Safe, Efficient, and Reproducible Gene Therapy of the Brain in the Dog Models of Sanfilippo and Hurler Syndromes

Abstract

Recent trials in patients with neurodegenerative diseases documented the safety of gene therapy based on adeno-associated virus (AAV) vectors deposited into the brain. Inborn errors of the metabolism are the most frequent causes of neurodegeneration in pre-adulthood. In Sanfilippo syndrome, a lysosomal storage disease in which heparan sulfate oligosaccharides accumulate, the onset of clinical manifestation is before 5 years. Studies in the mouse model showed that gene therapy providing the missing enzyme α-N-acetyl-glucosaminidase to brain cells prevents neurodegeneration and improves behavior. We now document safety and efficacy in affected dogs. Animals received eight deposits of a serotype 5 AAV vector, including vector prepared in insect Sf9 cells. As shown previously in dogs with the closely related Hurler syndrome, immunosuppression was necessary to prevent neuroinflammation and elimination of transduced cells. In immunosuppressed dogs, vector was efficiently delivered throughout the brain, induced α-N-acetyl-glucosaminidase production, cleared stored compounds and storage lesions. The suitability of the procedure for clinical application was further assessed in Hurler dogs, providing information on reproducibility, tolerance, appropriate vector type and dosage, and optimal age for treatment in a total number of 25 treated dogs. Results strongly support projects of human trials aimed at assessing this treatment in Sanfilippo syndrome.

Gene therapy for the neurological manifestations in lysosomal storage disorders

“…An indication of effi cacy from focal intraparenchymal injections has also been observed in large animal models (e.g., cats and dogs) of various LSDs ( 119,(124)(125)(126)(127). However, despite these encouraging results, scaling this strategy to an infant brain is estimated to nevertheless require between 50 and 350 injection tracts, which is arguably impractical ( 124,127 ).…”

“…The viability of providing multiple injections of recombinant AAV vectors to treat the CNS disease has been illustrated in both small and large animal models of several LSDs. The effi cacy of gene transfer using different AAV serotypes has been demonstrated in mouse models of infantile neuronal ceroid lipofuscinosis, LINCL, NiemannPick type A, metachromatic leukodystrophy, globoid cell leukodystrophy, Sandhoff, and MPS I, IIIB and VII diseases ( 34,37,47,48,103,111,(115)(116)(117)(118)(119)(120)(121)(122)(123). Treatment was associated with a clear reduction in the overall levels of the accumulated substrate in large regions of the mouse brain and was accompanied by measurable improvements in neuropathology and motor function.…”

Therapies for the bone in mucopolysaccharidoses

“…In addition, sleeping beauty-based therapy corrected thickening of the bone of the zygomatic arch and growth plate abnormalities in femur and tibia; but consistent positive effects were not observed in cortical thickness or diameters of mid-diaphyseal bone areas [118]. AAV vectors have been evaluated only to correct the neurological alterations of the disease in mice, showing significant improvement in accumulation of GAGs and neurocognitive dysfunction [123,124].…”

“…Here we summarize the recent achievements for bone lesions in gene therapies of animal models of MPS. [115,116], sleeping beauty transposon [117,118], gamma-retrovirus [58,[119][120][121], lentivectors [122], and adenoassociated virus (AAV) vectors [123,124]. Non-viral vectors (i.e.…”

Gene Therapy Approaches for Lysosomal Storage Disease: Next-Generation Treatment

“…To date, the majority of studies for direct CNS correction for LSDs have been done with rAAVs. In more recent studies, direct intracranial delivery of therapeutic rAAV resulted in reduction of lesions in the CNS in murine models of MPS I and Batten disease and canine models of Sanfilippo and Hurler syndromes (Cabrera-Salazar et al, 2007;Ellinwood et al, 2011;Wolf et al, 2011). Although these studies demonstrate the profound impact of rAAV-mediated transgene expression in the CNS, the effect is limited to this tissue and does not improve non-CNS-related pathology.…”