FIV Vectors for the Treatment of Hemophilia A

描述(由申请人提供)：目前治疗血友病A的标准是静脉注射FVIII蛋白，预防性或在出血期间进行。然而，由于可获得性有限、成本高以及由于静脉途径而对血液传播疾病的担忧，预防性治疗是有问题的。病毒载体的基因转移提供了一种有吸引力的替代治疗方法，具有长期纠正的潜力，因为只有5%的正常FVIII表达水平提供了实质性的临床益处。启动临床试验的下一个合乎逻辑的步骤包括详细调查媒介颗粒与宿主免疫系统的相互作用，以及在相关的大型动物模型--血友病狗身上测试基于FIV的FVIII疗法。我们的目标是产生编码犬B结构域缺失的FVIII(CFVIII)的FIV载体，优化其高表达水平。我们的第二个目标是更好地了解FIV载体颗粒本身可能的免疫反应。到目前为止，还没有发表过关于慢病毒载体成分在任何动物系统中的先天或获得性免疫反应的研究。这项提议的时间框架允许生产功能性FIV-cFVIII载体，并测试对具有三种不同包膜假型的FIV载体颗粒的第一先天免疫反应。

DESCRIPTION (provided by applicant): The current standard of care for hemophilia A is treatment with intravenous FVIII protein infusions, either prophylacticly or during bleeding episodes. Prophylactic treatment, however, is problematic due to limited availability, high costs and concerns for blood-borne diseases due to venous access. Gene transfer with viral vectors provides an attractive alternative therapeutic approach with the potential for long-term correction since only 5% of normal FVIII expression levels provide substantial clinical benefits. Success of clinical trials with adeno (Ad)- and oncoretroviral (MLV) FVIII therapy has been compromised to date by lack of transduction of non-proliferating cells (MLV) and high vector particle immunogenicity (Ad). Lentiviral vectors overcome both problems and our cumulative preclinical studies using Feline Immunodeficiency Virus (FIV)-based lentiviral vectors resulted in persistent and therapeutic FVIII expression levels in the hemophilia mouse model. The next logical steps towards the initiation of clinical trials include a detailed investigation of vector particle interactions with the host's immune system as well as the testing of FIV-based FVIII therapy in a relevant large animal model-the hemophilia dog. Our goal is to generate FIV vectors coding for canine B domain-deleted FVIII (cFVIII) optimized for high expression levels. Optimization of cFVIII expression is modeled after successful modifications of the human FVIII and thus better mimics advanced human FVIII therapy while facilitating detection of serum FVIII protein levels and therapeutic benefit in the dog model. Our second goal is aimed at gaining a better understanding of possible immune responses to the FIV vector particle itself. To date, there has been no published investigation of innate or adaptive immune responses to lentiviral vector components in any animal system. A thorough understanding of the level or extent of any immune responses to FIV particles is an important safety and efficacy concern since FVIII gene transfer therapy likely needs to be re-administered after some time. The timeframe of this proposal allows the production of functional FIV-cFVIII vectors and the testing of first innate immune responses to FIV vector particles pseudotyped with three different envelopes. Future studies beyond the scope of the current proposal will be aimed at investigating FIV-based cFVIII gene transfer in the hemophilia dog while monitoring therapeutic expression levels and adaptive anti-FIV immune responses during repeat administrations.