The Uptake, Trafficking, and Biodistribution of Bacteroides thetaiotaomicron Generated Outer Membrane Vesicles

Abstract

Gram-negative bacteria ubiquitously produce and release nano-size, non-replicative outer membrane vesicles (OMVs). In the gastrointestinal (GI-) tract, OMVs generated by members of the intestinal microbiota are believed to contribute to maintaining the intestinal microbial ecosystem and mediating bacteria-host interactions, including the delivery of bacterial effector molecules to host cells to modulate their physiology. Bacterial OMVs have also been found in the bloodstream although their origin and fate are unclear. Here we have investigated the interactions between OMVs produced by the major human gut commensal bacterium, Bacteroides thetaiotaomicron (Bt), with cells of the GI-tract. Using a combination of in vitro culture systems including intestinal epithelial organoids and in vivo imaging we show that intestinal epithelial cells principally acquire Bt OMVs via dynamin-dependent endocytosis followed by intracellular trafficking to LAMP-1 expressing endo-lysosomal vesicles and co-localization with the perinuclear membrane. We observed that Bt OMVs can also transmigrate through epithelial cells via a paracellular route with in vivo imaging demonstrating that within hours of oral administration Bt OMVs can be detected in systemic tissues and in particular, the liver. Our findings raise the intriguing possibility that OMVs may act as a long-distance microbiota-host communication system.

Bacteroides thetaiotaomicron-derived outer membrane vesicles promote regulatory dendritic cell responses in health but not in inflammatory bowel disease

“…Here, we present novel data showing that the response of intestinal mucosal cells to Bt involves a balance in the production of protective IL-6 and regulatory IL-10 to which DC both locally and systemically contribute. Furthermore, this balanced response is mediated by OMVs, nanosized vesicles produced by the bacteria which are known to cross the mucus layer of the intestine to directly interact with immune cells beneath the boundary epithelium [60]. Furthermore, we show that in individuals with CD and UC there is a loss of regulatory IL-10 response to Bt OMVs by bloodderived DC, while protective IL-6 responses are retained.…”

“…Unlike whole bacteria, OMVs can cross from the lumen of the intestine through the epithelial barrier and access organs and tissues beyond the GI tract [17,60]. Exploiting this property of OMV, Bt has been successfully engineered to generate OMVs containing both therapeutic proteins and vaccine antigens for treating mucosal inflammation and generating protective mucosal and systemic immunity [28,29].…”

Bacteroides thetaiotaomicron-derived outer membrane vesicles promote regulatory dendritic cell responses in health but not in inflammatory bowel disease

“…Here we present novel data showing that the response of intestinal mucosal cells to Bt involves a balance in the production of protective IL-6 and regulatory IL-10 to which DC both locally and systemically contribute. Furthermore, this balanced response is mediated by OMVs, nanosized vesicles produced by the bacteria which are known to cross the mucus layer of the intestine to directly interact with immune cells beneath the boundary epithelium 60 . Furthermore, we show that in individuals with CD and UC there is a loss of regulatory IL-10 response to Bt OMVs by blood-derived DC, while protective IL-6 responses are retained.…”

Bacteroides thetaiotaomicron-derived outer membrane vesicles promote regulatory dendritic cell responses in health but not in inflammatory bowel disease

“…Here we present novel data showing the response of intestinal mucosal cells to Bt involves a balance in the production of protective IL-6 and regulatory IL-10 to which DC both locally and systemically contribute. Furthermore, this balanced response is mediated by OMVs, nanosized microvesicles produced by the bacteria which are known to cross the mucus layer of the intestine to directly interact with immune cells beneath the boundary epithelium 59 . Furthermore, we show that in individuals with CD and UC there is a loss of regulatory IL-10 response to Bt OMVs by blood-derived DC, while protective IL-6 responses are retained.…”

“…Unlike whole bacteria, OMVs can cross from the lumen of the intestine through the epithelial barrier and access organs and tissues beyond the GI tract 17,59 . Exploiting this property of OMV, Bt has been successfully engineered to generate OMVs containing both therapeutic proteins and vaccine antigens for treating mucosal inflammation and generating protective mucosal and systemic immunity 28,29 .…”