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Academic literature on the topic 'Toxin A and Toxin B'

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Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Toxin A and Toxin B"

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McMillin, David E., Lycurgus L. Muldrow, and Shwanda J. Laggette. "Simultaneous detection of toxin A and toxin B genetic determinants of Clostridium difficile using the multiplex polymerase chain reaction." Canadian Journal of Microbiology 38, no. 1 (January 1, 1992): 81–83. http://dx.doi.org/10.1139/m92-013.

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A multiplex polymerase chain reaction was developed to simultaneously detect the presence of toxin A and toxin B genes of Clostridium difficile. A 1050-bp fragment of the toxin B gene and a 1217-bp fragment of the toxin A gene were amplified from 42 toxic strains of C. difficile; however, from 10 nontoxic strains the toxin gene fragments were not amplified; these data demonstrate that this multiplex polymerase chain reaction procedure can be used to differentiate between toxic and nontoxic strains. This sensitive and specific multiplex polymerase chain reaction for C. difficile toxins may prove to be a valuable diagnostic procedure. Key words: Clostridium difficile, polymerase chain reaction, bacterial toxins.
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Kobayashi, Kazuo. "Diverse LXG toxin and antitoxin systems specifically mediate intraspecies competition in Bacillus subtilis biofilms." PLOS Genetics 17, no. 7 (July 19, 2021): e1009682. http://dx.doi.org/10.1371/journal.pgen.1009682.

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Biofilms are multispecies communities, in which bacteria constantly compete with one another for resources and niches. Bacteria produce many antibiotics and toxins for competition. However, since biofilm cells exhibit increased tolerance to antimicrobials, their roles in biofilms remain controversial. Here, we showed that Bacillus subtilis produces multiple diverse polymorphic toxins, called LXG toxins, that contain N-terminal LXG delivery domains and diverse C-terminal toxin domains. Each B. subtilis strain possesses a distinct set of LXG toxin–antitoxin genes, the number and variation of which is sufficient to distinguish each strain. The B. subtilis strain NCIB3610 possesses six LXG toxin–antitoxin operons on its chromosome, and five of the toxins functioned as DNase. In competition assays, deletion mutants of any of the six LXG toxin–antitoxin operons were outcompeted by the wild-type strain. This phenotype was suppressed when the antitoxins were ectopically expressed in the deletion mutants. The fitness defect of the mutants was only observed in solid media that supported biofilm formation. Biofilm matrix polymers, exopolysaccharides and TasA protein polymers were required for LXG toxin function. These results indicate that LXG toxin-antitoxin systems specifically mediate intercellular competition between B. subtilis strains in biofilms. Mutual antagonism between some LXG toxin producers drove the spatial segregation of two strains in a biofilm, indicating that LXG toxins not only mediate competition in biofilms, but may also help to avoid warfare between strains in biofilms. LXG toxins from strain NCIB3610 were effective against some natural isolates, and thus LXG toxin–antitoxin systems have ecological impact. B. subtilis possesses another polymorphic toxin, WapA. WapA had toxic effects under planktonic growth conditions but not under biofilm conditions because exopolysaccharides and TasA protein polymers inhibited WapA function. These results indicate that B. subtilis uses two types of polymorphic toxins for competition, depending on the growth mode.
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Singh, Sunita, and Prachi Lad. "Assay of Bacillus cereus Emetic toxin produced in orange squash." EUREKA: Life Sciences, no. 2 (April 1, 2021): 41–55. http://dx.doi.org/10.21303/2504-5695.2021.001753.

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The contamination of squash by B. cereus, an enterotoxin producer, was found to range between 7.5×104 and 1.8×104 CFU/g in orange squash (during storage), that is hazardous. Orange squash is widely produced and consumed in India, but has a low rating of 3 on the scale of 10 (on feedback), mostly due to high sugars, not preferred these days. It can be preserved for >9 months due to added sugars and preservatives. During processing squash, if juice is not quickly cooled and/or squash is kept for long at temperatures <48 °C after processing, it can be a source of food poisoning. Reason, a large number of toxins can be produced by B. cereus. B. cereus strains, isolated from squash, produce heat stable toxin. Vacuolar assay confirmed them as emetic toxins, produced in squash. The toxin behaved like an ionophore in assay using mitochondria, extracted from liver cells of chicken with potassium ions in buffer. The toxicity of toxin by assay was 3200 IU/ng (BC IV strain) and 800 IU/ng (BC X strain). By the vacuolar expansions of mitochondria in assay, toxins of B. cereus demonstrated a toxic effect, in the range of 20.93 to 60.94 % by BC IV toxin and 43.28 to 45.02 % by BC X toxin, on the 3rd day growth of B. cereus in squash and toxin extraction for assay. It was also possible to produce antibodies against the B. cereus whole cell and toxin of BC IV, as an attempt to detect B. cereus contaminations in foods, by Ouchterlony’s immune-diffusion test
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de Melo, Janaina Viana, Gareth Wyn Jones, Colin Berry, Romero Henrique Teixeira Vasconcelos, Cláudia Maria Fontes de Oliveira, André Freire Furtado, Christina Alves Peixoto, and Maria Helena Neves Lobo Silva-Filha. "Cytopathological Effects of Bacillus sphaericus Cry48Aa/Cry49Aa Toxin on Binary Toxin-Susceptible and -Resistant Culex quinquefasciatus Larvae." Applied and Environmental Microbiology 75, no. 14 (June 5, 2009): 4782–89. http://dx.doi.org/10.1128/aem.00811-09.

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ABSTRACT The Cry48Aa/Cry49Aa mosquitocidal two-component toxin was recently characterized from Bacillus sphaericus strain IAB59 and is uniquely composed of a three-domain Cry protein toxin (Cry48Aa) and a binary (Bin) toxin-like protein (Cry49Aa). Its mode of action has not been elucidated, but a remarkable feature of this protein is the high toxicity against species from the Culex complex, besides its capacity to overcome Culex resistance to the Bin toxin, the major insecticidal factor in B. sphaericus-based larvicides. The goal of this work was to investigate the ultrastructural effects of Cry48Aa/Cry49Aa on midgut cells of Bin-toxin-susceptible and -resistant Culex quinquefasciatus larvae. The major cytopathological effects observed after Cry48Aa/Cry49Aa treatment were intense mitochondrial vacuolation, breakdown of endoplasmic reticulum, production of cytoplasmic vacuoles, and microvillus disruption. These effects were similar in Bin-toxin-susceptible and -resistant larvae and demonstrated that Cry48Aa/Cry49Aa toxin interacts with and displays toxic effects on cells lacking receptors for the Bin toxin, while B. sphaericus IAB59-resistant larvae did not show mortality after treatment with Cry48Aa/Cry49Aa toxin. The cytopathological alterations in Bin-toxin-resistant larvae provoked by Cry48Aa/Cry49Aa treatment were similar to those observed when larvae were exposed to a synergistic mixture of Bin/Cry11Aa toxins. Such effects seemed to result from a combined action of Cry-like and Bin-like toxins. The complex effects caused by Cry48Aa/Cry49Aa provide evidence for the potential of these toxins as active ingredients of a new generation of biolarvicides that conjugate insecticidal factors with distinct sites of action, in order to manage mosquito resistance.
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Koon, Hon Wai, David Q. Shih, Tressia C. Hing, Jun Hwan Yoo, Samantha Ho, Xinhua Chen, Ciarán P. Kelly, Stephan R. Targan, and Charalabos Pothoulakis. "Human Monoclonal Antibodies against Clostridium difficile Toxins A and B Inhibit Inflammatory and Histologic Responses to the Toxins in Human Colon and Peripheral Blood Monocytes." Antimicrobial Agents and Chemotherapy 57, no. 7 (April 29, 2013): 3214–23. http://dx.doi.org/10.1128/aac.02633-12.

