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Ascough S, Ingram RJ, Chu KK, Reynolds CJ, Musson JA, Doganay M, Metan G, Ozkul Y, Baillie L, Sriskandan S, Moore SJ, Gallagher TB, Dyson H, Williamson ED, Robinson JH, Maillere B, Boyton RJ, Altmann DM. Anthrax lethal factor as an immune target in humans and transgenic mice and the impact of HLA polymorphism on CD4+ T cell immunity. PLoS Pathog 2014; 10:e1004085. [PMID: 24788397 PMCID: PMC4006929 DOI: 10.1371/journal.ppat.1004085] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Accepted: 03/07/2014] [Indexed: 11/23/2022] Open
Abstract
Bacillus anthracis produces a binary toxin composed of protective antigen (PA) and one of two subunits, lethal factor (LF) or edema factor (EF). Most studies have concentrated on induction of toxin-specific antibodies as the correlate of protective immunity, in contrast to which understanding of cellular immunity to these toxins and its impact on infection is limited. We characterized CD4+ T cell immunity to LF in a panel of humanized HLA-DR and DQ transgenic mice and in naturally exposed patients. As the variation in antigen presentation governed by HLA polymorphism has a major impact on protective immunity to specific epitopes, we examined relative binding affinities of LF peptides to purified HLA class II molecules, identifying those regions likely to be of broad applicability to human immune studies through their ability to bind multiple alleles. Transgenics differing only in their expression of human HLA class II alleles showed a marked hierarchy of immunity to LF. Immunogenicity in HLA transgenics was primarily restricted to epitopes from domains II and IV of LF and promiscuous, dominant epitopes, common to all HLA types, were identified in domain II. The relevance of this model was further demonstrated by the fact that a number of the immunodominant epitopes identified in mice were recognized by T cells from humans previously infected with cutaneous anthrax and from vaccinated individuals. The ability of the identified epitopes to confer protective immunity was demonstrated by lethal anthrax challenge of HLA transgenic mice immunized with a peptide subunit vaccine comprising the immunodominant epitopes that we identified. Anthrax is of concern with respect to human exposure in endemic regions, concerns about bioterrorism and the considerable global burden of livestock infections. The immunology of this disease remains poorly understood. Vaccination has been based on B. anthracis filtrates or attenuated spore-based vaccines, with more recent trials of next-generation recombinant vaccines. Approaches generally require extensive vaccination regimens and there have been concerns about immunogenicity and adverse reactions. An ongoing need remains for rationally designed, effective and safe anthrax vaccines. The importance of T cell stimulating vaccines is inceasingly recognized. An essential step is an understanding of immunodominant epitopes and their relevance across the diverse HLA immune response genes of human populations. We characterized CD4 T cell immunity to anthrax Lethal Factor (LF), using HLA transgenic mice, as well as testing candidate peptide epitopes for binding to a wide range of HLA alleles. We identified anthrax epitopes, noteworthy in that they elicit exceptionally strong immunity with promiscuous binding across multiple HLA alleles and isotypes. T cell responses in humans exposed to LF through either natural anthrax infection or vaccination were also examined. Epitopes identified as candidates were used to protect HLA transgenic mice from anthrax challenge.
