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Tian H, Li B, Xu T, Yu H, Chen J, Yu H, Li S, Zeng L, Huang X, Liu Q. Outer Membrane Vesicles Derived from Salmonella enterica Serotype Typhimurium Can Deliver Shigella flexneri 2a O-Polysaccharide Antigen To Prevent Shigella flexneri 2a Infection in Mice. Appl Environ Microbiol 2021; 87:e0096821. [PMID: 34319809 PMCID: PMC8432525 DOI: 10.1128/aem.00968-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 07/19/2021] [Indexed: 11/20/2022] Open
Abstract
Shigellosis has become a serious threat to health in many developing countries due to the severe diarrhea it causes. Shigella flexneri 2a is the principal species responsible for this endemic disease. Despite multiple attempts to design a vaccine against shigellosis, no effective vaccine has been developed yet. Lipopolysaccharide (LPS) is both an essential virulence factor and an antigen protective against Shigella, due to its outer domain, termed O-polysaccharide antigen. In the present study, S. flexneri 2a O-polysaccharide antigen was innovatively biosynthesized in Salmonella and attached to core-lipid A via the ligase WaaL, with purified outer membrane vesicles (OMVs) utilized as vaccine vectors. Here, we identified the expression of the heterologous O-antigen and have described the isolation, characterization, and immune protection efficiency of the OMV vaccine. Furthermore, the results of animal experiments indicated that immunization of mice with the OMV vaccine induced significant specific anti-Shigella LPS antibodies in the serum, with similar trends in IgA levels from vaginal secretions and fluid from bronchopulmonary lavage, both intranasally and intraperitoneally. The OMV vaccine derived from both routes of administration provided significant protection against virulent S. flexneri 2a infection, as judged by a serum bactericidal assay, opsonization assay, and challenge test. This vaccination strategy represents a novel and improved approach to control shigellosis by the combination of Salmonella glycosyl carrier lipid bioconjugation with OMVs. IMPORTANCEShigella, the cause of shigellosis or bacillary dysentery, is a major public health concern, especially for children in developing countries. An effective vaccine would control the spread of the disease to some extent. However, no licensed vaccine against Shigella infection in humans has so far been developed. The Shigella O-antigen polysaccharide is effective in stimulating the production of protective antibodies and so could represent a vaccine antigen candidate. In addition, bacterial outer membrane vesicles (OMVs) have been used as antigen delivery platforms due to their nanoscale properties and ease of antigen delivery to trigger an immune response. Therefore, the present study provides a new strategy for vaccine design, combining a glycoconjugated vaccine with OMVs. The design concept of this strategy is the expression of Shigella O-antigen via the LPS synthesis pathway in recombinant Salmonella, from which the OMV vaccine is then isolated. Based on these findings, we believe that the novel vaccine design strategy in which polysaccharide antigens are delivered via bacterial OMVs will be effective for the development and clinical application of an effective Shigella vaccine.
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Affiliation(s)
- Huizhen Tian
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Biaoxian Li
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Tian Xu
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Haolin Yu
- School of Ophthalmology and Optometry, Nanchang University, Nanchang, China
| | - Jingxuan Chen
- School of Ophthalmology and Optometry, Nanchang University, Nanchang, China
| | - Haiyan Yu
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Shan Li
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Lingbing Zeng
- The First Affiliated Hospital of Nanchang University, Nanchang, China
| | - Xiaotian Huang
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
| | - Qiong Liu
- Department of Medical Microbiology, School of Medicine, Nanchang University, Nanchang, China
- Institute of Preventive Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
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