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Hong Y, Hu D, Verderosa AD, Qin J, Totsika M, Reeves PR. Repeat-Unit Elongations To Produce Bacterial Complex Long Polysaccharide Chains, an O-Antigen Perspective. EcoSal Plus 2023; 11:eesp00202022. [PMID: 36622162 DOI: 10.1128/ecosalplus.esp-0020-2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 12/02/2022] [Indexed: 01/10/2023]
Abstract
The O-antigen, a long polysaccharide that constitutes the distal part of the outer membrane-anchored lipopolysaccharide, is one of the critical components in the protective outer membrane of Gram-negative bacteria. Most species produce one of the structurally diverse O-antigens, with nearly all the polysaccharide components having complex structures made by the Wzx/Wzy pathway. This pathway produces repeat-units of mostly 3-8 sugars on the cytosolic face of the cytoplasmic membrane that is translocated by Wzx flippase to the periplasmic face and polymerized by Wzy polymerase to give long-chain polysaccharides. The Wzy polymerase is a highly diverse integral membrane protein typically containing 10-14 transmembrane segments. Biochemical evidence confirmed that Wzy polymerase is the sole driver of polymerization, and recent progress also began to demystify its interacting partner, Wzz, shedding some light to speculate how the proteins may operate together during polysaccharide biogenesis. However, our knowledge of how the highly variable Wzy proteins work as part of the O-antigen processing machinery remains poor. Here, we discuss the progress to the current understanding of repeat-unit polymerization and propose an updated model to explain the formation of additional short chain O-antigen polymers found in the lipopolysaccharide of diverse Gram-negative species and their importance in the biosynthetic process.
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Affiliation(s)
- Yaoqin Hong
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
- School of Life and Environmental Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Dalong Hu
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
| | - Anthony D Verderosa
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Jilong Qin
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Makrina Totsika
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Peter R Reeves
- School of Life and Environmental Sciences, The University of Sydney, Camperdown, New South Wales, Australia
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Sears KT, Nasrin S, Baliban SM, Council DN, Pasetti MF, Tennant SM. Evaluation of Three Candidate Live-Attenuated Salmonella enterica Serovar Typhimurium Vaccines to Prevent Non-Typhoidal Salmonella Infection in an Infant Mouse Model. Vaccines (Basel) 2023; 11:1562. [PMID: 37896965 PMCID: PMC10610874 DOI: 10.3390/vaccines11101562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 09/22/2023] [Accepted: 09/26/2023] [Indexed: 10/29/2023] Open
Abstract
Nontyphoidal Salmonella enterica (NTS) is a leading cause of foodborne illness worldwide, including in the United States, where infants show the highest incidence amongst all age groups. S. enterica serovar Typhimurium is one of the most frequently isolated serovars from NTS infections. We have developed several candidate live-attenuated S. Typhimurium vaccines to prevent NTS infection. The goal of the current study was to assess three live S. Typhimurium vaccine strains (CVD 1921, CVD 1921 ∆htrA and CVD 1926, which have two, three and four gene deletions, respectively) with various levels of reactogenicity and immunogenicity in infant BALB/c mice to predict how they would perform following peroral immunization of infants. We first tested intranasal immunization of 14-day-old mice with three doses delivered at 1-week intervals and evaluated antibody responses and protection against lethal infection with wild-type S. Typhimurium. The vaccines were administered to 14-day-old mice via the peroral route at 1- or 2-week intervals and to 28-day-old mice at 2-week intervals. The three vaccine strains were immunogenic following intranasal immunization of infant mice with vaccine efficacies of 80% (CVD 1921), 63% (CVD 1921 ∆htrA) and 31% (CVD 1926). In contrast, peroral immunization of 14-day-old mice yielded much poorer protection against lethal infection and only immunization of 28-day-old mice at 2-week intervals showed similar protective capacity as intranasal administration (CVD 1921: 83%, CVD 1921 ∆htrA: 43% and CVD 1926: 58%). CVD 1921 was consistently more protective than both CVD 1921 ∆htrA and CVD 1926, regardless of the route of vaccination, immunization schedule and age of mice. Anti-LPS serum IgG responses were similar between the three strains and did not correlate with protection. Due to previously observed reactogenicity of CVD 1921, CVD 1921 ∆htrA and CVD 1926 are our preferred vaccines, but these data show that further improvements would need to be made to achieve suitable protection in young infants when using peroral immunization.
