Comparison of lipid-mediated and adenoviral gene transfer in human monocyte-derived macrophages and COS-7 cells

Lipid-mediated transfection was compared to adenoviral-mediated gene transf er in COS-7 cells as well as human monocyte-derived macrophages (HMDM). For this purpose, we monitored enhanced green fluorescent protein (EGFP) expre ssion by fluorescence microscopy and quantified gene transfer by competitiv e PCR. Transfection of COS-7 cells with a novel lipid formulation for DNA t ransfer was highly effective in COS-7 cells. On average, 30% of the cells w ere fluorescent 48 h after transfection. In HMDM, the same formulation resu lted in the expression of EGFP in less than 0.5% of cells. We measured plas mid DNA by quantitative PCR in lipid-transfected macrophages and found that each macrophage contained on average 2 fg of plasmid DNA 24 h after transf ection, that is, more than 400 molecules of plasmid DMA entered each cell. Despite the high level of reporter DNA in lipid transfected cells, expressi on of the fluorescent protein was suppressed in more than 99.5% of the macr ophages. We also used adenoviral gene transfer to introduce the foreign DNA into both COS-7 cells and HMDM. Even through the multiplicity of infection was less than 30, expression of EGFP was observed in nearly all COS-7 cell s and in more than 80% of HMDM 48 h after transfection. Despite major advan ces in the field of lipid-mediated transfection of HMDM, the lipid formulat ions that are available commercially cannot compete with the efficiency of adenoviral gene transfer.