Barber, N. M. | Search bioRxiv

bioRxiv2024

Structure-guided design of a Plasmodium vivax Duffy binding protein-based vaccine immunogen

Plasmodium vivax remains one of the major causative agents of human malaria and a vaccine is urgently required. It is an obligate intracellular parasites and replication within red blood cells is essential for development of disease and for transmission. The interaction between PvDBP on the parasite surface and the DARC receptor on human reticulocytes is essential for a Plasmodium vivax blood stage infection. Human vaccination with the RII region of PvDBP slowed parasite replication, showing that PvDBP is a promising vaccine candidate. However, it did not induce sterile protection, and further development is required to generate a vaccine which protects from clinical malaria. In this study, we develop a vaccine immunogen containing a region of PvDBP-RII, known as subdomain 3, which contains the epitope for a broadly-reactive growth-inhibitory antibody, DB9. We used structure-guided approaches to resurface subdomain 3 such that it folds as an isolated molecule. We show that this engineered subdomain 3 is more stable and more easily produced than PvDBP-RII and induces a more effective growth-inhibitory antibody response. We therefore present an improved PvDBP-based immunogen for use in blood stage vaccines to prevent malaria due to Plasmodium vivax. One sentence summaryStructure-guided design leads to a more effective Duffy-binding protein-based vaccine immunogen to prevent Plasmodium vivax.

immunology↗

bioRxiv2019

Structure-guided design of a synthetic mimic of an EPCR-binding PfEMP1 protein

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 have 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 the PfEMP1 to present a helix-kinked-helix motif which 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 its capacity to effectively elicit antibodies that prevent EPCR binding and analysed the degree of cross-reactivity of these antibodies across a diverse repertoire of EPCR-binding PfEMP1. This provides a case study of immunogen design, assessing the effect of designing a focused immunogen that contains the core features of a ligand binding site, rather than those of a neutralizing antibody epitope.

microbiology↗