NFATc1 Mediates Toll-Like Receptor-Independent Innate Immune Responses during Trypanosoma cruzi Infection

Host defense against the intracellular protozoan parasite Trypanosoma cruzi depends on Toll-like receptor (TLR)-dependent innate immune responses. Recent studies also suggest the presence of TLR-independent responses to several microorganisms, such as viruses, bacteria, and fungi. However, the TLR-independent responses to protozoa remain unclear. Here, we demonstrate a novel TLR-independent innate response pathway to T. cruzi. Myd88 ^−/− Trif ^−/− mice lacking TLR signaling showed normal T. cruzi-induced Th1 responses and maturation of dendritic cells (DCs), despite high sensitivity to the infection. IFN-γ was normally induced in T. cruzi-infected Myd88 ^−/− Trif ^−/− innate immune cells, and further was responsible for the TLR-independent Th1 responses and DC maturation after T. cruzi infection. T. cruzi infection induced elevation of the intracellular Ca²⁺ level. Furthermore, T. cruzi-induced IFN-γ expression was blocked by inhibition of Ca²⁺ signaling. NFATc1, which plays a pivotal role in Ca²⁺ signaling in lymphocytes, was activated in T. cruzi-infected Myd88^−/−Trif^−/− innate immune cells. T. cruzi-infected Nfatc1 ^−/− fetal liver DCs were impaired in IFN-γ production and DC maturation. These results demonstrate that NFATc1 mediates TLR-independent innate immune responses in T. cruzi infection.     

Signaling pathways that regulate Trypanosoma cruzi infection and immune response

Current understanding of key cellular pathways, which are activated by the interaction between T. cruzi and host immunity, is crucial for controlling T. cruzi infection and also for limiting the development of the immunopathological symptoms of Chagas´ disease. Here, we focus on recent advances in the knowledge of modulation of innate receptors such as TLRs and NLRs, especially NLRP3, by T. cruzi in different cells of the immune system. On the other hand, the modulation of macrophage activation may be instrumental in allowing parasite persistence and long-term host survival. In this sense, we discuss the importance of the metabolism of two amino acids: L-arginine and tryptophan, and evaluate the role of iNOS, arginase and IDO enzymes in the regulation of innate and adaptive immune response during this infection; and, finally, we also discuss how T. cruzi exploits the AhR, mTOR and Wnt signaling pathways to promote their intracellular replication in macrophages, thus evading the host's immune response.     

Inefficient Complement System Clearance of Trypanosoma cruzi Metacyclic Trypomastigotes Enables Resistant Strains to Invade Eukaryotic Cells

The complement system is the main arm of the vertebrate innate immune system against pathogen infection. For the protozoan Trypanosoma cruzi, the causative agent of Chagas disease, subverting the complement system and invading the host cells is crucial to succeed in infection. However, little attention has focused on whether the complement system can effectively control T. cruzi infection. To address this question, we decided to analyse: 1) which complement pathways are activated by T. cruzi using strains isolated from different hosts, 2) the capacity of these strains to resist the complement-mediated killing at nearly physiological conditions, and 3) whether the complement system could limit or control T. cruzi invasion of eukaryotic cells. The complement activating molecules C1q, C3, mannan-binding lectin and ficolins bound to all strains analysed; however, C3b and C4b deposition assays revealed that T. cruzi activates mainly the lectin and alternative complement pathways in non-immune human serum. Strikingly, we detected that metacyclic trypomastigotes of some T. cruzi strains were highly susceptible to complement-mediated killing in non-immune serum, while other strains were resistant. Furthermore, the rate of parasite invasion in eukaryotic cells was decreased by non-immune serum. Altogether, these results establish that the complement system recognizes T. cruzi metacyclic trypomastigotes, resulting in killing of susceptible strains. The complement system, therefore, acts as a physiological barrier which resistant strains have to evade for successful host infection.     

