RESUMEN
BACKGROUND: The venom of Bothrops lanceolatus, a viperid species endemic to the Lesser Antillean Island of Martinique, induces thrombosis in a number of patients. Previous clinical observations indicate that thrombotic events are more common in patients bitten by juvenile specimens. There is a need to develop an experimental model of this effect in order to study the mechanisms involved. METHODOLOGY/PRINCIPAL FINDINGS: The venoms of juvenile and adult specimens of B. lanceolatus were compared by (a) describing their proteome, (b) assessing their ability to induce thrombosis in a mouse model, and (c) evaluating their in vitro procoagulant activity and in vivo hemostasis alterations. Venom proteomes of juvenile and adult specimens were highly similar, albeit showing some differences. When injected by the intraperitoneal (i.p.) route, the venom of juvenile specimens induced the formation of abundant thrombi in the pulmonary vasculature, whereas this effect was less frequent in the case of adult venom. Thrombosis was not abrogated by the metalloproteinase inhibitor Batimastat. Both venoms showed a weak in vitro procoagulant effect on citrated mouse plasma and bovine fibrinogen. When administered intravenously (i.v.) venoms did not affect classical clotting tests (prothrombin time and activated partial thromboplastin time) but caused a partial drop in fibrinogen concentration. The venom of juvenile specimens induced partial alterations in some rotational thromboelastometry parameters after i.v. injection. When venoms were administered i.p., only minor alterations in classical clotting tests were observed with juvenile venom, and no changes occurred for either venom in rotational thromboelastometry parameters. Both juvenile and adult venoms induced a marked thrombocytopenia after i.p. injection. CONCLUSIONS/SIGNIFICANCE: An experimental model of the thrombotic effect induced by B. lanceolatus venom was developed. This effect is more pronounced in the case of venom of juvenile specimens, despite the observation that juvenile and adult venom proteomes are similar. Adult and juvenile venoms do not induce a consumption coagulopathy characteristic of other Bothrops sp venoms. Both venoms induce a conspicuous thrombocytopenia. This experimental model reproduces the main clinical findings described in these envenomings and should be useful to understand the mechanisms of the thrombotic effect.
RESUMEN
Venom-induced consumption coagulopathy and thrombocytopenia are common and potentially severe manifestations of viperid snakebite envenoming since they contribute to local and systemic hemorrhage. Therefore, the assessment of the efficacy of antivenoms to neutralize coagulopathic and thrombocytopenic toxins should be part of the preclinical evaluation of these drugs. To evaluate the efficacy of the polyvalent (Crotalinae) antivenom produced in Costa Rica, in this study we have used a mouse model of coagulopathy and thrombocytopenia induced by the venom of Bothrops asper, based on the bolus intravenous (i.v.) injection of venom. When venom and antivenom were incubated before injection, or when antivenom was administered i.v. immediately after venom injection, venom-induced hemostatic alterations were largely abrogated. We also studied the recovery rate of clotting parameters in conditions where antivenom was administered when mice were coagulopathic. Some parameters recovered more rapidly in antivenom-treated mice than in control envenomed animals, but others showed a spontaneous recovery without antivenom. This is due to a rapid clearance of plasma venom levels in these experimental conditions. This implies that models based on the bolus i.v. injection of venom have limitations for assessing the effect of antivenom in the recovery of clotting alterations once coagulopathy has developed. It is suggested that alternative models should be developed based on a slower systemic absorption of venom. Overall, our findings provide a protocol for the preclinical evaluation of antivenoms and demonstrate that the polyvalent antivenom is effective in neutralizing the toxins of B. asper venom responsible for coagulopathy and thrombocytopenia.
RESUMEN
Viperid snakebite envenoming is often characterized by a venom-induced consumption coagulopathy due to the procoagulant effect of venom components, resulting in the alteration of clotting laboratory tests. There is a growing trend to use rotational thromboelastometry in the assessment of clotting disturbances in a variety of pathologies, although its use in experimental models of envenoming has been limited. An in vivo murine model was implemented to assess the coagulopathy induced by three Central American viperid venoms which have different mechanisms of action on clotting factors, i.e., Bothrops asper, Crotalus simus and Bothriechis lateralis. Venom was injected by the intravenous route and blood samples were collected at 1, 3, 5 and 24 h after envenoming. Coagulopathy was assessed by standard clotting tests and by routine rotational thromboelastometric parameters. In addition, the changes in platelet number were followed. B. asper and C. simus venoms induced coagulopathy and thrombocytopenia 1 h after injection, followed by a slow recovery at 3, 5 and 24 h, although the majority of clotting parameters were still significantly affected by 3 and 5 h, and were corrected by 24 h. In general, a similar time-course of alterations was observed for standard clotting tests and most rotational thromboelastomeric assays. However, some thromboelastometric parameters, especially those related to Fibtem, showed more drastic alterations than standard tests and remained altered even at 24 h in some cases. This is likely related to the low fibrinogen concentration observed at most time intervals. B. lateralis venom did not induce a consumption coagulopathy, although it caused a marked thrombocytopenia.