Treatment of neuromyelitis optica: state-of-the-art and emerging therapies

Variable sensitivity to complement-dependent cytotoxicity in murine models of neuromyelitis optica

Background

Studies of neuromyelitis optica (NMO), an autoimmune disease of the central nervous system (CNS), have demonstrated that autoantibodies against the water channel aquaporin-4 (AQP4) induce astrocyte damage through complement-dependent cytotoxicity (CDC). In developing experimental models of NMO using cells, tissues or animals from mice, co-administration of AQP4-IgG and normal human serum, which serves as the source of human complement (HC), is required. The sensitivity of mouse CNS cells to HC and CDC in these models is not known.

Methods

We used HC and recombinant monoclonal antibodies (rAbs) against AQP4 to investigate CDC on mouse neurons, astrocytes, differentiated oligodendrocytes (OLs), and oligodendrocyte progenitors (OPCs) in the context of purified monocultures, neuroglial mixed cultures, and organotypic cerebellar slices.

Results

We found that murine neurons, OLs, and OPCs were sensitive to HC in monocultures. In mixed murine neuroglial cultures, HC-mediated toxicity to neurons and OLs was reduced; however, astrocyte damage induced by an AQP-specific rAb #53 and HC increased neuronal and oligodendroglial loss. OPCs were resistant to HC toxicity in neuroglial mixed cultures. In mouse cerebellar slices, damage to neurons and OLs following rAb #53-mediated CDC was further reduced, but in contrast to neuroglial mixed cultures, astrocyte damage sensitized OPCs to complement damage. Finally, we established that some injury to neurons, OLs, and OPCs in cell and slice cultures resulted from the activation of HC by anti-tissue antibodies to mouse cells.

Conclusions

Murine neurons and oligodendroglia demonstrate variable sensitivity to activated complement based on their differentiation and culture conditions. In organotypic cultures, the protection of neurons, OLs, and OPCs against CDC is eliminated by targeted astrocyte destruction. The activation of human complement proteins on mouse CNS cells necessitates caution when interpreting the results of mouse experimental models of NMO using HC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0767-4) contains supplementary material, which is available to authorized users.

Benefit in long-term response and mortality of treatment with intravenous immunoglobulin prior to plasmapheresis in peripheral polyneuropathies

OBJECTIVES

The benefits of plasmapheresis (PA) for neurologic autoimmune diseases have been widely demonstrated. Little is known about the long-term neurologic prognosis and course after PA and immunosuppressive (IS) and/or intravenous immunoglobulin (IVIG) treatment. We aimed to analyse features associated with short-term response and long-term outcome and prognosis (neurologic status and mortality) of peripheral polyneuropathy (PP) and central nervous system acute inflammatory disease (CNSAID) treated with PA.

PATIENTS AND METHODS

A descriptive, retrospective single-centre study from January 2005 to December 2012.

RESULTS

There were 26 episodes, which included 16 CNSAID and 10 PP cases. First line therapy included PA (n=4), IS drugs (n=15), and IVIG (n=7). Responses were achieved in 80% and 50% of PP and CNSAID cases, respectively. For PP, first line treatment with IVIG and no IS treatment prior to or during PA were variables associated with short-term response (P=0.067), good or stable neurologic status at the end of follow-up (P=0.008), and lower mortality rate (P=0.008). For CNSAID, initial EDSS score≥7 (P=0.019) was related to long-term good or stable neurologic status. During the study period, 177 sessions were conducted; 3.4% had technical complications and 8.5% clinical complications. However, these incidents were all minor and no PA session had to be discontinued.

CONCLUSION

The response rates achieved in our patients were similar to those of other research. PA has a safe profile but double-blind, controlled studies are needed to evaluate the synergy of sequential treatment with IGIV followed by PA and the possible benefit for long-term outcome.

Neuromyelitis Optica Masquerading as Lumbosacral Radiculopathy: A Case Report

Neuromyelitis optica spectrum disorders (NMOSD) is a demyelinating syndrome of the central nervous system. This case report describes a 31-year-old woman whose electromyography revealed radiculopathy in the left L5-S1 spinal segment without anatomical abnormalities on lumbosacral magnetic resonance imaging (MRI). She was diagnosed with NMOSD based on gadolinium contrast whole spine and brain MRI and anti-aquaporin-4 antibody findings. Her peripheral nervous system might have been damaged during the early course of NMOSD. Therefore, it is necessary to consider NMOSD for patients who have radiculopathy in electromyography if lumbosacral MRI shows no abnormalities.

Complement-independent retinal pathology produced by intravitreal injection of neuromyelitis optica immunoglobulin G

Background

Neuromyelitis optica (NMO), an autoimmune inflammatory disease of the central nervous system, is often associated with retinal abnormalities including thinning of the retinal nerve fiber layer and microcystic changes. Here, we demonstrate that passive transfer of an anti-aquaporin-4 autoantibody (AQP4-IgG) produces primary retinal pathology.

Methods

AQP4-IgG was delivered to adult rat retinas by intravitreal injection. Rat retinas and retinal explant cultures were assessed by immunofluorescence.

Results

Immunofluorescence showed AQP4-IgG deposition on retinal Müller cells, with greatly reduced AQP4 expression and increased glial fibrillary acidic protein by 5 days. There was mild retinal inflammation with microglial activation but little leukocyte infiltration and loss of retinal ganglion cells by 30 days with thinning of the ganglion cell complex. Interestingly, the loss of AQP4 was complement independent as seen in cobra venom factor-treated rats and in normal rats administered a mutated AQP4-IgG lacking complement effector function. Exposure of ex vivo retinal cultures to AQP4-IgG produced a marked reduction in AQP4 expression by 24 h, which was largely prevented by inhibitors of endocytosis or lysosomal acidification.

Conclusions

Passive transfer of AQP4-IgG results in primary, complement-independent retinal pathology, which might contribute to retinal abnormalities seen in NMO patients.

Aquaporin modulators: a patent review (2010-2015)

INTRODUCTION

Since the discovery of aquaporin-1 (AQP1) as a water channel, more than 2,000 articles, reviews and chapters have been published. The wide tissue expression, functional and biological roles have documented the major and essential physiological importance of these channels both in health and disease. Thus, over the years, studies have revealed essential importance of aquaporins in mammalian pathophysiology revealing aquaporins as potential drug targets. Areas covered: Starting from a brief description of the main structural and functional features of aquaporins, their roles in physiology and pathophysiology of different human diseases, this review describes the main classes of small molecules and biologicals patented, published from 2010 to 2015, able to regulate AQPs for diagnostic and therapeutic applications. Expert opinion: Several patents report on AQP modulators, mostly inhibitors, and related pharmaceutical formulations, to be used for treatments of water imbalance disorders, such as edema. Noteworthy, a unique class of gold-based compounds as selective inhibitors of aquaglyceroporin isoforms may provide new chemical tools for therapeutic applications, especially in cancer. AQP4-targeted therapies for neuromyelitis optica, enhancement of AQP2 function for nephrogenic diabetes insipidus and AQP1-5 gene transfer for the Sjogren's syndrome represent promising therapies that deserve further investigation by clinical trials.

