An optimized and validated protocol for inducing chronic experimental autoimmune encephalomyelitis in C57BL/6J mice

Background: Myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis (EAE) is the most commonly used animal model of multiple sclerosis. However, variations in the induction protocol can affect EAE progression, and may reduce the comparability of data. Optimized method: In the present study, we investigated the influence of the different components used for EAE induction in C57BL/6J mice on disease progression. MOG(35-55)-induced chronic EAE in C57BL/6J mice has been applied as a model to challenge optimal pertussis toxin (PTx) dosing, while considering variations in batch potency. Results: We demonstrate that the dosage of PTx, adjusted to its potency, influences EAE development in a dose -dependent manner. Our data show that with our protocol, which considers PTx potency, C57BL/6J mice consistently develop symptoms of EAE. The mice show a typical chronic course with symptom onset after 10.5 +/- 1.08 days and maximum severity around day 16 postimmunization followed by a mild remission of symptoms. Comparison with existing methods: Previously studies reveal that alterations in PTx dosing directly modify EAE progression. Our present study highlights that PTx batches differ in potency, resulting in inconsistent EAE induction. We also provide a clear protocol that allows a reduction in the number of mice used in EAE experiments, while maintaining consistent results. Conclusion: Higher standards for comparability and reproducibility are needed to ensure and maximize the generation of reliable EAE data. Specifically, consideration of PTx potency. With our method of establishing consistent EAE pathogenesis, improved animal welfare standards and a reduction of mice used in experimen-tation can be achieved.