ABSTRACT
In order to study genetic variation diversity of porcine circovirus type 2 (PCV2) strains in Shanxi,the genomic sequences of nine PCV2 strains including SXQX,SXCZ,SXTY2,SXJC,SXJX,SXLL,SXPY,SXPG and SXXY recently isolated from some areas of Shanxi from 2013 to 2016,was cloned,sequenced and received by GenBank.The amplified PCV2 genomic sequences,ORF2 sequences and Cap protein amino acid of these nine strains were analysed and compared with those of published 28 PCV2 strains by DNAStar,drawing phylogenetic tree.The results showed that the genomic sequences of SXJX,SXJC and SXXY PCV2 strains were 1 768 bp,and the others were 1 767 bp,which accounted for 33％ and 67％,respectively.The homologies of nucleotide sequences of the nine strains were 94.7％-99.8％,the homologies of nucleotide sequences of the nine strains with the 28 isolates from different regions of the world PCV strain were 93.9％-99.9％,and the homologies of nucleotide sequences of the nine strains with the domestic vaccine strains were 95.1％-99.8％.The phylogenetic analysed that SXJX,SXJC and SXXY belonged to genotype PCV-2D,SXLL,SXPY and SXCZ belonged to genotype PCV-1C,and SXTY14,SXPG and SXQX belonged to genotype PCV-1A/1B.Thus it proved that the epidemic strain of PCV2 was mainly PCV-2b in Shanxi.The homologies of ORF2 nucleotide sequences and Cap amino acid of the nine strains were 90.0％-100.0％ and 87.1 ％-100.0％ respectively,the homologies of ORF2 nucleotide sequences and Cap amino acid of the nine strains with the 28 isolates from different regions of the world PCV strain were 87.6％-100.0％ and 84.1％-100.0％ respectively,and the homologies of ORF2 nucleotide sequences and Cap amino acid of the nine strains with the domestic vaccine strains were 91.0％-100.0％ and 89.3％-100.0％ respectively.The Cap amino acids of SXQX,SXJX,SXTY14,SXPG,SXJC and SXXY PCV2 were 233,ORF2 of SXQX,SXTY14 and SXPG located at 1 033-1 734 bp,ORF2 of SXXY,SXJX and SXJC located at 1 033-1 734 bp,and the Cap amino acids of SXCZ,SXLL and SXPY PCV2 were 234,ORF2 of them located at 1 030-1 734 bp,in addition,the positions of 1 030-1 734 bp were more three bases TCA than other ORF2 genome sequence of 1 767 bp,resulting in increasing a K (Lys) of amino acid sequencein at the 234 position.Also Cap protein of 9 PCV2 strains showed more amino acid variation in addition to the only high-ly conserved glycosylation sites (NYS) (pp.143-145 amino acid).It provided theoretical basis for the PCV2 immune prevention of research in Shanxi,and the data of basic theory of molecular pathogenesis of PCV2.