Optimization of the Linker Length of Mannose-Cholesterol Conjugates for Enhanced mRNA Delivery to Dendritic Cells by Liposomes

Abstract

Liposomes (LPs) as commonly used mRNA delivery systems remain to be rationally designed and optimized to ameliorate the antigen expression of mRNA vaccine in dendritic cells (DCs). In this study, we synthesized mannose-cholesterol conjugates (MPn-CHs) by click reaction using different PEG units (PEG100, PEG1000, and PEG2000) as linker molecules. MPn-CHs were fully characterized and subsequently used to prepare DC-targeting liposomes (MPn-LPs) by a thin-film dispersion method. MPn-LPs loaded with mRNA (MPn-LPX) were finally prepared by a simple self-assembly method. MPn-LPX displayed bigger diameter (about 135 nm) and lower zeta potential (about 40 mV) compared to MPn-LPs. The in vitro transfection experiment on DC2.4 cells demonstrated that the PEG length of mannose derivatives had significant effect on the expression of GFP-encoding mRNA. MP1000-LPX containing MP1000-CH can achieve the highest transfection efficiency (52.09 ± 4.85%), which was significantly superior to the commercial transfection reagent Lipo 3K (11.47 ± 2.31%). The optimal DC-targeting MP1000-LPX showed an average size of 132.93 ± 4.93 nm and zeta potential of 37.93 ± 2.95 mV with nearly spherical shape. Moreover, MP1000-LPX can protect mRNA against degradation in serum with high efficacy. The uptake study indicated that MP1000-LPX enhanced mRNA expression mainly through the over-expressing mannose receptor (CD206) on the surface of DCs. In conclusion, mannose modified LPs might be a potential DC-targeting delivery system for mRNA vaccine after rational design and deserve further study on the in vivo delivery profile and anti-tumor efficacy.

<p>Mannose-Modified Liposome Co-Delivery of Human Papillomavirus Type 16 E7 Peptide and CpG Oligodeoxynucleotide Adjuvant Enhances Antitumor Activity Against Established Large TC-1 Grafted Tumors in Mice</p>

“…Mannose-modified vectors can specifically target and activate DC-mediated antitumor activities through mannose receptors. 20,24,25 Cationic liposomes have shown great potential as effective vaccine delivery systems. [26][27][28] Based on the rationale that mannose acts synergistically with lipid as previously reported, 22 we developed a vaccination strategy by assembling DC-targeting mannose on the surface of cationic liposomes which were loaded with HPV16 E7 peptide and CpG ODN.…”

Opportunities and Challenges in the Delivery of mRNA-Based Vaccines

“…Alternatively, DCs and macrophages express receptors with the ability to present antigens, e.g., C-type lectin receptors [179], which recognize sugar groups such as mannoseand fucose-terminated glycans [180] and mediate the endocytosis of mannose-modified nanoparticles. This has been exploited for transfection of GFP mRNA into DCs by self-assembly of mannose-cholesterol conjugates with varying PEG units as linkers [181].…”

mRNA vaccine for cancer immunotherapy

“…To improve the specific delivery of LNPs to APCs, targeting ligand was further added to modify the LNPs. For instance, mannose-cholesterol conjugates (MPn-CHs) was added to LNPs post formulation preparation through click reaction with the PEG units [ 104 ]. The mannose modified LNPs were shown to impove the uptake of the particles in DCs through mannose receptor CD206.…”