Rationale for immunotherapy in multiple sclerosis

The effect of inflammation and its reduction on brain plasticity in multiple sclerosis: MRI evidence

Brain plasticity is the basis for systems‐level functional reorganization that promotes recovery in multiple sclerosis (MS). As inflammation interferes with plasticity, its pharmacological modulation may restore plasticity by promoting desired patterns of functional reorganization. Here, we tested the hypothesis that brain plasticity probed by a visuomotor adaptation task is impaired with MS inflammation and that pharmacological reduction of inflammation facilitates its restoration. MS patients were assessed twice before (sessions 1 and 2) and once after (session 3) the beginning of Interferon beta (IFN beta), using behavioural and structural MRI measures. During each session, 2 functional MRI runs of a visuomotor task, separated by 25‐minutes of task practice, were performed. Within‐session between‐run change in task‐related functional signal was our imaging marker of plasticity. During session 1, patients were compared with healthy controls. Comparison of patients' sessions 2 and 3 tested the effect of reduced inflammation on our imaging marker of plasticity. The proportion of patients with gadolinium‐enhancing lesions reduced significantly during IFN beta. In session 1, patients demonstrated a greater between‐run difference in functional MRI activity of secondary visual areas and cerebellum than controls. This abnormally large practice‐induced signal change in visual areas, and in functionally connected posterior parietal and motor cortices, was reduced in patients in session 3 compared with 2. Our results suggest that MS inflammation alters short‐term plasticity underlying motor practice. Reduction of inflammation with IFN beta is associated with a restoration of this plasticity, suggesting that modulation of inflammation may enhance recovery‐oriented strategies that rely on patients' brain plasticity. Hum Brain Mapp 37:2431–2445, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Acute disseminated encephalomyelitis in childhood: epidemiologic, clinical and laboratory features

BACKGROUND

Acute disseminated encephalomyelitis (ADEM) is a central nervous system demyelinating disease that usually follows an apparently benign infection in otherwise healthy young persons. The epidemiology, infectious antecedents and pathogenesis of ADEM are poorly characterized, and some ADEM patients are subsequently diagnosed with multiple sclerosis (MS).

METHODS

We retrospectively (1991-1998) and prospectively (1998-2000) studied all persons aged < 20 years diagnosed with ADEM from the 3 principal pediatric hospitals in San Diego County, CA, during 1991-2000. Acute neurologic abnormalities and imaging evidence of demyelination were required for study inclusion. Epidemiologic variables, risk factors, clinical course, laboratory and radiographic findings, neuropathology and treatment data were analyzed. Interleukin (IL)-12, interferon-gamma (IFN-gamma) and IL-10 were assayed in blinded manner on cerebrospinal fluid (CSF) obtained prospectively from a subset of ADEM cases and compared with CSF from patients with enteroviral (EV) meningoencephalitis confirmed by polymerase chain reaction (PCR) and controls without pleocytosis.

RESULTS

Data were analyzed on 42 children and adolescents diagnosed with ADEM during 1991-2000, and CSF IL-12, IFN-gamma and IL-10 levels were compared among ADEM (n = 14), EV meningoencephalitis (n = 14) and controls without pleocytosis (n = 28). Overall incidence of ADEM was 0.4/100,000/year; incidence quadrupled during 1998-2000 compared with earlier years. No gender, age stratum, ethnic group or geographic area was disproportionately affected. A total of 4 (9.5%) patients initially diagnosed with ADEM were subsequently diagnosed with MS after multiple episodes of demyelination. Although most children eventually recovered, 2 died, including 1 of the 3 ultimately diagnosed with MS. Magnetic resonance imaging was required for diagnosis among 74% of patients; computerized tomography findings were usually normal. Patients with EV had significantly higher mean CSF IFN-gamma (P = 0.005) and IL-10 (P = 0.05) than patients with ADEM and controls without CSF pleocytosis. CSF from ADEM patients had CSF cytokine values statistically similar to those of 3 patients subsequently diagnosed with MS.

CONCLUSIONS

ADEM is a potentially severe demyelinating disorder likely to be increasingly diagnosed as more magnetic resonance imaging studies are performed on patients with acute encephalopathy. Further characterization of the central nervous system inflammatory response will be needed to understand ADEM pathogenesis, to improve diagnostic and treatment strategies and to distinguish ADEM from MS.

