| A large number of single gene disorders affect the central nervous system (CNS), many of which are caused by deficiencies of specific enzymes in metabolic pathways. Somatic gene transfer has the potential to permanently correct the underlying metabolic deficiency by transferring a normal copy of a defective gene into a patient's own cells. In the mouse brain, widespread enzyme expression by direct intracranial injection of viral vectors has been achieved. However, there is little data on gene transfer to the CNS of large animals. The goal of this study was to develop a large animal model of a lysosomal storage disease (LSD) in order to characterize CNS pathology and gene therapy using quantitative magnetic resonance imaging (MRI) and clinical/pathological assessments.; We evaluated the ability of three adeno-associated virus (AAV) serotypes to transduce and express the lysosomal enzyme beta-glucuronidase (GUSB) in the normal cat brain. The human GUSB cDNA was packaged into AAV1, 2, and 5 serotype capsids and injected into the brains of 8-week-old cats. The brains were examined for gene expression 10 weeks after surgery. The AAV2 vector transduced cells in the gray matter, while the AAV1 vector resulted in greater transduction of the gray matter than AAV2 as well as transduction of the white matter. AAV5 did not result in detectable transduction in the cat brain.; We next studied cats with the lysosomal storage disease alpha-mannosidosis (AMD). First, the clinical, MRI, and pathological aspects of the CNS disease were defined. Then, an AAV1 vector carrying a wild type copy of the feline lysosomal alpha-mannosidase cDNA was injected into the brains of 8-week-old affected cats. Weekly neurological examinations were performed on affected, treated, and normal cats. Magnetic resonance imaging was performed at 16 weeks of age followed by post mortem analysis by histology, in situ hybridization, and biochemistry. Our data reveal expression of lysosomal alpha-mannosidase in the brains of AMD cats and marked improvement in clinical, MRI, and neuropathological evidence of disease. |