Accuracy of the Fluorescence-Activated Cell Sorting Assay for the Aquaporin-4 Antibody (AQP4-Ab): Comparison with the Commercial AQP4-Ab Assay Kit

BACKGROUND

The aquaporin-4 antibody (AQP4-Ab) is a disease-specific autoantibody to neuromyelitis optica (NMO). We aimed to evaluate the accuracy of the FACS assay in detecting the AQP4-Ab compared with the commercial cell-based assay (C-CBA) kit.

METHODS

Human embryonic kidney-293 cells were transfected with human aquaporin-4 (M23) cDNA. The optimal cut off values of FACS assay was tested using 1123 serum samples from patients with clinically definite NMO, those at high risk for NMO, patients with multiple sclerosis, patients with other idiopathic inflammatory demyelinating diseases, and negative controls. The accuracy of FACS assay and C-CBA were compared in consecutive 225 samples that were collected between January 2014 and June 2014.

RESULTS

With a cut-off value of MFIi of 3.5 and MFIr of 2.0, the receiver operating characteristic curve for the FACS assay showed an area under the curve of 0.876. Among 225 consecutive sera, the FACS assay and C-CBA had a sensitivity of 77.3% and 69.7%, respectively, in differentiating the sera of definite NMO patients from sera of controls without IDD or of MS. Both assay had a good specificity of 100% in it. The overall positivity of the C-CBA among FACS-positive sera was 81.5%; moreover, its positivity was low as 50% among FACS-positive sera with relatively low MFIis.

CONCLUSIONS

Both the FACS assay and C-CBA are sensitive and highly specific assays in detecting AQP4-Ab. However, in some sera with relatively low antibody titer, FACS-assay can be a more sensitive assay option. In real practice, complementary use of FACS assay and C-CBA will benefit the diagnosis of NMO patients, because the former can be more sensitive among low titer sera and the latter are easier to use therefore can be widely used.

Plasma complement biomarkers distinguish multiple sclerosis and neuromyelitis optica spectrum disorder

Background:

Multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) are autoimmune inflammatory demyelinating diseases of the central nervous system. Although distinguished by clinicoradiological and demographic features, early manifestations can be similar complicating management. Antibodies against aquaporin-4 support the diagnosis of NMOSD but are negative in some patients. Therefore, there is unmet need for biomarkers that enable early diagnosis and disease-specific intervention.

Objective:

We investigated whether plasma complement proteins are altered in MS and NMOSD and provide biomarkers that distinguish these diseases.

Methods:

Plasma from 54 NMOSD, 40 MS and 69 control donors was tested in multiplex assays measuring complement activation products and proteins. Using logistic regression, we tested whether combinations of complement analytes distinguished NMOSD from controls and MS.

Results:

All activation products were elevated in NMOSD compared to either control or MS. Four complement proteins (C1inh, C1s, C5 and FH) were higher in NMOSD compared to MS or controls. A model comprising C1inh and terminal complement complex (TCC) distinguished NMOSD from MS (area under the curve (AUC): 0.98), while C1inh and C5 distinguished NMOSD from controls (AUC: 0.94).

Conclusion:

NMOSD is distinguished from MS by plasma complement biomarkers. Selected complement analytes enable differential diagnosis. Findings support trials of anti-complement therapies in NMOSD.

Mapping autoantigen epitopes: molecular insights into autoantibody-associated disorders of the nervous system

BACKGROUND

Our knowledge of autoantibody-associated diseases of the central (CNS) and peripheral (PNS) nervous systems has expanded greatly over the recent years. A number of extracellular and intracellular autoantigens have been identified, and there is no doubt that this field will continue to expand as more autoantigens are discovered as a result of improved clinical awareness and methodological practice. In recent years, interest has shifted to uncover the target epitopes of these autoantibodies.

MAIN BODY

The purpose of this review is to discuss the mapping of the epitope targets of autoantibodies in CNS and PNS antibody-mediated disorders, such as N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), leucine-rich glioma-inactivated protein 1 (Lgi1), contactin-associated protein-like 2 (Caspr2), myelin oligodendrocyte glycoprotein (MOG), aquaporin-4 (AQP4), 65 kDa glutamic acid decarboxylase (GAD65), acetylcholine receptor (AChR), muscle-specific kinase (MuSK), voltage-gated calcium channel (VGCC), neurofascin (NF), and contactin. We also address the methods used to analyze these epitopes, the relevance of their determination, and how this knowledge can inform studies on autoantibody pathogenicity. Furthermore, we discuss triggers of autoimmunity, such as molecular mimicry, ectopic antigen expression, epitope spreading, and potential mechanisms for the rising number of double autoantibody-positive patients.

CONCLUSIONS

Molecular insights into specificity and role of autoantibodies will likely improve diagnosis and treatment of CNS and PNS neuroimmune diseases.

Efficacy of Polyvalent Human Immunoglobulins in an Animal Model of Neuromyelitis Optica Evoked by Intrathecal Anti-Aquaporin 4 Antibodies

Neuromyelitis Optica Spectrum Disorders (NMOSD) are associated with autoantibodies (ABs) targeting the astrocytic aquaporin-4 water channels (AQP4-ABs). These ABs have a direct pathogenic role by initiating a variety of immunological and inflammatory processes in the course of disease. In a recently-established animal model, chronic intrathecal passive-transfer of immunoglobulin G from NMOSD patients (NMO-IgG), or of recombinant human AQP4-ABs (rAB-AQP4), provided evidence for complementary and immune-cell independent effects of AQP4-ABs. Utilizing this animal model, we here tested the effects of systemically and intrathecally applied pooled human immunoglobulins (IVIg) using a preventive and a therapeutic paradigm. In NMO-IgG animals, prophylactic application of systemic IVIg led to a reduced median disease score of 2.4 on a 0-10 scale, in comparison to 4.1 with sham treatment. Therapeutic IVIg, applied systemically after the 10th intrathecal NMO-IgG injection, significantly reduced the disease score by 0.8. Intrathecal IVIg application induced a beneficial effect in animals with NMO-IgG (median score IVIg 1.6 vs. sham 3.7) or with rAB-AQP4 (median score IVIg 2.0 vs. sham 3.7). We here provide evidence that treatment with IVIg ameliorates disease symptoms in this passive-transfer model, in analogy to former studies investigating passive-transfer animal models of other antibody-mediated disorders.

