Avaliação do efeito da saliva de triatomíneos (Heteroptera: Reduviidae) sobre a biologia de células dendríticas murinas

Abstract

Triatomines are blood-sucking arthropods of great medical interest because they are vectors of Trypanosoma cruzi, the ethiological agent of Chagas disease. During feeding triatomines need to overcome two major barriers imposed by the host defense systems: hemostasis and the immune system. While it is known that several molecules are capable of subverting the host hemostatic barriers, only few molecules capable of subverting the immune system have been characterized by these ectoparasites. Dendritic cells (DCs), present in the skin of all vertebrates, are key components of the innate immune response playing a crucial role in the induction of acquired immunity to many aggressive agents, including bloodsucking arthropods, and are of great interest to understand whether triatomines evade the responses by modulating these cells. Thus, the purpose of this study was to investigate the effect of the saliva from triatomines Panstrongylus herreri, Meccus pallidipennis, Rhodnius prolixus and Triatoma lecticularia on differentiation, maturation (expression of stimulatory and costimulatory molecules and cytokine production) and apoptosis of DCs. In this work we also try to identify if the saliva of these species have prostaglandin E2 (PGE2) in its constitution. Saliva from adult triatomines were obtained by dissection of salivary glands and the DCs were obtained from the differentiation of mouse bone marrow precursor cells in the presence of GM-CSF (25 ng/mL). The influence of saliva on DCs differentiation was analyzed by incubation of stem cells from C57BL/6 mice for 7 days in the presence of saliva and after this time the expression of molecular markers CD11c, CD11b, MHC-II, CD40, and CD86 were evaluated by flow cytometry. To assess the cell maturation, differentiated DCs were stimulated with LPS in the presence or absence of saliva and the expression of MHC-II, CD40, CD80 and CD86 was evaluated by flow cytometry and the production of cytokines TNF-α, IL-12p40, IL-10 and IL-6 was evaluated by ELISA. The differentiation of DCs was inhibited by the four tested saliva and this inhibitory activity (dilution 1:30 v / v) reached 79% for the specie P. herreri, 57% for M. pallidipennis, 38% for T. lecticularia and 76% for R. prolixus. The expression of MHC-II, CD40 and CD86 in DCs was differentially modulated depending on the saliva from each species. Regarding maturation, saliva differentially inhibited the expression of MHC-II, CD40, CD80 and CD86 in LPS-matured DCs but the CD40 molecule was the only inhibited by the saliva of the four species. Except for the saliva of R. prolixus, that induced IL-6 cytokine production, TNF-α, IL-12 and IL-6 were inhibited and IL-10 was increased in the saliva of the other three species tested. It is noteworthy that the saliva, per se, depending on the species, induced the production of IL-12, IL-6 and IL-10. The saliva of R. prolixus was the only one that induced DCs apoptosis. The presence of PGE2 in the saliva of the four evaluated triatomines was not detected. These results demonstrate that triatomines saliva has molecules that modulate the biology of DCs and this effect is PGE2- independent. We believe that the decrease in differentiation, the modulation of stimulatory and co-stimulatory molecules and the inhibition of pro-inflammatory cytokines and the induction of IL-10 generates a much less aggressive environment for the feeding that could also facilitate the transmission of pathogens, including T. cruzi.