Synthesis and anti-HIV activity of thiocholesteryl-coupled phosphodiester antisense oligonucleotides incorporated into immunoliposomes

Abstract

Encapsulation of oligonucleotides in antibody-targeted liposomes (immunoliposomes) which bind to target cells permits intracellular delivery of the oligonucleotides. This approach circumvents problems of extracellular degradation by nucleases and poor membrane permeability which free phosphodiester oligonucleotides are subject to, but leaves unresolved the inefficiency of encapsulation of oligonucleotides in liposomes. We have coupled oligonucleotides to cholesterol via a reversible disulfide bond. This modification of oligonucleotides improved their association with immunoliposomes by a factor of about 10 in comparison to unmodified oligonucleotides. The presence of cholesteryl-modified oligonucleotides incorporated in the bilayer of liposomes did not interfere with the coupling of the targeting protein to the liposome surface. Free or cholesterol coupled oligonucleotides associated with liposomes and directed against the tat gene of HIV-1 were tested for inhibition of HIV-1 proliferation in acutely infected cells. We demonstrate that the cholesteryl-modified as well as unmodified oligonucleotides acquire the target specificity of the antibody on the liposome. Their antiviral activity when delivered into cells is sequence-specific. The activity of these modified or unmodified oligonucleotides to inhibit the replication of HIV was the same on an equimolar basis (ECs0 around 0.1 /~M). Cholesterol coupled oligonucleotides thus offer increased liposome association without loss of antiviral activity.

Recent Trends of Polymer Mediated Liposomal Gene Delivery System

“…Trapping efficiency is restricted (usually less than 30%) by the trapped volume confined in the liposomes and drug solubility. Additional method to enhance the passive encapsulation of water-soluble drugs is to give an amphipathic nature to the drugs by conjugating or complexing the drugs to lipids [59, 60]. Instead, water-soluble drugs that have ionizable amine functions are actively entrapped by employing pH gradients [61], which results in trapping efficiencies approaching 100%.…”

Role of cationic lipids for the formulation of lipoplexes

“…They communicate with cell membrane that clear the way for the endocytosis. [49] They are difficult to produce as compared to other complexes. They are more toxic as compared to other lipids.…”

Innovations in Oligonucleotide Drug Delivery

“…Liposomes have been modified for targeted delivery by coupling receptor ligands [47][48][49] or antibodies (immunoliposomes) [50][51][52][53][54][55][56] to the liposome. For example, maleylated-ON-BSA conjugates effectively delivered ON into Leishmania-infected macrophages via the scavenger receptor system, resulting in nearly a 5-fold decrease in parasiteinfected macrophages compared with the results with free ON.…”