| Classical swine fever (CSF) is highly pathogenic and contagious infectiondisease to both domestic and wild pig worldwide. It causes major losses in stockfarming and affects the pig products of international trade. CSF was listed as A classinfectious diseases by Office International Des Epizooties (OIE). The pathogenclassical swine fever virus was considered as animal’s bioterrorism pathogen orbiological agent by the biological weapons convention. Therefore,this has caused a highly attention in the international society.Classical swine fever virus (CSFV) is a single—stranded, non-segmented,positive-sense RNA virus，which belongs to the family Flaviviridae, genus Pestivirus.The diameter of this lipid-enveloped RNA virus is40~60nm. CSFV genome isapproximately12,300nucleotides in length and comprises a long open reading frame(ORF) flanked by5’ and3’untranslated regions (UTRs). The ORF is translated to aprimary polyprotein，subsequently processed into12mature proteins by cellular andviral proteases, which are8nonstructural proteins（Npro，P7，NS2，NS3，NS4A，NS4B，NS5A，NS5B） and4structural proteins（C，Erns，E1，E2），Moreover,two precursor protein E2-p7and NS2-3were produced. E2is the main neutralizingantigen, which induced the body’s immune response.Part one is a review of the recent progress on the molecular characteristic ofclassical swine fever virus.In part two, we found best antigenicity region of E2gene through bioinformaticanalysis combined with previously studies. Prokaryotic expression system was used toexpress and purify the region of E2protein through PET30a-c-E2vector. The purifiedprotein was administrated to mice by abdominal injection, in order to obtain the E2 antibody detecting CSFV.In part three, we modified the vector PMC18C-CSFV through adding the HDVribozyme and T7terminator following the3’UTR of genome in order to transcribeCSFV C strain cDNA in vivo, and the modified vector was namedPMC18-CSFV-rz-T7. This modification avoid complex operation andeasily degradable RNA in vitro transcription. In addition, this modified vector wasused to reconstruct two new plasmids, named PMC18C-CSFV-rz-T7(NS5B）andPMC18C-CSFV-rz-T7（without NS5B）. These modifications were used to investigateif double strand CSFV is viable and to distinguish wild strain and vaccine strain inorder to purify CSFV. However，we found that NS5B is a cis-factor in replication andcannot be trans complemented.In part four, we conducted a systemic analysis of the impact of vaccination onthe evolution of CSFV by comparing vaccine-related and non-vaccine-related CSFVgroups. We found that vaccination may affect strain diversity and immune escapethrough recombination and point mutation. We also found that vaccination mayinfluence the population dynamics, evolutionary rate and adaptive evolution ofClassical swine fever virus. Our evidence suggests that the vaccination might alsochange host adaptation through influencing codon usage of the virus in swine. Thesefindings suggest that it is necessary to avoid excessive use of CSFV attenuatedvaccines. |