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ABSTRACTClostridium difficileinfection (CDI) is a common and debilitating nosocomial infection with high morbidity and mortality.C. difficilemediates diarrhea and colitis by releasing two toxins, toxin A and toxin B. Since both toxins stimulate proinflammatory signaling pathways in human colonocytes and both are involved in the pathophysiology of CDI, neutralization of toxin A and B activities may represent an important therapeutic approach against CDI. Recent studies indicated that human monoclonal antibodies (MAbs) against toxins A and B reduce their cytotoxic and secretory activities and prevent CDI in hamsters. Moreover, anti-toxin A and anti-toxin B MAbs together with antibiotics also effectively reduced recurrent CDI in humans. However, whether these MAbs neutralize toxin A- and toxin B-associated immune responses in human colonic mucosa or human peripheral blood monocyte cells (PBMCs) has never been examined. We used fresh human colonic biopsy specimens and peripheral blood monocytes to evaluate the effects of these antibodies against toxin A- and B-associated cytokine release, proinflammatory signaling, and histologic damage. Incubation of anti-toxin A (MK3415) or anti-toxin B (MK6072) MAbs with human PBMCs significantly inhibited toxin A- and toxin B-mediated tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) expression. MK3415 and MK6072 also diminished toxin A- and toxin B-mediated NF-κB p65 phosphorylation in human monocytes, respectively, and significantly reduced toxin A- and B-induced TNF-α and IL-1β expression as well as histologic damage in human colonic explants. Our results underline the effectiveness of MK3415 and MK6072 in blockingC. difficiletoxin A- and toxin B-mediated inflammatory responses and histologic damage.
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Kato, Haru, Naoki Kato, Kunitomo Watanabe, Naoichi Iwai, Haruhi Nakamura, Toshinobu Yamamoto, Kanzo Suzuki, Shin-Moo Kim, Yunsop Chong, and Eddy Bagus Wasito. "Identification of Toxin A-Negative, Toxin B-Positive Clostridium difficile by PCR." Journal of Clinical Microbiology 36, no. 8 (1998): 2178–82. http://dx.doi.org/10.1128/jcm.36.8.2178-2182.1998.

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Toxigenic strains of Clostridium difficile have been reported to produce both toxins A and B nearly always, and nontoxigenic strains have been reported to produce neither of these toxins. Recent studies indicate that it is not always true. We established a PCR assay to differentiate toxin A-negative, toxin B-positive (toxin A−, toxin B+) strains from both toxin-positive (toxin A+, toxin B+) strains and both toxin-negative (toxin A−, toxin B−) strains as an alternative to cell culture assay and enzyme-linked immunosorbent assay (ELISA). By using the PCR primer set NK11 and NK9 derived from the repeating sequences of the toxin A gene, a shorter segment (ca. 700 bp) was amplified from toxin A−, toxin B+ strains compared to the size of the segment amplified from toxin A+, toxin B+ strains (ca. 1,200 bp), and no product was amplified from toxin A−, toxin B− strains. We examined a total of 421 C. difficile isolates by PCR. Of these, 48 strains showed a shorter segment by the PCR, were negative by ELISAs for the detection of toxin A, and were positive by cell culture assay. Although the cytotoxin produced by the toxin A−, toxin B+ strains was neutralized by anti-toxin B serum, the appearance of the cytotoxic effects on Vero cell monolayers was distinguishable from that of toxin A+, toxin B+ strains. By immunoblotting, the 44 toxin A−, toxin B+ strains were typed to serogroup F and the remaining four strains were serogroup X. Pulsed-field gel electrophoresis separated the 48 strains into 19 types. The PCR assay for the detection of the repeating sequences combined with PCR amplification of the nonrepeating sequences of either the toxin A or the toxin B gene is indicated to be useful for differentiating toxin A−, toxin B+ strains from toxin A+, toxin B+ and toxin A−, toxin B− strains and will contribute to elucidation of the precise role of toxin A−, toxin B+ strains in intestinal diseases.
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Jarraud, Sophie, Grégoire Cozon, François Vandenesch, Michèle Bes, Jerome Etienne, and Gerard Lina. "Involvement of Enterotoxins G and I in Staphylococcal Toxic Shock Syndrome and Staphylococcal Scarlet Fever." Journal of Clinical Microbiology 37, no. 8 (1999): 2446–49. http://dx.doi.org/10.1128/jcm.37.8.2446-2449.1999.

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We investigated the involvement of the recently described staphylococcal enterotoxins G and I in toxic shock syndrome. We reexamined Staphylococcus aureus strains isolated from patients with menstrual and nonmenstrual toxic shock syndrome (nine cases) or staphylococcal scarlet fever (three cases). These strains were selected because they produced none of the toxins known to be involved in these syndromes (toxic shock syndrome toxin 1 and enterotoxins A, B, C, and D), enterotoxin E or H, or exfoliative toxin A or B, despite the fact that superantigenic toxins were detected in a CD69-specific flow cytometry assay measuring T-cell activation. Sets of primers specific to the enterotoxin G and I genes (seg andsei, respectively) were designed and used for PCR amplification. All of the strains were positive for seg andsei. Sequence analysis confirmed that the PCR products, corresponded to the target genes. We suggest that staphylococcal enterotoxins G and I may be capable of causing human staphylococcal toxic shock syndrome and staphylococcal scarlet fever.
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Griffiths, S. L., R. A. Finkelstein, and D. R. Critchley. "Characterization of the receptor for cholera toxin and Escherichia coli heat-labile toxin in rabbit intestinal brush borders." Biochemical Journal 238, no. 2 (September 1, 1986): 313–22. http://dx.doi.org/10.1042/bj2380313.

