Conformational Antibodies to Proteolipid Protein-1 and Its Peripheral Isoform DM20 in Patients With CNS Autoimmune Demyelinating Disorders

Background and ObjectivesAntibodies to proteolipid protein-1 (PLP1-IgG), a major central myelin protein also expressed in the peripheral nervous system (PNS) as the isoform DM20, have been previously identified mostly in patients with multiple sclerosis (MS), with unclear clinical implications. However, most studies relied on nonconformational immunoassays and included few patients with non-MS CNS autoimmune demyelinating disorders (ADDs). We aimed to investigate conformational PLP1-IgG in the whole ADD spectrum. METHODS We devised a new live cell-based assay (CBA) for PLP1-IgG and used it to test 2 cohorts (retrospective exploratory, n = 284; prospective validation, n = 824) of patients with ADDs and controls (n = 177). Patients were classified as MS, neuromyelitis optica spectrum disorders (NMOSDs), myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD), and other ADDs. PLP1-IgG-positive samples were tested for IgG subclasses, DM20-IgG, and on rat brain tissue-based ...