Cristiane Maria Milanezi

CCR5 Plays a Critical Role in the Development of Myocarditis and Host Protection in Mice Infected with Trypanosoma cruzi

Abstract The pathogenesis of myocarditis during Trypanosoma cruzi infection is poorly understood. We investigated the role played by chemokine receptor 5 (CCR5) in the influx of T cells to the cardiac tissue of T. cruzi—infected mice. mRNA and protein for the CCR5 ligands CCL3, CCL4, and CCL5 were detected in the hearts of infected mice in association with CD4+ and CD8+ T cells. There was a high level of CCR5 expression on CD8+ T cells in the hearts of infected mice. Moreover, CCR5 expression on CD8+ T cells was positively modulated by T. cruzi infection. CCR5-deficient mice infected with T. cruzi experienced a dramatically inhibited migration of T cells to the heart and were also more susceptible to infection. These results suggest that CCR5 and its ligands play a central role in the control of T cell influx in T. cruzi-infected mice. Knowledge of the mechanisms that trigger and control the migration of cells to the heart in patients with Chagas disease may help in the design of drugs that prevent myocarditis and protect against the development of severe disease.

IL-17 Produced during Trypanosoma cruzi Infection Plays a Central Role in Regulating Parasite-Induced Myocarditis

Background 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. Conclusion/Significance 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.

Increased Activities of Cardiac Matrix Metalloproteinases Matrix Metalloproteinase (MMP)-2 and MMP-9 Are Associated with Mortality during the Acute Phase of Experimental Trypanosoma cruzi Infection

The strong inflammatory reaction that occurs in the heart during the acute phase of Trypanosoma cruzi infection is modulated by cytokines and chemokines produced by leukocytes and cardiomyocytes. Matrix metalloproteinases (MMPs) have recently emerged as modulators of cardiovascular inflammation. In the present study we investigated the role of MMP-2 and MMP-9 in T. cruzi-induced myocarditis, by use of immunohistochemical analysis, gelatin zymography, enzyme-linked immunosorbent assay, and real-time polymerase chain reaction to analyze the cardiac tissues of T. cruzi-infected C57BL/6 mice. Increased transcripts levels, immunoreactivity, and enzymatic activity for MMP-2 and MMP-9 were observed by day 14 after infection. Mice treated with an MMP inhibitor showed significantly decreased heart inflammation, delayed peak in parasitemia, and improved survival rates, compared with the control group. Reduced levels of cardiac tumor necrosis factor-alpha, interferon-gamma, serum nitrite, and serum nitrate were also observed in the treated group. These results suggest an important role for MMPs in the induction of T. cruzi-induced acute myocarditis.

The involvement of CD4+CD25+ T cells in the acute phase of Trypanosoma cruzi infection

The infection with Trypanosoma cruzi leads to a vigorous and apparently uncontrolled inflammatory response in the heart. Although the parasites trigger specific immune response, the infection is not completely cleared out, a phenomenon that in other parasitic infections has been attributed to CD4+CD25+ T cells (Tregs). Then, we examined the role of natural Tregs and its signaling through CD25 and GITR in the resistance against infection with T. cruzi. Mice were treated with mAb against CD25 and GITR and the parasitemia, mortality and heart pathology analyzed. First, we demonstrated that CD4+CD25+GITR+Foxp3+ T cells migrate to the heart of infected mice. The treatment with anti-CD25 or anti-GITR resulted in increased mortality of these infected animals. Moreover, the treatment with anti-GITR enhanced the myocarditis, with increased migration of CD4+, CD8+, and CCR5+ leukocytes, TNF-alpha production, and tissue parasitism, although it did not change the systemic nitric oxide synthesis. These data showed a limited role for CD25 signaling in controlling the inflammatory response during this protozoan infection. Also, the data suggested that signaling through GITR is determinant to control of the heart inflammation, parasite replication, and host resistance against the infection.

Modulation of mucosal immunity in a murine model of food-induced intestinal inflammation

Background Hypersensitivity or uncontrolled responses against dietary antigens can lead to inflammatory disorders like food allergy and current models reflect a variety of causes but do not reveal the detailed modulation of gut immunity in response to food antigens after breakdown in mucosal tolerance.

