A role for humoral mechanisms in the pathogenesis of Devic's neuromyelitis optica

The CSF Levels of Neutrophil-Related Chemokines in Patients with Neuromyelitis Optica

Pathologic findings showed that neutrophils played an important role in the pathogenesis of NMO. This study aims to investigate the CSF levels of neutrophil‐related chemokines in NMO. CXCL1, CXCL5, and CXCL7 were measured in 95 patients with NMO, 15 patients with MS, 18 patients with GFAP astrocytopathy, and 16 controls. The CSF level of CXCL1, CXCL5, and CXCL7 was significantly elevated in the NMO group but not correlated with the patient clinical severity. Besides, the CSF CXCL1, CXCL5, and CXCL7 could act as biomarkers to distinguish NMO from MS with good reliability, especially the CXCL7.

Inflammation-related plasma and CSF biomarkers for multiple sclerosis

Effective biomarkers for multiple sclerosis diagnosis, assessment of prognosis, and treatment responses, in particular those measurable in blood, are largely lacking. We have investigated a broad set of protein biomarkers in cerebrospinal fluid (CSF) and plasma using a highly sensitive proteomic immunoassay. Cases from two independent cohorts were compared with healthy controls and patients with other neurological diseases. We identified and replicated 10 cerebrospinal fluid proteins including IL-12B, CD5, MIP-1a, and CXCL9 which had a combined diagnostic efficacy similar to immunoglobulin G (IgG) index and neurofilament light chain (area under the curve [AUC] = 0.95). Two plasma proteins, OSM and HGF, were also associated with multiple sclerosis in comparison to healthy controls. Sensitivity and specificity of combined CSF and plasma markers for multiple sclerosis were 85.7% and 73.5%, respectively. In the discovery cohort, eotaxin-1 (CCL11) was associated with disease duration particularly in patients who had secondary progressive disease (P _CSF < 4 × 10^-5, P _plasma < 4 × 10^-5), and plasma CCL20 was associated with disease severity (P = 4 × 10^-5), although both require further validation. Treatment with natalizumab and fingolimod showed different compartmental changes in protein levels of CSF and peripheral blood, respectively, including many disease-associated markers (e.g., IL12B, CD5) showing potential application for both diagnosing disease and monitoring treatment efficacy. We report a number of multiple sclerosis biomarkers in CSF and plasma for early disease detection and potential indicators for disease activity. Of particular importance is the set of markers discovered in blood, where validated biomarkers are lacking.

Spinal Cord Involvement in MS and Other Demyelinating Diseases

Diagnostic accuracy is poor in demyelinating myelopathies, and therefore a challenge for neurologists in daily practice, mainly because of the multiple underlying pathophysiologic mechanisms involved in each subtype. A systematic diagnostic approach combining data from the clinical setting and presentation with magnetic resonance imaging (MRI) lesion patterns, cerebrospinal fluid (CSF) findings, and autoantibody markers can help to better distinguish between subtypes. In this review, we describe spinal cord involvement, and summarize clinical findings, MRI and diagnostic characteristics, as well as treatment options and prognostic implications in different demyelinating disorders including: multiple sclerosis (MS), neuromyelitis optica spectrum disorder, acute disseminated encephalomyelitis, anti-myelin oligodendrocyte glycoprotein antibody-associated disease, and glial fibrillary acidic protein IgG-associated disease. Thorough understanding of individual case etiology is crucial, not only to provide valuable prognostic information on whether the disorder is likely to relapse, but also to make therapeutic decision-making easier and reduce treatment failures which may lead to new relapses and long-term disability. Identifying patients with monophasic disease who may only require acute management, symptomatic treatment, and subsequent rehabilitation, rather than immunosuppression, is also important.

Targeting IL-6 receptor in the treatment of neuromyelitis optica spectrum: a review of emerging treatment options

Introduction: Recent research has shown that IL-6 receptor (IL-6 R) inhibitors like tocilizumab and satralizumab are effective in reducing the relapse rate in patients with NMOSD.Areas covered: This review article explores current concepts in NMOSD management and focuses on IL-6 R as a therapeutic target. The authors delve into the biological and immunological role of IL-6 in the pathogenesis of NMOSD. Further, the authors summarize the most recent findings on the use of anti-IL-6 R monoclonal antibodies, tocilizumab and satralizumab, in the treatment of NMOSD.Expert opinion: A better understanding of the role of cytokines in NMOSD may provide the neurologist with novel therapies for this disease. IL-6 R appears to be a central hub to NMOSD pathogenesis and a relevant therapeutic target.

Changes in mitochondrial function in patients with neuromyelitis optica; correlations with motor and cognitive disabilities

Background

Neuromyelitis Optica (NMO) is an inflammatory demyelinating disease that mainly affects optic nerves and spinal cord. Besides, loss of motor and cognitive function has been reported as important symptoms of disease.

Objective

Here we investigated the mitochondrial dysfunction and metabolic alterations in NMO patients and evaluate their correlation with disease progress, disability and cognitive impairment.

Methods

The individuals (12 controls and 12 NMO) were assessed for disease severity by expanded disease status scale (EDSS), cognitive function via symbol digit modalities test (SDMT) and fine motor disability by 9-hole peg test (9-HPT). We have measured Sirtuin 1 (SIRT1), SIRT3, mitochondrial complex I, complex IV, aconitase and α-ketoglutarate dehydrogenase (α-KGD) activity in peripheral blood mononuclear cells (PBMCs). Furthermore, SIRT1, pyruvate, lactate and cytochrome c (Cyt c) were determined in plasma.

Results

Our results exhibited increased 9-HPT time in NMO patients. 9-HPT results correlated with EDSS; and SDMT negatively correlated with disease duration and number of attacks in patients. Investigation of PBMCs of NMO patients exhibited a decrease of mitochondrial complex I and IV activity that was significant for complex IV. Besides, complex I activity was negatively correlated with 9-HPT time in NMO group. In the plasma samples, a correlation between pyruvate to lactate ratio and EDSS in NMO patients was found and a negative correlation between Cyt c concentration and SDMT was detected.

Conclusion

Our data support the hypothesis that mitochondrial dysfunction occurred in the CNS and the peripheral blood may contribute to disease progress, disability level and the cognitive impairment in NMO patients.

Emerging therapeutic targets for neuromyelitis optica spectrum disorder

Introduction: Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory demyelinating disease of the central nervous system affecting primarily the spinal cord and optic nerves. Most NMOSD patients are seropositive for immunoglobulin G autoantibodies against astrocyte water channel aquaporin-4, called AQP4-IgG, which cause astrocyte injury leading to demyelination and neurological impairment. Current therapy for AQP4-IgG seropositive NMOSD includes immunosuppression, B cell depletion, and plasma exchange. Newer therapies target complement, CD19 and IL-6 receptors.Areas covered: This review covers early-stage pre-clinical therapeutic approaches for seropositive NMOSD. Targets include pathogenic AQP4-IgG autoantibodies and their binding to AQP4, complement-dependent and cell-mediated cytotoxicity, blood-brain barrier, remyelination and immune effector and regulatory cells, with treatment modalities including small molecules, biologics, and cells.Expert opinion: Though newer NMOSD therapies appear to have increased efficacy in reducing relapse rate and neurological deficit, increasingly targeted therapies could benefit NMOSD patients with ongoing relapses and could potentially be superior in efficacy and safety. Of the various early-stage therapeutic approaches, IgG inactivating enzymes, aquaporumab blocking antibodies, drugs targeting early components of the classical complement system, complement regulator-targeted drugs, and Fc-based multimers are of interest. Curative strategies, perhaps involving AQP4 tolerization, remain intriguing future possibilities.