Impact of Autologous Mesenchymal Stem Cell Infusion on Neuromyelitis Optica Spectrum Disorder: A Pilot, 2-Year Observational Study

AIMS

We evaluate safety and efficacy of autologous bone marrow-derived mesenchymal stem cells (MSCs) as a potential treatment for neuromyelitis optica spectrum disorder (NMOSD).

METHODS

Fifteen patients with NMOSD were recruited. All patients received a single intravenous infusion of 1.0 × 10(8) autologous MSC within 3-4 generations derived from bone marrow. The primary endpoints of the study were efficacy as reflected by reduction in annualized relapse rates (ARRs) and inflammatory lesions observed by MRI.

RESULTS

At 12 months after MSC infusion, the mean ARR was reduced (1.1 vs. 0.3, P = 0.002), and the T2 or gadolinium-enhancing T1 lesions decreased in the optic nerve and spinal cord. Disability in these patients was reduced (EDSS, 4.3 vs. 4.9, P = 0.021; visual acuity, 0.4 vs. 0.5, P = 0.007). The patients had an increase in retinal nerve fiber layer thickness, optic nerve diameters and upper cervical cord area. We did not identify any serious MSC-related adverse events. At 24 months of MSC infusion, of 15 patients, 13 patients (87%) remained relapse-free, the mean ARR decreased to 0.1; the disability of 6 patients (40%) was improved, and the mean EDSS decreased to 4.0.

CONCLUSIONS

This pilot trial demonstrates that MSC infusion is safe, reduces the relapse frequency, and mitigates neurological disability with neural structures in the optic nerve and spinal cord recover in patients with NMOSD. The beneficial effect of MSC infusion on NMOSD was maintained, at least to some degree, throughout a 2-year observational period.

Human Aquaporin-4 and Molecular Modeling: Historical Perspective and View to the Future

Among the different aquaporins (AQPs), human aquaporin-4 (hAQP4) has attracted the greatest interest in recent years as a new promising therapeutic target. Such a membrane protein is, in fact, involved in a multiple sclerosis-like immunopathology called Neuromyelitis Optica (NMO) and in several disorders resulting from imbalanced water homeostasis such as deafness and cerebral edema. The gap of knowledge in its functioning and dynamics at the atomistic level of detail has hindered the development of rational strategies for designing hAQP4 modulators. The application, lately, of molecular modeling has proved able to fill this gap providing a breeding ground to rationally address compounds targeting hAQP4. In this review, we give an overview of the important advances obtained in this field through the application of Molecular Dynamics (MD) and other complementary modeling techniques. The case studies presented herein are discussed with the aim of providing important clues for computational chemists and biophysicists interested in this field and looking for new challenges.

Increased plasma levels of epithelial neutrophil-activating peptide 78/CXCL5 during the remission of Neuromyelitis optica

BACKGROUND

In neuromyelitis optica (NMO), one of the underlying pathogenic mechanisms is the formation of antigen-antibody complexes which can trigger an inflammatory response by inducing the infiltration of neutrophils in lesions. Epithelial neutrophil-activating peptide 78 (ENA 78), known as Chemokine (C-X-C motif) ligand 5 (CXCL5), belongs to the ELR-CXCL family. It recruits and activates neutrophils. The aim of this study was to evaluate ENA 78, IL-1β and TNF-α plasma levels in multiple sclerosis (MS) and neuromyelitis optica (NMO) patients.

METHODS

ENA 78, IL-1β and TNF-α plasma levels were detected in 20 healthy controls (HC), 25 MS and 25 NMO patients using MILLIPLEX® map Human High Sensitivity Cytokine/Chemokine Panels.

RESULTS

Plasma levels of ENA 78 were significantly higher in NMO patients than in HC (P < 0.001) and MS patients (P < 0.05). The NMO patients showed higher plasma levels of IL-1β compared with HC (P < 0.01). Further, increased plasma levels of TNF-α were found in the MS (P < 0.05) and NMO patients (P < 0.001). In addition, NMO patients had higher Expanded Disability Status Scale (EDSS) scores compared with MS patients (P < 0.05). EDSS scores were correlated with plasma levels of ENA 78 in NMO patients (P < 0.05). There were no significant correlations between EDSS scores and plasma levels of ENA 78 in MS patients (P > 0.05).

CONCLUSIONS

The overproduction of pro-inflammatory cytokines such as IL-1β and TNF-α during the remission of NMO activates ENA 78, which in turn leads to neutrophil infiltration in lesions. ENA 78 plasma levels were correlated with EDSS scores in NMO patients. Elevated secretion of ENA 78 may be a critical step in neutrophil recruitment during the remission of NMO.

Circulating microRNAs as biomarkers for rituximab therapy, in neuromyelitis optica (NMO)

Background

Neuromyelitis optica (NMO) is a chronic autoimmune disease of the central nervous system (CNS). The main immunological feature of the disease is the presence of autoantibodies to Aquaporin 4 (AQP4+), identified in about 82 % of cases. Currently, there are no reliable biomarkers for monitoring treatment response in patients with NMO. In an effort to identify biomarkers, we analyzed microRNAs (miRNAs) in the blood of rituximab-treated NMO patients before and after therapy.

Methods

Total RNA extracted from whole blood of nine rituximab-responsive NMO patients before and 6 months following treatment was subjected to small RNAseq analysis. The study included an additional group of seven untreated AQP4+ seropositive NMO patients and 15 healthy controls (HCs).

Results

Fourteen miRNAs were up regulated and 32 were downregulated significantly in the blood of NMO patients following effective therapy with rituximab (all p < 0.05). Furthermore, we show that expression of 17 miRNAs was significantly higher and of 25 miRNAs was significantly lower in untreated NMO patients compared with HCs (all p < 0.05). Following rituximab treatment, the expression levels of 10 of the 17 miRNAs that show increased expression in NMO reverted to the levels seen in HCs. Six of these “normalized” miRNAs are known as brain-specific/enriched miRNAs.

Conclusions

Specific miRNA signatures in whole blood of patients with NMO might serve as biomarkers for therapy response. Furthermore, monitoring the levels of brain-specific/enriched miRNAs in the blood might reflect the degree of disease activity in the CNS of inflammatory demyelinating disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0648-x) contains supplementary material, which is available to authorized users.

