Forsythoside A Regulate IRF7 Expression And Suppress The Replication Of Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus(BVDV)infects cattle,sheep,pigs,and other animals,causing diarrhea,high fever,mucosal disease,and immunosuppression,which seriously endangers the healthy development of animal husbandry.At present,the prevention and control measures of BVDV are mainly vaccination and elimination of persistently infected animals,and there is still a lack of effective treatment for BVDV-infected animals.Forsythiaside A(FTA)is a phenylethanolamine extracted from Forsythia suspensa.It has anti-virus,anti-inflammatory,antioxidation,and immune regulatory effects.The specific mechanism of its anti-virus has not been clear.Interferon(IFN)is the most important innate defense mechanism in antiviral infection.Interferon regulatory factor 7(IRF7)is an indispensable part of the positive feedback regulation of IFN signal pathway.This study focused on the effect of replication of BVDV by FTA,detected the BVDV replication and the expression of IRF7 related signal pathway factors by fluorescence quantitative PCR and Western blot,studied the regulation of FTA on the expression and distribution of IRF7 in BVDV infected cells,explored the effect of BVDV replication in knockdown IRF7 cells by lentivirus packaging cell line,and clarified the molecular mechanism of FTA suppressing BVDV infection.1.FTA suppresses adsorption and intracellular proliferation of BVDVThe FTA was treated at different stages of BVDV infection and detected BVDV virus copies,viral titers,and BVDV-E2 protein expression by fluorescence quantitative PCR,TCID50,and Western blot.The results showed that FTA extremely significantly suppressed BVDV adsorption(P<0.01).FTA significantly reduced BVDV RNA copies,BVDV titer,and BVDV-E2 protein expression(P<0.01).2.FTA regulates the expression and localization of IRF7 to suppress the replication of BVDVMDBK cells infected with BVDV or stimulated by polyinosinic acid(poly(I:C))were treated with FTA.The expression and localization of IRF7 and related signal factors were detected by fluorescence quantitative PCR and Western blot.The results showed that FTA significantly downregulated the expression of IRF7 stimulated by BVDV and poly(I:C)(P<0.01),and significantly downregulated the expression of TLR3,TLR7,IFN-α,IFN-β,JAK1,STAT1,and p65 stimulated by BVDV(P<0.01),and FTA significantly up-regulated SOCS1 transcription level(P<0.01);FTA suppressed BVDV stimulated IRF7 from the cytoplasm to nucleus.BVDV infected MDBK cells were respectively treated with BAY117082(IRF7 inhibitor)or knockdown IRF7.IRF7 expression and BVDV replication were detected by Western blot.The results showed that both FTA and BAY117082 could suppress the expression of IRF7 and significantly down-regulate the expression of BVDV-E2 protein(P<0.01).3.BVDV Npro regulates the expression of IRF7 and IRF3BVDV Npro eukaryotic expression plasmid was constructed and was transfected with different quality in 293T cells,Western blot to detect IRF7 and IRF3 expression,and the results showed that the BVDV Npro up-regulated IRF7 expression(P<0.01),suppressed IRF3 expression(P<0.01).Therefore,this study initially clarifies FTA to regulate IRF7-related molecules,expression and position suppressed the molecular mechanism of BVDV infection and laid the theoretical basis for screening anti-BVDV drugs.