Function of the Rh5 complex in invasion of human erythrocytes

The most severe form of malaria is caused by Plasmodium falciparum. These parasites invade human erythrocytes and an essential step in this process involves the ligand PfRh5, which forms a complex with CyRPA and PfRipr (RCR complex) and binds basigin on the host cell. We identified a heteromeric disulphide-linked complex consisting of PfPTRAMP and PfCSS and have shown it binds RCR to form a pentameric complex PCRCR. Using P. falciparum lines with conditional knockouts and invasion inhibitory nanobodies to both PfPTRAMP and PfCSS we utilised lattice light-sheet microscopy and show they are essential for merozoite invasion. The PCRCR complex functions to anchor the contact between merozoite and erythrocyte membranes brought together by strong parasite deformations. We solved the structure of nanobody/PfCSS complexes to identify an inhibitory epitope. Our results define the function of the PCRCR complex and identify invasion neutralising epitopes providing a roadmap for structure-guided development of these proteins for a blood stage malaria vaccine.