LPS priming enhanced DV-induced IL-1β and IL-18 processing in GM-Mφ. (A) Secretion of IL-1β and IL-18 from DV-infected GM-Mφ. Cytokine levels in DV-infected Mφ were harvested and determined by ELISA. Each dot represents an individual donor; horizontal bars represent mean values for each group. ***P < .001 (Student t test). (B-C) LPS priming enhanced IL-1β secretion and pro-IL-1β processing from DV-infected GM-Mφ. GM-Mφ were primed with LPS (5 ng/mL) or without priming for 4 hours, followed by incubation with DV (MOI = 5 and 30) or mock (C6/36 culture medium) for 2 hours at 37°C. Cytokine levels in the culture supernatants and cell lysates were determined by ELISA at various time points after infection (B), whereas mature and immature forms of IL-1β and IL-18 in cell lysates were harvested at 24 hours after infection and determined by Western blot (C). Sup. indicates supernatant.