A large deletion virus reveals the presence of previously uncharacterized vaccinia virus inhibitors of NF-kB signaling

Abstract

The classical Nuclear Factor kappa B (NF-κB) signaling pathway is an important regulator of inflammation and innate immune responses. Poxviruses, including vaccinia virus, encode multiple immune evasion proteins, including a growing number of NF-κB inhibitors. To determine if additional vaccinia virus gene products disrupted NF-κB signaling, we utilized VV811, a mutant virus missing 55 open reading frames and devoid of the known inhibitors of TNFα-induced NF-κB activation. NF-κB nuclear translocation was inhibited in VV811 infected cells stimulated with TNFα. Furthermore, VV811 infection suppressed IκBα degradation and resulted in accumulation of phosphorylated IκBα in cells stimulated with TNFα. Coimmunoprecipitation assays demonstrated that the inhibitory IκBα-p65-p50 complex was intact in VV811 infected cells, and, significantly, treatment with AraC revealed the involvement of late protein synthesis in stabilization of IκBα. This work indicates that unidentified inhibitors of NF-κB exist in vaccinia virus and illustrates the importance of NF-κB activation in the antiviral response.