title: Receptor-based antidote for diphtheria.
abstract: Although equine diphtheria antitoxin may be an effective therapy for human diphtheria, its use often induces serum sickness. We describe here a strategy for developing an alternative treatment based on the human diphtheria toxin (DT) receptor/heparin-binding epidermal growth factor-like growth factor (HB-EGF) precursor. Recombinant mature human HB-EGF acts as a soluble receptor analog, binding radioiodinated DT and preventing its binding to the cellular DT receptor/HB-EGF precursor. However, the possibility existed that radioiodinated DT-HB-EGF complexes associate with cells due to the binding of the heparin-binding domain of recombinant HB-EGF to cell surface heparan sulfate proteoglycans. This possibility was confirmed by performing DT binding studies in the presence of heparin. A recombinant truncated HB-EGF (residues 106 to 149), which lacks most of the heparin-binding domain, showed an essentially heparin-independent binding of radioiodinated DT to cells. Furthermore, it was a more effective inhibitor of DT binding than was recombinant mature HB-EGF. Since mature HB-EGF is a known ligand for the EGF receptor and is thus highly mitogenic (tumorigenic), we then changed amino acid residues in the EGF-like domain of the recombinant truncated HB-EGF and demonstrated that this DT receptor analog (I117A/L148A) displayed a low mitogenic effect. The truncated (I117A/L148A) HB-EGF protein retained high DT binding affinity, as confirmed by using surface plasmon resonance. Our results suggest that the truncated (I117A/L148A) HB-EGF protein could be an effective, safe antidote for human diphtheria.
authors.affiliation: Department of Microbiology, The University of Texas Southwestern Medical Center, Dallas, Texas 75390-9048, USA.
authors.forename: Jeong-Heon
authors.initials: JH
authors.lastname: Cha
authors.forename: Joanna S
authors.initials: JS
authors.lastname: Brooke
authors.forename: Mee Young
authors.initials: MY
authors.lastname: Chang
authors.forename: Leon
authors.initials: L
authors.lastname: Eidels
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D000931:Antidotes / Q000627:therapeutic use*; D004165:Diphtheria / Q000188:drug therapy*; D004167:Diphtheria Toxin / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use*; D006493:Heparin / Q000494:pharmacology; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D008969:Molecular Sequence Data; D011956:Receptors, Cell Surface / Q000378:metabolism*
chemical_list: D000931:Antidotes; D004167:Diphtheria Toxin; C587883:HBEGF protein, human; C587884:Hbegf protein, mouse; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens; D011956:Receptors, Cell Surface; D004815:Epidermal Growth Factor; D006493:Heparin