Effects of Ocrelizumab on B-cell Tolerance Defect in Relapsing Multiple Sclerosis

B-cells have an important role in the pathogenesis of multiple sclerosis (MS). Ocrelizumab, a medication that targets B-cells have been found to be highly effective in stopping the disease activity in relapsing-remitting MS. The efficacy of ocrelizumab might be related to the specific pattern of B-cell tolerance defect in patients with MS and the potential of its normalization with treatment with ocrelizumab. By analyzing the reactivity of recombinant antibodies expressed from single B-cells, the investigators' collaborators have demonstrated that the pattern of B-cell tolerance defect is different in people with MS who only display an impaired removal of developing autoreactive B-cells in the periphery while central B-cell tolerance in the bone marrow is functional in most patients. In contrast, patients with rheumatoid arthritis (RA), type-1 diabetes (T1D) or Sjögren's syndrome (SS) show defective central and peripheral B-cell tolerance checkpoints. As a consequence, while anti-B-cell therapy does not correct defective early B-cell tolerance checkpoints in T1D and only temporarily slows down autoimmune processes before newly generated autoreactive B-cells likely induce patient relapse, the investigators postulate that the efficacy of ocrelizumab in MS may be linked to normal central B-cell tolerance and the production of a normal B-cell and T-cell compartment after ocrelizumab therapy. In an open-label study, 10 patients with relapsing MS will be treated with two courses of ocrelizumab and will be followed clinically and radiologically for at least two and a half years. Assessment of T and B-cell phenotypes and function at baseline and 18-24 months post-B-cell depletion will be the primary outcome of the study.