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125I-labelled heat-labile toxin (from Escherichia coli) and 125I-labelled cholera toxin bound to immobilized ganglioside GM1 and Balb/c 3T3 cell membranes with identical specificities, i.e. each toxin inhibited binding of the other. Binding of both toxins to Balb/c 3T3 cell membranes was saturable, with 50% of maximal binding occurring at 0.3 nM for cholera toxin and 1.1 nM for heat-labile toxin, and the number of sites for each toxin was similar. The results suggest that both toxins recognize the same receptor, namely ganglioside GM1. In contrast, binding of 125I-heat-labile toxin to rabbit intestinal brush borders at 0 degree C was not inhibited by cholera toxin, although heat-labile toxin inhibited 125I-cholera toxin binding. In addition, there were 3-10-fold more binding sites for heat-labile toxin than for cholera toxin. At 37 degrees C cholera toxin, but more particularly its B-subunit, did significantly inhibit 125I-heat-labile toxin binding. Binding of 125I-cholera toxin was saturable, with 50% maximal of binding occurring at 1-2 nM, and was quantitatively inhibited by 10(-8) M unlabelled toxin or B-subunit. By contrast, binding of 125I-heat-labile toxin was non-saturable (up to 5 nM), and 2 × 10(-7) M unlabelled B-subunit was required to quantitatively inhibit binding. Neuraminidase treatment of brush borders increased 125I-cholera toxin but not heat-labile toxin binding. Extensive digestion of membranes with Streptomyces griseus proteinase or papain did not decrease the binding of either toxin. The additional binding sites for heat-labile toxin are not gangliosides. Thin-layer chromatograms of gangliosides which were overlayed with 125I-labelled toxins showed that binding of both toxins was largely restricted to ganglioside GM1. However, 125I-heat-labile toxin was able to bind to brush-border galactoproteins resolved by SDS/polyacrylamide-gel electrophoresis and transferred to nitrocellulose.
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Ma, Jie, Erich Gulbins, Michael J. Edwards, Charles C. Caldwell, Martin Fraunholz, and Katrin Anne Becker. "Staphylococcus aureus α-Toxin Induces Inflammatory Cytokines via Lysosomal Acid Sphingomyelinase and Ceramides." Cellular Physiology and Biochemistry 43, no. 6 (2017): 2170–84. http://dx.doi.org/10.1159/000484296.

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Background/Aims: Staphylococcus aureus (S. aureus) infections are a major clinical problem and range from mild skin and soft-tissue infections to severe and even lethal infections such as pneumonia, endocarditis, sepsis, osteomyelitis, and toxic shock syndrome. Toxins that are released from S. aureus mediate many of these effects. Here, we aimed to identify molecular mechanisms how α-toxin, a major S. aureus toxin, induces inflammation. Methods: Macrophages were isolated from the bone marrow of wildtype and acid sphingomyelinase-deficient mice, stimulated with S. aureus α-toxin and activation of the acid sphingomyelinase was quantified. The subcellular formation of ceramides was determined by confocal microscopy. Release of cathepsins from lysosomes, activation of inflammasome proteins and formation of Interleukin-1β (IL-1β) and Tumor Necrosis Factor-α (TNF-α) were analyzed by western blotting, confocal microscopy and ELISA. Results: We demonstrate that S. aureus α-toxin activates the acid sphingomyelinase in ex vivo macrophages and triggers a release of ceramides. Ceramides induced by S. aureus α-toxin localize to lysosomes and mediate a release of cathepsin B and D from lysosomes into the cytoplasm. Cytosolic cathepsin B forms a complex with Nlrc4. Treatment of macrophages with α-toxin induces the formation of IL-1β and TNF-α. These events are reduced or abrogated, respectively, in cells lacking the acid sphingomyelinase and upon treatment of macrophages with amitriptyline, a functional inhibitor of acid sphingomyelinase. Pharmacological inhibition of cathepsin B prevented activation of the inflammasome measured as release of IL-1β, while the formation of TNF-α was independent of cathepsin B. Conclusion: We demonstrate a novel mechanism how bacterial toxins activate the inflammasome and mediate the formation and release of cytokines: S. aureus α-toxin triggers an activation of the acid sphingomyelinase and a release of ceramides resulting in the release of lysosomal cathepsin B and formation of pro-inflammatory cytokines.
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Morgan, D. G., B. R. DasGupta, G. Stubbs, and J. P. Robinson. "Two dimensional crystals of botulinum toxin, serotype B." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 1034–35. http://dx.doi.org/10.1017/s0424820100157152.

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Botulinum toxin is a powerful, protein neurotoxin produced by Clostridium botulinum which exerts its toxic action by inhibiting the release of acetyl choline. There are several immunologically distinguishable types of botulinum toxin and most of these have been shown to bind the ganglioside GTlb. The ganglioside binding property of these neurotoxins has allowed us to prepare two dimensional crystals of serotypes A, B, and E. We report here our preliminary observations of two dimensional crystals of serotype B.Type B botulinum toxin was purified by methods reported by DasGupta and Woody. The two dimensional crystals were prepared by slightly modified procedures used previously to prepare similar crystals of tetanus and cholera toxins. Purified toxin was dialyzed into citric acid-sodium phosphate buffer at pH 4.0 to 6.5 and ionic strength of about 0.04. Dialyzed toxin was placed into the wells of microtiter dishes in 20 μl volumes at a concentration of fifty to one hundred μgm per ml. The toxin solutions were then layered with one to two μl of a solution of one to two mg per ml of egg lecithin (Sigma Cat. No. P- 2772) in chloroform containing five to ten percent by weight of the ganglioside GT1B (Supelco Cat. No. 4-6035). The microtiter dishes were then placed in the cold and crystallization was allowed to proceed for one to four days at 4°C. The crystals were then picked up on carbon coated electron microscope grids, negatively stained with one to two percent uranium acetate and examined in the electron microscope.
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Dissertations / Theses on the topic "Toxin A and Toxin B"

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Fernandes, da Costa Sérgio Paulo. "Molecular and structural characterisation of epsilon toxin and necrotic enteritis toxin B : two pore-forming toxins from Clostridium perfringens." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14608.

