Fig. 1.

SVV inhibits the expression of IFNγ-stimulated genes. (a) BSC-1 cells were transiently transfected to express firefly luciferase under a STAT1-responsive promotor [19, 20] and renilla luciferase under a constitutively active SV40 promotor. The next day, cells were mock- or SVV-infected for 72 h and subsequently cultured with or without recombinant human IFNγ (1000 U ml⁻¹) for an additional 6 h, after which luciferase activity was measured. The relative STAT1 promotor activity of IFNγ-stimulated cells compared to medium control cells, after normalization to renilla luciferase activity, is shown. Bars represent average ± standard error of the mean (SEM) of three replicates measured in duplicate. **P<0.01 by unpaired Student’s t-test. (b) BSC-1 cells were mock- or SVV-infected for 72 h and subsequently cultured with or without recombinant human IFNγ (1000 U ml⁻¹) for an additional 24 h. The transcript levels of C-X-C motif chemokine 10 (CXCL10), interferon regulatory factor 1 (IRF1) and SVV open reading frame 21 (ORF21) were determined in cells by real-time PCR. Relative transcript levels were normalized to the cellular oncostatin-M control transcript and expressed as log₁₀ values. Bars represent average ± sem of two experiments, each performed in duplicate. nd, not detected. *P<0.05 by the Mann–Whitney U test.