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DELAFONTAINE, M. Bothrops lanceolatus snake venom: characterization, activation of the complement system and potential mechanisms involved in envenoming. 2016, 123 p. PhD thesis (Immunology) – Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, 2016. Bothrops lanceolatus, commonly named “Fer-de-Lance”, is the endemic snake of the French Caribbean Island of Martinique. Envenomations by B. lanceolatus present clinical aspects characterized by a systemic thrombotic syndrome and important local inflammation, involving oedema and pain, but limited haemorrhage; which differes from the haemorrhagic syndrome exhibited in South American bothropic envenomations. Several Bothrops venoms can activate complement (C) system, involving their metallo and/or serine proteínases in this process. With the aim to investigate the mechanisms of venom-induced inflammation, we fully characterized B. lanceolatus venom and investigated the cross-reactivity of an antibothropic antivenom, the C-cascade activation by the venom and its cytotoxicity on human keratinocytes and vascular cells. We used electrophoretic separation, zymography, colorimetric or fluorimetric (FRET) enzymatic assays, and hemolytic assays, in addition to immunochemical assays to characterize B. lanceolatus venom. We confirmed that B. lanceolatus venom has phospholipase, gelatinolytic and strong fibrinogenolytic activities. Compared to other bothropic venoms, its hyaluronidase activity was particularly low. Several components of B. lanceolatus venom shared antigenic similarities with South American Bothrops species, since the therapeutical antibothropic antivenom, raised against Brazilian snakes, cross-reacted with the venom and completely abolished its phospholipase, hyaluronidase and cytotoxic (for keratinocytes) activities. However, the results obtained with fluorescent peptides, specific inhibitors and the antivenom, emphasized the substrate specificity of B. lanceolatus venom proteases. The cytotoxicity of the venom was tested on human keratinocytes (HaCaT) and vascular endothelial cells (EAhy926), and compared to B. jararaca venom toxicity. Both venoms showed to be cytotoxic on HaCaT cells cultures. However, B. jararaca venom was about ten times more cytotoxic for vascular cells than B. lanceolatus venom. The patterns of cytokine and chemokine production by the two cell lines exposed to the venoms were highly pro-inflammatory. In human serum, B. lanceolatus venom activated the C-cascade by the alternative, classical and lectin pathways, releasing the anaphylatoxins C4a and C5a, and the terminal C complex. It also showed a direct proteolytic activity upon the purified human C-proteins C3, C4, and C5, releasing active C5a. The venom cleaved the inhibitor of the classical and lectin C-pathways and the coagulation cascade, C1INH, into a smaller compound, reducing its inhibitory potential by 40%. These data indicate that B. lanceolatus venom displays important pro-inflammatory properties, as it activates the complement cascade, inducing a strong release of the anaphylatoxin C5a and C-terminal complex. The discrepancy of toxicity on vascular endothelial cells between B. lanceolatus venom and B. jararaca venom may reflect the difference between the thrombotic and haemorrhagic syndromes, they respectively induce.

Veneno da serpente &lt;i&gt;Bothrops lanceolatus&lt;/i&gt;: caracterização, ativação do sistema complemento e mecanismos potenciais envolvidos no envenenamento.