Molecular basis for the role of Ripr in Plasmodium falciparum invasion of human erythrocytes

Abstract

Plasmodium falciparum causes the majority of severe malaria, and merozoite invasion of erythrocytes is a vulnerable, antibody-accessible step of the blood-stage cycle. PfRipr is an essential component of the PCRCR invasion complex, yet the structural basis for antibody-mediated neutralisation remains unclear. Here, we map inhibitory and non-inhibitory epitopes across PfRipr and show that all potent inhibitors localise to the tail region (EGF6-8). Crystal structures reveal that inhibitory antibodies restrict the flexibility surrounding EGF7. Indeed, EGF7 buried surface area correlates strongly with inhibitory potency, identifying this domain as the principal invasion-inhibitory determinant. Pairwise antibody combinations revealed unexpected synergy, with non-inhibitory mAbs potentiating anti-Rh5 activity. Conditional deletion, sequence replacement or positional swapping of EGF6-8 abolished invasion, demonstrating that both sequence and spatial arrangement are indispensable. These data define EGF7 as a conserved, functionally essential vulnerability and provide a blueprint for rational EGF6-8 immunogen design capable of eliciting P. falciparum strain-transcending protection against blood-stage malaria.