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Tessier E, Cheutin L, Garnier A, Vigne C, Tournier JN, Rougeaux C. Early Circulating Edema Factor in Inhalational Anthrax Infection: Does It Matter? Microorganisms 2024; 12:308. [PMID: 38399712 PMCID: PMC10891819 DOI: 10.3390/microorganisms12020308] [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: 11/29/2023] [Revised: 01/22/2024] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
Anthrax toxins are critical virulence factors of Bacillus anthracis and Bacillus cereus strains that cause anthrax-like disease, composed of a common binding factor, the protective antigen (PA), and two enzymatic proteins, lethal factor (LF) and edema factor (EF). While PA is required for endocytosis and activity of EF and LF, several studies showed that these enzymatic factors disseminate within the body in the absence of PA after intranasal infection. In an effort to understand the impact of EF in the absence of PA, we used a fluorescent EF chimera to facilitate the study of endocytosis in different cell lines. Unexpectedly, EF was found inside cells in the absence of PA and showed a pole-dependent endocytosis. However, looking at enzymatic activity, PA was still required for EF to induce an increase in intracellular cAMP levels. Interestingly, the sequential delivery of EF and then PA rescued the rise in cAMP levels, indicating that PA and EF may functionally associate during intracellular trafficking, as well as it did at the cell surface. Our data shed new light on EF trafficking and the potential location of PA and EF association for optimal cytosolic delivery.
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Affiliation(s)
- Emilie Tessier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Laurence Cheutin
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Annabelle Garnier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Clarisse Vigne
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
| | - Jean-Nicolas Tournier
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
- Institut Pasteur, 75015 Paris, France
| | - Clémence Rougeaux
- Département des Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France (C.R.)
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2
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Varrone E, Carnicelli D, He X, Grasse M, Stampfer K, Huber S, Kellnerová S, Tazzari PL, Ricci F, Paterini P, Ardissino G, Morabito S, Orth-Höller D, Würzner R, Brigotti M. Detection of Cleaved Stx2a in the Blood of STEC-Infected Patients. Toxins (Basel) 2023; 15:690. [PMID: 38133194 PMCID: PMC10747961 DOI: 10.3390/toxins15120690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 11/24/2023] [Accepted: 12/04/2023] [Indexed: 12/23/2023] Open
Abstract
Typical hemolytic uremic syndrome (HUS) is mainly caused by Shiga toxin-producing Escherichia coli (STEC) releasing Shiga toxin 2 (Stx2). Two different structures of this AB5 toxin have been described: uncleaved, with intact B and A chains, and cleaved, with intact B and a nicked A chain consisting of two fragments, A1 and A2, connected by a disulfide bond. Despite having the same toxic effect on sensitive cells, the two forms differ in their binding properties for circulating cells, serum components and complement factors, thus contributing to the pathogenesis of HUS differently. The outcome of STEC infections and the development of HUS could be influenced by the relative amounts of uncleaved or cleaved Stx2 circulating in patients' blood. Cleaved Stx2 was identified and quantified for the first time in four out of eight STEC-infected patients' sera by a method based on the inhibition of cell-free translation. Cleaved Stx2 was present in the sera of patients with toxins bound to neutrophils and in two out of three patients developing HUS, suggesting its involvement in HUS pathogenesis, although in association with other bacterial or host factors.
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Affiliation(s)
- Elisa Varrone
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Via San Giacomo 14, 40126 Bologna, Italy; (E.V.); (D.C.); (P.P.)
| | - Domenica Carnicelli
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Via San Giacomo 14, 40126 Bologna, Italy; (E.V.); (D.C.); (P.P.)
| | - Xiaohua He
- Western Regional Research Center, U.S. Department of Agriculture, Agricultural Research Service, 800 Buchanan Street, Albany, CA 94710, USA;
| | - Marco Grasse
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.G.); (K.S.); (S.H.); (S.K.); (R.W.)
| | - Karin Stampfer
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.G.); (K.S.); (S.H.); (S.K.); (R.W.)
| | - Silke Huber
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.G.); (K.S.); (S.H.); (S.K.); (R.W.)
| | - Sára Kellnerová
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.G.); (K.S.); (S.H.); (S.K.); (R.W.)
| | - Pier Luigi Tazzari
- Immunohematology and Transfusion Center, S. Orsola-Malpighi Hospital, Via Massarenti 9, 40138 Bologna, Italy; (P.L.T.); (F.R.)
| | - Francesca Ricci
- Immunohematology and Transfusion Center, S. Orsola-Malpighi Hospital, Via Massarenti 9, 40138 Bologna, Italy; (P.L.T.); (F.R.)
| | - Paola Paterini
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Via San Giacomo 14, 40126 Bologna, Italy; (E.V.); (D.C.); (P.P.)
- Center for Applied Biomedical Research-CRBA, University of Bologna, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy
| | - Gianluigi Ardissino
- Center for HUS Control, Prevention and Management, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Via Commenda 9, 20122 Milano, Italy;
| | - Stefano Morabito
- European Reference Laboratory for Escherichia coli, Istituto Superiore di Sanità, 00161 Rome, Italy;
| | | | - Reinhard Würzner
- Institute of Hygiene and Medical Microbiology, Medical University of Innsbruck, 6020 Innsbruck, Austria; (M.G.); (K.S.); (S.H.); (S.K.); (R.W.)
| | - Maurizio Brigotti
- Department of Medical and Surgical Sciences (DIMEC), University of Bologna, Via San Giacomo 14, 40126 Bologna, Italy; (E.V.); (D.C.); (P.P.)
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3
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Boyer AE, Gallegos-Candela M, Lins RC, Solano MI, Woolfitt AR, Lee JS, Sanford DC, Knostman KAB, Quinn CP, Hoffmaster AR, Pirkle JL, Barr JR. Comprehensive characterization of toxins during progression of inhalation anthrax in a non-human primate model. PLoS Pathog 2022; 18:e1010735. [PMID: 36534695 PMCID: PMC9810172 DOI: 10.1371/journal.ppat.1010735] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 01/03/2023] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
Inhalation anthrax has three clinical stages: early-prodromal, intermediate-progressive, and late-fulminant. We report the comprehensive characterization of anthrax toxins, including total protective antigen (PA), total lethal factor (LF), total edema factor (EF), and their toxin complexes, lethal toxin and edema toxin in plasma, during the course of inhalation anthrax in 23 cynomolgus macaques. The toxin kinetics were predominantly triphasic with an early rise (phase-1), a plateau/decline (phase-2), and a final rapid rise (phase-3). Eleven animals had shorter survival times, mean±standard deviation of 58.7±7.6 hours (fast progression), 11 animals had longer survival times, 113±34.4 hours (slow progression), and one animal survived. Median (lower-upper quartile) LF levels at the end-of-phase-1 were significantly higher in animals with fast progression [138 (54.9-326) ng/mL], than in those with slow progression [23.8 (15.6-26.3) ng/mL] (p = 0.0002), and the survivor (11.1 ng/mL). The differences were also observed for other toxins and bacteremia. Animals with slow progression had an extended phase-2 plateau, with low variability of LF levels across all time points and animals. Characterization of phase-2 toxin levels defined upper thresholds; critical levels for exiting phase-2 and entering the critical phase-3, 342 ng/mL (PA), 35.8 ng/mL (LF), and 1.10 ng/mL (EF). The thresholds were exceeded earlier in animals with fast progression (38.5±7.4 hours) and later in animals with slow progression (78.7±15.2 hours). Once the threshold was passed, toxin levels rose rapidly in both groups to the terminal stage. The time from threshold to terminal was rapid and similar; 20.8±7.4 hours for fast and 19.9±7.5 hours for slow progression. The three toxemic phases were aligned with the three clinical stages of anthrax for fast and slow progression which showed that anthrax progression is toxin- rather than time-dependent. This first comprehensive evaluation of anthrax toxins provides new insights into disease progression.
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Affiliation(s)
- Anne E. Boyer
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
| | | | - Renato C. Lins
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- Battelle Atlanta Analytical Services, Atlanta, Georgia, United States of America
| | - Maria I. Solano
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Adrian R. Woolfitt
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - John S. Lee
- Biomedical Advanced Research and Development Authority, Washington, DC, United States of America
| | - Daniel C. Sanford
- Battelle Biomedical Research Center, West Jefferson, Ohio, United States of America
| | | | - Conrad P. Quinn
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Alex R. Hoffmaster
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - James L. Pirkle
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - John R. Barr
- Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
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4
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Cryan LM, Tsang TM, Stiles J, Bazinet L, Lee SL, Garrard S, Madrian E, Roberts C, Payne J, Jensen A, Frankel AE, Ackroyd PC, Christensen KA, Rogers MS. Capillary morphogenesis gene 2 (CMG2) mediates growth factor-induced angiogenesis by regulating endothelial cell chemotaxis. Angiogenesis 2022; 25:397-410. [PMID: 35212873 PMCID: PMC9250616 DOI: 10.1007/s10456-022-09833-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/06/2022] [Indexed: 11/28/2022]
Abstract
Anthrax protective antigen (PA) is a potent inhibitor of pathological angiogenesis with an unknown mechanism. In anthrax intoxication, PA interacts with capillary morphogenesis gene 2 (CMG2) and tumor endothelial marker 8 (TEM8). Here, we show that CMG2 mediates the antiangiogenic effects of PA and is required for growth-factor-induced chemotaxis. Using specific inhibitors of CMG2 and TEM8 interaction with natural ligand, as well as mice with the CMG2 or TEM8 transmembrane and intracellular domains disrupted, we demonstrate that inhibiting CMG2, but not TEM8 reduces growth-factor-induced angiogenesis in the cornea. Furthermore, the antiangiogenic effect of PA was abolished when the CMG2, but not the TEM8, gene was disrupted. Binding experiments demonstrated a broad ligand specificity for CMG2 among extracellular matrix (ECM) proteins. Ex vivo experiments demonstrated that CMG2 (but not TEM8) is required for PA activity in human dermal microvascular endothelial cell (HMVEC-d) network formation assays. Remarkably, blocking CMG2-ligand binding with PA or CRISPR knockout abolishes endothelial cell chemotaxis but not chemokinesis in microfluidic migration assays. These effects are phenocopied by Rho inhibition. Because CMG2 mediates the chemotactic response of endothelial cells to peptide growth factors in an ECM-dependent fashion, CMG2 is well-placed to integrate growth factor and ECM signals. Thus, CMG2 targeting is a novel way to inhibit angiogenesis.
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Affiliation(s)
- Lorna M Cryan
- Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA
| | - Tsz-Ming Tsang
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Jessica Stiles
- Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA
| | - Lauren Bazinet
- Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA
| | - Sai Lun Lee
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Samuel Garrard
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA.,Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA
| | - Erika Madrian
- Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA
| | - Cody Roberts
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Jessie Payne
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Andrew Jensen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Arthur E Frankel
- Department of Medicine, West Palm Beach VA Medical Center, 7305 N Military Trail, West Palm Beach, FL, 33410, USA
| | - P Christine Ackroyd
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Kenneth A Christensen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, 84602, USA
| | - Michael S Rogers
- Vascular Biology Program, Department of Surgery, Boston Children's Hospital, Harvard Medical School, 11.211 Karp Family Research Bldg., 300 Longwood Ave., Boston, MA, 02115, USA.
