Adeno-associated Virus Type 5 Reduces Learning Deficits and Restores Glutamate Receptor Subunit Levels in MPS VII Mice CNS

A major challenge in treating lysosomal storage diseases with enzyme therapy is correcting symptoms in the central nervous system (CNS). This study used a murine model of mucopolysaccharidosis type VII (MPS VII) to test whether pathological and functional CNS defects could be corrected by expressing β-glucuronidase via bilateral intrastriatal injection of adeno-associated virus type 5 (AAV5βgluc) vectors. After injecting AAV5βgluc, different brain regions expressed active β-glucuronidase, which corrected lysosomal storage defects. Compared to age-matched littermates, adult MPS VII mice were impaired in spatial learning and memory, as measured by the repeated acquisition and performance chamber (RAPC) assay. AAV5βgluc-treated MPS VII mice improved significantly in the RAPC assay, relative to saline-injected littermates. Moreover, our studies reveal that cognitive changes in MPS VII mice correlate with decreased N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid receptor expression. Importantly, AAV5βgluc delivery restored glutamate receptor levels. Together, these data demonstrate that AAV5 vectors deliver a therapeutically effective β-glucuronidase gene to the CNS and further suggest a possible mechanism underlying spatial learning defects in MPS VII mice.