FIGURE 4.

Monoclonal antibodies can inhibit both Ail-mediated Y. pestis host cell binding and Yop delivery. Strain KIM5 D27 Δpla or ΔplaΔail was allowed to bind HEp-2 cells at a multiplicity of infection of 100 for 105 min at 37 °C 5% CO₂. Bacterial binding was performed in the presence of 40 μg/ml antibody after allowing a 1-h preincubation with antibody. Unbound bacteria were washed off with PBS, and bound bacteria were released following cell lysis with 0.1% Triton X-100 and enumeration by cfu analysis. *, p = 0.056; **, p < 0.05. Error bars, S.D.