Close encounters between Trypanosoma cruzi and the host mammalian cell: Lessons from genome-wide expression studies

Trypanosoma cruzi amastigote transcriptome analysis reveals heterogenous populations with replicating and dormant parasites

Trypanosoma cruzi is a protozoan parasite causing Chagas disease, with a complex life cycle involving different stages in insect vectors and mammalian hosts. Amastigotes are an intracellular form that replicates in the cytoplasm of host cells, and recent studies suggested that dormant forms may be contributing to parasite persistence, suggesting cellular heterogeneity among amastigotes. We investigated here if a transcriptomic approach could identify some heterogeneity in intracellular amastigotes and identify a dormant population. We used gene expression data derived from bulk RNA-sequencing of T. cruzi infection of human fibroblasts for deconvolution using CDSeq, which allows to simultaneously estimate amastigote cell-type proportions and cell-type-specific expression profiles. Six amastigote subpopulations were identified, confirming intracellular amastigotes heterogeneity, and one population presented characteristics of non-replicative dormant parasites, based on replication markers and TcRAD51 expression. Transcriptomic approaches appear to be powerful to understand T. cruzi cell differentiation and expansion of these studies could provide further insight on the role different cell types in parasite persistence and Chagas disease pathogenesis.

Comparative microRNA profiling of Trypanosoma cruzi infected human cells

Introduction

Trypanosoma cruzi, the causative agent of Chagas disease, can infect almost any nucleated cell in the mammalian host. Although previous studies have described the transcriptomic changes that occur in host cells during parasite infection, the understanding of the role of post-transcriptional regulation in this process is limited. MicroRNAs, a class of short non-coding RNAs, are key players in regulating gene expression at the post-transcriptional level, and their involvement in the host-T. cruzi interplay is a growing area of research. However, to our knowledge, there are no comparative studies on the microRNA changes that occur in different cell types in response to T. cruzi infection.

Methods and results

Here we investigated microRNA changes in epithelial cells, cardiomyocytes and macrophages infected with T. cruzi for 24 hours, using small RNA sequencing followed by careful bioinformatics analysis. We show that, although microRNAs are highly cell type-specific, a signature of three microRNAs -miR-146a, miR-708 and miR-1246, emerges as consistently responsive to T. cruzi infection across representative human cell types. T. cruzi lacks canonical microRNA-induced silencing mechanisms and we confirm that it does not produce any small RNA that mimics known host microRNAs. We found that macrophages show a broad response to parasite infection, while microRNA changes in epithelial and cardiomyocytes are modest. Complementary data indicated that cardiomyocyte response may be greater at early time points of infection.

Conclusions

Our findings emphasize the significance of considering microRNA changes at the cellular level and complement previous studies conducted at higher organizational levels, such as heart samples. While miR-146a has been previously implicated in T. cruzi infection, similarly to its involvement in many other immunological responses, miR-1246 and miR-708 are demonstrated here for the first time. Given their expression in multiple cell types, we anticipate our work as a starting point for future investigations into their role in the post-transcriptional regulation of T. cruzi infected cells and their potential as biomarkers for Chagas disease.

Kinetic Characterization and Inhibition of Trypanosoma cruzi Hypoxanthine–Guanine Phosphoribosyltransferases

