(257c) Reduced Immunostimulation and Improved Protein Down-Regulation of Antisense Oligonucleotide through Immunoliposomal Nanoparticles

Down-regulation of anti-apoptotic proteins and immunostimulation through Toll-like receptor (TLR) activation are often two competing phenomena associated with oligonucleotide therapeutics. In this study, we show that a clinically used antisense oligodeoxyribonucleotide (ODN) for Bcl-2, can not down-regulate Bcl-2 in B cells when used at low dosage because of the dominant TLR9 effects caused by CpG motifs. However, ODN encapsulated in antibody mediated immunoliposomal nanoparticles (INPs) is able to alter this result. These INPs are 50~100 nm in mean diameter and slightly positively charged (zeta potential 2~5mV). They showed preferential uptake by B cells in PBMC cells and INPs mediated ODN delivery enhanced Bcl-2 down-regulation, leading to greatly increased sensitivity to a chemotherapy drug. Comparing to free ODN, INPs reduced TLR9-driven activation. This inhibition was also observed in other CpG ODNs. Cross-linking of INPs on cell surface and shielding of ODNs by INPs may be possible reasons of the observed inhibition of co-stimulation. In summary, regulation control of anti-apoptotic proteins and TLR activation of nucleic acids through antibody-mediated delivery of nanoparticles may provide a highly valuable approach to improving the clinical efficacy of oligonucleotide therapeutics.