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Monteiro R, Chafsey I, Caccia N, Ageorges V, Leroy S, Viala D, Hébraud M, Livrelli V, Pizza M, Pezzicoli A, Desvaux M. Specific Proteomic Identification of Collagen-Binding Proteins in Escherichia coli O157:H7: Characterisation of OmpA as a Potent Vaccine Antigen. Cells 2023; 12:1634. [PMID: 37371104 DOI: 10.3390/cells12121634] [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: 03/24/2023] [Revised: 06/02/2023] [Accepted: 06/09/2023] [Indexed: 06/29/2023] Open
Abstract
Escherichia coli is a versatile commensal species of the animal gut that can also be a pathogen able to cause intestinal and extraintestinal infections. The plasticity of its genome has led to the evolution of pathogenic strains, which represent a threat to global health. Additionally, E. coli strains are major drivers of antibiotic resistance, highlighting the urgent need for new treatment and prevention measures. The antigenic and structural heterogeneity of enterohaemorrhagic E. coli colonisation factors has limited their use for the development of effective and cross-protective vaccines. However, the emergence of new strains that express virulence factors deriving from different E. coli diarrhoeagenic pathotypes suggests that a vaccine targeting conserved proteins could be a more effective approach. In this study, we conducted proteomics analysis and functional protein characterisation to identify a group of proteins potentially involved in the adhesion of E. coli O157:H7 to the extracellular matrix and intestinal epithelial cells. Among them, OmpA has been identified as a highly conserved and immunogenic antigen, playing a significant role in the adhesion phenotype of E. coli O157:H7 and in bacterial aggregation. Furthermore, antibodies raised against recombinant OmpA effectively reduced the adhesion of E. coli O157:H7 to intestinal epithelial cells. The present work highlights the role of OmpA as a potent antigen for the development of a vaccine against intestinal pathogenic E. coli.
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Affiliation(s)
- Ricardo Monteiro
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
- GSK, 53100 Siena, Italy
- Instituto de Investigação e Inovação em Saúde-i3S, Universidade do Porto, 4150-564 Porto, Portugal
| | - Ingrid Chafsey
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
| | - Nelly Caccia
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
| | | | - Sabine Leroy
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
| | - Didier Viala
- INRAE, Metabolism Exploration Platform, Proteomic Component (PFEMcp), 63122 Saint-Genès Champanelle, France
| | - Michel Hébraud
- INRAE, UCA, UMR0454 MEDIS, 63000 Clermont-Ferrand, France
- INRAE, Metabolism Exploration Platform, Proteomic Component (PFEMcp), 63122 Saint-Genès Champanelle, France
| | | | - Mariagrazia Pizza
- GSK, 53100 Siena, Italy
- Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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2
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Bashir S, Fitaihi R, Abdelhakim HE. Advances in formulation and manufacturing strategies for the delivery of therapeutic proteins and peptides in orally disintegrating dosage forms. Eur J Pharm Sci 2023; 182:106374. [PMID: 36623699 DOI: 10.1016/j.ejps.2023.106374] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 01/08/2023]
Abstract
Therapeutic proteins and peptides (TPPs) are increasingly favoured above small drug molecules due to their high specificity to the site of action and reduced adverse effects resulting in increased use of these agents for medical treatments and therapies. Consequently, there is a need to formulate TPPs in dosage forms that are accessible and suitable for a wide range of patient groups as the use of TPPs becomes increasingly prevalent in healthcare settings worldwide. Orally disintegrating dosage forms (ODDF) are formulations that can ensure easy-to-administer medication to a wider patient population including paediatrics, geriatrics and people in low-resource countries. There are many challenges involved in developing suitable pharmaceutical strategies to protect TPPs during formulation and manufacturing, as well as storage, and maintenance of a cold-chain during transportation. This review will discuss advances being made in the research and development of pharmaceutical and manufacturing strategies used to incorporate various TPPs into ODDF systems.
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Affiliation(s)
- Shazia Bashir
- School of Cancer and Pharmaceutical Sciences, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK
| | - Rawan Fitaihi
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK; Department of Pharmaceutics, College of pharmacy, King Saud University, Riyadh, KSA
| | - Hend E Abdelhakim
- Department of Pharmaceutics, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK.
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Pokharel P, Dhakal S, Dozois CM. The Diversity of Escherichia coli Pathotypes and Vaccination Strategies against This Versatile Bacterial Pathogen. Microorganisms 2023; 11:344. [PMID: 36838308 PMCID: PMC9965155 DOI: 10.3390/microorganisms11020344] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2023] [Revised: 01/24/2023] [Accepted: 01/25/2023] [Indexed: 02/03/2023] Open
Abstract
Escherichia coli (E. coli) is a gram-negative bacillus and resident of the normal intestinal microbiota. However, some E. coli strains can cause diseases in humans, other mammals and birds ranging from intestinal infections, for example, diarrhea and dysentery, to extraintestinal infections, such as urinary tract infections, respiratory tract infections, meningitis, and sepsis. In terms of morbidity and mortality, pathogenic E. coli has a great impact on public health, with an economic cost of several billion dollars annually worldwide. Antibiotics are not usually used as first-line treatment for diarrheal illness caused by E. coli and in the case of bloody diarrhea, antibiotics are avoided due to the increased risk of hemolytic uremic syndrome. On the other hand, extraintestinal infections are treated with various antibiotics depending on the site of infection and susceptibility testing. Several alarming papers concerning the rising antibiotic resistance rates in E. coli strains have been published. The silent pandemic of multidrug-resistant bacteria including pathogenic E. coli that have become more difficult to treat favored prophylactic approaches such as E. coli vaccines. This review provides an overview of the pathogenesis of different pathotypes of E. coli, the virulence factors involved and updates on the major aspects of vaccine development against different E. coli pathotypes.
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Affiliation(s)
- Pravil Pokharel
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), 531 Boul des Prairies, Laval, QC H7V 1B7, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Faculté de Médecine Vétérinaire, Université de Montréal Saint-Hyacinthe, Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Sabin Dhakal
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), 531 Boul des Prairies, Laval, QC H7V 1B7, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Faculté de Médecine Vétérinaire, Université de Montréal Saint-Hyacinthe, Saint-Hyacinthe, QC J2S 2M2, Canada
| | - Charles M. Dozois
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), 531 Boul des Prairies, Laval, QC H7V 1B7, Canada
- Centre de Recherche en Infectiologie Porcine et Avicole (CRIPA), Faculté de Médecine Vétérinaire, Université de Montréal Saint-Hyacinthe, Saint-Hyacinthe, QC J2S 2M2, Canada
- Pasteur Network, Laval, QC H7V 1B7, Canada
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Upadhyay I, Lauder KL, Li S, Ptacek G, Zhang W. Intramuscularly Administered Enterotoxigenic Escherichia coli (ETEC) Vaccine Candidate MecVax Prevented H10407 Intestinal Colonization in an Adult Rabbit Colonization Model. Microbiol Spectr 2022; 10:e0147322. [PMID: 35762781 PMCID: PMC9431210 DOI: 10.1128/spectrum.01473-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 06/14/2022] [Indexed: 11/20/2022] Open
Abstract
Currently, there are no vaccines licensed for enterotoxigenic Escherichia coli (ETEC), a leading cause of children's diarrhea in developing countries and the most common cause of travelers' diarrhea. A vaccine preventing ETEC bacteria from colonization at small intestines and neutralizing enterotoxin toxicity is expected to be effective against ETEC diarrhea. Protein-based multivalent vaccine candidate MecVax was demonstrated recently to induce antibodies neutralizing heat-labile toxin (LT) and heat-stable toxin (STa) enterotoxicity and inhibiting adherence of seven ETEC adhesins (CFA/I, CS1 to CS6) but also to protect against ETEC toxin-mediated clinical diarrhea in a pig challenge model. To further evaluate MecVax preclinical efficacy against ETEC colonization at small intestines, in this study, we intramuscularly immunized adult rabbits with MecVax, challenged rabbits with ETEC strain H10407 (CFA/I, LT, STa), and examined prevention of bacteria intestinal colonization. Data showed that rabbits immunized with MecVax developed antibodies to both ETEC toxins (LT, STa) and seven adhesins (CFA/I, CS1 to CS6) and had over 99.9% reduction of H10407 intestinal colonization, indicating that the broadly immunogenic ETEC vaccine candidate MecVax is protective against ETEC H10407 intestinal colonization. This study also confirmed that parenteral administration of a protein-based vaccine can prevent bacteria intestinal colonization. Protection against ETEC intestinal colonization demonstrated by this rabbit study, in conjugation with protection against ETEC enterotoxin-mediated clinical diarrhea from a previous pig challenge study, suggested that MecVax can potentially be an effective ETEC vaccine and a combined pig and rabbit challenge model can evaluate ETEC vaccine preclinical efficacy. IMPORTANCE An effective ETEC vaccine would prevent hundreds of millions of diarrhea clinical cases and save nearly 100,000 lives annually. MecVax, a protein-based injectable multivalent ETEC vaccine candidate, has been shown for the first time to induce functional antibodies against both ETEC enterotoxins (STa, LT) produced by all ETEC strains and seven ETEC adhesins (CFA/I, CS1 to CS6) expressed by ETEC strains causing a majority of ETEC diarrhea clinical cases and the moderate-to-severe cases. Moreover, MecVax was demonstrated to protect against ETEC STa or LT toxin-mediated diarrhea in a pig model. If it also protects against ETEC intestinal colonization, MecVax can be validated as an effective ETEC vaccine candidate. This adult rabbit colonization model study showed that intramuscular administration of MecVax effectively prevented intestinal colonization by H10407, perhaps the most virulent ETEC strain, affirming MecVax vaccine candidacy and accelerating vaccine development against ETEC children's diarrhea and travelers' diarrhea.
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Affiliation(s)
- Ipshita Upadhyay
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
| | - Kathryn L. Lauder
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
| | - Siqi Li
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
| | - Galen Ptacek
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
| | - Weiping Zhang
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
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Fleckenstein JM. Confronting challenges to enterotoxigenic Escherichia coli vaccine development. FRONTIERS IN TROPICAL DISEASES 2021; 2:709907. [PMID: 35937717 PMCID: PMC9355458 DOI: 10.3389/fitd.2021.709907] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/02/2023] Open
Abstract
The enterotoxigenic Escherichia coli (ETEC) are a diverse and genetically plastic pathologic variant (pathovar) of E. coli defined by their production of heat-labile (LT) and heat-stable (ST) enterotoxins. These pathogens, which came to recognition more than four decades ago in patients presenting with severe cholera-like diarrhea, are now known to cause hundreds of millions of cases of symptomatic infection annually. Children in low-middle income regions of the world lacking access to clean water and basic sanitation are disproportionately affected by ETEC. In addition to acute diarrheal morbidity, these pathogens remain a significant cause of mortality in children under the age of five years and have also been linked repeatedly to sequelae of childhood malnutrition and growth stunting. Vaccines that could prevent ETEC infections therefore remain a high priority. Despite several decades of effort, a licensed vaccine that protects against the breadth of these pathogens remains an aspirational goal, and the underlying genetic plasticity of E. coli has posed a fundamental challenge to development of a vaccine that can encompass the complete antigenic spectrum of ETEC. Nevertheless, novel strategies that include toxoids, a more complete understanding of ETEC molecular pathogenesis, structural details of target immunogens, and the discovery of more highly conserved antigens essential for virulence should accelerate progress and make a broadly protective vaccine feasible.
