PHD thesis defense Nuno Gomes Graça

On 20 May 2021 (10:00) Nuno Gomes Graça will defend his thesis 'A suit of armor around ADAMTS13 -Exploring paths towards resistance against autoantibodies of immune TTP patients'. Nuno created mutants of the protein ADAMTS13 that retain high levels of activity but resist binding of the autoantibodies. These could impact future treatment of TTP.

In autoimmune Thrombotic Thrombocytopenic Purpura (iTTP), ADAMTS13 activity is lost due to antibodies which neutralize and/or clear the protein from circulation. The consequences of this rare disease are dramatic if left untreated (high fatality rates). Survival has relied on plasma-exchange and immunosuppression, strategies that have failed to improve long-term morbidity so far. The 100th anniversary of the first TTP case described in literature is approaching. Knowledge surrounding this disease has seen great transformations recently.

In Chapter 1, a historical perspective, with a focus on current TTP patient management and unmet medical needs is presented. In Chapter 2 we focus on iTTP and its pathophysiology in greater depth, in a more thorough review which serves as a complement to Chapter 1.

In Chapter 3 we investigate the spacer domain of ADAMTS13 as the most prevalent ADAMTS13 epitope target. We show that beyond the classic epitope on exosite-3 (R568/F592/R660/Y661/Y665), the spacer domain has several hotspots targeted by the polyclonal autoantibodies’ mixtures of iTTP patients.

In Chapter 4 the classic ADAMTS13 spacer domain exosite-3 epitope is explored with 4 types of mutations (highly-conservative, semi-conservative, non-conservative and classic alanine scans) to assess impact on both autoantibody binding and ADAMTS13 activity simultaneously. The most conservative mutations tend to keep both binding and activity, while the less conservative mutations abrogate both.

One of the main goals has been to find ADAMTS13 mutants that resist binding of autoantibodies, but retain high levels of activity. In Chapter 5 we show that by inserting an artificial N-glycan site into one of the spacer domain epitope hotspots found in Chapter 3, we can create such an “ideal” variant. The impact of this finding in the future treatment of this disease is considered.

In Chapter 6 we present another way in which the ADAMTS13 conformational status may be altered. Prior work shows that an open conformation is achieved by disrupting the spacer-CUB1/2 interactions through conservative mutations in the classic spacer exosite-3 epitope. In this bioinformatics-driven study, we show evidence that for certain mutations of CUB1/2 this is also the case. The implications of these basic findings may help to explain some phenomena observed in certain clinical contexts, and are placed in perspective.An in-depth discussion of the contents of this thesis is presented in Chapter 7.

Promotores:  J.J. Voorberg, K. Vanhoorelbeke

Co-promotores: A. Männik, G.A.F. Nicolaes

Venue:  University  of Amsterdam, Agnietenkapel and online