Renato Sathler-Avelar

Are increased frequency of macrophage-like and natural killer (NK) cells, together with high levels of NKT and CD4+CD25high T cells balancing activated CD8+ T cells, the key to control Chagas’ disease morbidity?

The immunological response during early human Trypanosoma cruzi infection is not completely understood, despite its role in driving the development of distinct clinical manifestations of chronic infection. Herein we report the results of a descriptive flow cytometric immunophenotyping investigation of major and minor peripheral blood leucocyte subpopulations in T. cruzi‐infected children, characterizing the early stages of the indeterminate clinical form of Chagas’ disease. Our results indicated significant alterations by comparison with uninfected children, including increased values of pre‐natural killer (NK)‐cells (CD3– CD16+ CD56–), and higher values of proinflammatory monocytes (CD14+ CD16+ HLA‐DR++). The higher values of activated B lymphocytes (CD19+ CD23+) contrasted with impaired T cell activation, indicated by lower values of CD4+ CD38+ and CD4+ HLA‐DR+ lymphocytes, a lower frequency of CD8+ CD38+ and CD8+ HLA‐DR+ cells; a decreased frequency of CD4+ CD25HIGH regulatory T cells was also observed. These findings reinforce the hypothesis that simultaneous activation of innate and adaptive immunity mechanisms in addition to suppression of adaptive cellular immune response occur during early events of Chagas’ disease. Comparative cross‐sectional analysis of these immunophenotypes with those exhibited by patients with late chronic indeterminate and cardiac forms of disease suggested that a shift toward high values of macrophage‐like cells extended to basal levels of proinflammatory monocytes as well as high values of mature NK cells, NKT and regulatory T cells, may account for limited tissue damage during chronic infection favouring the establishment/maintenance of a lifelong indeterminate clinical form of the disease. On the other hand, development of an adaptive cell‐mediated inflammatory immunoprofile characterized by high levels of activated CD8+ cells and basal levels of mature NK cells, NKT and CD4+ CD25HIGH cells might lead to late chronic pathologies associated with chagasic heart disease.

Variation Rhythms of Lymphocyte Subsets during Healthy Aging

Immunological alterations associated with aging (immunosenescence) do not represent a simple unidirectional decline in all functions but develop as a complex remodeling of the immune system, involving multiple reorganization and developmentally regulated changes. In general, most data available about aging were obtained at particular age intervals and most of them come from Caucasian individuals from either Europe or the United States. Here, we report the frequencies of major lymphocyte subsets in healthy Brazilian individuals from 2 distinct geographic regions (Southeast and South) at several age intervals spanning a lifetime period (0–86 years). Overall, we demonstrated that changes in the frequencies of cells related to both innate and adaptive immunity clearly occur with aging in these individuals. These changes were not progressive and equally steady for all cell populations tested but instead showed an oscillatory or rhythmic behavior that was distinctive of each population at different age intervals. We also observed that abrupt changes in the frequencies of immune cells may occur in healthy individuals over 75 years old, suggesting there is an impaired flexibility of the immune system at late stages of life to sustain homeostasis via immune mechanisms. We presented reference ranges for healthy Brazilian individuals at all ages. The knowledge of these parameters in further detail will allow interventions to optimize immune function in advanced age and to improve the quality of life in the elderly.

Etiological treatment during early chronic indeterminate Chagas disease incites an activated status on innate and adaptive immunity associated with a type 1-modulated cytokine pattern.

Pro-inflammatory immune response is usually associated with Chagas disease pathogenesis, but is also relevant to treatment effectiveness. Cross-sectional studies have suggested that this activated state may persist for years after therapeutic intervention. However, short-term longitudinal investigation has suggested that the Benznidazole treatment (Bz-treatment) leads to decreased immunological activation. In order to elucidate this issue, we performed a longitudinal study to evaluate the immunological status following Bz-treatment during early indeterminate Chagas disease. Our results demonstrated that Bz-treatment led to higher activation status of circulating monocytes but was negatively associated with the number of IL-12(+)CD14(+) cells. Moreover, Bz-treatment triggered a high frequency of circulating CD3(-)CD16(+)CD56(-) NK cells, in addition to elevated activation status associated with a type 1-modulated cytokine pattern. Bz-treatment induced substantial T and B-cell activation status associated with an overall IL-10 modulated type 1 cytokine profile. In summary, these findings provide new information regarding immune activation status following the etiological treatment of Chagas disease. These results suggest that in addition to the increased number of activated leukocytes in the peripheral blood, Bz-treatment may also involve a qualitative change in their functional capacity that drives their activation state toward a modulated cytokine profile. These changes may account for the benefits of etiological treatment of Chagas disease.

Benznidazole treatment during early-indeterminate Chagas' disease shifted the cytokine expression by innate and adaptive immunity cells toward a type 1-modulated immune profile.