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Affiliation(s)
- James M. Fleckenstein
- Department of Medicine, Division of Infectious Diseases, Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri, USA
- Medicine Service, Infectious Diseases, John Cochran Saint Louis Veterans Affairs Health Care System, Saint Louis, Missouri, USA
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6
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Zhao Z, Ma X, Zhang R, Hu F, Zhang T, Liu Y, Han MH, You F, Yang Y, Zheng W. A novel liposome-polymer hybrid nanoparticles delivering a multi-epitope self-replication DNA vaccine and its preliminary immune evaluation in experimental animals. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2020; 35:102338. [PMID: 33197626 PMCID: PMC7664365 DOI: 10.1016/j.nano.2020.102338] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/06/2020] [Accepted: 11/04/2020] [Indexed: 12/12/2022]
Abstract
DNA vaccine is an attractive immune platform for the prevention and treatment of infectious diseases, but existing disadvantages limit its use in preclinical and clinical assays, such as weak immunogenicity and short half-life. Here, we reported a novel liposome-polymer hybrid nanoparticles (pSFV-MEG/LNPs) consisting of a biodegradable core (mPEG-PLGA) and a hydrophilic shell (lecithin/PEG-DSPE-Mal 2000) for delivering a multi-epitope self-replication DNA vaccine (pSFV-MEG). The pSFV-MEG/LNPs with optimal particle size (161.61 ± 15.63 nm) and high encapsulation efficiency (87.60 ± 8.73%) induced a strong humoral (3.22-fold) and cellular immune responses (1.60-fold) compared to PBS. Besides, the humoral and cellular immune responses of pSFV-MEG/LNPs were 1.58- and 1.05-fold than that of pSFV-MEG. All results confirmed that LNPs was a very promising tool to enhance the humoral and cellular immune responses of pSFV-MEG. In addition, the rational design and delivery platform can be used for the development of DNA vaccines for other infectious diseases.
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Affiliation(s)
- Zhangting Zhao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China
| | - Xingyuan Ma
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China
| | - Ruihuan Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China
| | - Fabiao Hu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China
| | - Tong Zhang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, PR China
| | - Yuping Liu
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, PR China
| | - Myong Hun Han
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, PR China; Department of Genetics, Faculty of Life Science, KIM IL SUNG University, Pyongyang, Democratic People's Republic of Korea
| | - Fang You
- Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore
| | - Yi Yang
- SinGENE Biotech Pte Ltd, Singapore Science Park, Singapore 118258, Singapore.
| | - Wenyun Zheng
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, Shanghai, PR China.
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7
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Abstract
Enteric viral and bacterial infections continue to be a leading cause of mortality and morbidity in young children in low-income and middle-income countries, the elderly, and immunocompromised individuals. Vaccines are considered an effective and practical preventive approach against the predominantly fecal-to-oral transmitted gastroenteritis particularly in the resource-limited countries or regions where implementation of sanitation systems and supply of safe drinking water are not quickly achievable. While vaccines are available for a few enteric pathogens including rotavirus and cholera, there are no vaccines licensed for many other enteric viral and bacterial pathogens. Challenges in enteric vaccine development include immunological heterogeneity among pathogen strains or isolates, a lack of animal challenge models to evaluate vaccine candidacy, undefined host immune correlates to protection, and a low protective efficacy among young children in endemic regions. In this article, we briefly updated the progress and challenges in vaccines and vaccine development for the leading enteric viral and bacterial pathogens including rotavirus, human calicivirus, Shigella, enterotoxigenic Escherichia coli (ETEC), cholera, nontyphoidal Salmonella, and Campylobacter, and introduced a novel epitope- and structure-based vaccinology platform known as MEFA (multiepitope fusion antigen) and the application of MEFA for developing broadly protective multivalent vaccines against heterogenous pathogens.
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Affiliation(s)
- Hyesuk Seo
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
| | - Qiangde Duan
- University of Yangzhou, Institute of Comparative Medicine, Yangzhou, PR China
| | - Weiping Zhang
- University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA,CONTACT Weiping Zhang, University of Illinois at Urbana-Champaign, Department of Pathobiology, Urbana, Illinois, USA
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8
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Booster vaccination with a fractional dose of an oral cholera vaccine induces comparable vaccine-specific antibody avidity as a full dose: A randomised clinical trial. Vaccine 2020; 38:655-662. [DOI: 10.1016/j.vaccine.2019.10.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 10/16/2019] [Accepted: 10/17/2019] [Indexed: 01/06/2023]
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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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Interrogation of a live-attenuated enterotoxigenic Escherichia coli vaccine highlights features unique to wild-type infection. NPJ Vaccines 2019; 4:37. [PMID: 31482013 PMCID: PMC6713706 DOI: 10.1038/s41541-019-0131-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 08/01/2019] [Indexed: 01/01/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) infections are a common cause of severe diarrheal illness in low- and middle-income countries. The live-attenuated ACE527 ETEC vaccine, adjuvanted with double mutant heat-labile toxin (dmLT), affords clear but partial protection against ETEC challenge in human volunteers. Comparatively, initial wild-type ETEC challenge completely protects against severe diarrhea on homologous re-challenge. To investigate determinants of protection, vaccine antigen content was compared to wild-type ETEC, and proteome microarrays were used to assess immune responses following vaccination and ETEC challenge. Although molecular interrogation of the vaccine confirmed expression of targeted canonical antigens, relative to wild-type ETEC, vaccine strains were deficient in production of flagellar antigens, immotile, and lacked production of the EtpA adhesin. Similarly, vaccination ± dmLT elicited responses to targeted canonical antigens, but relative to wild-type challenge, vaccine responses to some potentially protective non-canonical antigens including EtpA and the YghJ metalloprotease were diminished or absent. These studies highlight important differences in vaccine and wild-type ETEC antigen content and call attention to distinct immunologic signatures that could inform investigation of correlates of protection, and guide vaccine antigen selection for these pathogens of global importance. Adjuvanted ACE527 is an experimental oral live-attenuated vaccine for enterotoxigenic E. coli (ETEC) but has been shown to elicit only partial protection. James M. Fleckenstein and colleagues perform a genomic and proteomic characterization of ACE527 and compare it to H10407 – a wildtype virulent strain of E. coli that can generate fully protective acquired immunity. While sharing many canonical antigens with wild-type ETEC, the attenuated E. coli strains composing ACE527 lack a number of critical characteristics, in particular they lack core components of the flagellar machinery or the adhesin EtpA and are immotile. Accordingly, and in contrast to wildtype challenge, vaccination with ACE527 fails to elicit robust antibody responses to these non-canonical antigens and this might underpin the incomplete protection afforded by this vaccine.
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11
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Chakraborty S, Brubaker J, Harro C, Weirzba T, Sack D. Development of a novel multiplex electrochemiluminescent-based immunoassay to aid enterotoxigenic Escherichia coli vaccine development and evaluations. J Immunol Methods 2019; 470:6-14. [PMID: 31004579 PMCID: PMC6538825 DOI: 10.1016/j.jim.2019.04.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 03/10/2019] [Accepted: 04/16/2019] [Indexed: 12/30/2022]
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a leading cause of bacterial diarrhea both among children in low and middle income countries and in travelers to these regions. Although there are several approaches to develop an effective vaccine for ETEC, no licensed vaccines are currently available. The most advanced ETEC vaccine candidates include multiple colonization factors along with the heat labile toxin B subunit. In the absence of known correlates of protection, and to understand the mechanism of protection, monitoring immune responses to a majority of the vaccine associated antigens using various types of samples is needed. Unfortunately, a traditional ELISA is time consuming, labor intensive and requires substantial amounts of antigens and sample volumes. To address these constraints, we developed and validated a novel high throughput electrochemiluminescent (ECL) - based multiplex immunoassay using Meso Scale Discovery (MSD) platform for analyzing immune responses to ETEC antigens. The ETEC multiplex ECL assay is an 8-plex assay which includes the ETEC colonization factor antigens (CFA/I, CS1, CS2, CS3, CS5 and CS6) along with the two subunits of heat labile toxin (LTA and LTB). Our data suggested that a single dilution of sample provides a quantifiable result for a wide range of sample titers. To compare ETEC multiplex ECL with ELISA, we carried out assays using the same antigens with the two immunoassay platforms using a common sample set of serum and ALS (antibodies in lymphocyte supernatant) specimens. The MSD platform achieved excellent correlations with ELISA for the antigens tested, consistently detecting comparable antibody levels in the samples. The ETEC multiplex ECL can serve as a fundamental platform in evaluating performances of candidate ETEC vaccines in future field trials. A novel ETEC multiplex ECL assay was developed which achieved excellent correlations with conventional ELISA. ETEC multiplex ECL assay would minimize volumes of samples and antigens as well as save time and labor. The ETEC multiplex assay could serve as an improved platform for evaluation of candidate ETEC vaccines.
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Affiliation(s)
- Subhra Chakraborty
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
| | - Jessica Brubaker
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Clayton Harro
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - David Sack
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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12
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Harro C, Louis Bourgeois A, Sack D, Walker R, DeNearing B, Brubaker J, Maier N, Fix A, Dally L, Chakraborty S, Clements JD, Saunders I, Darsley MJ. Live attenuated enterotoxigenic Escherichia coli (ETEC) vaccine with dmLT adjuvant protects human volunteers against virulent experimental ETEC challenge. Vaccine 2019; 37:1978-1986. [PMID: 30797634 PMCID: PMC6434318 DOI: 10.1016/j.vaccine.2019.02.025] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 02/12/2019] [Accepted: 02/14/2019] [Indexed: 01/10/2023]
Abstract
Background There is no licensed vaccine against enterotoxigenic Escherichia coli (ETEC), a major cause of diarrhea-associated morbidity and mortality among infants and children in low-income countries and travelers. The results of this vaccination/challenge study demonstrate strong protection by an attenuated ETEC vaccine candidate, ACE527, when co-administered with a mucosal adjuvant, the double-mutant heat-labile toxin (dmLT) of ETEC. Methods Sixty healthy adults participated in a randomized, placebo-controlled, double-blind study with three doses of lyophilized ACE527 (∼3 × 109 of each strain per dose) administered orally with or without dmLT adjuvant (25 µg/dose). Six months later, 36 of these volunteers and a control group of 21 unvaccinated volunteers were challenged with virulent ETEC strain H10407. The primary outcome was severe diarrhea, defined as passing >800 g of unformed stools during the inpatient period following challenge. Findings The vaccine was well tolerated and induced robust immune responses to key antigens. The protective efficacy (PE) against the primary outcome of severe diarrhea was 65.9% (95% confidence interval [CI] 5.4–87.7, p = 0.003). Among subjects receiving the adjuvanted vaccine, the attack rate of severe diarrhea was 23.1, while in unimmunized controls it was 67.7%. The PE against diarrhea of any severity was 58.5% (95% CI 3.8– 82.1, p = 0.016). There was a strong inverse correlation between shedding of the vaccine strain after either of the first two doses and absence of severe diarrhea upon challenge (RR = 0.29, 95% CI 0.08–1.05, p = 0.041). Challenge strain shedding was 10-fold lower in those receiving the adjuvant than in those receiving vaccine alone. The unadjuvanted vaccine was not protective (PE = 23.1%). Interpretation The results of this study support further development of ACE527 + dmLT as a vaccine for children in endemic countries and travelers. This is the first clinical demonstration that dmLT can contribute significantly to vaccine efficacy and may warrant testing with other oral vaccines. (ClinicalTrials.gov registration: NCT01739231).
