Acute Clinical Events Identified as Relapses With Stable Magnetic Resonance Imaging in Multiple Sclerosis.

Importance: Understanding the association between clinically defined relapses and radiological activity in multiple sclerosis (MS) is essential for patient treatment and therapeutic development. Objective: To investigate clinical events identified as relapses but not associated with new T2 lesions or gadolinium-enhanced T1 lesions on brain and spinal cord magnetic resonance imaging (MRI). Design, Setting, and Participants: This multicenter observational cohort study was conducted between January 2015 and June 2023. Data were extracted on June 8, 2023, from the French MS registry. All clinical events reported as relapses in patients with relapsing-remitting MS were included if brain and spinal cord MRI was performed within 12 and 24 months before the event, respectively, and 50 days thereafter with gadolinium injection. Exposures: Events were classified as relapses with active MRI (RAM) if a new T2 lesion or gadolinium-enhanced T1 lesion appeared on brain or spinal cord MRI or as acute clinical events with stable MRI (ACES) otherwise. Main Outcomes and Measures: Factors associated with ACES were investigated; patients with ACES and RAM were compared regarding Expanded Disability Status Scale (EDSS) course, relapse rate, confirmed disability accrual (CDA), relapse-associated worsening (RAW), progression independent of relapse activity (PIRA), and transition to secondary progressive (SP) MS, and ACES and RAM rates under each disease-modifying therapy (DMT) were estimated. Results: Among 31 885 clinical events, 637 in 608 patients (493 [77.4%] female; mean [SD] age, 35.8 [10.7] years) were included. ACES accounted for 166 (26.1%) events and were more likely in patients receiving highly effective DMTs, those with longer disease duration (odds ratio [OR], 1.04; 95% CI, 1.01-1.07), or those presenting with fatigue (OR, 2.14; 95% CI, 1.15-3.96). ACES were associated with significant EDSS score increases, lower than those found for RAM. Before the index event, patients with ACES experienced significantly higher rates of relapse (relative rate [RR], 1.21; 95% CI, 1.01-1.46), CDA (hazard ratio [HR], 1.54; 95% CI, 1.13-2.11), and RAW (HR, 1.72; 95% CI, 1.20-2.45). Patients with ACES were at significantly greater risk of SP transition (HR, 2.58; 95% CI, 1.02-6.51). Although RAM rate decreased with DMTs according to their expected efficacy, ACES rate was stable across DMTs. Conclusions and Relevance: The findings in this study introduce the concept of ACES in MS, which accounted for one-fourth of clinical events identified as relapses.

Early Maintenance Treatment Initiation and Relapse Risk Mitigation After a First Event of MOGAD in Adults: The MOGADOR2 Study.

BACKGROUND AND OBJECTIVES: Because myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a recently identified autoimmune disorder, the natural history of MOGAD is still not well described. The objective of this study was to describe the long-term outcomes of adult patients with MOGAD. In addition, we aimed to identify factors affecting relapse risk and neurologic outcomes. METHODS: Clinical and biological data were obtained from patients with a first event of MOGAD and included in the French nationwide incident cohort between February 2014 and March 2017. Only patients aged 18 years or older at disease onset and with observation period of at least 3 months were included. Data were collected prospectively until July 2023 and registered in the dedicated French nationwide database. This form includes every relapse with phenotype description during follow-up, date of last assessment, final clinical outcome with Expanded Disability Status Scale score and visual acuity, and maintenance therapy. The probability of recurrence-free survival was assessed using the Kaplan-Meier method. RESULTS: We included 128 patients. The onset phenotype was isolated optic neuritis in 81 patients (63.3%) and isolated myelitis in 25 patients (19.5%). The median follow-up duration was 77.8 months (range 3.2-111.2), with 49 patients (38.3%) experienced at least one relapse. Median times from onset to second and third attacks were 3.2 (1.0-86.2) and 13.0 (2.6-64.4) months, respectively. At the last assessment, Expanded Disability Status Scale Score was ≥3 and ≥6 in 22 (17.2%) and 6 (4.7%) patients, respectively. Eighty patients received at least one maintenance treatment. This treatment was initiated after the first attack in 47 patients (36.7% of the whole cohort) and at the time of a second attack in 25 (19.5%). Multivariate analysis revealed that initiating maintenance treatment after the first attack was associated with a lower relapse risk (OR = 0.26 [95% CI 0.11-0.62], p = 0.002). In patients receiving maintenance therapy after first attack, the 2-year, 4-year, 6-year, and 8-year relapse risks were 11%, 15%, 20%, and 20%, respectively. In other patients, the risks were 41%, 46%, 51%, and 56%. DISCUSSION: The highest risk of a relapse in MOGAD occurs early, and initiating maintenance therapy from the first attack substantially reduced the relapse risk. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that initiating maintenance therapy from the first attack in patients with MOGAD reduces the relapse risk.

