Search tips
Search criteria

Results 1-10 (10)

Clipboard (0)

Select a Filter Below

more »
Year of Publication
Document Types
1.  Tr-1–Like CD4+CD25−CD127−/lowFOXP3− Cells Are the Main Source of Interleukin 10 in Patients With Cutaneous Leishmaniasis Due to Leishmania braziliensis 
The Journal of Infectious Diseases  2014;211(5):708-718.
CD4+CD25+FOXP3+ regulatory T cells have long been shown to mediate susceptibility to Leishmania infection, mainly via interleukin 10 production. In this work, we showed that the main sources of interleukin 10 in peripheral blood mononuclear cells (PBMCs) from patients with cutaneous leishmaniasis due to Leishmania braziliensis are CD4+CD25−CD127−/lowFOXP3− cells. Compared with uninfected controls, patients with CL had increased frequencies of circulating interleukin 10–producing CD4+CD25−CD127−/low cells, which efficiently suppressed tumor necrosis factor α production by the total PBMC population. Also, in CL lesions, interleukin 10 was mainly produced by CD4+CD25− cells, and interleukin 10 messenger RNA expression was associated with interleukin 27, interleukin 21, and interferon γ expression, rather than with FOXP3 or transforming growth factor β expressions. Active production of both interleukin 27 and interleukin 21, together with production of interferon γ and interleukin 10, was also detected in the lesions. Since these cytokines are associated with the differentiation and activity of Tr-1 cells, our results suggest that this cell population may play an important role in the immunomodulation of CL. Therefore, development of treatments that interfere with this pathway may lead to faster parasite elimination.
PMCID: PMC4402371  PMID: 25139022
L. braziliensis; tegumentary leishmaniasis; Tr-1 cells; IL-10
2.  Nucleosides Present on Phlebotomine Saliva Induce Immunossuppression and Promote the Infection Establishment 
PLoS Neglected Tropical Diseases  2015;9(4):e0003600.
Sand fly saliva plays a crucial role in establishing Leishmania infection. We identified adenosine (ADO) and adenosine monophosphate (AMP) as active pharmacologic compounds present in Phlebotomus papatasi saliva that inhibit dendritic cell (DC) functions through a PGE2/IL 10-dependent mechanism.
Methodology/Principal Findings
Herein, we prepared a mixture of ADO and AMP in equimolar amounts similar to those present in the salivary-gland extract (SGE) form one pair of salivary glands of P. papatasi and co-injected it with Leishmania amazonensis or L. major into mouse ears. ADO+AMP mimicked exacerbative effects of P. papatasi saliva in leishmaniasis, increasing parasite burden and cutaneous lesions. Enzymatic catabolism of salivary nucleosides reversed the SGE-induced immunosuppressive effect associated with IL-10 enhancement. Immunosuppressive factors COX2 and IL-10 were upregulated and failed to enhance ear lesion and parasite burden in IL 10-/- infected mice. Furthermore, nucleosides increased regulatory T cell (Treg) marker expression on CD4+CD25- cells, suggesting induction of Tregs on effector T cells (T eff). Treg induction (iTreg) was associated with nucleoside-induced tolerogenic dendritic cells (tDCs) expressing higher levels of COX2 and IL-10. In vitro generation of Tregs was more efficient in DCs treated with nucleosides. Suppressive effects of nucleosides during cutaneous leishmaniasis were mediated through an A2AR-dependent mechanism. Using BALB/c mice deficient in A2A ADO receptor (A2AR–/–), we showed that co-inoculated mice controlled infection, displaying lower parasite numbers at infection sites and reduced iTreg generation.
We have demonstrated that ADO and AMP in P. papatasi saliva mediate exacerbative effects of Leishmania infection by acting preferentially on DCs promoting a tolerogenic profile in DCs and by generating iTregs in inflammatory foci through an A2AR mechanism.