Reaching for the Holy Grail: insights from infection/cure models on the prospects for vaccines for Trypanosoma cruzi infection

Prevention of Trypanosoma cruzi infection in mammals likely depends on either prevention of the invading trypomastigotes from infecting host cells or the rapid recognition and killing of the newly infected cells by T. cruzi-specific T cells. We show here that multiple rounds of infection and cure (by drug therapy) fails to protect mice from reinfection, despite the generation of potent T cell responses. This disappointing result is similar to that obtained with many other vaccine protocols used in attempts to protect animals from T. cruzi infection. We have previously shown that immune recognition of T. cruzi infection is significantly delayed both at the systemic level and at the level of the infected host cell. The systemic delay appears to be the result of a stealth infection process that fails to trigger substantial innate recognition mechanisms while the delay at the cellular level is related to the immunodominance of highly variable gene family proteins, in particular those of the trans-sialidase family. Here we discuss how these previous studies and the new findings herein impact our thoughts on the potential of prophylactic vaccination to serve a productive role in the prevention of T. cruzi infection and Chagas disease.     

Polyfunctional T Cell Responses in Children in Early Stages of Chronic Trypanosoma cruzi Infection Contrast with Monofunctional Responses of Long-term Infected Adults

Background

Adults with chronic Trypanosoma cruzi exhibit a poorly functional T cell compartment, characterized by monofunctional (IFN-γ-only secreting) parasite-specific T cells and increased levels of terminally differentiated T cells. It is possible that persistent infection and/or sustained exposure to parasites antigens may lead to a progressive loss of function of the immune T cells.

Methodology/Principal Findings

To test this hypothesis, the quality and magnitude of T. cruzi-specific T cell responses were evaluated in T. cruzi-infected children and compared with long-term T. cruzi-infected adults with no evidence of heart failure. The phenotype of CD4⁺ T cells was also assessed in T. cruzi-infected children and uninfected controls. Simultaneous secretion of IFN-γ and IL-2 measured by ELISPOT assays in response to T. cruzi antigens was prevalent among T. cruzi-infected children. Flow cytometric analysis of co-expression profiles of CD4⁺ T cells with the ability to produce IFN-γ, TNF-α, or to express the co-stimulatory molecule CD154 in response to T. cruzi showed polyfunctional T cell responses in most T. cruzi-infected children. Monofunctional T cell responses and an absence of CD4⁺TNF-α⁺-secreting T cells were observed in T. cruzi-infected adults. A relatively high degree of activation and differentiation of CD4⁺ T cells was evident in T. cruzi-infected children.

Conclusions/Significance

Our observations are compatible with our initial hypothesis that persistent T. cruzi infection promotes eventual exhaustion of immune system, which might contribute to disease progression in long-term infected subjects.     

NLRP3 Controls Trypanosoma cruzi Infection through a Caspase-1-Dependent IL-1R-Independent NO Production

Trypanosoma cruzi (T. cruzi) is an intracellular protozoan parasite and the etiological agent of Chagas disease, a chronic infectious illness that affects millions of people worldwide. Although the role of TLR and Nod1 in the control of T. cruzi infection is well-established, the involvement of inflammasomes remains to be elucidated. Herein, we demonstrate for the first time that T. cruzi infection induces IL-1β production in an NLRP3- and caspase-1-dependent manner. Cathepsin B appears to be required for NLRP3 activation in response to infection with T. cruzi, as pharmacological inhibition of cathepsin B abrogates IL-1β secretion. NLRP3^−/− and caspase1^−/− mice exhibited high numbers of T. cruzi parasites, with a magnitude of peak parasitemia comparable to MyD88^−/− and iNOS^−/− mice (which are susceptible models for T. cruzi infection), indicating the involvement of NLRP3 inflammasome in the control of the acute phase of T. cruzi infection. Although the inflammatory cytokines IL-6 and IFN-γ were found in spleen cells from NLRP3^−/− and caspase1^−/− mice infected with T. cruzi, these mice exhibited severe defects in nitric oxide (NO) production and an impairment in macrophage-mediated parasite killing. Interestingly, neutralization of IL-1β and IL-18, and IL-1R genetic deficiency demonstrate that these cytokines have a minor effect on NO secretion and the capacity of macrophages to control T. cruzi infection. In contrast, inhibition of caspase-1 with z-YVAD-fmk abrogated NO production by WT and MyD88^−/− macrophages and rendered them as susceptible to T. cruzi infection as NLRP3^−/− and caspase-1^−/− macrophages. Taken together, our results demonstrate a role for the NLRP3 inflammasome in the control of T. cruzi infection and identify NLRP3-mediated, caspase-1-dependent and IL-1R-independent NO production as a novel effector mechanism for these innate receptors.     

