CASP1 and infection: Consistent with these results, the processing of caspase-1 substrate IL-1β that could be prevented by the YVAD caspase-1 inhibitor was detected at 1 h and more evidently at 4 h post-infection in the culture supernatant of infected LEW macrophages and not in that of permissive LEW.BNc10-F macrophages (Figure 9E).