{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,20]],"date-time":"2026-06-20T01:52:49Z","timestamp":1781920369208,"version":"3.54.5"},"reference-count":39,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,7,2]],"date-time":"2025-07-02T00:00:00Z","timestamp":1751414400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012226","name":"Fundamental Research Funds for the Central Universities","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100012226","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Vet. Sci."],"abstract":"<jats:p>Porcine reproductive and respiratory syndrome (PRRS) is a severe viral disease in pigs caused by porcine reproductive and respiratory syndrome virus (PRRSV). It poses a severe threat to the global swine breeding industry. Recently, the emergence of PRRSV lineage 1C.5 in the United States and China with the RFLP 1\u20134-4 pattern has raised worldwide attention; however, there are few studies on the genome and pathogenic characteristics of the L1C.5 RFLP 1\u20134-4 PRRSV in China. In this study, a novel PRRSV-2 variant, designated GX2024, was isolated from a RespPRRS MLV-vaccinated piglet in China using Marc-145 cells and porcine alveolar macrophages (PAMs). The complete viral genome was further determined and analyzed. Phylogenetic analysis of its ORF5 gene showed that GX2024 belonged to PRRSV-2 L1C.5 (RFLP-1-4-4) group, whereas the complete genome sequence clustered into L8E (JXA1-like) group and it contains a discontinuous 131-aa deletion in NSP2 when compared to the NADC30 strain. Notably, recombination analyses indicated that GX2024 is a multiple recombinant virus from two wild-type PRRSVs L1C.5 (NADC30-like) and L8E (JXA1-like), and a RespPRRS MLV vaccine (L5A) strain. To tested the pathogenicity of GX2024, nine four-week-old piglets were divided into two groups (GX2024-challenge group, <jats:italic>n<\/jats:italic>\u202f=\u202f5; negative control, <jats:italic>n<\/jats:italic>\u202f=\u202f4). GX2024 infection caused high fever (40\u201342\u00b0C) and severe hemorrhagic pneumonia with pulmonary edema. The lymph nodes exhibited obvious hemorrhagic spots with lymphadenopathy. Of note, all GX2024-infected piglets died within 14\u202fdays with 100% mortality, indicating that GX2024 is a highly pathogenic PRRSV strain. Our study reports the emergence of a novel highly pathogenic L1C.5 RFLP-1-4-4 recombinant strain, which merits special attention in control and vaccine strategies in China.<\/jats:p>","DOI":"10.3389\/fvets.2025.1627238","type":"journal-article","created":{"date-parts":[[2025,7,2]],"date-time":"2025-07-02T04:14:49Z","timestamp":1751429689000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":6,"title":["A novel L1C.5 RFLP-1-4-4 recombinant porcine reproductive and respiratory syndrome virus between wild-type virus and a modified-live virus vaccine is highly pathogenic to piglets"],"prefix":"10.3389","volume":"12","author":[{"given":"Xue","family":"Gao","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jun","family":"Zhou","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Runmin","family":"Kang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Haohao","family":"Lu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuo","family":"Feng","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yiwen","family":"Pei","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jie","family":"Liu","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhidong","family":"Zhang","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Long","family":"Zhou","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2025,7,2]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"1002","DOI":"10.3390\/v14051002","article-title":"PRRSV 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