TGFB1 and infection: 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.