Structure and Characterisation of a Key Epitope in the Conserved C-Terminal Domain of the Malaria Vaccine Candidate MSP2

Seow, Jeffrey and Morales, Rodrigo AV and MacRaild, Christopher A and Krishnarjuna, Bankala and McGowan, Sheena and Dingjan, Tamir and Jaipuria, Garima and Rouet, Romain and Wilde, Karyn L and Atreya, Hanudatta S and Richards, Jack S and Anders, Robin F and Christ, Daniel and Drinkwater, Nyssa and Norton, Raymond S (2017) Structure and Characterisation of a Key Epitope in the Conserved C-Terminal Domain of the Malaria Vaccine Candidate MSP2. In: JOURNAL OF MOLECULAR BIOLOGY, 429 (6). pp. 836-846.

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Abstract

Merozoite surface protein 2 (MSP2) is an intrinsically disordered antigen that is abundant on the surface of the malaria parasite Plasmodium falciparum. The two allelic families of MSP2, 3D7 and FC27, differ in their central variable regions, which are flanked by highly conserved C-terminal and N-terminal regions. In a vaccine trial, full-length 3D7 MSP2 induced a strain-specific protective immune response despite the detectable presence of conserved region antibodies. This work focuses on the conserved C-terminal region of MSP2, which includes the only disulphide bond in the protein and encompasses key epitopes recognised by the mouse monoclonal antibodies 4D11 and 9H4. Although the 4D11 and 9H4 epitopes are overlapping, immunofluorescence assays have shown that the mouse monoclonal antibody 4D11 binds to MSP2 on the merozoite surface with a much stronger signal than 9H4. Understanding the structural basis for this antigenic difference between these antibodies will help direct the design of a broad-spectrum and MSP2-based malaria vaccine. 4D11 and 9H4 were reengineered into antibody fragments variable region fragment (Fv) and single-chain Fv (scFv)] and were validated as suitable models for their full-sized IgG counterparts by surface plasmon resonance and isothermal titration calorimetry. An alanine scan of the 13-residue epitope 3D7-MSP2(207-222) identified the minimal binding epitope of 4D11 and the key residues involved in binding. A 2.2-angstrom crystal structure of 4D11 Fv bound to the eight-residue epitope NKENCGAA provided valuable insight into the possible conformation of the C-terminal region of MSP2 on the parasite. This work underpins continued efforts to optimise recombinant MSP2 constructs for evaluation as potential vaccine candidates. (C) 2017 Elsevier Ltd. All rights reserved.

Item Type:	Journal Article
Publication:	JOURNAL OF MOLECULAR BIOLOGY
Publisher:	ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND
Additional Information:	Copy right for this article belongs to the ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 24-28 OVAL RD, LONDON NW1 7DX, ENGLAND
Department/Centre:	Division of Chemical Sciences > NMR Research Centre (Formerly Sophisticated Instruments Facility)
Date Deposited:	20 May 2017 05:02
Last Modified:	26 Feb 2019 06:24
URI:	http://eprints.iisc.ac.in/id/eprint/56877

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