A novel class of self-complementary AAV vectors with multiple advantages based on cceAAV lacking mutant ITR

Abstract

Self-complementary AAV vectors (scAAV) employ a mutant inverted terminal repeat (mITR) for efficient packaging of complementary stranded DNA, enabling rapid transgene expression. Yet, inefficient resolution at the mITR leads to the packaging of monomeric or subgenomic AAV genomes. These non-canonical particles reduce transgene expression and may affect the safety of gene transfer. To address these issues, we have developed a novel class of scAAV vectors termed covalently closed-end double-stranded AAV (cceAAV) that eliminate the mITR resolution step during production. Instead of employing a mutant ITR, we utilized a 56-bp recognition sequence of protelomerase (TelN) to covalently join the top and bottom strands, allowing the vector to be generated with just a single ITR. To produce cceAAV vectors, the vector plasmid is initially digested with TelN, purified, and then subjected to a standard triple-plasmid transfection protocol followed by traditional AAV vector purification procedures. Such cceAAV vectors demonstrate yields comparable to scAAV vectors. Notably, we observed enhanced transgene expression as compared to traditional scAAV vector. Treatment of mice with hemophilia B with cceAAV-FIX resulted in significantly enhanced long-term FIX expression. The cceAAV vectors hold several advantages over scAAV vectors, potentially leading to development of improved human gene therapy drugs.