Lysosomal enzyme replacement of the brain with intravenous non-viral gene transfer

Purpose. The delivery of non-viral plasmid DNA to brain across the blood-brain barrier (BBB) with intravenous administration of non-viral plasmid DNA encoding a lysosomal enzyme, beta-glucuronidase (GUSB), was examined in GUSB null mice, a model of type VII mucopolysaccharidosis. Methods. The plasmid, designated pCMV-GUSB, is encapsulated in Trojan horse liposomes, which are targeted across the BBB, and the brain cell membrane, with a monoclonal antibody to the mouse transferrin receptor. Results. The GUSB enzyme activity was increased > 50-fold in cell culture of fibroblasts obtained from GUSB null mice, following application of the antibody-targeted liposomes carrying the pCMV-GUSB, and enzyme activity remained high for > 2 weeks. Adult GUSB null mice were treated with a single intravenous administration of 0.2 ml of Trojan horse liposomes carrying the pCMV-GUSB at a dose of 10 mu g/mouse of plasmid DNA. The GUSB enzyme activity was increased greater than tenfold in brain, liver, spleen, lung, and kidney, but not in heart. Conclusions. Intravenous Trojan horse liposome administration increased brain GUSB enzyme activity to the therapeutic range of brain GUSB enzyme activity. These studies show it is possible to deliver non-viral plasmid DNA encoding lysosomal enzymes to the brain following intravenous administration of receptor-specific Trojan horse liposomes.