Neuromyelitis Optica Patient Research Articles

Aquaporin-4 Autoantibodies in Neuromyelitis Optica: AQP4 Isoform-Dependent Sensitivity and Specificity

Neuromyelitis Optica (NMO) is an autoimmune demyelinating disease, characterized by the presence of autoantibody (NMO-IgG) to Aquaporin-4 (AQP4). NMO-IgG identification supports NMO diagnosis and several diagnostic tests have been developed, but their sensitivity is too variable, and some assay show low sensitivity. This impairs correct diagnosis of NMO. By cell based assay (CBA) we here evaluate the efficacy of different strategies to express AQP4 in mammalian cells in terms of: a) AQP4 translation initiation signals; b) AQP4 isoforms (M1 and M23) and fluorescent tag position; c) NMO serum concentration and AQP4 degradation. Our results demonstrate that when using AQP4-M1, the nucleotide in position −3 of the AUG greatly affects the AQP4-M1/M23 protein ratio, NMO-IgG binding, and consequently test sensitivity. Test sensitivity was highest with M23 expressing cells (97.5%) and only 27.5% with AQP4-M1. The fluorescent tag added to the N-terminus of AQP4-M23 considerably affected the NMO-IgG binding, and test sensitivity, due to disruption of AQP4 suprastructures. Furthermore, sera used at high concentration resulted in AQP4 degradation which affected test sensitivity. To further evaluate the reliability of the M23 based CBA test, samples of one NMO patient collected during about 2 years clinical follow-up were tested. The results of serum titer correlated with disease activity and treatment response. In conclusion, we provide a molecular explanation for the contrasting CBA test data reported and suggest the use of M23 with a C-terminus fluorescent tag as the proper test for NMO diagnosis.

C1q-targeted monoclonal antibody prevents complement-dependent cytotoxicity and neuropathology in in vitro and mouse models of neuromyelitis optica

Neuromyelitis optica (NMO) is an autoimmune disorder with inflammatory demyelinating lesions in the central nervous system, particularly in the spinal cord and optic nerve. NMO pathogenesis is thought to involve binding of anti-aquaporin-4 (AQP4) autoantibodies to astrocytes, which causes complement-dependent cytotoxicity (CDC) and downstream inflammation leading to oligodendrocyte and neuronal injury. Vasculocentric deposition of activated complement is a prominent feature of NMO pathology. Here, we show that a neutralizing monoclonal antibody against the C1q protein in the classical complement pathway prevents AQP4 autoantibody-dependent CDC in cell cultures and NMO lesions in ex vivo spinal cord slice cultures and in mice. A monoclonal antibody against human C1q with 11nM binding affinity prevented CDC caused by NMO patient serum in AQP4-transfected cells and primary astrocyte cultures, and prevented complement-dependent cell-mediated cytotoxicity (CDCC) produced by natural killer cells. The anti-C1q antibody prevented astrocyte damage and demyelination in mouse spinal cord slice cultures exposed to AQP4 autoantibody and human complement. In a mouse model of NMO produced by intracerebral injection of AQP4 autoantibody and human complement, the inflammatory demyelinating lesions were greatly reduced by intracerebral administration of the anti-C1q antibody. These results provide proof-of-concept for C1q-targeted monoclonal antibody therapy in NMO. Targeting of C1q inhibits the classical complement pathway directly and causes secondary inhibition of CDCC and the alternative complement pathway. As C1q-targeted therapy leaves the lectin complement activation pathway largely intact, its side-effect profile is predicted to differ from that of therapies targeting downstream complement proteins.

Aquaporin 4 molecular mimicry and implications for neuromyelitis optica

Neuromyelitis optica (NMO) is associated with antibodies to aquaporin 4 (AQP4). We hypothesized that antibodies to AQP4 can be triggered by exposure to environmental proteins. We compared human AQP4 to plant and bacterial proteins to investigate the occurrence of significantly similar structures and sequences. High similarity to a known epitope for NMO-IgG, AQP4(207–232), was observed for corn ZmTIP4-1. NMO and non-NMO sera were assessed for reactivity to AQP4(207–232) and the corn peptide. NMO patient serum showed reactivity to both peptides as well as to plant tissue. These findings warrant further investigation into the role of the environment in NMO etiology.

