Pseudorabies virus TK protein antagonizes alpha interferon response by interfering with the JAK1-STAT1 interaction

Pseudorabies virus (PRV), a member of the Alphaherpesvirinae subfamily, is the causative agent of Aujeszky's disease, which severely affects swine health and poses a potential zoonotic risk. PRV can evade the type I interferon (IFN-I)-mediated antiviral response, thus enabling persistent infection, yet the molecular basis for this immune evasion remains unclear. Here, we identify a novel role for thymidine kinase (TK), a key PRV virulence factor, in suppressing IFN-I signaling. Ectopic expression of TK markedly inhibited IFNα-induced transcription and expression of interferon-stimulated genes (ISGs), whereas TK-deficient PRV (PRV-ΔTK) showed increased sensitivity to IFN-I, elevated ISG expression, and reduced replication following IFNα treatment. Mechanistic analyses revealed that TK interacts with both Janus kinase 1 (JAK1) and signal transducer and activator of transcription 1 (STAT1), disrupting the JAK1-STAT1 complex formation and impairing STAT1 phosphorylation and downstream ISG induction. This inhibition is mediated by amino acids 107-212 of TK, a region independent of its catalytic site, and is essential for its immunosuppressive activity. These findings uncover a previously unrecognized function of TK in antagonizing the IFN-I response through interference with JAK1-STAT1 signaling. Beyond its established role in nucleotide metabolism and virulence, this immune evasion function may account for the strong conservation of TK among PRV strains. Collectively, our results expand the understanding of PRV pathogenesis and identify TK as a potential target for antiviral intervention.