Signal transducer and activator of transcription 1 (STAT-1) plays a critical role in control of Trypanosoma cruzi infection

The expression of immune response genes in patients with chronic Chagas disease is shifted toward the levels observed in healthy subjects as a result of treatment with Benznidazole

Introduction

Chagas disease, caused by the Trypanosoma cruzi parasite infection, is a potentially life-threatening neglected tropical disease with a worldwide distribution. During the chronic phase of the disease, there exists a fragile balance between the host immune response and parasite replication that keeps patients in a clinically-silent asymptomatic stage for years or even decades. However, in 40% of patients, the disease progresses to clinical manifestations mainly affecting and compromising the cardiac system. Treatment is recommended in the chronic phase, although there are no early markers of its effectiveness. The aim of this study is to identify differential expression changes in genes involved in the immune response in antigen-restimulated PBMC from chronic patients with Chagas disease due to benznidazole treatment.

Methods

Thus, high-throughput real-time qPCR analysis has been performed to simultaneously determine global changes in the expression of 106 genes involved in the immune response in asymptomatic (IND) and early cardiac manifestations (CCC I) Chagas disease patients pre- and post-treatment with benznidazole.

Results and discussion

The results revealed that 7 out of the 106 analyzed genes were differentially expressed (4 up- and 3 downregulated) after treatment in IND patients and 15 out of 106 (3 up- and 12 downregulated) after treatment of early cardiac Chagas disease patients. Particularly in CCC I patients, regulation of the expression level of some of these genes towards a level similar to that of healthy subjects suggests a beneficial effect of treatment and supports recommendation of benznidazole administration to early cardiac Chagas disease patients. The data obtained also demonstrated that both in asymptomatic patients and in early cardiac chronic patients, after treatment with benznidazole there is a negative regulation of the proinflammatory and cytotoxic responses triggered as a consequence of T. cruzi infection and the persistence of the parasite. This downregulation of the immune response likely prevents marked tissue damage and healing in early cardiac patients, suggesting its positive effect in controlling the pathology.

Differential gene expression response to acute and chronic Cytauzxoon felis infection in domestic cats (Felis catus)

Cytauxzoonosis is a severe tick transmitted protozoan disease of domestic cats, caused by Cytauxzoon felis. The disease is characterized by acute onset of high fever, depression, lethargy, inappentence, anorexia, icterus, dehydration, hemolytic anemia, and alteration of immune response. The aim of our study was to further detail the immune response of domestic cats to C. felis infection by comparing the differential expression of feline immune transcriptional elements during acute and chronic cytauxzoonosis. True single molecule sequencing (tSMS) was used to analyze the whole genome of acutely and chronically infected C. felis cats, focusing on the analysis of genes involved on the immune response. Two C. felis donor cats were infested with Amblyomma americanum nymphs, which after repletion were collected and kept in humidity chambers until they molted. The resulting A. americanum were randomly selected to infest three C. felis naïve principal cats. Infection of these cats was confirmed by nested PCR of the 18S rRNA C. felis gene and clinical signs. RNA was extracted from whole blood at different time points and used for tSMS analyses, the results revealed overexpression in transcripts involved in type I interferon signaling, cellular and cytokine responses during the acute stage of infection, while cell cycle, and metabolic processes were downregulated. Genes involved in cell adhesion increased their expression in the chronic infected cats, whereas inflammatory and apoptotic related genes were downregulated. This study provided information on the host immune response to C. felis in domestic cats, demonstrating that inflammatory, apoptotic, and cell adhesion are some of the pathways altered during acute and chronic infection.

Differential expression profile of genes involved in the immune response associated to progression of chronic Chagas disease

BACKGROUND

Patients with chronic Chagas disease present marked clinical and immunological heterogeneity. During the disease, multiple immune mechanisms are activated to fight the parasite. The purpose of this study was to investigate the expression patterns of genes involved in relevant immunological processes throughout the disease in patients with chronic Chagas disease.