Therapeutic Cleavage of Anti–Aquaporin-4 Autoantibody in Neuromyelitis Optica by an IgG-Selective Proteinase

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system caused by binding of pathogenic IgG autoantibodies (NMO-IgG) to astrocyte water channel aquaporin-4 (AQP4). Astrocyte damage and downstream inflammation require NMO-IgG effector function to initiate complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC). Here, we evaluated the potential therapeutic utility of the bacterial enzyme IdeS (IgG-degrading enzyme of Streptococcus pyogenes), which selectively cleaves IgG antibodies to yield Fc and F(ab')(2) fragments. In AQP4-expressing cell cultures, IdeS treatment of monoclonal NMO-IgGs and NMO patient sera abolished CDC and ADCC, even when IdeS was added after NMO-IgG was bound to AQP4. Binding of NMO-IgG to AQP4 was similar to that of the NMO-F(ab')(2) generated by IdeS cleavage. NMO-F(ab')(2) competitively displaced pathogenic NMO-IgG, preventing cytotoxicity, and the Fc fragments generated by IdeS cleavage reduced CDC and ADCC. IdeS efficiently cleaved NMO-IgG in mice in vivo, and greatly reduced NMO lesions in mice administered NMO-IgG and human complement. IgG-selective cleavage by IdeS thus neutralizes NMO-IgG pathogenicity, and yields therapeutic F(ab')(2) and Fc fragments. IdeS treatment, by therapeutic apheresis or direct administration, may be beneficial in NMO.

Detection of anti-aquaporin-4 autoantibodies in the sera of Chinese neuromyelitis optica patients.

In this study, we recruited 10 neuromyelitis optica patients, two multiple sclerosis patients and two myelitis patients. Chinese hamster lung fibroblast (V79) cells transfected with a human aquaporin-4-mCherry fusion protein gene were used to detect anti-aquaporin-4 antibody in neuromyelitis optica patient sera by immunofluorescence. Anti-aquaporin-4 autoantibody was stably detected by immunofluorescence in neuromyelitis optica patient sera exclusively. The sensitivity of the assay for neuromyelitis optica was 90% and the specificity for neuromyelitis optica was 100%. The anti-aquaporin-4 antibody titers in sera were tested with serial dilutions until the signal disappeared. A positive correlation was detected between Expanded Disability Status Scale scores and serum anti-aquaporin-4 antibody titers. The anti-aquaporin-4 antibody assay is highly sensitive and specific in the sera of Chinese neuromyelitis optica patients. Detection of aquaporin-4 autoantibody is important for the diagnosis and treatment of neuromyelitis optica.

Neuromyelitis optica-like pathology is dependent on type I interferon response

Neuromyelitis optica is an antibody-mediated autoimmune inflammatory disease of the central nervous system. Reports have suggested that interferon beta which is beneficial for multiple sclerosis, exacerbates neuromyelitis optica. Our aim was to determine whether type I interferon plays a role in the formation of neuromyelitis optica lesions. Immunoglobulin G from a neuromyelitis optica patient was injected intracerebrally with human complement to type I interferon receptor deficient and wildtype mice. Loss of aquaporin-4 and glial fibrillary acidic protein was reduced in type I interferon receptor deficient mice brain. Our findings suggest that type I interferon signaling contributes to neuromyelitis optica pathogenesis.

