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

Effect of CXCR2 Inhibition on Behavioral Outcomes and Pathology in Rat Model of Neuromyelitis Optica

OBJECTIVE

To reduce immune-mediated damage in a rat model of neuromyelitis optica (NMO) by blocking neutrophil migration using SCH527123, a drug that inhibits CXCR2.

BACKGROUND

Neuromyelitis optica is a relapsing autoimmune disease that preferentially targets the optic nerves and spinal cord leading to blindness and paralysis. Part of the immunopathogenesis of this disease is thought to involve neutrophils, which are present within NMO lesions. We tested the effect of blocking neutrophil migration in an NMO rat model.

METHODS

The Lewis rat model of NMO uses a myelin-reactive experimental autoimmune encephalomyelitis (EAE) background with passive transfer of pooled human antibody from patients with aquaporin-4 (AQP4) seropositive NMO at onset of EAE symptoms. We treated rats early in the course of EAE with CXCR2 inhibitor and assessed the extent of neutrophil infiltration into the spinal cord and the extent of AQP4 depletion.

RESULTS

CXCR2 inhibitor decreased neutrophil migration into the spinal cord of AQP4 IgG-treated EAE rats. However, there was no difference in the acute behavioral signs of EAE or the extent and distribution of AQP4 lesions. This suggests that neutrophils are not centrally involved in the immunopathogenesis of the Lewis rat NMO disease model.

CONCLUSIONS

CXCR2 inhibitor blocks neutrophil migration into the spinal cord during EAE but does not significantly reduce inflammation or AQP4 lesions in the Lewis rat model of NMO.

Neuromyelitis optica spectrum disorders: Features of aquaporin-4, myelin oligodendrocyte glycoprotein and double-seronegative-mediated subtypes

The new diagnostic classification of neuromyelitis optica spectrum disorder (NMOSD) in 2015 highlights the central role of biomarkers, such as antibodies against aquaporin-4 (AQP4-Ab), in diagnosis. Also, in approximately 20-25% of patients without AQP4-Ab (NMOSD^AQP4-) the presence of an antibody directed against myelin oligodendrocyte glycoprotein (MOG) characterizes a specific population of NMOSD patients (NMOSD^MOG+), according to their demographic and clinical data and prognoses. While double-seronegative cases (NMOSD^NEG) have not been fully described, they may correspond to the very first patients with opticospinal demyelination reported by Devic and Gault in 1894. The present report reviews the current knowledge of the pathophysiology and clinical features of NMOSD^AQP4+, NMOSD^MOG+ and NMOSD^NEG patients, and also discusses the relationship between the extended spectrum of MOG disease and NMOSD^MOG+. Finally, the current treatments for acute relapses and relapse prevention are described, with a focus on serological-based therapeutic responses and the promising new therapeutic targets.

Quantitative radiomic biomarkers for discrimination between neuromyelitis optica spectrum disorder and multiple sclerosis

BACKGROUND

Precise diagnosis and early appropriate treatment are of importance to reduce neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS) morbidity. Distinguishing NMOSD from MS based on clinical manifestations and neuroimaging remains challenging.

PURPOSE

To investigate radiomic signatures as potential imaging biomarkers for distinguishing NMOSD from MS, and to develop and validate a diagnostic radiomic-signature-based nomogram for individualized disease discrimination.

STUDY TYPE

Retrospective, cross-sectional study.

SUBJECTS

Seventy-seven NMOSD patients and 73 MS patients.

FIELD STRENGTH/SEQUENCE

3T/T₂ -weighted imaging.

ASSESSMENT

Eighty-eight patients and 62 patients were respectively enrolled in the primary and validation cohorts. Quantitative radiomic features were automatically extracted from lesioned regions on T₂ -weighted imaging. A least absolute shrinkage and selection operator analysis was used to reduce the dimensionality of features. Finally, we constructed a radiomic nomogram for disease discrimination.

STATISTICAL TESTS

Features were compared using the Mann-Whitney U-test with a nonnormal distribution. We depicted the nomogram on the basis of the results of the logistic regression using the rms package in R. The Hmisc package was used to investigate the performance of the nomogram via Harrell's C-index.

RESULTS

A total of 273 quantitative radiomic features were extracted from lesions. A multivariable analysis selected 11 radiomic features and five clinical features to be included in the model. The radiomic signature (P < 0.001 for both the primary and validation cohorts) showed good potential for building a classification model for disease discrimination. The area under the receiver operating characteristic curve was 0.9880 for the training cohort and 0.9363 for the validation cohort. The nomogram exhibited good discrimination, a concordance index of 0.9363, and good calibration in the primary cohort. The nomogram showed similar discrimination, concordance (0.9940), and calibration in the validation cohort.

DATA CONCLUSION

The diagnostic radiomic-signature-based nomogram has potential utility for individualized disease discrimination of NMOSD from MS in clinical practice.

LEVEL OF EVIDENCE

4 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1113-1121.

Complement-dependent bystander injury to neurons in AQP4-IgG seropositive neuromyelitis optica

Background

Aquaporin-4-immunoglobulin G (AQP4-IgG) seropositive neuromyelitis optica spectrum disorder (herein called NMO) is an autoimmune disease of the central nervous system in which AQP4-IgG binding to AQP4 on astrocytes results in complement-dependent astrocyte injury and secondary inflammation, demyelination, and neuron loss. We previously reported evidence for a complement bystander mechanism for early oligodendrocyte injury in NMO. Herein, we tested the hypothesis that complement bystander injury, which involves diffusion to nearby cells of activated soluble complement components from complement-injured astrocytes, is a general phenomenon that may contribute to neuronal injury in NMO.

Methods

Primary cocultures of rat astrocytes and cortical neurons were established to study complement-dependent cell death after exposure to AQP4-IgG and complement. In animal experiments, AQP4-IgG was delivered to adult rats by intracerebral injection. Cell cultures and rat brain were studied by immunofluorescence.

Results

In primary astrocyte-neuron cocultures, addition of AQP4-IgG and complement resulted in death of neurons nearby astrocytes. Deposition of complement membrane attack complex C5b-9 was seen on neurons nearby astrocytes, whereas C1q, the initiating protein in the complement pathway, was seen only on astrocytes. Neuron death was not seen with a complement inhibitor, with C1q- or C6-depleted complement, in pure neuron cultures exposed to AQP4-IgG and complement or in cocultures exposed to an astrocyte toxin. Intracerebral injection in rats of AQP4-IgG and a fixable dead cell fluorescent marker produced death of neurons near astrocytes, with C5b-9 deposition. Neuron death was not seen in rats receiving a complement inhibitor or in AQP4-IgG-injected AQP4 knockout rats.

Conclusion

These results support a novel mechanism for early neuron injury in NMO and provide evidence that complement bystander injury may be a general phenomenon for brain cell injury following AQP4-IgG-targeted astrocyte death.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1333-z) contains supplementary material, which is available to authorized users.