High-Efficacy Therapy Discontinuation vs Continuation in Patients 50 Years and Older With Nonactive MS.

Importance: A recent randomized clinical trial concluded that discontinuing medium-efficacy therapy might be a reasonable option for older patients with nonactive multiple sclerosis (MS), but there is a lack of data on discontinuing high-efficacy therapy (HET). In younger patients, the discontinuation of natalizumab and fingolimod is associated with a risk of rebound of disease activity. Objective: To determine whether discontinuing HET in patients 50 years and older with nonactive MS is associated with an increased risk of relapse compared with continuing HET. Design, Setting, and Participants: This observational cohort study used data from 38 referral centers from the French MS registry (Observatoire Français de la Sclérose en Plaques [OFSEP] database). Among 84704 patients in the database, data were extracted for 1857 patients 50 years and older with relapsing-remitting MS treated by HET and with no relapse or magnetic resonance imaging activity for at least 2 years. After verification of the medical records, 1620 patients were classified as having discontinued HET or having remained taking treatment and were matched 1:1 using a dynamic propensity score (including age, sex, disease phenotype, disability, treatment of interest, and time since last inflammatory activity). Patients were included from February 2008 to November 2021, with a mean (SD) follow-up of 5.1 (2.9) years. Data were extracted in June 2022. Exposures: Natalizumab, fingolimod, rituximab, and ocrelizumab. Main Outcomes and Measures: Time to first relapse. Results: Of 1620 included patients, 1175 (72.5%) were female, and the mean (SD) age was 54.7 (4.8) years. Among the 1452 in the HET continuation group and 168 in the HET discontinuation group, 154 patients in each group were matched using propensity scores (mean [SD] age, 57.7 [5.5] years; mean [SD] delay since the last inflammatory activity, 5.6 [3.8] years; mean [SD] follow-up duration after propensity score matching, 2.5 [2.1] years). Time to first relapse was significantly reduced in the HET discontinuation group compared with the HET continuation group (hazard ratio, 4.1; 95% CI, 2.0-8.5; P < .001) but differed between HETs, with a hazard ratio of 7.2 (95% CI, 2.1-24.5; P = .001) for natalizumab, 4.5 (95% CI, 1.3-15.5; P = .02) for fingolimod, and 1.1 (95% CI, 0.3-4.8; P = .85) for anti-CD20 therapy. Conclusion and Relevance: As in younger patients, in patients 50 years and older with nonactive MS, the risk of relapse increased significantly after stopping HETs that impact immune cell trafficking (natalizumab and fingolimod). There was no significant increase in risk after stopping HETs that deplete B-cells (anti-CD20 therapy). This result may inform decisions about stopping HETs in clinical practice.

Improving the decision to switch from first- to second-line therapy in multiple sclerosis: A dynamic scoring system.

