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Piquet P, Saadi J, Fenaille F, Kalb SR, Becher F. Rapid detection of ricin at trace levels in complex matrices by asialofetuin-coated beads and bottom-up proteomics using high-resolution mass spectrometry. Anal Bioanal Chem 2024; 416:5145-5153. [PMID: 39046503 PMCID: PMC11377644 DOI: 10.1007/s00216-024-05452-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Revised: 07/10/2024] [Accepted: 07/15/2024] [Indexed: 07/25/2024]
Abstract
Ricin is a toxic protein regarded as a potential chemical weapon for bioterrorism or criminal use. In the event of a ricin incident, rapid analytical methods are essential for ricin confirmation in a diversity of matrices, from environmental to human or food samples. Mass spectrometry-based methods provide specific toxin identification but require prior enrichment by antibodies to reach trace-level detection in matrices. Here, we describe a novel assay using the glycoprotein asialofetuin as an alternative to antibodies for ricin enrichment, combined with the specific detection of signature peptides by high-resolution mass spectrometry. Additionally, optimizations made to the assay reduced the sample preparation time from 5 h to 80 min only. Method evaluation confirmed the detection of ricin at trace levels over a wide range of pH and in protein-rich samples, illustrating challenging matrices. This new method constitutes a relevant antibody-free solution for the fast and specific mass spectrometry detection of ricin in the situation of a suspected toxin incident, complementary to active ricin determination by adenine release assays.
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Affiliation(s)
- Paloma Piquet
- Département Médicaments Et Technologies Pour La Santé (DMTS), INRAE, CEA, Université Paris-Saclay, 91191, Gif-Sur-Yvette, France
| | - Justyna Saadi
- Département Médicaments Et Technologies Pour La Santé (DMTS), INRAE, CEA, Université Paris-Saclay, 91191, Gif-Sur-Yvette, France
| | - François Fenaille
- Département Médicaments Et Technologies Pour La Santé (DMTS), INRAE, CEA, Université Paris-Saclay, 91191, Gif-Sur-Yvette, France
| | - Suzanne R Kalb
- Division of Laboratory Sciences, Centers for Disease Control and Prevention, National Center for Environmental Health, Atlanta, GA, 30341, USA
| | - François Becher
- Département Médicaments Et Technologies Pour La Santé (DMTS), INRAE, CEA, Université Paris-Saclay, 91191, Gif-Sur-Yvette, France.
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Josuran R, Wenger A, Müller C, Kampa B, Worbs S, Dorner BG, Gerber S. Glycan Profile and Sequence Variants of Certified Ricin Reference Material and Other Ricin Samples Yield Unique Molecular Signature Features. Toxins (Basel) 2024; 16:243. [PMID: 38922138 PMCID: PMC11209631 DOI: 10.3390/toxins16060243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 05/16/2024] [Accepted: 05/17/2024] [Indexed: 06/27/2024] Open
Abstract
A certified reference material of ricin (CRM-LS-1) was produced by the EuroBioTox consortium to standardise the analysis of this biotoxin. This study established the N-glycan structures and proportions including their loci and occupancy of ricin CRM-LS-1. The glycan profile was compared with ricin from different preparations and other cultivars and isoforms. A total of 15 different oligomannosidic or paucimannosidic structures were identified in CRM-LS-1. Paucimannose was mainly found within the A-chain and oligomannose constituted the major glycan type of the B-chain. Furthermore, the novel primary structure variants E138 and D138 and four different C-termini of the A-chain as well as two B-chain variants V250 and F250 were elucidated. While the glycan proportions and loci were similar among all variants in CRM-LS-1 and ricin isoforms D and E of all cultivars analysed, a different stoichiometry for isoforms D and E and the amino acid variants were found. This detailed physicochemical characterization of ricin regarding the glycan profile and amino acid sequence variations yields unprecedented insight into the molecular features of this protein toxin. The variable attributes discovered within different cultivars present signature motifs and may allow discrimination of the biotoxin's origin that are important in molecular forensic profiling. In conclusion, our data of in-depth CRM-LS-1 characterization combined with the analysis of other cultivars is representative for known ricin variants.
