Novel lineage 1 recombinants of porcine reproductive and respiratory syndrome virus isolated from vaccinated herds: geno
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ORIGINAL ARTICLE
Novel lineage 1 recombinants of porcine reproductive and respiratory syndrome virus isolated from vaccinated herds: genome sequences and cytokine production profiles Jonghyun Park1 · Subin Choi1 · Ji Hyun Jeon1 · Kyung‑Won Lee2 · Changhee Lee1 Received: 30 March 2020 / Accepted: 18 June 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Porcine reproductive and respiratory syndrome virus (PRRSV) is a widely disseminated, macrophage-tropic arterivirus that exhibits profound genetic and pathogenic heterogeneity. The present study was conducted to determine the complete genome sequences of two novel Korean lineage 1 PRRSV-2 strains, KNU-1901 and KNU-1902, which were isolated from vaccinated pig farms experiencing unusually high morbidity and mortality. Both isolates contained notable discontinuous 423-nucleotide deletions (DELs) within the genes encoding nonstructural protein 2 (nsp2) and GP3 when compared with the prototype strain VR-2332. In particular, the nsp2 DEL viruses had unique quadripartite discontinuous DEL signatures (111-1-19-9) in nsp2; this is an expanded version of the tripartite 111-1-19 DEL previously identified in virulent lineage 1 PRRSV-2 strains. Phylogenetic analysis revealed that both novel nsp2 DEL viruses belong to the Korean clade (KOR C) of lineage 1 isolates based on ORF5 but cluster with lineage KOR A strains based on the nsp2 or complete genome sequence. Recombination detection analysis suggested that both novel isolates are recombinants and may have evolved via natural interlineage recombination between circulating KOR A and KOR C strains. Interestingly, compared with the prototype VR-2332 virus, the novel nsp2 DEL variants were less efficient at promoting the expression of immune response genes in porcine alveolar macrophage culture. Taken together, we conclude that KNU-1901 and KNU-1902 are recently evolved recombinant variants of the virulent lineage 1 family that caused the regional severe PRRS outbreaks.
Introduction Porcine reproductive and respiratory syndrome (PRRS) is a ubiquitous and economically important viral disease that threatens commercial pork production worldwide [1]. PRRS virus (PRRSV), the causative agent of the disease, is an enveloped single-stranded positive-sense RNA virus that is a member of the genus Betaarterivirus, family Arteriviridae, Handling Editor: John Ziebuhr. Jonghyun Park and Subin Choi contributed equally to this work and share co-first authorship. * Changhee Lee [email protected] 1
Animal Virology Laboratory, School of Life Sciences, College of Natural Sciences, BK21 plus KNU Creative BioResearch Group, Kyungpook National University, Daegu 41566, Republic of Korea
Smart Pig Clinic, Cheonan 31008, Republic of Korea
2
order Nidovirales [2]. The PRRSV genome is approximately 15 kb in length, with a 5′ cap and 3′ polyadenylated tail; it includes a 5′-untranslated region (UTR), 10 open reading frames (ORFs; ORF1a, ORF1b, ORF2a, ORF2b, and ORFs 3 through 7 including ORF5a), and a 3′-UTR. ORF1a and O
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