FIG 2.

IBV HA0 is efficiently cleaved by a broad range of TTSPs. (A) Experiment setup. HEK293T cells were transfected with two plasmids, one encoding IAV or IBV HA and one encoding the indicated TTSP, KLK, or furin. The HA cleavage state was determined at 48 h posttransfection. (B) Representative Western blots showing the bands of uncleaved HA0 and cleaved HA1 or HA2. The trypsin controls (second lanes on each row) consisted of cells transfected with HA and a protease-lacking empty plasmid and exposed to trypsin for 15 min just before cell extraction. (C) Quantitative data for TTSP- and KLK-mediated HA0 cleavage. For each HA, the intensity of the HA1 or HA2 band was normalized to that of clathrin, and the percent cleaved HA (mean ± SEM; N = 3) was expressed relative to that of the trypsin control. P values for results versus the no-trypsin sample are indicated as follows: *, ≤0.05; **, ≤0.01; ***, ≤0.001; ****, ≤0.0001 (ordinary one-way ANOVA, followed by Dunnett’s test).