T3SS
To examine whether mAb-EspB-B7 can bind to the native protein in the assembled T3SS, we used flow cytometry. For this purpose, the bacterial strains grown under T3SS-inducing conditions were incubated first with mAb-EspB-B7 and then with a secondary antibody conjugated to a fluorophore. As expected, mAb-EspB-B7 binding was detected in WT EPEC and in the ΔespB strain overexpressing EspB, whereas no or minimal binding was detected in the ΔescN and ΔespB mutant strains (Figure 2B).