Chagas disease, caused by the parasitic protozoan Trypanosoma cruzi, affects over 8 million people worldwide. Current antiparasitic treatments for Chagas disease are ineffective in treating advanced, chronic stages of the disease, and are noted for their toxicity. Like most parasitic protozoa, T. cruzi is unable to synthesize purines de novo, and relies on the salvage of preformed purines from the host. Hypoxanthine–guanine phosphoribosyltransferases (HGPRTs) are enzymes that are critical for the salvage of preformed purines, catalyzing the formation of inosine monophosphate (IMP) and guanosine monophosphate (GMP) from the nucleobases hypoxanthine and guanine, respectively. Due to the central role of HGPRTs in purine salvage, these enzymes are promising targets for the development of new treatment methods for Chagas disease. In this study, we characterized two gene products in the T. cruzi CL Brener strain that encodes enzymes with functionally identical HGPRT activities in vitro: TcA (TcCLB.509693.70) and TcC (TcCLB.506457.30). The TcC isozyme was kinetically characterized to reveal mechanistic details on catalysis, including identification of the rate-limiting step(s) of catalysis. Furthermore, we identified and characterized inhibitors of T. cruzi HGPRTs originally developed as transition-state analogue inhibitors (TSAIs) of Plasmodium falciparum hypoxanthine–guanine–xanthine phosphoribosyltransferase (PfHGXPRT), where the most potent compound bound to T. cruzi HGPRT with low nanomolar affinity. Our results validated the repurposing of TSAIs to serve as selective inhibitors for orthologous molecular targets, where primary and secondary structures as well as putatively common chemical mechanisms are conserved.

Different Transcriptomic Response to T. cruzi Infection in hiPSC-Derived Cardiomyocytes From Chagas Disease Patients With and Without Chronic Cardiomyopathy

Chagas disease is a tropical zoonosis caused by Trypanosoma cruzi. After infection, the host present an acute phase, usually asymptomatic, in which an extensive parasite proliferation and intense innate immune activity occurs, followed by a chronic phase, characterized by low parasitemia and development of specific immunity. Most individuals in the chronic phase remain without symptoms or organ damage, a state called indeterminate IND form. However, 20 to 40% of individuals develop cardiac or gastrointestinal complications at any time in life. Cardiomyocytes have an important role in the development of Chronic Chagas Cardiomyopathy (CCC) due to transcriptional and metabolic alterations that are crucial for the parasite survival and replication. However, it still not clear why some infected individuals progress to a cardiomyopathy phase, while others remain asymptomatic. In this work, we used hiPSCs-derived cardiomyocytes (hiPSC-CM) to investigate patterns of infection, proliferation and transcriptional response in IND and CCC patients. Our data show that T. cruzi infection and proliferation efficiency do not differ significantly in PBMCs and hiPSC-CM from both groups. However, RNA-seq analysis in hiPSC-CM infected for 24 hours showed a significantly different transcriptional response to the parasite in cells from IND or CCC patients. Cardiomyocytes from IND showed significant differences in the expression of genes related to antigen processing and presentation, as well as, immune co-stimulatory molecules. Furthermore, the downregulation of collagen production genes and extracellular matrix components was significantly different in these cells. Cardiomyocytes from CCC, in turn, showed increased expression of mTORC1 pathway and unfolded protein response genes, both associated to increased intracellular ROS production. These data point to a differential pattern of response, determined by baseline genetic differences between groups, which may have an impact on the development of a chronic outcome with or without the presentation of cardiac symptoms.

MicroRNAs: master regulators in host-parasitic protist interactions

MicroRNAs (miRNAs) are a group of small non-coding RNAs present in a wide diversity of organisms. MiRNAs regulate gene expression at a post-transcriptional level through their interaction with the 3' untranslated regions of target mRNAs, inducing translational inhibition or mRNA destabilization and degradation. Thus, miRNAs regulate key biological processes, such as cell death, signal transduction, development, cellular proliferation and differentiation. The dysregulation of miRNAs biogenesis and function is related to the pathogenesis of diseases, including parasite infection. Moreover, during host-parasite interactions, parasites and host miRNAs determine the probability of infection and progression of the disease. The present review is focused on the possible role of miRNAs in the pathogenesis of diseases of clinical interest caused by parasitic protists. In addition, the potential role of miRNAs as targets for the design of drugs and diagnostic and prognostic markers of parasitic diseases is also discussed.

