616. Tailored Expression of a Transgene to Specific Cell Types in the Central Nervous System After Peripheral Injection of AAV9

Abstract

Because of their efficient tropism for the neural tissue and their well-established safety and tolerability profile, adeno-associated vectors (AAV) hold great potential to express therapeutic genes in the context of various neurodegenerative disorders. Importantly, the characterization of novel AAV serotypes (AAV9; rhAAV10, etc …) that can cross the blood brain barrier after intravenous delivery now offer an opportunity for non-invasive delivery to the brain. However, in absence of a well-tailored system, the use of a peripheral route injection may lead to undesirable transgene expression in various cell types of the nervous system as well as in other organs. In order to refine this approach, the present study characterizes the transduction profiles of newly engineered self-complement AAV9 (scAAV9) expressing the Green Fluorescent Protein (GFP) either under an astrocyte (GFA’) or neuronal (Synapsin, Syn) promoter, after a single injection in the lateral tail vein of adult mice (5×10e11vg/animal). We report that our scAAV9-GFA’-GFP and scAAV9-Syn-GFP respectively led to robust and long-lasting transduction of astrocytes (10%) and neurons (8%) throughout the entire cerebral tissue, in the absence of aberrant expression leakage in other cell types of the brain or in the liver. GFP positive excitatory as well as inhibitory neurons could be observed in the CNS, while motor neurons were also efficiently transduced in the PNS. In addition, both activated (GFAP positive) and resting astrocytes expressed the reporter gene. Quantitative stereological assessment demonstrated an increase in reactive astrocytes after transduction with scAAV9 but did not lead to any obvious detrimental phenotype in any animals. These data suggest the potential interest of tailoring AAV to drive expression of therapeutic genes specifically in astrocytes or neurons of the CNS after intravenous delivery, thus preventing adverse side-effects associated with peripheral expression.