title: The receptor binding domain of botulinum neurotoxin serotype A (BoNT/A) inhibits BoNT/A and BoNT/E intoxications in vivo.
abstract: The receptor binding domain of botulinum neurotoxin (BoNT), also designated the C terminus of the heavy chain (H(C)), is a promising vaccine candidate against botulism. In this study, a highly efficient expression system for the protein was developed in Escherichia coli, which provided yields that were 1 order of magnitude higher than those reported to date (350 mg H(C) per liter). The product was highly immunogenic, protecting mice from a challenge with 10(5) 50% lethal dose (LD(50)) after a single vaccination and generating a neutralizing titer of 49.98 IU/ml after three immunizations. In addition, a single boost with HC increased neutralizing titers by up to 1 order of magnitude in rabbits hyperimmunized against toxoid. Moreover, we demonstrate here for the first time in vivo inhibition of BoNT/A intoxication by H(C)/A, presumably due to a blockade of the neurotoxin protein receptor SV2. Administration of HC/A delayed the time to death from 10.4 to 27.3 h in mice exposed to a lethal dose of BoNT/A (P = 0.0005). Since BoNT/A and BoNT/E partially share SV2 isoforms as their protein receptors, the ability of H(C)/A to cross-inhibit BoNT/E intoxication was evaluated. The administration of H(C)/A together with BoNT/E led to 50% survival and significantly delayed the time to death for the nonsurviving mice (P = 0.003). Furthermore, a combination of H(C)/A and a subprotective dose of antitoxin E fully protected mice against 850 mouse LD(50) of BoNT/E, suggesting complementary mechanisms of protection consisting of toxin neutralization by antibodies and receptor blocking by H(C)/A.
authors.affiliation: Department of Biotechnology, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Alon
authors.initials: A
authors.lastname: Ben David
authors.forename: Eran
authors.initials: E
authors.lastname: Diamant
authors.forename: Ada
authors.initials: A
authors.lastname: Barnea
authors.forename: Osnat
authors.initials: O
authors.lastname: Rosen
authors.forename: Amram
authors.initials: A
authors.lastname: Torgeman
authors.forename: Ran
authors.initials: R
authors.lastname: Zichel
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000097:blood; D001904:Botulinum Antitoxin / Q000097:blood; D001905:Botulinum Toxins / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D019274:Botulinum Toxins, Type A / Q000235:genetics / Q000276:immunology* / Q000633:toxicity*; D003429:Cross Reactions; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D051379:Mice; D011041:Poisoning / Q000517:prevention & control*; D011817:Rabbits; D016019:Survival Analysis; D013997:Time Factors; D014611:Vaccination / Q000379:methods*
chemical_list: D057134:Antibodies, Neutralizing; D001904:Botulinum Antitoxin; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A; C096326:botulinum toxin type E