Entry Without Expression: Internalisation Does Not Predict mRNA Translation for Targeted Lipid Nanoparticles.

Lipid nanoparticle (LNP) delivery systems offer efficient encapsulation and protection of mRNA, making them a popular platform in nucleic acid therapeutics, including mRNA vaccines. Conventional LNPs rely on non-specific cellular interactions and internalisation which can result in poor delivery to target cells and increased off-target delivery. Surface functionalization of LNPs with antibodies can enhance target cell accumulation, reducing off target effects. However, selecting antibody-receptor pairs based on abundance does not result in optimal delivery. Here, we present a novel approach to quantify internalisation and mRNA delivery efficiency of antibody-functionalised LNP/mRNA in primary human T and B cells. By targeting LNPs to a range of clinically relevant T and B cell receptors, we demonstrate that LNP internalisation does not necessarily predict successful mRNA delivery. Our findings highlight that receptor mediated internalisation can improve targeted delivery of LNPs, however favourable receptor-specific post-internalisation trafficking of LNP/mRNA is critical to successful cytosolic mRNA release and translation.