Neuromyelitis optica: a pilot study of clinical presentation and status of serological biomarker AQP4 among patients admitted to a tertiary centre in NCNS, Sudan

Background

Neuromyelitis optica (NMO) is a demyelinating disease primarily affecting the optic nerves and spinal cord. It is distinguished from other demyelinating conditions by the presence of AQP4-IgG and serum aquaporin 4 (AQP4), found mainly in the blood–brain barrier. This descriptive study was conducted from January 2015 to June 2018 at the National Center for Neurological Sciences (NCNS) in Khartoum, Sudan. All participants were Sudanese patients diagnosed with NMO. In our study the selection of cases was based on Dean Wingerchuk diagnostic criteria (2006), which states that the diagnosis of NMO should meet two absolute criteria and two supportive criteria. The absolute criteria are myelitis and optic neuritis, whereas supportive criteria include radiological findings obtained from brain and spinal cord MRI. Furthermore, AQP4-IgG levels were measured from cerebrospinal fluid (CSF) and serum using immunofluorescence. Data were collected by a pre-designed questionnaire and analyzed using SPSS version 17. A p value < 0.05 was considered statistically significant.

Results

A total of 31 patients were enrolled in this study [6 male (19.4%) and 25 female (80.6%)]. The mean age was 38 ± 12.8 years. Motor and visual difficulties were the initial symptoms and occurred in 21 (67.7%) and 10 (32.3%) patients, respectively. Fundoscopy confirmed optic atrophy in 22 (71.0%) patients. The course of the disease revealed one relapse in 21 patients (67.7%). Seropositive AQP4-IgG were seen in 23 patients (79.31%). There was a significant correlation between AQP4 and response to treatment (p ≤ 0.038). The correlation between serum AQP4-IgG, showed that, complete improvement was detected in 2 patients (6.9%) one of them was positive and the other was negative, 20 (69.0%) patients presented with some disability, among them 18 (62.1%) were positive and 2 (6.9%) were negative, while 7 patients showed no improvement (24.1%) 4 out of them were positive (13.8%) and 3 were negative (10.3%).

Conclusion

At the initial presentation of NMO, longitudinal myelitis was observed more frequently than optic neuritis. More than two third of the patients showed strong seropositivity for serum AQP4. Most seropositive patients showed a good response to treatment but with residual disabilities.

Lower serum interleukin-22 and interleukin-35 levels are associated with disease status in neuromyelitis optica spectrum disorders

AIMS

The exact pathogenesis of neuromyelitis optica spectrum disorder (NMOSD) remains unclear. A variety of cytokines are involved, but few studies have been performed to explore the novel roles of interleukin-22 (IL-22) and interleukin-35 (IL-35) in NMOSD. Therefore, this study was designed to investigate serum levels of IL-22 and IL-35, and their correlations with clinical and laboratory characteristics in NMOSD.

METHODS

We performed a cross-section study, 18 patients with acute NMOSD, 23 patients with remission NMOSD, and 36 healthy controls were consecutively enrolled. Serum levels of IL-22 and IL-35 were measured by enzyme-linked immunosorbent assay (ELISA). The correlations between serum IL-22 and IL-35 levels and clinical and laboratory characteristics were evaluated by Spearman's rank or Pearson's correlation coefficient.

RESULTS

The serum levels of IL-22 and IL-35 were significantly lower in patients with acute NMOSD and remission NMOSD than in healthy controls (IL-22: 76.96 ± 13.62 pg/mL, 87.30 ± 12.79 pg/mL, and 94.02 ± 8.52 pg/mL, respectively, P < .0001; IL-35: 45.52 ± 7.04 pg/mL, 57.07 ± 7.68 pg/mL, and 60.05 ± 20.181 pg/mL, respectively, P < .0001). Serum levels of IL-35 were negatively correlated with EDSS scores and cerebrospinal fluid protein levels (r = -.5438, P = .0002 and r = -.3523, P = .0258, respectively) in all patients.

CONCLUSIONS

Lower serum levels of IL-22 and IL-35 are associated with disease status in NMOSD. Additionally, lower serum levels of IL-35 are associated with disease severity in NMOSD.

The history of neuromyelitis optica. Part 2: 'Spinal amaurosis', or how it all began

Neuromyelitis optica (NMO) was long considered a clinical variant of multiple sclerosis (MS). However, the discovery of a novel and pathogenic anti-astrocytic serum autoantibody targeting aquaporin-4 (termed NMO-IgG or AQP4-Ab), the most abundant water channel protein in the central nervous system, led to the recognition of NMO as a distinct disease entity in its own right and generated strong and persisting interest in the condition. NMO is now studied as a prototypic autoimmune disorder, which differs from MS in terms of immunopathogenesis, clinicoradiological presentation, optimum treatment, and prognosis. While the history of classic MS has been extensively studied, relatively little is known about the history of NMO. In Part 1 of this series we focused on the late 19th century, when the term 'neuromyelitis optica' was first coined, traced the term's origins and followed its meandering evolution throughout the 20th and into the 21st century. Here, in Part 2, we demonstrate that the peculiar concurrence of acute optic nerve and spinal cord affliction characteristic for NMO caught the attention of physicians much earlier than previously thought by re-presenting a number of very early cases of possible NMO that date back to the late 18th and early 19th century. In addition, we comprehensively discuss the pioneering concept of 'spinal amaurosis', which was introduced into the medical literature by ophthalmologists in the first half of the 19th century.

Low-Density Granulocytes Are a Novel Immunopathological Feature in Both Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorder

Objective: To investigate whether low-density granulocytes (LDGs) are an immunophenotypic feature of patients with multiple sclerosis (MS) or neuromyelitis optica spectrum disorder (NMOSD). Methods: Blood samples were collected from 20 patients with NMOSD and 17 patients with MS, as well as from 15 patients with Systemic Lupus Erythematosus (SLE) and 23 Healthy Donors (HD). We isolated peripheral blood mononuclear cells (PBMCs) with density gradient separation and stained the cells with antibodies against CD14, CD15, CD16, and CD45, and analyzed the cells by flow cytometry or imaging flow cytometry. We defined LDGs as CD14-CD15high and calculated their share in total PBMC leukocytes (CD45+) as well as the share of CD16hi LDGs. Clinical data on disease course, medication, and antibody status were obtained. Results: LDGs were significantly more common in MS and NMOSD than in HDs, comparable to SLE samples (median values HD 0.2%, MS 0.9%, NMOSD 2.1%, SLE 4.3%). 0/23 of the HDs, but 17/20 NMOSD and 11/17 MS samples as well as 13/15 SLE samples had at least 0.7 % LDGs. NMOSD patients without continuous immunosuppressive treatment had significantly more LDGs compared to their treated counterparts. LDG nuclear morphology ranged from segmented to rounded, suggesting a heterogeneity within the group. Conclusion: LDGs are a feature of the immunophenotype in some patients with MS and NMOSD.

