Retrovirus-mediated correction of the metabolic defect in cultured Farber disease cells

Farber disease is a rare severe lysosomal storage disorder due to a deficie nt activity of the enzyme acid ceramidase (AC), Patients have granulomas al ong with lipid-laden macrophages that accumulate in a number of tissues, le ading to multiple diverse clinical symptoms. There is no therapy for the di sorder and most patients succumb to the disease in early childhood. The sev erity of the disease progression seems to correlate with the amount of the accumulated ceramide substrate. Since the cDNA for human AC has been elucid ated we sought to establish if genetic transfer of this sequence would lead to enzymatic and, especially, functional correction of the catabolic defec t in Farber patient cells. To do this, a novel amphotropic recombinant retr ovirus was constructed that engineers transfer of the human AC cDNA, On inf ection of patient fibroblasts, AC enzyme activity in cell extracts was comp letely restored. Further, substrate-loading assays of intact living cells s howed a fully normalized catabolism of lysosomal ceramide, Lastly, as repor ted for some other corrected enzymatic defects of lysosomes, metabolic coop erativity was seen, in that functionally corrected patient fibroblasts secr eted AC that was taken up through the mannose 6-phosphate receptor and used by uncorrected fibroblasts as well as recipient Farber lymphoblastoid cell s. This overall transduction and uptake scenario for Farber disease allows future treatment of this severe disorder to be envisioned using gene transf er approaches.