| Classical swine fever (CSF) is an acute, febrile and highly contagious disease,mainly causing damage to the pigs (including wild boars), while other animalsgenerally survive from it. The main feature of this disease involves continued highfever, microvascular degeneration, systemic hemorrhage, necrosis and infarction;caused by classical swine fever virus(CSFV), CSF does great harm to the swineindustry with a high mortality, and is considered as one of the major infectiousdiseases which affected breeding industry seriously. Hence, CSF is classified by theOffice International des épizooties(OIE) as a list A disease. Genetic evolutionaryrelationships of CSFV strains of a different time and different regions were studied bygene sequencing, which constituted an approach to research the molecularepidemiology of CSFV, and it was of great importance to understand the CSFV.In this study,842materials of swine fever-suspected cases from10provinces(Guangxi, Xinjiang, Sichuan, Shandong, Fujian, Hebei, Henan, Hunan, Hubei,Yunnan) in China during2012were tested for CSFV by multiplex RT-PCR, amongwhich112cases were found positive, and positive rate was13.3%, which included allthe tested areas. According to the current standard of prevention and control of CSF,we thought that10provinces involved in the test had a risk of CSF. However,because of the implementation of compulsory vaccination for CSF in China, theprobability of hog cholera’s pandemic was very low, primarily with a typicallysporadic feature. The obtained positive materials were sent to sequence, then the E2gene nucleotide homology analysis and phylogenetic tree were built, the resultindicated that sequences homology among the26CSFV strains from10provinceswas88.3%to100.0%, with a max homology of87.9%to98.0%compared with thereference strain Zj080(street strain), and a min homology of78.1%to82.9%compared with the reference strain TWN2007. Phylogenetic tree revealed that thepositive experimental cases shared entirely the genotype2.1type with referencestrains Zj080and96TD, which was identical to report of Professor Xu Zhangchun[11]on the current genotype of swine fever in China.Recently, epidemic patterns of CSF have been various with the locally sporadicfeature, the emergence of atypical swine fever, adaptive proliferation of CSFV todifferent cells with increasing passage numbers, heterogeneity or antigenic drift thatthe vaccine strains might have, coupled with antigenic variation that CSFV might occur under the pressure of large-scale inoculation over decades, the traditionalvaccine will probably not provide well protection to CSFV in the near future, it is agreat trend to study and develop a new type of vaccine of CSF, for which the rise anddevelopment of molecular biology techniques will lay the foundation. In this study,recombinant construction of CSFV was accomplished by replacement of wild virusE2gene in the corresponding gene of the vaccine strain, providing a good platformfor research of vaccine and pathogenic mechanisms of CSFV. In the experiment ofCSFV recombinant construction, Smart technique was used to amplify the5’and3’end to overcome the influence of virus with or without cap structure; In-Fusionconnection technique was used in the connection between virus and vector to avoidthe multi-digested tedious steps. After the transfection of cells by virus, a novelinfectious swine fever virus particle was successful obtained by observation ofinfectious particles, RT-PCR technology, immunohistochemical assay and indirectimmunofluorescence assay; thus providing a scientific basis for further study ofpathogenicity of CSFV and new vaccines. |
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