| With immunosupperssion caused by PCV-2 infection,reduce pigs for other diseases resistance and vaccine immune response ability,make the secondary infecttion probably occurred.To date,PCV-2 have been wildly popular and spread between pigs, brought large economic loss in worldwide swine industry. In order to more fully understand the infection situation of PCV-2 in Fujian province, in present study TaqMan-based real-time PCR assay is used to detection tissue samples for PCV-2 from Fuzhou,Longyan,Nanpin,Ningde,Putian,Quanzhou, Sanming,Xiameng and Zhangzhou. To investigate the genetic variation of Fujian Province ,in present study,tissue samples extracted DNA from Fuzhou, Nanpin, Zhangzhou, Ninghua, Shanghang,Fuqing, Zhaoan was used as PCR templates to amplification PCV-2 complete genome sequence。After purification cloning amplified PCR product,sequencing the genomic nucleotide. The result demonstrates :1. The results suggest that all the detection farms there exists different degree of PCV-2 infecton.Between 2008-2010,PCV-2 antigen positive rate of scale farms illness pigs were 55.28% (293/530),62.26% (424/681) and 72.1% (328/455),respective;PCV-2 antigen positive rate of backyard households illness pigs were67.14% (94/140),72.08% (253/351) and 81.00% (243/300);clinical healthy pigs were 40.47% (291/719),45.34% (185/408) and 80.61%(420/521),respectively。PCV-2 etiology survey in this study reveal that,the pig herds from Fujian province is height infected PCV-2 and increasing year by year.2. 9 PCV-2 strains isolated from Fujian were sequenced,4 isolates genome length were 1767 bp,5 isolates were 1768 bp.Using DNASTAR software,9 strains isolated from Fujian were compared with other PCV-2 isolated strains in the GenBank.These 9 strains were colsely related to each other displaying 95.8%～98.6% overall nucleotide homology,compare with 19 domestic and overseas PCV-2 strains displaying 93.7%～99.5%.PCV-2 genome contains three open reading frames (ORF):ORF1,ORF2 and ORF3. Sequence comparisons of ORF1,ORF2 and ORF3 of these 28 PCV-2 strains shared 97.0%～99.8%,88.6%～99.7% and 96.2%～100% nucelotide sequence identity, respectively and also 97.0%～99.8%,76.5%～99.6% and 90.5%～100% amino acid sequence identity,respectively.3. 9 strains Fujian epidemic strains Cap protein amino acid sequence exist in the following four variation high-frequency area: V1(52～90 aa),V2(120～140 aa),V3(60～170 aa),V4(179～191 aa), the top three high variable district is located in the main immunoreactive regions of the capsid protein. In some viruses, these regions may lead epitopes under positive slection since they are submitted to high immunologic pressure. ORF3 protein 40-41 aa and 102-105 aa for variable frequency area, May influence of virus pathogenicity.4. Phylogenetic relationships among sequence were analyzed by a neighbor-joining using MEGA5.03.Confidence in the tree was estimated by 1000 Bootstrap.A phylogenetic tree was constructed including the ORF2 of the 9 Fujian PCV-2 strains,as well as 45 ORF2 sequence from GenBank. Phylogenetic tree could be divided into PCV-2a,PCV-2b and PCV-2c branches,4 PCV-2 strains of 9 isolats were genotype 2a, 5 PCV-2 strains of 9 isolats were genotype 2b, genotype 2b is not appear. |
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