425. AAV2-Mediated Expression of Iduronate Sulfatase in Peripheral Tissues and the CNS in Mucopolysaccharidosis II Mouse Model by Combined Intravenous and Intracisternal Vector Delivery

Abstract

Mucopolysaccharidosis II (MPS II, Hunter syndrome) is an X-linked disease due to the deficiency of the lysosomal enzyme iduronate sulfatase (Id-S). Deficiency of iduronate sulfatase results in lysosomal accumulation of dermatan sulfate and heparan sulfate, with progressive tissue and organ dysfunction, and premature death. No definite treatment is available for MPS II patients. Clinical trials of peripheral administration of recombinant Id-S in MPS II patients are in progress, but CNS disease is not expected to be improved. Therapeutic effects of AAV gene delivery on both somatic and the CNS features in adult MPS II |[ldquo]|knockout|[rdquo]| mice were studied using combined intravenous (IV) and intracisternal (IC) injections after pretreatment with mannitol. An AAV serotype 2 vector, AAV2-CMV-hIdS, was used, containing a human iduronate sulfatase cDNA (hIdS) driven by a cytomegalovirus promoter (CMV). A dose of AAV2-CMV-hIdS viral vector (2|[ndash]|4|[times]|1011 viral particles in 200|[mu]|l) was delivered into adult (4|[ndash]|6 week old) MPS II mice (n=20) by tail vein injection 10 minutes after an IV infusion of mannitol (1|[ndash]|2 mg/gm of body weight). A dose of AAV2-CMV-hIdS (2|[ndash]|4|[times]|1010 viral particles in 20 |[mu]|l) was delivered into the posterior cistern after the tail vein injection of AAV2 vector. Treated MPS II mice were scarified when they developed severe neurological symptoms, such as bladder distension, weight loss and gait abnormalities, at 15 to 23 months of age. Our results demonstrated the correction of GAG storage in multiple organs/tissues after the AAV-mediated gene transfer. Complete correction of GAG accumulation in liver was achieved (P<0.01) and partial correction in spleen, heart, muscle, and lung was observed (P<0.05). No decrease of GAG content was observed in the kidney of the mice after AAV delivery. Id-S enzyme activity was detected in the treated MPS II mouse liver (50%|[ndash]|100% of normal mouse liver). The non-treated MPS II mice have no detectable Id-S activity in any tissue. Histopathology and transmission electron microscopy studies demonstrated clearance of lysosomal storage in liver. Decreased CNS lysosomal storage was shown by histopathology in Purkinje cells and also in the neurons of the hippocampus, thalamus and cerebral cortex after AAV-mediated gene transfer. Id-S enzyme was also detected in the brain of the AAV injected mice (1%|[ndash]|7% of normal mouse brain). Physical appearances of treated MPS II mice, such as facial feature and spinal curvature, were clearly improved. Our results demonstrated that the life span of the MPS II mice after the AAV gene therapy was prolonged (means 17.8 months), compared with the life span of the non-treated group (means 13.4 months) (p<0.01). Our results suggest that IV injection combined with an IC injection of AAV2 vector following mannitol pretreatment is a promising approach for treating both somatic and CNS disease in lysosomal storage disorders.