A bispecific nanobody to provide full protection against lethal scorpion envenoming

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 Fab'(2) 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 NbAahI'F12 fully protected mice against 100 LD(50) of AahI' administered intracerebroventricularly. Moreover, where PAS failed completely to neutralize 2 LD(50) of crude venom injected subcutaneously, the designed bispecific NbF12-10 against AahI'/AahII toxins succeeded in neutralizing 5 LD(50). Finally, in a challenge assay in which mice were subcutaneously injected with a lethal dose of scorpion venom, the subsequent intravenous injection of 85 microg 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.

Neutralization of Clostridium difficile Toxin A with Single-domain Antibodies Targeting the Cell Receptor Binding Domain

“…54). Several of these V H Hs were effective neutralizers of toxins, viruses, and enzymes as follows: scorpion toxin AahIЈ (55,56); Escherichia coli heat-labile toxin (57); foot and mouth disease virus (58); ART2.2, an ecto-enzyme related to ADP-ribosylating bacterial toxins (59); verotoxin 1 (60); HIV-1 envelope protein gp120 (61); rotovirus (62,63); and p2 phage (64). These V H Hs neutralized or inhibited the function of their targets by blocking enzyme-active sites (59), preventing protein-receptor binding through site-specific binding or steric hindrance (56,57), and by possibly inducing conformational changes in the target protein (62).…”

Nanobody-derived nanobiotechnology tool kits for diverse biomedical and biotechnology applications

“…By far, nanobodies for antiscorpion toxins, antibacterial toxins, and anti-snake venom are actively being investigated. [83][84][85][86][87] Owing to their small size and extended CDR3, nanobodies also showed special advantages as therapeutics for infectious disease, including the infection of viruses, bacteria, and parasites, over conventional antibodies that usually obstruct the access of hidden and essential epitopes on pathogens. [88][89][90][91][92][93][94][95][96] The added value of the nanobodies as targeting therapeutics stems from their capacity to distinguish the cognate target from closely related variants.…”

New Applications of Nanotechnology for Neuroimaging

“…They consist of heavy chains only and have desirable features such as small size, decreased immunogenicity, and high binding affinities. 56 Nanobodies have been designed for use in cancer therapy, 57,58 antivenoms, 59 inflammatory conditions, 60 and immunoimaging. [60][61][62][63][64] Nanobodies can detect vascular and parenchymal amyloid beta (A␤) deposits in vivo to differentiate cerebral ␤-amyloid indicative of Alzheimer disease and vascular A␤ plaques associated with cerebral amyloid angiopathy.…”