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Affiliation(s)
- Roland Josuran
- Institute of Chemistry and Biotechnology, ZHAW Zurich University of Applied Sciences, 8820 Wädenswil, Switzerland
| | - Andreas Wenger
- Institute of Chemistry and Biotechnology, ZHAW Zurich University of Applied Sciences, 8820 Wädenswil, Switzerland
| | - Christian Müller
- Spiez Laboratory, Federal Office for Civil Protection, 3700 Spiez, Switzerland
| | - Bettina Kampa
- Biological Toxins (ZBS3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany
| | - Sylvia Worbs
- Biological Toxins (ZBS3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany
| | - Brigitte G. Dorner
- Biological Toxins (ZBS3), Centre for Biological Threats and Special Pathogens, Robert Koch Institute, 13353 Berlin, Germany
| | - Sabina Gerber
- Institute of Chemistry and Biotechnology, ZHAW Zurich University of Applied Sciences, 8820 Wädenswil, Switzerland
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Botelho FD, Franca TCC, LaPlante SR. The Search for Antidotes Against Ricin. Mini Rev Med Chem 2024; 24:1148-1161. [PMID: 38350844 DOI: 10.2174/0113895575270509231121060105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 09/30/2023] [Accepted: 10/18/2023] [Indexed: 02/15/2024]
Abstract
The castor plant (Ricinus communis) is primarily known for its seeds, which contain a unique fatty acid called ricinoleic acid with several industrial and commercial applications. Castor seeds also contain ricin, a toxin considered a chemical and biological warfare agent. Despite years of investigation, there is still no effective antidote or vaccine available. However, some progress has been made, and the development of an effective treatment may be on the horizon. To provide an updated overview of this issue, we have conducted a comprehensive review of the literature on the current state of research in the fight against ricin. This review is based on the reported research and aims to address the challenges faced by researchers, as well as highlight the most successful cases achieved thus far. Our goal is to encourage the scientific community to continue their efforts in this critical search.
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Affiliation(s)
- Fernanda Diniz Botelho
- Laboratory of Molecular Modeling Applied to the Chemical and Biological Defense (LMCBD), Military Institute of Engineering, Praça General Tibúrcio 80, 22290-270, Rio de Janeiro, RJ, Brazil
| | - Tanos Celmar Costa Franca
- Laboratory of Molecular Modeling Applied to the Chemical and Biological Defense (LMCBD), Military Institute of Engineering, Praça General Tibúrcio 80, 22290-270, Rio de Janeiro, RJ, Brazil
- Université de Québec, INRS - Centre Armand-Frappier Santé Biotechnologie, 531 boulevard des Prairies, Laval, Québec, H7V 1B7, Canada
- Department of Chemistry, Faculty of Science, University of Hradec Králové, Hradec Králové, Czech Republic
| | - Steven R LaPlante
- Université de Québec, INRS - Centre Armand-Frappier Santé Biotechnologie, 531 boulevard des Prairies, Laval, Québec, H7V 1B7, Canada
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Bolt HM, Hengstler JG. Ricin: an ancient toxicant, but still an evergreen. Arch Toxicol 2023; 97:909-911. [PMID: 36881026 PMCID: PMC10025221 DOI: 10.1007/s00204-023-03472-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Accepted: 02/21/2023] [Indexed: 03/08/2023]
Affiliation(s)
- Hermann M Bolt
- Leibniz Research Centre for Working Environment and Human Factor at TU Dortmund (IfADo), Ardeystr. 67, 44139, Dortmund, Germany.
