Plasmid construction and vacuolation activity verification of CARDS toxin. a Schematic diagram of plasmid construction. CARDS toxin gene (MPN372) eukaryotic expression vector was constructed and purified. b Purity of CARDS toxin by SDS-PAGE. c HeLa cells were co-cultured with 50 μg/mL CARDS toxin or not for 24 h. CARDS toxin exhibited the ability to induce vacuolization in HeLa cells compared with the control group.