Scavenger receptor-mediated delivery of antisense mini-exon phosphorothioate oligonucleotide to Leishmania-infected macrophages. Selective and efficient elimination of the parasite.

Targeted delivery of a 17-mer antisense phosphorothioate oligodeoxyribonucleotide, complementary to the common 5'-end of every mRNA of the parasite cells, to the phagolysosomes of cultured murine macrophages infected with Leishmania mexicana amazonensis selectively and efficiently eliminated the parasite cells without causing any detectable harm to the host cells. The antisense mini-exon oligonucleotide (ASM) was encapsulated into liposomes coated with maleylated bovine serum albumin (MBSA), the artificial ligand for macrophage scavenger receptors. MBSA-coating of the liposomes allowed specific binding of the liposomes to the macrophages, their receptor-mediated uptake, and subsequent degradation of the liposomes inside macrophage phagolysosomes to release ASM. When incubated with Leishmania-infected macrophages, MBSA-liposome-encapsulated ASM (10 microM) was able to kill >90% of the parasites within 5 hr as compared with 20% killing within this time period by free ASM. Oligonucleotides with complementary nucleotide sequence or with the same base composition as ASM but scrambled sequence had no antileishmanial effect under the conditions of the assay. This study reflects the efficacy of scavenger-receptor-mediated delivery of antisense phosphorothioate oligos in killing intraphagolysosomal pathogens.