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PubMed1980

Characterization of iodinated derivatives of alpha-bungarotoxin.

The iodination of alpha-bungarotoxin and the reactivity of iodinated derivatives towards nicotinic acetylcholine receptor are described. 125I2- and 125I-alpha-bungarotoxin can be resolved, but the latter was not separated from unreacted alpha-bungarotoxin. A study of the reactivities of the various forms of the toxin towards nicotinic acetylcholine receptor indicated that di-iodination had modified its reactivity. The 125I2-form bound with a slower rate constant than alpha-bungarotoxin to the receptor. 125I-alpha-bungarotoxin showed no modification of reactivity towards the receptor. Apart from the A280, two methods for calibrating 125I-alpha-bungarotoxin are described. They may be employed in the presence of other proteins. The first of these is an immunological assay using the complex formed between toxin and antitoxin antibodies. The second is a dilution assay, where competition between iodinated and noniodinated toxins for binding sites on nicotinic acetylcholine receptor is exploited.

Animals↗
PubMed1978

[1st stage of infectious allergy].

In administration of bacterial exotoxins (diphtheria, botulinic) to guinea pigs in doses of 1/100 Dlm at an interval of one hour there developed a typical sickness with the lethal outcome in the course of 2-3 days from the beginning of the exotoxin administration. Low bacterial exotoxin doses induced allergic reaction of the organism before the cell producing specific antibodies began to act in defence. Lymphatic system cells responded rapidly to the low doses of bacterial exotoxins, but the process of formation of cells producing antibodies failed to reach mature plasmocytes, and no antibodies formed. With increase of the interval between the administration of low bacterial exotoxin doses to 24 hours specific antibodies did form, but these antibodies failed to protect the animals which were in the state of infectious allergy. The first stage of infectious allergy induced by low bacterial doses was nonspecific. Animals which were in the state of infectious allergy to diphtheria exotoxin perished of low botulinic (exotoxin) doses, and vice versa.

Antibodies, Bacterial↗
PubMed1993

[Comparison of EBL cells and ELISA in the culture and serological diagnosis of rhinitis atrophicans in swine].

Pasteurella multocida isolates from 271 nasal swabs of pigs were tested in EBL cell culture for toxin production. Mixed bacteria cultures of the same swabs were examined in the P. multocida toxin ELISA K462 (Dakopatts). In the ELISA 114 swabs reacted positive, whereas toxigenic P. multocida were detected by the EBL cell test in 86 swabs. In a neutralization test (SNT) combined with EBL cell culture and with the ELISA 111 sera were examined for P. multocida antitoxin. The toxin had to be more concentrated for the ELISA than for the cell culture; therefore the SNT with EBL cells was more sensitive. Whereas 101 sera had titres of 1:4 or higher in the cell culture, 68 of these sera were positive in the ELISA.

Animals↗
PubMed2001

Antisense RNA regulation of the par post-segregational killing system: structural analysis and mechanism of binding of the antisense RNA, RNAII and its target, RNAI.

The par stability determinant of the Enterococcus faecalis plasmid pAD1 is the first antisense RNA regulated post-segregational killing system (PSK) identified in a Gram-positive organism. Par encodes two small, convergently transcribed RNAs, designated RNAI and RNAII, which are the toxin and antitoxin of the par PSK system respectively. RNAI encodes an open reading frame for a 33 amino acid toxin called Fst. Expression of fst is regulated post-transcriptionally by RNAII. RNAII interacts with RNAI by a unique antisense RNA mechanism involving binding at the 5' and 3' ends of both RNAs. Par RNA interaction requires a complementary transcriptional terminator stem-loop and a set of direct repeat sequences, DRa and DRb, located at the 5' end of both RNAs. The secondary structures of RNAI, RNAII and the RNAI-RNAII complex were analysed by partial digestion with Pb(II) and ribonucleases. Probing data for RNAI and RNAII are consistent with previously reported computer generated models, and also confirm that complementary direct repeat and terminator sequences are involved in the formation of the RNAI-RNAII complex. Mutant par RNAs were used to show that the binding reaction occurs in at least two steps. The first step is the formation of an initial kissing interaction between the transcriptional terminator stem-loops of both RNAs. The subsequent step(s) involves an initial pairing of the complementary direct repeat sequences followed by complete hybridization of the 5' nucleotides to stabilize the RNAI-RNAII complex.

Amino Acid Sequence↗
PubMed2007

Interactions between the toxin Kid of the bacterial parD system and the antitoxins Kis and MazE.

