scAAV PHP.eB-CAG-GFP

One of the biggest obstacles to the treatment of neurological diseases is finding ways to effectively deliver therapeutic drugs to the central nervous system (CNS). Recombinant adeno-associated virus (rAAV) vectors have long been one of the most favored gene therapy vectors for CNS diseases because of their ability to achieve stable, long-lasting transgene expression in non-dividing cells. From a clinical perspective, therapeutic drugs that can be administered via a non-invasive systemic route are essential for large-scale application in humans. However, naturally occurring AAV capsid serotypes have limited ability to penetrate the blood-brain barrier (BBB). This means that they must be administered at extremely high doses intravenously (i.v.) or by local injection into the central nervous system (CNS), making them unsuitable for use as non-invasive treatments.

To address this issue, a variety of techniques have been investigated to improve the efficiency of rAAV gene transfer from the blood to the brain, including the use of drugs or ultrasound to increase BBB permeability and the use of shuttle peptides to improve the ability of capsids to cross the BBB. Arguably, one of the most successful strategies has been the in vivo directed evolution of AAV9 capsids through the Cre recombinase-based targeted evolution (CREATE) system. The CREATE system generated a novel family of AAV-PHP.B capsids (including AAV-PHP.B and second-generation AAV-PHP.eB), which differ from AAV9 by the insertion of a heptamer of amino acids into the capsid sequence. These capsids were generated by the Cre recombinase system, which was selected for capsids that efficiently transduced the central nervous system of adult C57BL/6J mice after intravenous injection. Injection of AAV-PHP.eB increased cell transduction in multiple brain regions by more than 50-fold.