Fig. 4.

B. anthracis-induced IL-1β secretion depends on NOD2, NALP1, and caspase-1. (A) NALP1 is required for IL-1β release in B. anthracis-infected TDM. TDM were infected with scrambled or NALP1 shRNA lentivirus as above and cultured for 72 h before B. anthracis infection. Supernatants were collected 6 h postinfection, and secretion of mature IL-1β and expression of NALP1 were examined by immunoblotting. (B and C) NOD2 is necessary for IL-1β, but not TNF-α, secretion in B. anthracis-infected mouse macrophages. Peritoneal macrophages from WT, Nod2^−/− and caspase1^−/− mice were infected or not with the indicated B. anthracis Sterne strains (BaWT or BaΔLT) at a multiplicity of infection of 2. Macrophages were also pretreated with LPS and then pulsed with ATP as a positive control. Supernatants were collected 6 h postinfection, and secreted IL-1β (B) and TNF-α (C) were measured. (D and E) NOD2 is required for IL-1β, but not TNF-α, release by LT-treated macrophages. Macrophages were left untreated or treated with LT (200 ng/ml LF + 2.5 μg/ml PA₆₃) in the absence or presence LPS (100 ng/ml) for 18 h. Supernatants were analyzed for secreted IL-1β (D) and TNF-α (E). Significant differences, **, P < 0.01; *, P < 0.05. (F) IL-1β secretion in B. anthracis infected mice requires caspase-1 and NOD2. Mice (n = 5) were injected i.p. with 10⁷ cfu of early log-phase B. anthracis BaWT. IL-1β in plasma was measured 17 h after infection.