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Title: Plasmodium falciparum infected erythrocyte induced modulation of host endothelial cells
Author: Othman, Basim Ahmed
ISNI:       0000 0004 6496 5194
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
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Cerebral malaria is one of the complications of the broad clinical syndrome named 'severe malaria'. The pathogenesis of cerebral malaria is thought to be due to the ability of infected red blood cell (iRBC) to sequester in the blood microvasculature of vital organs. Sequestration, resulting from the interaction (often called cytoadherence) between parasite proteins expressed on the surface of iRBC such as PfEMP-1, and host endothelial cell adhesion molecules such as ICAM-1, CD36 and EPCR, can modulate the downstream effects of several biological processes in the endothelial cells such as EC activation, intracellular signalling, endothelial cell permeability and endothelial apoptosis. The aim of this thesis is to gain a better understanding of how the P. falciparum parasite can modulate the gene expression of the host endothelial cells response to cytoadherence using the RNA-seq technique. We used an in vitro co-culture model of IT4var14 strain with HBMEC in the presence of 10ng/ml TNF. RNA-seq analysis of HBMEC transcriptome following co-culture showed significant differential regulation of genes which defined gene ontologies such as 'immune system' at 2 hours, 'immune response', 'arachidonic acid', 'positive and negative apoptotic pathways' at 6 hours, and 'immune response' and 'cell cycle pathways' at 20 hours of co-incubation. However, another co-culture model using IT4var37 isolate with HBMEC in the presence of TNF found that exposure of HBMEC to iRBC expressed genes in brain EC often in opposite levels compared to the IT4var14 strain under the same condition. These findings emphasize the ability of different PfEMP-1 variants from the same genetic background (IT4) to modulate different gene expression in host cells, and also the potential ability of the malaria parasite to use PfEMP-1 var gene switching technique to protect itself from the host defensive system. We conducted further co-culture experiments to assess the ability of IT4var14 parasite to modulate the transcriptional levels of different endothelial cells (HDMEC and HBMEC) that differentially express ICAM-1 and CD36 receptors; we demonstrated that there are similarities and differences in gene expression between TNF-stimulated HDMEC and HBMEC exposed to IT4var14 strain, which might be due to ICAM-1 expression in both ECs but the lack of CD36 on HBMEC, leading to the transduction of different signalling pathways in HDMEC and HBMEC. The ability of TNF stimulation in modulating the expression of genes in HBMEC exposed to IT4var14 parasite isolate, and uninfected erythrocytes on endothelium has also been examined in this study. It was found that the TNF plays a role in mediating the gene expression in human brain EC incubated with IT4var14 strain and uninfected RBC, this might be due to stimulation of TNF to HBMEC to induce expression of ICAM-1. These results are presented and discussed in the thesis with an aim to better understanding of the CM syndrome and the potential to lead to the discovery and development of new therapies for cerebral malaria.
Supervisor: Craig, A. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral