Retrovirus-mediated enzymatic correction of Tay-Sachs defect in transduced and non-transduced cells

Tay-Sachs disease is a severe neurodegenerative disorder due to mutationsin the HEXA gene coding for the alpha-chain of the alpha-beta heterodimericlysosomal enzyme beta-hexosaminidase A (HexA). Because no treatment isavailable for this disease, we have investigated the possibility ofenzymatic correction of HexA-deficient cells by HEXA gene transfer. HumanHEXA cDNA was subcloned into a retroviral plasmid generating to G.HEXAvector. The best Psi-CRIP producer clone of G.HEXA retroviral particles wasisolated, and murine HexA-deficient fibroblasts derived from hexa -/- micewere transduced with the G.HEXA vector. Transduced cells overexpressed thealpha-chain, resulting in the synthesis of interspecific HexA (humanalpha-chain/murine beta- chain) and in a total correction of HexAdeficiency. The alpha-chain was secreted in the culture medium and taken upby HexA-deficient cells via mannose-6-phosphate receptor binding, allowingfor the restoration of intracellular HexA activity in non-transduced cells.