EFS-SpCas9HF AAV (Serotype 9)

To date, more than a dozen AAV serotypes have been isolated from human and non-human primate tissues. In general, these serotypes exhibit broad tropism, although different serotypes have preferences for different tissues. The cell and tissue specificity of different serotypes can be used to develop therapeutic vectors. For example, AAV8 can effectively transduce hepatocytes in mice and non-human primates after systemic administration and is therefore a preferred vector for gene delivery to the liver. AAV1 exhibits skeletal and cardiac muscle tropism and was used by Glybera to deliver a gene encoding a gain-of-function variant of lipoprotein lipase to muscle cells to treat LPL deficiency.

AAV9 preferentially binds to galactose as its primary receptor, which is thought to contribute to its ability to cross the blood-brain barrier. Therefore, this serotype effectively targets motor neurons after intravenous injection and has been successfully used to deliver genes to the brain and spinal cord in clinical trials. In addition, AAV9 can effectively infect muscle tissue. Therefore, this serotype is a preferred choice for muscle-directed gene therapy in preclinical and clinical trials. ITR stands for structural cis-acting DNA elements required for AAV genome replication and packaging. A typical AAV-based vector system is generated by flanking the transcription unit of interest with the ITRs and providing the genetic information for rep and cap in trans. Helper virus functions required for high-titer production of AAV can be provided by infecting the producer cell line with a helper virus such as adenovirus or by co-transfection of a plasmid encoding adenoviral helper genes.