MOG antibody non-P42 epitope is associated with a higher risk of relapse in paediatric MOGAD

BACKGROUND: Biomarkers for predicting myelin oligodendrocyte glycoprotein antibody (Ab)-associated disease (MOGAD) clinical course are still missing. Binding capacity to a mutant MOG protein variant (MOG-P42S; non-P42) was shown to correlate with an increased relapse risk in adult patients.The objective of our study was to assess the frequency of binding to the non-P42 MOG variant in a cohort of paediatric MOGAD and to investigate its association with specific clinical profiles and disease course. METHODS: We included children with MOG-Ab seropositive samples collected after their first demyelinating episode from five different centres. We performed live cell-based assays with native full-length MOG (MOG-FL) and mutant MOG-P42S and correlated the results with clinical data. RESULTS: Of the 81 MOG-FL identified patients serum, 40 bound the non-P42 MOG. Non-P42 patients exhibited an earlier median age of onset (p=0.002). Phenotype distribution was different between groups (p=0.001), with non-P42 patients predominantly exhibiting acute disseminated encephalomyelitis phenotype. Notably, the non-P42 group was associated with a higher relapse rate (relative rate: 2.6 (95% CI 1.1 to 6.2), p=0.03), adjusted for clinical phenotype. CONCLUSION: Non-P42 is a promising biomarker for predicting relapse in paediatric MOGAD patients.