Molecular Epidemiological Studies Of Classical Swine Fever Virus And Analysis Of The Complete Genome Of Epidemic Strains

Classical swine fever (CSF) blonged to the genus Pestivirus in the family Flaviviridae which was caused by classical swine fever virus (CSFV).CSFV was an acute, fever and contact sexually transmitted infections of pigs. CSFV had caused significant economic losses to annual pig industry and was notifiabled as a major animal disease animal diseases by the Office Intertional des Epizooties (OIE). In recent years, the nationwide rabbit attenuated vaccine was used to control the epidemic of CSFV, but CSFV was not cleaned up, which still was prevalent in many farms our country.Some scholars consider that the current epidemic strain have shifted away with vaccine strains HCLV.which leaded the limited immune protection.it is one reason the failure of immune by vaccine strains. In order to understand the epidemiology and the genetic variation of CSFV in our country provide a theoretical basis for effective prevention and treatment of CSFV,this paper studied the following content:(1) CSFV E2gene genetic variation.The hypervariable region190bp of E2gene was amplified from234tissue samples of12provinces collected in2012-2014by RT-nestPCR,and234gene fragment was sequenced. Further, E2complete gene of some representative strains was amplified by RT-nestPCR and sequenced. Using software MEGA and DNAstar, the phylogenetic trees of234epidemic strain was constructed using the hypervariable region190bp of E2gene fragment sequences,the nucleotide and amino acid homology of E2and the variations in their E2protein was compared between some representative strains with the reference strains.(2) Research on isolates HuN23/2013and GXF29/2013complete genome. Depending on the reference CSFV complete gene sequence published in Genbank, primers were designed. Four fragments of the CSFV isolates HuN23/2013and GXF29/2013genome were amplified by RT-PCR, and the homology and cell epitope variation of two isolates were analyzed.The results show that:the CSFV of subgenotype2.1b in genotype2.1were still the predominant strain of CSFV, but there have been some new changes, virulent strain of genotype1.1represented by Shimen strain almost disappeared in our country, subgenotype2.1c strains after epidemiced in2011, had a rising trend. The major epidemic strains of subgenotype2.1b and new subgenotype2.1c had some amino acids mutations in some important antigenic epitope sites and glycosylation sites with rabbit swine fever vaccine used in the clinical. These may affect the immune effect and cause the atypical CSF currently longstanding. Analysis of whole genome sequences of two2013epidemic strains HuN23/2013and GXF29/2013showed:the full-length of HuN23/2013and GXF29/2013was12295bp and12296bp, HuN23/2013blonged to the major epidemic strains of subgenotype2.1b,and GXF29/2013blonged to a new subgenotype2.1c. The complete genome of the HuN23/2013、 GXF29/2013strain will make it possible to establishing the reverse genetic system of the field strain of CSFV in the future.