A Web of Coagulotoxicity: Failure of Antivenom to Neutralize the Destructive (Non-Clotting) Fibrinogenolytic Activity of Loxosceles and Sicarius Spider Venoms

Abstract

Envenomations are complex medical emergencies that can have a range of symptoms and sequelae. The only specific, scientifically-validated treatment for envenomation is antivenom administration, which is designed to alleviate venom effects. A paucity of efficacy testing exists for numerous antivenoms worldwide, and understanding venom effects and venom potency can help identify antivenom improvement options. Some spider venoms can produce debilitating injuries or even death, yet have been largely neglected in venom and antivenom studies because of the low venom yields. Coagulation disturbances have been particularly under studied due to difficulties in working with blood and the coagulation cascade. These circumstances have resulted in suboptimal spider bite treatment for medically significant spider genera such as Loxosceles and Sicarius. This study identifies and quantifies the anticoagulant effects produced by venoms of three Loxoscles species (L. reclusa, L. boneti, and L. laeta) and that of Sicarius terrosus. We showed that the venoms of all studied species are able to cleave the fibrinogen Aα-chain with varying degrees of potency, with L. reclusa and S. terrosus venom cleaving the Aα-chain most rapidly. Thromboelastography analysis revealed that only L. reclusa venom is able to reduce clot strength, thereby presumably causing anticoagulant effects in the patient. Using the same thromboelastography assays, antivenom efficacy tests revealed that the commonly used Loxoscles-specific SMase D recombinant based antivenom failed to neutralize the anticoagulant effects produced by Loxosceles venom. This study demonstrates the fibrinogenolytic activity of Loxosceles and Sicarius venom and the neutralization failure of Loxosceles antivenom, thus providing impetus for antivenom improvement.

Evidence for Resistance to Coagulotoxic Effects of Australian Elapid Snake Venoms by Sympatric Prey (Blue Tongue Skinks) but Not by Predators (Monitor Lizards)

“…Thromboelastography was utilised to test the in vitro viscoelastic clotting properties of plasma in the absence and presence of venom. Thromboelastography assays were adapted and utilised from previously published protocols [ 36 , 37 , 38 ]. For all assays, 7 µL of either venom (1 mg/mL) or control reagent was added to 72 µL calcium, 72 µL phospholipid, 20 µL Owren Koller buffer and 189 µL plasma.…”

Getting stoned: Characterisation of the coagulotoxic and neurotoxic effects of reef stonefish (Synanceia verrucosa) venom

“…Thromboelastography testing was utilised to investigate the coagulotoxic activity of both lyophilised and fresh S. verrucosa venom on human plasma. Assays conducted were adapted from previously published protocols which have utilised thromboelastography assays to measure the effect of the venom on the clotting time and clotting strength of recalcified human plasma (Grashof et al, 2020;Youngman et al, 2019a). For each assay, 7 mL of venom (1 mg/mL in 50 % glycerol) was added to 72 mL calcium, 72 mL phospholipid, 20 mL Owren Koller buffer and 189 mL human plasma.…”