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Affiliation(s)
- Clayton Harro
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - David Sack
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - Barbara DeNearing
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Jessica Brubaker
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | | | - Len Dally
- The Emmes Corporation, Rockville, MD, USA
| | - Subhra Chakraborty
- Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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13
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Kumar P, Kuhlmann FM, Chakraborty S, Bourgeois AL, Foulke-Abel J, Tumala B, Vickers TJ, Sack DA, DeNearing B, Harro CD, Wright WS, Gildersleeve JC, Ciorba MA, Santhanam S, Porter CK, Gutierrez RL, Prouty MG, Riddle MS, Polino A, Sheikh A, Donowitz M, Fleckenstein JM. Enterotoxigenic Escherichia coli-blood group A interactions intensify diarrheal severity. J Clin Invest 2018; 128:3298-3311. [PMID: 29771685 DOI: 10.1172/jci97659] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 05/03/2018] [Indexed: 12/27/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) infections are highly prevalent in developing countries, where clinical presentations range from asymptomatic colonization to severe cholera-like illness. The molecular basis for these varied presentations, which may involve strain-specific virulence features as well as host factors, has not been elucidated. We demonstrate that, when challenged with ETEC strain H10407, originally isolated from a case of cholera-like illness, blood group A human volunteers developed severe diarrhea more frequently than individuals from other blood groups. Interestingly, a diverse population of ETEC strains, including H10407, secrete the EtpA adhesin molecule. As many bacterial adhesins also agglutinate red blood cells, we combined the use of glycan arrays, biolayer inferometry, and noncanonical amino acid labeling with hemagglutination studies to demonstrate that EtpA is a dominant ETEC blood group A-specific lectin/hemagglutinin. Importantly, we have also shown that EtpA interacts specifically with glycans expressed on intestinal epithelial cells from blood group A individuals and that EtpA-mediated bacterial-host interactions accelerate bacterial adhesion and effective delivery of both the heat-labile and heat-stable toxins of ETEC. Collectively, these data provide additional insight into the complex molecular basis of severe ETEC diarrheal illness that may inform rational design of vaccines to protect those at highest risk.
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Affiliation(s)
- Pardeep Kumar
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - F Matthew Kuhlmann
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Subhra Chakraborty
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - A Louis Bourgeois
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Jennifer Foulke-Abel
- Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Brunda Tumala
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Tim J Vickers
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA
| | - David A Sack
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Barbara DeNearing
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Clayton D Harro
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - W Shea Wright
- Center for Cancer Research, Chemical Biology Laboratory, National Cancer Institute, Fredrick, Maryland, USA
| | - Jeffrey C Gildersleeve
- Center for Cancer Research, Chemical Biology Laboratory, National Cancer Institute, Fredrick, Maryland, USA
| | - Matthew A Ciorba
- Department of Medicine, Division of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Srikanth Santhanam
- Department of Medicine, Division of Gastroenterology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Chad K Porter
- Enteric Disease Department, Infectious Disease Directorate, Naval Medical Research Center, Silver Spring, Maryland, USA
| | - Ramiro L Gutierrez
- Enteric Disease Department, Infectious Disease Directorate, Naval Medical Research Center, Silver Spring, Maryland, USA
| | - Michael G Prouty
- Enteric Disease Department, Infectious Disease Directorate, Naval Medical Research Center, Silver Spring, Maryland, USA
| | - Mark S Riddle
- Enteric Disease Department, Infectious Disease Directorate, Naval Medical Research Center, Silver Spring, Maryland, USA
| | - Alexander Polino
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Alaullah Sheikh
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Mark Donowitz
- Department of Medicine, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - James M Fleckenstein
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, USA.,Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri, USA.,Medicine Service, Veterans Affairs Medical Center, St. Louis, Missouri, USA
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14
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Hitch G, Fleming N. Antibiotic resistance in travellers' diarrhoeal disease, an external perspective. J Travel Med 2018; 25:S27-S37. [PMID: 29718437 DOI: 10.1093/jtm/tay014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 02/08/2018] [Indexed: 01/31/2023]
Abstract
BACKGROUND There are many recommendations on the use of antibiotics for prophylaxis and treatment of travellers' diarrhoea (TD). As pharmacists with a special interest in antimicrobial stewardship, we examine and offer our perspective on advice that is recommended to travellers in terms of prevention, treatment and management of TD with a focus on antibiotic use and resistance. METHODS Publications on TD were identified through PubMed, Google Scholar and Cochrane Library databases searches using search terms 'travellers diarrhoea', 'travellers diarrhoea', 'travellers' diarrhoea' 'guidelines', 'expert opinion', 'expert reviews', 'South Asia' and 'South East Asia' (S and SE Asia), 'antibiotics', 'resistance genes', 'travel advice', 'pharmacists', 'guidelines', 'prevention' and 'treatment'. References of articles were also screened for additional relevant studies. RESULTS Whilst most guidelines and expert reviews were in agreement with the restricted use of antibiotics unless there was a clinical need, the literature review identified gaps in research into behaviours of travellers regarding non-compliance with the pre-travel advice provided and the need for in depth training and education for all healthcare professionals in providing 'tailored' advice for travellers going to high-risk destinations. CONCLUSIONS Travellers should be made aware of the problems of antimicrobial resistance in their destination and home countries and offered alternative forms of prophylaxis for TD. Strategies for prevention of TD, other than the use of antibiotics, also need to be emphasized. All healthcare professionals involved in giving advice about TD should be familiar with the epidemiology of the condition as this will inform responsible behaviours, risk assessment and management strategies in different geographical areas.
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Affiliation(s)
- Geeta Hitch
- Department of Life Sciences/Pharmacy, JMS Building, University of Sussex, Falmer, Brighton BN1 9RH, UK
| | - Naomi Fleming
- Department of Pharmacy, Kettering General Hospital, Rothwell Road, Kettering, Northamptonshire NN16 8UZ, UK
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15
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Chakraborty S, Harro C, DeNearing B, Brubaker J, Connor S, Maier N, Dally L, Flores J, Bourgeois AL, Walker R, Sack DA. Impact of lower challenge doses of enterotoxigenic Escherichia coli on clinical outcome, intestinal colonization and immune responses in adult volunteers. PLoS Negl Trop Dis 2018; 12:e0006442. [PMID: 29702652 PMCID: PMC5942845 DOI: 10.1371/journal.pntd.0006442] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 05/09/2018] [Accepted: 04/10/2018] [Indexed: 11/18/2022] Open
Abstract
A reliable and effective human challenge model is needed to help down-select the most promising ETEC vaccines currently under development. Such a model would need to reliably induce diarrhea in a high proportion of volunteers using the lowest possible inoculum to maximize safety and sensitivity. Previously we validated a challenge model that utilized a dose of 2x107 CFU of ETEC strain H10407 (LT+, ST+, CFA/I+ and O78+) to induce attack rates for moderate to severe diarrhea (MSD) of ~60-70%. Here we detail efforts to further refine the model in an attempt to determine if a lower challenge dose of H10407 can be used. Thirty subjects were randomized 1:1 to receive an oral administration of H10407 at doses of 106 or 105 CFU in bicarbonate buffer. After challenge, subjects were monitored for signs and symptoms of enteric illness and stool samples were collected to detect shedding of the challenge strain. Systemic and mucosal immune responses were measured using serum, antibody in lymphocyte supernatant and fecal samples. The attack rate was 13.3% (2/15) and 26.7% (4/15) for MSD in the 105 and 106 groups, respectively. Four MSD cases met criteria for early antibiotic treatment. All subjects but one shed the challenge strain in fecal samples. The frequency and magnitude of anti-LT toxin, CFA/I and LPS O78 immune responses were antigen, dose, severity of diarrhea and shedding levels dependent. Notably, although of lower magnitude, there were considerable immune responses in the subjects with no diarrhea. This may indicate that immune responses to asymptomatic infections of ETEC in children in the endemic countries may contribute to protection. Based on this and our prior studies, we conclude that a dose of 2x107 H10407 remains the lowest practical dose for use in future volunteer studies evaluating candidate vaccines and other preventive or therapeutic ETEC interventions. TRIAL REGISTRATION ClinicalTrials.gov NCT00844493.
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Affiliation(s)
- Subhra Chakraborty
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- * E-mail:
| | - Clayton Harro
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Barbara DeNearing
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Jessica Brubaker
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | - Sean Connor
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
| | | | - Len Dally
- The EMMES Corporation, Rockville, Maryland, United States of America
| | | | - A. Louis Bourgeois
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
- PATH, Washington, DC, United States of America
| | | | - David A. Sack
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America
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16
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Rojas-Lopez M, Monterio R, Pizza M, Desvaux M, Rosini R. Intestinal Pathogenic Escherichia coli: Insights for Vaccine Development. Front Microbiol 2018; 9:440. [PMID: 29615989 PMCID: PMC5869917 DOI: 10.3389/fmicb.2018.00440] [Citation(s) in RCA: 56] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 02/26/2018] [Indexed: 12/13/2022] Open
Abstract
Diarrheal diseases are one of the major causes of mortality among children under five years old and intestinal pathogenic Escherichia coli (InPEC) plays a role as one of the large causative groups of these infections worldwide. InPECs contribute significantly to the burden of intestinal diseases, which are a critical issue in low- and middle-income countries (Asia, Africa and Latin America). Intestinal pathotypes such as enteropathogenic E. coli (EPEC) and enterotoxigenic E. coli (ETEC) are mainly endemic in developing countries, while ETEC strains are the major cause of diarrhea in travelers to these countries. On the other hand, enterohemorrhagic E. coli (EHEC) are the cause of large outbreaks around the world, mainly affecting developed countries and responsible for not only diarrheal disease but also severe clinical complications like hemorrhagic colitis and hemolytic uremic syndrome (HUS). Overall, the emergence of antibiotic resistant strains, the annual cost increase in the health care system, the high incidence of traveler diarrhea and the increased number of HUS episodes have raised the need for effective preventive treatments. Although the use of antibiotics is still important in treating such infections, non-antibiotic strategies are either a crucial option to limit the increase in antibiotic resistant strains or absolutely necessary for diseases such as those caused by EHEC infections, for which antibiotic therapies are not recommended. Among non-antibiotic therapies, vaccine development is a strategy of choice but, to date, there is no effective licensed vaccine against InPEC infections. For several years, there has been a sustained effort to identify efficacious vaccine candidates able to reduce the burden of diarrheal disease. The aim of this review is to summarize recent milestones and insights in vaccine development against InPECs.
