Immune Responses To AAV-Mediated FIX Gene Transfer

描述(由申请人提供)：本申请的目标是进一步表征可导致重组腺相关病毒(RAAV)转导细胞消除的免疫反应。大多数人自然地接触到AAV-2和辅助病毒，因此对AAV-2有免疫记忆。记忆T细胞比幼稚淋巴细胞更容易被触发，这一点到目前为止还没有被进行的临床前动物实验考虑在内。一项临床试验的结果证实了人们对rAAV介导的基因转移的免疫学后果的担忧。在该临床试验中，人类血友病B患者将rAAV-2-F.IX载体注入肝脏。只有一名患者达到了治疗水平，持续了4周，然后开始下降。与此同时，患者出现了转氨炎，在F.IX水平下降到基线水平后，症状消失了。总体而言，患者的临床病程与免疫介导的rAAV转导的肝细胞破坏是一致的。此后产生的更多数据证实了我们的假设，即自然感染诱导的AAV-2特异性T细胞可以导致rAAV转导的肝细胞的消除。为了进一步确定在泰国模仿人类血友病患者的条件下对AAV和rAAV编码的转基因的免疫反应，然后设计出知情的策略来规避这些问题，我们提出了4个相互关联的项目，由2个核心支持。项目1将确定人类和非人类灵长类动物对AAV衣壳蛋白的T细胞反应，并评估它们对肝脏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将定义调节性免疫反应，以防止诱导CD8+T细胞对rAAV编码的转基因产品的反应。项目4将集中于调节性T细胞的潜在用途，以消除对rAAV介导的基因转移的不必要的免疫反应。这些项目将得到一个行政核心和一个媒介核心的支持，前者将提供必要的监督，后者将向调查人员提供纯净和质量受控的媒介。

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.