Genomic characterization and pathogenicity of a strain of type 1 porcine reproductive and respiratory syndrome virus

The emergence of type 1 porcine reproductive and respiratory syndrome virus (PRRSV) has been noticed recently in China. In the present study, the complete genomic characterization of a strain of type 1 PRRSV (designated GZ11-G1) was described and its pathogenicity for piglets was analyzed. The results showed that the complete genome of GZ11-G1 with a size of 15,094 nt, excluding the poly (A) tails, shared 80.2-96.3% identity with the representative strains of type 1 PRRSV, and in particular, it had highest homology (96.3%) with Amervac PRRS, a live vaccine virus of type 1 PRRSV and SHE, a rescued virus from an infectious clone of Amervac PRRS virus. Compared with the vaccine virus, the nonstructural and structural proteins of GZ11-G1 displayed extensive amino acid variations except for its ORF5a. GZ11-G1 was clustered with the strains of type 1 PRRSV including Cresa3267, Cresa3249, Cresa3256, Olot/91, 9625/2012, ESP-1991-Olot91 and Amervac PRRS vaccine virus by further phylogenetic analysis. Moreover, GZ11-G1 was shown to cause fever, higher viremia and lung and lymph node lesions in piglets. Our findings indicate that GZ11-G1 is genetically related to type 1 PRRSV strains within the cluster formed by Cresa3267, Cresa3249, Cresa3256, Olot/91, 9625/2012, ESP-1991-Olot91 and Amervac PRRS vaccine virus, and it is a pathogenic for piglets. This study aids in understanding the genetic variation and evolution of type 1 PRRSV.