PLP1 and subacute sclerosing panencephalitis: Overall, 4 of 37 MS CSF–derived rAbs and 0 of 18 inflammatory control CSF-derived rAbs (neuromyelitis optica [NMO], subacute sclerosing panencephalitis [SSPE], chronic meningitis, pediatric opsoclonus myoclonus syndrome) visibly bound to PLP1-transfected cells.