B cell-specific mAb-siRNA conjugates improve experimental myasthenia.

Myasthenia gravis (MG) is a debilitating autoimmune disease characterized by muscle fatigue and weakness caused by autoantibody- and complement-mediated damage to the neuromuscular junction. This study sought to compare the efficacy of unique sets of monoclonal antibody-siRNA conjugates, individually (mono) or in combination (duo), against the crucial receptors predominantly or solely expressed on two subsets of B cells-plasma B cells and their precursor (transitional mature B) cells in a mouse model of MG. At the optimized doses, the conjugates, likely due to the combined activities of mAb and siRNA, substantially decreased the expression levels of CD268 (B cell-activating factor receptor) in mature B cells and CD269 (B-cell maturation antigen) in plasma cells concomitantly with reducing the levels of acetylcholine receptor (AChR)-specific autoantibodies. PEGylation, but not pretreatment with an antibody against type 1 interferon receptor, further improved duoconjugate-induced reduction in the autoantibody levels. Our results show that the duoconjugate treatment significantly improved the clinical symptoms of MG, consistent with the preservation of bungarotoxin-bound functional AChRs. In the future, developing similar target-specific combination molecules can potentially turn into a new and effective therapeutic approach for MG.

A Bead-Based Nonradioactive Immunoassay for Autoantibody Testing in a Mouse Model of Myasthenia Gravis.

Serological testing for anti-acetylcholine receptor (AChR) autoantibodies is not only crucial for the diagnosing, disease monitoring, and treatment management of patients with myasthenia gravis (MG) but also for preclinical studies utilizing MG disease models. However, there are no specific guidelines on which methods to use in clinical diagnostic or research laboratories to detect or quantify any MG-specific autoantibodies. Conventional autoantibody assays, particularly those for anti-AChR antibodies, are varied and mostly laboratory-specific. Here, we report our new nonradioactive immunoprecipitation-immunoblotting method for assessing autoantibodies (anti-AChR antibodies) in a mouse model of MG. This simple, efficient, reproducible, and cost-effective assay appears superior to the enzyme-linked immunosorbent assay but comparable to the radioimmunoprecipitation or cell-based assay in specificity and sensitivity. Thus, the newly developed assay can serve as a valuable alternative to classical assays and is suitable for routine testing of AChR-specific autoantibodies in preclinical studies. The further optimization of our assay may facilitate its application in the diagnosis and therapeutic management of patients with MG.

Histone Deacetylase Isoforms Differentially Modulate Inflammatory and Autoantibody Responses in a Mouse Model of Myasthenia Gravis.

Myasthenia gravis (MG) is an autoimmune disease characterized by chronic muscle fatigue and weakness caused by autoantibodies and complement-mediated damage at neuromuscular junctions. Histone deacetylases (HDACs) are crucial epigenetic regulators of proinflammatory gene expression; however, it is unclear whether HDACs modulate chronic inflammation or autoantibody production associated with MG pathogenesis. We examined expression profiles and serum levels of key inflammatory cytokines (IL-6 and IL-21) and acetylcholine receptor (AChR)-specific autoantibodies following pharmacological inhibition of key HDAC isoforms in a mouse model of MG. We found that HDAC inhibition significantly reduced the production of IL-6, but not IL-21, in AChR-stimulated PBMCs and splenocytes (n = 5 per group). Trichostatin (pan-HDAC inhibitor) treatment of MG-PBMCs (n = 2) also exhibited reduced production of induced IL-6. Although HDAC1 inhibition lowered IL-6 levels the most, HDAC2 inhibition depleted intracellular IL-6 and markedly reduced serum anti-AChR IgG2b in EAMG mice. The transcriptomic profiling and pathway mapping also revealed that autoimmunity-linked, major cell signaling pathways were differentially altered by HDAC1/2 inhibition. HDAC inhibition-mediated reduction in IL-6 and autoantibody levels also correlated with milder disease and preservation of muscle AChR in the treated mice. Overall, our findings revealed isoform-specific functional variance of HDACs in reducing inflammation and identified HDAC-regulated many genes underlying specific inflammatory and autoantibody pathways in EAMG. Thus, the study provides a rationale for further research to evaluate the HDACs or their gene targets as a potential adjunct treatment for MG.