Characterization of the binding-patterns underlying the cytoadhesion of Plasmodium falciparum infected erythrocytes (POP-WS)

Abstract text

Despite the advances in malaria control programs, malaria remains one of the most detrimental infectious diseases worldwide. In 2020, about 241 million cases of malaria were recorded, leading to 627,000 deaths. Infection with Plasmodium falciparum is the main cause of death among malaria patients. Therefore, developing new therapeutic strategies is needed to lower the burden of this infection.

A major difficulty in developing treatments and vaccines against P. falciparum malaria is the parasites" ability to switch the expression of antigens presented on the surface of infected erythrocytes (iEs). These antigens not only allow the iEs to evade recognition by the immune system but also to adhere to each other and the endothelium of blood vessels. Cytoadhesion is mediated primarily by members of the P. falciparum erythrocyte membrane protein 1 (PfEMP1) family, encoded by approximately 60 var genes per parasite genome. At least 24 endothelial cell receptors (ECRs) have been described as binding partners for iEs, including CD36, ICAM-1, and EPCR. PfEMP1s are mutually exclusively expressed and randomly switched with a frequency of 0.025–3 % per replication cycle to evade detection by the immune system.

Until recently, this has been a major challenge in studying PfEMP1-mediated cytoadhesion. We now established a method to generate transfectants that express only the var gene of interest and therefore present the corresponding PfEMP1 population on the surface of iEs, through the selection-linked integration (SLI) approach. With a library of SLI-var transfectants, it is now possible to further characterize endothelial binding partners in static- and flow adhesion assays as well as using single cell force spectroscopy. Static binding assays with transgenic CHO cells presenting ECRs on the surface and with parasite transfectants presenting Var01 or Var16 have already led to the identification of the novel binding partners (e.g. TNFR2, VCAM-1, and P-selectin). The use of shear stress in an in vitro flow system has been shown to play a key role, as some receptor-ligand pairs form so-called slip-bonds, which only bind if shear force is applied. One such receptor might be ICAM-1, whereas binding to this receptor correlates with the development of severe malaria.