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Fischer ES, Campbell WA, Liu S, Ghirlando R, Fattah RJ, Bugge TH, Leppla SH. Bismaleimide cross-linked anthrax toxin forms functional octamers with high specificity in tumor targeting. Protein Sci 2019; 28:1059-1070. [PMID: 30942916 DOI: 10.1002/pro.3613] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 04/01/2019] [Indexed: 12/12/2022]
Abstract
In recent years, anthrax toxin has been reengineered to act as a highly specific antiangiogenic cancer therapeutic, shown to kill tumors in animal models. This has been achieved by modifying protective antigen (PA) so that its activation and toxicity require the presence of two proteases, matrix metalloproteinase (MMP) and urokinase plasminogen activator (uPA), which are upregulated in tumor microenvironments. These therapeutics consist of intercomplementing PA variants, which are individually nontoxic, but form functional toxins upon complementary oligomerization. Here, we have created a dual-protease requiring PA targeting system which utilizes bismaleimide cross-linked PA (CLPA) rather than the intercomplementing PA variants. Three different CLPA agents were tested and, as expected, found to exclusively form octamers. Two of the CLPA agents have in vitro toxicities equal to those of previous intercomplementing agents, while the third CLPA agent had compromised in vitro cleavage and was significantly less cytotoxic. We hypothesize this difference was due to steric hindrance caused by cross-linking two PA monomers in close proximity to the PA cleavage site. Overall, this work advances the development and use of the PA and LF tumor-targeting system as a practical cancer therapeutic, as it provides a way to reduce the drug components of the anthrax toxin drug delivery system from three to two, which may lower the cost and simplify testing in clinical trials. HIGHLIGHT: Previously, anthrax toxin has been reengineered to act as a highly specific antiangiogenic cancer therapeutic. Here, we present a version, which utilizes bismaleimide cross-linked protective antigen (PA) rather than intercomplementing PA variants. This advances the development of anthrax toxin as a practical cancer therapeutic as it reduces the components of the drug delivery system to two, which may lower the cost and simplify testing in clinical trials.
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Affiliation(s)
- Elyse S Fischer
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
| | - Warren A Campbell
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
| | - Shihui Liu
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, Bethesda, Maryland
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, 20892
| | - Rasem J Fattah
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
| | - Thomas H Bugge
- Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, Bethesda, Maryland
| | - Stephen H Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland
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2
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Weir GM, MacDonald LD, Rajagopalan R, Sivko GS, Valderas MW, Rayner J, Berger BJ, Sammatur L, Stanford MM. Single dose of DPX-rPA, an enhanced-delivery anthrax vaccine formulation, protects against a lethal Bacillus anthracis spore inhalation challenge. NPJ Vaccines 2019; 4:6. [PMID: 30774997 PMCID: PMC6368554 DOI: 10.1038/s41541-019-0102-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 01/16/2019] [Indexed: 01/15/2023] Open
Abstract
Anthrax is a serious biological threat caused by pulmonary exposure to aerosolized spores of Bacillus anthracis. Biothrax® (anthrax vaccine adsorbed (AVA)) is the only Food and Drug Administration-licensed vaccine and requires five administrations over 12 months with annual boosting to maintain pre-exposure prophylaxis. Here we report the evaluation of a single intramuscular injection of recombinant B. anthracis-protective antigen (rPA) formulated in the DPX delivery platform. Immune responses were compared to an alum-based formulation in mice and rabbits. Serological analysis of anti-rPA immunoglobulin G and toxin neutralization activity demonstrated higher responses induced by DPX-rPA when compared to rPA in alum. DPX-rPA was compared to AVA in rabbits and non-human primates (NHPs). In both species, DPX-rPA generated responses after a single immunization, whereas AVA required two immunizations. In rabbits, single injection of DPX-rPA or two injections of AVA conferred 100% protection from anthrax challenge. In NHPs, single-dose DPX-rPA was 100% protective against challenge, whereas one animal in the two-dose AVA group and all saline administered animals succumbed to infection. DPX-rPA was minimally reactogenic in all species tested. These data indicate that DPX-rPA may offer improvement over AVA by reducing the doses needed for protective immune responses and is a promising candidate as a new-generation anthrax vaccine. A lipid-based anthrax vaccine formulation offers immunity from the first injection. Bacillus anthracis is a lethal pathogen at high risk for use in biological warfare. The only FDA-licensed vaccine for anthrax, AVA, requires multiple doses over six months followed by regular boosters, indicating a need for rapidly immunizing vaccines. Genevieve Weir and Lisa MacDonald, from IMV Inc., with Canadian and US collaborators, here describe a prophylactic consisting of B. anthracis antigens suspended in a lipid-in-oil formulation. Their candidate, DPX-rPA, generated antigen-specific antibodies in rabbits and monkeys after one dose, compared to two for AVA. DPX-rPA also protected both species from B. anthracis spores after one dose. The results indicate that single-dose DPX-rPA is equally protective as two doses of AVA and could serve as pre-exposure and post-exposure prophylaxis. Future studies may confirm its potential as a vaccine for humans.
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Affiliation(s)
- Genevieve M Weir
- IMV Inc., 130 Eileen Stubbs Avenue, Suite 19, Dartmouth, NS B3B 2C4 Canada
| | - Lisa D MacDonald
- IMV Inc., 130 Eileen Stubbs Avenue, Suite 19, Dartmouth, NS B3B 2C4 Canada
| | | | - Gloria S Sivko
- 2Battelle, 1425 Plain City Georgesville Road, West Jefferson, OH 43162 USA
| | | | - Jonathan Rayner
- 3Southern Research, 2000 9th Avenue S, Birmingham, AL 35205 USA
| | - Bradley J Berger
- 4Suffield Research Centre, Defence Research and Development Canada, Medicine Hat, AB T1A 8K6 Canada
| | - Leeladhar Sammatur
- IMV Inc., 130 Eileen Stubbs Avenue, Suite 19, Dartmouth, NS B3B 2C4 Canada
| | - Marianne M Stanford
- IMV Inc., 130 Eileen Stubbs Avenue, Suite 19, Dartmouth, NS B3B 2C4 Canada.,5Department of Microbiology and Immunology, Dalhousie University, 5850 College Street, Room 7-C, PO BOX 15000, Halifax, NS B3H 4R2 Canada
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Sharma AK, Leppla SH, Pomerantsev AP, Shiloach J. Effect of over expressing protective antigen on global gene transcription in Bacillus anthracis BH500. Sci Rep 2018; 8:16108. [PMID: 30382110 PMCID: PMC6208434 DOI: 10.1038/s41598-018-34196-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 10/08/2018] [Indexed: 01/22/2023] Open
Abstract
Protective antigen (PA) of Bacillus anthracis is being considered as a vaccine candidate against anthrax and its production has been explored in several heterologous host systems. Since the systems tested introduced adverse issues such as inclusion body formation and endotoxin contamination, the production from B. anthracis is considered as a preferred method. The present study examines the effect of PA expression on the metabolism of B. anthracis producing strain, BH500, by comparing it with a control strain carrying an empty plasmid. The strains were grown in a bioreactor and RNA-seq analysis of the producing and non-producing strain was conducted. Among the observed differences, the strain expressing rPA had increased transcription of sigL, the gene encoding RNA polymerase σ54, sigB, the general stress transcription factor gene and its regulators rsbW and rsbV, as well as the global regulatory repressor ctsR. There were also decreased expression of intracellular heat stress related genes such as groL, groES, hslO, dnaJ, and dnaK and increased expression of extracellular chaperons csaA and prsA2. Also, major central metabolism genes belonging to TCA, glycolysis, PPP, and amino acids biosynthesis were up-regulated in the PA-producing strain during the lag phase and down-regulated in the log and late-log phases, which was associated with decreased specific growth rates. The information obtained from this study may guide genetic modification of B. anthracis to improve PA production.
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Affiliation(s)
- Ashish K Sharma
- Biotechnology Core Laboratory, National Institute of Diabetes and Digestives and Kidney Diseases (NIDDK) NIH, Maryland, USA
| | - Stephen H Leppla
- Microbial Pathogenesis Section, National Institute of Allergy and Infectious diseases (NIAID), NIH, Maryland, USA
| | - Andrei P Pomerantsev
- Microbial Pathogenesis Section, National Institute of Allergy and Infectious diseases (NIAID), NIH, Maryland, USA
| | - Joseph Shiloach
- Biotechnology Core Laboratory, National Institute of Diabetes and Digestives and Kidney Diseases (NIDDK) NIH, Maryland, USA.
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4
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Tao P, Mahalingam M, Zhu J, Moayeri M, Kirtley ML, Fitts EC, Andersson JA, Lawrence WS, Leppla SH, Chopra AK, Rao VB. A Bivalent Anthrax-Plague Vaccine That Can Protect against Two Tier-1 Bioterror Pathogens, Bacillus anthracis and Yersinia pestis. Front Immunol 2017; 8:687. [PMID: 28694806 PMCID: PMC5483451 DOI: 10.3389/fimmu.2017.00687] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 05/26/2017] [Indexed: 01/14/2023] Open
Abstract
Bioterrorism remains as one of the biggest challenges to global security and public health. Since the deadly anthrax attacks of 2001 in the United States, Bacillus anthracis and Yersinia pestis, the causative agents of anthrax and plague, respectively, gained notoriety and were listed by the CDC as Tier-1 biothreat agents. Currently, there is no Food and Drug Administration-approved vaccine against either of these threats for mass vaccination to protect general public, let alone a bivalent vaccine. Here, we report the development of a single recombinant vaccine, a triple antigen consisting of all three target antigens, F1 and V from Y. pestis and PA from B. anthracis, in a structurally stable context. Properly folded and soluble, the triple antigen retained the functional and immunogenicity properties of all three antigens. Remarkably, two doses of this immunogen adjuvanted with Alhydrogel® elicited robust antibody responses in mice, rats, and rabbits and conferred complete protection against inhalational anthrax and pneumonic plague. No significant antigenic interference was observed. Furthermore, we report, for the first time, complete protection of animals against simultaneous challenge with Y. pestis and the lethal toxin of B. anthracis, demonstrating that a single biodefense vaccine can protect against a bioterror attack with weaponized B. anthracis and/or Y. pestis. This bivalent anthrax–plague vaccine is, therefore, a strong candidate for stockpiling, after demonstration of its safety and immunogenicity in human clinical trials, as part of national preparedness against two of the deadliest bioterror threats.
