Tatsuro Misu

Neuromyelitis optica: pathogenicity of patient immunoglobulin in vivo.

Severe inflammation and astrocyte loss with profound demyelination in spinal cord and optic nerves are typical pathological features of neuromyelitis optica (NMO). A diagnostic hallmark of this disease is the presence of serum autoantibodies against the water channel aquaporin‐4 (AQP‐4) on astrocytes.

Distinction between MOG antibody–positive and AQP4 antibody–positive NMO spectrum disorders

Objective: To evaluate clinical features among patients with neuromyelitis optica spectrum disorders (NMOSD) who have myelin oligodendrocyte glycoprotein (MOG) antibodies, aquaporin-4 (AQP4) antibodies, or seronegativity for both antibodies. Methods: Sera from patients diagnosed with NMOSD in 1 of 3 centers (2 sites in Brazil and 1 site in Japan) were tested for MOG and AQP4 antibodies using cell-based assays with live transfected cells. Results: Among the 215 patients with NMOSD, 7.4% (16/215) were positive for MOG antibodies and 64.7% (139/215) were positive for AQP4 antibodies. No patients were positive for both antibodies. Patients with MOG antibodies represented 21.1% (16/76) of the patients negative for AQP4 antibodies. Compared with patients with AQP4 antibodies or patients who were seronegative, patients with MOG antibodies were more frequently male, had a more restricted phenotype (optic nerve more than spinal cord), more frequently had bilateral simultaneous optic neuritis, more often had a single attack, had spinal cord lesions distributed in the lower portion of the spinal cord, and usually demonstrated better functional recovery after an attack. Conclusions: Patients with NMOSD with MOG antibodies have distinct clinical features, fewer attacks, and better recovery than patients with AQP4 antibodies or patients seronegative for both antibodies.

Clinical and MRI features of Japanese patients with multiple sclerosis positive for NMO-IgG

This study investigates the relation between the serological status of NMO (neuromyelitis optica)-IgG and the clinical and MRI features in Japanese patients with multiple sclerosis. Serum NMO-IgG was tested in 35 Japanese patients diagnosed with multiple sclerosis, including 19 with the optic–spinal form of multiple sclerosis (OSMS), three with the spinal form of multiple sclerosis (SMS), and 13 with the conventional form of multiple sclerosis (CMS), which affects the brain. NMO-IgG was detected in 14 patients, 12 with OSMS and 2 with CMS. In these patients, longitudinally extensive (>3 vertebral segments) spinal cord lesions (93% v 57%) and permanent, complete blindness (no perception of light) in at least one eye (50% v 0%) were the noticeable features as compared with NMO-IgG-negative OSMS. The two patients having CMS with NMO-IgG had unusual brain lesions, but in other respects had features suggesting OSMS. NMO-IgG was detected in more than half the number of patients with OSMS and in some patients with CMS. This newly discovered serum autoantibody was markedly associated with longitudinally extensive spinal cord lesions and with complete blindness, suggesting severe optic–spinal disease.

Prognostic factors and disease course in aquaporin-4 antibody-positive patients with neuromyelitis optica spectrum disorder from the United Kingdom and Japan

Neuromyelitis optica and neuromyelitis optica spectrum disorders have been recently associated with the disease-specific autoantibody aquaporin-4, thought to be pathogenic. Identifying this antibody has allowed the clinical phenotype to be broadened. It is clear that some patients with similar clinical features do not have this antibody and may have a different condition with different outcomes and prognosis. Previous clinical neuromyelitis optica and neuromyelitis optica spectrum disorder studies have included such patients. We investigated clinical outcomes and prognostic characteristics of 106 aquaporin-4 antibody-seropositive patients from the UK and Japan. We looked at predictors of disability outcomes, namely visual disability (permanent bilateral visual loss with visual acuity of <6/36 in the best eye), motor disability (permanent inability to walk further than 100 m unaided), wheelchair dependence and mortality. Data were collected largely retrospectively through review of case records. After median disease duration of 75 months, 18% had developed permanent bilateral visual disability, 34% permanent motor disability, 23% had become wheelchair dependent and 9% had died. Age at disease onset appeared to be an important predictor of disability type. Young-onset patients in the UK, but not the Japanese cohort, commonly presenting with optic neuritis, had a high risk of visual disability while older patients in both cohorts had a high risk of motor disability, regardless of their onset symptom. Genetic factors also appeared important. The UK cohort seemed to have more severe disease than the Japanese cohort, with more severe onset attacks, a higher relapse frequency and greater disability at follow-up, despite earlier immunosuppression. Moreover, within the UK cohort, there were important differences between ethnic groups, with Afro-Caribbean patients having a younger age at disease onset, more brain and multifocal attacks and higher likelihood of visual disability than Caucasian patients. Thus, age at disease onset and genetic factors are both likely to be important in determining clinical outcomes in aquaporin-4 disease. This has important implications for interpreting clinical neuromyelitis optica and neuromyelitis optica spectrum disorder studies, since clinical features and outcomes appear not to be generic across populations and may need to be tailored to individual groups. These factors need to be explored further in future prospective neuromyelitis optica and neuromyelitis optica spectrum disorder studies.

