Long-term disability progression in aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder: a retrospective analysis of 101 patients.

BACKGROUND: Anti-aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4Ab+NMOSD) is an inflammatory disorder of the central nervous system with relapse-dependent progression. Few studies have reported the effects of prednisolone and biologics on disability progression in AQP4Ab+NMOSD, although it is established that they prevent clinical relapses. This retrospective study investigated long-term disability progression and the effects of therapeutic interventions on disability progression in AQP4Ab+NMOSD. METHODS: This study included a total of 101 patients with AQP4Ab+NMOSD. Disease progression was investigated in the following two cohorts: (1) duration from disease onset to Expanded Disability Status Scale (EDSS) 3.0 in patients who did or did not receive oral prednisolone or biologics before reaching EDSS 3.0 and (2) duration from disease onset to EDSS 6.0 in patients who did or did not receive oral prednisolone or biologics before reaching EDSS 6.0. RESULTS: Approximately half of the untreated patients reached EDSS 3.0 and 6.0 at 10 and 46 months after disease onset, respectively. In addition, 88% and 71% of the untreated patients reached EDSS 3.0 and 6.0 within 10 years after disease onset, respectively. Disability progression, clinical relapses and attack severity were suppressed by prednisolone and biologics. CONCLUSIONS: AQP4Ab+NMOSD is a severely disabling disease. Treatment interventions using prednisolone and biologics are useful in suppressing disability progression in AQP4Ab+NMOSD.

Silent progression of brain atrophy in aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder.

OBJECTIVE: To investigate longitudinal brain atrophy in patients with neuromyelitis optica spectrum disorder (NMOSD). METHODS: We investigated the longitudinal brain atrophy rate in patients with aquaporin-4 antibody-positive NMOSD (AQP4+NMOSD) and those with multiple sclerosis (MS) in a retrospective cohort study. Brain volume was calculated with statistical parametric mapping-12. RESULTS: We enrolled 36 patients with AQP4+NMOSD and 60 with MS. Patients with NMOSD were older and had a higher Kurtzke's expanded disability status scale score at baseline MRI compared with those with MS. Disease duration, annual relapse rate and intervals from the last attack and from disease-modifying drugs initiation were not significantly different between the two groups. Lower normalised lesion volume and higher normalised white matter volume were found in patients with NMOSD compared with those with MS at baseline MRI. However, the annualised atrophy rate of normalised brain volume was similar between the NMOSD (median 0.47; IQR 0.75; p=0.49) and MS (median 0.46; IQR 0.84) groups. After adjustment of age and the presence of clinical relapse, no differences of the annualised atrophy rate of normalised brain volume also were found for NMOSD and MS. Patients with AQP4+NMOSD with long cord lesion showed higher annualised atrophy rate of normalised grey matter volume compared with those without long cord lesion. CONCLUSIONS: Silent progression of brain atrophy was present in patients with AQP4+NMOSD, as shown in patients with MS, even in the clinically inactive age-matched cases. Subclinical dying back degeneration may explain the brain atrophy in patients with AQP4 +NMOSD.

Peripheral blood helper T cell profiles and their clinical relevance in MOG-IgG-associated and AQP4-IgG-associated disorders and MS.

OBJECTIVE: To investigate the immunological characteristics and their clinical relevance in anti-myelin oligodendrocyte glycoprotein (MOG)-IgG-associated and anti-aquaporin-4 (AQP4)-IgG-associated disorders (MOGAD and AQPAD) and multiple sclerosis (MS). METHODS: We measured peripheral blood helper T cell subsets (Th1, Th2, Th17 and regulatory T cell (Treg)) in patients with MOGAD (n=26), AQPAD (n=32) and MS (n=28) in the attack and remission phases by flow cytometry with intracellular cytokine staining. We also studied their correlation with clinical parameters. Ten normal subjects served as healthy controls. RESULTS: In all the three disorders, Th17 significantly increased at attack, and downregulated in the remission phases, although still elevated compare with healthy controls. MOGAD and AQPAD patients shared the common T cell profiles, while the extent of Th17 shift was more prominent in AQPAD. Patients with MS showed decreased Th2 than ones with MOGAD and AQPAD at attack. In terms of clinical correlation, MS patients showed that higher Th1 and Th17 proportion was associated with more frequent relapse and more severe clinical disability, whereas in MOGAD, higher Treg was associated with milder clinical severity. In AQPAD, no obvious correlation of Th profiles with clinical manifestation was found. CONCLUSIONS: The present study first investigated intracellular cytokine levels among MOGAD, AQPAD and MS. The different patterns and extent of helper T cell profiles could reflect the pathogenesis of each disorders, and may affect disease severity and activity.

