TLR9 and infection: To study the effects of HSV-1 infections on TLR gene expression in U937 cells, the mRNA levels of TLR2, TLR3, TLR4 and TLR9 were studied with quantitative real-time PCR at 5 h and 24 h p.i. The d120 infection significantly increased the TLR3 mRNA expression at 5 h p.i. when compared to its parental virus HSV-1 (KOS)-infected cells (5 moi, P = 0.033) (Figure 1A).