Astrocytic damage is far more severe than demyelination in NMO A clinical CSF biomarker study

Introduction: Loss of aquaporin 4 and glial fibrillary acidic protein (GFAP) with necrosis and demyelination is a prominent pathologic feature of neuromyelitis optica (NMO). However, the clinicopathologic significance of astrocytic damage and its relation with demyelination are unknown. Objective: To analyze clinical and pathologic values of a CSF biomarker of astrocytic damage in NMO. Methods: We measured the levels of GFAP, S100B, myelin basic protein (MBP), and neurofilament H (NF-H) in CSF obtained from patients with NMO (n = 33), multiple sclerosis (MS) (n = 27), acute disseminated encephalomyelitis (ADEM), ischemia, meningitis, and other neurologic disease controls (OND). Results: The CSF-GFAP levels during relapse in NMO (2,476.6 ± 8,815.0 ng/mL) were significantly higher than those in MS (0.8 ± 0.4 ng/mL) and OND (0.7 ± 0.5 ng/mL), and much beyond those in ADEM (14.1 ± 27.4 ng/mL). The sensitivity and specificity of CSF-GFAP for NMO was 90.9% and 76.9% in all, but the specificity improved above 90% in cases limited to demyelinating diseases. CSF-S100B showed a similar trend but was less remarkable. In contrast, MBP and NF-H are not different between NMO and MS. Following treatments, the CSF-GFAP rapidly decreased to a normal level, but CSF-MBP remained high. There were strong correlations between the CSF-GFAP, CSF-S100B, or CSF-MBP levels and Expanded Disability Status Scale (EDSS) or spinal lesion length in the acute phase (r > 0.6). Only CSF-GFAP correlated with EDSS at 6-month follow-up (r = 0.51) in NMO. Conclusions: Astrocytic damage reflected by elevated CSF glial fibrillary acidic protein is a clinically relevant, primary pathologic process in neuromyelitis optica, and is far more severe than demyelination.

Chemokine receptor expression on T cells in blood and cerebrospinal fluid at relapse and remission of multiple sclerosis: imbalance of Th1/Th2-associated chemokine signaling

The expression of chemokine receptors on lymphocytes in the blood and CSF of multiple sclerosis (MS) patients was analyzed at relapse and remission. Both CD4+ and CD8+ cells in CSF at relapse were enriched for Th1-type receptors CXCR3 and CCR5 expression, and were reduced for Th2-type receptors CCR3 and CCR4 expression compared with those of the blood. CCR1 and CCR2 expressions on T cells were increased in CSF and blood, respectively. At remission, CCR5 expression, but not CXCR3 expression, was reduced in CSF CD4+ cells. A biased Th1/Th2 balance may play a critical role in active inflammation and CCR5 on CSF CD4+ cells is a good marker of the disease activity.

Intractable hiccup and nausea in neuromyelitis optica with anti-aquaporin-4 antibody: a herald of acute exacerbations

Background: Intractable hiccup and nausea (IHN) are unique symptoms in neuromyelitis optica (NMO). Recent studies have strongly suggested that the pathogenesis of NMO is closely associated with anti-aquaporin-4 (AQP4) antibody. However, clinical implications of IHN and the relationship with anti-AQP4 antibody remain unknown. Methods: The past medical records of 35 patients with seropositivity for anti-AQP4 antibody were reviewed. We also followed the titres of anti-AQP4 antibody in a patient with NMO, who had newly developed IHN. Results: Of the 35 patients, 15 patients (43%) had episodes of IHN. There was a total of 35 episodes of IHN in these 15 patients and, of the 35 episodes, hiccup was seen in 23 episodes (66%) and nausea was seen in 28 episodes (80%). The IHN frequently preceded (54%) or accompanied (29%) myelitis or optic neuritis. The IHN was often preceded by an episode of viral infection. The titres of anti-AQP4 antibody were remarkably increased when the intractable hiccup appeared in a case. Conclusions: IHN could be a clinical marker for the early phase of an exacerbation. Careful observation may be needed when INH is seen in patients with NMO, and the early initiation of the treatment could prevent subsequent neurological damage.

