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Duan Q, Xia P, Nandre R, Zhang W, Zhu G. Review of Newly Identified Functions Associated With the Heat-Labile Toxin of Enterotoxigenic Escherichia coli. Front Cell Infect Microbiol 2019; 9:292. [PMID: 31456954 PMCID: PMC6700299 DOI: 10.3389/fcimb.2019.00292] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 07/29/2019] [Indexed: 12/11/2022] Open
Abstract
Heat-labile toxin (LT) is a well-characterized powerful enterotoxin produced by enterotoxigenic Escherichia coli (ETEC). This toxin is known to contribute to diarrhea in young children in developing countries, international travelers, as well as many different species of young animals. Interestingly, it has also been revealed that LT is involved in other activities in addition to its role in enterotoxicity. Recent studies have indicated that LT toxin enhances enteric pathogen adherence and subsequent intestinal colonization. LT has also been shown to act as a powerful adjuvant capable of upregulating vaccine antigenicity; it also serves as a protein or antigenic peptide display platform for new vaccine development, and can be used as a naturally derived cell targeting and protein delivery tool. This review summarizes the epidemiology, secretion, delivery, and mechanisms of action of LT, while also highlighting new functions revealed by recent studies.
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Affiliation(s)
- Qiangde Duan
- College of Veterinary Medicine, Institute of Comparative Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Pengpeng Xia
- College of Veterinary Medicine, Institute of Comparative Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
| | - Rahul Nandre
- Department of Microbiology and Immunology, Uniformed Services University, Bethesda, MD, United States
| | - Weiping Zhang
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, IL, United States
| | - Guoqiang Zhu
- College of Veterinary Medicine, Institute of Comparative Medicine, Yangzhou University, Yangzhou, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety of Ministry of Education of China, Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou, China
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ADP-ribosylating enterotoxins as vaccine adjuvants. Curr Opin Pharmacol 2018; 41:42-51. [PMID: 29702466 DOI: 10.1016/j.coph.2018.03.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 03/30/2018] [Indexed: 01/18/2023]
Abstract
Most infections are caused by pathogens that access the body at mucosal sites. Hence, development of mucosal vaccines to prevent local infection or invasion of pathogens appears highly warranted, especially since only mucosal immunization will stimulate strong local IgA responses and tissue resident memory CD4 and CD8 T cells. The most significant obstacle to developing such vaccines is the lack of approved adjuvants that can effectively and safely enhance relevant mucosal and systemic immune responses. The most potent mucosal adjuvants known today are the adenosine diphosphate (ADP)-ribosylating bacterial enterotoxins cholera toxin (CT) and Escherichia coli heat-labile toxins (LTs). Unfortunately, these molecules are also very toxic, which precludes their clinical use. However, much effort has been devoted to developing derivatives of these enterotoxins with low or no toxicity and retained adjuvant activity. Although it is fair to say that we know more about how these toxins affect the immune system than ever before, we still lack a detailed understanding of how and why these toxins are effective adjuvants. In the present review, we provide a state-of-the-art overview of the mechanism of action of the holotoxins and the strategies used for improving the toxin-based adjuvants.
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Lyons NA, Lyoo YS, King DP, Paton DJ. Challenges of Generating and Maintaining Protective Vaccine-Induced Immune Responses for Foot-and-Mouth Disease Virus in Pigs. Front Vet Sci 2016; 3:102. [PMID: 27965966 PMCID: PMC5127833 DOI: 10.3389/fvets.2016.00102] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 11/01/2016] [Indexed: 12/31/2022] Open
Abstract
Vaccination can play a central role in the control of outbreaks of foot-and-mouth disease (FMD) by reducing both the impact of clinical disease and the extent of virus transmission between susceptible animals. Recent incursions of exotic FMD virus lineages into several East Asian countries have highlighted the difficulties of generating and maintaining an adequate immune response in vaccinated pigs. Factors that impact vaccine performance include (i) the potency, antigenic payload, and formulation of a vaccine; (ii) the antigenic match between the vaccine and the heterologous circulating field strain; and (iii) the regime (timing, frequency, and herd-level coverage) used to administer the vaccine. This review collates data from studies that have evaluated the performance of foot-and-mouth disease virus vaccines at the individual and population level in pigs and identifies research priorities that could provide new insights to improve vaccination in the future.