A highly specific and sensitive nanoimmunosensor for the diagnosis of neuromyelitis optica spectrum disorders

A precise diagnosis for neuromyelitis optica spectrum disorders (NMOSD) is crucial to improve patients' prognostic, which requires highly specific and sensitive tests. The cell-based assay with a sensitivity of 76% and specificity of 100% is the most recommended test to detect anti-aquaporin-4 antibodies (AQP4-Ab). Here, we tested four AQP4 external loop peptides (AQP461-70, AQP4131-140, AQP4141-150, and AQP4201-210) with an atomic force microscopy nanoimmunosensor to develop a diagnostic assay. We obtained the highest reactivity with AQP461-70-nanoimunosensor. This assay was effective in detecting AQP4-Ab in sera of NMOSD patients with 100% specificity (95% CI 63.06-100), determined by the cut-off adhesion force value of 241.3 pN. NMOSD patients were successfully discriminated from a set of healthy volunteers, patients with multiple sclerosis, and AQP4-Ab-negative patients. AQP461-70 sensitivity was 81.25% (95% CI 56.50-99.43), slightly higher than with the CBA method. The results with the AQP461-70-nanoimmunosensor indicate that the differences between NMOSD seropositive and seronegative phenotypes are related to disease-specific epitopes. The absence of AQP4-Ab in sera of NMOSD AQP4-Ab-negative patients may be interpreted by assuming the existence of another potential AQP4 peptide sequence or non-AQP4 antigens as the antibody target.

Affinity-matured 'aquaporumab' anti-aquaporin-4 antibody for therapy of seropositive neuromyelitis optica spectrum disorders

Pathogenesis in seropositive neuromyelitis optica spectrum disorders (herein called NMO) involves binding of IgG1 autoantibodies to aquaporin-4 (AQP4) on astrocytes in the central nervous system, which initiates complement and cellular injury. We previously developed an antibody blocking approach for potential therapy of NMO in which an engineered, monoclonal, anti-AQP4 antibody lacking cytotoxicity effector functions (called aquaporumab) blocked binding of NMO autoantibodies to astrocyte AQP4 (Tradtrantip et al. Ann. Neurol. 71, 314-322, 2012). Here, a high-affinity aquaporumab, which was generated by affinity maturation using saturation mutagenesis, was shown to block cellular injury caused by NMO patient sera. Anti-AQP4 antibody rAb-53, a fully human antibody with effector function neutralizing Fc mutations L234A/L235A and affinity-enhancing Fab mutations Y50R/S56R, called AQmab^AM, bound to AQP4 in cell cultures with K_d ~ 18 ng/ml (~0.12 nM), ~8-fold greater affinity than the original antibody. AQmab^AM, but without L234A/L235A Fc mutations, produced complement-dependent cytotoxicity (CDC) with EC₅₀ ~ 82 ng/ml. AQmab^AM prevented CDC produced by sera from eight NMO patients with IC₅₀ ranging from 40 to 80 ng/ml, and similarly prevented antibody-dependent cellular cytotoxicity (ADCC). Mechanistic studies demonstrated that AQmab^AM blocked binding of serum NMO autoantibodies to AQP4. AQmab^AM offers a targeted, non-immunosuppressive approach for therapy of seropositive NMO. Autoantibody blocking may be a useful therapeutic strategy for other autoimmune diseases as well.

Experimental animal models of aquaporin-4-IgG-seropositive neuromyelitis optica spectrum disorders: progress and shortcomings

Neuromyelitis optica spectrum disorders (NMOSD) is a heterogeneous group of neuroinflammatory conditions associated with demyelination primarily in spinal cord and optic nerve, and to a lesser extent in brain. Most NMOSD patients are seropositive for IgG autoantibodies against aquaporin-4 (AQP4-IgG), the principal water channel in astrocytes. There has been interest in establishing experimental animal models of seropositive NMOSD (herein referred to as NMO) in order to elucidate NMO pathogenesis mechanisms and to evaluate drug candidates. An important outcome of early NMO animal models was evidence for a pathogenic role of AQP4-IgG. However, available animal models of NMO, based largely on passive transfer to rodents of AQP4-IgG or transfer of AQP4-sensitized T cells, often together with pro-inflammatory maneuvers, only partially recapitulate the clinical and pathological features of human NMO, and are inherently biased toward humoral or cellular immune mechanisms. This review summarizes current progress and shortcomings in experimental animal models of seropositive NMOSD, and opines on the import of advancing animal models.

Pregnancy-Related Immune Changes and Demyelinating Diseases of the Central Nervous System

Demyelinating diseases of the central nervous system comprise a heterogeneous group of autoimmune disorders characterized by myelin loss with relative sparing of axons occurring on a background of inflammation. Some of the most common demyelinating diseases are multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Besides showing clinical, radiological, and histopathological features that complicate their diagnosis, demyelinating diseases often involve different immunological processes that produce distinct inflammatory patterns. Evidence of demyelination diseases derives mostly from animal studies of experimental autoimmune encephalomyelitis (EAE), a model that relies on direct antibody–antigen interactions induced by encephalitogenic T cells. Pregnancy is characterized by non-self-recognition, immunomodulatory changes and an altered Th1/Th2 balance, generally considered a Th2-type immunological state that protects the mother from infections. During pregnancy, the immune response of patients with autoimmune disease complicated with pregnancy is different. Immune tolerance in pregnancy may affect the course of some diseases, which may reach remission or be exacerbated. In this review, we summarize current knowledge on the immune status during pregnancy and discuss the relationship between pregnancy-related immune changes and demyelinating diseases of the central nervous system.

Functional Connectivity Alterations in Neuromyelitis Optica Spectrum Disorder : Correlation with Disease Duration and Cognitive Impairment

PURPOSE

The aim of this study was to investigate resting state functional connectivity alterations within the main brain networks in neuromyelitis optica spectrum disorder (NMOSD) and their associations with disease duration, disability and cognitive dysfunction progression.

METHODS

Resting state functional magnetic resonance imaging (rs-fMRI), clinical and neuropsychological evaluations were obtained from 41 NMOSD patients and 41 healthy controls. Seed-voxel functional connectivity was analyzed in seven major hubs, including the default mode network, dorsal attention network, visual network, sensorimotor network, cerebellar network, thalamic network and reward-emotion network. Abnormalities of functional connectivity and correlations with disease duration, scores of the expanded disability status scale (EDSS), mini-mental state examination (MMSE) and Montreal cognitive assessment (MoCA) were further explored.

RESULTS

Compared with healthy controls, NMOSD patients showed increased functional connectivity in the default mode network, dorsal attention network and thalamic network, while decreased in the visual network and cerebellum networks. At the regional level, increased functional connectivity involved the right superior temporal gyrus, left fusiform gyrus, left inferior parietal lobule, bilateral middle frontal gyrus and right precuneus, whereas functional connectivity was decreased in the right parahippocampal gyrus and left precuneus. Functional connectivity reduction in the right parahippocampal gyrus positively correlated with disease duration (r = 0.488, p = 0.001) and negatively correlated with MoCA scores (r = -0.330, p = 0.035).

