Development of a Diagnostic Autoantibody Assay to a Consensus Motif for the Risk Prediction of Epstein-Barr Virus–Related Multiple Sclerosis

BACKGROUND AND OBJECTIVES: Multiple sclerosis (MS) is a chronic progressive, demyelinating autoimmune CNS disease. Autoantibodies to the motif P-(SA)-x-(SGA)-R-(SN)-(LRKH) are a class of predictive markers specific to MS that could add to emerging diagnostic criteria for MS. In this study, we describe the discovery of an MS patient-derived monoclonal antibody (mAb) specific to this motif from memory B cells, and we develop a proof-of-principle autoantibody test to report the prevalence of seropositivity, predict MS early in disease, and identify underlying tolerance-breaking antigens in Epstein-Barr virus (EBV) and the CNS. METHODS: Peptide tetramers containing the motif were used to screen activated memory B cells, collected from a patient with MS, on the Beacon Optofluidic system. A mAb to the motif and serum samples from clinically diagnosed patients with MS and healthy controls were used to qualify a Luminex xMAP autoantibody serologic test. Antigen discovery methods included phage-immunoprecipitation sequencing (PhIP-Seq), biolayer interferometry, human protein microarrays, isoelectric focusing gels and blots, and immunofluorescence staining of mouse brain cell cultures. RESULTS: A mAb cloned from an MS patient's memory B cells binds diverse peptides containing the MS signature motif with affinities ranging from 2 to 25 nM. Consensus peptides defined by alanine scanning PhIP-Seq were used to develop an autoimmune IgG test with a sensitivity equivalent to 0.5 ng/mL mAb, a precision of