1
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Zegeye ED, Chaukimath P, Diaz Y, Visweswariah SS, Puntervoll P. Coupling enterotoxigenic Escherichia coli heat-stable peptide toxin with 8-arm PEG enhances immunogenicity. J Pept Sci 2024:e3647. [PMID: 39091086 DOI: 10.1002/psc.3647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Revised: 07/06/2024] [Accepted: 07/09/2024] [Indexed: 08/04/2024]
Abstract
Enterotoxigenic Escherichia coli (ETEC) strains, which produce the heat-stable enterotoxin (ST) either alone or in combination with the heat-labile enterotoxin, contribute to the bulk of the burden of child diarrheal disease in resource-limited countries and are associated with mortality. Developing an effective vaccine targeting ST presents challenges due to its potent enterotoxicity, non-immunogenicity, and the risk of autoimmune reaction stemming from its structural similarity to the human endogenous ligands, guanylin, and uroguanylin. This study aimed to assess a novel synthetic vaccine carrier platform employing a single chemical coupling step for making human ST (STh) immunogenic. Specifically, the method involved cross-linking STh to an 8-arm N-hydroxysuccinimide (NHS) ester-activated PEG cross-linker. A conjugate of STh with 8-arm structure was prepared, and its formation was confirmed through immunoblotting analysis. The impact of conjugation on STh epitopes was assessed using ELISAs with polyclonal and monoclonal antibodies targeting various epitopes of STh. Immunization of mice with the conjugate induced the production of anti-STh antibodies, exhibiting neutralizing activity against STh.
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Affiliation(s)
- Ephrem Debebe Zegeye
- Marine Biotechnology, NORCE Norwegian Research Centre, Bergen, Norway
- Department of Paraclinical Sciences, Faculty of Veterinary Medicine, Norwegian University of Life Sciences (NMBU), Ås, Norway
| | - Pooja Chaukimath
- Department of Developmental Biology and Genetics, Indian Institute of Science, Bengaluru, India
| | - Yuleima Diaz
- Marine Biotechnology, NORCE Norwegian Research Centre, Bergen, Norway
| | - Sandhya S Visweswariah
- Department of Developmental Biology and Genetics, Indian Institute of Science, Bengaluru, India
| | - Pål Puntervoll
- Marine Biotechnology, NORCE Norwegian Research Centre, Bergen, Norway
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2
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Xu C, Fu F, She Y, Yang D, Peng K, Lin Y, Xu C. Development of a new candidate vaccine against piglet diarrhea caused by Escherichia coli. Open Life Sci 2023; 18:20220804. [PMID: 38196514 PMCID: PMC10775170 DOI: 10.1515/biol-2022-0804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 11/02/2023] [Accepted: 11/14/2023] [Indexed: 01/11/2024] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is an important type of pathogenic bacteria that causes diarrhea in humans and young livestock. The pathogen has a high morbidity and mortality rate, resulting in significant economic losses in the pig industry. To effectively prevent piglet diarrhea, we developed a new tetravalent genetically engineered vaccine that specifically targets ETEC. To eliminate the natural toxin activity of ST1 enterotoxin and enhance the preventive effect of the vaccine, the mutated ST 1, K88ac, K99, and LT B genes were amplified by PCR and site-specific mutation techniques. The recombinant strain BL21(DE3)(pXKK3SL) was constructed and achieved high expression. Animal experiments showed that the inactivated vaccine had eliminated the natural toxin activity of ST1. The immune protection test demonstrated that the inclusion body and inactivated vaccine exhibited a positive immune effect. The protection rates of the inclusion body group and inactivated vaccine group were 96 and 98%, respectively, when challenged with 1 minimum lethal dose, indicating that the constructed K88ac-K99-3ST1-LTB vaccine achieved a strong immune effect. Additionally, the minimum immune doses for mice and pregnant sows were determined to be 0.2 and 2 mL, respectively. This study suggests that the novel K88ac-K99-3ST1-LTB vaccine has a wide immune spectrum and can prevent diarrhea caused by ETEC through enterotoxin and fimbrial pathways. The aforementioned research demonstrates that the K88ac-K99-3ST1-LTB vaccine offers a new genetically engineered vaccine that shows potential for preventing diarrhea in newborn piglets.
