FIG 5.
Catalytically active CT is required for induction of IL-1β secretion. (A) IL-1β secretion from THP-1 (gray bars), ASCdef THP-1 (white bars), or NLRP3def THP-1 (striped bars) cells treated at an MOI of 25 with V. cholerae multitoxin-deficient strain KFV101 transformed with a PBAD-TOPO plasmid or plasmids for the expression of CT (ctxAB) or catalytically inactive CT (ctxAB/E112K) under the control of the araBAD promoter for 3 h, followed by incubation in gentamicin for 13 h to amplify the detection of low-level release of IL-1β. (B) CT secretion into RPMI medium measured by ELISA. (C) cAMP levels in THP-1 cells. Data are presented as the mean ± the standard deviation of triplicate samples. *, P < 0.05; ns, not statistically significant; <d. l., below the limit of detection of the assay.