TTSS modulate IL-8 secretion by intestinal epithelial cells in response to V. parahaemolyticus. A: IL-8 RT-PCR on cellular extracts after co-incubation with V. parahaemolyticus. Caco-2 cells were co-incubated for 2 h with - Lane 1: medium alone, Lane 2: 20 ηg/ml IL-1β, Lane 3: V. parahaemolyticus WT, Lane 4: ΔvscN1, Lane 5: ΔvscN2, lane 6: Δvp1680 and lane 7: heat killed WT V. parahaemolyticus. RNA was extracted and reverse-transcribed. PCR amplification of IL-8, and β-actin as a control, was performed on the cDNA and visualized after migration on agarose gel by SYBRsafe staining. Results are a representative experiment of three independent experiments. B: Quantification of band intensity was performed on the samples described in Panel A and results are presented as the ratio between IL-8 mRNA quantification and β-actin mRNA quantification. Results indicate mean ± SEM of three independent experiments. ++P < 0.01 vs medium. C: ELISA to detect secreted IL-8 6 h and 24 h after co-incubation with V. parahaemolyticus. Caco-2 cells were co-incubated with V. parahaemolyticus WT RIMD2210633, ΔvscN1, ΔvscN2, Δvp1680 and heat killed WT V. parahaemolyticus for 2 h. Then cells were washed with PBS and the remaining extracellular bacteria killed by addition of gentamicin. Supernatant was recovered 4 h and 22 h after that and thus 6 h and 24 h, respectively, after the beginning of the co-incubation for quantification of IL-8 by ELISA. Results indicate mean ± SEM of three independent experiments. ++P < 0.01; +++P < 0.001 vs medium and **P < 0.01; ***P < 0.001 vs WT.