Correction of deficient enzyme activity in a lysosomal storage disease, aspartylglucosaminuria, by enzyme replacement and retroviral gene transfer.

The ability of lysosomal enzymes to be secreted and subsequently captured by adjacent cells provides an excellent basis for investigating different therapy strategies in lysosomal storage disorders. Aspartylglucosaminuria (AGU) is caused by deficiency of aspartylglucosaminidase (AGA) leading to interruption of the ordered breakdown of glycoproteins in lysosomes. As a consequence of the disturbed glycoprotein catabolism, patients with AGU exhibit severe cell dysfunction especially in the central nervous system (CNS). The uniform phenotype observed in these patients will make effective evaluation of treatment trials feasible in future. Here we have used fibroblasts and lymphoblasts from AGU patients and murine neural cell lines as targets to evaluate in vitro the feasibility of enzyme replacement and gene therapy in the treatment of this disorder. Complete correction of the enzyme deficiency was obtained both with recombinant AGA enzyme purified from CHO-K1 cells and with retrovirus-mediated transfer of the AGA gene. Furthermore, we were able to demonstrate enzyme correction by cell-to-cell interaction of transduced and nontransduced cells.