546. Identification of Optimal AAV Vector and Route of Administration for Neonatal Treatment Using the Murine MPS IIIB Model

Mucopolysaccharidoses IIIB (MPS IIIB), is an autosomal recessive lysosomal storage disease caused by defective production of the enzyme α-N-acetylglucosaminidase and is characterized by retention and accumulation of heparan sulfate. It is defined by severe and complex central nervous system (CNS) pathology. No cure exists. Treatment options are limited by the need to overcome the blood-brain barrier and gain successful entry to the CNS. Research suggests that the optimal therapeutic window occurs prior to toddlerhood. Based on this knowledge, using the murine neonatal MPS IIIB model, we evaluate and describe for the first time, therapeutic assessment of two capsid mutated Adeno-associated virus serotype 8 variants for the treatment of MPS IIIB. Our goal is to assess biodistribution and transduction profiles of GFP expressing AAV8(double Y-F) and AAV8(double Y-F+T-V) variants, compared to normal AAV8, administered through four intracranial routes: six site (IC6), thalamic (TH), intracerebroventricular (ICV) and ventral tegmental area (VTA). The serotype exhibiting the best treatment potential is defined by broadest distribution and transduction profiles. Comparative evaluation of vector biodistribution of each of the four administration methods revealed that IC6u003eICVu003eTHu003eVTA. Surprisingly, evaluation of transduction profiles revealed that AAV8(double Y-F+T-V)u003eAAV8u003eAAV8(double Y-F). Based on functional significance, the cortex, hippocampus, thalamus and cerebellum were assessed in each animal. In IC6 administered AAV8(double Y-F+T-V) treated animals, cortical layers II/III, IV and V/VI; as well as, all hippocampal layers were robustly transduced, while the thalamus and cerebellum were modestly transduced. The ICV method yielded heavy localization of vector in the hippocampus and proximal thalamic areas with modest cortical deposition of vector along needle track. The TH and VTA methods proved least desirable to facilitate vector biodistribution. Phenotypic assessment of transduced cells suggest primary robust transduction of neurons compared to astrocytes. For the first time, we have provided proof of concept for the utility of IC6 administration of AAV8(double Y-F+T-V) as a valid therapeutic approach for the early treatment of MPS IIIB with further implications for other monogenic diseases.