Abstract:[Objective] Bovine viral diarrhea virus (BVDV) is the key pathogen that causes bovine viral diarrhea-mucosal disease. The structural protein Erns of BVDV can weaken the host immune defense at the initial stage of virus infection and induce an inflammatory response in cattle. Nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing protein 3 (NLRP3) inflammasome is an important member of the NLR family, regulating the occurrence and development of inflammatory diseases. The activated NLRP3 inflammasome can cause pyroptosis of host cells, thereby inducing cascading inflammatory responses. However, the molecular mechanism of the Ern protein in inducing an inflammatory response in BVDV infection remains unclear. [Methods] To explore the effect of Erns protein on the NLRP3 inflammasome-induced pyroptosis during BVDV infection, we constructed a eukaryotic expression plasmid pCMV-HA-Erns to overexpress the Ern protein of BVDV. The mRNA and protein levels of cysteine-dependent aspartate-specific protease 1 (caspase-1), apoptosis-associated speck-like protein containing CARD (ASC), NLRP3, and interleukin-1 beta (IL-1β) in BVDV-infected cells were determined. The gene expression and cleavage of gasdermin D (GSDMD) were examined. Furthermore, electron microscopy was employed to observe the bovine testis (BT) cells and examine the pyroptosis. [Results] The Erns protein significantly activated the NLRP3 inflammasome and caspase-1. The activated caspase-1 cleaved GSDMD to produce active GSDMD-N and create holes on the BT cell membrane for the contents releasing, thereby inducing pyroptosis. Furthermore, the activated caspase-1 cut pro-IL-1β to produce activated IL-1β in the BT cell supernatant. [Conclusion] We systematically analyze the role of BVDV Erns protein in activating NLRP3 inflammasome to mediate pyroptosis, which is vital for the development of vaccines and therapeutic drugs for the prevention of BVDV.
