(298f) Co-Delivery of cDNA and siRNA Using Viral/Nonviral Chimeric Nanoparticles for Synergistic Cancer Gene Therapy

Development of safe and efficient delivery vectors has been a pivotal demand in gene therapy. Viral vectors are popularly used in clinical trials, due to their high transduction efficiency, but their utilities have been limited by immunogenicity, pathogenicity, oncogenicity, limited gene packaging capacity, and difficulties in large-scale preparation and purification. Importantly, engineering viral vectors for versatile and multi-functional gene delivery is a cumbersome task and often infeasible. Nonviral vectors, on the other hand, offer relatively low immunogenicity, unlimited size in gene cargos, and high structural and functional flexibility for modifications, although their low transfection efficiency compared to viral counterparts is still a major drawback. Therefore, the advantages of viral vectors (i.e., high transduction efficiency) and nonviral vectors (i.e., low immunogenicity, and versatility in engineering structure and functions) were combined in viral/nonviral chimeric nanoparticles (ChNPs) with adeno-associated virus (AAV) as the viral core with acid-degradable polyketal (PK) shell as nonviral polymeric shell. The AAV core, which is one of the smallest viral vectors used in clinical gene therapy with no known linkages to human diseases, was shelled with PK shell that is designed to protect the AAV core from immune responses, promote endosomal escape, and enable the conjugation of targeting ligands on the surface. Most importantly, siRNA was incorporated in the PK shell during surface-initiated photopolymerization, in order to achieve dual modal gene delivery (i.e., simultaneous expression and silencing of multiple genes).

            The core-shell structure of the resulting ChNPs, and the ordered release of siRNA and the AAV core in the presence of multiple intracellular stimuli were confirmed. Confocal microscopy demonstrated that ChNPs selectively released siRNA into the cytoplasm from the PK shell and facilitated the transnuclear localization of the AAV core. In vitro study with human lymphoma B cells showed significantly enhanced transduction by ChNPs, compared to free AAVs, with simultaneous gene silencing of additional target gene. It was also shown that the PK shell of ChNPs effectively shielded their AAV core from AAV-neutralizing antibodies and sialic acid-conjugated ChNPs selectively transduced CD22+ B-cells. Efficient and synergistic eradication of Philadelphia chromosome-positive (Ph+) leukemia was explored using ChNPs with Bim-encoding AAV core and Mcl-1 siRNA-encapsulating PK shell. Ph+ leukemia cells over-express a pro-survival Mcl-1 while down-regulating pro-apoptotic Bim. Cell apoptosis assay as well as cell growth kinetics indicated synergistic gene therapy for leukemia using ChNPs.  This talk will highlight the design, synthesis, and characterization of novel gene carriers, along with a clinically relevant application.