CONCLUSION

The study demonstrated functional alterations in the rs-fMRI of NMOSD, which provide a novel insight into the large-scale selective functional reorganization and could be useful to reveal the characteristics of the physiological mechanism.

Rehabilitation of neuromyelitis optica: Two CARE-compliant case reports

RATIONALE

Neuromyelitis optica (NMO), also known as Devic syndrome, is a central nervous system demyelinating disease consisting of optic neuritis and myelitis. Several studies have reported the effects of rehabilitation programs and specific exercises on outcomes in individuals with multiple sclerosis, but few have considered individuals with NMO. We present 2 cases of paraplegia due to NMO with rehabilitation outcome.

PATIENT CONCERNS

The first case corresponds to a 65-year-old woman with NMO presented with C4 incomplete American Spinal Injury Association (ASIA) scale D, and the second case is a 41-year-old woman with NMO presented with C1 incomplete ASIA-C.

DIAGNOSES

Two cases were confirmed by positive anti-aquaporin-4 antibody and presence of T2-weighted hyperintense lesion in spinal cord on magnetic resonance imaging.

INTERVENTION

The first patient planned for focusing on left hand fine motor training through occupational therapy by strengthening and stretching muscle using E-link (Biometrics Ltd, Newport, UK) during 4 weeks, and the second patient received strengthening lower extremity and gait training using a lower-body positive pressure treadmill (AlterG, Anti-Gravity Treadmill, Fremont, CA) during 4 weeks.

OUTCOMES

After a 4-week rehabilitation, the first patient's manual muscle testing was improved to grade 2/5 to 3+/5 in left upper limb specifically. Also, Spinal Cord Independence Measure (SCIM) was improved 79 to 88. Functional gains were made in bathing, upper-extremity dressing, and using chopsticks independently. Also, the second patient's manual muscle testing improved to grades 1 to 2/5 to 3 to 4/5 generally, and ASIA scale improved C5 incomplete ASIA-D. SCIM was improved to by allowing walking independently and increasing lower-extremity dressing and toileting ability.

LESSONS

An intensive, multidisciplinary rehabilitation program may lead to neurological and functional gains in patients with NMO.

Myelin in the Central Nervous System: Structure, Function, and Pathology

Oligodendrocytes generate multiple layers of myelin membrane around axons of the central nervous system to enable fast and efficient nerve conduction. Until recently, saltatory nerve conduction was considered the only purpose of myelin, but it is now clear that myelin has more functions. In fact, myelinating oligodendrocytes are embedded in a vast network of interconnected glial and neuronal cells, and increasing evidence supports an active role of oligodendrocytes within this assembly, for example, by providing metabolic support to neurons, by regulating ion and water homeostasis, and by adapting to activity-dependent neuronal signals. The molecular complexity governing these interactions requires an in-depth molecular understanding of how oligodendrocytes and axons interact and how they generate, maintain, and remodel their myelin sheaths. This review deals with the biology of myelin, the expanded relationship of myelin with its underlying axons and the neighboring cells, and its disturbances in various diseases such as multiple sclerosis, acute disseminated encephalomyelitis, and neuromyelitis optica spectrum disorders. Furthermore, we will highlight how specific interactions between astrocytes, oligodendrocytes, and microglia contribute to demyelination in hereditary white matter pathologies.

Identifying the culprits in neurological autoimmune diseases

The target organ of neurological autoimmune diseases (NADs) is the central or peripheral nervous system. Multiple sclerosis (MS) is the most common NAD, whereas Guillain-Barré syndrome (GBS), myasthenia gravis (MG), and neuromyelitis optica (NMO) are less common NADs, but the incidence of these diseases has increased exponentially in the last few years. The identification of a specific culprit in NADs is challenging since a myriad of triggering factors interplay with each other to cause an autoimmune response. Among the factors that have been associated with NADs are genetic susceptibility, epigenetic mechanisms, and environmental factors such as infection, microbiota, vitamins, etc. This review focuses on the most studied culprits as well as the mechanisms used by these to trigger NADs.

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Neurological autoimmune diseases are caused by a complex interaction between genes, environmental factors, and epigenetic deregulation.

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Infectious agents can cause an autoimmune reaction to myelin epitopes through molecular mimicry and/or bystander activation.

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Gut microbiota dysbiosis contributes to neurological autoimmune diseases.

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Smoking increases the risk of NADs through inflammatory signaling pathways, oxidative stress, and Th17 differentiation.

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Deficiency in vitamin D favors NAD development through direct damage to the central and peripheral nervous system.

Mechanisms of Below-Level Pain Following Spinal Cord Injury (SCI)

Mechanisms of below-level pain are discoverable as neural adaptations rostral to spinal injury. Accordingly, the strategy of investigations summarized here has been to characterize behavioral and neural responses to below-level stimulation over time following selective lesions of spinal gray and/or white matter. Assessments of human pain and the pain sensitivity of humans and laboratory animals following spinal injury have revealed common disruptions of pain processing. Interruption of the spinothalamic pathway partially deafferents nocireceptive cerebral neurons, rendering them spontaneously active and hypersensitive to remaining inputs. The spontaneous activity among these neurons is disorganized and unlikely to generate pain. However, activation of these neurons by their remaining inputs can result in pain. Also, injury to spinal gray matter results in a cascade of secondary events, including excitotoxicity, with rostral propagation of excitatory influences that contribute to chronic pain. Establishment and maintenance of below-level pain results from combined influences of injured and spared axons in the spinal white matter and injured neurons in spinal gray matter on processing of nociception by hyperexcitable cerebral neurons that are partially deafferented. A model of spinal stenosis suggests that ischemic injury to the core spinal region can generate below-level pain. Additional questions are raised about demyelination, epileptic discharge, autonomic activation, prolonged activity of C nocireceptive neurons, and thalamocortical plasticity in the generation of below-level pain. PERSPECTIVE: An understanding of mechanisms can direct therapeutic approaches to prevent development of below-level pain or arrest it following spinal cord injury. Among the possibilities covered here are surgical and other means of attenuating gray matter excitotoxicity and ascending propagation of excitatory influences from spinal lesions to thalamocortical systems involved in pain encoding and arousal.

Role of complement and potential of complement inhibitors in myasthenia gravis and neuromyelitis optica spectrum disorders: a brief review

The complement system is a powerful member of the innate immune system. It is highly adept at protecting against pathogens, but exists in a delicate balance between its protective functions and overactivity, which can result in autoimmune disease. A cascade of complement proteins that requires sequential activation, and numerous complement regulators, exists to regulate a proportionate response to pathogens. In spite of these mechanisms there is significant evidence for involvement of the complement system in driving the pathogenesis of variety of diseases including neuromyelitis optica spectrum disorders (NMOSD) and myasthenia gravis (MG). As an amplification cascade, there are an abundance of molecular targets that could be utilized for therapeutic intervention. Clinical trials assessing complement pathway inhibition in both these conditions have recently been completed and include the first randomized placebo-controlled trial in NMOSD showing positive results. This review aims to review and update the reader on the complement system and the evolution of complement-based therapeutics in these two disorders.

