961. AAV1-Mediated Gene Delivery to the Adult GM1-Gangliosidosis Mouse Hippocampus Leads to Marked Reduction in Storage in Physically and Synaptically-Connected Areas of the Brain

Abstract

GM1-gangliosidosis is a lysosomal storage disease caused by an autosomal recessive deficiency of lysosomal acid beta-galactosidase (b-gal) leading to accumulation of GM1-ganglioside in the central nervous system, and often accompanied by severe mental retardation. Knock-out mouse models (GM1 KO) of this disease mimic the biochemical findings in humans, with absence of b-gal activity and extensive GM1-ganglioside storage throughout the brain. The experiments reported here were conducted to: 1) Investigate the efficiency of adeno-associated virus (AAV) vector-mediated delivery of mouse b-gal to the GM1 KO mouse brain; 2) Characterize the mechanisms by which this enzyme is distributed in the brain from the injection site; 3) Evaluate the therapeutic potential of this strategy by its ability to decrease GM1-ganglioside storage. The AAV vectors used in this study, AAV-CBA-MBG-W (mouse b-gal) and AAV-CBA-GFP-W (GFP), carry AAV2 ITRs, a CBA promoter to control transgene expression, a WPRE element, and a BGH polyA signal. One l of each virus stock was infused stereotaxically into the left hippocampus of 6 weeks old GM1 KO mice by convection-enhanced delivery (CED) at 0.1 l.min-1. One month later the brains were analyzed for b-gal expression by X-gal staining at pH 4.5, GFP expression in control mice, and GM1-ganglioside storage levels by immunofluorescence with an anti-GM1 ganglioside antibody. In mice injected with AAV-CBA-MBG-W, the ipsilateral hippocampus showed robust X-gal staining in most structures, while in the contralateral hippocampus staining was evident in the CA1-CA3 oriens, pyramidal, and radiatum layers, and the granule cell layer of the dentate gyrus (DG). Strong X-gal staining was also evident in the overlying ipsilateral cortex, while there was no apparent staining in the contralateral cortex. No X-gal staining was evident in control mice injected with GFP-encoding vector. In these mice there was strong GFP expression in the granule and pyramidal cell layer of the ipsilateral DG and CA3, respectively, and in the CA1-CA3 oriens and radiatum layers in both hemispheres. The Ipsilateral hippocampus in AAV-CBA-MBG-W injected mice was completely devoid of GM1-ganglioside storage while in the contralateral hippocampus there was a significant decrease in storage in the CA1-CA3 pyramidal layer and granule cell layer of the DG. A significant reduction in storage was also observed in the ipsilateral overlying cortex. In mice injected with the GFP-encoding vector there was strong storage in the CA1-CA3 pyramidal layer, granule cell layer of the DG, and cortex.