Monoclonal antibody therapy in experimental allergic encephalomyelitis and multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is a T-cell-mediated demyelinating disease of the central nervous system that has been used as an animal model for multiple sclerosis (MS). Based on the exciting results in EAE, a number of novel immunotherapies employing biotechnological products, rather than conventional immunosuppressants, are being developed for the treatment of MS. In this review, we delineate the rationale for monoclonal antibody (MAb) therapy in EAE and MS and summarize the various levels at which immune intervention was performed. For each approach, we discuss the role of MAbs at the level of lymphocyte and cytokine networks, chemokines, and adhesion molecules or their receptors.

Myelin basic protein-primed T cells induce nitric oxide synthase in microglial cells. Implications for multiple sclerosis

The presence of autoreactive T cells recognizing self myelin antigens is necessary for the development of central nervous system autoimmune diseases such as multiple sclerosis (MS). The present study was undertaken to investigate the role of myelin basic protein (MBP)-primed T cells in the expression of inducible nitric oxide synthase (iNOS) in microglial cells. MBP-primed T cells alone markedly induced the production of NO and the expression of iNOS protein and mRNA in mouse BV-2 microglial cells. Similarly, MBP-primed T cells also induced the production of NO in mouse primary microglia. This induction of NO production was primarily dependent on the contact between MBP-primed T cells and microglia. The expression of very late antigen-4 (VLA-4) on the surface of MBP-primed T cells and inhibition of MBP-primed T cell-induced microglial NO production by functional blocking of antibodies to the alpha(4) chain of VLA-4 (CD49d) suggest that VLA-4 integrin on MBP-primed T cells plays an important role in contact-mediated induction of iNOS. Since IFN-beta has been used to treat MS patients, we examined the effect of IFN-beta on MBP-primed T cell-induced the production of NO. Surprisingly, IFN-beta alone induced the production of NO in microglial cells. However, the pretreatment of MBP-primed T cells with IFN-beta inhibited the expression of VLA-4 integrin on the surface of MBP-primed T cells and thereby inhibited the ability of those T cells to induce the production of NO in microglial cells. This study illustrates a novel role of neuroantigen-primed T cells in inducing contact-mediated expression of iNOS in microglial cells that may participate in the pathogenesis of MS.

Treatment of experimental autoimmune encephalomyelitis with adenylate deaminase from Penicillium lanoso-viride

The effect of intramuscularly administered immunomodulator, adenylate deaminase (E.C. 3.5.4.6), from Penicillium lanoso-viride on the clinical score of acute experimental autoimmune encephalomyelitis (EAE), a T cell-mediated autoimmune disease, was examined by inoculation of guinea pigs with rabbit brain and spinal cord homogenate (encephalitogen) and complete Freund's adjuvant. Adenylate deaminase (ADA) was effective in delaying the onset of clinical disease. ADA inhibited the severity of EAE. There was a significant decrease in clinical signs. A decrease in the number of morbid and dead animals was observed. Of ADA treated animals, 50-80% developed no clinical manifestations of EAE. The optimal version of treatment was a single preventive injection of ADA 1 day before the sensitization and then every second day after immunization for 20 days. ADA treatment of immunized animals diminished the activity of 2', 3'-cyclic nucleotide 3'-phosphodiesterase in the cerebrospinal fluid, as well the amount of complement fixing antiencephalitogenic antibodies in the blood serum. The mechanism of ADA cerebroprotective action is discussed. Significant skin-allergic cross-reaction of delayed-type hypersensitivity between ADA and encephalitogen was observed.

Interferon-beta-1-b (IFN-B) decreases induced nitric oxide (NO) production by a human astrocytoma cell line

Inducible nitric oxide synthase (iNOS) is expressed by astrocytes in demyelinating regions of multiple sclerosis (MS) brain plaques, suggesting that NO contributes to MS pathology. Since the immunosuppressive cytokine IFN-B ameliorates MS disease activity, it is of interest to assess the modulatory role of IFN-B on NO production. We studied the effects of IFN-B, as well as dexamethasone, IL-10, and transforming growth factor-beta (TGF-B), on cytokine-induced NO production by the human astrocytoma cell line, A172. L-NMMA and aminoguanidine, competitive inhibitors of iNOS suppressed NO production as measured by the NO byproduct, nitrite, as did IFN-B. Dexamethasone enhanced NO production, and IFN-B decreased the amount of the enhancement. Neither IL-10 nor TGF-B inhibited nitrite production. The therapeutic effect of IFN-B in MS may be partly due to suppression of pathogenic NO production.