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Affiliation(s)
- Maricarmen Rojas-Lopez
- GSK, Siena, Italy.,Institut National de la Recherche Agronomique, Université Clermont Auvergne, UMR454 MEDiS, Clermont-Ferrand, France
| | - Ricardo Monterio
- Institut National de la Recherche Agronomique, Université Clermont Auvergne, UMR454 MEDiS, Clermont-Ferrand, France
| | | | - Mickaël Desvaux
- Institut National de la Recherche Agronomique, Université Clermont Auvergne, UMR454 MEDiS, Clermont-Ferrand, France
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17
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Duan Q, Lee KH, Nandre RM, Garcia C, Chen J, Zhang W. MEFA (multiepitope fusion antigen)-Novel Technology for Structural Vaccinology, Proof from Computational and Empirical Immunogenicity Characterization of an Enterotoxigenic Escherichia coli (ETEC) Adhesin MEFA. ACTA ACUST UNITED AC 2017; 8. [PMID: 28944092 PMCID: PMC5606245 DOI: 10.4172/2157-7560.1000367] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vaccine development often encounters the challenge of virulence heterogeneity. Enterotoxigenic Escherichia coli (ETEC) bacteria producing immunologically heterogeneous virulence factors are a leading cause of children's diarrhea and travelers' diarrhea. Currently, we do not have licensed vaccines against ETEC bacteria. While conventional methods continue to make progress but encounter challenge, new computational and structure-based approaches are explored to accelerate ETEC vaccine development. In this study, we applied a structural vaccinology concept to construct a structure-based multiepitope fusion antigen (MEFA) to carry representing epitopes of the seven most important ETEC adhesins [CFA/I, CFA/II (CS1-CS3), CFA/IV (CS4-CS6)], simulated antigenic structure of the CFA/I/II/IV MEFA with computational atomistic modeling and simulation, characterized immunogenicity in mouse immunization, and examined the potential of structure-informed vaccine design for ETEC vaccine development. A tag-less recombinant MEFA protein (CFA/I/II/IV MEFA) was effectively expressed and extracted. Molecular dynamics simulations indicated that this MEFA immunogen maintained a stable secondary structure and presented epitopes on the protein surface. Empirical data showed that mice immunized with the tagless CFA/I/II/IV MEFA developed strong antigen-specific antibody responses, and mouse serum antibodies significantly inhibited in vitro adherence of bacteria expressing these seven adhesins. These results revealed congruence of antigen immunogenicity between computational simulation and empirical mouse immunization and indicated this tag-less CFA/I/II/IV MEFA potentially an antigen for a broadly protective ETEC vaccine, suggesting a potential application of MEFA-based structural vaccinology for vaccine design against ETEC and likely other pathogens.
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Affiliation(s)
- Qiangde Duan
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS 66506, USA
| | - Kuo Hao Lee
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Rahul M Nandre
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS 66506, USA
| | - Carolina Garcia
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS 66506, USA
| | - Jianhan Chen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Weiping Zhang
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS 66506, USA
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18
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McArthur MA, Maciel M, Pasetti MF. Human immune responses against Shigella and enterotoxigenic E. coli: Current advances and the path forward. Vaccine 2017; 35:6803-6806. [PMID: 28558984 PMCID: PMC5749635 DOI: 10.1016/j.vaccine.2017.05.034] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 04/04/2017] [Accepted: 05/10/2017] [Indexed: 11/28/2022]
Abstract
Robust and well-established immunological assays and firm immune correlates of protection that can predict disease outcome and/or vaccine efficacy are essential to adequately assess human immune responses to infection and vaccination. The availability of reagents and calibrated controls is also critically important to standardize assays and generate comparable results among different laboratories. The workshop “Human Immune Responses against Shigella and ETEC: Current Advances and the Path Forward” held during the VASE meeting provided an opportunity to disseminate and discuss recent advances in the field of Shigella and ETEC immunology, identify research needs, and propose collaborative activities to advance the field. Four presentations featured current knowledge on humoral and cellular immune responses to Shigella and ETEC during infection and vaccination. A discussion followed on immunological methods relevant for clinical studies, immune parameters associated with protection, harmonization of assays among laboratories, and availability of reagents and standards. Specific recommendations proposed to facilitate “the path forward” included supporting communication among scientists, harmonization of assays and sharing of protocols, the creation of a repository of reagents and calibrated controls and distribution of such material to the research community, and expansion of exploratory studies to better understand the interactions between these pathogens and the human immune system and the ensuing responses.
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Affiliation(s)
- Monica A McArthur
- Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Milton Maciel
- Enteric Diseases Department, Naval Medical Research Center/ETEC Vaccine Program, Silver Spring, MD, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
| | - Marcela F Pasetti
- Department of Pediatrics, Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD, USA.
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19
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Kinetics of antibody-secreting cell and fecal IgA responses after oral cholera vaccination in different age groups in a cholera endemic country. Vaccine 2017; 35:321-328. [DOI: 10.1016/j.vaccine.2016.11.055] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 11/10/2016] [Accepted: 11/13/2016] [Indexed: 11/20/2022]
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20
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Kharat VB, Ahmed M, Jiang ZD, Riddle MS, DuPont HL. Colonization Factors in Enterotoxigenic Escherichia coli Strains in Travelers to Mexico, Guatemala, and India Compared with Children in Houston, Texas. Am J Trop Med Hyg 2016; 96:83-87. [PMID: 28077742 DOI: 10.4269/ajtmh.16-0405] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 08/23/2016] [Indexed: 12/15/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) can be attributed to around 200 million diarrheal episodes and 380,000 deaths in the developing regions. Travelers' diarrhea occurs in 15-40% of travelers to developing regions with ETEC being the most important etiologic agent. This study aims to describe the distribution of enterotoxins and colonization factor (CF) profiles of ETEC isolates from stool samples of adult travelers acquiring diarrhea in Mexico, Guatemala, and India and a group of children with acute diarrhea in Houston, TX, between 2007 and 2012. The heat-labile/heat-stable (LT/ST) enterotoxins and CFs from 252 patients were determined using polymerase chain reaction assay. Among the 252 ETEC isolates, 15% were LT-only, 58% were ST-only, and 28% produced both LT and ST. The distribution of LT-only (12-15%) and ST-only (55-56%) isolates was similar between Latin American and Indian sites. The most prevalent CF was CS21, expressed in 65% of the isolates followed by CS6 (25%) and CS3 (17%). Among the international travelers, 64% of the ETEC isolates expressed CS21. CS21 was expressed in 46% of isolates from Latin America compared with 96% of isolates from India (P < 0.0001). CS21 was expressed in 85% isolates from Houston children. CS21 was increasingly found in ST-only (P = 0.003) and ST/LT (P = 0.026) ETEC compared with LT-only ETEC. High frequency of finding CS21 among recent isolates of ETEC over a wide geographic distribution warrants additional studies on this CF. Highly conserved CS21 is an important target for potential multivalent ETEC vaccines.
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Affiliation(s)
- Vineetkumar B Kharat
- University of Texas School of Public Health, Center for Infectious Diseases, Houston, Texas
| | - Makhdum Ahmed
- University of Texas School of Public Health, Center for Infectious Diseases, Houston, Texas
| | - Zhi-Dong Jiang
- University of Texas School of Public Health, Center for Infectious Diseases, Houston, Texas.
| | - Mark S Riddle
- Enteric Disease Department, Naval Medical Research Center, Silver Spring, Maryland
| | - Herbert L DuPont
- University of Texas School of Public Health, Center for Infectious Diseases, Houston, Texas.,Baylor College of Medicine, Houston, Texas
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21
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Induction of long term mucosal immunological memory in humans by an oral inactivated multivalent enterotoxigenic Escherichia coli vaccine. Vaccine 2016; 34:3132-3140. [DOI: 10.1016/j.vaccine.2016.04.055] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Revised: 03/31/2016] [Accepted: 04/19/2016] [Indexed: 11/15/2022]
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22
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Tennant SM, Steele AD, Pasetti MF. Highlights of the 8th International Conference on Vaccines for Enteric Diseases: the Scottish Encounter To Defeat Diarrheal Diseases. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2016; 23:272-81. [PMID: 26936100 PMCID: PMC4820512 DOI: 10.1128/cvi.00082-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Infectious diarrhea is a leading cause of morbidity and of mortality; the burden of disease affects individuals of all ages but particularly young children, especially those living in poor regions where the disease is endemic. It is also a health concern for international travelers to these areas. Experts on vaccines and enteric infections and advocates for global health improvement gathered in Scotland from 8 to 10 July 2015 to discuss recent advances in the assessment and understanding of the burden of enteric diseases and progress in the development and implementation of strategies to prevent these infections. Highlights of the meeting included description of advances in molecular assays to estimate pathogen-specific prevalence, methods to model epidemiologic trends, novel approaches to generate broad-spectrum vaccines, new initiatives to evaluate vaccine performance where they are most needed, renewed interest in human challenge models, immunological readouts as predictors of vaccine efficacy, maternal immunization to prevent enteric infections, and the impact of maternal immunity on the vaccine take of infants. A follow-up scientific gathering to advance Shigella and enterotoxigenic Escherichia coli (ETEC) vaccine efforts will be held from 28 to 30 June 2016 in Washington, DC.
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Affiliation(s)
- Sharon M Tennant
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - A Duncan Steele
- Enteric and Diarrheal Diseases, Bill & Melinda Gates Foundation, Seattle, Washington, USA
| | - Marcela F Pasetti
- Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, Maryland, USA
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23
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Abstract
Diarrheal diseases remain a leading cause of global childhood mortality and morbidity. Several recent epidemiological studies highlight the rate of diarrheal diseases in different parts of the world and draw attention to the impact on childhood growth and survival. Despite the well-documented global burden of diarrheal diseases, currently there are no combination diarrheal vaccines, only licensed vaccines for rotavirus and cholera, and Salmonella typhi-based vaccines for typhoid fever. The recognition of the impact of diarrheal episodes on infant growth, as seen in resource-poor countries, has spurred action from governmental and non-governmental agencies to accelerate research toward affordable and effective vaccines against diarrheal diseases. Both travelers and children in endemic countries will benefit from a combination diarrheal vaccine, but it can be argued that the greater proportion of any positive impact will be on the public health status of the latter. The history of combination pediatric vaccines indicate that monovalent or single disease vaccines are typically licensed first prior to formulation in a combination vaccine, and that the combinations themselves undergo periodic revision in response to need for improvement in safety or potential for wider coverage of important pediatric pathogens. Nevertheless combination pediatric vaccines have proven to be an effective tool in limiting or eradicating communicable childhood diseases worldwide. The landscape of diarrheal vaccine candidates indicates that there now several in active development that offer options for potential testing of combinations to combat those bacterial and viral pathogens responsible for the heaviest disease burden—rotavirus, ETEC, Shigella, Campylobacter, V. cholera and Salmonella.
