Alpiniae oxyphyllae fructus polysaccharide 3 inhibits porcine epidemic diarrhea virus entry into IPEC-J2 cells

Porcine epidemic diarrhea virus (PEDV) is deadly for suckling piglets and is a significant threat to most pig farms. Alpiniae oxyphyllae fructus polysaccharide 3 (AOFP3) shows antiviral activity against PEDV. However, the anti-PEDV mechanism of AOFP3 is unknown. Entering the host cell is important for viral infection, and many drugs play antiviral roles by inhibiting this process. To understand the antiviral mechanism of AOFP3 against PEDV, the effect of AOFP3 on PEDV entering IPEC-J2 cells was investigated in the present study. Real-time PCR and immunofluorescence were used to study the effect of AOFP3 on PEDV binding and penetrating IPEC-J2 cells. The effect of PEDV on AOFP3 attachment to IPEC-J2 cells was also investigated. Afterward, the effect of AOFP3 on PEDV spike (S) protein binding to porcine aminopeptidase was tested by using coimmunoprecipitation, and the effect of AOFP3 on the cholesterol level of IPEC-J2 cells was detected. The results showed that AOFP3 competitively inhibited PEDV adsorption on IPEC-J2 cells by blocking PEDV S protein binding to porcine aminopeptidase in IPEC-J2 cells. Furthermore, AOFP3 decreased PEDV penetration into host cells by decreasing the cholesterol level in IPEC-J2 cells.