The risk of infections for multiple sclerosis and neuromyelitis optica spectrum disorder disease-modifying treatments: Eighth European Committee for Treatment and Research in Multiple Sclerosis Focused Workshop Review. April 2021

Over the recent years, the treatment of multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) has evolved very rapidly and a large number of disease-modifying treatments (DMTs) are now available. However, most DMTs are associated with adverse events, the most frequent of which being infections. Consideration of all DMT-associated risks facilitates development of risk mitigation strategies. An international focused workshop with expert-led discussions was sponsored by the European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS) and was held in April 2021 to review our current knowledge about the risk of infections associated with the use of DMTs for people with MS and NMOSD and corresponding risk mitigation strategies. The workshop addressed DMT-associated infections in specific populations, such as children and pregnant women with MS, or people with MS who have other comorbidities or live in regions with an exceptionally high infection burden. Finally, we reviewed the topic of DMT-associated infectious risks in the context of the current SARS-CoV-2 pandemic. Herein, we summarize available evidence and identify gaps in knowledge which justify further research

DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Identification of oligodendroglial secreted factors involved in CNS nodal clustering

L’aggrégation des canaux sodiques (Nav) aux nœuds de Ranvier est une étape importante pour l’établissement d’une conduction électrique saltatoire rapide le long des axones myélinisés. L’assemblage des nœuds dans le SNC est sous la dépendance de trois mécanismes complémentaires : la restriction de la diffusion des protéines nodales sous l’influence de la formation des paranœuds, l’ancrage aux protéines du cytosquelette, et l’interaction avec les protéines de matrice extracellulaire (MEC). L’interaction avec les cellules gliales myélinisantes (oligodendrocytes) influence à la fois la formation des nœuds par la formation des jonctions paranodales, et sous l’influence de facteurs oligodendrocytaires sécrétés qui sont capables de déclencher le clustering des protéines nodales. La formation de clusters de Nav en l’absence de myéline, sous l’influence du milieu conditionné d’oligodendrocytes (MCO), sur des axones de cellules ganglionnaires de la rétine, ou de neurones GABAergiques de l’hippocampe a ainsi été décrite. Lors de ma thèse, je me suis focalisé sur la compréhension des mécanismes à l’œuvre dans le clustering des protéines nodales sous l’influence du MCO. Ce travail montre que parmi les protéines identifiées dans le MCO, la contactin-1 (CNTN) est capable, en association à des protéines de MEC, la Tenascin-R ou le Phosphacan, d’induire la formation de prénœuds le long d’axones en l’absence de myéline. L’importance de la CNTN a été démontrée par trois stratégies expérimentales complémentaires : l’induction des prénœuds sous l’inflence de l’ajout de protéines recombiante, la dimiution de l’activité du MCO après déplétion en CNTN, et la restauration de cette activité avec la supplémentation du MCO déplété en CNTN recombinante. Sur le versant neuronal, la formation de ces prénœuds nécessite une réponse cellulaire complexe, impliquant synthèse et trafficking protéique ainsi que la maturation neuronale. Dans l’ensemble, ces résultats renforcent notre connaissance des mécanismes d’assemblage des nœuds de Ranvier dans le SNC, en permettant pour la première fois l’identification précise d’un facteur oligodendroglial sécrété capable d’induire le regroupement des protéines nodales.The clustering of sodium channels (Nav) at the nodes of Ranvier is a crucial step to allow fast saltatory conduction along myelinated axons. Three complementary mechanisms that can compensate for each other have been shown to work together to assemble a node of Ranvier (CNS): restriction of nodal protein diffusion by paranodal junction formation, anchoring to scaffolding proteins and interaction with extracellular matrix (ECM) proteins. Oligodendrocytes, the myelinating glial cells of the CNS contribute to nodal assembly both by direct contact at the paranodes and through the influence of secreted cues, that are able to induce nodal protein clustering. Nav cluster formation on unmyelinated axons under the influence of oligodendrocyte conditioned medium (OCM) has been previously described on retinal ganglional cells and hippocampal GABAergic neurons. However, the precise nature of the factors carrying this effect remains elusive. During this thesis, I focused on the description of mechanisms underlying the clustering of nodal protein under OCM influence, and more precisely on the identification of the factors carrying this effect. This work shows that among proteins identified in the OCM, contactin-1 (CNTN) is able, in association with MEC proteins, either Tenascin-R or Phosphacan, to induce clusters of Nav on axons, in the absence of myelin. The key role of CNTN has been demonstrated by three experimental strategies: induction of prenodes formation under the influence of recombinant protein, reduction of OCM ability to induce clustering after CNTN depletion and restoration of its activity after recombinant protein supplementation. Another aspect of this work was the study of mechanisms at stake on the neuronal side. Nav clustering requieres a complex neuronal response involving protein synthesis, trafficking and neuronal maturation. Taken together, theses results allow a better understanding of CNS nodes of Ranvier assembly mechanisms, by the precise identification for the first time of oligodendroglial-secreted CNTN as able to induce CNS nodal protein clustering

