Antibody-mediated remyelination operates through mechanism independent of immunomodulation

Результати ретроспективного аналізу застосування нормального внутрішньовенного імуноглобуліну людини у високій дозі для лікування імунозалежної енцефалопатії з клінічною картиною розладів аутистичного спектра в дітей з генетичним дефіцитом фолатного циклу

Актуальність. Раніше неодноразово повідомлялося про ефективність внутрішньовенної імуноглобулінотерапії в деяких дітей з розладами аутистичного спектра (РАС) без уточнення критеріїв відбору потенційних респондентів на імунотерапію. Мета: оцінити ефективність і безпечність 6-місячного курсу високодозової імуноглобулінотерапії при імунозалежній енцефалопатії з клінічною картиною РАС у дітей з генетичним дефіцитом фолатного циклу (ГДФЦ). Матеріали та методи. Досліджувану групу (ДГ) ретроспективного аналізу становили 225 дітей віком від 2 до 9 років із РАС, асоційованим із ГДФЦ, які отримували імуноглобулін внутрішньовенно в дозі 2 г/кг/міс протягом 6 місяців. До контрольної групи (КГ) увійшли діти з РАС, асоційованим із ГДФЦ, з аналогічним розподілом за віком і статтю, які отримували лише немедикаментозну реабілітаційну підтримку. Методом полімеразної ланцюгової реакції з рестрикцією виявляли такі патогенні поліморфізми, як MTHFR 677 C>T, MTHFR 1298 A>C, MTRR A>G і MTR A>G у різних комбінаціях. Динаміку психіатричних симптомів оцінювали за шкалою Aberrant Behavior Checklist (ABC). Результати. Вірогідне покращення за шкалою ABC було досягнуто в 199 із 225 дітей ДГ (88% випадків; p < 0,05; Z < Z0,05). Паралельно відзначали позитивну динаміку інших клінічних проявів фенотипу ГДФЦ: PANS/PITANDS/PANDAS (у 27 із 32 % випадків; p < 0,05; Z < Z0,05), епілепсії (у 33 із 43% випадків; p < 0,05; Z < Z0,05) та шлунково-кишкового синдрому (у 69 із 82 % випадків; p < 0,05; Z< Z0,05). Позитивної динаміки з боку симптомів ураження пірамідного та мозочкового трактів зареєстровано не було (p > 0,05; Z > Z0,05). Досягнуто зниження загального герпесвірусного навантаження та збільшення абсолютної кількості природних кілерів (NK) у периферичній крові (p<0,05; Z < Z0,05). Майже повне зникнення МР-симптомів лейкоенцефалопатії спостерігалося в 69 із 88 % випадків у ДГ (p < 0,05; Z< Z0,05). Висновки. Внутрішньовенний імуноглобулін у високій дозі справляє комплексний полімодальний позитивний вплив на прояви ГДФЦ, включаючи РАС, екстрапірамідні порушення, обсесивно-компульсивний синдром, епілептиформну активність кори головного мозку, імунозапальне ураження кишечника, дефіцит NK-клітин і лейкоенцефалопатію.

IgM Natural Autoantibodies in Physiology and the Treatment of Disease

Antibodies are vital components of the adaptive immune system for the recognition and response to foreign antigens. However, some antibodies recognize self-antigens in healthy individuals. These autoreactive antibodies may modulate innate immune functions. IgM natural autoantibodies (IgM-NAAs) are a class of primarily polyreactive immunoglobulins encoded by germline V-gene segments which exhibit low affinity but broad specificity to both foreign and self-antigens. Historically, these autoantibodies were closely associated with autoimmune disease. Nevertheless, not all human autoantibodies are pathogenic and compelling evidence indicates that IgM-NAAs may exert a spectrum of effects from injurious to protective depending upon cellular and molecular context. In this chapter, we review the current state of knowledge regarding the potential physiological and therapeutic roles of IgM-NAAs in different disease conditions such as atherosclerosis, cancer, and autoimmune disease. We also describe the discovery of two reparative IgM-NAAs by our laboratory and delineate their proposed mechanisms of action in central nervous system (CNS) disease.