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Affiliation(s)
- Khandra T. Sears
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Shamima Nasrin
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Scott M. Baliban
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Danielle N. Council
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Marcela F. Pasetti
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Sharon M. Tennant
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD 21201, USA; (K.T.S.); (S.M.B.); (M.F.P.)
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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3
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Allen JC, Toapanta FR, Baliban SM, Sztein MB, Tennant SM. Reduced immunogenicity of a live Salmonella enterica serovar Typhimurium vaccine in aged mice. Front Immunol 2023; 14:1190339. [PMID: 37207226 PMCID: PMC10188964 DOI: 10.3389/fimmu.2023.1190339] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 04/13/2023] [Indexed: 05/21/2023] Open
Abstract
Introduction Non-typhoidal Salmonella (NTS) is responsible for a high burden of foodborne infections and deaths worldwide. In the United States, NTS infections are the leading cause of hospitalizations and deaths due to foodborne illnesses, and older adults (≥65 years) are disproportionately affected by Salmonella infections. Due to this public health concern, we have developed a live attenuated vaccine, CVD 1926 (I77 ΔguaBA ΔclpP ΔpipA ΔhtrA), against Salmonella enterica serovar Typhimurium, a common serovar of NTS. Little is known about the effect of age on oral vaccine responses, and due to the decline in immune function with age, it is critical to evaluate vaccine candidates in older age groups during early product development. Methods In this study, adult (six-to-eight-week-old) and aged (18-month-old) C57BL/6 mice received two doses of CVD 1926 (109 CFU/dose) or PBS perorally, and animals were evaluated for antibody and cell-mediated immune responses. A separate set of mice were immunized and then pre-treated with streptomycin and challenged orally with 108 CFU of wild-type S. Typhimurium SL1344 at 4 weeks postimmunization. Results Compared to PBS-immunized mice, adult mice immunized with CVD 1926 had significantly lower S. Typhimurium counts in the spleen, liver, and small intestine upon challenge. In contrast, there were no differences in bacterial loads in the tissues of vaccinated versus PBS aged mice. Aged mice exhibited reduced Salmonella-specific antibody titers in the serum and feces following immunization with CVD 1926 compared to adult mice. In terms of T cell responses (T-CMI), immunized adult mice showed an increase in the frequency of IFN-γ- and IL-2-producing splenic CD4 T cells, IFN-γ- and TNF-α-producing Peyer's Patch (PP)-derived CD4 T cells, and IFN-γ- and TNF-α-producing splenic CD8 T cells compared to adult mice administered PBS. In contrast, in aged mice, T-CMI responses were similar in vaccinated versus PBS mice. CVD 1926 elicited significantly more PP-derived multifunctional T cells in adult compared to aged mice. Conclusion These data suggest that our candidate live attenuated S. Typhimurium vaccine, CVD 1926, may not be sufficiently protective or immunogenic in older humans and that mucosal responses to live-attenuated vaccines decrease with increasing age.
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Affiliation(s)
- Jessica C. Allen
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Franklin R. Toapanta
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Scott M. Baliban
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Marcelo B. Sztein
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Sharon M. Tennant
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
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Han Y, Luo P, Zeng H, Wang P, Xu J, Chen P, Chen X, Chen Y, Cao Q, Zhai R, Xia J, Deng S, Cheng A, Cheng C, Song H. The effect of O-antigen length determinant wzz on the immunogenicity of Salmonella Typhimurium for Escherichia coli O2 O-polysaccharides delivery. Vet Res 2023; 54:15. [PMID: 36849993 PMCID: PMC9969949 DOI: 10.1186/s13567-023-01142-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2022] [Accepted: 12/15/2022] [Indexed: 03/01/2023] Open
Abstract
Attenuated Salmonella Typhimurium is a promising antigen delivery system for live vaccines such as polysaccharides. The length of polysaccharides is a well-known key factor in modulating the immune response induced by glycoconjugates. However, the relationship between the length of Lipopolysaccharide (LPS) O-antigen (OAg) and the immunogenicity of S. Typhimurium remains unclear. In this study, we assessed the effect of OAg length determined by wzzST on Salmonella colonization, cell membrane permeability, antimicrobial activity, and immunogenicity by comparing the S. Typhimurium wild-type ATCC14028 strain to those with various OAg lengths of the ΔwzzST mutant and ΔwzzST::wzzECO2. The analysis of the OAg length distribution revealed that, except for the very long OAg, the short OAg length of 2-7 repeat units (RUs) was obtained from the ΔwzzST mutant, the intermediate OAg length of 13-21 RUs was gained from ΔwzzST::wzzECO2, and the long OAg length of over 20 RUs was gained from the wild-type. In addition, we found that the OAg length affected Salmonella colonization, cell permeability, and antibiotic resistance. Immunization of mice revealed that shortening the OAg length by altering wzzST had an effect on serum bactericidal ability, complement deposition, and humoral immune response. S. Typhimurium mutant strain ΔwzzST::wzzECO2 possessed good immunogenicity and was the optimum option for delivering E. coli O2 O-polysaccharides. Furthermore, the attenuated strain ATCC14028 ΔasdΔcrpΔcyaΔrfbPΔwzzST::wzzECO2-delivered E. coli O2 OAg gene cluster outperforms the ATCC14028 ΔasdΔcrpΔcyaΔrfbP in terms of IgG eliciting, cytokine expression, and immune protection in chickens. This study sheds light on the role of OAg length in Salmonella characteristics, which may have a potential application in optimizing the efficacy of delivered polysaccharide vaccines.