Plasma exchange therapy for a severe relapse of Devic's disease in a pregnant woman: A case report and concise review

Neuromyelitis optica (NMO) or Devic's disease is an autoimmune inflammatory demyelinating condition affecting the central nervous system (CNS). It was initially believed to be a variant of multiple sclerosis (MS). However, the discovery of NMO-IgG anti-AQP4 antibodies marked an objective distinction between these conditions. Treatment of acute attacks is generally based on pulsed steroids, followed by long-term immunosuppression with azathioprine, oral steroids, and rituximab as first-line therapies. Plasma exchange therapy is indicated for steroid-resistant relapses. We describe a case report of a pregnant woman with a severe relapse of Devic's disease, initially misdiagnosed as MS, unresponsive to pulsed steroids, and who underwent plasma exchange therapy safely, with excellent clinical response and with no adverse outcome for the fetus.

The binding property of a monoclonal antibody against the extracellular domains of aquaporin-4 directs aquaporin-4 toward endocytosis

Neuromyelitis optica (NMO), an autoimmune disease of the central nervous system, is characterized by an autoantibody called NMO-IgG that recognizes the extracellular domains (ECDs) of aquaporin-4 (AQP4). In this study, monoclonal antibodies (mAbs) against the ECDs of mouse AQP4 were established by a baculovirus display method. Two types of mAb were obtained: one (E5415A) recognized both M1 and M23 isoforms, and the other (E5415B) almost exclusively recognized the square-array-formable M23 isoform. While E5415A enhanced endocytosis of both M1 and M23, followed by degradation in cells expressing AQP4, including astrocytes, E5415B did so to a much lesser degree, as determined by live imaging using fluorescence-labeled antibodies and by Western blotting of lysate of cells treated with these mAbs. E5415A promoted cluster formation of AQP4 on the cell surface prior to endocytosis as determined by immunofluorescent microscopic observation of bound mAbs to astrocytes as well as by Blue native PAGE analysis of AQP4 in the cells treated with the mAbs. These observations clearly indicate that an anti-AQP4-ECDs antibody possessing an ability to form a large cluster of AQP4 by cross-linking two or more tetramers outside the AQP4 arrays enhances endocytosis and the subsequent lysosomal degradation of AQP4.

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Two mAbs against the ECD of mAQP4 with different binding properties was established.

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One of them, E5415A, bound to mAQP4 independent of OAP-formation of AQP4.

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E5415A but not E5415B strongly enhanced endocytosis of endogenous AQP4 in astrocytes.

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E5415A formed large clusters of AQP4 cross-linking multiple AQP4 functional units.

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It is the cluster formation of AQP4 that triggers AQP4 endocytosis.

Clobetasol promotes remyelination in a mouse model of neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system that can produce marked neurological deficit. Current NMO therapies include immunosuppressants, plasma exchange and B-cell depletion. Here, we evaluated 14 potential remyelinating drugs emerging from prior small molecule screens done to identify drugs for repurposing in multiple sclerosis and other demyelinating neurological diseases. Compounds were initially evaluated in oligodendrocyte precursor cell (OPC) and cerebellar slice cultures, and then in a mouse model of NMO produced by intracerebral injection of anti-AQP4 autoantibody (AQP4-IgG) and human complement characterized by demyelination with minimal axonal damage. The FDA-approved drug clobetasol promoted differentiation in OPC cultures and remyelination in cerebellar slice cultures and in mice. Intraperitoneal administration of 2 mg/kg/day clobetasol reduced myelin loss by ~60 %, even when clobetasol was administered after demyelination occurred. Clobetasol increased the number of mature oligodendrocytes within lesions without significantly altering initial astrocyte damage or inflammation. These results provide proof-of-concept for the potential utility of a remyelinating approach in the treatment of NMO.

Experimental Neuromyelitis Optica Induces a Type I Interferon Signature in the Spinal Cord

Neuromyelitis optica (NMO) is an acute inflammatory disease of the central nervous system (CNS) which predominantly affects spinal cord and optic nerves. Most patients harbor pathogenic autoantibodies, the so-called NMO-IgGs, which are directed against the water channel aquaporin 4 (AQP4) on astrocytes. When these antibodies gain access to the CNS, they mediate astrocyte destruction by complement-dependent and by antibody-dependent cellular cytotoxicity. In contrast to multiple sclerosis (MS) patients who benefit from therapies involving type I interferons (I-IFN), NMO patients typically do not profit from such treatments. How is I-IFN involved in NMO pathogenesis? To address this question, we made gene expression profiles of spinal cords from Lewis rat models of experimental neuromyelitis optica (ENMO) and experimental autoimmune encephalomyelitis (EAE). We found an upregulation of I-IFN signature genes in EAE spinal cords, and a further upregulation of these genes in ENMO. To learn whether the local I-IFN signature is harmful or beneficial, we induced ENMO by transfer of CNS antigen-specific T cells and NMO-IgG, and treated the animals with I-IFN at the very onset of clinical symptoms, when the blood-brain barrier was open. With this treatment regimen, we could amplify possible effects of the I-IFN induced genes on the transmigration of infiltrating cells through the blood brain barrier, and on lesion formation and expansion, but could avoid effects of I-IFN on the differentiation of pathogenic T and B cells in the lymph nodes. We observed that I-IFN treated ENMO rats had spinal cord lesions with fewer T cells, macrophages/activated microglia and activated neutrophils, and less astrocyte damage than their vehicle treated counterparts, suggesting beneficial effects of I-IFN.

Th17 Cells Pathways in Multiple Sclerosis and Neuromyelitis Optica Spectrum Disorders: Pathophysiological and Therapeutic Implications

Several animal and human studies have implicated CD4+ T helper 17 (Th17) cells and their downstream pathways in the pathogenesis of central nervous system (CNS) autoimmunity in multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), challenging the traditional Th1-Th2 paradigm. Th17 cells can efficiently cross the blood-brain barrier using alternate ways from Th1 cells, promote its disruption, and induce the activation of other inflammatory cells in the CNS. A number of environmental factors modulate the activity of Th17 pathways, so changes in the diet, exposure to infections, and other environmental factors can potentially change the risk of development of autoimmunity. Currently, new drugs targeting specific points of the Th17 pathways are already being tested in clinical trials and provide basis for the development of biomarkers to monitor disease activity. Herein, we review the key findings supporting the relevance of the Th17 pathways in the pathogenesis of MS and NMOSD, as well as their potential role as therapeutic targets in the treatment of immune-mediated CNS disorders.