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Affiliation(s)
- Stephanie Ascough
- Department of Medicine, Imperial College London, London, United Kingdom
| | - Rebecca J. Ingram
- Centre for Infection and Immunity, Queen's University Belfast, Belfast, United Kingdom
| | - Karen K. Chu
- Department of Medicine, Imperial College London, London, United Kingdom
| | | | - Julie A. Musson
- Institute for Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mehmet Doganay
- Department of Infectious Disease, Erciyes University Hospital, Kayseri, Turkey
| | - Gökhan Metan
- Department of Infectious Disease, Erciyes University Hospital, Kayseri, Turkey
| | - Yusuf Ozkul
- Department of Medical Genetics, Erciyes University Hospital, Kayseri, Turkey
| | - Les Baillie
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, United Kingdom
| | | | - Stephen J. Moore
- BIOMET, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Theresa B. Gallagher
- BIOMET, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Hugh Dyson
- Defence Science Technology Laboratory, Porton Down, Salisbury, United Kingdom
| | - E. Diane Williamson
- Defence Science Technology Laboratory, Porton Down, Salisbury, United Kingdom
| | - John H. Robinson
- Institute for Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Bernard Maillere
- CEA, iBiTecS, Service d'Ingénierie Moléculaire des Protéines (SIMOPRO), Gif Sur Yvette, France
| | | | - Daniel M. Altmann
- Department of Medicine, Imperial College London, London, United Kingdom
- * E-mail:
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Dumas EK, Cox PM, Fullenwider CO, Nguyen M, Centola M, Frank MB, Dozmorov I, James JA, Farris AD. Anthrax lethal toxin-induced gene expression changes in mouse lung. Toxins (Basel) 2011; 3:1111-30. [PMID: 22039574 PMCID: PMC3202878 DOI: 10.3390/toxins3091111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 08/24/2011] [Accepted: 09/06/2011] [Indexed: 11/16/2022] Open
Abstract
A major virulence factor of Bacillus anthracis is the anthrax Lethal Toxin (LeTx), a bipartite toxin composed of Protective Antigen and Lethal Factor. Systemic administration of LeTx to laboratory animals leads to death associated with vascular leakage and pulmonary edema. In this study, we investigated whether systemic exposure of mice to LeTx would induce gene expression changes associated with vascular/capillary leakage in lung tissue. We observed enhanced susceptibility of A/J mice to death by systemic LeTx administration compared to the C57BL/6 strain. LeTx-induced groups of both up- and down-regulated genes were observed in mouse lungs 6 h after systemic administration of wild type toxin compared to lungs of mice exposed to an inactive mutant form of the toxin. Lungs of the less susceptible C57BL/6 strain showed 80% fewer differentially expressed genes compared to lungs of the more sensitive A/J strain. Expression of genes known to regulate vascular permeability was modulated by LeTx in the lungs of the more susceptible A/J strain. Unexpectedly, the largest set of genes with altered expression was immune specific, characterized by the up-regulation of lymphoid genes and the down-regulation of myeloid genes. Transcripts encoding neutrophil chemoattractants, modulators of tumor regulation and angiogenesis were also differentially expressed in both mouse strains. These studies provide new directions for the investigation of vascular leakage and pulmonary edema induced by anthrax LeTx.
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Affiliation(s)
- Eric K. Dumas
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Philip M. Cox
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Charles O’Connor Fullenwider
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Melissa Nguyen
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Michael Centola
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Microarray Research Facility, Oklahoma Medical Research Foundation, 825 NE 13th Street, MS 53, Oklahoma City, OK 73104, USA
| | - Mark Barton Frank
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Microarray Research Facility, Oklahoma Medical Research Foundation, 825 NE 13th Street, MS 53, Oklahoma City, OK 73104, USA
| | - Igor Dozmorov
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - Judith A. James
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
| | - A. Darise Farris
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, 1100 N. Lindsay, Oklahoma City, OK 73104, USA; (E.K.D.); (M.N.); (J.A.J.)
- Arthritis and Clinical Immunology Program, Oklahoma Medical Research Foundation; 825 NE 13 Street, MS 53, Oklahoma City, OK 73104, USA; (P.M.C.); (C.O.F.); (M.C.); (M.B.K.); (I.D.)
- Author to whom correspondence should be addressed; ; Tel.: +1-405-271-7389; Fax: +1-405-271-706
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Donaldson DS, Williams NA. Bacterial toxins as immunomodulators. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 666:1-18. [PMID: 20054971 DOI: 10.1007/978-1-4419-1601-3_1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Bacterial toxins are the causative agent at pathology in a variety of diseases. Although not always the primary target of these toxins, many have been shown to have potent immunomodulatory effects, for example, inducing immune responses to co-administered antigens and suppressing activation of immune cells. These abilities of bacterial toxins can be harnessed and used in a therapeutic manner, such as in vaccination or the treatment of autoimmune diseases. Furthermore, the ability of toxins to gain entry to cells can be used in novel bacterial toxin based immuno-therapies in order to deliver antigens into MHC Class I processing pathways. Whether the immunomodulatory properties of these toxins arose in order to enhance bacterial survival within hosts, to aid spread within the population or is pure serendipity, it is interesting to think that these same toxins potentially hold the key to preventing or treating human disease.