Blockade of IL-6 signaling in neuromyelitis optica

Neuromyelitis optica (NMO) and neuromyelitis optica spectrum disorder (NMOSD) are autoimmune diseases associated with a disease-specific autoantibody directed against the water channel protein aquaporin-4. Standard immunotherapy, immunosuppressive agents, and corticosteroids can prevent acute attacks and maintain remission in most patients with NMOSD. However, there is a strong need for additional options for patients who are refractory to standard treatments. Emerging therapies targeting specific molecules related to the pathogenicity of NMOSD are currently being developed. The review focuses on improving preventive treatments for NMOSD, including ongoing randomized clinical trials using biological drugs targeting CD19 and CD20 on B cells, interleukin-6, and complement protein C5. The anti-IL-6 receptor monoclonal antibody tocilizumab (TCZ), which can block IL-6 signaling, was shown to be highly effective for refractory patients with NMOSD. Notably, TCZ has marked effects on chronic neuropathic pain and general fatigue in patients refractory to standard medications. TCZ is a promising drug for preventing acute attacks in patients with NMOSD.

The role of the laboratory in the expanding field of neuroimmunology: Autoantibodies to neural targets

Accelerated identification of autoantibodies associated with previously idiopathic neurological disease has provided insights into disease mechanisms, enhanced understanding of neurological function, and opportunities for improved therapeutic interventions. The role of the laboratory in the expanding field of neuroimmunology is critical as specific autoantibody identification provides guidance to clinicians in diagnosis, prognosis, tumor search strategies, and therapeutic interventions. The number of specific autoantibodies identified continues to increase and newer testing strategies increase efficiencies in the laboratory and availability to clinicians. The need for broadly targeted efficient testing is underscored by the variability in clinical presentation and tumor associations attributable to a specific autoantibody, and conversely the various autoantibody specificities that can be the cause of a given clinical presentation. While many of the antineural antibodies were first recognized in the setting of neoplastic disease, idiopathic autoimmune neurological disease in the absence of underlying tumor is increasingly recognized. Appropriation of therapeutic modalities used to treat autoimmune disease to treat these autoantibody mediated neurological diseases has improved patient outcomes. Interaction between clinicians and laboratorians is critical to our understanding of these diseases and optimization of the clinical benefits of our increasing knowledge in neuroimmunology.

Neuromyelitis optica with unilateral diaphragmatic paralysis

In this case report, we describe the course of a female patient who is known to have neuromyelitis optica (NMO) and developed left hemiparesis and unilateral diaphragmatic paralysis. She was initially treated with intravenous methylprednisolone 1 g daily for 5 days without improvement. Subsequently, she received five sessions of a plasmapheresis. Her hemiparesis had improved after few days. however, the phrenic nerve palsy remained.

Rebound After Fingolimod and a Single Daclizumab Injection in a Patient Retrospectively Diagnosed With NMO Spectrum Disorder-MRI Apparent Diffusion Coefficient Maps in Differential Diagnosis of Demyelinating CNS Disorders

Objective: Differential diagnosis of neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis (MS) or mimics can be challenging, especially in patients with atypical presentations and negative serostatus for aquaporin-4 antibodies (AQP4-Ab). This brief research report describes magnetic resonance imaging (MRI) findings focusing on quantitative apparent diffusion coefficient (ADC) histogram analysis as a potential tool to differentiate NMOSD from MS.

Methods: Longitudinal MRI data obtained during routine clinical examinations were retrospectively analyzed in a patient with histologically determined cerebral NMOSD, a patient with an acute tumefactive MS lesion, and a patient with ischemic stroke. Histogram analyses of ADC maps were evaluated.

Results: A patient diagnosed with MS experienced a severe rebound after fingolimod withdrawal and a single daclizumab injection. Cerebral NMOSD manifestation was confirmed by brain biopsy. However, the patient did not fulfill consensus criteria for NMOSD and was AQP4-Ab negative. Comparison of ADC histogram analyses of this patient with those from a patient with MS and one with ischemic stroke revealed differential ADC characteristics: namely a more pronounced and prolonged ADC leftward shift in inflammatory than in ischemic pathology, even more accentuated in NMOSD versus MS.

Conclusion: ADC map histograms and ADC threshold values for different conditions may be useful for differentiation of large inflammatory brain lesions and further studies are merited.

TRPM2 Exacerbates Central Nervous System Inflammation in Experimental Autoimmune Encephalomyelitis by Increasing Production of CXCL2 Chemokines

Multiple sclerosis (MS) is a chronic inflammatory disorder of the CNS characterized by demyelination and axonal injury. Current therapies that mainly target lymphocytes do not fully meet clinical need due to the risk of severe side effects and lack of efficacy against progressive MS. Evidence suggests that MS is associated with CNS inflammation, although the underlying molecular mechanism is poorly understood. Transient receptor potential melastatin 2 (TRPM2), a Ca2+-permeable nonselective cation channel, is expressed at high levels in the brain and by immune cells, including monocyte lineage cells. Here, we show that TRPM2 plays a pathological role in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Knockout (KO) or pharmacological inhibition of TRPM2 inhibited progression of EAE and TRPM2-KO mice showed lower activation of Iba1-immunopositive monocyte lineage cells and neutrophil infiltration of the CNS than WT mice. Moreover, CXCL2 production in TRPM2-KO mice was significantly reduced at day 14, although the severity of EAE was the same as that in WT mice at that time point. In addition, we used BM chimeric mice to show that TRPM2 expressed by CNS-infiltrating macrophages contributes to progression of EAE. Because CXCL2 induces migration of neutrophils, these results indicate that reduced expression of CXCL2 in the CNS suppresses neutrophil infiltration and slows progression of EAE in TRPM2-KO mice. Together, the results suggest that TRPM2 plays an important role in progression of EAE pathology and shed light on its putative role as a therapeutic target for MS.SIGNIFICANCE STATEMENT Current therapies for multiple sclerosis (MS), which mainly target lymphocytes, carry the risk of severe side effects and lack efficacy against the progressive form of the disease. Here, we found that the transient receptor potential melastatin 2 (TRPM2) channel, which is abundantly expressed in CNS-infiltrating macrophages, plays a crucial role in development of experimental autoimmune encephalomyelitis (EAE), an animal model of MS. EAE progression was suppressed by Knockout (KO) or pharmacological inhibition of TRPM2; this was attributed to a reduction in CXCL2 chemokine production by CNS-infiltrating macrophages in TRPM2-KO mice, resulting in suppression of neutrophil infiltration into the CNS. These results reveal an important role of TRPM2 in the pathogenesis of EAE and shed light on its potential as a therapeutic target.

Prevalence of anti-aquaporin 4 antibody in a diagnostic cohort of patients being investigated for possible neuromyelitis optica spectrum disorder in Western Australia

OBJECTIVE

To evaluate the prevalence of anti-AQP4 antibody in serum and CSF samples from patients being investigated for possible neuromyelitis optica spectrum disorder (NMOSD) referred to the PathWest State reference laboratory using a sensitive cell-based assay (CBA).

BACKGROUND

NMOSD is an inflammatory CNS disease distinct from MS, which is relatively rare in Western countries. A proportion of patients with NMOSD have detectable serum IgG antibodies that target the water channel aquaporin-4 (AQP4-IgG), but the frequency varies in different populations studied and according to the assay method employed.

