1063. In Utero β-Glucuronidase Gene Transfer with AAV Vectors Results in Widespread Transduction, Enzyme Activity, and Disease Correction in the MPS VII Mouse Brain

Abstract

Mucopolysaccharidosis (MPS) VII is a heritable lysosomal storage disease caused by the deficiency of b-glucuronidase (GUSB) enzyme. MPS VII is a chronic and progressive multiorgan disorder with signs of pathology already present during fetal life. Most therapeutic approaches for MPS VII have focused on postnatal treatments. Although these approaches can reverse storage lesions, the central nervous system (CNS) is more difficult to treat. We investigated in utero gene transfer in the MPS VII mouse CNS with AAV 1 and AAV2. We injected 1 μl of AAV1 (3.3×1013 genomes/ml) or AAV2 (1.4×1012 genomes/ml) into the lateral ventricle of the fetal brain on day 15.5 of gestation. AAV1 injected brains demonstrated extensive and widespread GUSB activity and mRNA expression the brain. There was retrograde transport of GUSB to the ganglion cells of the retina. GUSB activity was detected in the gray matter throughout most of the spinal cord segments. Storage lesions were reversed in the brain and spinal cord. Ubiquitin immunoreactivity was significantly reduced compared to the affected control. This suggested that in utero gene transfer with AAV1 corrected the disease and prevented the subsequent neurodegeneration. The AAV2 treated brains were treated with a lower dose of vector than the AAV1 experimental group, and these brains have significantly lower levels of enzyme and vector transduction. Very few GUSB positive ganglion cells were detected in the retina, and low levels of GUSB activity was present in the gray matter of the spinal cord. Evaluation of disease correction in the eye, spinal cord and brain for the AAV2 treated brains is ongoing. These results suggest that fetal gene therapy with AAV vectors may provide a therapeutic strategy capable widespread enzyme distribution and disease correction in the CNS.