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Affiliation(s)
- Pan Tao
- Department of Biology, The Catholic University of America, Washington, DC, United States
| | - Marthandan Mahalingam
- Department of Biology, The Catholic University of America, Washington, DC, United States
| | - Jingen Zhu
- Department of Biology, The Catholic University of America, Washington, DC, United States
| | - Mahtab Moayeri
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Michelle L Kirtley
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
| | - Eric C Fitts
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
| | - Jourdan A Andersson
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
| | - William S Lawrence
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States.,Galveston National Laboratory, University of Texas Medical Branch, Galveston, TX, United States
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Ashok K Chopra
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States.,Galveston National Laboratory, University of Texas Medical Branch, Galveston, TX, United States.,Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States.,Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX, United States.,Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX, United States
| | - Venigalla B Rao
- Department of Biology, The Catholic University of America, Washington, DC, United States
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Soluble Expression and Characterization of Biologically Active Bacillus anthracis Protective Antigen in Escherichia coli. Mol Biol Int 2016; 2016:4732791. [PMID: 26966576 PMCID: PMC4761392 DOI: 10.1155/2016/4732791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Accepted: 01/12/2016] [Indexed: 12/19/2022] Open
Abstract
Bacillus anthracis secretory protein protective antigen (PA) is primary candidate for subunit vaccine against anthrax. Attempts to obtain large quantity of PA from Escherichia coli expression system often result in the formation of insoluble inclusion bodies. Therefore, it is always better to produce recombinant proteins in a soluble form. In the present study, we have obtained biologically active recombinant PA in small scale E. coli shake culture system using three different expression constructs. The PA gene was cloned in expression vectors bearing trc, T5, and T7 promoters and transformed into their respective E. coli hosts. The growth conditions were optimized to obtain maximum expression of PA in soluble form. The expression construct PA-pET32c in DE3-pLysS E. coli host resulted in a maximum production of soluble PA (15 mg L(-1)) compared to other combinations. Purified PA was subjected to trypsin digestion and binding assay with lethal factor to confirm the protein's functionality. Biological activity was confirmed by cytotoxicity assay on J774.1 cells. Balb/c mice were immunized with PA and the immunogenicity was tested by ELISA and toxin neutralization assay. This study highlights the expression of soluble and biologically active recombinant PA in larger quantity using simpler E. coli production platform.
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Bekdash A, Darwish M, Timsah Z, Kassab E, Ghanem H, Najjar V, Ghosn M, Nasser S, El-Hajj H, Bazerbachi A, Liu S, Leppla SH, Frankel AE, Abi-Habib RJ. Phospho-MEK1/2 and uPAR Expression Determine Sensitivity of AML Blasts to a Urokinase-Activated Anthrax Lethal Toxin (PrAgU2/LF). Transl Oncol 2015; 8:347-357. [PMID: 26500025 PMCID: PMC4630967 DOI: 10.1016/j.tranon.2015.07.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 07/09/2015] [Accepted: 07/14/2015] [Indexed: 02/04/2023] Open
Abstract
In this study, we attempt to target both the urokinase plasminogen activator and the mitogen-activated protein kinase pathway in acute myeloid leukemia (AML) cell lines and primary AML blasts using PrAgU2/LF, a urokinase-activated anthrax lethal toxin. PrAgU2/LF was cytotoxic to five out of nine AML cell lines. Cytotoxicity of PrAgU2/LF appeared to be nonapoptotic and was associated with MAPK activation and urokinase activity because all the PrAgU2/LF-sensitive cell lines showed both uPAR expression and high levels of MEK1/2 phosphorylation. Inhibition of uPAR or desensitization of cells to MEK1/2 inhibition blocked toxicity of PrAgU2/LF, indicating requirement for both uPAR expression and MAPK activation for activity. PrAgU2/LF was also cytotoxic to primary blasts from AML patients, with blasts from four out of five patients showing a cytotoxic response to PrAgU2/LF. Cytotoxicity of primary AML blasts was also dependent on uPAR expression and phos-MEK1/2 levels. CD34(+) bone marrow blasts and peripheral blood mononuclear cells lacked uPAR expression and were resistant to PrAgU2/LF, demonstrating the lack of toxicity to normal hematological cells and, therefore, the tumor selectivity of this approach. Dose escalation in mice revealed that the maximal tolerated dose of PrAgU2/LF is at least 5.7-fold higher than that of the wild-type anthrax lethal toxin, PrAg/LF, further demonstrating the increased safety of this molecule. We have shown, in this study, that PrAgU2/LF is a novel, dual-specific molecule for the selective targeting of AML.
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Affiliation(s)
- Amira Bekdash
- Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon
| | - Manal Darwish
- Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon
| | - Zahra Timsah
- School of Molecular & Cellular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Elias Kassab
- Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon
| | - Hadi Ghanem
- Department of Internal Medicine, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon
| | - Vicky Najjar
- Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon
| | - Marwan Ghosn
- Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon
| | - Selim Nasser
- Department of Pathology, School of Medicine, Lebanese American University, Beirut 1102-2801, Lebanon
| | - Hiba El-Hajj
- Department of Internal Medicine and Experimental Pathology, School of Medicine, American University of Beirut, Lebanon; Department of Immunology and Microbiology, School of Medicine, American University of Beirut, Lebanon
| | - Ali Bazerbachi
- Department of Internal Medicine, School of Medicine, American University of Beirut, Lebanon; Department of Anatomy, School of Medicine, American University of Beirut, Lebanon; Department of Cell Biology and Physiological Sciences, School of Medicine, American University of Beirut, Lebanon
| | - Shihui Liu
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Stephen H Leppla
- Microbial Pathogenesis Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892
| | - Arthur E Frankel
- Simmons Comprehensive Cancer Center, UT Southwestern Medical Center, Dallas, Texas 75390
| | - Ralph J Abi-Habib
- Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Beirut 1102 2801, Lebanon.
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7
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Immunization with a Recombinant, Pseudomonas fluorescens-Expressed, Mutant Form of Bacillus anthracis-Derived Protective Antigen Protects Rabbits from Anthrax Infection. PLoS One 2015. [PMID: 26207820 PMCID: PMC4514824 DOI: 10.1371/journal.pone.0130952] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Protective antigen (PA), one of the components of the anthrax toxin, is the major component of human anthrax vaccine (Biothrax). Human anthrax vaccines approved in the United States and Europe consist of an alum-adsorbed or precipitated (respectively) supernatant material derived from cultures of toxigenic, non-encapsulated strains of Bacillus anthracis. Approved vaccination schedules in humans with either of these vaccines requires several booster shots and occasionally causes adverse injection site reactions. Mutant derivatives of the protective antigen that will not form the anthrax toxins have been described. We have cloned and expressed both mutant (PA SNKE167-ΔFF-315-E308D) and native PA molecules recombinantly and purified them. In this study, both the mutant and native PA molecules, formulated with alum (Alhydrogel), elicited high titers of anthrax toxin neutralizing anti-PA antibodies in New Zealand White rabbits. Both mutant and native PA vaccine preparations protected rabbits from lethal, aerosolized, B. anthracis spore challenge subsequent to two immunizations at doses of less than 1 μg.
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8
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Bacillus anthracis Capsular Conjugates Elicit Chimpanzee Polyclonal Antibodies That Protect Mice from Pulmonary Anthrax. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2015; 22:902-8. [PMID: 26041039 DOI: 10.1128/cvi.00137-15] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Accepted: 05/17/2015] [Indexed: 01/12/2023]
Abstract
The immunogenicity of Bacillus anthracis capsule (poly-γ-D-glutamic acid [PGA]) conjugated to recombinant B. anthracis protective antigen (rPA) or to tetanus toxoid (TT) was evaluated in two anthrax-naive juvenile chimpanzees. In a previous study of these conjugates, highly protective monoclonal antibodies (MAbs) against PGA were generated. This study examines the polyclonal antibody response of the same animals. Preimmune antibodies to PGA with titers of >10(3) were detected in the chimpanzees. The maximal titer of anti-PGA was induced within 1 to 2 weeks following the 1st immunization, with no booster effects following the 2nd and 3rd immunizations. Thus, the anti-PGA response in the chimpanzees resembled a secondary immune response. Screening of sera from nine unimmunized chimpanzees and six humans revealed antibodies to PGA in all samples, with an average titer of 10(3). An anti-PA response was also observed following immunization with PGA-rPA conjugate, similar to that seen following immunization with rPA alone. However, in contrast to anti-PGA, preimmune anti-PA antibody titers and those following the 1st immunization were ≤300, with the antibodies peaking above 10(4) following the 2nd immunization. The polyclonal anti-PGA shared the MAb 11D epitope and, similar to the MAbs, exerted opsonophagocytic killing of B. anthracis. Most important, the PGA-TT-induced antibodies protected mice from a lethal challenge with virulent B. anthracis spores. Our data support the use of PGA conjugates, especially PGA-rPA targeting both toxin and capsule, as expanded-spectrum anthrax vaccines.
