P24

Biodistribution and immune response against CNS-targeting AAV vectors in non-human primates

C Gaston(1) C Josephine(1) A Fayard(1) C M Fovet(1) M C Gaillard(1) N Dufour(1) G Aurégan(1) F Petit(1) P Gipchtein(1) S Lecourtois(1) M Guillermier(1) P Hantraye(1) R Aron Badin(1) A P Bemelmans(1)

1: MIRCen, CEA

Adeno-associated viruses (AAV)-based gene transfer progressed in the last decade, up to the ability to treat single-gene disorders such as spinal muscular atrophy with great success. However, with the increase in clinical trials using AAV vectors, it appears that AAV are more immunogenic than previously estimated, when used at high doses. Several clinical trials were put on hold after severe adverse events occurred, related to hepatotoxicity and upregulated immune response. To better bridge the gap between preclinical studies and clinical trials, we evaluated the biodistribution and immune response against three of the most-used AAV capsids, i.e. 6, 9 and rh10, to target the central nervous system (CNS) in non-human primates (Macaca fascicularis). The animals received combinations of vectors, each containing a fluorescent reporter, detected by qPCR and immunofluorescence to evaluate their tropism and distribution. To target the CNS, we used intraparenchymal (IP) injection or intrathecal (IT) injection with 3E12vg and 3E13vg, respectively. IT delivery led to higher viral load than IP and broader distribution in the peripheral tissues, notably the lymphatic organs (spleen, lymph nodes, dorsal root ganglia), but also in non-lymphatic organs. For the IP group, the AAVs were detected in the injected areas, the spinal cord and dorsal root ganglia, but almost indetectable in the peripheral organs. The immune response data is now under analysis. This work will help to better characterize the influence of serotype and injection route on vector biodistribution, and the related immune response, thus allowing the identification of targets for immunosuppression in clinical trials.