Iterative delivery of mRNA by MEFI

Conventional therapeutic mRNA delivery systems are inherently single-use, limiting expression potency, duration, and penetration across biological barriers. To address this, we engineered the mRNA Exporting and Ferrying Implement (MEFI), a platform that enables iterative cell-to-cell transfer of cargo mRNA, allowing a single mRNA molecule to be utilized multiple times across various cells. MEFI encodes a fusion protein that assembles virus-like particles (VLPs) and encapsulates both itself and cargo mRNA into these VLPs, orchestrating reproduction of VLPs from targeted cells and continuous intercellular spreading. MEFI significantly amplified cargo protein expression in the transfected cell populations (∼20-fold) and in organs (∼500-fold in lung) from mice administered systemically. Notably, through intramuscular injection of naked plasmids, MEFI promoted robust (∼20-fold) and durable (∼2-month) cargo expression, interorgan mRNA transfer, and successful crossing of the blood-brain barrier. Moreover, modified MEFI demonstrated cell-type-specific targeting, mediating the elimination of antigen-expressing cells. Collectively, MEFI establishes a modular platform for enhancing mRNA delivery, leveraging the concept of iterative delivery of mRNA.