Trypanosoma cruzi: Genetic diversity influences the profile of immunoglobulins during experimental infection

The clonal evolution model postulated for Trypanosoma cruzi predicts a correlation between the phylogenetic divergence of T. cruzi clonal genotypes and their biological properties. In the present study, the linkage between phylogenetic divergence of the parasite and IgG, IgG1, IgG2a and IgG2b response has been evaluated during the acute and chronic phases of the experimental infection. Eight laboratory-cloned stocks representative of this phylogenetic diversity and including the lineages T. cruzi I (genotypes 19 and 20), T. cruzi II (genotype 32) and T. cruzi (genotype 39) have been studied. The results showed that the pattern of humoral immune response was correlated with T. cruzi genotype, and that stocks included in genotype 20 were responsible for the high IgG response in the acute and chronic phases. Moreover, T. cruzi I lineage was more efficient in over-expressing all subclasses of specific anti-parasite IgG than either T. cruzi II or T. cruzi lineages. Curiously, the alteration in the pattern of antibodies induced by Benznidazole treatment was related to the phase of the infection but not to the genotype of the parasite. The data suggest that genotypes of T. cruzi are able to drive levels/subclasses of specific IgG, hence giving rise to further concerns about the sensitivity of serological assays in the diagnosis of human Chagas disease.     

Trypanosoma cruzi: the T-cell dependence of the primary immune response and the effects of depletion of T cells and Ig-bearing cells on immunological memory

The effects of T-cell depletion on primary infection with Trypanosoma cruzi and on immunological memory to this parasite were studied in a syngeneic mouse system. Exacerbation of T. cruzi infections occurred in thymectomized, irradiated, bone marrow-reconstituted (TX) C57BL/6J mice compared to sham thymectomized, irradiated, bone marrow-reconstituted (STX) mice. Reconstitution of TX mice with thymocytes restored the resistance to a level equivalent to that of STX mice. Immunological memory against T. cruzi present in spleen cells in mice recovered from T. cruzi infections could be ablated by treatment with rabbit anti-brain-associated theta serum but not with rabbit anti-mouse immunoglobulin serum prior to adoptive transfer of immune spleen cells into TX mice. These experiments suggest that modulation of the primary immune response and memory against T. cruzi depends largely on the thymus-derived lymphocyte. The possible implications of this T-cell regulation on previously reported effector mechanisms againt this parasite are discussed.     

Low Frequency of Circulating CD8+ T Stem Cell Memory Cells in Chronic Chagasic Patients with Severe Forms of the Disease

Background

CD8+ T cells have been shown to play a crucial role in Trypanosoma cruzi infection. Memory CD8+ T cells can be categorised based on their distinct differentiation stages and functional activities as follows: stem cell memory (TSCM), central memory (TCM), transitional memory (TTM), effector memory (TEM) and terminal effector (TTE) cells. Currently, the immune mechanisms that control T. cruzi in the chronic phase of the infection are unknown.

Methodology/Principal Findings

To characterise the CD8+ T cell subsets that could be participating in the control of T. cruzi infection, in this study, we compared total and T. cruzi-specific circulating CD8+ T cells with distinctive phenotypic and functional features in chronic chagasic patients (CCPs) with different degrees of cardiac dysfunction. We observed a decreased frequency of total TSCM along with an increased frequency of TTE in CCPs with severe disease. Antigen-specific TSCM cells were not detectable in CCPs with severe forms of the disease. A functional profile of CD8+ T cell subsets among CCPs revealed a high frequency of monofunctional CD8+ T cells in the most severe patients with IFN-γ+- or TNF-α+-producing cells.

Conclusions/Significance

These findings suggest that CD8+ TSCM cells may be associated with the immune response to T. cruzi and outcome of Chagas disease, given that these cells may be involved in repopulating the T cell pool that controls infection.     

Trypanosoma cruzi: effects of adrenalectomy during the acute phase of experimental infection

Glucocorticoid hormones have been implicated as an important modulator of Trypanosoma cruzi pathogenesis. Since adrenal steroid hormones play a fundamental role in modulating the immune response, we hypothesized that adrenalectomy affect the course of the experimental T. cruzi infection. This study was undertaken to determine the effects of adrenalectomy during the acute phase of T. cruzi infection. Blood and tissue parasitism, macrophages, nitric oxide (NO) production and IFN-γ were evaluated in male Wistar rats infected with the Y strain of T. cruzi. Our results show that adrenalectomized rats displayed increased number of blood and heart parasites accompanied by decreases in the total number of peritoneal macrophages and IFN-γ when compared to controls. Adrenalectomy also reduced the levels of NO released from peritoneal macrophages of infected animals. These results suggest that adrenal corticosteroid insufficiency due to adrenalectomy could be considered an important factor during development of acute phases of experimental Chagas’ disease, enhancing pathogenesis through disturbance of the host’s immune system.     

