RESUMEN
Apical membrane antigen-1 (AMA1) is a conserved malarial vaccine candidate essential for the formation of tight junctions with the rhoptry neck protein (RON) complex, enabling Plasmodium parasites to invade human erythrocytes, hepatocytes, and mosquito salivary glands. Despite its critical role, extensive surface polymorphisms in AMA1 have led to strain-specific protection, limiting the success of AMA1-based interventions beyond initial clinical trials. Here, we identify an i-body, a humanised single-domain antibody-like molecule that recognises a conserved pan-species conformational epitope in AMA1 with low nanomolar affinity and inhibits the binding of the RON2 ligand to AMA1. Structural characterisation indicates that the WD34 i-body epitope spans the centre of the conserved hydrophobic cleft in AMA1, where interacting residues are highly conserved among all Plasmodium species. Furthermore, we show that WD34 inhibits merozoite invasion of erythrocytes by multiple Plasmodium species and hepatocyte invasion by P. falciparum sporozoites. Despite a short half-life in mouse serum, we demonstrate that WD34 transiently suppressed P. berghei infections in female BALB/c mice. Our work describes the first pan-species AMA1 biologic with inhibitory activity against multiple life-cycle stages of Plasmodium. With improved pharmacokinetic characteristics, WD34 could be a potential immunotherapy against multiple species of Plasmodium.
Asunto(s)
Antígenos de Protozoos , Eritrocitos , Hígado , Proteínas de la Membrana , Ratones Endogámicos BALB C , Proteínas Protozoarias , Animales , Proteínas Protozoarias/inmunología , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , Antígenos de Protozoos/inmunología , Antígenos de Protozoos/metabolismo , Femenino , Proteínas de la Membrana/inmunología , Proteínas de la Membrana/metabolismo , Ratones , Humanos , Eritrocitos/parasitología , Eritrocitos/inmunología , Hígado/parasitología , Hígado/inmunología , Hígado/metabolismo , Vacunas contra la Malaria/inmunología , Malaria/inmunología , Malaria/parasitología , Malaria/prevención & control , Reacciones Cruzadas/inmunología , Plasmodium falciparum/inmunología , Plasmodium berghei/inmunología , Epítopos/inmunología , Hepatocitos/parasitología , Hepatocitos/inmunología , Hepatocitos/metabolismo , Plasmodium/inmunología , Merozoítos/inmunología , Merozoítos/metabolismoRESUMEN
Apicomplexan parasites are aetiological agents of numerous diseases in humans and livestock. Functional genomics studies in these parasites enable the identification of biological mechanisms and protein functions that can be targeted for therapeutic intervention. Recent improvements in forward genetics and whole-genome screens utilising CRISPR/Cas technology have revolutionised the functional analysis of genes during Apicomplexan infection of host cells. Here, we highlight key discoveries from CRISPR/Cas9 screens in Apicomplexa or their infected host cells and discuss remaining challenges to maximise this technology that may help answer fundamental questions about parasite-host interactions.
