As shown in Figure 2B,D, compared with the control group, PCV2 infection significantly upregulated the expression levels of HAT1 mRNA and significantly downregulated the expression levels of HDAC1 mRNA in 3D4/2 cells at 8, 12, 24 or 36 h post-infection (p < 0.05 or p < 0.01). This evidence concerns the gene HAT1 and infection.