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Epsilon toxin (Etx) and necrotic enteritis toxin B (NetB) are two pore-forming toxins produced by C. perfringens. While Etx has been shown to be the key virulence factor for enterotoxemia in goats and sheep, NetB has been associated with the pathogenesis of avian necrotic enteritis (NE), a gastro-intestinal disease causing economic damage to the poultry industry worldwide. The crystal structure of Etx H149A (an Etx variant with 6x reduced toxicity relative to wild type toxin) was solved to 2.4 Å and showed that the H149A mutation in domain III does not affect organization of the receptor binding region in domain I. The Etx H149A structure also revealed a second putative glycan binding site in domain III. In addition, site-directed mutagenesis in domain I of Etx H149A affirmed the important role of tyrosine residues for toxin binding and demonstrated the capability of Etx H149A to be used as a platform for further receptor binding studies in the future. The crystal structure of the pore-form of NetB was solved to 3.9 Å and revealed high similarities to the Staphylococcus aureus α-hemolysin heptameric structure. However, in particular the region thought to interact with the target cell membrane showed some interesting divergence in amino acid composition. Site-directed mutagenesis within this domain significantly affected binding and toxicity of NetB to target cells. Mutagenesis within the β-sandwich domain of NetB revealed important amino acid residues for toxin oligomerisation and pore-formation. In order to test NetB toxoids as candidate vaccines, a NetB genetic toxoid and a formaldehyde NetB toxoid were used to immunise poultry in an in vivo NE disease model. Vaccination with any of the two antigens resulted in the induction of specific antibody responses against NetB and provided significant protection against disease.
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Balmforth, Matthew Royce. "Piggybacking on the cholera toxin : using cholera toxin B chain for the targeted delivery of proteins to motor neurones." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/20115/.

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A significant unmet need exists for the delivery of biologics to the central nervous system for the treatment and understanding of neurodegenerative diseases. Naturally occurring toxoids such as the non-toxic B subunit of the cholera toxin have been considered as tools to meet this need. However, due to the complexity of tethering macromolecular drugs to toxins, and the inherent dangers of working with large quantities of recombinant toxin, no such route has been successfully exploited. Developing a method where toxoid and drug can be assembled immediately prior to administration could therefore be extremely useful. Using phage-display, two cholera toxin-binding antibody mimetics (Affimers) were identified that non-covalently associate with the non-GM1 binding face of the cholera toxin B subunit (CTB). The two unique interactions were characterised using a range of techniques to dissect the Affimer-CTB assembly process. Internalisation of the complex was demonstrated in tissue culture, and the system was used to deliver GFP to mammalian cells. Finally, the complex was shown to be successfully internalised into the motor neurones of the brainstem in a mouse model. A second route to modular assembly of a protein delivery system was also explored. By using a high affinity peptide staple, a cholergenoid-botulinum toxin chimera was produced that could be assembled in vitro and used to deliver the functional catalytic domain of botulinum neurotoxin to cultured neuronal cells.
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Flagler, Michael J. "Determination of the Molecular Basis for the Difference in Potency between Shiga Toxins 1 and 2." Cincinnati, Ohio : University of Cincinnati, 2010. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1267131436.

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Thesis (Ph.D.)--University of Cincinnati, 2010.
Advisor: Alison A. Weiss. Title from electronic thesis title page (viewed Apr. 26, 2010). Keywords: Shiga toxin; Shiga-like toxin; Verotoxin; Verocytotoxin; B-subunit; B-pentamer. Includes abstract. Includes bibliographical references.
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檀東煇 and T. F. Tan. "Elucidation of ganglioside binding domain in the B-subunit of cholera toxin." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31223448.

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Tan, T. F. "Elucidation of ganglioside binding domain in the B-subunit of cholera toxin." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23636634.

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Batisse, Cornélie. "Targeting strategies using B-subunit of Shiga toxin : innovative drug-delivery systems." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCB220.

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Les stratégies thérapeutiques mises en place contre le cancer ont de nos jours besoin de nouveaux médicaments, à la fois plus actifs que ceux déjà existants et induisant moins d’effets secondaires. Ces nouvelles stratégies visent à cibler spécifiquement les cellules cancéreuses. Parmi ces stratégies, ces travaux de thèse concernent la vectorisation active, à l’aide d’un vecteur protéique dérivé de la toxine de Shiga, STxB. STxB reconnait spécifiquement son récepteur biologique Gb3, surexprimé à la surface des cellules cancéreuses humaines. Ce projet de recherche porte sur la conception et la synthèse de conjugués, combinant STxB et un agent cytotoxique. Le linker chimique, qui relie ces deux espèces, a été soigneusement conçu pour respecter les deux critères suivants : être suffisamment stable et néanmoins pouvoir être clivé pour libérer l’agent cytotoxique une fois les cellules cancéreuses atteintes. Un premier linker a été construit autour du motif mercaptoethanol, lié au vecteur STxB par une liaison disulfure. La libération de l’agent cytotoxique peut donc être initiée par un réducteur biologique comme le glutathion, puis par une étape d’auto-immolation. Ce linker a été appliqué à deux composés cytotoxiques très puissants, dérivés de l’auristatine, et a conduit à des résultats prometteurs in vitro. La labilité de la liaison ester à pH acide a également été mise à profit dans l’élaboration de deux linkers, conçus autour de motifs glutamate et thréoninate. L’utilisation d’un agent cytotoxique modérément puissant a été l’occasion de développer une stratégie de multivalence, consistant à augmenter la charge d’agents cytotoxiques sur STxB. Une autre option a été de considérer les nano-batônnets d’or comme une plate-forme nanométrique multimodale, capable de lier plusieurs milliers d’agents cytotoxiques et STxB. Enfin l’incorporation d’une séquence peptidique, connue pour être substrat d’une protéase, a donné lieu à une troisième étude, reposant sur un linker clivable plus sélectivement. Plusieurs linkers ont été étudiées, selon qu’ils libèrent l’agent cytotoxique sous sa forme native ou non
We need new therapeutic strategies to treat cancerous patients by the discovery of new drugs that would be more active than those existing and especially assigning fewer side effects. These new therapies aim to specifically target cancer cells. Among the strategies for cancer targeting, we investigated drug-targeted strategies using a proteic carrier, STxB, derived from Shiga toxin. This protein recognizes specifically its biological receptor Gb3, which is over-expressed on human cancer cells. This work consisted in the design and synthesis of conjugates combining STxB and a cytotoxic drug. The chemical linker binding these two moieties was carefully designed in order to fit requirements of both stability and ability to trigger a drug-delivery. A first linker was designed around a mercaptoethanol core, able to be conjugated to STxB by a disulfide bond. This constitutes a drug-delivery trigger, activated by a biological reducing agent such as glutathion, and followed by a self-immolative step. Two highly potent conjugates of auristatin derivatives were obtained and showed promising results in vitro. The ester bonds lability in acidic pH was exploited for the design of two amino acid based linker. With the aim of increasing the ratio of drug on STxB, we investigated several multivalent linkers. Another option was to consider gold nanorods as a nanometric platform, able to carry thousands of drugs and STxB. The incorporation of a protease substrate to produce an enzyme-cleavable linker was investigated. Several spacers, which induced release of the drug under native form or under prodrug form, were designed and tested
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Lipscombe, Martin John. "Construction and characterisation of Escherichia coli heat-labile toxin B-subunit fusion proteins." Thesis, University of Warwick, 1991. http://wrap.warwick.ac.uk/108070/.

