Small molecule inhibitor E-64 exhibiting the activity against African swine fever virus pS273R.


Liu B(1), Cui Y(1), Lu G(1), Wei S(2), Yang Z(2), Du F(1), An T(3), Liu J(1), Shen G(1), Chen Z(1).
Author information:
(1)Key Laboratory of Livestock Infectious Diseases in Northeast China, Ministry of Education, College of Animal Science & Veterinary Medicine, Shenyang Agricultural University, Shenyang, China, No.120, Dongling Road, Shenhe District 110866, PR China
(2)The Preventive and Control Center of Animal Disease of Liaoning Province, Liaoning Agricultural Development Service Center, No. 95, Renhe Road, Shenbei District, Shenyang 110164, PR China
(3)State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, No. 678, Haping Road, Xiangfang District, Harbin 150069, PR China


African swine fever (ASF) is a viral disease in swine that results in high mortality in domestic pigs and causes considerable economic losses. Currently, there is no effective vaccine or drugs available for treatment. Identification of new anti-ASFV drugs is urgently needed. Here, the pS273R protein of the African swine fever virus (ASFV) is a specific SUMO-1-like cysteine protease that plays an important role in its replication process. To inhibit virus replication and improve treatment options, a set of small-molecule compounds, targeted inhibitors against the ASFV pS273R protease, were obtained through molecular screening by homology modeling and molecular docking based on structural information of pS273R. Our results clearly demonstrated that the 14th carbon atom of the cysteinase inhibitor E-64 could form one CS covalent bond with the Cys 232 amino acid of the pS273R protease and seven additional hydrogen bonds to maintain a stable binding state. Simultaneously, cell viability, immunophenotyping, and in vitro enzyme activity inhibition assays were performed to comprehensively evaluate E-64 characteristics. Our findings demonstrated that 4 mmol/L E-64 could effectively inhibit the enzyme activity center of the pS273R protease by preventing pS273R protease from lysing pp62, while promoting the upregulation of immune-related cytokines at the transcription level. Moreover, cell viability results revealed that 4 mmol/L E-64 was not cytotoxic. Taken together, we identified a novel strategy to potentially prevent ASFV infection in pigs by blocking the activity of pS273R protease with a small-molecule inhibitor.