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D'Agnillo F, Williams MC, Moayeri M, Warfel JM. Anthrax lethal toxin downregulates claudin-5 expression in human endothelial tight junctions. PLoS One 2013; 8:e62576. [PMID: 23626836 PMCID: PMC3633853 DOI: 10.1371/journal.pone.0062576] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 03/22/2013] [Indexed: 01/22/2023] Open
Abstract
Vascular leakage pathologies such as pleural effusion and hemorrhage are hallmarks of anthrax pathogenesis. We previously reported that anthrax lethal toxin (LT), the major virulence factor of anthrax, reduces barrier function in cultured primary human microvascular endothelial cells. Here, we show that LT-induced barrier dysfunction is accompanied by the reduced expression of the endothelial tight junction (TJ) protein claudin-5 but no change in the expression of other TJ components occludin, ZO-1, ZO-2, or the adherens junction (AJ) protein VE-cadherin. The downregulation of claudin-5 correlated temporally and dose-dependently with the reduction of transendothelial electrical resistance. LT-induced loss of claudin-5 was independent of cell death and preceded the appearance of actin stress fibers and altered AJ morphology. Pharmacological inhibition of MEK-1/2, two kinases that are proteolytically inactivated by LT, showed a similar reduction in claudin-5 expression. We found that LT reduced claudin-5 mRNA levels but did not accelerate the rate of claudin-5 degradation. Mice challenged with LT also showed significant reduction in claudin-5 expression. Together, these findings support a possible role for LT disruption of endothelial TJs in the vascular leakage pathologies of anthrax.
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Affiliation(s)
- Felice D'Agnillo
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, United States of America.
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10
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Cytotoxicity of anthrax lethal toxin to human acute myeloid leukemia cells is nonapoptotic and dependent on extracellular signal-regulated kinase 1/2 activity. Transl Oncol 2013; 6:25-32. [PMID: 23418614 DOI: 10.1593/tlo.12313] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 11/16/2012] [Accepted: 11/19/2012] [Indexed: 12/13/2022] Open
Abstract
In this study, we attempt to target the mitogen-activated protein kinase (MAPK) pathway in acute myeloid leukemia (AML) cells using a recombinant anthrax lethal toxin (LeTx). LeTx consists of protective antigen (PrAg) and lethal factor (LF). PrAg binds cells, is cleaved by furin, oligomerizes, binds three to four molecules of LF, and undergoes endocytosis, releasing LF into the cytosol. LF cleaves MAPK kinases, inhibiting the MAPK pathway. We tested potency of LeTx on a panel of 11 human AML cell lines. Seven cell lines showed cytotoxic responses to LeTx. Cytotoxicity of LeTx was mimicked by the specific mitogen-activated protein/extracellular signal-regulated kinase kinase 1/2 (MEK1/2) inhibitor U0126, indicating that LeTx-induced cell death is mediated through the MEK1/2-extracellular signal-regulated kinase (ERK1/2) branch of the MAPK pathway. The four LeTx-resistant cell lines were sensitive to the phosphatidylinositol 3-kinase inhibitor LY294002. Co-treatment of AML cells with both LeTx and LY294002 did not lead to increased sensitivity, showing a lack of additive/synergistic effects when both pathways are inhibited. Flow cytometry analysis of MAPK pathway activation revealed the presence of phospho-ERK1/2 only in LeTx-sensitive cells. Staining for Annexin V/propidium iodide and active caspases showed an increase in double-positive cells and the absence of caspase activation following treatment, indicating that LeTx-induced cell death is caspase-independent and nonapoptotic. We have shown that a majority of AML cell lines are sensitive to the LF-mediated inhibition of the MAPK pathway. Furthermore, we have demonstrated that LeTx-induced cytotoxicity in AML cells is nonapoptotic and dependent on phospho-ERK1/2 levels.
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11
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Kandadi MR, Yu X, Frankel AE, Ren J. Cardiac-specific catalase overexpression rescues anthrax lethal toxin-induced cardiac contractile dysfunction: role of oxidative stress and autophagy. BMC Med 2012; 10:134. [PMID: 23134810 PMCID: PMC3520786 DOI: 10.1186/1741-7015-10-134] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 11/07/2012] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Lethal and edema toxins secreted by Bacillus anthracis during anthrax infection were found to incite serious cardiovascular complications. However, the underlying mechanisms in anthrax lethal toxin-induced cardiac anomalies remain unknown. This study was designed to evaluate the impact of antioxidant enzyme catalase in anthrax lethal toxin-induced cardiomyocyte contractile dysfunction. METHODS Wild type (WT) and cardiac-specific catalase overexpression mice were challenged with lethal toxin (2 μg/g, intraperotineally (i.p.)). Cardiomyocyte contractile and intracellular Ca(2+) properties were assessed 18 h later using an IonOptix edge-detection system. Proteasome function was assessed using chymotrypsin-like and caspase-like activities. GFP-LC3 puncta and Western blot analysis were used to evaluate autophagy and protein ubiquitination. RESULTS Lethal toxin exposure suppressed cardiomyocyte contractile function (suppressed peak shortening, maximal velocity of shortening/re-lengthening, prolonged duration of shortening/re-lengthening, and impaired intracellular Ca(2+) handling), the effects of which were alleviated by catalase. In addition, lethal toxin triggered autophagy, mitochondrial and ubiquitin-proteasome defects, the effects of which were mitigated by catalase. Pretreatment of cardiomyocytes from catalase mice with the autophagy inducer rapamycin significantly attenuated or ablated catalase-offered protection against lethal toxin-induced cardiomyocyte dysfunction. On the other hand, the autophagy inhibitor 3-MA ablated or significantly attenuated lethal toxin-induced cardiomyocyte contractile anomalies. CONCLUSIONS Our results suggest that catalase is protective against anthrax lethal toxin-induced cardiomyocyte contractile and intracellular Ca(2+) anomalies, possibly through regulation of autophagy and mitochondrial function.
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Affiliation(s)
- Machender R Kandadi
- Center for Cardiovascular Research and Alternative Medicine, University of Wyoming College of Health Sciences, Laramie, WY 82071, USA
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12
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Glycoconjugates prevent B. anthracis toxin-induced cell death through binding while activating macrophages. Glycoconj J 2011; 29:25-33. [PMID: 22134879 DOI: 10.1007/s10719-011-9360-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Revised: 10/09/2011] [Accepted: 11/02/2011] [Indexed: 10/15/2022]
Abstract
Bacillus anthracis toxins may be attenuated if macrophages could neutralize toxins upon contact or exposure. Glycoconjugate-bearing polymers, which have been shown to bind to Bacillus spores, were tested for recognition and binding of protective antigen (PA), lethal factor (LF), and edema factor (EF) toxins. We have demonstrated modulation of macrophage activity following exposure to these toxins. Without glycoconjugate (GC) activation, murine macrophages were killed by Bacillus toxins. GCs were shown to have a protective influence, sparing macrophages from toxin-induced cell death, as shown by increased macrophage cell viability based on trypan blue assay. Increased levels of inducible nitric oxide (NO) production by macrophages in presence of GCs suggest that GCs provide an activation signal for macrophages and stimulate their function. Results hint to GCs that promote neutralization of Bacillus toxins, block toxin-induced macrophage death, while increasing macrophage activation. Polymeric GCs may suggest novel approaches to improve existing or develop new vaccines as well as immunotherapeutics.
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Occurrence, recognition, and reversion of spontaneous, sporulation-deficient Bacillus anthracis mutants that arise during laboratory culture. Microbes Infect 2011; 14:387-91. [PMID: 22166343 DOI: 10.1016/j.micinf.2011.11.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 11/16/2011] [Accepted: 11/17/2011] [Indexed: 11/22/2022]
Abstract
Bacillus anthracis is a spore-forming, soil-dwelling bacterium. This review describes the occurrence of spontaneous mutations leading to loss of sporulation and the selective pressures that can lead to their enrichment. We also discuss recognition of the associated phenotypes on solid medium, thereby allowing researchers to employ measures that either prevent or favor selection of sporulation-deficient mutants.
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Anthrax vaccine antigen-adjuvant formulations completely protect New Zealand white rabbits against challenge with Bacillus anthracis Ames strain spores. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2011; 19:11-6. [PMID: 22089245 DOI: 10.1128/cvi.05376-11] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In an effort to develop an improved anthrax vaccine that shows high potency, five different anthrax protective antigen (PA)-adjuvant vaccine formulations that were previously found to be efficacious in a nonhuman primate model were evaluated for their efficacy in a rabbit pulmonary challenge model using Bacillus anthracis Ames strain spores. The vaccine formulations include PA adsorbed to Alhydrogel, PA encapsulated in liposomes containing monophosphoryl lipid A, stable liposomal PA oil-in-water emulsion, PA displayed on bacteriophage T4 by the intramuscular route, and PA mixed with Escherichia coli heat-labile enterotoxin administered by the needle-free transcutaneous route. Three of the vaccine formulations administered by the intramuscular or the transcutaneous route as a three-dose regimen induced 100% protection in the rabbit model. One of the formulations, liposomal PA, also induced significantly higher lethal toxin neutralizing antibodies than PA-Alhydrogel. Even 5 months after the second immunization of a two-dose regimen, rabbits vaccinated with liposomal PA were 100% protected from lethal challenge with Ames strain spores. In summary, the needle-free skin delivery and liposomal formulation that were found to be effective in two different animal model systems appear to be promising candidates for next-generation anthrax vaccine development.
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15
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Warfel JM, D’Agnillo F. Anthrax lethal toxin-mediated disruption of endothelial VE-cadherin is attenuated by inhibition of the Rho-associated kinase pathway. Toxins (Basel) 2011; 3:1278-93. [PMID: 22069696 PMCID: PMC3210462 DOI: 10.3390/toxins3101278] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2011] [Revised: 10/01/2011] [Accepted: 10/09/2011] [Indexed: 01/01/2023] Open
Abstract
Systemic anthrax disease is characterized by vascular leakage pathologies. We previously reported that anthrax lethal toxin (LT) induces human endothelial barrier dysfunction in a cell death-independent manner with actin stress fiber formation and disruption of adherens junctions (AJs). In the present study, we further characterize the molecular changes in the AJ complex and investigate whether AJ structure and barrier function can be preserved by modulating key cytoskeletal signaling pathways. Here, we show that LT reduces total VE-cadherin protein and gene expression but the expression of the key linker protein beta-catenin remained unchanged. The changes in VE-cadherin expression correlated temporally with the appearance of actin stress fibers and a two-fold increase in phosphorylation of the stress fiber-associated protein myosin light chain (p-MLC) and cleavage of Rho-associated kinase-1 (ROCK-1). Co-treatment with ROCK inhibitors (H-1152 and Y27632), but not an inhibitor of MLC kinase (ML-7), blocked LT-induced p-MLC enhancement and stress fiber formation. This was accompanied by the restoration of VE-cadherin expression and membrane localization, and attenuation of the LT-induced increase in monolayer permeability to albumin. Together, these findings suggest the ROCK pathway may be a relevant target for countering LT-mediated endothelial barrier dysfunction.
