Cloning And Sequence Analysis Of E2 Gene Of The Epidemic Virulent Strains Of Classical Swine Fever Virus In Guangxi

In this study, the whole E2 genes of two strains of Classical Swine Fever Virus (CSFV) isolated from Guangxi (GX) were amplified by reverse transcriptase polymerse chain reaction (RT-PCR) method and seqenced .The E2 gene fragments of CSFV were 1090 base pair in length and encoded 364 amino acid residues. Comparing the two epidemic strains (GXNN, GXLZ) with other 16 reference strains sequence reported in GenBank by software DNAStar, it was found that strains GXNN, GXLZ and Hog Cholera Lapinised Virus (HCLV) were 82.0%, 82.6% for nucleotide sequence and 88.7%, 87.6% for amino acid sequence in homology. The nucleotide homology among strains GXNN, GXLZ with Shimen were 83.5% and 84.1%; and that of amino acid were 90.1% and 89.0%. But compared the E2 genes of strains GXNN, GXLZ with Paderborn strain, the homology of nucleotide were 95.5% and 95.6%; and that of amino acid were 96.7%, 97.5% respectively. The homology between the two epidemic strains and Italy strain were higher and were 95.0%, 95.1% for nucleotide sequence and 96.3%, 97.0% for amino acid sequence. The result showed that therewere some differences among GX epidemic strains of CSFV, strains HCLV and Shimen. GX epidemic strains perhaps have a close relation to the CSFV occurred in Germany and Italy.It also indicated that there were some mutations in 710,713,725, 729, 734 and 738 amino acid of B, C high variable region of strains GXNN, GXLZ by comparing the amino acid sequence. It was very impossible that those mutations of GX epidemic strains of CSFV can cause the incompleted protection of HCLV vaccine.Computer- base phylogenetic tree among the two strains of GX and other 16 strains mentioned above were obtained by analyzing nucleotide sequences of E2 gene. It showed that these eighteen strains can be classified into two major groups and a special individual, which agreed with domestic and foreign scholors' conclusion. Strains GXNN, GXLZ belonged to group II ,which also included strains Italy, Paderborn, Thielll096 and 39. And another nine strains and strains HCLV, Shimen of two major reference strains of china belonged to group I. In addition, strain p97 was the special individual. The phylogenetic tree revealed that GX epidemic strains in recent years were genetically divergent from strains Shimen and HCLV.