Present and Future Therapies in Neuromyelitis Optica Spectrum Disorders

Neuromyelitis optica spectrum disorders (NMOSD) are important evolving entities, which have reached much attention in the recent years. NMOSD are characterized by inflammatory lesions in the optic nerves, spinal cord, and central parts of the brain, as well as an autoimmune process directed against aquaporin-4. As disability in NMOSD accumulates by inflammatory damage from attacks, both the treatment and prevention of attacks are decisive for the long-term outcome. NMOSD attacks are treated with high-dose intravenous corticosteroids and apheresis therapies, in particular therapeutic plasma exchange. In cases of incomplete remission, escalation of attack treatment is recommended. Preventive therapy is immunosuppressive and should by commenced as early as possible. Apart from classical immunosuppressants such as azathioprine and mycophenolate mofetil, repurposed biologicals are increasingly used. B-cell depletion with rituximab and other agents, inhibition of the interleukin-6 receptor with tocilizumab, and blockade of complement-mediated damage by eculizumab all are promising therapeutic strategies evaluated in randomized controlled trials. In this review, we will discuss present and future immunotherapies for NMOSD and also consider combination of treatments, plasma, cellular and other therapies. Current advances in immunopathological knowledge are translated into innovative concepts and begin a new era of NMOSD therapy.

Autoantibodies to central nervous system neuronal surface antigens: psychiatric symptoms and psychopharmacological implications

RATIONALE

Autoantibodies to central nervous system (CNS) neuronal surface antigens have been described in association with autoimmune encephalopathies which prominently feature psychiatric symptoms in addition to neurological symptoms. The potential role of these autoantibodies in primary psychiatric diseases such as schizophrenia or bipolar affective disorder is of increasing interest.

OBJECTIVES

We aimed to review the nature of psychiatric symptoms associated with neuronal surface autoantibodies, in the context of autoimmune encephalopathies as well as primary psychiatric disorders, and to review the mechanisms of action of these autoantibodies from a psychopharmacological perspective.

RESULTS

The functional effects of the autoantibodies on their target antigens are described; their clinical expression is at least in part mediated by their effects on neuronal receptor function, primarily at the synapse, usually resulting in receptor hypofunction. The psychiatric effects of the antibodies are related to known functions of the receptor target or its complexed proteins, with reference to supportive genetic and pharmacological evidence where relevant. Evidence for a causal role of these autoantibodies in primary psychiatric disease is increasing but remains controversial; relevant methodological controversies are outlined. Non-receptor-based mechanisms of autoantibody action, including neuroinflammatory mechanisms, and therapeutic implications are discussed.

CONCLUSIONS

An analysis of the autoantibodies from a psychopharmacological perspective, as endogenous, bioactive, highly specific, receptor-targeting molecules, provides a valuable opportunity to understand the neurobiological basis of associated psychiatric symptoms. Potentially, new treatment strategies will emerge from the improving understanding of antibody-antigen interaction within the CNS.

Autoimmune AQP4 channelopathies and neuromyelitis optica spectrum disorders

Neuromyelitis optica (NMO) spectrum disorders (SD) represent an evolving group of central nervous system (CNS)-inflammatory autoimmune demyelinating diseases unified by a pathogenic autoantibody specific for the aquaporin-4 (AQP4) water channel. It was historically misdiagnosed as multiple sclerosis (MS), which lacks a distinguishing biomarker. The discovery of AQP4-IgG moved the focus of CNS demyelinating disease research from emphasis on the oligodendrocyte and myelin to the astrocyte. NMO is recognized today as a relapsing disease, extending beyond the optic nerves and spinal cord to include brain (especially in children) and skeletal muscle. Brain magnetic resonance imaging abnormalities, identifiable in 60% of patients at the second attack, are consistent with MS in 10% of cases. NMOSD-typical lesions (another 10%) occur in AQP4-enriched regions: circumventricular organs (causing intractable nausea and vomiting) and the diencephalon (causing sleep disorders, endocrinopathies, and syndrome of inappropriate antidiuresis). Advances in understanding the immunobiology of AQP4 autoimmunity have necessitated continuing revision of NMOSD clinical diagnostic criteria. Assays that selectively detect pathogenic AQP4-IgG targeting extracellular epitopes of AQP4 are promising prognostically. When referring to AQP4 autoimmunity, we suggest substituting the term "autoimmune aquaporin-4 channelopathy" for the term "NMO spectrum disorders." Randomized clinical trials are currently assessing the efficacy and safety of newer immunotherapies. Increasing therapeutic options based on understanding the molecular pathogenesis is anticipated to improve the outcome for patients with AQP4 channelopathy.

Placebo-controlled study in neuromyelitis optica-Ethical and design considerations

BACKGROUND

To date, no treatment for neuromyelitis optica (NMO) has been granted regulatory approval, and no controlled clinical studies have been reported.

OBJECTIVE

To design a placebo-controlled study in NMO that appropriately balances patient safety and clinical-scientific integrity.

METHODS

We assessed the "standard of care" for NMO to establish the ethical framework for a placebo-controlled trial. We implemented measures that balance the need for scientific robustness while mitigating the risks associated with a placebo-controlled study. The medical or scientific community, patient organizations, and regulatory authorities were engaged early in discussions on this placebo-controlled study, and their input contributed to the final study design.

RESULTS

The N-MOmentum study (NCT02200770) is a clinical trial that randomizes NMO patients to receive MEDI-551, a monoclonal antibody that depletes CD19+ B-cells, or placebo. The study design has received regulatory, ethical, clinical, and patient approval in over 100 clinical sites in more than 20 countries worldwide.

CONCLUSION

The approach we took in the design of the N-MOmentum trial might serve as a roadmap for other rare severe diseases when there is no proven therapy and no established clinical development path.

Clinical efficacy, safety, and tolerability of fingolimod for the treatment of relapsing-remitting multiple sclerosis

Fingolimod is a selective immunosuppressive agent approved worldwide for the treatment of relapsing-remitting multiple sclerosis (MS), a chronic and potentially disabling neurological condition. Randomized double-blind clinical trials have shown that fingolimod significantly reduces relapse rate and ameliorates a number of brain MRI measures, including cerebral atrophy, compared to both placebo and intramuscular interferon-β1a. The effect on disability progression remains controversial, since one Phase III trial showed a significant benefit of treatment while two others did not. Although fingolimod has a very convenient daily oral dosing, the possibility of serious cardiac, ocular, infectious, and other rare adverse events justified the decision of the European Medicines Agency to approve the drug as a second-line treatment for MS patients not responsive to first-line therapy, or those with rapidly evolving course. In the United States, fingolimod is instead authorized as a first-line treatment. The aim of this review is to describe and discuss the characteristics of fingolimod concerning its efficacy, safety, and tolerability in the clinical context of multiple sclerosis management.

