230. Neural Progenitor Cell Transduction with AAV Serotypes 1 and 4

Abstract

The mucopolysaccharidoses (MPS) and the ceroid lipofuscinoses (NCLs) are devastating childhood onset diseases. Some forms of MPS and all NCLs have a severe CNS component. MPS VII, or beta-glucuronidase deficiency, and late-infantile NCL, or tripeptidyl protease deficiency are due to mutations in mRNAs encoding soluble lysosomal enzymes. Prior work in our laboratory and others' demonstrated that overexpression of beta-glucurondiase or TPP-1 from transduced cells in brain can lead to enzyme activity in non-transduced cells remote from the injection site, and improvements in cellular pathology and behavioral deficits. This occurs through a process called cross-correction. We hypothesized that cross-correction could also occur from gene-corrected endogenous neural progenitor cells (NPCs). Transduction of endogenous NPCs with virus expressing beta-glucuronidase or TPP-1 may allow enzyme secretion at several sites: 1) in the SVZ (with enzyme secreted into the ventricular system); 2) during migration through the corpus callosum (with enzyme secreted along the extensive white matter tracts of the corpus callosum); and 3) from differentiated neurons in the olfactory bulb (OB). We tested AAV1 and AAV4 for their ability to target endogenous neural progenitors. AAV4 vector injected unilateral into the lateral ventricle of adult or P0 C57BL/6 mice resulted in highly specific transduction of ependymal cells along the ventricular wall. Only scattered transgene positive cells were observed in the rostral migratory stream (RMS) and olfactory bulb in tissues harvested from several days to 8 weeks after gene transfer, regardless of injection time. Transgene positive cells did not express neuronal cell marker, indicating that NPCs were not a major target of AAV4 transduction in vivo. In contrast to AAV4, transgene positive migrating neuroblasts and olfactory bulb neurons were obvious after unilateral intraventricular injection of AAV1. However, numbers remained too few to consider AAV1-transduced NPCs as a significant source of recombinant lysosomal enzymes. Thus, transduction of endogenous NPCs with AAV4 does not occur, and with AAV1 is limited, preclude the use of these vectors for therapeutic application via NPCs.