Fig. 3

Neutralization of BoNT/A₁ and BoNT/A₂ by the scFv A1HC38 in the mouse phrenic nerve-hemidiaphragm assay. Neutralization of BoNT/A₁ and BoNT/A₂ by decreasing concentrations of the scFv A1HC38. a Neutralization of BoNT/A₁ holotoxin (20 LD₅₀.ml⁻¹) induced by scFv A1HC38 at decreasing concentrations. b Neutralization of BoNT/A₂ as a form of complexes (10 LD₅₀.ml⁻¹) induced by the scFv A1HC38 at decreasing concentrations. The toxins were premixed with 7, 5, 1, 0.5 or 0.1 μg.mL⁻¹ of A1HC38 or with 20 mIU.mL⁻¹ (anti BoNT/A antibodies) of the commercial polyvalent F(ab’)₂ antitoxin. The toxins alone were used as controls to determine the time required to observed a 50 % decrease in the twitch height. No significant neutralization was observed with an irrelevant scFv directed against the ricin toxin (referred as “negative control”), tested at a single concentration of 9 μg.mL⁻¹ in all experiments. The experiments were run until a decrease of at least 50 % in the twitch height was observed, until the phrenic nerve hemidiaphragm preparation was no longer viable or until no more twitch was detected. Control tissues, not exposed to the toxin were included to demonstrate stability of recordings (referred as “No toxin”)