Study On The Bovine Parainfluenza Virus Type 3 C And V Protein Antagonism Against Type ? Interferon Producting Mediated By IRF7

Bovine parainfluenza virus type 3(BPIV3)belongs to paramyxoviridae,respirovims.BPIV3 is a single strand of negative RNA virus,can induce the production of bovine respiratory syndrome,causing cattle to produce influenza.Most cattle infected with BPIV3 after onset,showing loss of appetite,fever,conjunctivitis and cough,asthma,poor breathing and other symptoms of respiratory infections,can cause pregnant cows can cause milk production decreased,a small number of sick cattle was a transient condition,no obvious clinical symptoms.The incidence of herds is as high as 90%,usually in the case of infection with the virus accompanied by bacterial secondary infection to exacerbate the disease,the cost of treatment for the cattle caused serious economic losses in China.It has been reported that respiratory viruses are able to resist innate immunity by inhibiting the production of interferon.For example,Sendai virus,human parainfluenza virus C and V proteins are able to inhibit the production of type I interferons by regulating a variety of signaling molecules in the interferon signaling pathway.BPIV3 C,V protein capable of inhibiting the helicase retinoic acid-inducible gene I(RIG-I)and melanoma differentiation-associated expression of protein 5(MDA5)to suppress the generation of IFN-?,and whether C,V protein capable to native antiviral action immunological response to to escape host immunity by other molecules has not been reported.In order to further explore the mechanism of BPIV3 antagonizing natural immunity,it was found that BPIV3 infected fetal bovine kidney cells(MDBK)and bovine lung cells(BL)were used to detect the mRNA of interferon signaling pathway molecules,and the virus could significantly inhibit the inhibition of interferon regulatory factor 7(IRF7)mediated expression of type I interferon.It is found that Overexpression of IRF7 could promote the activation of IFN-? and IFN-? transcription.Lentiviral-mediated sh RNA knockdown the expression of IRF7 gene(named LV-IRF7 sh RNA-MDBK)in MDBK cells and found that the expression of IFN-? and IFN-? and interferon stimulating factor 15(ISG15),interferon stimulating factor 56(ISG56)and Mx1 were decreased,and the replication of BPIV3 was not inhibited in LV-IRF7 sh RNA-MDBK cells,and it was confirmed that IRF7 was the key factor in the body's antiviral mechanism.The polyclonal antibody of C,V protein was prepared by cloning and expressing BPV3 protein with BPIV3 genome as template.C and V gene vectors were transfected into MDBK cells and BL cells respectively.The results of q PCR and Western blot showed that C and V proteins could inhibit the transcription and protein expression of IRF7.At the same time with the inhibition of IRF7,transfected C,V gene is also inhibited intracellular type I interferon and downstream related molecular expression.C,V protein can inhibit the expression of IRF7-induced IRF7 and IFN-?,IFN-? transcription,indicating that C,V protein may inhibit IRF7 inhibition of type I interferon pathway.In the detection of promoter activity,it was found that C and V proteins were effective in inhibiting the activity of luciferase activated by Bo IRF7,Bo IFN-? promoter and NF-?B in a dose-dependent manner,and C and V protein were not inhibited ISRE-activated luciferase activity.LV-IRF7 sh RNA-MDBK cells do not affect the expression of NF-?B,whereas C and V proteins inhibit NF-?B protein expression suggesting that the inhibition of NF-?B by C and V proteins may be mediated by negative regulation of other signaling molecules in interferon-producing pathway.In conclusion,this study confirms that C and V proteins can induce the formation of type I interferon by the presence of BPIV3 in infected cells,and this antagonism to type I interferon production is largely due to negatively regulated of IRF7 to evade host immune response.