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Affiliation(s)
- Malabi M Venkatesan
- a Bacterial Diseases Branch; Walter Reed Army Institute of Research ; Silver Spring , MD , USA
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24
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Zhang C, Iqbal J, Gómez-Duarte OG. Murine immunization with CS21 pili or LngA major subunit of enterotoxigenic Escherichia coli (ETEC) elicits systemic and mucosal immune responses and inhibits ETEC gut colonization. Vet Microbiol 2016; 202:90-100. [PMID: 26878971 DOI: 10.1016/j.vetmic.2016.02.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Revised: 01/24/2016] [Accepted: 02/04/2016] [Indexed: 02/07/2023]
Abstract
CS21 pili of enterotoxigenic Escherichia coli (ETEC) is one of the most prevalent ETEC colonization factors. CS21 major subunit, LngA, mediates ETEC adherence to intestinal cells, and contributes to ETEC pathogenesis in a neonatal mouse infection model. The objectives of this work were to evaluate LngA major subunit purified protein and CS21 purified pili on immunogenicity and protection against ETEC colonization of mice intestine. Recombinant LngA purified protein or purified CS21 pili from E9034A ETEC strain were evaluated for immunogenicity after immunization of C57BL/6 mice. Specific anti-LngA antibodies were detected from mice serum, feces, and intestine fluid samples by ELISA assays. Protection against gut colonization was evaluated on immunized mice orally challenged with wild type E9034A ETEC strain and by subsequent quantification of bacterial colony forming units (CFU) recovered from feces. Recombinant LngA protein and CS21 pili induced specific humoral and mucosal anti-LngA antibodies in the mouse model. CS21 combined with CT delivered intranasally as well as LngA combined with incomplete Freund adjuvant delivered intraperitoneally inhibited ETEC gut colonization in a mouse model. In conclusion, both LngA purified protein and CS21 pili from ETEC are highly immunogenic and may inhibit ETEC intestinal shedding. Our data on immunogenicity and immunoprotection indicates that CS21 is a suitable vaccine candidate for a future multivalent vaccine against ETEC diarrhea.
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Affiliation(s)
- Chengxian Zhang
- Division of Infectious Diseases, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Junaid Iqbal
- Division of Infectious Diseases, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA
| | - Oscar G Gómez-Duarte
- Division of Infectious Diseases, Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA.
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25
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Leitner DR, Lichtenegger S, Temel P, Zingl FG, Ratzberger D, Roier S, Schild-Prüfert K, Feichter S, Reidl J, Schild S. A combined vaccine approach against Vibrio cholerae and ETEC based on outer membrane vesicles. Front Microbiol 2015; 6:823. [PMID: 26322032 PMCID: PMC4531250 DOI: 10.3389/fmicb.2015.00823] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 07/27/2015] [Indexed: 11/28/2022] Open
Abstract
Enteric infections induced by pathogens like Vibrio cholerae and enterotoxigenic Escherichia coli (ETEC) remain a massive burden in developing countries with increasing morbidity and mortality rates. Previously, we showed that the immunization with genetically detoxified outer membrane vesicles (OMVs) derived from V. cholerae elicits a protective immune response based on the generation of O antigen antibodies, which effectively block the motility by binding to the sheathed flagellum. In this study, we investigated the potential of lipopolysaccharide (LPS)-modified and toxin negative OMVs isolated from V. cholerae and ETEC as a combined OMV vaccine candidate. Our results indicate that the immunization with V. cholerae or ETEC OMVs induced a species-specific immune response, whereas the combination of both OMV species resulted in a high-titer, protective immune response against both pathogens. Interestingly, the immunization with V. cholerae OMVs alone resulted in a so far uncharacterized and cholera toxin B-subunit (CTB) independent protection mechanism against an ETEC colonization. Furthermore, we investigated the potential use of V. cholerae OMVs as delivery vehicles for the heterologously expression of the ETEC surface antigens, CFA/I, and FliC. Although we induced a detectable immune response against both heterologously expressed antigens, none of these approaches resulted in an improved protection compared to a simple combination of V. cholerae and ETEC OMVs. Finally, we expanded the current protection model from V. cholerae to ETEC by demonstrating that the inhibition of motility via anti-FliC antibodies represents a relevant protection mechanism of an OMV-based ETEC vaccine candidate in vivo.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Stefan Schild
- Institute of Molecular Biosciences, University of GrazGraz, Austria
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Kumar A, Hays M, Lim F, Foster LJ, Zhou M, Zhu G, Miesner T, Hardwidge PR. Protective Enterotoxigenic Escherichia coli Antigens in a Murine Intranasal Challenge Model. PLoS Negl Trop Dis 2015; 9:e0003924. [PMID: 26244636 PMCID: PMC4526226 DOI: 10.1371/journal.pntd.0003924] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 06/19/2015] [Indexed: 12/19/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is an endemic health threat in underdeveloped nations. Despite the significant effort extended to vaccine trials using ETEC colonization factors, these approaches have generally not been especially effective in mediating cross-protective immunity. We used quantitative proteomics to identify 24 proteins that differed in abundance in membrane protein preparations derived from wild-type vs. a type II secretion system mutant of ETEC. We expressed and purified a subset of these proteins and identified nine antigens that generated significant immune responses in mice. Sera from mice immunized with either the MltA-interacting protein MipA, the periplasmic chaperone seventeen kilodalton protein, Skp, or a long-chain fatty acid outer membrane transporter, ETEC_2479, reduced the adherence of multiple ETEC strains differing in colonization factor expression to human intestinal epithelial cells. In intranasal challenge assays of mice, immunization with ETEC_2479 protected 88% of mice from an otherwise lethal challenge with ETEC H10407. Immunization with either Skp or MipA provided an intermediate degree of protection, 68 and 64%, respectively. Protection was significantly correlated with the induction of a secretory immunoglobulin A response. This study has identified several proteins that are conserved among heterologous ETEC strains and may thus potentially improve cross-protective efficacy if incorporated into future vaccine designs.
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Affiliation(s)
- Amit Kumar
- College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
| | - Mike Hays
- College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
| | - Francis Lim
- Department of Biochemistry & Molecular Biology and Centre for High-Throughput Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Leonard J. Foster
- Department of Biochemistry & Molecular Biology and Centre for High-Throughput Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Mingxu Zhou
- College of Veterinary Medicine, Yangzhou University and Jiangsu Co-Innovation Center for Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, China
| | - Guoqiang Zhu
- College of Veterinary Medicine, Yangzhou University and Jiangsu Co-Innovation Center for Important Animal Infectious Diseases and Zoonoses, Yangzhou, Jiangsu, China
| | - Tracy Miesner
- College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
| | - Philip R. Hardwidge
- College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
- * E-mail:
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Current Progress in Developing Subunit Vaccines against Enterotoxigenic Escherichia coli-Associated Diarrhea. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2015; 22:983-91. [PMID: 26135975 DOI: 10.1128/cvi.00224-15] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Diarrhea continues to be a leading cause of death in children <5 years of age, and enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of children's diarrhea. Currently, there are no available vaccines against ETEC-associated diarrhea. Whole-cell vaccine candidates have been under development but require further improvements because they provide inadequate protection and produce unwanted adverse effects. Meanwhile, a newer approach using polypeptide or subunit vaccine candidates focusing on ETEC colonization factor antigens (CFAs) and enterotoxins, the major virulence determinants of ETEC diarrhea, shows substantial promise. A conservative CFA/I adhesin tip antigen and a CFA MEFA (multiepitope fusion antigen) were shown to induce cross-reactive antiadhesin antibodies that protected against adherence by multiple important CFAs. Genetic fusion of toxoids derived from ETEC heat-labile toxin (LT) and heat-stable toxin (STa) induced antibodies neutralizing both enterotoxins. Moreover, CFA-toxoid MEFA polypeptides, generated by fusing CFA MEFA to an STa-LT toxoid fusion, induced antiadhesin antibodies that broadly inhibited adherence of the seven most important ETEC CFAs associated with about 80% of the diarrhea cases caused by ETEC strains with known CFAs. This same antigen preparation also induced antitoxin antibodies that neutralized both toxins that are associated with all cases of ETEC diarrhea. Results from these studies suggest that polypeptide or subunit vaccines have the potential to effectively protect against ETEC diarrhea. In addition, novel adhesins and mucin proteases have been investigated as potential alternatives or, more likely, additional antigens for ETEC subunit vaccine development.
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Ruan X, Sack DA, Zhang W. Genetic fusions of a CFA/I/II/IV MEFA (multiepitope fusion antigen) and a toxoid fusion of heat-stable toxin (STa) and heat-labile toxin (LT) of enterotoxigenic Escherichia coli (ETEC) retain broad anti-CFA and antitoxin antigenicity. PLoS One 2015; 10:e0121623. [PMID: 25803825 PMCID: PMC4372207 DOI: 10.1371/journal.pone.0121623] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 02/02/2015] [Indexed: 12/21/2022] Open
Abstract
Immunological heterogeneity has long been the major challenge in developing broadly effective vaccines to protect humans and animals against bacterial and viral infections. Enterotoxigenic Escherichia coli (ETEC) strains, the leading bacterial cause of diarrhea in humans, express at least 23 immunologically different colonization factor antigens (CFAs) and two distinct enterotoxins [heat-labile toxin (LT) and heat-stable toxin type Ib (STa or hSTa)]. ETEC strains expressing any one or two CFAs and either toxin cause diarrhea, therefore vaccines inducing broad immunity against a majority of CFAs, if not all, and both toxins are expected to be effective against ETEC. In this study, we applied the multiepitope fusion antigen (MEFA) strategy to construct ETEC antigens and examined antigens for broad anti-CFA and antitoxin immunogenicity. CFA MEFA CFA/I/II/IV [CVI 2014, 21(2):243-9], which carried epitopes of seven CFAs [CFA/I, CFA/II (CS1, CS2, CS3), CFA/IV (CS4, CS5, CS6)] expressed by the most prevalent and virulent ETEC strains, was genetically fused to LT-STa toxoid fusion monomer 3xSTaA14Q-dmLT or 3xSTaN12S-dmLT [IAI 2014, 82(5):1823-32] for CFA/I/II/IV-STaA14Q-dmLT and CFA/I/II/IV-STaN12S-dmLT MEFAs. Mice intraperitoneally immunized with either CFA/I/II/IV-STa-toxoid-dmLT MEFA developed antibodies specific to seven CFAs and both toxins, at levels equivalent or comparable to those induced from co-administration of the CFA/I/II/IV MEFA and toxoid fusion 3xSTaN12S-dmLT. Moreover, induced antibodies showed in vitro adherence inhibition activities against ETEC or E. coli strains expressing these seven CFAs and neutralization activities against both toxins. These results indicated CFA/I/II/IV-STa-toxoid-dmLT MEFA or CFA/I/II/IV MEFA combined with 3xSTaN12S-dmLT induced broadly protective anti-CFA and antitoxin immunity, and suggested their potential application in broadly effective ETEC vaccine development. This MEFA strategy may be generally used in multivalent vaccine development.
