The Important Role of Superoxide Dismutase 2 in Controlling Poxvirus Proliferation and Pathogenicity.

Superoxide dismutase 2 (SOD2), a key mitochondrial antioxidant enzyme, is essential for maintaining cellular redox homeostasis by scavenging superoxide radicals. While viruses often induce oxidative stress, the specific role of SOD2 in antiviral defense remains unclear. Here, we report that vaccinia virus (VACV) infection triggers mitochondrial and cellular reactive oxygen species (ROS) and selectively upregulates SOD2, but not SOD1. Genetic knockout of SOD2 exacerbated mitochondrial ROS (mtROS) accumulation and significantly enhanced VACV replication and spread, resulting in larger viral plaques. Conversely, SOD2 overexpression constrained plaque formation and suppressed viral dissemination. Mechanistically, the antiviral function of SOD2 does not strictly rely on its enzymatic activity or mitochondrial targeting, as neither the deacetylation-mimicking mutant nor the mutant lacking the mitochondrial localization signal peptide appreciably impaired its antiviral potency. Furthermore, in a rabbit model, local overexpression of human SOD2 attenuated the poxvirus lesion formation. Our findings unveil an important yet easily overlooked role of SOD2 in antiviral defense and posit it as a promising candidate for the development of host-directed therapeutics against poxviruses.