Trypanosoma cruzi‐infected children was treated with benznidazole (Bz) during the early‐indeterminate disease (E‐IND) and the cytokine pattern of innate and adaptive immune compartments were evaluated prior to the treatment and 1 year after it. At first, we observed that the ex vivo cytokine profile of circulating leukocytes from E‐IND (n = 6) resembled the one observed for healthy schoolchildren (n = 7). Additionally, in vitro stimulation with T. cruzi antigens drove the E‐IND cytokine pattern toward a mixed immune profile with higher levels of IFN‐γ+, TNF‐α+ and IL‐4+ NK cells, increased numbers of IFN‐γ+, TNF‐α+ and IL‐10+ CD4+ T cells in addition to enhanced frequency of TNF‐α+/IL‐4+ CD19+ lymphocytes. Interestingly, upon T. cruzi antigen in vitro stimulation, E‐IND CD8+ lymphocytes displayed a selective enhancement of IFN‐γ expression, accounting for a global type 1‐modulated cytokine microenvironment. A shift toward a type 1‐modulated profile was also the hallmark of Bz‐treated children (E‐INDT). In this context, despite the mixed overall ex vivo cytokine profile observed for NK and CD8+ T cells, increased ability of these leukocytes to produce IFN‐γ in response to T. cruzi antigens was reported. Most noteworthy was the IL‐10 production evidenced at T lymphocytes, mainly CD4+ cells, as well as B lymphocytes, both ex vivo and upon antigen stimulation. Together, these findings gave evidence that NK cells and CD8+ T lymphocytes are the major sources of IFN‐γ, a pivotal cytokine for successful therapeutic response in human Chagas’ disease. Moreover, our data have also brought additional information, pointing out IL‐10 production by CD4+ cells and B lymphocytes, as the putative key element for parasite clearance in the absence of deleterious tissue damage.

Blood leukocytes from benznidazole-treated indeterminate chagas disease patients display an overall type-1-modulated cytokine profile upon short-term in vitro stimulation with trypanosoma cruzi antigens

BackgroundBenznidazole (Bz)-chemotherapy is recommended to prevent Chagas disease progression, despite its limited efficacy during chronic disease. However, the host mechanisms underlying these benefits still remain to be elucidated.MethodsIn this study, we have used short-term whole blood cultures to describe the cytokine profile of Bz-treated Indeterminate Chagas disease patients-(INDt) as compared to untreated patients-(IND).ResultsOur findings showed that IND presented increased levels of IL-10+neutrophils, IL-12+ and IL-10+monocytes and IFN-γ+NK-cells. Moreover, IND showed slight increase of IL-4+CD4+T-cells and enhanced levels of IL-10+CD8+T-cells and B-cells. Additional analysis of cytokine Low and High producers also highlighted the presence of High cytokine producers within IND, including IL-10 from CD4+ T-cells and IFN-γ from CD8+ T-cells, as compared to NI. The Bz-treatment lead to an overall cytokine down-regulation in the innate and adaptive compartments, including low levels of IL-12+ and IL-10+neutrophils and monocytes, IFN-γ+NK-cells, IL-12+, TNF-α+, IFN-γ+ and IL-5+CD4+T-cells and IL-10+B-cells, along with basal levels of cytokine-expressing CD8+T-cells in INDt as compared to IND. The in vitro antigen stimulation shifted the cytokine profile toward a type 1-modulated profile, with increased levels of IL-12+ and IL-10+ monocytes, IFN-γ+ and IL-4+NK-cells along with TNF-α+ and IFN-γ+CD8+T-cells. Analysis of Low and High cytokine producers, upon in vitro antigen stimulation, further confirm these data.ConclusionTogether, our findings showed that the Bz treatment of Indeterminate Chagas’ disease patients shifts the cytokine patterns of peripheral blood monocytes, NK-cells and CD8+ T-cells towards a long-lasting Type-1-modulated profile that could be important to the maintenance of a non-deleterious immunological microenvironment.

Phenotypic Features of Circulating Leukocytes from Non-human Primates Naturally Infected with Trypanosoma cruzi Resemble the Major Immunological Findings Observed in Human Chagas Disease.

Background Cynomolgus macaques (Macaca fascicularis) represent a feasible model for research on Chagas disease since natural T. cruzi infection in these primates leads to clinical outcomes similar to those observed in humans. However, it is still unknown whether these clinical similarities are accompanied by equivalent immunological characteristics in the two species. We have performed a detailed immunophenotypic analysis of circulating leukocytes together with systems biology approaches from 15 cynomolgus macaques naturally infected with T. cruzi (CH) presenting the chronic phase of Chagas disease to identify biomarkers that might be useful for clinical investigations. Methods and Findings Our data established that CH displayed increased expression of CD32+ and CD56+ in monocytes and enhanced frequency of NK Granzyme A+ cells as compared to non-infected controls (NI). Moreover, higher expression of CD54 and HLA-DR by T-cells, especially within the CD8+ subset, was the hallmark of CH. A high level of expression of Granzyme A and Perforin underscored the enhanced cytotoxicity-linked pattern of CD8+ T-lymphocytes from CH. Increased frequency of B-cells with up-regulated expression of Fc-γRII was also observed in CH. Complex and imbricate biomarker networks demonstrated that CH showed a shift towards cross-talk among cells of the adaptive immune system. Systems biology analysis further established monocytes and NK-cell phenotypes and the T-cell activation status, along with the Granzyme A expression by CD8+ T-cells, as the most reliable biomarkers of potential use for clinical applications. Conclusions Altogether, these findings demonstrated that the similarities in phenotypic features of circulating leukocytes observed in cynomolgus macaques and humans infected with T. cruzi further supports the use of these monkeys in preclinical toxicology and pharmacology studies applied to development and testing of new drugs for Chagas disease.

