Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice
ABSTRACT The development of safe and efficient vaccines against coronavirus disease 2019 (COVID-19) is necessary for global public health. The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major target for the COVID-19 vaccines. Among the available vaccine types,...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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American Society for Microbiology
2023-12-01
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| Series: | Microbiology Spectrum |
| Subjects: | |
| Online Access: | https://journals.asm.org/doi/10.1128/spectrum.02549-23 |
| _version_ | 1827586782973132800 |
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| author | Li Song Qiaoju Wang Yaya Wen Ruimeng Tan Yaodan Cui Dan Xiong Xinan Jiao Zhiming Pan |
| author_facet | Li Song Qiaoju Wang Yaya Wen Ruimeng Tan Yaodan Cui Dan Xiong Xinan Jiao Zhiming Pan |
| author_sort | Li Song |
| collection | DOAJ |
| description | ABSTRACT The development of safe and efficient vaccines against coronavirus disease 2019 (COVID-19) is necessary for global public health. The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major target for the COVID-19 vaccines. Among the available vaccine types, DNA vaccines are a promising alternative to conventional vaccines. Here, we developed a novel DNA vaccine containing the SARS-CoV-2 S1 subunit and an optimized flagellin adjuvant (FliCΔD2D3) from Salmonella typhimurium. The S1 gene and S1-fliCΔD2D3 fusion gene were codon optimized and then cloned into the antibiotic-resistance-gene-free vector asd-pVAX1, producing asd-pVAX1-S1 and asd-pVAX1-S1-fliCΔD2D3, respectively. The expression of S1 and S1-FliCΔD2D3 proteins was confirmed after transient expression in HEK293T cells. After in vitro characterization of the vaccine candidates, we evaluated the humoral and cellular immune responses induced in BALB/c mice. The DNA vaccine induced a long-lasting humoral response for approximately 4 months, and the elicited serum antibodies efficiently blocked the binding of the SARS-CoV-2 S1 receptor-binding domain to its entry receptor (angiotensin-converting enzyme 2). Moreover, the DNA vaccine induced strong Th1/Th2-mixed immune responses, as demonstrated by the similar levels of S1-specific immunoglobulin (Ig) G1 and IgG2a in the serum and the significantly elevated Th1-type (IFN-γ and TNF-α) and Th2-type (IL-4 and IL-6) cytokine expression from splenic lymphocytes. Importantly, asd-pVAX1-S1-fliCΔD2D3 immunization in mice could significantly enhance the levels of immune responses compared to asd-pVAX1-S1. This study provides crucial information regarding the selection of a safer DNA vector and a new adjuvant for the vaccine development of SARS-CoV-2 and other infectious diseases. IMPORTANCE The development of safe and effective vaccines is needed to control the transmission of coronavirus disease 2019 (COVID-19). Synthetic DNA vaccines represent a promising platform in response to such outbreaks. Here, DNA vaccine candidates were developed using an optimized antibiotic-resistance gene-free asd-pVAX1 vector. An optimized flagellin (FliC) adjuvant was designed by fusion expression to increase the immunogenicity of the S1 antigen. S1 and S1-FliCΔD2D3 proteins were strongly expressed in mammalian cells. The FliCΔD2D3-adjuvanted DNA vaccine induced Th1/Th2-mixed immune responses and high titers of neutralizing antibodies. This study provides crucial information regarding the selection of a safer DNA vector and adjuvant for vaccine development. Our FliCΔD2D3-adjuvanted S1 DNA vaccine is more potent at inducing both humoral and cellular immune responses than S1 alone. This finding provides a new idea for the development of novel DNA vaccines against COVID-19 and could be further applied for the development of other vaccines. |
| first_indexed | 2024-03-09T00:06:44Z |
| format | Article |
| id | doaj.art-ed113d002d0e4da3905a2d939d026404 |
| institution | Directory Open Access Journal |
| issn | 2165-0497 |
| language | English |
| last_indexed | 2024-03-09T00:06:44Z |
| publishDate | 2023-12-01 |
| publisher | American Society for Microbiology |
| record_format | Article |
| series | Microbiology Spectrum |
