Characterization of haemagglutinin activity of Clostridium botulinum type C and D 16S toxins, and one subcomponent of haemagglutinin (HA1).

The 16S toxin and one subcomponent of haemagglutinin (HA), designated HA1, were purified from a type D culture of Clostridium botulinum by a newly established procedure, and their HA activities as well as that of purified type C 16S toxin were characterized. SDS-PAGE analysis indicated that the free HA1 forms a polymer with a molecular mass of approximately 200 kDa. Type C and D 16S toxins agglutinated human erythrocytes in the same manner. Their HA titres were dramatically reduced by employing erythrocytes that had been previously treated with neuraminidase, papain or proteinase K, and were inhibited by the addition of N-acetylneuraminic acid to the reaction mixtures. In a direct-binding test to glycolipids such as SPG (NeuAc alpha2-3Gal beta1-4GlcNAc beta1-3Gal beta1-4Glc beta1-Cer) and GM3 (NeuAc alpha2-3Gal beta1-4Glc beta1-Cer), and glycoproteins such as glycophorin A and/or B prepared from the erythrocytes, both toxins bound to sialylglycolipids and sialoglycoproteins, but bound to neither neutral glycolipids nor asialoglycoproteins. On the basis of these results, it was concluded that type C and D 165 toxins bind to erythrocytes through N-acetylneuraminic acid. HA1 showed no haemagglutination activity, although it did bind to sialylglycolipids. We therefore speculate that binding to glycoproteins rather than to glycolipids may be important in causing haemagglutination by type C and D 16S toxins.