Figure 4: Effects of sTfR on F81 cell morphology and viral tilters after CPV infection. (a) Effects of sTfR on F81 cell morphology: CPV (1 × 105 TCID50/mL) was incubated with same volume of 10 μg/mL sTfR or 10 μg/mL BSA (control). F81 cells seeded into 96-well plate at the density of 1 × 105 cells/mL (50 μL). The sTfR-incubated or BSA-incubated (as a control) CPV was added to the well and incubated at 37°C for 6 h. Unbound viruses were removed by extensive washing with DMEM. The cells were continuously cultured until CPE occurred. Figure 4(a) shows the morphology of F81 cells infected with BSA-incubated CPV (left) and sTfR-incubated CPV (right) at 48 h postinfection, respectively. (b) Effects of sTfR on CPV titer in F81 cells: F81 cells were infected by CPV preincubated with different amounts of sTfR and BSA. The infected cells were harvested at 48 h postinfection. The virus particles were released from the cells by the repeated freezing/shawing. The virus titer was estimated by TCID50.