Elevated serum level of IL-4 in neuromyelitis optica and multiple sclerosis patients

Mediators have important roles in the pathogenesis of autoimmune diseases. Interleukin 4 (IL-4) is one of the most important cytokines that has a regulatory effect on immune cells. In the current study, the serum level of IL-4 was assessed in the newly diagnosed neuromyelitis optica (NMO) and multiple sclerosis (MS) patients compared to healthy subjects. ELISA technique was used for assessment of the serum level of IL-4, and data analysis was performed by SPSS software. Serum level of IL-4 was elevated in both NMO and MS patients compared with healthy individuals (P < .001), but no statistically significant difference was identified between MS and NMO patients (P = .071). Furthermore, gender (female) and AQP4-Ab had significant impacts on the level of IL-4 in NMO patients (P < .001). These data show the crucial role of IL-4 in the pathogenesis of NMO and MS diseases. However, we suggest future studies to investigate the serum level of IL-4 in NMO and MS patients to clarify more roles of this cytokine in the pathogenesis of both diseases.

Review: Recent advances in the understanding of the pathophysiology of neuromyelitis optica spectrum disorder

Neuromyelitis optica is an autoimmune inflammatory disorder of the central nervous system that preferentially targets the spinal cord and optic nerve. Following the discovery of circulating antibodies against the astrocytic aquaporin 4 (AQP4) water channel protein, recent studies have expanded our knowledge of the unique complexities of the pathogenesis of neuromyelitis optica and its relationship with the immune response. This review describes and summarizes the recent advances in our understanding of the molecular mechanisms underlying neuromyelitis optica disease pathology and examines their potential as therapeutic targets. Additionally, we update the most recent research by proposing major unanswered questions regarding how peripheral AQP4 antibodies are produced and their entry into the central nervous system, the causes of AQP4-IgG-seronegative disease, why peripheral AQP4-expressing organs are spared from damage, and the impact of this disease on pregnancy.

Aquaporin-4 IgG seropositivity is associated with worse visual outcomes after optic neuritis than MOG-IgG seropositivity and multiple sclerosis, independent of macular ganglion cell layer thinning

BACKGROUND

Comparative studies of characteristics of optic neuritis (ON) associated with myelin oligodendrocyte glycoprotein-IgG (MOG-ON) and aquaporin-4-IgG (AQP4-ON) seropositivity are limited.

OBJECTIVE

To compare visual and optical coherence tomography (OCT) measures following AQP4-ON, MOG-ON, and multiple sclerosis associated ON (MS-ON).

METHODS

In this cross-sectional study, 48 AQP4-ON, 16 MOG-ON, 40 MS-ON, and 31 healthy control participants underwent monocular letter-acuity assessment and spectral-domain OCT. Eyes with a history of ON >3 months prior to evaluation were analyzed.

RESULTS

AQP4-ON eyes exhibited worse high-contrast letter acuity (HCLA) compared to MOG-ON (-22.3 ± 3.9 letters; p < 0.001) and MS-ON eyes (-21.7 ± 4.0 letters; p < 0.001). Macular ganglion cell + inner plexiform layer (GCIPL) thickness was lower, as compared to MS-ON, in AQP4-ON (-9.1 ± 2.0 µm; p < 0.001) and MOG-ON (-7.6 ± 2.2 µm; p = 0.001) eyes. Lower GCIPL thickness was associated with worse HCLA in AQP4-ON (-16.5 ± 1.5 letters per 10 µm decrease; p < 0.001) and MS-ON eyes (-8.5 ± 2.3 letters per 10 µm decrease; p < 0.001), but not in MOG-ON eyes (-5.2 ± 3.8 letters per 10 µm decrease; p = 0.17), and these relationships differed between the AQP4-ON and other ON groups (p < 0.01 for interaction).

CONCLUSION

AQP4-IgG seropositivity is associated with worse visual outcomes after ON compared with MOG-ON and MS-ON, even with similar severity of macular GCIPL thinning.

Pharmacotherapy for Neuromyelitis Optica Spectrum Disorders: Current Management and Future Options

Neuromyelitis optica (NMO) is an inflammatory and demyelinating disease of the central nervous system. Although the prevalence of NMO is low, the rapid and severe impairment observed in patients has led to extensive development of research in the fields of diagnostic criteria and therapy in the past 15 years. With improved understanding of the pathophysiology of NMO and the role of aquaporin-4 (AQP4) or myelin oligodendrocyte glycoprotein antibodies, numerous therapeutic approaches have been proposed and are currently undergoing evaluation. In this review, we describe the rationale for existing therapeutics and their benefit/risk ratio. We also discuss the pharmacological and clinical interest of future approaches targeting, among others, B or T cells, the blood-central nervous system barrier, complement, polynuclear cells, AQP4-antibody linkage and AQP4 activity. The numerous agents under development are the result of a major collaborative effort all over the world. After the considerable progress on diagnosis, we are now close to class I evidence for a therapeutic effect of several drugs in NMO spectrum disorders, most notably with the anti-interleukin-6 receptor antibody (satralizumab) and anti-complement-5 antibody (eculizumab).

Complement-independent bystander injury in AQP4-IgG seropositive neuromyelitis optica produced by antibody-dependent cellular cytotoxicity

Cellular injury in AQP4-IgG seropositive neuromyelitis spectrum disorder (herein called NMO) involves AQP4-IgG binding to astrocytes, resulting in astrocyte injury by complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) mechanisms. The rapid disease progression, severe tissue damage, and abundant leukocyte infiltration seen in some NMO patients suggest a more direct mechanism for demyelination and neurologic deficit than secondary injury from astrocyte loss. Here, we report evidence for an ‘ADCC bystander mechanism’ in NMO involving injury to nearby cells by leukocytes following their activation by AQP4-bound AQP4-IgG on astrocytes. In model cocultures containing AQP4-expressing and null CHO cells, AQP4-IgG and complement killed bystander null cells to ~ 100 μm away from AQP4-expressing cells; AQP4-IgG and NK cells produced bystander killing to ~ 300 μm, with perforin deposition seen on injured null cells. Bystander cytotoxicity was also seen with neutrophil-mediated ADCC and in astrocyte-neuron cocultures. Mechanistic studies, including real-time imaging, suggested that leukocytes activated by an AQP4-dependent ADCC mechanism injure bystander cells by direct targeted exocytosis on neighboring cells and not by diffusion of soluble granule contents. In support of this conclusion, ADCC bystander injury was preferentially reduced by an RGDS peptide that inhibits integrin adhesion. Evidence for ADCC bystander injury to oligodendrocytes and neurons was also found in mice following intracerebral injection of AQP4-IgG and NK cells, which was inhibited by RGDS peptide. These results establish a novel cellular pathogenesis mechanism in AQP4-IgG seropositive NMO and provide evidence that inflammatory mechanisms can cause widespread tissue damage in NMO independently of the secondary effects from astrocyte loss.

Angiotensin AT2 receptor–induced interleukin-10 attenuates neuromyelitis optica spectrum disorder–like pathology

Background:

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing inflammatory central nervous system (CNS) disease for which there is no cure. Immunoglobulin G autoantibodies specific for the water channel aquaporin-4 are a serum biomarker, believed to induce complement-dependent astrocyte damage with secondary demyelination.

