Extracellular Vesicles in Host–Pathogen Interactions: Roles of Exosomes and Bacterial Outer Membrane Vesicles in Immunity and Microbial Communication

Extracellular vesicles, encompassing eukaryotic exosomes and bacterial outer membrane vesicles (OMVs), play multifaceted roles in mediating host–pathogen interactions. These nanoscale structures act as critical mediators of intercellular communication, transporting diverse bioactive cargo such as miRNAs, cytokines, proteins, and bacterial components. Exosomes contribute to host immunity by delivering antimicrobial agents and modulating inflammatory responses, but they can also be hijacked by pathogens to suppress defenses and promote persistent infection. OMVs, on the other hand, enable bacteria to disseminate virulence factors, deliver toxins directly into host cells, and modulate immune signaling. For example, exosomes from infected macrophages can stimulate dendritic cell activation and T-cell priming, whereas bacterial OMVs have been shown to suppress host immunity or trigger excessive inflammation depending on their molecular cargo. Importantly, OMVs facilitate horizontal gene transfer and nutrient exchange within microbial communities, thereby influencing microbiome composition and adaptation. Together, these complex dynamics position both exosomes and OMVs as central players in immunity and pathogenesis. This review synthesizes recent insights into how host- and pathogen-derived vesicles modulate infection biology and immune responses, while also exploring their potential as diagnostic biomarkers and therapeutic carriers, and discussing current limitations in their clinical translation.