Gene Replacement in Acid Maltase Deficiency Using DNA Viral Vectors. • 98

The lysosomal enzyme acid maltase catalyzes the breakdown of glycogen. Complete absence of this enzyme results in infantile Pompe's disease, characterized by hypertrophic cardiomyopathy, skeletal muscle weakness, and fatal heart failure by two years of age. To examine the feasibility and efficacy of gene replacement therapy in Pompe's disease, we have constructed an El-deleted recombinant adenovirus (Ad-GAA) and a recombinant adeno-associated viral (AAV) vector (AAV-GAA) that encode human acidα-glucosidase. AAV vectors are able to lead to sustained transduction of differentiated cells, particularly striated muscle, which is affected in Pompe's disease. Transduction of fibroblasts isolated from Pompe's disease patients demonstrates a dose-dependent increase in GAA expression and complete restoration of cellular GAA activity. A portion of the GAA protein is secreted and, therefore is transferable to nontransduced deficient cells. Appropriate subcellular targeting of GAA produced in Ad-GAA or AAV-GAA treated cells was confirmed by immunocytochemistry with a GAA-specific antibody and co-localization with lysosomal membrane associated protein (LAMP-1). In vivo expression was tested following intracardiac injection of 8 × 108 pfu of Ad-GAA in newborn rodents resulting in acid maltase activity in cardiac tissue of 10-fold the control activity. Following i.m. injection of 2 × 1010 particles of AAV-GAA in the tibialis anterior muscle of adult mice, the GAA activity in muscle was 4-fold control activities for up to 3 months following transduction. Protein blotting with human-specific antibody detects a 76 kDa species, consistent with the size of the fully processed lysosomal enzyme. These data demonstrate the feasibility of gene replacement for correction of the enzyme deficiency in Pompe's disease using DNA viral vectors. The authors have pending patent applications relating to AAV gene delivery and are entitled to related royalty payments.

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(Spon by: Robert H. Yolken, M.D.)

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Byrne, B., Pauly, D., Zhang, G. et al. Gene Replacement in Acid Maltase Deficiency Using DNA Viral Vectors. • 98. Pediatr Res 41, 19 (1997).

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