Objective:

To investigate the effect of angiotensin AT2 receptor (AT2R) stimulation on NMOSD-like pathology and its underlying mechanism.

Methods:

NMOSD-like pathology was induced in mice by intracerebral injection of immunoglobulin-G isolated from NMOSD patient serum, with complement. This mouse model produces the characteristic histological features of NMOSD. A specific AT2R agonist, Compound 21 (C21), was given intracerebrally at day 0 and by intrathecal injection at day 2.

Results:

Loss of aquaporin-4 and glial fibrillary acidic protein was attenuated by treatment with C21. Administration of C21 induced mRNA for interleukin-10 in the brain. NMOSD-like pathology was exacerbated in interleukin-10-deficient mice, suggesting a protective role. C21 treatment did not attenuate NMOSD-like pathology in interleukin-10-deficient mice, indicating that the protective effect of AT2R stimulation was dependent on interleukin-10.

Conclusion:

Our findings identify AT2R as a novel potential therapeutic target for the treatment of NMOSD. Interleukin-10 signaling is an essential part of the protective mechanism counteracting NMOSD pathology.

Neuromyelitis optica spectrum disorder occurred after interferon alpha therapy in malignant melanoma

BACKGROUND

Several cases of neuromyelitis optica spectrum disorder (NMOSD) caused by interferon alpha (IFN-α) treatment in hepatitis C were reported in past literatures, but NMOSD resulted from IFN-α treatment in tumor has not yet been reported previously.

METHODS

A unique case of NMOSD caused by IFN-α therapy in malignant melanoma is presented. Related cases about NMOSD caused by IFN-α therapy on Pubmed were reviewed further.

RESULTS

A 40-year-old Chinese woman was diagnosed as right breast skin malignant melanoma and received melanoma resection in April 2012, then underwent IFN-α-2b therapy (5 million IU every time, 3 times/week) from May 2012 to Sep 2016. In December 2016, the patient developed bilateral optic neuritis, with no light perception at her worst. After a month-long glucocorticoid treatment, she could see finger movement from 40 cm. Serum positive anti-AQP-4 antibody was found by enzyme-linked immunosorbent assay (ELISA, 75.9 u/ml) in Feb 2017 and indirect immunofluorescence testing (IIFT, 1:320) in Sep 2017. Methylprednisolone (8 mg/day) and rituximab (0.1 g/every 6 months) were used for prevention. On the follow up visit in Jan 2019, she could see finger movement from 1 m, and no melanoma and NMOSD relapse were complained. Literature review only found 3 cases of NMOSD caused by IFN-α treatment in hepatitis.

CONCLUSIONS

A unique case of NMOSD with positive anti-AQP-4 antibody after IFN-α treatment in malignant melanoma was reported. Type I IFNs may be pro-inflammatory in NMOSD and this possible consequence of IFNs use should be cautioned in future practice.

The clinical value of complement proteins in differentiating AQP4-IgG-positive from MOG-IgG-positive neuromyelitis optica spectrum disorders

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) refers to a range of autoimmune inflammatory demyelinating diseases affecting the optic nerves, spinal cord, and periependymal regions of the brain. Classical NMOSD is characterized by the presentation of autoantibodies against the water channel aquaporin-4 (AQP4). However, a subset of patients fulfilling the clinical criteria for NMOSD is negative for AQP4-IgG but positive for autoantibodies against myelin oligodendrocyte glycoprotein (MOG); these patients are associated with different clinical manifestations and pathogenesis.

METHODS

Patients who received a first diagnosis of NMOSD were reviewed retrospectively between April 2015 and December 2018. Patients were classified according to the presence of AQP4-IgG and MOG-IgG in serum and/or cerebrospinal fluid. Clinical characteristics, magnetic resonance imaging findings, disease severity, and serum C3 and C4 levels at the first episode were compared between the groups.

RESULTS

The NMOSD patients with AQP4-IgG and MOG-IgG demonstrated specific, differential clinical features. The AQP4-IgG group featured more women, the presentation of transverse myelitis attacks and simultaneous occurrence of optic neuritis and transverse myelitis were more common, and intrathecal synthesis was more evident. The MOG-IgG group featured younger patients, more acute disseminated encephalomyelitis (ADEM) or ADEM-like attacks, more frequent cerebrospinal fluid pleocytosis, and a better overall outcome. C3 levels were significantly lower in AQP4-IgG-positive patients and higher in MOG-IgG-positive patients relative to healthy controls. C4 levels were significantly lower in the AQP4-IgG-positive NMOSD group when compared to both MOG-IgG-positive patients and controls. C3 and C4 were then combined in a receiver operating characteristic model. The area under the curve of the model was calculated to differentiate the AQP4-IgG-positive group from the MOG-IgG-positive group was 0.787, which was considered moderately predictive.

CONCLUSION

The combination of C3 and C4 could assist in the differential diagnosis of AQP4-IgG-positive NMOSD from MOG-IgG-positive NMOSD.

Neuromyelitis Optica Spectrum Disorder and Anti-MOG Syndromes

Neuromyelitis optica spectrum disorder (NMOSD) and anti-myelin oligodendrocyte glycoprotein (anti-MOG) syndromes are immune-mediated inflammatory conditions of the central nervous system that frequently involve the optic nerves and the spinal cord. Because of their similar clinical manifestations and habitual relapsing course they are frequently confounded with multiple sclerosis (MS). Early and accurate diagnosis of these distinct conditions is relevant as they have different treatments. Some agents used for MS treatment may be deleterious to NMOSD. NMOSD is frequently associated with antibodies which target aquaporin-4 (AQP4), the most abundant water channel in the CNS, located in the astrocytic processes at the blood-brain barrier (BBB). On the other hand, anti-MOG syndromes result from damage to myelin oligodendrocyte glycoprotein (MOG), expressed on surfaces of oligodendrocytes and myelin sheaths. Acute transverse myelitis with longitudinally extensive lesion on spinal MRI is the most frequent inaugural manifestation of NMOSD, usually followed by optic neuritis. Other core clinical characteristics include area postrema syndrome, brainstem, diencephalic and cerebral symptoms that may be associated with typical MRI abnormalities. Acute disseminated encephalomyelitis and bilateral or recurrent optic neuritis are the most frequent anti-MOG syndromes in children and adults, respectively. Attacks are usually treated with steroids, and relapses prevention with immunosuppressive drugs. Promising emerging therapies for NMOSD include monoclonal antibodies and tolerization.

Epidemiology of NMOSD in Sweden from 1987 to 2013: A nationwide population-based study

Objective

To report the yearly incidence rate and prevalence of neuromyelitis spectrum disorder (NMOSD) in Sweden and to investigate clinical characteristics, treatment, and outcome.

Methods

We conducted a retrospective study of hospital case records of 294 individuals diagnosed with neuromyelitis optica (NMO) (G36.0 ICD-10, 341.0 ICD-9) in the Swedish National Patient Register from 1987 to end of 2013 or detected by the presence of aquaporin-4 (AQP4) immunoglobulin G (IgG) in serum during the study period. Ninety-two patients (51 NMO and 41 NMOSD) met the 2006 Wingerchuk criteria and were included in the study. Ten patients with an onset of NMO prior to 1987 and alive at the end of 2013 were included when estimating the prevalence.

