LIVER-DIRECTED GENE-TRANSFER IN NONHUMAN-PRIMATES

To develop a primate model for liver-directed gene therapy, we studied several gene transfer vehicles and routes in eight rhesus monkeys (Ma caca mulatta). For this purpose, we used first-generation, replication -deficient adenoviral vectors carrying the Escherichia coli lacZ gene (Ad.CMVlacZ) or a lacZ-containing plasmid (pCMV beta) with lipofectami ne for transfection. The reporter gene construct was infused into eith er the portal vasculature, common bile duct, or saphenous vein. Adenov irus-mediated gene transfer via the portal vein resulted in expression of lacZ in over 70% of hepatocytes by days 3-7, but was accompanied b y acute hepatitis. Adenovirus-mediated gene transfer via the common bi le duct resulted in lacZ expression in less than 10% of hepatocytes an d was accompanied by portal inflammation. The animals mounted a signif icant immune response, as demonstrated by adenoviral antigen-induced T -cell proliferation and production of neutralizing anti-adenovirus ant ibodies and antibodies to E. coli beta-galactosidase (beta-Gal). Activ ation of the immune response was associated with rapid decrease of the reporter gene by days 13-21. Lipofectamine-mediated gene transfer was inefficient, and no lacZ expression in the liver was detected. To lim it the host immune response, 4 animals were immunosuppressed by cyclop hosphamide/prednisone and then infused with the Ad.CMVlacZ via the por tal vein or the saphenous vein. The monkeys showed sustained expressio n of lacZ for up to 35 days with no evidence of inflammation. The prim ates transduced via the saphenous vein showed a level of beta-Gal expr ession in the liver similar to that of the portal vein-infused animals . In conclusion, adenovirus-mediated gene transfer to non-human primat e livers via the portal vein or saphenous vein is efficient, but it re sults in transient expression and is accompanied by an immune response to both vector and transgene products and acute hepatitis, whereas li pofectamine-mediated transfer is inefficient. Manipulation of the host immune response may expand potential applications of adenoviral vecto rs for liver-directed gene transfer.