Incorporating immunostimulatory lipids into lipid nanoparticles: exploring expression and immune responses

Area of Science:

• Biotechnology
• Vaccine Development
• Nanomedicine

Background:

• Lipid nanoparticles (LNPs) are crucial for mRNA vaccine delivery.
• Understanding lipid composition's impact on LNP immunogenicity is vital.
• Dimethyldioctadecylammonium bromide (DDAB) is a cationic lipid with potential immunostimulatory properties.

Purpose of the Study:

• To investigate the effect of incorporating DDAB into SM-102 LNPs on mRNA vaccine delivery and immunogenicity.
• To evaluate how varying DDAB ratios influence LNP physicochemical properties and biological performance.
• To determine if DDAB enhances cellular uptake, antigen expression, and immune activation for vaccine applications.

Main Methods:

• Formulated LNPs with varying ratios of SM-102 and DDAB (0-50 mol%), alongside DSPC, cholesterol, and DMG-PEG2000.
• Characterized formulations for particle size, PDI, zeta potential, and mRNA encapsulation efficiency.
• Assessed in vitro mRNA expression in HEK293 cells and in vivo luciferase expression after intramuscular administration.
• Evaluated antibody responses in mice post-immunization.

Main Results:

• Increasing DDAB content increased particle size but maintained low PDI, neutral surface charge, and high mRNA encapsulation.
• DDAB incorporation altered LNP pKa, indicating increased cationic charge dominance at higher percentages.
• In vitro, 10% DDAB LNP showed a six-fold increase in mRNA expression; however, in vivo expression was significantly reduced.
• Low DDAB levels (10-30%) did not affect antibody responses, while higher levels (≥40%) reduced immunogenicity.

Conclusions:

• Incorporating DDAB into SM-102 LNPs did not enhance in vivo mRNA vaccine performance or immunogenicity.
• Higher DDAB concentrations negatively impacted in vivo expression and overall immune response.
• The study indicates no advantage in using DDAB-modified SM-102 LNPs for mRNA vaccine development based on current findings.