Abstract

African swine fever (ASF), an acute, severe, highly contagious disease caused by African swine fever virus (ASFV) infection in domestic pigs and boars, has a mortality rate of up to 100%. Because effective vaccines and treatments for ASF are lacking, effective control of the spread of ASF remains a great challenge for the pig industry. Host epigenetic regulation is essential for the viral gene transcription. Bromodomain and extraterminal (BET) family proteins, including BRD2, BRD3, BRD4, and BRDT, are epigenetic "readers" critical for gene transcription regulation. Among these proteins, BRD4 recognizes acetylated histones via its two bromodomains (BD1 and BD2) and recruits transcription factors, thereby playing a pivotal role in transcriptional regulation and chromatin remodeling during viral infection. However, how BET/BRD4 regulates ASFV replication and gene transcription is unknown. Here, we randomly selected 12 representative BET family inhibitors and compared their effects on ASFV infection in pigs primary alveolar macrophages (PAMs). They were found to inhibit viral infection by interfering with the different stages of viral life cycle (attachment, internalization, desencapsidation and formation of viral factories). The four most effective inhibitors (ARV-825, ZL0580, I-BET-762 and PLX51107) were selected for further antiviral activity analysis. These BET/BRD4 inhibitors dose-dependently decreased the ASFV titer, viral RNA transcription and protein production in PAMs. Collectively,our study reported novel activity of BET/BRD4 inhibitors in inducing suppression of ASFV infection, providing insights into role of BET/BRD4 in epigenetic regulation of ASFV and potential new strategies for ASF prevention and control. IMPORTANCESince the continuing spread of the ASFV in the world, and lack of commercial vaccines, the development of improved control strategies including antiviral drugs are urgently needed. BRD4 is an important epigenetic factor and has been commonly used for drug development for tumor treatment. Furthermore, the latest research showed that BET/BRD4 inhibition could suppress replication of virus. In this study, we first showed the inhibitory effect of agents targeting BET/BRD4 on ASFV infection with no significant host cytotoxicity. Then, we found 4 BET/BRD4 inhibitors which can inhibit ASFV replication, RNA transcription and protein synthesis. Finally, we analyzed 4 inhibitors biological effect on BRD4 according to the structure of BRD4, and docking analysis of BET-762, PLX51107, ARV-825 and ZL0580 binding to BD1 and BD2 domains of BRD4 was performed. Our findings support the hypothesis that BET/BRD4 can be considered as attractive host targets in antiviral drug discovery against ASFV.