Growth hormone modulates Trypanosoma cruzi infection in vitro

OBJECTIVE

Chagas disease (CD) is caused by the protozoan parasite, Trypanosoma cruzi. It affects 7 to 8 million people worldwide and leads to approximately 50,000 deaths per year. In vitro and in vivo studies had demonstrated that Trypanosoma cruziinfection causes an imbalance in the hypothalamic-pituitary-adrenal (HPA) axis that is accompanied by a progressive decrease in growth hormone (GH) and prolactin (PRL) production. In humans, inactivating mutations in the GH receptor gene cause Laron Syndrome (LS), an autosomal recessive disorder. Affected subjects are short, have increased adiposity, decreased insulin-like growth factor-I (IGFI), increased serum GH levels, are highly resistant to diabetes and cancer, and display slow cognitive decline. In addition, CD incidence in these individuals is diminished despite living in highly endemic areas. Consequently, we decided to investigate the in vitro effect of GH/IGF-I on T. cruzi infection.

DESIGN

We first treated the parasite and/or host cells with different peptide hormones including GH, IGFI, and PRL. Then, we treated cells using different combinations of GH/IGF-I attempting to mimic the GH/IGF-I serum levels observed in LS subjects.

RESULTS

We found that exogenous GH confers protection against T. cruzi infection. Moreover, this effect is mediated by GH and not IGFI. The combination of relatively high GH (50 ng/ml) and low IGF-I (20 ng/ml), mimicking the hormonal pattern seen in LS individuals, consistently decreased T. cruzi infection in vitro.

CONCLUSIONS

The combination of relatively high GH and low IGF-I serum levels in LS individuals may be an underlying condition providing partial protection against T. cruzi infection.

Co-Therapy of Albendazole and Dexamethasone Reduces Pathological Changes in the Cerebral Parenchyma of Th-1 and Th-2 Dominant Mice Heavily Infected with Angiostrongylus cantonensis: Histopathological and RNA-seq Analyses

Administration of albendazole alone was not very suitable for the treatment of cerebral angiostrongyliasis. This study was designed to evaluate the effects of the co-therapy of this drug and dexamethasone in Th-1 and Th-2 dominant mice infected with Angiostrongylus cantonensis. Each of BALB/c and C57BL/6 mice infected with 50 A. cantonensis third-stage larvae were administered albendazole (10 mg/kg/day) alone, dexamethasone (0.5 mg/kg/day) alone, or co-therapy of the two drugs from day 7 or 14 post-infection for 7 or 14 days. After sacrifice, coronal slices were prepared from five brain regions and stained with hematoxylin and eosin. Eight pathological changes were employed to determine the therapeutic effectiveness using a scoring system. RNA-seq analysis was performed to confirm the histopathological findings. The infected BALB/c and C57BL/6 mice had similar patterns in the pathological changes. Meningitis, hemorrhage, size of worms, and encephalitis in the cerebral parenchyma were slighter in the mice treated with co-therapy than the remaining groups. Mice treated from day 14 had more severe changes than those from day 7. The histopathological findings were found to be consistent to immune responses determined by RNA-seq analysis. Co-therapy was determined to reduce pathological changes after administration to mice infected with A. cantonensis.

All Roads Lead to Cytosol: Trypanosoma cruzi Multi-Strategic Approach to Invasion

T. cruzi has a complex life cycle involving four developmental stages namely, epimastigotes, metacyclic trypomastigotes, amastigotes and bloodstream trypomastigotes. Although trypomastigotes are the infective forms, extracellular amastigotes have also shown the ability to invade host cells. Both stages can invade a broad spectrum of host tissues, in fact, almost any nucleated cell can be the target of infection. To add complexity, the parasite presents high genetic variability with differential characteristics such as infectivity. In this review, we address the several strategies T. cruzi has developed to subvert the host cell signaling machinery in order to gain access to the host cell cytoplasm. Special attention is made to the numerous parasite/host protein interactions and to the set of signaling cascades activated during the formation of a parasite-containing vesicle, the parasitophorous vacuole, from which the parasite escapes to the cytosol, where differentiation and replication take place.

