Complete genomic characterization of a Chinese isolate of porcine reproductive and respiratory syndrome virus.

The genome of one isolate of porcine reproductive and respiratory syndrome virus (PRRSV) from China, designated GDQY2, was sequenced and analyzed. The full length of GDQY2 was 15,215 nucleotides, excluding the poly(A) tail. Comparative analysis with the genomic sequences of numerous worldwide North American isolates revealed that GDQY2 shared 85.0-98.9% identity with these isolates, but only 60.9% with the European virus-LV (Lelystad Virus), indicating that this new Chinese isolate was closely related to the North American PRRSV genotype. Phylogenetic analysis based on the nucleotide sequences of the full length and ORF5 showed that this new isolate belong to the same genetic group with all other Chinese isolates. Comparison with North American PRRSV isolates revealed that GDQY2 exhibited variations in the non-structural protein 2 (NSP2) encoded by ORF1a, namely that an additional 35-amino acid deletion in NSP2 was found in GDQY2. Therefore, GDQY2 was a novel strain with unique deletions. Furthermore, our study demonstrated that North American genotype PRRSVs in China have evolved independently from other countries, indicating that geographic separation might be one factor influencing the molecular evolution of PRRSV.