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Laboratory for Infection Cell Biology, International Research Center for Infectious Diseases, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamada-oka, Suita, Osaka 565–0871, Japan
Correspondence
Yukako Fujinaga
yukafuji{at}biken.osaka-u.ac.jp
Orally ingested botulinum neurotoxin (BoNT) causes food-borne botulism, but BoNT must pass through the gut lining and enter the bloodstream. We have previously found that type B haemagglutinin (HA) proteins in the toxin complex play an important role in the intestinal absorption of BoNT by disrupting the paracellular barrier of the intestinal epithelium, and therefore facilitating the transepithelial delivery of BoNT. Here, we show that type A HA proteins in the toxin complex have a similar disruptive activity and a greater potency than type B HA proteins in the human intestinal epithelial cell lines Caco-2 and T84 and in the canine kidney epithelial cell line MDCK I. In contrast, type C HA proteins in the toxin complex (up to 300 nM) have no detectable effect on the paracellular barrier in these human cell lines, but do show a barrier-disrupting activity and potent cytotoxicity in MDCK I. These findings may indicate that type A and B HA proteins contribute to the development of food-borne botulism, at least in humans, by facilitating the intestinal transepithelial delivery of BoNTs, and that the relative inability of type C HA proteins to disrupt the paracellular barrier of the human intestinal epithelium is one of the reasons for the relative absence of food-borne human botulism caused by type C BoNT.
These authors contributed equally to this work.
Three supplementary figures showing the dose-dependent reduction in TER of Caco-2 cells with the apical or basolateral addition of type A or B HA-positive toxin complexes, the dose-dependent reduction in TER of MDCK I cells with apically added type A and basolaterally added type A, B and C HA-positive toxin complexes, and the effects of HA-positive complexes on rat intestinal epithelial cell lines ACL-15 and RCN-9, are available with the online version of this paper.
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