A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years

ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen for the global pork industry. Modified live virus (MLV) vaccines are widely used for PRRSV prevention and control. However, MLV vaccines can still infect hosts and replicate in the target cells...

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Main Authors: Weixin Wu, Lin Lin, Zian Ye, Ruoning Hou, Qiongqiong Zhou, Lei Zhou, Hanchun Yang
Format: Article
Language:English
Published: American Society for Microbiology 2025-07-01
Series:Microbiology Spectrum
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Online Access:https://journals.asm.org/doi/10.1128/spectrum.00728-25
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author Weixin Wu
Lin Lin
Zian Ye
Ruoning Hou
Qiongqiong Zhou
Lei Zhou
Hanchun Yang
author_facet Weixin Wu
Lin Lin
Zian Ye
Ruoning Hou
Qiongqiong Zhou
Lei Zhou
Hanchun Yang
author_sort Weixin Wu
collection DOAJ
description ABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen for the global pork industry. Modified live virus (MLV) vaccines are widely used for PRRSV prevention and control. However, MLV vaccines can still infect hosts and replicate in the target cells, increasing the risk of virus recombination and reversion to virulence. Recently, a highly pathogenic PRRSV strain appeared in December 2024, causing severe outbreaks on a PRRSV-negative pig farm in Yunnan, China. The isolated strain exhibited 99.4%–99.5% nucleotide similarity to the historical JXA1-R vaccine-derived revertant isolated in 2012, despite the farm never using JXA1-R vaccines. Ten unique amino acid mutations confirmed that this strain was a revertant derived from JXA1-R vaccines, which reverted to cause an outbreak in 2012 and vanished for 12 years.IMPORTANCECurrently, there is a relative consensus that porcine reproductive and respiratory syndrome modified live virus (PRRS MLV) has the highest protective efficacy against the genetically homologous virus, compared with commercially available killed vaccines or other kinds of vaccines under development. However, risks of virulence reversion remain in such live vaccines. This case reveals the unpredictable risks of live-attenuated vaccines. The findings underscore the inherent flaws in highly pathogenic PRRSV MLV vaccines, emphasizing the need for safer vaccine designs. The re-emergence of that revertant draws our attention to its source, and the similar mutation site compared with 12 years ago could indicate key nucleotide sites for the reversion of virulence of this strain.
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spelling doaj-art-d2a58367462f426da2d5a93d388c8efe2025-08-20T02:41:58ZengAmerican Society for MicrobiologyMicrobiology Spectrum2165-04972025-07-0113710.1128/spectrum.00728-25A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 yearsWeixin Wu0Lin Lin1Zian Ye2Ruoning Hou3Qiongqiong Zhou4Lei Zhou5Hanchun Yang6National Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaNational Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaNational Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaCollege of Veterinary Medicine, Northeast Agricultural University, Harbin, Heilongjiang, ChinaNational Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaNational Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaNational Key Laboratory of Veterinary Public Health Safety, College of Veterinary Medicine, China Agricultural University, Beijing, ChinaABSTRACT Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen for the global pork industry. Modified live virus (MLV) vaccines are widely used for PRRSV prevention and control. However, MLV vaccines can still infect hosts and replicate in the target cells, increasing the risk of virus recombination and reversion to virulence. Recently, a highly pathogenic PRRSV strain appeared in December 2024, causing severe outbreaks on a PRRSV-negative pig farm in Yunnan, China. The isolated strain exhibited 99.4%–99.5% nucleotide similarity to the historical JXA1-R vaccine-derived revertant isolated in 2012, despite the farm never using JXA1-R vaccines. Ten unique amino acid mutations confirmed that this strain was a revertant derived from JXA1-R vaccines, which reverted to cause an outbreak in 2012 and vanished for 12 years.IMPORTANCECurrently, there is a relative consensus that porcine reproductive and respiratory syndrome modified live virus (PRRS MLV) has the highest protective efficacy against the genetically homologous virus, compared with commercially available killed vaccines or other kinds of vaccines under development. However, risks of virulence reversion remain in such live vaccines. This case reveals the unpredictable risks of live-attenuated vaccines. The findings underscore the inherent flaws in highly pathogenic PRRSV MLV vaccines, emphasizing the need for safer vaccine designs. The re-emergence of that revertant draws our attention to its source, and the similar mutation site compared with 12 years ago could indicate key nucleotide sites for the reversion of virulence of this strain.https://journals.asm.org/doi/10.1128/spectrum.00728-25porcine reproductive and respiratory syndrome virusvaccinevirulence reversionoutbreak
spellingShingle Weixin Wu
Lin Lin
Zian Ye
Ruoning Hou
Qiongqiong Zhou
Lei Zhou
Hanchun Yang
A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
Microbiology Spectrum
porcine reproductive and respiratory syndrome virus
vaccine
virulence reversion
outbreak
title A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
title_full A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
title_fullStr A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
title_full_unstemmed A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
title_short A vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus: re-emergence after lurking for 12 years
title_sort vaccine revertant of highly pathogenic porcine reproductive and respiratory syndrome virus re emergence after lurking for 12 years
topic porcine reproductive and respiratory syndrome virus
vaccine
virulence reversion
outbreak
url https://journals.asm.org/doi/10.1128/spectrum.00728-25
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