Isolation，identification and genetic variation analysis of South China strain GDgz of porcine reproductive and respiratory syndrome virus

To understand the evolution of porcine reproductive and respiratory syndrome virus（PRRSV） in South China，we isolated a PRRSV strain in Marc-145 cell from lung of suspected PRRSV-positive pig in South China and named GDgz. GDgz strain could cause typical cenotaphic effect. The results of phylogenetic tree and homology alignment analysis showed that GDgz belonged to the same cluster with high pathogenetic PRRSV（HPPRRSV） strains in China；GDgz had a far distance with European strain Lelystad virus，the nucleotide homology was only 60.3%，with American classic strain VR-2332 was 88.8%，with Chinese HP-PRRSV strains JXA1 and HuN4 were 98.8% and 98.9%，with the vaccine strain JXA1-P80 of JXA1 was 99.1%，with NADC30 and NADC30-like strains CHsx1401 and JL580 were 84.5%，87.2 and 83.6%，respectively. The result of sequence alignment showed that there were 30 discontinuous amino acids deletion in the high variable region of NSP2. These results showed that GDgz belonged to vaccine strain of high pathogenetic North American type PRRSV and had some mutations in the epitope region.