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Affiliation(s)
- Yue Han
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China ,grid.80510.3c0000 0001 0185 3134Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130 China
| | - Ping Luo
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Huan Zeng
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Pu Wang
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Jiali Xu
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Pengju Chen
- Henan Institute of Morden Chinese Veterinary Medicine, Zhengzhou, 450002 China ,Shangdong Xindehui Biotechnology Co., Ltd, Yunchengxian, 274700 China
| | - Xindan Chen
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Yuji Chen
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Qiyu Cao
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Ruidong Zhai
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Jing Xia
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Simin Deng
- grid.443483.c0000 0000 9152 7385Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300 China
| | - Anchun Cheng
- grid.80510.3c0000 0001 0185 3134Institute of Preventive Veterinary Medicine, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130 China
| | - Changyong Cheng
- Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300, China.
| | - Houhui Song
- Key Laboratory of Applied Technology On Green-Eco-Healthy Animal Husbandry of Zhejiang Province, Zhejiang Provincial Engineering Research Center for Animal Health Diagnostics & Advanced Technology, Zhejiang International Science and Technology Cooperation Base for Veterinary Medicine and Health Management, China-Australia Joint Laboratory for Animal, Health Big Data Analytics, College of Animal Science and Technology & College of Veterinary Medicine, Zhejiang A & F University, 666 Wusu Street, Hangzhou, 311300, China.
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Stefanetti G, MacLennan CA, Micoli F. Impact and Control of Sugar Size in Glycoconjugate Vaccines. Molecules 2022; 27:molecules27196432. [PMID: 36234967 PMCID: PMC9572008 DOI: 10.3390/molecules27196432] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 09/23/2022] [Accepted: 09/24/2022] [Indexed: 11/17/2022] Open
Abstract
Glycoconjugate vaccines have contributed enormously to reducing and controlling encapsulated bacterial infections for over thirty years. Glycoconjugate vaccines are based on a carbohydrate antigen that is covalently linked to a carrier protein; this is necessary to cause T cell responses for optimal immunogenicity, and to protect young children. Many interdependent parameters affect the immunogenicity of glycoconjugate vaccines, including the size of the saccharide antigen. Here, we examine and discuss the impact of glycan chain length on the efficacy of glycoconjugate vaccines and report the methods employed to size polysaccharide antigens, while highlighting the underlying reaction mechanisms. A better understanding of the impact of key parameters on the immunogenicity of glycoconjugates is critical to developing a new generation of highly effective vaccines.