Anti-MOG antibody-associated disorders: differences in clinical profiles and prognosis in Japan and Germany.

BACKGROUND: Neurological disorders with IgG antibodies against myelin-oligodendrocyte glycoprotein (MOG-IgG) have been increasingly recognised as a new type of neuroinflammatory disorder. OBJECTIVE: The study aimed to identify regional and ethnic differences in clinical profiles of MOG-IgG-associated disorders between East Asian (Japanese) and Caucasian (German) patients. METHODS: Demographic, clinical and therapeutic data from 68 MOG-IgG-positive adults were collected (Japanese, n=44; German, n=24). RESULTS: Age and sex were similar between cohorts, with optic neuritis occurring most frequently at onset (Japanese: 61%; German: 58%). However, Japanese patients had a lower annualised relapse rate (0.4 vs 0.8, p=0.019; no relapse, 64% vs 25%, p=0.002) and lower Expanded Disability Status Scale score at the last visit (1.0 vs 2.0; p=0.008), despite similar follow-up periods (mean, 73.9 months vs 73.4 months), than those of German patients, respectively. Cerebral syndromes were more common (27% vs 4%; p=0.021) and myelitis less common (21% vs 50%; p=0.012) in Japanese than in German patients, respectively. Japanese patients were more commonly treated with long-term corticosteroids (73%), whereas German patients were more commonly treated with rituximab or other immunosuppressants (63%). CONCLUSIONS: Among patients with MOG-IgG, Japanese tended to have a monophasic milder disease, whereas the majority of German patients had a relapsing course and more frequent myelitis, findings compatible with neuromyelitis optica spectrum disorder. Although the attack-prevention treatment regimens were considerably different, genetic and environmental factors may be important to determine clinical phenotypes and disease activity.

Increased cerebrospinal fluid metalloproteinase-2 and interleukin-6 are associated with albumin quotient in neuromyelitis optica: Their possible role on blood-brain barrier disruption.

BACKGROUND: Inflammation in neuromyelitis optica (NMO) is triggered by a serum antibody against the aquaporin-4 (AQP4). This process requires antibody penetration of the blood-brain barrier (BBB), but the mechanisms for BBB disruption in NMO remain unknown. OBJECTIVE: We examined whether changes in cerebrospinal fluid (CSF) and serum matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and cytokines are associated with BBB disruption in NMO. METHODS: The concentrations 9 MMPs, 4 TIMPs, and 14 cytokines were measured by multiplex assay in CSF and serum samples from 29 NMO patients, 29 relapsing-remitting multiple sclerosis (MS) patients, and 27 patients with other neurological disorders. We also performed immunohistochemistry for MMP-2 and TIMP-1 expression in post-mortem brain tissues from NMO patients. RESULTS: NMO patients exhibited significantly elevated MMP-2, TIMP-1, interleukin-6, and MMP-2/TIMP-2 ratio in CSF (but not sera) than the other groups. The CSF/serum albumin ratio, an index of BBB permeability, was most strongly correlated with CSF MMP-2 concentration, which in turn correlated with CSF interleukin-6 levels. Immunohistochemistry revealed MMP-2- and TIMP-1-positive cells surrounding vessels in NMO lesions. CONCLUSION: In NMO, increased CSF MMP-2, likely induced by interleukin-6 signaling, may disrupt the BBB and enable serum anti-AQP-4 antibodies migration into the central nervous system (CNS).

Seronegative neuromyelitis optica spectrum disorder patients diagnosed using new diagnostic criteria.

BACKGROUND: Recently, new diagnostic criteria for neuromyelitis optica spectrum disorders (NMOSD) were published. OBJECTIVE: Our primary aim was to evaluate the usefulness of the new diagnostic criteria in anti-aquaporin 4 (AQP4) antibody-negative cases. METHODS: Consecutive 471 patients whose anti-AQP4 antibody was measured at Chiba University were reviewed. RESULTS: Four anti-AQP4 antibody negative-patients, who fulfilled the new diagnostic criteria for NMOSD but not 2006 diagnostic criteria for neuromyelitis optica (NMO), were identified. They showed high cerebrospinal fluid interleukin-6 and glial fibrillary acidic protein levels, an absence of oligoclonal bands and/or cloud-like enhancement on magnetic resonance imaging, which are compatible findings for NMO. CONCLUSION: The new diagnostic criteria are clinically useful in seronegative NMOSD.

