The Influence Of Untranslated Region(UTR) On Virulence Of Foot-and-Mouth Disease Virus

Foot-and-Mouth Disease (FMD) is one of the world’s most cute, contagious disease of cloven-hooved animals including pigs, cattle and sheep caused by Foot-and-Mouth Disease virus(FMDV). For its characteristics of spreading fast,strong infectivity,broad host range and huge damage,FMD is called "Political and Economic disease", and had attracted much attention in the world. The pathogen Foot-and-Mouth Disease Virus (FMDV) is a mumber of the Aphthovirus genus of the family Picornaviridae, the genome of FMDV is about8.4kb including untranslated region(UTR) at its both ends, some1.4kb. The UTR of FMDV played an important role in replication,transcription and translation. Multiple alignment reveals that the there are large differences among UTR sequences of vaccine strain O/HN/93, epidemic strain O/NX/CHA/99(linage Mya98) and O/BY/CHA/2010(linage PanAisa). There also are44base pairs insert in the5’-UTR of strain O/NX/CHA/99and strain O/BY/CHA/2010. In addition,the secondary structure of UTR of these three strains predicted is different from each other. In order to study the influence of the UTR of FMDV on virulence deeply, we constructed six full-length-cDNA clones, which are based on full-length cDNA clone of O/HN/93strain. the first three clones is constructed via replacing5’-UTR,3’-UTR,5’-UTR and3’-UTR of strain O/HN/93by the corresponding sequence of epidemic strain O/NX/CHA/99separately. and the other three full-length cDNA clones are constructed using the same method except the source strain is O/BY/CHA/2010.The every cDNA clone together with plasmid pcDNAT7P which can express T7RNA polymerase was transfected into BHK-21cells respectively and60h later Cytopathic Effect(CPE) were found in the transfacting BHK cells. The chimeric virus were respectively confirmed by RT-PCR and IFAT. After analysing the TCID50growth curves we found that the virus titer of FMDV is weaken if either of the non-coding regions is replaced, but not obvious if the noncoding regions is replaced together. The LD50of these chimeric virus shows that the pathogenic of FMDV is attenuated if either of the non-coding regions is replaced, but not obvious different if the non-coding regions is replaced together. The characterism of plaques of these virus are all the same, but real-time fluorescence quantification RT-PCR shows that the RNA replicate level of the virus is different from each other.In conclusion, the replacment of the untranslated regions of O/HN/93by two epidemic strain O/NX/CHA/99and O/BY/CHA/2010respectively make no different on rescuing virus successfully, but can affect the virulence of FMDV, and the influence on virulence is the result of affecting the replication, transcription and (or) translation of the virus. This paper lay us a theoretical basis to explain the function of UTR of FMDV deeply.