METHODS

Sera or CSF from a diagnostic cohort of 196 consecutive patients with possible NMOSD which had previously been screened by indirect immunofluorescence (IIF) on primate cerebellum were re-tested for AQP4-IgG reactivity to the M1 and M23 isoforms of AQP4 using a commercial CBA. A control group of 205 patients with definite MS was also included in the study.

RESULTS

Of the 196 patients, only 5 sera were AQP4-IgG positive, representing 2.6% of patients in the diagnostic cohort. All 5 AQP4-IgG positive patients fulfilled the 2015 revised diagnostic criteria for NMOSD and were females of varied ethnic origins, 4 of whom had longitudinally extensive transverse myelitis. The CBA confirmed AQP4-IgG positivity in the four patients previously reported as positive by IIF, and an additional patient with NMOSD who had previously been diagnosed as MS was also identified. None of the 205 MS sera were AQP4-IgG positive.

CONCLUSIONS

Our study confirms the utility and greater reliability of the M1/M23 CBA for detecting AQP4-IgG in patients with possible NMOSD, and indicates a prevalence of seropositive NMOSD in the Western Australian population similar to that in other Western populations.

Reduced expression of the IL7Ra signaling pathway in Neuromyelitis optica

Neuromyelitis optica (NMO) is a chronic inflammatory demyelinating autoimmune disease of the central nervous system that most commonly affects the optic nerves and spinal cord. To characterize the immunological pathways involved in NMO, whole blood RNA expression array was performed using Nanostring nCounter technology. Two major clusters of genes were found associated with NMO: T cell-associated genes and the TNF/NF-kB signaling pathway. Analysis of the genes within the first cluster confirmed significantly reduced expression of IL7Ra (CD127) in the peripheral blood of NMO patients vs that in healthy controls. IL7Ra upstream transcription factors and its downstream survival signaling pathway were also markedly reduced. In line with the essential role of IL7Ra in T cell maturation and survival, a significantly lower number of naïve T cells, and reduced T cell survival signaling mediated by increased BID (BH3-interacting domain death agonist) expression and increased apoptosis was observed. Cumulatively, these findings indicate that the IL7Ra signaling pathway may play a role in the autoimmune process in NMO.

Altered Macular Microvasculature in Neuromyelitis Optica Spectrum Disorders

PURPOSE

To evaluate macular microvascular changes in neuromyelitis optica spectrum disorders (NMOSD) by using optical coherence tomography angiography (OCT-A) and investigate their correlations with neuroaxonal structural damage evaluated with spectral-domain OCT (SD-OCT).

DESIGN

Cross-sectional study.

METHODS

Twenty eyes of 20 patients with NMOSD and 21 eyes from 21 healthy controls were enrolled. OCT-A was used to obtain microvascular network images of the whole, superficial, and deep retinal capillary plexuses (WRCP, SRCP, and DRCP) in a 3-mm-diameter area around the macula. SD-OCT was used to obtain the intraretinal thickness. Custom automated algorithms quantified the thickness of the intraretinal layers as well as microvascular density of the retinal capillary layers.

RESULTS

NMOSD patients showed significantly decreased microvascular density in both SRCP and DRCP (P < .05) compared to controls. The decreased microvascular density in SRCP and DRCP significantly correlated with the frequency of optic neuritis attack (P < .05). Both SRCP and DRCP microvascular density significantly correlated (P < .05) with retinal nerve fiber layer and ganglion cell layer with inner plexiform layer. SRCP microvascular density moderately correlated with visual acuity, while a stronger correlation was found between DRCP and visual acuity.

CONCLUSIONS

Decreased microvascular density in NMOSD patients correlated with the worsening of their visual acuity. Correlation between microvascular impairment and neuroaxonal thinning revealed that retinal microvascular alteration may contribute to neuroaxonal loss in NMOSD patients. OCT-A with measurable analysis offers a new path of study and will likely be useful as an objective biomarker for detecting microvascular impairment in NMOSD.

C5a-Preactivated Neutrophils Are Critical for Autoimmune-Induced Astrocyte Dysregulation in Neuromyelitis Optica Spectrum Disorder

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune neuroinflammatory disease. In contrast to multiple sclerosis, autoantibodies against aquaporin-4 (AQP4) expressed on astrocytic end-feet have been exclusively detected in sera of NMOSD patients. Several lines of evidence suggested that anti-AQP4 autoantibodies are pathogenic, but the mechanism triggering inflammation, impairment of astrocyte function, and the role of neutrophils presented in NMOSD cerebrospinal fluid remains unknown. In this study, we tested how human neutrophils affect astrocytes in the presence of anti-AQP4 Ab-positive serum derived from NMOSD patients. An in vitro model of inflammation consisted of human astrocyte line, NMOSD serum, and allogenic peripheral blood neutrophils from healthy individuals. We showed evidence of pathogenicity of NMOSD serum, which by consecutive action of anti-AQP4 Abs, complement system, and neutrophils affected astrocyte function. Anti-AQP4 Ab binding astrocytes initiated two parallel complementary reactions. The first one was dependent on the complement cytotoxicity via C5b-9 complex formation, and the second one on the reverse of astrocyte glutamate pump into extracellular space by C5a-preactivated neutrophils. As a consequence, astrocytes were partially destroyed; however, a major population of astrocytes polarized into proinflammatory cells which were characterized by pathological glutamate removal from extracellular space.

Neuromyelitis Optica: Review and Utility of Testing Aquaporin-4 Antibody in Typical Optic Neuritis

Neuromyelitis optica (NMO) is an autoimmune, inflammatory demyelinating disorder often leading to severe vision impairment and disability. The discovery of a diagnostic biomarker, the aquaporin-4 antibody (AQP4-IgG), transformed the clinical diagnosis and treatment of NMO and broadened the spectrum of disease [NMO spectrum disorders (NMOSD)]. Though the antibody is highly sensitive and specific to NMOSD, routine testing in patients with typical optic neuritis is considered controversial. This article will provide a brief review of NMOSD and highlight the pros and cons of routine testing in typical optic neuritis.

Aquaporin-4 Autoantibodies From Neuromyelitis Optica Spectrum Disorder Patients Induce Complement-Independent Immunopathologies in Mice

Neuromyelitis optica spectrum disorders (NMOSD) are central nervous system inflammatory disorders causing significant morbidities and mortality. The majority of NMOSD patients have autoimmunity against aquaporin-4 (AQP4), evidenced by seropositivity for autoantibodies against aquaporin-4 (AQP4–IgG). AQP4–IgG is pathogenic with neuroinflammation initiated upon binding of AQP4–IgG to astrocytic AQP4. Complement activation contributes to astrocytic cytotoxicity, neuroinflammation, and tissue necrosis in NMOSD, but the role of complement-independent mechanisms is uncertain. We studied the complement-independent pathogenic effects of AQP4–IgG by passive transfer of IgG from NMOSD patients to mice with breached blood–brain barrier (BBB). Mice, pretreated with bacterial proteins, received daily intraperitoneal injections of IgG purified from AQP4–IgG-seropositive NMOSD patients [IgG_(AQP4+)], or IgG from AQP4–IgG-seronegative patients [IgG_(AQP4−)] or healthy subjects [IgG_(Healthy)] for 8 days. Motor function was tested by walking across narrow beams, and spinal cords were collected for immunofluorescent analysis. We found that human IgG infiltrated into cord parenchyma of mice with breached BBB without deposition of complement activation products. Spinal cord of mice that received IgG_(AQP4+) demonstrated loss of AQP4 and glial fibrillary acidic protein (suggestive of astrocyte loss), decrease in excitatory amino acid transporter 2, microglial/macrophage activation, neutrophil infiltration, patchy demyelination, and loss in axonal integrity. Mice that received IgG_(AQP4+) required longer time with more paw slips to walk across narrow beams indicative of motor slowing and incoordination. Our findings suggest that AQP4–IgG induces complement-independent cord pathologies, including astrocytopathy, neuroinflammation, demyelination, and axonal injuries/loss, which are associated with subtle motor impairments. These complement-independent pathophysiologies likely contribute to early NMOSD lesion development.

