Clinica Chimica Acta 440 (2015) 64–71

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Biomarkers for neuromyelitis optica Kuo-Hsuan Chang, Long-Sun Ro, Rong-Kuo Lyu, Chiung-Mei Chen ⁎ Department of Neurology, Chang Gung Memorial Hospital, Linkou Medical Center and College of Medicine, Chang-Gung University, Taoyuan, Taiwan

a r t i c l e

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Article history: Received 2 May 2014 Received in revised form 31 October 2014 Accepted 1 November 2014 Available online 7 November 2014 Keywords: Neuromyelitis optica Anti-AQP4 antibody Biomarker Th17 Astrocytopathy

a b s t r a c t Neuromyelitis optica (NMO) is an acquired, heterogeneous inflammatory disorder, which is characterized by recurrent optic neuritis and longitudinally extensive spinal cord lesions. The discovery of the serum autoantibody marker, anti-aquaporin 4 (anti-AQP4) antibody, revolutionizes our understanding of pathogenesis of NMO. In addition to anti-AQP4 antibody, other biomarkers for NMO are also reported. These candidate biomarkers are particularly involved in T helper (Th)17 and astrocytic damages, which play a critical role in the development of NMO lesions. Among them, IL-6 in the peripheral blood is associated with anti-AQP4 antibody production. Glial fibrillary acidic protein (GFAP) in CSF demonstrates good correlations with clinical severity of NMO relapses. Detecting these useful biomarkers may be useful in the diagnosis and evaluation of disease activity of NMO. Development of compounds targeting these biomarkers may provide novel therapeutic strategies for NMO. This article will review the related biomarker studies in NMO and discuss the potential therapeutics targeting these biomarkers. © 2014 Elsevier B.V. All rights reserved.

Contents 1. 2.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . Anti-AQP4 autoimmunity in NMO . . . . . . . . . . . . . . . . 2.1. Biological roles of AQP4 . . . . . . . . . . . . . . . . . 2.2. Autoimmune marker NMO-IgG/anti-AQP4 antibody for NMO 2.3. Proposed immunopathogenesis based on the presence of anti-AQP4 antibody . . . . . . . . . . . . . . . . . . . 2.4. Other auto-antibodies in neuromyelitis optica . . . . . . . 3. Biomarkers for NMO other than autoantibodies . . . . . . . . . . 3.1. IL-6 and other Th17-mediated biomarkers for NMO . . . . . 3.2. Th2-mediated biomarkers for NMO . . . . . . . . . . . . 3.3. Th1- and Treg-mediated biomarkers for NMO . . . . . . . 3.4. Biomarkers related to astrocytic injuries for NMO . . . . . . 3.5. Other candidate biomarkers for NMO . . . . . . . . . . . 4. Immunomodulatory therapies for NMO targeting anti-AQP4 antibody and other biomarkers . . . . . . . . . . . . . . . . . 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction Neuromyelitis optica (NMO) is an inflammatory disease of the central nervous system (CNS) that is characterized by severe attacks ⁎ Corresponding author at: Department of Neurology, Chang Gung Memorial Hospital, Linkou Medical Center, 333 Kueishan, Taoyuan, Taiwan. Tel.: +886 3 3281200x8347; fax: +886 3 3288849. E-mail address: [email protected] (C.-M. Chen).

http://dx.doi.org/10.1016/j.cca.2014.11.004 0009-8981/© 2014 Elsevier B.V. All rights reserved.

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of optic neuritis and myelitis with long-segmental spinal cord lesions (LESCLs) [1]. It was firstly recognized in the early 19th century by several European physicians [2], and was once thought to be a variant of multiple sclerosis (MS). The discovery of a serum autoantibody marker anti-aquaporin 4 (anti-AQP4) antibody further supports that NMO and MS are belonging to two distinct disease entities [3]. Now the spectrum of NMO includes typical NMO, as well as clinical variants such as antiAQP4 antibody-positive optic neuritis, longitudinally extensive myelitis, and myelitis or optic neuritis associated with brain lesions particularly

K.-H. Chang et al. / Clinica Chimica Acta 440 (2015) 64–71

at hypothalamus, periventricular or periaqueductal area [4]. Population-based studies show that the prevalence of NMO, which may be similar in Caucasians and non-Caucasians, is between 0.5 and 4/105 [5–9]. Compared with MS, NMO has the characteristic features including older age at onset, female preponderance, greater disability due to severe optic nerve and spinal cord damage, fewer brain MRI lesions, LESCLs extending greater than three vertebral segments in spinal cord, marked pleocytosis and neutrophilia in cerebrospinal fluid (CSF), and absence of oligoclonal bands in CSF [4]. Although anti-AQP4 antibody is thought as a sensitive diagnostic biomarker for NMO [1], the associations between serum reactivity of anti-AQP4 antibody and various clinical parameters in NMO patients are still controversial. A correlation between serum anti-AQP4 antibody titre and length of spinal cord lesions has been reported [10]. Serum anti-AQP4 antibody levels are increased by NMO relapses and these changes can be reversed following immunosuppressive therapy [11, 12]. On the other hand, Dujmovic et al. showed that CSF but not serum anti-AQP4 antibody titres was associated with scores of Kurtzke's extended disability scale (EDSS) in NMO patients [13]. Hinson et al. found that patients with mild and severe NMO attacks did not differ significantly with respect to anti-AQP4 antibody titres [14]. Neither relapse nor high EDSS scores are associated with high serum anti-AQP4 antibody levels in Chanson's study [15]. These controversies and the presence of anti-AQP4 negative NMO patients [8–10] urge the development of more biomarkers, particularly those involved in T-cell immunity and astrocytic damage, to determine specific therapeutic targets and test clinical efficacy for future NMO treatments. 2. Anti-AQP4 autoimmunity in NMO 2.1. Biological roles of AQP4 AQP4, the principal water channel throughout the CNS, is expressed at astrocyte end-feet at the blood–brain barrier (BBB) and facilitates water movement across BBB [16,17]. In models of cytotoxic oedema induced by bacterial infection, water intoxication or ischemia, AQP4knockout mice demonstrate reduced accumulation of water in the brain and better survival than wild-type mice [18–21]. On the other hand, AQP4 also facilitates water exit from the brain through brain ventricles [22]. Thus AQP4-knockout mice have greater water accumulation in the brain of vasogenic oedema models by intraparenchymal fluid infusion and obstructive hydrocephalus [22,23]. By slowing water and potassium uptake, AQP4 knockout mice prolong seizure duration [24]. AQP4 modulators reveal potentials of improving brain oedema, hydrocephalus, epilepsy, traumatic brain and spinal cord injuries in mouse models [25]. 2.2. Autoimmune marker NMO-IgG/anti-AQP4 antibody for NMO In 2004, Lennon et al. found a serum autoantibody NMO-IgG, which demonstrated 73% sensitivity and 91% specificity, for NMO [26], and showed that NMO-IgG selectively binds to the AQP4 [3]. Shortly these observations are wildly validated by studies from various groups [27–31]. Multiple immune assays, including tissue-based fluorescence immunohistochemistry [26], cell-based immunocytochemistry [10], cell lysate immunoprecipitation [32,33], and enzyme-linked immunosorbent assay employing purified recombinant AQP4 protein [34], have been used to validate the specificity of anti-AQP4 antibody in identifying NMO. All techniques demonstrate high specificities, ranging from 91 to 100%, with the cell-based immunocytochemistry having a specificity of 100% [32]. Their sensitivities range from 57 to 91%, with cell-based immunocytochemistry showing the highest sensitivities at 91% [32]. These differences may reflect variations in sex, age, ethnic background, disease and treatment status at the time of blood sampling [9,35]. Although cell-based immunocytochemistry seems to be the most sensitive and specific, some limitations apply to this type of assay. The

