Generation and Efficacy Evaluation of Recombinant Classical Swine Fever Virus E2 Glycoprotein Expressed in Stable Transgenic Mammalian Cell Line

PLOS ONE, Dec 2019

Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), which is a highly contagious swine disease that causes significant economic loses to the pig industry worldwide. The envelope E2 glycoprotein of CSFV is the most important viral antigen in inducing protective immune response against CSF. In this study, we generated a mammalian cell clone (BCSFV-E2) that could stably produce a secreted form of CSFV E2 protein (mE2). The mE2 protein was shown to be N-linked glycosylated and formed a homodimer. The vaccine efficacy of mE2 was evaluated by immunizing pigs. Twenty-five 6-week-old Landrace piglets were randomly divided into five groups. Four groups were intramuscularly immunized with mE2 emulsified in different adjuvants twice at four-week intervals. One group was used as the control group. All mE2-vaccinated pigs developed CSFV-neutralizing antibodies two weeks after the first vaccination with neutralizing antibody titers ranging from 1∶40 to 1∶320. Two weeks after the booster vaccination, the neutralizing antibody titers increased greatly and ranged from 1∶10,240 to 1∶81,920. At 28 weeks after the booster vaccine was administered, the neutralizing antibody titers ranged from 1∶80 to 1∶10240. At 32 weeks after the first vaccination, pigs in all the groups were challenged with a virulent CSFV strain at a dose of 1×105 TCID50. At two weeks after the challenge, all the mE2-immunized pigs survived and exhibited no obvious symptoms of CSF. The neutralizing antibody titer at this time was 20,480. Unvaccinated pigs in the control group exhibited symptoms of CSF 3–4 days after challenge and were euthanized from 7–9 days after challenge when the pigs became moribund. These results indicate that the mE2 is a good candidate for the development of a safe and effective CSFV subunit vaccine.

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Generation and Efficacy Evaluation of Recombinant Classical Swine Fever Virus E2 Glycoprotein Expressed in Stable Transgenic Mammalian Cell Line

et al. (2014) Generation and Efficacy Evaluation of Recombinant Classical Swine Fever Virus E2 Glycoprotein Expressed in Stable Transgenic Mammalian Cell Line. PLoS ONE 9(9): e106891. doi:10.1371/journal.pone.0106891 Generation and Efficacy Evaluation of Recombinant Classical Swine Fever Virus E2 Glycoprotein Expressed in Stable Transgenic Mammalian Cell Line Rong-Hong Hua 0 Hong Huo 0 Ye-Nan Li 0 Yao Xue 0 Xiao-Lei Wang 0 Li-Ping Guo 0 Bin Zhou 0 Yong Song 0 Zhi-Gao Bu 0 Shan Lu, University of Massachusetts Medical Center, United States of America 0 1 State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences , Harbin, Heilongjiang , People's Republic of China, 2 College of Life Science, Heilongjiang University , Harbin, Heilongjiang , People's Republic of China, 3 Key Laboratory of Animal Diseases Diagnosis and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agricultural University , Nanjing, Jiangsu , People's Republic of China Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), which is a highly contagious swine disease that causes significant economic loses to the pig industry worldwide. The envelope E2 glycoprotein of CSFV is the most important viral antigen in inducing protective immune response against CSF. In this study, we generated a mammalian cell clone (BCSFV-E2) that could stably produce a secreted form of CSFV E2 protein (mE2). The mE2 protein was shown to be N-linked glycosylated and formed a homodimer. The vaccine efficacy of mE2 was evaluated by immunizing pigs. Twenty-five 6-week-old Landrace piglets were randomly divided into five groups. Four groups were intramuscularly immunized with mE2 emulsified in different adjuvants twice at four-week intervals. One group was used as the control group. All mE2-vaccinated pigs developed CSFV-neutralizing antibodies two weeks after the first vaccination with neutralizing antibody titers ranging from 1:40 to 1:320. Two weeks after the booster vaccination, the neutralizing antibody titers increased greatly and ranged from 1:10,240 to 1:81,920. At 28 weeks after the booster vaccine was administered, the neutralizing antibody titers ranged from 1:80 to 1:10240. At 32 weeks after the first vaccination, pigs in all the groups were challenged with a virulent CSFV strain at a dose of 16105 TCID50. At two weeks after the challenge, all the mE2-immunized pigs survived and exhibited no obvious symptoms of CSF. The neutralizing antibody titer at this time was 20,480. Unvaccinated pigs in the control group exhibited symptoms of CSF 3-4 days after challenge and were euthanized from 7-9 days after challenge when the pigs became moribund. These results indicate that the mE2 is a good candidate for the development of a safe and effective CSFV subunit vaccine. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files Funding: This work was supported by grants from the Special Fund from Agro-scientific Research in the Public Interest of China (201203082). The funders had no roles in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have the following interests: Rong-Hong Hua and Zhi-Gao Bu have the following patent application of BCSFV-E2 cell line for CSF subunit vaccine generation (A recombinant mammalian cell line stably expressing classical swine fever virus E2 protein and its application in preparation of classical swine fever subunit vaccine; application number: 201310300549.8). This does not alter the authors adherence to all the PLOS ONE policies on sharing data and materials. Classical swine fever (CSF), which is caused by the CSF virus (CSFV), is a highly contagious severe and often fatal disease of pigs. CSFV is a member of the Pestivirus genus and the Flavivirade family [1]. The CSFV genome consists of a singlestranded, positive-sense RNA with a single open reading frame (ORF) encoding a polyprotein which is cleaved into 11 mature viral proteins. Of these 11 proteins, four proteins including nucleocapsid protein C and three envelope glycoproteins Erns, E1, and E2 are structural proteins. E2 is the most immunodominant protein in the envelope and plays an important role in virus neutralization [2,3]. E2 is the target of CSF subunit vaccine research, and has been expressed in baculovirus [4,5], yeast [6], and adenovirus [7,8] expression systems. In particular, many studies have investigated a baculovirus expression system expressing the E2 protein for use as a subunit vaccine. This expression system was found to be effective and has been licensed for commercial use [919]. As CSFV is a mammalian virus, the CSFV E2 expressed in mammalian cells would be more similar to its native conformation and glycosyl (...truncated)


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Rong-Hong Hua, Hong Huo, Ye-Nan Li, Yao Xue, Xiao-Lei Wang, Li-Ping Guo, Bin Zhou, Yong Song, Zhi-Gao Bu. Generation and Efficacy Evaluation of Recombinant Classical Swine Fever Virus E2 Glycoprotein Expressed in Stable Transgenic Mammalian Cell Line, PLOS ONE, 2014, Volume 9, Issue 9, DOI: 10.1371/journal.pone.0106891