Mechanisms of Innate and Adaptive Immune Responses to AAV-FVIII Gene Transfer

项目总结/摘要 腺相关病毒（AAV）载体肝内基因转移治疗X连锁出血 血友病已经进入多个I/II期和4个III期临床试验，所有这些试验都寻求稳定恢复 通过在肝细胞中的长期表达来止血。与其他治疗方式不同，基因治疗 治疗有可能治愈疾病，从而消除了频繁注射凝血剂的需要。 因素或其他药物。然而，实现持续纠正贫困一直是一个重大挑战。 血友病A（凝血因子VIII缺乏，约占血友病患者的80%）。FVIII是 很难在高层次上表达。因此，需要高载体剂量。尽管如此，正常人中的FVIII活性 达到了超生理范围。虽然这一结果在2017年得到了广泛的庆祝， 因为很明显，在这些高水平FVIII表达是不稳定的。在所有患者中， 在第2-4年观察到，下降到治疗范围的低端，引起了对持久性的严重关切。 其他研究开始显示类似的结果，而更低的FVIII水平，由更温和的载体 剂量，似乎持续。肝毒性和类固醇治疗是第一次治疗期间的典型特征。 高剂量基因转移的一年现在人们越来越认识到，基础科学研究对 达到安全有效。我们的初步数据强烈支持这一假设，即密切相关的 对FVIII和载体的细胞应激和先天免疫应答（其实质上受载体的影响） 设计）限制了治疗表达的稳定性，也驱动了适应性免疫。已充分证实 高水平的FVIII表达导致未折叠蛋白在ER中的积累，细胞应激， 毒性、聚集和未折叠蛋白反应（UPR）的诱导。我们的数据表明，肝AAV 基因转移虽然有可能诱导对转基因产物的免疫耐受，但也激活了先天性免疫耐受。 免疫途径和细胞因子反应，可导致细胞免疫反应。AAV载体引入 病原体相关分子模式（PAMPs）。细胞应激和先天免疫是相互关联的， 损伤相关分子模式（DAMP）驱动免疫。事实上，我们看到FVIII表达逐渐丧失， 在血友病A小鼠模型中，尽管缺乏抗体形成。该项目具体建议：i） 定义“亚基因组颗粒”引起对AAV的先天性和适应性免疫应答的机制- 原代人肝细胞/先天免疫细胞和鼠模型中的FVIII; ii）定义免疫应答 作为载体和转基因设计的函数的肝AAV基因转移中针对FVIII的机制;和iii） 定义导致FVIII表达逐渐丧失的机制，并制定持续治疗方案 和免疫耐受性。

PROJECT SUMMARY/ABSTRACT Hepatic in vivo gene transfer with adeno-associated viral (AAV) vectors for treatment of the X-linked bleeding disorder hemophilia has advanced to multiple Phase I/II and 4 Phase III clinical trials, all seeking to stably restore hemostasis through long-term expression in hepatocytes. As opposed to other treatment modalities, gene therapy has the potential to cure the disease, thus eliminating the need for frequent injections of coagulation factors or other medicines. However, it has been a major challenge to accomplish sustained correction of hemophilia A (deficiency in coagulation factor VIIII, FVIII, representing ~80% of hemophilic patients). FVIII is difficult to express at high levels. Hence, high vector doses are required. Nonetheless, FVIII activity in the normal to super-physiological range was achieved in clinical trial. While this result was widely celebrated in 2017, it has since become clear that FVIII expression at these high levels is not stable. A gradual decline in all patients was observed in years 2-4, down to the lower end of the therapeutic range, raising serious concerns about durability. Other studies begin to show similar outcome, whereas lower FVIII levels, resulting from more modest vector doses, appear to be sustained. Hepatotoxicity and treatment with steroids were typical features during the first year of high-dose gene transfer. There is now a growing realization that basic science studies are paramount to achieve safety and efficacy. Our preliminary data strongly support the hypothesis that the closely interlinked cellular stress and innate immune responses to FVIII and the vector (which are substantially impacted by vector design) limit stability of therapeutic expression and also drive adaptive immunity. It is well established that expression of FVIII at high levels results in the accumulation of unfolded protein in the ER, cellular stress and toxicity, aggregation, und induction of the unfolded protein response (UPR). Our data show that hepatic AAV gene transfer, while having the potential to induce immune tolerance to transgene products, also activates innate immune pathways and cytokine responses that can lead to cellular immune responses. AAV vectors introduce pathogen-associated molecular patterns (PAMPs). Cellular stress and innate immunity are interlinked, and damage-associated molecular patters (DAMPs) drive immunity. In fact, we see gradual loss of FVIII expression in a hemophilia A mouse models despite a lack of antibody formation. This project specifically proposes to: i) Define the mechanisms by which “subgenomic particles” cause innate and adaptive immune responses to AAV- FVIII in primary human hepatocytes/innate immune cells and in murine models; ii) define immune response mechanisms against FVIII in hepatic AAV gene transfer as a function of vector and transgene design; and iii) define the mechanisms that lead to gradual loss of FVIII expression and develop protocols for sustained therapy and immune tolerance.