unlike relapsing remitting multiple sclerosis, there are very few therapeutic options for patients with progressive forms of multiple sclerosis. While immune mechanisms are key participants in the pathogenesis of relapsing remitting multiple sclerosis, the mechanisms underlying the development of progressive multiple sclerosis are less well understood. Putative mechanisms behind progressive multiple sclerosis have been put forth: insufficient energy production via mitochondrial dysfunction, activated microglia, iron accumulation, oxidative stress, activated astrocytes, Wallerian degeneration, apoptosis, etc. Furthermore, repair processes such as remyelination are incomplete. Experimental therapies that strive to improve metabolism within neurons and glia, e.g., oligodendrocytes, could act to counter inadequate energy supplies and/or support remyelination. Most experimental approaches have been examined as standalone interventions; however, it is apparent that the biochemical steps being targeted are part of larger pathways, which are further intertwined with other metabolic pathways. Thus, the potential benefits of a tested intervention, or of an established therapy, e.g., ocrelizumab, could be undermined by constraints on upstream and/or downstream steps. If correct, then this argues for a more comprehensive, multifaceted approach to therapy. Here we review experimental approaches to support neuronal and glial metabolism, and/or promote remyelination, which may have potential to lessen or delay progressive multiple sclerosis.     

IFN-β induces the proliferation of CD4+CD25+Foxp3+ regulatory T cells through upregulation of GITRL on dendritic cells in the treatment of multiple sclerosis

IFN-β is a major disease-modifying agent used for the treatment of multiple sclerosis (MS). Its mechanisms are complex and it has broad immunomodulatory effects on many types of immune cells. It was observed clinically that the quantity of CD4(+)CD25(+)Foxp3(+) regulatory T cells increases in some MS patients treated with IFN-β. In this study, we show that IFNAR engagement by IFN-β expands naturally occurring CD4(+)CD25(+)Foxp3(+) regulatory T cell population through the modulation of dendritic cells (DCs). IFN-β has no effect on the conversion of CD4(+)CD25(-) T cells to adaptive Treg cells. The IFN-β-induced upregulation of GITRL on DC and downregulation of CTLA-4 on Treg cell work together to facilitate the proliferation of anergic Treg cells. In MS patients treated with Avonex or Rebif (IFN-β), it was found that GITRL expression is markedly upregulated on peripheral CD14(+) cells. Our findings help the better understanding of the complex effects of IFN-β in the treatment of MS.     

Statins in the treatment of central nervous system autoimmune disease

Statins, inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, are widely prescribed for their cholesterol-lowering properties to reduce atherogenesis and cardiovascular morbidity. Over recent years, statins have also been shown to exert pleiotropic immunomodulatory effects that might be of therapeutic benefit in autoimmune disorders. The primary mechanism by which statins alter immune function appears to be mediated through the inhibition of post-translational protein prenylation of small GTP-binding proteins and is largely independent of lipid-lowering. In experimental autoimmune encephalomyelitis (EAE), the mouse model for multiple sclerosis (MS), statins prevent or reverse paralysis and were recently shown to exert synergistic benefit when combined with agents approved for MS therapy. Based primarily upon the beneficial effects in EAE, statins are now being tested in patients in MS clinical trials.     

Interferon beta inhibits the Th17 cell-mediated autoimmune response in patients with relapsing–remitting multiple sclerosis

Interferon (IFN)β has been used over the past decades as an effective first-line therapy against relapsing–remitting multiple sclerosis (RR MS), however its in vivo operative mechanisms of action are not fully understood. Current advances in our understanding of the development of the autoimmune response, including its induction by a recently discovered Th17 cell lineage, may allow us to identify the biomarkers of this effective therapy. Our in vitro human studies have characterized IFNβ’s immunoregulatory effects on Th17 cell differentiation. IFNβ inhibited IL-1β, IL-23 and transforming growth factor (TGF)-β (which induce Th17 cell differentiation), and induced IL-27, IL-12p35 and IL-10 (which suppress it) in dendritic cells (DCs) and B-cells. The effect on IL-1β, IL-23 and IL-27 production in DCs was mediated by the up-regulation of Toll-like receptor (TLR)7 and its downstream signaling molecules. IFNβ’s direct effect on naïve T-cells suppressed in vitro Th17 differentiation by inhibiting Th17 cell lineage markers (retinoic acid-related orphan nuclear hormone receptor (ROR)c, IL-17A, IL-23R and CCR6), and by inducing IL-10 production by CD4 cells, which constrains Th17 cell expansion. Our results have identified novel therapeutic mechanisms of IFNβ, which inhibit Th17 cell differentiation in the context of the autoimmune response in MS.     

