FIG. 4.

Infection at pH 6 is less efficient. HRV2 was preincubated for 20 min and subsequently bound to HeLa cells (MOI of 1) at pH 7.4 (control) and at 6.0 for 1 h at 4°C. Cells were washed, unbound virus was removed, and cells were further incubated in infection medium at 34°C for 17 h. (A) Cells were fixed, and HRV2 was stained with MAb 8F5 followed by antimouse Alexa 488-conjugated IgG. Nuclei were revealed with Hoechst stain. Bars, 100 μm. (B) The percentage of cells synthesizing viral antigen was determined in two different experiments with a total of 1,500 cells counted.