Trypanosoma cruzi infection down-modulates the immunoproteasome biosynthesis and the MHC class I cell surface expression in HeLa cells

Immunologic changes are detectable in the peripheral blood transcriptome of clinically asymptomatic Chagas cardiomyopathy patients

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is a neglected parasitic disease that affects approximately 6 million individuals worldwide. Of those infected, 20-30% will go on to develop chronic Chagas cardiomyopathy (CCC), and ultimately many of these individuals will progress to advanced heart failure. The mechanism by which this progression occurs is poorly understood, as few studies have focused on early CCC. In this study, we sought to understand the physiologic changes associated with T. cruzi infection and the development of CCC. We analyzed gene expression in the peripheral blood of asymptomatic Chagas patients with early structural heart disease, Chagas patients without any signs or symptoms of disease, and Chagas-negative patients with and without early structural heart disease. Our analysis shows that early CCC was associated with a downregulation of various peripheral immune response genes, with gene expression changes suggestive of reduced antigen presentation and T cell activation. Notably, these genes and processes were distinct from those of early cardiomyopathy in Chagas-negative patients, suggesting that the processes mediating CCC may be unique from those mediating progression to other cardiomyopathies. This work highlights the importance of the immune response in early CCC, providing insight into the early pathogenesis of this disease. The changes we have identified may serve as biomarkers of progression and could inform strategies for the treatment of CCC in its early stages, before significant cardiac damage has occurred.

The Effect of the Nanoparticle Shape on T Cell Activation

The mechanism of extracellular ligand nano-geometry in ex vivo T cell activation for immunotherapy remains elusive. Herein, the authors demonstrate large aspect ratio (AR) of gold nanorods (AuNRs) conjugated on cell culture substrate enhancing both murine and human T cell activation through the nanoscale anisotropic presentation of stimulatory ligands (anti-CD3(αCD3) and anti-CD28(αCD28) antibodies). AuNRs with large AR bearing αCD3 and αCD28 antibodies significantly promote T cell expansion and key cytokine secretion including interleukin-2 (IL-2), interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α). High membrane tension observed in large AR AuNRs regulates actin filament and focal adhesion assembly and develops maturation-related morphological features in T cells such as membrane ruffle formation, cell spreading, and large T cell receptor (TCR) cluster formation. Anisotropic stimulatory ligand presentation promotes differentiation of naïve CD8⁺ T cells toward the effector phenotype inducing CD137 expression upon co-culture with human cervical carcinoma. The findings suggest the importance of manipulating extracellular ligand nano-geometry in optimizing T cell behaviors to enhance therapeutic outcomes.

African Trypanosomiasis: Extracellular Vesicles Shed by Trypanosoma brucei brucei Manipulate Host Mononuclear Cells

African trypanosomiasis or sleeping sickness is a zoonotic disease caused by Trypanosoma brucei, a protozoan parasite transmitted by Glossina spp. (tsetse fly). Parasite introduction into mammal hosts triggers a succession of events, involving both innate and adaptive immunity. Macrophages (MΦ) have a key role in innate defence since they are antigen-presenting cells and have a microbicidal function essential for trypanosome clearance. Adaptive immune defence is carried out by lymphocytes, especially by T cells that promote an integrated immune response. Like mammal cells, T. b. brucei parasites release extracellular vesicles (TbEVs), which carry macromolecules that can be transferred to host cells, transmitting biological information able to manipulate cell immune response. However, the exact role of TbEVs in host immune response remains poorly understood. Thus, the current study examined the effect elicited by TbEVs on MΦ and T lymphocytes. A combined approach of microscopy, nanoparticle tracking analysis, multiparametric flow cytometry, colourimetric assays and detailed statistical analyses were used to evaluate the influence of TbEVs in mouse mononuclear cells. It was shown that TbEVs can establish direct communication with cells of innate and adaptative immunity. TbEVs induce the differentiation of both M1- and M2-MΦ and elicit the expansion of MHCI⁺, MHCII⁺ and MHCI⁺MHCII⁺ MΦ subpopulations. In T lymphocytes, TbEVs drive the overexpression of cell-surface CD3 and the nuclear factor FoxP3, which lead to the differentiation of regulatory CD4⁺ and CD8⁺ T cells. Moreover, this study indicates that T. b. brucei and TbEVs seem to display opposite but complementary effects in the host, establishing a balance between parasite growth and controlled immune response, at least during the early phase of infection.