Inhibition of mammalian host cell infection by insect-derived, metacyclic forms of Trypanosoma cruzi in the presence of human or rabbit anti-T. cruzi antibodies

The presence of serum from chronic chagasic patients or rabbits immunized with killed epimastigote forms of Trypanosoma cruzi inhibited infection of rat heart myoblasts by insect-vector (Triatoma infestans)-derived, metacyclic forms of Trypanosoma cruzi. The effect was produced even after diluting the chagasic serum to non-agglutinating levels and was evidenced by marked reductions in both the percentage of infected myoblasts and the number of parasites per 100 cells. Human IgG or IgM purified from chronic chagasic serum and serum from rabbits immunized with killed T. cruzi epimastigotes also reduced both parameters. While previous work has shown that immunological destruction of invasive forms of T. cruzi may underlie the protective effects of the humoral immune response against this parasite, the present in vitro results suggest that specific anti- T. cruzi antibodies could also contribute to protection via inhibition of host cell infection by the vectortransmissible form of the parasite.     

Immunization with Hexon Modified Adenoviral Vectors Integrated with gp83 Epitope Provides Protection against Trypanosoma cruzi Infection

Background

Trypanosoma cruzi is the causative agent of Chagas disease. Chagas disease is an endemic infection that affects over 8 million people throughout Latin America and now has become a global challenge. The current pharmacological treatment of patients is unsuccessful in most cases, highly toxic, and no vaccines are available. The results of inadequate treatment could lead to heart failure resulting in death. Therefore, a vaccine that elicits neutralizing antibodies mediated by cell-mediated immune responses and protection against Chagas disease is necessary.

Methodology/Principal Findings

The “antigen capsid-incorporation” strategy is based upon the display of the T. cruzi epitope as an integral component of the adenovirus'' capsid rather than an encoded transgene. This strategy is predicted to induce a robust humoral immune response to the presented antigen, similar to the response provoked by native Ad capsid proteins. The antigen chosen was T. cruzi gp83, a ligand that is used by T. cruzi to attach to host cells to initiate infection. The gp83 epitope, recognized by the neutralizing MAb 4A4, along with His₆ were incorporated into the Ad serotype 5 (Ad5) vector to generate the vector Ad5-HVR1-gp83-18 (Ad5-gp83). This vector was evaluated by molecular and immunological analyses. Vectors were injected to elicit immune responses against gp83 in mouse models. Our findings indicate that mice immunized with the vector Ad5-gp83 and challenged with a lethal dose of T. cruzi trypomastigotes confer strong immunoprotection with significant reduction in parasitemia levels, increased survival rate and induction of neutralizing antibodies.

Conclusions/Significance

This data demonstrates that immunization with adenovirus containing capsid-incorporated T. cruzi antigen elicits a significant anti-gp83-specific response in two different mouse models, and protection against T. cruzi infection by eliciting neutralizing antibodies mediated by cell-mediated immune responses, as evidenced by the production of several Ig isotypes. Taken together, these novel results show that the recombinant Ad5 presenting T. cruzi gp83 antigen is a useful candidate for the development of a vaccine against Chagas disease.     

Experimental Chagas’ disease in orchiectomized Calomys callosus infected with the CM strain of Trypanosoma cruzi

The incidence and progression of disorders associated with an unbalanced immune response has among many factors the gender as a contributory factor. The aims of this work were to evaluate the effects of orchiectomy and the immune response during the experimental Trypanosoma cruzi infection. Young adult, male Calomys callous were i.p. inoculated with 1 × 10⁵ blood trypomastigotes of the CM strain of T. cruzi and divided in groups: Control, Sham and Castrated. Castrated group displayed significantly lower values for prostate and seminal vesicle weights indicating a drastic drop of testosterone plasmatic levels. Orchiectomized animals also displayed lesser number of blood parasites, enhanced lytic antibody percentage, splenocyte proliferation and NO concentration when compared to its sham and control counterparts, indicating that steroid gonadal ablation actually influences immune response triggering a more efficient cellular and humoral response which led animals to become more resistant against T. cruzi infection.     

