1
|
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.
Collapse
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
| |
Collapse
|
2
|
Pajuelo MJ, Noazin S, Cabrera L, Toledo A, Velagic M, Arias L, Ochoa M, Moulton LH, Saito M, Gilman RH, Chakraborty S. Epidemiology of enterotoxigenic Escherichia coli and impact on the growth of children in the first two years of life in Lima, Peru. Front Public Health 2024; 12:1332319. [PMID: 38584932 PMCID: PMC10995271 DOI: 10.3389/fpubh.2024.1332319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/11/2024] [Indexed: 04/09/2024] Open
Abstract
Background Enterotoxigenic E. coli (ETEC) is a leading cause of diarrheal morbidity and mortality in children, although the data on disease burden, epidemiology, and impact on health at the community level are limited. Methods In a longitudinal birth cohort study of 345 children followed until 24 months of age in Lima, Peru, we measured ETEC burden in diarrheal and non-diarrheal samples using quantitative PCR (LT, STh, and STp toxin genes), studied epidemiology and measured anthropometry in children. Results About 70% of children suffered from one or more ETEC diarrhea episodes. Overall, the ETEC incidence rate (IR) was 73 per 100 child-years. ETEC infections began early after birth causing 10% (8.9-11.1) ETEC-attributable diarrheal burden at the population level (PAF) in neonates and most of the infections (58%) were attributed to ST-ETEC [PAF 7.9% (1.9-13.5)] and LT + ST-ETEC (29%) of which all the episodes were associated with diarrhea. ETEC infections increased with age, peaking at 17% PAF (4.6-27.7%; p = 0.026) at 21 to 24 months. ST-ETEC was the most prevalent type (IR 32.1) with frequent serial infections in a child. The common colonization factors in ETEC diarrhea cases were CFA/I, CS12, CS21, CS3, and CS6, while in asymptomatic ETEC cases were CS12, CS6 and CS21. Only few (5.7%) children had repeated infections with the same combination of ETEC toxin(s) and CFs, suggested genotype-specific immunity from each infection. For an average ETEC diarrhea episode of 5 days, reductions of 0.060 weight-for-length z-score (0.007 to 0.114; p = 0.027) and 0.061 weight-for-age z-score (0.015 to 0.108; p = 0.009) were noted in the following 30 days. Conclusion This study showed that ETEC is a significant pathogen in Peruvian children who experience serial infections with multiple age-specific pathotypes, resulting in transitory growth impairment.
Collapse
Affiliation(s)
- Monica J. Pajuelo
- Laboratorio Microbiología Molecular – Laboratorios de Investigación y Desarrollo, Facultad de Ciencias e Ingeniería, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Sassan Noazin
- Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | | | - Angie Toledo
- Laboratorio Microbiología Molecular – Laboratorios de Investigación y Desarrollo, Facultad de Ciencias e Ingeniería, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Mirza Velagic
- Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Lucero Arias
- Laboratorio Microbiología Molecular – Laboratorios de Investigación y Desarrollo, Facultad de Ciencias e Ingeniería, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Mayra Ochoa
- Laboratorio Microbiología Molecular – Laboratorios de Investigación y Desarrollo, Facultad de Ciencias e Ingeniería, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Lawrence H. Moulton
- Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Mayuko Saito
- Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Robert H. Gilman
- Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| | - Subhra Chakraborty
- Department of International Health, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, United States
| |
Collapse
|
3
|
Goto M, Yoshino S, Hiroshima K, Kawakami T, Murota K, Shimamoto S, Hidaka Y. The Molecular Basis of Heat-Stable Enterotoxin for Vaccine Development and Cancer Cell Detection. Molecules 2023; 28:molecules28031128. [PMID: 36770798 PMCID: PMC9920858 DOI: 10.3390/molecules28031128] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 01/19/2023] [Accepted: 01/20/2023] [Indexed: 01/24/2023] Open
Abstract
