N. Duzgunes et al., Liposome-mediated delivery of antiviral agents to human immunodeficiency virus-infected cells, MOL MEMBR B, 16(1), 1999, pp. 111-118
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.