Molecular Epidemiology And Antigenic Differentiation Of Classical Swine Fever Virus In China

Classical swine fever (CSF) is a highly contagious febrile disease of domestic and feral pigs.Once outbreaks can cause heavy losses to swine industry and hamper international trade with animals and animal products, especially serious in developing countries. Therefore CSF is a notifiable disease to Office International des Epizooties (OIE) and to the European Union(EU).It is one hundred and seventies years since the first outbreak of CSF which is still prevalence in many country worldwide,such as parts countriesand region in South America, Asia, Europe. Other countries such as Franch,Netherland,Genman, Belgium occurrenced CSF again when they had proclaimed the eliminating of CSF.Due to carraying out inoculation of HCLV vaccine,CSF is well controlled in China with large scale outbreaks rarely seen. However,sporadic onsets still be found every year. It is noteworthy that a mild and atypical form of CSF with a long duration ,atypical clinical and pathological symptoms, low morbidity and mortality has been observed. The variability of CSFV has been mostly studied by two approaches. From phylogenetic analysis, CSFV can be divided into different genogroups and subgroups.The other approach took use of the monoclonal antibodies to assay antigenic variation.Both of the studies are important for the epidemiology of CSF. Phylogenetic comparison of CSFV isolates in China has been studied and reported ,but the the antigenic variation among CSFv isolates is still unknown. RNA viruses exhibit the highest mutation rates of any group of organisms due to the lack of proofreading activity in their polymerase proteins ,so the variability of CSFV may be occur in immune pressure,but have not any such study report.In this study,152 tissue samples from the clinically suspecting were collected.The samples were collected from 10 provinces of China after 2000. From which 29 field viruses were detected nested RT-PCR and subjected to nucleotide sequence analysis for their phylogenic relationship. The result revealed the existence of two major groups and three subgroups, they are 1.1,2.1,2.2 subgroups, phylogenentic analysis revealed one distinct virus population as subgroup 2.1existing inChina after 2000.Only one isolate sampled was classified into subgroup 2.2.The CSFV isolates belong to 3 group was still not found in China.The lowest percent identify of the 29 strains is 79.1% on the nucleic acid and 80.3% on the amino acids.31 epidemic CSFV strains were isolated from the CSF positive tissue samples. The first CSFV epidemic strains database was set up. The epidemic background and the passages of the strains were clearly.It is very important for the strains future biological studies and the well control CSF in our country.And identified the multiple infection of the CSFV and PRV .In order to study the antigenic differences of classical swine fever viruses a panels of 28 monoclonal antibodies against the pestiviruses were used analyze 22 CSFV field viruses isolated from China in comparison with the virulent strain Shimen and vaccine strain HCLV (lapinised virus) used in the country.The reactivies of the McAbs with the CSF isolates can be divided three patterns based on the fluorescence character:â… strong reaction,â…¡moderate reaction,â…¢weak reaction. The results showed that all of the strains could be recognized by CSFV-specific McAbs but not by the McAbs directed to pestivirusAmong. The panel of 9 McAbs against the glycoproteins E2 WH303 ,302 had the largest identify spectrums can be recognized by all strains and reacted strongly. We find that WH220 can recognize the most isolates after 2005 but a few of the isolates before 99, it indicates that the antigenic variation of CSFV occurs by the time.At first,we want to find the relationship between the genetype and the reactivities of the McAbs with the isolates,but we failed. The present study showed that although there is antigenic differences, the antigenicity of the virus is unlikely used to type the viruses as phylogeny does, highly supporting the concept that CSFV has only one serotype. Meanwhile there is no accordance between antigenic differentiation and phylogenetic analysis.This is the first about the antigenic differences of classical swine fever viruses in China.We study the CSFV Shimen strain replication regularity under the immune pressure.The result showed the virus is stable in cell culture under immune pressure, and no variant occurs , still can be neutralized by the neutralization antibody.