Secretion of the ActA-GUCY2C fusion protein was confirmed in the J774A.1 macrophage cell line 6 h after infection with Lm-GUCY2C or control Lm strain by western blot (Fig. 1b) and immunofluorescence (Fig. 1c) staining with a GUCY2C-specific antibody. This evidence concerns the gene ACTA1 and infection.