METHODOLOGY/PRINCIPAL FINDINGS

High-throughput RT-qPCR with QuantStudio 12K Flex real-time PCR system was used to evaluate the expression of 106 immune-related genes in PBMC from a cohort of cardiac Chagas disease patients (CCC I), asymptomatic patients (IND) and healthy donors (HD) after being stimulated with T. cruzi soluble antigens. Principal component analysis (PCA), cluster analysis and volcano plots were used to identify differentially expressed genes. In addition, gene set enrichment analysis (GSEA) was employed to identify the enriched immunological pathways in which these genes are involved. PCA revealed the existence of a statistically divergent expression profile of the 36 genes correlated with PC1 between CCC I patients and HD (p < 0.0001). Differential gene expression analysis revealed upregulation of 41 genes (expression fold-change > 1.5) and downregulation of 14 genes (expression fold-change < 0.66) (p = 8.4x10-13 to p = 0.007) in CCC I patients versus HD. Furthermore, significant differences in the expression level of specific genes have been identified between CCC I and IND patients (8 up and 1 downregulated). GSEA showed that several upregulated genes in CCC I patients participate in immunological pathways such as antigen-dependent B cell activation, stress induction of HSP regulation, NO2-dependent IL12 pathway in NK cells, cytokines-inflammatory response and IL-10 anti-inflammatory signaling.

CONCLUSIONS

Cardiac Chagas disease patients show an antigen-specific differential gene expression profile in which several relevant immunological pathways seem to be activated. Assessment of gene expression profiles reveal unique insights into the immune response that occurs along chronic Chagas disease.

The macrophage infectivity potentiator of Trypanosoma cruzi induces innate IFN-γ and TNF-α production by human neonatal and adult blood cells through TLR2/1 and TLR4

We previously identified the recombinant (r) macrophage (M) infectivity (I) potentiator (P) of the protozoan parasite Trypanosoma cruzi (Tc) (rTcMIP) as an immuno-stimulatory protein that induces the release of IFN-γ, CCL2 and CCL3 by human cord blood cells. These cytokines and chemokines are important to direct a type 1 adaptive immune response. rTcMIP also increased the Ab response and favored the production of the Th1-related isotype IgG2a in mouse models of neonatal vaccination, indicating that rTcMIP could be used as a vaccine adjuvant to enhance T and B cell responses. In the present study, we used cord and adult blood cells, and isolated NK cells and human monocytes to investigate the pathways and to decipher the mechanism of action of the recombinant rTcMIP. We found that rTcMIP engaged TLR1/2 and TLR4 independently of CD14 and activated the MyD88, but not the TRIF, pathway to induce IFN-γ production by IL-15-primed NK cells, and TNF-α secretion by monocytes and myeloid dendritic cells. Our results also indicated that TNF-α boosted IFN-γ expression. Though cord blood cells displayed lower responses than adult cells, our results allow to consider rTcMIP as a potential pro-type 1 adjuvant that might be associated to vaccines administered in early life or later.

STAT1 Controls the Functionality of Influenza-Primed CD4 T Cells but Therapeutic STAT4 Engagement Maximizes Their Antiviral Impact

It is generally accepted that influenza A virus (IAV) infection promotes a Th1-like CD4 T cell response and that this effector program underlies its protective impact. Canonical Th1 polarization requires cytokine-mediated activation of the transcription factors STAT1 and STAT4 that synergize to maximize the induction of the "master regulator" Th1 transcription factor, T-bet. Here, we determine the individual requirements for these transcription factors in directing the Th1 imprint primed by influenza infection in mice by tracking virus-specific wild-type or T-bet-deficient CD4 T cells in which STAT1 or STAT4 is knocked out. We find that STAT1 is required to protect influenza-primed CD4 T cells from NK cell-mediated deletion and for their expression of hallmark Th1 attributes. STAT1 is also required to prevent type I IFN signals from inhibiting the induction of the Th17 master regulator, Rorγt, in Th17-prone T-bet-/- cells responding to IAV. In contrast, STAT4 expression does not appreciably impact the phenotypic or functional attributes of wild-type or T-bet-/- CD4 T cell responses. However, cytokine-mediated STAT4 activation in virus-specific CD4 T cells enhances their Th1 identity in a T-bet-dependent manner, indicating that influenza infection does not promote maximal Th1 induction. Finally, we show that the T-bet-dependent protective capacity of CD4 T cell effectors against IAV is optimized by engaging both STAT1 and STAT4 during Th1 priming, with important implications for vaccine strategies aiming to generate T cell immunity.

