FIG 4.

Antibody neutralization of pseudotyped E-S-FLU virus, H5-S-FLU virus, and EBOV-GP-pseudotyped lentivirus. Viruses were preincubated for 2 h with antibody KZ52 (anti-GP) or 21D85A (anti-H5) before MDCK-SIAT1 indicator cells were added. Antibodies were titrated in 2-fold dilutions from 10 μg/ml. After 24 h, infection was quantified by measuring eGFP expression (influenza virus) or luminescence (lentivirus). Titration curves are shown in panels A to C. A summary of the EC₅₀s of MAbs KZ52 and 21D85A for the three pseudotyped viruses is shown in panel D. Multiple EC₅₀s from repeat experiments are shown with the geometric means and 95% CIs. A value of 10,000 ng/ml was assigned to antibodies that did not neutralize. (E and F) Microscopy (10× objective) of assays showing the specificity of MN by antibodies. For “Virus only,” the E-S-FLU and H5-S-FLU viruses were added directly to MDCK-SIAT1 cells. Infected cells express eGFP, shown as green cells. In the MN assay, virus was preincubated with 10 μg/ml MAb KZ52 (anti-GP) or 21D85A (anti-H5) before the infection of MDCK-SIAT1 cells. Inhibition is visualized as a significantly reduced number of green fluorescent cells.