VHH-expressing Salmonella do not significantly invade CD20⁻ cells. Representative immunofluorescence images of empty vector–transfected (A) MCA203 and (B) CT26 cells infected with control AT-Salmonella (left panels) or 2G9-Salmonella (right panels) at MOI 10, showing extracellular bacteria (Cy5-positive [blue]), intracellular bacteria (Cy3-Cy5-double positive [red]), and cytoplasm/phalloidin (FITC [green]) staining. Images shown are representatives of 3 separate immunofluorescence-infection experiments comprising at least 4 randomly selected fields of view per infection. (C) Quantification of total number of bound per infection (extracellular + intracellular), determined from 4 immunofluorescence images per infection, normalized per the cell count in field of view. (D) Quantification of invasiveness of bound bacteria (intracellular/[intracellular + extracellular]) shown in Figure 3C.