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Author

Ada Barnea

Bio: Ada Barnea is an academic researcher from Israel Institute for Biological Research. The author has contributed to research in topics: Antitoxin & Botulism. The author has an hindex of 8, co-authored 20 publications receiving 221 citations.

Papers
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Journal ArticleDOI
TL;DR: Results indicate that a combined treatment of antibiotics together with a PA-based vaccine could provide long-term protection to prevent reoccurrence of anthrax disease.
Abstract: The efficiency of postexposure prophylaxis against Bacillus anthracis infection was tested in guinea pigs infected intranasally with either Vollum or strain ATCC 6605 spores (75 times the 50% lethal dose [LD50] and 87 times LD50, respectively). Starting 24 h postinfection, animals were treated three times per day for 14 days with ciprofloxacin, tetracycline, erythromycin, cefazolin, and trimethoprim-sulfamethoxazole (TMP-SMX). Administration of cefazolin and TMP-SMX failed to protect the animals, while ciprofloxacin, tetracycline, and erythromycin prevented death. Upon cessation of treatment all erythromycin-treated animals died; of the tetracycline-treated animals, two of eight infected with Vollum and one of nine infected with ATCC 6605 survived; and of the ciprofloxacin group injected with either 10 or 20 mg/kg of body weight, five of nine and five of five animals, respectively, survived. To test the added value of extending the treatment period, Vollum-infected (46 times the LD50) animals were treated for 30 days with ciprofloxacin or tetracycline, resulting in protection of eight of nine and nine of nine animals, respectively. Once treatment was discontinued, only four of eight and five of nine animals, respectively, survived. Following rechallenge (intramuscularly) of the survivors with 30 times the LD50 of Vollum spores, all ciprofloxacin-treated animals were protected while none of the tetracycline-treated animals survived. In an attempt to confer protective immunity lasting beyond the termination of antibiotic administration, Vollum-infected animals were immunized with a protective antigen (PA)-based vaccine concurrently with treatment with either ciprofloxacin or tetracycline. The combined treatment protected eight of eight and nine of nine animals. Following cessation of antibiotic administration seven of eight and eight of eight animals survived, of which six of seven and eight of eight resisted rechallenge. These results indicate that a combined treatment of antibiotics together with a PA-based vaccine could provide long-term protection to prevent reoccurrence of anthrax disease.

63 citations

Journal ArticleDOI
TL;DR: This work presents an alternative strategy in which the native genes encoding Hc proteins of botulinum toxins A, B, and E were used to express the recombinant Hc fragments in a cell-free expression system, which offers alternative routes for the preparation ofBotulinum vaccine.
Abstract: Botulinum toxins produced by the anaerobic bacterium Clostridium botulinum are the most potent biological toxins in nature. Traditionally, people at risk are immunized with a formaldehyde-inactivated toxin complex. Second generation vaccines are based on the recombinant carboxy-terminal heavy-chain (Hc) fragment of the neurotoxin. However, the materialization of this approach is challenging, mainly due to the high AT content of clostridial genes. Herein, we present an alternative strategy in which the native genes encoding Hc proteins of botulinum toxins A, B, and E were used to express the recombinant Hc fragments in a cell-free expression system. We used the unique property of this open system to introduce different combinations of chaperone systems, protein disulfide isomerase (PDI), and reducing/oxidizing environments directly to the expression reaction. Optimized expression conditions led to increased production of soluble Hc protein, which was successfully scaled up using a continuous exchange (CE) cell-free system. Hc proteins were produced at a concentration of more than 1 mg/ml and purified by one-step Ni(+) affinity chromatography. Mice immunized with three injections containing 5 microg of any of the in vitro-expressed, alum-absorbed, Hc vaccines generated a serum enzyme-linked immunosorbent assay (ELISA) titer of 10(5) against the native toxin complex, which enabled protection against a high-dose toxin challenge (10(3) to 10(6) mouse 50% lethal dose [MsLD(50)]). Finally, immunization with a trivalent HcA, HcB, and HcE vaccine protected mice against the corresponding trivalent 10(5) MsLD(50) toxin challenge. Our results together with the latest developments in scalability of the in vitro protein expression systems offer alternative routes for the preparation of botulinum vaccine.