BACKGROUND: In relapsing-remitting multiple sclerosis (RRMS), early identification of suboptimal responders can prevent disability progression. OBJECTIVE: We aimed to develop and validate a dynamic score to guide the early decision to switch from first- to second-line therapy. METHODS: Using time-dependent propensity scores (PS) from a French cohort of 12,823 patients with RRMS, we constructed one training and two validation PS-matched cohorts to compare the switched patients to second-line treatment and the maintained patients. We used a frailty Cox model for predicting individual hazard ratios (iHRs). RESULTS: From the validation PS-matched cohort of 348 independent patients with iHR ⩽ 0.69, we reported the 5-year relapse-free survival at 0.14 (95% confidence interval (CI) 0.09-0.22) for the waiting group and 0.40 (95% CI 0.32-0.51) for the switched group. From the validation PS-matched cohort of 518 independent patients with iHR > 0.69, these values were 0.37 (95% CI 0.30-0.46) and 0.44 (95% CI 0.37-0.52), respectively. CONCLUSIONS: By using the proposed dynamic score, we estimated that at least one-third of patients could benefit from an earlier switch to prevent relapse.

Investigating the Long-term Effect of Pregnancy on the Course of Multiple Sclerosis Using Causal Inference.

BACKGROUND AND OBJECTIVES: The question of the long-term safety of pregnancy is a major concern in patients with multiple sclerosis (MS), but its study is biased by reverse causation (women with higher disability are less likely to experience pregnancy). Using a causal inference approach, we aimed to estimate the unbiased long-term effects of pregnancy on disability and relapse risk in patients with MS and secondarily the short-term effects (during the perpartum and postpartum years) and delayed effects (occurring beyond 1 year after delivery). METHODS: We conducted an observational cohort study with data from patients with MS followed in the Observatoire Français de la Sclérose en Plaques registry between 1990 and 2020. We included female patients with MS aged 18-45 years at MS onset, clinically followed up for more than 2 years, and with ≥3 Expanded Disease Status Scale (EDSS) measurements. Outcomes were the mean EDSS score at the end of follow-up and the annual probability of relapse during follow-up. Counterfactual outcomes were predicted using the longitudinal targeted maximum likelihood estimator in the entire study population. The patients exposed to at least 1 pregnancy during their follow-up were compared with the counterfactual situation in which, contrary to what was observed, they would not have been exposed to any pregnancy. Short-term and delayed effects were analyzed from the first pregnancy of early-exposed patients (who experienced it during their first 3 years of follow-up). RESULTS: We included 9,100 patients, with a median follow-up duration of 7.8 years, of whom 2,125 (23.4%) patients were exposed to at least 1 pregnancy. Pregnancy had no significant long-term causal effect on the mean EDSS score at 9 years (causal mean difference [95% CI] = 0.00 [-0.16 to 0.15]) or on the annual probability of relapse (causal risk ratio [95% CI] = 0.95 [0.93-1.38]). For the 1,253 early-exposed patients, pregnancy significantly decreased the probability of relapse during the perpartum year and significantly increased it during the postpartum year, but no significant delayed effect was found on the EDSS and relapse rate. DISCUSSION: Using a causal inference approach, we found no evidence of significantly deleterious or beneficial long-term effects of pregnancy on disability. The beneficial effects found in other studies were probably related to a reverse causation bias.

Non-ischemic cerebral enhancing lesions after thrombectomy: a multicentric retrospective French national registry.