A gliotoxic factor and multiple sclerosis

The pathogenesis of multiple sclerosis (MS) is unknown. Searching for possible toxic factors, it was found that 3-day exposure to heat-treated cerebrospinal fluid (CSF) from MS patients caused apoptotic death of astrocytes and oligodendrocytes, but not fibroblasts, myoblasts, Schwann cells, endothelial cells and neurons, in vitro. CSFs from other inflammatory or non-inflammatory neurological diseases showed no toxicity. Exposure of these glial cells to partially purified MS CSF produced DNA fragmentation, apoptotic bodies, chromatin condensation, cell shrinkage, and changes in the levels of known cytokines. A cytotoxic factor, called gliotoxin, was characterized chromatographically as a stable 17-kDa glycoprotein. Since this protein is highly cytotoxic for astrocytes and oligodendrocytes, it may represent an initial pathogenic factor, leading to the neuropathological features of MS, such as blood-brain barrier involvement and demyelination.

Current immunotherapy in multiple sclerosis

The underlying pathophysiology of multiple sclerosis is presumed to be autoimmune in nature. Attempts to find an effective treatment for this common disease of the central nervous system have primarily focused on immune-mediated therapies, both immunosuppressive and immunomodulatory. The wide variety of immunological abnormalities detected in multiple sclerosis and its animal model, experimental allergic encephalomyelitis, has prompted the testing of a diverse array of drugs to be used for treatment. Recent successes in the treatment of relapsing-remitting multiple sclerosis with interferon beta and glatiramer acetate have renewed interest in and raised expectations for the effective control of this neurological disorder. Improved methodology in clinical trials, the development of surrogate markers and the availability of novel therapies bode well for more rapid advances.

Rational clinical immunotherapy for multiple sclerosis

In this article, we assess the roles and the efficacy of immunopharmacologic agents in the treatment of multiple sclerosis (MS) and other demyelinating disease syndromes. The initial clinical manifestations of demyelinating disease, immunotherapeutic goals, efficacy of individual agents, and specific immunopharmacologic recommendations are discussed. MS and other idiopathic demyelinating disease syndromes can be effectively managed with immunotherapy. Exacerbations are treatable, and the frequency and severity of exacerbations can be reduced. Although some agents have a minor effect on progression of disability, current approaches have not proved to have a major influence on treatment of progressive MS. Immunotherapy for inflammatory demyelinating disease necessitates a high degree of clinical certainty about the diagnosis. Because all available therapeutic agents have limitations and significant toxic effects, careful consideration is necessary before use. Treatment should be individualized on the basis of the clinical course of the disease and the degree of patient disability.

Investigational drug therapies of treatment of multiple sclerosis

The licensing of interferon beta-1b dramatically changed the treatment of multiple sclerosis (MS) in the United States. Although it was the first therapeutic agent shown to affect the natural course of the disease, interferon beta-1b is not appropriate for all patients and is far from being a cure. Several other promising therapies now under study include immunosuppressive and immunomodulatory drugs to limit inflammation; oral administration of myelin to induce tolerance; monoclonal antibodies designed to deliver targeted immunotherapy; potassium channel blockers to facilitate conduction along demyelinated axons; and glial growth factors to promote remyelination. Clinical trials of potential therapeutic agents have proliferated in the past decade in conjunction with rapid advances in our understanding of the immunologic basis of MS. Some investigational therapies are associated with problematic toxicities, others benefit only a minority of patients, and many are still in the early stages of development. Nevertheless, because current therapeutic options are limited, and because the history of MS therapy is one of disappointment and frustration, it is essential that legitimate, scientifically based advances be widely disseminated to the neurologic community. This article reviews some of the most promising current and investigational therapies for MS.

