Figure 1.

Optimization of cell density. A) HEp-2 cells were resuspended in DMEM/F12 medium at different pHs and plated into 384-well plates at 3000 cells per well. B) HEp-2 cells were plated into 384-well plates at the indicated cell number per well. The percent cell viability was used to calculate the signal-to-background and signal-to-noise ratios as per the Materials and Methods. C) HEp-2 cells were plated into 384-well plates at the indicated cell number per well. The percent cell viability was used to calculate Z factors as per the Materials and Methods. For all assays 100 TCID₅₀ doses of RSV were added to the appropriate well which corresponds to an MOI of 0.2 infectious particles/cell. Percent cell viability was determined by the addition of Cell Titer Glo reagent (Promega). Error bars indicate the range from triplicate plates.