Outer membrane vesicles produced by pathogenic strains of Escherichia coli block autophagic flux and exacerbate inflammasome activation

Abstract

Escherichia coli strains are responsible for a majority of human extra-intestinal infections, resulting in huge direct medical and social costs. We had previously shown that HlyF encoded by a large virulence plasmid harbored by pathogenic E. coli is not a hemolysin but a cytoplasmic enzyme leading to the overproduction of outer membrane vesicles (OMVs). Here, we show that these specific OMVs inhibit the autophagic flux by impairing the autophagosome – lysosome fusion, thus preventing the formation of acidic autophagolysosome and autophagosome clearance. Furthermore, HlyF-associated OMVs are more prone to activate the non-canonical inflammasome pathway. Since autophagy and inflammation are crucial in the host’s response to infection especially during sepsis, our findings reveal an unsuspected role of OMVs in the crosstalk between bacteria and their host, highlighting the fact that these extracellular vesicles have exacerbated pathogenic properties.