Successful therapy with anti-CD20 monoclonal antibodies (mAbs) has reinforced the key role of B cells in the immunopathology of multiple sclerosis. While treatment with currently available anti-CD20 mAbs results in rapid and robust elimination of vascular B cells, B cells residing within compartments of the central nervous system (CNS) are not well targeted. The aim of this study was to determine the effects of a novel class of anti-CD20 mAbs on vascular and extravascular CNS-infiltrating B cells in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis.
Male double transgenic hCD20xhIgR3 mice and male wild-type C57BL/6 (B6) mice were injected with human myelin oligodendrocyte glycoprotein (MOG)1–125 to induce chronic EAE. On days 19, 22, and 25 after immunization, the hCD20xhIgR3 mice were injected intravenously with an anti-human CD20 mAb (5 mg/kg), either rituximab (a type I anti-CD20 mAb) or obinutuzumab (a type II humanized anti-CD20 mAb). The B6 mice received a dose of the murine anti-mouse CD20 antibody 18B12. Development of EAE was assessed daily. Seven days after the last injection, mice were euthanized, splenic B-cell subsets were analyzed by flow cytometry, and differential gene expression determined by single-cell RNA sequencing. Total serum immunoglobulin (Ig)G and anti-MOG1–125 IgG titers were measured by enzyme-linked immunosorbent assay. Reduction in CNS-infiltrated CD19+ and CD3+ cells was analyzed by immunohistochemistry, and ultrastructural CNS pathology was studied by transmission electron microscopy.
Treatment with either anti-CD20 mAb had no effect on the clinical course of the disease, animal weight, or serum antibody levels. Obinutuzumab was superior to rituximab in reducing both splenic and CNS-infiltrated B cells. At the single-cell level, obinutuzumab showed pronounced effects on germinal center B cells as well as on CD4+ T cells, which acquired a regulatory-gene signature. In addition, obinutuzumab had beneficial effects on spinal cord myelination. B-cell depletion rates in the 18B12/B6 model were comparable with those observed in obinutuzumab-treated hCD20xhIgR3 mice.
Our results demonstrate differential effects of anti-CD20 mAbs on peripheral immune response and CNS pathology, with type II antibodies potentially being superior to type I in the depletion of tissue-infiltrating B cells.