Genomic Characterization of HLJDZD55: The First L1B PRRSV in China

Porcine reproductive and respiratory syndrome virus (PRRSV) critically threatens the pig industry in China. Lineage 1 PRRSV, which is divided into L1A-L1F and L1H-L1J, is widely recognized as the most extensively genetically diverse lineage globally. L1A (NADC34-like) and L1C (NADC30-like) PRRSVs have become the current major circulating strains in China. Notably, strains from other branches of L1 have not been reported in China. During our epidemiological investigation of PRRSV, we identified a new strain named HLJDZD55. Phylogenetic analysis of the ORF5 gene revealed that HLJDZD55 belongs to the L1B branch. Alignment of deduced amino acid sequences based on the Nsp2 gene indicated that HLJDZD55 has a discontinuous deletion of 131 amino acids (111 + 1 + 19). We further sequenced the whole genome of HLJDZD55, and phylogenetic analysis based on the whole-genome sequence revealed that HLJDZD55 belongs to the L1C branch. Recombination analysis of the whole genome demonstrated that HLJDZD55 is a recombinant strain of TJZH-1607 (L1C, identified in China) and Minnesota 14 (L1B, identified in the USA). These findings suggested that HLJDZD55 is a newly emerged lineage 1 PRRSV in China and is closely related to L1B PRRSV in the US, which may have been introduced from the U.S. strain and subsequently recombined with the local Chinese strain and underwent evolution. Taken together, these results demonstrated the emergence of L1B PRRSV in China for the first time.