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Affiliation(s)
- Jason M. Warfel
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, MD 20892, USA;
- Department of Microbiology and Immunology, Georgetown University Medical Center, Washington, DC 20057, USA
| | - Felice D’Agnillo
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland, MD 20892, USA;
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Hicks CW, Li Y, Okugawa S, Solomon SB, Moayeri M, Leppla SH, Mohanty A, Subramanian GM, Mignone TS, Fitz Y, Cui X, Eichacker PQ. Anthrax edema toxin has cAMP-mediated stimulatory effects and high-dose lethal toxin has depressant effects in an isolated perfused rat heart model. Am J Physiol Heart Circ Physiol 2011; 300:H1108-18. [PMID: 21217068 PMCID: PMC3064307 DOI: 10.1152/ajpheart.01128.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2010] [Accepted: 01/04/2011] [Indexed: 12/23/2022]
Abstract
While anthrax edema toxin produces pronounced tachycardia and lethal toxin depresses left ventricular (LV) ejection fraction in in vivo models, whether these changes reflect direct cardiac effects as opposed to indirect ones related to preload or afterload alterations is unclear. In the present study, the effects of edema toxin and lethal toxin were investigated in a constant pressure isolated perfused rat heart model. Compared with control hearts, edema toxin at doses comparable to or less than a dose that produced an 80% lethality rate (LD(80)) in vivo in rats (200, 100, and 50 ng/ml) produced rapid increases in heart rate (HR), coronary flow (CF), LV developed pressure (LVDP), dP/dt(max), and rate-pressure product (RPP) that were most pronounced and persisted with the lowest dose (P ≤ 0.003). Edema toxin (50 ng/ml) increased effluent and myocardial cAMP levels (P ≤ 0.002). Compared with dobutamine, edema toxin produced similar myocardial changes, but these occurred more slowly and persisted longer. Increases in HR, CF, and cAMP with edema toxin were inhibited by a monoclonal antibody blocking toxin uptake and by adefovir, which inhibits the toxin's intracellular adenyl cyclase activity (P ≤ 0.05). Lethal toxin at an LD(80) dose (50 ng/ml) had no significant effect on heart function but a much higher dose (500 ng/ml) reduced all parameters (P ≤ 0.05). In conclusion, edema toxin produced cAMP-mediated myocardial chronotropic, inotropic, and vasodilatory effects. Vasodilation systemically with edema toxin could contribute to shock during anthrax while masking potential inotropic effects. Although lethal toxin produced myocardial depression, this only occurred at high doses, and its relevance to in vivo findings is unclear.
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Affiliation(s)
- Caitlin W Hicks
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
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Rao M, Peachman KK, Li Q, Matyas GR, Shivachandra SB, Borschel R, Morthole VI, Fernandez-Prada C, Alving CR, Rao VB. Highly effective generic adjuvant systems for orphan or poverty-related vaccines. Vaccine 2010; 29:873-7. [PMID: 21115053 DOI: 10.1016/j.vaccine.2010.11.049] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 11/14/2010] [Accepted: 11/15/2010] [Indexed: 11/19/2022]
Abstract
Safe and effective adjuvants are needed for many vaccines with limited commercial appeal, such as vaccines to infrequent (orphan) diseases or to neglected and poverty-related diseases. Here we found that three nonproprietary liposome formulations containing monophosphoryl lipid A each induced 3-fold to 5-fold increased titers of binding and neutralizing antibodies to anthrax protective antigen compared to aluminum hydroxide-adsorbed antigen in monkeys. All vaccinated monkeys were protected against lethal challenge with aerosolized Ames strain spores.
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Affiliation(s)
- Mangala Rao
- Division of Retrovirology, U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 1600 East Gude Drive, Rockville, MD 20850, USA
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18
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Duverger A, Carré JM, Jee J, Leppla SH, Cormet-Boyaka E, Tang WJ, Tomé D, Boyaka PN. Contributions of edema factor and protective antigen to the induction of protective immunity by Bacillus anthracis edema toxin as an intranasal adjuvant. THE JOURNAL OF IMMUNOLOGY 2010; 185:5943-52. [PMID: 20952678 DOI: 10.4049/jimmunol.0902795] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have shown that intranasal coapplication of Bacillus anthracis protective Ag (PA) together with a B. anthracis edema factor (EF) mutant having reduced adenylate cyclase activity (i.e., EF-S414N) enhances anti-PA Ab responses, but also acts as a mucosal adjuvant for coadministered unrelated Ags. To elucidate the role of edema toxin (EdTx) components in its adjuvanticity, we examined how a PA mutant lacking the ability to bind EF (PA-U7) or another mutant that allows the cellular uptake of EF, but fails to efficiently mediate its translocation into the cytosol (PA-dFF), would affect EdTx-induced adaptive immunity. Native EdTx promotes costimulatory molecule expression by macrophages and B lymphocytes, and a broad spectrum of cytokine responses by cervical lymph node cells in vitro. These effects were reduced or abrogated when cells were treated with EF plus PA-dFF, or PA-U7 instead of PA. We also intranasally immunized groups of mice with a recombinant fusion protein of Yersinia pestis F1 and LcrV Ags (F1-V) together with EdTx variants consisting of wild-type or mutants PA and EF. Analysis of serum and mucosal Ab responses against F1-V or EdTx components (i.e., PA and EF) revealed no adjuvant activity in mice that received PA-U7 instead of PA. In contrast, coimmunization with PA-dFF enhanced serum Ab responses. Finally, immunization with native PA and an EF mutant lacking adenylate cyclase activity (EF-K346R) failed to enhance Ab responses. In summary, a fully functional PA and a minimum of adenylate cyclase activity are needed for EdTx to act as a mucosal adjuvant.
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Affiliation(s)
- Alexandra Duverger
- Department of Veterinary Biosciences, Ohio State University, Columbus, OH 43210, USA
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19
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Gupta PK, Liu S, Leppla SH. Characterization of a Chinese hamster ovary cell mutant having a mutation in elongation factor-2. PLoS One 2010; 5:e9078. [PMID: 20140093 PMCID: PMC2816718 DOI: 10.1371/journal.pone.0009078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 01/11/2010] [Indexed: 11/24/2022] Open
Abstract
Retroviral insertional mutagenesis provides an effective forward genetic method for identifying genes involved in essential cellular pathways. A Chinese hamster ovary cell line mutant resistant to several bacterial ADP-ribosylating was obtained by this approach. The toxins used catalyze ADP-ribosylation of eukaryotic elongation factor 2 (eEF-2), block protein synthesis, and cause cell death. Strikingly, in the CHO PR328 mutant cells, the eEF-2 substrate of these ADP-ribosylating toxins was found to be modified, but the cells remained viable. A systematic study of these cells revealed the presence of a structural mutation in one allele of the eEF-2 gene. This mutation, Gly717Arg, is close to His715, the residue that is modified to become diphthamide. This Arg substitution prevents diphthamide biosynthesis at His715, rendering the mutated eEF-2 non-responsive to ADP-ribosylating toxins, while having no apparent effect on protein synthesis. Thus, CHO PR328 cells are heterozygous, having wild type and mutant eEF-2 alleles, with the latter allowing the cells to survive even in the presence of ADP-ribosylating toxins. Here, we report the comprehensive characterization of these cells.
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Affiliation(s)
- Pradeep K. Gupta
- Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Shihui Liu
- Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Hu H, Leppla SH. Anthrax toxin uptake by primary immune cells as determined with a lethal factor-beta-lactamase fusion protein. PLoS One 2009; 4:e7946. [PMID: 19956758 PMCID: PMC2775957 DOI: 10.1371/journal.pone.0007946] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2009] [Accepted: 10/27/2009] [Indexed: 12/28/2022] Open
Abstract
Background To initiate infection, Bacillus anthracis needs to overcome the host innate immune system. Anthrax toxin, a major virulence factor of B. anthracis, impairs both the innate and adaptive immune systems and is important in the establishment of anthrax infections. Methodology/Principal Findings To measure the ability of anthrax toxin to target immune cells, studies were performed using a fusion of the anthrax toxin lethal factor (LF) N-terminal domain (LFn, aa 1–254) with β-lactamase (LFnBLA). This protein reports on the ability of the anthrax toxin protective antigen (PA) to mediate LF delivery into cells. Primary immune cells prepared from mouse spleens were used in conjunction with flow cytometry to assess cleavage and resulting FRET disruption of a fluorescent β-lactamase substrate, CCF2/AM. In spleen cell suspensions, the macrophages, dendritic cells, and B cells showed about 75% FRET disruption of CCF2/AM due to cleavage by the PA–delivered LFnBLA. LFnBLA delivery into CD4+ and CD8+ T cells was lower, with 40% FRET disruption. When the analyses were done on purified samples of individual cell types, similar results were obtained, with T cells again having lower LFnBLA delivery than macrophages, dendritic cells, and B cells. Relative expression levels of the toxin receptors CMG2 and TEM8 on these cells were determined by real-time PCR. Expression of CMG2 was about 1.5-fold higher in CD8+ cells than in CD4+ and B cells, and 2.5-fold higher than in macrophages. Conclusions/Significance Anthrax toxin entry and activity differs among immune cells. Macrophages, dendritic cells, and B cells displayed higher LFnBLA activity than CD4+ and CD8+ T cells in both spleen cell suspension and the purified samples of individual cell types. Expression of anthrax toxin receptor CMG2 is higher in CD4+ and CD8+ T cells, which is not correlated to the intracellular LFnBLA activity.
