CXCL8 and infection: For this, the concentration of IL-8 in the supernatants of Caco-2 and HEK-293 cells infected with M90T wild-type, ΔybjX, ΔvirK or ΔybjXΔvirK strains, was evaluated by ELISA 4 hours p.i. As shown in Figure 6A, infection with M90T ΔybjX did not significantly alter the level of IL-8 released by Caco-2 cells compared to wild-type M90T cells.