Author Summary
Leishmania parasites are transmitted to their vertebrate hosts by infected Phlebotomine sand flies during the blood meal of the flies. During the Leishmania transmission, the saliva is inoculated together with parasites and exhibit several pharmacological compounds that facilitate blood feeding, interfering on homeostasis and avoiding inflammation. Thus, these compounds allow the establishment of pathogen infection. We recently identified adenosine (ADO) and adenosine monophosphate (AMP) as major immunomodulatory compounds present within the Old World sand fly species Phlebotomus papatasii, which protected mice from extreme inflammatory insults. ADO limits the magnitude of immune response by displaying a potent anti-inflammatory activity. Here, we demonstrated that ADO and AMP present in Phlebotomus papatasi saliva are involved in the establishment of parasite infection. Such nucleosides act through adenosine A2A receptor (A2AR), inducing a tolerogenic profile on dendritic cells (tDC) that may generate regulatory T cells differentiation, thus leading to suppression of the immune response and parasite survival. The identification of the active salivary constituents could serve as a strategy for the development of new vaccines to control pathogen transmission.
PMCID: PMC4388340  PMID: 25849562
3.  In Vitro and In Vivo Trypanocidal Activity of H2bdtc-Loaded Solid Lipid Nanoparticles 
The parasite Trypanosoma cruzi causes Chagas disease, which remains a serious public health concern and continues to victimize thousands of people, primarily in the poorest regions of Latin America. In the search for new therapeutic drugs against T. cruzi, here we have evaluated both the in vitro and the in vivo activity of 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyl dithiocarbazate) (H2bdtc) as a free compound or encapsulated into solid lipid nanoparticles (SLN); we compared the results with those achieved by using the currently employed drug, benznidazole. H2bdtc encapsulated into solid lipid nanoparticles (a) effectively reduced parasitemia in mice at concentrations 100 times lower than that normally employed for benznidazole (clinically applied at a concentration of 400 µmol kg−1 day−1); (b) diminished inflammation and lesions of the liver and heart; and (c) resulted in 100% survival of mice infected with T. cruzi. Therefore, H2bdtc is a potent trypanocidal agent.
Author Summary
The protozoan parasite Trypanosoma cruzi causes Chagas disease, a condition that affects the poorest regions of Latin America mainly. The chronic phase of this disease disables thousands of patients, constituting an important public health issue. The pharmacotherapy that is currently applied to treat the disease emerged many decades ago, is ineffective in most patients, mainly during the chronic phase, and has serious side effects. In a recent study, we showed that the compound 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) (H2bdtc) is a potential drug candidate against the in vitro trypomastigote form of Tulahuen strains of T. cruzi. Here we report that H2bdtc loaded into solid lipid nanoparticles (H2bdtc-SLNs) displays good trypanocidal activity against the trypomastigote form of the Y strain of T. cruzi both in vitro and in vivo. Our in vivo experiments revealed that H2bdtc-SLN is 100 times more active than benznidazole (BZN), the drug that is commercially available to treat Chagas disease. Surprisingly, this compound has no side effects on the T. cruzi acute phase. Hence, we propose that H2bdtc-SLNs possesses interesting anti-Trypanosoma properties.
PMCID: PMC4014426  PMID: 24810753
4.  Toxoplasma gondii Soluble Tachyzoite Antigen Triggers Protective Mechanisms against Fatal Intestinal Pathology in Oral Infection of C57BL/6 Mice 
PLoS ONE  2013;8(9):e75138.
Toxoplasma gondii induces a potent IL-12 response early in infection that results in IFN-γ-dependent control of parasite growth. It was previously shown that T. gondii soluble tachyzoite antigen (STAg) injected 48 hr before intraperitoneal infection reduces lipoxin A4 and 5-lipoxygenase (5-LO)-dependent systemic IL-12 and IFN-γ production as well as hepatic immunopathology. This study investigated the ability of STAg-pretreatment to control the fatal intestinal pathology that develops in C57BL/6 mice orally infected with 100 T. gondii cysts. STAg-pretreatment prolonged the animals’ survival by decreasing tissue parasitism and pathology, mainly in the ilea. Protection was associated with decreases in the systemic IFN-γ levels and IFN-γ and TNF message levels in the ilea and with increased TGF-β production in this tissue, but protection was independent of 5-LO and IL-4. STAg-pretreatment decreased CD4+ T cell, NK cell, CD11b+ monocyte and CD11b+CD11c+ dendritic cell numbers in the lamina propria and increased CD8+ T cells in the intestinal epithelial compartment. In parallel, decreases were observed in iNOS and IL-17 expression in this organ. These results demonstrate that pretreatment with STAg can induce the recruitment of protective CD8+ T cells to the intraepithelial compartment and decrease proinflammatory immune mechanisms that promote intestinal pathology in T. gondii infection.
