Autoimmune responses to myelin-associated proteins as diagnostic and prognostic biomarkers of relapsing-remitting multiple sclerosis: Associations with human herpesvirus-6 and Epstein-Barr virus reactivation

• IgG, IgA, and IgM against myelin proteins accurately distinguish RRMS from controls with 96.6% accuracy. • Elevated IgG-MBP, IgA-MOG, and IgM-MAG correlate with higher EDSS and MSSS scores. • EBV and HHV-6 reactivation drive autoimmune responses targeting myelin proteins in RRMS. • Author’s contributions. • AFA supervised the blood sample collection and patient procedures. Serum biomarker quantification was performed by AV and EV at Immunosciences Lab, who assumed the costs of testing. MM conducted the statistical analysis. MM and AV created the visualizations. AFA drafted the initial manuscript, which was reviewed and revised by MM, AV, EV, JL and YZ. All authors approved the last version of the manuscript. The pathogenesis of relapsing-remitting multiple sclerosis (RRMS) is linked to autoimmune attacks against myelin proteins, and reactivation of Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6). However, the connection between viral reactivation and autoimmune biomarkers has remained unclear. To investigate immunoglobulin (Ig)G/IgA/IgM responses targeting myelin-related proteins in association with EBV and HHV-6 replication markers in RRMS. We recruited 55 patients with RRMS and 63 healthy controls and assessed IgG/IgA/IgM responses against seven myelin-related components, as well as EBV nuclear antigen 1 (EBNA-1) and deoxyuridine-triphosphate nucleotidohydrolase (dUTPases). Disability was evaluated using the Expanded Disability Status Scale (EDSS) and disease progression using the Multiple Sclerosis Severity Score (MSSS). IgG/IgA/IgM levels targeting seven myelin-related proteins were significantly higher in RRMS than in controls. IgG against myelin basic protein (MBP) (IgG-MBP), IgM-myelin-associated glycoprotein (IgM-MAG)-37–60, IgA-MBP, and IgA-myelin-oligodendrocyte-glycoprotein (IgA-MOG-31–55) distinguished RRMS from controls with a predictive accuracy of 96.6 % (sensitivity = 95.7 %, specificity = 95.2 %) and an area under the ROC curve of 0.991. A large part of the variance in the EDSS (around 75 %) and MSSS score (62.8 %) was explained by IgG-MBP, IgM-MBP, IgA-MOG-31–55, and IgM-MAG. Part of the variance (47.4 %) in the IgG/IgA/IgM responses to myelin-related proteins was explained by immune responses to EBNA and dUTPases of EBV and HHV-6. Autoimmune reactivities targeting myelin-related proteins are valuable biomarkers of RRMS and the severity and progression of RRMS. Reactivation of EBV and HHV-6 may trigger or maintain these autoimmune responses thereby impacting disease progression.