FIG. 13.

Effects of neutralizing antibodies on the neuromuscular blocking properties of BoNT/A. Toxin (1 × 10⁻⁸ M) was incubated alone or with antiserum from animals that had been immunized with trivalent vaccine (0.1 ml; 30 min; room temperature). The mixtures were then added to phrenic nerve-hemidiaphragm preparations (four preparations per group) to obtain a final toxin concentration of 1 × 10⁻¹¹ M. Untreated toxin caused paralysis of transmission (i.e., a 90% reduction in twitch amplitude) within 100 to 140 min (⧫). In the same time frame, antibody-pretreated toxin did not paralyze transmission (▴). An equivalent experiment was done in which toxin was preincubated with preimmune serum (inset). This pretreatment did not significantly affect the potency of the toxin.