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Affiliation(s)
- Haijing Hu
- Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Stephen H. Leppla
- Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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21
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Cybulski RJ, Sanz P, O'Brien AD. Anthrax vaccination strategies. Mol Aspects Med 2009; 30:490-502. [PMID: 19729034 DOI: 10.1016/j.mam.2009.08.006] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Accepted: 08/24/2009] [Indexed: 01/10/2023]
Abstract
The biological attack conducted through the US postal system in 2001 broadened the threat posed by anthrax from one pertinent mainly to soldiers on the battlefield to one understood to exist throughout our society. The expansion of the threatened population placed greater emphasis on the reexamination of how we vaccinate against Bacillus anthracis. The currently-licensed Anthrax Vaccine, Adsorbed (AVA) and Anthrax Vaccine, Precipitated (AVP) are capable of generating a protective immune response but are hampered by shortcomings that make their widespread use undesirable or infeasible. Efforts to gain US Food and Drug Administration (FDA) approval for licensure of a second generation recombinant protective antigen (rPA)-based anthrax vaccine are ongoing. However, this vaccine's reliance on the generation of a humoral immune response against a single virulence factor has led a number of scientists to conclude that the vaccine is likely not the final solution to optimal anthrax vaccine design. Other vaccine approaches, which seek a more comprehensive immune response targeted at multiple components of the B. anthracis organism, are under active investigation. This review seeks to summarize work that has been done to build on the current PA-based vaccine methodology and to evaluate the search for future anthrax prophylaxis strategies.
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Affiliation(s)
- Robert J Cybulski
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814-4799, United States
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Abstract
Anthrax lethal toxin (LT) activates the NLRP1b (NALP1b) inflammasome and caspase-1 in macrophages from certain inbred mouse strains, but the mechanism by which this occurs is poorly understood. We report here that similar to several NLRP3 (NALP3, cryopyrin)-activating stimuli, LT activation of the NLRP1b inflammasome involves lysosomal membrane permeabilization (LMP) and subsequent cytoplasmic cathepsin B activity. CA-074Me, a potent cathepsin B inhibitor, protects LT-sensitive macrophages from cell death and prevents the activation of caspase-1. RNA interference knockdown of cathepsin B expression, however, cannot prevent LT-mediated cell death, suggesting that CA-074Me may also act on other cellular proteases released during LMP. CA-074Me appears to function downstream of LT translocation to the cytosol (as assessed by mitogen-activated protein kinase kinase cleavage), K(+) effluxes, and proteasome activity. The initial increase in cytoplasmic activity of cathepsin B occurs at the same time or shortly before caspase-1 activation but precedes a larger-scale lysosomal destabilization correlated closely with cytolysis. We present results suggesting that LMP may be involved in the activation of the NLRP1b inflammasome.
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Warfel JM, D'Agnillo F. Anthrax lethal toxin enhances IkappaB kinase activation and differentially regulates pro-inflammatory genes in human endothelium. J Biol Chem 2009; 284:25761-71. [PMID: 19620708 DOI: 10.1074/jbc.m109.036970] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Anthrax lethal toxin (LT) was previously shown to enhance transcriptional activity of NF-kappaB in tumor necrosis factor-alpha-activated primary human endothelial cells. Here we show that this LT-mediated increase in NF-kappaB activation is associated with the enhanced degradation of the inhibitory proteins IkappaBalpha and IkappaBbeta but not IkappaBepsilon. Moreover, this was accompanied by enhanced activation of the IkappaB kinase complex (IKK), which is responsible for targeting IkappaB proteins for degradation. Importantly, LT enhancement of IkappaBalpha degradation was completely blocked by a selective IKKbeta inhibitor, whereas IkappaBbeta degradation was attenuated, suggesting a mechanistic link. Consistent with the above data, LT-cotreated cells show elevated phosphorylation of two IKK substrates, IkappaBalpha and p65, both of which were blocked by incubation with the IKKbeta inhibitor. Consistent with NF-kappaB activation, LT increased transcription of the NF-kappaB regulated gene CD40. Conversely, LT inhibited transcription of another NF-kappaB-regulated gene, CCL2. This inhibition was linked to the LT-mediated suppression of another CCL2-regulating transcription factor, AP-1 (activator protein-1). These data suggest that LT-mediated enhancement of NF-kappaB is IKK-dependent, but importantly, the net effect of LT on the transcription of proinflammatory genes is driven by the cumulative effect of LT on the particular set of transcription factors that regulate a given promoter. Together, these findings provide new mechanistic insight on how LT may disrupt the host response to anthrax.
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Affiliation(s)
- Jason M Warfel
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA
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Li Q, Peachman KK, Sower L, Leppla SH, Shivachandra SB, Matyas GR, Peterson JW, Alving CR, Rao M, Rao VB. Anthrax LFn-PA Hybrid Antigens: Biochemistry, Immunogenicity, and Protection Against Lethal Ames Spore Challenge in Rabbits. ACTA ACUST UNITED AC 2009; 2:92-99. [PMID: 20390054 DOI: 10.2174/1875035400902010092] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We describe a novel hybrid anthrax toxin approach that incorporates multiple components into a single vaccine product. The key domains of protective antigen (PA) and lethal factor (LF) that may be critical for inducing protective immunity are combined into one recombinant molecule. Two LF N-terminal domain-PA hybrids, one with wild-type PA and another with furin cleavage-minus PA, were expressed in E. coli and purified in a native form. Both the hybrids bind to the extracellular domain of the host receptor, CMG2; the wild-type hybrid can be cleaved by furin exposing the LF interacting domain, allowing it to oligomerize into lethal toxin as well as translocation pore-like complexes. The hybrid antigens are immunogenic in Dutch-belted rabbits, eliciting strong PA-specific and LF-specific antibodies. However, the lethal toxin neutralizing antibody titers are 3-7 times lower than those elicited by PA-alum. The hybrid antigens conferred 100% (6/6) protection in rabbits challenged intranasally with a 100 LD(50) dose of Bacillus anthracis Ames strain spores.
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Affiliation(s)
- Qin Li
- Department of Biology, 103 McCort Ward Hall, The Catholic University of America, 620 Michigan Ave., NE, Washington, DC 20064, USA
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Li Y, Cui X, Su J, Haley M, Macarthur H, Sherer K, Moayeri M, Leppla SH, Fitz Y, Eichacker PQ. Norepinephrine increases blood pressure but not survival with anthrax lethal toxin in rats. Crit Care Med 2009; 37:1348-54. [PMID: 19242337 PMCID: PMC3401929 DOI: 10.1097/ccm.0b013e31819cee38] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
OBJECTIVES The response of anthrax lethal toxin (LeTx) induced shock and lethality to conventional therapies has received little study. Previously, fluids worsened outcome in LeTx-challenged rats in contrast to its benefit with lipopolysaccharide (LPS) or Escherichia coli. The current study investigated norepinephrine treatment. MEASUREMENTS AND MAIN RESULTS Sprague-Dawley rats (n = 232) weighing between 230 and 250 g were challenged with similar lethal (80%) 24-hour infusions of either LPS or LeTx, or with diluent only. Toxin-challenged animals were also randomized to receive 24-hour infusions with one of three doses of norepinephrine (0.03, 0.3, or 3.0 microg/kg/min) or placebo started 1 hour after initiation of challenge. All toxin animals received similar volumes of fluid over the 24 hours (equivalent to 4.0-4.3 mL/kg/hr). Although the intermediate norepinephrine dose (0.3 microg/kg/min for 24 hours) improved survival with LPS (p = 0.04) and increased blood pressure before the onset of lethality with LeTx (p < 0.0001), it did not improve survival with the latter (p = ns). Furthermore, neither increasing nor decreasing norepinephrine doses improved survival with LeTx. CONCLUSION Hypotension with LeTx may not be a primary cause of lethality in this model. Rather, LeTx may cause direct cellular injury insensitive to vasopressors. These findings suggest that during anthrax infection and shock, along with hemodynamic support, toxin-directed treatments may be necessary as well.
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Affiliation(s)
- Yan Li
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Xizhong Cui
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Junwu Su
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Michael Haley
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
- Carolinas Medical Center, Department of Internal Medicine, Charlotte, NC 28232
| | - Heather Macarthur
- Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, MO 63104
| | - Kevin Sherer
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Mahtab Moayeri
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Stephen H. Leppla
- National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
| | - Yvonne Fitz
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
| | - Peter Q. Eichacker
- Critical Care Medicine Department, Clinical Center, National Institutes of Health, Bethesda, MD 20892
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Anthrax protective antigen delivered by Salmonella enterica serovar Typhi Ty21a protects mice from a lethal anthrax spore challenge. Infect Immun 2009; 77:1475-82. [PMID: 19179420 DOI: 10.1128/iai.00828-08] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Bacillus anthracis, the etiological agent of anthrax disease, is a proven weapon of bioterrorism. Currently, the only licensed vaccine against anthrax in the United States is AVA Biothrax, which, although efficacious, suffers from several limitations. This vaccine requires six injectable doses over 18 months to stimulate protective immunity, requires a cold chain for storage, and in many cases has been associated with adverse effects. In this study, we modified the B. anthracis protective antigen (PA) gene for optimal expression and stability, linked it to an inducible promoter for maximal expression in the host, and fused it to the secretion signal of the Escherichia coli alpha-hemolysin protein (HlyA) on a low-copy-number plasmid. This plasmid was introduced into the licensed typhoid vaccine strain, Salmonella enterica serovar Typhi strain Ty21a, and was found to be genetically stable. Immunization of mice with three vaccine doses elicited a strong PA-specific serum immunoglobulin G response with a geometric mean titer of 30,000 (range, 5,800 to 157,000) and lethal-toxin-neutralizing titers greater than 16,000. Vaccinated mice demonstrated 100% protection against a lethal intranasal challenge with aerosolized spores of B. anthracis 7702. The ultimate goal is a temperature-stable, safe, oral human vaccine against anthrax infection that can be self-administered in a few doses over a short period of time.