Trypanosoma cruzi: Role of different antibody classes in protection against infection in the mouse

Immune serum obtained from mice with a chronic infection of Trypanosoma cruzi was fractionated on Sephadex G-200 or on protein ASepharose 4B. Mice were infected with a standard infective dose of T. cruzi 24 hr after injection with either IgM, IgG, IgG1, or IgG2 + IgG3 fractions. Mice were also pretreated with immune serum depleted by affinity chromatography of either IgG2a, IgG2b, or both subclasses before infection with T. cruzi. Control mice were pretreated with normal mouse serum or immune serum depleted of IgG. The parasitemia and survival of the animals were determined and used as parameters of protection. The results of these experiments demonstrated that the protective antibodies were mostly IgG2 and seem to be preferentially located in IgG2b subclass. IgM and IgG1 fractions were very little, if any, protection.     

Identification and Functional Analysis of Trypanosoma cruzi Genes That Encode Proteins of the Glycosylphosphatidylinositol Biosynthetic Pathway

Background

Trypanosoma cruzi is a protist parasite that causes Chagas disease. Several proteins that are essential for parasite virulence and involved in host immune responses are anchored to the membrane through glycosylphosphatidylinositol (GPI) molecules. In addition, T. cruzi GPI anchors have immunostimulatory activities, including the ability to stimulate the synthesis of cytokines by innate immune cells. Therefore, T. cruzi genes related to GPI anchor biosynthesis constitute potential new targets for the development of better therapies against Chagas disease.

Methodology/Principal Findings

In silico analysis of the T. cruzi genome resulted in the identification of 18 genes encoding proteins of the GPI biosynthetic pathway as well as the inositolphosphorylceramide (IPC) synthase gene. Expression of GFP fusions of some of these proteins in T. cruzi epimastigotes showed that they localize in the endoplasmic reticulum (ER). Expression analyses of two genes indicated that they are constitutively expressed in all stages of the parasite life cycle. T. cruzi genes TcDPM1, TcGPI10 and TcGPI12 complement conditional yeast mutants in GPI biosynthesis. Attempts to generate T. cruzi knockouts for three genes were unsuccessful, suggesting that GPI may be an essential component of the parasite. Regarding TcGPI8, which encodes the catalytic subunit of the transamidase complex, although we were able to generate single allele knockout mutants, attempts to disrupt both alleles failed, resulting instead in parasites that have undergone genomic recombination and maintained at least one active copy of the gene.

Conclusions/Significance

Analyses of T. cruzi sequences encoding components of the GPI biosynthetic pathway indicated that they are essential genes involved in key aspects of host-parasite interactions. Complementation assays of yeast mutants with these T. cruzi genes resulted in yeast cell lines that can now be employed in high throughput screenings of drugs against this parasite.     

Trypanosome Lytic Factor,an Antimicrobial High-Density Lipoprotein,Ameliorates Leishmania Infection

Innate immunity is the first line of defense against invading microorganisms. Trypanosome Lytic Factor (TLF) is a minor sub-fraction of human high-density lipoprotein that provides innate immunity by completely protecting humans from infection by most species of African trypanosomes, which belong to the Kinetoplastida order. Herein, we demonstrate the broader protective effects of human TLF, which inhibits intracellular infection by Leishmania, a kinetoplastid that replicates in phagolysosomes of macrophages. We show that TLF accumulates within the parasitophorous vacuole of macrophages in vitro and reduces the number of Leishmania metacyclic promastigotes, but not amastigotes. We do not detect any activation of the macrophages by TLF in the presence or absence of Leishmania, and therefore propose that TLF directly damages the parasite in the acidic parasitophorous vacuole. To investigate the physiological relevance of this observation, we have reconstituted lytic activity in vivo by generating mice that express the two main protein components of TLFs: human apolipoprotein L-I and haptoglobin-related protein. Both proteins are expressed in mice at levels equivalent to those found in humans and circulate within high-density lipoproteins. We find that TLF mice can ameliorate an infection with Leishmania by significantly reducing the pathogen burden. In contrast, TLF mice were not protected against infection by the kinetoplastid Trypanosoma cruzi, which infects many cell types and transiently passes through a phagolysosome. We conclude that TLF not only determines species specificity for African trypanosomes, but can also ameliorate an infection with Leishmania, while having no effect on T. cruzi. We propose that TLFs are a component of the innate immune system that can limit infections by their ability to selectively damage pathogens in phagolysosomes within the reticuloendothelial system.     

