Poxvirus A51R proteins regulate microtubule stability and antagonize a cell-intrinsic antiviral response

Numerous viruses alter host microtubule (MT) networks during infection, but how and why they induce these changes is unclear in many cases. We show that the vaccinia virus (VV)-encoded A51R protein is a MT-associated protein (MAP) that directly binds MTs and stabilizes them by both promoting their growth and preventing their depolymerization. Furthermore, we demonstrate that A51R-MT interactions are conserved across A51R proteins from multiple poxvirus genera, and highly conserved, positively charged residues in A51R proteins mediate these interactions. Strikingly, we find that viruses encoding MT interaction-deficient A51R proteins fail to suppress a reactive oxygen species (ROS)-dependent antiviral response in macrophages that leads to a block in virion morphogenesis. Moreover, A51R-MT interactions are required for VV virulence in mice. Collectively, our data show that poxviral MAP-MT interactions overcome a cell-intrinsic antiviral ROS response in macrophages that would otherwise block virus morphogenesis and replication in animals. [Display omitted] •Poxvirus A51R proteins directly bind to, and stabilize, microtubules•A51R promotes microtubule polymerization and blocks microtubule depolymerization•A51R-microtubule interactions suppress reactive oxygen species in macrophages•A51R-microtubule interactions are critical for viral replication and pathogenesis Seo et al. show that poxvirus A51R proteins directly bind to, and stabilize, microtubules. These A51R-microtubule interactions inhibit a reactive oxygen species-dependent antiviral response, enabling viral replication in macrophages. Poxviruses encoding mutant A51R proteins that cannot interact with microtubules display attenuated virulence in mice, suggesting that A51R-microtubule interactions drive viral pathogenesis.