Nitric oxide made by iNOS is involved in the IRF3- and IFN-independent antiviral response.

<p>The efficacy of the iNOS inhibitors AMG and L-NIL to block nitric oxide production was determined by Griess assay following a 5 hour poly I∶C treatment of WT (A) and IRF3^−/−9^−/− (B) MEFs. Initiation of HSV-1gfp replication in WT (C) and IRF3^−/−9^−/− (D) MEFs following treatment with poly I∶C in the presence or absence of the iNOS inhibitors was measured relative to untreated cells, where fluorescence levels were set to 100% in each experiment. WT MEFs, which maintain the capacity to respond to IFN, are completely protected against HSV challenge following 24 hr pre-treatment with IFNβ. *, p<0.05, **, p<0.01, ***, p<0.0001. Data are expressed as the mean of three replicates ± SEM.