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Affiliation(s)
- Nicholas A. Lyons
- The Pirbright Institute, Pirbright, UK
- European Commission for the Control of Foot-and-Mouth Disease, Food and Agriculture Organization of the United Nations, Rome, Italy
| | - Young S. Lyoo
- College of Veterinary Medicine, Konkuk University, Seoul, South Korea
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Ma Y. Recent advances in nontoxicEscherichia coliheat-labile toxin and its derivative adjuvants. Expert Rev Vaccines 2016; 15:1361-1371. [DOI: 10.1080/14760584.2016.1182868] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Gong Y, Tao L, Wang F, Liu W, Jing L, Liu D, Hu S, Xie Y, Zhou N. Chitosan as an adjuvant for a Helicobacter pylori therapeutic vaccine. Mol Med Rep 2015; 12:4123-4132. [PMID: 26095723 PMCID: PMC4526086 DOI: 10.3892/mmr.2015.3950] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 05/13/2015] [Indexed: 11/05/2022] Open
Abstract
The aim of the present study was to delineate the therapeutic effect of a Helicobacter pylori vaccine with chitosan as an adjuvant, as well as to identify the potential mechanism against H. pylori infection when compared with an H. pylori vaccine, with cholera toxin (CT) as an adjuvant. Mice were first infected with H. pylori and, following the establishment of an effective infection model, were vaccinated using an H. pylori protein vaccine with chitosan as an adjuvant. Levels of H. pylori colonization, H. pylori‑specific antibodies and cytokines were determined by enzyme‑linked immunosorbent assay. The TLR4 and Foxp3 mRNA and protein levels were determined by reverse transcription polymerase chain reaction and immunohistochemistry, respectively. It was identified that the H. pylori elimination rate of the therapeutic vaccine with chitosan as an adjuvant (58.33%) was greater than the therapeutic vaccine with CT as an adjuvant (45.45%). The therapeutic H. pylori vaccine with chitosan as an adjuvant induced significantly greater antibody and cytokine levels when compared with the control groups. Notably, the IL‑10 and IL‑4 levels in the groups with chitosan as an adjuvant to the H. pylori vaccine were significantly greater than those in the groups with CT as an adjuvant. The mRNA expression levels of TLR4 and Foxp3 were significantly elevated in the mice that were vaccinated with chitosan as an adjuvant to the H. pylori vaccine, particularly in mice where the H. pylori infection had been eradicated. The H. pylori vaccine with chitosan as an adjuvant effectively increased the H. pylori elimination rate, the humoral immune response and the Th1/Th2 cell immune reaction; in addition, the therapeutic H. pylori vaccine regulated the Th1 and Th2 response. The significantly increased TLR4 expression and decreased CD4+CD25+Foxp3+Treg cell number contributed to the immune clearance of the H. pylori infection. Thus, the present findings demonstrate that in mice the H. pylori vaccine with chitosan as an adjuvant exerts an equivalent immunotherapeutic effect on H. pylori infection when compared with the H. pylori vaccine with CT as an adjuvant.
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Affiliation(s)
- Yanfeng Gong
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Liming Tao
- Department of Obstetrics, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Fucai Wang
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Wei Liu
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Lei Jing
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Dongsheng Liu
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Sijun Hu
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Yong Xie
- Department of Gastroenterology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi 330000, P.R. China
| | - Nanjin Zhou
- Department of Biochemistry and Molecular Biology, Jiangxi Medical Science Institute, Nanchang, Jiangxi 330006, P.R. China
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Newsted D, Fallahi F, Golshani A, Azizi A. Advances and challenges in mucosal adjuvant technology. Vaccine 2015; 33:2399-405. [PMID: 25865473 DOI: 10.1016/j.vaccine.2015.03.096] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 03/17/2015] [Accepted: 03/26/2015] [Indexed: 12/23/2022]
Abstract
Adjuvants play attractive roles in enhancement of immune response during vaccination; however, due to several challenges, only a limited number of adjuvants are licensed by health authorities. The lack of an effective mucosal adjuvant is even more significant as none of the licensed adjuvants revealed a strong enhancement in immune system after mucosal administration. Over the past two decades, several mucosal adjuvants have been developed to deliver antigens to the target cells in the mucosal immune system and increase specific immune responses. However, the safety and efficacy of these adjuvants for testing in human trials is still an important issue, requiring further study. In this article, we briefly review the challenges associated with most common mucosal adjuvants and discuss potential strategies for targeting the mucosal immune system.
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Affiliation(s)
- Daniel Newsted
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main St W, Hamilton, ON, Canada
| | | | - Ashkan Golshani
- Department of Biology, Carleton University, 1125 Colonel by Drive, Ottawa, ON, Canada
| | - Ali Azizi
- Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, Canada; Department of Biotechnology, University of Ontario Institute of Technology, Toronto, ON, Canada.
