FIG. 3.

Binding and entry kinetics of measles viruses. (A) KAS-6/1 cells were chilled and infected on ice at an MOI of 1.0 to allow virus binding but not entry. After incubation, the cells were transferred to 37°C for specified time intervals, at which point they were centrifuged and washed with acidic buffer (pH = 3.0) for 2 min to remove any bound virus that had not entered. Cells were then incubated for 48 h, at which point the fraction of GFP-positive cells was determined by flow cytometry. MVeGFP (red) entered cells at a much higher rate than MV-I98A (black), although, in time, both reached approximately the same level of infection. For panel B, the incubation on ice was for 1 h to ensure equilibration of the virus on binding sites without entry.