| Porcine circovirus type 2 (PCV2) is one of the most important virus that affect the swine industry nowadays. PCV2 could cause progressive weight lose and high wasting ,on the other hand the virus proliferates in the immune system of piglet ,and cause disorder of immune function. The virus has caused great economic loss in the pig industry. PCV2 has been widespread in the world, it could cause PMWS(Post-weaning pigs multisystemic wasting syndrome),PDNS(procine dermatitis and nephropathy syndrome),PRDC(porcine respiratory disease complex),CT(congenital tremors) and reproductive disturbance.It is reported that There are two kinds of PCV2 gene length, 1767bp and 1768bp respectively.Some study indicated that the protein (Rep)that ORF1 encoded is associated with the replication of the virus. Its encoded protein(Cap)is the major ingredient of the capsule which has good immunogenicity, It also has become a research hotspot recently.In this study, the virus materials are from the pig farm from the outskirts of Fuzhou, we use PCR methods for DNA detection of PCV2 and carried out the whole gene cloning and molecular analysis of structural characteristics of PCV2.The sequence length of Fuzhou strains is 1767bp with 11 open reading frames, ORF1 has 945 base pairs, encoding 314 amino acids. It has three glycosylation sites from the deduction of the amino acid sequence(23～25aa(NPS),256～258aa(NQT),286～288aa(NAT)), ORF2 has 705bp ,encoding 233 amino acids and there is only one glycosylation sites from the view of the amino acid sequence(143～145aa).The protein secondary structure prediction of ORF1 and ORF2 showed that, in ORF1 H:α-helix, E:β-folding, space: each other or random coil, the ratio of each is 24.2%, 20.38%, 55.41%; in ORF2 the corresponding ratio of each is 6.41%, 31.20%, 62.39%. We made a prediction of hydrophilic and antigenic epitopes of ORF2 at the same time. The results showed that the 10 amino acids at N-terminal are highly hydrophilic of the protein that ORF2 encoded. There are possible epitopes at 3 ~ 18, 32 ~ 43, 84 ~ 87, 113 ~ 118, 176 ~ 181, 227 ~ 231.We made an analysis with DNAstar on homology between isolates of Fuzhou and domestic and foreign isolates, the results showed the homology is 94.3%～99.8%. After the comparison of the phylogenetic tree between domestic and foreign strains , we can see, Fuzhou and Longyan isolates have a faraway relationship with other isolates, they are at an independent branch. And other strains on the graph showed the law of non-regional. These facts showed that the law of non-regional of the PCV2.As we made the analysis on the nucleotide sequence and deduced amino acid sequence of the two main open reading frame (ORF1, ORF2) of the strain, we found that the ORF1 nucleotide sequence homology between isolates of Fuzhou, Canadian isolates and 3 strains from Fuzhou province is 97%～99.5%; amino acid homology is 97.8%～99%;ORF2 nucleotide sequence homology is 91.3%～99.7%; amino acid homology is 92.3%～98.7%. Thus, ORF2 has a greater variation than the ORF1. |
