Effect of the saliva from different triatomine species on the biology and immunity of TLR-4 ligand and Trypanosoma cruzi-stimulated dendritic cells.

Background: Triatomines are blood-sucking vectors of Trypanosoma cruzi, the causative agent of Chagas disease. During feeding, triatomines surpass the skin host response through biomolecules present in their saliva. Dendritic cells (DCs) play a crucial role in the induction of the protection to aggressive agents, including blood-sucking arthropods. Here, we evaluated if salivary components of triatomines from different genera evade the host immunity by modulating the biology and the function of LPS- or T. cruzi-stimulated DCs.

Methods: Saliva of Panstrongylus lignarius, Meccus pallidipennis, Triatoma lecticularia and Rhodnius prolixus were obtained by dissection of salivary glands and the DCs were obtained from the differentiation of mouse bone marrow precursors.

Results: The differentiation of DCs was inhibited by saliva of all species tested. Saliva differentially inhibited the expression of MHC-II, CD40, CD80 and CD86 in LPS-matured DCs. Except for the saliva of R. prolixus, which induced IL-6 cytokine production, TNF-α, IL-12 and IL-6 were inhibited by the saliva of the other three tested species and IL-10 was increased in all of them. Saliva per se, also induced the production of IL-12, IL-6 and IL-10. Only the saliva of R. prolixus induced DCs apoptosis. The presence of PGE was not detected in the saliva of the four triatomines studied. Finally, T. cruzi invasion on DCs is enhanced by the presence of the triatomine saliva.

Conclusions: These results demonstrate that saliva from different triatomine species exhibit immunomodulatory effects on LPS and T. cruzi-stimulated DCs. These effects could be related to hematophagy and transmission of T. cruzi during feeding.