We and others have shown that MNV-infected cells increase the transcription of cytokine (IFN-β, TNF-α, and IL-6) mRNAs (Fig. 4) (56, 57), indicating that pattern recognition receptors (PRRs) such as MDA5 (58) have successfully detected the viral infection and activated an antiviral response against it. Here, TNF is linked to viral infectious disease.