Gene expression network analyses during infection with virulent and avirulent Trypanosoma cruzi strains unveil a role for fibroblasts in neutrophil recruitment and activation

Chagas disease is caused by Trypanosoma cruzi, a protozoan parasite that has a heterogeneous population composed of a pool of strains with distinct characteristics, including variable levels of virulence. In previous work, transcriptome analyses of parasite genes after infection of human foreskin fibroblasts (HFF) with virulent (CL Brener) and non-virulent (CL-14) clones derived from the CL strain, revealed a reduced expression of genes encoding parasite surface proteins in CL-14 compared to CL Brener during the final steps of the intracellular differentiation from amastigotes to trypomastigotes. Here we analyzed changes in the expression of host genes during in vitro infection of HFF cells with the CL Brener and CL-14 strains by analyzing total RNA extracted from cells at 60 and 96 hours post-infection (hpi) with each strain, as well as from uninfected cells. Similar transcriptome profiles were observed at 60 hpi with both strains compared to uninfected samples. However, at 96 hpi, significant differences in the number and expression levels of several genes, particularly those involved with immune response and cytoskeleton organization, were observed. Further analyses confirmed the difference in the chemokine/cytokine signaling involved with the recruitment and activation of immune cells such as neutrophils upon T. cruzi infection. These findings suggest that infection with the virulent CL Brener strain induces a more robust inflammatory response when compared with the non-virulent CL-14 strain. Importantly, the RNA-Seq data also exposed an unexplored role of fibroblasts as sentinel cells that may act by recruiting neutrophils to the initial site of infection. This role for fibroblasts in the regulation of the inflammatory response during infection by T. cruzi was corroborated by measurements of levels of different chemokines/cytokines during in vitro infection and in plasma from Chagas disease patients as well as by neutrophil activation and migration assays.

Trypanosoma cruzi is the causative agent of Chagas disease, a debilitating and often life-threatening illness that affects 6 to 7 million people mainly in Latin America. The parasite, transmitted to humans by an insect vector, needs to invade different cells from the infected person in order to multiply and spread the infection to various organs, including the heart and the gut. In this study, we investigated how the host cell responds to the infection by analyzing changes in the expression of human genes in fibroblasts infected with the CL Brener and CL-14 strains, which are strains that present highly distinct virulent phenotypes during infection in mice. We showed that human fibroblasts build a strong immune response upon infection by T. cruzi and that this response is different depending on the parasite strain: infection with the virulent CL Brener strain induces a more robust inflammatory response compared with the infection with the avirulent CL-14 strain. We also showed that, in response to the infection, fibroblasts produce molecules that can recruit and activate neutrophils, which are important immune cells that controls the infection.

Experimental Strategies to Explore Drug Action and Resistance in Kinetoplastid Parasites

Kinetoplastids are the causative agents of leishmaniasis, human African trypanosomiasis, and American trypanosomiasis. They are responsible for high mortality and morbidity in (sub)tropical regions. Adequate treatment options are limited and have several drawbacks, such as toxicity, need for parenteral administration, and occurrence of treatment failure and drug resistance. Therefore, there is an urgency for the development of new drugs. Phenotypic screening already allowed the identification of promising new chemical entities with anti-kinetoplastid activity potential, but knowledge on their mode-of-action (MoA) is lacking due to the generally applied whole-cell based approach. However, identification of the drug target is essential to steer further drug discovery and development. Multiple complementary techniques have indeed been used for MoA elucidation. In this review, the different 'omics' approaches employed to define the MoA or mode-of-resistance of current reference drugs and some new anti-kinetoplastid compounds are discussed.

Comparative high-throughput analysis of the Trypanosoma cruzi response to organometallic compounds

An in-depth, comparative look at the effects of two structurally related organometallic Pd and Pt compounds on the global gene expression pattern of T. cruzi epimastigotes. This parasite is the causative agent of Chagas disease.