Our analyses of cytokine production further support MDV3100 supplier the idea that SGE affects the inflammatory cell influx. Interestingly, our data show that in vitro stimulation of draining lymph node cells from SGE-1X mice with parasitic antigens results in higher levels of IL-10, whereas the IL-10 level in SGE-3X-derived draining lymph nodes cell cultures remained unchanged. Whereas the production of IL-10 was unchanged in the SGE-3X mice, IFN-γ production increased in the supernatant of SGE-3X lymph node-derived cell cultures, indicating that the inhibition of IL-10 in the SGE-3X mice may have resulted in better control of Leishmania infection.

In fact, the severity of disease represented by the lesion size and parasitic burden was not observed in mice pre-sensitized with saliva (SGE-3X). IL-10 is an anti-inflammatory cytokine produced by several cell types including macrophages, neutrophils and Treg cells, and IL-10 displays diverse immunomodulatory functions [31, 32]. In regard to leishmaniasis, IL-10 inhibits cytokine production by T cells (e.g., IL-2), monocytes/macrophages and dendritic cells (e.g., IL-1α and IL-1β, IL-6, IL-8, IL-12, TNF-α, and granulocyte-macrophage colony-stimulating factor) as well as the production of NO and H2O2 ultimately

favoring parasitic survival [32, 33]. The hypothesis that IL-10 induced by saliva is involved in disease progression during Leishmania infection is supported by a significant enhancement in PP2 mouse lesion development and parasitic burden in mice that were co-inoculated with saliva and parasites. The increase in IL-10 production has been reported

in treatment with other Phlebotomine saliva sources. In previous studies, we demonstrated that the saliva from the Old World species Phlebotomines P. papatasi and P. duboscqi act mainly on dendritic cells and induce the production of IL-10 by a mechanism dependent of PGE2. In turn, PGE2 acts in an autocrine manner to reduce the antigen-presenting ability of DCs [13]. Previous studies have also shown in vitro and in vivo examples of Lutzomyia longipalpis saliva promotes Org 27569 inducing IL-10 production by macrophages and T cells, which exacerbates Leishmania infection [34]. Moreover, the genetic ablation of IL-10 prevents the detrimental effect of SGE on Leishmania major and L. amazonensis infections. The reduced ability of SGE-3X- inoculated mice to produce IL-10 may be associated with an increase in IFN-γ production. Consistently, the depletion of IFN-γ using IFN-γ-neutralizing monoclonal antibody reduced the protective profile of saliva upon Leishmania disease. Despite the significant increase in CD8+ T cells in the ears of mice that were pre-inoculated with saliva three times (SGE-3X), our evidence suggests that CD4+ T cells and CD8+ T cells contributed to the increased ex vivo production of IFN-γ during Leishmania infection.