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Affiliation(s)
- David S Donaldson
- Department of Cellular and Molecular Medicine, School of Medicine Sciences, University of Bristol, Bristol, UK
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Brey RN. Molecular basis for improved anthrax vaccines. Adv Drug Deliv Rev 2005; 57:1266-92. [PMID: 15935874 DOI: 10.1016/j.addr.2005.01.028] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Accepted: 01/25/2005] [Indexed: 01/26/2023]
Abstract
The current vaccine for anthrax has been licensed since 1970 and was developed based on the outcome of human trials conducted in the 1950s. This vaccine, known as anthrax vaccine adsorbed (AVA), consists of a culture filtrate from an attenuated strain of Bacillus anthracis adsorbed to aluminum salts as an adjuvant. This vaccine is considered safe and effective, but is difficult to produce and is associated with complaints about reactogenicity among users of the vaccine. Much of the work in the past decade on generating a second generation vaccine is based on the observation that antibodies to protective antigen (PA) are crucial in the protection against exposure to virulent anthrax spores. Antibodies to PA are thought to prevent binding to its cellular receptor and subsequent binding of lethal factor (LF) and edema factor (EF), which are required events for the action of the two toxins: lethal toxin (LeTx) and edema toxin (EdTx). The bacterial capsule as well as the two toxins are virulence factors of B. anthracis. The levels of antibodies to PA must exceed a certain minimal threshold in order to induce and maintain protective immunity. Immunity can be generated by vaccination with purified PA, as well as spores and DNA plasmids that express PA. Although antibodies to PA address the toxemia component of anthrax disease, antibodies to additional virulence factors, including the capsule or somatic antigens in the spore, may be critical in development of complete, sterilizing immunity to anthrax exposure. The next generation anthrax vaccines will be derived from the thorough understanding of the interaction of virulence factors with human and animal hosts and the role the immune response plays in providing protective immunity.
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Affiliation(s)
- Robert N Brey
- DOR BioPharma, Inc., 1691 Michigan Avenue, Suite 435, Miami, FL 33139, USA.
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Popov SG, Villasmil R, Bernardi J, Grene E, Cardwell J, Popova T, Wu A, Alibek D, Bailey C, Alibek K. Effect of Bacillus anthracis lethal toxin on human peripheral blood mononuclear cells. FEBS Lett 2002; 527:211-5. [PMID: 12220662 DOI: 10.1016/s0014-5793(02)03228-3] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Lethal toxin (LeTx) plays a central role in anthrax pathogenesis, however a cytotoxicity of LeTx has been difficult to demonstrate in vitro. No cytolytic effect has been reported for human cells, in contrast to murine cell lines, indicating that cell lysis can not be considered as a marker of LeTx activity. We have recently shown that murine macrophage-like RAW 264.7 cells treated with LeTx or infected with anthrax spores underwent changes typical of apoptotic death. Here we demonstrate that cells from human peripheral blood display a proapoptotic behavior similar to murine cells. TUNEL assay detected a nucleosomal degradation typical of apoptosis in peripheral blood mononuclear cells (PBMC) treated with LeTx. Membrane staining with apoptotic dyes was detected in macrophages derived from monocytes in presence of LeTx. The toxin inhibited production of proinflammatory cytokines in PBMC stimulated with a preparation of Bacillus anthracis cell wall. Infection of PBMC with anthrax spores led to the appearance of a large population of cells stained positively for apoptosis, with a reduced capacity to eliminate spores and vegetative bacteria. The aminopeptidase inhibitor, bestatin, capable of protecting cells from LeTx, restored a bactericidal activity of infected cells. These findings may be explained by LeTx expression within phagocytes and support an important role of LeTx as an early intracellular virulence factor contributing to bacterial dissemination and disease progression.
