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Abstract

Plasmodium falciparum infected erythrocytes are able to bind to a multitude of extracellular receptors through adhesins expressed on their membrane. The molecular interactions involved in parasite binding to these receptors are only partly understood, although the trait itself is well-known and used as an early indicator of severe malaria diagnosis and progress of infection. Binding to the microvasculature of blood vessels or the intervillous spaces of the placenta, ensures the survival of the parasite as it avoids splenic clearance in the later stages of maturation. In this thesis, the importance of sheer flow and cell morphology in binding dynamics of parasitized erythrocytes is further highlighted. While static adhesion assays would showcase similar amounts of cells adhering in different maturation stages, when observed in flow, this picture changes drastically. Trophozoite stage parasites seem to bind less frequently but more efficiently onto the simulated endothelium. In the last stage of maturation, schizont stage parasites alter the cell morphology to such an extent that adhesion is more likely but with less contact area and density of involved receptors. Changes in the membrane morphology between AA and AS erythrocytes also underline the significance of receptor presentation and accessibility influencing binding efficiency. The effects of a P. falciparum infection during primigravida are threatening to both the mother and the foetus, as infected erythrocytes sequester to the maternal side of the syncytiotrophoblast that lines the placenta. Despite the tremendous efforts in the field, the adhesive tropism of infected erythrocytes that leads to placental sequestration remains unsolved. In this thesis, I determined that measurements are not possible without the full length protein and interactions between the receptor and its erythrocyte-expressed ligand are not specific enough to distinguish from negative control experiments. Another form of cell adhesion investigated in this thesis is the formation of so-called rosettes, that form when an infected erythrocyte binds to non-infected erythrocytes. Rosette formation is considered either an indication of severe malaria or a symptom of progressed infection and is believed to propagate the severity of infection by obstructing smaller vasculature and normal blood flow. in this thesis, I developed a platform to study the position of rosettes within a channel in flow, in order to determine their margination tendance. In those experiments, I verified that regardless of haematocrit value and size of rosette, rosettes remain in flow and do not marginate towards the walls of the flow chamber.