Immune Responses To AAV-Mediated FIX Gene Transfer

描述（由申请人提供）：本申请的目的是进一步表征可导致消除重组腺相关病毒（rAAV）转导细胞的免疫应答。大多数人天然暴露于AAV-2和辅助病毒，因此对AAV-2具有免疫记忆。记忆性T细胞可以比初始淋巴细胞更容易被触发，这在迄今为止进行的临床前动物实验中没有考虑到。对rAAV介导的基因转移的免疫学后果的担忧通过临床试验的结果得到证实，在该临床试验中，将人血友病B患者用rAAV-2-F.IX载体输注到肝脏中。只有一名患者达到治疗水平的F.IX，这是持续4周，然后开始下降。与此同时，患者出现转氨酶升高，在F.IX水平降至基线水平后消退。总的来说，患者的临床病程与rAAV转导的肝细胞的免疫介导的破坏相容。此后产生的其他数据证实了我们的假设，即由自然感染诱导的AAV-2特异性T细胞可以引起rAAV转导的肝细胞的消除。为了进一步定义在模拟人类血友病患者的条件下对AAV和rAAV编码的转基因的免疫应答，然后设计出明智的策略来规避这些问题，我们提出了由2个核心支持的4个相互关联的项目。项目1将定义人类和非人灵长类动物中T细胞对AAV衣壳蛋白的应答，并评估其对肝脏rAAV介导的基因转移的影响。项目2将阐明预先存在的AAV-2特异性T细胞介导的免疫对小鼠肝脏rAAV载体介导的基因转移的影响。项目3将定义调节性免疫应答，其防止诱导CD 8 + T细胞对rAAV编码的转基因产物的应答。项目4将重点关注调节性T细胞消除rAAV介导的基因转移的不必要的免疫反应的潜在用途。这些项目将得到行政核心和载体核心的支持，前者将提供必要的监督，后者将为研究人员提供纯化和质量受控的载体。

DESCRIPTION (provided by applicant): The goal of this application is to further characterize immune responses that can cause the elimination of recombinant adeno-associated virus (rAAV) transduced cells. Most humans are naturally exposed to AAV-2 together with a helper virus and thus have immunological memory to AAV-2. Memory T cells can be triggered more readily than naive lymphocytes, which was not taken into account by pre-clinical animal experiments conducted thus far. Concerns about immunological consequences of rAAV-mediated gene transfer were substantiated by the outcome of a clinical trial in which human hemophilia B patients were infused into the liver with rAAV-2-F.IX vectors. Only one patient achieved therapeutic levels of F.IX, which were sustained for 4 weeks and then started to decline. At the same time the patient developed a transaminitis, which resolved after F.IX levels decreased to baseline levels. Overall, the patient's clinical course was compatible with immune-mediated destruction of rAAV-transduced hepatocytes. Additional data generated since substantiated our hypothesis that AAV-2-specific T cells induced by a natural infection can cause elimination of rAAV-transduced hepatocytes. To further define immune responses to AAV and rAAV-encoded transgenes under conditions thai mimic those of human hemophilia patients and to then devise informed strategies to circumvent such problems we are proposing 4 interlinked Projects supported by 2 Cores. Project 1 will define T cell responses to AAV capsid proteins in humans and in non-human primates and assess their effect on hepatic rAAV-mediated gene transfer. Project 2 will elucidate the effect of pre-existing AAV-2-specific T cell-mediated immunity on hepatic rAAV vector-mediated gene transfer in mice. Project 3 will define regulatory immune responses that prevent induction of CD8+ T cell responses to a rAAV-encoded transgene product. Project 4 will focus on the potential use of regulatory T cells to ablate unwanted immune responses to rAAV-mediated gene transfer. The projects will be supported by an Administrative Core, which will provide the needed oversight, and a Vector Core, which will provide the investigators with purified and quality controlled vectors.