Extracellular vesicles: Antiviral functions and applications in therapeutics and vaccines.

Extracellular vesicles (EVs) are nanoscale membranous vesicles secreted by nearly all cell types, exhibiting dual regulatory mechanisms during viral infection: they facilitate infection spread by packaging whole infectious viral particles or functional viral genomes while concurrently delivering immunoactive substances to participate in host antiviral immune responses. Additionally, EVs themselves can exert direct antiviral effects, such as by competing with virions for binding to host cell receptors such as phosphatidylserine (PS) receptor. As natural nanocarriers, EVs have emerged as novel therapeutic delivery vehicles owing to their superior biocompatibility, low immunogenicity, and efficient penetration across physiological barriers. Through engineering strategies such as surface modification and cargo loading, EVs enable targeted delivery of therapeutic agents, including antiviral molecules and gene-editing tools, effectively suppressing viral replication and enhancing host immune responses. Furthermore, their unique antigen-presenting mechanisms and immunostimulatory properties underscore significant potential in vaccine development.