NOUVEAUX MÉCANISMES DE L’IMPLICATION DES OLIGODENDROCYTES DANS LA CONDUCTION DE L’INFLUX NERVEUX

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Generation of Oligodendrocytes and Oligodendrocyte-Conditioned Medium for Co-Culture Experiments

International audienceIn the central nervous system, oligodendrocytes are well-known for their role in axon myelination, that accelerates the propagation of action potentials through saltatory conduction. Moreover, an increasing number of reports suggest that oligodendrocytes interact with neurons beyond myelination, notably through the secretion of soluble factors. Here, we present a detailed protocol allowing purification of oligodendroglial lineage cells from glial cell cultures also containing astrocytes and microglial cells. The method relies on overnight shaking at 37 °C, which allows selective detachment of the overlying oligodendroglial cells and microglial cells, and the elimination of microglia by differential adhesion. We then describe the culture of oligodendrocytes and production of oligodendrocyte-conditioned medium (OCM). We also provide the kinetics of OCM treatment or oligodendrocytes addition to purified hippocampal neurons in co-culture experiments, studying oligodendrocyte-neuron interactions

An alternative mechanism of early nodal clustering and myelination onset in GABAergic neurons of the central nervous system

International audienceIn vertebrates, fast saltatory conduction along myelinated axons relies on the node of Ranvier. How nodes assemble on CNS neurons is not yet fully understood. We previously described that node‐like clusters can form prior to myelin deposition in hippocampal GABAergic neurons and are associated with increased conduction velocity. Here, we used a live imaging approach to characterize the intrinsic mechanisms underlying the assembly of these clusters prior to myelination. We first demonstrated that their components can partially preassemble prior to membrane targeting and determined the molecular motors involved in their trafficking. We then demonstrated the key role of the protein β2Nav for node‐like clustering initiation. We further assessed the fate of these clusters when myelination proceeds. Our results shed light on the intrinsic mechanisms involved in node‐like clustering prior to myelination and unravel a potential role of these clusters in node of Ranvier formation and in guiding myelination onset

Demyelination Causes Adult CNS Progenitors to Revert to an Immature State and Express Immune Cues That Support Their Migration

International audienceThe declining efficiency of myelin regeneration in individuals with multiple sclerosis has stimulated a search for ways by which it might be therapeutically enhanced. Here we have used gene expression profiling on purified murine oligodendrocyte progenitor cells (OPCs), the remyelinating cells of the adult CNS, to obtain a comprehensive picture of how they become activated after demyelination and how this enables them to contribute to remyelination. We find that adult OPCs have a transcriptome more similar to that of oligodendrocytes than to neonatal OPCs, but revert to a neonatal-like transcriptome when activated. Part of the activation response involves increased expression of two genes of the innate immune system, IL1 β and CCL2 , which enhance the mobilization of OPCs. Our results add a new dimension to the role of the innate immune system in CNS regeneration, revealing how OPCs themselves contribute to the postinjury inflammatory milieu by producing cytokines that directly enhance their repopulation of areas of demyelination and hence their ability to contribute to remyelination

Anti-CD20 therapies decrease humoral immune response to SARS-CoV-2 in patients with multiple sclerosis or neuromyelitis optica spectrum disorders