The pathology of an autoimmune astrocytopathy: lessons learned from neuromyelitis optica.

Neuromyelitis optica (NMO) is a disabling autoimmune astrocytopathy characterized by typically severe and recurrent attacks of optic neuritis and longitudinally extensive myelitis. Until recently, NMO was considered an acute aggressive variant of multiple sclerosis (MS), despite the fact that early studies postulated that NMO and MS may be two distinct diseases with a common clinical picture. With the discovery of a highly specific serum autoantibody (NMO‐IgG), Lennon and colleagues provided the first unequivocal evidence distinguishing NMO from MS and other central nervous system (CNS) inflammatory demyelinating disorders. The target antigen of NMO‐IgG was confirmed to be aquaporin‐4 (AQP4), the most abundant water channel protein in the CNS, mainly expressed on astrocytic foot processes at the blood–brain barrier, subpial and subependymal regions. Pathological studies demonstrated that astrocytes were selectively targeted in NMO as evidenced by the extensive loss of immunoreactivities for the astrocytic proteins, AQP4 and glial fibrillary acidic protein (GFAP), as well as perivascular deposition of immunoglobulins and activation of complement even within lesions with a relative preservation of myelin. In support of these pathological findings, GFAP levels in the cerebrospinal fluid (CSF) during acute NMO exacerbations were found to be remarkably elevated in contrast to MS where CSF‐GFAP levels did not substantially differ from controls. Additionally, recent experimental studies showed that AQP4 antibody is pathogenic, resulting in selective astrocyte destruction and dysfunction in vitro, ex vivo and in vivo. These findings strongly suggest that NMO is an autoimmune astrocytopathy where damage to astrocytes exceeds both myelin and neuronal damage. This chapter will review recent neuropathological studies that have provided novel insights into the pathogenic mechanisms, cellular targets, as well as the spectrum of tissue damage in NMO.

Characteristic brain magnetic resonance imaging abnormalities in central nervous system aquaporin-4 autoimmunity:

Background: Although neuromyelitis optica has been traditionally regarded as a disease without brain involvement, brain abnormalities are not uncommon in patients with neuromyelitis optica-related disorders. Methods: We aimed to characterize the brain magnetic resonance imaging (MRI) abnormalities in neuromyelitis optica spectrum disorder patients who are seropositive for anti-aquaporin-4 autoantibody (AQP4 Ab). Of 236 consecutive patients with inflammatory demyelinating central nervous system diseases, we retrospectively analyzed MRI characteristics of 78 patients who were seropositive for AQP4 Ab. Results: For an average observational period of 6.3 years, 62 patients (79%) had brain lesions on MRI. Twenty-four patients (31%) had brain MRI abnormalities at the onset of disease, and 35 (45%) had symptomatic brain involvement. Characteristic brain MRI abnormalities were classified into five categories: (1) lesions involving corticospinal tracts (e.g. posterior limb of internal capsule and cerebral peduncle (44%); (2) extensive hemispheric lesions likely due to vasogenic edema (29%); (3) periependymal lesions surrounding aqueduct and the third and fourth ventricles (22%); (4) periependymal lesions surrounding lateral ventricles (40%); and (5) medullary lesions, often contiguous with cervical lesions (31%). Fifty-four patients (69%) showed at least one kind of brain abnormality among the five characteristic MRI lesions. Ten patients showed gadolinium-enhancing lesions, which were characterized by multiple patchy enhancing patterns with blurred margins. Conclusions: In central nervous system AQP4 autoimmunity, brain MRI abnormalities were more common than is generally appreciated and were characterized by their unique localization and configuration.

Inflammation induced by innate immunity in the central nervous system leads to primary astrocyte dysfunction followed by demyelination

Primary loss and dysfunction of astrocytes may trigger demyelination, as seen in neuromyelitis optica, an inflammatory disease of the central nervous system. In most patients affected by this disease, injury to astrocytes is initiated by the action of autoantibodies targeting aquaporin 4 (AQP-4), a water channel on astrocytes. We show here that damage of astrocytes and subsequent demyelination can also occur in the absence of autoantibody-mediated mechanisms. Following injection of lipopolysaccharide into the white matter initial microglia activation is followed by a functional disturbance of astrocytes, mainly reflected by retraction of astrocytic foot processes at the glia limitans and loss of AQP-4 and connexins, which are involved in the formation of gap junctions between astrocytes and oligodendrocytes. Demyelination and oligodendrocyte degeneration in this model follows astrocyte pathology. Similar structural abnormalities were also seen in a subset of active lesions in multiple sclerosis. Our studies suggest that astrocyte injury may be an important early step in the cascade of lesion formation in brain inflammation.