Differential Regulation of Interferon Responses by Ebola and Marburg Virus VP35 Proteins

• Ebola and Marburg viruses regulate interferon responses to different extents
• Ebola and Marburg VP35 proteins block RIG-I signaling with different efficiencies
• Ebola and Marburg VP35s have different binding modes and affinities for dsRNA
• Ebola virus VP35 caps the ends of dsRNA for superior RIG-I suppressing function

SummarySuppression of innate immune responses during filoviral infection contributes to disease severity. Ebola (EBOV) and Marburg (MARV) viruses each encode a VP35 protein that suppresses RIG-I-like receptor signaling and interferon-α/β (IFN-α/β) production by several mechanisms, including direct binding to double stranded RNA (dsRNA). Here, we demonstrate that in cell culture, MARV infection results in a greater upregulation of IFN responses as compared to EBOV infection. This correlates with differences in the efficiencies by which EBOV and MARV VP35s antagonize RIG-I signaling. Furthermore, structural and biochemical studies suggest that differential recognition of RNA elements by the respective VP35 C-terminal IFN inhibitory domain (IID) rather than affinity for RNA by the respective VP35s is critical for this observation. Our studies reveal functional differences in EBOV versus MARV VP35 RNA binding that result in unexpected differences in the host response to deadly viral pathogens.

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