Abstract: Suspected specimens collected from pigs with porcine reproductive and respiratory syndrome virus (PRRSV) in Jiangxi province, was ORF7 gene positive tested by RT-PCR. The result of sequence analysis showed that ORF7 gene of this strain shared 93.9% to 69.8% homologies with those of American standard strain and European strain. Brains and lungs from clinical specimens had regular cytopathic effect (CPE) over 6 passages on Marc-145 cell culture, ORF7 gene can be detected at cell cultures; sequence analysis of Nsp2 (non-structural protein) gene showed that there was a high amino acid homology between JX0708 and other Chinese local PRRSV strains isolated in recent years, while this strain had 30 amino acid deletion at the residues 481 and 532 to 560 compare with the American standard strain. Electron microscopy demonstrated that typical virions were found in the purified cell cultures. Cell cultures of 8^th passages was used to do regression test on the piglets of 30 day-old. After the inoculation, all piglets showed typical clinical signs and patiological changes of PRRS. So an America variant PRRSV stain was isolated successfully, and named JX0708 strain.

Key words: PRRSV; JX0708 strain; isolation and identification; Nsp2 gene; analysis of genetic variation