244. AAV Vector-Mediated Gene Therapy of Mucopolysaccharidosis Type I

Mucopolysaccharidosis type I (MPSI) is a lysosomal storage disorder caused by loss of activity of the enzyme |[alpha]|-L-iduronidase (IDUA), which is responsible for the catabolism of the glycosaminoglycans dermatan and heparan sulfate. The most severely manifested form of the disease is Hurler syndrome, in which death affects children by the first decade, due to respiratory failure and cardiac disease.We recently reported the correction of metabolic, neurologic and craniofacial manifestations of MPSI in a murine model of the disease treated at birth by intravenous injection of an AAV vector transducing the IDUA gene (Hartung et al, Mol. Ther. 9:866-875, 2004). Our current goal is to evaluate the effect of AAV vector mediated transduction of the IDUA gene-both in the brain and in peripheral tissues of adult IDUA (-/-) mice using different AAV serotypes and routes of administration. We have constructed a bicistronic vector containing the human IDUA cDNA under transcriptional regulation of the hybrid Cags promoter with a downstream enhanced GFP (eGFP) reporter gene preceded by an ECMV IRES facilitating translation of eGFP. We have also constructed a similar bicistronic vector in which an epitope tag has been engineered onto the carboxyl terminus of IDUA in order to identify cells that have been cross corrected by IDUA expression. This vector was tested both in vitro and in vivo for expression of both IDUA and GFP. IDUA enzyme levels in vitro were 20-fold higher than background untransfected controls, 500-fold higher in plasma and 20-fold higher in the liver of injected mice, compared to wild type control animals. This vector upon packaging was shown to efficiently transduce cells in vitro as determined by IDUA enzyme assay and GFP fluorescence. Experiments to evaluate the efficacy of this vector in reversing or attenuating the brain disease as well as other abnormalities observed in adult MPS type I mice are currently in progress.