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A plasmid vector was constructed which allowed for the in-frame insertion of peptide-encoding sequences at the 3’ terminal of the Escherichia coli (E. coli) heat-labile enterotoxin B-subunit (LT-B) structural gene. Several synthetic oligonucleotides, encoding various B and T cell epitopes from other proteins, were ligated into this vector. The sequence across the junctions of these novel plasmid constructs was determined and found to be as predicted. The chimeric fusion proteins expressed by these constructs were characterised in vitro by SDS-PAGE, Western blotting and GM1-linked ELISA. All the fusion proteins were shown to behave like native LT-B in that they were transported to the periplasmic space when expressed in E. coli. In addition they formed pentamers which dissociated into their constituent monomers upon boiling. Furthermore, the pentameric forms were found to retain G,,,-binding properties as determined by G,,,-linked ELISA. Some of these plasmids, expressing LT-B fusion proteins containing T cell epitopes, were transferred into an aromatic-dependent attenuated strain of Salmonella typhlmurium SL1344, and these strains were used to inoculate mice. A weak serum antibody response to one of these epitopes was demonstrated. However, a consistent in vitro T cell response to these epitopes could not be detected. Another of the fusion proteins, termed LT-B69, was partially purified by ion-exchange chromatography and used to inoculate mice intranasally. Mice immunised in this way developed serum antibodies against LT-B and P.69 (an important Bordetella pertussis antigen). Additionally, LT-B-specific and P.69-specific antibody secreting cells could be detected in their lungs. There was some evidence to suggest that these mice were slightly protected against colonisation by B. pertussis after an aerosol challenge with live organisms, compared to the levels of colonisation in a control group.
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Schneider, Olivia Dawn. "An Analysis of the Effects of Pertussis Toxin on T Cell Signaling." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1258667926.

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Péré-Védrenne, Christelle. "Etude de la Cytolethal Distending Toxin B des Hélicobacters dans l’inflammation et la carcinogenèse digestive." Thesis, Bordeaux, 2015. http://www.theses.fr/2015BORD0404/document.

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La démonstration du rôle de la CDT (« Cytolethal Distending Toxin ») de Helicobacterhepaticus dans le développement de l’hépatocarcinome murin fait de cette toxine un candidatpertinent dans l'activation de processus pro-cancéreux. Comme la toxine CagA de Helicobacterpylori, la sous-unité active CdtB de la CDT pourrait être une oncoprotéine. Nous avons étudié lerôle de la CdtB des Hélicobacters dans l’inflammation et la carcinogenèse digestive via unestratégie lentivirale d’expression constitutive ou conditionnelle de la CdtB ou de son mutant pourl’activité DNase. Nous avons réalisé une étude du transcriptome et montré que la CdtB deH. hepaticus induisait une réponse inflammatoire en surexprimant des cytokines, chimiokines,peptides antimicrobiens et en activant la voie du NF-κB des cellules épithéliales. La CdtB réguleégalement l’expression et la localisation nucléaire du facteur de transcription et oncogène MafB.Ces résultats ont été confirmés pour la CdtB de Helicobacter pullorum. Des expériencesd'infection des cellules avec des souches sauvages et mutées pour la CDT (deH. hepaticus & H. pullorum) ont permis de valider les résultats obtenus et de les attribuer à laCdtB et notamment à son activité DNase. Nous avons aussi développé un nouveau modèle dexénogreffes de cellules épithéliales inductibles pour l’expression de la CdtB de H. hepaticus.Dans ce modèle, la CdtB, en plus de ses effets déjà connus, retarde la croissance tumorale,induit l’apoptose, la sénescence et la surexpression du marqueur nucléaire de prolifération,Ki-67, suggérant la survie cellulaire. L’ensemble de ces résultats fournit de nouveaux argumentsen faveur du potentiel oncogénique de la CDT
The demonstration of the role of the Cytolethal Distending Toxin (CDT) of Helicobacter hepaticusin the development of hepatocarcinoma in mice, makes this toxin a relevant candidate in theactivation of precancerous processes. As in the case of the CagA toxin of Helicobacter pylori, theCdtB active subunit of CDT could be an oncoprotein. We studied the role of Helicobacter CdtB ininflammation and digestive carcinogenesis using a lentiviral strategy for constitutive or conditionalexpression of the CdtB subunit or its corresponding DNase mutant. We conducted a study of thetranscriptome and showed that CdtB induced an inflammatory response by overexpressingcytokines, chemokines, antimicrobial peptides and activating the NF-kB pathway in epithelialcells. The CdtB also regulated the expression and nuclear localization of the transcription factorand oncogene MafB. These results were confirmed for the CdtB of Helicobacter pullorum.Infection of cells with wild type strains and the corresponding CDT-mutant strains (of H. hepaticus& H. pullorum) were used to validate the results and to attribute the effects to the CdtB and, inparticular, to its DNase activity. We also developed a novel epithelial cell xenograft model toevaluate the inducible expression of H. hepaticus CdtB. In this model, the CdtB, in addition to itspreviously well-known effects, delayed tumor growth, induced apoptosis, senescence and theoverexpression of nuclear proliferation marker, Ki-67, suggesting cell survival. All of these resultsprovide new arguments in favor of the oncogenic potential of the CDT
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Kalluri, Anila. "EXPRESSION OF CHOLERA TOXIN B SUBUNIT-ROTAVIRUS NSP4 ENTEROTOXIN FUSION PROTEIN IN TRANSGENIC CHLOROPLASTS." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3069.