Results

The average yearly incidence rate per 1,000,000 individuals increased significantly from 0.30 (confidence interval [CI] 0.19–0.41) between 1987 and 2006 to 0.79 (CI 0.55–1.03) between 2007 and 2013. The prevalence was 10.4 (CI 8.5–12.6) per 1,000,000 individuals at end of 2013. The median time from onset to first relapse was 1.42 years (range 0.58–3.90). The probability of relapse was 60% and 75% after 5 and 10 years after onset. More than 80% were treated with immunosuppressive drugs. Three patients died during the study period.

Conclusion

The increased incidence rate during the study period was likely due to heightened awareness and increased access to MRI and AQP4-IgG analysis. Incidence and prevalence of NMO in Sweden correspond to other countries with a predominately Caucasian population. We found that most patients were treated with immunosuppressant drugs, presumably resulting in low mortality among the detected cases.

Type 2 Inflammatory Responses in Autoimmune Demyelination of the Central Nervous System: Recent Advances

Type 2 immunity has long been confined to a restricted spectrum of responses, mostly including allergic reactions to innocuous environmental triggers. However, growing evidence suggests that cells and mediators typically associated with type 2 inflammation are involved in several physiopathological conditions, such as defense against toxic substances, anticancer immunity, and autoimmune diseases. In neuromyelitis optica, an autoimmune demyelinating disorder of the spinal cord and optic nerve, eosinophils extensively infiltrate lesions in the central nervous system (CNS) and promote tissue pathology in experimental models of this disease. Next-generation sequencing of CD4⁺ T cells isolated from a specific subtype of multiple sclerosis plaque has uncovered an unexpectedly Th2 profile of these cells. Even mast cells and other allergic mediators have been implicated in the modulation and/or effector mechanisms of autoimmune reactions against the CNS. In this review article, the most recent developments showing the involvement of type 2 inflammatory components in CNS autoimmunity are summarised and possible lines of further investigation are discussed.

Complement Therapeutics in Autoimmune Disease

Many autoimmune diseases are characterized by generation of autoantibodies that bind to host proteins or deposit within tissues as a component of immune complexes. The autoantibodies can activate the complement system, which can mediate tissue damage and trigger systemic inflammation. Complement inhibitory drugs may, therefore, be beneficial across a large number of different autoimmune diseases. Many new anti-complement drugs that target specific activation mechanisms or downstream activation fragments are in development. Based on the shared pathophysiology of autoimmune diseases, some of these complement inhibitory drugs may provide benefit across multiple different diseases. In some antibody-mediated autoimmune diseases, however, unique features of the autoantibodies, the target antigens, or the affected tissues may make it advantageous to block individual components or pathways of the complement system. This paper reviews the evidence that complement is involved in various autoimmune diseases, as well as the studies that have examined whether or not complement inhibitors are effective for treating these diseases.

Cerebral adrenoleukodystrophy is associated with loss of tolerance to profilin

Childhood cerebral adrenoleukodystrophy (cALD) is a devastating manifestation of ALD accompanied by demyelination, inflammation, and blood brain barrier (BBB) disruption with shared characteristics of an auto-immune disease. We utilized plasma samples pre- and postdevelopment of cALD to determine the presence of specific auto-antibodies. Mass spectrometry of protein specifically bound with post-cALD plasma antibody identified Profilin1 (PFN1) as the target. In a screen of 94 boys with cALD 48 (51%) had anti-PFN1 antibodies, whereas only 2/29 boys with ALD but without cerebral disease, and 0/30 healthy controls showed anti-PFN1 immunoreactivity. Cerebral spinal fluid from those with cALD showed higher levels of PFN1 protein compared with non-cALD samples (324 ± 634 versus 42 ± 23 pg/mL, p = 0.04). Boys that were anti-PFN positive had a significant increase in the amount of gadolinium signal observed on MRI when compared to boys that were anti-PFN1 negative (p = 0.04) possibly indicating increased BBB disruption. Anti-PFN1 positivity was also associated with elevated levels of very long chain fatty acids (C26 of 1.12 ± 0.41 versus 0.97 ± 0.30 mg/dL, p = 0.03) and increased plasma BAFF (973 ± 277 versus 733 ± 269 pg/mL, p = 0.03). In conclusion, anti-PFN may be a novel biomarker associated with the development of cALD in boys with ALD.

CD55 upregulation in astrocytes by statins as potential therapy for AQP4-IgG seropositive neuromyelitis optica

Background

Neuromyelitis optica spectrum disorder (herein called NMO) is an inflammatory demyelinating disease that can be initiated by binding of immunoglobulin G autoantibodies (AQP4-IgG) to aquaporin-4 on astrocytes, causing complement-dependent cytotoxicity (CDC) and downstream inflammation. The increased NMO pathology in rodents deficient in complement regulator protein CD59 following passive transfer of AQP4-IgG has suggested the potential therapeutic utility of increasing the expression of complement regulator proteins.

Methods

A cell-based ELISA was developed to screen for pharmacological upregulators of endogenous CD55 and CD59 in a human astrocyte cell line. A statin identified from the screen was characterized in cell culture models and rodents for its action on complement regulator protein expression and its efficacy in models of seropositive NMO.

Results

Screening of ~ 11,500 approved and investigational drugs and nutraceuticals identified transcriptional upregulators of CD55 but not of CD59. Several statins, including atorvastatin, simvastatin, lovastatin, and fluvastatin, increased CD55 protein expression in astrocytes, including primary cultures, by three- to four-fold at 24 h, conferring significant protection against AQP4-IgG-induced CDC. Mechanistic studies revealed that CD55 upregulation involves inhibition of the geranylgeranyl transferase pathway rather than inhibition of cholesterol biosynthesis. Oral atorvastatin at 10–20 mg/kg/day for 3 days strongly increased CD55 immunofluorescence in mouse brain and spinal cord and reduced NMO pathology following intracerebral AQP4-IgG injection.

Conclusion

Atorvastatin or other statins may thus have therapeutic benefit in AQP4-IgG seropositive NMO by increasing CD55 expression, in addition to their previously described anti-inflammatory and immunomodulatory actions.

Mechanisms for lesion localization in neuromyelitis optica spectrum disorders

Purpose of review

Neuromyelitis optica spectrum disorders (NMOSD) are severe inflammatory diseases of the central nervous system (CNS), with the presence of aquaporin 4 (AQP4)-specific serum antibodies in the vast majority of patients, and with the presence of myelin oligodendrocyte glycoprotein (MOG)-specific antibodies in approximately 40% of all AQP4-antibody negative NMOSD patients. Despite differences in antigen recognition, the preferred sites of lesions are similar in both groups of patients: They localize to the spinal cord and to the anterior visual pathway including retina, optic nerves, chiasm, and optic tracts, and – to lesser extent – also to certain predilection sites in the brain.

