Plasma lipoproteins in visceral leishmaniasis and their effect on Leishmania-infected macrophages.

This work aimed at investigating the lipid profile of zoonotic visceral leishmaniasis (VL) patients' sera and the effect of lipoproteins on the in vitro production of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, IL-10 and IL-12 by Leishmania infantum-infected and uninfected macrophages. Lipids were quantified in 26 VL patients' sera and 26 healthy controls from a VL endemic area. The patients' sera had higher triglyceride and very low density lipoprotein (VLDL) levels, and much lower apolipoprotein A1, total cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) levels than the control sera. Lipoprotein fractions were obtained by ultracentrifugation of sera. The addition of LDL and HDL to Leishmania-infected and uninfected macrophages, in physiological concentrations, enhanced the production of IL-6 and IL-10, but not of IL-12. LDL stimulated the production of TNF-alpha only in infected macrophages, whereas HDL stimulated the production of lower amounts of TNF-alpha in both infected and uninfected macrophages. VLDL stimulated only the production of IL-10. It is proposed herein that LDL may influence the development of VL by promoting the production of TNF-alpha by infected macrophages. A decrease in plasma LDL in some VL patients (to 20 mg/mL or less); however, would tend to reduce the production of TNF-alpha and therefore to limit the development of immune-mediated pathology, not withstanding the fact that it would perhaps increase the permissiveness of macrophages to Leishmania growth.

Schistosoma mansoni triose phosphate isomerase peptide MAP4 is able to trigger naïve donor immune response towards a type-1 cytokine profile.

We evaluated the ability of naïve monocyte-derived dendritic cells (DC) to sensitize autologous peripheral blood mononuclear cells (PBMC) to the schistosome vaccine candidate MAP4 using a priming in vitro (PIV) assay. MAP4 is a multiple antigen peptide containing B- and T-cell epitopes derived from the glycolytic enzyme triose phosphate isomerase. PBMC primed and restimulated with MAP4 first and secondary recalls (MAP4 PIV cells) were examined for cell phenotype and cytokine production. We found that after the first recall stimulation with MAP4, the major cell population was predominantly CD4(+) T-cell subsets (68.5%), CD8(+high) (16%) and CD19(+) (10%). Additionally, MAP4 PIV cells significantly expressed CD4(+)-HLA-DR(+), -CD54(+), -CD45RO(+) (P < 0.0001) and -CD25(+) (P < 0.0004) together with significant expression of CD80(+) on CD19(+) B cells (P < 0.007). Cytokine production from activated MAP4 PIV cells was predominantly Th1-like, consisting mainly of IFN-gamma. Interestingly, IFN-gamma production was suppressed when Schistosoma mansoni-soluble egg antigen (SEA) was added to a MAP4 PIV cell culture. Furthermore, addition of MAP4 to a SEA PIV cell culture significantly reduced secretion of IL-10. The present findings add to the knowledge gained from studies in the mouse model, and our results show that naïve donor DC, sensitized with MAP4, were able to prime and clonally expand MAP4-specific T cells towards a Th1-type response.

Naïve donor responses to Schistosoma mansoni soluble egg antigens.

Schistosome infection induces profound Th-biasing and immune suppression. Although much has been examined in mice, few studies have examined responses of naïve humans to schistosome antigens. In this study, we examined the response of naïve human peripheral blood mononuclear cells (nPBMC) to stimulation with Schistosoma mansoni soluble egg antigen (SEA) using a priming in vitro (PIV) assay. We found that SEA induced a pronounced CD4+ T-helper cell response based on cytokine secretion and phenotyping markers. SEA-stimulated nPBMC (SEA cells) at day 7 post-priming and after the first recall consisted predominantly of Th0-like CD4+ T cells. Following the second recall, the majority of donor (10/12) responses were Th2-like. The cell population consisted of approximately 64% CD4+, 17% CD8(+high), 12% CD19+, and 7% CD23+ cells. The CD4+ population also expressed HLA-DR+, CD54+, CD45RO+ and CD25+ whereas the CD19+ cells expressed CD80 and CD86. Following priming, we detected high levels of IL-6, IFN-gamma, IL-12p40, IL-10 and IL-5. Upon restimulation, SEA cells secreted IL-5 and high levels of IL-10, typical of a Th2-like response. The data presented herein shows that the majority of naïve donor dendritic cells, following stimulation with SEA, prime and clonally expand SEA-specific T cells towards a Th2-type response. However, two donors responded with an atypical response, producing IFN-gamma coincident with low levels of IL-10. Whether this differential response was due to HLA or other genes was not determined but is currently under investigation.