Serotype-specific replicating AAV helper constructs increase recombinant AAV type 2 vector production

One of the major limitations of the use of adeno-associated virus (AAV) as a tool for gene therapy is the difficulty in providing sufficient quantities of the virus for pre-clinical and clinical trials. Here, we report a novel approach for amplifying AAV helper functions, which mimics the normal replication of wild type (wt) AAV resulting in a high yield of AAV vectors. Cotransfection of replicating but non-packaging AAV helper constructs in the presence of adenovirus (Ad) produces a high level of Rep and Cap proteins. Yield of AAV2/GFP vector obtained from this helper DNA replication system was approximately 20-fold higher than traditional methods. Molecular analysis suggested that virus yield was associated with capsid protein production. The transfection ratio was optimized using these novel helper constructs, resulting in an additional 2-fold increase in vector yield without presence of replication competent AAV (rcAAV). This strategy supports development of AAV packaging systems that retain normal virus replication capability without helper virus encapsidation.