[Show abstract][Hide abstract] ABSTRACT: Leishmaniasis is a neglected vector-borne tropical disease caused by Leishmania protozoa that are transmitted to mammalian hosts by infected sand flies. Infection is associated with distinct clinical manifestations that include cutaneous, mucocutaneous and visceral lesions. Visceral leishmaniasis (VL) is the most severe form of the disease and is considered second in terms of mortality and fourth in terms of morbidity among tropical diseases. IFN-γ-producing T cells are involved in protection against the disease.
CD43(+/+) and CD43(-/-) mice on a C57BL/6 background were intravenously injected with 5 × 10 (7) amastigotes of Leishmania (L.) infantum chagasi, and 30 days after infection the clinical signs of disease were examined; the splenocytes were isolated and assayed for cytokine production; and the livers were removed for phenotypic analysis of T cell subsets by flow cytometry.
We report that mice lacking CD43 display increased susceptibility to infection by Leishmania (L.) infantum chagasi, with higher parasite burdens than wild-type mice. The increased susceptibility of CD43(-/-) mice were associated with a weakened delayed hypersensitivity response and reduced levels of IgG2a antibodies to leishmania antigens. We further showed that expression of CD43 defines a major intrahepatic CD4(+) and CD8(+) T cell subsets with pro-inflammatory phenotypes and leads to increased levels of IFN-γ secretion by activated splenocytes.
Our findings point to a role of CD43 in the development of host resistance to visceral leishmaniasis.
Full-text · Article · Dec 2015 · Parasites & Vectors
[Show abstract][Hide abstract] ABSTRACT: The sphingosine-1-phosphate (S1P) system regulates both thymic and lymph nodes T cell egress which is essential for producing and maintaining the recycling T cell repertoire. Infection with the protozoan parasite
induces a hormonal systemic deregulation that has impact in the thymic S1P homeostasis that ultimately promotes the premature exit of immature CD4
T cells expressing TCR and proinflamatory cytokines to peripheral lymphoid organs, where they may interfere with adaptive immune responses. In what follows, we review recent findings revealing escape of these immature T cells exhibiting an activation profile to peripheral compartments of the immune system in both experimental murine and human models of Chagas disease.
[Show abstract][Hide abstract] ABSTRACT: Microbes have evolved a diverse range of strategies to subvert the host immune system. The protozoan parasite
, the causative agent of Chagas disease, provides a good example of such adaptations. This parasite targets a broad spectrum of host tissues including both peripheral and central lymphoid tissues. Rapid colonization of the host gives rise to a systemic acute response which the parasite must overcome. The parasite in fact undermines both innate and adaptive immunity. It interferes with the antigen presenting function of dendritic cells via an action on host sialic acid-binding Ig-like lectin receptors. These receptors also induce suppression of CD4
T cells responses, and we presented evidence that the sialylation of parasite-derived mucins is required for the inhibitory effects on CD4 T cells. In this review we highlight the major mechanisms used by
to overcome host immunity and discuss the role of parasite colonization of the central thymic lymphoid tissue in chronic disease.
Full-text · Article · Aug 2015 · Journal of Immunology Research
[Show abstract][Hide abstract] ABSTRACT: B-1 cells can be differentiated from B-2 cells because they are predominantly located in the peritoneal and pleural cavities and have distinct phenotypic patterns and activation properties. A mononuclear phagocyte derived from B-1 cells (B-1CDP) has been described. As the B-1CDP cells migrate to inflammatory/infectious sites and exhibit phagocytic capacity, the microbicidal ability of these cells was investigated using the Leishmania major infection model in vitro. The data obtained in this study demonstrate that B-1CDP cells are more susceptible to infection than peritoneal macrophages, since B-1CDP cells have a higher number of intracellular amastigotes forms and consequently release a larger number of promastigotes. Exacerbated infection by L. major required lipid bodies/PGE2 and IL-10 by B-1CDP cells. Both infection and the production of IL-10 were decreased when PGE2 production was blocked by NSAIDs. The involvement of IL-10 in this mechanism was confirmed, since B-1CDP cells from IL-10 KO mice are more competent to control L. major infection than cells from wild type mice. These findings further characterize the B-1CDP cells as an important mononuclear phagocyte that plays a previously unrecognized role in host responses to L. major infection, most likely via PGE2-driven production of IL-10.