Enzymatic deglycosylation converts pathogenic neuromyelitis optica anti–aquaporin‐4 immunoglobulin G into therapeutic antibody

Neuromyelitis optica (NMO) is caused by binding of pathogenic autoantibodies (NMO-immunoglobulin G [IgG]) to aquaporin-4 (AQP4) on astrocytes, which initiates complement-dependent cytotoxicity (CDC) and inflammation. We recently introduced mutated antibody (aquaporumab) and small-molecule blocker strategies for therapy of NMO, based on prevention of NMO-IgG binding to AQP4. Here, we investigated an alternative strategy involving neutralization of NMO-IgG effector function by selective IgG heavy-chain deglycosylation with bacteria-derived endoglycosidase S (EndoS). Cytotoxicity and NMO pathology were measured in cell and spinal cord slice cultures, and in mice exposed to control or EndoS-treated NMO-IgG. EndoS treatment of NMO patient serum reduced by >95% CDC and antibody-dependent cell-mediated cytotoxicity, without impairment of NMO-IgG binding to AQP4. Cytotoxicity was also prevented by addition of EndoS after NMO-IgG binding to AQP4. The EndoS-treated, nonpathogenic NMO-IgG competitively displaced pathogenic NMO-IgG bound to AQP4, and prevented NMO pathology in spinal cord slice culture and mouse models of NMO. EndoS deglycosylation converts pathogenic NMO-IgG autoantibodies into therapeutic blocking antibodies. EndoS treatment of blood may be beneficial in NMO, and may be accomplished, for example, by therapeutic apheresis using surface-immobilized EndoS.

Complement-dependent pathogenicity of brain-specific antibodies in cerebrospinal fluid

The specificity and potential pathogenicity of autoantibodies vary between neurological diseases. It is often unclear whether their detection in cerebrospinal fluid (CSF) is a consequence or a cause of pathology. The goal was to test whether administration of brain-specific antibodies into CSF would be sufficient for pathology. Purified immunoglobulin G from a neuromyelitis optica patient was injected intrathecally with complement to naïve mice. Histopathological analysis at 7days revealed damage to the ependyma, disruption of the CSF parenchymal barrier and pathologic lesions, distant from the site of injection. In the absence of complement there was no pathology. Autoantibody and complement in CSF are thus sufficient to initiate a pathologic cascade.

Epileptic seizures in Japanese patients with multiple sclerosis and neuromyelitis optica

To examine the incidence and clinical features of epileptic seizures in Japanese patients with multiple sclerosis (MS) and neuromyelitis optica (NMO). We reviewed medical records of all patients who visited the Neurology Clinic in Utano National Hospital between January and December, 2009, and enrolled 63 MS patients who fulfilled the McDonald criteria (2005) (mean age, 41.1 years) and 31 NMO patients who fulfilled the Wingerchuk criteria (2006) (mean age, 44.6 years). Patients with a history of epileptic seizures were selected and their clinical features were obtained. Four MS patients (6.3%; 2 men and 2 women; mean age, 32.5 years) and 4 NMO patients (12.9%; 4 women; mean age, 36.0 years) had epileptic seizures. Disease onset age of MS patients with seizures was significantly younger than those without seizures by 13.1 years, and Expanded Disability Status Scale of NMO patient with seizures was significantly higher than those without seizures by 2.2. All 8 patients showed brain lesions on magnetic resonance imaging and 2 MS patients had tumefactive demyelinating lesions. Electroencephalography showed interictal epileptiform discharges in 5 patients. Seizure types of 6 patients were recognized as partial seizures based on clinical semiology. All patients responded to antiepileptic therapy well. In both MS and NMO, there were both seizures with and without concurrent relapse. Similar to MS, NMO patients possibly have higher risk to develop epileptic seizures than general population.