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Levin TC, Wickliffe KE, Leppla SH, Moayeri M. Heat shock inhibits caspase-1 activity while also preventing its inflammasome-mediated activation by anthrax lethal toxin. Cell Microbiol 2008; 10:2434-46. [PMID: 18671821 DOI: 10.1111/j.1462-5822.2008.01220.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Anthrax lethal toxin (LT) rapidly kills macrophages from certain mouse strains in a mechanism dependent on the breakdown of unknown protein(s) by the proteasome, formation of the Nalp1b (NLRP1b) inflammasome and subsequent activation of caspase-1. We report that heat-shocking LT-sensitive macrophages rapidly protects them against cytolysis by inhibiting caspase-1 activation without upstream effects on LT endocytosis or cleavage of the toxin's known cytosolic substrates (mitogen-activated protein kinases). Heat shock protection against LT occurred through a mechanism independent of de novo protein synthesis, HSP90 activity, p38 activation or proteasome inhibition and was downstream of mitogen-activated protein kinase cleavage and degradation of an unknown substrate by the proteasome. The heat shock inhibition of LT-mediated caspase-1 activation was not specific to the Nalp1b (NLRP1b) inflammasome, as heat shock also inhibited Nalp3 (NLRP3) inflammasome-mediated caspase-1 activation in macrophages. We found that heat shock induced pro-caspase-1 association with a large cellular complex that could prevent its activation. Additionally, while heat-shocking recombinant caspase-1 did not affect its activity in vitro, lysates from heat-shocked cells completely inhibited recombinant active caspase-1 activity. Our results suggest that heat shock inhibition of active caspase-1 can occur independently of an inflammasome platform, through a titratable factor present within intact, functioning heat-shocked cells.
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Affiliation(s)
- Tera C Levin
- Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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28
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Wickliffe KE, Leppla SH, Moayeri M. Killing of macrophages by anthrax lethal toxin: involvement of the N-end rule pathway. Cell Microbiol 2008; 10:1352-62. [PMID: 18266992 DOI: 10.1111/j.1462-5822.2008.01131.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Macrophages from certain inbred mouse strains are rapidly killed (< 90 min) by anthrax lethal toxin (LT). LT cleaves cytoplasmic MEK proteins at 20 min and induces caspase-1 activation in sensitive macrophages at 50-60 min, but the mechanism of LT-induced death is unknown. Proteasome inhibitors block LT-mediated caspase-1 activation and can protect against cell death, indicating that the degradation of at least one cellular protein is required for LT-mediated cell death. Proteins can be degraded by the proteasome via the N-end rule, in which a protein's stability is determined by its N-terminal residue. Using amino acid derivatives that act as inhibitors of this pathway, we show that the N-end rule is required for LT-mediated caspase-1 activation and cell death. We also found that bestatin methyl ester, an aminopeptidase inhibitor protects against LT in vitro and in vivo and that the different inhibitors of the protein degradation pathway act synergistically in protecting against LT. We identify c-IAP1, a mammalian member of the inhibitor of apoptosis protein (IAP) family, as a novel N-end rule substrate degraded in macrophages treated with LT. We also show that LT-induced c-IAP1 degradation is independent of the IAP-antagonizing proteins Smac/DIABLO and Omi/HtrA2, but dependent on caspases.
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Affiliation(s)
- Katherine E Wickliffe
- Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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29
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Wickliffe KE, Leppla SH, Moayeri M. Anthrax lethal toxin-induced inflammasome formation and caspase-1 activation are late events dependent on ion fluxes and the proteasome. Cell Microbiol 2007; 10:332-43. [PMID: 17850338 PMCID: PMC2515708 DOI: 10.1111/j.1462-5822.2007.01044.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Anthrax lethal toxin (LT) is cytotoxic to macrophages from certain inbred mouse strains. The gene controlling macrophage susceptibility to LT is Nalp1b. Nalp1b forms part of the inflammasome, a multiprotein complex involved in caspase-1 activation and release of interleukin (IL)-1beta and IL-18. We confirm the role of caspase-1 in LT-mediated death by showing that caspase inhibitors differentially protected cells against LT, with the degree of protection corresponding to each compound's ability to inhibit caspase-1. Caspase-1 activation and cytokine processing and release were late events inhibited by elevated levels of KCl and sucrose, by potassium channel blockers, and by proteasome inhibitors, suggesting that inflammasome formation requires a protein-degradation event and occurs downstream of LT-mediated potassium efflux. In addition, IL-18 and IL-1beta release was dependent on cell death, indicating that caspase-1-mediated cytotoxicity is independent of these cytokines. Finally, inducing NALP3-inflammasome formation in LT-resistant macrophages did not sensitize cells to LT, suggesting that general caspase-1 activation cannot account for sensitivity to LT and that a Nalp1b-mediated event is specifically required for death. Our data indicate that inflammasome formation is a contributing, but not initiating, event in LT-mediated cytotoxicity and that earlier LT-mediated events leading to ion fluxes are required for death.
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Affiliation(s)
| | | | - Mahtab Moayeri
- Corresponding Author Dr. Mahtab Moayeri Building 33, Room 1W20B National Institutes of Health Bethesda, MD 20892 Phone: 301-496-1821 Fax: 301-480-0326
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Watson LE, Kuo SR, Katki K, Dang T, Park SK, Dostal DE, Tang WJ, Leppla SH, Frankel AE. Anthrax toxins induce shock in rats by depressed cardiac ventricular function. PLoS One 2007; 2:e466. [PMID: 17520025 PMCID: PMC1867860 DOI: 10.1371/journal.pone.0000466] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2007] [Accepted: 05/01/2007] [Indexed: 12/05/2022] Open
Abstract
Anthrax infections are frequently associated with severe and often irreversible hypotensive shock. The isolated toxic proteins of Bacillus anthracis produce a non-cytokine-mediated hypotension in rats by unknown mechanisms. These observations suggest the anthrax toxins have direct cardiovascular effects. Here, we characterize these effects. As a first step, we administered systemically anthrax lethal toxin (LeTx) and edema toxin (EdTx) to cohorts of three to twelve rats at different doses and determined the time of onset, degree of hypotension and mortality. We measured serum concentrations of the protective antigen (PA) toxin component at various time points after infusion. Peak serum levels of PA were in the µg/mL range with half-lives of 10–20 minutes. With doses that produced hypotension with delayed lethality, we then gave bolus intravenous infusions of toxins to groups of four to six instrumented rats and continuously monitored blood pressure by telemetry. Finally, the same doses used in the telemetry experiments were given to additional groups of four rats, and echocardiography was performed pretreatment and one, two, three and twenty-four hours post-treatment. LeTx and EdTx each produced hypotension. We observed a doubling of the velocity of propagation and 20% increases in left ventricular diastolic and systolic areas in LeTx-treated rats, but not in EdTx-treated rats. EdTx-but not LeTx-treated rats showed a significant increase in heart rate. These results indicate that LeTx reduced left ventricular systolic function and EdTx reduced preload. Uptake of toxins occurs readily into tissues with biological effects occurring within minutes to hours of serum toxin concentrations in the µg/mL range. LeTx and EdTx yield an irreversible shock with subsequent death. These findings should provide a basis for the rational design of drug interventions to reduce the dismal prognosis of systemic anthrax infections.
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Affiliation(s)
- Linley E. Watson
- Division of Cardiology, Scott and White Memorial Hospital, Scott, Sherwood and Brindley Foundation, Temple, Texas, United States of America
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Division of Molecular Cardiology, Texas A&M University System, Health Science Center College of Medicine, and Central Texas Veterans Health Care System, Temple, Texas, United States of America
| | - Shu-ru Kuo
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - Khurshed Katki
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
| | - Tongyun Dang
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - Seong Kyu Park
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
| | - David E. Dostal
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Division of Molecular Cardiology, Texas A&M University System, Health Science Center College of Medicine, and Central Texas Veterans Health Care System, Temple, Texas, United States of America
| | - Wei-Jen Tang
- Ben May Institute for Cancer Research, The University of Chicago, Chicago, Illinois, United States of America
| | - Stephen H. Leppla
- Bacterial Toxins and Therapeutics Section, National Institutes of Allergy and Infectious Diseases, Bethesda, Maryland, United States of America
| | - Arthur E. Frankel
- Department of Medicine, Texas A&M University System, Health Science Center College of Medicine, Temple, Texas, United States of America
- Scott and White Cancer Research Institute, Temple, Texas, United States of America
- * To whom correspondence should be addressed. E-mail:
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31
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Chen KH, Liu S, Bankston LA, Liddington RC, Leppla SH. Selection of anthrax toxin protective antigen variants that discriminate between the cellular receptors TEM8 and CMG2 and achieve targeting of tumor cells. J Biol Chem 2007; 282:9834-9845. [PMID: 17251181 PMCID: PMC2530824 DOI: 10.1074/jbc.m611142200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Anthrax toxin, a three-component protein toxin secreted by Bacillus anthracis, assembles into toxic complexes at the surface of receptor-bearing eukaryotic cells. The protective antigen (PA) protein binds to receptors, either tumor endothelial cell marker 8 (TEM8) or CMG2 (capillary morphogenesis protein 2), and orchestrates the delivery of the lethal and edema factors into the cytosol. TEM8 is reported to be overexpressed during tumor angiogenesis, whereas CMG2 is more widely expressed in normal tissues. To extend prior work on targeting of tumor with modified anthrax toxins, we used phage display to select PA variants that preferentially bind to TEM8 as compared with CMG2. Substitutions were randomly introduced into residues 605-729 of PA, within the C-terminal domain 4 of PA, which is the principal region that contacts receptor. Candidates were characterized in cellular cytotoxicity assays with Chinese hamster ovary (CHO) cells expressing either TEM8 or CMG2. A PA mutant having the substitutions R659S and M662R had enhanced specificity toward TEM8-overexpressing CHO cells. This PA variant also displayed broad and potent tumoricidal activity to various human tumor cells, especially to HeLa and A549/ATCC cells. By contrast, the substitution N657Q significantly reduced toxicity to TEM8 but not CMG2-overexpressing CHO cells. Our results indicate that certain amino acid substitutions within PA domain 4 create anthrax toxins that selectively kill human tumor cells. The PA R659S/M662R protein may be useful as a therapeutic agent for cancer treatment.