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use of transfected cells requires the cell line to be freshly transfected prior to testing. The AQP4 expression level of transfected cells may decline overtime. Fusion of AQP4 to fluorescent protein (GFP or EGFP), as used in immunocytochemistry, may alter the structure of the protein. The semiquantitative and observer-dependent natures of immunocytochemistry further challenge the reproducibility of the assay. Confirmation in a second methodologically independent assay is generally recommended and is particularly important in patients presenting with NMO spectrum disorders. AQP4 has two isoforms: the full length M1 isoform and the truncated M23 isoform lacking 22 amino acids in N-terminal [36]. Only the presence of the M23 isoform induces the formation of an orthogonal array of particles (OAPs), while M1 is thought to inhibit and limit the formation of OAPs [37]. The epitope of NMO-IgG has been reported intrinsically in OAPs [38]. Several studies indicate more binding of serum antiAQP4 antibody with cells expressing M23 than M1 isoform [38–41]. However, a wide variation of anti-AQP4 antibody binding affinity to M1 and M23 isoforms between patients with NMO has been noted [40]. More validations have to be performed to elucidate the role of M23 isoform in the immunogenicity of NMO. The levels of anti-AQP4 antibody is roughly 500 times more concentrated in plasma than in CSF, which suggests that anti-AQP4 antibody is generated peripherally [42]. However, Klawiter et al. found that three patients present anti-AQP4 antibody in CSF but not in serum [43]. Bennett et al. reported the presence of anti-AQP4 antibody-secreting plasma cells in CSF [44]. Dujmovic et al. found that CSF anti-AQP4 antibody titers were positively correlated with the lengths of spinal cord lesions [13], while Jarius et al. noted that high CSF levels of anti-AQP4 antibody were associated with NMO relapses [42]. The clinical significance of testing the CSF for anti-AQP4 antibody needs further elucidation. Even with the most sensitive assays, a significant proportion of patients with NMO are seronegative for anti-AQP4 antibody. Seroconversion from negative to positive or vice versa during follow-up has been observed in 15–55% of NMO patients [45,46]. This seronegativity may be resulted by treatment with immunosuppressants or plasma exchange [47,48]. Given the diagnostic impact of anti-AQP4 antibody seropositivity in NMO, repeat testing in patients with an initially negative result is necessary. The association of infectious (Helicobacter pylori and Chlamydia pneumonia infection) and genetic factors (HLADRB1*1602 and DPB1*0501 alleles) on major histocompatibility complex class II with anti-AQP4 positive patients suggests the immunological nature in NMO pathogenesis. However, no specific contributing factors have been identified for anti-AQP4 antibody negative NMO, which suggests different risk factors or pathogenic mechanism in this type of NMO [49]. 2.3. Proposed immunopathogenesis based on the presence of anti-AQP4 antibody In addition to above clinical observations, pathological and animal studies show that anti-AQP4 antibody plays a pivotal role in the generation of NMO lesions. The pathological features of NMO lesions include necrosis with cavitation, hyalinization of small vessels and perivascular inflammatory infiltrates [50,51]. Vasculocentric deposition of immunoglobulin and activated complement components in NMO lesions suggest humoral immunity against a perivascular antigen [51–53], which may subsequently cause the loss of perivascular AQP4-positive and glial fibrillary acidic protein (GFAP)-positive astrocyte foot processes [51–53]. Prominent astrocyte destruction with relative preservation of myelin in early NMO lesions further supports the involvement of astrocyte injury in the pathogenesis in NMO [52,54]. Intracerebral injection of anti-AQP4 antibody in rodents generates brain lesions similar to NMO [55,56], providing direct evidence to support the pathogenic role of anti-AQP4 antibody in NMO. The binding of anti-AQP4 antibody activates complement and initiates a cascade of inflammatory events to

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recruit granulocytes and macrophages, causing further disruption of BBB, vascular hyalinization, necrosis, demyelination and axonal injury in the affected segments of spinal cord [4]. Interestingly, pronounced complement-dependent astrocyte death can be induced by serum from anti-AQP4 antibody-negative NMO patients, indicating the presence of unidentified antibodies in seronegative NMO patients [57]. The beneficial effects of plasma exchange in some anti-AQP4 antibodynegative patients also provide support to this hypothesis [58]. 2.4. Other auto-antibodies in neuromyelitis optica Non-organ-specific autoantibodies are frequently seen in patients with NMO, and systemic autoimmune disorders such as Sjogren's syndrome and systemic lupus erythematous can occur concomitantly with NMO [59–61]. Pittock et al. reported that 44% of NMO patients had a positive antinuclear antibody [62]. Anti-SSA antibody is also seen in 16% of NMO patients [62]. In addition, anti-cardiolipin and perinuclear anti-neutrophil cytoplasmic antibodies have been reported in NMO patients as well [63,64]. A Greek's study has shown that a proportion of NMO patients display anti-aquaporin-1 antibody in their sera [65]. The pathogenic role of these autoantibodies in NMO needs further clarification. 3. Biomarkers for NMO other than autoantibodies In addition to anti-AQP4 antibody, a number of studied molecular biomarkers may be helpful to elucidate immunopathogenesis of NMO. These findings expand our understanding of NMO pathogenesis and also provide important insights into the development of novel therapeutic strategies. 3.1. IL-6 and other Th17-mediated biomarkers for NMO Several lines of evidence strongly suggest the involvement of T helper (Th)17 and Th2 axes in NMO. Th17 cells are highly proinflammatory effector T cells that are characterized by their production of high amounts of IL-8, IL-17, IL-21, and IL-23 and granulocyte colonystimulating factor (G-CSF) [66]. This subset of T cells may induce chronic inflammatory and autoimmune diseases as well as function as B-cell helpers by induction of B cell proliferation and stimulation of antibody

production [66,67]. Peripheral blood T cells from NMO patients demonstrated greater proliferation to AQP4 [68]. In NMO, these AQP4-specific T cells exhibited Th17 polarization, and monocytes produced more interleukin 6 (IL-6), a Th17-polarizing cytokine [68]. A number of Th17-mediated cytokines has been reported as candidate biomarkers for NMO (Table 1). Secreted by macrophages, dendritic cells, and B cells, IL-6 is a proinflammatory cytokine that promotes antibody synthesis in activated B cells and differentiation of naïve T cells into Th17 cells [69,70]. Accumulated evidence suggests that IL-6 may serve as a biomarker to diagnose NMO and differentiate it from MS. Icoz et al. reported that serum IL-6 levels in patients with NMO were significantly higher than those in patients with optic neuritis, MS or healthy controls (HCs) [71]. This finding is recapitulated by Uzawa et al. who found that NMO patients have higher serum IL-6 levels than those with other non-inflammatory neurological disorders (ONNDs) [72], and Wang et al., who repeatedly found that plasma IL-6 levels are higher in NMO patients than that in HC [73]. A further study found that intracellular IL-6 production in monocytes is amplified in NMO patients [68]. A higher number of anti-myelin oligodendrocyte glycoprotein IL-6-secreting cells in the peripheral blood and CSF of NMO patients than that of MS patients or HC was reported by Correale and Fiol [74]. Linhares et al. found that the production of IL-6 by lipopolysaccharide-activated mononuclear cells was higher in NMO patients than that in HCs [75]. Importantly, Chihara et al. reported that IL-6 enhances survival and anti-AQP4 antibody production of a small population of peripheral plasmablasts that secrete anti-AQP4 antibodies, while the application of anti-IL-6 receptor antibody reduces their survival [76]. IL-6 levels of CSF also show a strong clinical correlation in NMO. Patients with NMO have higher CSF IL-6 levels than those with MS [71,72, 74,77–81], ONNDs [71,72,77–82], or HCs [74]. IL-6 levels in the CSF of NMO patients show correlations with EDSS scores and anti-AQP4 antibody titers in CSF [71]. Wang et al. reported that CSF IL-6 and IL-6 receptor levels are higher in patients with NMO than those in patients with MS or ONNDs [80]. Interestingly, a low CSF IL-6 level could indicate a good recovery from NMO relapses [82]. The CSF/serum ratio of IL-6 is significantly higher in NMO than in ONNDs, suggestive of increased intrathecal IL-6 synthesis [72]. It is possible that activated astrocytes by the binding of anti-AQP4 antibodies produce IL-6 in the CNS of NMO patients.