Epstein-Barr virus persistence and reactivation in neuromyelitis optica.

OBJECTIVE: Epstein-Barr virus (EBV) infection has been thought to be a key environmental factor in the development of multiple sclerosis (MS). The aim of this study is to investigate the association of EBV infection with neuromyelitis optica (NMO). METHODS: We measured levels of serum antibodies against EBV antigens, including anti-viral capsid antigen (VCA) IgM, anti-VCA IgG, anti-early antigen (EA) IgM, anti-EA IgG and anti-EBV nuclear antigen-1 IgG, in 50 patients with NMO (including 12 partial form with antiaquaporin 4 antibodies), 51 patients with MS, and 52 healthy controls, and cerebrospinal fluid (CSF) antibodies in 37 patients with NMO and 33 patients with MS with ELISA. RESULT: Compared with patients with MS and normal participants, patients with NMO more frequently had serum anti-EA IgG antibodies (52%), indicating more active viral replication than patients with MS (26%) and controls (25%). The antibody titres were significantly higher in the NMO group than in the MS (p=0.005) and control (p=0.005) groups. The CSF antibody titres were also higher in patients with NMO than in those with MS (p=0.03). CONCLUSIONS: Our results raise the hypothesis that persistent, active EBV replication is present in NMO, and may contribute to the immunological alterations that play a pathogenetic role in the disorder.

Benign neuromyelitis optica is rare in Japanese patients.

Good-outcome neuromyelitis optica (NMO) is defined as an Expanded Disability Status Scale (EDSS) score of ≤3.0 at 10 years after onset. The clinical courses of 80 consecutive patients with NMO were analyzed to identify the frequency and features of Japanese patients with good-outcome NMO. Of the 80 patients, 37 had a disease duration of >10 years; of these, eight (21.6%) presented a good outcome. These cases presented lower EDSS scores during the early phase of disease compared with those with conventional NMO. However, half of these patients developed severe disabilities later on, indicating that truly benign NMO is rare.

Elevated serum levels of bone morphogenetic protein-9 are associated with better outcome in AQP4-IgG seropositive NMOSD.

Lymphatic drainage in the central nervous system is regulated by meningeal lymphatic vasculature, and recurrent neuroinflammation alters lymphatic vessel remodeling. Patients with aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4 + NMOSD) were reported to demonstrate worse outcomes compared with patients with anti-myelin oligodendrocyte glycoprotein-associated disorders (MOGAD). This study aimed to investigate the serum cytokines relevant to vascular remodeling after attacks and their prognostic role in patients with AQP4 + NMOSD. This study measured the serum levels of 12 cytokines relevant to vascular remodeling, including bone morphogenetic protein-9 (BMP-9) and leptin, in 20 patients with AQP4 + NMOSD and 17 healthy controls (HCs). Disease controls included 18 patients with MOGAD. Serum and cerebrospinal fluid interleukin-6 levels were also measured. Clinical severity was evaluated with Kurtzke's Expanded Disability Status Scale (EDSS). Compared with HCs, patients with AQP4 + NMOSD showed higher BMP-9 (median; 127 vs. 80.7 pg/mL; P = 0.0499) and leptin levels (median; 16,081 vs. 6770 pg/mL; P = 0.0224), but not those with MOGAD. Better improvement in EDSS at 6 months was associated with baseline BMP-9 levels in patients with AQP4 + NMOSD (Spearman's rho = - 0.47; P = 0.037). Serum BMP-9 is upregulated at relapse and may contribute to vascular remodeling in AQP4 + NMOSD. Serum BMP-9 levels could predict clinical recovery 6 months after the attack.

Higher longitudinal brain white matter atrophy rate in aquaporin-4 IgG-positive NMOSD compared with healthy controls.

