Genomic sequence and virulence of a novel NADC30-like porcine reproductive and respiratory syndrome virus isolate from the Hebei province of China

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of porcine reproductive and respiratory syndrome (PRRS), which results in immense economic losses in the swine industry. Outbreaks of disease caused by NADC30-like PRRSV are of great concern in China. Here, a novel variant, NADC30-like PRRSV strain HB17A, was analyzed and its pathogenicity in pigs was examined. The full-length genome sequence of HB17A shared 83.6-95.1% nucleotide similarity with NADC30-like and NADC30 PRRSV without any gene insertions, but with a unique 2-amino acid deletion in Nsp2. A phylogenetic analysis showed that HB17A clustered with NADC30 strains. Different degrees of variation in the signal peptide, transmembrane region (TM), primary neutralizing epitope (PNE), non-neutral epitopes, and N-glycosylation sites were observed in GP5. Challenge experiments showed that HB17A infection resulted in persistent fever, moderate respiratory clinical signs, low levels of viremia and viral loads in serum, and mild gross and microscopic lung lesions. Moreover, IFN-γ, IL-6, and IL-10 cytokine levels were significantly elevated in serum, but the levels of IFN-α and IL-2 were similar to those of the negative controls. HB17A was less pathogenic but was secreted longer in nasal discharge than HP-PRRSV FZ06A. Our findings indicate that HB17A is a novel NADC30-like strain with certain deletions and mutations but with no evidence of genomic recombination. This strain exhibits intermediate virulence in pigs. This research will be help define the evolutionary characteristics of Chinese NADC30-like PRRSV.