Adeno-associated virus serotype 9 carrying the human NAGLU gene under the control of a CMV enhancer/promoter (rAAV9.CMV.hNAGLU) will be delivered one-time through a venous catheter inserted into a peripheral limb vein. The vector will be delivered undiluted over 10 to 20 minutes, under light to moderate sedation as needed. Dosing volume will be approximately 2-5 mL/kg, depending on final vector product concentration and subject cohort. A tapering course of prophylactic enteral prednisolone will be administered.