FIG. 5.

Comparison of infectious HAV doses determined by the conventional 8-day plaque assay and the MB-based fluorescence assay. FRhK-4 cells infected with unknown viral doses for 6 h were fixed and permeabilized before 1 h of incubation with 5 μM MB H1. The number of fluorescent cells from 30 different fields within a chosen chamber well was recorded, and the PFU value was calculated based on the calibration equation from Fig. 4. In parallel, the infectious viral doses were determined independently by using the 8-day plaque assay. Error bars represent the standard deviations (SD) for three replicate experiments. The inset shows the infectivity data obtained from two assays.