A Luciferase Reporter Gene Assay to Measure Ebola Virus Viral Protein 35–Associated Inhibition of Double-Stranded RNA–Stimulated, Retinoic Acid–Inducible Gene 1–Mediated Induction of Interferon β

During Ebola virus (EBOV) infection, the type I interferon α / β (IFN- α / β ) innate immune response is sup- pressed by EBOV viral protein 35 (VP35), a validated drug target. Identi fi cation of EBOV VP35 inhibitors re- quires a cellular system able to assess the VP35-based inhibitory functions of viral double-stranded RNA (dsRNA) IFN- β induction. We established a miniaturized luciferase gene reporter assay in A549 cells that mea- sures IFN- β induction by viral dsRNA and is dose-dependently inhibited by VP35 expression. When compared to in fl uenza A virus NS1 protein, EBOV VP35 showed improved inhibition of viral dsRNA – based IFN- β induc- tion. This assay can be used to screen for EBOV VP35 inhibitors.