title: Protection against anthrax toxin by recombinant antibody fragments correlates with antigen affinity.
abstract: The tripartite toxin produced by Bacillus anthracis is the key determinant in the etiology of anthrax. We have engineered a panel of toxin-neutralizing antibodies, including single-chain variable fragments (scFvs) and scFvs fused to a human constant kappa domain (scAbs), that bind to the protective antigen subunit of the toxin with equilibrium dissociation constants (K(d)) between 63 nM and 0.25 nM. The entire antibody panel showed high serum, thermal, and denaturant stability. In vitro, post-challenge protection of macrophages from the action of the holotoxin correlated with the K(d) of the scFv variants. Strong correlations among antibody construct affinity, serum half-life, and protection were also observed in a rat model of toxin challenge. High-affinity toxin-neutralizing antibodies may be of therapeutic value for alleviating the symptoms of anthrax toxin in infected individuals and for medium-term prophylaxis to infection.
authors.affiliation: Department of Chemical Engineering, University of Texas, Austin, TX 78712, USA.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Maynard
authors.forename: Catharina B M
authors.initials: CB
authors.lastname: Maassen
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Leppla
authors.forename: Kathleen
authors.initials: K
authors.lastname: Brasky
authors.forename: Jean L
authors.initials: JL
authors.lastname: Patterson
authors.forename: Brent L
authors.initials: BL
authors.lastname: Iverson
authors.forename: George
authors.initials: G
authors.lastname: Georgiou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000881:Anthrax / Q000188:drug therapy / Q000276:immunology; D000907:Antibodies, Bacterial / Q000096:biosynthesis* / Q000235:genetics* / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000008:administration & dosage* / Q000235:genetics*; D000915:Antibody Affinity / Q000276:immunology*; D000942:Antigens, Bacterial / Q000187:drug effects / Q000235:genetics / Q000276:immunology; D001408:Bacillus anthracis / Q000187:drug effects / Q000276:immunology; D001427:Bacterial Toxins / Q000276:immunology*; D001667:Binding, Competitive / Q000235:genetics / Q000276:immunology; D005786:Gene Expression Regulation; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use; D007145:Immunoglobulin kappa-Chains / Q000235:genetics / Q000276:immunology; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D015202:Protein Engineering; D051381:Rats; D011916:Rats, Inbred F344; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000907:Antibodies, Bacterial; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D007128:Immunoglobulin Fragments; D007145:Immunoglobulin kappa-Chains; D011994:Recombinant Proteins; C030325:anthrax toxin; C055966:immunoglobulin Fv