3.7 | Effect of mAb-EspB-B7 on bacterial-host cell interaction
To examine the ability of mAb-EspB-B7 to directly interfere with the bacterial infection of host cells, we examined the translocation activity of WT EPEC in the presence or absence of mAb-EspB-B7. For that purpose, we infected HeLa cells with EPEC strains (WT and ΔescN ) and examined the cleavage pattern of JNK, a host protein that is cleaved by a translocated EPEC effector known as NleD (Figure 7A) (Baruch et al., 2011). WT EPEC caused extensive degradation of JNK, relative to the uninfected sample and the samples infected with the ΔescN  mutant strain (Figure 7B). Unfortunately, HeLa cells infected by WT EPEC in the presence of a high concentration of mAb-EspB-B7 (400 nM) showed translocation activity similar to that of WT EPEC infection with no addition of antibody. These results suggest that while mAb-EspB-B7 was capable of binding EspB with high affinity and specificity, this binding did not interfere with the protein function and did not inhibit the T3SS translocation activity in an ex vivo model.