New Insight into the Mechanism of <i>Lonomia obliqua</i> Envenoming: Toxin Involvement and Molecular Approach

Abstract

Despite the nearly worldwide distribution of Lepidoptera, there are few species with clear documentation of adverse reactions in humans. Most syndromes caused by Lepidoptera are consequences of direct contact with the hairs or setae of caterpillars. In most instances, the adverse effects caused by moth and caterpillars are self-limited and the treatment is based on the removal of hairs, application of topical antipruritics and, in some cases, the use of oral antihistamines. However, in the case of envenoming by South American Lonomiaobliqua caterpillars, the antilonomic serum produced at Instituto Butantan in Brazil is the only effective treatment to re-establish the physiological coagulation parameters in poisoned patients and to abolish the complications seen in severe cases (e.g. consumptive coagulopathy, intracerebral hemorrhage, and acute renal failure). Many studies have been carried out to understand the pathophysiological mechanism of envenoming by L. obliqua. Several toxic principles were found in bristle extract and the hemolymph, probably related to the envenoming. An interesting fact is that some toxins from the venom usually have more than one function. With the advent of molecular biology techniques it has become possible to analyze these processes at a molecular level, thus giving rise to hypotheses on the molecular basis of envenomation. This review contributes to enhance our understanding of the dramatic alterations that hemorrhagic syndrome causes in patients, current treatment, and the diversity of the molecules involved in this pathology.

Losac, the First Hemolin that Exhibits Procogulant Activity through Selective Factor X Proteolytic Activation

“…Contact of the human skin with L. obliqua bristles may induce a severe consumptive coagulopathy, which, in turn, can lead to a hemorrhagic syndrome (1,2). Many studies have been carried out to understand the pathophysiological mechanism of the envenoming by L. obliqua (2).…”

“…2 In order to support the hypothesis that rLosac is a procoagulant protein and based on experiments using deficient plasmas, we demonstrate that rLosac could induce blood coagulation through selective factor X proteolytic activation. Interestingly, Losac has no homology to known proteases.…”

“…Lonomia obliqua caterpillar envenomings have medical importance in South/Southern Brazil because they can lead to hemorrhagic syndrome, the most important clinical complication in people who experience contact with its bristles (1,2). The pathophysiologic process involved in the hemorrhagic syndrome is not completely known.…”

“…The pathophysiologic process involved in the hemorrhagic syndrome is not completely known. However, several studies have indicated that this effect is mediated mainly by thrombin formation due to procoagulant proteins present in the venom followed by the activation of fibrinolysis secondary to these events (1,2). Two procoagulant proteins were reported: Lopap, a prothrombin activator (3), and Losac, a factor X activator (4,5).…”

“…Two procoagulant proteins were reported: Lopap, a prothrombin activator (3), and Losac, a factor X activator (4,5). Many studies indicate that Lopap, the most studied molecule from L. obliqua, could contribute to the pathophysiological mechanism of the envenomation through a complex mechanism affecting both coagulation and endothelial function (2). In the case of Losac, little is known about its precise role in the pathophysiology of L. obliqua envenoming.…”