LpqH-tagged microvesicles as mRNA vaccine carriers for specific delivery of mRNA into macrophages

Insufficient accumulation of lipid nanoparticle (LNP)-encapsulated mRNA vaccines within antigen-presenting cells (APCs) remains a key barrier to eliciting potent immune responses. Genetically engineered extracellular vesicles (EVs) present a highly adaptable and precisely tunable platform for the efficient delivery of small molecules to specific types of cells. In this study, we exploited a pseudotyping-based approach to load both exosome and microvesicle (MV) membranes with the ectodomain of LpqH (LpqH^48-159) by engineering the vesicular stomatitis virus (VSV) glycoprotein. Our findings demonstrated that loading the LpqH ectodomain onto the surface of exosomes or MVs led to an increase in targeting macrophages compared with commercialized LNPs. Meanwhile, LpqH^48-159-tagged MVs (LpqH-MVs) exhibit not only a higher efficiency in macrophage targeting but also greater mRNA encapsulation efficiency compared to LpqH^48-159-tagged exosomes. In a vaccine-related application, compared to the LNPs, the LpqH-MVs loaded with mRNA encoding the enterovirus 71 capsid protein (VP1) or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain (RBD) elicited stronger humoral and adaptive immune responses against viral infection via intramuscular or inhalable immunization, respectively. Our study demonstrated that LpqH-MVs serve as a promising platform for mRNA vaccine delivery, enhancing APC targeting capabilities and thereby providing robust immune protection.