Background: The bite of spiders belonging to the genus Loxosceles can induce a variety of clinical symptoms, including dermonecrosis, thrombosis, vascular leakage, haemolysis, and persistent inflammation. In order to examine the transcripts expressed in venom gland of Loxosceles laeta spider and to unveil the potential of its products on cellular structure and functional aspects, we generated 3,008 expressed sequence tags (ESTs) from a cDNA library.

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Loxoscelism is caused by envenomation by spiders from Loxosceles genus. Clinical symptoms only appear a few hours after envenomation and can evolve in local reactions, such as dermonecrosis, and systemic reactions, such as intravascular haemolysis, intravascular coagulation and renal failure. Current therapies are not effective, often not based in scientific research and can be even detrimental. A lack of understanding of the mechanism of action of the venom of the Loxosceles spider had thus far prevented development of effective therapies. In this review we aim to give an overview of our contributions to the understanding of the mechanism of action of the Loxosceles venom and propose targets and therapeutics for medical intervention.

ABSTRACT. The present paper deals with the phlebotomine species captured during the period from January 1998 to June 2000 in 12 caves located in the Serra da Bodoquena, situated in the south central region of Mato Grosso do Sul State, Brazil. Three of the caves are situated further north (in Bodoquena county), seven in the central area (Bonito county) and two in the south (Jardim county). These last two caves and three of those in Bonito are located at the west side of the ridge. Eighteen species of phlebotomines were captured within the caves: Brumptomyia avellari (Costa Lima, 1932) (Shannon & Del Ponte, 1927) and Sciopemyia sp. A total of 29,599 phlebotomine sandflies was obtained. Lutzomyia almerioi was absolutely predominant (91.5%) over the other species on both sides of the Bodoquena ridge, with the exception of the southern caves in which it was absent. It presents summer predominance, with nocturnal and diurnal activities. The species breeds in the caves and was captured during daytime both in the dark area and in the mouth of the caves. Martinsmyia oliveirai, the second most frequent sandfly, also presents a summer peak and only predominated over the other species in one cave, in which there were human residues.0

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BackgroundThe caterpillar of the moth Premolis semirufa (Lepidoptera: Arctiidae), commonly named Pararama, is endemic of the Amazon basin. Accidental contact with these caterpillar bristles causes local symptoms such as intense heat, pain, edema and itching which last for three to seven days; however, after multiples contacts, it may induce joint-space narrowing and bone alteration, as well as degeneration of the articular cartilage and immobilization of the affected joints. Specific treatment for this disease does not exist, but corticosteroids are frequently administered. Despite of the public health hazard of Premolis semirufa caterpillar poisoning, little is known about the nature of the toxic components involved in the induction of the pathology.Methodology/Principal FindingsHere we have investigated the biological and immunochemical characteristics of the caterpillar's bristles components. Analysis of the bristles extract in in vitro assays revealed the presence of proteolytic and hyaluronidase activities but no phospholipase A2 activity. In vivo, it was observed that the bristles extract is not lethal but can induce an intense inflammatory process, characterized by the presence of neutrophils in the paw tissues of injected mice. Furthermore, the bristles components stimulated an intense and specific antibody response but autoantibodies such as anti-DNA or anti-collagen type II were not detected.ConclusionThe results suggest that Premolis semirufa caterpillar bristles secretion contains a mixture of different enzymes that may act together in the generation and development of the clinical manifestations of the Pararama envenomation. Moreover, the high immunogenicity of the caterpillar bristles components, as shown by the generation of high antibody titers, may also contribute to the induction and establishment of the inflammatory disease.

Envenomation by spiders belonging to the Loxosceles genus (brown spider) often results in local dermonecrotic lesions. We have previously shown that Loxosceles sphingomyelinase D (SMase D), the venom component responsible for all the pathological effects, induced the expression of matrix metalloproteinases (MMPs) in rabbits and in human keratinocytic cells. We also showed that the SMase D-induced apoptosis and MMP expression of keratinocytes was inhibited by tetracyclines. We have further investigated the ability of tetracyclines to inhibit or prevent the dermonecrotic lesion induced by Loxosceles venom in vivo and in vitro models. Primary cultures of rabbit fibroblasts incubated with increasing concentrations of venom or SMase D showed a decrease in cell viability, which was prevented by tetracyclines. In vivo experiments showed that topical treatments with tetracycline of rabbits, inoculated with crude Loxosceles intermedia venom or recombinant SMase D, significantly reduced the progression of the dermonecrotic lesion. Furthermore, tetracyclines also reduced the expression of MMP-2 and prevented the induction of MMP-9. Our results suggest that tetracycline may be an effective therapeutic agent for the treatment of cutaneous loxoscelism.

BackgroundThe spider family Sicariidae includes two genera, Sicarius and Loxosceles. Bites by Sicarius are uncommon in humans and, in Brazil, a single report is known of a 17-year old man bitten by a Sicarius species that developed a necrotic lesion similar to that caused by Loxosceles. Envenomation by Loxosceles spiders can result in dermonecrosis and severe ulceration. Sicarius and Loxosceles spider venoms share a common characteristic, i.e., the presence of Sphingomyelinases D (SMase D). We have previously shown that Loxosceles SMase D is the enzyme responsible for the main pathological effects of the venom. Recently, it was demonstrated that Sicarius species from Africa, like Loxosceles spiders from the Americas, present high venom SMase D activity. However, despite the presence of SMase D like proteins in venoms of several New World Sicarius species, they had reduced or no detectable SMase D activity. In order to contribute to a better understanding about the toxicity of New World Sicarius venoms, the aim of this study was to characterize the toxic properties of male and female venoms from the Brazilian Sicarius ornatus spider and compare these with venoms from Loxosceles species of medical importance in Brazil.Methodology/Principal FindingsSDS-PAGE analysis showed variations in the composition of Loxosceles spp. and Sicarius ornatus venoms. Differences in the electrophoretic profiles of male and female venoms were also observed, indicating a possible intraspecific variation in the composition of the venom of Sicarius spider. The major component in all tested venoms had a Mr of 32–35 kDa, which was recognized by antiserum raised against Loxosceles SMases D. Moreover, male and female Sicarius ornatus spiders' venoms were able to hydrolyze sphingomyelin, thus showing an enzymatic activity similar to that determined for Loxosceles venoms. Sicarius ornatus venoms, as well as Loxosceles venoms, were able to render erythrocytes susceptible to lysis by autologous serum and to induce a significant loss of human keratinocyte cell viability; the female Sicarius ornatus venom was more efficient than male.ConclusionWe show here, for the first time, that the Brazilian Sicarius ornatus spider contains active Sphingomyelinase D and is able to cause haemolysis and keratinocyte cell death similar to the South American Loxosceles species, harmful effects that are associated with the presence of active SMases D. These results may suggest that envenomation by this Sicarius spider has the potential to cause similar pathological events as that caused by Loxosceles envenomation. Our results also suggest that, in addition to the interspecific differences, intraspecific variations in the venoms composition may play a role in the toxic potential of the New World Sicarius venoms species.