Varicella-Zoster Virus ORF9 Is an Antagonist of the DNA Sensor cGAS

Varicella-Zoster virus (VZV) causes chickenpox and shingles. Although infection is associated with severe morbidity in some individuals, molecular mechanisms that determine innate immune responses remain poorly defined. We found that the cGAS/STING DNA sensing pathway was required for type I interferon (IFN) induction during VZV infection and that recognition of VZV by cGAS restricted its replication. Viral gene overexpression screening identified the essential VZV tegument protein ORF9 as a cGAS antagonist. Ectopically and virally expressed ORF9 bound to endogenous cGAS. Confocal microscopy revealed co-localisation of cGAS and ORF9, which reduced the type I IFN response to transfected DNA. ORF9 and cGAS also interacted directly in a cell-free system and phase-separated together with DNA. Furthermore, ORF9 inhibited cGAMP production by cGAS. Taken together, we uncovered the importance of the cGAS/STING DNA sensing pathway for VZV recognition and identified a VZV immune antagonist that directly interferes with DNA sensing via cGAS.