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Affiliation(s)
- Xiaosai Ruan
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS, 66506, United States of America
| | - David A. Sack
- Department of International Health, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, 21205, United States of America
- * E-mail: (DAS); (WZ)
| | - Weiping Zhang
- Department of Diagnostic Medicine/Pathobiology, Kansas State University College of Veterinary Medicine, Manhattan, KS, 66506, United States of America
- * E-mail: (DAS); (WZ)
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Luo Q, Qadri F, Kansal R, Rasko DA, Sheikh A, Fleckenstein JM. Conservation and immunogenicity of novel antigens in diverse isolates of enterotoxigenic Escherichia coli. PLoS Negl Trop Dis 2015; 9:e0003446. [PMID: 25629897 PMCID: PMC4309559 DOI: 10.1371/journal.pntd.0003446] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Accepted: 11/26/2014] [Indexed: 12/12/2022] Open
Abstract
Background Enterotoxigenic Escherichia coli (ETEC) are common causes of diarrheal morbidity and mortality in developing countries for which there is currently no vaccine. Heterogeneity in classical ETEC antigens known as colonization factors (CFs) and poor efficacy of toxoid-based approaches to date have impeded development of a broadly protective ETEC vaccine, prompting searches for novel molecular targets. Methodology Using a variety of molecular methods, we examined a large collection of ETEC isolates for production of two secreted plasmid-encoded pathotype-specific antigens, the EtpA extracellular adhesin, and EatA, a mucin-degrading serine protease; and two chromosomally-encoded molecules, the YghJ metalloprotease and the EaeH adhesin, that are not specific to the ETEC pathovar, but which have been implicated in ETEC pathogenesis. ELISA assays were also performed on control and convalescent sera to characterize the immune response to these antigens. Finally, mice were immunized with recombinant EtpA (rEtpA), and a protease deficient version of the secreted EatA passenger domain (rEatApH134R) to examine the feasibility of combining these molecules in a subunit vaccine approach. Principal Findings EtpA and EatA were secreted by more than half of all ETEC, distributed over diverse phylogenetic lineages belonging to multiple CF groups, and exhibited surprisingly little sequence variation. Both chromosomally-encoded molecules were also identified in a wide variety of ETEC strains and YghJ was secreted by 89% of isolates. Antibodies against both the ETEC pathovar-specific and conserved E. coli antigens were present in significantly higher titers in convalescent samples from subjects with ETEC infection than controls suggesting that each of these antigens is produced and recognized during infection. Finally, co-immunization of mice with rEtpA and rEatApH134R offered significant protection against ETEC infection. Conclusions Collectively, these data suggest that novel antigens could significantly complement current approaches and foster improved strategies for development of broadly protective ETEC vaccines. Infectious diarrhea is one of the leading causes of death among young children in developing countries, and a major cause of morbidity in all age groups. The enterotoxigenic Escherichia coli contribute substantially to this burden of diarrheal illness, and have been a focus of vaccine development efforts for more than forty years following their discovery as a cause of severe diarrheal illness. The heat-labile, and/or heat stable enterotoxins that define ETEC are produced by a diverse population of Escherichia coli. This inherent genetic plasticity of E. coli has made it difficult to identify antigens specific to ETEC that are highly conserved. Therefore, identification of protective antigens shared by many ETEC strains will likely play an essential role in development of the next iteration of vaccines.
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Affiliation(s)
- Qingwei Luo
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Bangladesh, Mohakhali, Dhaka, Bangladesh
| | - Rita Kansal
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - David A. Rasko
- Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Alaullah Sheikh
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - James M. Fleckenstein
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Medicine Service, Veterans Affairs Medical Center, St. Louis, Missouri, United States of America
- * E-mail:
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31
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Walker RI. An assessment of enterotoxigenic Escherichia coli and Shigella vaccine candidates for infants and children. Vaccine 2014; 33:954-65. [PMID: 25482842 DOI: 10.1016/j.vaccine.2014.11.049] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Revised: 11/25/2014] [Accepted: 11/27/2014] [Indexed: 02/06/2023]
Abstract
Despite improvements to water quality, sanitation, and the implementation of current prevention and treatment interventions, diarrhea remains a major cause of illness and death, especially among children less than five years of age in the developing world. Rotavirus vaccines have already begun making a real impact on diarrhea, but several more enteric vaccines will be necessary to achieve broader reductions of illness and death. Among the many causes of diarrheal disease, enterotoxigenic Escherichia coli (ETEC) and Shigella are the two most important bacterial pathogens for which there are no currently licensed vaccines. Vaccines against these two pathogens could greatly reduce the impact of disease caused by these infections. This review describes the approaches to ETEC and Shigella vaccines that are currently under development, including a range of both cellular and subunit approaches for each pathogen. In addition, the review discusses strategies for maximizing the potential benefit of these vaccines, which includes the feasibility of co-administration, consolidation, and combination of vaccine candidates, as well as issues related to effective administration of enteric vaccines to infants. Recent impact studies indicate that ETEC and Shigella vaccines could significantly benefit global public health. Either vaccine, particularly if they could be combined together or with another enteric vaccine, would be an extremely valuable tool for saving lives and promoting the health of infants and children in the developing world, as well as potentially providing protection to travelers and military personnel visiting endemic areas.
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Affiliation(s)
- Richard I Walker
- PATH, 455 Massachusetts Avenue NW, Suite 1000, Washington, DC 20001, USA.
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Safety and immunogenicity of an improved oral inactivated multivalent enterotoxigenic Escherichia coli (ETEC) vaccine administered alone and together with dmLT adjuvant in a double-blind, randomized, placebo-controlled Phase I study. Vaccine 2014; 32:7077-84. [PMID: 25444830 DOI: 10.1016/j.vaccine.2014.10.069] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 10/24/2014] [Accepted: 10/27/2014] [Indexed: 11/24/2022]
Abstract
BACKGROUND We have developed a new oral vaccine against enterotoxigenic Escherichia coli (ETEC), which is the most common cause of bacterial diarrhea in children in developing countries and in travelers. METHODS The vaccine was tested for safety and immunogenicity alone and together with double-mutant heat-labile toxin (dmLT) adjuvant in a double-blind, placebo-controlled Phase I study in 129 Swedish adults. The vaccine consists of four inactivated recombinant E. coli strains overexpressing the major ETEC colonization factors (CFs) CFA/I, CS3, CS5, and CS6 mixed with an LT B-subunit related toxoid, LCTBA. Volunteers received two oral doses of vaccine alone, vaccine plus 10 μg or 25 μg dmLT or placebo. Secretory IgA antibody responses in fecal samples and IgA responses in secretions from circulating intestine-derived antibody secreting cells were assessed as primary measures of vaccine immunogenicity. RESULTS The vaccine was safe and well tolerated; adverse events were few and generally mild with no significant differences between subjects receiving placebo or vaccine with or without adjuvant. As many as 74% of subjects receiving vaccine alone and 83% receiving vaccine plus 10 μg dmLT showed significant mucosal IgA responses to all five primary vaccine antigens and about 90% of all vaccinees responded to at least four of the antigens. Subjects receiving vaccine plus 10 μg dmLT responded with significantly increased intestine-derived anti-CS6 responses compared to subjects receiving vaccine alone. CONCLUSIONS The vaccine was safe and broadly immunogenic. dmLT further enhanced mucosal immune responses to CF antigens present in low amounts in the vaccine. Based on these encouraging results, the vaccine will be tested for safety and immunogenicity in different age groups including infants in Bangladesh and for protective efficacy in travelers.
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Bhatia B, Solanki AK, Kaushik H, Dixit A, Garg LC. B-cell epitope of beta toxin of Clostridium perfringens genetically conjugated to a carrier protein: Expression, purification and characterization of the chimeric protein. Protein Expr Purif 2014; 102:38-44. [DOI: 10.1016/j.pep.2014.06.014] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 06/24/2014] [Accepted: 06/25/2014] [Indexed: 10/25/2022]
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Fleckenstein JM, Sheikh A. Designing vaccines to neutralize effective toxin delivery by enterotoxigenic Escherichia coli. Toxins (Basel) 2014; 6:1799-812. [PMID: 24918359 PMCID: PMC4073130 DOI: 10.3390/toxins6061799] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Revised: 04/23/2014] [Accepted: 05/15/2014] [Indexed: 12/03/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) are a leading cause of diarrheal illness in developing countries. Despite the discovery of these pathogens as a cause of cholera-like diarrhea over 40 years ago, and decades of vaccine development effort, there remains no broadly protective ETEC vaccine. The discovery of new virulence proteins and an improved appreciation of the complexity of the molecular events required for effective toxin delivery may provide additional avenues to pursue in development of an effective vaccine to prevent severe diarrhea caused by these important pathogens.
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Affiliation(s)
- James M Fleckenstein
- Division of Infectious Diseases, Washington University School of Medicine, 660 South Euclid Avenue; Saint Louis, MO 63110, USA.
| | - Alaullah Sheikh
- Molecular Microbiology and Microbiobial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, Campus Box 8051, 660 South Euclid Avenue; Saint Louis, MO 63110, USA.
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Abstract
Enterotoxigenic Escherichia coli (ETEC) are the most common bacterial pathogens causing diarrhea in developing countries where they lead to hundreds of thousands of deaths, mostly in children. These organisms are a leading cause of diarrheal illness in travelers to endemic countries. ETEC pathogenesis, and consequently vaccine approaches, have largely focused on plasmid-encoded enterotoxins or fimbrial colonization factors. To date these approaches have not yielded a broadly protective vaccine. However, recent studies suggest that ETEC pathogenesis is more complex than previously appreciated and involves additional plasmid and chromosomally encoded virulence molecules that can be targeted in vaccines. Here, we review recent novel antigen discovery efforts, potential contribution of these proteins to the molecular pathogenesis of ETEC and protective immunity, and the potential implications for development of next generation vaccines for important pathogens. These proteins may help to improve the effectiveness of future vaccines by making them simpler and possibly broadly protective because of their conserved nature.