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Affiliation(s)
- Chongli Xu
- College of Medical Technology, Chongqing Medical and Pharmaceutical College, 82 Daxuecheng Road, Chongqing401331, PR China
| | - Fengyang Fu
- College of Medical Technology, Chongqing Medical and Pharmaceutical College, 82 Daxuecheng Road, Chongqing401331, PR China
| | - Yuhan She
- College of Medical Technology, Chongqing Medical and Pharmaceutical College, 82 Daxuecheng Road, Chongqing401331, PR China
| | - Danni Yang
- College of Medical Technology, Chongqing Medical and Pharmaceutical College, 82 Daxuecheng Road, Chongqing401331, PR China
| | - Kun Peng
- College of Medical Technology, Chongqing Medical and Pharmaceutical College, 82 Daxuecheng Road, Chongqing401331, PR China
| | - Yimin Lin
- Chongqing Key Laboratory of Translational Research for Cancer Metastasis and Individualized Treatment, Chongqing University Cancer Hospital, Chongqing400030, PR China
| | - ChongBo Xu
- School of Biology and Agriculture, Shaoguan University, Shaoguan512005, PR China
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3
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Girardi P, Bhuiyan TR, Lundin SB, Harutyunyan S, Neuhauser I, Khanam F, Nagy G, Szijártó V, Henics T, Nagy E, Harandi AM, Qadri F. Anti-Toxin Responses to Natural Enterotoxigenic Escherichia coli (ETEC) Infection in Adults and Children in Bangladesh. Microorganisms 2023; 11:2524. [PMID: 37894182 PMCID: PMC10609113 DOI: 10.3390/microorganisms11102524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/01/2023] [Accepted: 10/02/2023] [Indexed: 10/29/2023] Open
Abstract
A sero-epidemiology study was conducted in Dhaka, Bangladesh between January 2020 and February 2021 to assess the immune responses to ETEC infection in adults and children. (1) Background: Enterotoxigenic Escherichia coli infection is a main cause of diarrheal disease in endemic countries. The characterization of the immune responses evoked by natural infection can guide vaccine development efforts. (2) Methods: A total of 617 adult and 480 pediatric diarrheal patients were screened, and 43 adults and 46 children (below 5 years of age) with an acute ETEC infection completed the study. The plasma samples were analyzed for antibody responses against the ETEC toxins. (3) Results: Heat-stable toxin (ST)-positive ETEC is the main cause of ETEC infection in adults, unlike in children in an endemic setting. We detected very low levels of anti-ST antibodies, and no ST-neutralizing activity. However, infection with ETEC strains expressing the heat-labile toxin (LT) induced systemic antibody responses in less than 25% of subjects. The antibody levels against LTA and LTB, as well as cholera toxin (CT), correlated well. The anti-LT antibodies were shown to have LT- and CT- neutralizing activity. The antibody reactivity against linear LT epitopes did not correlate with toxin-neutralizing activity. (4) Conclusions: Unlike LT, ST is a poor antigen and even adults have low anti-ST antibody levels that do not allow for the detection of toxin-neutralizing activity.
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Affiliation(s)
- Petra Girardi
- Eveliqure Biotechnologies GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (S.H.); (I.N.); (T.H.); (E.N.)
| | - Taufiqur Rahman Bhuiyan
- Infectious Diseases Division, International Centre for Diarrhoeal Disease Research Bangladesh (ICDDR,B), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh; (T.R.B.); (F.K.); (F.Q.)
| | - Samuel B. Lundin
- Department of Microbiology and Immunology, University of Gothenburg, 405 30 Goteborg, Sweden; (S.B.L.); (A.M.H.)
| | - Shushan Harutyunyan
- Eveliqure Biotechnologies GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (S.H.); (I.N.); (T.H.); (E.N.)
| | - Irene Neuhauser
- Eveliqure Biotechnologies GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (S.H.); (I.N.); (T.H.); (E.N.)
| | - Farhana Khanam
- Infectious Diseases Division, International Centre for Diarrhoeal Disease Research Bangladesh (ICDDR,B), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh; (T.R.B.); (F.K.); (F.Q.)
| | - Gábor Nagy
- CEBINA GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (G.N.); (V.S.)
| | - Valéria Szijártó
- CEBINA GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (G.N.); (V.S.)
| | - Tamás Henics
- Eveliqure Biotechnologies GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (S.H.); (I.N.); (T.H.); (E.N.)
| | - Eszter Nagy
- Eveliqure Biotechnologies GmbH, Karl-Farkas-Gasse 22, 1030 Vienna, Austria; (S.H.); (I.N.); (T.H.); (E.N.)
| | - Ali M. Harandi
- Department of Microbiology and Immunology, University of Gothenburg, 405 30 Goteborg, Sweden; (S.B.L.); (A.M.H.)
- Vaccine Evaluation Center, BC Children’s Hospital Research Institute, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Firdausi Qadri
- Infectious Diseases Division, International Centre for Diarrhoeal Disease Research Bangladesh (ICDDR,B), 68 Shaheed Tajuddin Ahmed Sarani, Mohakhali, Dhaka 1212, Bangladesh; (T.R.B.); (F.K.); (F.Q.)
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4
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Svennerholm AM, Lundgren A. Developments in oral enterotoxigenic Escherichia coli vaccines. Curr Opin Immunol 2023; 84:102372. [PMID: 37523966 DOI: 10.1016/j.coi.2023.102372] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 06/11/2023] [Accepted: 07/04/2023] [Indexed: 08/02/2023]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a leading cause of diarrhea in children in developing countries and in travelers. WHO has affirmed ETEC as a priority vaccine target, but there is no licensed ETEC vaccine available yet. We here describe recent, promising developments of different live, inactivated, and subunit ETEC candidate vaccines expressing or containing nontoxic enterotoxin and/or colonization factor antigens with a focus on oral vaccines. Many of the ETEC candidate vaccines have been tested in clinical trials for safety and immunogenicity and some of them also for protective efficacy in field trials or in challenge studies.