Reply to Rossi et al.: Immunohistopathological findings in neuromyelitis optica concur with immunobiological observations in vitro

Aquaporin-4 (AQP4) water-channel–specific IgG unifies a spectrum of autoimmune astrocytopathies exemplified by neuromyelitis optica (NMO): relapsing inflammatory myelopathy, optic neuritis, and disorders affecting AQP4-rich circumventricular organs. AQP4-IgG detection in serum distinguishes these disorders from other inflammatory demyelinating disorders. The points of our study (1) were to emphasize that (i) IgG-AQP4 interaction has multiple molecular sequelae that plausibly account for diverse pathology (edema, inflammation, demyelination, and necrosis) and (ii) some outcomes are AQP4 isoform (M1 or M23)-specific. Our study involves immunocytochemistry and freeze-fracture EM of cultured rodent astrocytes, HEK293 cells transfected with non-tagged human AQP4s, Xenopus oocytes expressing GFP-tagged human AQP4s, and NMO patient brain immunohistopathology. Because serum IgG is polyclonal, we used high-titered sera (or IgG) pooled from at least 50 patients with NMO (binding > 1,000 nmol AQP4/L) to broadly investigate potentially pathogenic, AQP4-specific outcomes of IgG-AQP4 interaction in live cells. The correspondents question our data’s validity (2), citing conflicting data they obtained by using various AQP4 isoform-transfected cell types, sera from six individual patients with NMO, and mouse neuropathology.

Neuromyelitis Optica Experience in an Argentinian Neuroimmunology Clinic (P07.067)

Objective: To analyze the epidemiological, clinical features, diagnosis, associated diseases and treatment implemented in Argentinean patients with Neuromyelitis Optica (NMO). Background NMO is a disease that affects the optic nerves and the spinal cord. A new serum autoantibody (NMO-IgG) has been recently detected in NMO patients. Studies on diagnosis, management and randomized controlled trials evaluating drug regimens are limited. Design/Methods: We retrospectively reviewed medical records of patients with NMO seen at the Neuroimmunology Clinic from 2006 to 2011. Results: Thirty patients, 24 were women, median age at onset of disease was 39 years (range 24-58), median time of follow-up was 6.25 years (range 2-15). Their mean EDSS (SD) score at first and last appointment were 4.9 (1.8) and 4.5 (2.3) respectively. 19/21 developed tonic spasms during the course of the disease. Among fourteen patients who have cognitive evaluation 5 (35.71%) had abnormal performance in verbal memory, 2 (14.28%) in visual memory, 10 (71.42%) in attention and 6 (42.85%) in verbal fluency. Ten (33%) patients have associated diseases, 9 were autoimmune. 14/17 patients were NMO-IgG positive and 15/30 showed one or more non organ specific autoantibodies elevated. CSF showed total protein levels higher in 47% and Index IgG abnormal in the 23%. Positive oligoclonal bands were found in 17% of the 30 samples. 14 (53%) patients had MRI evidence of brain abnormalities. Four of them localized at sites of high AQP4 expression. At the last visit 21 patients (70%) were taking azathioprine, 2 prednisone, one glatiramer acetate, 5 rituximab and one antiretroviral therapy. Conclusions: It is noteworthy that there are no previous studies in our NMO patient population. This retrospective study showed similar findings as described in others series. Interestingly we founded a 30% of association with others autoimmune diseases, an important cognitive impairment and the presence of tonic spasms as frequent clinical manifestations of NMO. Disclosure: Dr. Luciana has nothing to disclose. Dr. Vanotti has nothing to disclose. Dr. Villa has nothing to disclose.

Neutrophil protease inhibition reduces neuromyelitis optica–immunoglobulin G–induced damage in mouse brain