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5
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Tsilibary EPC, Souto EP, Kratzke M, James LM, Engdahl BE, Georgopoulos AP. Anthrax Protective Antigen 63 (PA63): Toxic Effects in Neural Cultures and Role in Gulf War Illness (GWI). Neurosci Insights 2020; 15:2633105520931966. [PMID: 32656531 PMCID: PMC7328487 DOI: 10.1177/2633105520931966] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 05/14/2020] [Indexed: 12/11/2022] Open
Abstract
Protective antigen (PA) 63 (PA63) is a protein derived from the PA83 component contained in the anthrax vaccine. The anthrax vaccine ("Biothrax") was administered together with other vaccines to Gulf War veterans, about 35% of whom later developed a multisymptom disease (Gulf War Illness [GWI]), with prominent neurological/cognitive/mood symptoms, among others. The disease has been traditionally attributed to exposures to toxic chemicals during the war but other factors could be involved, including vaccines received. Of these, the anthrax vaccine is the most toxic. Here, we assessed directly the PA63 toxin's harmful effects on cultured neuroblastoma 2A (N2A) cells with respect to cell spreading, process formation, apoptosis, and integrity of cell membrane, cytoskeleton, and mitochondria. We found that, when added in N2A cultures, PA63 toxin led to decreased cell spreading and cell aggregation, leading to apoptosis. The mechanisms of PA63-induced cell damage included compromised cell membrane permeability indicated by enhanced access of propidium iodide in cells. In addition, signaling pathways leading to organization of N2A cytoskeleton were negatively affected, as both actin and microtubular networks were compromised. Finally, the mitochondrial membrane potential was impaired in specific assays. Altogether, these alterations led to apoptosis as a collective toxic effect of PA63 which was substantially reduced by the concomitant addition of specific antibodies against PA63.
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Affiliation(s)
- Effie-Photini C Tsilibary
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA.,Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, USA
| | - Eric P Souto
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA
| | - Marian Kratzke
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA.,Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, USA
| | - Lisa M James
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA.,Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, USA.,Department of Psychiatry, Medical School, University of Minnesota, Minneapolis, MN, USA
| | - Brian E Engdahl
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA.,Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, USA.,Department of Psychology, University of Minnesota, Minneapolis, MN, USA
| | - Apostolos P Georgopoulos
- Brain Sciences Center, Department of Veterans Affairs Health Care System, Minneapolis, MN, USA.,Department of Neuroscience, Medical School, University of Minnesota, Minneapolis, MN, USA.,Department of Psychiatry, Medical School, University of Minnesota, Minneapolis, MN, USA.,Department of Neurology, Medical School, University of Minnesota, Minneapolis, MN, USA
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6
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Larkin IN, Garimella V, Yamankurt G, Scott AW, Xing H, Mirkin CA. Dual-Readout Sandwich Immunoassay for Device-Free and Highly Sensitive Anthrax Biomarker Detection. Anal Chem 2020; 92:7845-7851. [PMID: 32437125 PMCID: PMC7418077 DOI: 10.1021/acs.analchem.0c01090] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We report a dual-readout, AuNP-based sandwich immunoassay for the device-free colorimetric and sensitive scanometric detection of disease biomarkers. An AuNP-antibody conjugate serves as a signal transduction and amplification agent by promoting the reduction and deposition of either platinum or gold onto its surface, generating corresponding colorimetric or light scattering (scanometric) signals, respectively. We apply the Pt-based colorimetric readout of this assay to the discovery of a novel monoclonal antibody (mAb) sandwich pair for the detection of an anthrax protective antigen (PA83). The identified antibody pair detects PA83 down to 1 nM in phosphate-buffered saline and 5 nM in human serum, which are physiologically relevant concentrations. Reducing gold rather than platinum onto the mAb-AuNP sandwich enables scanometric detection of subpicomolar PA83 concentrations, over 3 orders of magnitude more sensitive than the colorimetric readout.
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Affiliation(s)
- Isaac N Larkin
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
- Department of Interdisciplinary Biological Sciences, Northwestern University, 2205 Tech Drive, Evanston, Illinois 60608, United States
| | - Viswanadham Garimella
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
| | - Gokay Yamankurt
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
- Department of Interdisciplinary Biological Sciences, Northwestern University, 2205 Tech Drive, Evanston, Illinois 60608, United States
| | - Alexander W Scott
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
- Department of Biomedical Engineering, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
| | - Hang Xing
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
| | - Chad A Mirkin
- International Institute for Nanotechnology, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60608, United States
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7
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Potential Therapeutic Targeting of Coronavirus Spike Glycoprotein Priming. Molecules 2020; 25:molecules25102424. [PMID: 32455942 PMCID: PMC7287953 DOI: 10.3390/molecules25102424] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/18/2020] [Accepted: 05/20/2020] [Indexed: 12/12/2022] Open
Abstract
Processing of certain viral proteins and bacterial toxins by host serine proteases is a frequent and critical step in virulence. The coronavirus spike glycoprotein contains three (S1, S2, and S2′) cleavage sites that are processed by human host proteases. The exact nature of these cleavage sites, and their respective processing proteases, can determine whether the virus can cross species and the level of pathogenicity. Recent comparisons of the genomes of the highly pathogenic SARS-CoV2 and MERS-CoV, with less pathogenic strains (e.g., Bat-RaTG13, the bat homologue of SARS-CoV2) identified possible mutations in the receptor binding domain and in the S1 and S2′ cleavage sites of their spike glycoprotein. However, there remains some confusion on the relative roles of the possible serine proteases involved for priming. Using anthrax toxin as a model system, we show that in vivo inhibition of priming by pan-active serine protease inhibitors can be effective at suppressing toxicity. Hence, our studies should encourage further efforts in developing either pan-serine protease inhibitors or inhibitor cocktails to target SARS-CoV2 and potentially ward off future pandemics that could develop because of additional mutations in the S-protein priming sequence in coronaviruses.
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8
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de Oliveira FFM, Mamillapalli S, Gonti S, Brey RN, Li H, Schiffer J, Casadevall A, Bann JG. Binding of the von Willebrand Factor A Domain of Capillary Morphogenesis Protein 2 to Anthrax Protective Antigen Vaccine Reduces Immunogenicity in Mice. mSphere 2020; 5:e00556-19. [PMID: 31941807 PMCID: PMC6968648 DOI: 10.1128/msphere.00556-19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 12/09/2019] [Indexed: 11/24/2022] Open
Abstract
Protective antigen (PA) is a component of anthrax toxin that can elicit toxin-neutralizing antibody responses. PA is also the major antigen in the current vaccine to prevent anthrax, but stability problems with recombinant proteins have complicated the development of new vaccines containing recombinant PA. The relationship between antigen physical stability and immunogenicity is poorly understood, but there are theoretical reasons to think that this parameter can affect immune responses. We investigated the immunogenicity of anthrax PA, in the presence and absence of the soluble von Willebrand factor A domain of the human form of receptor capillary morphogenesis protein 2 (sCMG2), to elicit antibodies to PA in BALB/c mice. Prior studies showed that sCMG2 stabilizes the 83-kDa PA structure to pH, chemical denaturants, temperature, and proteolysis and slows the hydrogen-deuterium exchange rate of histidine residues far from the binding interface. In contrast to a vaccine containing PA without adjuvant, we found that mice immunized with PA in stable complex with sCMG2 showed markedly reduced antibody responses to PA, including toxin-neutralizing antibodies and antibodies to domain 4, which correlated with fewer toxin-neutralizing antibodies. In contrast, mice immunized with PA in concert with a nonbinding mutant of sCMG2 (D50A) showed anti-PA antibody responses similar to those observed with PA alone. Our results suggest that addition of sCMG2 to a PA vaccine formulation is likely to result in a significantly diminished immune response, but we discuss the multitude of factors that could contribute to reduced immunogenicity.IMPORTANCE The anthrax toxin PA is the major immunogen in the current anthrax vaccine (anthrax vaccine adsorbed). Improving the anthrax vaccine for avoidance of a cold chain necessitates improvements in the thermodynamic stability of PA. We address how stabilizing PA using sCMG2 affects PA immunogenicity in BALB/c mice. Although the stability of PA is increased by binding to sCMG2, PA immunogenicity is decreased. This study emphasizes that, while binding of a ligand retains or improves conformational stability without affecting the native sequence, epitope recognition or processing may be affected, abrogating an effective immune response.
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Affiliation(s)
- Fabiana Freire Mendes de Oliveira
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
| | | | - Srinivas Gonti
- Department of Chemistry, Wichita State University, Wichita, Kansas, USA
| | | | - Han Li
- Division of Bacterial Disease, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Jarad Schiffer
- Division of Bacterial Disease, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA
| | - James G Bann
- Department of Chemistry, Wichita State University, Wichita, Kansas, USA
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9
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McCall RM, Sievers ME, Fattah R, Ghirlando R, Pomerantsev AP, Leppla SH. Bacillus anthracis Virulence Regulator AtxA Binds Specifically to the pagA Promoter Region. J Bacteriol 2019; 201:e00569-19. [PMID: 31570528 PMCID: PMC6832065 DOI: 10.1128/jb.00569-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 09/05/2019] [Indexed: 01/12/2023] Open
Abstract
Anthrax toxin activator (AtxA) is the master virulence gene regulator of Bacillus anthracis It regulates genes on the chromosome as well as the pXO1 and pXO2 plasmids. It is not clear how AtxA regulates these genes, and direct binding of AtxA to its targets has not been shown. It has been previously suggested that AtxA and other proteins in the Mga/AtxA global transcriptional regulators family bind to the curvature of their DNA targets, although this has never been experimentally proven. Using electrophoretic mobility shift assays, we demonstrate that AtxA binds directly to the promoter region of pagA upstream of the RNA polymerase binding site. We also demonstrate that in vitro, CO2 appears to have no role in AtxA binding. However, phosphomimetic and phosphoablative substitutions in the phosphotransferase system (PTS) regulation domains (PRDs) do appear to influence AtxA binding and pagA regulation. In silico, in vitro, and in vivo analyses demonstrate that one of two hypothesized stem-loops located upstream of the RNA polymerase binding site in the pagA promoter region is important for AtxA binding in vitro and pagA regulation in vivo Our study clarifies the mechanism by which AtxA interacts with one of its targets.IMPORTANCE Anthrax toxin activator (AtxA) regulates the major virulence genes in Bacillus anthracis The bacterium produces the anthrax toxins, and understanding the mechanism of toxin production may facilitate the development of therapeutics for B. anthracis infection. Since the discovery of AtxA 25 years ago, the mechanism by which it regulates its targets has largely remained a mystery. Here, we provide evidence that AtxA binds to the promoter region of the pagA gene encoding the main central protective antigen (PA) component of the anthrax toxin. These data suggest that AtxA binding plays a direct role in gene regulation. Our work also assists in clarifying the role of CO2 in AtxA's gene regulation and provides more evidence for the role of AtxA phosphorylation in virulence gene regulation.