Table 1 Th17-mediated biomarkers for NMO. Candidate marker

Proposed relevant cell or pathway

Origin

Change

Clinical correlation

Reference

IL-6

Th17

Serum

↑ (versus HC) ↑ (versus MS) ↑ (vs. ONNDs) ↑ (versus HC) ↑ (versus MS) ↑(versus ONNDs) ↑ (versus HC) ↑(versus MS) ↑(versus NMO without LESCLs) ↑(versus HC) ↑(versus MS) ↑ (versus ONNDs) ↑ (versus HC) ↑ (versus HC) ↑ (versus MS) ≅ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus MS) ↑ (versus ONNDs)

EDSS [75]

[68,71,73–75] [74] [71,72] [74] [71,72,74,77–81] [71,72,77–82] [83,85–87] [84,85] [88] [80] [80] [71,72,77–82] [75,85] [75,83,85] [72,89] [90] [72] [72] [72] [84] [72] [72,77]

CSF

IL-17

Th17

Serum

CSF

IL-21 IL-23 IL-8

Th17 Th17 Th17

Serum Serum CSF

IL-1RA

Th17

CSF

G-CSF

Th17

Serum CSF

EDSS [71,80], anti-AQP4 antibody titer in CSF [71]

Length of involved spinal cord [88]

EDSS [71]; Relapse free duration [82] EDSS [75] EDSS [72] EDSS [72]

CSF: cerebrospinal fluid; EDSS: Expanded Disability Status Scale; G-CSF: granulocyte colony-stimulating factor; HC: healthy control; IL: interleukin; IL-1RA: IL-1 receptor antagonist; LESCL: long-segmental spinal cord lesion; MS: multiple sclerosis; ONND: other non-inflammatory neurological disease, Th: T helper. ↑: up-regulation; ≅: unchanged.

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A number of studies indicate the potential of other Th17-related cytokines as a biomarker of NMO. It has been shown that serum/plasma levels of IL-17, a signature cytokine of Th17, increase in NMO patients compared with HC or MS patients [83–87]. NMO patients with LESCLs have higher serum IL-17 levels than those without LESCLs [88]. CSF of NMO patients had higher IL-17 levels than those of MS and ONND patients [71,72,77–82], and HCs [80]. Serum IL-21 and IL-23 levels are elevated in NMO patients compared with those in HCs [75,83,85]. Serum granulocyte colony-stimulating factor (G-CSF) levels are higher in patients with NMO than in those with MS [75,83–85], while CSF levels of G-CSF are elevated in NMO patients compared with MS and ONND patients [72,77]. Uzawa et al. reported that CSF levels of IL-8 and IL-1 receptor agonist (IL-1RA) are also higher in NMO than in MS and ONNDs [72]. Hosokawa et al., also found increased IL-8 levels in CSF of NMO patients compared to MS patients [89]. However, similar IL-8 levels in the CSF of NMO and MS patients were reported by Yanagawa et al. [90]. 3.2. Th2-mediated biomarkers for NMO The production of anti-AQP4 antibody in NMO patients indicates that Th2-mediated humoral autoimmunity may be another important factor for the pathogenesis of NMO [91,92]. Candidate Th2-mediated biomarkers for NMO are summarized in Table 2. Serum level of IL-4, a representative Th2-related cytokine [93], is higher in NMO patients compared with that in MS patients and HCs [86,94]. However, elevated IL-4 levels in CSF are not detected in NMO [72]. With immunological effects similar to IL-4 [95], IL-13 levels in CSF are higher in patients with NMO than in those with MS or ONNDs [72]. Eosinophil infiltration is frequently found in NMO lesions [74,94]. It has been shown that the levels of IL-5, a selective cytokine regulating eosinophil growth, differentiation and survival [96], in CSF are significantly higher in NMO patients than in MS patients or HCs [74]. Increases of EOTAXIN-2 and EOTAXIN-3, two selective eosinophil chemoattractants and activators [96], have been shown in CSF of NMO patients compared with MS patients or HCs [74], although their serum levels in NMO patients are not elevated [72]. C–C motif ligand 17 (CCL17) is a T cell-specific chemokine. Narikawa et al. found that CCL17 levels in CSF are significantly higher in patients with NMO than in those with ONNDs [97].

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[75]. Contrarily, Uzawa et al. found that TNF-α levels in CSF of patients with NMO were lower than in those with MS [72]. C–X–C motif chemokine 10 (CXCL10), a downstream target of IFN-γ [98], is up-regulated in the CSF of patients with NMO compared with MS and ONND patients [72,77,97]. Osteopontin, expressed in activated CD4+ T cells, acts as an inflammatory cytokine to promote Th1 cell responses [99]. Shimizu et al. reported that plasma osteopontin levels in patients with NMO and MS are significantly higher than in those with HCs [100]. In addition, plasma osteopontin levels demonstrating a significant correlation with EDSS scores are significantly higher during relapse compared with remission in both NMO and MS patients [100]. Regulatory T (Treg)-related cytokines have shown the potential to inhibit proinflammatory cytokine synthesis. There have been contradictory reports as to whether the serum or CSF levels of Treg-mediated cytokines reflect the disease activity of NMO (Table 3). Wang et al. reported that serum levels of Treg-related cytokines IL-2 and IL-10 are higher in NMO patients than those in MS patients and HCs [86]. Levels of IL-10 in the CSF of NMO patients are also higher than those of ONNDs [72], but not different from those of MS patients [72,90]. Uzawa et al. further find the positive correlation between IL-10 levels and anti-AQP4 antibody titer in CSF [72]. An opposite way about IL-2 was reported by Linhares et al., who found lower serum IL-2 levels in NMO patients compared with controls [75]. 3.4. Biomarkers related to astrocytic injuries for NMO As described above, astrocytopathy is proposed as a primary pathological change in NMO [101]. The immunological activation and damage of astrocytes prompt the development of astrocytic markers in monitoring disease progression and treatment responses for NMO (Table 4). Levels of GFAP, the most well-studied astrocytic marker, in CSF of NMO patients are higher than those of MS and ONNDs [101,102]. CSF GFAP levels in NMO patients correlate with EDSS scores and length of involved spinal cord [101,102], and are particularly up-regulated during clinical relapse, and returns to normal levels following intravenous methylprednisolone treatment [101]. Therefore GFAP in CSF has a potential role as a biomarker for NMO activity. CSF S100B, predominantly expressed in astrocytes, belonging to a family of calcium-binding proteins, also shows a similar trend to GFAP but may be less remarkable [101–103].

3.3. Th1- and Treg-mediated biomarkers for NMO 3.5. Other candidate biomarkers for NMO Among patients carrying anti-AQP4 antibodies, the percentage of Th1 cells demonstrates a negative correlation with anti-AQP4 antibody titer, supporting that NMO was not a Th1-dominant disease [92]. However, up-regulations of a number of Th1-mediated cytokines were reported in NMO patients (Table 3). Wang et al. reported that serum levels of the interferon-γ (IFN-γ) and tumor necrosis factor-α (TNFα), two representative Th1-related cytokines, are higher in NMO patients than those in MS patients and HCs [86,87]. However, Linhares et al. found that IFN-γ levels in serum are not elevated in NMO patients

Other inflammation-mediated or neurodegenerative molecular markers have been reported in literature (Table 4). Active NMO lesions are characterized by perivascular deposition of activated complements [16,91,104]. A significant increase of C5a levels in CSF during relapse has been shown in patients with NMO compared with those with ONNDs [105,106], and the levels are correlated with EDSS scores of NMO patients [105]. CSF levels of sC5b-9, a membrane-attack complex that has been used as an indicator of total complement activity [107],

Table 2 Th2-mediated biomarkers for NMO. Candidate marker

Proposed relevant cell or pathway

Origin

Change

IL-4

Th2

Serum

IL-13

Th2

CSF

IL-5

Th2

CSF

EOTAXIN-2 EOTAXIN-3

Th2 Th2

CSF CSF

CCL17

Th2

CSF

↑ (versus HC) ↑(versus MS) ↑ (versus MS) ↑ (vs. ONNDs) ↑ (versus HC) ↑ (versus MS) ↑ (versus HC) ↑ (versus HC) ↑ (versus MS) ↑ (versus ONNDs)

Clinical correlation

Reference [86,94] [86] [72] [72] [74] [74] [74] [74] [74] [97]

CCL: C–C motif ligand; CSF: cerebrospinal fluid; HC: healthy control; IL: interleukin; MS: multiple sclerosis; ONND: other non-inflammatory neurological disease; Th: T helper. ↑: up-regulation.

