Adjuvant-free animal model for studying CNS autoimmunity

Summary. Multiple sclerosis (MS) is a chronic inflammatory, demyelinating, and neurodegenerative disorder of the central nervous system. More than 2.5 million people suffer from this disease worldwide. It is assumed that the autoimmune response to myelin antigens in the CNS is the main cause of the disease. Experimental autoimmune encephalomyelitis (EAE) is a widely used animal model for studying MS. However, EAE models resemble only particular aspects of MS pathogenesis. EAE is classically induced with the CNS antigens emulsified in complete Freund’s adjuvant (CFA). CFA consists of paraffin oil supplemented with Mycobacterium, and its application potentiates the innate immune response and prolongs the presence and effective transport of antigen in the lymphatic system. However, CFA has a confounding influence on the results and the translational capacity as a multiple sclerosis model. Our group has successfully excluded CFA from the immunization regime. In a recent study, we compared clinical, histological, cellular, and molecular properties between spinal cord homogenate (SCH) and SCH+CFA immunized Dark Agouti rats. We have observed a higher clinical score in rats without CFA, and a more significant number of immune cell infiltrates at the peak of EAE in the same animals. Further, a stronger myelin basic protein-specific T cell immune response is evoked in the draining lymph nodes of CFA-free compared to CFA immunized rats. In the CNS, a high abundance of CD8+ T cells is detected at the onset of the disease. Also, enrichment in CD8+ and CD4+ macrophages was observed in the CNS during EAE. Therefore, CFA-free EAE is a reliable model for studying CNS autoimmunity.