HSV-1 ICP27 targets the TBK1-activated STING signalsome to inhibit virus-induced type I IFN expression

Herpes simplex virus (HSV) 1 stimulates type I IFN expression through the cGAS–STING–TBK1 signaling axis. Macrophages have recently been proposed to be an essential source of IFN during viral infection. However, it is not known how HSV‐1 inhibits IFN expression in this cell type. Here, we show that HSV‐1 inhibits type I IFN induction through the cGAS–STING–TBK1 pathway in human macrophages, in a manner dependent on the conserved herpesvirus protein ICP27. This viral protein was expressed de novo in macrophages with early nuclear localization followed by later translocation to the cytoplasm where ICP27 prevented activation of IRF3. ICP27 interacted with TBK1 and STING in a manner that was dependent on TBK1 activity and the RGG motif in ICP27. Thus, HSV‐1 inhibits expression of type I IFN in human macrophages through ICP27‐dependent targeting of the TBK1‐activated STING signalsome. Synopsis Type I interferon (IFN) is important for control of infection with viruses, including herpes simplex virus (HSV)‐1. DNA viruses, such as HSV‐1, induce IFN expression after sensing of viral DNA by cGAS and signaling through the STING–TBK1–IRF3 signaling pathway. Here, we demonstrate that the HSV‐1 protein ICP27 targets the STING‐TBK1 signalsome and inhibits IRF3 activation, thus preventing IFN expression. ICP27 prevents activation of IRF3 but not TBK1. ICP27 is translocated to the cytoplasm at late time points of infection where is co‐localizes with TBK1 and STING. ICP27 associates with STING and TBK1 in a manner dependent on expression of both host proteins. ICP27 from the Simplexvirus genera of Alphaherpesvirinae inhibits IFN production in a manner dependent on the RGG box. Graphical Abstract Herpes simplex virus evades cGAS/STING/TBK1‐mediated innate immunity activation in human macrophages by nuclear translocation of its ICP27 effector protein and suppression of IRF3 signaling.