Exploring The Molecular Mechanism For The Establishment Of Persistent Infection Of Foot-and-mouth Disease Virus

FMDV is a highly contagious virus which seriously threaten the development of animal husbandry,and the persistent infection makes the situation even worse.Currently,the mechanisms involved in FMDV persistent infection remain unclear.Most of the well-studied mechanisms of persistence of RNA viruses in primary cell cultures or established cell lines involved genetic variation of the virus,the cell,or both.For lytic viruses,one way to limit cell death is by generating and accumulating replication-defective viral mutants to compete and inhibit the infection of normal viruses or by selecting non-cytolytic viral mutants and selecting host cells that are restricted to viral infection to limit cell disease.However,the mechanisms involved in FMDV persistent infection remain unclear.Using the previously established O-type FDMV BHK-21 persistent infection cell lines,we found that many FMDV-free cells occupied in the persistent infection cell lines.These cells showed resistance to the parent FMDV and FMDV-Op(virus supernatant of persistent infection cell lines)and and re-established a persistent infection when infected with FMDV-Op,suggested that the host cells had evolved;On the other hand,the virus evolved too,but it was more adapt to the evolutionary environment,and the virus lytic BHK-21 to death.This meant that the establishment of FMDV infection is not due to the generation of defective viral particles or other replication-defective mutations during viral infection.Instead,it is due to the host cells rapidly dividing into large numbers of evolved cells with increased resistance to the virus.Moreover,the limitations of these evolved cells on FMDV infection were due to the complete blockage of viral RNA replication,making the virus proliferation process ineffective.By using RNA-seq,we found that 4686 genes were differentially expressed in BHK_VEC which were enriched in categories related to metabolic processes,cell division and cell cycle,cellular protein catabolic process and binding process.In addition,1229 alternative splicing events,especially skipped exon events,were induced in BHK_VEC,which were enriched in cellular components,cell metabolism processes,transcriptional regulation,protein modification process,chromatin modification as well as amino sugar and nucleotide glucose metabolism and lysine degradation pathway.Moreover,these evolved cells have a stronger immune response and a weaker MAPK signal response than normal cells.At the same time,MAPK signaling pathway-related genes were found significantly down-regulated in BHK VEC when compared with BHK-21;and up-regulated in BHK-Op when compared with BHK_VEC,suggested that they were involved in the replication of virus.When the MAPK/ERK pathway was specifically attenuated with U0126,the proliferation of FDMV was significantly impaired and showed a trend toward persistent infection which implied that MAPK/ERK signaling pathways involved in the establishment of FMDV persistent infection.These comprehensive transcriptome analyses not only facilitated the screening for genes associated with resistance to FMDV infection,but also provided useful information for exploring the precise mechanism of FMDV persistent infection.