A single extracellular vesicle-based platform supporting both RBD protein and mRNA vaccination against SARS-CoV-2

The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syn-drome coronavirus 2 (SARS-CoV-2) has highlighted the need for novel, effective, and safe vaccine platforms. Extracellular vesicles (EVs) facilitate cell-to-cell communication and can modulate immune responses by delivering antigens. Here, we propose a versatile EV-based vaccine plat-form in which immune-stimulating EVs, engineered using acoustic shock waves (SW), are used to deliver either protein or mRNA antigens. Immunostimulatory EVs derived from LPS-activated THP-1 monocytes (aTEVs) were loaded with SARS-CoV-2 receptor-binding domain (RBD) protein or RBD-encoding mRNA via SW post-loading. Both aTEV-RBD-Pro and aTEV-RBD-mRNA elicited robust RBD-specific humoral and cellular immune responses in mice without the need for external adjuvants. Moreover, lyophilized aTEV-RBD-Pro vaccines retained immunogenicity after storage, supporting their chain-independent stability. These results demonstrate that a single EV-based platform can independently support both protein- and mRNA-based vaccination, highlighting its flexibility for next-generation vaccine development.