| | - Jan G Hengstler
- Leibniz Research Centre for Working Environment and Human Factor at TU Dortmund (IfADo), Ardeystr. 67, 44139, Dortmund, Germany
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Rasetti-Escargueil C, Avril A. Medical Countermeasures against Ricin Intoxication. Toxins (Basel) 2023; 15:toxins15020100. [PMID: 36828415 PMCID: PMC9966136 DOI: 10.3390/toxins15020100] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 12/14/2022] [Accepted: 01/16/2023] [Indexed: 01/22/2023] Open
Abstract
Ricin toxin is a disulfide-linked glycoprotein (AB toxin) comprising one enzymatic A chain (RTA) and one cell-binding B chain (RTB) contained in the castor bean, a Ricinus species. Ricin inhibits peptide chain elongation via disruption of the binding between elongation factors and ribosomes, resulting in apoptosis, inflammation, oxidative stress, and DNA damage, in addition to the classically known rRNA damage. Ricin has been used in traditional medicine throughout the world since prehistoric times. Because ricin toxin is highly toxic and can be readily extracted from beans, it could be used as a bioweapon (CDC B-list). Due to its extreme lethality and potential use as a biological weapon, ricin toxin remains a global public health concern requiring specific countermeasures. Currently, no specific treatment for ricin intoxication is available. This review focuses on the drugs under development. In particular, some examples are reviewed to demonstrate the proof of concept of antibody-based therapy. Chemical inhibitors, small proteins, and vaccines can serve as alternatives to antibodies or may be used in combination with antibodies.
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Affiliation(s)
- Christine Rasetti-Escargueil
- Unité des Bactéries Anaérobies et Toxines, Institut Pasteur, 25 Avenue du Docteur Roux, 75015 Paris, France
- Correspondence:
| | - Arnaud Avril
- Unité Immunopathologies, Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France
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Pruvost T, Mathieu M, Dubois S, Maillère B, Vigne E, Nozach H. Deciphering cross-species reactivity of LAMP-1 antibodies using deep mutational epitope mapping and AlphaFold. MAbs 2023; 15:2175311. [PMID: 36797224 PMCID: PMC9980635 DOI: 10.1080/19420862.2023.2175311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Accepted: 01/20/2023] [Indexed: 02/18/2023] Open
Abstract
Delineating the precise regions on an antigen that are targeted by antibodies has become a key step for the development of antibody therapeutics. X-ray crystallography and cryogenic electron microscopy are considered the gold standard for providing precise information about these binding sites at atomic resolution. However, they are labor-intensive and a successful outcome is not guaranteed. We used deep mutational scanning (DMS) of the human LAMP-1 antigen displayed on yeast surface and leveraged next-generation sequencing to observe the effect of individual mutants on the binding of two LAMP-1 antibodies and to determine their functional epitopes on LAMP-1. Fine-tuned epitope mapping by DMS approaches is augmented by knowledge of experimental antigen structure. As human LAMP-1 structure has not yet been solved, we used the AlphaFold predicted structure of the full-length protein to combine with DMS data and ultimately finely map antibody epitopes. The accuracy of this method was confirmed by comparing the results to the co-crystal structure of one of the two antibodies with a LAMP-1 luminal domain. Finally, we used AlphaFold models of non-human LAMP-1 to understand the lack of mAb cross-reactivity. While both epitopes in the murine form exhibit multiple mutations in comparison to human LAMP-1, only one and two mutations in the Macaca form suffice to hinder the recognition by mAb B and A, respectively. Altogether, this study promotes a new application of AlphaFold to speed up precision mapping of antibody-antigen interactions and consequently accelerate antibody engineering for optimization.