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system associated with pathogenic autoantibodies against the astrocyte water channel protein aquaporin-4 (AQP4). The presence of neutrophils is a characteristic feature in NMO lesions in humans. Neutrophils are not generally found in multiple sclerosis lesions. We evaluated the role of neutrophils in a mouse NMO model. NMO lesions were produced in mice by intracerebral injection of immunoglobulin G (IgG) isolated from NMO patient serum and human complement. We previously reported that this mouse model produces the characteristic histological features of NMO, including perivascular complement activation, inflammatory cell infiltration, and loss of myelin, AQP4, and glial fibrillary acidic protein. Lesions are absent when AQP4 null mice are used or when IgG from non-NMO patients is injected. We found remarkably reduced neuroinflammation, myelin loss, and AQP4 loss in brains of neutropenic mice at 24 hours and 7 days, and increased severity of NMO lesions in mice made neutrophilic by granulocyte colony stimulating factor. NMO lesions were greatly reduced by intracerebral administration of the neutrophil protease inhibitors Sivelestat and cathepsin G inhibitor I or by intraperitoneal injection of Sivelestat alone. Immunostaining of human NMO lesions for neutrophil elastase revealed many degranulating perivascular neutrophils, with no equivalent perivascular neutrophils in human multiple sclerosis lesions. Our data implicate a central role of neutrophils in the pathogenesis of early NMO lesions and suggest the potential utility of neutrophil protease inhibitors such as Sivelestat in NMO therapy.

Small-molecule inhibitors of NMO-IgG binding to aquaporin-4 reduce astrocyte cytotoxicity in neuromyelitis optica.

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of spinal cord and optic nerve caused by pathogenic autoantibodies (NMO-IgG) against astrocyte aquaporin-4 (AQP4). We developed a high-throughput screen to identify blockers of NMO-IgG binding to human AQP4 using a human recombinant monoclonal NMO-IgG and transfected Fisher rat thyroid cells stably expressing human M23-AQP4. Screening of ∼60,000 compounds yielded the antiviral arbidol, the flavonoid tamarixetin, and several plant-derived berbamine alkaloids, each of which blocked NMO-IgG binding to AQP4 without affecting AQP4 expression, array assembly, or water permeability. The compounds inhibited NMO-IgG binding to AQP4 in NMO patient sera and blocked NMO-IgG-dependent complement- and cell-mediated cytotoxicity with IC(50) down to ∼5 μM. Docking computations identified putative sites of blocker binding at the extracellular surface of AQP4. The blockers did not affect complement-dependent cytotoxicity caused by anti-GD3 antibody binding to ganglioside GD3. The blockers reduced by >80% the severity of NMO lesions in an ex vivo spinal cord slice culture model of NMO and in mice in vivo. Our results provide proof of concept for a small-molecule blocker strategy to reduce NMO pathology. Small-molecule blockers may also be useful for other autoimmune diseases caused by binding of pathogenic autoantibodies to defined targets.

Rituximab dosing and monitoring strategies in neuromyelitis optica patients: creating strategies for therapeutic success

Background: Neuromyelitis optica (NMO) is an autoimmune condition that predominantly causes severe optic neuritis and transverse myelitis. Rituximab therapy has dramatically improved patient care, but standardized dosing regimens and guidelines are lacking. Objectives: The objective of this study was to define a rituximab dosing strategy for NMO patients that achieves the lowest rate of relapses. Methods: This was a retrospective chart review of patients treated with various doses of rituximab. Results: Combining data from the NMO and multiple sclerosis (MS) patients, identified that the mean number of days after a 100 mg dose of rituximab until the CD19 population was greater than 2% was 99 days (standard deviation 36, range 43–172). When allowed to rise, the mean number of days after a 1000 mg dose of rituximab until the CD19 population was greater than 2% was 184 (standard deviation 72, range 52–288). The median number of days until a CD19 percentage of 2% was achieved was 133 days in the 100 mg dosing arm and 259 days in the 1000 mg dosing arm. Analysis of the survival curves via both the Mantel–Cox log-rank test and the Wilcoxon test determined that the difference between medial survival for 100 and 1000 mg doses was statistically significant with p-values <0.0001. Conclusions: Low doses of rituximab have a high rate of early B-cell repopulation. Any NMO patient treated with rituximab should be followed with monthly CD19 counts in order to identify the rare, but clinically significant, early repopulators.