Heat-stable enterotoxin (STa) produced by Enterotoxigenic E. coli is responsible for causing acute diarrhea in infants in developing countries. However, the chemical synthesis of STa peptides with the native conformation and the correct intra-molecular disulfide bonds is a major hurdle for vaccine development. To address this issue, we herein report on the design and preparation of STa analogs and a convenient chemical method for obtaining STa molecules with the correct conformation. To develop an STa vaccine, we focused on a structure in a type II β-turn in the STa molecule and introduced a D-Lys residue as a conjugation site for carrier proteins. In addition, the -Glu-Leu- sequence in the STa molecule was replaced with a -Asp-Val- sequence to decrease the toxic activity of the peptide to make it more amenable for use in vaccinations. To solve several issues associated with the synthesis of STa, such as the formation of non-native disulfide isomers, the native disulfide pairings were regioselectively formed in a stepwise manner. A native form or topological isomer of the designed STa peptide, which possesses a right-handed or a left-handed spiral structure, respectively, were synthesized in high synthetic yields. The conformation of the synthetic STa peptide was also confirmed by CD and NMR spectroscopy. To further utilize the designed STa peptide, it was labeled with fluorescein for fluorescent detection, since recent studies have also focused on the use of STa for detecting cancer cells, such as Caco-2 and T84. The labeled STa peptide was able to specifically and efficiently detect 293T cells expressing the recombinant STa receptor (GC-C) protein and Caco-2 cells. The findings reported here provide an outline of the molecular basis for using STa for vaccine development and in the detection of cancer cells.
Collapse
Affiliation(s)
- Masaya Goto
- Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Shinya Yoshino
- Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Kyona Hiroshima
- Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
| | - Toru Kawakami
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Kaeko Murota
- Faculty of Life and Environmental Sciences, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan
| | - Shigeru Shimamoto
- Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
- Correspondence: (S.S.); (Y.H.); Tel.: +81-6-6721-2332 (S.S.)
| | - Yuji Hidaka
- Faculty of Science and Engineering, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka 577-8502, Japan
- Correspondence: (S.S.); (Y.H.); Tel.: +81-6-6721-2332 (S.S.)
| |
Collapse
|
4
|
Choy RKM, Bourgeois AL, Ockenhouse CF, Walker RI, Sheets RL, Flores J. Controlled Human Infection Models To Accelerate Vaccine Development. Clin Microbiol Rev 2022; 35:e0000821. [PMID: 35862754 PMCID: PMC9491212 DOI: 10.1128/cmr.00008-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The timelines for developing vaccines against infectious diseases are lengthy, and often vaccines that reach the stage of large phase 3 field trials fail to provide the desired level of protective efficacy. The application of controlled human challenge models of infection and disease at the appropriate stages of development could accelerate development of candidate vaccines and, in fact, has done so successfully in some limited cases. Human challenge models could potentially be used to gather critical information on pathogenesis, inform strain selection for vaccines, explore cross-protective immunity, identify immune correlates of protection and mechanisms of protection induced by infection or evoked by candidate vaccines, guide decisions on appropriate trial endpoints, and evaluate vaccine efficacy. We prepared this report to motivate fellow scientists to exploit the potential capacity of controlled human challenge experiments to advance vaccine development. In this review, we considered available challenge models for 17 infectious diseases in the context of the public health importance of each disease, the diversity and pathogenesis of the causative organisms, the vaccine candidates under development, and each model's capacity to evaluate them and identify correlates of protective immunity. Our broad assessment indicated that human challenge models have not yet reached their full potential to support the development of vaccines against infectious diseases. On the basis of our review, however, we believe that describing an ideal challenge model is possible, as is further developing existing and future challenge models.
