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Open AccessArticle

Role of Homologous Fc Fragment in the Potency and Efficacy of Anti‐Botulinum Antibody Preparations

Department of Biotechnology, Israel Institute for Biological Research, Ness Ziona 7410001, Israel
Author to whom correspondence should be addressed.
Toxins 2017, 9(6), 180;
Received: 25 April 2017 / Revised: 24 May 2017 / Accepted: 27 May 2017 / Published: 29 May 2017
(This article belongs to the Special Issue Botulinum Neurotoxins Antibody and Vaccine)
PDF [1022 KB, uploaded 31 May 2017]


The only approved treatment for botulism relies on passive immunity which is mostly based on antibody preparations collected from hyper‐immune horses. The IgG Fc fragment is commonly removed from these heterologous preparations to reduce the incidence of hyper‐sensitivity reactions. New‐generation therapies entering the pipeline are based on a combination of humanized monoclonal antibodies (MAbs), which exhibit improved safety and pharmacokinetics. In the current study, a systematic and quantitative approach was applied to measure the direct contribution of homologous Fc to the potency of monoclonal and polyclonal antitoxin preparations in mice. Homologous Fc increased the potency of three individual anti‐botulinum toxin MAbs by up to one order of magnitude. Moreover, Fc fragment removal almost completely abolished the synergistic potency obtained from a combined preparation of these three MAbs. The MAb mixture neutralized a 400‐mouse median lethal dose (MsLD50) of botulinum toxin, whereas the F(ab′)2 combination failed to neutralize 10 MsLD50 of botulinum toxin. Notably, increased avidity did not compensate for this phenomenon, as a polyclonal, hyper‐immune, homologous preparation lost 90% of its potency as well upon Fc removal. Finally, the addition of homologous Fc arms to a heterologous pharmaceutical anti‐botulinum toxin polyclonal horse F(ab′)2 preparation improved its efficacy when administered to intoxicated symptomatic mice. Our study extends the aspects by which switching from animal‐based to human‐based antitoxins will improve not only the safety but also the potency and efficacy of passive immunity against toxins. View Full-Text
Keywords: botulinum; antitoxin; potency; efficacy; monoclonal antibodies; polyclonal antibodies botulinum; antitoxin; potency; efficacy; monoclonal antibodies; polyclonal antibodies

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Torgeman, A.; Ozeri, E.; Ben David, A.; Diamant, E.; Rosen, O.; Schwartz, A.; Barnea, A.; Makovitzki, A.; Mimran, A.; Zichel, R. Role of Homologous Fc Fragment in the Potency and Efficacy of Anti‐Botulinum Antibody Preparations. Toxins 2017, 9, 180.

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