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K.-H. Chang et al. / Clinica Chimica Acta 440 (2015) 64–71

Table 3 Th1- and Treg-mediated markers for NMO. Candidate marker

Proposed relevant cell or pathway

Origin

Change

IFN-γ

Th1

Serum

TNF-α

Th1

CXCL10

Th1

Serum CSF CSF

Osteopontin

Th1 and Th17

Serum

IL-2

Treg

Serum

IL-10

Treg

Serum

↑ (versus HC) ↓(versus HC) ↑(versus MS) ↑ (versus HC) ↓ (versus HC) ↑(versus MS) ↑ (versus ONNDs) ↑ (versus HC) ≅ (versus MS) ↑ (versus HC) ↓ (versus HC) ↑ (versus MS) ↑ (versus HC) ↑ (versus MS) ≅ (versus MS) ↑ (versus ONNDs)

CSF

Clinical correlation

Reference

EDSS [100] EDSS [100]

[86,87] [75] [86] [86,87] [72] [77] [72,77,97] [100] [100] [86] [75] [86] [86] [86] [72,90] [72]

Serum level of anti-AQP4 antibody [72]

CSF: cerebrospinal fluid; CXCL: C–X–C motif chemokine; EDSS: Expanded Disability Status Scale; HC: healthy control; IL: interleukin; IFN: interferon; MS: multiple sclerosis; ONND: other non-inflammatory neurological disease, Th: T helper; TNF: tumor necrosis factor. ↑: up-regulation; ≅: unchanged; ↓: down-regulation.

are increased in the patients with NMO compared with those with MS and ONNDs, and also demonstrate significant correlation with EDSS scores [106]. High-mobility group box protein 1 (HMGB1), released by neutrophils and macrophages, acts as a proinflammatory cytokine [108]. Plasma HMGB1 levels are significantly higher in patients with NMO compared to those with MS [87]. However, this elevation was not recapitulated in Uzawa's study [79]. In CSF, HMGB1 levels of patients with NMO are higher than those with MS and ONNDs [79,80].

Haptoglobin is an acute phase protein with anti-inflammatory and anti-oxidant activities [109]. We found that levels of haptoglobin were elevated in CSF of NMO patients compared with patients with MS, AD and ONNDs [110]. In NMO patients, CSF haptoglobin levels significantly correlate with EDSS scores as well [110]. Elevated serum levels of matrix metalloproteinase-9 (MMP-9) are present in NMO patients compared with MS patients and HCs, and correlated with EDSS scores of patients with NMO [89]. CCL4, produced by macrophages,

Table 4 Astrocytic and other biomarkers for NMO. Candidate marker

Proposed relevant cell or pathway

Origin

Change

Clinical correlation

Reference

GFAP

Astrocyte

CSF

S100B

Astrocyte

CSF

C5a C5b-9

Complement Complement

CSF CSF

EDSS and length of involved spinal cord [101,102] EDSS and length of involved spinal cord [101,102] EDSS and length of involved spinal cord [101,102] EDSS and length of involved spinal cord [101,102] EDSS [105] EDSS [106] EDSS [106]

HMGB1

Macrophage

Serum

↑ (versus MS) ↑(versus ONNDs) ↑ (versus MS) ↑(versus ONNDs) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ≅ (versus MS) ≅ (versus ONNDs) ↑ (versus MS) ↑(versus ONNDs) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus HC) ↑ (versus MS) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus HC) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus ONNDs) ↑ (versus ONNDs) ↑ (versus MS) ≅ (versus MS) ↑ (versus ONNDs) ↑ (versus MS) ↑ (versus HC) ↑ (versus MS) ↓ (versus MS)

[101,102] [101,102] [101,102] [101,102] [105,106] [106] [106] [87] [79] [79] [79,80] [79,80] [110] [110] [89] [89] [84] [77] [112] [112] [112] [112] [112] [77] [77] [115] [114] [115] [114,115] [117] [118] [118] [118]

CSF Haptoglobin

Neutrophils, macrophages, astrocytes

CSF

MMP-9

Neutrophils, macrophages

Serum

CCL4

Macrophages

sICAM-1,

Cell adhesion

Serum CSF Serum CSF

sVCAM-1

Cell adhesion

CSF

CXCL8

Neutrophils

CSF

CXCL13

B cells

Serum CSF

NFHSM135 Acetate

Neurofilament Metabolites

CSF Serum

Scyllo-inositol

Metabolites

EDSS [110] EDSS [89]

CSF: cerebrospinal fluid; CCL: C–C motif ligand; CXCL: C–X–C motif chemokine; EDSS: Expanded Disability Status Scale; GFAP: glial fibrillary acid protein; HC: healthy control; HMGB: High-mobility group box protein; IL: interleukin; MMP: matrix metalloproteinase; MS: multiple sclerosis; NFH: neurofilament heavy chain; ONND: other non-inflammatory neurological disease, sICAM: soluble intercellular adhesion molecule; sVCAM: soluble vascular cell adhesion molecule; Th: T helper; TNF: tumor necrosis factor. ↑: up-regulation; ≅: unchanged; ↓: down-regulation.

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mediates inflammatory responses by stimulating Th1 cells, macrophages, eosinophils and other inflammatory cells [111]. Serum CCL4 levels are elevated in NMO patients compared with MS patients [84], and CSF CCL5 levels are higher in patients with NMO than in those with ONNDs [77]. Uzawa et al. reported that serum levels of soluble intercellular adhesion molecule-1 (sICAM-1) were elevated in patients with NMO compared with HCs [112], and CSF levels of sICAM-1 and soluble vascular cell adhesion molecule-1 (sVCAM-1) were elevated in NMO patients compared with MS patients and ONNDs [112]. Matsushita et al. reported that CSF levels of CXCL8, a neutrophil chemotaxin, are elevated in NMO patients compared with MS and ONND patients [77]. CXCL13 is a selective B cell chemotaxin [113]. It has been reported that serum levels of CXCL13 are elevated in patients with NMO compared with ONNDs. Zhong et al. reported that CSF levels of CXCL13 were higher in patients with NMO compared with MS or ONND patients [114]. However, Alvarez et al. reported elevated CSF CXCL13 levels in both NMO and MS patients [115]. Neurofilament (NF) is a group of specific biomarkers for neuronal death and axonal degeneration [116]. Elevated CSF NF heavy chain NFHSMI35 levels are found in patients with NMO but not in those with MS [117]. Recently, a metabolomics study by Moussallieh et al. reported that serum levels of acetate were elevated in NMO patients compared with MS patients and HCs, while NMO patients present lower serum scyllo-inositol levels than MS patients [118]. The role of these metabolites in the pathogenesis of NMO remains to be investigated.