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Affiliation(s)
- Giuseppe Stefanetti
- Department of Biomolecular Sciences, University of Urbino Carlo Bo, 61029 Urbino, Italy
- Correspondence:
| | - Calman Alexander MacLennan
- Enteric and Diarrheal Diseases, Global Health, Bill & Melinda Gates Foundation, 500 5th Ave. N, Seattle, WA 98109, USA
- The Jenner Institute, Nuffield Department of Medicine, University of Oxford, Oxford OX3 7DQ, UK
- The Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham B15 2TT, UK
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Vandana, Das S. Genetic regulation, biosynthesis and applications of extracellular polysaccharides of the biofilm matrix of bacteria. Carbohydr Polym 2022; 291:119536. [DOI: 10.1016/j.carbpol.2022.119536] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 04/22/2022] [Accepted: 04/22/2022] [Indexed: 11/02/2022]
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Anish C, Beurret M, Poolman J. Combined effects of glycan chain length and linkage type on the immunogenicity of glycoconjugate vaccines. NPJ Vaccines 2021; 6:150. [PMID: 34893630 PMCID: PMC8664855 DOI: 10.1038/s41541-021-00409-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 11/01/2021] [Indexed: 11/09/2022] Open
Abstract
The development and use of antibacterial glycoconjugate vaccines have significantly reduced the occurrence of potentially fatal childhood and adult diseases such as bacteremia, bacterial meningitis, and pneumonia. In these vaccines, the covalent linkage of bacterial glycans to carrier proteins augments the immunogenicity of saccharide antigens by triggering T cell-dependent B cell responses, leading to high-affinity antibodies and durable protection. Licensed glycoconjugate vaccines either contain long-chain bacterial polysaccharides, medium-sized oligosaccharides, or short synthetic glycans. Here, we discuss factors that affect the glycan chain length in vaccines and review the available literature discussing the impact of glycan chain length on vaccine efficacy. Furthermore, we evaluate the available clinical data on licensed glycoconjugate vaccine preparations with varying chain lengths against two bacterial pathogens, Haemophilus influenzae type b and Neisseria meningitidis group C, regarding a possible correlation of glycan chain length with their efficacy. We find that long-chain glycans cross-linked to carrier proteins and medium-sized oligosaccharides end-linked to carriers both achieve high immunogenicity and efficacy. However, end-linked glycoconjugates that contain long untethered stretches of native glycan chains may induce hyporesponsiveness by T cell-independent activation of B cells, while cross-linked medium-sized oligosaccharides may suffer from suboptimal saccharide epitope accessibility.
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Affiliation(s)
- Chakkumkal Anish
- grid.497529.40000 0004 0625 7026Bacterial Vaccines Discovery and Early Development, Janssen Vaccines and Prevention B.V., Leiden, Netherlands
| | - Michel Beurret
- Bacterial Vaccines Discovery and Early Development, Janssen Vaccines and Prevention B.V., Leiden, Netherlands.
| | - Jan Poolman
- grid.497529.40000 0004 0625 7026Bacterial Vaccines Discovery and Early Development, Janssen Vaccines and Prevention B.V., Leiden, Netherlands
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8
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Su H, Liu Q, Bian X, Wang S, Curtiss R 3rd, Kong Q. Synthesis and delivery of Streptococcus pneumoniae capsular polysaccharides by recombinant attenuated Salmonella vaccines. Proc Natl Acad Sci U S A 2021; 118:e2013350118. [PMID: 33380455 DOI: 10.1073/pnas.2013350118] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pneumococcal infection-caused diseases are responsible for substantial morbidity and mortality worldwide. Traditional pneumococcal vaccines are developed based on purified capsular polysaccharides (CPS) or CPS conjugated to a protein carrier. Production processes of the traditional vaccines are laborious, and thereby increase the vaccine cost and limit their use in developing nations. A cost-effective pneumococcal vaccine using the recombinant attenuated Salmonella vaccine (RASV) was developed in this study. We cloned and expressed genes for seven serotypes of CPSs in the RASV strain. The RASV-delivered CPSs induced robust humoral and cell-mediated responses and mediated efficient protection of mice against pneumococcal infection. Our work provides an innovative strategy for mass producing low-cost bioconjugated polysaccharide vaccines for needle-free mucosal delivery against pneumococcal infections. Streptococcus pneumoniae capsular polysaccharides (CPSs) are major determinants of bacterial pathogenicity. CPSs of different serotypes form the main components of the pneumococcal vaccines Pneumovax, Prevnar7, and Prevnar13, which substantially reduced the S. pneumoniae disease burden in developed countries. However, the laborious production processes of traditional polysaccharide-based vaccines have raised the cost of the vaccines and limited their impact in developing countries. The aim of this study is to develop a kind of low-cost live vaccine based on using the recombinant attenuated Salmonella vaccine (RASV) system to protect against pneumococcal infections. We cloned genes for seven different serotypes of CPSs to be expressed by the RASV strain. Oral immunization of mice with the RASV-CPS strains elicited robust Th1 biased adaptive immune responses. All the CPS-specific antisera mediated opsonophagocytic killing of the corresponding serotype of S. pneumoniae in vitro. The RASV-CPS2 and RASV-CPS3 strains provided efficient protection of mice against challenge infections with either S. pneumoniae strain D39 or WU2. Synthesis and delivery of S. pneumoniae CPSs using the RASV strains provide an innovative strategy for low-cost pneumococcal vaccine development, production, and use.
