Small extracellular vesicles (sEVs) produced by antigen-presenting cells represent a novel mechanism of cell-to-cell communication. The sEVs have been shown to drive Th1-type adaptive immune responses against intracellular infections such as Salmonella. Researchers from the University of Florida have demonstrated that an administration of sEVs produced by Salmonella-infected macrophages to BALB/c mice that were then challenged with Salmonella infection decreased bacterial load in infected animals and led to protection against a lethal dose of Salmonella. Second, the same sEVs induced a robust production of IgA anti-Salmonella antibodies (Abs) in BALB/c mice, including IgA anti-OmpD Abs. These results show that the nanoscale sEVs stimulate adaptive immune responses against intracellular pathogens and that these sEVs can be used to provide animals with complete protection against lethal infection, such as the systemic bacterial infection in immunodeficient BALB/c mice.
(A). Schematic of the sEV isolation. RAW-264.7 cells were infected with S. Typhimurium for 24–48 h and isolated by differential ultracentrifugation to obtain sEVs. (B). NanoSight Tracking Analysis of sEVs derived from RAW264.7 macrophages infected with S. Typhimurium. (C). Schematic of the immunization regimen for IgA and IgG studies