Fingolimod alters intrathecal B cell maturation in multiple sclerosis patients

Abstract

Background: B cells are postulated to play multiple roles in the pathogenesis of multiple sclerosis (MS) including pathogenic antibody production, antigen-presentation and pro-inflammatory cytokine secretion. Natalizumab and fingolimod are effective MS therapies that disrupt lymphocyte migration but exert differential effects on B cell maturation and trafficking. Herein, we investigated their effects on peripheral blood and cerebrospinal fluid (CSF) B cell repertoires.Methods: Paired CSF and peripheral blood (PB) lymphocytes were collected from MS patients at baseline and after 6 months of treatment with fingolimod (n = 4) or natalizumab (n = 4). B cell subsets including naïve, CD27+ memory, CD27-IgD- double-negative B cells and plasmablasts were collected by FACS and their respective heavy-chain variable region (VH) repertoires assessed by next generation deep sequencing (Illumina MiSeq).Results: Treatment with fingolimod lead to a distinct contraction of the PB B cell pool whereas natalizumab resulted in an expansion of circulating PB B cells. In contrast, CSF B cell numbers remained stable under treatment with fingolimod but decreased following natalizumab therapy. Clonal overlap between CSF and peripheral blood B cells was reduced following natalizumab treatment (-24% reduction of clonal groups) but remained stable with fingolimod therapy. Lineage analyses of CSF B cell repertoires at baseline and following therapy revealed large, clonally expanded B cell clusters in natalizumab-treated MS patients but no intrathecal clonal expansion following fingolimod therapy. Conclusions: Our findings suggest that natalizumab treatment diminishes the exchange of peripheral and intrathecal B cells but does not impact intrathecal clonal expansion. In contrast, fingolimod treatment fails to alter B cell exchange across the blood-brain-barrier but affects intrathecal clonal expansion. Sphingosine-1 phosphate receptor inhibition may impact MS disease progression by inhibiting intrathecal germinal center activity.

Memory B Cells in Multiple Sclerosis: Emerging Players in Disease Pathogenesis

“…In agreement with these findings, B cells populating the CSF, including Bmem, bear extensive somatic mutations and exhibit clonal expansion (88). Conversely, in a recent pre-print, Bmem in peripheral blood from MS patients displayed an Ig isotype distribution of 50% IgM, 30% IgA, and 20% IgG (93). In MS patients, ASC populating the CSF exhibit a selective enrichment towards the IgG1 allotype G1m1 compared to the peripheral blood (94).…”

“…Glatiramer acetate-treated MS patients also show alterations in B cell function, resulting in reduced activation markers (CD69, CD95), decreased TNF production, and increased IL-10 production ( 173 ). Fingolimod, which targets SIP receptor-expressing lymphocytes such as T cells and B cells results in impaired CSF B cell clonal expansion ( 93 ), including Bmem, and reduced Bmem activation in peripheral blood from MS patients ( 177 ). Dimethyl fumarate treatment results in similar modulation reducing B cell activation ( 183 ) and the production of the pro-inflammatory cytokines GM-CSF, TNF, and IL-6 ( 181 , 183 ), while IL-10 production is unaltered ( 182 ).…”

“…Mitoxantrone treatment, immunosuppressive to T cells and B cells, does not affect B cell proliferation ( 188 ), but results in the preferential death of CD27-expressing B cells and a shift to an anti-inflammatory state, with reduced LT and TNF production, and increased IL-10 production in vitro ( 85 ). Conversely, natalizumab, which blocks leukocyte α 4 β 1- mediated entry into the CNS, results in a 2.4-fold increase in Bmem in the peripheral blood ( 178 , 193 ), but a reduction of Bmem in the CSF ( 93 ). In contrast to the aforementioned therapies, B cell activation (CD95, CD40, MHCII expression) and TNF and IL-6 production was increased in the peripheral blood of natalizumab-treated MS patients ( 178 ).…”