Immunization with a Trypanosoma cruzi cyclophilin-19 deletion mutant protects against acute Chagas disease in mice

Human infection with the protozoan parasite Trypanosoma cruzi causes Chagas disease for which there are no prophylactic vaccines. Cyclophilin 19 is a secreted cis-trans peptidyl isomerase expressed in all life stages of Trypanosoma cruzi. This protein in the insect stage leads to the inactivation of insect anti-parasitic peptides and parasite transformation whereas in the intracellular amastigotes it participates in generating ROS promoting the growth of parasites. We have generated a parasite mutant with depleted expression of Cyp19 by removal of 2 of 3 genes encoding this protein using double allelic homologous recombination. The mutant parasite line failed to replicate when inoculated into host cells in vitro or in mice indicating that Cyp19 is critical for infectivity. The mutant parasite line also fails to replicate in or cause clinical disease in immuno-deficient mice further validating their lack of virulence. Repeated inoculation of mutant parasites into immuno-competent mice elicits parasite-specific trypanolytic antibodies and a Th-1 biased immune response and challenge of mutant immunized mice with virulent wild-type parasites is 100% effective at preventing death from acute disease. These results suggest that parasite Cyp19 may be candidate for small molecule drug targeting and that the mutant parasite line may warrant further immunization studies for prevention of Chagas disease.

Circular RNA ciRS-7 affects the propagation of Cryptosporidium parvum in HCT-8 cells via regulating miR-135a-5p/stat1 axis

Cryptosporidium spp. are protozoan parasites that mainly inhabit intestinal epithelial cells, causing diarrheal diseases in humans and a great number of animals. Cryptosporidium parvum is the most common zoonotic species, responsible for nearly 45% of human cryptosporidiosis worldwide. Understanding the interaction mechanisms between C. parvum and host gastrointestinal epithelial cells has significant implications to control cryptosporidiosis. One up-regulated circRNA ciRS-7 was found previously by our group to promote in vitro propagation of C. parvum in HCT-8 cells. In the present study, miR-135a-5p, was found to be a miRNA target of ciRS-7. Cryptosporidium parvum infection induced significantly down-regulation of miR-135a-5p and dramatic up-regulation of its potential target stat1 gene at mRNA and protein levels. Dual luciferase reporter assays validated the physical interactions between miR-135a-5p and stat1, and between ciRS-7 and miR-135a-5p. Further study revealed that ciRS-7 could sponge miR-135a-5p to positively regulate the protein levels of STAT1 and phosphorylated STAT1 (p-STAT1) and thus promote C. parvum propagation in HCT-8 cells. Our findings further reveal the mystery of regulatory roles of host circRNAs during Cryptosporidium infection, and provide a novel insight to develop strategies to control cryptosporidiosis.

Trypanosoma cruzi Dysregulates piRNAs Computationally Predicted to Target IL-6 Signaling Molecules During Early Infection of Primary Human Cardiac Fibroblasts

Trypanosoma cruzi, the etiological agent of Chagas disease, is an intracellular protozoan parasite, which is now present in most industrialized countries. About 40% of T. cruzi infected individuals will develop severe, incurable cardiovascular, gastrointestinal, or neurological disorders. The molecular mechanisms by which T. cruzi induces cardiopathogenesis remain to be determined. Previous studies showed that increased IL-6 expression in T. cruzi patients was associated with disease severity. IL-6 signaling was suggested to induce pro-inflammatory and pro-fibrotic responses, however, the role of this pathway during early infection remains to be elucidated. We reported that T. cruzi can dysregulate the expression of host PIWI-interacting RNAs (piRNAs) during early infection. Here, we aim to evaluate the dysregulation of IL-6 signaling and the piRNAs computationally predicted to target IL-6 molecules during early T. cruzi infection of primary human cardiac fibroblasts (PHCF). Using in silico analysis, we predict that piR_004506, piR_001356, and piR_017716 target IL6 and SOCS3 genes, respectively. We validated the piRNAs and target gene expression in T. cruzi challenged PHCF. Secreted IL-6, soluble gp-130, and sIL-6R in condition media were measured using a cytokine array and western blot analysis was used to measure pathway activation. We created a network of piRNAs, target genes, and genes within one degree of biological interaction. Our analysis revealed an inverse relationship between piRNA expression and the target transcripts during early infection, denoting the IL-6 pathway targeting piRNAs can be developed as potential therapeutics to mitigate T. cruzi cardiomyopathies.