[Show abstract][Hide abstract] ABSTRACT: Macrophages are present in almost all tissues of the body and are endowed with alternative differentiation programs resulting in a variety of terminal differentiated cells. They have role in the innate responses as well as in development and maintenance of adaptive immunity against invading pathogens. These cells have phagocytic activity and can sense the microenvironmental stimuli including microbial components that result in differentiation of distinct marker expression patterns and functions that clearly define macrophage subsets. Here we review the functional plasticity of macrophages in response to infections and their integration into adaptive immunity.
[Show abstract][Hide abstract] ABSTRACT: The protozoan parasite Trypanosoma cruzi is able to target the thymus and induce alterations of the thymic microenvironmental and lymphoid compartments. Acute infection results in severe atrophy of the organ and early release of immature thymocytes into the periphery. To date, the pathophysiological effects of thymic changes promoted by parasite-inducing premature release of thymocytes to the periphery has remained elusive. Herein, we show that sphingosine-1-phosphate (S1P), a potent mediator of T cell chemotaxis, plays a role in the exit of immature double-negative thymocytes in experimental Chagas disease. In thymuses from T. cruzi-infected mice we detected reduced transcription of the S1P kinase 1 and 2 genes related to S1P biosynthesis, together with increased transcription of the SGPL1 sphingosine-1-lyase gene, whose product inactivates S1P. These changes were associated with reduced intrathymic levels of S1P kinase activity. Interestingly, double-negative thymocytes from infected animals expressed high levels of the S1P receptor during infection, and migrated to lower levels of S1P. Moreover, during T. cruzi infection, this thymocyte subset expresses high levels of IL-17 and TNF-α cytokines upon polyclonal stimulation. In vivo treatment with the S1P receptor antagonist FTY720 resulted in recovery the numbers of double-negative thymocytes in infected thymuses to physiological levels. Finally, we showed increased numbers of double-negative T cells in the peripheral blood in severe cardiac forms of human Chagas disease.
[Show abstract][Hide abstract] ABSTRACT: The Trypanosoma cruzi infection is associated with severe T cell unresponsiveness to antigens and mitogens characterized by decreased IL-2 synthesis. Trypanosoma cruzi mucin (Tc Muc) has been implicated in this phenomenom. These molecules contain a unique type of glycosylation consisting of several sialylated O-glycans linked to the protein backbone via N-acetylglucosamine residues.
In this study, we evaluated the ability of Tc Muc to modulate the activation of CD4(+) T cells. Our data show that cross-linking of CD3 on naïve CD4(+) T cells in the presence of Tc Muc resulted in the inhibition of both cytokine secretion and proliferation. We further show that the sialylated O-Linked Glycan residues from tc mucin potentiate the suppression of T cell response by inducing G1-phase cell cycle arrest associated with upregulation of mitogen inhibitor p27(kip1). These inhibitory effects cannot be reversed by the addition of exogenous IL-2, rendering CD4(+) T cells anergic when activated by TCR triggering. Additionally, in vivo administration of Tc Muc during T. cruzi infection enhanced parasitemia and aggravated heart damage. Analysis of recall responses during infection showed lower frequencies of IFN-γ producing CD4(+) T cells in the spleen of Tc Muc treated mice, compared to untreated controls.
Our results indicate that Tc Muc mediates inhibitory efects on CD4(+) T expansion and cytokine production, by blocking cell cycle progression in the G1 phase. We propose that the sialyl motif of Tc Muc is able to interact with sialic acid-binding Ig-like lectins (Siglecs) on CD4(+) T cells, which may allow the parasite to modulate the immune system.
[Show abstract][Hide abstract] ABSTRACT: No successful therapies are available for pulmonary fibrosis, reinforcing the need of new treatments. In this regard, lipoxins (LX) and their 15-epimers, aspirin-triggered LX (ATL), present potent anti-inflammatory and pro-resolution effects, emerging as potential substances of clinical interest (Martins et al, 2009;1). Here, we show that ATLa, an ATL synthetic analog, therapeutically reversed a well-established pulmonary fibrotic process induced by bleomycin (BLM) in mice. Thus, we further investigated the mechanisms involved in its effect. We found that ATLa systemic treatment 1 week after BLM instillation considerably reversed the inflammatory response, total collagen and collagen type 1 deposition, vascular endothelial growth factor (VEGF) and transforming growth factor β (TGF-β) expression in the lung, as well as restored the surfactant protein C (SP-C) expression levels. ATLa also inhibited BLM-induced apoptosis and cellular accumulation in the bronchoalveolar lavage fluid (BALF) and in the lung parenchyma as evaluated by light microscopy and flow cytometry (Ly6G+, F4/80+, CD11c+, CD4+, and B220+ cells) assays. Moreover, ATLa inhibited the lung production of interleukin (IL)-1β, IL-17, tumor necrosis factor (TNF)-α, and TGF-β induced by BLM-challenged mice. ATLa restored the balance of iNOS and arginase positive cells in the lungs, suggesting a prevalence of M2 vs M1 macrophages. Together, these effects resulted in benefits to pulmonary mechanics, as ATLa treatment brought to normal levels both lung resistance and elastance, which were clearly altered at 7 days post BLM challenge. Our findings indicate and reinforce ATLa as a promising therapeutic agent to treat lung fibrosis.