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Rotavirus, the major cause of life-threatening infantile gastroenteritis, is a member of the Reoviridae family and is considered to be the single most important cause of virus-based severe diarrheal illness in infants and young children particularly 6 months to 2 years of age in industrialized and developing countries. Infection in infants and young children is often accompanied by severe life threatening diarrhea, most commonly following primary infection. Diarrhea is the major cause of death among children around the world. Responsible for 4 to 6 million deaths per year according to the World Health Organization (WHO), diarrhea is especially dangerous for infants and young children. Globally, it is estimated that 1.4 billion episodes of diarrhea occur in children less than five years of age annually. In the United States alone, rotavirus causes more than 3 million cases of childhood diarrhea each year, leading to an estimated 55,000 to 100,000 hospitalizations and 20 to 100 deaths. And is a major cause of mortality for children in developing countries with approximately one million deaths annually. Rotaviruses belong to the family Reoviridae and are spherical 70-nm particles. The virus genome contains 11 segments of double-stranded RNA, each encoding a viral capsid or nonstructural protein. The identification of a rotavirus nonstructural protein gene (NSP4) encoding a peptide, which functions both as a viral enterotoxin and as a factor involved in the acquisition of host cell membrane during virus budding from cells, provides a new approach for mucosal immunization. Protein expression through chloroplast transformation system offers a number of advantages like high level of transgene expression, transgene containment via maternal inheritance, lack of gene silencing and position effect due to site specific gene integration and also the possibility of multi gene engineering in single transformation event. It is also an environmentally friendly approach due to effective gene containment and lack of transgene expression in pollen. To achieve an enhanced immune response to rotavirus infection, a fusion gene encoding the cholera toxin B subunit linked to rotavirus enterotoxin 90 aa protein (CTB-NSP490) was introduced into transgenic chloroplast and was transformed into chloroplast genome of Nicotiana tabacum by homologous recombination. The chloroplast integration of CTB-NSP4(90) fusion gene was confirmed in transgenic tobacco plants by PCR analysis. Southern blot analysis further confirmed site specific gene integration and homoplasmy. Immunoblot analysis of transformed chloroplast confirmed the expression of CTBNSP490 fusion protein both in monomeric and pentameric forms that retained the binding affinity to the enterocytes GM1 ganglioside receptor. Expression levels of CTB-NSP4 protein was quantified by GM1 ganglioside binding ELISA assay; mature leaves expressed CTB-NSP4 fusion protein to upto 2.45 % in total soluble protein, 100-400 fold higher than nuclear expression which was only 0.006%-0.026%. Antibody titration and virus challenge experiments will be performed in mice at Loma Linda University to evaluate the antigenic and protective properties of the chloroplast derived CTB-NSP4 fusion protein.
M.S.
Department of Molecular Biology and Microbiology
Burnett College of Biomedical Sciences
Molecular Biology and Microbiology
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Books on the topic "Toxin A and Toxin B"

1

Lipscombe, Martin John. Construction and characterisation of "Escherichia coli" heat-labile toxin B-subunit fusion proteins. [s.l.]: typescript, 1991.

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Binnington-Boyd, Beth A. Studies to determine the vaccine potential of the B-subunit of Shiga-like toxin 1 and its peptide fragments. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1992.

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Robin, Cook. Toxin. Thorndike, Me: G.K. Hall, 1998.

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Robin, Cook. Toxin. New York: Berkley Books, 1999.

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Robin, Cook. Toxin. London: BCA, 1998.

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Toxin. London: Collins Crime, 1995.

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Robin, Cook. Toxin. New York: Berkley Books, 1999.

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Robin, Cook. Toxin. New York: Putnam, 1998.

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NIH Consensus Development Conference on Clinical Use of Botulinum Toxin (1990 Bethesda, Md.). Botulinum toxin. Bethesda, Md: U.S. Dept. of Health and Human Services, Public Health Service, National Institutes of Health, Office of Medical Applications of Research, 1990.

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Ronald, Sekura, Moss Joel, Vaughan Martha 1926-, National Institute of Child Health and Human Development (U.S.), National Heart, Lung, and Blood Institute., and Pertussis Toxin Conference (1984 : National Institutes of Health), eds. Pertussis toxin. Orlando: Academic Press, 1985.

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Book chapters on the topic "Toxin A and Toxin B"

1

Merritt, Ethan A., Focco van den Akker, and Wim G. J. Hol. "E. Coli Heat Labile Enterotoxin and Cholera Toxin B-Pentamer—Crystallographic Studies of Biological Activity." In Protein Toxin Structure, 147–72. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-662-22352-9_8.

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Leis, Susanne, Jenny Spindler, Jochen Reiter, Frank Breinig, and Manfred J. Schmitt. "S. cerevisiae K28 toxin – a secreted virus toxin of the A/B family of protein toxins." In Microbial Protein Toxins, 111–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b100194.

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van der Heijden, P. J., A. T. J. Bianchi, M. A. Dol, J. W. Pals, W. Stok, and R. Zwart. "Enhancement of enteric mucosal immune responses by cholera toxin or cholera toxin B-subunit." In Advances in Mucosal Immunology, 371–72. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-1848-1_102.

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Valášek, L., V. Vondrejs, M. Bartúněk, and B. Janderová. "Exploitation of Rhodamine B in the Killer Toxin Research." In Fluorescence Microscopy and Fluorescent Probes, 163–67. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4899-1866-6_23.

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Aktories, K. "Molekularer Mechanismus von Clostridium difficile Toxin A und B." In Ökosystem Darm VII, 89–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-80327-7_8.

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Donohue-Rolfe, Arthur, David W. K. Acheson, Gerald T. Keusch, Marcia B. Goldberg, Stephanie A. Boyko, and Stephen B. Calderwood. "A System for Production and Rapid Purification of Large Amounts of the Shiga Toxin/Shiga-Like Toxin B Subunit." In Molecular Pathogenesis of Gastrointestinal Infections, 299–301. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-5982-1_39.

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Nguyen, V. K., C. Heckel, F. Bisseret, B. Rihn, R. Girardot, and H. Monteil. "Enzyme-Linked Immunosorbent Assay for Detection of Clostridium difficile Toxin B." In Archives of Toxicology, 453–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-73113-6_89.

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Arakawa, Takeshi, Jie Yu, and William H. R. Langridge. "Food Plant-Delivered Cholera Toxin B Subunit for Vaccination and Immunotolerization." In Advances in Experimental Medicine and Biology, 161–78. Boston, MA: Springer US, 1999. http://dx.doi.org/10.1007/978-1-4615-4729-7_13.

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Moyer, E. D., E. A. Stephens, F. Esch, M. Litwak, and J. Arezzo. "Effects of Intramuscular Injection of Botulinum Toxin Type B in Nonhuman Primates." In Botulinum and Tetanus Neurotoxins, 655–56. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4757-9542-4_73.

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Elson, C. O., S. Solomon, and S. Woogen. "T cell activation and inhibition by cholera toxin and its B subunit." In Advances in Mucosal Immunology, 153–57. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-1848-1_44.

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Conference papers on the topic "Toxin A and Toxin B"

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Couture, O., M. Tanter, E. Dransart, S. Dehay, and L. Johannes. "Targeting microbubbles with Shiga-Toxin B-subunit." In 2009 IEEE International Ultrasonics Symposium. IEEE, 2009. http://dx.doi.org/10.1109/ultsym.2009.5441692.

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Bachran, Christopher, Suzanne Abdelazim, Radka Hasikova, Shihui Liu, and Stephen H. Leppla. "Abstract 5601: Efficient tumor therapy by anthrax toxin fusion proteins that contain cytolethal distending toxin B." In Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC. American Association for Cancer Research, 2013. http://dx.doi.org/10.1158/1538-7445.am2013-5601.

