Investigating anti-MOG antibody-associated disease with single cell technologies

Abstract

Myelin oligodendrocyte glycoprotein (MOG) is a transmembrane protein exclusively expressed in the central nervous system on oligodendrocytes and the myelin sheath. Anti-MOG antibodies are clinically associated with CNS demyelinating disorders including optic neuritis, transverse myelitis, and acute disseminated encephalomyelitis in children. Although these autoantibodies have been studied for their contribution to disease biology, due to the common use of polyclonal patient sera and similar materials, the specific role of anti-MOG antibodies cannot be deduced. In order to obtain the resolution necessary for this, the immune response must be broken down to the single cell level. Recombinant antibodies (rAbs) were cloned from single B cells of MOGAD patients and healthy controls and assessed for their binding to MOG using a live cell-based flow cytometry assay. Although MOG-specific rAbs were not identified, several B cell sequence features including IGHV4 family bias, complementarity determining region 3 (CDR3) length and mutation frequency were specific to the MOGAD repertoire, suggesting the presence of developmental abnormalities in these patients. Immunophenotypic analysis of B cells by flow cytometry also revealed reduced proportions of non-switched memory B cells in MOGAD patients compared to controls. scRNA-seq was also performed on three MOGAD patients and one healthy control, which confirmed the preferential use of IGHV4 and downregulation of non-switched memory B cells in MOGAD patients. Furthermore, MOGAD repertoires exhibited a kappa light chain preponderance, as well as CDR3 features reminiscent of a low affinity antibody response. Together, these findings corroborate the existence of defective tolerance maintenance mechanisms in MOGAD patients, which may also facilitate the development of low affinity, autoreactive antibodies.