Structure-guided design of a synthetic mimic of an endothelial protein c receptor-binding PfEMP1 protein

DOI: 10.1128/mSphere.01081-20

Authors: Natalie M. Barber (University of Oxford) , Clinton K. Y. Lau (University of Oxford) , Louise Turner (University of Copenhagen) , Gareth Watson (University of Oxford) , Susan Thrane (University of Copenhagen) , John P. A. Lusingu (National Institute for Medical Research, Tanzania) , Thomas Lavstsen (University of Copenhagen) , Matthew K. Higgins (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Msphere , VOL 6

State: Published (Approved)
Published: February 2021

Abstract: Structure-guided vaccine design provides a route to elicit a focused immune response against the most functionally important regions of a pathogen surface. This can be achieved by identifying epitopes for neutralizing antibodies through structural methods and recapitulating these epitopes by grafting their core structural features onto smaller scaffolds. In this study, we conducted a modified version of this protocol. We focused on the PfEMP1 protein family found on the surfaces of erythrocytes infected with Plasmodium falciparum. A subset of PfEMP1 proteins bind to endothelial protein C receptor (EPCR), and their expression correlates with development of the symptoms of severe malaria. Structural studies revealed that PfEMP1 molecules present a helix-kinked-helix motif that forms the core of the EPCR-binding site. Using Rosetta-based design, we successfully grafted this motif onto a three-helical bundle scaffold. We show that this synthetic binder interacts with EPCR with nanomolar affinity and adopts the expected structure. We also assessed its ability to bind to antibodies found in immunized animals and in humans from malaria-endemic regions. Finally, we tested the capacity of the synthetic binder to effectively elicit antibodies that prevent EPCR binding and analyzed the degree of cross-reactivity of these antibodies across a diverse repertoire of EPCR-binding PfEMP1 proteins. Despite our synthetic binder adopting the correct structure, we find that it is not as effective as the CIDRα domain on which it is based for inducing adhesion-inhibitory antibodies. This cautions against the rational design of focused immunogens that contain the core features of a ligand-binding site of a protein family, rather than those of a neutralizing antibody epitope.

Subject Areas: Biology and Bio-materials, Chemistry


Instruments: I02-Macromolecular Crystallography

Documents:
mSphere-2021-Barber-e01081-20.full.pdf

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