Future research directions in multiple sclerosis therapies

The success of presently available injectable immunomodulatory therapies in treating multiple sclerosis has led to heightened interest in finding even more efficacious and better tolerated therapies. Several oral agents have shown efficacy in phase-II clinical trials and are now entering phase-III pivotal trials. In addition, monoclonal antibodies targeting surface receptors on various cells of the peripheral immune system have also shown efficacy in early studies and will soon be entering phase III. All of these approaches target immune molecules that are not specific for multiple sclerosis (MS) and carry inherent risk of infection and systemic side effects. Novel immunotherapies in preclinical or phases I to IIa testing are attempting to more selectively target pathogenic effector cells and thereby block abnormal immune cell activation without compromising normal healthy immune responses. The induction of tolerance to self-proteins continues to be a goal of MS immunotherapy, but as yet has not been accomplished outside of the laboratory. There is increasing awareness of the need to understand and modulate nonclassical immune targets as well as central nervous system degenerative processes. The roles of vitamins, antimicrobials, and hormones continue to be studied. The mechanisms of neurodegeneration in MS are likely multifactorial and include direct damage by T cells and humoral immunity as well as oxidative stress, glutamate-mediated excitotoxicity, and neuronal and oligodendrocyte apoptosis. Neuroprotective drugs that were once only considered for classical degenerative diseases, such as amyotrophic lateral sclerosis and Parkinson's disease, are now being considered in MS.     

Hematopoietic stem cell transplantation for multiple sclerosis: current status and future challenges

PURPOSE OF REVIEW: This article reviews recent advances in clinical trials of hematopoietic stem cell transplantation as a therapy for multiple sclerosis, and progress in exploring the potential for neural repair of hematopoietic-derived precursors. RECENT FINDINGS: Important recent findings are that hematopoietic stem cell transplantation can completely suppress the inflammatory component of multiple sclerosis, hematopoietic stem cells can migrate into the central nervous systems of rodents and humans, and can differentiate into cells expressing neural and glial markers. Hematopoietic stem cells also have neural and myelin repair potential. The heterogeneity of transplant regimens, the selection of patients at different stages of disease in clinical trials, and the limited duration of follow-up all currently preclude the evaluation of the long-term clinical benefits of hematopoietic stem cell transplantation for multiple sclerosis. SUMMARY: Hematopoietic stem cell transplantation is an experimental treatment that shows strong effects on the inflammatory component of multiple sclerosis. On the basis of experience acquired from initial pilot studies, controlled clinical trials are now being designed to verify long-term clinical efficacy. Selecting patients at high risk in the earlier stages of the disease that is dominated by inflammation, and monitoring objectively disease activity by magnetic resonance imaging will be critically important in these studies. Recent advances on the migratory potential and on the differentiation plasticity of hematopoietic stem cells have opened new opportunities for remyelination and axonal repair strategies for multiple sclerosis.     

Combination therapy in multiple sclerosis

The multifaceted pathogenesis of multiple sclerosis (MS) involves complex interactions between the immune and the central nervous systems which provide a multitude of targets for therapeutic interventions. Current therapies for MS are only partially effective. One potential strategy to increase treatment efficacy is the combination of two or more drugs with complementary mechanisms of action, which may result in additive or synergistic therapeutic effects. In this review, we discuss the rationale and requirements and review the evidence for combination therapy in MS from in-vitro experiments, animal studies and clinical trials. Encouraging experience to date and further well-designed clinical trials with combination therapy may lead to the implementation of specific combinations of drugs in the treatment of MS.     

Rituximab and multiple sclerosis

B lymphocytes seem to have a fundamental role in multiple sclerosis, acting as sensors, coordinators, and regulators of the immune response. Furthermore, they are important in activating T cells and they can mediate tissue injury through diverse mechanisms. Such findings have important therapeutic implications in autoimmune central nervous system diseases in a fashion similar to other autoimmune processes. The best known monoclonal antibody targeting B cells that has been used as a novel therapy for various autoimmune conditions, as well as multiple sclerosis, is rituximab. This review summarizes the available data on the role of B cell in multiple sclerosis and further reports on current knowledge on the B-cell-depleting monoclonal antibody rituximab, its mechanism of action, and its efficacy on multiple sclerosis. Data presented were categorized in 3 groups based on the nature of data presented (radiological, clinical, and immunological data). Both case-control studies and case reports were included, while table classification was in chronological order.