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Affiliation(s)
- Kuang-Hua Chen
- Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-3202
| | - Shihui Liu
- Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-3202
| | - Laurie A Bankston
- Infectious and Inflammatory Disease Center, Burnham Institute for Medical Research, La Jolla, California 92037
| | - Robert C Liddington
- Infectious and Inflammatory Disease Center, Burnham Institute for Medical Research, La Jolla, California 92037
| | - Stephen H Leppla
- Laboratory of Bacterial Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-3202.
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32
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Shivachandra SB, Li Q, Peachman KK, Matyas GR, Leppla SH, Alving CR, Rao M, Rao VB. Multicomponent anthrax toxin display and delivery using bacteriophage T4. Vaccine 2006; 25:1225-35. [PMID: 17069938 PMCID: PMC1888565 DOI: 10.1016/j.vaccine.2006.10.010] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2006] [Revised: 09/25/2006] [Accepted: 10/05/2006] [Indexed: 01/08/2023]
Abstract
We describe a multicomponent antigen display and delivery system using bacteriophage T4. Two dispensable outer capsid proteins, Hoc (highly antigenic outer capsid protein, 155 copies) and Soc (small outer capsid protein, 810 copies), decorate phage T4 capsid. These proteins bind to the symmetrically localized capsid sites, which appear following prohead assembly and expansion. We hypothesized that multiple antigens fused to Hoc can be displayed on the same capsid and such particles can elicit broad immunological responses. Anthrax toxin proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF), and their functional domains, were fused to Hoc with an N-terminal hexa-histidine tag and the recombinant proteins were over-expressed in E. coli and purified. Using a defined in vitro assembly system, the anthrax-Hoc fusion proteins were efficiently displayed on T4 capsid, either individually or in combinations. All of the 155 Hoc binding sites can be occupied by one antigen, or they can be split among two or more antigens by varying their molar ratio in the binding reaction. Immunization of mice with T4 phage carrying PA, LF, and EF elicited strong antigen-specific antibodies against all antigens as well as lethal toxin neutralization titers. The triple antigen T4 phage elicited stronger PA-specific immune responses than the phage displaying PA alone. These features offer novel avenues to develop customized multicomponent vaccines against anthrax and other pathogenic diseases.
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Affiliation(s)
- Sathish B Shivachandra
- Department of Biology, 103 McCort Ward Hall, The Catholic University of America, 620 Michigan Ave., NE, Washington, DC 20064, USA
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33
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Kubler-Kielb J, Liu TY, Mocca C, Majadly F, Robbins JB, Schneerson R. Additional conjugation methods and immunogenicity of Bacillus anthracis poly-gamma-D-glutamic acid-protein conjugates. Infect Immun 2006; 74:4744-9. [PMID: 16861662 PMCID: PMC1539631 DOI: 10.1128/iai.00315-06] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2006] [Revised: 04/03/2006] [Accepted: 04/28/2006] [Indexed: 11/20/2022] Open
Abstract
The capsule of Bacillus anthracis, composed of poly-gamma-d-glutamic acid (gammaDPGA), is an essential virulence factor of B. anthracis. The capsule inhibits innate host defense through its antiphagocytic action. gammaDPGA is a poor immunogen, but when covalently bound to a carrier protein, it elicits serum antibodies. To identify the optimal construct for clinical use, synthetic gammaDPGAs of different lengths were bound to carrier proteins at different densities. The advantages of the synthetic over the natural polypeptide are the homogeneous chain length and end groups, allowing conjugates to be accurately characterized and standardized and their chemical compositions to be related to their immunogenicities. In the present study, we evaluated, in addition to methods reported by us, hydrazone, oxime, and thioether linkages between gammaDPGA and several proteins, including bovine serum albumin, recombinant Pseudomonas aeruginosa exotoxin A, recombinant B. anthracis protective antigen (rPA), and tetanus toxoid (TT). The effects of the dosage and formulation on the immunogenicities of the conjugates were evaluated in mice. All conjugates were immunogenic. The optimal gammaDPGA chain length of 10 to 15 amino acids and the density, an average of 15 mol gammaDPGA per mol of protein, were confirmed. The thioether bond was the optimal linkage type, and TT and rPA were the best carriers. The optimal dosage was 1.2 to 2.5 microg of gammaDPGA per mouse, and adsorption of the conjugates onto aluminum hydroxide significantly increased the antibody response to the protein with a lesser effect on anti-gammaDPGA levels.
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Affiliation(s)
- Joanna Kubler-Kielb
- Laboratory of Developmental and Molecular Immunity, National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bldg. 6, Rm. 1A05, Bethesda, Maryland 20892, USA.
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34
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Peachman KK, Rao M, Alving CR, Burge R, Leppla SH, Rao VB, Matyas GR. Correlation between lethal toxin-neutralizing antibody titers and protection from intranasal challenge with Bacillus anthracis Ames strain spores in mice after transcutaneous immunization with recombinant anthrax protective antigen. Infect Immun 2006; 74:794-7. [PMID: 16369043 PMCID: PMC1346607 DOI: 10.1128/iai.74.1.794-797.2006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcutaneous immunization of mice with recombinant protective antigen (rPA) of Bacillus anthracis resulted in significantly higher lethal toxin-neutralizing antibody titers than did intramuscular injection of alum-adsorbed rPA. Immunized mice were partially protected against intranasal challenge with 235,000 (10 50% lethal doses) Ames strain B. anthracis spores. A highly significant correlation was observed between toxin-neutralizing antibody titer and survival after challenge. Future experiments with rabbits and nonhuman primates should confirm the significance of protection by this vaccine strategy.
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Affiliation(s)
- Kristina K Peachman
- Department of Vaccine Production and Delivery, Division of Retrovirology, U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 1600 East Gude Drive, Rockville, MD 20850, USA
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35
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Koya V, Moayeri M, Leppla SH, Daniell H. Plant-based vaccine: mice immunized with chloroplast-derived anthrax protective antigen survive anthrax lethal toxin challenge. Infect Immun 2005; 73:8266-74. [PMID: 16299323 PMCID: PMC1307059 DOI: 10.1128/iai.73.12.8266-8274.2005] [Citation(s) in RCA: 142] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2005] [Revised: 08/11/2005] [Accepted: 09/04/2005] [Indexed: 11/20/2022] Open
Abstract
The currently available human vaccine for anthrax, derived from the culture supernatant of Bacillus anthracis, contains the protective antigen (PA) and traces of the lethal and edema factors, which may contribute to adverse side effects associated with this vaccine. Therefore, an effective expression system that can provide a clean, safe, and efficacious vaccine is required. In an effort to produce anthrax vaccine in large quantities and free of extraneous bacterial contaminants, PA was expressed in transgenic tobacco chloroplasts by inserting the pagA gene into the chloroplast genome. Chloroplast integration of the pagA gene was confirmed by PCR and Southern analysis. Mature leaves grown under continuous illumination contained PA as up to 14.2% of the total soluble protein. Cytotoxicity measurements in macrophage lysis assays showed that chloroplast-derived PA was equal in potency to PA produced in B. anthracis. Subcutaneous immunization of mice with partially purified chloroplast-derived or B. anthracis-derived PA with adjuvant yielded immunoglobulin G titers up to 1:320,000, and both groups of mice survived (100%) challenge with lethal doses of toxin. An average yield of about 150 mg of PA per plant should produce 360 million doses of a purified vaccine free of bacterial toxins edema factor and lethal factor from 1 acre of land. Such high expression levels without using fermenters and the immunoprotection offered by the chloroplast-derived PA should facilitate development of a cleaner and safer anthrax vaccine at a lower production cost. These results demonstrate the immunogenic and immunoprotective properties of plant-derived anthrax vaccine antigen.
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Affiliation(s)
- Vijay Koya
- Dept. Molecular Biology & Microbiology, Biomolecular Science Bldg 20, Room 336, University of Central Florida, Central Florida Blvd., Orlando, FL 32816-2364, USA
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Warfel JM, Steele AD, D'Agnillo F. Anthrax lethal toxin induces endothelial barrier dysfunction. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 166:1871-81. [PMID: 15920171 PMCID: PMC1602427 DOI: 10.1016/s0002-9440(10)62496-0] [Citation(s) in RCA: 123] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hemorrhage and pleural effusion are prominent pathological features of systemic anthrax infection. We examined the effect of anthrax lethal toxin (LT), a major virulence factor of Bacillus anthracis, on the barrier function of primary human lung microvascular endothelial cells. We also examined the distribution patterns of cytoskeletal actin and vascular endothelial-cadherin (VE-cadherin), both of which are involved in barrier function regulation. Endothelial monolayers cultured on porous membrane inserts were treated with the LT components lethal factor (LF) and protective antigen (PA) individually, or in combination. LT induced a concentration- and time-dependent decrease in transendothelial electrical resistance that correlated with increased permeability to fluorescently labeled albumin. LT also produced a marked increase in central actin stress fibers and significantly altered VE-cadherin distribution as revealed by immunofluorescence microscopy and cell surface enzyme-linked immunosorbent assay. Treatment with LF, PA, or the combination of an inactive LF mutant and PA did not alter barrier function or the distribution of actin or VE-cadherin. LT-induced barrier dysfunction was not dependent on endothelial apoptosis or necrosis. The present findings support a possible role for LT-induced barrier dysfunction in the vascular permeability changes accompanying systemic anthrax infection.