To report the occurrence of non-ischemic cerebral enhancing (NICE) lesions following mechanical thrombectomy (MT) through the retrospective French nationwide registry of NICE lesions. All thrombectomy capable stroke centers (TSC) in France were invited to fill out a questionnaire disseminated through a trainee-led research network (JENI-RC: Jeunes en Neuroradiologie Interventionnelle-Research Collaborative). NICE lesions were defined according to previous literature as delayed onset punctate, nodular, or annular foci enhancements with peri-lesion edema and vascular distribution in the territory of the MT with no other confounding disease. All 43 TSC French centers responded. Three patients were reported by 3 different centers over a total of 34,824 MT (2015-2020). Patient no. 1 developed symptomatic NICE lesions 8 weeks after MT with combination of aspiration and stentriever for a right middle cerebral artery occlusion. Patient no. 2 developed asymptomatic NICE lesions 5 weeks after MT with direct thromboaspiration for a right middle cerebral artery occlusion. Patient no. 3 developed symptomatic NICE lesions 6 weeks after MT with direct thromboaspiration, and combination of aspiration and stentriever for a basilar artery occlusion. This study provides evidence that NICE lesions following MT are a possible rare complication with a similar presentation as previously described following endovascular aneurysm treatment. Both radiologists and neurologists should be aware of this adverse event and make use of MRI contrast agents in case of unexplained symptoms/images during follow-up after MT.

Comparative Effectiveness of Natalizumab Versus Anti-CD20 in Highly Active Relapsing-Remitting Multiple Sclerosis After Fingolimod Withdrawal.

In France, two therapeutic strategies can be offered after fingolimod (FNG) withdrawal to highly active relapsing-remitting multiple sclerosis (RRMS) patients: natalizumab (NTZ) or anti-CD20. We compared the effectiveness of these two strategies as a switch for FNG within the OFSEP database. The primary endpoint was the time to first relapse. Other outcomes were the relapse rates over 3-month periods, time to worsening the EDSS score, proportion of patients with worsened 24-month MRI, time to treatment discontinuation, and incidence rates of serious adverse events. The dynamics of event rates over time were modeled using multidimensional penalized splines, allowing the possibility to model the effects of covariates in a flexible way, considering non-linearity and interactions. A total of 740 patients were included (337 under anti-CD20 and 403 under NTZ). There was no difference between the two treatments regarding the dynamic of the first occurrence of relapse, with a monthly probability of 5.0% at initiation and 1.0% after 6 months. The rate of EDSS worsening increased in both groups until 6 months and then decreased. No difference in the proportion of patients with new T2 lesions at 24 months was observed. After 18 months of follow-up, a greater risk of NTZ discontinuation was found compared to anti-CD20. This study showed no difference between NTZ and anti-CD20 after the FNG switch regarding the clinical and radiological activity. The effect of these treatments was optimal after 6 months and there was more frequent discontinuation of NTZ after 18 months, probably mainly related to JC virus seroconversions.

Untreated patients with multiple sclerosis: A study of French expert centers.

BACKGROUND AND PURPOSE: Disease-modifying therapies (DMTs) have an impact on relapses and disease progression. Nonetheless, many patients with multiple sclerosis (MS) remain untreated. The objectives of the present study were to determine the proportion of untreated patients with MS followed in expert centers in France and to determine the predictive factors of nontreatment. METHODS: We conducted a retrospective cohort study. Data were extracted from the 38 centers participating in the European Database for Multiple Sclerosis (EDMUS) on December 15, 2018, and patients with MS seen at least once during the study period (from June 15, 2016 to June 14, 2017) were included. RESULTS: Of the 21,189 patients with MS (age 47.1 ± 13.1 years; Expanded Disability Status Scale (EDSS) score 3.4 ± 2.4), 6,631 (31.3%; 95% confidence interval [CI] 30.7-31.9) were not receiving any DMT. Although patients with a relapsing-remitting course (n = 11,693) were the most likely to receive DMT, 14.8% (95% CI 14.2-15.4) were still untreated (6.8% never treated). After multivariate analysis among patients with relapsing-remitting MS, the main factors explaining never having been treated were: not having ≥9 lesions on brain magnetic resonance imaging (odds ratio [OR] 0.52 [95% CI 0.44-0.61]) and lower EDSS score (OR 0.78 [95% CI 0.74-0.82]). Most patients with progressive MS (50.4% for secondary and 64.2% for primary progressive MS) did not receive any DMT during the study period, while 11.6% of patients with secondary and 34.0% of patients with primary progressive MS had never received any DMT. CONCLUSION: A significant proportion of patients with MS did not receive any DMT, even though such treatments are reimbursed by the healthcare system for French patients. This result highlights the unmet need for current DMTs for a large subgroup of patients with MS.

