Figure 2B shows that Smad3 phosphorylation was elevated in A549 cells post-infection, indicating activation of the TGF-β/Smad3 pathway. Phosphorylated Smad3 functions as a transcription factor and translocates to the nucleus. Therefore, Smad3 levels in the nucleus were assessed. As depicted in Figure 2C, phosphorylated Smad3 levels increased within the nuclei following viral infection. This evidence concerns the gene SMAD3 and viral infectious disease.