Full-text · Article · Jul 2013 · American Journal of Respiratory Cell and Molecular Biology
[Show abstract][Hide abstract] ABSTRACT: In experimental Trypanosoma cruzi infections, severe thymic atrophy leads to release of activated CD4+CD8+ double-positive (DP) T cells to the periphery. In humans, activated DP T cells are found in the blood in association with severe cardiac forms of human chronic Chagas disease. The mechanisms underlying the premature thymocyte release during the chagasic thymic atrophy remain elusive. We tested whether the migratory properties of intrathymic thymocytes are modulated by the parasite trans-sialidase (TS). We found that TS affected the dynamics of thymocytes undergoing intrathymic maturation, and these changes were accompanied by an increase in the number of recent DP thymic emigrants in the peripheral lymphoid organs. We demonstrated that increased percentages of blood DP T cell subsets were associated with augmented antibody titers against TS in chagasic patients with chronic cardiomyopathy. In vitro studies showed that TS was able to activate the MAPK pathway and actin filament mobilization in thymocytes. These effects were correlated with its ability to modulate the adhesion of thymocytes to thymic epithelial cells and their migration toward extracellular matrix. These findings point to effects of TS that could influence the escape of immature thymocytes in Chagas disease.
Full-text · Article · Feb 2013 · Microbes and Infection
[Show abstract][Hide abstract] ABSTRACT: Clearance of apoptotic exudate neutrophils (efferocytosis) induces either pro- or anti-inflammatory responses in mouse macrophages depending on host genetic background. In this study, we investigated whether neutrophil efferocytosis induces a stable macrophage phenotype that could be recalled by late restimulation with LPS. Bone marrow-derived macrophages previously stimulated by pro- but not anti-inflammatory neutrophil efferocytosis expressed a regulatory/M2b phenotype characterized by low IL-12 and high IL-10 production following restimulation, increased expression of LIGHT/TNF superfamily 14, Th2-biased T cell responses, and permissive replication of Leishmania major. Induction of regulatory/M2b macrophages required neutrophil elastase activity and was partially dependent on TLR4 signaling. These results suggested that macrophage differentiation to a regulatory phenotype plays a role in resolution of inflammation but could contribute to increased humoral Ab responses and parasite persistence in the infected host.
Full-text · Article · Aug 2010 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Interaction between apoptotic cells and phagocytes through phosphatidylserine recognition structures results in the production of TGF-beta, which has been shown to play pivotal roles in the anti-inflammatory and anti-immunogenic responses to apoptotic cell clearance. Using 3T3-TbetaRII and RAWTbetaRII cells in which a truncated dominant-negative TGF-beta receptor II was stably transfected to avoid autofeedback induction of TGF-beta, we investigate the mechanisms by which TGF-beta was produced through PSRS engagement. We show, in the present study, that TGF-beta was regulated at both transcriptional and translational steps. P38 MAPK, ERK, and JNK were involved in TGF-beta transcription, whereas translation required activation of Rho GTPase, PI3K, Akt, and mammalian target of rapamycin with subsequent phosphorylation of translation initiation factor eukaryotic initiation factor 4E. Strikingly, these induction pathways for TGF-beta production were different from those initiated in the same cells responding to LPS or PMA.