Progressive Multifocal Leukoencephalopathy Incidence and Risk Stratification Among Natalizumab Users in France.

Importance: Risk of developing progressive multifocal leukoencephalopathy (PML) is the major barrier to using natalizumab for patients with multiple sclerosis (MS). To date, the association of risk stratification with PML incidence has not been evaluated. Objective: To describe the temporal evolution of PML incidence in France before and after introduction of risk minimization recommendations in 2013. Design, Setting, and Participants: This observational study used data in the MS registry OFSEP (Observatoire Français de la Sclérose en Plaques) collected between April 15, 2007, and December 31, 2016, by participating MS expert centers and MS-dedicated networks of neurologists in France. Patients with an MS diagnosis according to current criteria, regardless of age, were eligible, and those exposed to at least 1 natalizumab infusion (n = 6318) were included in the at-risk population. A questionnaire was sent to all centers, asking for a description of their practice regarding PML risk stratification. Data were analyzed in July 2018. Exposures: Time from the first natalizumab infusion to the occurrence of PML, natalizumab discontinuation plus 6 months, or the last clinical evaluation. Main Outcomes and Measures: Incidence was the number of PML cases reported relative to the person-years exposed to natalizumab. A Poisson regression model for the 2007 to 2016 period estimated the annual variation in incidence and incidence rate ratio (IRR), adjusted for sex and age at treatment initiation and stratified by period (2007-2013 and 2013-2016). Results: In total, 6318 patients were exposed to natalizumab during the study period, of whom 4682 (74.1%) were female, with a mean (SD [range]) age at MS onset of 28.5 (9.1 [1.1-72.4]) years; 45 confirmed incident cases of PML were diagnosed in 22 414 person-years of exposure. The crude incidence rate for the whole 2007 to 2016 period was 2.00 (95% CI, 1.46-2.69) per 1000 patient-years. Incidence significantly increased by 45.3% (IRR, 1.45; 95% CI, 1.15-1.83; P = .001) each year before 2013 and decreased by 23.0% (IRR, 0.77; 95% CI, 0.61-0.97; P = .03) each year from 2013 to 2016. Conclusions and Relevance: The results of this study suggest, for the first time, a decrease in natalizumab-associated PML incidence since 2013 in France that may be associated with a generalized use of John Cunningham virus serologic test results; this finding appears to support the continuation and reinforcement of educational activities and risk-minimization strategies in the management of disease-modifying therapies for multiple sclerosis.

Pediatric laminopathies: Whole-body magnetic resonance imaging fingerprint and comparison with Sepn1 myopathy.

INTRODUCTION: We sought to define the whole-body MRI (WB-MRI) fingerprint of muscle involvement in pediatric LMNA-related dystrophy (LMNA-RD) and to compare it with SEPN1-related myopathy (SEPN1-RM). METHODS: Signal abnormality and atrophy in 109 muscles were scored by semiquantitative scales in 8 children with LMNA-RD and represented by heatmaps. These features were compared with those from 9 SEPN1-RM patients by random forests. RESULTS: LMNA-RD showed predominant signal abnormalities in erector spinae, serratus anterior, subscapularis, gluteus medius and minimus, vastii, adductor magnus and longus, semimembranosus, medial gastrocnemius, and soleus muscles. Psoas, sternocleidomastoid, gracilis, and sartorius muscles often had normal signal but showed atrophy. Cranial, flexor digitorum longus, and tibialis posterior muscles were spared. According to random forests, atrophied semimembranosus in SEPN1-RM was the most relevant feature to distinguish these patients from LMNA-RD. CONCLUSIONS: A selective pattern in WB-MRI for pediatric LMNA-RD exists and can be differentiated from SEPN1-RM by machine learning. Muscle Nerve 54: 192-202, 2016.

