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      Characterization of a novel tetravalent botulism antitoxin based on receptor-binding domain of BoNTs

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          Abstract

          Abstract

          Botulinum neurotoxin (BoNTs; serotypes A, B, E, and F) cause botulism disease in humans, which could be effectively treated using antitoxins. Herein, we established a novel receptor-binding domain (RBD)-based antitoxin using recombinant C terminal heavy chain (Hc) domains of BoNTs as immunogens. Immunization of horses with these recombinant Hc domains allowed the purification and digestion of IgGs from hyper-immune sera to produce high-quality and high-efficiency monovalent botulism antitoxin F(ab′) 2 against each BoNT (M-BATs). However, these M-BATs could not bind or neutralize other serotypes of BoNTs, and that there were no cross-protective effects among these M-BATs. This suggested the need to prepare tetravalent antitoxins to neutralize the four BoNTs simultaneously. Thus, these M-BATs were formulated into a novel tetravalent botulism antitoxin (T-BAT), in which a 10-ml volume contained 10000 IU of BoNT/A and 5000 IU of BoNT/B, BoNT/E, and BoNT/F antitoxins. The novel antitoxin preparation could prevent and treat the four mixed botulinum neurotoxins simultaneously in vivo, representing strong efficacy in an animal poisoning model. Moreover, these antibodies in T-BAT could bind the RBD, whereas conventional antitoxins based on inactivated toxins mainly bind the light chain or heavy chain translocation domain (HN) and weakly bind the important RBD in current experimental conditions. The high levels of RBD-specific novel antitoxins can efficiently bind the RBD and neutralize natural or recombinant toxins containing this RBD. The findings of the present study experimentally support the use of RBD-specific antitoxins to treat BoNT serotype A, B, E, and F-mediated botulism. This study demonstrated the concept of developing potent novel multivalent antitoxins against all BoNTs or other toxins, using the RBD of these toxins as an alternative antigen to inactivated toxins.

          Key points

          • Antitoxins based on the receptor-binding domains of botulinum neurotoxins were made.

          • Novel antitoxin binds RBD; traditional antitoxin mainly binds light chain or HN domain.

          • A tetravalent antitoxin could prevent and treat the four mixed neurotoxins in vivo.

          Supplementary Information

          The online version contains supplementary material available at 10.1007/s00253-023-12515-2.

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          Most cited references36

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          Is Open Access

          Botulinum Neurotoxins: Biology, Pharmacology, and Toxicology

          The study of botulinum neurotoxins (BoNT) is rapidly progressing in many aspects. Novel BoNTs are being discovered owing to next generation sequencing, but their biologic and pharmacological properties remain largely unknown. The molecular structure of the large protein complexes that the toxin forms with accessory proteins, which are included in some BoNT type A1 and B1 pharmacological preparations, have been determined. By far the largest effort has been dedicated to the testing and validation of BoNTs as therapeutic agents in an ever increasing number of applications, including pain therapy. BoNT type A1 has been also exploited in a variety of cosmetic treatments, alone or in combination with other agents, and this specific market has reached the size of the one dedicated to the treatment of medical syndromes. The pharmacological properties and mode of action of BoNTs have shed light on general principles of neuronal transport and protein-protein interactions and are stimulating basic science studies. Moreover, the wide array of BoNTs discovered and to be discovered and the production of recombinant BoNTs endowed with specific properties suggest novel uses in therapeutics with increasing disease/symptom specifity. These recent developments are reviewed here to provide an updated picture of the biologic mechanism of action of BoNTs, of their increasing use in pharmacology and in cosmetics, and of their toxicology.
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            Botulism: cause, effects, diagnosis, clinical and laboratory identification, and treatment modalities.

            Botulism is a neuroparalytic disease caused by neurotoxins produced by the bacteria Clostridium botulinum. Botulinum neurotoxins (BoNTs) are among the most potent naturally occurring toxins and are a category A biological threat agent. The 7 toxin serotypes of BoNTs (serotypes A-G) have different toxicities, act through 3 different intracellular protein targets, and exhibit different durations of effect. Botulism may follow ingestion of food contaminated with BoNT, from toxin production of C botulinum present in the intestine or wounds, or from inhalation of aerosolized toxin. Intoxication classically presents as an acute, symmetrical, descending flaccid paralysis. Early diagnosis is important because antitoxin therapy is most effective when administered early. Confirmatory testing of botulism with BoNT assays or C botulinum cultures is time-consuming, and may be insensitive in the diagnosis of inhalational botulism and in as many as 32% of food-borne botulism cases. Therefore, the decision to initiate botulinum antitoxin therapy is primarily based on symptoms and physical examination findings that are consistent with botulism, with support of epidemiological history and electrophysiological testing. Modern clinical practice and antitoxin treatment has reduced botulism mortality rates from approximately 60% to < or =10%. The pentavalent botulinum toxoid is an investigational product and has been used for more than 45 years in at-risk laboratory workers to protect against toxin serotypes A to E. Due to declining immunogenicity and potency of the pentavalent botulinum toxoid, novel vaccine candidates are being developed.
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              Botulism.

              Botulism is a rare disease with 4 naturally occurring syndromes: foodborne botulism is caused by ingestion of foods contaminated with botulinum toxin, wound botulism is caused by Clostridium botulinum colonization of a wound and in situ toxin production, infant botulism is caused by intestinal colonization and toxin production, and adult intestinal toxemia botulism is an even rarer form of intestinal colonization and toxin production in adults. Inhalational botulism could result from aerosolization of botulinum toxin, and iatrogenic botulism can result from injection of toxin. All forms of botulism produce the same distinct clinical syndrome of symmetrical cranial nerve palsies followed by descending, symmetric flaccid paralysis of voluntary muscles, which may progress to respiratory compromise and death. The mainstays of therapy are meticulous intensive care (including mechanical ventilation, when necessary) and timely treatment with antitoxin.
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                Author and article information

                Contributors
                yunzhouyu@163.com
                yy_xiao@126.com
                Journal
                Appl Microbiol Biotechnol
                Appl Microbiol Biotechnol
                Applied Microbiology and Biotechnology
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                0175-7598
                1432-0614
                14 April 2023
                : 1-12
                Affiliations
                [1 ]GRID grid.418873.1, Laboratory of Advanced Biotechnology, , Beijing Institute of Biotechnology, ; Beijing, 100071 China
                [2 ]Tianjin Institute of Environmental & Operational Medicine, Tianjin, 300050 China
                Article
                12515
                10.1007/s00253-023-12515-2
                10102682
                37058230
                3e32fd43-b8dc-427d-b3ee-803295941f77
                © This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2023

                This article is made available via the PMC Open Access Subset for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.

                History
                : 26 January 2023
                : 27 March 2023
                : 31 March 2023
                Funding
                Funded by: Biosafety Research Project
                Award ID: 20SWAQX23-002-002
                Categories
                Biotechnological Products and Process Engineering

                Biotechnology
                botulinum neurotoxin,botulism,receptor-binding domain,tetravalent botulism antitoxin,neutralizing antibody,immunotherapy

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