Dichotomous effects of microbial membrane vesicles on the regulation of immunity

Recent studies have shown that extracellular vesicles (EVs) from tumors and immune cells can carry various cargo, such as proteins, nucleic acids, lipids that have immune regulatory effects and therapeutic potential. However, the functions and possible applications of EVs from bacteria have begun to be realized recently. Like their eukaryotic equivalents, EVs from bacteria, called membrane vesicle (MVs), can transport diverse cargos to adjacent and distant sites. Microbial MVs have natural immunogenicity and self-adjuvanting capability that can be harnessed to induce immune response in vaccine design. Moreover, MVs from pathogens and probiotics may be considered as one of causative factors to promote and prevent diseases because of their dissemination respectively. Although studies have improved our understanding of the interplay between the host and bacteria-derived MVs, many questions remain to be answered. Here, we will review the current literature on the immunomodulatory effects of MVs from both gram-positive and gram-negative microorganisms and the significant advantages and disadvantages of their potential immunomodulatory and therapeutic applications.