CASP1 and infection: The mice were highly susceptible to spore infection when compared to their Nlrp1bS/SCasp1+/− and Nlrp1bS/SCasp1+/+ (Balb/c backcrossed, N4) littermates (Fig. 5A), implicating caspase-1 in Nlrp1bS-mediated resistance to anthrax infection.