ABSTRACT 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. Remarkably,
the NbAahIF12 fully protected mice against
100 LD50 of AahI administered intracerebroventricularly.
Moreover, where PAS failed completely to neutralize
2 LD50 of crude venom injected subcutaneously,
the designed bispecific NbF12-10 against AahI/AahII
toxins succeeded in neutralizing 5 LD50. Finally, in a
challenge assay in which mice were subcutaneously
injected with a lethal dose of scorpion venom, the
subsequent intravenous injection of 85 g of NbF12-10
protected all mice, even if the whole procedure was
repeated 3 times. Furthermore, the NbF12-10 remained
fully protective when mice with severe signs of envenoming
were treated a few minutes before the untreated
mice died.
Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalThe FASEB Journal
Publication statusPublished - 21 Apr 2010

    Research areas

  • Scorpion toxin, dromedary, single-domain antibody, recombinant antibody, anti-venom

ID: 1922155