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Affiliation(s)
- Ann-Mari Svennerholm
- Dept. of Microbiology and Immunology, Inst. of Biomedicine, University of Gothenburg, Sweden.
| | - Anna Lundgren
- Dept. of Microbiology and Immunology, Inst. of Biomedicine, University of Gothenburg, Sweden
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5
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Mubanga C, Simuyandi M, Mwape K, Chibesa K, Chisenga C, Chilyabanyama ON, Randall A, Liang X, Glashoff RH, Chilengi R. Use of an ETEC Proteome Microarray to Evaluate Cross-Reactivity of ETVAX ® Vaccine-Induced IgG Antibodies in Zambian Children. Vaccines (Basel) 2023; 11:vaccines11050939. [PMID: 37243042 DOI: 10.3390/vaccines11050939] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 04/02/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023] Open
Abstract
Developing a broadly protective vaccine covering most ETEC variants has been elusive. The most clinically advanced candidate yet is an oral inactivated ETEC vaccine (ETVAX®). We report on the use of a proteome microarray for the assessment of cross-reactivity of anti-ETVAX® IgG antibodies against over 4000 ETEC antigens and proteins. We evaluated 40 (pre-and post-vaccination) plasma samples from 20 Zambian children aged 10-23 months that participated in a phase 1 trial investigating the safety, tolerability, and immunogenicity of ETVAX® adjuvanted with dmLT. Pre-vaccination samples revealed high IgG responses to a variety of ETEC proteins including classical ETEC antigens (CFs and LT) and non-classical antigens. Post-vaccination reactivity to CFA/I, CS3, CS6, and LTB was stronger than baseline among the vaccinated compared to the placebo group. Interestingly, we noted significantly high post-vaccination responses to three non-vaccine ETEC proteins: CS4, CS14, and PCF071 (p = 0.043, p = 0.028, and p = 0.00039, respectively), suggestive of cross-reactive responses to CFA/I. However, similar responses were observed in the placebo group, indicating the need for larger studies. We conclude that the ETEC microarray is a useful tool for investigating antibody responses to numerous antigens, especially because it may not be practicable to include all antigens in a single vaccine.
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Affiliation(s)
- Cynthia Mubanga
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
- Division of Medical Microbiology, Department of Pathology, Stellenbosch University & National Health Laboratory Service, Tygerberg Hospital Francie van Zijl Drive, P.O. Box 241, Cape Town 8000, South Africa
| | - Michelo Simuyandi
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
| | - Kapambwe Mwape
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
- Water and Health Research Center, Faculty of Health Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein 2028, South Africa
| | - Kennedy Chibesa
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
- Division of Virology, School of Pathology, Faculty of Health Sciences, University of the Free State, 205 Nelson Mandela, P.O. Box 339, Bloemfontein 9300, South Africa
| | - Caroline Chisenga
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
| | | | - Arlo Randall
- Antigen Discovery Inc., 1 Technology Dr., Suite E309, Irvine, CA 92618, USA
| | - Xiaowu Liang
- Antigen Discovery Inc., 1 Technology Dr., Suite E309, Irvine, CA 92618, USA
| | - Richard H Glashoff
- Division of Medical Microbiology, Department of Pathology, Stellenbosch University & National Health Laboratory Service, Tygerberg Hospital Francie van Zijl Drive, P.O. Box 241, Cape Town 8000, South Africa
| | - Roma Chilengi
- Enteric Disease and Vaccine Research Unit, Centre for Infectious Disease Research in Zambia, Lusaka P.O. Box 34681, Zambia
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6
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Zhao H, Xu Y, Li X, Yin J, Li G, Zhao H, Li S, Li J, Wang L. Protective efficacy of a recombinant enterotoxin antigen in a maternal immunization model and the inhibition of specific maternal antibodies to neonatal oral vaccination. J Reprod Immunol 2023; 157:103946. [PMID: 37031607 DOI: 10.1016/j.jri.2023.103946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 02/19/2023] [Accepted: 04/03/2023] [Indexed: 04/11/2023]
Abstract
ETEC (enterotoxigenic Escherichia coli) infection is the leading cause of profuse watery diarrhea in mammals, especially among pre-weaning and post-weaning piglets in swine industry. Maternal immunization is a current rational strategy for providing protection to susceptive piglets and reducing the incidence of ETEC-associated diarrhea. Here we evaluated the protective efficiency of a recombinant antigen (MBP-SLS) fused by major enterotoxin subunits (STa-LTB-STb) via a maternal immunization model, and the impacts of maternal antibodies to neonatal oral vaccination were also investigated in the neonates. The high titers of specific IgG and sIgA in pups shown that the maternal antibodies could be transferred passively. Furthermore, the increases of IL-6 and IL-10 cytokines in breast milk and pup serum indicated that immunization on mother could effectively boost the immune system of neonates. Newborn rats from immunized mothers showed a 70% survival rate after ETEC infection. However, the mucosal immune responses of neonates were inhibited by the high level of maternal specific antibodies. Among the oral-vaccinated neonates, born from mock-immunized rats reached the highest survival after ETEC challenge. Collectively, the fusion MBP-SLS antigen could effectively induce strong immune responses in rats during pregnancy and the pups could receive passive protection through specific antibodies transferred via milk and placenta. However, the specific maternal antibodies exhibited an inhibition effect on the mucosal immune responses in offspring.
