ACTIVITY OF TYPE A BOTULINAL TOXIN AND HEMAGGLUTININ EXPOSED TO PROTEOLYTIC ENZYME

On the size of the toxic particle passing the intestinal barrier in botulism

On the basis of toxicity assays using partition centrifugation cells it was established that the sedimentation coefficient of type A botulinum toxin appearing in the lymph of orally poisoned rats was 7.9 x 10(-18) cm. per dyne sec. with 95 per cent confidence limits of 4.4 to 11.4 x 10(-13) cm. per dyne sec. This is a significantly lower value than that obtained for crystalline toxin but is well within the range of size for proteins. Exposure of crystalline toxin for 2 hours to digestive processes in a section of the duodenum of living rats did not significantly reduce the sedimentation coefficient of the toxin. The S(20) of crystalline toxin employed in the present study ranged between 12 and 21 with a mean value of 17.9. While it was observed that both botulinum toxin and albumin sedimented from lymph in glycerol gradient tubes to essentially the same level no evidence was developed to indicate association between toxin in lymph and serum albumin. The electrophoretic mobility of toxin in lymph is like that of crystalline toxin and not albumin. Dialysis of toxic lymph against serum albumin does not result in the appearance of toxin in the dialysate.

Suppression of 3H-acetylcholine release from primary nerve cell cultures by tetanus and botulinum-A toxin

Primary nerve cell cultures derived from embryonic rat central nervous system form [3H]ACh from exogenous [3H]Ch, and release it upon potassium depolarization. Pretreatment of the cultures with botulinum-A toxin or tetanus toxin diminishes the cellular accumulation of [3H]ACh. Poisoning the cultures during the period of [3H]Ch uptake fails to lower [H]ACh formation. Dependent on dosage, both toxins suppress the release of [3H]ACh upon potassium depolarization. Heat-denaturated toxins as well as tetanus toxin preincubated with tetanus antitoxin were without effect.

Correlation between oral toxicity and in vitro stability of Clostridium botulinum type A and B toxins of different molecular sizes

The in vitro sensitivity to acid and pepsin differed markedly among Clostridium botulinum type A and B toxins of different molecular sizes. The larger the molecular size of the toxin, the higher the resistance to these agents. Tye B derivative toxin was rapidly inactivated, but the progenitor toxins resisted in vitro exposure to rat intestinal juice. The molecular dissociation of the progenitor toxins did not occur in rat intestinal juice of pH 7.0, but did occur in a buffer solution of the same pH. The oral toxicity may depend mostly on the stability of toxin molecules in the stomach and, to a less extent, in the intestine. The present results seem to justify the conclusion that C. botulinum type A and B progenitor toxins with molecular sizes larger than 16S are more potent oral toxins than 12S progenitor toxins.

Proteases of Clostridium botulinum. VI. The role of trypsin, Clostridium botulinum proteases and protease inhibitors in the formation and activation of toxin in growing cultures of Clostridium botulinum

In this study the influence of bovine serum protease inhibitors, trypsin and proteases produced by different types of Clostridium botulinum has been investigated. Trypsin and botulinum proteases had the capability of increasing the toxicity in growing cultures in Clostridium botulinum types A, B and E. Trypsin increased the toxin level to a greater extent than proteases from Clostridium botulinum types A, B, C and F. Protease inhibitors did not influence the toxin formation to any extent compared with the controls. The combined effects of proteases and protease inhibitors on the development of toxin in Clostridium botulinum type B were also investigated by adding proteases and protease inhibitors to the same culture at different time intervals. Protease inhibitors did not reduce the toxicity of the cultures as compared to the controls. Altogether a complex relationship seems to exist between protoxin, toxin, proteases and inhibitors in the culture, and the order and time sequence of addition seem to be of importance. The results obtained in this investigation indicate that proteases of Clostridium botulinum play a part in the formation and/or activation of toxin in growing cultures of proteolytic strains such as Clostridium botulinum types A and B. As to the activation of protoxin and progenitor toxin produced by non-proteolytic Clostridium botulinum types B and E, botulinum proteases showed a marked capability of increasing the toxicity in these cultures. Trypsinization may be valuable for the detection of Clostridium botulinum types A and B in foods, as well as for type E, where it is commonly used.