The AAV9 variant capsid AAV-F mediates widespread transgene expression in non-human primate spinal cord after intrathecal administration.

Intrathecal delivery of AAV9 into the subarachnoid space has been shown to transduce spinal cord and brain and be less affected by pre-existing antibodies, which are lower in cerebral spinal fluid (CSF). Still, efficiency of transduction needs to be improved. Recently we identified a new capsid from a library selection in mice, called AAV-F, that allowed robust transduction of the spinal cord gray matter after lumbar injection. Here we test transduction of spinal cord by AAV-F (n=3) compared to AAV9 (n=2), using a reporter gene, in cynomolgus monkeys after lumbar intrathecal injection. Using an automated image analysis approach to sensitively quantitate reporter gene expression in spinal cord, we found that AAV-F capsid mediated slightly higher transgene expression (both in percentages of cells and intensity of immunostaining) in motor neurons and interneurons, in the lumbar and thoracic regions, compared to AAV9. Interestingly, although AAV-F mediated higher transgene expression in spinal cord, the number of genomes in spinal cord and periphery were on average lower for AAV-F than AAV9, which suggest lower numbers of genomes were able to mediate higher transgene expression in spinal cord with this capsid. In contrast DRG transduction efficiency was lower for AAV-F compared to AAV9 on average. Interestingly, we also observed transduction of Schwann cells in sciatic nerve in two NHPs injected with AAV-F but none with AAV9. Overall, our data demonstrates the utility of automated image analysis for quantitation of AAV transduction in the spinal cord and the favorable on target:off target transduction profile suggests that the AAV-F capsid be considered for gene therapy applications focused on treating the spinal cord after intrathecal delivery.