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Affiliation(s)
- Serguei G Popov
- Advanced Biosystems, Inc., 10900 University Blvd., MSN 1A8, Manassas, VA 20110, USA.
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Price BM, Liner AL, Park S, Leppla SH, Mateczun A, Galloway DR. Protection against anthrax lethal toxin challenge by genetic immunization with a plasmid encoding the lethal factor protein. Infect Immun 2001; 69:4509-15. [PMID: 11401993 PMCID: PMC98526 DOI: 10.1128/iai.69.7.4509-4515.2001] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The ability of genetic vaccination to protect against a lethal challenge of anthrax toxin was evaluated. BALB/c mice were immunized via gene gun inoculation with eucaryotic expression vector plasmids encoding either a fragment of the protective antigen (PA) or a fragment of lethal factor (LF). Plasmid pCLF4 contains the N-terminal region (amino acids [aa] 10 to 254) of Bacillus anthracis LF cloned into the pCI expression plasmid. Plasmid pCPA contains a biologically active portion (aa 175 to 764) of B. anthracis PA cloned into the pCI expression vector. One-micrometer-diameter gold particles were coated with plasmid pCLF4 or pCPA or a 1:1 mixture of both and injected into mice via gene gun (1 microg of plasmid DNA/injection) three times at 2-week intervals. Sera were collected and analyzed for antibody titer as well as antibody isotype. Significantly, titers of antibody to both PA and LF from mice immunized with the combination of pCPA and pCLF4 were four to five times greater than titers from mice immunized with either gene alone. Two weeks following the third and final plasmid DNA boost, all mice were challenged with 5 50% lethal doses of lethal toxin (PA plus LF) injected intravenously into the tail vein. All mice immunized with pCLF4, pCPA, or the combination of both survived the challenge, whereas all unimmunized mice did not survive. These results demonstrate that DNA-based immunization alone can provide protection against a lethal toxin challenge and that DNA immunization against the LF antigen alone provides complete protection.
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Affiliation(s)
- B M Price
- Department of Microbiology, The Ohio State University, Columbus, Ohio 43017-1292
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Brossier F, Weber-Levy M, Mock M, Sirard JC. Role of toxin functional domains in anthrax pathogenesis. Infect Immun 2000; 68:1781-6. [PMID: 10722564 PMCID: PMC97348 DOI: 10.1128/iai.68.4.1781-1786.2000] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We investigated the role of the functional domains of anthrax toxins during infection. Three proteins produced by Bacillus anthracis, the protective antigen (PA), the lethal factor (LF), and the edema factor (EF), combine in pairs to produce the lethal (PA+LF) and edema (PA+EF) toxins. A genetic strategy was developed to introduce by allelic exchange specific point mutations or in-frame deletions into B. anthracis toxin genes, thereby impairing either LF metalloprotease or EF adenylate cyclase activity or PA functional domains. In vivo effects of toxin mutations were analyzed in an experimental infection of mice. A tight correlation was observed between the properties of anthrax toxins delivered in vivo and their in vitro activities. The synergic effects of the lethal and edema toxins resulted purely from their enzymatic activities, suggesting that in vivo these toxins may act together. The PA-dependent antibody response to LF induced by immunization with live B. anthracis was used to follow the in vivo interaction of LF and PA. We found that the binding of LF to PA in vivo was necessary and sufficient for a strong antibody response against LF, whereas neither LF activity nor binding of lethal toxin complex to the cell surface was required. Mutant PA proteins were cleaved in mice sera. Thus, our data provide evidence that, during anthrax infection, PA may interact with LF before binding to the cell receptor. Immunoprotection studies indicated that the strain producing detoxified LF and EF, isogenic to the current live vaccine Sterne strain, is a safe candidate for use as a vaccine against anthrax.
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Affiliation(s)
- F Brossier
- Unité Toxines et Pathogénie Bactériennes, Institut Pasteur (CNRS URA 1858), 75724 Paris Cedex 15, France
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