The proteins Kid and Kis are the toxin and antitoxin, respectively, encoded by the parD operon of Escherichia coli plasmid R1. Kis prevents the inhibition of E. coli cell growth caused by the RNA cleavage activity of Kid. Overproduction of MazE, the chromosome-encoded homologue of Kis, has been demonstrated to neutralize Kid toxicity to a certain extent in the absence of native Kis. Here, we show that a high structural similarity exists between these antitoxins, using NMR spectroscopy. We report about the interactions between Kid and Kis that are responsible for neutralization of Kid toxicity and enhance autoregulation of parD transcription. Native macromolecular mass spectrometry data demonstrate that Kid and Kis form multiple complexes. At Kis:Kid ratios equal to or exceeding 1:1, as found in vivo in a plasmid-containing cell, various complexes are present, ranging from Kid(2)-Kis(2) tetramer up to Kis(2)-Kid(2)-Kis(2)-Kid(2)-Kis(2) decamer. When Kid is in excess of Kis, corresponding to an in vivo situation immediately after loss of the plasmid, the Kid(2)-Kis(2)-Kid(2) heterohexamer is the most abundant species. NMR chemical shift and intensity perturbations in the (1)H (15)N HSQC spectra of Kid and Kis, observed when titrating the partner protein, show that the interaction sites of Kid and Kis resemble those within the previously reported MazF(2)-MazE(2)-MazF(2) complex. Furthermore, we demonstrate that Kid(2)-MazE(2) tetramers can be formed via weak interactions involving a limited part of the Kis-binding residues of Kid. The functional roles of the identified Kid-Kis and Kid-MazE interaction sites and complexes in toxin neutralization and repression of transcription are discussed.

Antitoxins↗
PubMed1990

Isolation, purification and immunological evaluation of toxin Hb from scorpion Heterometrus bengalensis (C.L. Koch) venom.

Toxin-Hb, a lethal toxic antigenic protein, isolated from the venom of H. bengalensis by CM-cellulose ion-exchange chromatography was a heat labile basic protein with a molecular weight of 10 kDa. It produced irreversible blockade on the isolated rat phrenic nerve diaphragm and chick biventer cervicis. LD50 of toxin Hb was 0.48 mg/kg (iv) in mice. Antiserum was raised in mice by hyperimmunization against toxin Hb. Antitoxin Hb antiserum was immunologically potent as revealed by immunogel-diffusion and immunoelectrophoresis. Five fold protection against the lethal action of toxin Hb was achieved by the antiserum. It also effectively antagonised toxin Hb induced neuromuscular blockade on isolated rat phrenic nerve diaphragm and chick biventer cervicis preparations.

Animals↗
PubMed1978

Purification of Pseudomonas aeruginosa exotoxin by affinity chromatography.

Pseudomonas aeruginosa exotoxin A was purified by affinity chromatography from culture supernatants by elution of toxin from antitoxin immunoglobulin G-Sepharose 4B with 3 M NaSCN. The purity, toxicity, and enzymatic activity of exotoxin obtained were comparable to those of toxin purified by previously reported multiple-step procedures.

Animals↗
PubMed2003

Non-cytotoxic variants of the Kid protein that retain their auto-regulatory activity.

Kid and Kis are, respectively, the toxin and antitoxin encoded by the parD operon of plasmid R1. The recently solved crystal structure of Kid has revealed that this protein closely resembles the CcdB toxin of plasmid F. In CcdB, the residues involved in toxicity are located at the carboxy-terminal end of the protein. However, an analogous information on the Kid toxin was not available. Here, we have characterized a collection of non-toxic mutants of the Kid protein and identified the residues that affected the toxicity but not the co-regulatory activity of Kid. These are located in two discrete regions of the protein, at the amino and carboxy-terminal ends. Particularly, residues E18 and R85, that are conserved in the Escherichia coli ChpAK and RelE toxins, are affected by amino-acid changes that alter neither the overall structure of the protein nor its state of association, as shown by CD and sedimentation equilibrium analyses. However, thermal denaturation and intrinsic tryptophan fluorescence emission data point to subtle local changes at the N-terminal end of the protein. The implications of these results in the current model on the structure and function of Kid-related bacterial toxins are discussed.

Amino Acid Sequence↗
PubMed1975

[Competitive relations between tetanus anatoxin and toxin].

Experiments were conducted on albino mice; it was shown that preliminary injection of tetanus toxoid enhanced the animal resistance to tetanus toxin, this being expressed in increase in LD50. The effect increased the higher doses of the toxoid and their fractional injection. By using protagon and crude mitochondrial fraction isolated from the brain as a receptor of tetanus toxin in the nervous tissue there were established competitive relations for the receptor between the tetanus toxoid and the toxin. The results of investigations confirmed the authors' earlier statement that the molecule of the tetanus toxin contained different functional groups responsible for the toxin binding with the receptor in the nervous tissue, for the pathogenic action of the toxin and for the binding of the toxin with antitoxin.

Animals↗
PubMed1970

Immunization against neonatal tetanus in New Guinea. 4. Comparison of tetanus antitoxin titres obtained by haemagglutination and toxin neutralization in mice.

Haemagglutination (HA) has been used frequently for the titration of tetanus antitoxin but published results have varied in relation to the "unitage" determined by the mouse toxin-neutralization test (TN). This report gives the results of the titration of a group of sera by haemagglutination and compares them with the results obtained by toxin neutralization. Although there was marked variation between HA and TN titres of individual sera, results indicated that haemagglutination is a useful procedure for the over-all evaluation of the antitoxin responses to tetanus toxoids in field studies.

Animals↗
PubMed2004

Modular organization of the Phd repressor/antitoxin protein.

