Proteomic and functional characterization of the outer membrane vesicles from the gastric pathogen Helicobacter pylori.

The gastric pathogen Helicobacter pylori causes a spectrum of gastro-duodenal diseases, which may be mediated in part by the outer membrane vesicles (OMVs) constitutively shed by the pathogen. We aimed to determine the proteome of H. pylori OMV to help evaluate the mechanisms whereby these structures confer their known immuno-modulatory and cytotoxic activities to host cells, as such disease-associated activities are also conferred by the bacterium from which the vesicles are derived. We also evaluated the effect of the OMV on gastric/colonic epithelial cells, duodenal explants and neutrophils. A proteomic analysis of the OMV proteins separated by SDS-PAGE from two strains of H. pylori (J99 and NCTC 11637) was undertaken and 162 OMV-associated proteins were identified in J99 and 91 in NCTC 11637 by LC-MS/MS. The vesicles are rich in membrane proteins, porins, adhesins and several molecules known to modulate chemokine secretion, cell proliferation and other host cellular processes. Further, the OMVs are also vehicles for the carriage of the cytotoxin-associated gene A cytotoxin in addition to the previously documented toxin, vacuolating cytotoxin. Taken together, it is evident from the proteome of H. pylori OMV that these structures are equipped with the molecules required to interact with host cells in a manner not dissimilar from the intact pathogen.