A Type III Effector NleF from EHEC Inhibits Epithelial Inflammatory Cell Death by Targeting Caspase-4

Figure 1

NleF inhibits epithelial cell death during EHEC infection. (a-b). HT29 cells were infected with EDL933, ΔnleF, or ΔnleF/nleF at a MOI of 100 and then incubated at 37°C for the indicated time periods. (a) Aliquots of the cellular supernatants were subjected to the cytotoxicity assay and measured at 2 and 6 hr. (b) Infected cells were fixed at the indicated time points and then subjected to Giemsa staining. Red arrowheads indicate cells whose cytoplasm disappeared. The number of infected cells undergoing chromatin condensation was calculated from at least 300 cells and is shown in the lower panels. (c) HT29 cells were transfected with Myc-vector or Myc-NleF and then were infected and subjected to cytotoxicity as (a) lysates of cells expressing Myc-NleF were analyzed by immunoblotting, and α-tubulin was used as an equal-loading control. Graphs show the means ± SEM of triplicate wells; all data are representative of three independent experiments. . values were calculated using two-tailed Student’s -test.

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