RECEPTOR-MEDIATED GENE-TRANSFER INTO MACROPHAGES

Gene transfer systems targeting various receptors have been developed to introduce functional genes into cells in culture and into intact an imals. A synthetic molecular conjugate, consisting of mannosylated pol ylysine that exploits endocytosis via the macrophage mannose receptor, was constructed and complexed to expression plasmids containing eithe r the Photinus pyralis luciferase or Escherichia coil beta-galactosida se (lacZ) reporter genes. The DNA complexes were used to transfect mur ine macrophages isolated from peritoneal exudates in vitro, Luciferase and beta-galactosidase activity ,vas found in transfected cells in cu lture, whereas complexes consisting of an irrelevant plasmid hound to mannosylated polylysine or the expression plasmid bound to galactosyla ted polylysine resulted in no detectable transgene expression, Gene tr ansfer was inhibited by the addition of excess mannosylated bovine ser um albumin to the culture medium before transfection. Reporter genes w ere also transferred into macrophages residing in the spleen and liver of adult animals using this system. Luciferase activity was maximal a t 4 days after transfection and decreased to lower levels by 16 days. Transgene expression conformed to the distribution of cells that had n onspecific esterase, a cytochemical marker for macrophages. Thus, this system can be used to introduce functional genes into macrophages and may be an approach to the treatment of storage diseases that affect t he reticuloendothelial system.