lethal scorpion envenoming

Envenoming following scorpion sting is a common emergency in many parts of the world. Our aim was to ameliorate the current 100-kDa horse plasma antivenom serum (PAS)-derived Fab2 to more quickly reach the highly diffusible scorpion toxins (7 kDa). We immunized dromedaries with toxins from Androctonus australis hector (Aah) scorpions and cloned the single-domain antibody fragments or nanobodies (15 kDa) from their B cells. Nanobodies against AahI toxin (with AahII the most toxic compound of the venom) were retrieved from the libraries, and their AahI-toxin neutralization was monitored in mice. Re- markably, the NbAahIF12 fully protected mice against 100 LD50 of AahI administered intracerebroventricu- larly. Moreover, where PAS failed completely to neu-