Cognitive Function, Depression, Fatigue, and Activities of Daily Living in Patients With Neuromyelitis Optica After Acute Relapse

ABSTRACTThe status of fatigue, depression, and activities of daily living and their relationships with cognitive function in patients with neuromyelitis optica (NMO) after acute relapse has never been observed. This study investigated cognitive function, fatigue, depression, activities of daily living, and the relationships among them in NMO patients. Twenty-two NMO patients without visible lesions on conventional brain MRI after acute relapse, 22 depression patients, and 22 healthy comparison subjects received several scales to assess cognitive function, fatigue, and depression. Every NMO patient completed a survey of activities of daily living. Between-group comparisons and correlational analyses were applied to examine the differences and the relationships among them. We found that NMO patients had significantly impaired memory, decreased information processing speed, and damaged attention. Some impaired cognitive domains were significantly correlated with fatigue and depression, and activities of daily living were correlated with these impaired cognitive domains, fatigue, depression, and disability. These results confirm cognitive deficits in memory, information processing speed, and attention exist in NMO patients without visible brain lesions after acute relapse. Fatigue and depression may affect cognitive function and increase the negative impact of cognitive deficits on the activities of daily living in patients with NMO.

Identification of peptide targets in neuromyelitis optica

Neuromyelitis optica (NMO) is an inflammatory demyelinating disease that predominantly affects the optic nerves and spinal cord. Recombinant antibodies (rAbs) generated from clonally expanded plasma cells in an NMO patient are specific to AQP4 and pathogenic. We screened phage-displayed peptide libraries with these rAbs, and identified 14 high affinity linear and conformational peptides. The linear peptides shared sequence homologies with NMO autoantigen AQP4 on the extracellular surface. Competitive inhibition ELISA and immunocytochemistry demonstrated that these peptides represent epitopes of NMO autoantigen AQP4. Peptide epitopes/mimotopes may have potential uses for disease prognosis, monitoring, and therapy.

Binding Affinity and Specificity of Neuromyelitis Optica Autoantibodies to Aquaporin-4 M1/M23 Isoforms and Orthogonal Arrays

Autoantibodies against astrocyte water channel aquaporin-4 (AQP4) are highly specific for the neuroinflammatory disease neuromyelitis optica (NMO). We measured the binding of NMO autoantibodies to AQP4 in human astrocyte-derived U87MG cells expressing M1 and/or M23 AQP4, or M23 mutants that do not form orthogonal array of particles (OAPs). Binding affinity was quantified by two-color fluorescence ratio imaging of cells stained with NMO serum or a recombinant monoclonal NMO autoantibody (NMO-rAb), together with a C terminus anti-AQP4 antibody. NMO-rAb titrations showed binding with dissociation constants down to 44 ± 7 nm. Different NMO-rAbs and NMO patient sera showed a wide variation in NMO-IgG binding to M1 versus M23 AQP4. Differences in binding affinity rather than stoichiometry accounted for M1 versus M23 binding specificity, with consistently greater affinity of NMO-IgG binding to M23 than M1 AQP4. Binding and OAP measurements in cells expressing different M1:M23 ratios or AQP4 mutants indicated that the differential binding of NMO-IgG to M1 versus M23 was due to OAP assembly rather than to differences in the M1 versus M23 N termini. Purified Fab fragments of NMO-IgG showed similar patterns of AQP4 isoform binding, indicating that structural changes in the AQP4 epitope upon array assembly, and not bivalent cross-linking of whole IgG, result in the greater binding affinity to OAPs. Our study establishes a quantitative assay of NMO-IgG binding to AQP4 and indicates remarkable, OAP-dependent heterogeneity in NMO autoantibody binding specificity.