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Affiliation(s)
- Rita M McCall
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Mary E Sievers
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Rasem Fattah
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Andrei P Pomerantsev
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Stephen H Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA
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10
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Elvina Xavier MA, Liu S, Bugge TH, Torres JB, Mosley M, Hopkins SL, Allen PD, Berridge G, Vendrell I, Fischer R, Kersemans V, Smart S, Leppla SH, Cornelissen B. Tumor Imaging Using Radiolabeled Matrix Metalloproteinase-Activated Anthrax Proteins. J Nucl Med 2019; 60:1474-1482. [PMID: 30954944 PMCID: PMC6785798 DOI: 10.2967/jnumed.119.226423] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/13/2019] [Indexed: 11/20/2022] Open
Abstract
Increased activity of matrix metalloproteinases (MMPs) is associated with worse prognosis in different cancer types. The wild-type protective antigen (PA-WT) of the binary anthrax lethal toxin was modified to form a pore in cell membranes only when cleaved by MMPs (to form PA-L1). Anthrax lethal factor (LF) is then able to translocate through these pores. Here, we used a 111In-radiolabeled form of LF with the PA/LF system for noninvasive in vivo imaging of MMP activity in tumor tissue by SPECT. Methods: MMP-mediated activation of PA-L1 was correlated to anthrax receptor expression and MMP activity in a panel of cancer cells (HT1080, MDA-MB-231, B8484, and MCF7). Uptake of 111In-radiolabeled PA-L1, 111In-PA-WTK563C, or 111In-LFE687A (a catalytically inactive LF mutant) in tumor and normal tissues was measured using SPECT/CT imaging in vivo. Results: Activation of PA-L1 in vitro correlated with anthrax receptor expression and MMP activity (HT1080 > MDA-MB-231 > B8484 > MCF7). PA-L1-mediated delivery of 111In-LFE687A was demonstrated and was corroborated using confocal microscopy with fluorescently labeled LFE687A Uptake was blocked by the broad-spectrum MMP inhibitor GM6001. In vivo imaging showed selective accumulation of 111In-PA-L1 in MDA-MB-231 tumor xenografts (5.7 ± 0.9 percentage injected dose [%ID]/g) at 3 h after intravenous administration. 111In-LFE687A was selectively delivered to MMP-positive MDA-MB-231 tumor tissue by MMP-activatable PA-L1 (5.98 ± 0.62 %ID/g) but not by furin-cleavable PA-WT (1.05 ± 0.21 %ID/g) or a noncleavable PA variant control, PA-U7 (2.74 ± 0.24 %ID/g). Conclusion: Taken together, our results indicate that radiolabeled forms of mutated anthrax lethal toxin hold promise for noninvasive imaging of MMP activity in tumor tissue.
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Affiliation(s)
- Mary-Ann Elvina Xavier
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Shihui Liu
- Proteases and Tissue Remodeling Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland; and
| | - Thomas H Bugge
- Proteases and Tissue Remodeling Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland
| | - Julia Baguña Torres
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Michael Mosley
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Samantha L Hopkins
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Phillip D Allen
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Georgina Berridge
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Iolanda Vendrell
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Roman Fischer
- Target Discovery Institute, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Veerle Kersemans
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Sean Smart
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland; and
| | - Bart Cornelissen
- Department of Oncology, CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
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11
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Kondakova OA, Nikitin NA, Evtushenko EA, Ryabchevskaya EM, Atabekov JG, Karpova OV. Vaccines against anthrax based on recombinant protective antigen: problems and solutions. Expert Rev Vaccines 2019; 18:813-828. [PMID: 31298973 DOI: 10.1080/14760584.2019.1643242] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Introduction: Anthrax is a dangerous bio-terror agent because Bacillus anthracis spores are highly resilient and can be easily aerosolized and disseminated. There is a threat of deliberate use of anthrax spores aerosol that could lead to serious fatal diseases outbreaks. Existing control measures against inhalation form of the disease are limited. All of this has provided an impetus to the development of new generation vaccines. Areas сovered: This review is devoted to challenges and achievements in the design of vaccines based on the anthrax recombinant protective antigen (rPA). Scientific databases have been searched, focusing on causes of PA instability and solutions to this problem, including new approaches of rPA expression, novel rPA-based vaccines formulations as well as the simultaneous usage of PA with other anthrax antigens. Expert opinion: PA is a central anthrax toxin component, playing a key role in the defense against encapsulated and unencapsulated strains. Subunit rPA-based vaccines have a good safety and protective profile. However, there are problems of PA instability that are greatly enhanced when using aluminum adjuvants. New adjuvant compositions, dry formulations and resistant to proteolysis and deamidation mutant PA forms can help to handle this issue. Devising a modern anthrax vaccine requires huge efforts.
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Affiliation(s)
- Olga A Kondakova
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Nikolai A Nikitin
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Ekaterina A Evtushenko
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Ekaterina M Ryabchevskaya
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Joseph G Atabekov
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
| | - Olga V Karpova
- a Department of Virology, Faculty of Biology, Lomonosov Moscow State University , Moscow , Russian Federation
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12
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Solano MI, Woolfitt AR, Boyer AE, Lins RC, Isbell K, Gallegos-Candela M, Moura H, Pierce CL, Barr JR. Accurate and selective quantification of anthrax protective antigen in plasma by immunocapture and isotope dilution mass spectrometry. Analyst 2019; 144:2264-2274. [PMID: 30810119 PMCID: PMC7015108 DOI: 10.1039/c8an02479k] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Anthrax protective antigen (83 kDa, PA83) is an essential component of two major binary toxins produced by Bacillus anthracis, lethal toxin (LTx) and edema toxin (ETx). During infection, LTx and ETx contribute to immune collapse, endothelial dysfunction, hemorrhage and high mortality. Following protease cleavage on cell receptors or in circulation, the 20 kDa (PA20) N-terminus is released, activating the 63 kDa (PA63) form which binds lethal factor (LF) and edema factor (EF), facilitating their entry into their cellular targets. Several ELISA-based PA methods previously developed are primarily qualitative or semi-quantitative. Here, we combined protein immunocapture, tryptic digestion and isotope dilution liquid chromatography-mass spectrometry (LC-MS/MS), to develop a highly selective and sensitive method for detection and accurate quantification of total-PA (PA83 + PA63) and PA83. Two tryptic peptides in the 63 kDa region measure total-PA and three in the 20 kDa region measure PA83 alone. Detection limits range from 1.3-2.9 ng mL-1 PA in 100 μL of plasma. Spiked recovery experiments with combinations of PA83, PA63, LF and EF in plasma showed that PA63 and PA83 were quantified accurately against the PA83 standard and that LF and EF did not interfere with accuracy. Applied to a study of inhalation anthrax in rhesus macaques, total-PA suggested triphasic kinetics, similar to that previously observed for LF and EF. This study is the first to report circulating PA83 in inhalation anthrax, typically at less than 4% of the levels of PA63, providing the first evidence that activated PA63 is the primary form of PA throughout infection.
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Affiliation(s)
- Maria I Solano
- Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, 4770 Buford Highway, Atlanta, GA 30341, USA.
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13
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Crawford T, Fletcher N, Veitch M, Gonzalez Cruz JL, Pett N, Brereton I, Wells JW, Mobli M, Tesiram Y. Bacillus anthracis Protective Antigen Shows High Specificity for a UV Induced Mouse Model of Cutaneous Squamous Cell Carcinoma. Front Med (Lausanne) 2019; 6:22. [PMID: 30809524 PMCID: PMC6379334 DOI: 10.3389/fmed.2019.00022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2018] [Accepted: 01/24/2019] [Indexed: 11/13/2022] Open
Abstract
Squamous cell carcinoma (SCC) accounts for the majority of non-melanoma skin cancer related deaths, particularly in immunosuppressed persons. Identification of biomarkers that could be used to identify or treat SCC would be of significant benefit. The anthrax toxin receptors, Tumor Endothelial Marker 8 (TEM8) and Capillary Morphogenesis Gene 2 (CMG2), are endothelial receptors involved in extracellular matrix homeostasis and angiogenesis that are selectively upregulated on numerous tumors. One method of targeting these receptors is Protective Antigen (PA), a protein produced by B. anthracis that mediates binding and translocation of anthrax toxins into cells. PA targeted toxins have been demonstrated to selectively inhibit tumor growth and angiogenesis, but tumor selectivity of PA is currently unknown. In this work fluorescently labeled PA was shown to maintain receptor dependent binding and internalization in vitro. Utilizing a human papillomavirus transgenic mouse model that develops cutaneous SCC in response to ultraviolet irradiation we identified tumor uptake of PA in vivo. The intravenously administered PA resulted in tumor specific localization, with exclusive tumor detection 24 h post injection. Ex vivo analysis identified significantly higher fluorescence in the tumor compared to adjacent healthy tissue and major clearance organs, demonstrating low non-specific uptake and rapid clearance. While both TEM8 and CMG2 were observed to be overexpressed in SCC tumor sections compared to control skin, the intravenously administered PA was primarily co-localized with TEM8. These results suggest that PA could be systemically administered for rapid identification of cutaneous SCC, with potential for further therapeutic development.
