STAT1 and infection: Immunoblotting confirmed that BKPyV infection of dNHU cell cultures stimulated significant increases in the phosphorylated forms of signal transducer and activator of transcription 1 and 2 (pSTAT1 and pSTAT2) and expression of APOBEC3A, APOBEC3B, and interferon-induced protein with tetratricopeptide repeats 1 (IFIT1) proteins (Fig. 1C and fig.