Abstract 401: Development of an Adeno-Associated Viral (AAV) Vector targeted to Murine Myocardium by in vivo Selection of an AAV-2 Peptide Display Library
Alternative AAV serotype vectors may increase efficiency and specificity of cardiac gene transfer. Since they still efficiently transduce extracardiac tissue, our study aimed at targeting AAV vectors specifically to myocardium after systemic application. Envisioning the highly complex receptor expression profiles in living organisms, we have utilized an evolutionary approach by selecting an AAV-2 (NNK)7-random peptide display library in vivo. We selected AAV2 vectors for successful in vivo homing to mouse heart by intravenous injection of a random peptide AAV display library in adult NMRI mice. Specific peptide sequences could be enriched after three rounds of in vivo biopanning in mouse hearts. AAV vectors carrying selected mutants were then evaluated in vivo by tail-vein injection into adult mice. Biodistribution studies by detecting viral genomes upon co-injection of targeted and wild type AAV-2 vectors or AAV-9 vectors demonstrated the superior specificity of the two newly isolated vectors, which nearly exclusively accumulated in myocardium. AAV-9 vectors, which have been previously shown to efficiently transduce mouse heart after systemic application, mediated a comparable cardiac vector genome delivery, but resulted in body-wide genome distribution. Transduction efficiencies of targeted AAV-2 luciferase vectors were compared with wild type AAV-2 vectors in representative organs after four weeks. One of the two targeted AAV2 vectors revealed highly increased cardiac reporter activities close to 4 orders of magnitude compared to wild type AAV-2 vectors. In order to assess the potential of this targeted AAV-2 vector to systemically transfer a therapeutic gene, we intravenously injected 1011 genomic particles of targeted and non-targeted vectors harbouring the delta-sarcoglycan cDNA in delta-sarcoglycan knock out mice. The wild type AAV-2 vector revealed no significant delta-sarcoglycan expression, while the targeted AAV-2 resulted in expression within 30% of cardiomyocytes after four weeks. In summary, we have identified a novel targeted AAV-2-based vector for highly efficient and specific gene transfer. This approach may be versatile to develop AAV vectors with increased safety profile for future therapeutic applications.