Effects of Bothrops Spp. Snake Envenomation on Willebrand Factor Activity in Martinique and French Guiana

In 2017, the World Health Organization placed snakebites at the top of its list of neglected tropical diseases in an effort to facilitate funding for prevention programs, improve access to anti-venom, and stimulate new research in this area. Between 5 and 25 cases per 100 000 inhabitants are reported per year in French Guiana and Martinique. Before the era of anti-venom immunotherapy, envenomations by Bothrops snake bites in French Guiana and Martinique could quickly become life-threatening with a mortality rate close to 30%. Today, the administration of fragments of Fab or (Fab')2 immunoglobulins gives anti-venoms an excellent capacity to neutralise venom toxins, which has reduced mortality to less than 1% in the case of early hospital treatment In French Guiana, envenomation by Bothrops bites is characterized by local signs such as intense pain, rapidly expanding oedema, haemorrhagic phlyctenes and sometimes muscle necrosis. The local inflammatory and haemorrhagic damage is related to the enzymatic activities of the toxins contained in the venom (metallo-proteinases, disintegrins, and phospholipases A2, in particular). At the systemic level, venom serine proteases and metalloproteinases activate the coagulation cascade by multiple mechanisms (activation of coagulation factors X and V and of protrombin, thrombin-like and fibrinogenolytic enzymatic properties) and are responsible for the collapse of coagulation factors making the blood incoagulable. The metalloproteinases "hemorrhagins" destroy the vessel wall and are the cause of locoregional and systemic hemorrhage.

Envenomations by bites of Bothrops lanceolatus in Martinique have particular characteristics. Despite the genetic similarity with their congeners in French Guiana, envenomation by bites of Bothrops lanceolatus is characterized by the development of very intense local inflammatory signs (little haemorrhage) and the occurrence of thrombotic complications such as cerebral, pulmonary or myocardial infarction. The mechanisms behind this thrombotic presentation are not known. The large amount of metalloproteinases in the composition of Bothrops lanceolatus venom is believed to be responsible for destruction of vascular endothelium and pro-thrombotic state. Bothrops lanceolatus bite envenomations have been reported to be frequently complicated by generalized infections, disseminated intravascular coagulation and the occurrence of multi-visceral failure syndrome. This observation suggests abnormalities in endothelial function in which changes in Willebrand factor expression have been implicated.

The investigators hypothesize that plasma Willebrand factor (VW) activity and the intensity of endothelial activation are different depending on the Bothrops snake species involved in the bites in Guyana and Martinique. Due to the specific properties of the venoms of each Bothrops species, the activity of the Willebrand factor (VW) and the consequences in terms of endothelial activation would be different and responsible for the clinico-biological characteristics according to the geographical origin of the snakes.

The investigators will demonstrate that the accumulation of Willebrand factor (VW) and the increase in its activity are responsible for the endothelial activation and micro-thrombosis observed during envenomations by Bothrops lanceolatus bites, whereas the decrease in its activity induced by the venoms of endemic Bothrops from Guyana is responsible for haemorrhagic phenomena.

This study will highlight the importance of changes in Willebrand factor activity on endothelial activation and the initiation of micro-thrombosis in the case of Bothrops lanceolatus envenomations and on primary haemostasis and bleeding disorders in the case of endemic Bothrops in Guyana. This new knowledge is important insofar as individualised therapeutic management can be proposed. Indeed, several studies have shown that adjuvant treatment of thrombotic microangiopathies, such as thrombotic thrombocytopenic purpura, with blood products (fresh frozen plasma) or plasma exchange, improves endothelial dysfunction and the prognosis of patients.