A comparison of human natural monoclonal antibodies and aptamer conjugates for promotion of CNS remyelination: where are we now and what comes next?

INTRODUCTION

Multiple sclerosis (MS) is a chronic and progressive inflammatory demyelinating disease of the human central nervous system (CNS) and is the most common disabling neurological condition in young adults, resulting in severe neurological defects. No curative or long-term progression-inhibiting therapy has yet been developed. However, recent investigation has revealed potential strategies that do not merely modulate potentially pathogenic autoimmune responses, but stimulate remyelination within CNS lesions.

AREAS COVERED

We discuss the history and development of natural human IgM-isotype immunoglobulins (HIgMs) and recently-identified aptamer-conjugates that have been shown to enhance endogenous myelin repair in animal models of demyelination by acting on myelin-producing oligodendrocytes (OLs) or oligodendrocyte progenitor cells (OPCs) within CNS lesions. We also discuss future development aims and applications for these important novel technologies.

EXPERT OPINION

Aptamer conjugate Myaptavin-3064 and recombinant human IgM-isotype antibody rHIgM22 regenerate CNS myelin, thereby reducing axonal degeneration and offering the potential of recovery from MS relapses, reversal of disability and prevention of disease progression. Advancement of these technologies into the clinic for MS treatment is therefore a top priority. It remains unclear to what extent the therapeutic modalities of remyelinating antibodies and aptamers may synergize with other currently-approved therapies to yield enhanced therapeutic effects.

Progressive multiple sclerosis: from pathogenic mechanisms to treatment

During the past decades, better understanding of relapsing-remitting multiple sclerosis disease mechanisms have led to the development of several disease-modifying therapies, reducing relapse rates and severity, through immune system modulation or suppression. In contrast, current therapeutic options for progressive multiple sclerosis remain comparatively disappointing and challenging. One possible explanation is a lack of understanding of pathogenic mechanisms driving progressive multiple sclerosis. Furthermore, diagnosis is usually retrospective, based on history of gradual neurological worsening with or without occasional relapses, minor remissions or plateaus. In addition, imaging methods as well as biomarkers are not well established. Magnetic resonance imaging studies in progressive multiple sclerosis show decreased blood-brain barrier permeability, probably reflecting compartmentalization of inflammation behind a relatively intact blood-brain barrier. Interestingly, a spectrum of inflammatory cell types infiltrates the leptomeninges during subpial cortical demyelination. Indeed, recent magnetic resonance imaging studies show leptomeningeal contrast enhancement in subjects with progressive multiple sclerosis, possibly representing an in vivo marker of inflammation associated to subpial demyelination. Treatments for progressive disease depend on underlying mechanisms causing central nervous system damage. Immunity sheltered behind an intact blood-brain barrier, energy failure, and membrane channel dysfunction may be key processes in progressive disease. Interfering with these mechanisms may provide neuroprotection and prevent disability progression, while potentially restoring activity and conduction along damaged axons by repairing myelin. Although most previous clinical trials in progressive multiple sclerosis have yielded disappointing results, important lessons have been learnt, improving the design of novel ones. This review discusses mechanisms involved in progressive multiple sclerosis, correlations between histopathology and magnetic resonance imaging studies, along with possible new therapeutic approaches.

Role of Oligodendrocyte Dysfunction in Demyelination, Remyelination and Neurodegeneration in Multiple Sclerosis

Oligodendrocytes (OLs) are the myelinating cells of the central nervous system (CNS) during development and throughout adulthood. They result from a complex and well controlled process of activation, proliferation, migration and differentiation of oligodendrocyte progenitor cells (OPCs) from the germinative niches of the CNS. In multiple sclerosis (MS), the complex pathological process produces dysfunction and apoptosis of OLs leading to demyelination and neurodegeneration. This review attempts to describe the patterns of demyelination in MS, the steps involved in oligodendrogenesis and myelination in healthy CNS, the different pathways leading to OLs and myelin loss in MS, as well as principles involved in restoration of myelin sheaths. Environmental factors and their impact on OLs and pathological mechanisms of MS are also discussed. Finally, we will present evidence about the potential therapeutic targets in re-myelination processes that can be accessed in order to develop regenerative therapies for MS.