Preview · Article · Oct 2008 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Apoptotic cells are rapidly engulfed by adjacent tissue cells or macrophages before they can release pro-inflammatory/proimmunogenic intracellular contents. In addition, recognition of the apoptotic cells is actively anti-inflammatory and anti-immunogenic with generation of anti-inflammatory mediators such as transforming growth factor-beta (TGF-beta) and anti-inflammatory eicosanoids. Here, we have investigated the role played by the induction of TGF-beta in the coordinate expression of anti-inflammatory eicosanoids or peroxisome proliferator-activated receptor-gamma and in the suppression of pro-inflammatory lipid mediators and nitric oxide (NO). By use of a dominant negative TGFbetaII receptor, TGF-beta signaling was blocked, and its participation in the consequences of apoptotic cell stimulation was determined. The induction of TGF-beta itself could be attributed to exposed phosphatidylserine on the apoptotic cells, which therefore appears to drive the balanced inflammatory mediator responses. Arachidonic acid release, COX-2, and prostaglandin synthase expression were shown to be significantly dependent on the TGF-beta production. On the other hand, a requirement for TGF-beta was also shown in the inhibition of thromboxane synthase and thromboxanes, of 5-lipoxygenase and sulfidopeptide leukotrienes, as well as of inducible nitric-oxide synthase and NO. TGF-beta-dependent induction of arginase was also found and would further limit the NO generation. Finally, apoptotic cells stimulated production of 15-lipoxygenase and 15-hydroxyeicosatetraenoic acid, a potentially anti-inflammatory pathway acting through peroxisome proliferator-activated receptor-gamma, and lipoxin A(4) production, which were also up-regulated by a TGF-beta-dependent pathway in this system. These results strongly suggest that the apoptotic cell inhibition of pro-inflammatory mediator production is pleiotropic and significantly dependent on the stimulation of TGF-beta production.
No preview · Article · Jan 2007 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Although TGF-beta inhibits the production of proinflammatory mediators in vitro and in vivo, its anti-inflammatory activities may be ineffective in early or severe acute inflammatory circumstances. In this study, we suggest a role for oxidative stress on TGF-beta signaling, leading to prevention of its normal anti-inflammatory effects but leaving its Smad-driven effects on cellular differentiation or matrix production unaffected. Stimulation of the RAW 264.7 macrophage cells, human or mouse alveolar macrophages with LPS led to NF-kappaB-driven production of proinflammatory mediators, which were inhibited by TGF-beta. This inhibition was prevented in the presence of hydrogen peroxide. We found that hydrogen peroxide acted by inducing p38 MAPK activation, which then prevented the ERK activation and MAPK phosphatase-1 up-regulation normally induced by TGF-beta. This was mediated through Src tyrosine kinases and protein phosphatase-1/2A. By contrast, hydrogen peroxide had no effects on TGF-beta-induced Smad2 phosphorylation and SBE-luc reporter gene transcription.
Full-text · Article · Feb 2006 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: Persistence of Trypanosoma cruzi is associated with damage to the heart, which is a characteristic of Chagas disease. In this article, we discuss recently identified mechanisms of aberrant T-cell activation that are responsible for persistence of T. cruzi and cardiac injury. Among them, apoptosis of host cells drives T. cruzi replication in macrophages and is present in cardiac inflammation. It is proposed that phagocytic removal of infected apoptotic cardiomyocytes, combined with signaling through innate immune receptors, is required to initiate immune responses that damage the heart.
Full-text · Article · Jun 2005 · Trends in Parasitology
[Show abstract][Hide abstract] ABSTRACT: The aqueous fraction of the ethanolic extract (AFL) of Cissampelos sympodialis Eichl (Menispermaceae), popularly known as milona, has been shown to have both immunosuppressive and anti-inflammatory effects. In the present study we investigated the modulation of macrophage antimicrobicidal activity by in vitro treatment with the extract from C. sympodialis. Normal and thioglycolate-elicited mouse peritoneal macrophages were infected in vitro with the protozoan Trypanosoma cruzi DM28c clone. We observed that the AFL (used at doses ranging from 13 to 100 microg/ml) increased T. cruzi growth and induced a 75% reduction in nitric oxide production. This inhibition could be mediated by the stimulation of macrophage interleukin-10 (IL-10) secretion since the in vitro treatment with the AFL stimulated IL-10 production by T. cruzi-infected macrophages. These results suggest that the anti-inflammatory effect of the AFL from C. sympodialis could be, at least in part, mediated by the inhibition of macrophage functions and that the inhibition of macrophage microbicidal activity induced by the C. sympodialis extract may be mediated by the decrease in macrophage function mediated by interleukin-10 production.
Full-text · Article · Mar 2003 · Brazilian Journal of Medical and Biological Research
[Show abstract][Hide abstract] ABSTRACT: Apoptosis is induced in the course of immune responses to infectious agents. The last step of apoptosis is recognition and ingestion of the dying cells by phagocytes. Here, Marcela F. Lopes and colleagues discuss recent studies and argue that phagocytosis of apoptotic cells plays a previously unrecognized role in regulating the nature of immune responses against pathogens.