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Affiliation(s)
- James M. Fleckenstein
- Department of Medicine, Division of Infectious Diseases, Washington University School of Medicine, USA
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, USA
- Medicine Service, Veterans Affairs Medical Center, St. Louis, Missouri, USA
| | - Alaullah Sheikh
- Molecular Microbiology and Microbial Pathogenesis Program, Division of Biology and Biomedical Sciences, Washington University School of Medicine, USA
| | - Firdausi Qadri
- Centre for Vaccine Sciences, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh
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Steele D, Riddle M, van de Verg L, Bourgeois L. Vaccines for enteric diseases: a meeting summary. Expert Rev Vaccines 2014; 11:407-9. [DOI: 10.1586/erv.12.9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Multiepitope fusion antigen induces broadly protective antibodies that prevent adherence of Escherichia coli strains expressing colonization factor antigen I (CFA/I), CFA/II, and CFA/IV. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2013; 21:243-9. [PMID: 24351757 DOI: 10.1128/cvi.00652-13] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Diarrhea is the second leading cause of death in children younger than 5 years and continues to be a major threat to global health. Enterotoxigenic Escherichia coli (ETEC) strains are the most common bacteria causing diarrhea in developing countries. ETEC strains are able to attach to host small intestinal epithelial cells by using bacterial colonization factor antigen (CFA) adhesins. This attachment helps to initiate the diarrheal disease. Vaccines that induce antiadhesin immunity to block adherence of ETEC strains that express immunologically heterogeneous CFA adhesins are expected to protect against ETEC diarrhea. In this study, we created a CFA multiepitope fusion antigen (MEFA) carrying representative epitopes of CFA/I, CFA/II (CS1, CS2, and CS3), and CFA/IV (CS4, CS5, and CS6), examined its immunogenicity in mice, and assessed the potential of this MEFA as an antiadhesin vaccine against ETEC. Mice intraperitoneally immunized with this CFA MEFA exhibited no adverse effects and developed immune responses to CFA/I, CFA/II, and CFA/IV adhesins. Moreover, after incubation with serum of the immunized mice, ETEC or E. coli strains expressing CFA/I, CFA/II, or CFA/IV adhesins were significantly inhibited in adherence to Caco-2 cells. Our results indicated this CFA MEFA elicited antibodies that not only cross-reacted to CFA/I, CFA/II and CFA/IV adhesins but also broadly inhibited adherence of E. coli strains expressing these seven adhesins and suggested that this CFA MEFA could be a candidate to induce broad-spectrum antiadhesin protection against ETEC diarrhea. Additionally, this antigen construction approach (creating an MEFA) may be generally used in vaccine development against heterogenic pathogens.
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Lal M, Priddy S, Bourgeois L, Walker R, Pebley W, Brown J, Desai J, Darsley MJ, Kristensen D, Chen D. Development of a fast-dissolving tablet formulation of a live attenuated enterotoxigenic E. coli vaccine candidate. Vaccine 2013; 31:4759-64. [DOI: 10.1016/j.vaccine.2013.08.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Revised: 06/28/2013] [Accepted: 08/05/2013] [Indexed: 12/29/2022]
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Croxen MA, Law RJ, Scholz R, Keeney KM, Wlodarska M, Finlay BB. Recent advances in understanding enteric pathogenic Escherichia coli. Clin Microbiol Rev 2013; 26:822-80. [PMID: 24092857 PMCID: PMC3811233 DOI: 10.1128/cmr.00022-13] [Citation(s) in RCA: 822] [Impact Index Per Article: 74.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Although Escherichia coli can be an innocuous resident of the gastrointestinal tract, it also has the pathogenic capacity to cause significant diarrheal and extraintestinal diseases. Pathogenic variants of E. coli (pathovars or pathotypes) cause much morbidity and mortality worldwide. Consequently, pathogenic E. coli is widely studied in humans, animals, food, and the environment. While there are many common features that these pathotypes employ to colonize the intestinal mucosa and cause disease, the course, onset, and complications vary significantly. Outbreaks are common in developed and developing countries, and they sometimes have fatal consequences. Many of these pathotypes are a major public health concern as they have low infectious doses and are transmitted through ubiquitous mediums, including food and water. The seriousness of pathogenic E. coli is exemplified by dedicated national and international surveillance programs that monitor and track outbreaks; unfortunately, this surveillance is often lacking in developing countries. While not all pathotypes carry the same public health profile, they all carry an enormous potential to cause disease and continue to present challenges to human health. This comprehensive review highlights recent advances in our understanding of the intestinal pathotypes of E. coli.
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Ahmed T, Bhuiyan TR, Zaman K, Sinclair D, Qadri F. Vaccines for preventing enterotoxigenic Escherichia coli (ETEC) diarrhoea. Cochrane Database Syst Rev 2013; 2013:CD009029. [PMID: 23828581 PMCID: PMC6532719 DOI: 10.1002/14651858.cd009029.pub2] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
BACKGROUND Infection with enterotoxigenic Escherichia coli (ETEC) bacteria is a common cause of diarrhoea in adults and children in developing countries and is a major cause of 'travellers' diarrhoea' in people visiting or returning from endemic regions. A killed whole cell vaccine (Dukoral®), primarily designed and licensed to prevent cholera, has been recommended by some groups to prevent travellers' diarrhoea in people visiting endemic regions. This vaccine contains a recombinant B subunit of the cholera toxin that is antigenically similar to the heat labile toxin of ETEC. This review aims to evaluate the clinical efficacy of this vaccine and other vaccines designed specifically to protect people against diarrhoea caused by ETEC infection. OBJECTIVES To evaluate the efficacy, safety, and immunogenicity of vaccines for preventing ETEC diarrhoea. SEARCH METHODS We searched the Cochrane Infectious Disease Group Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, LILACS, and http://clinicaltrials.gov up to December 2012. SELECTION CRITERIA Randomized controlled trials (RCTs) and quasi-RCTs comparing use of vaccines to prevent ETEC with use of no intervention, a control vaccine (either an inert vaccine or a vaccine normally given to prevent an unrelated infection), an alternative ETEC vaccine, or a different dose or schedule of the same ETEC vaccine in healthy adults and children living in endemic regions, intending to travel to endemic regions, or volunteering to receive an artificial challenge of ETEC bacteria. DATA COLLECTION AND ANALYSIS Two authors independently assessed each trial for eligibility and risk of bias. Two independent reviewers extracted data from the included studies and analyzed the data using Review Manager (RevMan) software. We reported outcomes as risk ratios (RR) with 95% confidence intervals (CI). We assessed the quality of the evidence using the GRADE approach. MAIN RESULTS Twenty-four RCTs, including 53,247 participants, met the inclusion criteria. Four studies assessed the protective efficacy of oral cholera vaccines when used to prevent diarrhoea due to ETEC and seven studies assessed the protective efficacy of ETEC-specific vaccines. Of these 11 studies, seven studies presented efficacy data from field trials and four studies presented efficacy data from artificial challenge studies. An additional 13 trials contributed safety and immunological data only. Cholera vaccinesThe currently available, oral cholera killed whole cell vaccine (Dukoral®) was evaluated for protection of people against 'travellers' diarrhoea' in a single RCT in people arriving in Mexico from the USA. We did not identify any statistically significant effects on ETEC diarrhoea or all-cause diarrhoea (one trial, 502 participants, low quality evidence).Two earlier trials, one undertaken in an endemic population in Bangladesh and one undertaken in people travelling from Finland to Morocco, evaluated a precursor of this vaccine containing purified cholera toxin B subunit rather than the recombinant subunit in Dukoral®. Short term protective efficacy against ETEC diarrhoea was demonstrated, lasting for around three months (RR 0.43, 95% CI 0.26 to 0.71; two trials, 50,227 participants). This vaccine is no longer available. ETEC vaccinesAn ETEC-specific, killed whole cell vaccine, which also contains the recombinant cholera toxin B-subunit, was evaluated in people travelling from the USA to Mexico or Guatemala, and from Austria to Latin America, Africa, or Asia. We did not identify any statistically significant differences in ETEC-specific diarrhoea or all-cause diarrhoea (two trials, 799 participants), and the vaccine was associated with increased vomiting (RR 2.0, 95% CI 1.16 to 3.45; nine trials, 1528 participants). The other ETEC-specific vaccines in development have not yet demonstrated clinically important benefits. AUTHORS' CONCLUSIONS There is currently insufficient evidence from RCTs to support the use of the oral cholera vaccine Dukoral® for protecting travellers against ETEC diarrhoea. Further research is needed to develop safe and effective vaccines to provide both short and long-term protection against ETEC diarrhoea.
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Affiliation(s)
- Tanvir Ahmed
- Variation Biotechnologies Inc.1740 Woodroffe Ave, Building 400OttawaCanadaK2G 3R8
| | - Taufiqur R Bhuiyan
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b)Centre for Vaccine Sciences68 Shaheed Tajuddin Ahamed Sharani, MohakhaliDhakaBangladesh1212
| | - K Zaman
- International Centre for Diarrhoeal Disease Research, BangladeshChild Health Unit68 Shaheed Tajuddin AhmedSarani, MohakhaliDhakaBangladesh1212
| | - David Sinclair
- Liverpool School of Tropical MedicineDepartment of Clinical SciencesPembroke PlaceLiverpoolUKL3 5QA
| | - Firdausi Qadri
- International Centre for Diarrhoeal Disease Research, Bangladesh (icddr,b)Centre for Vaccine Sciences68 Shaheed Tajuddin Ahamed Sharani, MohakhaliDhakaBangladesh1212
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Different kinetics of circulating antibody-secreting cell responses after primary and booster oral immunizations: a tool for assessing immunological memory. Vaccine 2013; 31:3035-8. [PMID: 23664997 DOI: 10.1016/j.vaccine.2013.04.066] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 04/02/2013] [Accepted: 04/24/2013] [Indexed: 12/25/2022]
Abstract
We show that the kinetics of circulating IgA as well as IgG antibody-secreting cell (ASC) responses differs considerably after primary and booster vaccination with the oral cholera vaccine Dukoral(®), as determined by the antibody in lymphocyte supernatant (ALS) as well as ELISPOT methods. Thus, whereas the antitoxin ASC responses did not peak until 7-9 days after primary vaccination, peak responses to a second dose given after two weeks, or a single booster dose given 6 months to 14 years later, were recorded already after 4-5 days and then rapidly declined. Our results indicate that many previous studies reporting ASC results 7-10 days after repeated immunization may have substantially underestimated the magnitudes of the responses. The results also suggest that detection of peak ASC responses at an early time point after booster immunization can be used as a simple tool to assess immunological memory.
