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A coiled conformation of amyloid-? recognized by antibody C706.

ABSTRACT: BACKGROUND:?-Amyloid (A?) peptide is believed to play a pivotal role in the development of Alzheimer's disease. Passive immunization with anti-A? monoclonal antibodies may facilitate the clearance of A? in the brain and may thus prevent the downstream pathology. Antibodies targeting the immunodominant N-terminal epitope of A? and capable of binding both the plaques and soluble species have been most efficacious in animal models. Structural studies of such antibodies with bound A? peptides provided the basis for understanding the mechanisms of action and the differences in potency. To gain further insight into the structural determinants of antigen recognition and the preferential A? conformations, we determined the crystal structure of murine antibody C706 in complex with the N-terminal A? 1-16 peptide sequence. METHODS:The antigen-binding fragment of C706 was expressed in HEK293 cells and was crystallized in complex with the A? peptide. The X-ray structure was determined at 1.9-Å resolution. RESULTS:The binding epitope of C706 is centered on residues Arg5 and His6, which provide the majority of interactions. Unlike most antibodies, C706 recognizes a coiled rather than extended conformation of A?. CONCLUSIONS:Comparison with other antibodies targeting the N-terminal section of A? suggests that the conformation of the bound peptide may be linked to the immunization protocol and may reflect the preference for the extended conformation in the context of a longer A? peptide as opposed to the coiled conformation in the isolated short peptide.

SUBMITTER: Teplyakov A

PROVIDER: S-EPMC5568176 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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A coiled conformation of amyloid-β recognized by antibody C706.

Teplyakov Alexey A Obmolova Galina G Gilliland Gary L GL

Alzheimer's research & therapy 20170822 1

<h4>Background</h4>β-Amyloid (Aβ) peptide is believed to play a pivotal role in the development of Alzheimer's disease. Passive immunization with anti-Aβ monoclonal antibodies may facilitate the clearance of Aβ in the brain and may thus prevent the downstream pathology. Antibodies targeting the immunodominant N-terminal epitope of Aβ and capable of binding both the plaques and soluble species have been most efficacious in animal models. Structural studies of such antibodies with bound Aβ peptide ...[more]

PMID: 28830506

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Project description:IntroductionImmunotherapy targeting amyloid-β peptide is under active clinical investigation for treatment of Alzheimer's disease (AD). Among the hypotheses being investigated for impact on clinical outcome are the preferred epitope or conformation of amyloid-β to target for treatment, and the mechanism of action underlying immunotherapy. Bapineuzumab (humanized 3D6), a neo-epitope specific antibody recognizing amyloid-β1-5 with strong preference for an exposed Asp residue at the N-terminus of the peptide, has undergone advanced clinical testing for treatment of AD.MethodsTo gain further insight into the epitope conformation, we interrogated structural details of amino-terminal epitopes in amyloid-β using x-ray crystallography of 3D6Fab:amyloid-β complexes. Humanization of 3D6 was carried out using standard procedures integrating recombinant methods, sequence informatics, and homology modeling predictions to identify important mouse framework residues for retention in the finished humanized product.ResultsHere we report the crystal structure of a recombinant Fab fragment of 3D6 in complex with amyloid-β1-7 solved at 2.0 Å resolution. The N-terminus of amyloid-β is bound to 3D6 as a 310 helix. The amino-terminal Asp residue is buried deepest in the antibody binding pocket, with the Cβ atom of residue 6 visible at the entrance to the binding pocket near the surface of the antibody. We further evaluate homology model based predictions used to guide humanization of 3D6 to bapineuzumab, with actual structure of the Fab. The structure of the Fab:amyloid-β complex validates design of the humanized antibody, and confirms the amyloid-β epitope recognized by 3D6 as previously mapped by ELISA.ConclusionsThe conformation of amyloid-β antigen recognized by 3D6 is novel and distinct from other antibodies recognizing N-terminal epitopes. Our result provides the first report demonstrating structural conservation of antigen contact residues, and conformation of antigen recognized, between the parent murine antibody and its humanized version.

Dataset Information

A coiled conformation of amyloid-? recognized by antibody C706.

Publications

A coiled conformation of amyloid-β recognized by antibody C706.

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