PMCID: PMC3782460  PMID: 24086456
5.  Heme oxygenase-1 activity is involved in the control of Toxoplasma gondii infection in the lung of BALB/c and C57BL/6 and in the small intestine of C57BL/6 mice 
Veterinary Research  2013;44(1):89.
Heme oxygenase-1 (HO-1) is an enzyme that catabolizes free heme, which induces an intense inflammatory response. The expression of HO-1 is induced by different stimuli, triggering an anti-inflammatory response during biological stress. It was previously verified that HO-1 is able to induce indoleamine 2,3-dioxygenase (IDO), an enzyme that is induced by IFN-γ in Toxoplasma gondii infection. To verify the role of HO-1 during in vivo T. gondii infection, BALB/c and C57BL/6 mice were infected with the ME49 strain and treated with zinc protoporphyrin IX (ZnPPIX) or hemin, which inhibit or induce HO-1 activity, respectively. The results show that T. gondii infection induced high levels of HO-1 expression in the lung of BALB/c and C57BL6 mice. The animals treated with ZnPPIX presented higher parasitism in the lungs of both lineages of mice, whereas hemin treatment decreased the parasite replication in this organ and in the small intestine of infected C57BL/6 mice. Furthermore, C57BL/6 mice infected with T. gondii and treated with hemin showed higher levels of IDO expression in the lungs and small intestine than uninfected mice. In conclusion, our data suggest that HO-1 activity is involved in the control of T. gondii in the lungs of both mouse lineages, whereas the hemin, a HO-1 inducer, seems to be involved in the control of parasitism in the small intestine of C57BL/6 mice.
PMCID: PMC3851451  PMID: 24088531
6.  Nucleosides from Phlebotomus papatasi salivary gland ameliorate murine collagen-induced arthritis by impairing dendritic cell functions 
Among several pharmacological compounds, Phlebotomine saliva contains substances with anti-inflammatory properties. Herein, we demonstrated the therapeutic activity of salivary gland extract (SGE) of Phlebotomus papatasi in an experimental model of arthritis (collagen-induced arthritis [CIA]) and identified the constituents responsible for such activity. Daily administration of SGE, initiated at disease onset, attenuated the severity of CIA, reducing the joint lesion and pro-inflammatory cytokines release. In vitro incubation of dendritic cells (DC) with SGE limited specific CD4+Th17 cell response. We identified adenosine (ADO) and adenosine monophosphate (5′AMP) as the major salivary molecules responsible for anti-inflammatory activities. Pharmacologic inhibition of ADO A2A receptor or enzymatic catabolism of salivary nucleosides reversed the SGE-induced immunosuppressive effect. Importantly, CD73 (ecto-5′nucleotidase enzyme) is expressed on DC surface during stage of activation, suggesting that ADO is also generated by 5′AMP metabolism. Moreover, both nucleosides mimicked SGE-induced anti-inflammatory activity upon DC function in vitro and attenuated establishment of CIA in vivo. We reveal that ADO and 5′AMP are present in pharmacological amounts in P. papatasi saliva and act preferentially on DC function, consequently reducing Th17 subset activation and suppressing the autoimmune response. Thus, it is plausible that these constituents might be promising therapeutic molecules to target immune inflammatory diseases.
PMCID: PMC3195336  PMID: 21930966
7.  Regulation of Trypanosoma cruzi-Induced Myocarditis by Programmed Death Cell Receptor 1 ▿ †  
Infection and Immunity  2011;79(5):1873-1881.