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Affiliation(s)
- Theo Crawford
- Centre for Advanced Imaging (CAI), The University of Queensland, Brisbane, QLD, Australia
| | - Nicholas Fletcher
- Centre for Advanced Imaging (CAI), The University of Queensland, Brisbane, QLD, Australia.,Australian Institute for Bioengineering and Nanotechnology (AIBN), The University of Queensland, Brisbane, QLD, Australia.,Australian Research Council (ARC) Centre of Excellence in Convergent BioNano Science and Technology, Queensland Node, The University of Queensland, Brisbane, QLD, Australia
| | - Margaret Veitch
- Faculty of Medicine, Translational Research Institute, University of Queensland Diamantina Institute, Brisbane, QLD, Australia
| | - Jazmina L Gonzalez Cruz
- Faculty of Medicine, Translational Research Institute, University of Queensland Diamantina Institute, Brisbane, QLD, Australia
| | - Nicola Pett
- Faculty of Medicine, Translational Research Institute, University of Queensland Diamantina Institute, Brisbane, QLD, Australia
| | - Ian Brereton
- Centre for Advanced Imaging (CAI), The University of Queensland, Brisbane, QLD, Australia
| | - James W Wells
- Faculty of Medicine, Translational Research Institute, University of Queensland Diamantina Institute, Brisbane, QLD, Australia
| | - Mehdi Mobli
- Centre for Advanced Imaging (CAI), The University of Queensland, Brisbane, QLD, Australia
| | - Yasvir Tesiram
- Centre for Advanced Imaging (CAI), The University of Queensland, Brisbane, QLD, Australia
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14
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Karimi F, Alizadeh S, Alizadeh H. Immunogenicity of multi-walled carbon nanotubes functionalized with recombinant protective antigen domain 4 toward development of a nanovaccine against anthrax. J Drug Deliv Sci Technol 2018. [DOI: 10.1016/j.jddst.2018.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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15
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Serum-Mediated Cleavage of Bacillus anthracis Protective Antigen Is a Two-Step Process That Involves a Serum Carboxypeptidase. mSphere 2018; 3:3/3/e00091-18. [PMID: 29950379 PMCID: PMC6021598 DOI: 10.1128/msphere.00091-18] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 06/09/2018] [Indexed: 11/20/2022] Open
Abstract
Our findings identify a serum-mediated modification of PA20 that has not been previously described. These observations further imply that the processing of PA is more complex than currently thought. Additional study is needed to define the contribution of serum processing of PA to the host response and individual susceptibility to anthrax. Much of our understanding of the activity of anthrax toxin is based on in vitro systems, which delineate the interaction between Bacillus anthracis toxins and the cell surface. However, these systems fail to account for the intimate association of B. anthracis with the circulatory system, including the contribution of serum proteins to the host response and processing of anthrax toxins. Using a variety of immunological techniques to inhibit serum processing of B. anthracis protective antigen (PA) along with mass spectrometry analysis, we demonstrate that serum digests PA via 2 distinct reactions. In the first reaction, serum cleaves PA83 into 2 fragments to produce PA63 and PA20 fragments, similarly to that observed following furin digestion. This is followed by carboxypeptidase-mediated removal of the carboxy-terminal arginine and lysines from PA20. IMPORTANCE Our findings identify a serum-mediated modification of PA20 that has not been previously described. These observations further imply that the processing of PA is more complex than currently thought. Additional study is needed to define the contribution of serum processing of PA to the host response and individual susceptibility to anthrax.
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16
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Genome engineering in Bacillus anthracis using tyrosine site-specific recombinases. PLoS One 2017; 12:e0183346. [PMID: 28829806 PMCID: PMC5567495 DOI: 10.1371/journal.pone.0183346] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 08/02/2017] [Indexed: 01/07/2023] Open
Abstract
Tyrosine site-specific recombinases (T-SSR) are polynucleotidyltransferases that catalyze cutting and joining reactions between short specific DNA sequences. We developed three systems for performing genetic modifications in Bacillus anthracis that use T-SSR and their cognate target sequences, namely Escherichia coli bacteriophage P1 Cre-loxP, Saccharomyces cerevisiae Flp-FRT, and a newly discovered IntXO-PSL system from B. anthracis plasmid pXO1. All three tyrosine recombinase systems were used for creation of a B. anthracis sporulation-deficient, plasmid-free strain deleted for ten proteases which had been identified by proteomic analysis as being present in the B. anthracis secretome. This strain was used successfully for production of various recombinant proteins, including several that are candidates for inclusion in improved anthrax vaccines. These genetic tools developed for DNA manipulation in B. anthracis were also used for construction of strains having chromosomal insertions of 1, 2, or 3 adjacent atxA genes. AtxA is a B. anthracis global transcriptional regulator required for the response of B. anthracis virulence factor genes to bicarbonate. We found a positive correlation between the atxA copy number and the expression level of the pagA gene encoding B. anthracis protective antigen, when strains were grown in a carbon dioxide atmosphere. These results demonstrate that the three T-SSR systems described here provide effective tools for B. anthracis genome editing. These T-SSR systems may also be applicable to other prokaryotes and to eukaryotes.
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17
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Tram DTN, Wang H, Sugiarto S, Li T, Ang WH, Lee C, Pastorin G. Advances in nanomaterials and their applications in point of care (POC) devices for the diagnosis of infectious diseases. Biotechnol Adv 2016; 34:1275-1288. [PMID: 27686397 PMCID: PMC7127209 DOI: 10.1016/j.biotechadv.2016.09.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 07/13/2016] [Accepted: 09/23/2016] [Indexed: 01/17/2023]
Abstract
Nanotechnology has gained much attention over the last decades, as it offers unique opportunities for the advancement of the next generation of sensing tools. Point-of-care (POC) devices for the selective detection of biomolecules using engineered nanoparticles have become a main research thrust in the diagnostic field. This review presents an overview on how the POC-associated nanotechnology, currently applied for the identification of nucleic acids, proteins and antibodies, might be further exploited for the detection of infectious pathogens: although still premature, future integrations of nanoparticles with biological markers that target specific microorganisms will enable timely therapeutic intervention against life-threatening infectious diseases.
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Affiliation(s)
- Dai Thien Nhan Tram
- Pharmacy Department National University of Singapore, Singapore 117543, Singapore.
| | - Hao Wang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering, Drive 3, Singapore 117576, Singapore.
| | - Sigit Sugiarto
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
| | - Tao Li
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
| | - Wee Han Ang
- Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.
| | - Chengkuo Lee
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering, Drive 3, Singapore 117576, Singapore.
| | - Giorgia Pastorin
- Pharmacy Department National University of Singapore, Singapore 117543, Singapore; NanoCore, Faculty of Engineering, National University of Singapore, Singapore 117576, Singapore; NUS Graduate School for Integrative Sciences and Engineering, Centre for Life Sciences (CeLS), Singapore 117456, Singapore.
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18
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Shorter SA, Gollings AS, Gorringe-Pattrick MAM, Coakley JE, Dyer PDR, Richardson SCW. The potential of toxin-based drug delivery systems for enhanced nucleic acid therapeutic delivery. Expert Opin Drug Deliv 2016; 14:685-696. [DOI: 10.1080/17425247.2016.1227781] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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19
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Silin V, Kasianowicz JJ, Michelman-Ribeiro A, Panchal RG, Bavari S, Robertson JWF. Biochip for the Detection of Bacillus anthracis Lethal Factor and Therapeutic Agents against Anthrax Toxins. MEMBRANES 2016; 6:E36. [PMID: 27348008 PMCID: PMC5041027 DOI: 10.3390/membranes6030036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 01/18/2023]
Abstract
Tethered lipid bilayer membranes (tBLMs) have been used in many applications, including biosensing and membrane protein structure studies. This report describes a biosensor for anthrax toxins that was fabricated through the self-assembly of a tBLM with B. anthracis protective antigen ion channels that are both the recognition element and electrochemical transducer. We characterize the sensor and its properties with electrochemical impedance spectroscopy and surface plasmon resonance. The sensor shows a sensitivity similar to ELISA and can also be used to rapidly screen for molecules that bind to the toxins and potentially inhibit their lethal effects.
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Affiliation(s)
- Vitalii Silin
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
- Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, MD 20899, USA.
| | - John J Kasianowicz
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
| | - Ariel Michelman-Ribeiro
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
| | - Rekha G Panchal
- US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA.
| | - Sina Bavari
- US Army Medical Research Institute of Infectious Diseases, Fort Detrick, Frederick, MD 21702-5011, USA.
| | - Joseph W F Robertson
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899-8120, USA.
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20
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Dyer PDR, Shepherd TR, Gollings AS, Shorter SA, Gorringe-Pattrick MAM, Tang CK, Cattoz BN, Baillie L, Griffiths PC, Richardson SCW. Disarmed anthrax toxin delivers antisense oligonucleotides and siRNA with high efficiency and low toxicity. J Control Release 2015; 220:316-328. [PMID: 26546271 DOI: 10.1016/j.jconrel.2015.10.054] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 01/01/2023]
Abstract
Inefficient cytosolic delivery and vector toxicity contribute to the limited use of antisense oligonucleotides (ASOs) and siRNA as therapeutics. As anthrax toxin (Atx) accesses the cytosol, the purpose of this study was to evaluate the potential of disarmed Atx to deliver either ASOs or siRNA. We hypothesized that this delivery strategy would facilitate improved transfection efficiency while eliminating the toxicity seen for many vectors due to membrane destabilization. Atx complex formation with ASOs or siRNA was achieved via the in-frame fusion of either Saccharomyces cerevisiae GAL4 or Homo sapien sapien PKR (respectively) to a truncation of Atx lethal factor (LFn), which were used with Atx protective antigen (PA). Western immunoblotting confirmed the production of: LFN-GAL4, LFn-PKR and PA which were detected at ~45.9 kDa, ~37 kDa, and ~83 kDa respectively and small angle neutron scattering confirmed the ability of PA to form an annular structure with a radius of gyration of 7.0 ± 1.0 nm when placed in serum. In order to form a complex with LFn-GAL4, ASOs were engineered to contain a double-stranded region, and a cell free in vitro translation assay demonstrated that no loss of antisense activity above 30 pmol ASO was evident. The in vitro toxicity of both PA:LFn-GAL4:ASO and PA:LFn-PKR:siRNA complexes was low (IC50>100 μg/mL in HeLa and Vero cells) and subcellular fractionation in conjunction with microscopy confirmed the detection of LFn-GAL4 or LFn-PKR in the cytosol. Syntaxin5 (Synt5) was used as a model target gene to determine pharmacological activity. The PA:LFn-GAL4:ASO complexes had transfection efficiency approximately equivalent to Nucleofection® over a variety of ASO concentrations (24h post-transfection) and during a 72 h time course. In HeLa cells, at 200 pmol ASO (with PA:LFN-GAL4), 5.4 ± 2.0% Synt5 expression was evident relative to an untreated control after 24h. Using 200 pmol ASOs, Nucleofection® reduced Synt5 expression to 8.1 ± 2.1% after 24h. PA:LFn-GAL4:ASO transfection of non- or terminally-differentiated THP-1 cells and Vero cells resulted in 35.2 ± 19.1%, 36.4 ± 1.8% and 22.9 ± 6.9% (respectively) Synt5 expression after treatment with 200 pmol of ASO and demonstrated versatility. Nucleofection® with Stealth RNAi™ siRNA reduced HeLa Synt5 levels to 4.6 ± 6.1% whereas treatment with the PA:LFn-PKR:siRNA resulted in 8.5 ± 3.4% Synt5 expression after 24h (HeLa cells). These studies report for the first time an ASO and RNAi delivery system based upon protein toxin architecture that is devoid of polycations. This system may utilize regulated membrane back-fusion for the cytosolic delivery of ASOs and siRNA, which would account for the lack of toxicity observed. High delivery efficiency suggests further in vivo evaluation is warranted.
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Affiliation(s)
- Paul D R Dyer
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Thomas R Shepherd
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Alexander S Gollings
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Susan A Shorter
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Monique A M Gorringe-Pattrick
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Chun-Kit Tang
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
| | - Beatrice N Cattoz
- Department of Pharmaceutical, Chemical and Environmental Science, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK
| | - Les Baillie
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, King Edward VII Avenue, Cardiff CF10 3AX, UK
| | - Peter C Griffiths
- Department of Pharmaceutical, Chemical and Environmental Science, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK
| | - Simon C W Richardson
- Intercellular Delivery Solutions Laboratory, Faculty of Engineering and Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.
