Attenuation of N1347A MHV replication requires IFN-I signaling.

(A-D) BMDMs from WT, MAVS-/-, or IFNAR-/- mice were mock infected or infected with WT or N1347A MHV, and cells were collected at indicated timepoints. RNA levels were determined by RT-qPCR with primers specific to IFNβ (A) or genomic RNA (B), viral titers were determined by plaque assay (C), and viral protein expression was assessed by fluorescence microscopy (D). The data in (A-D) show one experiment representative of at least two independent experiments; n = 3. (E) BMDMs were pretreated with indicated amounts of IFNβ for 8 hours, media was removed, and the cells were infected with WT or N1347A virus. Cells were collected at 18 hpi, and virus titers were determined by plaque assay. The data in (E) show one experiment representative of three experiments; n = 3. Numbers above bars represent fold difference between WT and N1347A or between WT, MAVS-/-, and IFNAR-/- cells infected with N1347A virus.