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Yang H, Tu K, Zhao Y, Sun L, Zhao J, Zhang G. Development of SYBR green RT-qPCR assay for titrating bivalent live infectious bronchitis vaccines. J Virol Methods 2023; 313:114675. [PMID: 36592741 DOI: 10.1016/j.jviromet.2022.114675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 12/20/2022] [Accepted: 12/30/2022] [Indexed: 01/01/2023]
Abstract
Infectious bronchitis (IB) is a highly contagious viral disease of chickens caused by IB virus (IBV) that can cause substantial economic losses in the poultry industry. IBV variant infections have been continuously reported since the initial description in the 1930s. QX-like IBVs are the predominant circulating genotype globally. A homologous QX vaccine has superior protection efficacy compared with that of other available vaccines, and the combination of Massachusetts (Mass)-like and QX-like strains is being used to combat QX-like IBV infections. Inoculation of embryonated chicken eggs is the standard method for the titration of IBV, and the titer is expressed as 50% egg infectious dose (EID50). However, this method cannot effectively distinguish or quantify different genotypic strains in a mixture of different viruses, especially in the absence of neutralizing monoclonal antibodies. In this study, quantitative real-time PCR (RT-qPCR) was applied using specific primers for the QX- and Mass-like strains to quantitate IBV infection and for comparison with the conventional virus titration quantitative method. A strong positive correlation was observed between RT-qPCR cycle threshold values and the different EID50 concentrations. This method was further used to titrate bivalent IB vaccines, and the amount of individual genotype virus was determined based on specific primers. Thus, this RT-qPCR assay may be used as a highly specific, sensitive, and rapid alternative to the EID50 assay for titering IBVs.
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Affiliation(s)
- Huiming Yang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Kaihang Tu
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Ye Zhao
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Lu Sun
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China
| | - Jing Zhao
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
| | - Guozhong Zhang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, Beijing 100193, China.
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Weng W, Liu Q, Xue W, Wang H, Fang S, Sun Y, Tan L, Song C, Qiu X, Liu W, Ding C, Liao Y. Characterization of the Protective Efficacy Against QX Strain of a Recombinant Infectious Bronchitis Virus With H120 Backbone and QX Spike Gene. Front Microbiol 2022; 13:883642. [PMID: 35783402 PMCID: PMC9247577 DOI: 10.3389/fmicb.2022.883642] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 05/02/2022] [Indexed: 11/20/2022] Open
Abstract
Infectious bronchitis virus (IBV) has been prevalent in chicken farms for many years, and its control relies on extensive vaccine administration. The continuous emergence of new variants and the low cross-protection efficiency prompt the development of new vaccines. In this study, we develop a reverse genetics technique based on the classical vaccine strain H120 genome, via in vitro ligation method. Using the H120 genome as the backbone, we constructed the recombinant virus rH120-QX(S) by replacing the H120 S gene with the QX S gene, a prevalent strain in China. Biological characteristics of the rH120-QX(S) virus, such as 50% egg lethal dose (ELD50), 50% egg infectious dose (EID50), dwarf embryo, growth curve, and genetic stability, are measured, which are comparable to the parental virus H120. There are no clinical symptoms and tissue lesions in the trachea and kidney in the rH120-QX(S)-infected specific-pathogen-free (SPF) chickens, demonstrating that this recombinant virus does not confer pathogenicity. Furthermore, protection studies show that there is 100% homologous protection of rH120-QX(S) to the virulent QX strain, as shown by the absence of clinical signs and no lethality. Taken together, our results demonstrate that swapping the S gene onto the H120 genetic backbone is a precise and effective way to produce genetically defined IBV vaccine candidates.
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Affiliation(s)
- Wenlian Weng
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Qingyan Liu
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
- College of Agriculture, College of Animal Sciences, Yangtze University, Jingzhou, China
| | - Wenxiang Xue
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Huan Wang
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Shouguo Fang
- College of Agriculture, College of Animal Sciences, Yangtze University, Jingzhou, China
| | - Yingjie Sun
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Lei Tan
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Cuiping Song
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Xusheng Qiu
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Weiwei Liu
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Chan Ding
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
- Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China
| | - Ying Liao
- Department of Avian Diseases, Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
- *Correspondence: Ying Liao
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Shao L, Zhao J, Li L, Huang X, Yang H, Cheng J, Liu C, Zhang G. Pathogenic characteristics of a QX-like infectious bronchitis virus strain SD in chickens exposed at different ages and protective efficacy of combining live homologous and heterologous vaccination. Vet Res 2020; 51:86. [PMID: 32641162 PMCID: PMC7341716 DOI: 10.1186/s13567-020-00811-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Accepted: 06/12/2020] [Indexed: 12/13/2022] Open
Abstract
Continued reports of infections with infectious bronchitis virus (IBV) variants have occurred since its first isolation in the 1930s. Currently, QX-like IBVs are the predominant circulating genotype around the world. Here, the pathogenicity of QX-like IBV strain SD was characterized in chickens at different ages of exposure to the virus, and the protection efficacy of available vaccine combinations against IBV was evaluated. The results revealed that QX-like IBV strain SD was severely pathogenic in chickens, causing respiratory, urinary and reproductive infections, irrespective of age, based on clinical observations, viral distribution in tissues and a ciliostasis study. Severe respiratory signs, tracheal cilia injury, nephritis and abnormal development of the oviduct and ovarian follicles were evident throughout the experiment. A challenge experiment demonstrated that the homologous QX vaccine showed superior protection efficacy compared with other available vaccines, confirming the importance of IBV vaccine seed homology against the circulating IBV strains. Our findings aid an understanding of the pathogenicity of QX-like IBVs that may help to further control the infection.
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Affiliation(s)
- Lei Shao
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian, Beijing, 100193, China.,Beijing Huadu Yukou Poultry Company Limited, Beijing, 101206, China
| | - Jing Zhao
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian, Beijing, 100193, China
| | - Lihua Li
- Beijing Huadu Yukou Poultry Company Limited, Beijing, 101206, China
| | - Xiuying Huang
- Beijing Huadu Yukou Poultry Company Limited, Beijing, 101206, China
| | - Huiming Yang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian, Beijing, 100193, China
| | - Jinlong Cheng
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian, Beijing, 100193, China
| | - Changqing Liu
- Beijing Huadu Yukou Poultry Company Limited, Beijing, 101206, China
| | - Guozhong Zhang
- Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine, China Agricultural University, No. 2 Yuanmingyuan West Road, Haidian, Beijing, 100193, China.
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