Heterotypic interactions drive antibody synergy against a malaria vaccine candidate

Robert J Ragotte,Daniel G W Alanine,Paul W Bowyer,Edward D Lowe,David Pulido,Hannah Davies,Adéla Nacer,Matthew K Higgins,Elspeth F Garman,Geoffrey W Grime,Doris Quinkert,Abhishek Jamwal,Amelia M Lias,Robert F Donat,Simon J Draper,Joseph J Illingworth

doi:10.1038/s41467-022-28601-4

Abstract

Understanding mechanisms of antibody synergy is important for vaccine design and antibody cocktail development. Examples of synergy between antibodies are well-documented, but the mechanisms underlying these relationships often remain poorly understood. The leading blood-stage malaria vaccine candidate, CyRPA, is essential for invasion of Plasmodium falciparum into human erythrocytes. Here we present a panel of anti-CyRPA monoclonal antibodies that strongly inhibit parasite growth in in vitro assays. Structural studies show that growth-inhibitory antibodies bind epitopes on a single face of CyRPA. We also show that pairs of non-competing inhibitory antibodies have strongly synergistic growth-inhibitory activity. These antibodies bind to neighbouring epitopes on CyRPA and form lateral, heterotypic interactions which slow antibody dissociation. We predict that such heterotypic interactions will be a feature of many immune responses. Immunogens which elicit such synergistic antibody mixtures could increase the potency of vaccine-elicited responses to provide robust and long-lived immunity against challenging disease targets.

Highlights

Understanding mechanisms of antibody synergy is important for vaccine design and antibody cocktail development
Seven new chimeric anti-cysteinerich protective antigen (CyRPA) monoclonal antibodies (mAbs) were produced through immunization of chickens (Cy.[003], Cy.004, Cy.[007], and Cy.009) and mice (Cy.[002], Cy.005, and Cy.010), the former using HybriFree technology[21] to clone the variable domains of antiCyRPA IgY mAbs, and the latter using Sp2/0 hybridomas from which the variable domains were sequenced and synthesized
We describe our detailed characterization of a panel of monoclonal antibodies targeting the essential and highly conserved blood-stage malaria vaccine candidate antigen CyRPA, with the aim of using the insight gained to guide the design of improved CyRPA-based vaccine immunogens

Summary

Introduction

Understanding mechanisms of antibody synergy is important for vaccine design and antibody cocktail development. We show that pairs of non-competing inhibitory antibodies have strongly synergistic growth-inhibitory activity These antibodies bind to neighbouring epitopes on CyRPA and form lateral, heterotypic interactions which slow antibody dissociation. For antibodies against antigens with repeated structures, synergy can occur through homotypic interactions between copies of the same antibody that bind to neighbouring repeated epitopes Such interactions can drive enhanced B cell activation, as seen in the case of antibodies targeting the sporozoite-stage malaria vaccine antigen, PfCSP10–12. The leading vaccine candidates for a P. falciparum blood-stage malaria vaccine are members of a heterotrimeric complex containing reticulocyte-binding protein homolog 5 (RH5), cysteinerich protective antigen (CyRPA), and RH5-interacting protein (RIPR), collectively called the “RCR complex”[15] Each member of this complex is highly conserved, essential for erythrocyte invasion, and capable of inducing cross-strain neutralizing antibodies[16–18]

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