Whole-body muscle magnetic resonance imaging in SEPN1-related myopathy shows a homogeneous and recognizable pattern.

INTRODUCTION: The aim of this study was to delineate the spectrum of muscle involvement in patients with a myopathy due to mutations in SEPN1 (SEPN1-RM). METHODS: Whole-body magnetic resonance imaging (WBMRI) was used in 9 patients using T1-weighted turbo spin-echo (T1-TSE) sequences and short tau inversion recovery (STIR) in 5 patients. RESULTS: Analysis of signal and volume abnormalities by T1-TSE sequences in 109 muscles showed a homogeneous pattern characterized by a recognizable combination of atrophy and signal abnormalities in selected muscles of the neck, trunk, pelvic girdle, and lower limbs. Severe wasting of sternocleidomastoid muscle and atrophy of semimembranosus were detected. Selective paraspinal, gluteus maximus, and thigh muscle involvement was also observed. The lower leg was less constantly affected. CONCLUSIONS: WBMRI scoring of altered signal and atrophy in muscle can be represented by heatmaps and is associated with a homogeneous, recognizable pattern in SEPN1-RM, distinct from other genetic muscle diseases.

Atypical phenotypes in titinopathies explained by second titin mutations.

OBJECTIVE: Several patients with previously reported titin gene (TTN) mutations causing tibial muscular dystrophy (TMD) have more complex, severe, or unusual phenotypes. This study aimed to clarify the molecular cause of the variant phenotypes in 8 patients of 7 European families. METHODS: Clinical, histopathological, and muscle imaging data of patients and family members were reanalyzed. The titin protein was analyzed by Western blotting and TTN gene by reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing. RESULTS: Western blotting showed more pronounced C-terminal titin abnormality than expected for heterozygous probands, suggesting the existence of additional TTN mutations. RT-PCR indicated unequal mRNA expression of the TTN alleles in biopsies of 6 patients, 3 with an limb-girdle muscular dystrophy type 2J (LGMD2J) phenotype. Novel frameshift mutations were identified in 5 patients. A novel A-band titin mutation, c.92167C>T (p.P30723S), was found in 1 patient, and 1 Portuguese patient with a severe TMD phenotype proved to be homozygous for the previously reported Iberian TMD mutation. INTERPRETATION: The unequal expression levels of TTN transcripts in 5 probands suggested severely reduced expression of the frameshift mutated allele, probably through nonsense-mediated decay, explaining the more severe phenotypes. The Iberian TMD mutation may cause a more severe TMD rather than LGMD2J when homozygous. The Finnish patient compound heterozygous for the FINmaj TMD mutation and the novel A-band titin missense mutation showed a phenotype completely different from previously described titinopathies. Our results further expand the complexity of muscular dystrophies caused by TTN mutations and suggest that the coexistence of second mutations may constitute a more common general mechanism explaining phenotype variability.

T2 hypointense rims and ring-enhancing lesions in MS.