Persistent microscopic active inflammatory lesions in the central nervous system of a patient with neuromyelitis optica treated with oral prednisolone for more than 40 years

We have reported an autopsy case of neuromyelitis optica (NMO) that exhibited persisting active inflammatory lesions in the central nervous system (CNS) despite a 45-year-long treatment with oral corticosteroids. To our knowledge, our case had received the longest course of maintenance treatment. This case study suggests that the current treatment of NMO with immunosuppressive agents may offer a good prospect for improving life expectancy. On the other hand, it also suggest that microscopic active lesions which were clinically silent and difficult to detect by neurological examination or MRI studies may persist in the CNS in patients with NMO, despite prolonged and continuous immunosuppressive treatment.

Induced CNS expression of CXCL1 augments neurologic disease in a murine model of multiple sclerosis via enhanced neutrophil recruitment

Increasing evidence points to an important role for neutrophils in participating in the pathogenesis of the human demyelinating disease MS and the animal model EAE. Therefore, a better understanding of the signals controlling migration of neutrophils as well as evaluating the role of these cells in demyelination is important to define cellular components that contribute to disease in MS patients. In this study, we examined the functional role of the chemokine CXCL1 in contributing to neuroinflammation and demyelination in EAE. Using transgenic mice in which expression of CXCL1 is under the control of a tetracycline‐inducible promoter active within glial fibrillary acidic protein‐positive cells, we have shown that sustained CXCL1 expression within the CNS increased the severity of clinical and histologic disease that was independent of an increase in the frequency of encephalitogenic Th1 and Th17 cells. Rather, disease was associated with enhanced recruitment of CD11b⁺Ly6G⁺ neutrophils into the spinal cord. Targeting neutrophils resulted in a reduction in demyelination arguing for a role for these cells in myelin damage. Collectively, these findings emphasize that CXCL1‐mediated attraction of neutrophils into the CNS augments demyelination suggesting that this signaling pathway may offer new targets for therapeutic intervention.

Recombinant IgG1 Fc hexamers block cytotoxicity and pathological changes in experimental in vitro and rat models of neuromyelitis optica

Intravenous human immunoglobulin G (IVIG) may have therapeutic benefit in neuromyelitis optica spectrum disorders (herein called NMO), in part because of the anti-inflammatory properties of the IgG Fc region. Here, we evaluated recombinant Fc hexamers consisting of the IgM μ-tailpiece fused with the Fc region of human IgG1. In vitro, the Fc hexamers prevented cytotoxicity in aquaporin-4 (AQP4) expressing cells and in rat spinal cord slice cultures exposed to NMO anti-AQP4 autoantibody (AQP4-IgG) and complement, with >500-fold greater potency than IVIG or monomeric Fc fragments. Fc hexamers at low concentration also prevented antibody-dependent cellular cytotoxicity produced by AQP4-IgG and natural killer cells. Serum from rats administered a single intravenous dose of Fc hexamers at 50 mg/kg taken at 8 h did not produce complement-dependent cytotoxicity when added to AQP4-IgG-treated AQP4-expressing cell cultures. In an experimental rat model of NMO produced by intracerebral injection of AQP4-IgG, Fc hexamers at 50 mg/kg administered before and at 12 h after AQP4-IgG fully prevented astrocyte injury, complement activation, inflammation and demyelination. These results support the potential therapeutic utility of recombinant IgG1 Fc hexamers in AQP4-IgG seropositive NMO.

Selective localization of IgG from cerebrospinal fluid to brain parenchyma

Background

Encounter of autoantibodies with specific antigens can lead to hypersensitivity reactions and pathology. In multiple sclerosis and neuromyelitis optica spectrum disease (NMOSD), immunoglobulin-G (IgG) deposition has been observed in pathological lesions in the central nervous system. The paradigmatic autoantibodies in NMOSD are specific for the water channel aquaporin-4, localized to astrocytic end-feet at the blood-brain barrier and ependymal cells at the cerebrospinal fluid-brain barrier. We have previously observed that IgG antibodies from NMO patients (NMO-IgG) access brain parenchyma from the cerebrospinal fluid and induce subpial and periventricular NMO-like lesions and blood-brain barrier breakdown, in a complement-dependent manner.

Objective

To investigate how IgG trafficking from cerebrospinal fluid to brain parenchyma can be influenced by injury.

Methods

IgG from healthy donors was intrathecally injected into the cerebrospinal fluid via cisterna magna at 1, 2, 4, or 7 days after a distal stereotactic sterile needle insertion to the striatum.

Results

Antibody deposition, detected by staining for human IgG, peaked 1 day after the intrathecal injection and was selectively seen close to the needle insertion. When NMO-IgG was intrathecally injected, we observed complement-dependent NMO-like pathology (loss of aquaporin-4 and glial fibrillary acidic protein) proximal to the insertion site, with similar kinetics. A fluorescent tracer did not show the same distribution indicating IgG-selective localization.

Conclusion

These findings suggest that IgG from cerebrospinal fluid localize selectively in brain parenchyma at the site of injury and pathogenic NMO-IgG induce astrocyte pathology at the same location.

Short delay to initiate plasma exchange is the strongest predictor of outcome in severe attacks of NMO spectrum disorders

INTRODUCTION

Severe attacks of neuromyelitis optica spectrum disorder (NMO-SD) are improved by plasma exchange (PLEX) given as an adjunctive therapy. Initial studies failed to demonstrate a delay of PLEX treatment influenced clinical outcome; however PLEX was always used late. We examine the clinical consequences of delay in PLEX initiation on severe optic neuritis and spinal cord attacks in NMO-SD.

METHODS

All of our patients who suffered attacks of NMO-SD, treated in our centre by PLEX, were retrospectively considered for inclusion. Primary outcome was defined as complete improvement. Secondary poor/good outcomes were respectively defined to be the higher/lower third of Delta-Expanded Disability Status Scale (EDSS) (late minus baseline EDSS). Delays from clinical onset to PLEX initiation were categorised for multivariate analysis.

RESULTS

Of the 60 patients included, NMO-SD criteria (2015) were fulfilled in 92%. One hundred and fifteen attacks were included and received PLEX with a median of 7 days (0-54) after clinical onset. The probability to regain complete improvement continuously decreased from 50% for PLEX given at day 0 to 1%-5% after day 20. Through multivariate analysis, the baseline impairment and PLEX delay were associated with the probability to complete improvement (OR 5.3; 95% CI 1.8 to 15.9). Reducing the PLEX delay also influenced the good secondary outcome but not the poor secondary outcome.

