Poster Presentation Lorne Infection and Immunity 2013

Helicobacter pylori outer membrane vesicles enter host cells and are processed into exosomes that interact with immune cells (#161)

Lorinda Turner 1 , Maria Liaskos 1 , Stuart Mannering 2 , Stuart Cordwell 3
  1. Monash Institute of Medical Research, Clayton, VIC, Australia
  2. St Vincents Institue , Melbourne, VIC, Australia
  3. University of New South Wales, Sydney, New South Wales, Australia

Introduction Outer membrane vesicles (OMVs) are shed by Gram-negative bacteria during normal growth. We recently reported that OMVs enter epithelial cells in vitro, resulting in the generation of pro-inflammatory immune responses. Furthermore, we showed that when delivered orally to mice, these OMVs were able to induce adaptive immune responses in a manner dependent on the innate immune molecule, NOD1, in epithelial cells. The mechanisms whereby these OMV-specific adaptive immune responses are generated, however, remain unknown. 
The aim of this study was to determine the mechanism(s) whereby OMVs from Helicobacter pylori, enter non-phagocytic epithelial cells and induce adaptive immune responses. 

Results We identified that H. pylori OMVs enter epithelial cells via macropinocytosis and caveolin-mediated endocytosis as determined using chemical inhibition of the various endocytosis pathways. Following internalisation by polarised T84 epithelial cells, H. pylori OMVs induce the basolateral secretion of the pro-inflammatory chemokine, interleukin-8. Interestingly, we found that internalised OMVs up-regulated the expression in non-polarised epithelial cells of HLA Class I and II molecules, required for antigen presentation. Moreover, stimulation of polarised epithelial cells with H. pylori OMVs resulted in the production of exosomes secreted at their basolateral surface that contained OMV proteins within them. Proteomic analysis revealed several distinct H. pylori proteins, including the immunogenic outer membrane protein Lpp20. Importantly, we identified that exosomes containing OMV proteins induced proliferation of human T cells in an antigen-dependent manner.

Conclusion Collectively, our data suggest that proteins derived from internalised OMVs are packaged into secreted exosomes for presentation to immune cells. We speculate that through interactions with antigen presenting cells, these exosomes are capable of activating antigen specific T cells located beneath the epithelial cell layer, thereby providing a link between the generation of innate and adaptive immune responses to H. pylori at the mucosal epithelium.