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Nat Biotechnol. 2007 Jan;25(1):107-16. Epub 2006 Dec 17.

Molecular evolution of antibody cross-reactivity for two subtypes of type A botulinum neurotoxin.

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  • 1Department 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.

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 A, 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.

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PMID:
17173035
[PubMed - indexed for MEDLINE]
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