CONCLUSIONS

These results confirm an improved clinical benefit of early initiation of PLEX during severe attacks of NMO-SD. Perceiving PLEX as a rescue therapy only after steroid failure could be deleterious.

B cell-based therapies in CNS autoimmunity: differentiating CD19 and CD20 as therapeutic targets

Increasing recognition of the role of B cells in the adaptive immune response makes B cells an important therapeutic target in autoimmunity. Numerous current and developmental immunotherapies target B cells for elimination through recognition of cell-surface proteins expressed specifically on B cells, in particular CD19 and CD20. Similarities and differences in the function and expression of these two molecules predict some shared, and some distinct, pharmacological effects of agents targeting CD19 versus CD20, potentially leading to differences in the clinical safety and efficacy of such agents. Here, we review current knowledge of CD19 and CD20 function and biology, survey current and developmental therapies that target these molecules, and discuss potential differences in elimination of B cells by drugs that target CD19 versus CD20, with particular focus on the central nervous system autoimmune diseases multiple sclerosis and neuromyelitis optica. The principles and mechanisms herein discussed might also be relevant to a variety of other nervous system autoimmune disorders, including NMDA (N-methyl-D-aspartate) receptor encephalitis, transverse myelitis and myasthenia gravis.

Astrocytic Interleukin-15 Reduces Pathology of Neuromyelitis Optica in Mice

Astrocyte loss induced by neuromyelitis optica (NMO)-IgG and complement-dependent cytotoxicity (CDC) is the hallmark of NMO pathology. The survival of astrocytes is thought to reflect astrocyte exposure to environmental factors in the CNS and the response of astrocytes to these factors. However, still unclear are how astrocytes respond to NMO-IgG and CDC, and what CNS environmental factors may impact the survival of astrocytes. In a murine model of NMO induced by intracerebral injection of NMO-IgG and human complement, we found dramatic upregulation of IL-15 in astrocytes. To study the role of astrocytic IL-15 in NMO, we generated a transgenic mouse line with targeted expression of IL-15 in astrocytes (IL-15^tg), in which the expression of IL-15 is controlled by a glial fibrillary acidic protein promoter. We showed that astrocyte-targeted expression of IL-15 attenuates astrocyte injury and the loss of aquaporin-4 in the brain. Reduced blood–brain barrier leakage and immune cell infiltration are also found in the lesion of IL-15^tg mice subjected to NMO induction. IL-15^tg astrocytes are less susceptible to NMO-IgG-mediated CDC than their wild-type counterparts. The enhanced resistance of IL-15^tg astrocytes to cytotoxicity and cell death involves NF-κB signaling pathway. Our findings suggest that IL-15 reduces astrocyte loss and NMO pathology.

Elevated Plasma Chemokines for Eosinophils in Neuromyelitis Optica Spectrum Disorders during Remission

Background

A prominent pathological feature of neuromyelitis optica spectrum disorders (NMOSD) is markedly greater eosinophilic infiltration than that seen in other demyelinating diseases, like multiple sclerosis (MS). Eosinophils express the chemokine receptor CCR3, which is activated by eotaxins (CCL11/eotaxin-1, CCL24/eotaxin-2, CCL26/eotaxin-3) and CCL13 [monocyte chemoattractant protein (MCP)-4]. Moreover, CCL13 is part of the chemokine set that activates CCR2. The present study aimed to evaluate plasma levels of eotaxins (CCL11, CCL24, and CCL26) and MCPs (CCL13, CCL2, CCL8, and CCL7) in patients with NMOSD during remission.

Methods

Healthy controls (HC; n = 30) and patients with MS (n = 47) and NMOSD (n = 58) in remission were consecutively enrolled in this study between January 2016 and August 2017. Plasma CCL11, CCL24, CCL26, CCL2, CCL8, CCL7, CCL13, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β levels were detected using the human cytokine multiplex assay.

Results

Plasma CCL13, CCL11, and CCL26 levels were all significantly higher in patients with NMOSD than in HC and patients with MS. No significant differences were found in the CCL13, CCL11, or CCL26 levels between patients with NMOSD receiving and not receiving immunosuppressive therapy. The plasma levels of TNF-α and IL-1β, which stimulate the above chemokines, were higher in patients with NMOSD than in HC. There was no difference in CCL24 levels among the three groups. In most cases, the CCL7 levels were below the threshold value of the human cytokine multiplex assay, which is in line with other studies. Adjusted multiple regression analyses showed a positive association of CCL13 levels with the number of relapses after controlling gender, age, body mass index, and disease duration in patients with NMOSD.

Conclusion

The study indicates that in NMOSD, the overproduction of cytokines such as IL-1β and TNF-α during remission stimulates eosinophilic chemoattractants such as CCL13, CCL11, and CCL26, which in turn bind to their receptor (CCR3); this could lead to eosinophil hypersensitivity. These findings suggest that the elevated secretion of CCL13, CCL11, and CCL26 may be a critical step in eosinophil recruitment during NMOSD remission.

Diagnosis and management of neuromyelitis optica spectrum disorders - An update

Neuromyelitis optica (NMO) and Neuromyelitis optica spectrum disorders (NMOSD) are a group of autoimmune conditions characterized by inflammatory involvement of the optic nerve, spinal cord and central nervous system. Novel evidence showed a key role of autoantibodies against aquaporin-4 immunoglobulin G (AQP4 IgG) in the pathogenesis of NMOSD and, recently, new classification and diagnostic criteria have been adopted to facilitate an earlier identification and improve the management of these conditions. Diagnosis of NMOSD is currently based on clinical, neuroimaging and laboratory features. Standard treatment is based on the use of steroids and immunosuppressive drugs and aims to control the severity of acute attacks and to prevent relapses of the disease. This review gives an update of latest knowledge of NMOSD and NMO, emphasizing the novel diagnostic criteria and both current and future therapeutic approaches.

Neuromyelitis optica and neuromyelitis optica spectrum disorders

PURPOSE OF REVIEW

The discovery of highly specific auto-antibodies directed against the water channel aquaporin 4 was a quantum leap in the definition, classification and management of neuromyelitis optica (NMO). Herein, we propose an update on epidemiological, clinical and therapeutic advances in the field, underlining unmet needs.

RECENT FINDINGS

Large-scale epidemiological studies have recently provided a more precise evaluation of NMO prevalence and a better stratification regarding ethnicity and sex. New criteria have been proposed for so-called NMO spectrum disorders (NMOSD) and their relevance is currently being assessed. The identification of a new clinical entity associated to antibodies against myelin oligodendrocyte glycoprotein questions the border of NMOSD.

SUMMARY

The concept of NMOSD is opening a new era in clinical practice, allowing an easier and more homogeneous diagnosis and an increase in newly identified cases. This will facilitate clinical studies and support new therapeutic trial. Future researches should focus on the position of seronegative NMOSD and myelin oligodendrocyte glycoprotein-IgG disorders in the field and on promising strategies, including the immune tolerisation approaches, to eventually cure NMO.

