Plasmodium falciparum causes the deadliest form of malaria, especially in African children under five years. The parasite and its human host secrete small nanoparticles called extracellular vesicles (EVs) into their extracellular milieu. EVs contain bioactive molecules such as RNA and proteins reflecting that in the secreting cells. However, the biological contents of EVs are not well-characterized in the context of falciparum malaria. EVs are attractive sources of non-invasive biomarkers for diseases affecting inaccessible tissues such as the brain. Analysing the biological content of EVs will provide insights into their functions and could illuminate pathophysiological mechanisms of severe malaria syndromes, including cerebral malaria, respiratory distress, and severe malaria anaemia.
The first part of this thesis aimed to investigate the biological benefit of EVs to the secreting parasite. To achieve this purpose, I sequenced four-hourly RNA samples obtained from EVs secreted by six P. falciparum isolates and compared them to the RNA within the secreting whole parasites. The data suggest parasite-derived EVs might be part of a post-transcriptional gene regulatory mechanism that maintains RNA homeostasis in P. falciparum. The second part of this thesis aimed to understand the pathophysiology of severe malaria complications. To this purpose, I quantified the protein and RNA content of plasma EVs obtained from acute malaria patients. I developed temporal models of disease progression by applying manifold learning to the cross-sectionally collected EV samples. In a parallel approach, I used plasma EV transcriptomes to develop a pseudo-temporal model of cerebral malaria. I determined that cerebral malaria might feature a progressive decrease in neural gene expression and an increase in glial gene expression, which can be followed using peripheral blood EVs. I conclude that EVs are treasure troves of biomarkers that can be used to eavesdrop on biological mechanisms in P. falciparum and its human host.