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WANG, XIN-GUO, GUO-HUA ZHANG, RONG-XIANG FANG, CHUAN-XUAN LIU, YAN-HONG ZHANG, and CHENG-ZU XIAO. "PURIFIED CHOLERA TOXIN B SUBUNIT FROM TRANSGENIC TOBACCO PLANTS POSSESSES AUTHENTIC ANTIGENICITY." In International Seminar on Nuclear War and Planetary Emergencies 25th Session. Singapore: World Scientific Publishing Co. Pte. Ltd., 2001. http://dx.doi.org/10.1142/9789812797001_0012.

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Koya, T., A. Saito, H. Ueno, N. Sakai, M. Toyama, K. Tsukioka, Y. Kimura, et al. "Enhancement Effects of Sublingual Immunotherapy Using Cholera Toxin B in Murine Asthma Model." In American Thoracic Society 2020 International Conference, May 15-20, 2020 - Philadelphia, PA. American Thoracic Society, 2020. http://dx.doi.org/10.1164/ajrccm-conference.2020.201.1_meetingabstracts.a1289.

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Lee, Dongheon, Akshi Singla, Hung-Jen Wu, and Joseph Sang-Il Kwon. "Dynamic Modeling of Binding Kinetics Between GD1b Ganglioside and Cholera Toxin Subunit B." In 2018 Annual American Control Conference (ACC). IEEE, 2018. http://dx.doi.org/10.23919/acc.2018.8431824.

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Lyu, Mi-Ae, Lawrence H. Cheung, John W. Marks, and Michael G. Rosenblum. "Abstract 3378: The rGel/BLyS fusion toxin can overcome chemoresistance in malignant B cells.." In Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC. American Association for Cancer Research, 2013. http://dx.doi.org/10.1158/1538-7445.am2013-3378.

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Luster, Troy A., Ipsita Mukherjee, Jeffrey A. Carrell, Yun Hee Cho, Jeffrey Gill, Andy Garcia, Christopher Ward, Stephen Ullrich, Thi-Sau Migone, and Robin Humphreys. "Abstract 3861: Fusion toxin BLyS-gelonin inhibits growth of B-NHL cell linesin vitroandin vivo." In Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL. American Association for Cancer Research, 2012. http://dx.doi.org/10.1158/1538-7445.am2012-3861.

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Dexter, Hannah, and David M. Williams. "Synthesis of pterosin B analogues for use in studying DNA damage by the bracken toxin ptaquiloside." In XVIth Symposium on Chemistry of Nucleic Acid Components. Prague: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 2014. http://dx.doi.org/10.1135/css201414249.

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Nersesian, Sarah, Rodette Williams, Dr Andrew Evans, Dr John Allingham, and Dr Andrew Craig. "Abstract 3161: The macrolide toxin mycalolide B disrupts actin-driven invasion and metastasis of HER2-positive cancers." In Proceedings: AACR Annual Meeting 2018; April 14-18, 2018; Chicago, IL. American Association for Cancer Research, 2018. http://dx.doi.org/10.1158/1538-7445.am2018-3161.

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Mohamedali, Khalid A., Lawrence H. Cheung, Yu Cao, Walter N. Hittelman, and Michael G. Rosenblum. "Abstract 5479: The fully human pro-apoptotic fusion toxin Granzyme B/VEGF121targets vasculature and ablates tumor growth." In Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC. American Association for Cancer Research, 2013. http://dx.doi.org/10.1158/1538-7445.am2013-5479.

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Reports on the topic "Toxin A and Toxin B"

1

Mevarech, Moshe, Jeremy Bruenn, and Yigal Koltin. Virus Encoded Toxin of the Corn Smut Ustilago Maydis - Isolation of Receptors and Mapping Functional Domains. United States Department of Agriculture, September 1995. http://dx.doi.org/10.32747/1995.7613022.bard.

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Ustilago maydis is a fungal pathogen of maize. Some strains of U. maydis encode secreted polypeptide toxins capable of killing other susceptible strains of U. maydis. Resistance to the toxins is conferred by recessive nuclear genes. The toxins are encoded by genomic segments of resident double-strande RNA viruses. The best characterized toxin, KP6, is composed of two polypeptides, a and b, which are not covalently linked. It is encoded by P6M2 dsRNA, which has been cloned, sequenced and expressed in a variety of systems. In this study we have shown that the toxin acts on the membranes of sensitive cells and that both polypeptides are required for toxin activity. The toxin has been shown to function by creating new pores in the cell membrane and disrupting ion fluxes. The experiments performed on artificial phospholipid bilayers indicated that KP6 forms large voltage-independent, cation-selective channels. Experiments leading to the resolution of structure-function relationship of the toxin by in vitro analysis have been initiated. During the course of this research the collaboration also yielded X-ray diffracion data of the crystallized a polypeptide. The effect of the toxin on the pathogen has been shown to be receptor-mediated. A potential receptor protein, identified in membrane fractions of sensitive cells, was subjected to tryptic hydrolysis followed by amino-acid analysis. The peptides obtained were used to isolate a cDNA fragment by reverse PCR, which showed 30% sequence homology to the human HLA protein. Analysis of other toxins secreted by U. maydis, KP1 and KP4, have demonstrated that, unlike KP6, they are composed of a single polypeptide. Finally, KP6 has been expressed in transgenic tobacco plants, indicating that accurate processing by Kex2p-like activity occurs in plants as well. Using tobacco as a model system, we determined that active antifungal toxins can be synthesized and targeted to the outside of transgenic plant cells. If this methodology can be applied to other agronomically crop species, then U. maydis toxins may provide a novel means for biological control of pathogenic fungi.
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Zhang, Rong-Guang, M. L. Westbrook, P. R. Maulik, R. A. Reed, G. Shipley, E. M. Westbrook, D. L. Scott, and Z. Otwinowski. The 2.3 {angstrom} crystal structure of cholera toxin B subunit pentamer: Choleragenoid. Office of Scientific and Technical Information (OSTI), February 1996. http://dx.doi.org/10.2172/205742.

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Dang, Jessica, Suzanne Kracke, Peter A. Emanuel, Michael J. Gostomski, and Darrel E. Menking. Purification and Analysis of a Recombinant Human Anti-Cholera Toxin B Antibody. Fort Belvoir, VA: Defense Technical Information Center, February 1998. http://dx.doi.org/10.21236/ada341970.

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Zlotkin, Eliahu, Shizuo G. Kamita, Nor Chejanovsky, and S. Maeda. Targeting of an Expressed Insect Selective Neurotoxin by its Recombinant Baculovirus: Pharmacokinetic and Pharmacodynamic Aspects. United States Department of Agriculture, July 1995. http://dx.doi.org/10.32747/1995.7571354.bard.

