MMP-targeted viral gene delivery vectors for treatment of infarcted heart

 描述：腺相关病毒（AAV）已被证明对各种心脏疾病的基因治疗具有很大的前景。已经鉴定了几种AAV变体，例如AAV血清型9（AAV 9），其在心脏细胞中具有高递送效率。不幸的是，载体仍然遭受显著递送到非靶位点，如肝脏和骨骼肌。因此，AAV载体可能需要通过侵入性给药途径递送，以将基因递送物理定位于心脏。实现靶向递送的大多数当前策略集中于使载体能够结合在靶病变细胞上过表达的细胞表面受体。不幸的是，识别导致高递送的单一受体， 很难做到具体。作为一种替代策略，我们假设AAV载体可以被设计为靶向细胞外蛋白酶-几种心血管疾病，包括心肌梗死的标志。蛋白酶激活的病毒（PAV）将无法感染心脏细胞，直到它们检测到特定细胞外蛋白酶的病理浓度。为了增强基因递送的特异性，我们将联合收割机转录调控与蛋白酶激活相结合。特别地，PAV将携带由心脏特异性启动子驱动的转基因。如果仅使用转录控制，则基因表达将在所有心脏组织中发生。如果仅使用蛋白酶活化，则基因表达可能发生在也表现出升高的蛋白酶水平的脱靶位点。通过将转录控制与蛋白酶激活相结合，我们的目标是将基因表达限制在同样患病的心脏组织中。我们在体外和体内都有很好的概念验证数据，表明我们已经成功地创造了第一代PAV。在低水平的蛋白酶下，载体不能结合它们的细胞 表面受体并显示可忽略的细胞转导。在暴露于细胞外蛋白酶（单一靶蛋白酶或两种不同蛋白酶的组合）时，PAV“开启”其细胞受体结合行为并显著增加其转导效率。在目标1中，我们将产生基于单输入或双输入AAV 9的PAV的工具包，其对已知在心肌梗死中升高的细胞外蛋白酶有反应。在目标2中，我们将使用蛋白酶激活造影剂进行分子成像，以检测梗死心脏中的蛋白酶活性。成像研究将有助于指导和验证蛋白酶靶向AAV 9载体的设计和性能。如果成功的话，这里提出的研究将为开发能够特异性地向患病心脏组织提供基因治疗的载体奠定临床前基础。

 DESCRIPTION: Adeno-associated viruses (AAV) have demonstrated great promise for gene therapy of a variety of heart diseases. Several AAV variants, such as AAV serotype 9 (AAV9), have been identified with high delivery efficiencies in cardiac cells. Unfortunately, the vectors still suffer from significant delivery to non-target sites, such as liver and skeletal muscles. Consequently, AAV vectors may need to be delivered via invasive administration routes to physically localize gene delivery to the heart. Most current strategies to achieve targeted delivery focus on enabling vectors to bind cell surface receptors that are overexpressed on target diseased cells. Unfortunately, identification of single receptors that lead to high delivery specificity has been difficult to achieve. As an alternate strategy, we hypothesize AAV vectors can be designed to target extracellular proteases - a hallmark of several cardiovascular diseases, including myocardial infarction. The protease-activated viruses (PAVs) will be unable to transduce cardiac cells until they detect pathological concentrations of specific extracellular proteases. To enhance the gene delivery specificity, we will combine transcriptional control with protease activation. In particular, the PAVs will carry a transgene driven by a heart- specific promoter. If only transcriptional control is used, the gene expression will occur in all heart tissues. If only protease-activation is used, then gene expression may occur in off-target sites also exhibiting elevated protease levels. By combining transcriptional control with protease-activation, we aim to limit gene expression to heart tissues that are also diseased. We have promising proof-of-concept data both in vitro and in vivo showing we have successfully created the first generation of PAVs. At low levels of proteases, the vectors are unable to bind their cell surface receptor and display negligible cellular transduction. Upon exposure to extracellular proteases, either a single target protease or a combination of two different proteases, the PAVs "switch on" their cell receptor binding behavior and dramatically increase their transduction efficiency. In aim 1, we will generate a toolkit of single- or dual-input AAV9-based PAVs that are responsive to extracellular proteases known to be elevated in myocardial infarction. In aim 2, we will conduct molecular imaging with protease-activatable contrast agents to detect protease activity in the infarcted heart. The imaging studies will help guide and validate the design and performance of protease-targeted AAV9 vectors. If successful, the studies proposed here will lay the preclinical groundwork for the development of vectors that can deliver genetic therapies specifically to diseased heart tissues.