51 citations

Journal ArticleDOI
27 Jan 2014-PLOS ONE
TL;DR: This study presents an approach for the simultaneous generation of highly specific and neutralizing MAbs against botulinum serotypes A, B, and E in a single process that relies on immunization of mice with a trivalent mixture of recombinant C-terminal fragment of each of the three neurotoxins followed by differential robotic hybridoma screening.
Abstract: Botulinum neurotoxins (BoNT) are considered some of the most lethal known substances. There are seven botulinum serotypes, of which types A, B and E cause most human botulism cases. Anti-botulinum polyclonal antibodies (PAbs) are currently used for both detection and treatment of the disease. However, significant improvements in immunoassay specificity and treatment safety may be made using monoclonal antibodies (MAbs). In this study, we present an approach for the simultaneous generation of highly specific and neutralizing MAbs against botulinum serotypes A, B, and E in a single process. The approach relies on immunization of mice with a trivalent mixture of recombinant C-terminal fragment (Hc) of each of the three neurotoxins, followed by a parallel differential robotic hybridoma screening. This strategy enabled the cloning of seven to nine MAbs against each serotype. The majority of the MAbs possessed higher anti-botulinum ELISA titers than anti-botulinum PAbs and had up to five orders of magnitude greater specificity. When tested for their potency in mice, neutralizing MAbs were obtained for all three serotypes and protected against toxin doses of 10 MsLD50–500 MsLD50. A strong synergistic effect of up to 400-fold enhancement in the neutralizing activity was observed when serotype-specific MAbs were combined. Furthermore, the highly protective oligoclonal combinations were as potent as a horse-derived PAb pharmaceutical preparation. Interestingly, MAbs that failed to demonstrate individual neutralizing activity were observed to make a significant contribution to the synergistic effect in the oligoclonal preparation. Together, the trivalent immunization strategy and differential screening approach enabled us to generate highly specific MAbs against each of the A, B, and E BoNTs. These new MAbs may possess diagnostic and therapeutic potential.

23 citations

Journal ArticleDOI
TL;DR: In this paper, the authors describe the development of an in vitro RBD-ACE2 binding assay and its application to identify inhibitors of the interaction of the SARS-CoV-2 RBD to ACE2 by the high-throughput screening of two compound libraries (LOPAC®1280 and DiscoveryProbeTM) three compounds, heparin sodium, aurintricarboxylic acid (ATA), and ellagic acid, were found to exert an effective binding inhibition.
Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) global pandemic The first step of viral infection is cell attachment, which is mediated by the binding of the SARS-CoV-2 receptor binding domain (RBD), part of the virus spike protein, to human angiotensin-converting enzyme 2 (ACE2) Therefore, drug repurposing to discover RBD-ACE2 binding inhibitors may provide a rapid and safe approach for COVID-19 therapy Here, we describe the development of an in vitro RBD-ACE2 binding assay and its application to identify inhibitors of the interaction of the SARS-CoV-2 RBD to ACE2 by the high-throughput screening of two compound libraries (LOPAC®1280 and DiscoveryProbeTM) Three compounds, heparin sodium, aurintricarboxylic acid (ATA), and ellagic acid, were found to exert an effective binding inhibition, with IC50 values ranging from 06 to 55 µg/mL A plaque reduction assay in Vero E6 cells infected with a SARS-CoV-2 surrogate virus confirmed the inhibition efficacy of heparin sodium and ATA Molecular docking analysis located potential binding sites of these compounds in the RBD In light of these findings, the screening system described herein can be applied to other drug libraries to discover potent SARS-CoV-2 inhibitors

