Fig. 4.

L69,77A NS1 virus infection induces higher levels of IFN-β expression compared with WT NS1 virus infection. MDCK cells were mock infected or infected with WT NS1 or L69,77A NS1 viruses at an m.o.i. of 5. Total RNA was extracted and IFN-β expression was determined by quantitative real-time PCR following reverse transcription. Data are expressed as folds of induction over the mock-infected control. The folds of increased IFN-β expression in L69,77A NS1 virus-infected cells (empty bars) over WT NS1 virus-infected cells (filled bars) are also indicated. *, Significant difference relative to the WT NS1 virus within the same time point; #, significant difference between 6 and 12 h.