FIG 3.

Avirulent C. burnetii triggers caspase-dependent IL-1β production in hAMs and PCLS. (A and B) hAMs were infected with avirulent C. burnetii for the indicated times in the absence (A) or presence (B) of the caspase-1 inhibitor YVAD-CHO. Samples were subjected to immunoblot analysis using an IL-1β antibody, and the results shown are representative of three individual experiments. UI, uninfected cells; +, cells treated with LPS and ATP. Mature IL-1β production does not occur in the presence of YVAD-CHO, suggesting that caspase-1 activity is required. (C and D) hAMs (C) or PCLS (D) were left uninfected (UI), treated with LPS and ATP (+), or infected for the indicated times, and supernatants were harvested. YVAD-CHO was added where indicated, and IL-1β was detected in supernatants by sandwich ELISA. Avirulent C. burnetii triggers secretion of IL-1β by infected hAMs and PCLS, and this response is inhibited by YVAD-CHO. Error bars indicate the standard deviation from the mean; *, P < 0.05 according to two-way ANOVA comparing infected cells to uninfected and YVAD-CHO-treated cells. These results indicate that avirulent C. burnetii triggers IL-1β production and secretion through a caspase-dependent mechanism in hAMs and PCLS.