Expression of human glucocerebrosidase in murine macrophages: identification of efficient retroviral vectors

Gaucher's disease is an autosomal recessive disorder characterized by a functional deficiency in beta-glucocerebrosidase enzymatic activity and the resultant accumulation of the glycolipid glucocerebroside in macrophages. Due to the nature of the affected cells, Gaucher's disease is an excellent candidate for gene therapy of hematopoietic stem cells and autologous bone marrow transplantation of transduced cells using retroviral vectors containing the glucocerebrosidase (GC) gene. In order to identify a retroviral vector capable of high levels of expression of the GC gene in macrophages, we have used the murine myeloid leukemia cell line, M1, a cell line that can be differentiated with interleukin-6 (IL-6) from blasts to macrophages. Two vectors use the Moloney murine leukemia virus (MoMLV) enhancer/promoter (LG vector) or the myeloproliferative sarcoma virus (MPSV) enhancer/MoMLV promoter (MG vector), both located in the viral long-terminal repeat (LTR); the third vector uses the phosphoglycerate kinase (PGK) promoter located internally in the vector (PG vector). The amphotropic PA317 and GP+am12 packaging cell lines were used as virus producer cells, and the GP+am12 cell line demonstrated higher titers, higher levels of GC protein expression, and specific GC enzymatic activity as well as higher transduction efficiencies for all three vectors. The LG retroviral vector was the most efficient in transducing the M1 cells. On average, higher levels of RNA and protein expression were seen in the M1 clones transduced with the LG vector, and these levels increased after differentiation. Thus, the LG retroviral vector in which the expression of the GC gene is driven by the MoMLV LTR enhancer/promoter is the best vector of the three studied for future studies for gene therapy of Gaucher's disease and other hematopoietic disorders that involve macrophages.