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Regulation of T cells by vitamin D

English title Regulation of T cells by vitamin D
Applicant Engelhardt Britta
Number 189312
Funding scheme Project funding (Div. I-III)
Research institution Theodor Kocher Institut Medizinische Fakultät Universität Bern
Institution of higher education University of Berne - BE
Main discipline Immunology, Immunopathology
Start/End 01.01.2020 - 30.06.2023
Approved amount 309'000.00
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All Disciplines (2)

Discipline
Immunology, Immunopathology
Neurology, Psychiatry

Keywords (5)

multiple sclerosis; Vitamin D; CD46; T cell migration; regulatory T cells

Lay Summary (German)

Lead
Frankreich
Lay summary

Multiple Sklerose (MS) ist eine entzündliche Erkankung des Zentralnervensystems (ZNS), deren Ursache bis heute ungeklärt ist. Bei der Entstehung der Erkrankung spielen genetische und Umweltfaktoren eine Rolle.  Zahlreiche genetische Varianten, die mit einer Anfälligkeit für MS verbunden sind, sind Gene, die Schlüsselschritte der Immunantwort und hierbei vor allem die Funktion von T Zellen steuern. Bei den Umweltfaktoren scheint der Vitamin D Mangel, welcher ein wachsendes Problem der öffentlichen Gesundheit darstellt, ein Hauptrisikofaktor für die Entstehung der MS zu sein. Unsere vorläufigen Forschungsergebnisse deuten darauf hin, dass Vitamin D die Wanderung von T Zellen im Körper beeinflusst. In diesem Forschungsprojekt möchten wir daher herausfinden, welche Signalwege Vitamin D in T Zellen von gesunden Personen und MS Patienten auslöst. Dieses Forschungsprojekt führen wir gemeinsam mit Dr. Anne Astier in Tolouse und Dr. Eric Touvenaut, Montpellier in Frankreich durch. Diese Zusammenarbeit erlaubt die Kombination unserer verschiedenen Expertisen und somit Untersuchungen im Labor und am Patienten, um die immunmodulatorische Funktion von Vitamin D besser zu verstehen. Unsere Erkenntnisse aus diesem Forschungsprojekt werden entscheidend dazu beitragen, Nutzen und Risiken einer hochdosierten Vitamin D Behandlung von MS Patienten zu beurteilen.