4. Immunomodulatory therapies for NMO targeting anti-AQP4 antibody and other biomarkers Currently the long-term treatment for NMO has not been wellestablished. Low-dose oral corticosteroids, azathioprine, mitoxantrone, cyclophosphamide, mycophenolate mofetil, intravenous immunoglobulin and rituximab are used as maintenance treatments to prevent NMO relapses [119–124]. On the other hand, interferon-β, natalizumab and fingolimod, which are effective in preventing MS relapses, appear to be ineffective and may be harmful in treating NMO [125–127]. Based on progress in understanding the mechanisms that underlie NMO pathogenesis, new treatments for NMO targeting specific components of disease pathogenesis are developing. A recombinant monoclonal antibody against AQP4-IgG, called aquaporumab, has been engineered by Tradtrantip et al. [128]. Its mutated Fc lacks complement- and cell-mediated cytotoxicity following binding to AQP4 [128]. Aquaporumab competes sterically with pathogenic anti-AQP4 antibody and prevents the formation of NMO lesions in mouse spinal cord slice culture and in vivo models for NMO [128]. The authors also developed bacteria-derived endoglycosidase S that could selectively deglycosylate AQP4-IgG heavy-chain, prevent NMOIgG binding to AQP4, and thus neutralize NMO pathology in spinal cord slice culture and mouse models of NMO [129]. As described above, IL-6 enhances the survival of plasmablasts as well as their secretion of anti-AQP4 antibodies [76]. Tocilizumab, a recombinant monoclonal antibody against the IL-6 receptor, could be helpful in suppressing NMO relapses by reducing the production of anti-AQP4 antibody [130–134]. Ayzenberg et al. reported stabilized EDSS scores and reduced relapses after initiating tocilizumab administration in three NMO patients [132]. Araki et al. repeatedly reported that treatment with tocilizumab declined relapses and EDSS scores in seven patients with NMO [131]. Eculizumab, an anti-C5 monoclonal antibody, demonstrate a potential therapeutic impact on NMO as well [135]. Eculizumab administration suppresses serum complement activity and reduction of C5 levels in CSF [135]. Of the 14 NMO patients with eculizumab treatment, 12 became free from relapses within twelve months [135]. However, a return of relapses was noted in 5 patients after withdrawing eculizumab [135]. Anti-AQP4 antibody titers were not decreased after administration of eculizumab [135].

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5. Conclusion A growing number of recent immunological studies prompt the discovery of anti-AQP4 antibody and other potential biomarkers for NMO. Lines of evidence have shown that Th17- and Th2-mediated biomarkers, particularly Th17-related cytokines, may be the key players in NMO inflammation. IL-6 demonstrates implication in anti-AQP4 antibody generation, which plays a critical role in CNS inflammation and astrocytic damage in NMO patients. Blocking IL-6 receptor by tocilizumab may be a potential treatment option for NMO patients. Measuring astrocytic markers, especially CSF-GFAP, would be useful in assessing the astrocytic damages and clinical severity in NMO. Larger-scale studies in NMO, various CNS inflammatory diseases and controls are warranted to validate the usefulness of these reported biomarkers and further studies are also necessary to clarify the role they play in immunopathogenesis of NMO and may thus to unveil novel therapeutic targets.

References [1] Wingerchuk DM, Lennon VA, Pittock SJ, Lucchinetti CF, Weinshenker BG. Revised diagnostic criteria for neuromyelitis optica. Neurology 2006;66:1485–9. [2] Clifford Allbutt T. On the ophthalmoscopic signs of spinal disease. Lancet 1870;95: 76–8. [3] Lennon VA, Kryzer TJ, Pittock SJ, Verkman AS, Hinson SR. IgG marker of optic-spinal multiple sclerosis binds to the aquaporin-4 water channel. J Exp Med 2005;202: 473–7. [4] Wingerchuk DM, Lennon VA, Lucchinetti CF, Pittock SJ, Weinshenker BG. The spectrum of neuromyelitis optica. Lancet Neurol 2007;6:805–15. [5] Cossburn M, Tackley G, Baker K, et al. The prevalence of neuromyelitis optica in South East Wales. Eur J Neurol 2012;19:655–9. [6] Asgari N, Lillevang ST, Skejoe HP, Falah M, Stenager E, Kyvik KO. A populationbased study of neuromyelitis optica in Caucasians. Neurology 2011;76:1589–95. [7] Cabrera-Gomez JA, Kurtzke JF, Gonzalez-Quevedo A, Lara-Rodriguez R. An epidemiological study of neuromyelitis optica in Cuba. J Neurol 2009;256:35–44. [8] Cabre P, Gonzalez-Quevedo A, Lannuzel A, et al. Descriptive epidemiology of neuromyelitis optica in the Caribbean basin. Rev Neurol 2009;165:676–83. [9] Papais-Alvarenga RM, Vasconcelos CC, Alves-Leon SV, et al. The impact of diagnostic criteria for neuromyelitis optica in patients with MS: a 10-year follow-up of the South Atlantic Project. Mult Scler 2014;20:374–81. [10] Takahashi T, Fujihara K, Nakashima I, et al. Anti-aquaporin-4 antibody is involved in the pathogenesis of NMO: a study on antibody titre. Brain 2007;130:1235–43. [11] Waters P, Jarius S, Littleton E, et al. Aquaporin-4 antibodies in neuromyelitis optica and longitudinally extensive transverse myelitis. Arch Neurol 2008;65:913–9. [12] Jarius S, Aboul-Enein F, Waters P, et al. Antibody to aquaporin-4 in the long-term course of neuromyelitis optica. Brain 2008;131:3072–80. [13] Dujmovic I, Mader S, Schanda K, et al. Temporal dynamics of cerebrospinal fluid anti-aquaporin-4 antibodies in patients with neuromyelitis optica spectrum disorders. J Neuroimmunol 2011;234:124–30. [14] Hinson SR, McKeon A, Fryer JP, Apiwattanakul M, Lennon VA, Pittock SJ. Prediction of neuromyelitis optica attack severity by quantitation of complement-mediated injury to aquaporin-4-expressing cells. Arch Neurol 2009;66:1164–7. [15] Chanson JB, Alame M, Collongues N, et al. Evaluation of clinical interest of antiaquaporin-4 autoantibody followup in neuromyelitis optica. Clin Dev Immunol 2013;2013:146219. [16] Amiry-Moghaddam M, Ottersen OP. The molecular basis of water transport in the brain. Nat Rev Neurosci 2003;4:991–1001. [17] Nielsen S, Nagelhus EA, Amiry-Moghaddam M, Bourque C, Agre P, Ottersen OP. Specialized membrane domains for water transport in glial cells: high-resolution immunogold cytochemistry of aquaporin-4 in rat brain. J Neurosci 1997;17: 171–80. [18] Katada R, Akdemir G, Asavapanumas N, Ratelade J, Zhang H, Verkman AS. Greatly improved survival and neuroprotection in aquaporin-4-knockout mice following global cerebral ischemia. FASEB J 2014;28:705–14. [19] Papadopoulos MC, Verkman AS. Aquaporin-4 gene disruption in mice reduces brain swelling and mortality in pneumococcal meningitis. J Biol Chem 2005;280: 13906–12. [20] Haj-Yasein NN, Vindedal GF, Eilert-Olsen M, et al. Glial-conditional deletion of aquaporin-4 (Aqp4) reduces blood–brain water uptake and confers barrier function on perivascular astrocyte endfeet. Proc Natl Acad Sci U S A 2011;108: 17815–20. [21] Manley GT, Fujimura M, Ma T, et al. Aquaporin-4 deletion in mice reduces brain edema after acute water intoxication and ischemic stroke. Nat Med 2000;6: 159–63. [22] Papadopoulos MC, Manley GT, Krishna S, Verkman AS. Aquaporin-4 facilitates reabsorption of excess fluid in vasogenic brain edema. FASEB J 2004;18:1291–3. [23] Bloch O, Auguste KI, Manley GT, Verkman AS. Accelerated progression of kaolininduced hydrocephalus in aquaporin-4-deficient mice. J Cereb Blood Flow Metab 2006;26:1527–37.