Inhibition of RGMa alleviates symptoms in a rat model of neuromyelitis optica

Neuromyelitis optica (NMO) is an autoimmune disease associated with NMO immunoglobulin G (NMO-IgG), an antibody that selectively binds to the aquaporin-4. Here, we established a localized NMO model by injecting NMO-IgG into the spinal cord, and assessed the efficacy of treating its NMO-like symptoms by blocking repulsive guidance molecule-a (RGMa), an axon growth inhibitor. The model showed pathological features consistent with NMO. Systemic administration of humanized monoclonal anti-RGMa antibody delayed the onset and attenuated the severity of clinical symptoms. Further, it preserved astrocytes and reduced inflammatory-cell infiltration and axonal damage, suggesting that targeting RGMa is effective in treating NMO.

The Interleukin (IL)-23/T helper (Th)17 Axis in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

T helper (Th)17 cells are responsible for host defense against fungi and certain extracellular bacteria but have also been reported to play a role in a variety of autoimmune diseases. Th17 cells respond to environmental cues, are very plastic, and might also be involved in tissue homeostasis and regeneration. The imprinting of pathogenic properties in Th17 cells in autoimmunity seems highly dependent on interleukin (IL)-23. Since Th17 cells were first described in experimental autoimmune encephalomyelitis, they have been suggested to also promote tissue damage in multiple sclerosis (MS). Indeed, some studies linked Th17 cells to disease severity in MS, and the efficacy of anti-IL-17A therapy in MS supported this idea. In this review, we will summarize molecular features of Th17 cells and discuss the evidence for their function in experimental models of autoimmune diseases and MS.

Treatment strategies for neuromyelitis optica

Neuromyelitis optica (NMO) is an autoimmune demyelinating disease with pathogenic autoantibodies that act against the astrocyte water channel protein, i.e. aquaporin-4: the disease is associated with recurrent episodes of optic neuritis (ON) and transverse myelitis, often resulting in severe disability. The main goals in treatment of NMO include acute symptomatic therapy and long-term stabilization of symptoms by preventing relapse. In recent years, ongoing randomized controlled trials in NMO patients have studied evidence for treatment. Briefly, acute-stage management (with pulse therapy using corticosteroids and/or plasmapheresis) and maintenance therapy (including rituximab, mycophenolate mofetil, and azathioprine) have been recommended in some case series and retrospective studies. Because of the high prevalence of liver disease, all NMO patients in Taiwan should be screened for hepatitis B and C before treatment is initiated. Although immunosuppression and plasma exchange are the mainstays of therapy for NMO ON, several selective and potentially therapeutic strategies targeting specific steps in NMO pathogenesis including blockers of NMO-IgG binding and inhibitors of granulocyte function have been evaluated in recent years.

Therapeutic Efficacy of Plasma Exchange in Neuromyelitis Optica

Background

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that selectively affects the optic nerves and spinal cord and generally follows a relapsing course. Therapeutic plasma exchange (TPE) appears to be effective in patients with central nervous system inflammatory demyelinating disease who do not respond to first-line corticosteroid treatment.

Objective

We represent a retrospective review of the use of TPE in the treatment of an acute attack of NMO in five patients who failed to respond to initial immunomodulatory treatment.

Materials and Methods

We evaluated the effect of TPE on the degree of recovery from NMO. It was performed using a single volume plasma exchange with intermittent cell separator (Hemonetics Mobile Collection System plus) by femoral or central line access and scheduled preferably on alternate-day intervals from 8 to 10 days. Both subjective and objective clinical response to TPE was estimated, and final assessment of response was made at the time of the last TPE in the series.

Results

All patients were severely disabled before the initiation of TPE and they were female; with the mean age of these patients was 52.5 years (range = 36-69 years), the median age of NMO diagnosis was 49.4 years (range = 35-65 years), and the median duration of disease was 2.6 years (range = 0-5 years). Out of five patients, three had a history of bilateral optic neuritis, and all patients were anti-against protein aquaporin-4antibody positive. Totally 24 TPE procedures were performed on five patients, the mean time of start of TPE in the acute attack was 18.6 days. Patients were severely disabled at the initiation of TPE (range = expanded disability status scale 6.5-9), and improvement was observed early in the course of TPE treatment in most patients.

Conclusion

The present study provides clinical support for the importance of TPE in refractory acute attack in NMO. However, with new diagnostic technologies and increasing clinical awareness, we may see a more improved ways of TPE in these patients in the future; hence, TPE is more effective modality of treatment as it also removed the antibodies.

The Gut Microbiome in Neuromyelitis Optica

Neuromyelitis optica (NMO) is a rare, disabling, sometimes fatal central nervous system inflammatory demyelinating disease that is associated with antibodies ("NMO IgG") that target the water channel protein aquaporin-4 (AQP4) expressed on astrocytes. There is considerable interest in identifying environmental triggers that may elicit production of NMO IgG by AQP4-reactive B cells. Although NMO is considered principally a humoral autoimmune disease, antibodies of NMO IgG are IgG1, a T-cell-dependent immunoglobulin subclass, indicating that AQP4-reactive T cells have a pivotal role in NMO pathogenesis. When AQP4-specific proliferative T cells were first identified in patients with NMO it was discovered that T cells recognizing the dominant AQP4 T-cell epitope exhibited a T helper 17 (Th17) phenotype and displayed cross-reactivity to a homologous peptide sequence within a protein of Clostridium perfringens, a commensal bacterium found in human gut flora. The initial analysis of gut microbiota in NMO demonstrated that, in comparison to healthy controls (HC) and patients with multiple sclerosis, the microbiome of NMO is distinct. Remarkably, C. perfringens was the second most significantly enriched taxon in NMO, and among bacteria identified at the species level, C. perfringens was the one most highly associated with NMO. Those discoveries, along with evidence that certain Clostridia in the gut can regulate the balance between regulatory T cells and Th17 cells, indicate that gut microbiota, and possibly C. perfringens itself, could participate in NMO pathogenesis. Collectively, the evidence linking microbiota to humoral and cellular immunity in NMO underscores the importance for further investigating this relationship.

Inflammatory demyelinating diseases of the central nervous system

Inflammatory demyelinating diseases are a heterogeneous group of disorders, which occur against the background of an acute or chronic inflammatory process. The pathologic hallmark of multiple sclerosis (MS) is the presence of focal demyelinated lesions with partial axonal preservation and reactive astrogliosis. Demyelinated plaques are present in the white as well as gray matter, such as the cerebral or cerebellar cortex and brainstem nuclei. Activity of the disease process is reflected by the presence of lesions with ongoing myelin destruction. Axonal and neuronal destruction in the lesions is a major substrate for permanent neurologic deficit in MS patients. The MS pathology is qualitatively similar in different disease stages, such as relapsing remitting MS or secondary or primary progressive MS, but the prevalence of different lesion types differs quantitatively. Acute MS and Balo's type of concentric sclerosis appear to be variants of classic MS. In contrast, neuromyelitis optica (NMO) and spectrum disorders (NMOSD) are inflammatory diseases with primary injury of astrocytes, mediated by aquaporin-4 antibodies. Finally, we discuss the histopathology of other inflammatory demyelinating diseases such as acute disseminated encephalomyelitis and myelin oligodendrocyte glycoprotein antibody-associated demyelination. Knowledge of the heterogenous immunopathology in demyelinating diseases is important, to understand the clinical presentation and disease course and to find the optimal treatment for an individual patient.