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Sears KT, Galen JE, Tennant SM. Advances in the development of Salmonella-based vaccine strategies for protection against Salmonellosis in humans. J Appl Microbiol 2021; 131:2640-2658. [PMID: 33665941 PMCID: PMC9292744 DOI: 10.1111/jam.15055] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/18/2021] [Accepted: 03/02/2021] [Indexed: 11/29/2022]
Abstract
Salmonella spp. are important human pathogens globally causing millions of cases of typhoid fever and non‐typhoidal salmonellosis annually. There are only a few vaccines licensed for use in humans which all target Salmonella enterica serovar Typhi. Vaccine development is hampered by antigenic diversity between the thousands of serovars capable of causing infection in humans. However, a number of attenuated candidate vaccine strains are currently being developed. As facultative intracellular pathogens with multiple systems for transporting effector proteins to host cells, attenuated Salmonella strains can also serve as ideal tools for the delivery of foreign antigens to create multivalent live carrier vaccines for simultaneous immunization against several unrelated pathogens. Further, the ease with which Salmonella can be genetically modified and the extensive knowledge of the virulence mechanisms of this pathogen means that this bacterium has often served as a model organism to test new approaches. In this review we focus on (1) recent advances in live attenuated Salmonella vaccine development, (2) improvements in expression of foreign antigens in carrier vaccines and (3) adaptation of attenuated strains as sources of purified antigens and vesicles that can be used for subunit and conjugate vaccines or together with attenuated vaccine strains in heterologous prime‐boosting immunization strategies. These advances have led to the development of new vaccines against Salmonella which have or will soon be tested in clinical trials.
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Affiliation(s)
- K T Sears
- Center for Vaccine Development and Global Health, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - J E Galen
- Center for Vaccine Development and Global Health, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
| | - S M Tennant
- Center for Vaccine Development and Global Health, Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA
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Gasperini G, Raso MM, Arato V, Aruta MG, Cescutti P, Necchi F, Micoli F. Effect of O-Antigen Chain Length Regulation on the Immunogenicity of Shigella and Salmonella Generalized Modules for Membrane Antigens (GMMA). Int J Mol Sci 2021; 22:ijms22031309. [PMID: 33525644 PMCID: PMC7865430 DOI: 10.3390/ijms22031309] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 01/16/2021] [Accepted: 01/22/2021] [Indexed: 01/01/2023] Open
Abstract
Recently, generalized modules for membrane antigens (GMMA) technology has been proposed as an alternative approach to traditional glycoconjugate vaccines for O-antigen delivery. Saccharide length is a well-known parameter that can impact the immune response induced by glycoconjugates both in terms of magnitude and quality. However, the criticality of O-antigen length on the immune response induced by GMMA-based vaccines has not been fully elucidated. Here, Shigella and Salmonella GMMA-producing strains were further mutated in order to display homogeneous polysaccharide populations of different sizes on a GMMA surface. Resulting GMMA were compared in mice immunization studies. Athymic nude mice were also used to investigate the involvement of T-cells in the immune response elicited. In contrast with what has been reported for traditional glycoconjugate vaccines and independent of the pathogen and the sugar structural characteristics, O-antigen length did not result in being a critical parameter for GMMA immunogenicity. This work supports the identification of critical quality attributes to optimize GMMA vaccine design and improve vaccine efficacy and gives insights on the nature of the immune response induced by GMMA.
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Affiliation(s)
- Gianmarco Gasperini
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
| | - Maria Michelina Raso
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
- Department of Life Sciences, University of Trieste, Via L. Giorgieri 1, Bdg C11, 34127 Trieste, Italy;
| | - Vanessa Arato
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
| | - Maria Grazia Aruta
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
| | - Paola Cescutti
- Department of Life Sciences, University of Trieste, Via L. Giorgieri 1, Bdg C11, 34127 Trieste, Italy;
| | - Francesca Necchi
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
| | - Francesca Micoli
- GSK Vaccines Institute for Global Health (GVGH) s.r.l, Via Fiorentina 1, 53100 Siena, Italy; (G.G.); (M.M.R.); (V.A.); (M.G.A.); (F.N.)
