Development of Animal Models of Anti-MuSK Myasthenia

描述（由申请人提供）：抗肌肉特异性激酶（MuSK）肌无力症（AMM）是一种新发现的神经肌肉传递疾病，其特征是疲劳无力、肌肉萎缩和针对MuSK的循环抗体（Abs）， MuSK是一种跨膜受体激酶，对该突触的形成至关重要。AMM不同于重症肌无力（MG）的严重程度，更局灶性的虚弱和相关的肌肉萎缩。对于其发病机制或病因知之甚少，包括是否伴随有对MuSK的细胞免疫反应以及异常神经肌肉传递和肌肉萎缩的机制。这种疾病的治疗方法几乎完全未知。目前的临床实践是使用（血清阳性）MG的治疗方案。然而，积累的数据表明，许多这些治疗方法，如胆碱酯酶抑制剂、胸腺切除术和免疫球蛋白输注，效果最低。我们的总体目标是开发更具体和有效的AMM治疗方法。为了实现这一目标，我们在Lewis大鼠身上建立了一种AMM动物模型，称为实验性AMM (EAMM)，作为分析人类疾病潜在致病机制的平台，包括在神经肌肉连接处（NMJ）活跃的机制和对该突触的免疫攻击的机制。通过单次注射该蛋白的MuSK 60亚型诱导的模型疾病非常严重，导致疲劳性无力和肌肉萎缩，导致27天内死亡，同时NMJ的突触后和突触前成分严重破坏。拟议的研究将解决AMM是一种抗体介导的疾病的假设，而MuSK抗体改变了成熟NMJ中MuSK的功能，从而诱发了这种疾病的特征——无力和肌肉萎缩。该假设的一个推论是，除了在NMJ发育中已知的作用外，MuSK在维持成熟突触方面也起着重要作用。第一个具体目标是通过NMJ的临床、电生理和形态学研究，分析EAMM中NMJ的致病机制，重点研究MuSK激活的信号转导途径。第二个特定目的是分析EAMM自身免疫反应的性质，通过评估这些动物对MuSK的Ab和T细胞反应，以及研究EAMM血清中提取的免疫球蛋白和EAMM脾脏和淋巴结中的淋巴细胞对疾病的被动转移。

DESCRIPTION (provided by applicant): Anti-muscle-specific kinase (MuSK) myasthenia (AMM) is a newly-described disease of neuromuscular transmission characterized by fatigable weakness, muscle wasting and circulating antibodies (Abs) to MuSK, a transmembrane receptor kinase crucial to the formation of this synapse. AMM differs from myasthenia gravis (MG) in its severity, the more focal nature of the weakness and the associated muscle wasting. Remarkably little is known concerning its pathogenesis or etiology, including whether there is an accompanying cellular immune response to MuSK and what mechanisms underlie the abnormal neuromuscular transmission and muscle wasting. The treatment of this disease is nearly completely unknown. Current clinical practice is to use the treatment protocols developed for (seropositive) MG. However, data have accumulated demonstrating that many of these treatments, e.g. cholinesterase inhibitors, thymectomy and immunoglobulin infusion, are minimally effective. Our overall goal is to develop more specific and effective treatments of AMM. To accomplish this, we have produced an animal model of AMM in Lewis rats, termed experimental AMM (EAMM), to serve as a platform for analysis of the pathogenic mechanisms underlying the human disease, including the mechanisms active at the neuromuscular junction (NMJ) and the mechanisms underlying the immune attack on this synapse. The model disease, which is induced by a single injection of the MuSK 60 isoform of the protein is quite severe, resulting in fatigable weakness and muscle wasting leading to death within 27 days, along with severe disruption of both the postsynaptic and presynaptic components of the NMJ. The proposed studies will address the hypothesis that AMM is an Ab-mediated disease and that the MuSK Abs alter the function of MuSK at the mature NMJ, thereby inducing the weakness and muscle wasting that are characteristic of this disease. A corollary of that hypothesis is that MuSK, in addition to its known role in the developing NMJ, plays an important role in the maintenance of the mature synapse. The first specific aim involves the analysis of the pathogenic mechanisms operative at the NMJ in EAMM through clinical, electrophysiologic and morphologic studies of the NMJ, focusing on the signal transduction pathways activated by MuSK. The second specific aim analyzes the nature of the autoimmune response in EAMM by assessing both the Ab and T cell responses to MuSK in these animals, along with studies of passive transfer of the disease with both immunoglobulin derived from EAMM serum and lymphocytes from EAMM spleens and lymph nodes. PUBLIC HEALTH RELEVANCE: Relevance: Remarkably little is known concerning the pathogenesis or etiology of anti-muscle-specific kinase (MuSK) myasthenia (AMM), including whether the MuSK Abs are, in fact, pathogenic, whether there is an accompanying cellular immune response and what mechanisms underlie the abnormal neuromuscular transmission and muscle wasting. The treatment of this disease is also nearly completely unknown. This project will provide the means for determining the underlying mechanisms in AMM in order to identify new treatments and provide an animal model for testing these treatments.