The screening and identification of porcine epidemic diarrhea virus (PEDV) host restriction factors are of great significance for the prevention, control and treatment of porcine epidemic diarrhea (PED), but due to the lack of a suitable research platform, this field has been progressing slowly. In this study, label-free liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to quantitatively identify the differentially expressed proteins (DEPs) between porcine kidney cell lines LLC-PK1 and PK15, whose susceptibility to PEDV was distinct. We identified 118 and 69 specific expressed proteins (fold changes >20 and with p < 0.05) in LLC-PK1 and PK15 cells, respectively. In addition, another 1138 DEPs, including 652 upregulated and 486 downregulated proteins, were identified in LLC-PK1 cells. Alterations in the expression of selected proteins were verified by western blot. Bioinformatics analyses, including GO, KEGG, and STRING, further demonstrated that the DEPs are involved in numerous crucial biological processes and signaling pathways, such as organelle organization, nucleotide binding, phagosome, lysosome, focal adhesion pathways and metabolic pathways. Altogether, this is the first proteomic study of porcine cell lines with high homology but different infectivity to PEDV, which shall provide valuable clues for further investigation of PEDV pathogenesis.

The diarrhoea of pigs, in particular, for the newborns, is very harmful to the pig industry. Porcine circovirus-like virus (Po-Circo-like (PCL) virus) is a circular replication-associated protein (Rep)-encoding single-stranded (CRESS) DNA virus. Two PCL virus strains, with severe diarrhoea and hemorrhagic enteritis, have been found in two different pig farms in Guangdong province, China. Subsequently, the full genomes of two strains (PCL virus GD06 and PCL virus GD09) were sequenced. The two PCL viruses contains 3942 nucleotides and 3925 nucleotides, which vary from the genomes of other PCL virus strains with 3912, 3923, and 3942 nucleotides. Besides, the nucleotide identities between two strains and other strains of PCL viruses and Bo-Circo-like virus/CH were 78%-89%. A multiple sequence alignment of these strains showed a similarity of 86.2%-94.4% for the Rep gene sequence and 89.4%-97.7% for the Rep protein sequence. This study found that 9.5% (4/42) of diarrhoea samples and 11.8% (2/17) of pig farms were positive for PCL virus, suggesting that PCL virus may already be widespread in Pig farms in China. Further research on the pathogenicity and epidemiology of PCL virus is required.