Sequencing And Analysis Of Genome Of PCV2 Local Epidemic Strains

Porcine circovirus type2(PCV2) is not noly considerded the causal agent of postweaning multisystemic wasting syndrome (PMWS).but it is associated with various other clinical conditions.Imrmmodeficiency is a well-known consequence of PCV2 infection .Though PCV2 is able to induce immunosuppression .It often is ingored beause of its sub-clinical infection,so the study of the epidemiology and molecular disease of virus should be further investigatied.In this study,the collected samples which were based on clinical signs for PMWS were detected for PCV2 DNA by PCR test . eighteen of seventy-three samples were positive for PCV2 DNA.The genome of 6 porcine circovirus 2 strains of positive samples isolated from Guangxi(GX) and Guangdong(GD) were cloned and sequenced.The completegenome of each of the six isolates was 1768bp or 1767bp in length.Comparison of complete genome sequence between 6 strains in DNAstar software was carried out,the result showed that there was a 95.5%~100% identity of the complete genomic nucleotides among the six isolates.what's more ,we also analysised the two open reading frames(ORF1 and ORF2) and deduce their amino acid sequence in computer.The ORF1 of the 6 isolates showed 96.9% to 100% nucleotide sequence identidy and 98.1% to 100% amino acid identidy.The result showed a high degree of homology of ORF1 and demonstrated that ORF1 which encodes the Rep protein was very conserved.The ORF2 of the 6 isolates had 92.9% to 100% nucleotide sequence identidy and 92.3% to 100% amino acid identidy. Sequence analysis of ORF1 and ORF2 genes of 6 strains revealed that the extent ofnucleotide variation was greater for the ORF2 than for the ORFl.The amino acid sequences alignment of the PCV2 capsid protein identified three major regions of amino acid heterogeneity.Two of which correspond with dominant immunoreactive areas.lt may contribute to the different pathogenicity.Phylogenetic analysis of the 6 strains of PCV2 and other 34PCV2 and 2 PCV1 sequences published in GenBank was obtained in Mega and Clustal method.The result showed that the two viruses were found in different phylogenetic clusters.The clusters of PCV2 were divided into two small groups which showed an associated with geographic orign . France strains were found closely related to each other .The strains from Canada and the US were spread in small group.Comparison of nucleotide sequence confirmed that the six isolates were close to the isolates from France.