Corrective GUSB transfer to the canine mucopolysaccharidosis VII brain.

Severe deficiency in lysosomal ß-glucuronidase (ß-glu) enzymatic activity results in mucopolysaccharidosis (MPS) VII, an orphan disease with symptoms often appearing in early childhood. Symptoms are variable, but many patients have multiple organ disorders including neurological defects. At the cellular level, deficiency in ß-glu activity leads to abnormal accumulation of glycosaminoglycans (GAGs), and secondary accumulation of GM2 and GM3 gangliosides, which have been linked to neuroinflammation. There have been encouraging gene transfer studies in the MPS VII mouse brain, but this is the first study attempting the correction of the >200-fold larger and challenging canine MPS VII brain. Here, the efficacy of a helper-dependent (HD) canine adenovirus (CAV-2) vector harboring a human GUSB expression cassette (HD-RIGIE) in the MPS VII dog brain was tested. Vector genomes, ß-glu activity, GAG content, lysosome morphology and neuropathology were analyzed and quantified. Our data demonstrated that CAV-2 vectors preferentially transduced neurons and axonal retrograde transport from the injection site to efferent regions was efficient. HD-RIGIE injections, associated with mild and transient immunosuppression, corrected neuropathology in injected and noninjected structures throughout the cerebrum. These data support the clinical evaluation of HD CAV-2 vectors to treat the neurological defects associated with MPS VII and possibly other neuropathic lysosomal storage diseases.

Safe, efficient, and reproducible gene therapy of the brain in the dog models of Sanfilippo and Hurler syndromes.

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 of the brain in the dog model of Hurler's syndrome.

OBJECTIVE: A defect of the lysosomal enzyme alpha-L-iduronidase (IDUA) interrupts the degradation of glycosaminoglycans in mucopolysaccharidosis type I, causing severe neurological manifestations in children with Hurler's syndrome. Delivery of the missing enzyme through stereotactic injection of adeno-associated virus vectors coding for IDUA prevents neuropathology in affected mice. We examined the efficacy and the safety of this approach in enzyme-deficient dogs. METHODS: Because deficient dogs raise antibodies against IDUA in response to infusion, intracerebral vector injections were combined with an immunosuppressive regimen. RESULTS: Treatment was tolerated well. We observed broad dispersion of vector genomes in the brain of efficiently immunosuppressed dogs. The delivery of IDUA to large areas, which could encompass the entire brain, prevented glycosaminoglycan and secondary ganglioside accumulations. This condition was associated with drastic reduction of neuropathology throughout the encephalon. In contrast, vector injection combined with partial immunosuppression was associated with subacute encephalitis, production of antibodies against IDUA in brain tissues, and elimination of genetically modified cells. INTERPRETATION: Gene therapy directed to the entire brain is feasible and may be beneficial to children with Hurler's syndrome. The possibility of subacute encephalitis emphasizes the importance of preventing immune response against IDUA, a problem that needs to be considered in similar therapies for other genetic defects.