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Affiliation(s)
- Hong Zhao
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China
| | - Yongping Xu
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China; Dalian SEM Bio-Engineering Technology Co. Ltd., Dalian 116620, China; Center for Food Safety of Animal Origin, Ministry of Education, Dalian University of Technology, Dalian 116600, China
| | - Xiaoyu Li
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China
| | - Jiajun Yin
- Affiliated Zhongshan Hospital of Dalian University, Dalian 116001, China
| | - Gen Li
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China
| | - Haofei Zhao
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China
| | - Shuying Li
- Dalian SEM Bio-Engineering Technology Co. Ltd., Dalian 116620, China; Center for Food Safety of Animal Origin, Ministry of Education, Dalian University of Technology, Dalian 116600, China
| | - Jibin Li
- Dalian SEM Bio-Engineering Technology Co. Ltd., Dalian 116620, China
| | - Lili Wang
- School of Bioengineering, Dalian University of Technology, Dalian 116024, China.
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7
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Zhang Y, Tan P, Zhao Y, Ma X. Enterotoxigenic Escherichia coli: intestinal pathogenesis mechanisms and colonization resistance by gut microbiota. Gut Microbes 2022; 14:2055943. [PMID: 35358002 PMCID: PMC8973357 DOI: 10.1080/19490976.2022.2055943] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in children and travelers in developing countries. ETEC is characterized by the ability to produce major virulence factors including colonization factors (CFs) and enterotoxins, that bind to specific receptors on epithelial cells and induce diarrhea. The gut microbiota is a stable and sophisticated ecosystem that performs a range of beneficial functions for the host, including protection against pathogen colonization. Understanding the pathogenic mechanisms of ETEC and the interaction between the gut microbiota and ETEC represents not only a research need but also an opportunity and challenge to develop precautions for ETEC infection. Herein, this review focuses on recent discoveries about ETEC etiology, pathogenesis and clinical manifestation, and discusses the colonization resistances mediated by gut microbiota, as well as preventative strategies against ETEC with an aim to provide novel insights that can reduce the adverse effect on human health.
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Affiliation(s)
- Yucheng Zhang
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, China
| | - Peng Tan
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, China
| | - Ying Zhao
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, China
| | - Xi Ma
- State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, China,CONTACT Xi Ma State Key Laboratory of Animal Nutrition, Department of Animal Nutrition and Feed Science, China Agricultural University, Beijing, China
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8
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Fleckenstein JM, Bitoun JP. Changing the locks on intestinal signaling. Cell Host Microbe 2021; 29:1335-1337. [PMID: 34499858 DOI: 10.1016/j.chom.2021.08.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Endogenous peptides and structurally similar bacterial heat-stable enterotoxins (ST) bind guanylate cyclase-C (GC-C), resulting in fluid homeostasis or diarrhea, respectively. In this issue of Cell Host & Microbe, Carey et al., show how bats have evolutionarily maintained homeostatic signaling while avoiding pathogenic effects of ST.
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Affiliation(s)
- James M Fleckenstein
- Department of Medicine, Division of Infectious Diseases, Washington University in Saint Louis, School of Medicine, 660 South Euclid Avenue, Saint Louis, MO 63110, USA; Medicine Service, Infectious Diseases, Veterans Affairs Health Care System, Saint Louis, MO 63106, USA.
| | - Jacob P Bitoun
- Department of Microbiology and Immunology, Tulane University School of Medicine, New Orleans, LA, USA
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9
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Walker R, Kaminski RW, Porter C, Choy RKM, White JA, Fleckenstein JM, Cassels F, Bourgeois L. Vaccines for Protecting Infants from Bacterial Causes of Diarrheal Disease. Microorganisms 2021; 9:1382. [PMID: 34202102 PMCID: PMC8303436 DOI: 10.3390/microorganisms9071382] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 06/16/2021] [Accepted: 06/21/2021] [Indexed: 12/22/2022] Open
Abstract
The global diarrheal disease burden for Shigella, enterotoxigenic Escherichia coli (ETEC), and Campylobacter is estimated to be 88M, 75M, and 75M cases annually, respectively. A vaccine against this target trio of enteric pathogens could address about one-third of diarrhea cases in children. All three of these pathogens contribute to growth stunting and have demonstrated increasing resistance to antimicrobial agents. Several combinations of antigens are now recognized that could be effective for inducing protective immunity against each of the three target pathogens in a single vaccine for oral administration or parenteral injection. The vaccine combinations proposed here would result in a final product consistent with the World Health Organization's (WHO) preferred product characteristics for ETEC and Shigella vaccines, and improve the vaccine prospects for support from Gavi, the Vaccine Alliance, and widespread uptake by low- and middle-income countries' (LMIC) public health stakeholders. Broadly protective antigens will enable multi-pathogen vaccines to be efficiently developed and cost-effective. This review describes how emerging discoveries for each pathogen component of the target trio could be used to make vaccines, which could help reduce a major cause of poor health, reduced cognitive development, lost economic productivity, and poverty in many parts of the world.
