A three monoclonal antibody combination potently neutralizes multiple botulinum neurotoxin serotype F subtypes

PLoS One. 2017 Mar 21;12(3):e0174187. doi: 10.1371/journal.pone.0174187. eCollection 2017.

Abstract

Human botulism is primarily caused by botulinum neurotoxin (BoNT) serotypes A, B and E, with around 1% caused by serotype F (BoNT/F). BoNT/F comprises at least seven different subtypes with the amino acid sequence difference between subtypes as high as 36%. The sequence differences present a significant challenge for generating monoclonal antibodies (mAbs) that can bind, detect and neutralize all BoNT/F subtypes. We used repertoire cloning of immune mouse antibody variable (V) regions and yeast display to generate a panel of 33 lead single chain Fv (scFv) mAbs that bound one or more BoNT/F subtypes with a median equilibrium dissociation constant (KD) of 4.06 × 10-9 M. By diversifying the V-regions of the lead mAbs and selecting for cross reactivity we generated five mAbs that bound each of the seven subtypes. Three scFv binding non-overlapping epitopes were converted to IgG that had KD for the different BoNT/F subtypes ranging from 2.2×10-8 M to 1.47×10-12 pM. An equimolar combination of the mAbs was able to potently neutralize BoNT/F1, F2, F4 and F7 in the mouse neutralization assay. The mAbs have potential utility as diagnostics capable of recognizing the known BoNT/F subtypes and could be developed as antitoxins to prevent and treat type F botulism.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Antibodies, Monoclonal / immunology*
  • Antitoxins / genetics
  • Antitoxins / immunology*
  • Botulinum Toxins / immunology*
  • Botulism / diagnosis
  • Botulism / therapy
  • Catalytic Domain / immunology
  • Clostridium botulinum / metabolism
  • Cross Reactions / immunology
  • Epitope Mapping
  • Epitopes / immunology
  • Escherichia coli / genetics
  • Immunization
  • Mice
  • Saccharomyces cerevisiae / genetics
  • Single-Chain Antibodies / genetics
  • Single-Chain Antibodies / immunology*

Substances

  • Antibodies, Monoclonal
  • Antitoxins
  • Epitopes
  • Single-Chain Antibodies
  • Botulinum Toxins
  • botulinum toxin type F