Total RNA was harvested by Trizol reagent (Invitrogen), and Northern blot was performed as described previously [27, 64] . Briefly, total RNA was denatured and separated on 1.2% denaturing agarose-formaldehyde gels and transferred onto a nylon membrane (Nylon Membrane, positively charged, Roche). Northern blot analysis was performed by using strand-specific RNA probes for detecting IFN-b mRNA [64] , GAPDH mRNA [64] , rLuc mRNA [27] or RVFV antiviral-sense S-segment / N-mRNA [48] .