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Affiliation(s)
- Richard Walker
- Center for Vaccine Innovation and Access, PATH, Washington, DC 20001, USA;
| | - Robert W. Kaminski
- Department of Diarrheal Disease Research, Walter Reed Institute of Research, Silver Spring, MD 20910, USA;
| | - Chad Porter
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD 20910, USA;
| | - Robert K. M. Choy
- Center for Vaccine Innovation and Access, PATH, San Francisco, CA 94108, USA;
| | - Jessica A. White
- Center for Vaccine Innovation and Access, PATH, Seattle, WA 98121, USA; (J.A.W.); (F.C.)
| | - James M. Fleckenstein
- Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA;
- Medicine Service, Saint Louis VA Health Care System, St. Louis, MO 63106, USA
| | - Fred Cassels
- Center for Vaccine Innovation and Access, PATH, Seattle, WA 98121, USA; (J.A.W.); (F.C.)
| | - Louis Bourgeois
- Center for Vaccine Innovation and Access, PATH, Washington, DC 20001, USA;
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10
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Contribution of Noncanonical Antigens to Virulence and Adaptive Immunity in Human Infection with Enterotoxigenic E. coli. Infect Immun 2021; 89:IAI.00041-21. [PMID: 33558320 DOI: 10.1128/iai.00041-21] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 01/27/2021] [Indexed: 12/12/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) contributes significantly to the substantial burden of infectious diarrhea among children living in low- and middle-income countries. In the absence of a vaccine for ETEC, children succumb to acute dehydration as well as nondiarrheal sequelae related to these infections, including malnutrition. The considerable diversity of ETEC genomes has complicated canonical vaccine development approaches defined by a subset of ETEC pathovar-specific antigens known as colonization factors (CFs). To identify additional conserved immunogens unique to this pathovar, we employed an "open-aperture" approach to capture all potential conserved ETEC surface antigens, in which we mined the genomic sequences of 89 ETEC isolates, bioinformatically selected potential surface-exposed pathovar-specific antigens conserved in more than 40% of the genomes (n = 118), and assembled the representative proteins onto microarrays, complemented with known or putative colonization factor subunit molecules (n = 52) and toxin subunits. These arrays were then used to interrogate samples from individuals with acute symptomatic ETEC infections. Surprisingly, in this approach, we found that immune responses were largely constrained to a small number of antigens, including individual colonization factor antigens and EtpA, an extracellular adhesin. In a Bangladeshi cohort of naturally infected children <2 years of age, both EtpA and a second antigen, EatA, elicited significant serologic responses that were associated with protection from symptomatic illness. In addition, children infected with ETEC isolates bearing either etpA or eatA genes were significantly more likely to develop symptomatic disease. These studies support a role for antigens not presently targeted by vaccines (noncanonical) in virulence and the development of adaptive immune responses during ETEC infections. These findings may inform vaccine design efforts to complement existing approaches.
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11
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Zhao H, Xu Y, Li X, Li G, Zhao H, Wang L. Expression and Purification of a Recombinant Enterotoxin Protein Using Different E. coli Host Strains and Expression Vectors. Protein J 2021; 40:245-254. [PMID: 33721189 DOI: 10.1007/s10930-021-09973-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2021] [Indexed: 11/24/2022]
Abstract
Infection by Enterotoxigenic Escherichia coli is a common cause of diarrhea in animals. The development of vaccines against enterotoxins can effectively control the infection. We have previously constructed a recombinant antigen SLS fused by STa, LTB and STb enterotoxin and it showed a high immunogenicity in mice. Herein, we evaluated the expression of SLS in three different E. coli cells with corresponding plasmids. SLS proteins expressed in E. coli BL21 (DE3) and Rosetta-gami B (DE3) were aggregated as inclusion bodies, and the proteins solubility were not obviously promoted in low temperature combined with adjustment of inducer concentration. In contrast, SLS protein with maltose-binding protein (MBP) yielded from TB1 (DE3) cells were partially soluble. After increasing the IPTG concentration in the medium up to 2 mM and incubating at 37 ℃ for 4 h, the soluble protein yield reached the highest level (4.533 mg/0.2 L culture), which was significantly higher than the expression of SLS protein in Rosetta-gami B (DE3) (P < 0.05). Therefore, the TB1-pMAL expression system can be used for mass extraction and purification of SLS antigen prior to measuring its immunogenicity in pregnant mammals.
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Affiliation(s)
- Hong Zhao
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China
| | - Yongping Xu
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China.,Dalian SEM Bio-Engineering Technology Co. Ltd., Dalian, 116620, China
| | - Xiaoyu Li
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China
| | - Gen Li
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China
| | - Haofei Zhao
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China
| | - Lili Wang
- School of Bioengineering, Dalian University of Technology, Dalian, 116024, China.
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12
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Protective Immunity Against Enterotoxigenic Escherichia coli by Oral Vaccination of Engineered Lactococcus lactis. Curr Microbiol 2021; 78:3464-3473. [PMID: 34264362 PMCID: PMC8280578 DOI: 10.1007/s00284-021-02601-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 04/13/2021] [Indexed: 02/07/2023]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is one of the leading causes of diarrhea in children globally, and thus suitable vaccines are desired. Antigen display on lactic acid bacteria is a reliable approach for efficient oral vaccination and preventing bowel diseases. To develop an oral vaccine against ETEC, the gene of the binding domain from heat-labile toxin (LTB), a key ETEC virulence factor, was codon-optimized and cloned into a construct containing a signal peptide and an anchor for display on L. lactis. Bioinformatics analysis showed a codon adaptation index of 0.95 for the codon-optimized gene. Cell surface expression of LTB was confirmed by transmission electron microscopy and blotting. White New Zealand rabbits were immunized per os (PO) with the recombinant L. lactis, and the antibody titers were assayed with ELISA. In vitro neutralization assay was performed using mouse adrenal tumor cells and rabbit ileal loop test was performed as the in vivo assay. ELISA results indicated that oral administration of the engineered L. lactis elicited a significant production of IgA in the intestine. In vitro neutralization assay showed that the effect of the toxin could be neutralized with 500 µg/ml of IgG isolated from the oral vaccine group. Furthermore, the dose of ETEC causing fluid accumulation in the ileal loop test showed a tenfold increase in rabbits immunized with either recombinant L. lactis or LTB protein compared to other groups. Our results imply that recombinant L. lactis could potentially be an effective live oral vaccine against ETEC toxicity.
