Abstract
To better understand the role of host cell-derived molecules on enterohemorrhagic Escherichia coli (EHEC) infection, we studied EHEC virulence gene expression when exposed to cell-free spent (conditioned) medium (CM) from HCT-8 intestinal epithelial cells. Exposure to HCT-8 CM for 1h and 3h increased the expression of 32 of 41 EHEC locus of enterocyte effacement (LEE) virulence genes compared with fresh medium (FM). Expression of the Shiga toxin 1 (stx1B) gene was up-regulated at 1h of exposure. Seventeen genes encoded by prophage 933W, including those for Stx2, were also up-regulated at both time-points. The increase in 933W prophage expression was mirrored by a 2.7-fold increase in phage titers. Consistent with the increase in virulence gene expression, we observed a fivefold increase in EHEC attachment to epithelial cells when exposed to CM. The increase in EHEC attachment was abolished when CM was heated to 95°C or treated with proteinaseK to degrade the proteins. The host cell-derived molecule(s) were larger than 3kDa, which suggests that the molecule(s) that increase EHEC virulence and attachment are protein-based.
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