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At least 253 records · Page 14Linked to original sources
PubMed2001

Anomalous enhancement of botulinum toxin type A neurotoxicity in the presence of antitoxin.

The neutralization of botulinum toxin serotype A with polyclonal equine antitoxin was studied in isolated mouse hemidiaphragms and compared to the same action in live mice. The biological activity of the toxin in the isolated muscle could be markedly reduced with excess antitoxin, estimated as 3:1 molar ratios of IgG Ab:toxin or better. Toxin neutralization in vivo required higher ratios of Ab:toxin, ranging from 30:1 at high toxin doses and increasing to 100:1 at 10xLD50 toxin. At equimolar Ab to toxin ratios in the isolated muscle, the biological activity of the toxin underwent a statistically significant increase. This paradoxical effect of the polyclonal antisera was serotype selective and independent of the presence or absence of hemagglutinin in the toxin. The enhancement of toxin activity was subsequently localized to occupancy of one of four epitopes on the toxin using monoclonal antibodies to mimic the effect of the antitoxin. The enhancement of toxin activity suggests that botulinum toxin may undergo a conformational change upon binding antibodies to certain domains. This phenomenon could contribute to the observed concentration dependent changes in neutralization efficacy with antitoxin in vivo.

Animals↗
PubMed1980

Experimental studies of antibiotic associated colitis.

Clostridium difficile has been implicated as the major cause of antibiotic-associated pseudomembranous colitis. The laboratory diagnostic test of choice is a tissue culture assay that demonstrates the presence of a cytopathic toxin neutralized by antitoxin to Clostridium sordelli. This toxin is found in stools from patients with antibiotic-associated pseudomembranous colitis and in stools from patients with antibiotic-associated diarrhea. Neutralization of toxin by antitoxin to C. sordelli appears to represent antigenic cross-reactivity, since both cultures of C. difficile also contain a cytopathic toxin neutralized by this toxin. Strains of C. difficile are susceptible to vancomycin and the clinical experience with oral administration of this agent shows promising results.

Animals↗
PubMedDate not supplied

Colitis induced by Clostridium difficile.

Clostridium difficile has been implicated as the major cause of antibiotic-associated pseudomembranous colitis. The current laboratory diagnostic test of choice is a tissue culture assay that demonstrates the presence of a cytopathic toxin neutralized by antitoxin to Clostridium sordellii. This toxin was found in stools from 42 of 43 patients with antibiotic-associated pseudomembranous colitis and in stools from 12 of 78 patients with antibiotic-associated diarrhea. Specimens from patients with gastrointestinal conditions unrelated to administration of antibiotics and those from healthy controls were uniformly negative. Neutralization of toxin by antitoxin to C. sordellii appears to represent antigenic cross-reactivity, since broth cultures of C. difficile also contain a cytopathic toxin neutralized by this antitoxin. Strains of C. difficile are susceptible to vancomycin, and the initial clinical experience with oral administration of this agent shows promising results.

Animals↗
PubMed1990

Titration of botulinum antitoxin of low levels by the score method.

Botulinum antitoxin is commonly titrated by injecting a mixture of toxin and antitoxin into mice and by utilizing deaths as a marker to measure the amount of unneutralized toxin. We attempted to titrate antitoxin by converting the severity of symptoms (notably palsy) and time-to-death in days into scores. In neutralization tests with toxin levels at 5.9 LD50 and 23.5 LD50, a linear relationship was obtained for antitoxin dose in a range between 0.03 to 0.003 IU/ml. Statistical analysis showed that homogeneity of variance or slope was not denied for the scores obtained on any day from the first to the fourth days after injection, demonstrating that this method can titrate accurately antitoxin of such a low level as 0.003 IU/ml within 4 days after injection.

Animals↗
PubMed1981

Atypical toxin variant of Clostridium botulinum type B associated with infant botulism.

