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.
We will utilize adenovirus (Ad) for efficient and specific in vivo gene delivery to accomplish genome editing. The unique molecular promiscuities of Ad allow it to achieve targeted in vivo gene delivery and to circumvent pre- formed anti-vector immunity. Our strategy offers a novel tool to realize effective gene therapy via genome editing.