Elevation of AQP4 and selective cytokines in experimental autoimmune encephalitis mice provides some potential biomarkers in optic neuritis and demyelinating diseases

Idiopathic optic neuritis (ION) is an inflammation of the optic nerve that may result in a complete or partial loss of vision. ION is usually due to the immune attack of the myelin sheath covering the optic nerve. ION acts frequently as the first symptoms of multiple sclerosis (MS) and neuromyelitis optica (NMO), or other inflammatory demyelinating disorders. The pathogenic progression of ION remains unclear. Experimental autoimmune encephalitis (EAE) is a commonly used model of idiopathic inflammatory demyelinating disorders (IIDDs); the optic nerve is affected in EAE as well. The specific mediators of demyelination in optic neuritis are unknown. Recent studies have indicated what T-cell activation in peripheral blood is associated with optic neuritis pathogenesis. The object of the present study was to determine whether certain cytokines (IL-6, IL-17A, and IL-23) and AQP4 contribute to the demyelinating process using EAE model. We have found that IL-6R, AQP4 and IL-23R are significantly increased in mRNA and protein levels in optic nerves in EAE mice compared to control mice; serum AQP4, IL-6, IL-17A, IL-23 are increased whereas transforming growth factor beta (TGF-β) is decreased in EAE mice. These results suggest that AQP4 and selective cytokines in serum are associated with ION pathogenesis in the animal model, and these results shine light for future clinical diagnosis as potential biomarkers in ION patients.

Linear lesions may assist early diagnosis of neuromyelitis optica and longitudinally extensive transverse myelitis, two subtypes of NMOSD

PURPOSE

To investigate the relationship between linear lesions (LL) and the development of longitudinally extensive spinal cord lesions (LESCL) in Chinese patients with neuromyelitis optica or longitudinally extensive transverse myelitis.

METHOD

The clinical records of 143 patients with these conditions were reviewed. Forty-one patients with LL were divided into three groups according to the order of appearance of LL and LESCL (simultaneously [n=10], LL first [n=26], or LESCL first [n=5]). The remaining 102 patients without LL were used as a control group.

RESULTS

Patients who developed LL first demonstrated a lower annualized relapse rate than those in the simultaneous group (1.00 [0.23-10.00] vs. 4.38 [0.60-6.67], p=0.017) and the control group (1.00 [0.23-10.00] vs. 2.00 [0.24-10.00], p=0.007). Among all patients with LL, there were significantly more who developed them before LESCL than those who developed them after LESCL (p<0.001) or at the same time (p=0.008). The mean time before the appearance of LESCL was 9.0months (2-35months) in the 'LL-first' group, which was shorter than that in the control group (12months [1-60months], p=0.010). The rate of positivity for anti-aquaporin 4 IgG antibodies was higher in patients with LL compared with controls (90.24% vs. 64.71%, p=0.002).

CONCLUSION

LL may be a precursor to LESCL and assist early diagnosis of neuromyelitis optica and longitudinally extensive transverse myelitis.

Antibodies to MOG in adults with inflammatory demyelinating disease of the CNS

OBJECTIVE

To evaluate the clinical relevance of myelin oligodendrocyte glycoprotein antibody (MOG-Ab) in a cohort of adults with inflammatory demyelinating disease (IDD) of the CNS.

METHODS

Live cell-based assays for MOG-Ab (IgG1 subset) and antibody to aquaporin-4 (AQP4-Ab) were performed in a cohort of 270 adult patients with IDD and 72 controls. Patients were first grouped by positive antibody result as MOG-Ab or AQP4-Ab, and the remainder were grouped by published diagnostic criteria.

RESULTS

Seventeen patients with IDD (6.3%) had MOG-Abs and 49 patients (18.1%) had AQP4-Abs; none had both antibodies. The MOG-Ab patients predominantly manifested with isolated symptoms of optic neuritis (83%). One-third of these patients experienced relapses, which involved only the optic nerve, and all relapsed within 1 year of disease onset. At onset, MRI in the MOG-Ab group uniquely demonstrated perineural enhancement, extending to the soft tissues around the optic nerves (33%). Although about 30% of MOG-Ab patients had brain MRI lesions, they had fewer periventricular lesions than the 26 patients with relapsing-remitting multiple sclerosis (MS); none of these lesions were ovoid or perpendicular to the ventricle. Moreover, MOG-Ab patients did not meet the diagnostic criteria for definite neuromyelitis optica (NMO) and had less spinal cord involvement than the AQP4-Ab group. Four patients (23.5%) had poor visual outcomes (<0.2) or paraplegia.

CONCLUSIONS

MOG-Abs may be a disease-specific biomarker in adult patients with IDD who have a disease distinct from NMO or MS. The radiologic as well as clinical manifestations of MOG-Ab patients can be useful in their differential diagnosis.

Hypersensitivity Responses in the Central Nervous System

Immune-mediated tissue damage or hypersensitivity can be mediated by autospecific IgG antibodies. Pathology results from activation of complement, and antibody-dependent cellular cytotoxicity, mediated by inflammatory effector leukocytes include macrophages, natural killer cells, and granulocytes. Antibodies and complement have been associated to demyelinating pathology in multiple sclerosis (MS) lesions, where macrophages predominate among infiltrating myeloid cells. Serum-derived autoantibodies with predominant specificity for the astrocyte water channel aquaporin-4 (AQP4) are implicated as inducers of pathology in neuromyelitis optica (NMO), a central nervous system (CNS) demyelinating disease where activated neutrophils infiltrate, unlike in MS. The most widely used model for MS, experimental autoimmune encephalomyelitis, is an autoantigen-immunized disease that can be transferred to naive animals with CD4⁺ T cells, but not with antibodies. By contrast, NMO-like astrocyte and myelin pathology can be transferred to mice with AQP4–IgG from NMO patients. This is dependent on complement, and does not require T cells. Consistent with clinical observations that interferon-beta is ineffective as a therapy for NMO, NMO-like pathology is significantly reduced in mice lacking the Type I IFN receptor. In MS, there is evidence for intrathecal synthesis of antibodies as well as blood–brain barrier (BBB) breakdown, whereas in NMO, IgG accesses the CNS from blood. Transfer models involve either direct injection of antibody and complement to the CNS, or experimental manipulations to induce BBB breakdown. We here review studies in MS and NMO that elucidate roles for IgG and complement in the induction of BBB breakdown, astrocytopathy, and demyelinating pathology. These studies point to significance of T-independent effector mechanisms in neuroinflammation.

