Comparison of pathogenicity of different subgenotype porcine reproductive and respiratory syndrome viruses isolated in China.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an important pathogen causing huge economic losses to the swine industry worldwide, because of its rapid evolution and variation in genomes. It is necessary to monitor the newly emerging epidemic strains and compare their virulence diversity in swine. In this study, two strains of PRRSV2 were isolated from clinical samples by using primary porcine alveolar macrophage (PAMs) cells and designated as SD1805 and FJ1805, respectively. They were unable to grow in MARC-145 cells. Full-length genomes sequence analysis revealed that SD1805 strain has the molecular characterization of NADC30 strain from American, and belongs to the branch of NADC30-like PRRSV (NL-PRRSV) (lineagea 1). FJ1805 isolate came from the inter-subgenotype recombinant of NADC30 strain with a highly pathogenic PRRSV (HP-PRRSV) strain HUN4. Moreover, it belongs to a lineagea 3 represented by the Chinese isolate QYYZ. Pathogenicity analysis showed that SD1805 strain had similar mortality and viral loads in lungs to HP-PRRSV BB0907 strain. FJ1805 strain showed milder pathogenicity compared to NL-PRRSV strain FJ1402 that was previously isolated with Marc-145 cells. It provides evidence of the circulation of the different subgenotype PRRSV strains in China with variations in cell adaption and pathogenic abilities. • Two PRRSV-2 strains with different molecular characterization were isolated. • SD1805 is a novel NL-PRRSV strain with higher virulence than another NL-PRRSV FJ1402 strain adapted in Marc-145 cells. • FJ1805 is a novel inter-subgenotype recombinant of strains HP-PRRSV HUN4 and NADC30. • It illustrates the variation and evolutionary trends of epidemic PRRSV strains, which being helpful for preventing and controlling this disease in the future. [ABSTRACT FROM AUTHOR]