Antigen-encapsulating host extracellular vesicles derived from Salmonella-infected cells stimulate pathogen-specific Th1-type responses in vivo

Abstract

Salmonella Typhimurium is a causative agent of nontyphoidal salmonellosis, for which there is a lack of a clinically approved vaccine in humans. As an intracellular pathogen, Salmonella impacts many cellular pathways. However, the intercellular communication mechanism facilitated by host-derived small extracellular vesicles (EVs), such as exosomes, is an overlooked aspect of the host responses to this infection. We used a comprehensive proteome-based network analysis of exosomes derived from Salmonella-infected macrophages to identify host molecules that are trafficked via these EVs. This analysis predicted that the host-derived small EVs generated during macrophage infection stimulate macrophages and promote activation of T helper 1 (Th1) cells. We identified that exosomes generated during infection contain Salmonella proteins, including unique antigens previously shown to stimulate protective immune responses against Salmonella in murine studies. Furthermore, we showed that host EVs formed upon infection stimulate a mucosal immune response against Salmonella infection when delivered intranasally to BALB/c mice, a route of antigen administration known to initiate mucosal immunity. Specifically, the administration of these vesicles to animals stimulated the production of anti-Salmonella IgG antibodies, such as anti-OmpA antibodies. Exosomes also stimulated antigen-specific cell-mediated immunity. In particular, splenic mononuclear cells isolated from mice administered with exosomes derived from Salmonella-infected antigen-presenting cells increased CD4+ T cells secreting Th1-type cytokines in response to Salmonella antigens. These results demonstrate that small EVs, formed during infection, contribute to Th1 cell bias in the anti-Salmonella responses. Collectively, this study helps to unravel the role of host-derived small EVs as vehicles transmitting antigens to induce Th1-type immunity against Gram-negative bacteria. Understanding the EV-mediated defense mechanisms will allow the development of future approaches to combat bacterial infections.

Interaction with mammalian enteric viruses alters outer membrane vesicle production and content by commensal bacteria

“…The membrane was blocked with 5% nonfat milk followed by incubation with primary and then with secondary antibodies (CD9‐ 1:1000 and 1:10,000 dilutions, System Bioscience # EXOAB‐KIT‐1; HSP70‐ 1:1000 dilution, Invitrogen #MA3‐006; Lipid A LPS‐ 1:1000 dilution, Invitrogen #PA1‐73178;). The detection of the signal was done as previously described (Hui et al., 2021 ).…”

“…Samples were run through 30% of the length of 4%–12% Bis‐Tris SDS PAGE gel and stained using GelCode Blue. Sample lanes were cut into 1–2 mm cubes, and in‐gel tryptic digestion was performed as described previously (Bhar et al., 2021 ; Hui et al., 2021 ). The final peptide solution was lyophilized and analysed by mass spectrophotometry.…”

Yersinia pseudotuberculosisYopJ Limits Macrophage Response by Downregulating COX-2-Mediated Biosynthesis of PGE2 in a MAPK/ERK-Dependent Manner

“…Proteins were then separated by SDS-PAGE as a cleanup strategy, and an entire lane was excised by scalpel, which was subsequently diced into 1-mm 2 cubes. These protein samples were subjected to in-gel trypsin digestion performed precisely as we did previously ( 89 ), followed by C 18 ZilTip purification (Waters).…”

The Expression of Tax and HBZ Genes in Serum-Derived Extracellular Vesicles From HTLV-1 Carriers Correlates to Proviral Load and Inflammatory Markers

“…In naive PBMCs, the data suggest an increase in protein levels and transcription of IFN-γ after co-cultivation with EV tax+ HBZ+, though this is not statistical significant. Recent studies have shown that EVs are able to induce a pathogen-specific response in immune cells in studies regarding Salmonella typhimurium (Hui et al, 2021 ), human immunodeficiency virus (Sampey et al, 2016 ), hepatitis B virus (Kouwaki et al, 2016 ), and Epstein-Barr virus (Mrad et al, 2021 ).…”