Whole-Genome Characterization and Pathogenicity of Two Novel Recombinant NADC30-like Porcine Reproductive and Respiratory Syndrome Virus Strains in Southern China

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) continues to pose a substantial threat to the global swine industry, with recombination-driven evolution generating novel variants that complicate disease control. In this study, two novel recombinant PRRSV-2 strains, designated GXNN202004a and GXGG20210301, were isolated from PRRS-affected pig farms in southern China. Whole-genome sequencing and phylogenetic analysis revealed that both strains possess an NADC30-like backbone, with GXNN202004a arising from recombination between NADC30 and JXA1 and GXGG20210301 representing a multi-lineage recombinant derived from NADC30, JXA1, and QYYZ. Genomic characterization identified a characteristic discontinuous 131-amino-acid deletion (111+1+19 aa) in the NSP2 coding region, along with a previously unreported six-amino-acid deletion in GXGG20210301. Animal pathogenicity assays demonstrated that both strains induced moderate clinical signs, including persistent fever, respiratory symptoms, and growth impairment, without causing mortality in piglets. Viral loads were detectable in multiple tissues, serum, and nasal swabs, indicating broad organ tropism and shedding potential. These findings enrich the molecular epidemiological data on PRRSV in China, highlight the increasing genetic diversity and recombination complexity of circulating strains, and provide scientific evidence for improved PRRS surveillance and vaccine development strategies in southern China.