Mechanisms for immune tolerance in Pompe Disease

新生儿Pompe病筛查是可行的，使用人酸α葡萄糖苷酶（hGAA）的酶替代疗法（ERT）是有效的，ifERT是早期开始的，并且存在免疫耐受。了解庞贝病对hGAA免疫耐受的机制将指导庞贝病和其他溶酶体贮积性疾病的未来临床试验设计。我们建议使用一种创新的策略，在肝脏中表达hGAA，同时导致Pompe病小鼠对hGAA的免疫耐受和ERT的持久疗效。利用这些模型系统，我们将研究gaa缺失小鼠诱导免疫耐受所需的免疫机制，并评估免疫耐受对ERT或基因治疗效果的影响。这种策略可以很容易地转化为临床应用，因为与其他基因治疗方法不同，载体剂量非常低，风险同样很低，潜在的益处很大。一般假设：肝脏特异性表达hGAA可诱导免疫耐受，提高替代疗法（ERT和/或基因治疗）对Pompe病的疗效。特异性目的1将评估Pompe病诱导hGAA免疫耐受的机制。肝特异性表达hGAA与耐受性AAV载体将在gaa缺失小鼠中建立免疫耐受性。对hGAA的免疫耐受将通过重组hGAA和佐剂的挑战来证明。适应性免疫反应的关键参与者，包括Treg细胞和NKT细胞的作用，将在存在或不存在免疫耐受的情况下进行检查。Treg细胞耗竭会阻止对hGAA的免疫耐受。特异性目标2将证明hGAA治疗的疗效可以通过调节免疫应答hGAA来提高。用致耐受性载体进行减剂量实验，将确定实现对hGAA免疫耐受的较低阈值。免疫耐受将增强ERT的长期疗效，因为适应性免疫反应将被免疫原性较低的转基因所废除。对hGAA免疫耐受的益处将通过评估接受低剂量耐受性载体的gaa缺失小鼠的ERT来证明。我们将评估一种创新的免疫调节基因治疗方法，包括通过给小鼠低剂量的耐受性载体对hGAA蛋白脱敏，这些小鼠先前形成了hGAA抗体。脱敏可防止抗体阳性gaa缺失小鼠ERT期间过敏性反应的死亡率。这些比较将指导临床前实验进一步免疫调节基因治疗庞贝病和其他溶酶体储存疾病。

REVISED 3/21/2009 - Newborn screening for Pompe disease is available and enzyme replacement therapy (ERT) with human acid alpha glucosidase (hGAA) is effective, ifERT is started early and immune tolerance is present. Knowledge of the mechanisms for immune tolerance to hGAA in Pompe disease will guide the design of future clinical trials for Pompe disease and other lysosomal storage disorders.Wepropose to use an innovative strategy to express hGAA in the liver that simultaneously leads to immune tolerance to hGAA and long lasting efficacy from ERT in Pompe disease mice. Using these model systems, we will investigate the immunologic mechanisms required to induce immune tolerance in GAA-null mice, and evaluate the impact of immune tolerance on efficacy of ERT or gene therapy. This strategy can be translated to clinical applications very readily, because unlike other gene therapy approaches the vector dose is very low, risks are similarly low, and potential benefits are great.General Hypothesis: Liver-specific expression of hGAA will induce immune tolerance and enhance the efficacy of replacement therapy (ERT and/or gene therapy) in Pompe disease. Specific Aim 1 will evaluate mechanisms responsible for the induction of immune tolerance to hGAA by Pompe disease. Liver-specific expression of hGAA with a tolerogenic AAV vector will establish immune tolerance in GAA-null mice. Immune tolerance to hGAA will be demonstrated via challenges with recombinant hGAA and adjuvant. The role of key players of the adaptive immune response, including Treg cells and NKT cells, will be examined in the presence or absence of immune tolerance. Treg cell depletion will prevent immune tolerance to hGAA. Specific Aim 2 will demonstrate that efficacy of the hGAA therapy can be improved by modulating the immune response to hGAA. A dose reduction experiment with tolerogenic vector will determine a lower threshold for achieving immune tolerance to hGAA. Long-term efficacy from ERT will be enhanced by immune tolerance, because adaptive immune responses will be abrogated by the less immunogenic transgene. The benefit of immune tolerance to hGAA will be demonstrated by evaluating ERT in GAA-null mice that received low-dose tolerogenic vector. We will evaluate an innovative approach to immunodulatory gene therapy, consisting of desensitization to the hGAA protein by the administration of low-dose tolerogenic vector to mice that previously formed antibodies to hGAA. Desensitization prevents mortality from anaphylaxis during ERT in antibody-positive GAA-null mice. These comparisons will guide preclinical experiments to further immunomodulatory gene therapy in Pompe disease and other lysosomal storage disorders.