Protection against anthrax toxin by recombinant antibody fragments correlates with antigen affinity

• Published in: Nature biotechnology Vol. 20; no. 6; pp. 597 - 601
• Main Authors: Georgiou, George, Maynard, Jennifer A, Maassen, Catharina B.M, Leppla, Stephen H, Brasky, Kathleen, Patterson, Jean L, Iverson, Brent L
• Format: Journal Article
• Language: English
• Published: New York, NY Nature 01.06.2002; Nature Publishing Group
• Subjects: Amino Acid Sequence; Animals; Anthrax - drug therapy; Anthrax - immunology; Antibodies, Bacterial - biosynthesis; Antibodies, Bacterial - genetics; Antibodies, Bacterial - immunology; Antibodies, Monoclonal - administration & dosage; Antibodies, Monoclonal - genetics; Antibody Affinity - immunology; Antigens, Bacterial - drug effects; Antigens, Bacterial - genetics; Antigens, Bacterial - immunology; Bacillus anthracis; Bacillus anthracis - drug effects; Bacillus anthracis - immunology; Bacterial Toxins - immunology; Binding, Competitive - genetics; Binding, Competitive - immunology; Biological and medical sciences; Biotechnology; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation; Health. Pharmaceutical industry; Humans; Immunoglobulin Fragments - genetics; Immunoglobulin Fragments - immunology; Immunoglobulin Fragments - therapeutic use; Immunoglobulin kappa-Chains - genetics; Immunoglobulin kappa-Chains - immunology; Industrial applications and implications. Economical aspects; Mice; Molecular Sequence Data; Monoclonal antibodies; Production of active biomolecules; Protein Binding - genetics; Protein Binding - immunology; Protein Engineering; Rats; Rats, Inbred F344; Recombinant Proteins - administration & dosage; Recombinant Proteins - biosynthesis; Recombinant Proteins - genetics; Bacillus anthracis; Toxin; Bacillales; Biological warfare; Pathogenic; Bacteria; Dissociation constant; Monoclonal antibody; Recombinant protein; Bacillaceae; Passive immunization; Single chain antibody
• ISSN: 1087-0156; 1546-1696
• DOI: 10.1038/nbt0602-597

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.