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Objectives: 1) Clarification of the mode of potentiation of an expressed insect selective neurotoxin (AaIT) by its recombinant baculovirus. 2) In vitro formation and/or modification of neuroactive polypeptides for the design of new improved recombinant baculoviruses. Results: 1) A combined utilization of bioassays, LM-cytochemistry, the highly resolutive EM immunogold and electrical recording from the CNS of baculovirus and AaIT - expressing – recombinant baculovirus infected larvae it has been shown that the recombinant virus potentiates the effect of the toxin. Potentiation is achieved through its continuous expression in the infected tracheal epithelia thus providing a: a) Local supply of freshly produced toxin in the vicinity of its traget sites; b) Translocation of the expressed toxin to the insect CNS. The latter exposes the recombinant toxin to new, critical, target sites which are inaccessible through the natural route of scorpion envenomation. 2) Subjecting a recombinant AaIT toxin to a newly designed system of random mutagenesis results in large numbers of new AaIT genes with amino acid substitutions. The new or modified toxin genes were inserted into a linear BmNPV expressed in silkworm cell culture and assayed on blowfly and silkworm larvae. Thus a system for mass formation and screening of neuroactive agents was developed. Contribution to agriculture: 1) Demonstration of the insecticidal mechanism, capacity and utility of the combination of neuroactive polypeptides and recombinant pathogens. 2) Development of a simple in vitro system for the formation and selection of new neuroactive polypeptides.
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Shai, Yechiel, Arthur Aronson, Aviah Zilberstein, and Baruch Sneh. Study of the Basis for Toxicity and Specificity of Bacillus thuringiensis d-Endotoxins. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7573995.bard.

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The report contains three parts which summarizes the three years achievements of the three participating research groups; The Weizmann group, Tel-Aviv group and Purdue group. The firs part describes the achievements obtained by Shai's group toward the elucidation of the mechanism of membrane insertion and the structural organization of the pores formed by the Cry3A and Cry1Ac B. thuringiensis d-endotoxins. For that purpose Shai's group synthesized, fluorescently labeled and structurally and functionally characterized peptides corresponding to the seven helices that compose the pore-forming domain of Cry3A toxin, including mutants peptides and the hairpin a4G-a5 of both Cry3A and Cry 1Ac toxins composed of a4, a5 and the loop connecting a4-a5. Among the synthesized peptides were three mutated a4 helices based on site directed mutagenesis done at Aronson's group that decreased or increased Cry 1Ac toxicity. The results of these studies are consistent with a situation in which only helices a4 anda5 insert into the membrane as a helical hairpin in an antiparallel manner, while the other helices lie on the membrane surface like ribs of an umbrella (the "umbrella model"). In order to test this model Shai's group synthesized the helical hairpin a4<-->a5 of both Cry3A and Cry 1 Ac toxins, as well. Initial functional and structural studies showed direct correlation between the properties of the mutated helices and the mutated Cry1Ac. Based on Shai's findings that a4 is the second helix besides a5 that insert into the membrane, Aronson and colleagues performed extensive mutation on this helix in the CrylAc toxin, as well as in the loop connecting helices 4 and 5, and helix 3 (part two of the report). In addition, Aronson performed studies on the effect of mutations or type of insect which influence the oligomerization either the Cry 1Ab or Cry 1Ac toxins with vesicles prepared from BBMV. In the third part of the report Zilberstein's and Sneh's groups describe their studies on the three domains of Cry 1C, Cry 1E and crylAc and their interaction with the epithelial membrane of the larval midgut. In these studies they cloned all three domains and combinations of two domains, as well as cloning of the pore forming domain alone and studying its interaction with BBMV. In addition they investigated binding of Cry1E toxin and Cry1E domains to BBMV prepared from resistant (R) or sensitive larvae. Finally they initiated expression of the loop a4G<-->a5 Cry3A in E. coli to be compared with the synthetic one done by Shai's group as a basis to develop a system to express all possible pairs for structural and functional studies by Shai's group (together with Y. Shai).
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Chejanovsky, Nor, and Bruce D. Hammock. Enhancement of Baculoviruses' Insecticidal Potency by Expression of Synergistic Anti-Insect Scorpion Toxins. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7573070.bard.

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The extensive use or non-specific, hazardous, chemical insecticides demands the development of "healthier" alternative means for pest control. Insect-specific, baculoviruses expressing anti-insect toxin genes (from mites or scorpions) demonstrated in laboratory assays and field trials enhanced insecticidal activity and provided some protection from lepidopterous larvae to agricultural plantations. To utilize recombinant baculoviruses as commercial biopesticides in row crop agriculture, further increase in their speed of kill should be achieved and the reduction in crop damage should be comparable to the levels obtained with organic insecticides (the problem). In this project we developed strategies to improve further the efficacy of recombinant baculoviruses which included: I) Synergism among baculoviruses expressing different anti-insect toxins: a) Synergism among two complementary anti-insect scorpion neurotoxins each expressed by a separate recombinant baculovirus, both regulated by the same or a different viral promoter. b) Synergism among two complementary anti-insect scorpion neurotoxins expressed by the same recombinant virus, both regulated by the same or a different viral promoter respectively. The above included two classes of pharmacologically complementary toxins: i) toxins with strictly anti-insect selectivity (excitatory and depressant); ii) toxins with preferential anti-insect activity (anti-insect alpha toxins). c) Synergism among wild type viruses, recombinant baculoviruses and chemicals (insecticides and phytochemicals) II) Identification of more potent toxins against lepidopterous pests for their expression by baculoviruses. Our approach was based on the synergistic effect displayed by the combined application of pairs of anti-insect toxins to blowfly and lepidopterous larvae that resulted in 5 fold increase in their insecticidal activity without apparent increase in their anti-mammal toxicity (toxins LqhIT2 and LqhaIT, LqhIT2 and AaIT, and LqhaIT and AaIT (1). Thus, we developed new concepts and produced a "second generation" of recombinant baculoviruses with enhanced potencies and speeds of kill comparable to classical insecticides. These achievements contribute to make these biopesticides a viable alternative to minimize the use of hazardous chemicals in pest control. Also, our project contributed new tools and model systems to advance the study of insect sodium channels.
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Trammel, Harold L. Development of a Toxin Knowledge System. Fort Belvoir, VA: Defense Technical Information Center, November 1990. http://dx.doi.org/10.21236/adb152646.

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Leppla, Stephen H. Production and Purification of Anthrax Toxin. Fort Belvoir, VA: Defense Technical Information Center, May 1986. http://dx.doi.org/10.21236/ada170131.

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Iandolo, John J., and Stephen K. Chapes. Anti-Idiotype Probes for Toxin Detection. Fort Belvoir, VA: Defense Technical Information Center, September 1991. http://dx.doi.org/10.21236/ada242099.

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MAlfatti, M., M. Coleman, and E. Kuhn. A Rapid Response System for Toxin Removal. Office of Scientific and Technical Information (OSTI), December 2014. http://dx.doi.org/10.2172/1179118.

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