Edible Plant-Derived Extracellular Vesicles for Oral mRNA Vaccine Delivery

Abstract

Nucleic acid delivery through extracellular vesicles (EVs) is a well-preserved evolutionary mechanism in all life kingdoms including eukaryotes, prokaryotes, and plants. EVs naturally allow horizontal transfer of native as well as exogenous functional mRNA, that once incorporated in EVs is protected from enzymatic degradation. The possible use of EVs as carriers for vaccine has been investigated showing that EVs expressing recombinant SARS-CoV-2 S protein induced an immune response. Moreover, EV-based vaccines presenting the natural configuration of viral antigens have advantages in conferring long lasting immunization and lower toxicity than synthetic nanoparticles. To overcome the manufacturing limitations of EVs derived from eukaryotic cells, edible plant-derived EVs have been studied as an attractive alternative for vaccine delivery, especially for mucosal administration. We recently showed that EVs obtained from orange juice (oEVs) loaded with SARS-CoV-2 mRNAs protected their cargo from enzymatic degradation and were stable at room temperature for one year. Lyophilized oEVs containing the S1 mRNA were administered to rats by gavage and they induced a specific humoral immune response with generation of blocking antibodies, including IgA, that are the first mucosal barrier in the adaptive immune response. Moreover, a Th1 cytokine secretion occurred, suggesting a specific lymphocyte activation. In conclusion, mRNA-containing oEVs could be used for developing new oral vaccines due to optimal mucosal absorption, resistance to stress conditions, and the ability to stimulate a humoral and cellular immune response.