Cloud serpent coagulotoxicity: The biochemical mechanisms underpinning the anticoagulant actions of Mixcoatlus and Ophryacus venoms

Abstract

Mexico is home to an extreme diversity of herpetofauna, with venomous snakes imposing a significant burden upon public health. However, little is known about the pathophysiological venom actions of a number of potentially medically important species, including those from the genera Mixcoatlus and Ophryacus. Our study aimed to fill this knowledge gap by ascertaining the effects of Mixcoatlus melanurus, Ophryacus smaragdinus and Ophryacus sphenophrys venoms upon the coagulation cascade utilising a series of well-validated coagulation assays. While M. melanurus venom exhibited no significant coagulotoxic activities, both O. smaragdinus and O. sphenophrys venoms exerted multiple coagulotoxic activities upon the coagulation cascade which would be contributing towards a net anticoagulant venom activity. O. sphenophrys significantly inhibited the spontaneous clotting of plasma but O. smaragdinus did not. They differed in that O. sphenophrys inhibited the clotting enzymes factor IXa and factor XIa. However, O. smaragdinus was able to inhibit factor Xa in isolation-assays. Both O. smaragdinus and O. sphenophrys degraded fibrinogen, with O. smaragdinus venom causing a significantly weaker fibrinogen clot than O. sphenophrys. In vitro antivenom efficacy assays were undertaken to ascertain the efficacy of Antivipmyn-Tri antivenom (which is made using Bothrops, Crotalus, and Lachesis venoms). This antivenom was chosen due to the phylogenetic uncertain position of the Ophryacus, but with some molecular genetics' studies placing it as sister to Lachesis. Despite the complexity of the antivenom immunising mixture, the anticoagulant activity of O. sphenophrys venom was relatively poorly neutralised by the antivenom. This work contributes to the understanding of the functional activity of Mixcoatlus and Ophryacus venoms, laying a foundation for future work investigating the coagulotoxins present within Ophryacus venoms in addition to providing data useful for the evidence-based design of clinical management strategies for the envenomed patient.

Keywords: Anticoagulant; Antivenom; Coagulation; Mixcoatlus; Ophryacus; Viperidae.