Modulation of STAT-1, STAT-3, and STAT-6 activities in THP-1 derived macrophages infected with two Trypanosoma cruzi strains

Trypanosoma cruzi is the causative protozoan of Chagas' Disease, a neglected tropical disease that affects 6-7 million people worldwide. Interaction of the parasite with the host immune system is a key factor in disease progression and chronic symptoms. Although the human immune system is capable of controlling the disease, the parasite has numerous evasion mechanisms that aim to maintain intracellular persistence and survival. Due to the pronounced genetic variability of T. cruzi, co-infections or mixed infections with more than one parasite strain have been reported in the literature. The intermodulation in such cases is unclear. This study aimed to evaluate the co-infection of T. cruzi strains G and CL compared to their individual infections in human macrophages derived from THP-1 cells activated by classical or alternative pathways. Flow cytometry analysis demonstrated that trypomastigotes were more infective than extracellular amastigotes (EAs) and that strain G could infect more macrophages than strain CL. Classically activated macrophages showed lower number of infected cells and IL-4-stimulated cells displayed increased CL-infected macrophages. However, co-infection was a rare event. CL EAs decreased the production of reactive oxygen species (ROS), whereas G trypomastigotes displayed increased ROS detection in classically activated cells. Co-infection did not affect ROS production. Monoinfection by strain G or CL mainly induced an anti-inflammatory cytokine profile by decreasing inflammatory cytokines (IFN-γ, TNF-α, IL-1β) and/or increasing IL-4, IL-10, and TGF-β. Co-infection led to a predominant inflammatory milieu, with reduced IL-10 and TGF-β, and/or promotion of IFN-γ and IL-1β release. Infection by strain G reduced activation of intracellular signal transducer and activator of transcription (STAT) factors. In EAs, monoinfections impaired STAT-1 activity and promoted phosphorylation of STAT-3, both changes may prolong cell survival. Coinfected macrophages displayed pronounced activation of all STATs examined. These activations likely promoted parasite persistence and survival of infected cells. The collective results demonstrate that although macrophages respond to both strains, T. cruzi can modulate the intracellular environment, inducing different responses depending on the strain, parasite infective form, and co-infection or monoinfection. The modulation influences parasite persistence and survival of infected cells.

STAT1-Dependent Recruitment of Ly6ChiCCR2+ Inflammatory Monocytes and M2 Macrophages in a Helminth Infection

Signal Transducer and Activator of Transcription (STAT) 1 signaling is critical for IFN-γ-mediated immune responses and resistance to protozoan and viral infections. However, its role in immunoregulation during helminth parasitic infections is not fully understood. Here, we used STAT1^-/- mice to investigate the role of this transcription factor during a helminth infection caused by the cestode Taenia crassiceps and show that STAT1 is a central molecule favoring susceptibility to this infection. STAT1^-/- mice displayed lower parasite burdens at 8 weeks post-infection compared to STAT1^+/+ mice. STAT1 mediated the recruitment of inflammatory monocytes and the development of alternatively activated macrophages (M2) at the site of infection. The absence of STAT1 prevented the recruitment of CD11b⁺Ly6C^hiLy6G^- monocytic cells and therefore their suppressive activity. This failure was associated with the defective expression of CCR2 on CD11b⁺Ly6C^hiLy6G^- cells. Importantly, CD11b⁺Ly6C^hiLy6G^- cells highly expressed PDL-1 and suppressed T-cell proliferation elicited by anti-CD3 stimulation. PDL-1⁺ cells were mostly absent in STAT1^-/- mice. Furthermore, only STAT1^+/+ mice developed M2 macrophages at 8 weeks post-infection, although macrophages from both T. crassiceps-infected STAT1^+/+ and STAT1^-/- mice responded to IL-4 in vitro, and both groups of mice were able to produce the Th2 cytokine IL-13. This suggests that CD11b⁺CCR2⁺Ly6C^hiLy6G^- cells give rise to M2 macrophages in this infection. In summary, a lack of STAT1 resulted in impaired recruitment of CD11b⁺CCR2⁺Ly6C^hiLy6G^- cells, failure to develop M2 macrophages, and increased resistance against T. crassiceps infection.

