Characterization of the binding of botulinum type B 16S toxin to human intestinal epithelial cells

Botulinum neurotoxin produced by Clostridium botulinum type B is a complex of 12S and 16S toxins. 12S toxin consists of a neurotoxin and a nontoxic non-HA (NTNH). The 16S toxin consists of a neurotoxin, an NTNH, and a hemagglutinin (HA). Food-borne botulism is caused by these complex toxins, which are ingested orally and absorbed from the digestive tract across the epithelial barrier lining the gut. Here we show that the type B 16S toxin, but not the 12S toxin or the neurotoxin, binds to the T84 human intestinal epithelial cell line. We also demonstrate that the HA moiety in the 16S toxin mediates the toxin binding to the cells. The carbohydrates containing a galactose moiety inhibited the binding of the 16S toxin to the T84 cells, and neuraminidase treatment of the cells increased the 16S toxin binding. The binding of the 16S toxin to the neuraminidase-treated cells was also inhibited by carbohydrates containing a galactose moiety. These results suggest that the type B 16S toxin binds to human intestinal epithelial cells via the galactose moiety in the carbohydrate chain on the cell surface