- Correspondence: ; Tel.: +39-0577-539087
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11
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Liu MA, Kidambi A, Reeves PR. The low level of O antigen in Salmonella enterica Paratyphi A is due to inefficiency of the glycosyltransferase WbaV. FEMS Microbiol Lett 2021; 368:6105216. [PMID: 33476372 DOI: 10.1093/femsle/fnab009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/18/2021] [Indexed: 11/14/2022] Open
Abstract
The group A O antigen is the major surface polysaccharide of Salmonella enterica serovar Paratyphi A (SPA), and the focal point for most current vaccine development efforts. The SPA O-antigen repeat (O unit) is structurally similar to the group D1 O unit of S. enterica serovar Typhi, differing only in the presence of a terminal side-branch paratose (Par) in place of tyvelose (Tyv), both of which are attached by the glycosyltransferase WbaV. The two O-antigen gene clusters are also highly similar, but with a loss-of-function mutation in the group A tyv gene and the tandem amplification of wbaV in most SPA strains. In this study, we show that SPA strains consistently produce less O antigen than their group D1 counterparts and use an artificial group A strain (D1 Δtyv) to show this is due to inefficient Par attachment by WbaV. We also demonstrate that group A O-antigen production can be increased by overexpression of the wbaV gene in both the D1 Δtyv strain and two multi-wbaV SPA strains. These findings should be broadly applicable in ongoing vaccine development pipelines, where efficient isolation and purification of large quantities of O antigen is of critical importance.
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Affiliation(s)
- Michael A Liu
- School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia
| | - Aditi Kidambi
- School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia
| | - Peter R Reeves
- School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia
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12
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Huszczynski SM, Hao Y, Lam JS, Khursigara CM. Identification of the Pseudomonas aeruginosa O17 and O15 O-Specific Antigen Biosynthesis Loci Reveals an ABC Transporter-Dependent Synthesis Pathway and Mechanisms of Genetic Diversity. J Bacteriol 2020; 202:e00347-20. [PMID: 32690555 DOI: 10.1128/JB.00347-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 07/13/2020] [Indexed: 02/07/2023] Open
Abstract
Many bacterial cell surface glycans, such as the O antigen component of lipopolysaccharide (LPS), are produced via the so-called Wzx/Wzy- or ABC transporter-dependent pathways. O antigens are highly diverse polysaccharides that protect bacteria from their environment and engage in important host-pathogen interactions. The specific structure and composition of O antigens are the basis of classifying bacteria into O serotypes. In the opportunistic pathogen Pseudomonas aeruginosa, there are currently 20 known O-specific antigen (OSA) structures. The clusters of genes responsible for 18 of these O antigens have been identified, all of which follow the Wzx/Wzy-dependent pathway and are located at a common locus. In this study, we located the two unidentified O antigen biosynthesis clusters responsible for the synthesis of the O15 and the O17 OSA structures by analyzing published whole-genome sequence data. Intriguingly, these clusters were found outside the conserved OSA biosynthesis locus and were likely acquired through multiple horizontal gene transfer events. Based on data from knockout and overexpression studies, we determined that the synthesis of these O antigens follows an ABC transporter-dependent rather than a Wzx/Wzy-dependent pathway. In addition, we collected evidence to show that the O15 and O17 polysaccharide chain lengths are regulated by molecular rulers with distinct and variable domain architectures. The findings in this report are critical for a comprehensive understanding of O antigen biosynthesis in P. aeruginosa and provide a framework for future studies.IMPORTANCE P. aeruginosa is a problematic opportunistic pathogen that causes diseases in those with compromised host defenses, such as those suffering from cystic fibrosis. This bacterium produces a number of virulence factors, including a serotype-specific O antigen. Here, we identified and characterized the gene clusters that produce the O15 and O17 O antigens and show that they utilize a pathway for synthesis that is distinct from that of the 18 other known serotypes. We also provide evidence that these clusters have acquired mutations in specific biosynthesis genes and have undergone extensive horizontal gene transfer within the P. aeruginosa population. These findings expand on our understanding of O antigen biosynthesis in Gram-negative bacteria and the mechanisms that drive O antigen diversity.