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Sanchez V, Rosales-Mendoza S, Monreal-Escalante E, Murillo-Álvarez JI, Angulo C. Conjugation of β-glucans on heat-stable enterotoxin (ST) to enhance the immunogenic response in mouse leucocytes. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2020; 118:111464. [PMID: 33255046 DOI: 10.1016/j.msec.2020.111464] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 08/22/2020] [Accepted: 08/26/2020] [Indexed: 11/19/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is an important diarrhea-causing pathogen for humans. Heat-stable enterotoxin (ST) plays a crucial role in triggering diarrhea and ETEC pathogenesis. However, ST is a small peptide that lacks immunogenic activity itself but becomes immunogenic when it is coupled to a carrier molecule. In this study, the β-glucans (BG) from yeasts have been used to test their immunomodulatory activity and adjuvant effect on the properties of ST. This study aimed to synthesize and characterize a conjugate of yeast-derived β-glucan with the ST enterotoxin (BG-ST) and evaluate the antigenic and antioxidant activities in mouse splenocytes. Fourier transform infrared spectroscopy and scanning electron microscopy analysis showed new bands and changes in morphology, respectively, confirming ST was successfully coupled to beta glucan. Additionally, according to the enzyme-linked immunosorbent assay (ELISA), conjugation efficiency was almost 90%. Cellular viability, phagocytic cell proportion, and respiratory burst enhanced splenocytes stimulated by BG-ST. In addition, nitric oxide production and antioxidant enzymes increased in cells stimulated with BG-ST, BG and ST. In conclusion, the results revealed the successful conjugation of β-glucan with ST peptide enhancing immune and antioxidant parameters to a greater extent than their individual components.
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Affiliation(s)
- Veronica Sanchez
- Immunology & Vaccinology Group, Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Av. Instituto Politécnico Nacional 195, Playa Palo de Santa Rita, La Paz, B.C.S. 23096, Mexico; Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Av. Sierra Leona 550, Lomas 2ª, Sección, 78210 San Luis Potosí, Mexico
| | - Sergio Rosales-Mendoza
- Sección de Biotecnología, Centro de Investigación en Ciencias de la Salud y Biomedicina, Universidad Autónoma de San Luis Potosí, San Luis Potosí, Av. Sierra Leona 550, Lomas 2ª, Sección, 78210 San Luis Potosí, Mexico
| | - Elizabeth Monreal-Escalante
- Immunology & Vaccinology Group, Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Av. Instituto Politécnico Nacional 195, Playa Palo de Santa Rita, La Paz, B.C.S. 23096, Mexico; CONACYT-Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Instituto Politécnico Nacional 195, Playa Palo de Santa Rita Sur, La Paz, B.C.S 23090, Mexico
| | - Jesús I Murillo-Álvarez
- Centro Interdisciplinario de Ciencias Marinas-IPN (CICIMAR), Avenida IPN s/n, 23096 La Paz, B.C.S., Mexico
| | - Carlos Angulo
- Immunology & Vaccinology Group, Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Av. Instituto Politécnico Nacional 195, Playa Palo de Santa Rita, La Paz, B.C.S. 23096, Mexico.
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A new human challenge model for testing heat-stable toxin-based vaccine candidates for enterotoxigenic Escherichia coli diarrhea - dose optimization, clinical outcomes, and CD4+ T cell responses. PLoS Negl Trop Dis 2019; 13:e0007823. [PMID: 31665141 PMCID: PMC6844497 DOI: 10.1371/journal.pntd.0007823] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 11/11/2019] [Accepted: 10/02/2019] [Indexed: 12/17/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) are a common cause of diarrheal illness in young children and travelers. There is yet no licensed broadly protective vaccine against ETEC. One promising vaccine development strategy is to target strains expressing the heat-stable toxin (ST), particularly the human ST (STh), since infections with these strains are among the leading causes of diarrhea in children in low-and-middle income countries. A human challenge model based on an STh-only ETEC strain will be useful to evaluate the protective efficacy of new ST-based vaccine candidates. To develop this model, we experimentally infected 21 healthy adult volunteers with the epidemiologically relevant STh-only ETEC strain TW10722, identified a suitable dose, assessed safety, and characterized clinical outcomes and immune responses caused by the infection. Doses of 1×1010 colony-forming units (CFU) of TW10722 gave a suitable attack risk of 67% for moderate or severe diarrhea and an overall diarrhea attack risk of 78%. Non-diarrheal symptoms were mostly mild or moderate, and there were no serious adverse events. During the first month after ingesting the challenge strain, we measured significant increases in both activated CD4+ T cells and levels of serum IgG and IgA antibodies targeting coli surface antigen 5 (CS5) and 6 (CS6), as well as the E. coli mucinase YghJ. The CS5-specific CD4+ T cell and antibody responses were still significantly elevated one year after experimental infection. In conclusion, we have developed a safe STh-only ETEC-based human challenge model which can be efficiently used in Phase 2B trials to evaluate the protective efficacy of new ST-based vaccine candidates. Enterotoxigenic Escherichia coli (ETEC) is a common cause of diarrheal illness in young children living in low- and middle-income countries and in travelers to these countries. Several ETEC vaccine candidates are currently being developed, but so far, no broadly protective vaccines have been licensed. Since most moderate and severe ETEC diarrheal episodes are caused by strains that express the heat-stable enterotoxin (ST), ST represents a promising vaccine target. Here we present a human challenge model that can be used to estimate the protective efficacy of ST-based vaccine candidates in clinical vaccine trials. The model is based on the epidemiologically relevant ST-only ETEC strain TW10722, which we show is safe to ingest by volunteers and readily induce diarrhea.