The P1 plasmid addiction operon is a compact genetic structure consisting of promoter, operator, antitoxin gene (phd), and toxin gene (doc). The 73-amino-acid antitoxin protein, Phd, has two distinct functions: it represses transcription (by binding to its operator) and it prevents host death (by binding and neutralizing the toxin). Here, we show that the N terminus of Phd is required for repressor but not antitoxin activity. Conversely, the C terminus is required for antitoxin but not repressor activity. Only a quarter of the protein, the resolution limit of this analysis, was required for both activities. We suggest that the plasmid addiction operon is a composite of two evolutionarily separable modules, an operator-repressor module and an antitoxin-toxin module. Consideration of similar antitoxin proteins and their surroundings indicates that modular exchange may contribute to antitoxin and operon diversity.

Amino Acid Sequence↗
PubMed1980

Quantitative microtiter cytotoxicity assay for Shigella toxin.

The cytotoxic activity of Shigella dysenteriae 1 was assayed by exposing HeLa cells in microtiter cultures to dilutions of toxin. Exposure to toxin caused either failure of cells in suspension to attach or detachment of cells from established monolayers. Estimates of toxin potency were made by staining residual cells with crystal violet and visually inspecting the stained plates. Quantitation of the cytotoxic effect was made possible by eluting and spectrophotometrically measuring the stain. The dilution of toxin causing 50% cell detachment, the endpoint chosen for the assay, was estimated from plots of dye absorbance versus toxin dilution. The 50% cell detachment dilution of toxin varied as a function of cell concentration, incubation of toxin with cells in suspension or as established monolayers, and the cell line used for assay. The HeLa cell line was the most sensitive of the cell lines examined. The method was easily utilized to monitor toxin purification and to measure antitoxin neutralization of toxin activity.

Animals↗
PubMed1958

A comparison of human antisera to purified diphtheria toxoid with antisera to other purified antigens by quantitative precipitin and gel diffusion techniques.

The limits of sensitivity of three gel diffusion methods are compared and their utilization in the detection of small amounts of antibody to antigens present in traces in a preparation is illustrated with the diphtheria toxin-human antitoxin system. The Preer modification of the Oakley-Fulthorpe technique and the Oudin tube method were found more sensitive than the Ouchteriony plate method, and permitted the detection of as little as 3 microg. antibody N/ml. of serum. Antisera from eight Schick-negative individuals immunized with purified diphtheria toxoid have all been shown to contain, in addition to antitoxin, antibodies to substances present as impurities in the purified toxoid injected. The amounts of these antibodies in a serum and a partial characterization of their antigen-antibody curves have been determined through the combined use of quantitative precipitin and gel diffusion methods. Different amounts of antibody have been precipitated by toxin and toxoid from individual sera. Evidence is presented that this may have been due to slight differences in antigenic specificity. A serum, Hu, which had been held to contain no precipitating antibody, has now been shown, by the Preer and Oudin techniques, to contain at least 12 microg. of precipitating antibody N (per ml. serum) against an impurity in the toxoid preparation. This estimate has been confirmed by quantitative precipitin determinations. The presence of antibodies to impurities in all human antitoxins examined in the present work brings into question the assumption that human antitoxin as such has a skin-sensitizing capacity.

Antibodies↗
PubMed2007

Determination of low tetanus or diphtheria antitoxin titers in sera by a toxin neutralization assay and a modified toxin-binding inhibition test.

A method for the screening of tetanus and diphtheria antibodies in serum using anatoxin (inactivated toxin) instead of toxin was developed as an alternative to the in vivo toxin neutralization assay based on the toxin-binding inhibition test (TOBI test). In this study, the serum titers (values between 1.0 and 19.5 IU) measured by a modified TOBI test (Modi-TOBI test) and toxin neutralization assays were correlated (P < 0.0001). Titers of tetanus or diphtheria antibodies were evaluated in serum samples from guinea pigs immunized with tetanus toxoid, diphtheria-tetanus or triple vaccine. For the Modi-TOBI test, after blocking the microtiter plates, standard tetanus or diphtheria antitoxin and different concentrations of guinea pig sera were incubated with the respective anatoxin. Twelve hours later, these samples were transferred to a plate previously coated with tetanus or diphtheria antitoxin to bind the remaining anatoxin. The anatoxin was then detected using a peroxidase-labeled tetanus or diphtheria antitoxin. Serum titers were calculated using a linear regression plot of the results for the corresponding standard antitoxin. For the toxin neutralization assay, L+/10/50 doses of either toxin combined with different concentrations of serum samples were inoculated into mice for anti-tetanus detection, or in guinea pigs for anti-diphtheria detection. Both assays were suitable for determining wide ranges of antitoxin levels. The linear regression plots showed high correlation coefficients for tetanus (r(2) = 0.95, P < 0.0001) and for diphtheria (r(2) = 0.93, P < 0.0001) between the in vitro and the in vivo assays. The standardized method is appropriate for evaluating titers of neutralizing antibodies, thus permitting the in vitro control of serum antitoxin levels.

Animals↗