Transcriptome Profiling Reveals That the African Swine Fever Virus C315R Exploits the IL-6 STAT3 Signaling Axis to Facilitate Virus Replication.

African swine fever (ASF) is an acute and highly contagious disease that has caused great losses in the past years. It is caused by African swine fever virus (ASFV), which is a large DNA virus encoding about 165 genes. It has been shown that the purified extracellular ASFV is internalized by both constitutive macropinocytosis and clathrin-mediated endocytosis, and the virus utilizes apoptotic bodies for infection and cell cell transmission. The ASFV-encoded RNA polymerase subunit C315R is thought to play an important role in ASFV replication and transcription. However, its involvement in ASFV infection, particularly in host response, remains only partially understood. In this study, the role of C315R in enhancing ASFV replication was investigated through RNA-Seq transcriptomic analysis, which was based on 3D4/21 cells transfected the plasmid expressing HA-tagged C315R or the empty vector. Our findings revealed that C315R significantly upregulates the expression of inflammatory mediators with a particular emphasis on IL-6. The most differentially expressed genes (DEGs) were predominantly associated with the TNF, IL-17, MAPK, and JAK STAT signaling pathways. RNA-seq results were validated through RT-PCR. Subsequently, we observed that ASFV infection increases IL-6 expression and STAT3 phosphorylation, which is regulated by the ASFV C315R protein. Notably, inhibiting STAT3 phosphorylation with specific inhibitors suppressed ASFV replication. In conclusion, our study demonstrates that the ASFV C315R protein actives STAT3 phosphorylation through promoting the transcription of IL-6 to facilitate virus replication. These findings highlight C315R as a positive regulator in the IL-6 STAT3 signaling axis during ASFV infection.