We aimed to compare longitudinal brain atrophy in patients with neuromyelitis optica spectrum disorder (NMOSD) with healthy controls (HCs). The atrophy rate in patients with anti-aquaporin-4 antibody-positive NMOSD (AQP4 + NMOSD) was compared with age-sex-matched HCs recruited from the Japanese Alzheimer's Disease Neuroimaging Initiative study and another study performed at Chiba University. Twenty-nine patients with AQP4 + NMOSD and 29 HCs were enrolled in the study. The time between magnetic resonance imaging (MRI) scans was longer in the AQP4 + NMOSD group compared with the HCs (median; 3.2 vs. 2.9 years, P = 0.009). The annualized normalized white matter volume (NWV) atrophy rate was higher in the AQP4 + NMOSD group compared with the HCs (median; 0.37 vs. - 0.14, P = 0.018). The maximum spinal cord lesion length negatively correlated with NWV at baseline MRI in patients with AQP4 + NMOSD (Spearman's rho = - 0.41, P = 0.027). The annualized NWV atrophy rate negatively correlated with the time between initiation of persistent prednisolone usage and baseline MRI in patients with AQP4 + NMOSD (Spearman's rho = - 0.43, P = 0.019). Patients with AQP4 + NMOSD had a greater annualized NWV atrophy rate than HCs. Suppressing disease activity may prevent brain atrophy in patients with AQP4 + NMOSD.

Posterior reversible encephalopathy syndrome (PRES) of the isolated brainstem.

A 71-year-old man had disordered consciousness whose Glasgow Coma Scale was E4V1M5. His blood pressure was high, but there was no abnormality in the cerebrospinal fluid examination. The MRI finding reveals a high-intensity area at the pons without the blood flow interruption. Thus, he has diagnosed with brainstem PRES.

Clinical difference after the first optic neuritis between aquaporin-4-IgG-associated and myelin oligodendrocyte glycoprotein-IgG-associated disorders.

OBJECTIVE: To investigate the difference in clinical course after the first optic neuritis (ON) between aquaporin-4 IgG-associated disorder (AQPAD) and myelin oligodendrocyte glycoprotein-IgG-associated disorder (MOGAD) METHODS: In this study, 31 eyes in 24 patients with AQPAD and 26 eyes in 18 patients with MOGAD were included. The clinical course for the first 6 months after the first ON was monitored by a retrospective cohort study. Best-corrected visual acuity (BCVA) was observed before the onset and at nadir, 2 weeks (2 W), 1 month (1 M), 2 months (2 M), 3 months (3 M) and 6 months (6 M). The decimal BCVA was converted to the logarithm of the minimal angle of resolution (logMAR) for statistical analyses. RESULTS: MOGAD eyes showed longer median number of days from ON onset to nadir (6.0 vs. 11.5, P = 0.012) and to treatment (7.0 vs. 11.0, P = 0.020) than AQPAD eyes. The median logMAR was higher in AQPAD eyes than in MOGAD eyes at nadir (2.00 vs. 1.77, P = 0.050), 2 W (1.85 vs. 0.40, P = 0.001), 2 M (0.023 vs. - 0.079, P = 0.032) and 3 M (0.046 vs. - 0.079, P = 0.002). The median time to recovery of BCVA to 0.7 was longer in AQPAD eyes than in MOGAD eyes (44.0 vs. 21.0 days, P = 0.024), but that to BCVA 1.0 was not different between the two disorders (168.0 vs. 40.0 days, respectively, P = 0.056). CONCLUSION: Compared with MOGAD eyes, AQPAD eyes tended to show worse visual outcome even during the first ON episode.

Gerstmann's Syndrome in a Patient Double-positive for Antibodies against the N-methyl-D-aspartate Receptor and NH2-terminal of α-enolase.

We herein report a case of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis concurrent with NH2-terminal of α-enolase (NAE) antibodies. A 36-year-old Japanese woman presented with Gerstmann's syndrome followed by jerky involuntary movements, seizure, autonomic instability, and consciousness disturbance. NAE antibodies were detected in the serum; however, NMDAR antibodies were identified in the cerebrospinal fluid with a cell-based assay, confirming the diagnosis of anti-NMDAR encephalitis. This case highlights the fact that Gerstmann's syndrome can be a manifestation of anti-NMDAR encephalitis and that NAE may be identified concurrently with NMDAR antibodies, suggesting that the diagnosis of Hashimoto encephalopathy requires the reasonable exclusion of alternative diagnoses, including anti-NMDAR encephalitis.

Difference in fatigue and pain between neuromyelitis optica spectrum disorder and multiple sclerosis.