Immunopathogenesis in Myasthenia Gravis and Neuromyelitis Optica

Myasthenia gravis (MG) and neuromyelitis optica (NMO) are autoimmune channelopathies of the peripheral neuromuscular junction (NMJ) and central nervous system (CNS) that are mainly mediated by humoral immunity against the acetylcholine receptor (AChR) and aquaporin-4 (AQP4), respectively. The diseases share some common features, including genetic predispositions, environmental factors, the breakdown of tolerance, the collaboration of T cells and B cells, imbalances in T helper 1 (Th1)/Th2/Th17/regulatory T cells, aberrant cytokine and antibody secretion, and complement system activation. However, some aspects of the immune mechanisms are unique. Both targets (AChR and AQP4) are expressed in the periphery and CNS, but MG mainly affects the NMJ in the periphery outside of CNS, whereas NMO preferentially involves the CNS. Inflammatory cells, including B cells and macrophages, often infiltrate the thymus but not the target—muscle in MG, whereas the infiltration of inflammatory cells, mainly polymorphonuclear leukocytes and macrophages, in NMO, is always observed in the target organ—the spinal cord. A review of the common and discrepant characteristics of these two autoimmune channelopathies may expand our understanding of the pathogenic mechanism of both disorders and assist in the development of proper treatments in the future.

Neuromyelitis Optica (Devic's Syndrome): an Appraisal

Neuromyelitis optica (NMO) and neuromyelitis optica spectrum disorders (NMOSD), previously known as Devic's syndrome, are a group of inflammatory disorders of the central nervous system (CNS) characterized by severe, immune-mediated demyelination and axonal damage, predominantly targeting optic nerves and the spinal cord typically associated with a disease-specific serum NMO-IgG antibody that selectively binds aquaporin-4 (AQP4). The classic and best-defined features of NMOSD include acute attacks of bilateral or rapidly sequential optic neuritis (leading to visual loss) or transverse myelitis (often causing limb weakness and bladder dysfunction) or both with a typically relapsing course. The diagnosis of NMO/NMOSD requires a consistent history and examination with typical clinical presentations, findings on spinal cord neuroimaging with MRI, cerebrospinal fluid analysis along with determination of AQP4-IgG serum autoantibody status, and exclusion of other disorders. Two major advances in this field has been the development of diagnostic criteria and treatment recommendations. Consensus diagnostic criteria have been established and were recently revised and published in 2015, enhancing the ability to make a diagnosis and appropriately evaluate these disorders. Expert recommendations and uncontrolled trials form the basis of treatment guidelines. All patients with suspected NMOSD should be treated for acute attacks as soon as possible with high-dose intravenous methylprednisolone -1 gram daily for three to five consecutive days and in some cases, plasma exchange should be used. It is recommended that every patient with NMOSD be started on an immunosuppressive agent, such as, azathioprine, methotrexate, or mycophenolate and in some cases, rituximab, soon after the acute attack and usually be treated for about 5 years after the attack. These advances have helped improve the prognosis and outcome in these disorders.

The Role of Brain-Reactive Autoantibodies in Brain Pathology and Cognitive Impairment

Antibodies to different brain proteins have been recently found to be associated with an increasing number of different autoimmune diseases. They need to penetrate the blood–brain barrier (BBB) in order to bind antigens within the central nervous system (CNS). They can target either neuronal or non-neuronal antigen and result in damage either by themselves or in synergy with other inflammatory mediators. Antibodies can lead to acute brain pathology, which may be reversible; alternatively, they may trigger irreversible damage that persists even though the antibodies are no longer present. In this review, we will describe two different autoimmune conditions and the role of their antibodies in causing brain pathology. In systemic lupus erythematosus (SLE), patients can have double stranded DNA antibodies that cross react with the neuronal N-methyl-d-aspartate receptor (NMDAR), which have been recently linked to neurocognitive dysfunction. In neuromyelitis optica (NMO), antibodies to astrocytic aquaporin-4 (AQP4) are diagnostic of disease. There is emerging evidence that pathogenic T cells also play an important role for the disease pathogenesis in NMO since they infiltrate in the CNS. In order to enable appropriate and less invasive treatment for antibody-mediated diseases, we need to understand the mechanisms of antibody-mediated pathology, the acute and chronic effects of antibody exposure, if the antibodies are produced intrathecally or systemically, their target antigen, and what triggers their production. Emerging data also show that in utero exposure to some brain-reactive antibodies, such as those found in SLE, can cause neurodevelopmental impairment since they can penetrate the embryonic BBB. If the antibody exposure occurs at a critical time of development, this can result in irreversible damage of the offspring that persists throughout adulthood.

CNS inflammation and neurodegeneration

There is an increasing recognition that inflammation plays a critical role in neurodegenerative diseases of the CNS, including Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and the prototypic neuroinflammatory disease multiple sclerosis (MS). Differential immune responses involving the adaptive versus the innate immune system are observed at various stages of neurodegenerative diseases, and may not only drive disease processes but could serve as therapeutic targets. Ongoing investigations into the specific inflammatory mechanisms that play roles in disease causation and progression have revealed lessons about inflammation-driven neurodegeneration that can be applied to other neurodegenerative diseases. An increasing number of immunotherapeutic strategies that have been successful in MS are now being applied to other neurodegenerative diseases. Some approaches suppress CNS immune mechanisms, while others harness the immune system to clear deleterious products and cells. This Review focuses on the mechanisms by which inflammation, mediated either by the peripheral immune response or by endogenous CNS immune mechanisms, can affect CNS neurodegeneration.

Finding NMO: The Evolving Diagnostic Criteria of Neuromyelitis Optica

Neuromyelitis optica (NMO) is an autoimmune demyelinating disorder of the central nervous system (CNS) with predilection for the optic nerves and spinal cord. Since its emergence in the medical literature in the late 1800's, the diagnostic criteria for NMO has slowly evolved from the simultaneous presentation of neurologic and ophthalmic signs to a relapsing or monophasic CNS disorder defined by clinical, neuroimaging, and laboratory criteria. Due to the identification of a specific autoantibody response against the astrocyte water channel aquaporin-4 (AQP4) in the vast majority of affected individuals, the clinical spectrum of NMO has greatly expanded necessitating the development of new international criteria for the diagnosis of NMO spectrum disorder (NMOSD). The routine application of new diagnostic criteria for NMOSD in clinical practice will be critical for future refinement and correlation with therapeutic outcomes.