Differential Expression of Immune Response Genes in Asymptomatic Chronic Chagas Disease Patients Versus Healthy Subjects

Infection by the Trypanosoma cruzi parasite causes Chagas disease and triggers multiple immune mechanisms in the host to combat the pathogen. Chagas disease has a variable clinical presentation and progression, producing in the chronic phase a fragile balance between the host immune response and parasite replication that keeps patients in a clinically silent asymptomatic stage for years. Since the parasite is intracellular and replicates within cells, the cell-mediated response of the host adaptive immunity plays a critical role. This function is mainly orchestrated by T lymphocytes, which recognize parasite antigens and promote specific functions to control the infection. However, little is known about the immunological markers associated with this asymptomatic stage of the disease. In this large-scale analysis, the differential expression of 106 immune system-related genes has been analyzed using high-throughput qPCR in T. cruzi antigen-stimulated PBMC from chronic Chagas disease patients with indeterminate form (IND) and healthy donors (HD) from endemic and non-endemic areas of Chagas disease. This analysis revealed that there were no differences in the expression level of most genes under study between healthy donors from endemic and non-endemic areas determined by PCA and differential gene expression analysis. Instead, PCA revealed the existence of different expression profiles between IND patients and HD (p < 0.0001), dependent on the 32 genes included in PC1. Differential gene expression analysis also revealed 23 upregulated genes (expression fold change > 2) and 11 downregulated genes (expression fold change < 0.5) in IND patients versus HD. Enrichment analysis showed that several upregulated genes in IND patients participate in relevant immunological pathways such as antigen-dependent B cell activation, stress induction of HSP regulation, NO2-dependent IL12 pathway in NK cells, and cytokine-inflammatory response. The antigen-specific differential gene expression profile detected in these patients and the relevant immunological pathways that seem to be activated could represent potential biomarkers of the asymptomatic form of Chagas disease, helpful to diagnosis and infection control.

Mixed signals - how Trypanosoma cruzi exploits host-cell communication and signaling to establish infection

Chagas disease (American trypanosomiasis) is a 'neglected' pathology that affects millions of people worldwide, mainly in Latin America. Trypanosoma cruzi, the causative agent, is an obligate intracellular parasite with a complex and diverse biology that infects several mammalian species, including humans. Because of genetic variability among strains and the presence of four biochemically and morphologically distinct parasite forms, the outcome of T. cruzi infection varies considerably depending on host cell type and parasite strain. During the initial contact, cellular communication is established by host-recognition-mediated responses, followed by parasite adherence and penetration. For this purpose, T. cruzi expresses a variety of proteins that modify the host cell, enabling it to safely reach the cytoplasm. After entry into the host cell, T. cruzi forms a transitory structure termed 'parasitophorous vacuole' (PV), followed by its cytoplasmic replication and differentiation after PV rupture, and subsequent invasion of other cells. The success of infection, maintenance and survival inside host cells is facilitated by the ability of T. cruzi to subvert various host signaling mechanisms. We focus in this Review on the various mechanisms that induce host cytoskeletal rearrangements, activation of autophagy-related proteins and crosstalk among major immune response regulators, as well as recent studies on the JAK-STAT pathway.