Central nervous system remyelination clinical application of basic neuroscience principles

Studies in both humans and experimental animals have demonstrated that myelin repair in the CNS is a normal physiological response to myelin damage, similar to tissue injury elsewhere in the body. The unanswered question is why myelin repair is incomplete in multiple sclerosis patients. In this paper we review the morphological characteristics of remyelination, discuss the available animal models of CNS demyelination and their usefulness to identify the molecular, cellular, and morphological events involved in CNS myelin repair, examine the use of immunosuppression, immunoglobulins, protein growth factors, and glial cell transplantation at the primary experimental therapies designed to promote CNS remyelination, and address the potential electrophysiological and clinical benefits of myelin repair in the CNS.

Counteracting effect of IFN-beta on IFN-gamma-induced proliferation of human astrocytes in culture

Recent clinical trials have shown that interferon beta (IFN-beta) is effective in reducing exacerbations in relapsing-remitting MS, while interferon gamma (IFN-gamma) precipitates the relapses. To investigate mechanisms underlying the beneficial effects of IFN-beta and the detrimental effects of IFN-gamma in MS, cell growth-regulatory effects of IFNs were examined in astrocyte-enriched cultures isolated from fetal brains of 12-20 weeks' gestation. Treatment with IFN-gamma (50 or 500 IU ml-1) stimulated significantly the proliferation of astrocytes in 6 out of 9 culture series examined, while IFN-beta (50 or 500 IU ml-1) inhibited the astrocytic proliferation in 3 out of 9 cultures, and IFN-alpha (50 or 500 IU ml-1) did not affect the proliferation IFN-beta and to a lesser degree IFN-alpha reduced the astrocytic proliferation induced by IFN-gamma-treatment in 8 out of 9 culture series. The counteracting effect of IFN-alpha/IFN-beta against IFN-gamma-induced astrocytic proliferation was verified by the DNA content distribution analysis of propidium iodide-labeled cells. The antagonistic effect of IFN-alpha/IFN-beta on the growth-promoting activity of IFN-gamma in cultured human astrocytes suggests that interferons serve as growth regulators of astrocytes at sites of reactive gliosis lesions of MS.

Basic aspects of neuroimmunology as they relate to immunotherapeutic targets: present and future prospects

The neurological diseases with definite or putative immune pathogenesis include myasthenia gravis; Lambert-Eaton myasthenic syndrome; IgM monoclonal anti-myelin-associated glycoprotein-associated demyelinating polyneuropathy; Guillain-Barré syndrome; chronic inflammatory demyelinating polyneuropathy; multifocal motor neuropathy with or without GM1 antibodies; multiple sclerosis; inflammatory myopathies; stiff-man syndrome; autoimmune neuromyotonia; paraneoplastic neuronopathies and cerebellar degeneration; and neurological diseases associated with systemic autoimmune conditions, vasculitis, or viral infections. The events that lead to these autoimmune diseases are not clear but the following sequential steps are critical: (a) the breaking of tolerance, a process in which cytokines, molecular mimicry, or superantigens may play a role in rendering previously anergic T cells to recognize neural autoantigens; (b) antigen recognition by the T-cell receptor complex and processing of the antigen via the major histocompatibility complex class I or II; (c) costimulatory factors especially B7 and B7-binding proteins (CD28, CTLA-4) and intercellular adhesion molecule (ICAM)-1 and its leukocyte function-associated (LFA)-1 ligand; (d) traffic of the activated T cells across the blood-brain or blood-nerve barrier via a series of adhesion molecules that include selectins, leukocyte integrins (LFA-1, Mac-1, very late activating antigen [VLA]-4) and their counterreceptors (ICAM-1, vascular cell adhesion molecule [VCAM]) on the endothelial cells; and (e) tissue injury when the activated T cells, macrophages, or specific autoantibodies find their antigenic targets on glial cells, myelin, axon, calcium channels, or muscle. In designing specific immunotherapy, the main players involved in every step of the immune response need to be considered. Targets for specific therapy in neurological diseases include agents that (a) interfere or compete with antigen recognition or stimulation, (b) inhibit costimulatory signals or cytokines, (c) inhibit the traffic of the activated cells to tissues, and (d) intervene at the antigen recognition sites in the targeted organ. The various immunomodulating procedures and immunosuppressive drugs currently used for nonselective neuroimmunotherapy are discussed in the context of their interference with the above-described immune mediators.