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13
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Abstract
Shigella are gram-negative bacteria that cause severe diarrhea and dysentery, with a high level of antimicrobial resistance. Disease-induced protection against reinfection in Shigella-endemic areas provides convincing evidence on the feasibility of a vaccine and on the importance of Shigella lipopolysaccharides as targets of the host humoral protective immune response against disease. This article provides an overview of the original and current strategies toward the development of a Shigella glycan-protein conjugate vaccine that would cover the most commonly detected strains. Going beyond pioneering “lattice”-type polysaccharide-protein conjugates, progress, and challenges are addressed with focus on promising alternatives, which have reached phases I and II clinical trial. Glycoengineered bioconjugates and “sun”-type conjugates featuring well-defined synthetic carbohydrate antigens are discussed with insights on the molecular parameters governing the rational design of a cost-effective glycoconjugate vaccine efficacious in preventing diseases caused by Shigella in the most at risk populations, young children living in endemic areas.
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Affiliation(s)
- Louis-Antoine Barel
- a Chemistry of Biomolecules Unit, Department of Structural Biology and Chemistry , Institut Pasteur, UMR3523, CNRS , Paris , France.,b Université Paris Descartes , Paris , France
| | - Laurence A Mulard
- a Chemistry of Biomolecules Unit, Department of Structural Biology and Chemistry , Institut Pasteur, UMR3523, CNRS , Paris , France
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14
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Baliban SM, Curtis B, Amin MN, Levine MM, Pasetti MF, Simon R. Maternal Antibodies Elicited by Immunization With an O- Polysaccharide Glycoconjugate Vaccine Protect Infant Mice Against Lethal Salmonella Typhimurium Infection. Front Immunol 2019; 10:2124. [PMID: 31555302 PMCID: PMC6743215 DOI: 10.3389/fimmu.2019.02124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 08/23/2019] [Indexed: 12/17/2022] Open
Abstract
Non-typhoidal Salmonella (NTS) are a leading cause of pediatric invasive bacterial infections in sub-Saharan Africa with high associated case fatality rates in children under 5 years old. We have developed glycoconjugate vaccines consisting of the lipid A-removed surface polysaccharide of NTS, core and O-polysaccharide (COPS), and the flagellar monomer protein (FliC) from the homologous serovar as the carrier. We previously established that COPS:FliC was immunogenic and protective in mice immunized as adults or infants; however, the brief period of murine infancy precluded the evaluation of protection against invasive NTS (iNTS) disease in early life. In the present study, we used a mouse model of maternal immunization to investigate transmission of S. Typhimurium COPS:FliC-induced maternal antibodies and protection against lethal iNTS challenge in infant mice. We found that vaccinated dams developed high levels of COPS- and FliC-specific IgG, which were transferred to their offspring. Sera from both vaccinated mothers and their litters mediated complement-dependent bactericidal activity in-vitro. Passively immunized 2-week old infant mice born to vaccinated mothers were fully protected from challenge with an S. Typhimurium blood isolate from sub-Saharan Africa. The pre-clinical findings reported herein demonstrate that anti-COPS:FliC antibodies induced by vaccination are sufficient for protection of murine infants against experimental S. Typhimurium infection. By underscoring the protective role of antibody, our results suggest that maintaining an adequate titer of protective anti-Salmonella antibodies during early life, either through pediatric or maternal COPS:FliC vaccination, may reduce iNTS disease in young children in sub-Saharan Africa.
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Affiliation(s)
- Scott M. Baliban
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Brittany Curtis
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Mohammed N. Amin
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Myron Mike Levine
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Marcela F. Pasetti
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, United States
| | - Raphael Simon
- Center for Vaccine Development and Global Health, University of Maryland School of Medicine, Baltimore, MD, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, United States
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15
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Abstract
Introduction: Over the last decades, glycoconjugate vaccines have been proven to be a successful strategy to prevent infectious diseases. Many diseases remain to be controlled, especially in developing countries, and emerging antibiotic-resistant bacteria present an alarming public-health threat. The increasing complexity of future vaccines, and the need to accelerate development processes have triggered the development of faster approaches to glycoconjugate vaccines design. Areas covered: This review provides an overview of recent progress in glycoconjugation technologies toward faster vaccine design. Expert opinion: Among the different emerging approaches, glycoengineering has the potential to combine glycan assembly and conjugation to carrier systems (such as proteins or outer membrane vesicles) in one step, resulting in a simplified manufacturing process and fewer analytical controls. Chemical and enzymatic strategies, and their automation can facilitate glycoepitope identification for vaccine design. Other approaches, such as the liposomal encapsulation of polysaccharides, potentially enable fast and easy combination of numerous antigens in the same formulation. Additional progress is envisaged in the near future, and some of these systems still need to be further validated in humans. In parallel, new strategies are needed to accelerate the vaccine development process, including the associated clinical trials, up to vaccine release onto the market.
