African swine fever virus QP509L acts as a dual-targeted molecular breaker of innate immunity by interfering with STING trafficking and STAT1-dependent signaling

African swine fever virus (ASFV) is a highly virulent DNA virus that causes acute, often fatal, hemorrhagic disease in pigs and evades host antiviral immunity through multifaceted viral protein interactions. QP509L is transcribed early during ASFV infection but is expressed as a late protein. Here, we investigated the mechanism by which ASFV QP509L suppresses host type I interferon (IFN) responses through antagonism of both the stimulator of interferon genes (STING) pathway and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) axis. Mechanistically, QP509L interacts with the STING C-terminal region containing residues L333 and R334 and interferes with Sec 24 homolog C (Sec24C) association, a key component of the coat protein complex II (COPII), thereby reducing STING anterograde trafficking from the endoplasmic reticulum (ER) to the ER-Golgi intermediate compartment (ERGIC). This trafficking defect was associated with reduced downstream TBK1-IRF3 activation and altered STING-associated autophagic responses. Simultaneously, we identified that QP509L targets the C-terminal transactivation domain of signal transducer and activator of transcription 1 (STAT1), reducing STAT1 tyrosine 701 (Tyr701) phosphorylation and impairing the assembly and nuclear import of the heterotrimeric interferon-stimulated gene factor 3 (ISGF3) complex. Importantly, targeted siRNA knockdown of QP509L during pathogenic ASFV infection restored host antiviral gene expression. Collectively, our findings characterize QP509L as a multifunctional antagonist of innate immunity that interferes with both STING- and STAT1-dependent antiviral signaling, providing a mechanistic basis for further investigation of QP509L as a potential target for future ASFV attenuation strategies.