Generation of Anti-Murine ADAMTS13 Antibodies and Their Application in a Mouse Model for Acquired Thrombotic Thrombocytopenic Purpura.

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy linked to a deficiency in the metalloprotease ADAMTS13. In the current study, a novel mouse model for acquired TTP was generated to facilitate development and validation of new therapies for this disease. Therefore, a large panel (n = 19) of novel anti-mouse ADAMTS13 (mADAMTS13) monoclonal antibodies (mAbs) of mouse origin was generated. Inhibitory anti-mADAMTS13 mAbs were identified using the FRETS-VWF73 assay. Four mAbs strongly inhibited mADAMTS13 activity in vitro (∼68-90% inhibition). Injecting a combination of 2 inhibitory mAbs (13B4 and 14H7, 1.25 mg/kg each) in Adamts13+/+ mice resulted in full inhibition of plasma ADAMTS13 activity (96 ± 4% inhibition, day 1 post injection), leading to the appearance of ultra-large von Willebrand factor (UL-VWF) multimers. Interestingly, the inhibitory anti-mADAMTS13 mAbs 13B4 and 14H7 were ideally suited to induce long-term ADAMTS13 deficiency in Adamts13+/+ mice. A single bolus injection resulted in full ex vivo inhibition for more than 7 days. As expected, the mice with the acquired ADAMTS13 deficiency did not spontaneously develop TTP, despite the accumulation of UL-VWF multimers. In line with the Adamts13-/- mice, TTP-like symptoms could only be induced when an additional trigger (rVWF) was administered. On the other hand, the availability of our panel of anti-mADAMTS13 mAbs allowed us to further develop a sensitive ELISA to detect ADAMTS13 in mouse plasma. In conclusion, a novel acquired TTP mouse model was generated through the development of inhibitory anti-mADAMTS13 mAbs. Consequently, this model provides new opportunities for the development and validation of novel treatments for patients with TTP. In addition, these newly developed inhibitory anti-mADAMTS13 mAbs are of great value to specifically study the role of ADAMTS13 in mouse models of thrombo-inflammatory disease.