NFκB signaling drives pro-granulocytic astroglial responses to neuromyelitis optica patient IgG

Background

Astrocytes expressing the aquaporin-4 water channel are a primary target of pathogenic, disease-specific immunoglobulins (IgG) found in patients with neuromyelitis optica (NMO). Immunopathological analyses of active NMO lesions highlight a unique inflammatory phenotype marked by infiltration of granulocytes. Previous studies characterized this granulocytic infiltrate as a response to vasculocentric complement activation and localized tissue destruction. In contrast, we observe that granulocytic infiltration in NMO lesions occurs independently of complement-mediated tissue destruction or active demyelination. These immunopathological findings led to the hypothesis that NMO IgG stimulates astrocyte signaling that is responsible for granulocytic recruitment in NMO.

Methods

Histopathology was performed on archival formalin-fixed paraffin-embedded autopsy-derived CNS tissue from 23 patients clinically and pathologically diagnosed with NMO or NMO spectrum disorder. Primary murine astroglial cultures were stimulated with IgG isolated from NMO patients or control IgG from healthy donors. Transcriptional responses were assessed by microarray, and translational responses were measured by ELISA. Signaling through the NFκB pathway was measured by western blotting and immunostaining.

Results

Stimulation of primary murine astroglial cultures with NMO IgG elicited a reactive and inflammatory transcriptional response that involved signaling through the canonical NFκB pathway. This signaling resulted in the release of pro-granulocytic chemokines and was inhibited by the clinically relevant proteasome inhibitors bortezomib and PR-957.

Conclusions

We propose that the astrocytic NFκB-dependent inflammatory response to stimulation by NMO IgG represents one of the earliest events in NMO pathogenesis, providing a target for therapeutic intervention upstream of irreversible cell death and tissue damage.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-015-0403-8) contains supplementary material, which is available to authorized users.

Applying complement therapeutics to rare diseases

Around 350 million people worldwide suffer from rare diseases. These may have a genetic, infectious, or autoimmune basis, and several include an inflammatory component. Launching of effective treatments can be very challenging when there is a low disease prevalence and limited scientific insights into the disease mechanisms. As a key trigger of inflammatory processes, complement has been associated with a variety of diseases and has become an attractive therapeutic target for conditions involving inflammation. In view of the clinical experience acquired with drugs licensed for the treatment of rare diseases such as hereditary angioedema and paroxysmal nocturnal hemoglobinuria, growing evidence supports the safety and efficacy of complement therapeutics in restoring immune balance and preventing aggravation of clinical outcomes. This review provides an overview of the candidates currently in the pharmaceutical pipeline with potential to treat orphan diseases and discusses the molecular mechanisms triggered by complement involved with the disease pathogenesis.

Neuromyelitis optica and the evolving spectrum of autoimmune aquaporin-4 channelopathies: a decade later

The discovery of AQP4-IgG (a pathogenic antibody that targets the astrocytic water channel aquaporin-4), as the first sensitive and specific biomarker for any inflammatory central nervous system demyelinating disease (IDD), has shifted emphasis from the oligodendrocyte and myelin to the astrocyte as a central immunopathogenic player. Neuromyelitis optica (NMO) spectrum disorders (SDs) represent an evolving spectrum of IDDs extending beyond the optic nerves and spinal cord to include the brain (especially in children) and, rarely, muscle. NMOSD typical brain lesions are located in areas that highly express the target antigen, AQP4, including the circumventricular organs (accounting for intractable nausea and vomiting) and the diencephalon (accounting for sleep disorders, endocrinopathies, and syndrome of inappropriate antidiuresis). Magnetic resonance imaging brain abnormalities fulfill Barkoff criteria for multiple sclerosis in up to 10% of patients. As the spectrum broadens, the importance of highly specific assays that detect pathogenic AQP4-IgG targeting extracellular epitopes of AQP4 cannot be overemphasized. The rapid evolution of our understanding of the immunobiology of AQP4 autoimmunity necessitates continuing revision of NMOSD diagnostic criteria. Here, we describe scientific advances that have occurred since the discovery of NMO-IgG in 2004 and review novel targeted immunotherapies. We also suggest that NMOSDs should now be considered under the umbrella term autoimmune aquaporin-4 channelopathy.

Astrocyte barriers to neurotoxic inflammation

Astrocytes form borders (glia limitans) that separate neural from non-neural tissue along perivascular spaces, meninges and tissue lesions in the CNS. Transgenic loss-of-function studies reveal that astrocyte borders and scars serve as functional barriers that restrict the entry of inflammatory cells into CNS parenchyma in health and disease. Astrocytes also have powerful pro-inflammatory potential. Thus, astrocytes are emerging as pivotal regulators of CNS inflammatory responses. This Review discusses evidence that astrocytes have crucial roles in attracting and restricting CNS inflammation, with important implications for diverse CNS disorders.

Neuromyelitis optica and the evolving spectrum of autoimmune aquaporin-4 channelopathies: a decade later

The discovery of AQP4-IgG (a pathogenic antibody that targets the astrocytic water channel aquaporin-4), as the first sensitive and specific biomarker for any inflammatory central nervous system demyelinating disease (IDD), has shifted emphasis from the oligodendrocyte and myelin to the astrocyte as a central immunopathogenic player. Neuromyelitis optica (NMO) spectrum disorders (SDs) represent an evolving spectrum of IDDs extending beyond the optic nerves and spinal cord to include the brain (especially in children) and, rarely, muscle. NMOSD typical brain lesions are located in areas that highly express the target antigen, AQP4, including the circumventricular organs (accounting for intractable nausea and vomiting) and the diencephalon (accounting for sleep disorders, endocrinopathies, and syndrome of inappropriate antidiuresis). Magnetic resonance imaging brain abnormalities fulfill Barkoff criteria for multiple sclerosis in up to 10% of patients. As the spectrum broadens, the importance of highly specific assays that detect pathogenic AQP4-IgG targeting extracellular epitopes of AQP4 cannot be overemphasized. The rapid evolution of our understanding of the immunobiology of AQP4 autoimmunity necessitates continuing revision of NMOSD diagnostic criteria. Here, we describe scientific advances that have occurred since the discovery of NMO-IgG in 2004 and review novel targeted immunotherapies. We also suggest that NMOSDs should now be considered under the umbrella term autoimmune aquaporin-4 channelopathy.

