Estudo da inibição do sistema complemento humano pela saliva de anofelinos (Diptera; Anophelinae) neotropicais

Abstract

Anopheles mosquitoes are the natural vectors of malaria throughout theworld. The transmission occurs during bloodmeal, when the insects inject infective forms of Plasmodium together with the contents of their salivary glands. Their saliva presents active molecules important for hematophagy, such as vasodilators, anticoagulant and platelet inhibitors. However, little is known about the interactions of Anopheles salivary components with the hosts immune system. The aim of this work was to demonstrate and to characterize anticomplement activity in the saliva of neotropical anophelines, specially A. albimanus and A. aquasalis, important malaria vectors in Latin America. Hemolytic assays, ELISA assays and Western blots for detecting activation of complement components were performed in the presence and absence ofsalivary glands extracts of both mosquito species. The results showed significant and dose-dependent inhibition of the alternative pathway by the saliva of the two species. The salivary inhibitor of A. albimanus was then purified using HPLC and identified by mass spectrometry, as being a gSG7 protein. The gene of that protein was cloned and expressed in E. coli bacteria. The recombinant protein presented anti-complement activity as potent as the salivary glands extracts. Anti-recombinant gSG7 IgG antibodies produced in rabbits were able to detect both the recombinant and the native protein in the glands extract. The antibodies also blocked gSG7 activity in the hemolytic assays. Through ELISA and surface plasmon resonance, we showed that gSG7 binds directly to properdin, apositive regulator of the alternative pathway of the complement system. This is the first report of an anti-complement molecule in mosquito saliva, which has potential role in blood-feeding and parasite transmission by the vector.