Liposome-mediated delivery of antiviral agents to human immunodeficiency virus-infected cells

Intracellular delivery of novel macromolecular drugs against human immunode ficiency virus type-1 (HIV-1), including antisense oligodeoxynucleotides, r ibozymes and therapeutic genes, may be achieved by encapsulation in or asso ciation with certain types of liposomes. Liposomes may also protect these d rugs against nucleases. Low-molecular-weight, charged antiviral drugs may a lso be delivered more efficiently via liposomes. Liposomes were targeted to HIV-l-infected cells via covalently coupled soluble CD4. An HIV-1 protease inhibitor encapsulated in conventional negatively charged multilamellar li posomes was about 10-fold more effective and had a lower EC90 than the free drug in inhibiting HIV-1 production in human monocyte-derived macrophages. The drug encapsulated in sterically stabilized liposomes was as effective as the free drug. The EC50 Of the reverse transcriptase inhibitor 9-(2-phos phonylmethoxyethyl)adenine (PMEA) was reduced by an order of magnitude when delivered to HIV-l-infected macrophages in pH-sensitive liposomes. A 15-me r antisense oligodeoxynucleotide against the Rev response element was ineff ective in free form against HIV-I replication in macrophages, while deliver y of the oligonucleotide in pH-sensitive liposomes inhibited virus replicat ion. The oligodeoxynucleotide encapsulated in sterically stabilized pH-sens itive liposomes with prolonged circulation in vivo, which were recently dev eloped in the laboratories of the authors, was also highly effective. A rib ozyme complementary to HIV-1 5'-LTR delivered in pH-sensitive liposomes inh ibited virus production by 90%, while the free ribozyme caused only a sligh t inhibition. Cationic liposome-mediated co-transfection of the HIV-regulat ed diphtheria toxin A fragment gene and a proviral HIV clone into HeLa cell s completely inhibited virus production, while the frame-shifted mutant gen e was ineffective. Co-transfection of the proviral genome and a gene encodi ng a Rev-binding aptamer into HeLa cells via transferrin-associated cationi c liposomes inhibited virus production. These studies indicate that liposom es can be used to facilitate the intracellular delivery of certain anti-HIV agents and to enhance their therapeutic effects. These properties may be p articularly advantageous in the development of novel macromolecular drugs, which may be necessary because of the emergence of virus strains resistant to the currently available drugs.