Host-parasite dynamics in Chagas disease from systemic to hyper-local scales

Trypanosoma cruzi is a remarkably versatile parasite. It can parasitize almost any nucleated cell type and naturally infects hundreds of mammal species across much of the Americas. In humans, it is the cause of Chagas disease, a set of mainly chronic conditions predominantly affecting the heart and gastrointestinal tract, which can progress to become life threatening. Yet around two thirds of infected people are long-term asymptomatic carriers. Clinical outcomes depend on many factors, but the central determinant is the nature of the host-parasite interactions that play out over the years of chronic infection in diverse tissue environments. In this review, we aim to integrate recent developments in the understanding of the spatial and temporal dynamics of T. cruzi infections with established and emerging concepts in host immune responses in the corresponding phases and tissues.

Drug-cured experimental Trypanosoma cruzi infections confer long-lasting and cross-strain protection

BACKGROUND

The long term and complex nature of Chagas disease in humans has restricted studies on vaccine feasibility. Animal models also have limitations due to technical difficulties in monitoring the extremely low parasite burden that is characteristic of chronic stage infections. Advances in imaging technology offer alternative approaches that circumvent these problems. Here, we describe the use of highly sensitive whole body in vivo imaging to assess the efficacy of recombinant viral vector vaccines and benznidazole-cured infections to protect mice from challenge with Trypanosoma cruzi.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were infected with T. cruzi strains modified to express a red-shifted luciferase reporter. Using bioluminescence imaging, we assessed the degree of immunity to re-infection conferred after benznidazole-cure. Those infected for 14 days or more, prior to the onset of benznidazole treatment, were highly protected from challenge with both homologous and heterologous strains. There was a >99% reduction in parasite burden, with parasites frequently undetectable after homologous challenge. This level of protection was considerably greater than that achieved with recombinant vaccines. It was also independent of the route of infection or size of the challenge inoculum, and was long-lasting, with no significant diminution in immunity after almost a year. When the primary infection was benznidazole-treated after 4 days (before completion of the first cycle of intracellular infection), the degree of protection was much reduced, an outcome associated with a minimal T. cruzi-specific IFN-γ+ T cell response.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that a protective Chagas disease vaccine must have the ability to eliminate parasites before they reach organs/tissues, such as the GI tract, where once established, they become largely refractory to the induced immune response.

In vitro models for investigation of the host-parasite interface - possible applications in acute Chagas disease

Chagas disease (CD), caused by Trypanosoma cruzi, is the main parasitic disease in the Western Hemisphere, with an increasing number of cases, especially in non-endemic regions. The disease is characterized by cardiomegaly and mega viscera, nevertheless, the clinical outcome is hard to predict, underscoring the need for further research into the pathophysiology of CD. Even though most basic and translational research involving CD is performed using in vivo models, in vitro models arise as an ethical, rapidly evolving, and physiologically relevant alternative for CD research. In the present review, we discuss the past and recent in vitro models available to study the host-parasite interface in cardiac and intestinal CD, critically analyzing the possibilities and limitations of state-of-the-art alternatives for the CD host-parasite investigation.

