COMPLETE CORRECTION OF ACID ALPHA-GLUCOSIDASE DEFICIENCY IN POMPE-DISEASE FIBROBLASTS IN-VITRO, AND LYSOSOMALLY TARGETED EXPRESSION IN NEONATAL RAT CARDIAC AND SKELETAL-MUSCLE

The enzyme acid alpha-glucosidase catalyzes the breakdown of lysosomal glycogen. Absence of this enzyme results in infantile Pompe disease, characterized by hypertrophic cardiomyopathy, skeletal muscle weakness and fatal heart failure by 2 years of age. We have examined the possi bility of gene replacement therapy for this disease, by constructing a n E1-deleted recombinant adenovirus encoding human acid alpha-glucosid ase (Ad-GAA). The dose-response in fibroblasts from patients with Pomp e disease transduced with this vector is linear over the range tested (one to 2000 plaque forming units (p.f.u.) of Ad-GAA per cell), and ac id alpha-glucosidase activity comparable to that of normal fibroblasts is achieved at 100 p.f.u. per cell. Targeting of the recombinant prot ein to the lysosomal compartment was confirmed by immunocytochemistry. In vivo expression was examined by injecting Ad-GAA into newborn rats ; intracardiac administration produced 10 times the normal level of ac id alpha-glucosidase activity in whole heart lysates while a hind-limb i.m. injection increased activity in that muscle to six times the nor mal level. Western blotting of these tissues detected species at 76 kD a consistent with the size of processed lysosomal enzyme and levels of expression as high as 1.0 mg recombinant protein per gram of tissue w et weight were produced. These data demonstrate high-level, lysosomal expression of recombinant acid alpha-glucosidase in treated target tis sues and support the feasibility of gene replacement strategies for Po mpe disease.