Cristiane Alves da Silva Menezes

Cellular and genetic mechanisms involved in the generation of protective and pathogenic immune responses in human Chagas disease

Perhaps one of the most intriguing aspects of human Chagas disease is the complex network of events that underlie the generation of protective versus pathogenic immune responses during the chronic phase of the disease. While most individuals do not develop patent disease, a large percentage may develop severe forms that eventually lead to death. Although many efforts have been devoted to deciphering these mechanisms, there is still much to be learned before we can fully understand the pathogenesis of Chagas disease. It is clear that the hosts immune response is decisive in this process. While characteristics of the parasite influence the immune response, it is becoming evident that the host genetic background plays a fundamental role in the establishment of pathogenic versus protective responses. The involvement of three complex organisms, host, parasite and vector, is certainly one of the key aspects that calls for multidisciplinary approaches towards the understanding of Chagas disease. We believe that now, one hundred years after the discovery of Chagas disease, it is imperative to continue with highly interactive research in order to elucidate the immune response associated with disease evolution, which will be essential in designing prophylactic or therapeutic interventions.

Phenotypic and functional characteristics of CD28+ and CD28− cells from chagasic patients: distinct repertoire and cytokine expression

Chronic human Chagas’ disease ranges from an asymptomatic to a severe cardiac clinical form. The involvement of the hosts immune response in the development and maintenance of chagasic pathology has been demonstrated by several groups. We have shown that activated T‐cells lacking CD28 expression are increased in the peripheral blood of chagasic patients (CP), suggesting a relationship between these cells and disease. In order to better characterize this cell population, determining their possible role in immunoregulation of human Chagas’ disease, we evaluated the expression of TCR‐Vbeta regions 2, 3·1, 5, 8 and 17, as well as the expression of IFN‐γ, TNF‐α, IL‐4 and IL‐10 by CD28+ and CD28− cells from polarized indeterminate and cardiac CP. Flow cytometric analysis demonstrated equivalent TCR‐Vbeta usage between CD4+CD28+ and CD4+CD28− cells from all groups (chagasic and healthy controls). However, there was a predominance of Vbeta5 expression in the CD28+ and CD28− populations in the CP groups (indeterminate and cardiac). Interestingly, CD8+CD28− cells from CP, but not from nonchagasic individuals, displayed a reduced frequency of most analysed Vbetas when compared with the CD8+CD28+ subpopulation. Comparison of V‐beta expression in CD28+ or CD28− cell populations among individuals from different groups also showed several interesting differences. Functionally, cardiac CP displayed a higher frequency of IFN‐γ, TNF‐α and IL‐4 producing lymphocytes than indeterminate CP. Correlation analysis between the frequency of cytokine expressing cells, and the frequency of CD4+ T‐cells with differential expression of CD28 demonstrated that CD4+CD28− T‐cells were positively correlated with TNF‐α in cardiac and with IL‐10 in indeterminate CP, suggesting that these cells might have an important regulatory role in human Chagas’ disease.

Immunoregulatory networks in human Chagas disease

Chagas disease, caused by the infection with Trypanosoma cruzi, is endemic in all Latin America. Due to the increase in population migration, Chagas disease has spread worldwide and is now considered a health issue not only in endemic countries. While most chronically infected individuals remain asymptomatic, approximately 30% of the patients develop a potentially deadly cardiomyopathy. The exact mechanisms that underlie the establishment and maintenance of the cardiac pathology are not clear. However, there is consistent evidence that immunoregulatory cytokines are critical for orchestrating the immune response and thus influence disease development or control. While the asymptomatic (indeterminate) form represents a state of balance between the host and the parasite, the establishment of the cardiac form represents the loss of this balance. Analysis of data obtained from several studies has led to the hypothesis that the indeterminate form is associated with an anti‐inflammatory cytokine profile, represented by high expression of IL‐10, while cardiac form is associated with a high production of IFN‐gamma and TNF‐alpha in relation to IL‐10, leading to an inflammatory profile. Here, we discuss the immunoregulatory events that might influence disease outcome, as well as the mechanisms that influence the establishment of these complex immunoregulatory networks.

