Flanagan, Eoin P.

Objective To estimate the prevalence, incidence, and disease burden of autoimmune seizures and epilepsies in Olmsted County. Methods We conducted a retrospective, population‐based study using the Rochester Epidemiology Project (1996–2019). Age‐ and sex‐standardized rates (2019 United States standard population) per 100,000 were calculated with 95% confidence intervals (95% CIs). Temporal trends in incidence were assessed over 3 consecutive 8‐year intervals (1996–2003, 2004–2011, and 2012–2019) using Poisson regression to estimate rate ratios per period and trend. Disability‐adjusted life years (DALYs), years of life lost (YLL), and years lived with disability (YLD) and 95% uncertainty intervals (95% UIs) were estimated for 2019. Results Twenty‐three patients were identified between 1996 and 2019. In 2019, the standardized prevalence of all autoimmune seizures and epilepsies was 9.81 (95% CI, 5.59–15.21) per 100,000, including autoimmune‐associated epilepsy (AAE) 7.27 (3.74–11.95) and acute symptomatic seizures secondary to autoimmune encephalitis (ASSAE) 2.55 (0.69–5.60). From 1996 to 2019, the standardized incidence was 0.50 (0.29–0.77) per 100,000 person‐years overall, with AAE 0.36 (0.19–0.59) and ASSAE 0.15 (0.05–0.30). By period, the standardized incidence of all autoimmune seizures and epilepsies suggested a rising trend from 0.28 (95% CI, 0.06–0.68) in 1996 to 2003 to 0.60 (95% CI, 0.24–1.12) in 2004–2011, then plateaued at 0.53 (95% CI, 0.21–1.00) in 2012 to 2019 (rate ratio per 8‐year interval 1.30, 95% CI, 0.71–2.38), largely driven by the seropositive subgroup. The standardized DALY rate was 26.27 (95% Uncertainly intervals [UI], 5.30–67.09) per 100,000 (YLL 20.07 [0.00–60.21] and YLD 6.20 [5.06–7.39]). Interpretation Although autoimmune seizures and epilepsies remain rare, they result in a disproportionately high disease burden. ANN NEUROL 2026;100:74–83

Autoantibodies contribute to many autoimmune diseases, yet there is no approved therapy to neutralize them selectively. A popular mouse model, experimental autoimmune encephalomyelitis (EAE), could serve to develop such a therapy, provided we can better understand the nature and importance of the autoantibodies involved. Here, we report the finding of autoantibody-secreting extrafollicular plasmablasts in EAE induced with specific myelin oligodendrocyte glycoprotein (MOG) antigens. Single-cell RNA sequencing reveals that these cells produce nonaffinity-matured IgG antibodies. These include pathogenic antibodies competing for shared binding space on MOG’s extracellular domain. Interestingly, the synthetic anti-MOG antibody 8-18C5 can prevent the binding of pathogenic antibodies from either EAE mice or people with MOG antibody disease. Moreover, an 8-18C5 variant carrying the NNAS mutation, which inactivates its effector functions, can reduce EAE severity and promote functional recovery. In brief, this study provides not only a comprehensive characterization of the humoral response in EAE models but also a proof of concept for a therapy to antagonize pathogenic anti-MOG antibodies.