Molecular Characterization of a Recombinant NADC30-like PRRSV Strain with a Novel Gene Deletion Pattern in Nsp2 Gene

PRRSV poses a persistent global challenge to the swine industry due to its rapid evolution. This study aimed to characterize a novel PRRSV2 strain, HeB2023092, isolated from a suspected outbreak in China in September 2023. We performed virus isolation in porcine alveolar macrophages (PAMs), genome sequencing, phylogenetic analysis, and comprehensive genetic characterization. HeB2023092 replicated effectively in PAMs but not in Marc-145 cells. Phylogenetic analysis consistently grouped it with NADC30-like strains (L1.8). Notably, genomic analysis revealed a unique 41-amino acid deletion (478-518 aa) in Nsp2, in addition to the characteristic 111-amino acid deletion of NADC30-like strains. Significant amino acid variations were also found in the antigenic epitopes and N-glycosylation patterns of GP3 and GP5. Comprehensive recombination analysis identified three distinct recombinant regions, revealing a mosaic genome with a predominant NADC30-like backbone. The backbone incorporated genetic sequences from JXA1-like (L8.7) strains in two regions and from NADC34-like (L1.5) strains in one region. These findings highlight the continuous genetic evolution and complex epidemiology of PRRSV, underscoring the critical need for sustained surveillance and detailed characterization of circulating strains to inform effective control and vaccine development strategies.