724. A Comprehensive Map of CNS Transduction by Eight Recombinant Adeno-Associated Virus Serotypes upon Cerebrospinal Fluid Administration in Pigs

Abstract

Gene transfer of recombinant adeno-associated virus (rAAVs) holds promises to treat neurological disorders. Studies on different recombinant vector serotypes and modes of delivery to the central nervous system (CNS) showed that the combination of both rAAV serotype used and delivery routes play a key role in CNS transduction properties and thus in disease phenotype rescue outcome. However, one of the major hurdles to developing an effective clinical protocol for neurological disorders is the efficiency of vectors to reach the specific cell types in disease-specific CNS subdomains. An attractive vehicle to reach the CNS is represented by the cerebral spinal fluid (CSF) and different injection techniques (intrathecal cisterna magna, intra-ventricular and intrathecal lumbar injections) actually allow the central nervous system targeting by using the CSF flux. Along these years different AAV serotypes have been tested by intrathecal injections and some of these displayed a very specific tropism for the central nervous system. However, a quantitative and qualitative analysis of transduction patterns of the most promising rAAV serotypes for brain targeting in large animal models is missing. Here, we characterize distribution, transduction efficiency and cellular targeting of rAAV serotypes 1, 2, 5, 7, 9, rh.10, rh.39 and rh.43 delivered into the cisterna magna of wild type pigs. Despite the rAAV9 showed the highest transduction efficiency and the widest distribution capability among the vectors tested, the other serotypes showed a specific distribution pattern from the rostral to the caudal part of the CNS. rAAV9 robustly transduced both glia and neurons, including the motor neurons of the spinal cord. Relevant cell transduction specificity of the glia was observed after rAAV1 and rAAV7 delivery. rAAV7 also displayed a specific tropism to Purkinje cells. Evaluation of biochemical and hematological markers suggested that all rAAV serotypes tested were well tolerated. This study provides a comprehensive CNS transduction map in a useful pre-clinical large animal model enabling the selection of potentially clinically transferable rAAV serotypes based on disease specificity. Therefore, our data are instrumental for the clinical evaluation of these rAAV vectors in human neurodegenerative diseases.