Collapse
Affiliation(s)
- Robert K. M. Choy
- PATH, Center for Vaccine Innovation and Access, Seattle, Washington, USA
| | - A. Louis Bourgeois
- PATH, Center for Vaccine Innovation and Access, Seattle, Washington, USA
| | | | - Richard I. Walker
- PATH, Center for Vaccine Innovation and Access, Seattle, Washington, USA
| | | | - Jorge Flores
- PATH, Center for Vaccine Innovation and Access, Seattle, Washington, USA
| |
Collapse
|
5
|
Porter CK, Talaat KR, Isidean SD, Kardinaal A, Chakraborty S, Gutiérrez RL, Sack DA, Bourgeois AL. The Controlled Human Infection Model for Enterotoxigenic Escherichia coli. Curr Top Microbiol Immunol 2021. [PMID: 34669040 DOI: 10.1007/82_2021_242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The controlled human infection model (CHIM) for enterotoxigenic Escherichia coli (ETEC) has been instrumental in defining ETEC as a causative agent of acute watery diarrhea, providing insights into disease pathogenesis and resistance to illness, and enabling preliminary efficacy evaluations for numerous products including vaccines, immunoprophylactics, and drugs. Over a dozen strains have been evaluated to date, with a spectrum of clinical signs and symptoms that appear to replicate the clinical illness seen with naturally occurring ETEC. Recent advancements in the ETEC CHIM have enhanced the characterization of clinical, immunological, and microbiological outcomes. It is anticipated that omics-based technologies applied to ETEC CHIMs will continue to broaden our understanding of host-pathogen interactions and facilitate the development of primary and secondary prevention strategies.
Collapse
Affiliation(s)
- Chad K Porter
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA.
| | - Kawsar R Talaat
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD, 21205, USA
| | - Sandra D Isidean
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA
- Henry M. Jackson Foundation, Bethesda, MD, 20817, USA
| | - Alwine Kardinaal
- NIZO Food Research, Ede, P.O. Box 20, 6710 BA EDE, Kernhemseweg 2, 6718 ZB EDE, The Netherlands
| | - Subhra Chakraborty
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD, 21205, USA
| | - Ramiro L Gutiérrez
- Enteric Diseases Department, Naval Medical Research Center, Silver Spring, MD, 20910, USA
| | - David A Sack
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, 615 N. Wolfe Street, Baltimore, MD, 21205, USA
| | - A Louis Bourgeois
- PATH|Center for Vaccine Innovation and Access, 455 Massachusetts Avenue NW, Suite 1000, Washington, DC, 20001, USA
| |
Collapse
|
6
|
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.
Collapse
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;
| |
Collapse
|
7
|
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.
Collapse
|
8
|
Govasli ML, Diaz Y, Puntervoll P. Virus-like particle-display of the enterotoxigenic Escherichia coli heat-stable toxoid STh-A14T elicits neutralizing antibodies in mice. Vaccine 2019; 37:6405-6414. [PMID: 31515145 DOI: 10.1016/j.vaccine.2019.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 08/30/2019] [Accepted: 09/02/2019] [Indexed: 10/26/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) causes diarrhoea by secreting enterotoxins into the small intestine. Human ETEC strains may secrete any combination of three enterotoxins: the heat-labile toxin (LT) and the heat-stable toxins (ST), of which there are two variants, called human ST (STh) and porcine ST (STp). Strains expressing STh, either alone or in combination with LT and/or STp, are among the four most important diarrhoea-causing pathogens affecting children in low- and middle-income countries. ST is therefore an attractive target for ETEC vaccine development. To produce a safe ST-based vaccine, several challenges must be solved. ST must be rendered immunogenic and non-toxic, and antibodies elicited by an ST vaccine should neutralize ST but not cross-react with the endogenous ligands uroguanylin and guanylin. Virus-like particles (VLPs) tend to be highly immunogenic and are increasingly being used as carriers for presenting heterologous antigens in new vaccines. In this study, we have coupled native STh and the STh-A14T toxoid to the coat protein of Acinetobacter phage AP205 by using the SpyCatcher system and immunized mice with these VLPs without the use of adjuvants. We found that both STs were efficiently coupled to the VLP, that both the STh and STh-A14T VLPs were immunogenic in mice, and that the resulting serum antibodies could completely neutralize the toxic activities of native STh. The serum antibodies showed a high degree of immunological cross-reaction to STp, while there was little or no unwanted cross-reaction to uroguanylin and guanylin. Moreover, compared to native STh, the STh-A14T mutation did not seem to negatively impact the immunogenicity of the construct or the neutralizing ability of the resulting sera. Taken together, these findings demonstrate that VLPs are suitable carriers for making STs immunogenic, and that the STh-A14T-coupled AP205 VLP represents a promising ETEC vaccine candidate.