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Li P, Li Y, Shao G, Yu Q, Yang Q. Comparison of immune responses to intranasal and intrapulmonary vaccinations with the attenuated Mycoplasma hyopneumoniae 168 strain in pigs. J Vet Med Sci 2015; 77:519-25. [PMID: 25649413 PMCID: PMC4478730 DOI: 10.1292/jvms.14-0123] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The aim of this study was to evaluate the immune responses to intranasal and
intrapulmonary vaccinations with the attenuated Mycoplasma hyopneumoniae
(Mhp) 168 strain in the local respiratory tract in pigs. Twenty-four
pigs were randomly divided into 4 groups: an intranasal immunization group, an
intrapulmonary immunization group, an intramuscular immunization group and a control
group. The levels of local respiratory tract cellular and humoral immune responses were
investigated. The levels of interleukin (IL)-6 in the early stage of immunization
(P<0.01), local specific secretory IgA (sIgA) in nasal swab samples
(P<0.01); and IgA- and IgG-secreting cells in the nasal mucosa and
trachea were higher after intranasal vaccination (P<0.01) than in the
control group. Interestingly, intrapulmonary immunization induced much stronger immune
responses than intranasal immunization. Intrapulmonary immunization also significantly
increased the secretion of IL-6 and local specific sIgA and the numbers of IgA- and
IgG-secreting cells. The levels of IL-10 and interferon-γ in the nasal swab samples and
the numbers of CD4+ and CD8+ T lymphocytes in the lung and hilar
lymph nodes were significantly increased by intrapulmonary immunization compared with
those in the control group (P<0.01). These data suggest that
intrapulmonary immunization with attenuated Mhp is effective in evoking
local cellular and humoral immune responses in the respiratory tract. Intrapulmonary
immunization with Mhp may be a promising route for defense against
Mhp in pigs.
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Affiliation(s)
- Pengcheng Li
- College of Veterinary Medicine, Nanjing Agricultural University, Nanjing, PR China
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Alejo DM, Moraes MP, Liao X, Dias CC, Tulman ER, Diaz-San Segundo F, Rood D, Grubman MJ, Silbart LK. An adenovirus vectored mucosal adjuvant augments protection of mice immunized intranasally with an adenovirus-vectored foot-and-mouth disease virus subunit vaccine. Vaccine 2013; 31:2302-9. [PMID: 23499593 DOI: 10.1016/j.vaccine.2013.02.060] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 02/08/2013] [Accepted: 02/27/2013] [Indexed: 11/30/2022]
Abstract
Foot-and-mouth disease virus (FMDV) is a highly contagious pathogen that causes severe morbidity and economic losses to the livestock industry in many countries. The oral and respiratory mucosae are the main ports of entry of FMDV, so the stimulation of local immunity in these tissues may help prevent initial infection and viral spread. E. coli heat-labile enterotoxin (LT) has been described as one of the few molecules that have adjuvant activity at mucosal surfaces. The objective of this study was to evaluate the efficacy of replication-defective adenovirus 5 (Ad5) vectors encoding either of two LT-based mucosal adjuvants, LTB or LTR72. These vectored adjuvants were delivered intranasally to mice concurrent with an Ad5-FMDV vaccine (Ad5-A24) to assess their ability to augment mucosal and systemic humoral immune responses to Ad5-A24 and protection against FMDV. Mice receiving Ad5-A24 plus Ad5-LTR72 had higher levels of mucosal and systemic neutralizing antibodies than those receiving Ad5-A24 alone or Ad5-A24 plus Ad5-LTB. The vaccine plus Ad5-LTR72 group also demonstrated 100% survival after intradermal challenge with a lethal dose of homologous FMDV serotype A24. These results suggest that Ad5-LTR72 could be used as an important tool to enhance mucosal and systemic immunity against FMDV and potentially other pathogens with a common route of entry.
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Affiliation(s)
- Diana M Alejo
- Department of Animal Science, University of Connecticut, Storrs, CT 06269, United States
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Xenoepitope substitution avoids deceptive imprinting and broadens the immune response to foot-and-mouth disease virus. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:461-7. [PMID: 22323558 DOI: 10.1128/cvi.00035-12] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many RNA viruses encode error-prone polymerases which introduce mutations into B and T cell epitopes, providing a mechanism for immunological escape. When regions of hypervariability are found within immunodominant epitopes with no known function, they are referred to as "decoy epitopes," which often deceptively imprint the host's immune response. In this work, a decoy epitope was identified in the foot-and-mouth disease virus (FMDV) serotype O VP1 G-H loop after multiple sequence alignment of 118 isolates. A series of chimeric cyclic peptides resembling the type O G-H loop were prepared, each bearing a defined "B cell xenoepitope" from another virus in place of the native decoy epitope. These sequences were derived from porcine respiratory and reproductive syndrome virus (PRRSV), from HIV, or from a presumptively tolerogenic sequence from murine albumin and were subsequently used as immunogens in BALB/c mice. Cross-reactive antibody responses against all peptides were compared to a wild-type peptide and ovalbumin (OVA). A broadened antibody response was generated in animals inoculated with the PRRSV chimeric peptide, in which virus binding of serum antibodies was also observed. A B cell epitope mapping experiment did not reveal recognition of any contiguous linear epitopes, raising the possibility that the refocused response was directed to a conformational epitope. Taken together, these results indicate that xenoepitope substitution is a novel method for immune refocusing against decoy epitopes of RNA viruses such as FMDV as part of the rational design of next-generation vaccines.
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