A Natural Recombinant NADC30-Like PRRSV Strain in China: Intersection of CH-1a, QYYZ, and JXA1 Lineages.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a major threat to global swine production. In this study, a novel strain (PRRSV-AH1) was isolated during a respiratory disease outbreak at a commercial swine operation in Anhui Province, China. Viral replication in MARC-145 cells was confirmed by observing cytopathic effects (CPEs) and conducting immunofluorescence assays (IFAs). Whole-genome sequencing revealed a 15,020 bp genome exhibiting 90.0% identity with the NADC30 reference strain, including lineage 1-characteristic nonstructural polyprotein (Nsp)2 deletions. A distinctive L10S substitution in GP2 aligned with conserved residues of PRRSV-1. Recombination analysis identified PRRSV-AH1 as a novel chimera with a NADC30-like backbone incorporating CH-1a-like (lineage 8), JXA1-like (lineage 8), and QYYZ-like (lineage 3) sequences-representing the first reported instance of this specific recombination pattern. Experimental infection of piglets induced characteristic PRRSV pathology, including sustained pyrexia, reduced weight gain, prolonged viremia, and neutralizing antibody seroconversion. Comparative pathogenicity analysis revealed that the PRRSV-AH1 strain elicited febrile responses and peak body temperatures intermediate between classic NADC30-like strains and JXA1 strains. Notably, PRRSV-AH1 demonstrated a PRRSV-N-specific IgG induction capacity comparable to that of highly pathogenic variants. These findings establish PRRSV-AH1 as a multilineage recombinant (NADC30-like, CH-1a, QYYZ, and JXA1 Lineages) resulting from multiple genetic exchanges, underscoring the increasing complexity of PRRSV diversity in China. Accelerated mutation and recombination across lineages complicate disease control efforts, emphasizing the need for enhanced surveillance, mechanistic recombination studies, and the development of novel vaccines to mitigate future outbreaks.