| spelling | doaj.art-ed113d002d0e4da3905a2d939d0264042023-12-12T13:17:18ZengAmerican Society for MicrobiologyMicrobiology Spectrum2165-04972023-12-0111610.1128/spectrum.02549-23Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in miceLi Song0Qiaoju Wang1Yaya Wen2Ruimeng Tan3Yaodan Cui4Dan Xiong5Xinan Jiao6Zhiming Pan7Jiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaJiangsu Key Laboratory of Zoonosis, Yangzhou University , Yangzhou, Jiangsu, ChinaABSTRACT The development of safe and efficient vaccines against coronavirus disease 2019 (COVID-19) is necessary for global public health. The spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a major target for the COVID-19 vaccines. Among the available vaccine types, DNA vaccines are a promising alternative to conventional vaccines. Here, we developed a novel DNA vaccine containing the SARS-CoV-2 S1 subunit and an optimized flagellin adjuvant (FliCΔD2D3) from Salmonella typhimurium. The S1 gene and S1-fliCΔD2D3 fusion gene were codon optimized and then cloned into the antibiotic-resistance-gene-free vector asd-pVAX1, producing asd-pVAX1-S1 and asd-pVAX1-S1-fliCΔD2D3, respectively. The expression of S1 and S1-FliCΔD2D3 proteins was confirmed after transient expression in HEK293T cells. After in vitro characterization of the vaccine candidates, we evaluated the humoral and cellular immune responses induced in BALB/c mice. The DNA vaccine induced a long-lasting humoral response for approximately 4 months, and the elicited serum antibodies efficiently blocked the binding of the SARS-CoV-2 S1 receptor-binding domain to its entry receptor (angiotensin-converting enzyme 2). Moreover, the DNA vaccine induced strong Th1/Th2-mixed immune responses, as demonstrated by the similar levels of S1-specific immunoglobulin (Ig) G1 and IgG2a in the serum and the significantly elevated Th1-type (IFN-γ and TNF-α) and Th2-type (IL-4 and IL-6) cytokine expression from splenic lymphocytes. Importantly, asd-pVAX1-S1-fliCΔD2D3 immunization in mice could significantly enhance the levels of immune responses compared to asd-pVAX1-S1. This study provides crucial information regarding the selection of a safer DNA vector and a new adjuvant for the vaccine development of SARS-CoV-2 and other infectious diseases. IMPORTANCE The development of safe and effective vaccines is needed to control the transmission of coronavirus disease 2019 (COVID-19). Synthetic DNA vaccines represent a promising platform in response to such outbreaks. Here, DNA vaccine candidates were developed using an optimized antibiotic-resistance gene-free asd-pVAX1 vector. An optimized flagellin (FliC) adjuvant was designed by fusion expression to increase the immunogenicity of the S1 antigen. S1 and S1-FliCΔD2D3 proteins were strongly expressed in mammalian cells. The FliCΔD2D3-adjuvanted DNA vaccine induced Th1/Th2-mixed immune responses and high titers of neutralizing antibodies. This study provides crucial information regarding the selection of a safer DNA vector and adjuvant for vaccine development. Our FliCΔD2D3-adjuvanted S1 DNA vaccine is more potent at inducing both humoral and cellular immune responses than S1 alone. This finding provides a new idea for the development of novel DNA vaccines against COVID-19 and could be further applied for the development of other vaccines.https://journals.asm.org/doi/10.1128/spectrum.02549-23SARS-CoV-2S1antibiotic-resistance gene-free vectorDNA vaccineoptimized flagellin adjuvantimmunogenicity |
| spellingShingle | Li Song Qiaoju Wang Yaya Wen Ruimeng Tan Yaodan Cui Dan Xiong Xinan Jiao Zhiming Pan Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice Microbiology Spectrum SARS-CoV-2 S1 antibiotic-resistance gene-free vector DNA vaccine optimized flagellin adjuvant immunogenicity |
| title | Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice |
| title_full | Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice |
| title_fullStr | Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice |
| title_full_unstemmed | Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice |
| title_short | Enhanced immunogenicity elicited by a novel DNA vaccine encoding the SARS-CoV-2 S1 protein fused to the optimized flagellin of Salmonella typhimurium in mice |
| title_sort | enhanced immunogenicity elicited by a novel dna vaccine encoding the sars cov 2 s1 protein fused to the optimized flagellin of salmonella typhimurium in mice |
| topic | SARS-CoV-2 S1 antibiotic-resistance gene-free vector DNA vaccine optimized flagellin adjuvant immunogenicity |
| url | https://journals.asm.org/doi/10.1128/spectrum.02549-23 |
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