Based on quantitative RT-PCR analysis, we found that PRRSV infection at multiplicities of infection of 1.0 and 5.0 significantly upregulated SREBP2 mRNA expression in PK15CD163 cells (p < 0.01), indicating that the expression of SREBP2 was correlated with the number of PRRSVs (Figure 3A). This evidence concerns the gene SREBF2 and infection.