Recent Advances in Monoclonal Antibody Therapies for Multiple Sclerosis

INTRODUCTION

Multiple sclerosis (MS) is the most common chronic inflammatory, demyelinating disease of the CNS and results in neurological disability. Existing immunomodulatory and immunosuppressive approaches lower the number of relapses but do not cure or reverse existing deficits nor improve long-term disability in MS patients.

AREAS COVERED

Monogenic antibodies were described as treatment options for MS, however the immunogenicity of mouse antibodies hampered the efficacy of potential therapeutics in humans. Availability of improved antibody production technologies resulted in a paradigm shift in MS treatment strategies. In this review, an overview of immunotherapies for MS that use conventional monoclonal antibodies reactive to immune system and their properties and mechanisms of action will be discussed, including recent advances in MS therapeutics and highlight natural autoantibodies (NAbs) that directly target CNS cells.

EXPERT OPINION

Recent challenges for MS therapy are the identification of relevant molecular and cellular targets, time frame of treatment, and antibody toxicity profiles to identify safe treatment options for MS patients. The application of monoclonal antibody therapies with better biological efficacy associated with minimum side effects possesses huge clinical potential. Advances in monoclonal antibody technologies that directly target cells of nervous system may promote the CNS regeneration field from bench to bedside.

Intravenous immunoglobulin for the treatment of Alzheimer's disease: current evidence and considerations

Alzheimer's disease (AD) is a devastating neurodegenerative form of dementia with increasing incidence rates in most countries. AD is characterized by amyloid plaques and neurofibrillary tangles in the brains of AD individuals accompanied by global neuronal loss. The peptide amyloid-β (Aβ) aggregates to amyloid plaques in AD brains. As a result, many therapeutic approaches target Aβ. Human plasma and the plasma product intravenous immunoglobulin (IVIG) contain naturally-occurring anti-Aβ antibodies (Nabs-Aβ) that appear to reduce risks of developing AD. IVIG sequesters Aβ and thus interferes with AD progression. This study reviews the role of different Aβ species, Nabs-Aβ, preclinical data, and clinical studies of IVIG as potential AD treatments. The focus of this study is the outcomes of a recent Gammaglobulin Alzheimer's Partnership Phase III trial that did not reach primary endpoints, as well as efforts to compare IVIG with current anti-Aβ monoclonals such as bapineuzumab, solanezumab, and BIIB037. Moreover, this study critically examines current market and ethical consequences of potential off-label uses of IVIG, limits in IVIG supply, and subsequent challenges.

Promoting remyelination in multiple sclerosis-recent advances

We review the current state of knowledge of remyelination in multiple sclerosis (MS), concentrating on advances in the understanding of the pathology and the regenerative response, and we summarise progress on the development of new therapies to enhance remyelination aimed at reducing progressive accumulation of disability in MS. We discuss key target pathways identified in experimental models, as although most identified targets have not yet progressed to the stage of being tested in human clinical trials, they may provide treatment strategies for demyelinating diseases in the future. Finally, we discuss some of the problems associated with testing this class of drugs, where they might fit into the therapeutic arsenal and the gaps in our knowledge.

Using magnetic resonance imaging in animal models to guide drug development in multiple sclerosis

Major advances are taking place in the development of therapeutics for multiple sclerosis (MS), with a move past traditional immunomodulatory/immunosuppressive therapies toward medications aimed at promoting remyelination or neuroprotection. With an increase in diversity of MS therapies comes the need to assess the effectiveness of such therapies. Magnetic resonance imaging (MRI) is one of the main tools used to evaluate the effectiveness of MS therapeutics in clinical trials. As all new therapeutics for MS are tested in animal models first, it is logical that MRI be incorporated into preclinical studies assessing therapeutics. Here, we review key papers showing how MR imaging has been combined with a range of animal models to evaluate potential therapeutics for MS. We also advise on how to maximize the potential for incorporating MRI into preclinical studies evaluating possible therapeutics for MS, which should improve the likelihood of discovering new medications for the condition.