Captopril increases the intensity of monocyte infection by Trypanosoma cruzi and induces human T helper type 17 cells

The anti‐hypertensive drug captopril is used commonly to reduce blood pressure of patients with severe forms of Chagas disease, a cardiomyopathy caused by chronic infection with the intracellular protozoan Trypanosoma cruzi. Captopril acts by inhibiting angiotensin‐converting enzyme (ACE), the vasopressor metallopeptidase that generates angiotensin II and promotes the degradation of bradykinin (BK). Recent studies in mice models of Chagas disease indicated that captopril can potentiate the T helper type 1 (Th1)‐directing natural adjuvant property of BK. Equipped with kinin‐releasing cysteine proteases, T. cruzi trypomastigotes were shown previously to invade non‐professional phagocytic cells, such as human endothelial cells and murine cardiomyocytes, through the signalling of G protein‐coupled bradykinin receptors (B2KR). Monocytes are also parasitized by T. cruzi and these cells are known to be important for the host immune response during infection. Here we showed that captopril increases the intensity of T. cruzi infection of human monocytes in vitro. The increased parasitism was accompanied by up‐regulated expression of ACE in human monocytes. While T. cruzi infection increased the expression of interleukin (IL)‐10 by monocytes significantly, compared to uninfected cells, T. cruzi infection in association with captopril down‐modulated IL‐10 expression by the monocytes. Surprisingly, studies with peripheral blood mononuclear cells revealed that addition of the ACE inhibitor in association with T. cruzi increased expression of IL‐17 by CD4+ T cells in a B2KR‐dependent manner. Collectively, our results suggest that captopril might interfere with host–parasite equilibrium by enhancing infection of monocytes, decreasing the expression of the modulatory cytokine IL‐10, while guiding development of the proinflammatory Th17 subset.

Phenotypic, functional, and quantitative characterization of canine peripheral blood monocyte-derived macrophages

The yield as well as phenotypic and functional parameters of canine peripheral blood monocyte-derived macrophages were analyzed. The cells that remained adherent to Teflon after 10 days of culture had high phagocytic activity when inoculated with Leishmania chagasi. Flow cytometric analysis demonstrated that more than 80% of cultured cells were positive for the monocyte/macrophage marker CD14.

Clinical aspects of Chagas disease and implications for novel therapies

The interaction between the protozoan parasite Trypanosoma cruzi and the human host dates back 9,000 years, as demonstrated by molecular analysis of material obtained from Andean mummies indicating the presence of the parasites kinetoplast DNA in populations from Chile and Peru. This long‐established interaction, which persists today, demonstrates that T. cruzi has established a very well adapted relationship with the human host. From the point of view of a host–parasite relationship, this is desirable; however, such a high degree of adaptation is perhaps the foundation for many of the unknowns that surround this disease. Unveiling of the immunological mechanisms that underlie the establishment of pathology, identification of parasite‐associated factors that determine strain‐differential tissue tropism, discovery of host genetic elements that influence the development of different clinical forms of the disease, and understanding environmental factors that may influence the host–parasite interactions are some of the key questions that remain to be answered. The response to these questions will aid in addressing some of the current challenges in Chagas disease: fulfilling the need for efficient diagnosis, developing effective prophylactic measures, discovering effective therapeutics, and finding methods to control disease progression. Drug Dev Res 72:471–479, 2011.

