Anti-CD52 antibody treatment depletes B cell aggregates in the central nervous system in a mouse model of multiple sclerosis

Micha Simon,Rojda Ipek,György A Homola,Christoph Kleinschnitz,Stefanie Kuerten,Damiano M Rovituso,Andrea Schampel

doi:10.1186/s12974-018-1263-9

Abstract

BackgroundMultiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) for which several new treatment options were recently introduced. Among them is the monoclonal anti-CD52 antibody alemtuzumab that depletes mainly B cells and T cells in the immune periphery. Considering the ongoing controversy about the involvement of B cells and in particular the formation of B cell aggregates in the brains of progressive MS patients, an in-depth understanding of the effects of anti-CD52 antibody treatment on the B cell compartment in the CNS itself is desirable.MethodsWe used myelin basic protein (MBP)-proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) in C57BL/6 (B6) mice as B cell-dependent model of MS. Mice were treated intraperitoneally either at the peak of EAE or at 60 days after onset with 200 μg murine anti-CD52 vs. IgG2a isotype control antibody for five consecutive days. Disease was subsequently monitored for 10 days. The antigen-specific B cell/antibody response was measured by ELISPOT and ELISA. Effects on CNS infiltration and B cell aggregation were determined by immunohistochemistry. Neurodegeneration was evaluated by Luxol Fast Blue, SMI-32, and Olig2/APC staining as well as by electron microscopy and phosphorylated heavy neurofilament serum ELISA.ResultsTreatment with anti-CD52 antibody attenuated EAE only when administered at the peak of disease. While there was no effect on the production of MP4-specific IgG, the treatment almost completely depleted CNS infiltrates and B cell aggregates even when given as late as 60 days after onset. On the ultrastructural level, we observed significantly less axonal damage in the spinal cord and cerebellum in chronic EAE after anti-CD52 treatment.ConclusionAnti-CD52 treatment abrogated B cell infiltration and disrupted existing B cell aggregates in the CNS.

Highlights

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) for which several new treatment options were recently introduced
In order to determine the extent of depletion of circulating lymphocytes after anti-mCD52 treatment, we performed flow cytometry on tail vein blood obtained 10.37 ± 0.18 days post-treatment and we determined the percentages of viable CD4+ T cells and CD19+ B cells
We have previously shown that treatment with the S1P1 receptor agonist fingolimod, which inhibits lymphocyte egress from secondary lymphoid organs, prevented the development of B cell aggregates in the CNS in acute MBP-proteolipid protein (PLP) fusion protein (MP4)-induced EAE, while it did not affect existing infiltrates in the chronic stage of the disease [43]

Summary

Introduction

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) for which several new treatment options were recently introduced. The autoimmune pathology of MS has been considered to be mainly T cell-driven [3], while more recent clinical observations as well as experimental data suggest a close interaction of T cells and B cells. Along these lines, depositions of immunoglobulins and of complement components have been found in active demyelinating brain lesions of MS patients [4], and oligoclonal bands (OCB) in the cerebrospinal fluid (CSF) of the majority of patients demonstrate local antibody production. The overall clinical efficacy of B cell-depleting anti-CD20 antibody treatment and the therapeutic success of plasma exchange in a subset of MS patients with severe corticosteroid-resistant relapses further underlines the involvement of B cells in the immunopathology of MS [6, 7]

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