Mucopolysaccharidosis type I (MPS I) is an autosomal recessive storage disease caused by the absence of a-L-iduronidase (IDUA), resulting in systemic accumulation of glycosaminoglycan (GAG) storage materials, hepatosplenomegaly, skeletal dysplasias, cardiopulmonary obstruction, progressive neurologic impairment and death by age 15. MPS I is currently treated by enzyme replacement therapy (ERT) and by allogeneic hematopoietic stem cell transplantation (HSCT), but the neurologic effectiveness of these treatments is limited by the amount of IDUA enzyme provided to the brain. In this proposal, we present preliminary data demonstrating extraordinarily high levels of IDUA enzyme expression (2- to 40-fold normal) in all areas of the brain 10 months after intracerebroventricular infusion of neonatal (4-6 day old) MPS I mice with an adeno-associated virus serotype 8 (AAV8) vector transducing the human IDUA gene. This high level of IDUA expression prevented accumulation of GAG storage material, and completely prevented emergence of neurocognitive deficits exhibited by untreated animals in a Morris water maze test of spatial navigation and memory. These unprecedented results demonstrate that AAV-mediated IDUA gene transfer directly to the CNS has the potential to overcome the current limitations of ERT and HSCT in the treatment of MPS I. ReGenX, LLC, is a leading company in the development of AAV vectors for treatment of human disease. In this Phase I STTR project, we propose to combine ReGenX AAV vector technology with the University of Minnesota's experience in the treatment of lysosomal storage diseases to address key challenges that must be faced in the development of AAV mediated IDUA gene transfer to the CNS for treatment of MPS I in humans: (i) Which AAV serotype is most effective in mediating gene transfer into human neuronal cells? To address this question, we will compare the effectiveness of AAV8, AAV9 and AAVrh.10 for gene transfer efficiency in human neuronal primary cultures and brain tissue slices. (ii) Is there a less invasive route of AAV vector administration that can be used to achieve effective and widespread IDUA expression in the brain, and that would be more acceptable to IDUA-deficient patients and their families? To address this question, we will evaluate the effectiveness of intrathecal, intranasal, and endovascular (with blood brain barrier disruption) routes of AAV vector administration for human IDUA gene delivery and expression in the CNS. Results from these studies will directly impact the development of AAV-mediated IDUA gene transfer to the CNS as an approach for improved therapy of MPS I, and will also have significance for the application of AAV mediated gene transfer to the CNS for related metabolic and neurologic diseases.
Lysosomal storage disorders are a rare group of inherited diseases in which patients suffer from skeletal abnormalities, heart and breathing problems, mental retardation and death. It is envisioned in this grant application that one way to treat these diseases would be to restore the missing gene in patients'central nervous system (in the brain) to prevent neurodegeneration.