Effectiveness of low dose of rituximab compared with azathioprine in Chinese patients with neuromyelitis optica: an over 2-year follow-up study

Neuromyelitis optical (NMO) and neuromyelitis optical spectrum disorder (NMOSD) are inflammatory autoimmune demyelination diseases affecting the central nervous system. We investigated the efficiency of low-dose rituximab treatment in 31 Chinese patients with NMO/NMOSD across a median period of 2.29 ± 0.97 years and azathioprine combined with corticosteroid treatment in 34 Chinese patients with NMO/NMOSD across a median period of 2.61 ± 0.94 years. Among the rituximab-treated patients, the mean Expanded Disability Status Scale (EDSS) was 5.62 ± 1.35 before treatment and 4.48 ± 0.78 at last follow-up, and the mean annualized relapse rate (ARR) was 1.39 ± 0.42 before treatment and 0.03 ± 0.13 at last follow-up. Among the azathioprine-treated patients, the mean EDSS was 5.63 ± 1.29 before treatment and 5.05 ± 1.00 at last follow-up, and the mean ARR was 1.28 ± 0.34 before treatment and 0.49 ± 0.21 at last follow-up. In this study, we showed that using low-dosage rituximab could benefit Chinese patients with NMO by reducing the new occurrence of relapses dramatically. Compared with the azathioprine-treated patients, we concluded that rituximab is more effective in preventing NMO relapse and could improve the symptoms.

Paediatric Multiple Sclerosis: Update on Diagnostic Criteria, Imaging, Histopathology and Treatment Choices

Paediatric multiple sclerosis (MS) represents less than 5 % of the MS population, but patients with paediatric-onset disease reach permanent disability at a younger age than adult-onset patients. Accurate diagnosis at presentation and optimal long-term treatment are vital to mitigate ongoing neuroinflammation and irreversible neurodegeneration. However, it may be difficult to early differentiate paediatric MS from acute disseminated encephalomyelitis (ADEM) and neuromyelitis optica spectrum disorders (NMOSD), as they often have atypical presentation that differs from that of adult-onset MS. The purpose of this review is to summarize the updated views on diagnostic criteria, imaging, histopathology and treatment choices.

Neuronal Surface Autoantibodies in Neuropsychiatric Disorders: Are There Implications for Depression?

Autoimmune diseases are affecting around 7.6-9.4% of the general population. A number of central nervous system disorders, including encephalitis and severe psychiatric disorders, have been demonstrated to associate with specific neuronal surface autoantibodies (NSAbs). It has become clear that specific autoantibodies targeting neuronal surface antigens and ion channels could cause severe mental disturbances. A number of studies have focused or are currently investigating the presence of autoantibodies in specific mental conditions such as schizophrenia and bipolar disorders. However, less is known about other conditions such as depression. Depression is a psychiatric disorder with complex etiology and pathogenesis. The diagnosis criteria of depression are largely based on symptoms but not on the origin of the disease. The question which arises is whether in a subgroup of patients with depression, the symptoms might be caused by autoantibodies targeting membrane-associated antigens. Here, we describe how autoantibodies targeting membrane proteins and ion channels cause pathological effects. We discuss the physiology of these antigens and their role in relation to depression. Finally, we summarize a number of studies detecting NSAbs with a special focus on cohorts that include depression diagnosis and/or show depressive symptoms.

Bystander mechanism for complement-initiated early oligodendrocyte injury in neuromyelitis optica

Neuromyelitis optica spectrum disorder (herein called NMO) is an autoimmune inflammatory disease of the central nervous system in which immunoglobulin G antibodies against astrocyte water channel aquaporin-4 (AQP4-IgG) cause demyelination and neurological deficit. Injury to oligodendrocytes, which do not express AQP4, links the initiating pathogenic event of AQP4-IgG binding to astrocyte AQP4 to demyelination. Here, we report evidence for a complement 'bystander mechanism' to account for early oligodendrocyte injury in NMO in which activated, soluble complement proteins following AQP4-IgG binding to astrocyte AQP4 result in deposition of the complement membrane attack complex (MAC) on nearby oligodendrocytes. Primary cocultures of rat astrocytes and mature oligodendrocytes exposed to AQP4-IgG and complement showed early death of oligodendrocytes in close contact with astrocytes, which was not seen in pure oligodendrocyte cultures, in cocultures exposed to AQP4-IgG and C6-depleted serum, or when astrocytes were damaged by a complement-independent mechanism. Astrocyte-oligodendrocyte cocultures exposed to AQP4-IgG and complement showed prominent MAC deposition on oligodendrocytes in contact with astrocytes, whereas C1q, the initiating protein in the classical complement pathway, and C3d, a component of the alternative complement pathway, were deposited only on astrocytes. Early oligodendrocyte injury with MAC deposition was also found in rat brain following intracerebral injection of AQP4-IgG, complement and a fixable dead-cell stain. These results support a novel complement bystander mechanism for early oligodendrocyte injury and demyelination in NMO.

RETINAL VASCULITIS ASSOCIATED WITH NEUROMYELITIS OPTICA

PURPOSE

To report a case of retinal vasculitis in a patient with neuromyelitis optica.

METHODS

Clinical case report, imaging was obtained with photographs, fluorescein angiography, spectral domain optical coherence tomography, and magnetic resonance imaging.

RESULTS

The aforementioned patient presented with urinary incontinence and spastic paraparesis. She was found to have a transverse myelitis on magnetic resonance imaging and positive anti-aquaporin-4 (AQP4-Ab) testing. She had no associated visual symptoms. Examination revealed a retinal vasculitis. There have been no previous reports of retinal vasculitis associated with neuromyelitis optica or neuromyelitis optica spectrum disorder.

CONCLUSION

Retinal vasculitis can be associated with neuromyelitis optica.

The Role of Peripheral CNS-Directed Antibodies in Promoting Inflammatory CNS Demyelination

In central nervous system (CNS) demyelinating disorders, such as multiple sclerosis (MS), neuromyelitis optica (NMO) and related NMO-spectrum disorders (NMO-SD), a pathogenic role for antibodies is primarily projected into enhancing ongoing CNS inflammation by directly binding to target antigens within the CNS. This scenario is supported at least in part, by antibodies in conjunction with complement activation in the majority of MS lesions and by deposition of anti-aquaporin-4 (AQP-4) antibodies in areas of astrocyte loss in patients with classical NMO. A currently emerging subgroup of AQP-4 negative NMO-SD patients expresses antibodies against myelin oligodendrocyte glycoprotein (MOG), again suggestive of their direct binding to CNS myelin. However, both known entities of anti-CNS antibodies, anti-AQP-4- as well as anti-MOG antibodies, are predominantly found in the serum, which raises the questions why and how a humoral response against CNS antigens is raised in the periphery, and in a related manner, what pathogenic role these antibodies may exert outside the CNS. In this regard, recent experimental and clinical evidence suggests that peripheral CNS-specific antibodies may indirectly activate peripheral CNS-autoreactive T cells by opsonization of otherwise unrecognized traces of CNS antigen in peripheral compartments, presumably drained from the CNS by its newly recognized lymphatic system. In this review, we will summarize all currently available data on both possible roles of antibodies in CNS demyelinating disorders, first, directly enhancing damage within the CNS, and second, promoting a peripheral immune response against the CNS. By elaborating on the latter scenario, we will develop the hypothesis that peripheral CNS-recognizing antibodies may have a powerful role in initiating acute flares of CNS demyelinating disease and that these humoral responses may represent a therapeutic target in its own right.