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High-sensitivity MALDI-TOF MS quantification of anthrax lethal toxin for diagnostics and evaluation of medical countermeasures. Anal Bioanal Chem 2015; 407:2847-58. [PMID: 25673244 PMCID: PMC4369318 DOI: 10.1007/s00216-015-8509-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/13/2015] [Accepted: 01/21/2015] [Indexed: 11/15/2022]
Abstract
Inhalation anthrax has a rapid progression and high fatality rate. Pathology and death from inhalation of Bacillus anthracis spores are attributed to the actions of secreted protein toxins. Protective antigen (PA) binds and imports the catalytic component lethal factor (LF), a zinc endoprotease, and edema factor (EF), an adenylyl cyclase, into susceptible cells. PA-LF is termed lethal toxin (LTx) and PA-EF, edema toxin. As the universal transporter for both toxins, PA is an important target for vaccination and immunotherapeutic intervention. However, its quantification has been limited to methods of relatively low analytic sensitivity. Quantification of LTx may be more clinically relevant than LF or PA alone because LTx is the toxic form that acts on cells. A method was developed for LTx-specific quantification in plasma using anti-PA IgG magnetic immunoprecipitation of PA and quantification of LF activity that co-purified with PA. The method was fast (<4 h total time to detection), sensitive at 0.033 ng/mL LTx in plasma for the fast analysis (0.0075 ng/mL LTx in plasma for an 18 h reaction), precise (6.3–9.9 % coefficient of variation), and accurate (0.1–12.7 %error; n ≥ 25). Diagnostic sensitivity was 100 % (n = 27 animal/clinical cases). Diagnostic specificity was 100 % (n = 141). LTx was detected post-antibiotic treatment in 6/6 treated rhesus macaques and 3/3 clinical cases of inhalation anthrax and as long as 8 days post-treatment. Over the course of infection in two rhesus macaques, LTx was first detected at 0.101 and 0.237 ng/mL at 36 h post-exposure and increased to 1147 and 12,107 ng/mL in late-stage anthrax. This demonstrated the importance of LTx as a diagnostic and therapeutic target. This method provides a sensitive, accurate tool for anthrax toxin detection and evaluation of PA-directed therapeutics. Method schematic for analysis of anthrax lethal toxin activity by ID-MALDI-TOF MS ![]()
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Vance DJ, Rong Y, Brey RN, Mantis NJ. Combination of two candidate subunit vaccine antigens elicits protective immunity to ricin and anthrax toxin in mice. Vaccine 2015; 33:417-21. [PMID: 25475957 PMCID: PMC4274239 DOI: 10.1016/j.vaccine.2014.11.036] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/30/2014] [Accepted: 11/17/2014] [Indexed: 10/24/2022]
Abstract
In an effort to develop combination vaccines for biodefense, we evaluated a ricin subunit antigen, RiVax, given in conjunction with an anthrax protective antigen, DNI. The combination led to high endpoint titer antibody response, neutralizing antibodies, and protective immunity against ricin and anthrax lethal toxin. This is a natural combination vaccine, since both antigens are recombinant subunit proteins that would be given to the same target population.
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Affiliation(s)
- David J Vance
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Yinghui Rong
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | | | - Nicholas J Mantis
- Division of Infectious Disease, Wadsworth Center, New York State Department of Health, Albany, NY, USA; Department of Biomedical Sciences, University at Albany, Albany, NY, USA.
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Moayeri M, Leysath CE, Tremblay JM, Vrentas C, Crown D, Leppla SH, Shoemaker CB. A heterodimer of a VHH (variable domains of camelid heavy chain-only) antibody that inhibits anthrax toxin cell binding linked to a VHH antibody that blocks oligomer formation is highly protective in an anthrax spore challenge model. J Biol Chem 2015; 290:6584-95. [PMID: 25564615 DOI: 10.1074/jbc.m114.627943] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Anthrax disease is caused by a toxin consisting of protective antigen (PA), lethal factor, and edema factor. Antibodies against PA have been shown to be protective against the disease. Variable domains of camelid heavy chain-only antibodies (VHHs) with affinity for PA were obtained from immunized alpacas and screened for anthrax neutralizing activity in macrophage toxicity assays. Two classes of neutralizing VHHs were identified recognizing distinct, non-overlapping epitopes. One class recognizes domain 4 of PA at a well characterized neutralizing site through which PA binds to its cellular receptor. A second neutralizing VHH (JKH-C7) recognizes a novel epitope. This antibody inhibits conversion of the PA oligomer from "pre-pore" to its SDS and heat-resistant "pore" conformation while not preventing cleavage of full-length 83-kDa PA (PA83) by cell surface proteases to its oligomer-competent 63-kDa form (PA63). The antibody prevents endocytosis of the cell surface-generated PA63 subunit but not preformed PA63 oligomers formed in solution. JKH-C7 and the receptor-blocking VHH class (JIK-B8) were expressed as a heterodimeric VHH-based neutralizing agent (VNA2-PA). This VNA displayed improved neutralizing potency in cell assays and protected mice from anthrax toxin challenge with much better efficacy than the separate component VHHs. The VNA protected virtually all mice when separately administered at a 1:1 ratio to toxin and protected mice against Bacillus anthracis spore infection. Thus, our studies show the potential of VNAs as anthrax therapeutics. Due to their simple and stable nature, VNAs should be amenable to genetic delivery or administration via respiratory routes.
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Affiliation(s)
- Mahtab Moayeri
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Clinton E Leysath
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Jacqueline M Tremblay
- Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892
| | - Catherine Vrentas
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Devorah Crown
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Stephen H Leppla
- From the Department of Infectious Disease and Global Health, Cummings School of Veterinary Medicine at Tufts University North Grafton, Massachusetts 01536 and
| | - Charles B Shoemaker
- Laboratory of Parasitic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892
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Wade KR, Hotze EM, Briles DE, Tweten RK. Mouse, but not human, ApoB-100 lipoprotein cholesterol is a potent innate inhibitor of Streptococcus pneumoniae pneumolysin. PLoS Pathog 2014; 10:e1004353. [PMID: 25188225 PMCID: PMC4154877 DOI: 10.1371/journal.ppat.1004353] [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: 06/12/2014] [Accepted: 07/18/2014] [Indexed: 11/19/2022] Open
Abstract
Streptococcus pneumoniae produces the pore-forming toxin pneumolysin (PLY), which is a member of the cholesterol-dependent cytolysin (CDC) family of toxins. The CDCs recognize and bind the 3β-hydroxyl group of cholesterol at the cell surface, which initiates membrane pore formation. The cholesterol transport lipoproteins, which carry cholesterol in their outer monolayer, are potential off-pathway binding targets for the CDCs and are present at significant levels in the serum and the interstitial spaces of cells. Herein we show that cholesterol carried specifically by the ApoB-100-containing lipoprotein particles (CH-ApoB-100) in the mouse, but not that carried by human or guinea pig particles, is a potent inhibitor of the PLY pore-forming mechanism. Cholesterol present in the outer monolayer of mouse ApoB-100 particles is recognized and bound by PLY, which stimulates premature assembly of the PLY oligomeric complex thereby inactivating PLY. These studies further suggest that the vast difference in the inhibitory capacity of mouse CH-ApoB-100 and that of the human and the guinea pig is due to differences in the presentation of cholesterol in the outer monolayer of their ApoB-100 particles. Therefore mouse CH-ApoB-100 represents a significant innate CDC inhibitor that is absent in humans, which may underestimate the contribution of CDCs to human disease when utilizing mouse models of disease.
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Affiliation(s)
- Kristin R. Wade
- Department of Microbiology and Immunology, The University of Oklahoma Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - Eileen M. Hotze
- Department of Microbiology and Immunology, The University of Oklahoma Sciences Center, Oklahoma City, Oklahoma, United States of America
| | - David E. Briles
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Rodney K. Tweten
- Department of Microbiology and Immunology, The University of Oklahoma Sciences Center, Oklahoma City, Oklahoma, United States of America
- * E-mail:
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25
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Detection of anthrax protective antigen (PA) using europium labeled anti-PA monoclonal antibody and time-resolved fluorescence. J Immunol Methods 2014; 408:78-88. [PMID: 24857756 DOI: 10.1016/j.jim.2014.05.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 05/05/2014] [Accepted: 05/07/2014] [Indexed: 11/22/2022]
Abstract
Inhalation anthrax is a rare but acute infectious disease following adsorption of Bacillus anthracis spores through the lungs. The disease has a high fatality rate if untreated, but early and correct diagnosis has a significant impact on case patient recovery. The early symptoms of inhalation anthrax are, however, non-specific and current anthrax diagnostics are primarily dependent upon culture and confirmatory real-time PCR. Consequently, there may be a significant delay in diagnosis and targeted treatment. Rapid, culture-independent diagnostic tests are therefore needed, particularly in the context of a large scale emergency response. The aim of this study was to evaluate the ability of monoclonal antibodies to detect anthrax toxin proteins that are secreted early in the course of B. anthracis infection using a time-resolved fluorescence (TRF) immunoassay. We selected monoclonal antibodies that could detect protective antigen (PA), as PA83 and also PA63 and LF in the lethal toxin complex. The assay reliable detection limit (RDL) was 6.63×10(-6)μM (0.551ng/ml) for PA83 and 2.51×10(-5)μM (1.58ng/ml) for PA63. Despite variable precision and accuracy of the assay, PA was detected in 9 out of 10 sera samples from anthrax confirmed case patients with cutaneous (n=7), inhalation (n=2), and gastrointestinal (n=1) disease. Anthrax Immune Globulin (AIG), which has been used in treatment of clinical anthrax, interfered with detection of PA. This study demonstrates a culture-independent method of diagnosing anthrax through the use of monoclonal antibodies to detect PA and LF in the lethal toxin complex.
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Lowe DE, Ya J, Glomski IJ. In trans complementation of lethal factor reveal roles in colonization and dissemination in a murine mouse model. PLoS One 2014; 9:e95950. [PMID: 24763227 PMCID: PMC3999102 DOI: 10.1371/journal.pone.0095950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 04/02/2014] [Indexed: 12/04/2022] Open
Abstract
Lethal factor (LF) is a component of the B. anthracis exotoxin and critical for pathogenesis. The roles of LF in early anthrax pathogenesis, such as colonization and dissemination from the initial site of infection, are poorly understood. In mice models of infection, LF-deficient strains either have altered dissemination patterns or do not colonize, precluding analysis of the role of LF in colonization and dissemination from the portal of entry. Previous reports indicate rabbit and guinea pig models infected with LF-deficient strains have decreased virulence, yet the inability to use bioluminescent imaging techniques to track B. anthracis growth and dissemination in these hosts makes analysis of early pathogenesis challenging. In this study, the roles of LF early in infection were analyzed using bioluminescent signature tagged libraries of B. anthracis with varying ratios of LF-producing and LF-deficient clones. Populations where all clones produced LF and populations where only 40% of clones produce LF were equally virulent. The 40% LF-producing clones trans complimented the LF mutants and permitted them to colonize and disseminate. Decreases of the LF producing strains to 10% or 0.3% of the population led to increased host survival and decreased trans complementation of the LF mutants. A library with 10% LF producing clones could replicate and disseminate, but fewer clones disseminated and the mutant clones were less competitive than wild type. The inoculum with 0.3% LF producing clones could not colonize the host. This strongly suggests that between 10% and 0.3% of the population must produce LF in order to colonize. In total, these findings suggest that a threshold of LF must be produced in order for colonization and dissemination to occur in vivo. These observations suggest that LF has a major role in the early stages of colonization and dissemination.
