Figure 3.

Trypsin doesn’t affect PDCoV release. Release of PDCoV from (A) LLC-PK and (B) ST cells was analyzed with an MOI of 10 in the presence or absence of trypsin (5 μg/ml). The supernatant and the cell pellets were collected at 12 and 24 hpi respectively, and expression of viral N protein in both the supernatant and cell lysate was analyzed by western blot. LLC-PK cells were infected with PDCoV at MOI = 0.1 (C–D) or MOI = 1 (E–F) and treated with trypsin (5 μg/ml) for 24 h to increase virus replication, and the cells were further cultivated without trypsin for 48 h, then both cells were treated by indicated concentrations (5 and 20 μg/ml) of trypsin at 37°C for 5 min. Virus was titrated in the cells (C and E) and supernatant (D and F) using plaque assay. Experiments were repeated at least three times. Error bars represent the standard error of the mean. NS = no significant difference.