International audienceBackground: SARS-CoV-2 seroconversion rate after COVID-19 may be influenced by disease-modifying therapies (DMTs) in patients with multiple sclerosis (MS) or neuromyelitis optica spectrum disorders (NMO-SD).Objective: To investigate the seroprevalence and the quantity of SARS-CoV-2 antibodies in a cohort of patients with MS or NMO-SD.Methods: Blood samples were collected in patients diagnosed with COVID-19 between 19 February 2020 and 26 February 2021. SARS-CoV-2 antibody positivity rates and Ig levels (anti-S IgG titre, anti-S IgA index, anti-N IgG index) were compared between DMTs groups. Multivariate logistic and linear regression models were used to estimate the influence of DMTs and other confounding variables on SARS-CoV-2 serological outcomes.Results: 119 patients (115 MS, 4 NMO, mean age: 43.0 years) were analysed. Overall, seroconversion rate was 80.6% within 5.0 (SD 3.4) months after infection. 20/21 (95.2%) patients without DMT and 66/77 (85.7%) patients on DMTs other than anti-CD20 had at least one SARS-CoV-2 Ig positivity, while this rate decreased to only 10/21 (47.6%) for patients on anti-CD20 (p<0.001). Being on anti-CD20 was associated with a decreased odd of positive serology (OR, 0.07 (95% CI 0.01 to 0.69), p=0.02) independently from time to COVID-19, total IgG level, age, sex and COVID-19 severity. Time between last anti-CD20 infusion and COVID-19 was longer (mean (SD), 3.7 (2.0) months) in seropositive patients compared with seronegative patients (mean (SD), 1.9 (1.5) months, p=0.04).Conclusions: SARS-CoV-2 antibody response was decreased in patients with MS or NMO-SD treated with anti-CD20 therapies. Monitoring long-term risk of reinfection and specific vaccination strategies in this population may be warranted.Trial registration number: NCT04568707

Role of a Contactin multi‐molecular complex secreted by oligodendrocytes in nodal protein clustering in the CNS

International audienceThe fast and reliable propagation of action potentials along myelinated fibers relies on the clustering of voltage-gated sodium channels at nodes of Ranvier. Axo-glial communication is required for assembly of nodal proteins in the central nervous system, yet the underlying mechanisms remain poorly understood. Oligodendrocytes are known to support node of Ranvier assembly through paranodal junction formation. In addition, the formation of early nodal protein clusters (or prenodes) along axons prior to myelination has been reported, and can be induced by oligodendrocyte conditioned medium (OCM). Our recent work on cultured hippocampal neurons showed that OCM-induced prenodes are associated with an increased conduction velocity (Freeman et al., 2015). We here unravel the nature of the oligodendroglial secreted factors. Mass spectrometry analysis of OCM identified several candidate proteins (i.e., Contactin-1, ChL1, NrCAM, Noelin2, RPTP/Phosphacan, and Tenascin-R). We show that Contactin-1 combined with RPTP/Phosphacan or Tenascin-R induces clusters of nodal proteins along hippocampal GABAergic axons. Furthermore, Contactin-1-immunodepleted OCM or OCM from Cntn1-null mice display significantly reduced clustering activity, that is restored by addition of soluble Contactin-1. Altogether, our results identify Contactin-1 secreted by oligodendrocytes as a novel factor that may influence early steps of nodal sodium channel cluster formation along specific axon populations

Multiple Sclerosis: Is There a Risk of Worsening after Yellow Fever Vaccination?

Background: Yellow fever vaccine (YFV) is not advised for multiple sclerosis (MS) patients because of the potential risk of post-vaccine relapses. Objective: To assess the risk of relapsing-remitting multiple sclerosis (RR-MS) worsening after YFV. Methods: Non-interventional observational retrospective, exposed/non-exposed cohort study nested in the French national cohort including MS. Results: 128 RR-MS were included. The 1-year annualized relapse rate (ARR) following YFV did not differ between exposed: 0.219 (0.420) and non-exposed subjects: 0.208 (0.521) ( p\,= 0.92). Time to first relapse was not different between groups (adjusted hazard ratio (HR) = 1.33; 95% confidence interval (CI) = 0.53\textendash 3.30, p = 0.54). Conclusion: These results suggest that YFV does not worsen the course of RR-MS