Correction of brain oligodendrocytes by AAVrh.10 intracerebral gene therapy in metachromatic leukodystrophy mice

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder characterized by accumulation of sulfatides in glial cells and neurons, the result of an inherited deficiency of arylsulfatase A (ARSA; EC 3.1.6.8) and myelin degeneration in the central and peripheral nervous systems. No effective treatment is currently available for the most frequent late infantile (LI) form of MLD, which results in rapid neurological degradation and early death after the onset of clinical manifestations. To potentially arrest or reverse disease progression, ARSA enzyme must be rapidly delivered to brain oligodendrocytes of patients with LI MLD. We previously showed that brain gene therapy with adeno-associated virus serotype 5 (AAV5) driving the expression of human ARSA cDNA under the control of the murine phosphoglycerate kinase (PGK) promoter alleviated most long-term disease manifestations in MLD mice. Herein, we evaluated the short-term effects of AAVrh.10 driving the expression of human ARSA cDNA under the control of the cytomegalovirus/β-actin hybrid (CAG/cu) promoter in 8-month-old MLD mice that already show marked sulfatide accumulation and brain pathology. Within 2 months, and in contrast to results with the AAV5-PGK-ARSA vector, a single intrastriatal injection of AAVrh.10cuARSA resulted in correction of brain sulfatide storage, accumulation of specific sulfatide species in oligodendrocytes, and associated brain pathology in the injected hemisphere. Better potency of the AAVrh.10cuARSA vector was mediated by higher neuronal and oligodendrocyte transduction, axonal transport of the AAVrh.10 vector and ARSA enzyme, as well as higher CAG/cu promoter driven expression of ARSA enzyme. These results strongly support the use of AAVrh.10cuARSA vector for intracerebral gene therapy in rapidly progressing early-onset forms of MLD.