BACKGROUND: Hypointense rims peripherally on T2-weighted MRI (rim lesions) have been associated with gadolinium ring-enhancing lesions in multiple sclerosis (MS) in pathological studies. However, little is known about their frequency, we analyzed clinical significance in a cohort of MS sufferers according to routine clinical practice. METHODS: We retrospectively reviewed all available MRI scans performed on our MS patients between 2000 and 2009. A total of 580 MRI scans from 257 patients were analyzed. The presence of rim lesions and ring enhancement was assessed and counted blind. Furthermore, the correlation between both patterns, and with clinical characteristics, was evaluated. RESULTS: Thirty-five rim lesions were identified and 9% (24/257) of the patients showed at least one of these lesions. Forty ring-enhancing lesions were counted and 12% (29/245) of the patients who had undergone gadolinium MRI presented at least one such lesion. Thirteen lesions co-localized both patterns (40% of the rim lesions and 33% of the ring-enhancing lesions). Rim lesions and ring-enhancing lesions were observed in patients with clinically isolated syndrome (7%, 7%), relapsing-remitting (11%, 15%) and secondary progressive (13%, 9%) but none with primary progressive MS. Presence of ring-enhancing lesions was significantly associated with a shorter time to reach EDSS (Expanded Disability Status Scale) 4.0 and 6.0 (hazard ratio 7.6, 95% confidence interval 2.3-24.6). CONCLUSIONS: Rim lesions and ring-enhancing lesions are present in close to 10% of patients with MS, and frequently both lesions appear independently one to the other. The association of ring enhancement with worst prognosis needs to be confirmed in prospective studies.

Serum levels of CXCL13 are elevated in active multiple sclerosis.

There is increasing recognition of the important role that B cells play in the pathogenesis of multiple sclerosis (MS). Recently it was reported that the B cell chemokine CXCL13 is elevated in MS serum and cerebrospinal fluid. Here we study whether serum levels of CXCL13 are associated with active MS. We measured serum levels of CXCL13 by enzyme-linked immunosorbent assay in 74 patients with relapsing MS randomized to interferon beta 1b or glatiramer acetate and examined with monthly 3 T brain MRI scans optimized for detection of gadolinium-enhancement for up to 2 years. The median (range) serum levels of CXCL13 pre-treatment were 40 (3-171) pg/ml. Serum levels of CXCL13 were significantly higher at times of active brain MRI scans (p < 0.01). Furthermore, serum levels were higher in patients who never reached MRI remission compared with those in complete (p < 0.01) or partial (p = 0.01) remission. There was a significant positive correlation between the pattern of serum levels of CXCL13 and MRI activity during the first (r = 0.33, p < 0.05) and the full 2 years (r = 0.35, p < 0.01) of the study. Treatment with interferon beta 1b or glatiramer acetate did not affect serum CXCL13. We conclude that the serum levels of the B cell chemokine CXCL13 are associated with active MS.

Cytotoxic effect of neuromyelitis optica antibody (NMO-IgG) to astrocytes: an in vitro study.

NMO-IgG is a disease-specific autoantibody for neuromyelitis optica (NMO) that binds selectively to aquaporin-4 (AQ4), an astrocytic water channel. The normal distribution of AQP4 coincides with the sites of immunoglobulin and complement deposits in lesions found in autopsy studies. The underlying mechanisms of cytotoxicity by NMO-IgG on astrocytes are not well known. In this study we show that serum samples from seropositive NMO patients (21) induce a higher rate of cell death compared with sera from seronegative NMO (16), relapsing-remitting MS (20) patients, and healthy controls (24) on primary cultures of astrocytes. Similar results were obtained by two different techniques: lactate dehydrogenase release and tetrazolium-based viability assay. Cell death was only observed in the presence of active complement. The complement-dependent cytotoxicity was not accompanied by caspase-3/7 activation or increase in the percentage of apoptotic cells. Our data show that NMO-IgG induces a complement-dependent cytotoxicity of astrocytes in vitro, and suggest that a mechanism of cellular death by necrosis might be implicated in the pathophysiology of NMO.

Could Epstein-Barr virus or canine distemper virus cause multiple sclerosis?

Multiple sclerosis (MS) is thought to be an immune-mediated disease with a possible environmental trigger. Genetic and environmental factors, including infection by pathogens, may act synergistically to trigger the disease. There is growing epidemiologic, serologic, and pathologic evidence that Epstein-Barr virus may cause MS or contribute to its pathogenesis. The evidence that canine distemper virus is involved in MS is less robust. More definitive data are required to prove that Epstein-Barr virus or canine distemper virus causes some or most cases of MS.