Noninvasive monitoring of long-term lentiviral vector-mediated gene expression in rodent brain with bioluminescence imaging.

Gene transfer into the central nervous system is an emerging therapeutic strategy for a range of neurological diseases, including neurodegeneration. This approach would benefit from imaging technologies that could determine the extent, magnitude, and duration of transgene expression. We have used bioluminescence imaging (BLI) to image lentiviral vector-mediated gene transfer into the mouse brain. We constructed human immunodeficiency virus type 1 lentiviral vectors that encode firefly luciferase and transduce cells in culture. After stereotactic injection of these vectors into the brain, we were able to detect luciferase expression in living mice and rats. We characterized the signal in mouse brain in terms of localization, kinetics, resolution, and reproducibility and demonstrated that it correlates with the level of firefly luciferase expression. Although the signal decreased gradually to about 20% of the initial value in the first month, the signal remained constant thereafter for more than 10 months. We demonstrated that the light signal can be used as a reporter by using a bicistronic vector. This is the first study to document noninvasive monitoring of long-term transgene expression in the adult mouse brain and provides the basis for applying BLI in the study of brain disease and gene therapeutic strategies.