E. Coli-Epithelial Contact Is Key to Host Response Figure 5. Adherence significantly contributes to innate recognition of EPEC and EAEC. HEp-2 cells were either co-cultured with E69, E69 plus mannose (5 mg/ml), E69 31-6-1(1), E69 JPN15, E69 DespA; O42, O42 DAAF/II, O42 DAafB (MOI = 60), or stimulated with IL-1b (10 ng/ml) as a positive control. At 4 or 16 h post-infection with E69 or O42 co-culture supernatants were harvested and IL-8 (a & c) and CCL20 (b & d) evaluated by ELISA. Data shown is mean (+SD, */+P#0.05) induction of three independent experiments. doi:10.1371/journal.pone.0027030.g005 significantly enhanced with the DlifA strain (Figure 7b). Suggesting that lymphostatin may exert an inhibitory effect on epithelial responses. At 16 h however, the IL-8 and CCL20 levels induced by the DlifA mutant strain were similar to the WT strain. The DespF mutant induced IL-8 protein secretion at 4 and 16 h (Figure 7a) and CCL20 secretion at 16 h (Figure 7b). The levels of induction of IL-8 and CCL20 at 16 h in comparison to the WT were reduced, but not significantly, indicating a minimal role of EspF in modulating IL-8 and CCL20 responses in this system. EPEC BFP, TTSS and lymphostatin implicated in the balance between host induction and EPEC inhibition of IL-8 mRNA During the second stage of infection EPEC modulates signal transduction via the TTSS [2,4], if an inflammatory response ensues it is due to the host pro-inflammatory response to EPEC outweighing the bacterial mediated anti-inflammatory response [4]. To investigate the potential of EPEC to modulate IEC PLoS ONE | www.plosone.org 8 October 2011 | Volume 6 | Issue 10 | e27030