Systemic treatment of 2-day-old twitcher mice using the engineered AAV9 galactosylceramidase vector attenuated neuropathology. Top panels: representative photomicrographs of sciatic nerve toluidine blue staining from a normal mouse, an untreated twitcher mouse, and an AAV-treated twitcher mouse. Bottom panels: representative PAS staining photomicrographs of the cerebellum from a normal mouse (170 days old), an untreated twitcher mouse (48 days old), and an AAV-treated twitcher mouse (170 days old). Arrowhead, foamy macrophage. PAS, periodic acid-Schiff.