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Affiliation(s)
- Francesca Micoli
- Technology Platform, GSK Vaccines Institute for Global Health s.r.l , Siena , Italy
| | | | - Renzo Alfini
- Technology Platform, GSK Vaccines Institute for Global Health s.r.l , Siena , Italy
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Huszczynski SM, Coumoundouros C, Pham P, Lam JS, Khursigara CM. Unique Regions of the Polysaccharide Copolymerase Wzz 2 from Pseudomonas aeruginosa Are Essential for O-Specific Antigen Chain Length Control. J Bacteriol 2019; 201:e00165-19. [PMID: 31109993 DOI: 10.1128/JB.00165-19] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 05/15/2019] [Indexed: 12/13/2022] Open
Abstract
The outer leaflet of the outer membrane of nearly all Gram-negative bacteria contains lipopolysaccharide (LPS). The distal end of LPS may be capped with O antigen, a long polysaccharide that can range from a few to hundreds of sugars in length. The chain length of the polysaccharide has many implications for bacterial survival and consequently is tightly controlled. In the Wzx/Wzy-dependent route of O antigen synthesis, one or more Wzz proteins determine the chain length via an unknown mechanism. To gain insight into this mechanism, we identified and characterized important regions of two Wzz proteins in Pseudomonas aeruginosa serotype O13, which confer the production of "long" (Wzz1) and "very long" (Wzz2) chain lengths, respectively. We found that compared to Wzz1, Wzz2 has distinct amino acid insertions in the central α-helices (insα6 and insα7) and in membrane-distal (insL4) and -proximal (insIL) loops. When these regions were deleted in Wzz2, the mutant proteins conferred drastically shortened chain lengths. Within these regions we identified several conserved amino acid residues that were then targeted for site-directed mutagenesis. Our results implicate an RTE motif in loop 4 and a "hot spot" of charged and polar residues in insα7 in the function of Wzz2 We present evidence that the functionally important residues of insα7 are likely involved in stabilizing Wzz through coiled-coil interactions.IMPORTANCE O antigen is an important virulence factor presented on the cell surface of Gram-negative bacteria that is critical for bacterial physiology and pathogenesis. However, some aspects of O antigen biosynthesis, such as the mechanisms for determining polysaccharide chain length, are poorly understood. In this study, we identified unique regions in the O antigen chain length regulators (termed Wzz) of the problematic opportunistic pathogen Pseudomonas aeruginosa We show that these regions are critical for determining O antigen chain length, which provides new insight into the model of the Wzz mechanism. Ultimately, our work adds knowledge toward understanding an important step in the biosynthesis of this virulence factor, which is applicable to a wide range of Gram-negative pathogens.
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Stefanetti G, Okan N, Fink A, Gardner E, Kasper DL. Glycoconjugate vaccine using a genetically modified O antigen induces protective antibodies to Francisella tularensis. Proc Natl Acad Sci U S A 2019; 116:7062-70. [PMID: 30872471 DOI: 10.1073/pnas.1900144116] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Francisella tularensis is the causative agent of tularemia, a category A bioterrorism agent. The lipopolysaccharide (LPS) O antigen (OAg) of F. tularensis has been considered for use in a glycoconjugate vaccine, but conjugate vaccines tested so far have failed to confer protection necessary against aerosolized pulmonary bacterial challenge. When F. tularensis OAg was purified under standard conditions, the antigen had a small molecular size [25 kDa, low molecular weight (LMW)]. Using milder extraction conditions, we found the native OAg had a larger molecular size [80 kDa, high molecular weight (HMW)], and in a mouse model of tularemia, a glycoconjugate vaccine made with the HMW polysaccharide coupled to tetanus toxoid (HMW-TT) conferred better protection against intranasal challenge than a conjugate made with the LMW polysaccharide (LMW-TT). To further investigate the role of OAg size in protection, we created an F. tularensis live vaccine strain (LVS) mutant with a significantly increased OAg size [220 kDa, very high molecular weight (VHMW)] by expressing in F. tularensis a heterologous chain-length regulator gene (wzz) from the related species Francisella novicida Immunization with VHMW-TT provided markedly increased protection over that obtained with TT glycoconjugates made using smaller OAgs. We found that protective antibodies recognize a length-dependent epitope better expressed on HMW and VHMW antigens, which bind with higher affinity to the organism.
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