Immunization with a peptide of Semliki Forest virus promotes remyelination in experimental autoimmune encephalomyelitis

Remyelination is one of the elusive topics in treatment of multiple sclerosis (MS). Our previous studies have shown that Semliki Forest virus (SFV)-infected δ-knock-out (KO) mice did not exhibit the extensive remyelination, seen in wild type (WT) B6 mice, after viral clearance and demyelination. The Remyelination in SFV-infected WT mice started on day 15 and was completed by day 35 post-infection (pi), whereas the KO mice remained partially demyelinated through day 42 pi. Treatment with E2 peptide2 in incomplete Freund's adjuvant (IFA), resulted in higher antibody production and earlier remyelination in SFV-infected KO (day 28 pi), than WT mice. This finding suggested that anti-E2 peptide2 antibody could play a part in remyelination. In the current study, the effect of E2 peptide2 treatment was evaluated in the experimental autoimmune encephalomyelitis (EAE) model. Mice with established EAE were treated with E2 peptide2 in IFA to develop antibody. Treated EAE mice made significantly higher anti-E2 peptide2 antibody than untreated EAE group. Average clinical disease scores were significantly lower in peptide treated compared to untreated EAE mice. Furthermore, histopathological and immunohistochemical studies demonstrated increased remyelinating areas and higher number of activated oligodendrocytes and astrocytes, in treated compared to untreated EAE groups. Moreover, the anti-E2 peptide2 antibody showed higher binding to the myelinated areas of treated than untreated EAE mice. We conclude that treatment with, or antibody to, SFV E2 peptide2 triggers some mechanism that promotes remyelination.

Enhancing remyelination in disease--can we wrap it up?

Demyelinating disorders of the central nervous system are among the most crippling neurological diseases affecting patients at various stages of life. In the most prominent demyelinating disease, multiple sclerosis, the regeneration of myelin sheaths often fails due to a default of the resident stem/precursor cells (oligodendrocyte precursor cells) to differentiate into mature myelin forming cells. Significant advances have been made in our understanding of the molecular and cellular processes involved in remyelination. Furthermore, important insight has been gained from studies investigating the interaction of stem/precursor cells with the distinct environment of demyelinating lesions. These suggest that successful regeneration depends on a signalling environment conducive to remyelination, which is provided in the context of acute inflammation. However, multiple sclerosis lesions also contain factors that inhibit the differentiation of oligodendrocyte precursor cells into myelinating oligodendrocytes. The pattern by which remyelination inducers and inhibitors are expressed in multiple sclerosis lesions may determine a window of opportunity during which oligodendrocyte precursor cells can successfully differentiate. As the first molecules aiming at promoting remyelination are about to enter clinical trials, this review critically evaluates recent advances in our understanding of the biology of oligodendrocyte precursor cells and of the stage-dependent molecular pathology of multiple sclerosis lesions relevant to the regeneration of myelin sheaths. We propose a model that may help to provide cues for how remyelination can be therapeutically enhanced in clinical disease.

Role of γδ T cells in antibody production and recovery from SFV demyelinating disease

