Genetic and Respiratory Pathogenic Comparison of Two PRRSV-2 Isolates Classified as Lineage Korean A and B.

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to cause substantial economic losses worldwide, and certain lineages circulate in specific countries. Lineage Korean A (LKA), B (LKB), and C (LKC) have been reported exclusively in Korea. However, studies on LKA and LKB have been limited to strains isolated before 2015. In this study, we analyzed the genetic and pathogenic characteristics of SNUVP2403A and SNUVP2407B strains isolated in 2024. Based on ORF5 phylogenetic analysis, SNUVP2403A and SNUVP2407B were classified as LKA and LKB, respectively. No recombination was detected in SNUVP2403A, whereas SNUVP2407B was identified as a recombinant between NADC30 and JB15-N-PJ10-GN. In the animal infection study, the pigs inoculated with SNUVP2403A had a mortality rate of 8.3% (1/12 pigs), and clinical signs such as nasal discharge, coughing, eyelid edema, and cyanosis were observed. The group inoculated with SNUVP2407B exhibited only mild respiratory symptoms, and all pigs survived throughout the experiment. Therefore, it was demonstrated that SNUVP2403A is more virulent than SNUVP2407B. In addition, SNUVP2407B exhibited significantly lower pathogenicity than previously reported LKB strains. In conclusion, this study provides a systematic characterization of SNUVP2403A and SNUVP2407B and improves our understanding of the genetic diversity and pathogenicity of PRRSV circulating in Korea.