Figure 4.
ECTV type I IFN bp binds to mouse IFN-α with high affinity, blocks its biological activity in tissue culture, and complements Δ166 in vivo. (A) SPR sensorgrams for the interaction of mouse IFN-α 3 with the indicated Rec type I IFN bp. Values on the y axes are arbitrary response units. Continuous lines correspond to the experimental values after subtracting the control sensorgram; dashed lines correspond to the data fitted to a 1:1 Langmuir binding model. The graph corresponding to the ECTV protein produced in the baculovirus system (right) does not have dashed lines because the data could not be fitted to the 1:1 Langmuir model due to a slow Koff. Data are representative of two identical experiments. (B) MEFs were incubated with the indicated amounts of IFN-α or -β for 24 h in the presence or absence of the indicated amounts of Rec ECTV type I IFN bp, followed by infection with VSV. After an additional 24-h incubation, the cells were fixed and stained with crystal violet. Data are representative of two identical experiments. (C) Mice were inoculated i.v. with 50 μg of Rec ECTV type I IFN bp immediately, and 3 d PI with ECTV Δ166. A group of control-infected mice received PBS instead of Rec ECTV type I IFN bp, whereas a second control group received Rec ECTV type I IFN bp but remained uninfected. Survival was monitored. Data are representative of three experiments.