Exoproteome profiling of Trypanosoma cruzi during amastigogenesis early stages

Chagas disease is caused by the protozoan Trypanosoma cruzi, affecting around 8 million people worldwide. After host cell invasion, the infective trypomastigote form remains 2–4 hours inside acidic phagolysosomes to differentiate into replicative amastigote form. In vitro acidic-pH-induced axenic amastigogenesis was used here to study this step of the parasite life cycle. After three hours of trypomastigote incubation in amastigogenesis promoting acidic medium (pH 5.0) or control physiological pH (7.4) medium samples were subjected to three rounds of centrifugation followed by ultrafiltration of the supernatants. The resulting exoproteome samples were trypsin digested and analysed by nano flow liquid chromatography coupled to tandem mass spectrometry. Computational protein identification searches yielded 271 and 483 protein groups in the exoproteome at pH 7.4 and pH 5.0, respectively, with 180 common proteins between both conditions. The total amount and diversity of proteins released by parasites almost doubled upon acidic incubation compared to control. Overall, 76.5% of proteins were predicted to be secreted by classical or non-classical pathways and 35.1% of these proteins have predicted transmembrane domains. Classical secretory pathway analysis showed an increased number of mucins and mucin-associated surface proteins after acidic incubation. However, the number of released trans-sialidases and surface GP63 peptidases was higher at pH 7.4. Trans-sialidases and mucins are anchored to the membrane and exhibit an enzyme-substrate relationship. In general, mucins are glycoproteins with immunomodulatory functions in Chagas disease, present mainly in the epimastigote and trypomastigote surfaces and could be enzymatically cleaved and released in the phagolysosome during amastigogenesis. Moreover, evidence for flagella discard during amastigogenesis are addressed. This study provides the first comparative analysis of the exoproteome during amastigogenesis, and the presented data evidence the dynamism of its profile in response to acidic pH-induced differentiation.

A systematic review of the Trypanosoma cruzi genetic heterogeneity, host immune response and genetic factors as plausible drivers of chronic chagasic cardiomyopathy

Chagas disease is a complex tropical pathology caused by the kinetoplastid Trypanosoma cruzi. This parasite displays massive genetic diversity and has been classified by international consensus in at least six Discrete Typing Units (DTUs) that are broadly distributed in the American continent. The main clinical manifestation of the disease is the chronic chagasic cardiomyopathy (CCC) that is lethal in the infected individuals. However, one intriguing feature is that only 30-40% of the infected individuals will develop CCC. Some authors have suggested that the immune response, host genetic factors, virulence factors and even the massive genetic heterogeneity of T. cruzi are responsible of this clinical pattern. To date, no conclusive data support the reason why a few percentages of the infected individuals will develop CCC. Therefore, we decided to conduct a systematic review analysing the host genetic factors, immune response, cytokine production, virulence factors and the plausible association of the parasite DTUs and CCC. The epidemiological and clinical implications are herein discussed.

The High-Risk Human Papillomavirus E6 Oncogene Exacerbates the Negative Effect of Tryptophan Starvation on the Development of Chlamydia trachomatis

Chlamydia trachomatis is an obligate intracellular pathogen that requires specific essential nutrients from the host cell, one of which is the amino acid tryptophan. In this context interferon gamma (IFNγ) is the major host protective cytokine against chlamydial infections because it induces the expression of the host enzyme, indoleamine 2,3-dioxygenase 1, that degrades tryptophan, thereby restricting bacterial replication. The mechanism by which IFNγ acts has been dissected in vitro using epithelial cell-lines such as HeLa, HEp-2, or the primary-like endocervical cell-line A2EN. All these cell-lines express the high-risk human papillomavirus oncogenes E6 & E7. While screening cell-lines to identify those suitable for C. trachomatis co-infections with other genital pathogens, we unexpectedly found that tryptophan starvation did not completely block chlamydial development in cell-lines that were HR-HPV negative, such as C33A and 293. Therefore, we tested the hypothesis that HR-HPV oncogenes modulate the effect of tryptophan starvation on chlamydial development by comparing chlamydial development in HeLa and C33A cell-lines that were both derived from cervical carcinomas. Our results indicate that during tryptophan depletion, unlike HeLa, C33A cells generate sufficient intracellular tryptophan via proteasomal activity to permit C. trachomatis replication. By generating stable derivatives of C33A that expressed HPV16 E6, E7 or E6 & E7, we found that E6 expression alone was sufficient to convert C33A cells to behave like HeLa during tryptophan starvation. The reduced tryptophan levels in HeLa cells have a biological consequence; akin to the previously described effect of IFNγ, tryptophan starvation protects C. trachomatis from clearance by doxycycline in HeLa but not C33A cells. Curiously, when compared to the known Homo sapiens proteome, the representation of tryptophan in the HR-HPV E6 & E6AP degradome is substantially lower, possibly providing a mechanism that underlies the lowered intracellular free tryptophan levels in E6-expressing cells during starvation.

