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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.
Highlights
Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that has led to serious economic consequences in the global swine industry since it was first discovered in 1987 in the UnitedStates [1]
0.213 kg, respectively, and there was a significant difference between the two groups (p < 0.05). These results indicated that SCN17 is less pathogenic than the HP-porcine reproductive and respiratory syndrome viruses (PRRSVs) strain, SCwhn09CD
The results indicate that SCN17 is a natural recombinant strain between NADC30-like, JXA1-like, and the vaccine strain, RespPRRS modified live virus (MLV) that contains multiple novel aa/nt deletions within its genome, which has never been described in the literature so far
Summary
Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that has led to serious economic consequences in the global swine industry since it was first discovered in 1987 in the UnitedStates [1]. Porcine reproductive and respiratory syndrome (PRRS) is a viral disease that has led to serious economic consequences in the global swine industry since it was first discovered in 1987 in the United. The etiological agent of this disease, the PRRS virus (PRRSV), is an enveloped virus that contains a single-stranded, positive-sense RNA genome of 15.1–15.5 kilobases (kb) [2]. Two distinct types of PRRSV have been identified worldwide, namely PRRSV-1 (European origin, prototype strain Lelystad virus, LV) and PRRSV-2 (North American origin, prototype strain, VR-2332). The two types of PRRSV produce similar clinical symptoms and pathological changes in the infected pigs, they differ significantly in their antigenic properties and genetic content [6,8,9]
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