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Construction of an infectious bronchitis virus vaccine strain carrying chimeric S1 gene of a virulent isolate and its pathogenicity analysis.

ABSTRACT: Infectious bronchitis virus (IBV) is a member of genus gamma-coronavirus in the family Coronaviridae, causing serious economic losses to the poultry industry. Reverse genetics is a common technique to study the biological characteristics of viruses. So far, there is no BAC reverse genetic system available for rescue of IBV infectious clone. In the present study, a new strategy for the construction of IBV infectious cDNA clone was established. The full-length genomic cDNA of IBV vaccine strain H120 was constructed in pBAC vector from four IBV fragment subcloning vectors by homologous recombination, which contained the CMV promoter at the 5' end and the hepatitis D virus ribozyme (HDVR) sequence and bovine growth hormone polyadenylation (BGH) sequence after the polyA tail at the 3' end of the full-length cDNA. Subsequently, using the same technique, another plasmid pBAC-H120/SCS1 was also constructed, in which S1 gene from IBV H120 strain was replaced with that of a virulent SC021202 strain. Recombinant virus rH120 and rH120/SCS1 were rescued by transfecting the plasmids into BHK cells and passaged in embryonated chicken eggs. Finally, the pathogenicity of both the recombinant virus strains rH120 and rH120/SCS1 was evaluated in SPF chickens. The results showed that the chimeric rH120/SCS1 strain was not pathogenic compared with the wild-type IBV SC021202 strain and the chickens inoculated with rH120/SCS1 could resist challenge infection by IBV SC021202. Taken together, our results indicate that BAC reverse genetic system could be used to rescue IBV in vitro and IBV S1 protein alone might not be the key factor for IBV pathogenicity. KEY POINTS: • BAC vector was used to construct IBV full-length cDNA by homologous recombination. • Based on four subcloning vectors, a recombinant chimeric IBV H120/SCS1 was constructed and rescued. • Pathogenicity of H120/SCS1 was similar to that of H120, but different to that of SC021202.

SUBMITTER: Lv C

PROVIDER: S-EPMC7434845 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Construction of an infectious bronchitis virus vaccine strain carrying chimeric S1 gene of a virulent isolate and its pathogenicity analysis.

Lv Chenfei C Shi Tingting T Zhu Pengpeng P Peng Xing X Cao Shangshang S Yan Yan Y Ojha Nishant Kumar NK Liao Min M Zhou Jiyong J

Applied microbiology and biotechnology 20200819 19

Infectious bronchitis virus (IBV) is a member of genus gamma-coronavirus in the family Coronaviridae, causing serious economic losses to the poultry industry. Reverse genetics is a common technique to study the biological characteristics of viruses. So far, there is no BAC reverse genetic system available for rescue of IBV infectious clone. In the present study, a new strategy for the construction of IBV infectious cDNA clone was established. The full-length genomic cDNA of IBV vaccine strain H1 ...[more]

PMID: 32813067

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Project description:Avian infectious bronchitis virus (IBV) is the causative agent of infectious bronchitis, which results in considerable economic losses. It is imperative to develop safe and efficient candidate vaccines to control IBV infection. In the current study, recombinant baculoviruses co-expressing the S1 and N proteins and mono-expressing S1 or N proteins of the GX-YL5 strain of IBV were constructed and prepared into subunit vaccines rHBM-S1-N, rHBM-S1 and rHBM-N. The levels of immune protection of these subunit vaccines were evaluated by inoculating specific pathogen-free (SPF) chickens at 14 days of age, giving them a booster with the same dose 14 days later and challenging them with a virulent GX-YL5 strain of IBV 14 days post-booster (dpb). The commercial vaccine strain H120 was used as a control. The IBV-specific antibody levels, as well as the percentages of CD4+ and CD8+ T lymphocytes, were detected within 28 days post-vaccination (dpv). The morbidity, mortality and re-isolation of the virus from the tracheas and kidneys of challenged birds were evaluated at five days post-challenge (dpc). The results showed that the IBV-specific antibody levels and the percentages of CD4+ and CD8+ T lymphocytes were higher in the rHBM-S1-N vaccinated birds compared to birds vaccinated with the rHBM-S1 and rHBM-N vaccines. At 5 dpc, the mortality, morbidity and virus re-isolation rate of the birds vaccinated with the rHBM-S1-N vaccine were slightly higher than those vaccinated with the H120 control vaccine but were lower than those vaccinated with the rHBM-S1 and rHBM-N vaccines. The present study demonstrated that the protection of the recombinant baculovirus co-expressing S1 and N proteins was better than that of recombinant baculoviruses mono-expressing the S1 or N protein. Thus, the recombinant baculovirus co-expressing S1 and N proteins could serve as a potential IBV vaccine and this demonstrates that the bivalent subunit vaccine including the S1 and N proteins might be a strategy for the development of an IBV subunit vaccine.

Project description:Infectious bronchitis virus (IBV) is caused by avian coronavirus and poses a global economic threat to the poultry industry. In 2023, a highly pathogenic IBV strain, IBV/CN/GD20230501, was isolated and identified from chickens vaccinated with IBV-M41 in Guangdong, China. This study comprehensively investigated the biological characteristics of the isolated IBV strain, including its genotype, whole genome sequence analysis of its S1 gene, pathogenicity, host immune response, and serum non-targeted metabolomics. Through the analysis of the S1 gene sequence, serum neutralization tests, and comparative genomics, it was proven that IBV/CN/GD20230501 belongs to the GI-I type of strain and is serotype II. One alanine residue in the S1 subunit of the isolated strain was mutated into serine, and some mutations were observed in the ORF1ab gene and the terminal region of the genome. Animal challenge experiments using the EID50 and TCID50 calculations showed that IBV/CN/GD20230501 possesses strong respiratory pathogenicity, with early and long-term shedding of viruses and rapid viral spread. Antibody detection indicated that chickens infected with IBV/CN/GD20230501 exhibited delayed expression of early innate immune genes, while those infected with M41 showed rapid gene induction and effective viral control. Metabolomics analysis demonstrated that this virus infection led to differential expression of 291 ions in chicken serum, mainly affecting the citric acid cycle (tricarboxylic acid cycle).IMPORTANCEThis study identified an infectious bronchitis virus (IBV) strain isolated from vaccinated chickens in an immunized population that had certain sequence differences compared to IBV-M41, resulting in significantly enhanced pathogenicity and host defense. This strain has the potential to replace M41 as a more suitable challenge model for drug research. The non-targeted metabolomics analysis highlighting the citric acid cycle provides a new avenue for studying this highly virulent strain.

Dataset Information

Construction of an infectious bronchitis virus vaccine strain carrying chimeric S1 gene of a virulent isolate and its pathogenicity analysis.

Publications

Construction of an infectious bronchitis virus vaccine strain carrying chimeric S1 gene of a virulent isolate and its pathogenicity analysis.

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