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Phagocytosis of Plasmodium falciparum ring-stage parasites predicts protection against malaria

ABSTRACT: Ring-infected erythrocytes are the predominant asexual stage in the peripheral circulation but are rarely investigated in the context of acquired immunity against Plasmodium falciparum malaria. Here we compare antibody-dependent phagocytosis of ring-infected parasite cultures in samples from a controlled human malaria infection (CHMI) study (NCT02739763). Protected volunteers did not develop clinical symptoms, maintained parasitaemia below a predefined threshold of 500 parasites/μl and were not treated until the end of the study. Antibody-dependent phagocytosis of both ring-infected and uninfected erythrocytes from parasite cultures was strongly correlated with protection. A surface proteomic analysis revealed the presence of merozoite proteins including erythrocyte binding antigen-175 and -140 on ring-infected and uninfected erythrocytes, providing an additional antibody-mediated protective mechanism for their activity beyond invasion-inhibition. Competition phagocytosis assays support the hypothesis that merozoite antigens are the key mediators of this functional activity. Targeting ring-stage parasites may contribute to the control of parasitaemia and prevention of clinical malaria.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Plasmodium Falciparum (isolate 3d7)

DISEASE(S): Plasmodium Falciparum Malaria

SUBMITTER: James Tuju

LAB HEAD: Prof Faith Osier

PROVIDER: PXD033964 | Pride | 2022-08-11

REPOSITORIES: Pride

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Phagocytosis of Plasmodium falciparum ring-stage parasites predicts protection against malaria.

Musasia Fauzia K FK Nkumama Irene N IN Frank Roland R Kipkemboi Victor V Schneider Martin M Mwai Kennedy K Odera Dennis O DO Rosenkranz Micha M Fürle Kristin K Kimani Domitila D Tuju James J Njuguna Patricia P Hamaluba Mainga M Kapulu Melissa C MC Wardemann Hedda H Osier Faith H A FHA

Nature communications 20220714 1

Ring-infected erythrocytes are the predominant asexual stage in the peripheral circulation but are rarely investigated in the context of acquired immunity against Plasmodium falciparum malaria. Here we compare antibody-dependent phagocytosis of ring-infected parasite cultures in samples from a controlled human malaria infection (CHMI) study (NCT02739763). Protected volunteers did not develop clinical symptoms, maintained parasitaemia below a predefined threshold of 500 parasites/μl and were not ...[more]

PMID: 35835738

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Project description:Cerebral malaria is the most deadly manifestation of infection with Plasmodium falciparum. The pathology of cerebral malaria is characterised by the accumulation of infected erythrocytes in the microvasculature of the brain, due to parasite adhesins on the surface of infected erythrocytes binding to human receptors on microvascular endothelial cells. The parasite and host molecules involved in this interaction are unknown. We used the Human Brain Endothelial Cell line HBEC-5i to identify the malaria parasite ligands responsible for binding to human brain endothelial cells. Three P. falciparum strains (HB3, 3D7 and IT/FCR3) were selected for binding to HBEC5i and the whole transcriptome of selected and unselected parasites was analysed using a variant surface antigen-supplemented microarray chip. After selection, the only highly upregulated genes were a subset of group A-like var genes (HB3var3, 3D7_PFD0020c, ITvar7 and ITvar19), that showed 11 to >100-fold higher transcription levels in selected parasites. These genes are highly diverse in sequence, but do however show strong similarities in PfEMP1 architecture. Antibodies raised to the HB3var3 variant recognized the surface of infected erythrocytes and abolished the binding of infected erythrocytes to brain endothelial cells. The subset of Group A PfEMP1 variants identified here provides a new target for interventions to treat or prevent cerebral malaria. Unselected Plasmodium falciparum parasites (Uns) only poorly cytoadhere to human brain endothelial cells (HBEC-5i). Plasmodium falciparum HB3, 3D7 and IT/FCR3 strains were selected for binding to HBEC-5i (HB3-HBEC1, HB3-HBEC2, HB3-HBEC-TNF, 3D7-HBEC and IT-HBEC). HBEC-selected and unselected cultures were tightly synchronised before a timecourse experiment was performed. 6 samples, named time points 1 to 6, were taken every 8 hours. 12μg of RNA from the unselected parasites (HB3-Uns, 3D7-Uns or IT-Uns) at each of the 6 time points was combined together to form the reference pool. The pool and 12μg of each individual time point sample from both selected and unselectedparasites were then used for cDNA synthesis. For HB3-HBEC1 (pilot experiment), each HB3-HBEC1 time point (pilot experiment) was hybridised directly with HB3-Uns1 time points. For microarray hybridizations, each cDNA sample was coupled to Cy5 (red dye) while Cy3 (green dye) was added to the pool. Cy5-labelled time point samples were mixed with the same amount of Cy3-labelled pool sample. The solution was loaded on a microarray slide and hybridized for 14–16 h.

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Dataset Information

Phagocytosis of Plasmodium falciparum ring-stage parasites predicts protection against malaria

Publications

Phagocytosis of Plasmodium falciparum ring-stage parasites predicts protection against malaria.

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