Semliki Forest Virus (SFV) encephalomyelitis has been used to study the pathogenesis of virus-induced demyelination and serves as a model for multiple sclerosis. SFV-infection of mice invariably leads to clinical weakness accompanied by CNS inflammation, viral clearance and primary demyelination by day 21 postinfection (pi), followed by recovery and remyelination by day 35 pi. We have applied this model to the examination of the effects of γδ T cells in antibody production and the pathogenesis of demyelinating lesions. SFV-infection of γδ T cell KO mice resulted in more severe clinical signs than in wild type (WT) B6 mice. SFV-infected WT and γδ KO mice both cleared virus by day 10 pi and inflammation was comparable. Demyelination also appeared to be similar in both groups except that KO mice did not exhibit extensive remyelination which was seen in WT mice by day 21. SFV-infected WT mice showed widespread remyelination by day 35 pi, whereas KO mice still displayed some demyelination through day 42 pi. Both WT and KO mice developed serum antibodies to SFV. However, the reactivity of WT sera with the SFV epitope, E2 T(h) peptide₂, was significantly higher than in KO sera. Immunization with E2 T(h) peptide₂ resulted in elevated antibody production to this peptide (p<0.05) and earlier remyelination (day 28 pi) in KO mice. Thus, our study has shown for the first time that immunization of SFV-infected γδ T cell KO mice with a viral peptide, E2 T(h) peptide₂ led to enhanced recovery and repair of the CNS.

Method of identifying natural antibodies for remyelination

INTRODUCTION

Natural autoantibodies are part of the normal human immunoglobulin repertoire. These antibodies react to self-antigens, are usually polyreactive with relatively low affinity, and typically are of the IgM isotype. Natural IgMs in mice that stimulated remyelination in central nervous system (CNS) demyelinating disease all shared the characteristics of binding to the surface of live oligodendrocytes and myelinated tracts in living slices of CNS tissue.

METHODS

A screen for human IgMs with similar character resulted in two human natural antibodies, which when injected peripherally into animal models of demyelination induced remyelination. A recombinant human IgM (rHIgM22) that also promoted remyelination in vivo was constructed.

RESULTS

Very small doses of this IgM are required for the promotion of remyelination (EC50 is 460 ng per 20-g mouse). It is clear that after peripheral delivery, rHIgM22 enters the CNS and accumulates in CNS lesions. rHIgM22 was tracked in living mice using ferritin-labeled antihuman mu chain antibodies visualized by magnetic resonance imaging and traditional immunocytochemistry. Although the exact antigen recognized by rHIgM22 is not known, all mouse IgMs that promote remyelination bind to myelin membrane lipids, suggesting the antigen for rHIgM22 is similar.

CONCLUSIONS

We propose that the IgMs bind to CNS cells and reorganize the membrane, initiating a signal that results in oligodendrocyte proliferation and/or protection with an end result of increased myelin. Recombinant natural human antibodies are potentially important therapeutic molecules that may modulate a wide spectrum of human disease.

Invited article: human natural autoantibodies in the treatment of neurologic disease

Naturally occurring autoantibodies are molecules that are part of the normal immunoglobulin repertoire. This review focuses on three distinct groups of human monoclonal antibodies (mAb). These are human natural autoantibodies that, when injected into an animal model of human disease, stimulate remyelination in CNS demyelinating diseases, protect neurons and extend neuronal processes in CNS axonal disorders, and activate immune dendritic cells to produce cytotoxic T cells to clear metastatic tumors. Natural autoantibodies react to self antigens and are of relatively low affinity. They are derived from germline immunoglobulin genes and are usually polyreactive. Our experiments demonstrated CNS entry by autoradiography of labeled mAb and by MRI. Remyelinating mAb rHIgM22 clusters beta-integrin and mouse mAb O4 recognizes sulfatide. Neuronal outgrowth mAbs sHIgM42 and sHIgM12 appear to target carbohydrates on the surface of neurons. The mAb sHIgM12 (B7-DC-Xab) also is promising as therapeutic against metastatic tumors. It functions by binding and cross-linking the antigen B7-DC on dendritic cells, inducing tumor-specific cytotoxic T cells. All these mAbs activate a transient increase in intracellular calcium, signal via NFkappab, and prevent apoptosis. The mAbs engage downstream signaling events that induce the primary function of the cell (that is, remyelination for oligodendrocytes, axonal preservation and neurite extension for neurons, or antigen presentation for dendritic cells). Natural human auto mAbs are a potentially important therapeutic technique in combating a wide spectrum of disease processes.