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Seo H, Lu T, Nandre RM, Duan Q, Zhang W. Immunogenicity characterization of genetically fused or chemically conjugated heat-stable toxin toxoids of enterotoxigenic Escherichia coli in mice and pigs. FEMS Microbiol Lett 2019; 366:5322164. [PMID: 30772899 DOI: 10.1093/femsle/fnz037] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/15/2019] [Indexed: 01/16/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) producing type Ib heat-stable toxin (STa) are a main cause of children's diarrhea and travelers' diarrhea, thus STa needs to be targeted in ETEC vaccine development. However, because this 19-amino acid STa is poorly immunogenic, attempts to genetically fuse or chemically couple it to carrier proteins have been made to enhance STa immunogenicity. In this study, we selected one genetic fusion and one chemical conjugate to comparatively evaluate STa immunogenicity. The genetic fusion is 3xSTaN12S-mnLTR192G/L211A carrying three toxoid (STaN12S) genetically fused to a double mutant LT monomer (mnLTR192G/L211A); the chemical conjugate is BSA-STaA14T, which has toxoid STaA14T chemically coupled to bovine serum albumin (BSA). We immunized mice with the STa toxoid fusion and chemical conjugates, and examined antibody responses. Furthermore, we immunized pigs and evaluated derived antibodies for efficacy to passively provide protection against ETEC diarrhea using a piglet model. Data showed that mice subcutaneously immunized with BSA-STaA14T or 3xSTaN12S-mnLTR192G/L211A developed a strong anti-STa antibody, and the induced antibodies exhibited equivalent toxin-neutralizing activities. Pigs immunized with 3xSTaN12S-mnLTR192G/L211A or BSA-STaA14T developed similar levels of anti-STa antibodies; piglets with passively acquired antibodies induced by the genetic fusion appeared better protected against STa + ETEC. Results from the current study indicate that the fusion and conjugate approaches are viable options for facilitating STa immunogenicity and developing ETEC vaccines.
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Affiliation(s)
- Hyesuk Seo
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, Kansas, USA
| | - Ti Lu
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, Kansas, USA
| | - Rahul M Nandre
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, Kansas, USA
| | - Qiangde Duan
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, Kansas, USA
| | - Weiping Zhang
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, Kansas, USA
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Immunizations with Enterotoxigenic Escherichia coli Heat-Stable Toxin Conjugates Engender Toxin-Neutralizing Antibodies in Mice That Also Cross-React with Guanylin and Uroguanylin. Infect Immun 2019; 87:IAI.00099-19. [PMID: 31061144 DOI: 10.1128/iai.00099-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 04/30/2019] [Indexed: 12/17/2022] Open
Abstract
Infection with enterotoxigenic Escherichia coli (ETEC) is a common cause of childhood diarrhea in low- and middle-income countries, as well as of diarrhea among travelers to these countries. In children, ETEC strains secreting the heat-stable toxin (ST) are the most pathogenic, and there are ongoing efforts to develop vaccines that target ST. One important challenge for ST vaccine development is to construct immunogens that do not elicit antibodies that cross-react with guanylin and uroguanylin, which are endogenous peptides involved in regulating the activity of the guanylate cyclase-C (GC-C) receptor. We immunized mice with both human ST (STh) and porcine ST (STp) chemically coupled to bovine serum albumin, and the resulting sera neutralized the toxic activities of both STh and STp. This suggests that a vaccine based on either ST variant can confer cross-protection. However, several anti-STh and anti-STp sera cross-reacted with the endogenous peptides, suggesting that the ST sequence must be altered to reduce the risk of unwanted cross-reactivity. Epitope mapping of four monoclonal anti-STh and six anti-STp antibodies, all of which neutralized both STh and STp, revealed that most epitopes appear to have at least one amino acid residue shared with guanylin or uroguanylin. Despite this, only one monoclonal antibody displayed demonstrable cross-reactivity to the endogenous peptides, suggesting that targeted mutations of a limited number of ST residues may be sufficient to obtain a safe ST-based vaccine.
