Extracellular vesicles in vaccine development and therapeutic approaches for viral diseases

Extracellular vesicles (EVs) are lipid bilayer nanovesicles generated by almost all living cells which possess various size ranges depending on producer cells and biogenesis mechanisms. Several EV markers were determined including tetraspanins (e.g., CD9, CD63 and CD81), heat shock proteins (HSP70 and HSP90), some 14–3–3 proteins (a family of conserved regulatory molecules), major histocompatibility complex molecules (MHC-I/-II), and enzymes (Glyceraldehyde 3-phosphate dehydrogenase and enolase-1). EVs are known as an abundant source of antigens and immune molecules that can be used for vaccine development in human and animals. EV-based immunization could significantly activate immune responses in different infections such as Porcine reproductive and respiratory syndrome virus (PRRSV), Lymphocytic choriomeningitis virus (LCMV), Marek’s disease virus (MDV), and SARS-CoV-2 infections. The engineered and modified EVs showed a promising potential in development of anti-tumor vaccines and therapeutics, protection against parasitic diseases (e.g., Eimeria, and Plasmodium yoelii) and viral diseases (e.g., COVID-19), and improvement of biomarkers. Also, EVs possess a crucial role in antigen presentation in vivo. In this review, we describe the roles of EVs in vaccine development and therapeutic approaches for viral diseases.