No preview · Article · Nov 2000 · Immunology Today
[Show abstract][Hide abstract] ABSTRACT: After apoptosis, phagocytes prevent inflammation and tissue damage by the uptake and removal of dead cells. In addition, apoptotic cells evoke an anti-inflammatory response through macrophages. We have previously shown that there is intense lymphocyte apoptosis in an experimental model of Chagas' disease, a debilitating cardiac illness caused by the protozoan Trypanosoma cruzi. Here we show that the interaction of apoptotic, but not necrotic T lymphocytes with macrophages infected with T. cruzi fuels parasite growth in a manner dependent on prostaglandins, transforming growth factor-beta (TGF-beta) and polyamine biosynthesis. We show that the vitronectin receptor is critical, in both apoptotic-cell cytoadherence and the induction of prostaglandin E2/TGF-beta release and ornithine decarboxylase activity in macrophages. A single injection of apoptotic cells in infected mice increases parasitaemia, whereas treatment with cyclooxygenase inhibitors almost completely ablates it in vivo. These results suggest that continual lymphocyte apoptosis and phagocytosis of apoptotic cells by macrophages have a role in parasite persistence in the host, and that cyclooxygenase inhibitors have potential therapeutic application in the control of parasite replication and spread in Chagas' disease.
[Show abstract][Hide abstract] ABSTRACT: The effects of glycoinositolphospholipid (GIPL), from the pathogenic protozoan Trypanosoma cruzi, and its isolated glycan and lipid (dihydroceramide) components, were investigated in J774 cells and primary macrophages. Isolated GIPL ceramide, but not intact GIPL or its glycan, induced intense fluid phase endocytosis when added exogenously. In the presence of the cytokine IFN-gamma, GIPL ceramide induced marked apoptosis in J774 cells and macrophages, independent of nitric oxide secretion. When cells were preincubated with the GIPL-derived glycan chain, addition of intact GIPL induced macrophage apoptosis in the presence of IFN-gamma. Synthetic C2-dihydroceramide also induced apoptosis in the presence of IFN-gamma. Induction of apoptosis in T. cruzi-infected macrophages by GIPL ceramide plus IFN-gamma led to increased parasite release compared with IFN-gamma treatment alone. Viable parasites released comprised both infective trypomastigote and spheromastigote forms. These results identify a novel pathway by which T. cruzi glycosylphosphatidylinositol family molecules affect host macrophages, with implications for the infectious process.
Preview · Article · Dec 1998 · The Journal of Immunology
[Show abstract][Hide abstract] ABSTRACT: We have investigated CD4+ T-cell autoreactivity to normal syngeneic B cells in vitro in chronic experimental Chagas' disease. Resting B cells induced an intense proliferative response and lymphokine secretion by splenic CD4+ T cells from Trypanosoma cruzi-infected (8 months or more of infection) donors, compared to much lower responses by uninfected controls. On the other hand, lipopolysaccharide-activated B cells induced syngeneic CD4+ T-cell activation in both control and infected groups. The observed syngeneic T-B-cell cooperation was bidirectional. In the absence of any exogenous stimulus, CD4+ T cells from T. cruzi-infected animals induced much higher production of all tested immunoglobulin (Ig) isotypes (IgM, IgG1, IgG2a, IgG2b, IgG3) by syngeneic B cells, compared to T cells from uninfected donors. When lipopolysaccharide-treated B cells were used, CD4+ T cells from either control or infected donors enhanced IgG1 and IgG3 production, but only CD4+ T cells of infected origin induced IgG2a production in this system without addition of exogenous gamma interferon. Enhanced T-cell proliferation and Ig production were also observed with highly purified CD4+ T cells and in serum-free medium. Both proliferation and Ig production could be blocked with anti-major histocompatibility complex class II monoclonal antibodies. Enhanced reactivity and help for Ig production were seen only in response to syngeneic BALB B cells and not in response to allogeneic B10 B cells. These results indicate that chronic infection with T. cruzi results in increased CD4+ T-cell reactivity towards syngeneic B cells, which leads to spontaneous Ig production. These autoreactive T cells might play a role in polyclonal autoantibody production in chronic Chagas' disease.
Preview · Article · Aug 1996 · Infection and Immunity