title: A novel strategy for development of recombinant antitoxin therapeutics tested in a mouse botulism model.
abstract: Antitoxins are needed that can be produced economically with improved safety and shelf life compared to conventional antisera-based therapeutics. Here we report a practical strategy for development of simple antitoxin therapeutics with substantial advantages over currently available treatments. The therapeutic strategy employs a single recombinant 'targeting agent' that binds a toxin at two unique sites and a 'clearing Ab' that binds two epitopes present on each targeting agent. Co-administration of the targeting agent and the clearing Ab results in decoration of the toxin with up to four Abs to promote accelerated clearance. The therapeutic strategy was applied to two Botulinum neurotoxin (BoNT) serotypes and protected mice from lethality in two different intoxication models with an efficacy equivalent to conventional antitoxin serum. Targeting agents were a single recombinant protein consisting of a heterodimer of two camelid anti-BoNT heavy-chain-only Ab V(H) (VHH) binding domains and two E-tag epitopes. The clearing mAb was an anti-E-tag mAb. By comparing the in vivo efficacy of treatments that employed neutralizing vs. non-neutralizing agents or the presence vs. absence of clearing Ab permitted unprecedented insight into the roles of toxin neutralization and clearance in antitoxin efficacy. Surprisingly, when a post-intoxication treatment model was used, a toxin-neutralizing heterodimer agent fully protected mice from intoxication even in the absence of clearing Ab. Thus a single, easy-to-produce recombinant protein was as efficacious as polyclonal antiserum in a clinically-relevant mouse model of botulism. This strategy should have widespread application in antitoxin development and other therapies in which neutralization and/or accelerated clearance of a serum biomolecule can offer therapeutic benefit.
authors.affiliation: Department of Biomedical Sciences, Tufts Cummings School of Veterinary Medicine, North Grafton, Massachusetts, United States of America.
authors.forename: Jean
authors.initials: J
authors.lastname: Mukherjee
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Tremblay
authors.forename: Clinton E
authors.initials: CE
authors.lastname: Leysath
authors.forename: Kwasi
authors.initials: K
authors.lastname: Ofori
authors.forename: Karen
authors.initials: K
authors.lastname: Baldwin
authors.forename: Xiaochuan
authors.initials: X
authors.lastname: Feng
authors.forename: Daniela
authors.initials: D
authors.lastname: Bedenice
authors.forename: Robert P
authors.initials: RP
authors.lastname: Webb
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Wright
authors.forename: Leonard A
authors.initials: LA
authors.lastname: Smith
authors.forename: Saul
authors.initials: S
authors.lastname: Tzipori
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shoemaker
mesh_terms: D000818:Animals; D000915:Antibody Affinity; D000992:Antitoxins / Q000096:biosynthesis* / Q000378:metabolism / Q000627:therapeutic use*; D001904:Botulinum Antitoxin / Q000096:biosynthesis / Q000378:metabolism / Q000627:therapeutic use; D001906:Botulism / Q000276:immunology / Q000401:mortality / Q000473:pathology / Q000628:therapy*; D004195:Disease Models, Animal; D055808:Drug Discovery / Q000379:methods; D015507:Drugs, Investigational / Q000378:metabolism / Q000627:therapeutic use; D005260:Female; D007167:Immunotherapy / Q000379:methods / Q000639:trends*; D051379:Mice; D008954:Models, Biological; D055503:Protein Multimerization / Q000502:physiology; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000627:therapeutic use; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D000992:Antitoxins; D001904:Botulinum Antitoxin; D015507:Drugs, Investigational; D011994:Recombinant Proteins