Attenuated Porcine Reproductive and Respiratory Syndrome Virus Regains Its Fatal Virulence by Serial Passaging in Pigs or Porcine Alveolar Macrophages To Increase Its Adaptation to Target Cells

Wang, Jingjing; Zhang, Mengsi; Cui, Xiaochun; Gao, Xiang; Sun, Weifeng; Ge, Xinna; Zhang, Yongning; Guo, Xin; Han, Jun; Zhou, Lei; Yang, Hanchun

doi:10.1128/spectrum.03084-22

Cited by 13 publications

(12 citation statements)

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“…Interestingly, the titer of the Korean NADC34like strain JBNU-22-N01 was signifcantly higher than that of all other viruses at 24 hpi (Figure 4(c)), and the PRRSV-specifc CPE in JBNU-22-N01-inoculated PAMs was more severe, with more PAMs falling of the bottom of the cell culture plate (data not shown). A previous report suggested that PRRSV's replication abilities and adaptation to its target cells directly contribute to PRRSV pathogenicity and virulence in attenuated PRRSV in vivo and in vitro reversion to virulence studies [48]. As various strains of NADC34-like strains were reported, pathogenicity was also reported to be diverse, as the American NADC34 strain reveals high pathogenicity [17,22], while the Chinese PRSV-ZDXYL-China-2018-1 and HLDJZD32-1901 strains have moderate and low pathogenicity, respectively [17,49,50].…”

Section: Resultsmentioning

confidence: 99%

First Identification and Genomic Characterization of NADC34-Like PRRSV Strains Isolated from MLV-Vaccinated Pigs in Korea

Kim

Moon

et al. 2023

Transboundary and Emerging Diseases

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NADC34-like porcine reproductive and respiratory syndrome viruses (PRRSVs) are emerging globally. Although lineage 1 PRRSVs are emerging in Korea, NADC34-like PRRSV strains have not been detected to date. This study reports the isolation of the first NADC34-like PRRSV strains from samples of MLV-vaccinated animals on a Korean farm with a severe PRRS outbreak causing high mortality and abortion rates in July 2022. Three PRRSV strains with a whole genome length of 15,088 bp were isolated from the outbreaks, and their phylogenetic, recombination properties, and in vitro growth kinetics were evaluated comprehensively. These Korean strains clustered with those of American and Chinese sublineage 1.5 (NADC34-like strains), according to phylogenetic analyses based on the ORF5 gene and the whole genome. All three complete genome sequences originated from recombination between the RespPRRS MLV and NADC34-like strains, according to recombination analysis. Full-length Nsp2 sequence alignment indicated that all three isolates had a continuous deletion in 100 aa, which was similar to that of the IA/2014/NADC34. Based on phylogenetic analysis and the Nsp2 deletion pattern, the isolates are identified as NADC34-like PRRSV. Growth kinetic analysis based on primary porcine alveolar macrophages (PAMs) and MARC-145 cells has revealed that Korean NADC34-like PRRSV strains had better replication ability in primary PAMs than other Korean lineage 1 viruses or the reference strain VR2332, implying higher pathogenicity in pigs. Considering the fact that NADC34-like PRRSV strains were detected in MLV-vaccinated animals on a farm in the area of the highest pig population density in Korea, additional vaccine failure cases and the spread of the virus could be detected in the near future. Collectively, these results aid in comprehending the current epidemic state of PRRSVs in Korea and highlight the need for continuous surveillance.

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Section: Resultsmentioning

confidence: 99%

First Identification and Genomic Characterization of NADC34-Like PRRSV Strains Isolated from MLV-Vaccinated Pigs in Korea

Kim

Moon

et al. 2023

Transboundary and Emerging Diseases

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“…Although PRRS spreads and evolves rapidly, immunization still plays a very positive role in the prevention and control of PRRS ( 36 , 37 ). On the other hand, live vaccines still have many defects to be improved, including the risk of virulence reversion, which has been reported by many studies and has become one of our foremost concerns of PRRSV vaccine innovation and development ( 26 – 28 ).…”

Section: Discussionmentioning

confidence: 99%

“…Virulence reversion is determined by many factors, including the frequency, correct use of the vaccine, selection of generation to be used as vaccines, and the characteristic of the candidate vaccine strain. This vaccine strain, which was reported with virulence reversion, mainly used the virus that has been passaged on MARC-145 cells for <100 generations ( 26 – 28 ). rPRRSV-E2 was generated by the full-length infectious clone of the vaccine strain HuN4-F112, which was made from the serial passage of wild-type HuN4 on MARC-145 cells for 112 generations ( 24 , 41 ).…”

Section: Discussionmentioning

confidence: 99%

“…In China, many live vaccines have been developed and used for PRRS control and contributed to the development of the pig industry ( 24 , 25 ). However, the risk of virulence reversion of live vaccines has attracted extensive concerns and became one of the most important preclinical results in the innovation and development of a new vaccine ( 26 – 28 ).…”

Section: Introductionmentioning

confidence: 99%

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The rPRRSV-E2 strain exhibited a low level of potential risk for virulence reversion

Jiang

Gao²,

Li³

et al. 2023

Front. Vet. Sci.