Epidemiological, clinical, and immunological characteristics of neuromyelitis optica: A review

The aim of this study was to review the epidemiological and clinical characteristics of neuromyelitis optica (NMO) and the immunopathological mechanisms involved in the neuronal damage. NMO is an inflammatory demyelinating autoimmune disease of the central nervous system that most commonly affects the optic nerves and spinal cord. NMO is thought to be more prevalent among non-Caucasians and where multiple sclerosis (MS) prevalence is low. NMO follows a relapsing course in more than 80-90% of cases, which is more commonly in women. It is a complex disease with an interaction between host genetic and environmental factors and the main immunological feature is the presence of anti-aquaporin 4 (AQP4) antibodies in a subset of patients. NMO is frequently associated with multiple other autoantibodies and there is a strong association between NMO with other systemic autoimmune diseases. AQP4-IgG can cause antibody-dependent cellular cytotoxicity (ADCC) when effector cells are present and complement-dependent cytotoxicity (CDC) when complement is present. Acute therapies, including corticosteroids and plasma exchange, are designed to minimize injury and accelerate recovery. Several aspects of NMO pathogenesis remain unclear. More advances in the understanding of NMO disease mechanisms are needed in order to identify more specific biomarkers to NMO diagnosis.

Challenging AQP4 druggability for NMO-IgG antibody binding using molecular dynamics and molecular interaction fields

Neuromyelitis optica (NMO) is a multiple sclerosis-like immunopathology disease affecting optic nerves and the spinal cord. Its pathological hallmark is the deposition of a typical immunoglobulin, called NMO-IgG, against the water channel Aquaporin-4 (AQP4). Preventing NMO-IgG binding would represent a valuable molecular strategy for a focused NMO therapy. The recent observation that aspartate in position 69 (D69) is determinant for the formation of NMO-IgG epitopes prompted us to carry out intensive Molecular Dynamics (MD) studies on a number of single-point AQP4 mutants. Here, we report a domino effect originating from the point mutation at position 69: we find that the side chain of T62 is reoriented far from its expected position leaning on the lumen of the pore. More importantly, the strength of the H-bond interaction between L53 and T56, at the basis of the loop A, is substantially weakened. These events represent important pieces of a clear-cut mechanistic rationale behind the failure of the NMO-IgG binding, while the water channel function as well as the propensity to aggregate into OAPs remains unaltered. The molecular interaction fields (MIF)-based analysis of cavities complemented MD findings indicating a putative binding site comprising the same residues determining epitope reorganization. In this respect, docking studies unveiled an intriguing perspective to address the future design of small drug-like compounds against NMO. In agreement with recent experimental observations, the present study is the first computational attempt to elucidate NMO-IgG binding at the molecular level, as well as a first effort toward a less elusive AQP4 druggability.

Rituximab in neuromyelitis optica: A review of literature

Neuromyelitis optica spectrum disorders, or neuromyelitis optica (NMO), is an autoimmune disease of the central nervous system that must be distinguished from multiple sclerosis. Therapeutic approaches to relapse prevention in NMO include immunosuppressants and monoclonal antibodies. Rituximab, a monoclonal antibody that targets CD20 antigen expressed on the surface of pre-B, mature B-lymphocytes and a small subset of T-lymphocytes, has been widely used for the treatment of NMO. In this review, we aim to summarize global experience with rituximab in NMO. We identified 13 observational studies that involved a total of 209 NMO patients treated with rituximab. Majority of rituximab-treated patients evidenced stabilization or improvements in their disability scores compared to pre-treatment period and 66% of patients remained relapse-free during treatment period. Monitoring rituximab treatment response with CD19+ or CD27+ cell counts appears to improve treatment outcomes. We offer clinical pointers on rituximab use for NMO based on the literature and authors’ experience, and pose questions that would need to be addressed in future studies.

Systemic inflammation and the brain: novel roles of genetic, molecular, and environmental cues as drivers of neurodegeneration

The nervous and immune systems have evolved in parallel from the early bilaterians, in which innate immunity and a central nervous system (CNS) coexisted for the first time, to jawed vertebrates and the appearance of adaptive immunity. The CNS feeds from, and integrates efferent signals in response to, somatic and autonomic sensory information. The CNS receives input also from the periphery about inflammation and infection. Cytokines, chemokines, and damage-associated soluble mediators of systemic inflammation can also gain access to the CNS via blood flow. In response to systemic inflammation, those soluble mediators can access directly through the circumventricular organs, as well as open the blood–brain barrier. The resulting translocation of inflammatory mediators can interfere with neuronal and glial well-being, leading to a break of balance in brain homeostasis. This in turn results in cognitive and behavioral manifestations commonly present during acute infections – including anorexia, malaise, depression, and decreased physical activity – collectively known as the sickness behavior (SB). While SB manifestations are transient and self-limited, under states of persistent systemic inflammatory response the cognitive and behavioral changes can become permanent. For example, cognitive decline is almost universal in sepsis survivors, and a common finding in patients with systemic lupus erythematosus. Here, we review recent genetic evidence suggesting an association between neurodegenerative disorders and persistent immune activation; clinical and experimental evidence indicating previously unidentified immune-mediated pathways of neurodegeneration; and novel immunomodulatory targets and their potential relevance for neurodegenerative disorders.

Interferon-β-related tumefactive brain lesion in a Caucasian patient with neuromyelitis optica and clinical stabilization with tocilizumab

Background

Neuromyelitis optica (NMO) is a severely disabling inflammatory disorder of the central nervous system and is often misdiagnosed as multiple sclerosis (MS). There is increasing evidence that treatment options shown to be beneficial in MS, including interferon-β (IFN-β), are detrimental in NMO.

Case presentation

We here report the first Caucasian patient with aquaporin 4 (AQP4) antibody (NMO-IgG)-seropositive NMO presenting with a tumefactive brain lesion on treatment with IFN-β. Disease started with relapsing optic neuritis and an episode of longitudinally extensive transverse myelitis (LETM) in the absence of any brain MRI lesions or cerebrospinal fluid-restricted oligoclonal bands. After initial misdiagnosis of multiple sclerosis (MS) the patient received subcutaneous IFN-β1b and, subsequently, subcutaneous IFN-β1a therapy for several years. Under this treatment, the patient showed persisting relapse activity and finally presented with a severe episode of subacute aphasia and right-sided hemiparesis due to a large T2 hyperintensive tumefactive lesion of the left brain hemisphere and a smaller T2 lesion on the right side. Despite rituximab therapy two further LETM episodes occurred, resulting in severe neurological deficits. Therapeutic blockade of the interleukin (IL)-6 signalling pathway by tocilizumab was initiated, followed by clinical and radiological stabilization.

Conclusion

Our case (i) illustrates the relevance of correctly distinguishing NMO and MS since these disorders differ markedly in their responsiveness to immunomodulatory and -suppressive therapies; (ii) confirms and extends a previous report describing the development of tumefactive brain lesions under IFN-β therapy in two Asian NMO patients; and (iii) suggests tocilizumab as a promising therapeutic alternative in highly active NMO disease courses.