Active Immunization for Inducing Autoimmune Muscle-Specific Kinase (MuSK) Myasthenia Gravis in Mice

Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction. While most MG patients produce autoantibodies against the acetylcholine receptor (AChR), a subset of patients exhibits autoantibodies targeting the muscle-specific kinase (MuSK). MuSK MG is characterized by severe muscle weakness, treatment-resistant clinical manifestations, and myasthenic crises, often necessitating mechanical ventilation. Consequently, patients frequently require prolonged use of immunosuppressants, which are associated with long-term adverse effects. Given the severity and rarity of MuSK-MG, developing an experimental animal model is crucial for advancing new treatment modalities and a deeper understanding of the underlying pathophysiological mechanisms. Experimental autoimmune myasthenia gravis (EAMG) serves as an animal model for MuSK-MG, effectively but partly mimicking the clinical and immunological features of human MG. The induction of autoimmune animal models can be achieved through active or passive immunization. In the herein presented experimental protocol, active immunization was employed by subcutaneously administering the purified extracellular domain of human MuSK emulsified in complete Freund's adjuvant with heat-killed Mycobacterium tuberculosis. Immunization was performed at four sites, followed by a booster injection of MuSK on the 28th day. This adjuvant with M. tuberculosis enables activation of the immune system through TLR4 and enhanced phagocytosis of the administered antigen. This article comprehensively details the development and characterization of MuSK-EAMG from inception to conclusion.