Development of melittin-conjugated lipid nanoparticle (LNP-MEL) for mRNA-based respiratory syncytial virus (RSV) vaccination

Messenger RNA (mRNA) vaccines are recognized as a versatile tool for combating infectious diseases, but their effectiveness is reliant on efficient delivery systems. Although lipid nanoparticles (LNPs) have shown potential, challenges such as low cellular uptake and poor endosomal escape efficiency have persisted. To address these limitations, melittin, a cationic peptide from bee venom, was investigated due to its alpha-helical structure and positively charged C-terminal region that interacts with cell membranes. However, its cytotoxicity and hemolytic activity have hindered clinical applications. To mitigate these issues, lipid-C-MEL was developed by attaching a lipid moiety to melittin's C-terminus, retaining its alpha-helical structure while reducing toxicity. LNP-MEL was formulated by incorporating lipid-C-MEL into LNPs to enhance mRNA delivery. In vitro, LNP-MEL exhibited improved intracellular uptake and endosomal escape efficiency compared to conventional LNPs, attributed to lipid-C-MEL's enhanced membrane interactions. In subsequent in vivo experiments, LNP-MEL loaded with Respiratory Syncytial Virus (RSV) G glycoprotein mRNA elicited a robust immune response, providing protection against RSV and showed potential for minimizing vaccine-enhanced respiratory disease (VERD) by reducing Th2-biased immune responses and eosinophil activation in mice. This study highlights the potential of LNP-MEL as a safe, effective mRNA vaccine delivery platform against RSV.