EFFICIENT TRANSFER OF SYNTHETIC RIBOZYMES INTO CELLS USING HEMAGGLUTINATING VIRUS OF JAPAN (HVJ)-CATIONIC LIPOSOMES - APPLICATION FOR RIBOZYMES THAT TARGET HUMAN T-CELL LEUKEMIA-VIRUS TYPE-I TAX REX MESSENGER-RNA/

We investigated the usefulness of ribozymes in inhibiting the expressi on of human T cell leukemia virus type I (HTLV-I) gene, Two hammerhead ribozymes that were against HTLV-I rex (RR) and tax (TR) mRNA were sy nthesized. Both ribozymes were sequence-specific in the in vitro cleav age analysis of run-off transcripts from tax/rex cDNA. Intracellular a ctivities of the ribozymes were studied in HTLV-I tax cDNA-transfected rat embryonic fibroblasts (Rat/Tax cells), which expressed the Tax bu t not Rex. Ribozymes were delivered into cells using anionic or cation ic liposomes fused with hemagglutinating virus of Japan (HVJ). Cellula r uptake of ribozymes complexed with HVJ-cationic liposomes was 15-20 times higher cellular uptake than naked ribozymes, and 4-5 times highe r than that of ribozymes complexed with HVJ anionic liposomes. HVJ-cat ionic liposomes promoted accumulation of ribozymes in cytoplasm and ac celerated transport to the nucleus. Tax protein levels were decreased about 95% and were five times lower when the same amount of TR was int roduced into the cells using HVJ-cationic, rather than HVJ-anionic lip osomes. Inactive ribozyme and tax antisense oligodeoxynucleotides redu ced Tax expression by about 20%, whereas RR and tar sense oligodeoxynu cleotides had no effect. These results suggest that the ribozymes' eff ect against tax mRNA was sequence-specific, and HVJ-cationic liposomes can be useful for intracellular introduction of ribozymes.