An atypical toxin variant of Clostridium botulinum (strain 657) was isolated from the feces of a 6-week-old female infant whose symptoms and clinical history were consistent with infant botulism. Toxin detected in the feces and the toxin produced by isolates from the feces and from two rectal swabs could be neutralized by type B botulinal antitoxin only at very high ratios of of antitoxin to toxin in the neutralization mixture. One international unit of type B antitoxin neutralized only about 10 lethal doses of 657 toxin as compared with approximately 10,000 lethal doses of conventional type B toxin from the Beans strain. Antitoxin prepared against 657 toxin was 10 times more effective against the conventional toxin than against the homologous toxin. Toxoid-antitoxin-binding studies indicate that both 657 toxin and type B toxin are heterogeneous and that both toxins may contain the same molecular variants, but that the proportions of the variants are different in each.

Antigens, Bacterial↗
PubMed1988

Tetanus toxin and botulinum A and C neurotoxins inhibit noradrenaline release from cultured mouse brain.

Primary nerve cell cultures from the brainstem of embryonic mice take up [3H]noradrenaline. Release can be evoked by high K+ or sea anemone toxin II and depends on Ca2+. The cultures allow neurochemical studies on the long-term actions of clostridial neurotoxins. Tetanus and botulinum A and C neurotoxins partially inhibit the absolute and fractional release evoked by high K+, as well as the fractional basal release. The detection limit for the toxins is below 5 pM. Total radioactivity is higher in the poisoned cultures, although the initial velocity of uptake is not measurably influenced by tetanus or botulinum A toxin. Pretreatment with neuraminidase prevents the effects of botulinum A toxin and diminishes those of botulinum C and tetanus toxins. Within 6 days, the cultures partially recover from tetanus toxin poisoning. Antitoxin prevents the actions of the toxin, but only slightly promotes recovery. The data indicate close pharmacological analogies between the clostridial neurotoxins.

Animals↗
PubMedDate not supplied

Potency assay of diphtheria antitoxin in Vero cell microcultures.

Laboratory conditions were established for the titration of diphtheria toxin and antitoxin in Vero Cell Cultures (CCT) and a comparison was made with the intradermal test (IDT) as currently used throughout the world. Working dilutions and cut off values were established by reading both the change in color of phenol red used as pH indicator and changes in cell viability in the microscope. CCT shows high reproducibility and higher detectability than IDT in the titration of both WHO Reference Standard and high titer horse antisera. In sera of guinea pigs immunized for potency testing of diphtheria toxoid the titre was approximately 10 times lower than in the IDT. The explanation is a subject of speculation. The Vero cell titration might be adopted as such for titration of diphtheria antitoxin. In the case of the toxoid potency test it could be used if the limit for the titration is adjusted to 0.2 IU considering the equivalence obtained between the two tests, by taking into account a ratio of 1:10 between CCT and IDT.

Animals↗
PubMed2005

Genetic variation and cross-reactivity of Clostridium septicum alpha-toxin.

Clostridium septicum alpha-toxin genes were sequenced with the polymerase chain reaction (PCR) products amplified from DNAs of 25 C. septicum strains, and were classified into 10 patterns. Alpha-toxins were purified from the culture supernatant of four C. septicum strains (strains No. 44, Kagoshima 8, Mie and Tokachi) which were specially chosen from patterns of the deduced amino acid sequences. The molecular weights of the alpha-toxins were not different according to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. However, the isoelectric points between the alpha-toxins of No. 44 and Tokachi strains differed markedly. Cross-neutralization tests were performed with purified alpha-toxins and antitoxins in mice and in Vero cells. Each antitoxin showed roughly the same titers against the four alpha-toxins in mice and completely identical titers against these in Vero cells. Calves immunized with toxoid prepared from the culture supernatant of No.44 strain were challenged by exposure to spores of Mie strain. The toxoid conferred protection against the challenge in calves. From these results, although genetic variation has been observed within the C. septicum alpha-toxin gene, C. septicum strains toxoid of strain No.44 induces protective immunity against exposure to C. septicum that produce other subtypes of alpha-toxin containing several different amino acid residues.

Amino Acid Sequence↗