FIV Vectors for the Treatment of Hemophilia A

描述（由申请人提供）：目前甲型血友病的护理标准是静脉输注FVIII蛋白治疗，无论是预防性的还是在出血发作期间。然而，由于可用性有限、费用高以及由于静脉通道引起的血液传播疾病的担忧，预防性治疗存在问题。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。迄今为止，由于缺乏非增殖细胞（MLV）的转导和高载体颗粒免疫原性（Ad），腺病毒（Ad）和肿瘤逆转录病毒（MLV） FVIII治疗的临床试验的成功受到了影响。慢病毒载体克服了这两个问题，我们使用基于猫免疫缺陷病毒（FIV）的慢病毒载体进行的累积临床前研究导致血友病小鼠模型中持续和治疗性的FVIII表达水平。启动临床试验的下一个合乎逻辑的步骤包括对载体颗粒与宿主免疫系统相互作用的详细调查，以及在相关的大型动物模型（血友病犬）中测试基于fiv的FVIII疗法。我们的目标是生成编码犬B结构域缺失FVIII （cFVIII）的FIV载体，以优化其高表达水平。cFVIII表达的优化是在成功修饰人FVIII后建模的，因此可以更好地模拟先进的人FVIII治疗，同时便于在狗模型中检测血清FVIII蛋白水平和治疗效果。我们的第二个目标是更好地了解对FIV载体颗粒本身可能产生的免疫反应。迄今为止，还没有发表过任何动物系统对慢病毒载体成分的先天或适应性免疫反应的研究。彻底了解对FIV颗粒的任何免疫反应的水平或程度是一个重要的安全性和有效性问题，因为FVIII基因转移治疗可能需要在一段时间后重新施用。该建议的时间框架允许生产功能性FIV- cfviii载体，并测试对三种不同包膜假型FIV载体颗粒的首次先天免疫反应。超出当前提案范围的未来研究将旨在研究血友病犬中基于fiv的cFVIII基因转移，同时监测治疗表达水平和重复给药期间的适应性抗fiv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.