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Affiliation(s)
- David E. Lowe
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jason Ya
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
| | - Ian J. Glomski
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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27
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Liu S, Moayeri M, Leppla SH. Anthrax lethal and edema toxins in anthrax pathogenesis. Trends Microbiol 2014; 22:317-25. [PMID: 24684968 DOI: 10.1016/j.tim.2014.02.012] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 02/23/2014] [Accepted: 02/26/2014] [Indexed: 10/25/2022]
Abstract
The pathophysiological effects resulting from many bacterial diseases are caused by exotoxins released by the bacteria. Bacillus anthracis, a spore-forming bacterium, is such a pathogen, causing anthrax through a combination of bacterial infection and toxemia. B. anthracis causes natural infection in humans and animals and has been a top bioterrorism concern since the 2001 anthrax attacks in the USA. The exotoxins secreted by B. anthracis use capillary morphogenesis protein 2 (CMG2) as the major toxin receptor and play essential roles in pathogenesis during the entire course of the disease. This review focuses on the activities of anthrax toxins and their roles in initial and late stages of anthrax infection.
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Affiliation(s)
- Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
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28
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McKenzie AT, Pomerantsev AP, Sastalla I, Martens C, Ricklefs SM, Virtaneva K, Anzick S, Porcella SF, Leppla SH. Transcriptome analysis identifies Bacillus anthracis genes that respond to CO2 through an AtxA-dependent mechanism. BMC Genomics 2014; 15:229. [PMID: 24661624 PMCID: PMC3987803 DOI: 10.1186/1471-2164-15-229] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 03/12/2014] [Indexed: 11/30/2022] Open
Abstract
Background Upon infection of a mammalian host, Bacillus anthracis responds to host cues, and particularly to elevated temperature (37°C) and bicarbonate/CO2 concentrations, with increased expression of virulence factors that include the anthrax toxins and extracellular capsular layer. This response requires the presence of the pXO1 virulence plasmid-encoded pleiotropic regulator AtxA. To better understand the genetic basis of this response, we utilized a controlled in vitro system and Next Generation sequencing to determine and compare RNA expression profiles of the parental strain and an isogenic AtxA-deficient strain in a 2 × 2 factorial design with growth environments containing or lacking carbon dioxide. Results We found 15 pXO1-encoded genes and 3 chromosomal genes that were strongly regulated by the separate or synergistic actions of AtxA and carbon dioxide. The majority of the regulated genes responded to both AtxA and carbon dioxide rather than to just one of these factors. Interestingly, we identified two previously unrecognized small RNAs that are highly expressed under physiological carbon dioxide concentrations in an AtxA-dependent manner. Expression levels of the two small RNAs were found to be higher than that of any other gene differentially expressed in response to these conditions. Secondary structure and small RNA-mRNA binding predictions for the two small RNAs suggest that they may perform important functions in regulating B. anthracis virulence. Conclusions A majority of genes on the virulence plasmid pXO1 that are regulated by the presence of either CO2 or AtxA separately are also regulated synergistically in the presence of both. These results also elucidate novel pXO1-encoded small RNAs that are associated with virulence conditions.
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Affiliation(s)
| | - Andrei P Pomerantsev
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, USA.
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29
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Tournier JN, Ulrich RG, Quesnel-Hellmann A, Mohamadzadeh M, Stiles BG. Anthrax, toxins and vaccines: a 125-year journey targetingBacillus anthracis. Expert Rev Anti Infect Ther 2014; 7:219-36. [DOI: 10.1586/14787210.7.2.219] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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30
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Weiner ZP, Ernst SM, Boyer AE, Gallegos-Candela M, Barr JR, Glomski IJ. Circulating lethal toxin decreases the ability of neutrophils to respond toBacillus anthracis. Cell Microbiol 2013; 16:504-18. [DOI: 10.1111/cmi.12232] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 09/24/2013] [Accepted: 10/15/2013] [Indexed: 01/08/2023]
Affiliation(s)
- Zachary P. Weiner
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville VA USA
| | - Stephen M. Ernst
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville VA USA
| | - Anne E. Boyer
- National Center for Environmental Health; Centers for Disease Control and Prevention; Atlanta GA 30341 USA
| | - Maribel Gallegos-Candela
- National Center for Environmental Health; Centers for Disease Control and Prevention; Atlanta GA 30341 USA
| | - John R. Barr
- National Center for Environmental Health; Centers for Disease Control and Prevention; Atlanta GA 30341 USA
| | - Ian J. Glomski
- Department of Microbiology, Immunology, and Cancer Biology; University of Virginia; Charlottesville VA USA
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31
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Tevell Åberg A, Björnstad K, Hedeland M. Mass Spectrometric Detection of Protein-Based Toxins. Biosecur Bioterror 2013; 11 Suppl 1:S215-26. [DOI: 10.1089/bsp.2012.0072] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Annica Tevell Åberg
- Annica Tevell Åberg, PhD, is a Senior Researcher; Kristian Björnstad, PhD, is a Senior Researcher; and Mikael Hedeland, PhD, is an Associate Professor and Deputy Head of Department; all at the Department of Chemistry, Environment and Feed Hygiene, National Veterinary Institute (SVA), Uppsala, Sweden. Dr. Åberg and Dr. Hedeland are also affiliated with the Division of Analytical Pharmaceutical Chemistry, Uppsala University, Uppsala, Sweden
| | - Kristian Björnstad
- Annica Tevell Åberg, PhD, is a Senior Researcher; Kristian Björnstad, PhD, is a Senior Researcher; and Mikael Hedeland, PhD, is an Associate Professor and Deputy Head of Department; all at the Department of Chemistry, Environment and Feed Hygiene, National Veterinary Institute (SVA), Uppsala, Sweden. Dr. Åberg and Dr. Hedeland are also affiliated with the Division of Analytical Pharmaceutical Chemistry, Uppsala University, Uppsala, Sweden
| | - Mikael Hedeland
- Annica Tevell Åberg, PhD, is a Senior Researcher; Kristian Björnstad, PhD, is a Senior Researcher; and Mikael Hedeland, PhD, is an Associate Professor and Deputy Head of Department; all at the Department of Chemistry, Environment and Feed Hygiene, National Veterinary Institute (SVA), Uppsala, Sweden. Dr. Åberg and Dr. Hedeland are also affiliated with the Division of Analytical Pharmaceutical Chemistry, Uppsala University, Uppsala, Sweden
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32
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Lowe DE, Glomski IJ. Cellular and physiological effects of anthrax exotoxin and its relevance to disease. Front Cell Infect Microbiol 2012; 2:76. [PMID: 22919667 PMCID: PMC3417473 DOI: 10.3389/fcimb.2012.00076] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Accepted: 05/16/2012] [Indexed: 12/26/2022] Open
Abstract
Bacillus anthracis, the causative agent of anthrax, secretes a tri-partite exotoxin that exerts pleiotropic effects on the host. The purification of the exotoxin components, protective antigen, lethal factor, and edema factor allowed the rapid characterization of their physiologic effects on the host. As molecular biology matured, interest focused on the molecular mechanisms and cellular alterations induced by intoxication. Only recently have researchers begun to connect molecular and cellular knowledge back to the broader physiological effects of the exotoxin. This review focuses on the progress that has been made bridging molecular knowledge back to the exotoxin’s physiological effects on the host.
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Affiliation(s)
- David E Lowe
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia Health System, Charlottesville VA, USA
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33
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Dragan AI, Albrecht MT, Pavlovic R, Keane-Myers AM, Geddes CD. Ultra-fast pg/ml anthrax toxin (protective antigen) detection assay based on microwave-accelerated metal-enhanced fluorescence. Anal Biochem 2012; 425:54-61. [DOI: 10.1016/j.ab.2012.02.040] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 02/28/2012] [Accepted: 02/29/2012] [Indexed: 02/07/2023]
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Bann JG. Anthrax toxin protective antigen--insights into molecular switching from prepore to pore. Protein Sci 2012; 21:1-12. [PMID: 22095644 DOI: 10.1002/pro.752] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The protective antigen is a key component of the anthrax toxin, as it allows entry of the enzymatic components edema factor and lethal factor into the host cell, through the formation of a membrane spanning pore. This event is absolutely critical for the pathogenesis of anthrax, and although we have yet to understand the mechanism of pore formation, recent developments have provided key insights into how this process may occur. Based on the available data, a model is proposed for the kinetic steps for protective antigen conversion from prepore to pore. In this model, the driving force for pore formation is the formation of the phi (ϕ)-clamp, a region that forms a leak-free seal around the translocating polypeptide. Formation of the ϕ-clamp elicits movements within the prepore that provide steric freedom for the subsequent conformational changes required to form the membrane spanning pore.
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Affiliation(s)
- James G Bann
- Department of Chemistry, Wichita State University, Wichita, Kansas 67260-0051, USA.
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35
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Petersen LK, Phanse Y, Ramer-Tait AE, Wannemuehler MJ, Narasimhan B. Amphiphilic polyanhydride nanoparticles stabilize Bacillus anthracis protective antigen. Mol Pharm 2012; 9:874-82. [PMID: 22380593 DOI: 10.1021/mp2004059] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Advancements toward an improved vaccine against Bacillus anthracis, the causative agent of anthrax, have focused on formulations composed of the protective antigen (PA) adsorbed to aluminum hydroxide. However, due to the labile nature of PA, antigen stability is a primary concern for vaccine development. Thus, there is a need for a delivery system capable of preserving the immunogenicity of PA through all the steps of vaccine fabrication, storage, and administration. In this work, we demonstrate that biodegradable amphiphilic polyanhydride nanoparticles, which have previously been shown to provide controlled antigen delivery, antigen stability, immune modulation, and protection in a single dose against a pathogenic challenge, can stabilize and release functional PA. These nanoparticles demonstrated polymer hydrophobicity-dependent preservation of the biological function of PA upon encapsulation, storage (over extended times and elevated temperatures), and release. Specifically, fabrication of amphiphilic polyanhydride nanoparticles composed of 1,6-bis(p-carboxyphenoxy)hexane and 1,8-bis(p-carboxyphenoxy)-3,6-dioxaoctane best preserved PA functionality. These studies demonstrate the versatility and superiority of amphiphilic nanoparticles as vaccine delivery vehicles suitable for long-term storage.