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Heat-Stable Enterotoxins of Enterotoxigenic Escherichia coli and Their Impact on Host Immunity. Toxins (Basel) 2019; 11:toxins11010024. [PMID: 30626031 PMCID: PMC6356903 DOI: 10.3390/toxins11010024] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2018] [Revised: 12/31/2018] [Accepted: 01/03/2019] [Indexed: 01/12/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) are an important diarrhea-causing pathogen and are regarded as a global threat for humans and farm animals. ETEC possess several virulence factors to infect its host, including colonization factors and enterotoxins. Production of heat-stable enterotoxins (STs) by most ETEC plays an essential role in triggering diarrhea and ETEC pathogenesis. In this review, we summarize the heat-stable enterotoxins of ETEC strains from different species as well as the molecular mechanisms used by these heat-stable enterotoxins to trigger diarrhea. As recently described, intestinal epithelial cells are important modulators of the intestinal immune system. Thus, we also discuss the impact of the heat-stable enterotoxins on this role of the intestinal epithelium and how these enterotoxins might affect intestinal immune cells. Finally, the latest developments in vaccination strategies to protect against infections with ST secreting ETEC strains are discussed. This review might inform and guide future research on heat-stable enterotoxins to further unravel their molecular pathogenesis, as well as to accelerate vaccine design.
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Affiliation(s)
- Dani Cohen
- Department of Epidemiology and Preventive Medicine, School of Public Health, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Khitam Muhsen
- Department of Epidemiology and Preventive Medicine, School of Public Health, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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Akhtar M, Chowdhury MI, Bhuiyan TR, Kaim J, Ahmed T, Rafique TA, Khan A, Rahman SIA, Khanam F, Begum YA, Sharif MZ, Islam LN, Carlin N, Maier N, Fix A, Wierzba TF, Walker RI, Bourgeois AL, Svennerholm AM, Qadri F, Lundgren A. Evaluation of the safety and immunogenicity of the oral inactivated multivalent enterotoxigenic Escherichia coli vaccine ETVAX in Bangladeshi adults in a double-blind, randomized, placebo-controlled Phase I trial using electrochemiluminescence and ELISA assays for immunogenicity analyses. Vaccine 2018; 37:5645-5656. [PMID: 30473185 PMCID: PMC6717083 DOI: 10.1016/j.vaccine.2018.11.040] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/25/2018] [Accepted: 11/14/2018] [Indexed: 12/22/2022]
Abstract
The safety and immunogenicity of the second generation oral enterotoxigenic Escherichia coli (ETEC) vaccine ETVAX, consisting of inactivated recombinant E. coli strains over-expressing the colonization factors (CFs) CFA/I, CS3, CS5 and CS6 and the heat labile toxoid LCTBA, were evaluated in Bangladeshi volunteers. To enable analysis of antibody responses against multiple vaccine antigens for subsequent use in small sample volumes from children, a sensitive electrochemiluminescence (ECL) assay for analysis of intestine-derived antibody-secreting cell responses using the antibodies in lymphocyte secretions (ALS) assay was established using Meso Scale Discovery technology. Three groups of Bangladeshi adults (n = 15 per group) received two oral doses of ETVAX with or without double mutant LT (dmLT) adjuvant or placebo in the initial part of a randomized, double-blind, placebo-controlled, age-descending, dose-escalation trial. CF- and LTB-specific ALS and plasma IgA responses were analyzed by ECL and/or ELISA. ETVAX was safe and well tolerated in the adults. Magnitudes of IgA ALS responses determined by ECL and ELISA correlated well (r = 0.85 to 0.98 for the five primary antigens, P < 0.001) and ECL was selected as the ALS readout method. ALS IgA responses against each of the primary antigens were detected in 87-100% of vaccinees after the first and in 100% after the second vaccine dose. Plasma IgA responses against different CFs and LTB were observed in 62-93% and 100% of vaccinees, respectively. No statistically significant adjuvant effect of dmLT on antibody responses to any antigen was detected, but the overall antigenic breadth of the plasma IgA response tended to favor the adjuvanted vaccine when responses to 4 or more or 5 vaccine antigens were considered. Responses in placebo recipients were infrequent and mainly detected against single antigens. The promising results in adults supported testing ETVAX in descending age groups of children. ClinicalTrials.gov Identifier: NCT02531802.
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Affiliation(s)
- Marjahan Akhtar
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Mohiul I Chowdhury
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Taufiqur R Bhuiyan
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Joanna Kaim
- GUVAX (Gothenburg University Vaccine Research Institute), Dept. of Microbiology and Immunology, Inst. of Biomedicine, University of Gothenburg, Sweden
| | - Tasnuva Ahmed
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Tanzeem A Rafique
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Arifuzzaman Khan
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Sadia I A Rahman
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Farhana Khanam
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Yasmin A Begum
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Mir Z Sharif
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Laila N Islam
- Dept. of Biochemistry and Molecular Biology, University of Dhaka, Bangladesh
| | | | | | | | | | | | | | - Ann-Mari Svennerholm
- GUVAX (Gothenburg University Vaccine Research Institute), Dept. of Microbiology and Immunology, Inst. of Biomedicine, University of Gothenburg, Sweden
| | - Firdausi Qadri
- icddr,b (International Centre for Diarrhoeal Disease Research, Bangladesh), Dhaka, Bangladesh
| | - Anna Lundgren
- GUVAX (Gothenburg University Vaccine Research Institute), Dept. of Microbiology and Immunology, Inst. of Biomedicine, University of Gothenburg, Sweden.
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