INTERSPECIFIC VARIATIONS OF Loxosceles SPIDERs VENOMS

de-Oliveira-Lima, K.C.; Gonçalves-de-Andrade, R.M.; Magnoli, F.C.; Ferreira-Junior, J.M.C.; Tambourgi, D.V.

Laboratório de Imunoquímica, Instituto Butantan, Brazil

Loxosceles gaucho, Loxosceles intermedia and Loxosceles laeta are them ain spiders responsible for Brazilian aracneism. They provoke a local necrotic lesion and rarely cause systemic effects. Recently, we demonstrated that the variation in the genetic background of the victim and intraspecies differences in the composition of the venoms are important factors determining the severity of the loxoscelism. The aim of this study was to evaluate other factors that could contribute to gravity of the loxoscelism, as inter-species variations of the venoms. Comparative analysis of L. gaucho, L. laeta and L. intermedia venoms by SDS-PAGE revealed a distinct pattern of bands, ranging from 10 to 200 kDa. To assess the ability of Loxosceles venoms to induce C-dependent haemolysis, human erythrocytes were treated with different amounts of the three venoms species and incubated with NHS. Results showed that venoms were able to render erythrocytes susceptible to lysis, however, a more potent haemolytic inducer’s effect was determined for L. gaucho venoms. Dermonecrotic activity was tested in adult rabbits by intradermal injection of the Loxosceles venoms. Typical loxoscelic lesions were observed, although L. gaucho venoms induced a larger loxosceliclesion. L. laeta and L. intermedia venoms produced a stronger oedema reaction than L. gaucho venom. Beside the differences observed in the haemolytic and dermonecrotic assays we also investigated possible differences in the sphingomyelinase activity by testing the sphingomyelin cleaving ability of Loxosceles venoms. The results showed a similar sphingomyelinase activity among the species. In conclusion, Loxosceles venoms species exhibit differences in their toxic effects and these may contribute to the variability in the accidents severity caused by Loxosceles spiders.

Supported by FAPESP and The Wellcome Trust

CORRESPONDENCE TO:

Kátia Cristina de Oliveira de Lima, Rua Domingos Félix, 87 Apto 43, Bl-2, São Paulo, SP, Brasil, Email: kathyacris@yahoo.com.br