212. Delivery of Galactocerebrosidase Activity to the Peripheral Nervous System of Mice with Globoid Cell Leukodystrophy (Krabbe Disease) by Intramuscular Injection

Abstract

Globoid cell leukodystrophy (GLD) or Krabbe disease is a neurodegenerative disorder that affects both the central and peripheral nervous system (CNS and PNS). The deficiency of the lysosomal enzyme galactocerebrosidase (GALC) leads to the accumulation of psychosine, resulting in the death of oligodendrocytes and Schwann cells. Bone marrow transplantation (BMT) of the mouse models of GLD can prolong their lives up to one year compared to 40-50 days if untreated. Intracranial and intraventricular injections of adeno-associated virus (AAV) types 1 and 5 containing mouse GALC cDNA into affected mice results in widespread GALC expression in the brain, pathological improvement and modest extension of life span compared to untreated mice. Mice treated with either BMT or viral therapy still demonstrate mild twitching and premature death at least partially due to lack of correction of PNS pathology. In an attempt to improve the biochemical and pathological condition of the peripheral nerves in affected mice, AAV2/1-mGALC viral particles were injected into the gastrocnemius muscles of affected mice. Biochemical analysis of the different tissues from the treated mice demonstrated very high GALC activity in the injected muscle and significantly increased GALC activity in the contralateral muscles. This was confirmed by histochemical staining of GALC activity where a large number of myofibers and the sciatic nerve in the injected side were strongly positive. The sciatic nerve on the contralateral side was also positive for GALC activity. While the sciatic nerve of untreated affected mice was thickened due to edema, initial studies following intramuscular injection showed that the sciatic nerve was much thinner and similar to control mice. Sections from the spinal cord also demonstrated some GALC-positive motoneurons indicating retrograde transfer of AAV2/1-GALC from the intramusclar injections. Transgene expression in the injected muscle was still very strong three months after injection. Combining intramuscular injections with other therapeutic approaches that improve the CNS pathology may have additional advantages in the successful treatment of the animal models of GLD.