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Affiliation(s)
- Tiphanie Pruvost
- CEA, INRAE, Medicines and Healthcare Technologies Department, Université Paris-Saclay, SIMoS, France
- Sanofi, Large Molecule Research, Vitry-sur-Seine, France
| | - Magali Mathieu
- Sanofi, Integrated Drug Discovery, Vitry-sur-Seine, France
| | - Steven Dubois
- CEA, INRAE, Medicines and Healthcare Technologies Department, Université Paris-Saclay, SIMoS, France
| | - Bernard Maillère
- CEA, INRAE, Medicines and Healthcare Technologies Department, Université Paris-Saclay, SIMoS, France
| | | | - Hervé Nozach
- CEA, INRAE, Medicines and Healthcare Technologies Department, Université Paris-Saclay, SIMoS, France
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Integrated Transcriptome and Proteome Analysis Provides Insight into the Ribosome Inactivating Proteins in Plukenetia volubilis Seeds. Int J Mol Sci 2022; 23:ijms23179562. [PMID: 36076961 PMCID: PMC9455912 DOI: 10.3390/ijms23179562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 08/19/2022] [Accepted: 08/21/2022] [Indexed: 11/17/2022] Open
Abstract
Plukenetia volubilis is a highly promising plant with high nutritional and economic values. In our previous studies, the expression levels of ricin encoded transcripts were the highest in the maturation stage of P. volubilis seeds. The present study investigated the transcriptome and proteome profiles of seeds at two developmental stages (Pv-1 and Pv-2) using RNA-Seq and iTRAQ technologies. A total of 53,224 unigenes and 6026 proteins were identified, with functional enrichment analyses, including GO, KEGG, and KOG annotations. At two development stages of P. volubilis seeds, 8815 unique differentially expressed genes (DEGs) and 4983 unique differentially abundant proteins (DAPs) were identified. Omics-based association analysis showed that ribosome-inactivating protein (RIP) transcripts had the highest expression and abundance levels in Pv-2, and those DEGs/DAPs of RIPs in the GO category were involved in hydrolase activity. Furthermore, 21 RIP genes and their corresponding amino acid sequences were obtained from libraries produced with transcriptome analysis. The analysis of physicochemical properties showed that 21 RIPs of P. volubilis contained ricin, the ricin_B_lectin domain, or RIP domains and could be divided into three subfamilies, with the largest number for type II RIPs. The expression patterns of 10 RIP genes indicated that they were mostly highly expressed in Pv-2 and 4 transcripts encoding ricin_B_like lectins had very low expression levels during the seed development of P. volubilis. This finding would represent valuable evidence for the safety of oil production from P. volubilis for human consumption. It is also notable that the expression level of the Unigene0030485 encoding type I RIP was the highest in roots, which would be related to the antiviral activity of RIPs. This study provides a comprehensive analysis of the physicochemical properties and expression patterns of RIPs in different organs of P. volubilis and lays a theoretical foundation for further research and utilization of RIPs in P. volubilis.
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Ezan E, Simon S. Introduction to the Toxins Special Issue: "Antibodies for Toxins: From Detection to Therapeutics". Toxins (Basel) 2022; 14:toxins14050363. [PMID: 35622609 PMCID: PMC9146352 DOI: 10.3390/toxins14050363] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/16/2022] Open
Abstract
This Special Issue aims to provide an up-to-date investigation and reviews linked to antibody-based technologies for medical countermeasures and detection/diagnosis tools for toxins [...].
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9
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Ricin toxin and its neutralizing antibodies: A review. Toxicon 2022; 214:47-53. [PMID: 35595086 DOI: 10.1016/j.toxicon.2022.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 05/10/2022] [Accepted: 05/13/2022] [Indexed: 11/22/2022]
Abstract
Ricin toxin (RT) belongs to the ribosome-inactivating protein (RIP) family of toxins and is considered to be a moderate threat by the US Center of Disease Control and Prevention (CDC). RT poses a great potential threat to the public, but there has been a lack of effective treatment options so far. Over the past few decades, researches on the prevention and treatment of RT poisoning have been investigated, among which neutralizing antibodies targeting RT specifically have always been a research hotspot. In this review, we have summarized the mechanism of action of RT, the research results and the design strategies of RT neutralizing antibodies, and discussed the key issues in the development of RT neutralizing antibody researches.