MicroRNA-155 Deficiency Exacerbates Trypanosoma cruzi Infection

Chagas disease, caused by the intracellular protozoan parasite Trypanosoma cruzi, is a public health problem affecting 6 to 8 million people, mainly in Latin America. The role of microRNAs in the pathogenesis of Chagas disease has not been well described. Here, we investigate the role of microRNA-155 (miR-155), a proinflammatory host innate immune regulator responsible for T helper type 1 and type 17 (Th1 and Th17) development and macrophage responses during T. cruzi infection. For this, we compared the survival and parasite growth and distribution in miR-155^-/- and wild-type (WT) C57BL/6 mice. The lack of miR-155 caused robust parasite infection and diminished survival of infected mice, while WT mice were resistant to infection. Immunological analysis of infected mice indicated that, in the absence of miR-155, there was decreased interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) production. In addition, we found that there was a significant reduction of CD8-positive (CD8⁺) T cells, natural killer (NK) cells, and NK-T cells and increased accumulation of neutrophils and inflammatory monocytes in miR-155^-/- mice. Collectively, these data indicate that miR-155 is an important immune regulatory molecule critical for the control of T. cruzi infection.

Trypanosoma cruzi Promotes Transcriptomic Remodeling of the JAK/STAT Signaling and Cell Cycle Pathways in Myoblasts

Chagas disease is responsible for more than 10,000 deaths per year and about 6 to 7 million infected people worldwide. In its chronic stage, patients can develop mega-colon, mega-esophagus, and cardiomyopathy. Differences in clinical outcomes may be determined, in part, by the genetic background of the parasite that causes Chagas disease. Trypanosoma cruzi has a high genetic diversity, and each group of strains may elicit specific pathological responses in the host. Conflicting results have been reported in studies using various combinations of mammalian host-T. cruzi strains. We previously profiled the transcriptomic signatures resulting from infection of L6E9 rat myoblasts with four reference strains of T. cruzi (Brazil, CL, Y, and Tulahuen). The four strains induced similar overall gene expression alterations in the myoblasts, although only 21 genes were equally affected by all strains. Cardiotrophin-like cytokine factor 1 (Clcf1) was one of the genes found to be consistently upregulated by the infection with all four strains of T. cruzi. This cytokine is a member of the interleukin-6 family that binds to glycoprotein 130 receptor and activates the JAK/STAT signaling pathway, which may lead to muscle cell hypertrophy. Another commonly upregulated gene was tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein theta (Ywhaq, 14-3-3 protein Θ), present in the Cell Cycle Pathway. In the present work, we reanalyzed our previous microarray dataset, aiming at understanding in more details the transcriptomic impact that each strain has on JAK/STAT signaling and Cell Cycle pathways. Using Pearson correlation analysis between the expression levels of gene pairs in biological replicas from each pathway, we determined the coordination between such pairs in each experimental condition and the predicted protein interactions between the significantly altered genes by each strain. We found that although these highlighted genes were similarly affected by all four strains, the downstream genes or their interaction partners were not necessarily equally affected, thus reinforcing the idea of the role of parasite background on host cell transcriptome. These new analyses provide further evidence to the mechanistic understanding of how distinct T. cruzi strains lead to diverse remodeling of host cell transcriptome.

Molecular dissection of Chagas induced cardiomyopathy reveals central disease associated and druggable signaling pathways

Chagas disease, the clinical presentation of T. cruzi infection, is a major human health concern. While the acute phase of Chagas disease is typically asymptomatic and self-resolving, chronically infected individuals suffer numerous sequelae later in life. Cardiomyopathies in particular are the most severe consequence of chronic Chagas disease and cannot be reversed solely by parasite load reduction. To prioritize new therapeutic targets, we unbiasedly interrogated the host signaling events in heart tissues isolated from a Chagas disease mouse model using quantitative, multiplexed proteomics. We defined the host response to infection at both the proteome and phospho-proteome levels. The proteome showed an increase in the immune response and a strong repression of several mitochondrial proteins. Complementing the proteome studies, the phospho-proteomic survey found an abundance of phospho-site alterations in plasma membrane and cytoskeletal proteins. Bioinformatic analysis of kinase activity provided substantial evidence for the activation of NDRG2 and JNK/p38 kinases during Chagas disease. A significant activation of DYRK2 and AMPKA2 and the inhibition of casein family kinases were also predicted. We concluded our analyses by linking the diseased heart proteome profile to known therapeutic interventions, uncovering a potential to target mitochondrial proteins, secreted immune effectors and core kinases for the treatment of chronic Chagas disease. Together, this study provides molecular insight into host proteome and phospho-proteome responses to T. cruzi infection in the heart for the first time, highlighting pathways that can be further validated for functional contributions to disease and suitability as drug targets.