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Abstract
Pathogenic Escherichia coli that colonize the small intestine primarily cause gastrointestinal illness in infants and travelers. The main categories of pathogenic E. coli that colonize the epithelial lining of the small intestine are enterotoxigenic E. coli, enteropathogenic E. coli, and enteroaggregative E. coli. These organisms accomplish their pathogenic process by a complex, coordinated multistage strategy, including nonintimate adherence mediated by various adhesins. These so called "enteroadherent E. coli" categories subsequently produce toxins or effector proteins that are either secreted to the milieu or injected to the host cell. Finally, destruction of the intestinal microvilli results from the intimate adherence or the toxic effect exerted over the epithelia, resulting in water secretion and diarrhea. In this review, we summarize the current state of knowledge regarding these enteroadherent E. coli strains and the present clinical understanding of how these organisms colonize the human intestine and cause disease.
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43
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Lundgren A, Leach S, Tobias J, Carlin N, Gustafsson B, Jertborn M, Bourgeois L, Walker R, Holmgren J, Svennerholm AM. Clinical trial to evaluate safety and immunogenicity of an oral inactivated enterotoxigenic Escherichia coli prototype vaccine containing CFA/I overexpressing bacteria and recombinantly produced LTB/CTB hybrid protein. Vaccine 2013; 31:1163-70. [DOI: 10.1016/j.vaccine.2012.12.063] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Revised: 12/18/2012] [Accepted: 12/26/2012] [Indexed: 11/30/2022]
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44
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Zhang W, Sack DA. Progress and hurdles in the development of vaccines against enterotoxigenic Escherichia coli in humans. Expert Rev Vaccines 2012; 11:677-94. [PMID: 22873126 DOI: 10.1586/erv.12.37] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Diarrhea is the second leading cause of death in children younger than 5 years. Enterotoxigenic Escherichia coli (ETEC) strains are the most common bacterial cause of diarrhea in young children living in endemic countries and children and adults traveling to these areas. Pathogenesis of ETEC diarrhea has been well studied, and the key virulence factors are bacterial colonization factor antigens and enterotoxins produced by ETEC strains. Colonization factor antigens mediate bacteria attachment to host small intestinal epithelial cells and subsequent colonization, whereas enterotoxins including heat-labile and heat-stable toxins disrupt fluid homeostasis in host epithelial cells, which leads to fluid and electrolyte hypersecretion and diarrhea. Vaccines stimulating host anti-adhesin immunity to block ETEC attachment and colonization and also antitoxin immunity to neutralize enterotoxicity are considered optimal for prevention of ETEC diarrhea. Vaccines under development have been designed to stimulate local intestinal immunity and are either oral vaccines or transcutaneous vaccines. A cholera vaccine (Dukoral®) does stimulate anti-heat-labile toxin immunity and is licensed for short-term protection of ETEC diarrhea in travelers in some countries. Newer experimental ETEC vaccine candidates are being developed with hope to provide long-lasting and more broad-based protection against ETEC. Some have shown promising results in safety and immunogenicity studies and are approaching field trials for efficacy. A key problem is the development of a vaccine that is both practical and inexpensive so that it can be affordable for use in poor countries where it is needed.
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Affiliation(s)
- Weiping Zhang
- Veterinary & Biomedical Sciences Department, South Dakota State University, Brookings, SD, USA.
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45
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Darsley MJ, Chakraborty S, DeNearing B, Sack DA, Feller A, Buchwaldt C, Bourgeois AL, Walker R, Harro CD. The oral, live attenuated enterotoxigenic Escherichia coli vaccine ACE527 reduces the incidence and severity of diarrhea in a human challenge model of diarrheal disease. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:1921-31. [PMID: 23035175 PMCID: PMC3535858 DOI: 10.1128/cvi.00364-12] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 09/24/2012] [Indexed: 11/20/2022]
Abstract
An oral, live attenuated, three-strain recombinant bacterial vaccine, ACE527, was demonstrated to generate strong immune responses to colonization factor and toxin antigens of enterotoxigenic Escherichia coli (ETEC) in human volunteers. The vaccine was safe and well tolerated at doses of up to 10(11) CFU, administered in each of two doses given 21 days apart. These observations have now been extended in a phase 2b study with a total of 70 subjects. Fifty-six of these subjects were challenged 28 days after the second dose of vaccine with the highly virulent ETEC strain H10407 to obtain preliminary indicators of efficacy against disease and to support further development of the vaccine for both travelers and infants in countries where ETEC is endemic. The vaccine had a significant impact on intestinal colonization by the challenge strain, as measured by quantitative fecal culture 2 days after challenge, demonstrating the induction of a functional immune response to the CFA/I antigen. The incidence and severity of diarrhea were also reduced in vaccinees as measured by a number of secondary and ad hoc endpoints, although the 27% reduction seen in the primary endpoint, moderate to severe diarrhea, was not statistically significant. Together, these observations support the hypothesis that the ACE527 vaccine has a dual mode of action, targeting both colonization factors and the heat-labile enterotoxin (LT), and suggest that it should be further developed for more advanced trials to evaluate its impact on the burden of ETEC disease in field settings.
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46
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Qadri F, Bhuiyan TR, Sack DA, Svennerholm AM. Immune responses and protection in children in developing countries induced by oral vaccines. Vaccine 2012; 31:452-60. [PMID: 23153448 DOI: 10.1016/j.vaccine.2012.11.012] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2012] [Revised: 10/30/2012] [Accepted: 11/02/2012] [Indexed: 12/22/2022]
Abstract
Oral mucosal vaccines have great promise for generating protective immunity against intestinal infections for the benefit of large numbers of people especially young children. There however appears to be a caveat since these vaccines have to overcome the inbuilt resistance of mucosal surfaces and secretions to inhibit antigen stimulation and responses. Unfortunately, these vaccines are not equally immunogenic nor protective in different populations. When compared to industrialized countries, children living in developing countries appear to have lower responses, but the reasons for these lowered responses are not clearly defined. The most likely explanations relate to undernutrition, micronutrient deficiencies, microbial overload on mucosal surfaces, alteration of microbiome and microbolom and irreversible changes on the mucosa as well as maternal antibodies in serum or breast milk may alter the mucosal pathology and lower immune responses to interventions using oral vaccines. The detrimental effect of adverse environment and malnutrition may bring about irreversible changes in the mucosa of children especially in the first 1000 days of life from conception to after birth and up to two years of age. This review aims to summarize the information available on lowered immune responses to mucosal vaccines and on interventions that may help address the constraints of these vaccines when they are used for children living under the greatest stress and under harmful adverse circumstances.
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Affiliation(s)
- Firdausi Qadri
- Centre for Vaccine Sciences, International Centre for Diarrhoeal Disease Research Bangladesh, Dhaka, Bangladesh.
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47
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Roy SP, Rahman MM, Yu XD, Tuittila M, Knight SD, Zavialov AV. Crystal structure of enterotoxigenic Escherichia coli colonization factor CS6 reveals a novel type of functional assembly. Mol Microbiol 2012; 86:1100-15. [PMID: 23046340 DOI: 10.1111/mmi.12044] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2012] [Indexed: 11/28/2022]
Abstract
Coli surface antigen 6 (CS6) is a widely expressed enterotoxigenic Escherichia coli (ETEC) colonization factor that mediates bacterial attachment to the small intestinal epithelium. CS6 is a polymer of two protein subunits CssA and CssB, which are secreted and assembled on the cell surface via the CssC/CssD chaperone usher (CU) pathway. Here, we present an atomic resolution model for the structure of CS6 based on the results of X-ray crystallographic, spectroscopic and biochemical studies, and suggest a mechanism for CS6-mediated adhesion. We show that the CssA and CssB subunits are assembled alternately in linear fibres by the principle of donor strand complementation. This type of fibre assembly is novel for CU assembled adhesins. We also show that both subunits in the fibre bind to receptors on epithelial cells, and that CssB, but not CssA, specifically recognizes the extracellular matrix protein fibronectin. Taken together, structural and functional results suggest that CS6 is an adhesive organelle of a novel type, a hetero-polyadhesin that is capable of polyvalent attachment to different receptors.
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Affiliation(s)
- Saumendra P Roy
- Department of Molecular Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences, SE-753 24 Uppsala, Sweden
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48
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Unnikrishnan M, Rappuoli R, Serruto D. Recombinant bacterial vaccines. Curr Opin Immunol 2012; 24:337-42. [PMID: 22541723 DOI: 10.1016/j.coi.2012.03.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2012] [Accepted: 03/19/2012] [Indexed: 01/09/2023]
Abstract
Vaccines are currently available for many infectious diseases caused by several microbes and the prevention of disease and death by vaccination has profoundly improved public health globally. However, vaccines are not yet licensed for use against many other infectious diseases and new or improved vaccines are needed to replace suboptimal vaccines, and against newly emerging pathogens. Most of the vaccines currently licensed for human use include live attenuated and inactivated or killed microorganisms. Only a small subset is based on purified components and even fewer are recombinantly produced. Novel approaches in recombinant DNA technology, genomics and structural biology have revolutionized the way vaccine candidates are developed and will make a significant impact in the generation of safer and more effective vaccines.
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Affiliation(s)
- Meera Unnikrishnan
- Novartis Vaccines and Diagnostics, Via Fiorentina 1, 53100, Siena, Italy
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Generation and characterization of a live attenuated enterotoxigenic Escherichia coli combination vaccine expressing six colonization factors and heat-labile toxin subunit B. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2011; 18:2128-35. [PMID: 21994355 DOI: 10.1128/cvi.05345-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Live attenuated oral enterotoxigenic Escherichia coli (ETEC) vaccines have been demonstrated to be safe and immunogenic in human volunteers and to provide a viable approach to provide protection against this important pathogen. This report describes the construction of new ETEC vaccine candidate strains from recent clinical isolates and their characterization. All known genes for ETEC toxins were removed, and attenuating deletion mutations were made in the aroC, ompC, and ompF chromosomal genes. An isolate expressing coli surface antigen 2 (CS2), CS3, heat-labile toxin (LT), heat-stable toxin (ST), and enteroaggregative Escherichia coli heat-stable toxin 1 (EAST1) was attenuated to generate ACAM2007. The subsequent insertion of the operon encoding CS1 created ACAM2017, and this was further modified by the addition of an expression cassette containing the eltB gene, encoding a pentamer of B subunits of LT (LTB), to generate ACAM2027. Another isolate expressing CS5, CS6, LT, ST, and EAST1 was attenuated to generate ACAM2006, from which a lysogenic prophage was deleted to create ACAM2012 and an LTB gene was introduced to form ACAM2022. Finally, a previously described vaccine strain, ACAM2010, had the eltB gene incorporated to generate ACAM2025. All recombinant genes were incorporated into the chromosomal sites of the attenuating mutations to ensure maximal genetic stability. The expression of the recombinant antigens and the changes in plasmids accompanying the deletion of toxin genes are described. Strains ACAM2025, ACAM2022, and ACAM2027 have been combined to create the ETEC vaccine formulation ACE527, which has recently successfully completed a randomized, double-blind, placebo-controlled phase I trial and is currently undergoing a randomized, double-blind placebo-controlled phase II challenge trial, both in healthy adult volunteers.
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