Collapse
Affiliation(s)
- Morten L Govasli
- NORCE Norwegian Research Centre, Postboks 22 Nygårdstangen, 5838 Bergen, Norway
| | - Yuleima Diaz
- NORCE Norwegian Research Centre, Postboks 22 Nygårdstangen, 5838 Bergen, Norway
| | - Pål Puntervoll
- NORCE Norwegian Research Centre, Postboks 22 Nygårdstangen, 5838 Bergen, Norway; Centre for International Health, Department of Global Public Health and Primary Care, University of Bergen, Postboks 7804, 5020 Bergen, Norway.
| |
Collapse
|
9
|
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.
Collapse
|
10
|
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.
Collapse
|
11
|
Ran X, Chen X, Wang S, Chang C, Wen X, Zhai J, Ni H. Preparation of porcine enterotoxigenic Escherichia coli (ETEC) ghosts and immunogenic analysis in a mouse model. Microb Pathog 2018; 126:224-230. [PMID: 30428380 DOI: 10.1016/j.micpath.2018.11.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 11/08/2018] [Accepted: 11/09/2018] [Indexed: 01/23/2023]
Abstract
Enterotoxignenic Escherichia coli (ETEC)-associated colibacillosis causes high levels of morbidity and mortality in neonatal piglets. Vaccination is among effective strategy to fight against ETEC-related diseases. Bacterial ghosts (BGs) are empty bacterial envelopes, which substain subtle antigenic comformation in bacterial outer membrane. In this study, a BG vaccine was generated using porcine ETEC isolated strain DQ061 and evaluated its safety and immunogenicity in a mouse model. The recombinant bacteria were constructed by transformation of lysis plasmid pHH43 and generation of BGs was conducted in a lysis rate of 99.93% by incubation of the recombinant bacteria at 42 °C for 2 h. Mice were immunized subcutaneously twice in 2-week intervals with BGs, BGs emulsified with ISA 206 adjuvant, or formalin-inactivated ETEC vaccine after safety test. Mice with either of two BG vaccines developed higher titer of antibodies, secreted higher titer of interleukin 4, gamma interferon and alpha tumor necrosis factor after 2 doses than those with formalin-inactivated ETEC vaccine or those with adjuvant placebo (P < 0.01). The quantity of CD4+ and CD8+ T lymphocyte in spleen was higher in both BG groups than that in the inactivated vaccine group or adjuvant group 2 weeks post boost immunization (P < 0.05). The vaccinated mice were challenged intraperitoneally with 10 × LD50 dose of DQ061. Mice with the BGs plus adjuvant were completely protected against challenge, compared to 60% protection of mice with the inactivated vaccine. Mice exhibited decreased tissue lesion and reduced bacterial loads in the BGs groups by comparison with those with the inactivated vaccine or adjuvant only. Our results validated that the ETEC BGs bear high safety and immunogenicity in a mouse model, suggesting a potential of further evaluation in a pig model.
Collapse
Affiliation(s)
- Xuhua Ran
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Xiaohong Chen
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Shixia Wang
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Chunlong Chang
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Xiaobo Wen
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Junjun Zhai
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China
| | - Hongbo Ni
- College of Animal Science & Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province, 163319, China.
| |
Collapse
|