Trypanosoma cruzi infection causes intense myocarditis, leading to cardiomyopathy and severe cardiac dysfunction. Protective adaptive immunity depends on balanced signaling through a T cell receptor and coreceptors expressed on the T cell surface. Such coreceptors can trigger stimulatory or inhibitory signals after binding to their ligands in antigen-presenting cells (APC). T. cruzi modulates the expression of coreceptors in lymphocytes after infection. Deregulated inflammation may be due to unbalanced expression of these molecules. Programmed death cell receptor 1 (PD-1) is a negative T cell coreceptor that has been associated with T cell anergy or exhaustion and persistent intracellular infections. We aimed to study the role of PD-1 during T. cruzi-induced acute myocarditis in mice. Cytometry assays showed that PD-1 and its ligands are strongly upregulated in lymphocytes and APC in response to T. cruzi infection in vivo and in vitro. Lymphocytes infiltrating the myocardium exhibited high levels of expression of these molecules. An increased cardiac inflammatory response was found in mice treated with blocking antibodies against PD-1, PD-L1, and to a lesser extent, PD-L2, compared to that found in mice treated with rat IgG. Similar results in PD-1−/− mice were obtained. Moreover, the PD-1 blockade/deficiency led to reduced parasitemia and tissue parasitism but increased mortality. These results suggest the participation of a PD-1 signaling pathway in the control of acute myocarditis induced by T. cruzi and provide additional insight into the regulatory mechanisms in the pathogenesis of Chagas' disease.
PMCID: PMC3088162  PMID: 21357717
8.  Cell-Free Antigens from Paracoccidioides brasiliensis Drive IL-4 Production and Increase the Severity of Paracoccidioidomycosis 
PLoS ONE  2011;6(6):e21423.
The thermally dimorphic fungus Paracoccidioides brasiliensis (Pb) is the causative agent of paracoccidioidomycosis (PCM), one of the most frequent systemic mycosis that affects the rural population in Latin America. PCM is characterized by a chronic inflammatory granulomatous reaction, which is consequence of a Th1-mediated adaptive immune response. In the present study we investigated the mechanisms involved in the immunoregulation triggered after a prior contact with cell-free antigens (CFA) during a murine model of PCM. The results showed that the inoculation of CFA prior to the infection resulted in disorganized granulomatous lesions and increased fungal replication in the lungs, liver and spleen, that paralleled with the higher levels of IL-4 when compared with the control group. The role of IL-4 in facilitating the fungal growth was demonstrated in IL-4-deficient- and neutralizing anti-IL-4 mAb-treated mice. The injection of CFA did not affect the fungal growth in these mice, which, in fact, exhibited a significant diminished amount of fungus in the tissues and smaller granulomas. Considering that in vivo anti-IL-4-application started one week after the CFA-inoculum, it implicates that IL-4-CFA-induced is responsible by the mediation of the observed unresponsiveness. Further, the characterization of CFA indicated that a proteic fraction is required for triggering the immunosuppressive mechanisms, while glycosylation or glycosphingolipids moieties are not. Taken together, our data suggest that the prior contact with soluble Pb antigens leads to severe PCM in an IL-4 dependent manner.
PMCID: PMC3120880  PMID: 21731741
9.  BALB/c Mice Infected with Antimony Treatment Refractory Isolate of Leishmania braziliensis Present Severe Lesions due to IL-4 Production 
Leishmania braziliensis is the main causative agent of cutaneous leishmaniasis in Brazil. Protection against infection is related to development of Th1 responses, but the mechanisms that mediate susceptibility are still poorly understood. Murine models have been the most important tools in understanding the immunopathogenesis of L. major infection and have shown that Th2 responses favor parasite survival. In contrast, L. braziliensis–infected mice develop strong Th1 responses and easily resolve the infection, thus making the study of factors affecting susceptibility to this parasite difficult.
Methodology/Principal Findings
Here, we describe an experimental model for the evaluation of the mechanisms mediating susceptibility to L. braziliensis infection. BALB/c mice were inoculated with stationary phase promastigotes of L. braziliensis, isolates LTCP393(R) and LTCP15171(S), which are resistant and susceptible to antimony and nitric oxide (NO), respectively. Mice inoculated with LTCP393(R) presented larger lesions that healed more slowly and contained higher parasite loads than lesions caused by LTCP15171(S). Inflammatory infiltrates in the lesions and production of IFN-γ, TNF-α, IL-10 and TGF-β were similar in mice inoculated with either isolate, indicating that these factors did not contribute to the different disease manifestations observed. In contrast, IL-4 production was strongly increased in LTCP393(R)-inoculated animals and also arginase I (Arg I) expression. Moreover, anti-IL-4 monoclonal antibody (mAb) treatment resulted in decreased lesion thickness and parasite burden in animals inoculated with LTCP393(R), but not in those inoculated with LTCP15171(S).
