Global gene transfer into the CNS across the BBB after neonatal systemic delivery of single-stranded AAV vectors

Central nervous system (CNS) disorders are important targets for gene therapy; however, delivery of therapeutic proteins and/or genes to the brain remains a major challenge due to the difficulty of efficiently delivering viral vectors across the blood-brain barrier (BBB). In the present work, we tested the ability of several single-stranded adeno-associated viral (ssAAV) serotypes to deliver transgenes to the brain and spinal cord in neonatal mice. We injected ssAAV vectors encoding GFP (serotype-1, -8, -9 and -10: 1.5×10(11) vector genomes each) into the jugular vein of neonatal mice and assessed GFP expression immunohistochemically. Strong GFP signals were detected in both the brain and spinal cord after injection of any of these serotypes. ssAAV serotype-9 mediated gene transfer was the most efficient. GFP expression was detected throughout the brain, including the cortex, cerebellum, olfactory bulb and brainstem and was sustained for at least 18months. Immunohistochemical staining showed that the GFP signals were detected in GFAP positive astrocytes, NeuN positive neurons, and Calbindin positive purkinje cells. Our data suggest that systemic neonatal injection of ssAAV is an effective strategy for delivering transgenes to target neuronal systems that are not accessible to viral vectors in adult animals. These vectors should prove highly useful for efficient and long-term overexpression or downregulation of genes in CNS and spinal cord and could be a useful means of treating genetic neurological diseases.