Virtual Screening-Based Peptides Targeting Spike Protein to Inhibit Porcine Epidemic Diarrhea Virus (PEDV) Infection.

Due to the rapid mutation of porcine epidemic diarrhea virus (PEDV), existing vaccines cannot provide sufficient immune protection for pigs. Therefore, it is urgent to design the affinity peptides for the prevention and control of this disease. In this study, we made use of a molecular docking technology for virtual screening of affinity peptides that specifically recognized the PEDV S1 C-terminal domain (CTD) protein for the first time. Experimentally, the affinity, cross-reactivity and sensitivity of the peptides were identified by an enzyme-linked immunosorbent assay (ELISA) and a surface plasmon resonance (SPR) test, separately. Subsequently, Cell Counting Kit-8 (CCK-8), quantitative real-time PCR (qRT-PCR), Western blot and indirect immunofluorescence were used to further study the antiviral effect of different concentrations of peptide 110766 in PEDV. Our results showed that the P/N value of peptide 110766 at 450 nm reached 167, with a KD value of 216 nM. The cytotoxic test indicated that peptide 110766 was not toxic to vero cells. Results of the absolute quantitative PCR revealed that different concentrations (3.125 µM, 6.25 µM, 12.5 µM, 25 µM, 50 µM, 100 µM, 200 µM) of peptide 110766 could significantly reduce the viral load of PEDV compared with the virus group (p < 0.0001). Similarly, results of Western blot and indirect immunofluorescence also suggested that the antiviral effect of peptide 110766 at 3.125 is still significant. Based on the above research, high-affinity peptide 110766 binding to the PEDV S1-CTD protein was attained by a molecular docking technology. Therefore, designing, screening, and identifying affinity peptides can provide a new method for the development of antiviral drugs for PEDV.

The tyrosine phosphatase PTPN14 inhibits the activation of STAT3 in PEDV infected Vero cells.

Protein tyrosine phosphatase non-receptor type 14 (PTPN14) is a member of the protein tyrosine phosphatase (PTP) family which is a potential tumor suppressor. PTPs modulate the cellular level of tyrosine phosphorylation under normal and pathological conditions. Porcine epidemic diarrhea virus (PEDV) is one of the most important pathogens in the swine industry. Our previous membrane proteomics results showed that PTPN14 was markedly upregulated in PEDV-infected Vero cells. However, its biological roles in PEDV infection have not yet been investigated. In this study, we reported PTPN14 functions as a novel regulator of signal transducer and activator of transcription 3 (STAT3) phosphorylation during PEDV infection. Firstly, PTPN14 was markedly upregulated in PEDV-infected Vero cells with the decrease of STAT3 phosphorylation. Knockdown of PTPN14 or phosphatase inhibitor treatment promoted PEDV proliferation and increased the phosphorylation of STAT3 in Vero cells. On the contrary, overexpression of PTPN14 inhibits viral infection in Vero cells. Moreover, dephosphorylation of STAT3 by PTPN14 might occur in the cytoplasm but not in nucleus. Collectively, our results indicate that PTPN14 plays a negative role in regulating STAT3 activation in PEDV infected Vero cells and demonstrate another layer of regulation in PEDV infection.