AAV9-EF1a-FRT-mCherry

Adeno-associated virus (AAV), a member of the Parvoviridae family, is widely used as a vector for gene therapy due to its safety, ability to transduce both dividing and non-dividing cells, and low immunogenicity. AAV is a small, non-enveloped, single-stranded DNA virus that has been detected in many different tissues of a variety of animals but has not been associated with any disease. Over the past decade, the discovery and development of new AAV types with significantly improved in vivo performance, unique seroreactivity, and tissue tropism have brought AAV to the forefront of gene therapy trial vector development.

AAV is a non-enveloped virus of approximately 25 nanometers in diameter, containing a 5 kb single-stranded DNA genome surrounded by a protein capsid. The crystal structure of serotype 2 (AAV-2) shows a T = 1 icosahedral symmetry consisting of 60 subunits, each with a core β-barrel decorated with long loops on the surface that intertwine with adjacent loops to form protruding spikes around a 3-fold axis. The promise of AAV stems from the availability of a large number of natural viral isolates that possess unique properties that can be modulated or enhanced, including tissue specificity, transgene expression efficiency, and evasion of pre-existing or induced anti-AAV antibodies. This repurposing is often achieved in a high-throughput manner, involving the generation and iterative, top-down selection of synthetic AAV capsid libraries that are diversified using techniques such as DNA family shuffling, ancestral reconstruction, or peptide display.