Single-cell transcriptome profiling of disease-related lymphocytes in patients with multiple sclerosis

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Multiple sclerosis (MS) is a prevalent putative autoimmune disease with a variable and unpredictable disease course. It is characterized by demyelination, lymphocyte infiltrations in the central nervous system, and inflammatory lesions. The reasons for lymphocyte infiltration and their cellular and molecular targets are still enigmatic. We propose to extend project A5 "Synoptic analysis of adaptive immune reactions in very early multiple sclerosis: Repertoires and target antigens of B- and T-cells" of CRC128, where we focus on putatively disease-related B- and T-cells and their involvement in the pathogenesis of very early MS. In this project, we established whole transcriptome analyses of single cells from cerebrospinal fluid (CSF) by NGS and bioinformatics analyses. We completed a first series of experiments where we compared single cell transcriptomes of subjects with established and prodromal MS, and controls. In all these experiments, CSF samples were obtained at quiescent stages of MS. Preliminary data revealed that dramatic changes in the transcriptomes may be detected in CSF during an acute attack. Surprisingly, we found striking differences in the composition of lymphocyte subpopulations in two patients who underwent lumbar puncture during an acute attack. Thus, when cells were obtained during an acute attack, distinct subpopulations of CD4+ and CD8+ T cells were missing as compared to quiet stages of MS. Different subpopulations may express characteristic activation and homing markers, therefore we currently assume that these cells might have migrated into the brain where they probably contributed to lesion formation and deterioration of the disease. Continuation of these studies is limited because such experiments are extremely costly. Here we apply for additional funding to analyze a larger cohort of patients. We are planning to study 10 patients each where cells were obtained during an acute attack and at a quiet stage of the disease, 5 patients with progressive MS, and 5 subjects with non-inflammatory neurological diseases. From 10 of these patients we will additionally investigate cells from peripheral blood. Analysis of this cohort will allow us to confirm the preliminary results. We are optimistic that we may substantiate our data so that we may gain deeper insight in the characteristics of the cells that leave the CSF during an acute MS attack. We expect that these results may significantly contribute to explaining why particular T cell subtypes enter brain tissue and how they succeed in crossing the blood-brain barrier. This may reveal important insights into the immunopathology of MS, and may also have high clinical benefit. Our observations may guide us towards new biomarkers that predict disease courses, contribute to patient stratification and therapy selection, and may moreover pave new ways for rational therapies that influence the migrational behavior of T cells and prevent attack of brain tissue.