Helper virus-free, optically controllable, and two-plasmid-based production of adeno-associated virus vectors of serotypes 1 to 6

We present a simple and safe strategy for producing high-titer adeno-associated virus (AAV) vectors derived from six different AAV serotypes (AAV-1 to AAV-6). The method, referred to as "HOT," is helper virus free, optically controllable, and based on transfection of only two plasmids, i.e., an AAV vector construct and one of six novel AAV helper plasmids. The latter were engineered to carry AAV serotype rep and cap genes together with adenoviral helper functions, as well as unique fluorescent protein expression cassettes, allowing confirmation of successful transfection and identification of the transfected plasmid. Cross-packaging of vector DNA derived from AAV-2, -3, or -6 was up to 10-fold more efficient using our novel plasmids, compared to a conservative adenovirus-dependent method. We also identified a variety of useful antibodies, allowing detection of Rep or VP proteins, or assembled capsids, of all six AAV serotypes. Finally, we describe unique cell tropisms and kinetics of transgene expression for AAV serotype vectors in primary or transformed cells from four different species. In sum, the HOT strategy and the antibodies presented here, together with the reported findings, should facilitate and support the further development of AAV serotype vectors as powerful new tools for human gene therapy.