70

K.-H. Chang et al. / Clinica Chimica Acta 440 (2015) 64–71

[24] Binder DK, Yao X, Zador Z, Sick TJ, Verkman AS, Manley GT. Increased seizure duration and slowed potassium kinetics in mice lacking aquaporin-4 water channels. Glia 2006;53:631–6. [25] Papadopoulos MC, Verkman AS. Potential utility of aquaporin modulators for therapy of brain disorders. Prog Brain Res 2008;170:589–601. [26] Lennon VA, Wingerchuk DM, Kryzer TJ, et al. A serum autoantibody marker of neuromyelitis optica: distinction from multiple sclerosis. Lancet 2004;364:2106–12. [27] Wang KC, Tsai CP, Lee CL, Chen SY, Chen SJ. The prevalence of long spinal cord lesions and anti-aquaporin 4 antibodies in neuromyelitis optica patients in Taiwan. Eur Neurol 2011;65:99–104. [28] Jarius S, Franciotta D, Bergamaschi R, et al. NMO-IgG in the diagnosis of neuromyelitis optica. Neurology 2007;68:1076–7. [29] Marignier R, De Seze J, Vukusic S, et al. NMO-IgG and Devic's neuromyelitis optica: a French experience. Mult Scler 2008;14:440–5. [30] Nakashima I, Fujihara K, Miyazawa I, et al. Clinical and MRI features of Japanese patients with multiple sclerosis positive for NMO-IgG. J Neurol Neurosurg Psychiatry 2006;77:1073–5. [31] Chang KH, Lyu RK, Chen CM, et al. Distinct features between longitudinally extensive transverse myelitis presenting with and without anti-aquaporin 4 antibodies. Mult Scler 2013;19:299–307. [32] Waters P, Vincent A. Detection of anti-aquaporin-4 antibodies in neuromyelitis optica: current status of the assays. Int MS J 2008;15:99–105. [33] Paul F, Jarius S, Aktas O, et al. Antibody to aquaporin 4 in the diagnosis of neuromyelitis optica. PLoS Med 2007;4:e133. [34] Hayakawa S, Mori M, Okuta A, et al. Neuromyelitis optica and anti-aquaporin-4 antibodies measured by an enzyme-linked immunosorbent assay. J Neuroimmunol 2008;196:181–7. [35] Jarius S, Wildemann B. Aquaporin-4 antibodies (NMO-IgG) as a serological marker of neuromyelitis optica: a critical review of the literature. Brain Pathol 2013;23: 661–83. [36] Lu M, Lee MD, Smith BL, et al. The human AQP4 gene: definition of the locus encoding two water channel polypeptides in brain. Proc Natl Acad Sci U S A 1996;93:10908–12. [37] Furman CS, Gorelick-Feldman DA, Davidson KG, et al. Aquaporin-4 square array assembly: opposing actions of M1 and M23 isoforms. Proc Natl Acad Sci U S A 2003; 100:13609–14. [38] Nicchia GP, Mastrototaro M, Rossi A, et al. Aquaporin-4 orthogonal arrays of particles are the target for neuromyelitis optica autoantibodies. Glia 2009;57:1363–73. [39] Hinson SR, Romero MF, Popescu BF, et al. Molecular outcomes of neuromyelitis optica (NMO)-IgG binding to aquaporin-4 in astrocytes. Proc Natl Acad Sci U S A 2012;109:1245–50. [40] Crane JM, Lam C, Rossi A, Gupta T, Bennett JL, Verkman AS. Binding affinity and specificity of neuromyelitis optica autoantibodies to aquaporin-4 M1/M23 isoforms and orthogonal arrays. J Biol Chem 2011;286:16516–24. [41] Mader S, Lutterotti A, Di Pauli F, et al. Patterns of antibody binding to aquaporin-4 isoforms in neuromyelitis optica. PLoS ONE 2010;5:e10455. [42] Jarius S, Franciotta D, Paul F, et al. Cerebrospinal fluid antibodies to aquaporin-4 in neuromyelitis optica and related disorders: frequency, origin, and diagnostic relevance. J Neuroinflammation 2010;7:52. [43] Klawiter EC, Alvarez III E, Xu J, et al. NMO-IgG detected in CSF in seronegative neuromyelitis optica. Neurology 2009;72:1101–3. [44] Bennett JL, Lam C, Kalluri SR, et al. Intrathecal pathogenic anti-aquaporin-4 antibodies in early neuromyelitis optica. Ann Neurol 2009;66:617–29. [45] Kim W, Lee JE, Li XF, et al. Quantitative measurement of anti-aquaporin-4 antibodies by enzyme-linked immunosorbent assay using purified recombinant human aquaporin-4. Mult Scler 2012;18:578–86. [46] Matsuoka T, Matsushita T, Kawano Y, et al. Heterogeneity of aquaporin-4 autoimmunity and spinal cord lesions in multiple sclerosis in Japanese. Brain 2007;130: 1206–23. [47] Heerlein K, Jarius S, Jacobi C, Rohde S, Storch-Hagenlocher B, Wildemann B. Aquaporin-4 antibody positive longitudinally extensive transverse myelitis following varicella zoster infection. J Neurol Sci 2009;276:184–6. [48] Lotze TE, Northrop JL, Hutton GJ, Ross B, Schiffman JS, Hunter JV. Spectrum of pediatric neuromyelitis optica. Pediatrics 2008;122:e1039–47. [49] Yoshimura S, Isobe N, Matsushita T, et al. Distinct genetic and infectious profiles in Japanese neuromyelitis optica patients according to anti-aquaporin 4 antibody status. J Neurol Neurosurg Psychiatry 2013;84:29–34. [50] Ghezzi A, Bergamaschi R, Martinelli V, et al. Clinical characteristics, course and prognosis of relapsing Devic's neuromyelitis optica. J Neurol 2004;251:47–52. [51] Lucchinetti CF, Mandler RN, McGavern D, et al. A role for humoral mechanisms in the pathogenesis of Devic's neuromyelitis optica. Brain 2002;125:1450–61. [52] Misu T, Fujihara K, Kakita A, et al. Loss of aquaporin 4 in lesions of neuromyelitis optica: distinction from multiple sclerosis. Brain 2007;130:1224–34. [53] Roemer SF, Parisi JE, Lennon VA, et al. Pattern-specific loss of aquaporin-4 immunoreactivity distinguishes neuromyelitis optica from multiple sclerosis. Brain 2007; 130:1194–205. [54] Kinoshita M, Nakatsuji Y, Moriya M, et al. Astrocytic necrosis is induced by antiaquaporin-4 antibody-positive serum. Neuroreport 2009;20:508–12. [55] Asavapanumas N, Ratelade J, Verkman AS. Unique neuromyelitis optica pathology produced in naive rats by intracerebral administration of NMO-IgG. Acta Neuropathol 2014;127:539–51. [56] Saadoun S, Waters P, Bell BA, Vincent A, Verkman AS, Papadopoulos MC. Intracerebral injection of neuromyelitis optica immunoglobulin G and human complement produces neuromyelitis optica lesions in mice. Brain 2010;133:349–61. [57] Sabater L, Giralt A, Boronat A, et al. Cytotoxic effect of neuromyelitis optica antibody (NMO-IgG) to astrocytes: an in vitro study. J Neuroimmunol 2009;215:31–5.

