FIG. 7.

Anti-LcrV antibody significantly but incompletely inhibits delivery of Yops to J774A.1 cells infected by Y. pestis KIM5. J774A.1 cells were infected at a multiplicity of infection of 10 with 26/37°C-grown Y. pestis KIM5 in the presence of anti-YopM (αM) or anti-LcrV (αV) antibody. After 4 h, cleavage of the caspase substrate PARP was assayed to measure the ability of anti-LcrV antibody to inhibit delivery of YopJ, which activates the apoptotic cascade (A). (B) Delivery of YopH to the cytosol of J774A.1 cells was measured by immunoblot. Labels: 5, 5 μg of antibody/ml; 40, 40 μg of antibody/ml; No Ab, cells were infected in the absence of antibody; NI, noninfected J774A.1 cells. The illustrated experiment is representative of five experiments done on different days for YopH delivery. PARP cleavage was assayed twice; other downstream effects of caspase activation (TUNEL, trypan-blue exclusion) were measured in other experiments.