Cynomolgus macaques naturally infected with Trypanosoma cruzi-I exhibit an overall mixed pro-inflammatory/modulated cytokine signature characteristic of human Chagas disease.

Background Non-human primates have been shown to be useful models for Chagas disease. We previously reported that natural T. cruzi infection of cynomolgus macaques triggers clinical features and immunophenotypic changes of peripheral blood leukocytes resembling those observed in human Chagas disease. In the present study, we further characterize the cytokine-mediated microenvironment to provide supportive evidence of the utility of cynomolgus macaques as a model for drug development for human Chagas disease. Methods and findings In this cross-sectional study design, flow cytometry and systems biology approaches were used to characterize the ex vivo and in vitro T. cruzi-specific functional cytokine signature of circulating leukocytes from TcI-T. cruzi naturally infected cynomolgus macaques (CH). Results showed that CH presented an overall CD4+-derived IFN-γ pattern regulated by IL-10-derived from CD4+ T-cells and B-cells, contrasting with the baseline profile observed in non-infected hosts (NI). Homologous TcI-T. cruzi-antigen recall in vitro induced a broad pro-inflammatory cytokine response in CH, mediated by TNF from innate/adaptive cells, counterbalanced by monocyte/B-cell-derived IL-10. TcIV-antigen triggered a more selective cytokine signature mediated by NK and T-cell-derived IFN-γ with modest regulation by IL-10 from T-cells. While NI presented a cytokine network comprised of small number of neighborhood connections, CH displayed a complex cross-talk amongst network elements. Noteworthy, was the ability of TcI-antigen to drive a complex global pro-inflammatory network mediated by TNF and IFN-γ from NK-cells, CD4+ and CD8+ T-cells, regulated by IL-10+CD8+ T-cells, in contrast to the TcIV-antigens that trigger a modest network, with moderate connecting edges. Conclusions Altogether, our findings demonstrated that CH present a pro-inflammatory/regulatory cytokine signature similar to that observed in human Chagas disease. These data bring additional insights that further validate these non-human primates as experimental models for Chagas disease.

Systems Biology Reveals Relevant Gaps in Fc-γR Expression, Impaired Regulatory Cytokine Microenvironment Interfaced With Anti-Trypanosoma cruzi IgG Reactivity in Cardiac Chagas Disease Patients

The systems biology approach has become an innovative tool when it comes to shedding light on the complex immune response underlying the development/maintenance of distinct clinical forms of Chagas disease. The goal of this study was to describe an integrative overview of Fc-γR expression, cytokine microenvironment and anti-Trypanosoma cruzi IgG interface in indeterminate-(IND) and cardiac-(CARD) patients. Data demonstrated that IND displayed an overall higher Fcγ-R expression (CD16; CD32; CD64) on neutrophils-(NEU), along with (CD16; CD64) on monocytes-(MON) as compared to CARD. Additionally, CARD presented an increased expression of CD32 in B-cells. While preserved frequency of IL-10-producing cells was observed in IND, decreased levels of IL-10+ phagocytes and enhanced TNF+ MON and NK-cells were observed in CARD. T. cruzi-antigen recall in vitro induces a general decrease of Fc-γR expression in Chagas disease patients, especially in CARD. Moreover, T. cruzi-antigen stimuli triggered a concomitant increase of IFN-γ+NEU/TNF+NK-cells and IL-10+MON/IL-10+B-cells in IND. Biomarker signatures further emphasized the contrasting Fc-γR expression and cytokine microenvironment observed in Chagas disease patients with distinct clinical forms. Up-regulation of Fc-γR expression (CD16 on NEU;MON;NK) was observed in IND, whereas a general decrease was reported for CARD. Moreover, while a mixed cytokine microenvironment (TNF; IL-10) was observed in IND, CARD presented a contrasting profile with up-regulation of TNF+NEU and IL-12+NEU. Integrative network analysis revealed a distinct assemblage of biomarkers, with CARD presenting a large number of negative internode connectivity in comparison with IND. The relevant gaps in Fc-γR expression and impaired regulatory cytokine microenvironment interfaced with the anti-T. cruzi IgG reactivity throughout an exacerbated negative connectivity may account for the development/maintenance of the clinical status of cardiac Chagas disease.