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MAbs. 2014 Mar-Apr;6(2):446-59. doi: 10.4161/mabs.27773. Epub 2014 Jan 9.

Development of neutralizing scFv-Fc against botulinum neurotoxin A light chain from a macaque immune library.

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Technische Universität Braunschweig; Institut für Biochemie, Biotechnologie, und Bioinformatik; Abteilung Biotechnologie; Braunschweig, Germany.
National Institute for Biological Standards and Control (NIBSC); Medicines and Healthcare Products Regulatory Agency; Division of Bacteriology; Potters Bar, UK.
Institut de Recherche Biomédicale des Armées (IRBA-CRSSA); Département de Microbiologie; Unité de biotechnologie des anticorps et des toxines ; La Tronche Cedex, France.


Botulinum toxins (BoNTs) are among the most toxic substances on earth, with serotype A toxin being the most toxic substance known. They are responsible for human botulism, a disease characterized by flaccid muscle paralysis that occurs naturally through food poisoning or the colonization of the gastrointestinal tract by BoNT-producing clostridia. BoNT has been classified as a category A agent by the Centers for Disease Control, and it is one of six agents with the highest potential risk of use as bioweapons. Human or human-like neutralizing antibodies are thus required for the development of anti-botulinum toxin drugs to deal with this possibility. In this study, Macaca fascicularis was hyperimmunized with a recombinant light chain of BoNT/A. An immune phage display library was constructed and, after multistep panning, several scFv with nanomolar affinities that inhibited the endopeptidase activity of BoNT/A1 in vitro as scFv-Fc, with a molar ratio (ab binding site:toxin) of up to 1:1, were isolated. The neutralization of BoNT/A-induced paralysis by the SEM120-IID5, SEM120-IIIC1 and SEM120-IIIC4 antibodies was demonstrated in mouse phrenic nerve-hemidiaphragm preparations with the holotoxin. The neutralization observed is the strongest ever measured in the phrenic nerve-hemidiaphragm assay for BoNT/A1 for a monoclonal antibody. Several scFv-Fc inhibiting the endopeptidase activity of botulinum neurotoxin A were isolated. For SEM120-IID5, SEM120-IIIC1, and SEM120-IIIC4, inhibitory effects in vitro and protection against the toxin ex vivo were observed. The human-like nature of these antibodies makes them promising lead candidates for further development of immunotherapeutics for this disease.


BoNT/A; Clostridium botulinum; Macaca fascicularis; SNAP-25; botulinum neurotoxin; ex-vivo assay; in vitro assay; macaque; mouse phrenic nerve-hemidiaphragm assay; phage display; scFv; scFv-Fc

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