We conclude that the ability of L. braziliensis isolates to induce Th2 responses affects the susceptibility to infection with these isolates and contributes to the increased virulence and severity of disease associated with them. Since these data reflect what happens in human infection, this model could be useful to study the pathogenesis of the L. braziliensis infection, as well as to design new strategies of therapeutic intervention.
Author Summary
Leishmaniasis is a neglected disease that affects more than 12 million people worldwide. In Brazil, the cutaneous disease is more prevalent with about 28,000 new cases reported each year, and L. braziliensis is the main causative agent. The interesting data about the infection with this parasite is the wide variety of clinical manifestations that ranges from single ulcerated lesions to mucocutaneous and disseminated disease. However, experimental models to study the infection with this parasite are difficult to develop due to high resistance of most mouse strains to the infection, and the mechanisms underlying the distinct manifestations remain poorly understood. Here, the authors use a mouse experimental model of infection with different L. braziliensis isolates, known to induce diseases with distinct severity in the human hosts, to elucidate immune mechanisms that may be involved in the different manifestations. They showed that distinct parasite isolates may modulate host response, and increased IL-4 production and Arg I expression was related to more severe disease, resulting in longer length of disease with larger lesions and reduced parasite clearance. These findings may be useful in the identification of immunological targets to control L. braziliensis infection and potential clinical markers of disease progression.
PMCID: PMC3046967  PMID: 21390155
10.  IL-17 Produced during Trypanosoma cruzi Infection Plays a Central Role in Regulating Parasite-Induced Myocarditis 
Chagas disease is a neglected disease caused by the intracellular parasite Trypanosoma cruzi. Around 30% of the infected patients develop chronic cardiomyopathy or megasyndromes, which are high-cost morbid conditions. Immune response against myocardial self-antigens and exacerbated Th1 cytokine production has been associated with the pathogenesis of the disease. As IL-17 is involved in the pathogenesis of several autoimmune, inflammatory and infectious diseases, we investigated its role during the infection with T. cruzi.
Methodology/Principal Findings
First, we detected significant amounts of CD4, CD8 and NK cells producing IL-17 after incubating live parasites with spleen cells from normal BALB/c mice. IL-17 is also produced in vivo by CD4+, CD8+ and NK cells from BALB/c mice on the early acute phase of infection. Treatment of infected mice with anti-mouse IL-17 mAb resulted in increased myocarditis, premature mortality, and decreased parasite load in the heart. IL-17 neutralization resulted in increased production of IL-12, IFN-γ and TNF-α and enhanced specific type 1 chemokine and chemokine receptors expression. Moreover, the results showed that IL-17 regulates T-bet, RORγt and STAT-3 expression in the heart, showing that IL-17 controls the differentiation of Th1 cells in infected mice.
These results show that IL-17 controls the resistance to T. cruzi infection in mice regulating the Th1 cells differentiation, cytokine and chemokine production and control parasite-induced myocarditis, regulating the influx of inflammatory cells to the heart tissue. Correlations between the levels of IL-17, the extent of myocardial destruction, and the evolution of cardiac disease could identify a clinical marker of disease progression and may help in the design of alternative therapies for the control of chronic morbidity of chagasic patients.
Author Summary
Chagas disease is caused by the intracellular parasite Trypanosoma cruzi. This infection has been considered one of the most neglected diseases and affects several million people in the Central and South America. Around 30% of the infected patients develop digestive and cardiac forms of the disease. Most patients are diagnosed during the chronic phase, when the treatment is not effective. Here, we showed by the first time that IL-17 is produced during experimental T. cruzi infection and that it plays a significant role in host defense, modulating parasite-induced myocarditis. Applying this analysis to humans could be of great value in unraveling the elements involved in the pathogenesis of chagasic cardiopathy and could be used in the development of alternative therapies to reduce morbidity during the chronic phase of the disease, as well as clinical markers of disease progression. The understanding of these aspects of disease may be helpful in reducing the disability-adjusted life years (DALYs) and costs to the public health service in developing countries.
PMCID: PMC2821906  PMID: 20169058

Results 1-10 (10)