Hi all

Sorry for the brief hiatus but hopefully we are back up and running and on Tues we will be looking at this paper

Ståhl A-l, Arvidsson I, Johansson KE, Chromek M, Rebetz J, et al. (2015) A Novel Mechanism of Bacterial Toxin Transfer within Host Blood Cell-Derived Microvesicles. PLoS Pathog 11(2): e1004619. doi: 10.1371/journal.ppat.1004619


Shiga toxin (Stx) is the main virulence factor of enterohemorrhagic Escherichia coli, which are non-invasive strains that can lead to hemolytic uremic syndrome (HUS), associated with renal failure and death. Although bacteremia does not occur, bacterial virulence factors gain access to the circulation and are thereafter presumed to cause target organ damage. Stx was previously shown to circulate bound to blood cells but the mechanism by which it would potentially transfer to target organ cells has not been elucidated. Here we show that blood cell-derived microvesicles, shed during HUS, contain Stx and are found within patient renal cortical cells. The finding was reproduced in mice infected with Stx-producing Escherichia coliexhibiting Stx-containing blood cell-derived microvesicles in the circulation that reached the kidney where they were transferred into glomerular and peritubular capillary endothelial cells and further through their basement membranes followed by podocytes and tubular epithelial cells, respectively. In vitro studies demonstrated that blood cell-derived microvesicles containing Stx undergo endocytosis in glomerular endothelial cells leading to cell death secondary to inhibited protein synthesis. This study demonstrates a novel virulence mechanism whereby bacterial toxin is transferred within host blood cell-derived microvesicles in which it may evade the host immune system.

Author Summary

Shiga toxin-producing enterohemorrhagic Escherichia coli are non-invasive bacteria that, after ingestion, cause disease by systemic release of toxins and other virulence factors. These infections cause high morbidity, including hemolytic uremic syndrome with severe anemia, low platelet counts, renal failure, and mortality. The most common clinical isolate is E. coli O157:H7. In 2011 an E. coli O104:H4 strain caused a large outbreak in Europe with high mortality. After Shiga toxin damages intestinal cells it comes in contact with blood cells and thus gains access to the circulation. In this study we have shown that the toxin is released into circulating host blood cell-derived microvesicles, in which it retains its toxicity but evades the host immune response. Our results suggest that these microvesicles can enter target organ cells in the kidney and transfer toxin into these cells as well as between cells. Such a mechanism of virulence has not been previously described in bacterial infection.

Discussion Points

  1. Is the paper well/clearly written?
  2. Were the experiments appropriate?  Were there any extras you would like to see in the paper?  Were any stats used appropriate?
  3. What impact will the results have on a wider field?  Where else might you look for this mechanism?
  4. Any other further experiments you would like to do?
  5. Any other comments?

Hope to see you there…