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Deng M, Su D, Xiao N, Zhang Z, Wang Y, Zong F, Li S, Wang J, Zhou D, Zhao Y, Yang H. Gdf15 deletion exacerbates acute lung injuries induced by intratracheal inoculation of aerosolized ricin in mice. Toxicology 2022; 469:153135. [DOI: 10.1016/j.tox.2022.153135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 02/16/2022] [Accepted: 02/17/2022] [Indexed: 10/19/2022]
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Avril A, Tournier JN, Paucod JC, Fournes B, Thullier P, Pelat T. Antibodies against Anthrax Toxins: A Long Way from Benchlab to the Bedside. Toxins (Basel) 2022; 14:172. [PMID: 35324669 PMCID: PMC8955606 DOI: 10.3390/toxins14030172] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 02/01/2023] Open
Abstract
Anthrax is an acute disease caused by the bacterium Bacillus anthracis, and is a potential biowarfare/bioterrorist agent. Its pulmonary form, caused by inhalation of the spores, is highly lethal and is mainly related to injury caused by the toxins secretion. Antibodies neutralizing the toxins of B. anthracis are regarded as promising therapeutic drugs, and two are already approved by the Federal Drug Administration. We developed a recombinant human-like humanized antibody, 35PA83 6.20, that binds the protective antigen and that neutralized anthrax toxins in-vivo in White New Zealand rabbits infected with the lethal 9602 strain by intranasal route. Considering these promising results, the preclinical and clinical phase one development was funded and a program was started. Unfortunately, after 5 years, the preclinical development was cancelled due to industrial and scientific issues. This shutdown underlined the difficulty particularly, but not only, for an academic laboratory to proceed to clinical development, despite the drug candidate being promising. Here, we review our strategy and some preliminary results, and we discuss the issues that led to the no-go decision of the pre-clinical development of 35PA83 6.20 mAb. Our review provides general information to the laboratories planning a (pre-)clinical development.
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Affiliation(s)
- Arnaud Avril
- Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France; (J.-N.T.); (J.-C.P.); (P.T.); (T.P.)
| | - Jean-Nicolas Tournier
- Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France; (J.-N.T.); (J.-C.P.); (P.T.); (T.P.)
- Ecole du Val-de-Grâce, 75005 Paris, France
| | - Jean-Charles Paucod
- Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France; (J.-N.T.); (J.-C.P.); (P.T.); (T.P.)
| | - Bénédicte Fournes
- Laboratoire Français du Fractionnement et des Biotechnologies, 91940 Les Ulis, France;
| | - Philippe Thullier
- Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France; (J.-N.T.); (J.-C.P.); (P.T.); (T.P.)
| | - Thibaut Pelat
- Département Microbiologie et Maladies Infectieuses, Institut de Recherche Biomédicale des Armées, 91220 Brétigny-sur-Orge, France; (J.-N.T.); (J.-C.P.); (P.T.); (T.P.)
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Phatak P, Chauhan V, Dhaked RK, Pathak U, Saxena N. E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide targets abrin and ricin toxicity: Hitting two toxins with one stone. Biomed Pharmacother 2021; 143:112134. [PMID: 34479018 DOI: 10.1016/j.biopha.2021.112134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 08/25/2021] [Accepted: 08/25/2021] [Indexed: 10/20/2022] Open
Abstract
The efficacy of small molecule inhibitors (SMIs) against the enzymatic activity of Shiga toxin prompted the evaluation of their efficacy on related toxins viz. ricin and abrin. Ricin, like Shiga toxin, is listed as a category B bioweapon and belongs to the type II family of ribosome inactivating proteins (RIPs). Abrin though structurally and functionally similar to ricin, is considerably more toxic. In the present study, 35 compounds were evaluated in A549 cells in in vitro assays, of which 5 offered protection against abrin and 2 against ricin, with IC50 values ranging between 30.5-1379 μM and 300-341 μM, respectively. These findings are substantiated by fluorescence based thermal shift assay. Moreover, the binding of the promising compounds to the toxin components has been validated by Surface Plasmon Resonance assay and in vitro protein synthesis assay. In vivo studies reveal complete protection of mice with compound 4 E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide against orally administered lethal doses of, both, abrin and ricin. The present study thus proposes the emergence of E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide as a lead compound against RIPs.
