SNAP25 and botulism: Analysis of Clostridium-produced, recombinant, hybrid toxins, BoNT/A1A3 and BoNT/A3A1, relative to the parent toxins showed that both LC and HC contributed to the specific activity in mice and efficiency of SNAP-25 cleavage in cultured cells (Fig. 2 and 3), while LC defined the duration of BoNT/A action in cultured cells (Fig. 4) and in two mouse models of botulism (Fig. 5).