CNS application of AAV-CtsD prolonged lifetime of CtsD−/− mice. Survival times in days are shown for CtsD−/− mice injected with control virus (n = 6) or PBS (n = 8) (A), injected into visceral organs with AAV-CtsD (n = 10) (B), injected into brain either unilaterally (n = 4, black circles) or bilaterally (n = 3, white circles) with AAV-CtsD (total n = 7) (C), injected into brain plus periphery with AAV-CtsD (n = 6) (D), and injected with the enzymatically inactive CtsDAsn231 mutant into the brain (n = 7) (E). Survival times were significantly different between controls (PBS/AAV-EGFP) and AAV-CtsD brain-injected animals, and between animals survived for about 60, 130, or 190 days after AAV-CtsD brain + visceral injection, as assessed by Student’s t test at P < 0.01.