Western blot confirmation for three differentially expressed proteins (caspase-8, HSP90α, and TGF-β1).

Following TGEV and mock infection of the ST cells, equal amounts of protein were separated by SDS-PAGE and transferred to PVDF membranes. The membranes were then probed with the specified antibody, and the identified bands were visualized. GAPDH was used as an internal control to normalize the quantitative data. The representative images shown are typical of two independent experiments. At 48 hpi (I₄₈), integrated optical density (IOD) analysis showed an upregulation of caspase-8 (1.27 fold) and TGF-β1 (3.08 fold), but HSP90α was almost unchanged (0.90 fold). At 64 hpi (I₆₄), we observed an upregulation in both caspase-8 (3.11 fold) and TGF-β1 (4.58 fold), but a 5.82 fold downregulation of HSP90α. The IOD was normalized against GAPDH.