Abstract: Using RT-PCR identification,we obtained a PRRSV variant strain GD-ZQ,which came from the suspected porcine reproductive and respiratory syndrome areas. The variant strain could cause significant CPE in Marc-145 cell. Serial passage of GD-ZQ until it was stable,Nsp2,ORF3,ORF5 gene of the strain were amplified, the sequence determination,the comparative analysis and the cladogram was drawn up. The results indicated the amino acid sequence homology of the three GD-ZQ genes were 89.0% to 95.8% with the American VR-2332 and Ch-1a,and 48.2% to 49.3% with European LV. Further comparative analysis showed GD-ZQ was in the same branch with Ch-1a,amino acid sequence homology of GD-ZQ isolates Nsp2 was 98.3% to 99.4% with other variant strains as HEB1. The 5th generation was could cause regular CPE,with TCID₅₀ of 10^-5.6／0.1 mL. The analysis explained that GD-ZQ was a variant strain,with the characteristic of "high fever" disease mutation of PRRSV strain. The results layed a foundation for the further research on PRRSV in time and molecular level to understand genetic variation and the range of variation.

Key words: PRRSV variant strain GD-ZQ; genetic variation analysis; Nsp2 gene; ORF3 gene; ORF5 gene