To experimentally confirm executioner caspases activity upon infection, we infected HeLa cells with WT or LLO-deficient Lm (both strain 10403S) and monitored executioner caspases (DEVDase) activity using the chromogenic caspase-3 and -7 substrate, Ac-DEVD-pNA (Fig. 1A). This evidence concerns the gene CASP3 and infection.