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Affiliation(s)
- L K Petersen
- Department of Chemical and Biological Engineering, Iowa State University, Ames, Iowa 50011, USA
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36
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Vuyisich M, Sanders CK, Graves SW. Binding and cell intoxication studies of anthrax lethal toxin. Mol Biol Rep 2012; 39:5897-903. [PMID: 22219086 DOI: 10.1007/s11033-011-1401-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Accepted: 12/17/2011] [Indexed: 11/25/2022]
Abstract
Anthrax lethal toxin (LT) is a major virulence factor of Bacillus anthracis. The vast majority of the anthrax toxin-related literature describes the assembly of LT as a cell-dependent process. However, some reports have provided evidence for the existence of a fully assembled LT, either in vitro or in the bloodstream of anthrax-infected animals. To follow up on this work, we present studies on fully-assembled LT. We first demonstrate facile and cell-free assembly and purification of LT. We then show that fully assembled LT binds an anthrax toxin receptor with almost 100-fold higher affinity than the protective antigen (PA) alone. Quantitative cell intoxication assays were used to determine the LD(50) (lethal dose 50) for LT. The cell-binding studies revealed that LT binds mammalian cells using a different mode from PA. Even when PA-specific receptors were blocked, fully assembled LT was able to bind the cell surface. Our studies support the existing evidence that LT fully assembles in the blood stream and can bind and intoxicate mammalian cells with very high affinity and efficacy. More importantly, the data presented here invoke the possibility that LT may bind cells in a receptor-independent fashion, or recognize receptors that do not interact with PA. Hence, blood borne LT may emerge as a novel therapeutic target for combating anthrax.
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Affiliation(s)
- Momchilo Vuyisich
- Los Alamos National Lab, MS M888, P.O. Box 1663, Los Alamos, NM 87545, USA.
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Abstract
The anthrax edema toxin (ET) of Bacillus anthracis is composed of the receptor-binding component protective antigen (PA) and of the adenylyl cyclase catalytic moiety, edema factor (EF). Uptake of ET into cells raises intracellular concentrations of the secondary messenger cyclic AMP, thereby impairing or activating host cell functions. We report here on a new consequence of ET action in vivo. We show that in mouse models of toxemia and infection, serum PA concentrations were significantly higher in the presence of enzymatically active EF. These higher concentrations were not caused by ET-induced inhibition of PA endocytosis; on the contrary, ET induced increased PA binding and uptake of the PA oligomer in vitro and in vivo through upregulation of the PA receptors TEM8 and CMG2 in both myeloid and nonmyeloid cells. ET effects on protein clearance from circulation appeared to be global and were not limited to PA. ET also impaired the clearance of ovalbumin, green fluorescent protein, and EF itself, as well as the small molecule biotin when these molecules were coinjected with the toxin. Effects on injected protein levels were not a result of general increase in protein concentrations due to fluid loss. Functional markers for liver and kidney were altered in response to ET. Concomitantly, ET caused phosphorylation and activation of the aquaporin-2 water channel present in the principal cells of the collecting ducts of the kidneys that are responsible for fluid homeostasis. Our data suggest that in vivo, ET alters circulatory protein and small molecule pharmacokinetics by an as-yet-undefined mechanism, thereby potentially allowing a prolonged circulation of anthrax virulence factors such as EF during infection.
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38
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Rudenko NV, Abbasova SG, Grishin EV. [Preparation and characterization of monoclonal antibodies to Bacillus anthracis protective antigen]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2011; 37:354-60. [PMID: 21899050 DOI: 10.1134/s1068162011030162] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Anthrax is the widespread acute infection disease, affecting animals and humans, refers to the bioterrorist threat agents of category A, because of the high resistance of Bacillus anthracis spores to adverse environmental factors and the ease of receiving them. We obtain a representative panel of 20 monoclonal antibodies against the key component of pathogenic exotoxins, anthrax protective antigen. Quantitative sandwich-ELISA for protective antigen with antibody obtained was developed. Six pairs of monoclonal antibodies showed the detection limit up to 1 ng/ml concentration of the protective antigen in blood serum.
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39
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Mechanism of lethal toxin neutralization by a human monoclonal antibody specific for the PA(20) region of Bacillus anthracis protective antigen. Toxins (Basel) 2011; 3:979-90. [PMID: 22069752 PMCID: PMC3202870 DOI: 10.3390/toxins3080979] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 07/07/2011] [Accepted: 08/04/2011] [Indexed: 11/17/2022] Open
Abstract
The primary immunogenic component of the currently approved anthrax vaccine is the protective antigen (PA) unit of the binary toxin system. PA-specific antibodies neutralize anthrax toxins and protect against infection. Recent research has determined that in humans, only antibodies specific for particular determinants are capable of effecting toxin neutralization, and that the neutralizing epitopes recognized by these antibodies are distributed throughout the PA monomer. The mechanisms by which the majority of these epitopes effect neutralization remain unknown. In this report we investigate the process by which a human monoclonal antibody specific for the amino-terminal domain of PA neutralizes lethal toxin in an in vitro assay of cytotoxicity, and find that it neutralizes LT by blocking the requisite cleavage of the amino-terminal 20 kD portion of the molecule (PA20) from the remainder of the PA monomer. We also demonstrate that the epitope recognized by this human monoclonal does not encompass the 166RKKR169 furin recognition sequence in domain 1 of PA.
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Anthrax toxin-neutralizing antibody reconfigures the protective antigen heptamer into a supercomplex. Proc Natl Acad Sci U S A 2010; 107:14070-4. [PMID: 20660775 DOI: 10.1073/pnas.1006473107] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The tripartite protein exotoxin secreted by Bacillus anthracis, a major contributor to its virulence and anthrax pathogenesis, consists of binary complexes of the protective antigen (PA) heptamer (PA63h), produced by proteolytic cleavage of PA, together with either lethal factor or edema factor. The mouse monoclonal anti-PA antibody 1G3 was previously shown to be a potent antidote that shares F(C) domain dependency with the human monoclonal antibody MDX-1303 currently under clinical development. Here we demonstrate that 1G3 instigates severe perturbation of the PA63h structure and creates a PA supercomplex as visualized by electron microscopy. This phenotype, produced by the unconventional mode of antibody action, highlights the feasibility for optimization of vaccines based on analogous structural modification of PA63h as an additional strategy for future remedies against anthrax.
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Detection technologies for Bacillus anthracis: Prospects and challenges. J Microbiol Methods 2010; 82:1-10. [DOI: 10.1016/j.mimet.2010.04.005] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/09/2010] [Accepted: 04/12/2010] [Indexed: 01/20/2023]
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Bromberg-White J, Lee CS, Duesbery N. Consequences and utility of the zinc-dependent metalloprotease activity of anthrax lethal toxin. Toxins (Basel) 2010; 2:1038-53. [PMID: 22069624 PMCID: PMC3153234 DOI: 10.3390/toxins2051038] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 04/29/2010] [Accepted: 05/05/2010] [Indexed: 01/13/2023] Open
Abstract
Anthrax is caused by the gram-positive bacterium Bacillus anthracis. The pathogenesis of this disease is dependent on the presence of two binary toxins, edema toxin (EdTx) and lethal toxin (LeTx). LeTx, the major virulence factor contributing to anthrax, contains the effector moiety lethal factor (LF), a zinc-dependent metalloprotease specific for targeting mitogen-activated protein kinase kinases. This review will focus on the protease-specific activity and function of LF, and will include a discussion on the implications and consequences of this activity, both in terms of anthrax disease, and how this activity can be exploited to gain insight into other pathologic conditions.
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Affiliation(s)
- Jennifer Bromberg-White
- Laboratory of Cancer and Developmental Cell Biology, The Van Andel Research Institute, 333 Bostwick NE Grand Rapids, MI, 49503, USA; (J.B.-W.); (C.-S.L.)
| | - Chih-Shia Lee
- Laboratory of Cancer and Developmental Cell Biology, The Van Andel Research Institute, 333 Bostwick NE Grand Rapids, MI, 49503, USA; (J.B.-W.); (C.-S.L.)
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing MI 48824, USA
| | - Nicholas Duesbery
- Laboratory of Cancer and Developmental Cell Biology, The Van Andel Research Institute, 333 Bostwick NE Grand Rapids, MI, 49503, USA; (J.B.-W.); (C.-S.L.)
- Author to whom correspondence should be addressed; ; Tel.: 616-234-5258; Fax: 616-234-5259
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Kintzer AF, Sterling HJ, Tang II, Abdul-Gader A, Miles AJ, Wallace BA, Williams ER, Krantz BA. Role of the protective antigen octamer in the molecular mechanism of anthrax lethal toxin stabilization in plasma. J Mol Biol 2010; 399:741-58. [PMID: 20433851 DOI: 10.1016/j.jmb.2010.04.041] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2010] [Revised: 04/20/2010] [Accepted: 04/22/2010] [Indexed: 01/03/2023]
Abstract
Anthrax is caused by strains of Bacillus anthracis that produce two key virulence factors, anthrax toxin (Atx) and a poly-gamma-D-glutamic acid capsule. Atx is comprised of three proteins: protective antigen (PA) and two enzymes, lethal factor (LF) and edema factor (EF). To disrupt cell function, these components must assemble into holotoxin complexes, which contain either a ring-shaped homooctameric or homoheptameric PA oligomer bound to multiple copies of LF and/or EF, producing lethal toxin (LT), edema toxin, or mixtures thereof. Once a host cell endocytoses these complexes, PA converts into a membrane-inserted channel that translocates LF and EF into the cytosol. LT can assemble on host cell surfaces or extracellularly in plasma. We show that, under physiological conditions in bovine plasma, LT complexes containing heptameric PA aggregate and inactivate more readily than LT complexes containing octameric PA. LT complexes containing octameric PA possess enhanced stability, channel-forming activity, and macrophage cytotoxicity relative to those containing heptameric PA. Under physiological conditions, multiple biophysical probes reveal that heptameric PA can prematurely adopt the channel conformation, but octameric PA complexes remain in their soluble prechannel configuration, which allows them to resist aggregation and inactivation. We conclude that PA may form an octameric oligomeric state as a means to produce a more stable and active LT complex that could circulate freely in the blood.
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Anthrax toxin triggers the activation of src-like kinases to mediate its own uptake. Proc Natl Acad Sci U S A 2010; 107:1420-4. [PMID: 20080640 DOI: 10.1073/pnas.0910782107] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
AB-type toxins, like other bacterial toxins, are notably opportunistic molecules. They rely on target cell receptors to reach the appropriate location within the target cell where translocation of their enzymatic subunits occurs. The anthrax toxin, however, times its own uptake, suggesting that toxin binding triggers specific signaling events. Here we show that the anthrax toxin triggers tyrosine phosphorylation of its own receptors, capillary morphogenesis gene 2 and tumor endothelial marker 8, which are not endowed with intrinsic kinase activity. This is required for efficient toxin uptake because endocytosis of the mutant receptor lacking the cytoplasmic tyrosine residues is strongly delayed. Phosphorylation of the receptors was dependent on src-like kinases, which where activated upon toxin binding. Importantly, src-dependent phosphorylation of the receptor was required for its subsequent ubiquitination, which in turn was required for clathrin-mediated endocytosis. Consistently, we found that uptake of the anthrax toxin and processing of the lethal factor substrate MEK1 are inhibited by silencing of src and fyn, as well as in src and fyn knockout cells.