20 citations

Journal ArticleDOI
24 Sep 2016-Toxins
TL;DR: An innovative in vitro assay to mimic two fundamental steps in botulinum intoxication: receptor binding and catalytic activity is developed and has the potential to be considered, after validation, as a replacement to the mouse assay for quantitating neutralizing antibody concentrations in pharmaceuticalbotulinum antitoxin preparations.
Abstract: Botulinum neurotoxins are bacterial proteins that cause botulism, a life-threatening disease. Therapy relies mostly on post-intoxication antibody treatment. The only accepted method to measure the potency of, and to approve, antitoxin preparations is the mouse lethality neutralization bioassay. However, this assay is time-consuming, labor-intensive, costly, and raises ethical issues related to the large numbers of laboratory animals needed. Until now, all efforts to develop an alternative in vitro assay have not provided a valid replacement to the mouse potency assay. In the present study, we report the development of an innovative in vitro assay for determining botulinum antitoxin potency, using botulinum type B as a model. The concept of the assay is to mimic two fundamental steps in botulinum intoxication: receptor binding and catalytic activity. By simulating these steps in vitro we were able to accurately determine the potency of antitoxin preparations. The reproducibility of the assay was high with a CV < 13%. Most importantly, the antitoxin potency measured by the in vitro assay highly correlated with that measured by the standard in vivo mouse assay (r = 0.9842, p < 0.0001). Thus, this new in vitro assay has the potential to be considered, after validation, as a replacement to the mouse assay for quantitating neutralizing antibody concentrations in pharmaceutical botulinum antitoxin preparations. Future adoption of this in vitro assay would minimize the use of laboratory animals, speed up the time, and reduce the cost of botulinum antitoxin approval.

18 citations


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Journal ArticleDOI
TL;DR: In the coming years, cell-free protein synthesis promises new industrial processes where short protein production timelines are crucial as well as innovative approaches to a wide range of applications.

613 citations

Journal ArticleDOI
TL;DR: This review comprehensively surveys the literature and discusses the similarities and distinct differences between each Clostridium and Bacillus binary toxin in terms of their biochemistry, biology, genetics, structure, and applications in science and medicine.
Abstract: Certain pathogenic species of Bacillus and Clostridium have developed unique methods for intoxicating cells that employ the classic enzymatic “A-B” paradigm for protein toxins. The binary toxins produced by B. anthracis, B. cereus, C. botulinum, C. difficile, C. perfringens, and C. spiroforme consist of components not physically associated in solution that are linked to various diseases in humans, animals, or insects. The “B” components are synthesized as precursors that are subsequently activated by serine-type proteases on the targeted cell surface and/or in solution. Following release of a 20-kDa N-terminal peptide, the activated “B” components form homoheptameric rings that subsequently dock with an “A” component(s) on the cell surface. By following an acidified endosomal route and translocation into the cytosol, “A” molecules disable a cell (and host organism) via disruption of the actin cytoskeleton, increasing intracellular levels of cyclic AMP, or inactivation of signaling pathways linked to mitogen-activated protein kinase kinases. Recently, B. anthracis has gleaned much notoriety as a biowarfare/bioterrorism agent, and of primary interest has been the edema and lethal toxins, their role in anthrax, as well as the development of efficacious vaccines and therapeutics targeting these virulence factors and ultimately B. anthracis. This review comprehensively surveys the literature and discusses the similarities, as well as distinct differences, between each Clostridium and Bacillus binary toxin in terms of their biochemistry, biology, genetics, structure, and applications in science and medicine. The information may foster future studies that aid novel vaccine and drug development, as well as a better understanding of a conserved intoxication process utilized by various gram-positive, spore-forming bacteria.

396 citations

Journal ArticleDOI
22 Sep 2016-Cell
TL;DR: This paper presents a portable platform that provides the means for on-site, on-demand manufacturing of therapeutics and biomolecules and demonstrates the manufacture and functional validation of antimicrobial peptides and vaccines and presents combinatorial methods for the production of antibody conjugates and small molecules.

268 citations

Journal ArticleDOI
01 Jun 2008-Toxicon
TL;DR: BIG-IV as discussed by the authors neutralizes botulinum toxin types A and B in the lumen of the colon, which after absorption causes flaccid paralysis, and is used to treat infant botulism patients.

154 citations

Journal ArticleDOI
TL;DR: This work addresses the main issues to be considered for the development and manufacture of improved antivenoms and calls for concerted international partnerships between key stakeholders.

140 citations