Genetic Characterization and Pathogenicity of a Novel Recombined Porcine Reproductive and Respiratory Syndrome Virus 2 among Nadc30-Like, Jxa1-Like, and Mlv-Like Strains

Abstract

Recombination among porcine reproductive and respiratory syndrome viruses (PRRSVs), coupled with point mutations, insertions, and deletions occurring in the genome, is considered to contribute to the emergence of new variants. Here, we report the complete genome sequences of a PRRSV field strain, designated SCN17, isolated from a RespPRRS MLV-vaccinated piglet in China in 2017. Sequence alignment revealed that SCN17 had discontinuous 131-amino acid (111 + 1 + 19-aa) deletion in the NSP2-coding region identical to that of NADC30 when compared to VR-2332. Notably, the strain, SCN17, contained an additional 1-aa deletion in NSP2, a 1-aa deletion in ORF5, and a unique 3-nt deletion in the 3′-UTR. Phylogenetic analysis showed that SCN17 clustered into NADC30-like lineage based on ORF5 genotyping, whereas it belonged to an inter-lineage between the NADC30-like and VR-2332-like lineages as established based on the full-length genome. Importantly, the SCN17 was identified as a novel virus recombined between a NADC30-like (moderately pathogenic), a JXA1-like (highly pathogenic), and an attenuated vaccine strain, RespPRRS MLV (parental strain VR-2332). Furthermore, we tested its pathogenicity in piglets. SCN17 infection caused a persistent fever, moderate interstitial pneumonia, and increased the viremia and antibody levels in the inoculated piglets. Of note, all SCN17-infected piglets survived throughout the study. The new virus was showed to be a moderately virulent isolate and have lower pathogenicity than HP-PRRSV strain, SCwhn09CD. Our results provide evidence for the continuing evolution of PRRSV field strain by genetic recombination and mutation leading to outbreaks in the vaccinated pig populations in China.

Full Genomic Analysis of New Variants of Porcine Reproductive and Respiratory Syndrome Virus Revealed Multiple Recombination Events Between Different Lineages and Sublineages

“…GXNN1839 is a recombinant virus that originated from recombination events that occurred in nsp9 and GP2 between strains of lineages 1 (NADC30-like) and 5 (VR2332-like). Many recombinant PRRSV strains that originated from recombination events between NADC30-like and VR2332-like strains have also been identified in previous studies ( 23 , 32 , 38 , 40 ). Indeed, the NADC30-like strains seem to be prone to recombine with other PRRSV strains.…”

“…Indeed, the NADC30-like strains seem to be prone to recombine with other PRRSV strains. Numerous recombinant PRRSV strains originated from recombination events between NADC30-like strains and other lineages of PRRSV strains that were found in the field ( 14 , 23 , 24 , 34 , 40 – 42 ). GXYL1403 was detected as a recombinant virus from strains of sublineages 8.1 (Ch-1a-like) and 8.3 (JX1A-like) that have circulated in China in recent years.…”

The phosphorylation of the N protein could affect PRRSV virulence in vivo

“…It is difficult to distinguish the vaccines from the wild-type virus. The emergence of recombinant viruses has exacerbated this problem Zhou et al, 2018Zhou et al, , 2015. The N protein is the most conserved protein in PRRSV, and few sites have changed during passaging Y.…”

Molecular and Cellular Mechanisms for PRRSV Pathogenesis and Host Response to Infection

“…RNA recombination has experimentally been proven by coinfections of cells or swine with two different strains of PRRSV (Liu et al, 2011;Yuan et al, 1999). During the recent epidemiological investigations, recombination has been detected between two wild-type PRRSV strains (Franzo et al, 2014;Kwon et al, 2019;Zhao et al, 2015), between wild-type PRRSV and MLV vaccine (Bian et al, 2017;Wang et al, 2019a;Zhou et al, 2018) or between MLV vaccine strains (Eclercy et al, 2019).…”