scAAV PHP.B-CAG-GFP

Cre recombination-based AAV targeted evolution (CREATE) is a platform based on the selective recovery of capsid viral genomes from target cell nuclei expressing Cre recombinase in vivo or in vitro during screening campaigns, which enables the isolation of novel AAV variants with altered tropism. With this new technology based on AAV9 capsids, a family of AAV-PHP capsids emerged, among which AAV-PHP.B exhibits significantly improved tropism for various tissues in mice and is able to enter target cell populations that are difficult to reach due to their location (e.g., sympathetic nerves, tuberosity, dorsal root and cardiac ganglia) or widespread distribution (e.g., enteric nervous system), even after intravenous injection.

Although AAV9 is able to traffic to the basolateral zone via transendothelial transport, the efficiency is very low. AAV-PHP.B, on the other hand, crosses the BBB more efficiently, reaches the CNS and peripheral nervous system (PNS), is widely distributed in adult mice (strain dependent) and rats, and has a slightly reduced vector genome in the liver. AAV-PHP.B was 40- to 60-fold more efficient than AAV9 at transducing the mouse CNS, with 40- to 92-fold more vector genomes across CNS regions, 75-fold more in the spinal cord, and similar levels to AAV9 in heart and skeletal muscle. Interestingly, while AAV9 preferentially transduced astrocytes when injected intravenously into adult mice and nonhuman primates (NHPs), AAV-PHP.B transduced oligodendrocytes, neurons throughout the brain, and endothelial cells, but not microglia. In neonatal rat cerebellum, AAV-PHP.B achieved 2.4-fold higher transduction efficiency than AAV9 following intravenous injection, while intracerebroventricular (ICV) injection of AAV-PHP.B into adult rats resulted in transgene expression in central nervous system (CNS) regions and the spinal cord, demonstrating the potential for vector performance beyond mice.