Effect of cationic and neutral lipids in cationic liposomes on antibody production induced by systemic administration of mRNA lipoplexes into mice

We have previously developed a modified ethanol (EtOH) injection (MEI) method for mRNA transfection wherein cationic liposome/mRNA complexes (mRNA lipoplexes) were prepared by mixing a small volume of a lipid-EtOH solution with phosphate-buffered saline (PBS) containing mRNA. In the present study, five types of cationic lipids, namely N,N,N-trimethyl-2,3-bis(oleoyloxy)propan-1-aminium methyl sulfate salt (DOTAP), dimethyldioctadecylammonium bromide (DDAB), N-hexadecyl-N,N-dimethylhexadecan-1-aminium bromide (DC-1-16), 2-(bis(2-(tetradecanoyloxy)ethyl)amino)-N,N,N-trimethyl-2-oxoethan-1-aminium chloride (DC-6-14), and 11-[(1,3-bis(dodecanoyloxy)-2-((dodecanoyloxy)methyl)propan-2-yl)amino]-N,N,N-trimethyl-11-oxoundecan-1-aminium bromide (TC-1-12); two types of neutral lipid, cholesterol (Chol) and 1,2-dioleoyl-sn-glycero-3phosphoethanolamine (DOPE); and polyethylene glycol-cholesteryl ether (PEG-Chol) as a PEG-lipid were selected. Ten types of mRNA lipoplexes composed of each cationic and neutral lipid and PEG-Chol were prepared using the MEI method. mRNA lipoplexes containing DC-1-16 or DDAB with DOPE and PEG-Chol (LP-DC116/ DOPE and LP-DDAB/DOPE, respectively) were injectable and their systemic injection with ovalbumin (OVA) mRNA induced high anti-OVA IgG1 levels. Furthermore, systemic injection of the lipoplexes with luciferase (Luc) mRNA resulted in high Luc expression in the lungs and spleen of mice. These findings suggest that LP-DC116/ DOPE and LP-DDAB/DOPE lipoplexes effectively induce antibody production via increased protein expression in the spleen.