Trypanosoma cruzi-Infected Human Macrophages Shed Proinflammatory Extracellular Vesicles That Enhance Host-Cell Invasion via Toll-Like Receptor 2

Extracellular vesicles (EVs) shed by trypomastigote forms of Trypanosoma cruzi have the ability to interact with host tissues, increase invasion, and modulate the host innate response. In this study, EVs shed from T. cruzi or T.cruzi-infected macrophages were investigated as immunomodulatory agents during the initial steps of infection. Initially, by scanning electron microscopy and nanoparticle tracking analysis, we determined that T. cruzi-infected macrophages release higher numbers of EVs (50-300 nm) as compared to non-infected cells. Using Toll-like-receptor 2 (TLR2)-transfected CHO cells, we observed that pre-incubation of these host cells with parasite-derived EVs led to an increase in the percentage of infected cells. In addition, EVs from parasite or T.cruzi-infected macrophages or not were able to elicit translocation of NF-κB by interacting with TLR2, and as a consequence, to alter the EVs the gene expression of proinflammatory cytokines (TNF-α, IL-6, and IL-1β), and STAT-1 and STAT-3 signaling pathways. By proteomic analysis, we observed highly significant changes in the protein composition between non-infected and infected host cell-derived EVs. Thus, we observed the potential of EVs derived from T. cruzi during infection to maintain the inflammatory response in the host.

Disease Tolerance and Pathogen Resistance Genes May Underlie Trypanosoma cruzi Persistence and Differential Progression to Chagas Disease Cardiomyopathy

Chagas disease is caused by infection with the protozoan Trypanosoma cruzi and affects over 8 million people worldwide. In spite of a powerful innate and adaptive immune response in acute infection, the parasite evades eradication, leading to a chronic persistent infection with low parasitism. Chronically infected subjects display differential patterns of disease progression. While 30% develop chronic Chagas disease cardiomyopathy (CCC)—a severe inflammatory dilated cardiomyopathy—decades after infection, 60% of the patients remain disease-free, in the asymptomatic/indeterminate (ASY) form, and 10% develop gastrointestinal disease. Infection of genetically deficient mice provided a map of genes relevant for resistance to T. cruzi infection, leading to the identification of multiple genes linked to survival to infection. These include pathogen resistance genes (PRG) needed for intracellular parasite destruction, and genes involved in disease tolerance (protection against tissue damage and acute phase death—DTG). All identified DTGs were found to directly or indirectly inhibit IFN-γ production or Th1 differentiation. We hypothesize that the absolute need for DTG to control potentially lethal IFN-γ PRG activity leads to T. cruzi persistence and establishment of chronic infection. IFN-γ production is higher in CCC than ASY patients, and is the most highly expressed cytokine in CCC hearts. Key DTGs that downmodulate IFN-γ, like IL-10, and Ebi3/IL27p28, are higher in ASY patients. Polymorphisms in PRG and DTG are associated with differential disease progression. We thus hypothesize that ASY patients are disease tolerant, while an imbalance of DTG and IFN-γ PRG activity leads to the inflammatory heart damage of CCC.

Host-Directed Drug Therapies for Neglected Tropical Diseases Caused by Protozoan Parasites

The neglected tropical diseases (NTDs) caused by protozoan parasites are responsible for significant morbidity and mortality worldwide. Current treatments using anti-parasitic drugs are toxic and prolonged with poor patient compliance. In addition, emergence of drug-resistant parasites is increasing worldwide. Hence, there is a need for safer and better therapeutics for these infections. Host-directed therapy using drugs that target host pathways required for pathogen survival or its clearance is a promising approach for treating infections. This review will give a summary of the current status and advances of host-targeted therapies for treating NTDs caused by protozoa.