Genomic and pathogenic features of a novel subgroup 1-like PRRSV-1 strain XJEU2308 linked to reproductive failure in a swine herd in Xinjiang, China

Abstract Porcine reproductive and respiratory syndrome virus 1 (PRRSV-1) has emerged as a critical pathogen that threatens swine herds across China. In this study, a novel PRRSV-1 strain, designated XJEU2308, was isolated from a PRRSV outbreak in a previously confirmed PRRSV-negative (both RNA and antibody negative) swine herd in Xinjiang, China. During the outbreak surveillance period, production records revealed a mean stillbirth rate of 12.19% and a suckling piglet mortality rate of 56.07%. Phylogenetic analysis on the basis of the ORF5 gene classified XJEU2308 as a BJEU06-1-like strain, whereas whole-genome analysis clustered it within the newly identified "New subgroup 1" of Chinese PRRSV-1. Notably, this strain carried a unique 3-amino acid deletion (at positions 693–695) in nonstructural protein 2 (NSP2). In challenge experiments, XJEU2308 induced typical clinical symptoms and exhibited moderate pathogenicity. Importantly, the implementation of the load-close-exposure (LCE) strategy combined with field virus (FLV) exposure successfully restored the herd to a provisional PRRSV-negative status. Overall, this study isolated a new subgroup 1-like PRRSV-1 strain from a swine farm that experienced a reproductive failure outbreak; the strain is characterized by a unique 3-amino-acid deletion in the NSP2 gene and moderate pathogenicity. Additionally, this study validated the effectiveness of the LCE-FLV strategy for containing PRRSV-1.