Endothelial-targeted adenovirus for organ-selective gene editing in vivo

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PROJECT SUMMARY A wide range of biological applications have derived from the CRISPR/Cas9 site-specific nuclease system in recent years. Of note, the capacity to accomplish gene editing in a targeted manner has also impacted the design of gene therapy strategies for an expanding repertoire of disorders. Critical to realizing the gene editing functions of the CRISPR/Cas9 system in a gene therapeutic context is the requirement to accomplish effective co-delivery in vivo of the constituent components. This delivery issue has been approached applying both non-viral and viral vector systems. In selected instances, successful gene-editing facilitated gene therapies have been accomplished in model systems of inherited genetic disease. Despite these elegant proof-of-principle studies, limits in available vector technology have greatly restricted the application of CRISPR/Cas9-facilitated gene therapy. In this regard, effective in vivo co-delivery of CRISPR/Cas9 to target somatic cells is required for many of these applications. Such delivery should be restricted exclusively to the key cellular targets in vivo to minimize off-target effects. In addition, the mandated co-delivery must be accomplished in the potential presence of pre-formed anti-vector immunity. Finally, methods to limit Cas9 expression must be endeavored to limit the potential of off-target editing. Of note, these functionalities should ideally be configured into the context of a single vector particle context to facilitate practical upscaling and human clinical translation. To this end, we have exploited the molecular promiscuities of adenovirus (Ad) to address the requirements of CRISPR/Cas9-facilitated gene therapy. In this regard, we have endeavored capsid engineering of adenovirus to achieve targeted modifications of vector tropism. In addition to allowing for re-directed tropism, capsid engineering provides the means to allow Ad to circumvent pre-formed vector immunity. We have also applied a strategy of capsid engineering to accomplish transient expression of heterologous proteins. On this basis, during the UG3 Phase (3 years) we will establish proof-of-principle with respect to delivery of genome editing machinery into disease relevant cells and tissues in vivo. The follow-on UH3 Phase (1 year) will address scale up and testing of our novel approach in a large animal model. This will be accomplished in collaboration with the SCGE Large Animal Testing Centers.