Isolation, Identification Of Porcine Circovirus Type2in Henan And LH2Strain Pathogenesis In Kunming Mice

Porcine Circovirus (PCV) is a small nonenveloped virus with a single-stranded circular DNA genome, which belongs to the Circoviridae family, it is one of the smallest animal viruses. According to the pathogenicity, antigenicity and nucleotide sequence of PCV, PCV can be divided into two types, PCV1and PCV2. PCV1is considered to be non-pathogenic to pigs by experimental inoculation and was circulating widely in swine population in the world. Its complete genome was composed of1759nucleotides. However, PCV2genome consists of1767or1768nucleotides. Porcine circovirus type2(PCV2) is recognized as pivotal agent of postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), porcine respiratory disease complex, and reproductive disorder. Since the first isolation of PCV2from pigs with PMWS in2000, the rapid spread of PCV2associated disease was confirmed in China, caused significant economic losses and present a threat to the pig industry. So there has significance on the study of this disease and its pathogenySamples suspiciously infected with porcine circovirus type2(PCV2) were collected from several regions in Henan and detected by PCR. PCV2-positive samples were inoculated into non-PCV contaminated PK-15cells. They were detected after blind passaged in PK-15for6generations, and PCV1, PPV, PRV and PRRSV were all negative. Specificity fluorescence in the PK-15cells infected PCV2was observed by DFA. Nothing in the PK-15cells without infection.A pair of primers was designed, and11virus strains were amplified, then cloned and sequenced. The11strains were named LH1、ZZ1、ZZ2、ZZ3、ZZ4、JZ1、JZ2、LY1、 PDS1、JY1、NY1. The11strains and PCV2complete sequence at home and abroad in GenBank were aligned, it revealed that the length of10genomes was1767bp with the other one in1768bp indicating PCV2b was the main causative agent of PMWS in Henan. The homologies between the11strains were94.9%-100%, and they shared94.7%-100%homologies with other PCV2strains. Phylogenetic tree showed the10PCV2b strains were closely related.Thirty,6-week-old Kunming mice were randomly divided into there groups Group A was inoculated intraperitoneally with PCV2(LH1F10). Group B was inoculated intraperitoneally with PCV2(LH1F10) and a booster inoculation at days7after the first inoculation. Group C was inoculated with PBS as a control group. Each group was sacrificed at7,14,28,35and42days post-inoculation, respectively. Necropsy was checked on every mouse. Sera samples were collected for the test of PCV2specific antibody. Tissues were collected for histopathology study and polymerase chain reaction (PCR).PCR results showed that the virus replicated in the inoculated mice, and minor pathological damages were found in the tissues of the inoculated mice of histopathology.Special PCV2antibody could be found in PCV2inoculation mice and was significantly higher than that in the control.This study isolated11PCV2strains, and analyzed their homology according to PCV2strains at home and abroad. This work may provide some basis for studying the molecular epidemiology, variation and prevention of PCV2in Henan.