Construction and clinical application of lentivirus-AQP4 expressing vector

To construct the human aquaporin-4 (AQP4) expressing vector and detect anti-AQP4 antibody in serum of patients with neuromyelitis optica (NMO). RNA was extracted from human glioblastoma and AQP4 cDNA obtained through RT-PCR.The fragment was cloned into the lentiviral expressing vector (iDUET101) and transformed into competent strain Hb101 for later amplification; plasmids were extracted from the amplified positive-bacteria-colony, sequenced and transfected into HEK-293T cells. Expression of AQP4 was identified by RT-PCR, Western blot and immunofluorescence assay. And anti-AQP4 antibody in human serum was tested. The sequence of target fragment matched with that of human AQP4 fragment sequences (NM_001650) completely. The constructed AQP4 fragment transfected in HEK-293T cell was tested by immunofluorescent examination and it exhibited obvious fluorescence located in cell membrane. Western blot test was positive. And the fragment was about 34 KD. Cellular immunofluorescence examination showed 11 examples of 12 NMO patient serums (91.7%) were positive, 4 in 34 multiple sclerosis (11.8%) positive and negative in all 50 serum samples of healthy controls. The HEK-293T cell transfected with lentivirus-AQP4 vector can express stably. And the expressed fragment may be applied in clinical examination.

Intrathecal pathogenic anti–aquaporin‐4 antibodies in early neuromyelitis optica

The serum of most neuromyelitis optica (NMO) patients contains autoantibodies (NMO-IgGs) directed against the aquaporin-4 (AQP4) water channel located on astrocyte foot processes in the perivessel and subpial areas of the brain. Our objectives were to determine the source of central nervous system (CNS) NMO-IgGs and their role in disease pathogenesis. Fluorescence-activated cell sorting and single-cell reverse transcriptase polymerase chain reaction were used to identify overrepresented plasma cell immunoglobulin (Ig) sequences in the cerebrospinal fluid (CSF) of an NMO patient after a first clinical attack. Monoclonal recombinant antibodies (rAbs) were generated from the paired heavy and light chain sequences and tested for target specificity and Fc effector function. The effect of CSF rAbs on CNS immunopathology was investigated by delivering single rAbs to rats with experimental autoimmune encephalomyelitis (EAE). Repertoire analysis revealed a dynamic, clonally expanded plasma cell population with features of an antigen-targeted response. Using multiple independent assays, 6 of 11 rAbs generated from CSF plasma cell clones specifically bound to AQP4. AQP4-specific rAbs recognized conformational epitopes and mediated both AQP4-directed antibody-dependent cellular cytotoxicity and complement-mediated lysis. When administered to rats with EAE, an AQP4-specific NMO CSF rAb induced NMO immunopathology: perivascular astrocyte depletion, myelinolysis, and complement and Ig deposition. Molecular characterization of the CSF plasma cell repertoire in an early NMO patient demonstrates that AQP4-specific Ig is synthesized intrathecally at disease onset and directly contributes to CNS pathology. AQP4 is now the first confirmed antigenic target in human demyelinating disease.

Interferon-β1b Treatment in Neuromyelitis Optica

Background: The effects of interferon-β_1b (IFN-β_1b) administration in multiple sclerosis (MS) patients have been confirmed, however, those in neuromyelitis optica (NMO) patients have not been shown. In this study, we assessed the effects of IFN-β_1b treatment on disease exacerbation and disability progression in MS or NMO patients. Methods: We reviewed a series of 104 consecutive patients with relapsing-remitting MS (RRMS) (69) or NMO (35) treated with IFN-β_1b in the MS clinical center of a national hospital in Japan. Results: The relapse number in the RRMS patients significantly decreased within 1 year after IFN-β_1b treatment (p < 0.00001); however, that in the NMO patients did not show a significant decrease (p = 0.5601). The decrease in annualized relapse rates in each RRMS patient after treatment was significant (p < 0.01), but that in each NMO patient was not (p > 0.05). The change in Kurtzke’s Expanded Disability Status Scale score 1 year after treatment was higher in the NMO patients than in the RRMS patients (p = 0.0225). Conclusion: In NMO patients, IFN-β_1b treatment was not effective in reducing the relapse number and the disability progression.