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Affiliation(s)
- Jason M Warfel
- Laboratory of Biochemistry and Vascular Biology, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, 29 Lincoln Drive, Bldg. 29, Rm. 129, Bethesda, MD 20892, USA
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Wang JY, Roehrl MH. Anthrax vaccine design: strategies to achieve comprehensive protection against spore, bacillus, and toxin. MEDICAL IMMUNOLOGY (LONDON, ENGLAND) 2005; 4:4. [PMID: 15790405 PMCID: PMC1079933 DOI: 10.1186/1476-9433-4-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Accepted: 03/24/2005] [Indexed: 01/28/2023]
Abstract
The successful use of Bacillus anthracis as a lethal biological weapon has prompted renewed research interest in the development of more effective vaccines against anthrax. The disease consists of three critical components: spore, bacillus, and toxin, elimination of any of which confers at least partial protection against anthrax. Current remedies rely on postexposure antibiotics to eliminate bacilli and pre- and postexposure vaccination to target primarily toxins. Vaccines effective against toxin have been licensed for human use, but need improvement. Vaccines against bacilli have recently been developed by us and others. Whether effective vaccines will be developed against spores is still an open question. An ideal vaccine would confer simultaneous protection against spores, bacilli, and toxins. One step towards this goal is our dually active vaccine, designed to destroy both bacilli and toxin. Existing and potential strategies towards potent and effective anthrax vaccines are discussed in this review.
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Affiliation(s)
- Julia Y Wang
- Channing Laboratory, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Michael H Roehrl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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Kim C, Gajendran N, Mittrücker HW, Weiwad M, Song YH, Hurwitz R, Wilmanns M, Fischer G, Kaufmann SHE. Human alpha-defensins neutralize anthrax lethal toxin and protect against its fatal consequences. Proc Natl Acad Sci U S A 2005; 102:4830-5. [PMID: 15772169 PMCID: PMC555714 DOI: 10.1073/pnas.0500508102] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Anthrax caused by Bacillus anthracis represents a major bioterroristic threat. B. anthracis produces lethal toxin (LeTx), a combination of lethal factor (LF) and protective antigen that plays a major role in anthrax pathogenesis. We demonstrate that human neutrophil alpha-defensins are potent inhibitors of LF. The inhibition of LF by human neutrophil protein (HNP-1) was noncompetitive. HNP-1 inhibited cleavage of a mitogen-activated protein kinase kinase and restored impaired mitogen-activated protein kinase signaling in LeTx-treated macrophages. HNP-1 rescued murine macrophages from B. anthracis-induced cytotoxicity, and in vivo treatment with HNP-1-3 protected mice against the fatal consequences of LeTx.
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Affiliation(s)
- Chun Kim
- Department of Immunology, Max Planck Institute for Infection Biology, Schumannstrasse 21-22, D-10117 Berlin, Germany
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39
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Watson J, Koya V, Leppla SH, Daniell H. Expression of Bacillus anthracis protective antigen in transgenic chloroplasts of tobacco, a non-food/feed crop. Vaccine 2004; 22:4374-84. [PMID: 15474731 PMCID: PMC3481842 DOI: 10.1016/j.vaccine.2004.01.069] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2003] [Revised: 12/09/2003] [Accepted: 01/30/2004] [Indexed: 10/26/2022]
Abstract
The Centers for Disease Control (CDC) lists Bacillus anthracis as a category A agent and estimates the cost of an anthrax attack to exceed US$ 26 billion per 100,000 exposed individuals. Concerns regarding anthrax vaccine purity, a requirement for multiple injections, and a limited supply of the protective antigen (PA), underscore the urgent need for an improved vaccine. Therefore, the 83 kDa immunogenic Bacillus anthracis protective antigen was expressed in transgenic tobacco chloroplasts. The PA gene (pag) was cloned into a chloroplast vector along with the psbA regulatory signals to enhance translation. Chloroplast integration of the transgenes was confirmed by PCR and Southern blot analyses. Crude plant extracts contained up to 2.5 mg full length PA/g of fresh leaf tissue and this showed exceptional stability for several months in stored leaves or crude extracts. Maximum levels of expression were observed in mature leaves under continuous illumination. Co-expression of the ORF2 chaperonin from Bacillus thuringiensis did not increase PA accumulation or induce folding into cuboidal crystals in transgenic chloroplasts. Trypsin, chymotrypsin and furin proteolytic cleavage sites present in PA were protected in transgenic chloroplasts because only full length PA 83 was observed without any degradation products. Both CHAPS and SDS detergents extracted PA with equal efficiency and PA was observed in the soluble fraction. Chloroplast-derived PA was functionally active in lysing mouse macrophages when combined with lethal factor (LF). Crude leaf extracts contained up to 25 microg functional PA/ml. With an average yield of 172 mg of PA per plant using an experimental transgenic cultivar grown in a greenhouse, 400 million doses of vaccine (free of contaminants) could be produced per acre, a yield that could be further enhanced 18-fold using a commercial cultivar in the field.
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Affiliation(s)
- Jennifer Watson
- Department of Molecular Biology and Microbiology, University of Central Florida, Biomolecular Science Building #20, Room 336, Orlando, FL 32816-2364, USA
| | - Vijay Koya
- Department of Molecular Biology and Microbiology, University of Central Florida, Biomolecular Science Building #20, Room 336, Orlando, FL 32816-2364, USA
| | - Stephen H. Leppla
- Microbial Pathogenesis Section, National Institute of Allergy and Infectious Diseases, NIH, Building 30, Room 303, 30 Convent Dr. Bethesda, MD 20892-4350, USA
| | - Henry Daniell
- Department of Molecular Biology and Microbiology, University of Central Florida, Biomolecular Science Building #20, Room 336, Orlando, FL 32816-2364, USA
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40
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Schneerson R, Kubler-Kielb J, Liu TY, Dai ZD, Leppla SH, Yergey A, Backlund P, Shiloach J, Majadly F, Robbins JB. Poly(gamma-D-glutamic acid) protein conjugates induce IgG antibodies in mice to the capsule of Bacillus anthracis: a potential addition to the anthrax vaccine. Proc Natl Acad Sci U S A 2003; 100:8945-50. [PMID: 12857944 PMCID: PMC166418 DOI: 10.1073/pnas.1633512100] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Both the protective antigen (PA) and the poly(gamma-d-glutamic acid) capsule (gamma dPGA) are essential for the virulence of Bacillus anthracis. A critical level of vaccine-induced IgG anti-PA confers immunity to anthrax, but there is no information about the protective action of IgG anti-gamma dPGA. Because the number of spores presented by bioterrorists might be greater than encountered in nature, we sought to induce capsular antibodies to expand the immunity conferred by available anthrax vaccines. The nonimmunogenic gamma dPGA or corresponding synthetic peptides were bound to BSA, recombinant B. anthracis PA (rPA), or recombinant Pseudomonas aeruginosa exotoxin A (rEPA). To identify the optimal construct, conjugates of B. anthracis gamma dPGA, Bacillus pumilus gamma dLPGA, and peptides of varying lengths (5-, 10-, or 20-mers), of the d or l configuration with active groups at the N or C termini, were bound at 5-32 mol per protein. The conjugates were characterized by physico-chemical and immunological assays, including GLC-MS and matrix-assisted laser desorption ionization time-of-flight spectrometry, and immunogenicity in 5- to 6-week-old mice. IgG anti-gamma dPGA and antiprotein were measured by ELISA. The highest levels of IgG anti-gamma dPGA were elicited by decamers of gamma dPGA at 10 -20 mol per protein bound to the N- or C-terminal end. High IgG anti-gamma dPGA levels were elicited by two injections of 2.5 microg of gamma dPGA per mouse, whereas three injections were needed to achieve high levels of protein antibodies. rPA was the most effective carrier. Anti-gamma dPGA induced opsonophagocytic killing of B. anthracis tox-, cap+. gamma dPGA conjugates may enhance the protection conferred by PA alone. gamma dPGA-rPA conjugates induced both anti-PA and anti-gamma dPGA.
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Affiliation(s)
- Rachel Schneerson
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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Webster JI, Tonelli LH, Moayeri M, Simons SS, Leppla SH, Sternberg EM. Anthrax lethal factor represses glucocorticoid and progesterone receptor activity. Proc Natl Acad Sci U S A 2003; 100:5706-11. [PMID: 12724519 PMCID: PMC156265 DOI: 10.1073/pnas.1036973100] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We report here that a bacterial toxin, anthrax lethal toxin (LeTx), at very low concentrations represses glucocorticoid receptor (GR) transactivation in a transient transfection system and the activity of an endogenous GR-regulated gene in both a cellular system and an animal model. This repression is noncompetitive and does not affect ligand binding or DNA binding, suggesting that anthrax lethal toxin (LeTx) probably exerts its effects through a cofactor(s) involved in the interaction between GR and the basal transcription machinery. LeTx-nuclear receptor repression is selective, repressing GR, progesterone receptor B (PR-B), and estrogen receptor alpha (ERalpha), but not the mineralocorticoid receptor (MR) or ERbeta. GR repression was also caused by selected p38 mitogen-activated protein (MAP) kinase inhibitors, suggesting that the LeTx action may result in part from its known inactivation of MAP kinases. Simultaneous loss of GR and other nuclear receptor activities could render an animal more susceptible to lethal or toxic effects of anthrax infection by removing the normally protective antiinflammatory effects of these hormones, similar to the increased mortality seen in animals exposed to both GR antagonists and infectious agents or bacterial products. These finding have implications for development of new treatments and prevention of the toxic effects of anthrax.
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Affiliation(s)
- Jeanette I Webster
- Section on Neuroendocrine Immunology and Behavior, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
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