Fig. 7.

ERK activation is required at an early stage of PEDV infection but does not affect virus internalization. (A) Vero cells were pretreated with DMSO, U0126 (10 and 20 μM, upper panel), or PD98059 (50 and 100 μM, lower panel) and were mock or PEDV (MOI of 1) infected. At the indicated times post-infection, each inhibitor was added to achieve a final concentration. At 48 hpi, virus-infected cells were fixed and virus infectivity was determined by quantifying the percentage of cells expressing N proteins through FACS. (B) Virus internalization assay. Vero cells were infected at an MOI of 1 at 4 °C for 1 h. After washing with cold PBS, infected cells were maintained in the presence or absence of each inhibitor either at 4 °C or 37 °C for an additional hour. Bound but non-internalized virus particles were removed by treatment with proteinase K. The infected cells were then serially diluted and plated onto Vero cells in 96-well tissue culture plates. At 2 days post-incubation, internalized viruses were titrated by plaque assay. Results are expressed as the mean values from triplicate wells and error bars represent standard deviations. *, P=0.001 to 0.05; †, P<0.001.