CCR2 Receptor Is Essential to Activate Microbicidal Mechanisms to Control Toxoplasma gondii Infection in the Central Nervous System

Chemokines comprise a structurally related family of cytokines that regulate leukocyte trafficking. Because infection with Toxoplasma gondii can induce an important inflammatory reaction that, if left uncontrolled, can lead to death, we investigated the role of the chemokine receptor CCR2 in T. gondii infection. We orally infected CCR2(-/-) mice with five ME-49 T. gondii cysts and monitored morbidity, survival, and immune response thereafter. The CCR2(-/-) mice displayed higher susceptibility to infection as all mice died on day 28 after infection. Despite similar Th1 responses, a more evident anti-inflammatory response was induced in the peripheral organs of CCR2(-/-) mice compared with wild-type C57BL/6 mice. Additionally, CCR2(-/-) mice presented greater parasitism and a milder inflammatory reaction in their peripheral organs with lesser CD4(+) and MAC-1(+) and greater CD8(+) cell migration. The parasite load decreased in these organs in CCR2(-/-) mice but remained uncontrolled in the central nervous system. Additionally, we observed down-regulated inducible nitric oxide synthase expression in peripheral organs from CCR2(-/-) mice that was associated with a small nitric oxide production by spleen macrophages. In conclusion, in the absence of CCR2, another mechanism is activated to control tissue parasitism in peripheral organs. Nevertheless, CCR2 is essential for the activation of microbicidal mediators that control T. gondii replication in the central nervous system.

Toxoplasma gondii: the severity of toxoplasmic encephalitis in C57BL/6 mice is associated with increased ALCAM and VCAM-1 expression in the central nervous system and higher blood-brain barrier permeability.

In order to investigate the differential ALCAM, ICAM-1 and VCAM-1 adhesion molecules mRNA expression and the blood-brain barrier (BBB) permeability in C57BL/6 and BALB/c mice in Toxoplasma gondii infection, animals were infected with ME-49 strain. It was observed higher ALCAM on day 9 and VCAM-1 expression on days 9 and 14 of infection in the central nervous system (CNS) of C57BL/6 compared to BALB/c mice. The expression of ICAM-1 was high and similar in the CNS of both lineages of infected mice. In addition, C57BL/6 presented higher BBB permeability and higher IFN-gamma and iNOS expression in the CNS compared to BALB/c mice. The CNS of C57BL/6 mice presented elevated tissue pathology and parasitism. In conclusion, our data suggest that the higher adhesion molecules expression and higher BBB permeability contributed to the major inflammatory cell infiltration into the CNS of C57BL/6 mice that was not efficient to control the parasite.

IL-18 Triggered by the Nlrp3 Inflammasome Induces Host Innate Resistance in a Pulmonary Model of Fungal Infection

Pathogens are sensed by innate immune receptors that initiate an efficient adaptive immune response upon activation. The elements of the innate immune recognition process for Paracoccidioides brasiliensis include TLR-2, TLR-4, and dectin-1. However, there are additional receptors necessary for the host immune responses to P. brasiliensis. The nucleotide-binding oligomerization domain–like receptor (NLRs), which activate inflammasomes, are candidate receptors that deserve renewed investigation. After pathogen infection, the NLRs form large signaling platforms called inflammasomes, which lead to caspase-1 activation and maturation of proinflammatory cytokines (IL-18 and IL-1β). In this study, we showed that NLR family pyrin domain–containing 3 (Nlrp3) is required to induce caspase-1 activation and further secretion of IL-1β and IL-18 by P. brasiliensis–infected macrophages. Additionally, potassium efflux and lysosomal acidification induced by the fungus were important steps in the caspase-1 activation mechanism. Notably, Nlrp3 and caspase-1 knockout mice were more susceptible to infection than were the wild-type animals, suggesting that the Nlrp3-dependent inflammasomes contribute to host protection against P. brasiliensis. This protective effect occurred owing to the inflammatory response mediated by IL-18, as shown by an augmented fungus burden in IL-18 knockout mice. Taken together, our results show that the Nlrp3 inflammasome is essential for resistance against P. brasiliensis because it orchestrates robust caspase-1 activation and triggers an IL-18–dependent proinflammatory response.

BALB/c mice infected with antimony treatment refractory isolate of Leishmania braziliensis present severe lesions due to IL-4 production.

Background 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). Conclusion/Significance 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.

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. In this article, 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 proinflammatory cytokine release. In vitro incubation of dendritic cells (DCs) with SGE limited specific CD4+ Th17 cell response. We identified adenosine (ADO) and 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.