Fig 1.

SeV-induced activation of an NF-κB-responsive promoter is inhibited in LCMV-infected cells. (A) A549 cells were mock or LCMV infected (MOI = 0.1) and, 72 h p.i., seeded on 24-well plates (2 × 10⁵ cells/well) prior cotransfection with pNF-κB-Fluc (500 ng) and pSV40-RL (50 ng) plasmids for 5 h, followed by infection with SeV (MOI = 3) or TNF-α treatment (50 ng/ml) for 16 to 18 h or 4 h, respectively, at which time cell lysates were prepared to determine levels of Fluc (NF-κB activation) and RL (normalization of transfection efficiency). Statistical differences in NF-κB-dependent promoter induction between mock- and LCMV-infected cells during SeV infection (*, P = 0.001) and TNF-α treatment (#, P = 0.05) were determined using a 2-tailed paired Student's t test. Reporter gene activation is expressed as fold induction over the level seen with the empty vector-transfected and mock-treated (SeV-uninfected and TNF-α-untreated) control cells. (B and C) From duplicate wells, cells were fixed to determine percentages of LCMV antigen (Ag)-positive cells by immunofluorescence using monoclonal antibody 1.1.3 against LCMV-NP (B), and tissue culture supernatants (TCS) were collected to determine the production of infectious LCMV progeny (in FFU per milliliter) using a focus-forming-unit assay (C). Values shown correspond to averages ± SD of results from two of three independent experiments.