A Novel Vector Platform to Actualize T Cell Modification In Vivo

Washington University, Saint Louis MO

Investigators

Abstract

ABSTRACT To address the need for improved gene editing delivery systems, we propose constructing a chimeric “AdAAV” vector consisting of an adenovirus (Ad) with multiple adeno-associated viruses (AAVs) conjugated to its capsid's surface. We plan to employ the SpyTag/SpyCatcher technology to conjugate AAVs onto the Ad capsid. Of note in this regard, Ads are able to selectively target certain tissues (such as the liver in the case of huAd5) with high transduction efficiencies. Furthermore, our group has been able to engineer Ad fibers to facilitate tissue-specific targeting of T cells. In addition, by choosing an appropriate AAV serotype, and/or through capsid engineering AAVs can also selectively target desired tissues as well. AdAAVs may therefore provide superior targeting through the combined effects of both engineered Ad fiber and AAV capsid (which are matched to target the same tissue type). As a proof-of-concept, we plan to target T cells with AdAAVs. In addition, because AAVs carry single-stranded DNA, they can provide single-stranded donor templates, which are known to enhance the editing efficiency of homology directed repair (HDR). Within an AdAAV, the Cas protein can be encoded by the Ad genome while the single-stranded DNA template can be embodied within the genome of the AAVs. By virtue of the advantages of single-stranded donor templates for HDR, and by virtue of the high copy number of donor templates carried by the multiple AAVs associated with each Ad, this design might substantially increase editing efficiency. Finally, the AdAAV would possess a large packaging capacity since it would consist of a sum of the Ad's capacity (which is already high) and the AAV's capacity. Due to these factors, we suggest that AdAAVs may form a powerful and versatile new delivery system for gene editing therapies which overcomes many of the limitations associated with existing approaches. Our highly original AdAAV delivery system will greatly enhance the versatility of existing CRISPR-Cas gene editing therapies by circumventing several key obstacles to their broader applicability. The design features of AdAAV will potentially make it an ideal vector by which to address the challenges of gene editing delivery and thereby broadly enhance the general feasibility of gene editing-based therapies.