Blocking of CD1d Decreases Trypanosoma cruzi-Induced Activation of CD4-CD8- T Cells and Modulates the Inflammatory Response in Patients With Chagas Heart Disease

The control of inflammatory responses to prevent the deadly cardiac pathology in human Chagas disease is a desirable and currently unattained goal. Double-negative (DN) T cells are important sources of inflammatory and antiinflammatory cytokines in patients with Chagas heart disease and those with the indeterminate clinical form of Chagas disease, respectively. Given the importance of DN T cells in immunoregulatory processes and their potential as targets for controlling inflammation-induced pathology, we studied the involvement of CD1 molecules in the activation and functional profile of Trypanosoma cruzi-specific DN T cells. We observed that parasite stimulation significantly increased the expression of CD1a, CD1b, CD1c, and CD1d by CD14(+) cells from patients with Chagas disease. Importantly, among the analyzed molecules, only CD1d expression showed an association with the activation of DN T cells, as well as with worse ventricular function in patients with Chagas disease. Blocking of CD1d-mediated antigen presentation led to a clear reduction of DN T-cell activation and a decrease in the expression of interferon γ (IFN-γ) by DN T cells. Thus, our results showed that antigen presentation via CD1d is associated with activation of DN T cells in Chagas disease and that CD1d blocking leads to downregulation of IFN-γ by DN T cells from patients with Chagas heart disease, which may be a potential target for preventing progression of inflammation-mediated dilated cardiomyopathy.

Dendritic Cells: A Double-Edged Sword in Immune Responses during Chagas Disease

Dendritic cells (DCs) are the most important member of the antigen presenting cells group due to their ability to recognize antigen at the infection site and their high specialized antigen internalization capacity. These cells have central role in connecting the innate and adaptive immune responses against Trypanosoma cruzi, the causative agent of Chagas disease. These first line defense cells modulate host immune response depending on type, maturation level, cytokine milieu and DC receptor involved in the interactions with T. cruzi, influencing the development of the disease clinic forms. Here, we present a review of DCs-T. cruzi interactions both in human and murine models, pointing out the parasite ability to manipulate DCs activity for the purpose of evading innate immune response and assuring its own survival and persistence.

Cell surface proteome analysis of human-hosted Trypanosoma cruzi life stages

Chagas' disease is a neglected infectious illness, caused by the protozoan Trypanosoma cruzi. It remains a challenging health issue in Latin America, where it is endemic, and so far there is no immunoprophylatic vaccine or satisfactory chemotherapic treatment for its chronic stage. The present work addressed the analysis of the plasma membrane (PM) subproteome from T. cruzi human-hosted life stages, trypomastigote and axenic amastigote, by two complementary PM protein enrichment techniques followed by identification using an LC-MS/MS approach. The results revealed an extensive repertoire of proteins in the PM subproteomes, including enzymes that might be suitable candidates for drug intervention. The comparison of the cell surface proteome among the life forms revealed some potentially stage-specific enzymes, although the majority was shared by both stages. Bioinformatic analysis showed that the vast majority of the identified proteins are membrane-derived and/or possess predicted transmembrane domains. They are mainly involved in host cell infection, protein adhesion, cell signaling, and the modulation of mammalian host immune response. Several virulence factors and proteins potentially capable of acting at a number of metabolic pathways of the host and also to regulate cell differentiation of the parasite itself were also found.