In vitro selection for adhesion of Plasmodium falciparum-infected erythrocytes to ABO antigens does not affect PfEMP1 and RIFIN expression

William Van Der Puije,Trine Staalsoe,Jørgen A L Kurtzhals,Christian W Wang,Srinidhi Sudharson,Nanna Dalgaard,Michael F Ofori,Lars Hviid,Rebecca W Olsen,Casper Hempel

doi:10.1038/s41598-020-69666-9

Abstract

Plasmodium falciparum causes the most severe form of malaria in humans. The adhesion of the infected erythrocytes (IEs) to endothelial receptors (sequestration) and to uninfected erythrocytes (rosetting) are considered major elements in the pathogenesis of the disease. Both sequestration and rosetting appear to involve particular members of several IE variant surface antigens (VSAs) as ligands, interacting with multiple vascular host receptors, including the ABO blood group antigens. In this study, we subjected genetically distinct P. falciparum parasites to in vitro selection for increased IE adhesion to ABO antigens in the absence of potentially confounding receptors. The selection resulted in IEs that adhered stronger to pure ABO antigens, to erythrocytes, and to various human cell lines than their unselected counterparts. However, selection did not result in marked qualitative changes in transcript levels of the genes encoding the best-described VSA families, PfEMP1 and RIFIN. Rather, overall transcription of both gene families tended to decline following selection. Furthermore, selection-induced increases in the adhesion to ABO occurred in the absence of marked changes in immune IgG recognition of IE surface antigens, generally assumed to target mainly VSAs. Our study sheds new light on our understanding of the processes and molecules involved in IE sequestration and rosetting.

Highlights

Malaria remains a major cause of infectious disease mortality and morbidity in many parts of the World[1]
Whereas unselected erythrocytes infected by P. falciparum 3D7 bound only weakly to any of these antigens, selection for infected erythrocytes (IEs) adhesion to either bovine serum albumin (BSA)-A or BSA-B resulted in IEs that bound significantly better to both receptors, whereas selection for IE adhesion to BSA-H had little effect (Fig. 1)
Selection of four additional P. falciparum lines/clones yielded results similar to those obtained with 3D7 for two of them (FMG and FUP), whereas we were unable to improve the adhesion to blood group sugars of erythrocytes infected by P. falciparum FCR3 or HB3 (Supplementary Fig. 1)

Summary

Introduction

Malaria remains a major cause of infectious disease mortality and morbidity in many parts of the World[1]. Particular members of the three major parasite multi-gene families var (P. falciparum only)[14,15,16], rif[17,18], and stevor[19] have been implicated as ligands, while a range of glycoproteins, proteoglycans, and carbohydrate moieties on the erythrocyte surface have been proposed as host receptors. These latter molecules include the blood group determinants A and B 20, CD3621,22, heparan sulphate[23], complement receptor 1 (CR1)[14], and glycophorin C19,24. We selected IEs for their ability to adhere to blood group A, B and O blood group oligosaccharides in vitro by repeated panning on these antigens immobilized to plastic via bovine serum albumin, and examined associated changes in transcription of parasite genes encoding putative adhesion ligands

Methods

Results

Conclusion