Abstract: A porcine reproductive and respiratory syndrome virus (PRRSV) strain was isolated from visceral organs of a dead piglet obtained from a large-scale breeding farm and designated as PRRSV-CHD. It became cell-adapted and stable after several passages in Marc-145 cell line. The results showed that PRRSV-CHD could cause cytopathic effect (CPE) in Marc-145 cell line and the titer was 10^-6 TCID50/0.1 mL, while no CPE appeared in Vero cell line and BHK-21 cell line. The results of indirect immunofluorescent assay (IFA) tests indicated that the specific fluorescence could be detected in cytoplasm of infected cells. The strain we isolated was proved to be American genotype of PRRSV by sequence analysis and phylogenetic tree analysis with VR2332, CH-1a, HUN4 sequences. There were two non-continued deletions in the Nsp2 region of viral genome, that were 3 nucleotides deletions between
2780 and 2782 nt and 87 nucleotides deletions between 2933 and 3019 nt compared with VR2332, CH-1a, and so on, which proved the strain to be a variant PRRSV strain.

Key words: porcine reproductive and respiratory syndrome virus; isolation; identification