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Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Classical Swine Fever Virus (CSFV) are two important pathogens, which cause serious impact on swine industry worldwide. In our previous research, rPRRSV-E2, the recombinant PRRSV expressing CSFV E2 protein, could provide sufficient protection against the lethal challenge of highly pathogenic PRRSV and CSFV, and could maintained genetically stable in vitro. Here, to evaluate the virulence reversion potential risk, rPRRSV-E2 had been continuously passaged in vivo, the stability of E2 expression and virulence of the passage viruses were analyzed. The results showed that no clinical symptoms or pathological changes could be found in the inoculated groups, and there were no significant differences of viraemia among the test groups. Sequencing and IFA analysis showed that the coding gene of exogenous CSFV E2 protein existed in the passaged viruses without any sequence mutations, deletions or insertions, and could expressed steadily. It could be concluded that the foreign CSFV E2 gene in the genome of rPRRSV-E2 could be maintained genetically stable in vivo, and rPRRSV-E2 strain had relatively low level of potential risk for virulence reversion.

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“…However, the MLV strains can still infect the host and replicate in the target cells, which increases the risk of recombination with field strains and reversion to virulence. Our recent studies have confirmed that the HP-PRRSV strain JXwn06-P80 attenuated via passage in MARC-145 cells could regain its fatal virulence after increasing its adaptability in PAMs [ 8 ]. Additionally, MLV infection in PAM can also cause varying levels of immunosuppression, which is another concern regarding its safety.…”

Section: Introductionmentioning

confidence: 99%

A novel strategy to attenuate porcine reproductive and respiratory syndrome virus by inhibiting viral replication in the target pulmonary alveolar macrophages via hematopoietic-specific miR-142

Tan

et al. 2023

One Health Adv.

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Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important pathogen for the global pork industry. Although modified live virus (MLV) vaccines are commonly used for PRRSV prevention and control, they still carry a risk of infecting the host and replicating in target cells, thereby increasing the likehood of virus recombination and reversion to virulence. In this study, we inserted the target sequence of miR-142 into the nsp2 hypervariable region of PRRSV to inhibit viral replication in its host cells of pigs, with the aim of achieving virus attenuation. The chimeric virus RvJX-miR-142t was successfully rescued and retained its growth characteristics in MARC-145 cells. Furthermore, it did not replicate in MARC-145 cells transfected with miRNA-142 mimic. We also observed limited replication ability of RvJX-miR-142t in pulmonary alveolar macrophages, which are the main cell types that PRRSV infects. Our animal inoculation study showed that pigs infected with RvJX-miR-142t displayed less severe clinical symptoms, lower viremia titers, lighter lung lesions, and significantly lower mortality rates during the first 7 days post-inoculation, in comparison to pigs infected with the backbone virus RvJXwn. We detected a partially deletion of the miR-142 target sequence in the RvJX-miR-142t genome at 14 dpi. It is highly possible that the reversion of viral virulence observed in the later timepoints of our animal experiment was caused by that. Our study provided a new strategy for attenuating PRRSV and confirmed its effectiveness. However, further studies are necessary to increase the stability of this virus under host selection pressure.

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Attenuated Porcine Reproductive and Respiratory Syndrome Virus Regains Its Fatal Virulence by Serial Passaging in Pigs or Porcine Alveolar Macrophages To Increase Its Adaptation to Target Cells

Cited by 13 publications

References 50 publications

First Identification and Genomic Characterization of NADC34-Like PRRSV Strains Isolated from MLV-Vaccinated Pigs in Korea

First Identification and Genomic Characterization of NADC34-Like PRRSV Strains Isolated from MLV-Vaccinated Pigs in Korea

The rPRRSV-E2 strain exhibited a low level of potential risk for virulence reversion

A novel strategy to attenuate porcine reproductive and respiratory syndrome virus by inhibiting viral replication in the target pulmonary alveolar macrophages via hematopoietic-specific miR-142

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