Effect Of Macroautophagy On The Secretion Of BVDV

Bovine viral diarrhea(mucosal disease)is an infectious disease caused by bovine viral diarrhea virus(BVDV).BVDV can infect cattle of all ages,of which young cattle have the highest risk of contracting BVDV.The virus is present in the urine,feces,semen,blood and internal organs of infected cows and can be transmitted through various channels,which has caused huge losses to the economic development of the global cattle industry.Autophagy is a process of cell degradation and material circulation.It is a highly conserved across all eukaryotes.In mammalian cells.There are three main types of autophagy: microautophagy,macroautophagy,and chaperone-mediated autophagy(CMA).In macroautophagy,a double-membrane vesicle is formed,which encapsulates the substances that need to be degraded and transported in the cell.This double-membrane vesicle is named an autophagosome.Late endosomes,also known as multivesicular bodies(MVBs),contain a large number of small vesicles with a diameter of 40-100 nm.When the late endosomes are fused with the cell membrane,the small vesicles can be released extracelluLarly,which is called the small vesicles released into the extracelluLar body as exosomes.Autophagosomes can be fused with late endosomes to form intermediate autophagic vesicles,or lysosome fusion to form autophagosomes.When the intermediate autophagic vesicles fuse with the cell membrane,the substances encapsuLated in the exosomes can be released outside the cell.In this subject,we mainly studied the interrelationship between the secretion of BVDV and the process of autophagy,and found that the sretion process of the virus and the autophagy pathway showed a certain degree of correlation,BVDV can use the autophagy pathway to promote the extracellular sretion of virions.When the autophagy pathway was blocked by autophagy inhibitors 3-MA,WM and CQ,the intensity of autophagic flow was weakened.When autophagy was inhibited,there was no significant change in total viral copy number in the cells,while viral gene copy number in the supernatant were significantly reduced,these results showde that the amount of viral secretion to the outside of the cell has decreased to some extent.Beclin1 is an autophagy-related gene.By constructing cell lines where Beclin1 is stably down regulated,similar results have found after cell line infection with BVDV.There was no significant change in the total virus number and viral gene copy number in the cells,and the virus and viral gene copy number in the supernatant were significantly reduced,so the amount of virus sretion to the outside of the cell decreased to some extent.And then,the specific secretion pathways of BVDV also explored.The study found that the autophagosome-late endosomal pathway has a certain correlation with the sretion of the virus.EPG5 is a key gene in the autophagosome-endosome pathway.After EPG5 is stably down regulate in MDBK,the fusion rate of autophagosomes and lysosomes was significantly reduced.After infection with BVDV,virus virulence assay and Q-PCR assay showed that there was no significant change in the total virus virulence and viral gene copy number in the cells,while the virus virulence and viral gene copy number in the supernatant were significantly reduced.It is concluded that the amount of virus sreted to the outside of the cell has decreased to a certain extent,indicating that the sretion of BVDV is associated with autophagosome-late endosome pathway.In conclusion,our study suggests that BVDV may not use cell autophagy to complete its replication in MDBK cells,but autophagy to complete its secretion to the outside of the cell.