EFFICIENT FAS-LIGAND GENE-EXPRESSION IN RODENT LIVER AFTER INTRAVENOUS-INJECTION OF A RECOMBINANT ADENOVIRUS BY THE USE OF A CRE-MEDIATED SWITCHING-SYSTEM

An adenovirus vector AxCALNFasL was constructed in order to transduce a gene for rat Fas-ligand, requiring co-expression of Cre recombinase for ifs expression. In the cosmid cassette, pAxCALNFasL, a stuffer DNA fragment flanked with two loxP sequences was placed between the promo ter and Fas-ligand cDNA to prevent its expression in transfected 293 c ells. COS-7 cells infected with AxCALNFasL alone did not induce apopto sis in cocultivated Jurkat cells, hut the cells treated with AxCALNFas L and AxCANCre (an adenovirus expressing Cre recombinase with the CAG promoter) did. BALB/c mice injected with 10(9) plaque-forming units of AxCALNFasL and with different doses of AxCANCre, developed lethal acu te liver failure. The number of the apoptotic hepatocytes increased dr amatically with increased doses of injected AxCANCre, indicating that the level of transgene expression in the rodent liver appeared to be a djustable. Based on these observations, we conclude that Vectors expre ssing a gene to produce cytotoxic substances can be constructed by the use of a Cre-mediated switching system. Our system also demonstrated that efficient expression of the toxic gene in the rodent liver was ac hievable by co-infection of adenovirus vectors carrying the target gen e and Cre recombinase.