Towards novel therapies of iTTP Defining and shielding of antibody epitopes on ADAMTS13

Immune thrombotic thrombocytopenic purpura (iTTP) is characterized by the loss of ADAMTS13 activity due to pathogenic auto-antibodies. While a lot of progress has been made in the understanding and treatment of iTTP, much remains unknown about the development and functional impact of these auto-antibodies. This thesis aims to increase our understanding of iTTP, by investigating the antibody response against ADAMTS13.
Firstly, we focus on the characterization of antibodies that target the CUB domain of ADAMTS13. Here, we define the properties of anti-CUB domain antibodies that develop in patients with iTTP. We identified key residues in the CUB1 and CUB2 domain of ADAMTS13 that contribute to the binding sites of anti-CUB antibodies that develop in patients with iTTP. Additionally, we shed light on the effects of anti-CUB antibodies on the activity and conformation of ADAMTS13.
Next, we strategically introduced N-glycans in the spacer and CUB domains around the immunogenic hotspots on ADAMTS13. These N-glycans reduced the binding of the antibodies that are present in the plasma of patients with iTTP, resulting in an increase in the proteolytic activity of ADAMTS13.
Lastly, we study sites on ADAMTS13 that are citrullinated by PAD4, and assess the effect of these modifications on ADAMTS13 activity. Furthermore, the proteomic landscape of patients with iTTP that experienced an ADAMTS13 relapse was studied. Our results show that while these patients do not display a clinical relapse, we still observe signatures of increased hemolysis, clot formation, and organ damage, highlighting the need for earlier intervention.