Analysis of absorption of Clostridium botulinum neurotoxin-nontoxic component complex from the small intestine.

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Clostridium botulinum type A and C hemagglutinin positive progenitor toxins consist of three distinct components : neurotoxin (NTX), hemagglutinin (HA), and non-toxic non-HA (NTNH). The HA consists of four subcomponents designated HA1 (〜33kDa), 2 (〜17kDa), 3a (〜22kDa), and 3b (〜53kDa). Each HA subcomponent of types A and C was prepared as GST-fusion proteins. By employing purified HA-positive A and C toxins and GST-fusion proteins of each HA subcomponent, we found that the HA positive progenitor toxins, GST-HA1, and GST-HA3b of both A and C bound to human erythrocytes and microvilli of guinea pig upper small intestinal sections. In both A and C, GST-HA1bound via galactose moieties such as Gal- β1-4 GlcNAc, whereas GST-HA3b bound via sialic acid moieties. The HA positive type A toxin bound via galactose moieties, whereas type C bound via sialic acid moieties. Therefore, it was concluded that HA1 contributes to the type A toxin binding to the erythrocytes and microvilli, whereas HA3 contributes to the type C toxin binding. GST-HA2 and Gst-ha3a showed no detectable binding. On the binding test of A and C toxins to the glycolipids and glycoproteins extracted from the erythrocytes, type A toxin mainly bound glycophorin, whereas type C bound glycophorin and sialylparagloboside and GM3. Since glycophorin contains both sialylated and unsialylated branches of the sugar chains, type A toxin may bind to the unsialylated branch, whereas type C toxin binds to sialylated branch.