Copy number variations across the blood–brain barrier in multiple sclerosis

Abstract

Objective Multiple sclerosis (MS) is a neuroinflammatory disease where immune cells cross the blood–brain barrier (BBB) into the central nervous system (CNS). What predisposes these immune cells to cross the BBB is still unknown. Here, we examine the possibility that genomic rearrangements could predisposespecific immune cells in the peripheral blood to cross the BBB and form sub‐populations of cells involved in the inflammatory process in the CNS. Methods We compared copy number variations in paired peripheral blood mononuclear cells (PBMCs) and cerebrospinal fluid (CSF) cells from MS patients. Thereafter, using next generation sequencing, we studied the T‐cell receptor beta (TRB) locus rearrangements and profiled the αβ T cell repertoire in peripheral CD4+ and CD8+ T cells and in the CSF. Results We identified deletions in the T‐cell receptor alpha/delta (TRA/D), gamma (TRG), and TRB loci in CSF cells compared to PBMCs. Further characterization revealed diversity of the TRB locus which was used to describe the character and clonal expansion of T cells in the CNS. T‐cell repertoire profiling from either side of the BBB concluded that the most frequent clones in the CSF samples are unique to an individual. Furthermore, we observed a difference in the proportion of expanded T‐cell clones when comparing samples from MS patients in relapse and remission with opposite trends in CSF and peripheral blood. Interpretation This study provides a characterization of the T cells in the CSF and might indicate a role of expanded clones in MS pathogenicity.

Broader Epstein–Barr virus–specific T cell receptor repertoire in patients with multiple sclerosis

“…3 B ; q = 8.1 × 10 −3 ). As there have been reports of EBV-specific CD8 + T cells in the CSF ( Bedri et al, 2022 ; Lossius et al, 2014 ; van Nierop et al, 2016 ) and in the brain parenchyma ( Serafini et al, 2019 ) of MS patients, as well as lytic EBV proteins in MS lesions ( Moreno et al, 2018 ), our data would be consistent with an ongoing, potentially compartmentalized immune reaction against EBV in MS patients. This could cause continuous egress of EBV-specific clonotypes from the blood to CNS tissue.…”

“…To assess, whether the EBV response is altered in MS patients, CSF scRNAseq samples of six HD and five MS patients ( Pappalardo et al, 2020 ) were analyzed and the EBV-specific matches were annotated. MS patients presented with more EBV matches in the CSF, which has been suggested before ( Bedri et al, 2022 ; Lossius et al, 2014 ; van Nierop et al, 2016 ), and more interestingly, these sequence matches were predominantly directed against lytic epitopes and also differed in phenotype: HD CSF contained almost exclusively EBV-specific TEM_1 with 36% of sequences specific for lytic epitopes, whereas in MS CSF, the EBV-specific CD8 + T cells distributed evenly between TEM_1, TEM_3, and TCM_1 with 95% of sequences specific for lytic epitopes. TEM_3 cells are characterized by ITGA4 and ITGB1 (α and β chains of VLA-4), and CCR5 , while TCM_1 being characterized by ITGAE , KLRK1 , and integrin β 7 expression ( ITGB7 ).…”