Research abstract
Article abstract
Nature Biotechnology 25, 107 - 116 (2006)
Published online: 17 December 2006 | doi:10.1038/nbt1269
Molecular evolution of antibody cross-reactivity for two subtypes of type A botulinum neurotoxin
Consuelo Garcia-Rodriguez1,3, Raphael Levy1,3, Joseph W Arndt2, Charles M Forsyth1, Ali Razai1, Jianlong Lou1, Isin Geren1, Raymond C Stevens2 & James D Marks1
Abstract
Broadening antibody specificity without compromising affinity should facilitate detection and neutralization of toxin and viral subtypes. We used yeast display and a co-selection strategy to increase cross-reactivity of a single chain (sc) Fv antibody to botulinum neurotoxin type A (BoNT/A). Starting with a scFv that binds the BoNT/A1 subtype with high affinity (136 pM) and the BoNT/A2 subtype with low affinity (109 nM), we increased its affinity for BoNT/A2 1,250-fold, to 87 pM, while maintaining high-affinity binding to BoNT/A1 (115 pM). To find the molecular basis for improved cross-reactivity, we determined the X-ray co-crystal structures of wild-type and cross-reactive antibodies complexed to BoNT/A1 at resolutions up to 2.6 Å, and measured the thermodynamic contribution of BoNT/A1 and A2 amino acids to wild-type and cross-reactive antibody binding. The results show how an antibody can be engineered to bind two different antigens despite structural differences in the antigen-antibody interface and may provide a general strategy for tuning antibody specificity and cross-reactivity.
- Department of Anesthesia and Pharmaceutical Chemistry, University of California, San Francisco Rm. 3C-38, San Francisco General Hospital, 1001 Potrero Ave., San Francisco, California 94110, USA.
- Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, California 92037, USA.
- These authors contributed equally to this work.
Correspondence to: James D Marks1 e-mail: marksj@anesthesia.ucsf.edu
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