Gene Transfer by DNA/Glycosylated Polylysine Complexes into Human Blood Monocyte-Derived Macrophages

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Abstract
Macrophages are putative target cells for expressing an exogenous gene with therapeutical effects. Knowing that macrophages express membrane lectins mediating endocytosis of their ligands, DNA/glycosylated polylysine complexes were used to transfect human blood monocyte-derived macrophages. Monocytes from human peripheral blood were matured in culture for 7 days to differentiate into macrophage-like cells in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Adherent cells, which displayed characteristic macrophage markers, CD 14, CD 11b, HLA-DR, and HLA-ABC antigens and mannose receptor, were transfected by DNA/glycosylated polylysine complexes in the presence of chloroquine. The luciferase reporter gene expression was maximal 24 hr after transfection with a DNA/mannosylated polylysine complex and by using plasmids in which the promoters (either the long terminal repeat of the human immunodeficiency virus or the human cytomegalovirus) drove the luciferase gene expression. Luciferase gene expression was lower when the promoter was the early region of the large T antigen of SV40 virus. Transfection mediated by DNA/mannosylated polylysine complexes was much more efficient than with DEAE-dextran or lipofectin. The possibility of transferring and expressing an exogenous gene into macrophage-like cells by using a nonimmunogenic synthetic vector as a DNA carrier opens new ways to develop nonviral gene therapy strategies. Several receptor-mediated gene delivery systems have been developed to target cells specifically. Macrophages are known to express several membrane lectins mediating endocytosis. In this report, we show that macrophages obtained by in vitro culture of human blood monocytes in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) for 7 days were transfected by DNA/glycosylated polylysine complexes in the presence of chloroquine. Several parameters were studied to get an efficient gene transfer into monocyte-derived macrophages, including the conditions of in vitro maturation of monocytes, the type of sugar residues bound to polylysine, the nature of the promoter, the chloroquine concentration, and the time course of luciferase gene expression.