Pure Botulinum Neurotoxin Is Absorbed from the Stomach and Small Intestine and Produces Peripheral Neuromuscular Blockade

Abstract

Clostridium botulinum serotype A produces a neurotoxin composed of a 100-kDa heavy chain and a 50-kDa light chain linked by a disulfide bond. This neurotoxin is part of a ca. 900-kDa complex, formed by noncovalent association with a single nontoxin, nonhemagglutinin subunit and a family of hemagglutinating proteins. Previous work has suggested, although never conclusively demonstrated, that neurotoxin alone cannot survive passage through the stomach and/or cannot be absorbed from the gut without the involvement of auxiliary proteins in the complex. Therefore, this study compared the relative absorption and toxicity of three preparations of neurotoxin in an in vivo mouse model. Equimolar amounts of serotype A complex with hemagglutinins, complex without hemagglutinins, and purified neurotoxin were surgically introduced into the stomach or into the small intestine. In some experiments, movement of neurotoxin from the site of administration was restricted by ligation of the pylorus. Comparison of relative toxicities demonstrated that at adequate doses, complex with hemagglutinins, complex without hemagglutinins, and pure neurotoxin can be absorbed from the stomach. The potency of neurotoxin in complex was greater than that of pure neurotoxin, but the magnitude of this difference diminished as the dosage of neurotoxin increased. Qualitatively similar results were obtained when complex with hemagglutinins, complex without hemagglutinins, and pure neurotoxin were placed directly into the intestine. This work establishes that pure botulinum neurotoxin serotype A is toxic when administered orally. This means that pure neurotoxin does not require hemagglutinins or other auxiliary proteins for absorption from the gastrointestinal system into the general circulation.

Host-cell specificity and transcytosis of nontoxic nonhemagglutinin protein of botulinum neurotoxin serotype D

“…We thus hypothesized that NTNHA and BoNT were similar in functional terms. Pure BoNT of serotype A can be absorbed if the toxin is injected directly into the stomach or intestine (Maksymowych et al, 1999). Additionally, serotype D BoNT can move across a rat intestinal cell monolayer (Niwa et al, 2010).…”

Development of real-time PCR tests for detecting botulinum neurotoxins A, B, E, F producingClostridium botulinum,Clostridium baratiiandClostridium butyricum

“…The NTNH protein that is closely associated with the BoNT protein is present in all toxin clusters but its function is not fully understood. It is thought that this protein assists in stability of the neurotoxin within the acidic and protease-rich environment of the stomach and assists in transport of the toxin from the intestinal area to the bloodstream (Maksymowych et al 1999).…”

Differential entry of botulinum neurotoxin A into neuronal and intestinal cells

“…Botulism usually results from the ingestion of preformed neurotoxin in contaminated food or ingestion of spores or bacteria, which under certain circumstances may colonize the gut and produce neurotoxin in situ (Tacket and Rogawski, 1989). In either case, BoNT escapes the gastro-intestinal tract to reach the target cholinergic nerve endings, possibly through the blood and lymph circulation (Maksymowych et al, 1999). Penetration of BoNT through an epithelial cell barrier and its subsequent migration to cholinergic nerve endings are the essential first steps of botulinum intoxication.…”