Improved leishmanicidal effect of phosphorotioate antisense oligonucleotides by LDL-mediated delivery

We have designed antisense oligonucleotides that can interact with lipoproteins in order to use them as vectors to facilitate the uptake by those cells expressing the corresponding receptor. Phosphorothioate (PS) oligonucleotides were linked at the 5' end to a palmityl group giving rise to PSPal conjugates. Such a modification enables the oligonucleotide to form a stable non-covalent complex with low density lipoproteins (LDL) through hydrophobic interactions. The antisense effect of LDL-oligonucleotide complexes was assayed by targeting the mini-exon sequence of Leishmania amazonensis in infected mouse peritoneal macrophages. A 16-mer antisense PSPal oligonucleotide/LDL complex exerted a more pronounced sequence-specific effect than the free oligomer: about 25% and 10% of infected macrophages were cured by a 48 h incubation in the presence of 2.5 microM of the complexed and the free oligomer, respectively. When oxidized LDL was used instead of the native one for complexation, a further 2-fold increase in the antisense effect was observed suggesting that alternative (unregulated) scavenger receptor can be used for more efficient delivery of antisense oligonucleotides into macrophages. In addition, a significant reduction of the parasitic load was observed in those cells that were not fully cured.