Beyond envenomation: functional dissection of Podalia orsilochus venom uncovers a procoagulant protein and additional toxic activities.

Envenomation by urticating caterpillars of the family Megalopygidae is an underestimated public health issue in South America, with Podalia orsilochus being the main species implicated in cases reported in northeastern Argentina. This study aimed to characterize the toxicological properties of its venom, focusing on hematological and hemostatic effects. Venom extracts were analyzed using electrophoresis, zymography, hemolysis and coagulation assays, and chromatographic fractionation followed by immunodetection. Electrophoretic profiles revealed predominant proteins in the 10-37 kDa range, with several gelatinolytic bands detected by zymography. The venom exhibited thrombin-like and dose-dependent procoagulant activity, although weaker than that of Lonomia obliqua. A mild, direct hemolytic effect on human erythrocytes was observed, associated with degradation of Band 3, a major membrane protein. A 33-kDa protein was purified and shown to induce procoagulant activity while cross-reacting with antibodies against Losac, a Factor X-activating protein from L. obliqua venom, indicating the recognition of specific epitope(s) or protein domain(s) shared by both proteins. Proteomic data are available via ProteomeXchange with identifier PXD074932. In conclusion, P. orsilochus venom contains components with proteolytic, hemolytic, and coagulant activities, including a Losac-like protein, expanding current knowledge of lepidopteran venoms and their potential impact on human health.