Protective autoimmunity in the nervous system

The immune system can play both detrimental and beneficial roles in the nervous system. Multiple arms of the immune system, including T cells, B cells, NK cells, mast cells, macrophages, dendritic cells, microglia, antibodies, complement and cytokines participate in limiting damage to the nervous system during toxic, ischemic, hemorrhagic, infective, degenerative, metabolic and immune-mediated insults and also assist in the process of repair after injury has occurred. Immune cells have been shown to produce neurotrophic growth factors and interact with neurons and glial cells to preserve them from injury and stimulate growth and repair. The immune system also appears to participate in proliferation of neural progenitor stem cells and their migration to sites of injury. Neural stem cells can also modify the immune response in the central and peripheral nervous system to enhance neuroprotective effects. Evidence for protective and reparative functions of the immune system has been found in diverse neurologic diseases including traumatic injury, ischemic and hemorrhagic stroke, multiple sclerosis, infection, and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis). Existing therapies including glatiramer acetate, interferon-beta and immunoglobulin have been shown to augment the protective and regenerative aspects of the immune system in humans, and other experimental interventions such as vaccination, minocycline, antibodies and neural stem cells, have shown promise in animal models of disease. The beneficent aspects of the immune response in the nervous system are beginning to be appreciated and their potential as pharmacologic targets in neurologic disease is being explored.

Autoantibodies and neurodegeneration in multiple sclerosis

Neurodegeneration develops in association with inflammation and demyelination in multiple sclerosis. Available data suggest that the progressive neuroaxonal loss begins in the earliest stages of the disease and underlies the accumulation of clinical disability. The loss of neurons and their processes is driven by a complex molecular mechanism involving cellular and humoral immune histotoxicity, demyelination, reduced neurotrophic support, metabolic impairment, and altered intracellular processes. Here we survey available data concerning the role of autoreactive immunoglobulins in neurotoxicity. A better understanding of molecular pathways leading to immune-mediated neurodegeneration may have key importance in the successful treatment of the disease.

Basic principles of intravenous immunoglobulin (IVIg) treatment

The original rationale for the therapeutic application of immunoglobulins was prevention and treatment of infectious diseases. With the description of agammaglobulinemia, substitution therapy became the primary indication for the use of immunoglobulins. Limitations and side effects of the intramuscular administration of immunoglobulins led to the development of preparations for intravenous use (IVIg). In the early 1980s an immunomodulatory effect of IVIg was described. Since then, the efficacy of IVIg has been established in controlled trials for diseases like idiopathic thrombocytopenic purpura, Kawasaki disease, Guillain-Barré syndrome, dermatomyositis, and many others. There is a large body of evidence that IVIg can modulate an immune reaction at the level of T cells, B cells, and macrophages, interferes with antibody production and degradation, modulates the complement cascade, and has effects on the cytokine network. However, the precise mechanism of action is not yet clear.

Effectors of demyelination and remyelination in the CNS: implications for multiple sclerosis

Most of the research on multiple sclerosis (MS) has focused on the early events that trigger demyelination and subsequent remyelination. Less attention has been given to the factors that directly mediate the demyelination that is the hallmark of the disease. Effector cells or molecules are those factors directly responsible for mediating the damage in the disease. Similarly, there are effector molecules that are critical for remyelination in the central nervous system (CNS). By understanding those effector molecules in demyelination and remyelination that directly influence the pathologic process, we should be able to generate specific therapies with the greatest potential for benefiting MS patients. This review focuses on effector cells and molecules that are critical for demyelination and remyelination in MS but also in experimental models of the disease including experimental autoimmune encephalomyelitis (EAE), virus-induced models of demyelination (Theiler's virus, murine hepatitis virus), and toxic models of demyelination (lysolecithin, ethidium bromide, and cuprizone). These are models in which the effector molecules for demyelination and remyelination have been most precisely evaluated.