OBJECTIVE: To investigate the difference of fatigue and pain in patients with neuromyelitis optica spectrum disorder (NMOSD) and multiple sclerosis (MS). METHODS: Data from the Modified Fatigue Impact Scale (MFIS) and Pain Effects Scale (PES) were compared between 51 NMOSD and 85 MS patients. Each score was compared in each disease group with or without clinical abnormalities. Since almost no MS patients are without brain magnetic resonance imaging abnormalities, volumetry analysis by the Lesion Segmentation Tool and statistical parametric mapping 12 were added to obtain total lesion volume and intracranial volume in MS patients, and the correlations between total lesion volume/intracranial volume and each score were investigated. RESULTS: Compared to the MS group, the NMOSD group showed a higher PES score (median, 15.0 vs. 7.0, P = 0.045), no difference in MFIS, and an increased percentage of patients with extended spinal cord lesions (58.8% vs. 8.2%, P < 0.001). Moreover, NMOSD and MS patients with extended spinal cord lesions tended to demonstrate higher PES scores than those without. A positive correlation between MFIS and PES were found in patients with NMOSD and MS. On the other hand, MS patients showed a higher percentage of brain abnormalities (80.4% vs. 97.6%, P = 0.001) and a positive correlation between total lesion volume/intracranial volume and MFIS (Spearman's ρ = 0.50, P = 0.033). CONCLUSIONS: The origin of fatigue may be associated with spinal cord lesions causing pain in NMOSD patients, but with brain lesions in MS patients.

Relapse numbers and earlier intervention by disease modifying drugs are related with progression of less brain atrophy in patients with multiple sclerosis.

Long term effect between disease-modifying drugs (DMDs) treatment duration and brain atrophy rate has not been fully investigated in patients with relapsing-remitting MS (RRMS). The aim of this study was to investigate whether DMDs could slow down the progression of brain atrophy in patients with RRMS by comparing DMDs-treated group with non-treated group during a certain period of time. This was a retrospective investigation. Forty-nine RRMS patients underwent two brain MRI scans more than one year apart. Between scans, patients were treated with fingolimod (n = 16), interferon-beta (n = 23) or not treated with DMD (n = 10). Correlations between clinical characteristics and brain volume were calculated by statistical parametric mapping-12. In all 49 patients, the total attack number before 1st MRI scan and the annualized rate of total lesion volume change between the two scans showed a positive correlation with annualized atrophy rate of grey matter volume (GMV) plus white matter volume (WMV). In patients with DMDs (n = 39), the period from drug initiation to 1st MRI scan was negatively correlated with the annualized atrophy rate of GMV + WMV and number of attacks between scans. The number of total previous attacks could be a predictor of subsequent MS progression. Early intervention by DMDs could prevent brain atrophy in patients with MS.

The accuracy of flow cytometric cell-based assay to detect anti-myelin oligodendrocyte glycoprotein (MOG) antibodies determining the optimal method for positivity judgement.

To illustrate the accuracy of the fluorescence-activated cell sorting cell-based assay (FACS-CBA) and to detect anti-myelin oligodendrocyte glycoprotein (MOG) antibodies and ascertain the optimal method for positivity judgement, referencing the findings of microscopic CBA. We tested serum anti-MOG antibodies in 57 patients with central nervous system inflammatory disorders (CIDs), 30 healthy controls (HCs), and 63 disease controls (DCs) by FACS-CBA. To assess the diagnostic performance of 2 positive judgement methods for FACS-CBA, we evaluated the ratio of positive cells (RPC) and median fluorescence intensity (MFIratio); samples from 57 CIDs and 3 antiaquaporin-4 antibody-positive patients whose anti-MOG antibody levels were relatively high but negative by FACS-CBA were tested by microscopic CBA. Blinded to the RPC and MFIratio results, we classified the acquired dot plot into 3 patterns-"upright," "broadband," and "oblique"-as pattern analysis. The sample with the highest RPC in CIDs was subjected to serial dilution analysis. Finally, we analyzed the clinical and laboratory data of anti-MOG antibody-positive patients in the acute phase. Referencing results by microscopic CBA and receiver-operating characteristic curve analysis, the area under the curve, sensitivity, specificity, and cutoff value were 0.952, 92%, 94%, and 1.52 for RPC and 0.931, 79%, 94%, and 6.39 for MFIratio, respectively, suggesting the optimality of RPC for positive judgement. Titers by microscopic CBA analysis significantly correlated with RPC (P = .031). In the validation study, the positive rate of RPC for anti-MOG antibodies was 42.1% in CIDs, but 0% in HCs and DCs (both P < .001). In the pattern analysis, all anti-MOG antibody-positive patients but none of the HCs and DCs exhibited the "oblique" pattern. Serial dilution curve analysis fit a quaternary polymodal. FACS-CBA using RPC analysis for anti-MOG antibodies displayed relatively higher specificity, sensitivity, and semiquantitative property, indicating it could become another acceptable test to detect anti-MOG antibodies.