Beneficial effects of acetylsalicylic acid (aspirin) on the actions of extracellular vesicles shed by Trypanosoma cruzi in macrophages

Trypomastigote forms of Trypanosoma cruzi, the causative agent of Chagas disease, shed extracellular vesicles (EVs) that promote the susceptibility of host cells to infection. During T. cruzi infection, the immune response of the host is important for controlling parasitism, which is necessary for survival. Macrophages produce inflammatory mediators, such as eicosanoids and nitric oxide (NO), with trypanocidal effects that control the parasite load in the early stages of the disease. In this study, we evaluated the contribution of host cyclooxygenase (COX) to the actions of EVs shed by T. cruzi strain Y (EVs-Y) in infected macrophages. RAW 264.7 macrophages exposed to EVs-Y and then infected with trypomastigote forms of T. cruzi produced less NO, and an increased number of trypomastigote forms were internalized in the cell compared to the controls, indicating that the effects exerted by EVs-Y favor the parasite. Interestingly, when macrophages were pretreated with acetylsalicylic acid, a dual COX inhibitor, before exposure to EVs-Y and subsequent infection with trypomastigote forms, there was an increase in NO production and a decrease in trypomastigote uptake compared to the controls. These results suggest that EVs-Y modulates the macrophage response in favor of T. cruzi and indicate a role for COX in the effects of EVs.     

Trypanosoma cruzi Experimental Infection Impacts on the Thymic Regulatory T Cell Compartment

The dynamics of regulatory T cells in the course of Trypanosoma cruzi infection is still debated. We previously demonstrated that acute murine T. cruzi infection results in an impaired peripheral CD4⁺Foxp3⁺ T cell differentiation due to the acquisition of an abnormal Th1-like phenotype and altered functional features, negatively impacting on the course of infection. Moreover, T. cruzi infection induces an intense thymic atrophy. As known, the thymus is the primary lymphoid organ in which thymic-derived regulatory T cells, known as tTregs, differentiate. Considering the lack of available data about the effect of T. cruzi infection upon tTregs, we examined tTreg dynamics during the course of disease. We confirmed that T. cruzi infection induces a marked loss of tTreg cell number associated to cell precursor exhaustion, partially avoided by glucocorticoid ablation- and IL-2 survival factor depletion. At the same time, tTregs accumulate within the CD4 single-positive compartment, exhibiting an increased Ki-67/Annexin V ratio compared to controls. Moreover, tTregs enhance after the infection the expression of signature markers (CD25, CD62L and GITR) and they also display alterations in the expression of migration-associated molecules (α chains of VLAs and chemokine receptors) such as functional fibronectin-driven migratory disturbance. Taken together, we provide data demonstrating profound alterations in tTreg compartment during acute murine T. cruzi infection, denoting that their homeostasis is significantly affected. The evident loss of tTreg cell number may compromise the composition of tTreg peripheral pool, and such sustained alteration over time may be partially related to the immune dysregulation observed in the chronic phase of the disease.     

A human astrocytoma cell line is highly susceptible to infection with Trypanosoma cruzi

Astrocytes play a vital role in neuronal protection, homeostasis, vascular interchange and the local immune response. Some viruses and parasites can cross the blood-brain barrier and infect glia. Trypanosoma cruzi, the aetiological agent of Chagas disease, can seriously compromise the central nervous system, mainly in immune-suppressed individuals, but also during the acute phase of the infection. In this report, the infective capacity of T. cruzi in a human astrocyte tumour-derived cell line was studied. Astrocytes exposed to trypomastigotes (1:10 ratio) produced intracellular amastigotes and new trypomastigotes emerged by day 4 post-infection (p.i.). At day 6 p.i., 93% of the cells were infected. Using flow cytometry, changes were observed in both the expression of major histocompatibility complex class I and II molecules and the chemokine secretion pattern of astrocytes exposed to the parasite. Blocking the low-density lipoprotein receptor on astrocytes did not reduce parasite intracellular infection. Thus, T. cruzi can infect astrocytes and modulate the immune response during central nervous system infection.