THE HEMAGGLUTININ OF CLOSTRIDIUM-BOTULINUM TYPE-C PROGENITOR TOXIN PLAYS AN ESSENTIAL ROLE IN BINDING OF TOXIN TO THE EPITHELIAL-CELLS OF GUINEA-PIG SMALL-INTESTINE, LEADING TO THE EFFICIENT ABSORPTION OF THE TOXIN

Binding of the purified type C 7S (neurotoxin), 12S and 16S botulinum toxins to epithelial cells of ligated small intestine or colon of the guinea pig (in vivo test) and to pre-fixed gastrointestinal tissue sec tions (in vitro test) wasanalysed. The 165 toxin bound intensely to th e microvilli of epithelial cells of the small intestine in both in viv o and in vitro tests, but did not bind to cells of the stomach or colo n. The neurotoxin and 12S toxin did not bind to epithelial cells of th e small intestine or to cells of the stomach or colon. Absorption of t he toxins was assessed by determining the toxin titre in the sera of g uinea pigs 6-8 h after the intra-intestinal administration of the toxi ns. When the 165 toxin [1 x 10(5) minimum lethal dose (MLD)] was injec ted, 200-660 MLD ml(-1) was detected in the sera, whereas when the 12S toxin (2 x 10(5) MLD) or 7S toxin (2 x 10(5) MLD) was injected, littl e toxin activity was detected in the sera. Therefore, the haemagglutin in of type C 16S toxin is apparently very important in the binding and absorption of botulinum toxin in the small intestine.