[58] Bonnan M, Valentino R, Olindo S, Mehdaoui H, Smadja D, Cabre P. Plasma exchange in severe spinal attacks associated with neuromyelitis optica spectrum disorder. Mult Scler 2009;15:487–92. [59] Mochizuki A, Hayashi A, Hisahara S, Shoji S. Steroid-responsive Devic's variant in Sjogren's syndrome. Neurology 2000;54:1391–2. [60] Bonnet F, Mercie P, Morlat P, et al. Devic's neuromyelitis optica during pregnancy in a patient with systemic lupus erythematosus. Lupus 1999;8:244–7. [61] April RS, Vansonnenberg E. A case of neuromyelitis optica (Devic's syndrome) in systemic lupus erythematosus. Clinicopathologic report and review of the literature. Neurology 1976;26:1066–70. [62] Pittock SJ, Lennon VA, de Seze J, et al. Neuromyelitis optica and non organ-specific autoimmunity. Arch Neurol 2008;65:78–83. [63] Karussis D, Leker RR, Ashkenazi A, Abramsky O. A subgroup of multiple sclerosis patients with anticardiolipin antibodies and unusual clinical manifestations: do they represent a new nosological entity? Ann Neurol 1998;44:629–34. [64] Harada T, Ohashi T, Harada C, et al. A case of bilateral optic neuropathy and recurrent transverse myelopathy associated with perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA). J Neuro Ophthalmol 1997;17:254–6. [65] Tzartos JS, Stergiou C, Kilidireas K, Zisimopoulou P, Thomaidis T, Tzartos SJ. Antiaquaporin-1 autoantibodies in patients with neuromyelitis optica spectrum disorders. PLoS ONE 2013;8:e74773. [66] Korn T, Bettelli E, Oukka M, Kuchroo VK. IL-17 and Th17 Cells. Annu Rev Immunol 2009;27:485–517. [67] Mitsdoerffer M, Lee Y, Jäger A, et al. Proinflammatory T helper type 17 cells are effective B-cell helpers. Proc Natl Acad Sci U S A 2010;107:14292–7. [68] Varrin-Doyer M, Spencer CM, Schulze-Topphoff U, et al. Aquaporin 4-specific T cells in neuromyelitis optica exhibit a Th17 bias and recognize clostridium ABC transporter. Ann Neurol 2012;72:53–64. [69] Kishimoto T. Interleukin-6: from basic science to medicine—40 years in immunology. Annu Rev Immunol 2005;23:1–21. [70] Bettelli E, Carrier Y, Gao W, et al. Reciprocal developmental pathways for the generation of pathogenic effector TH17 and regulatory T cells. Nature 2006;441:235–8. [71] Icoz S, Tuzun E, Kurtuncu M, et al. Enhanced IL-6 production in aquaporin-4 antibody positive neuromyelitis optica patients. Int J Neurosci 2010;120:71–5. [72] Uzawa A, Mori M, Arai K, et al. Cytokine and chemokine profiles in neuromyelitis optica: significance of interleukin-6. Mult Scler 2010;16:1443–52. [73] Wang H, Wang K, Wang C, Xu F, Qiu W, Hu X. Increased plasma interleukin-32 expression in patients with neuromyelitis optica. J Clin Immunol 2013;33:666–70. [74] Correale J, Fiol M. Activation of humoral immunity and eosinophils in neuromyelitis optica. Neurology 2004;63:2363–70. [75] Linhares UC, Schiavoni PB, Barros PO, et al. The ex vivo production of IL-6 and IL-21 by CD4+ T cells is directly associated with neurological disability in neuromyelitis optica patients. J Clin Immunol 2013;33:179–89. [76] Chihara N, Aranami T, Sato W, et al. Interleukin 6 signaling promotes antiaquaporin 4 autoantibody production from plasmablasts in neuromyelitis optica. Proc Natl Acad Sci U S A 2011;108:3701–6. [77] Matsushita T, Tateishi T, Isobe N, et al. Characteristic cerebrospinal fluid cytokine/ chemokine profiles in neuromyelitis optica, relapsing remitting or primary progressive multiple sclerosis. PLoS ONE 2013;8:e61835. [78] Uzawa A, Mori M, Ito M, et al. Markedly increased CSF interleukin-6 levels in neuromyelitis optica, but not in multiple sclerosis. J Neurol 2009;256:2082–4. [79] Uzawa A, Mori M, Masuda S, Muto M, Kuwabara S. CSF high-mobility group box 1 is associated with intrathecal inflammation and astrocytic damage in neuromyelitis optica. J Neurol Neurosurg Psychiatry 2013;84:517–22. [80] Wang H, Wang K, Wang C, et al. Cerebrospinal fluid high-mobility group box protein 1 in neuromyelitis optica and multiple sclerosis. Neuroimmunomodulation 2013;20:113–8. [81] Wang H, Wang K, Zhong X, et al. Notable increased cerebrospinal fluid levels of soluble interleukin-6 receptors in neuromyelitis optica. Neuroimmunomodulation 2012;19:304–8. [82] Uzawa A, Mori M, Sato Y, Masuda S, Kuwabara S. CSF interleukin-6 level predicts recovery from neuromyelitis optica relapse. J Neurol Neurosurg Psychiatry 2012; 83:339–40. [83] Li Y, Wang H, Long Y, Lu Z, Hu X. Increased memory Th17 cells in patients with neuromyelitis optica and multiple sclerosis. J Neuroimmunol 2011;234:155–60. [84] Michael BD, Elsone L, Griffiths MJ, et al. Post-acute serum eosinophil and neutrophil-associated cytokine/chemokine profile can distinguish between patients with neuromyelitis optica and multiple sclerosis; and identifies potential pathophysiological mechanisms — a pilot study. Cytokine 2013;64:90–6. [85] Wang HH, Dai YQ, Qiu W, et al. Interleukin-17-secreting T cells in neuromyelitis optica and multiple sclerosis during relapse. J Clin Neurosci 2011;18:1313–7. [86] Wang KC, Lee CL, Chen SY, et al. Distinct serum cytokine profiles in neuromyelitis optica and multiple sclerosis. J Interferon Cytokine Res 2013;33:58–64. [87] Wang KC, Tsai CP, Lee CL, Chen SY, Chin LT, Chen SJ. Elevated plasma high-mobility group box 1 protein is a potential marker for neuromyelitis optica. Neuroscience 2012;226:510–6. [88] Herges K, de Jong BA, Kolkowitz I, et al. Protective effect of an elastase inhibitor in a neuromyelitis optica-like disease driven by a peptide of myelin oligodendroglial glycoprotein. Mult Scler 2012;18:398–408. [89] Hosokawa T, Nakajima H, Doi Y, et al. Increased serum matrix metalloproteinase-9 in neuromyelitis optica: implication of disruption of blood–brain barrier. J Neuroimmunol 2011;236:81–6. [90] Yanagawa K, Kawachi I, Toyoshima Y, et al. Pathologic and immunologic profiles of a limited form of neuromyelitis optica with myelitis. Neurology 2009;73:1628–37. [91] Lucchinetti CF, Mandler RN, McGavern D, et al. A role for humoral mechanisms in the pathogenesis of Devic's neuromyelitis optica. Brain 2002;125:1450–61.

