Caspase 1

Following RSV infection for 36 h, total A549 cells in 6-well plates were washed twice with PBS, then harvested and lysed using RIPA buffer (CST, USA) containing PMSF (CST, USA) on ice. Lysates were centrifuged at 14,000 g for 10 min at 4 o C to obtain the supernatants. Samples containing equal quantities of protein were resolved in 10% SDS-PAGE and then transferred onto PVDF membranes (MERCK MILLIOPORE, Germany). The membranes were blocked with 5% BSA for 1 h and probed with primary antibodies against Caspase-1 (1:1000; Zen-bio, China), cleaved Caspase-1 (1:1000; Abcam, UK), cleaved IL-1β (1:1000; A nity, China), N terminal of GSDMD (1:1000; Abcam, UK), Bcl-2 (1:1000; Proteintech Group, USA) at 4 o C overnight. The GADPH (1:5000; Proteintech Group, USA) was probed as internal reference. Alkaline phosphatase-conjugated goat anti-mouse antibody (1:5000; Proteintech Group, USA) and goat anti-rabbit antibody (1:5000; Proteintech Group, USA) were used as secondary antibodies, and incubated at room temperature for 1 h. The protein bands were detected by using an ECL kit (MERCK MILLIOPORE, Germany).