Cytosolic Bacterial Subversions of Mucosal Immunity

Download or read book Cytosolic Bacterial Subversions of Mucosal Immunity written by Camille Rey and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cytosolic bacterial pathogens S. flexneri and L. monocytogenes subvert extracellular mucosal immunity by inducing their uptake and intracellular lifestyle in the intestinal epithelium. Within the host, they are able to rapidly escape their internalization vacuole, invade the cytosol and escape cellular degradation by spreading from cell-to-cell. Antigen sampling M cells overlying immune induction sites are targeted by these pathogens to initiate intestinal invasion. However, the intracellular lifestyle of these pathogens within M cells, the mechanism of spread of the infection toneigh boring enterocytes from this entry point and the mechanism of S. flexneri evasion of adaptive immunity is poorly characterized. We present a novel physiologic model of apical S. flexneri infection of human in vitro M cells which recapitulates the early steps of epithelial invasion. We show that a subset of S. flexneri is rapidly transcytosed, within 15 minutes, through M cells. We establish a newtime-lapse imaging approach of M cell infections, which reveals that another subset of bacteriainduces apical ruffling upon entry, vacuolar rupture and replicates within the M cells at later timepoints. Remarkably, these bacteria are able to spread from M cells to neighboring cells by actinbased-motility, which we show constitutes the main route of basolateral spreading of the infection.As we extend our study to L. monocytogenes, we observe that unlike S. flexneri, the bacterium diverts M cell transcytosis via the virulence factor ActA. However, we discover that L. monocytogenes spreads within the epithelium exclusively by actin-based motility, similar to S. flexneri. We propose that subversion of M cell transcytosis and avoidance of underlying immune tissues are features shared by cytosolic pathogens, allowing their escape from induction of adaptive immunity.In addition, we submit a pipeline of fluorescence-based single cell sorting of enterocytes atsuccessive stages of infection combined with transcriptional analysis by multiplex qPCR. This methodreveals the production of distinct responses in host enterocytes according to subcellular pathogen localizations. We observe the production of a strong bystander response involving multiplecorrelated host pathways in non-infected enterocytes. Moreover, we detect the output of distinct host response patterns according to vacuolar or cytosolic bacterial localizations in infectedenterocytes. We further show that the virulence effector OspF contributes to dampen infected host responses and disrupt otherwise correlated host signaling pathways. To conclude, our studies expose new immune subversion strategies linked to the intracellular life styles of cytosolic enteric bacteria, highlighting the importance of M cells in initial bacterial dissemination and diversion of adaptive immunity, and the organization and disruption of innate immune responses provoked in enterocytes during infection.