K.-H. Chang et al. / Clinica Chimica Acta 440 (2015) 64–71 [92] Matsushita T, Isobe N, Matsuoka T, et al. Aquaporin-4 autoimmune syndrome and anti-aquaporin-4 antibody-negative opticospinal multiple sclerosis in Japanese. Mult Scler 2009;15:834–47. [93] Adorini L, Trembleau S. Immune deviation towards Th2 inhibits Th-1-mediated autoimmune diabetes. Biochem Soc Trans 1997;25:625–9. [94] Alves-Leon SV, Pimentel ML, Sant'Anna G, Malfetano FR, Estrada CD, Quirico-Santos T. Immune system markers of neuroinflammation in patients with clinical diagnose of neuromyelitis optica. Arq Neuropsiquiatr 2008;66:678–84. [95] Wynn TA. IL-13 effector functions. Annu Rev Immunol 2003;21:425–56. [96] Collins PD, Marleau S, Griffiths-Johnson DA, Jose PJ, Williams TJ. Cooperation between interleukin-5 and the chemokine eotaxin to induce eosinophil accumulation in vivo. J Exp Med 1995;182:1169–74. [97] Narikawa K, Misu T, Fujihara K, Nakashima I, Sato S, Itoyama Y. CSF chemokine levels in relapsing neuromyelitis optica and multiple sclerosis. J Neuroimmunol 2004;149:182–6. [98] Loetscher M, Gerber B, Loetscher P, et al. Chemokine receptor specific for IP10 and mig: structure, function, and expression in activated T-lymphocytes. J Exp Med 1996;184:963–9. [99] Ashkar S, Weber GF, Panoutsakopoulou V, et al. Eta-1 (osteopontin): an early component of type-1 (cell-mediated) immunity. Science 2000;287:860–4. [100] Shimizu Y, Ota K, Ikeguchi R, Kubo S, Kabasawa C, Uchiyama S. Plasma osteopontin levels are associated with disease activity in the patients with multiple sclerosis and neuromyelitis optica. J Neuroimmunol 2013;263:148–51. [101] Takano R, Misu T, Takahashi T, Sato S, Fujihara K, Itoyama Y. Astrocytic damage is far more severe than demyelination in NMO: a clinical CSF biomarker study. Neurology 2010;75:208–16. [102] Misu T, Takano R, Fujihara K, Takahashi T, Sato S, Itoyama Y. Marked increase in cerebrospinal fluid glial fibrillar acidic protein in neuromyelitis optica: an astrocytic damage marker. J Neurol Neurosurg Psychiatry 2009;80:575–7. [103] Sen J, Belli A. S100B in neuropathologic states: the CRP of the brain? J Neurosci Res 2007;85:1373–80. [104] Wingerchuk DM. Neuromyelitis optica: potential roles for intravenous immunoglobulin. J Clin Immunol 2013;33(Suppl. 1):S33–7. [105] Kuroda H, Fujihara K, Takano R, et al. Increase of complement fragment C5a in cerebrospinal fluid during exacerbation of neuromyelitis optica. J Neuroimmunol 2013;254:178–82. [106] Wang H, Wang K, Wang C, Qiu W, Lu Z, Hu X. Increased soluble C5b-9 in CSF of neuromyelitis optica. Scand J Immunol 2014;79:127–30. [107] Rinder CS, Rinder HM, Smith MJ, et al. Selective blockade of membrane attack complex formation during simulated extracorporeal circulation inhibits platelet but not leukocyte activation. J Thorac Cardiovasc Surg 1999;118:460–6. [108] Naglova H, Bucova M. HMGB1 and its physiological and pathological roles. Bratisl Lek Listy 2012;113:163–71. [109] Sadrzadeh SM, Bozorgmehr J. Haptoglobin phenotypes in health and disorders. Am J Clin Pathol 2004;121(Suppl.):S97–S104. [110] Chang KH, Tseng MY, Ro LS, et al. Analyses of haptoglobin level in the cerebrospinal fluid and serum of patients with neuromyelitis optica and multiple sclerosis. Clin Chim Acta 2013;417:26–30. [111] Menten P, Wuyts A, Van Damme J. Macrophage inflammatory protein-1. Cytokine Growth Factor Rev 2002;13:455–81. [112] Uzawa A, Mori M, Masuda S, Kuwabara S. Markedly elevated soluble intercellular adhesion molecule 1, soluble vascular cell adhesion molecule 1 levels, and blood– brain barrier breakdown in neuromyelitis optica. Arch Neurol 2011;68:913–7. [113] Ansel KM, Harris RB, Cyster JG. CXCL13 is required for B1 cell homing, natural antibody production, and body cavity immunity. Immunity 2002;16:67–76. [114] Zhong X, Wang H, Dai Y, et al. Cerebrospinal fluid levels of CXCL13 are elevated in neuromyelitis optica. J Neuroimmunol 2011;240–241:104–8.

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[115] Alvarez E, Piccio L, Mikesell RJ, et al. CXCL13 is a biomarker of inflammation in multiple sclerosis, neuromyelitis optica, and other neurological conditions. Mult Scler 2013;19:1204–8. [116] Lalonde R, Strazielle C. Neurobehavioral characteristics of mice with modified intermediate filament genes. Rev Neurosci 2003;14:369–85. [117] Miyazawa I, Nakashima I, Petzold A, Fujihara K, Sato S, Itoyama Y. High CSF neurofilament heavy chain levels in neuromyelitis optica. Neurology 2007;68:865–7. [118] Moussallieh FM, Elbayed K, Chanson J, et al. Serum analysis by 1H Nuclear Magnetic Resonance spectroscopy: a new tool for distinguishing neuromyelitis optica from multiple sclerosis. Mult Scler 2014;20:558–65. [119] Bakker J, Metz L. Devic's neuromyelitis optica treated with intravenous gamma globulin (IVIG). Can J Neurol Sci 2004;31:265–7. [120] Kim SH, Kim W, Li XF, Jung IJ, Kim HJ. Repeated treatment with rituximab based on the assessment of peripheral circulating memory B cells in patients with relapsing neuromyelitis optica over 2 years. Arch Neurol 2011;68:1412–20. [121] Kim SH, Kim W, Park MS, Sohn EH, Li XF, Kim HJ. Efficacy and safety of mitoxantrone in patients with highly relapsing neuromyelitis optica. Arch Neurol 2011;68:473–9. [122] Jacob A, Matiello M, Weinshenker BG, et al. Treatment of neuromyelitis optica with mycophenolate mofetil: retrospective analysis of 24 patients. Arch Neurol 2009;66: 1128–33. [123] Costanzi C, Matiello M, Lucchinetti CF, et al. Azathioprine: tolerability, efficacy, and predictors of benefit in neuromyelitis optica. Neurology 2011;77:659–66. [124] Watanabe S, Misu T, Miyazawa I, et al. Low-dose corticosteroids reduce relapses in neuromyelitis optica: a retrospective analysis. Mult Scler 2007;13:968–74. [125] Min JH, Kim BJ, Lee KH. Development of extensive brain lesions following fingolimod (FTY720) treatment in a patient with neuromyelitis optica spectrum disorder. Mult Scler 2012;18:113–5. [126] Kleiter I, Hellwig K, Berthele A, et al. Failure of natalizumab to prevent relapses in neuromyelitis optica. Arch Neurol 2012;69:239–45. [127] Uzawa A, Mori M, Hayakawa S, Masuda S, Kuwabara S. Different responses to interferon beta-1b treatment in patients with neuromyelitis optica and multiple sclerosis. Eur J Neurol 2010;17:672–6. [128] Tradtrantip L, Zhang H, Saadoun S, et al. Anti-aquaporin-4 monoclonal antibody blocker therapy for neuromyelitis optica. Ann Neurol 2012;71:314–22. [129] Tradtrantip L, Ratelade J, Zhang H, Verkman AS. Enzymatic deglycosylation converts pathogenic neuromyelitis optica anti-aquaporin-4 immunoglobulin G into therapeutic antibody. Ann Neurol 2013;73:77–85. [130] Lauenstein AS, Stettner M, Kieseier BC, Lensch E. Treating neuromyelitis optica with the interleukin-6 receptor antagonist tocilizumab. BMJ Case Rep 2014;2014. [131] Araki M, Matsuoka T, Miyamoto K, et al. Efficacy of the anti-IL-6 receptor antibody tocilizumab in neuromyelitis optica: a pilot study. Neurology 2014;82:1302–6. [132] Ayzenberg I, Kleiter I, Schroder A, et al. Interleukin 6 receptor blockade in patients with neuromyelitis optica nonresponsive to anti-CD20 therapy. JAMA Neurol 2013; 70:394–7. [133] Kieseier BC, Stuve O, Dehmel T, et al. Disease amelioration with tocilizumab in a treatment-resistant patient with neuromyelitis optica: implication for cellular immune responses. JAMA Neurol 2013;70:390–3. [134] Araki M, Aranami T, Matsuoka T, Nakamura M, Miyake S, Yamamura T. Clinical improvement in a patient with neuromyelitis optica following therapy with the antiIL-6 receptor monoclonal antibody tocilizumab. Mod Rheumatol 2013;23:827–31. [135] Pittock SJ, Lennon VA, McKeon A, et al. Eculizumab in AQP4-IgG-positive relapsing neuromyelitis optica spectrum disorders: an open-label pilot study. Lancet Neurol 2013;12:554–62.