Distinct Macrophage Fates after in vitro Infection with Different Species of Leishmania: Induction of Apoptosis by Leishmania (Leishmania) amazonensis, but Not by Leishmania (Viannia) guyanensis

Leishmania is an intracellular parasite in vertebrate hosts, including man. During infection, amastigotes replicate inside macrophages and are transmitted to healthy cells, leading to amplification of the infection. Although transfer of amastigotes from infected to healthy cells is a crucial step that may shape the outcome of the infection, it is not fully understood. Here we compare L. amazonensis and L. guyanensis infection in C57BL/6 and BALB/c mice and investigate the fate of macrophages when infected with these species of Leishmania in vitro. As previously shown, infection of mice results in distinct outcomes: L. amazonensis causes a chronic infection in both strains of mice (although milder in C57BL/6), whereas L. guyanensis does not cause them disease. In vitro, infection is persistent in L. amazonensis-infected macrophages whereas L. guyanensis growth is controlled by host cells from both strains of mice. We demonstrate that, in vitro, L. amazonensis induces apoptosis of both C57BL/6 and BALB/c macrophages, characterized by PS exposure, DNA cleavage into nucleosomal size fragments, and consequent hypodiploidy. None of these signs were seen in macrophages infected with L. guyanensis, which seem to die through necrosis, as indicated by increased PI-, but not Annexin V-, positive cells. L. amazonensis-induced macrophage apoptosis was associated to activation of caspases-3, -8 and -9 in both strains of mice. Considering these two species of Leishmania and strains of mice, macrophage apoptosis, induced at the initial moments of infection, correlates with chronic infection, regardless of its severity. We present evidence suggestive that macrophages phagocytize L. amazonensis-infected cells, which has not been verified so far. The ingestion of apoptotic infected macrophages by healthy macrophages could be a way of amastigote spreading, leading to the establishment of infection.

Highly conserved CDR3 region in circulating CD4+Vβ5+ T cells may be associated with cytotoxic activity in Chagas disease

Human infection with Trypanosoma cruzi leads to Chagas disease, which presents as several different clinical conditions ranging from an asymptomatic form to a severe dilated cardiomyopathy. Several studies have demonstrated that T cells play a critical role in the development of cardiac pathology, as well as in immunoregulation during chronic disease. However, the mechanisms that drive protective or pathogenic T cell response are not known. We have shown that CD4+ T cells from chagasic patients preferentially express T cell receptor (TCR) β‐chain variable region (Vβ) 5. The aim of this work was to determine whether T cells expressing this particular Vβ region displayed variable or restricted CDR3 sequences, as an indicator of the nature of the stimulus leading to the activation of these T cells in vivo. Additionally, we aimed to evaluate phenotypic characteristics of these cells that might be associated with pathology. CDR3 junctional region sequencing of Vβ5·1 expressing CD4+ T cells revealed the occurrence of a highly homologous CDR3 region with conserved TCR Jβ region usage among patients with cardiac, but not indeterminate, Chagas disease. Moreover, correlation analysis indicated that the frequency of CD4+Vβ5·1+ cells is associated with granzyme A expression, suggesting that these cells might display cytotoxic function. Together these results provide new insight into T cell recognition of antigens involved in Chagas disease and suggest that these cells may be implicated in the pathogenesis of chagasic cardiomyopathy.

Vitamin D receptor expression and hepcidin levels in the protection or severity of leprosy: a systematic review

Leprosy is a chronic infectious disease whose disequilibrium in the hosts genetic, immunological and clinical mechanisms leads to distinct manifestations defining the type of immunological response. This review focuses its attention on the influence of the Vitamin D Receptor and hepcidin expressions that can suggest the protection or severity of leprosy.

Regulatory and Pro-Inflammatory Cytokines in Brazilian Living-Related Renal Transplant Recipients According to Creatinine Plasma Levels

The maintenance of stable graft function in renal transplanted recipients (RTR) is a challenge for healthcare staff. The ideal biomarkers must have significant predictive values to monitor the intricate renal function response triggered after renal transplantation. The main purpose in this study was to evaluate the regulatory and pro‐inflammatory cytokines as biomarkers of allograft function in living‐related renal transplant patients.