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Affiliation(s)
- Pooja Phatak
- Division of Pharmacology & Toxicology, Defence Research Development & Establishment, Defence Research Development Organization, Gwalior 474002, India
| | - Vinita Chauhan
- Biotechnology Division, Defence Research Development & Establishment, Defence Research Development Organization, Gwalior 474002, India
| | - Ram Kumar Dhaked
- Biotechnology Division, Defence Research Development & Establishment, Defence Research Development Organization, Gwalior 474002, India
| | - Uma Pathak
- Synthetic Chemistry Division, Defence Research Development & Establishment, Defence Research Development Organization, Gwalior 474002, India
| | - Nandita Saxena
- Division of Pharmacology & Toxicology, Defence Research Development & Establishment, Defence Research Development Organization, Gwalior 474002, India.
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Rudolph MJ, Poon AY, Kavaliauskiene S, Myrann AG, Reynolds-Peterson C, Davis SA, Sandvig K, Vance DJ, Mantis NJ. Structural Analysis of Toxin-Neutralizing, Single-Domain Antibodies that Bridge Ricin's A-B Subunit Interface. J Mol Biol 2021; 433:167086. [PMID: 34089718 DOI: 10.1016/j.jmb.2021.167086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 05/18/2021] [Accepted: 05/27/2021] [Indexed: 01/20/2023]
Abstract
Ricin toxin kills mammalian cells with notorious efficiency. The toxin's B subunit (RTB) is a Gal/GalNAc-specific lectin that attaches to cell surfaces and promotes retrograde transport of ricin's A subunit (RTA) to the trans Golgi network (TGN) and endoplasmic reticulum (ER). RTA is liberated from RTB in the ER and translocated into the cell cytoplasm, where it functions as a ribosome-inactivating protein. While antibodies against ricin's individual subunits have been reported, we now describe seven alpaca-derived, single-domain antibodies (VHHs) that span the RTA-RTB interface, including four Tier 1 VHHs with IC50 values <1 nM. Crystal structures of each VHH bound to native ricin holotoxin revealed three different binding modes, based on contact with RTA's F-G loop (mode 1), RTB's subdomain 2γ (mode 2) or both (mode 3). VHHs in modes 2 and 3 were highly effective at blocking ricin attachment to HeLa cells and immobilized asialofetuin, due to framework residues (FR3) that occupied the 2γ Gal/GalNAc-binding pocket and mimic ligand. The four Tier 1 VHHs also interfered with intracellular functions of RTB, as they neutralized ricin in a post-attachment cytotoxicity assay (e.g., the toxin was bound to cell surfaces before antibody addition) and reduced the efficiency of toxin transport to the TGN. We conclude that the RTA-RTB interface is a target of potent toxin-neutralizing antibodies that interfere with both extracellular and intracellular events in ricin's cytotoxic pathway.
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Affiliation(s)
| | - Amanda Y Poon
- Department of Biomedical Sciences, University at Albany, Albany, NY, USA; Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Simona Kavaliauskiene
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, Oslo, Norway
| | - Anne Grethe Myrann
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, Oslo, Norway
| | - Claire Reynolds-Peterson
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Simon A Davis
- New York Structural Biology Center, New York, NY, USA
| | - Kirsten Sandvig
- Department of Molecular Cell Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo University Hospital, Montebello, Oslo, Norway; Department of Biosciences, University of Oslo, Oslo, Norway
| | - David J Vance
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA
| | - Nicholas J Mantis
- Division of Infectious Diseases, Wadsworth Center, New York State Department of Health, Albany, NY, USA.
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