Different time courses of recovery after poisoning with botulinum neurotoxin serotypes A and E in humans

Botulinum toxin serotypes A and E (BoNT/A and /E) cleave the carboxy-termin us of synaptosomal associated protein-25 (SNAP-25) removing nine and 26 res idues, respectively. To investigate the effect of these lesions of the same target molecule, 11 volunteers were injected with 3 IU of BoNT/A in the ex tensor digitorum brevis (EDB) muscle of one foot and with 3 IU of BoNT/E in the contralateral one. In addition, seven volunteers were similarly inject ed with mixtures of BoNT/A + BoNT/E. Compound muscular action potential (CM AP) was measured at different time intervals and the percentage variation o f CMAP (%CMAP) was calculated. Unexpectedly, a much faster recovery of %CMA P after BoNT/E injections was observed. Double poisoned EBD muscles recover ed similarly to BoNT/E. So, a larger deletion of the SNAP-25 molecule cause d by BoNT/E leads to a faster functional recovery. (C) 1998 Elsevier Scienc e Ireland Ltd. All rights reserved.