Pseudorabies (PR), caused by the PR virus (PRV), is an acute infectious disease in livestock and various wild animals. PRV has developed several immune evasion mechanisms to antagonize the host's antiviral immune response. However, the precise role of PRV-encoded proteins in regulating the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon (IFN) gene (STING) signal for immune evasion remains unclear. In this study, we demonstrate that the PRV UL42 protein (pUL42) inhibited cGAS-mediated antiviral signaling by modulating cGAS recognition of dsDNA. Mechanistically, pUL42 interacts with the DNA-binding domain of cGAS, thereby inhibiting its recognition of double-stranded DNA, leading to the inhibition of its dimerization and oligomerization activation. Furthermore, knocking down the expression of the Ul42 gene in the PRV genome diminishes the antagonistic effect on type I IFN production and inhibits PRV replication. Ultimately, we have established that pUL42 targets cGAS-mediated signaling, thereby inhibiting the production of type I IFN and facilitating viral replication. Overall, our findings suggest that PRV pUL42 functions as an antagonist to evade the host's antiviral response by targeting the cGAS-STING axis.

Importance: Cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) axis is essential for host resistance to DNA virus infections by regulating type I interferon production. However, whether pseudorabies virus (PRV) antagonizes the cGAS-STING signaling pathway to immune evasion is not fully investigated. In this study, we clearly demonstrated that the PRV pUL42 protein inhibits the recognition of double-stranded DNA of cGAS, leading to inhibiting the oligomerization and activation of cGAS, thereby suppressing the cGAS-mediated host antiviral immune responses. Taken together, our results reveal a novel strategy employed by PRV to evade host defenses, which will provide theoretical support for the development of anti-PRV drugs for the prevention and control of PRV.

Keywords: DNA polymerase processivity factor; cGAS-STING; interferon; pUL42; pseudorabies virus.