In vivo neutralization of botulinum neurotoxins serotype E with heavy-chain camelid antibodies (VHH).

Ingestion of botulinum neurotoxin (BoNT) results in botulism, a severe and frequent fatal disease known in the world. Current treatments rely on antitoxins, such as equine antitoxin and human botulism immunoglobulin. In some cases, side effects have been reported, including early anaphylactic shock and late serum sickness. Thus, diagnosis and treatment measure of BoNT are necessary and crucial. In the present study, a single-domain variable heavy-chain (VHH) antibody fragment was obtained from an immune dromedary phage display library against the putative binding domain of botulinum neurotoxin E (BoNT/E), a non-toxic 50-kDa fragment. The characteristics of nanobody VHH include excellent production, superior heat stability and specific binding capacity to soluble antigen without cross-reaction to other relevant or irrelevant antigens. A total of 150 ng/Kg of nanobody entirely neutralized 3LD50 of the BoNT/E in an in vivo challenge of the mice. This phenomenon indicates BoNT/E toxin neutralizing capacity of the produced nanobody. These results also suggest possession of unique properties by the nanobody applicable in diagnostics or therapeutic purposes.