BackgroundVisceral leishmaniasis (VL) is a severe disease caused by infection with protozoa of the genus Leishmania. Classic VL is characterized by a systemic infection of phagocytic cells and an intense activation of the inflammatory response. It is unclear why 90% of infected individuals do not develop the disease while a minority develop the classical form. Furthermore, among those that develop disease, a small group progresses to more severe form that is unresponsive to treatment. The presence of inflammatory mediators in serum could theoretically help to control the infection. However, there is also a release of anti-inflammatory mediators that could interfere with the control of parasite multiplication. In this study, we took advantage of the spectrum of outcomes to test the hypothesis that the immune profile of individuals infected with Leishmania (L.) infantum is associated with the development and severity of disease.Methodology/Principal FindingsSera from patients with confirmed diagnosis of VL were evaluated for the presence of numerous molecules, and levels compared with healthy control and asymptomatic infected individuals.Conclusions/Principal FindingsAlthough differences were not observed in LPS levels, higher levels of sCD14 were detected in VL patients. Our data suggest that L. infantum may activate the inflammatory response via CD14, stimulating a generalized inflammatory response with production of several cytokines and soluble molecules, including IFN-γ, IL-27, IL-10, IL-6 and sCD14. These molecules were strongly associated with hepatosplenomegaly, neutropenia and thrombocytopenia. We also observed that IL-6 levels greater than 200 pg/ml were strongly associated with death. Together our data reinforce the close relationship of IFN-γ, IL-10, IL-6, TNF-α and IL-27 in the immune dynamics of VL and suggest the direct participation of sCD14 in the activation of the immune response against L. infantum.

Background Despite visceral leishmaniasis (VL) being epidemic in most Brazilian regions, the Northeast region is responsible for the highest morbidity and mortality outcomes within the country. Objective To analyse the spatiotemporal dynamics of VL cases to identify the temporal trends and high-risk areas for VL transmission, as well as the association of the disease with social vulnerability in Brazilian Northeast. Methods We carried out an ecological time series study employing spatial analysis techniques using all VL confirmed cases of 1,794 municipalities of Brazilian Northeast between the years 2000 to 2017. The Social Vulnerability Index (SVI) was used to represent the social vulnerability. Incidence rates were standardized and smoothed by the Local Empirical Bayesian Method. Time trends were examined through segmented linear regression. Spatiotemporal analysis consisted of uni- and bivariate Global and Local Moran indexes and space-time scan statistics. Results Incidence rate remained stable and ranged from 4.84 to 3.52 cases/100,000 inhabitants. There was higher case prevalence between males (62.71%), children and adolescents (63.27%), non-white (69.75%) and urban residents (62.58%). Increasing trends of new cases were observed among adult male subjects (≥ 40 years old) and urban residents. Importantly, VL incidence showed a direct spatial dependence. Spatial and space-time clusters were identified in sertão and meio-norte sub-regions, overlapping with high social vulnerability areas. Conclusions VL is a persistent health issue in Brazilian Northeast and associated with social vulnerability. Space-time clustering of VL cases in socially vulnerable municipalities demands intersectoral public policies of surveillance and control, with focus on reducing inequalities and improving living conditions for regional inhabitants.

Until recently, chemotherapy for visceral leishmaniasis (VL; also known as kala-azar) was severely limited by factors such as high cost, route of administration, generation of side effects and potential for resistance. Although largely effective chemotherapies have become available with the introduction of new drugs and multi-drug regimens for VL, these could be further improved by the identification of biomarkers that are altered during effective treatment. The identification of such biomarkers in the circulation would also simplify efficacy trials. In this study we determined immunological signatures within the serum of ethnically and geographically-distinct VL patients (from Bangladesh and Brazil). Our results indicate that inflammatory and regulatory cytokines (IFNγ, TNFα, IL-10, IL-17), as well as levels of growth factors (FGF, VEGF), are elevated within the serum of VL patients from these sites. Examination of samples from Brazilian VL patients during and beyond standard treatment with meglumine antimoniate identified multiple parameters that revert to levels comparable to those of healthy endemic control individuals. The consolidation of these results provides a `response to treatment' signature that could be used within efficacy trials to rapidly and simply determine successful interruption of VL.

It is well established that helper T cell responses influence resistance or susceptibility to Mycobacterium leprae infection, but the role of more recently described helper T cell subsets in determining severity is less clear. To investigate the involvement of Th17 cells in the pathogenesis of leprosy, we determined the immune profile with variant presentations of leprosy. Firstly, IL-17A, IFN-γ and IL-10 were evaluated in conjunction with CD4 T cell staining by confocal microscopy of lesion biopsies from tuberculoid (TT) and lepromatous leprosy (LL) patients. Secondly, inflammatory cytokines were measured by multiplex assay of serum samples from Multibacillary (MB, n = 28) and Paucibacillary (PB, n = 23) patients and household contacts (HHC, n = 23). Patients with leprosy were also evaluated for leprosy reaction occurrence: LR+ (n = 8) and LR- (n = 20). Finally, peripheral blood mononuclear cells were analysed by flow cytometry used to determine the phenotype of cytokine-producing cells. Lesions from TT patients were found to have more CD4 IL-17A cells than those from LL patients. Higher concentrations of IL-17A and IL-1β were observed in serum from PB than MB patients. The highest serum IFN-γ concentrations were, however, detected in sera from MB patients that developed leprosy reactions (MB LR ). Together, these results indicate that Th1 cells were associated with both the PB presentation and also with leprosy reactions. In contrast, Th17 cells were associated with an effective inflammatory response that is present in the PB forms but were not predictive of leprosy reactions in MB patients.

Visceral leishmaniasis (VL) remains a major public health problem worldwide. Cytokine balance is thought to play a critical role in the development of this disease. Here, we perform a prospective exploratory study addressing whether simultaneous assessment of circulating levels of different lipid mediators and cytokines could highlight specific pathways involved with VL pathogenesis. VL patients displayed substantial increases in serum levels of Prostaglandin F2α (PGF2α), Leukotriene B4 (LTB4), Resolvin D1 (RvD1), IL-1β, IL-6, IL-8, IL-10, IL-12p70 and TNF-α compared with uninfected endemic control group, while exhibiting decreased levels of TGF-β1. Hierarchical cluster analysis of the prospective changes in the expression level of theses parameters upon anti-Leishmania treatment initiation revealed that the inflammatory profile observed in active disease gradually changed over time and was generally reversed at day 30 of therapy. Furthermore, not only the individual concentrations of most of the inflammatory biomarkers changed upon treatment, but the correlations between those and several biochemical parameters used to characterize VL disease activity were also modified over time. These results demonstrate that an inflammatory imbalance hallmarks active VL disease and open perspective for manipulation of these pathways in future studies examining a potential host-directed therapy against VL.