# ADAMTS13 in Bothrops lanceolatus snakebite envenoming: Crude venom-induced reduction of in vitro enzymatic activity and clinical correlation in snakebite patients

## TL;DR

This study shows that Bothrops lanceolatus snake venom reduces ADAMTS13 activity, which may increase the risk of thrombosis in patients.

## Contribution

The first evidence that ADAMTS13 activity is reduced in Bothrops lanceolatus envenoming and its clinical implications.

## Key findings

- B. lanceolatus venom reduces ADAMTS13 activity in vitro in a dose-dependent manner.
- 22% of patients had ADAMTS13 activity below 75%, associated with older age and higher inflammation markers.
- Reduced ADAMTS13 activity may contribute to thrombosis risk and longer hospital stays in envenomed patients.

## Abstract

Envenoming by Bothrops lanceolatus, a viperid endemic to Martinique an island in the Lesser Antilles, induces a unique clinical manifestation, i.e., thrombosis. Pathophysiological signaling leading to thrombotic events remains poorly understood. Among others, proposed mechanisms include increased expression of multimerized forms of von Willebrand factor (VWF). Prothrombotic effects of VWF are regulated by ADAMTS13, a metalloprotease which cleaves VWF multimers. Whether ADAMTS13 activity is reduced in B. lanceolatus envenoming has not been previously investigated.

ADAMTS13 activity was evaluated via chromogenic assay in experimental and clinical studies. Human plasma with known ADAMTS13 activities (0.70 IU/mL) was incubated with increasing doses of B. lanceolatus venom. Incubation with B. lanceolatus venom (concentrations 10–1000 ng/mL) induced a dose-dependent reduction of ADAMTS13 activity. In our series of 46 patients bitten by B. lanceolatus snake, ADAMTS13 activity was determined at admission before antivenom therapy. In these patients, the median plasmatic ADAMTS13 activity was 94% (IQR: 78–122%). Ten patients (22%) displayed ADAMTS13 activity less than 75%. Compared with patients with normal ADAMTS13 activity (n = 36), those with moderately low ADAMTS13 activity (n = 10) were older, had a lower platelet count, and displayed increased concentrations of creatine kinase, fibrinogen and C-reactive protein. Multivariate linear regression retained only grade severity of envenoming as independent predictor of increase length of hospital stay, while reduced ADAMTS13 activity and increased C-reactive protein levels bordered on statistical significance.

For the first time, our study provided evidence suggesting that ADAMTS13 activity is reduced in experimental B. lanceolatus venom exposure and patients with B. lanceolatus envenoming. Thanks to its role on the VWF regulation, it is suggested that reduced ADAMTS13 activity can increase the risk of thrombosis in B. lanceolatus envenoming by favoring the circulation of prothrombotic VWF multimers. Low ADAMTS13 activity was associated with increased length of stay in envenomed patients.

The clinical manifestations of envenoming by Bothrops sp. typically include local tissue injury and disturbances of hemostasis characterized by consumption coagulopathy leading to incoagulable blood. In contrast, B. lanceolatus envenoming can elicit thrombotic events, such as ischemic stroke and myocardial infarction. Proposed mechanisms include the combination of procoagulant and systemic inflammatory processes leading to thrombotic state. The factor von Willebrand (VWF) is an active biomolecule critical for coagulation and thrombosis processes. The amount of multimerized forms of VWF increases the risk of thrombosis. VWF is regulated by ADAMTS13, an enzyme that cleaves VWF multimers and reduced their prothrombotic effects. Whether ADAMTS13 activity is reduced in B. lanceolatus envenoming has not been previously investigated, while only few case reports have previously evaluated the levels of ADAMTS13 activity in human envenoming. For the first time in this study, we study provided evidence suggesting that ADAMTS13 activity is reduced in experimental B. lanceolatus venom exposure and in human B. lanceolatus envenoming. Our study results further suggest that, together with high grade severity score of envenoming and systemic inflammation, moderately reduced levels of ADAMTS13 activity are associated with increased length of hospital stays.