CATIONIC LIPOSOME-MEDIATED EXPRESSION OF HIV-REGULATED LUCIFERASE ANDDIPHTHERIA-TOXIN A GENES IN HELA-CELLS INFECTED WITH OR EXPRESSING HIV

HIV-regulated expression of the diphtheria toxin A fragment gene (HIV- DT-A) is a potential gene therapy approach to AIDS. Since cationic lip osomes are safe and non-immunogenic for in vivo gene delivery, we exam ined whether LipofectAMINE or DMRIE reagent could mediate the transfec tion of HIV-DT-A (pTHA43) or the HIV-regulated luciferase gene (pLUCA4 3) into HIV-infected or uninfected HeLa cells. pLUCA43 was expressed a t a 10(3)-fold higher level in HeLa/LAV cells than in uninfected HeLa cells, while the extent of expression of RSV-regulated luciferase was the same in both cell lines. Co-transfection of HeLa cells with pTHA43 and the proviral HIV clone, HXB Delta Bgl, resulted in complete inhib ition of virus production. In contrast, the delivery of HIV-DT-A to ch ronically infected HeLa/LAV or HeLa/IIIB cells, or to HeLa CD4(+) cell s before infection, did not have a specific effect on virus production , since treatment of cells with control plasmids also reduced virus pr oduction. This reduction could be ascribed to cytotoxicity of the reag ents. The efficiency of transfection, as measured by the percentage of cells expressing beta-gal, was similar to 5%. Thus, cationic liposome -mediated transfection was too inefficient to inhibit virus production when the DT-A was delivered by cationic liposomes to chronically- or de novo- infected cells. However, when both the virus and DT-A genes w ere delivered into the same cells by cationic liposomes, DT-A was very effective at inhibiting virus production. Our results indicate that t he successful use of cationic liposomes for gene therapy will require the improvement of their transfection efficiency.