Future of multiple sclerosis therapy: combining antigen-specific immunotherapy with strategies to promote myelin repair

Persistent CNS inflammation and the failure of myelin repair during multiple sclerosis (MS) trigger a progressive deterioration in neurophysiological function and permanent clinical debilitation. Current treatment consists of immunosuppressive therapies targeted against the immune response, which have only been moderately successful in ameliorating disease relapses and have little or no benefit in slowing disease progression or enhancing remyelination. Recent breakthroughs have revealed new targets and more selective techniques for inhibiting autoreactive T-cell responses and promoting lesion repair in animal models of MS. In light of these new findings and the limitations of current treatments, the authors hypothesize that the future of MS therapy will progress towards the development of a combinatorial therapeutic strategy that consists of specific tolerance of autoreactive T cells, myelin repair and axonal protection.

The neuroprotective role of inflammation in nervous system Injuries

The contribution of inflammation to the pathogenesis of several nervous system disorders has long been established. Other observations, however, indicate that both inflammatory cells and mediators may also have beneficial functions, assisting in repair and recovery processes. There is compelling evidence to indicate that in the injured nervous system, as in other tissues, macrophages are needed at an early stage after injury in order for healing to take place. Likewise, activated T cells of a particular specificity can reduce the spread of damage. This neuroprotective effect of T cells may be caused, at least in part, by the production of neurotrophic factors such as neurotrophin-3 or brain-derived neurotrophic factor. Interestingly, recent findings indicate that immune cells are able to produce a variety of neurotrophic factors which promote neuronal survival and may also mediate anti-inflammatory effects. Numerous cytokines are induced after nervous system injuries. Some cytokines, such as TNF-alpha, IL-1 and IFN-gamma, are well known for their promotion of inflammatory responses. However, these cytokines also have immunosuppressive functions and their subsequent expression also assists in repair or recovery processes, suggesting a dual role for some pro-inflammatory cytokines. This should be clarified, as it may be crucial in the design of therapeutic strategies to target specific cytokine(s). Finally, there is a growing body of evidence to show that autoreactive IgM antibodies may constitute an endogenous system of tissue repair, and therefore prove of value as a therapeutic strategy. Available evidence would appear to indicate that the inflammatory response observed in several neurological conditions is more complex than previously thought. Therefore, the design of more effective therapies depends on a clear delineation of the beneficial and detrimental effects of inflammation.

A human antibody that promotes remyelination enters the CNS and decreases lesion load as detected by T2‐weighted spinal cord MRI in a virus‐induced murine model of MS

The human monoclonal antibody rHIgM22 enhances remyelination following spinal cord demyelination in a virus-induced murine model of multiple sclerosis. Using three-dimensional T2-weighted in vivo spinal cord magnetic resonance imaging (MRI), we have therefore assessed the extent of spinal cord demyelination, before and after 5 weeks of treatment with rHIgM22, to determine whether antibody enhanced remyelination can be detected by MRI. A significant decrease was seen in T2 high signal lesion volume following antibody treatment. Histologic examination of the spinal cord tissue reveals that this decrease in lesion volume correlates with antibody promoted remyelination. To show that rHIgM22 enters the spinal cord and colocalizes with demyelinating lesions, we used ultrasmall superparamagnetic iron oxide particle (USPIO)-labeled antibodies. This may be considered as additional evidence to the hypothesis that rHIgM22 promotes remyelination by local effects in the lesions, likely by binding to CNS cells. The reduction in high signal T2-weighted lesion volume may be an important outcome measure in future clinical trials in humans.

How the brain repairs itself: new therapeutic strategies in inflammatory and degenerative CNS disorders

In the early 20th century, seminal work by Tello and Cajal showed that the CNS has the ability to regenerate itself after injury. In the most recent years, this pivotal observation has been rejuvenated by detailed in vitro and in vivo evidence supporting the idea of an innate self-maintenance programme to sustain brain homoeostasis and repair. These observations support the idea that chronic inflammatory and degenerative disorders of the brain might result from defective repair mechanisms rather than uncontrollable pathogenetic events. Investigation of the molecular and cellular events sustaining intrinsic brain-repair mechanisms and a better understanding of why they fail over time in chronic disorders might, therefore, provide an attractive conceptual framework within which to develop new and efficacious therapies for neurological diseases.