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Boyer AE, Quinn CP, Hoffmaster AR, Kozel TR, Saile E, Marston CK, Percival A, Plikaytis BD, Woolfitt AR, Gallegos M, Sabourin P, McWilliams LG, Pirkle JL, Barr JR. Kinetics of lethal factor and poly-D-glutamic acid antigenemia during inhalation anthrax in rhesus macaques. Infect Immun 2009; 77:3432-41. [PMID: 19506008 PMCID: PMC2715684 DOI: 10.1128/iai.00346-09] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 05/05/2009] [Accepted: 06/02/2009] [Indexed: 12/21/2022] Open
Abstract
Systemic anthrax manifests as toxemia, rapidly disseminating septicemia, immune collapse, and death. Virulence factors include the anti-phagocytic gamma-linked poly-d-glutamic acid (PGA) capsule and two binary toxins, complexes of protective antigen (PA) with lethal factor (LF) and edema factor. We report the characterization of LF, PA, and PGA levels during the course of inhalation anthrax in five rhesus macaques. We describe bacteremia, blood differentials, and detection of the PA gene (pagA) by PCR analysis of the blood as confirmation of infection. For four of five animals tested, LF exhibited a triphasic kinetic profile. LF levels (mean +/- standard error [SE] between animals) were low at 24 h postchallenge (0.03 +/- 1.82 ng/ml), increased at 48 h to 39.53 +/- 0.12 ng/ml (phase 1), declined at 72 h to 13.31 +/- 0.24 ng/ml (phase 2), and increased at 96 h (82.78 +/- 2.01 ng/ml) and 120 h (185.12 +/- 5.68 ng/ml; phase 3). The fifth animal had an extended phase 2. PGA levels were triphasic; they were nondetectable at 24 h, increased at 48 h (2,037 +/- 2 ng/ml), declined at 72 h (14 +/- 0.2 ng/ml), and then increased at 96 h (3,401 +/- 8 ng/ml) and 120 h (6,004 +/- 187 ng/ml). Bacteremia was also triphasic: positive at 48 h, negative at 72 h, and positive at euthanasia. Blood neutrophils increased from preexposure (34.4% +/- 0.13%) to 48 h (75.6% +/- 0.08%) and declined at 72 h (62.4% +/- 0.05%). The 72-h declines may establish a "go/no go" turning point in infection, after which systemic bacteremia ensues and the host's condition deteriorates. This study emphasizes the value of LF detection as a tool for early diagnosis of inhalation anthrax before the onset of fulminant systemic infection.
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Affiliation(s)
- Anne E Boyer
- Centers for Disease Control and Prevention, Atlanta, GA 30341, USA
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Abboud N, De Jesus M, Nakouzi A, Cordero RJB, Pujato M, Fiser A, Rivera J, Casadevall A. Identification of linear epitopes in Bacillus anthracis protective antigen bound by neutralizing antibodies. J Biol Chem 2009; 284:25077-86. [PMID: 19617628 DOI: 10.1074/jbc.m109.022061] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Protective antigen (PA), the binding subunit of anthrax toxin, is the major component in the current anthrax vaccine, but the fine antigenic structure of PA is not well defined. To identify linear neutralizing epitopes of PA, 145 overlapping peptides covering the entire sequence of the protein were synthesized. Six monoclonal antibodies (mAbs) and antisera from mice specific for PA were tested for their reactivity to the peptides by enzyme-linked immunosorbent assays. Three major linear immunodominant B-cell epitopes were mapped to residues Leu(156) to Ser(170), Val(196) to Ile(210), and Ser(312) to Asn(326) of the PA protein. Two mAbs with toxin-neutralizing activity recognized two different epitopes in close proximity to the furin cleavage site in domain 1. The three-dimensional complex structure of PA and its neutralizing mAbs 7.5G and 19D9 were modeled using the molecular docking method providing models for the interacting epitope and paratope residues. For both mAbs, LeTx neutralization was associated with interference with furin cleavage, but they differed in effectiveness depending on whether they bound on the N- or C-terminal aspect of the cleaved products. The two peptides containing these epitopes that include amino acids Leu(156)-Ser(170) and Val(196)-Ile(210) were immunogenic and elicited neutralizing antibody responses to PA. These results identify the first linear neutralizing epitopes of PA and show that peptides containing epitope sequences can elicit neutralizing antibody responses, a finding that could be exploited for vaccine design.
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Affiliation(s)
- Nareen Abboud
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Membrane translocation by anthrax toxin. Mol Aspects Med 2009; 30:413-22. [PMID: 19563824 DOI: 10.1016/j.mam.2009.06.003] [Citation(s) in RCA: 121] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 06/19/2009] [Indexed: 12/14/2022]
Abstract
Much attention has been focused on anthrax toxin recently, both because of its central role in the pathogenesis of Bacillus anthracis and because it has proven to be one of the most tractable toxins for studying how enzymic moieties of intracellularly acting toxins traverse membranes. The Protective Antigen (PA) moiety of the toxin, after being proteolytically activated at the cell surface, self-associates to form a heptameric pore precursor (prepore). The prepore binds up to three molecules of Edema Factor (EF), Lethal Factor (LF), or both, forming a series of complexes that are then endocytosed. Under the influence of acidic pH within the endosome, the prepore undergoes a conformational transition to a mushroom-shaped pore, with a globular cap and 100A-long stem that spans the membrane. Electrophysiological studies in planar bilayers indicate that EF and LF translocate through the pore in unfolded form and in the N- to C-terminal direction. The pore serves as an active transporter, which translocates its proteinaceous cargo across the endosomal membrane in response to DeltapH and perhaps, to a degree, Deltapsi. A ring of seven Phe residues (Phe427) in the lumen of the pore forms a seal around the translocating polypeptide and blocks the passage of ions, presumably preserving the pH gradient. A charge state-dependent Brownian ratchet mechanism has been proposed to explain how the pore translocates EF and LF. This transport mechanism of the pore may function in concert with molecular chaperonins to effect delivery of effector proteins in catalytically active form to the cytosolic compartment of host cells.
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Alfano RW, Leppla SH, Liu S, Bugge TH, Meininger CJ, Lairmore TC, Mulne AF, Davis SH, Duesbery NS, Frankel AE. Matrix metalloproteinase-activated anthrax lethal toxin inhibits endothelial invasion and neovasculature formation during in vitro morphogenesis. Mol Cancer Res 2009; 7:452-61. [PMID: 19372576 DOI: 10.1158/1541-7786.mcr-08-0451] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Solid tumor growth is dependent on angiogenesis, the formation of neovasculature from existing vessels. Endothelial activation of the extracellular signal-regulated kinase 1/2, c-jun NH(2)-terminal kinase, and p38 mitogen-activated protein kinase pathways is central to this process, and thus presents an attractive target for the development of angiogenesis inhibitors. Anthrax lethal toxin (LeTx) has potent catalytic mitogen-activated protein kinase inhibition activity. Preclinical studies showed that LeTx induced potent tumor growth inhibition via the inhibition of xenograft vascularization. However, LeTx receptors and the essential furin-like activating proteases are expressed in many normal tissues, potentially limiting the specificity of LeTx as an antitumor agent. To circumvent nonspecific LeTx activation and simultaneously enhance tumor vascular targeting, a substrate preferably cleaved by the gelatinases class of matrix metalloproteinases (MMP) was substituted for the furin LeTx activation site. In vivo efficacy studies showed that this MMP-activated LeTx inhibited tumor xenografts growth via the reduced migration of endothelial cells into the tumor parenchyma. Here we have expanded on these initial findings by showing that this MMP-activated LeTx reduces endothelial proangiogenic MMP expression, thus causing a diminished proteolytic capacity for extracellular matrix remodeling and endothelial differentiation into capillary networks. Additionally, our data suggest that inhibition of the c-jun NH(2)-terminal kinase and p38, but not extracellular signal-regulated kinase-1/2, pathways is significant in the antiangiogenic activity of the MMP-activated LeTx. Collectively, these results support the clinical development of the MMP-activated LeTx for the treatment of solid tumors.
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Affiliation(s)
- Randall W Alfano
- Cancer Research Institute of Scott and White, Temple, TX 76502, USA
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Vuyisich M, Gnanakaran S, Lovchik JA, Lyons CR, Gupta G. A dual-purpose protein ligand for effective therapy and sensitive diagnosis of anthrax. Protein J 2009; 27:292-302. [PMID: 18649128 DOI: 10.1007/s10930-008-9137-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This article reports the design of a bivalent protein ligand with dual use in therapy and diagnosis of anthrax caused by Bacillus anthracis. The ligand specifically binds to PA and thereby blocks the intracellular delivery of LF and EF toxins that, respectively, cause cell lysis and edema. The ligand is a chimeric scaffold with two PA-binding domains (called VWA) linked to an IgG-Fc frame. Molecular modeling and binding measurements reveal that the VWA-Fc dimer binds to PA with high affinity (K(D)=0.2 nM). An in vitro bio-luminescence assay shows that VWA-Fc (at nanomolar concentration) protects mouse macrophages from lysis by PA/LF. In vivo studies demonstrate that VWA-Fc at low doses (approximately 50 microg/animal) are able to rescue animals from lethal doses of PA/LF and B. anthracis spores. Finally, VWA-Fc is utilized as the capture molecule in the sensitive (down to 30 picomolar) detection of PA using surface plasmon resonance.
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Affiliation(s)
- Momchilo Vuyisich
- Biosciences Division, Group B-7, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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Frequency and domain specificity of toxin-neutralizing paratopes in the human antibody response to anthrax vaccine adsorbed. Infect Immun 2009; 77:2030-5. [PMID: 19223482 DOI: 10.1128/iai.01254-08] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Protective antigen (PA) is the cell surface recognition unit of the binary anthrax toxin system and the primary immunogenic component in both the current and proposed "next-generation" anthrax vaccines. Several studies utilizing animal models have indicated that PA-specific antibodies, acquired by either active or passive immunization, are sufficient to protect against infection with Bacillus anthracis. To investigate the human antibody response to anthrax immunization, we have established a large panel of human PA-specific monoclonal antibodies derived from multiple individuals vaccinated with the currently approved anthrax vaccine BioThrax. We have determined that although these antibodies bind PA in standard binding assays such as enzyme-linked immunosorbent assay, Western blotting, capture assays, and dot blots, less than 25% are capable of neutralizing lethal toxin (LT) in vitro. Nonneutralizing antibodies also fail to neutralize toxin when present in combination with other nonneutralizing paratopes. Although neutralizing antibodies recognize determinants throughout the PA monomer, they are significantly less common among those paratopes that bind to the immunodominant amino-terminal portion of the molecule. These findings demonstrate that PA binding alone is not sufficient to neutralize LT and suggest that for an antibody to effectively block PA-mediated toxicity, it must bind to PA such that one of the requisite toxin functions is disrupted. A vaccine design strategy that directed a higher percentage of the antibody response toward neutralizing epitopes may result in a more efficacious vaccine for the prevention of anthrax infection.
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