Direct link to Lay Summary Last update: 18.09.2019

Responsible applicant and co-applicants

Employees

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Abstract

This proposal aims to determine novel mechanisms triggered by Vitamin D (VitD) in controlling inflammation and restoring defective immune regulatory pathways in multiple sclerosis (MS). This application results from ongoing collaboration between several groups with complementary expertise, in both France and Switzerland. MS is a chronic inflammatory disease of the central nervous system (CNS) due to a complex interplay between environmental triggers and genetic predisposition. Numerous genetic variants associated with MS susceptibility are found in genes controlling key steps of immune responses, including the genes encoding the T-cell adhesion/activation molecules CD6 and CD226. T cells play a pivotal role in MS since the pathology is associated with a functional defect of regulatory T cells (Tregs) and an increased function of effector T cells recognizing auto-antigens. Another key component for MS pathogenesis is the migration of activated T cells to the CNS, and several treatments target this step, albeit with rare but severe side effects.VitD deficiency is a growing public health problem that is proposed as a major risk factor in MS pathogenesis. VitD might impact MS via its known properties as a modulator of T-cell responses. Indeed, VitD induces both CD25+Foxp3+Tregs and IL-10-secreting Type I regulatory T cells (Tr1). The complement regulator CD46 converts Th1 cells to Tr1 cells by reducing IFN? secretion and increasing IL-10 production. This CD46-mediated Th1 to Tr1 “switch” is defective in MS. Our unpublished data suggest the immunomodulatory effect of Vitamin D may be due, at least in part, by acting on CD46, notably through a crosstalk between the CD46 and VitD pathways. Active VitD promotes the switch to Tr1, and partially restores the IL-10:IFN? switch in MS T cells. CD46 costimulation in the presence of VitD strongly promotes expression of CD6 and CD226. The molecular mechanisms by which VitD regulates Tr1 differentiation are however still unknown. The preliminary data presented in this proposal lead us to postulate that VitD modulates signaling and adhesion molecules at the surface of CD4+ T cells to favor Tr1/Treg differentiation and promote preferential migration of tolerogenic T cells over pathogenic T cells, hence potentially providing a mean to manipulate the migration of pathogenic T cells into the CNS. We will identify the molecular mechanisms involved in vitro, first with healthy donor T cells, then using T cells from MS patients by dissecting the signaling pathways triggered by activation in the presence of VitD in the different human T cell subsets. We will assess their migratory potential both in vitro and in vivo in animal models. We will test the in vivo effects in humans in the frame of a high dose VitD supplementation trial in MS patients. These studies will be completed by a single-cell RNA sequencing approach to monitor the global impact of VitD on immune cells in the context of MS in order to identify novel immunoregulatory pathways triggered by VitD in humans. Therefore, to unravel the mechanisms by which VitD modulates T-cell activity in MS, our project is organized around 3 work packages (WP) addressing the following questions: WP1: what are the molecular mechanisms by which VitD regulates CD46-mediated Tr1 differentiation? Recruitment of signaling molecules to the immunological synapse (IS) during T cell activation is key to control T cell fate. We have recently shown that TCR activation controls the glycosylation of CD46 and its subsequent recruitment to the IS. Strikingly, TCR-mediated glycosylation changes do not occur in MS T cells, and this may be partly responsible for the defective CD46 pathway in these patients. The adhesion/activation molecules CD226, CD6 and LFA-1 that are modulated by CD46 activation, are also recruited to the IS. We will characterize whether VitD i) modulates CD46 glycosylation and its recruitment to the IS in both healthy and MS patients’ T cells; ii) regulates recruitment of CD226, CD6 and LFA-1 at the IS of Tregs and conventional T cells; iii) modifies signaling in Tregs and conventional T cells in healthy donors and patients with MS.WP2: what is the role of VitD in T-cell migration? i) we will follow Treg and Teff recruitment into the CNS in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, following VitD treatment. We will also characterize the migratory abilities of human effector and regulatory T-cell subsets treated by VitD using in vitro and in vivo live cell imaging of the multi-step extravasation of T cells across the blood-brain-barrier (BBB) employing ii) a novel microfluidic in vitro model of human BBB under physiological flow; and iii) by in vivo live cell imaging of human T-cell interaction with the inflamed BBB in EAE. We will characterize the molecules involved and investigate the effect of MS-associated CD226 and CD6 SNPs on the impact of VitD on T cell migration.WP3: what novel immunoregulatory pathways are mediated by VitD in MS patients? We will explore the impact of VitD supplementation on the T cell transcriptome of MS patients. This study is indeed affiliated to a French randomized clinical trial (NCT01817166) on high doses of vitamin D supplementation as a monotherapy vs. placebo for Clinically Isolated Syndrome (CIS). We will i) assess the phenotype and functions of T cells isolated from patients before and after 3 months of supplementation with VitD or placebo in vivo and compare these data with that obtained in vitro in WP1 and 2; ii) identify novel immunoregulatory pathways by analyzing by single-cell RNAseq the global transcriptomic changes in these patients after supplementation by VitD, and validating the best candidates by in vitro analyses; iii) correlate the immunophenotype with the clinical and imaging parameters of the disease (MRI and clinical activity over 2 years of follow-up).Combining pre-clinical in vitro and in vivo studies with clinical evaluations, we will be able to identify novel immunomodulatory functions of VitD that will provide new clinically relevant information on its mode of action. This may allow deciding on the benefit of high dose VitD supplementation in MS.
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