Extensive peripheral immunoglobulin repertoire analyses in people with multiple sclerosis reveal disease-specific signatures and distinct treatment effects of disease modifying drugs

B cells are crucial players in the pathogenesis of multiple sclerosis (MS), however, limited information is available on peripheral immunoglobulin (Ig) repertoires of people with MS (pwMS) in comparison to healthy individuals and during different treatments. Next generation sequencing of Ig heavy chains (VH) originating from bulk-sorted B cell populations was performed in 33 pwMS and ten healthy controls. All 33 pwMS were examined longitudinally at baseline and six months after treatment with ozanimod, fingolimod, dimethyl fumarate, teriflunomide, cladribine or natalizumab. Ig peptides were obtained longitudinally in a subset of treated pwMS by Ig mass spectrometry, overlapped with VH transcriptomes through nf-core bioinformatics workflow analysis and additionally Ig serum level and anti-Epstein-Barr virus IgG level (EBNA1) were measured. VH repertoires of treatment-naïve pwMS showed a significantly decreased diversity in the double negative B cells and different usage of IGHV genes when compared with healthy controls. Quantitative changes in B cell subsets during treatment were accompanied by qualitative changes in Ig repertoires with a significantly decreased diversity in the naive, memory B cells and plasmablasts during ozanimod treatment. A similar trend was noticeable for all other treatments except natalizumab. No qualitative change in Ig peptides overlapping with Ig transcriptome repertoires was observed. This study provides first evidence for an altered peripheral Ig repertoire in pwMS. In addition, various treatments seem to shift the composition of B cells towards an increased fraction and activation of the naive B cell pool and a reduced fraction of memory B cells with reduced clonal diversity.