Potent Neutralization of Staphylococcal Enterotoxin B In Vivo by Antibodies that Block Binding to the T-Cell Receptor

J Mol Biol. 2019 Oct 4;431(21):4354-4367. doi: 10.1016/j.jmb.2019.03.017. Epub 2019 Mar 27.


To develop an antibody (Ab) therapeutic against staphylococcal enterotoxin B (SEB), a potential incapacitating bioterrorism agent and a major cause of food poisoning, we developed a "class T" anti-SEB neutralizing Ab (GC132) targeting an epitope on SEB distinct from that of previously developed "class M" Abs. A systematic engineering approach was applied to affinity-mature Ab GC132 to yield an optimized therapeutic candidate (GC132a) with sub-nanomolar binding affinity. Mapping of the binding interface by hydrogen-deuterium exchange coupled to mass spectrometry revealed that the class T epitope on SEB overlapped with the T-cell receptor binding site, whereas other evidence suggested that the class M epitope overlapped with the binding site for the major histocompatibility complex. In the IgG format, GC132a showed ∼50-fold more potent toxin-neutralizing efficacy than the best class M Ab in vitro, and fully protected mice from lethal challenge in a toxic shock post-exposure model. We also engineered bispecific Abs (bsAbs) that bound tetravalently by utilizing two class M binding sites and two class T binding sites. The bsAbs displayed enhanced toxin neutralization efficacy compared with the respective monospecific Ab subunits as well as a mixture of the two, indicating that enhanced efficacy was due to heterotypic tetravalent binding to two non-overlapping epitopes on SEB. Together, these results suggest that class T anti-SEB Ab GC132a is an excellent candidate for clinical development and for bsAb engineering.

Keywords: SEB toxin; hydrogen–deuterium exchange coupled to mass spectrometry; phage display; protein engineering; synthetic antibody.

Publication types

  • Research Support, N.I.H., Extramural
  • Review

MeSH terms

  • Animals
  • Antibodies, Bacterial / metabolism*
  • Antibodies, Bispecific / metabolism
  • Antibodies, Neutralizing / metabolism*
  • Cell Surface Display Techniques
  • Enterotoxins / metabolism
  • Humans
  • Mass Spectrometry
  • Models, Biological
  • Protein Engineering / methods
  • Receptors, Antigen, T-Cell / metabolism*


  • Antibodies, Bacterial
  • Antibodies, Bispecific
  • Antibodies, Neutralizing
  • Enterotoxins
  • Receptors, Antigen, T-Cell
  • enterotoxin B, staphylococcal