Classical swine fever virus (CSFV), the pathogen of classical swine fever (CSF), causes severe hemorrhagic fever and vascular necrosis in domestic pigs and wild boar. A large number of evidence has proven that non-structural 5A (NS5A) is not only a very important part of viral replication complex, but also can regulate host cell’s function; however, the underlying mechanisms remain poorly understood. In the current study, aiming to find more clues in understanding the molecular mechanisms of CSFV NS5A’s function, the yeast two-hybrid (Y2H) system was adopted to screen for CSFV NS5A interactive proteins in the cDNA library of the swine umbilical vein endothelial cell (SUVEC). Alignment with the NCBI database revealed 16 interactive proteins: DDX5, PSMC3, NAV1, PHF5A, GNB2L1, CSDE1, HSPA8, BRMS1, PPP2R3C, AIP, TMED10, POLR1C, TMEM70, METAP2, CHORDC1 and COPS6. These proteins are mostly related to gene transcription, protein folding, protein degradation and metabolism. The interactions detected by the Y2H system should be considered as preliminary results. Since identifying novel pathways and host targets, which play essential roles during infection, may provide potential targets for therapeutic development. The finding of proteins obtained from the SUVEC cDNA library that interact with the CSFV NS5A protein provide valuable information for better understanding the interactions between this viral protein and the host target proteins.

Porcine circovirus type 2 (PCV2) is the primary infectious agent of PCV-associated disease (PCVAD) in swine. ORF4 protein is a newly identified viral protein of PCV2 and is involved in virus-induced apoptosis. However, the molecular mechanisms of ORF4 protein regulation of apoptosis remain unclear, especially given there is no information regarding any cellular partners of the ORF4 protein. Here, we have utilized the yeast two-hybrid assay and identified four host proteins (FHC, SNRPN, COX8A and Lamin C) interacting with the ORF4 protein. Specially, FHC was chosen for further characterization due to its important role in apoptosis. GST pull-down, subcellular co-location and co-immunoprecipitation assays confirmed that the PCV2 ORF4 protein indeed interacted with the heavy-chain ferritin, which is an interesting clue that will allow us to determine the role of the ORF4 protein in apoptosis.