FIG. 2.

MHV does not induce IFN-β production, as measured by luciferase assay. 17Cl-1 fibroblasts were transfected with pLuc-IFN-β for 16 to 18 h and then infected with MHV-A59 at an MOI of 100 or MHV-JHM at an MOI of 10 for 12 h (A) or 24 h (B). 17Cl-1 cells were also tested after MHV infection at an MOI of 0.1 or 1 (C). 293T cells were transfected with pcDNA-CEACAM1a and pLuc-IFN-β and then infected with MHV-A59 or MHV-JHM for 12 h (D). As positive controls, cells were transfected with poly(I:C) or infected with SenV for the same period of time. As an internal control, a Renilla luciferase construct was transfected concomitantly with pLuc-IFN-β. Cells were harvested and subjected to a dual-luciferase assay as described in Materials and Methods. Data were analyzed, and the ratio of firefly luciferase expression to Renilla luciferase activity is shown. Each sample was assayed in triplicate. Levels of luciferase in poly(I:C)-transfected or SenV-infected cells were significantly greater than levels in mock- or MHV-infected cells (P < 0.005). Data are representative of at least three independent experiments.