Soluble CD40 ligand disrupts the blood-brain barrier and exacerbates inflammation in experimental autoimmune encephalomyelitis.

Serum soluble CD40 ligand (sCD40L) has been reported to positively correlate with the albumin quotient, a marker of blood-brain barrier (BBB) breakdown, in patients with multiple sclerosis (MS). To clarify the mechanisms of sCD40L in MS pathophysiology, sCD40L was administered to experimental autoimmune encephalomyelitis (EAE) mice and a human brain microvascular endothelial cell (HBMEC)-based BBB model. The high-dose sCD40L group showed a worse EAE score than the low-dose and control groups. BBB permeability was increased by administering sCD40L in a HBMEC-based BBB model. Thus, sCD40L induces more severe inflammation in the central nervous system by disrupting the BBB.

Risk factors for fingolimod-induced lymphopenia in multiple sclerosis.

BACKGROUND: Lymphopenia is a well-known adverse event of fingolimod, a disease-modifying drug for multiple sclerosis (MS). OBJECTIVES: The objective of this paper is to investigate risk factors for predicting fingolimod-induced lymphopenia in MS by frequent hematological monitoring. METHODS: We retrospectively reviewed data of fingolimod-treated MS patients. Data assessed were sex, age, disease duration, medication history, body mass index, all attacks, Kurtzke's Expanded Disability Status Scale score, and absolute lymphocyte count (ALC) within two days before initiating fingolimod (baseline), on the day after first administration (day 2), and at least every other month after initiating fingolimod therapy. RESULTS: Of 41 MS patients, marked lymphopenia (ALC <200/µl) was confirmed in 12 patients (lymphopenia group) within one year. A significantly more frequent history of treatment with any interferon-beta and lower median baseline ALC was observed in the lymphopenia group than in the non-lymphopenia group (n = 29) (91.7% vs. 44.8%; p = 0.006 and 1469/µl vs. 1879/µl; p = 0.005). An ALC of ≤952/µl on day 2 was the most responsible risk factor for predicting marked lymphopenia (sensitivity, 92%; specificity, 76%; area under the curve, 0.823; p < 0.001). CONCLUSIONS: Low baseline ALC and treatment history with any interferon-beta were risk factors for fingolimod-induced lymphopenia, possibly predicted from ALC on day 2.

Serum anti-JCV antibody indexes in Japanese patients with multiple sclerosis: elevations along with fingolimod treatment duration.

BACKGROUND: The risk of developing progressive multifocal leukoencephalopathy in natalizumab-treated multiple sclerosis (MS) patients is related to serum anti-JCV antibody (JCVAb) index. However, the correlation of JCVAb index with other disease-modifying treatments (DMTs) is not well understood. OBJECTIVE: In this study, we investigated the JCVAb seropositivity rate/JCVAb indexes and its correlation with clinical profiles in Japanese MS patients, and the relationship between JCVAb indexes and DMTs. METHODS: JCVAb indexes were measured in 149 serum samples from 105 patients with MS. JCVAb indexes and seropositivity, and their correlation with age, sex, disease duration, Kurtzke expanded disability status scale and the duration of the DMTs were evaluated in each patient. RESULTS: JCVAb was positive in 73 of 105 MS patients. Within 40 fingolimod-treated patients, 27 were positive for JCVAb and JCVAb indexes were positively correlated with the duration of fingolimod treatment. No significant relation was found between JCVAb indexes and the duration of treatment for the other disease-modifying drugs. CONCLUSION: JCVAb seropositivity was comparatively high in Japanese MS patients. Fingolimod treatment is likely to increase serum JCVAb index, possibly leading to the development of PML. Therefore, it is advised that JCVAb index should be serially monitored during fingolimod treatment to decrease PML risk.