MyD88, IRAK1, and TRAF6 are involved in HSV-1–induced IL-15 up-regulation in THP1 cells. (A) THP1 cells were transfected with either adaptor-specific siRNAs or control siRNA. Cells were harvested 48 hours later, and protein lysates were analyzed for MyD88, IRAK1, TRAF6, and β-actin expression by immunoblotting. Representative Western blots are shown. (B) Wild-type THP1 cells as well as MyD88-, IRAK1-, or TRAF6-deficient cells were incubated with mock or HSV-1. Cells were harvested 6 hours after treatment for total RNA extraction, and IL-15 gene expression was examined by RT-PCR. The PCR products were 550 and 640 bp for IL-15 (representing the 2 isoforms) and 310 bp for the internal control 18S rRNA and are representative of 3 independent experiments. (C) Total RNA was also used to determine IL-15 gene expression by real-time RT-PCR. Data are expressed as the ratio of IL-15 mRNA in treated samples to the untreated sample (after normalization with reference dye and housekeeping gene).