ABSTRACT
Background: Cladribine is a highly effective immunotherapy that is applied in two short-term courses over 2 years and reduces relapse rate and disease progression in patients with relapsing multiple sclerosis (MS). Despite the short treatment period, cladribine has a long-lasting effect on disease activity even after recovery of lymphocyte counts, suggesting a yet undefined long-term immune modulating effect. Objectives: Our aim was to provide a more profound understanding of the detailed effects of cladribine, also with regard to the patients' therapy response. Design: We performed an open-labeled, explorative, prospective, single-arm study, in which we examined the detailed lymphocyte subset development of MS patients who received cladribine treatment over 2 years. Methods: We performed in-depth profiling of the effects of cladribine on peripheral blood lymphocytes by flow cytometry, bulk RNA sequencing of sorted CD4+ T cells, CD8+ T cells, and CD19+ B cells as well as single-cell RNA sequencing of peripheral blood mononuclear cells in a total of 23 MS patients before and at different time points up to 24 months after cladribine treatment. Data were correlated with clinical and cranial magnetic resonance imaging (MRI) disease activity. Results: Flow cytometry revealed a predominant and sustained reduction of memory B cells compared to other B cell subsets after cladribine treatment, whereas T cell subsets were slightly reduced in a more uniform pattern. The overall transcriptional profile of total blood B cells exhibited reduced expression of proinflammatory and T cell activating genes, while single-cell transcriptomics revealed that gene expression within each B cell cluster did not change over time. Stable patients displayed stronger reductions of selected memory B cell clusters as compared to patients with clinical or cerebral MRI disease activity. Conclusion: We describe a pronounced and sustained effect of cladribine on the memory B cell compartment, and the resulting change in B cell subset composition causes a significant alteration of B cell transcriptional profiles resulting in reduced proinflammatory and T cell activating capacities. The extent of reduction in selected memory B cell clusters by cladribine may predict treatment response.
ABSTRACT
After natalizumab (NAT) cessation, some multiple sclerosis (MS) patients experience a severe disease rebound. The rebound pathophysiology is still unclear; however, it has been linked to interleukin-17-producing T-helper (Th17) cells. We demonstrate that during NAT treatment, MCAM+CCR6+Th17 cells gradually acquire a pathogenic profile, including proinflammatory cytokine production, pathogenic transcriptional signatures, brain endothelial barrier impairment, and oligodendrocyte damage via induction of apoptotic pathways. This is accompanied by an increase in Th17 cell frequencies in the cerebrospinal fluid of NAT-treated patients. Notably, Th17 cells derived from NAT-treated patients, who later developed a disease rebound upon treatment cessation, displayed a distinct transcriptional pathogenicity profile associated with altered migratory properties. Accordingly, increased brain infiltration of patient Th17 cells was illustrated in a humanized mouse model and brain histology from a rebound patient. Therefore, peripheral blood-accumulated MCAM+CCR6+Th17 cells might be involved in rebound pathophysiology, and monitoring of changes in Th17 cell pathogenicity in patients before/during NAT treatment cessation might enable rebound risk assessment in the future.