Recent findings

The involvement of T cells in the formation of NMOSD lesions has been challenged for quite some time. However, several recent findings demonstrate the key role of T cells for lesion formation and localization. Studies on the evolution of lesions in the spinal cord of NMOSD patients revealed a striking similarity of early NMOSD lesions with those observed in corresponding T-cell-induced animal models, both in lesion formation and in lesion localization. Studies on retinal abnormalities in NMOSD patients and corresponding animals revealed the importance of T cells for the very early stages of retinal lesions which eventually culminate in damage to Müller cells and to the retinal nerve fiber layer. Finally, a study on cerebrospinal fluid (CSF) barrier pathology demonstrated that NMOSD immunopathology extends beyond perivascular astrocytic foot processes to include the pia, the ependyma, and the choroid plexus, and that diffusion of antibodies from the CSF could further influence lesion formation in NMOSD patients.

Summary

The pathological changes observed in AQP4-antibody positive and MOG-antibody positive NMOSD patients are strikingly similar to those found in corresponding animal models, and many mechanisms which determine lesion localization in experimental animals seem to closely reflect the human situation.

Circulating AQP4-specific auto-antibodies alone can induce neuromyelitis optica spectrum disorder in the rat

It is well established that the binding of pathogenic aquaporin-4 (AQP4)-specific autoantibodies to astrocytes may initiate a cascade of events culminating in the destruction of these cells and in the formation of large tissue-destructive lesions typical for patients with neuromyelitis optica spectrum disorders (NMOSD). To date, not a single experimental study has shown that the systemic presence of the antibody alone can induce any damage to the central nervous system (CNS), while pathological studies on brains of NMOSD patients suggested that there might be ways for antibody entry and subsequent tissue damage. Here, we systemically applied a highly pathogenic, monoclonal antibody with high affinity to AQP4 over prolonged period of time to rats, and show that AQP4-abs can enter the CNS on their own, via circumventricular organs and meningeal or parenchymal blood vessels, that these antibodies initiate the formation of radically different lesions with AQP4 loss, depending on their mode and site of entry, and that lesion formation is much more efficient in the presence of encephalitogenic T-cell responses. We further demonstrate that the established tissue-destructive lesions trigger the formation of additional lesions by short and far reaching effects on blood vessels and their branches, and that AQP4-abs have profound effects on the AQP4 expression in peripheral tissues which counter-act possible titer loss by antibody absorption outside the CNS. Cumulatively, these data indicate that directly induced pathological changes caused by AQP4-abs inside and outside the CNS are efficient drivers of disease evolution in seropositive organisms.

The Role of B Cells and Antibodies in Multiple Sclerosis, Neuromyelitis Optica, and Related Disorders

Our pathophysiological concept of the most common central nervous system demyelinating disease, multiple sclerosis, strikingly evolved by recent discoveries suggesting that B lymphocytes substantially contribute in its initiation and chronic propagation. In this regard, activated B cells are nowadays considered to act as important antigen-presenting cells for the activation of T cells and as essential source of pro-inflammatory cytokines. Hereby, they create a milieu in which other immune cells differentiate and join an orchestrated inflammatory infiltration of the CNS. Without a doubt, this scientific leap was critically pioneered by the empirical use of anti-CD20 antibodies in recent clinical MS trials, which revealed that the therapeutic removal of immature and mature B cells basically halted development of new inflammatory flares in otherwise relapsing MS patients. This stabilization occurred largely independent of any indirect effect on plasma cell-produced antibody levels. On the contrary, peripherally produced autoantibodies are probably the most important B cell component in two other CNS demyelinating diseases which are currently in the process of being delineated as separate disease entities. The first one is neuromyelitis optica in which an antibody response against aquaporin-4 targets and destroys astrocytes, the second, likely distinct entity embraces a group of patients containing antibodies against myelin oligodendrocyte glycoprotein. In this review, we will describe and summarize pro-inflammatory B cell properties in these three CNS demyelinating disorders; we will however also provide an overview on the emerging concept that B cells or B cell subsets may exert immunologically counterbalancing properties, which may be therapeutically desirable to maintain and foster in inflammatory CNS demyelination. In an outlook, we will discuss accordingly, how this potentially important aspect can be harnessed to advance future B cell-directed therapeutic approaches in multiple sclerosis and related diseases.

Clinical, neuroimaging and therapeutic response in AQP4-positive NMO patients from India

BACKGROUND

Neuromyelitis Optica (NMO) is an autoimmune astrocytopathic disorder due to AQP4 antibodies.

OBJECTIVES

To analyse clinical, neuroimaging features in NMO patients and assess the efficacy of various therapeutics.

METHODS

AQP4+ve NMO patients were diagnosed based on consensus diagnostic criteria.

RESULTS

101 AQP4+ve NMO patients were seen with female (90) predominance. Adult population (71.3%) formed the larger group followed by pediatric (19.8%) and late-onset (8.9%). Myelopathy (36.2%) was most commonly seen followed by optic neuritis (19.1%), brainstem (17.1%), opticomyelopathy (16.1%), area postrema involvement (10.5%) and encephalopathy (1%). Encephalopathy and brainstem/cerebellar involvement were most common in pediatric population while opticomyelopathy was more common in late-onset patients. Hyperintensities of lower medulla was seen in 67.3% subjects and 49.5% had involvement of obex. Differential T2 hyperintensity of the long segment myelitis was found in 30.7%. Plasmapheresis was given in 71 subjects followed by maintenance therapy. Most of them showed significant improvement with EDSS score of 1 in 30.7%.

CONCLUSIONS

Clinical manifestations in AQP4+ve NMO patients may vary depending on the age at onset of illness. MRI features affecting cervicomedullary junction, obex, differential T2 hyperintensities of the spinal cord may form a useful diagnostic clue. Plasmapheresis is helpful in achieving remission along with immunomodulation.

Pontine hemorrhage accompanied by neuromyelitis optica spectrum disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune disorder caused by antibody to aquaporin-4 (AQP4). NMOSD can infrequently present as a complication of posterior reversible encephalopathy syndrome (PRES). Moreover, few cases of NMOSD patients with brain hemorrhage have been reported. We report a rare case of PRES together with NMOSD recurrence, subsequent to pontine hemorrhage after intravenous methylprednisolone (IVMP) therapy. A 51-year-old Japanese woman, with a history of hypertension and dyslipidemia, and recurrent episodes of left visual acuity disorder related to AQP4-positive NMOSD, developed blindness in the left eye. Brain MRI showed a hyperintense lesion in pons. She was initially diagnosed with recurrence of NMOSD and 1000 mg of IVMP was administered for 3 days. After the 3rd course of IVMP, she developed left-sided sensory disturbance, and blood pressure was increased to 202/127 mmHg. Brain computed tomography (CT) showed pontine hemorrhage, and she was referred to our hospital again. We diagnosed PRES associated with NMOSD recurrence, along with development of pontine hemorrhage induced by the increase in blood pressure resulting from IVMP. The patient was treated with nicardipine to strictly control blood pressure, and tranexamic acid and glycerol for pontine hemorrhage and PRES. We also extended IVMP for 5 consecutive days in total, followed by plasmapheresis. After therapy, blindness in the left eye improved to light perception. Collectively, anti-AQP4 antibody could induce PRES together with recurrent NMOSD, and pontine hemorrhage could thus be induced by blood pressure increases resulting from IVMP.