Mannitol-facilitated CNS entry of rAAV2 vector significantly delayed the neurological disease progression in MPS IIIB mice.

The presence of the blood-brain barrier (BBB) presents the most critical challenge in therapeutic development for mucopolysaccharidosis (MPS) IIIB, a lysosomal storage disease with severe neurological manifestation, because of alpha-N-acetylglucosaminidase (NaGlu) deficiency. Earlier, we showed a global central nervous system (CNS) transduction in mice by mannitol-facilitated entry of intravenous (IV)-delivered recombinant adeno-associated viral serotype 2 (rAAV2) vector. In this study, we optimized the approach and showed that the maximal transduction in the CNS occurred when the rAAV2 vector was IV injected at 8 min after mannitol administration, and was approximately 10-fold more efficient than IV delivery of the vector at 5 or 10 min after mannitol infusion. Using this optimal (8 min) regimen, a single IV infusion of rAAV2-CMV-hNaGlu vector is therapeutically beneficial for treating the CNS disease of MPS IIIB in adult mice, with significantly extended survival, improved behavioral performance, and reduction of brain lysosomal storage pathology. The therapeutic benefit correlated with maximal delivery to the CNS, but not peripheral tissues. This milestone data shows the first effective gene delivery across the BBB to treat CNS disease. The critical timing of vector delivery and mannitol infusion highlights the important contribution of this pretreatment to successful intervention, and the long history of safe use of mannitol in patients bodes well for its application in CNS gene therapy.

Significantly increased lifespan and improved behavioral performances by rAAV gene delivery in adult mucopolysaccharidosis IIIB mice.

Mucopolysaccharidosis (MPS) IIIB is an inherited lysosomal storage disease, caused by the deficiency of alpha-N-acetylglucosaminidase (NaGlu), resulting in severe global neurological involvement with high mortality. One major hurdle in therapeutic development for MPS IIIB is the presence of the blood-brain barrier, which impedes the global central nervous system (CNS) delivery of therapeutic materials. In this study, we used a minimal invasive strategy, combining an intravenous (i.v.) and an intracisternal (i.c.) injection, following an i.v. infusion of mannitol, to complement the CNS delivery of adeno-associated viral (AAV) vector for treating MPS IIIB in young adult mice. This treatment resulted in a significantly prolonged lifespan of MPS IIIB mice (11.1-19.5 months), compared with that without treatment (7.9-11.3), and correlated with significantly improved behavioral performances, the restoration of functional NaGlu, and variable correction of lysosomal storage pathology in the CNS, as well as in different somatic tissues. This study demonstrated the great potential of combining i.v. and i.c. administration for improving rAAV CNS gene delivery and developing rAAV gene therapy for treating MPS IIIB in patients.