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Title: An investigation of the function of human IgM and IgG antibodies recognizing P. falciparum erythrocyte membrane protein 1 (PfEMP1)
Author: Ghouma, S. M.
ISNI:       0000 0004 7428 7323
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2018
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Glycosylation in the Fc region of IgG has been widely studied in health and disease. The Nglycans in the identical heavy chains have been shown to be critical for maintaining structural integrity, binding with the Fc receptors, and the downstream immunological response. Although, the IgM molecule is the most glycosylated antibody in humans, less is known about it and its ability to interact with glycan receptors. Thus, in the first part of this thesis, we aimed to identify novel glycan receptors for human IgM (hIgM) and characterize this binding. A panel of seventeen glycan receptors were investigated for their ability to bind hIgM. For the first time, Siglec-1 has been determined as a novel receptor for hIgM. A characteristic feature of malaria infection caused by P. falciparum is the cytoadherence of infected erythrocytes to the microvasculature of the host vital organs. This cytoadherence is mediated mainly through the binding of P. falciparum erythrocyte membrane protein-1 (PfEMP1) proteins expressed on the surface of infected erythrocytes to non-infected erythrocytes and different endothelial host receptors such as intracellular adhesion molecule 1 (ICAM-1). The PfEMP1/ICAM-1 interactions are hypothesized as an important virulence factor in cerebral malaria and blocking of these interactions with recombinant antibodies is an attractive option for attenuating sequestration and thereby severity of disease (Smith et al., 2000a). In the laboratories of Professor Alister Craig and Professor Richard Pleass, a panel of mouse monoclonal antibodies targeting DBLß domains from PfEMP1 were developed from hybridoma technology. However, one of the main limitations of using these hybridomaderived monoclonal antibodies is that human-anti-mouse antibody (HAMA) responses can occur as a result of the human immune system seeing mouse antibodies as foreign. Thus, it is critical to convert mouse antibodies into human-mouse chimeric form for human therapeutic applications that maintain their binding affinity towards targeted antigens. So, in the second part of this thesis, we have aimed to develop chimeric human/mouse IgG1 and IgM antibodies against DBLß domain of PfEMP1 protein. Both variable domains of mouse IgM antibodies have been cloned from productive hybridoma clone (E11) and were grafted to human IgG1 and IgM constant domains in suitable expression vectors. Mammalian cells were transfected with these plasmids to express and produce recombinant human chimeric antibodies specific for DBLß domain of PfEMP1 protein. The generation of anti-DBLß chimeric antibodies was challenging, and ultimately not successful. Further work is required to produce intact antibodies that could be used as therapeutic agent for cerebral malaria.
Supervisor: Pleass, Richard Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral