Interferon-? Inhibits Ebola Virus Infection

Rhein, Bethany A.; Powers, Linda S.; Rogers, Kai; Anantpadma, Manu; Singh, Brajesh K.; Sakurai, Yasuteru; Bair, Thomas; Miller-Hunt, Catherine; Sinn, Patrick; Davey, Robert A.; Monick, Martha M.; Maury, Wendy

Transfection of the construct expressing IRF1 strongly inhibited EBOV GP/rVSV and EBOV replication, as has been previously shown for positive strand and other negative strand RNA viruses (Fig 4B and 4C ) [39, 40] . As IRF1 is a transcription factor critical for IFNγ signaling by driving downstream expression of many IFNγ target genes [19] , we also assessed if knock down of IRF1 in M-CSF-treated and M-CSF/IFNγ-treated macrophages altered infection of EBOV GP/rVSV in peritoneal macrophages. IRF1 siRNA or scrambled control siRNA was delivered to peritoneal macrophages by exosomes since direct siRNA transfection of macrophages is highly inefficient. To validate this siRNA delivery method, we initially demonstrated that exosomes are efficiently engulfed by murine peritoneal macrophages (S7 Fig). In the context of EBOV GP/rVSV infection, delivery of IRF1 siRNA containing exosomes knocked down IRF1 mRNA levels by approximately 50% in both M-CSF-and M-CSF/IFNγtreated macrophages ( Fig 4D) . With IRF1 knock down, a significant increase in EBOV GP/ rVSV RNA was observed 24 hours following infection, consistent with the importance of IRF1 expression in controlling virus infection by IFNγ.