[Binding and degenerative effect of Clostridium botulinum type A, C and E toxins on cultured neurons]

Binding of purified Clostridium botulinum type A, C1, and E toxins to cultured cells was studied by biotinylated antitoxin-avidin (FITC) method. Type A and C toxins were bound strongly to the neuron culture prepared from brains of fetal mice, but type E toxin was weakly bound. No fluorescence was observed on the feeder layer which was composed of nonneuronal cells. Type C toxin was bound to cell lines of neuronal origin, and its heavy chain component but not light chain component contributed to the binding. When type C toxin (4 X 10(2) LD50) was added into the primary neuron culture in 96 well plate, degeneration of neuronal processes and rounding of neuronal soma were observed, but type A and E toxins showed no such cytotoxic activity. The binding and cytotoxic activities of type C toxin were blocked by heat treatment at 80 degrees C for 30 minutes or preincubation of the toxin with various polyclonal and monoclonal antibodies which neutralized the toxin activity in mice. Electron microscopic examination indicated a number of degenerated mitochondria, membranous dense bodies and vesicles in the neuronal processes. The ultrastructural change is similar to that of Wallerian degeneration, suggesting that the toxin may inhibit the axonal flow.