Extracellular Vesicles: Potential Role in Remote Signaling and Inflammation in Trypanosoma cruzi-Triggered Disease

Clinical trials for Chagas disease: etiological and pathophysiological treatment

Chagas disease (CD) is caused by the flagellate protozoan Trypanosoma cruzi. It is endemic in Latin America. Nowadays around 6 million people are affected worldwide, and 75 million are still at risk. CD has two evolutive phases, acute and chronic. The acute phase is mostly asymptomatic, or presenting unspecific symptoms which makes it hard to diagnose. At the chronic phase, patients can stay in the indeterminate form or develop cardiac and/or digestive manifestations. The two trypanocide drugs available for the treatment of CD are benznidazole (BZ) and nifurtimox (NFX), introduced in the clinic more than five decades ago. WHO recommends treatment for patients at the acute phase, at risk of congenital infection, for immunosuppressed patients and children with chronic infection. A high cure rate is seen at the CD acute phase but better treatment schemes still need to be investigated for the chronic phase. There are some limitations within the use of the trypanocide drugs, with side effects occurring in about 40% of the patients, that can lead patients to interrupt treatment. In addition, patients with advanced heart problems should not be treated with BZ. This is a neglected disease, discovered 114 years ago that still has no drug effective for their chronic phase. Multiple social economic and cultural barriers influence CD research. The high cost of the development of new drugs, in addition to the low economical return, results in the lack of investment. More economic support is required from governments and pharmaceutical companies on the development of more research for CD treatment. Two approaches stand out: repositioning and combination of drugs, witch drastically decrease the cost of this process, when compared to the development of a new drug. Here we discuss the progress of the clinical trials for the etiological and pathophysiological treatment for CD. In summary, more studies are needed to propose a new drug for CD. Therefore, BZ is still the best option for CD. The trials in course should clarify more about new treatment regimens, but it is already possible to indicate that dosage and time of treatment need to be adjusted.

Extracellular vesicles in the context of Chagas Disease - A systematic review

Extracellular vesicle (EVs) traffic is considered an important cellular communication process between cells that can be part of a single organism or belong to different living beings. The relevance of EV-mediated cellular communication is increasingly studied and appreciated, especially in relation to pathological conditions, including parasitic disorders, in which the EV release and uptake processes have been documented. In the context of Chagas Disease (CD), EVs have been explored, however, current data have not been systematically revised in order to provide an overview of the published literature and the main results obtained thus far. In this systematic review, 25 studies involving the investigation of EVs in CD were identified. The studies involved Trypanosoma cruzi (Tc)-derived EVs (Tc-EVs), as well as EVs derived from T. cruzi-infected mammalian cells-derived EVs, mainly isolated by ultracentrifugation and poorly characterized. The objectives of the identified studies included the characterization of the protein and RNA cargo of Tc-EVs, as well as investigation of EVs in parasitic infections and immune-related processes. Overall, our systematic review reveals that EVs play critical roles in several mechanisms related to the interaction between T. cruzi and mammalian hosts, their contribution to immune system evasion by the parasite, and to chronic inflammation in the host. Future studies will benefit from the consolidation of isolation and characterization methods, as well as the elucidation of the role of EVs in CD.

Biogenesis of extracellular vesicles in protozoan parasites: The ESCRT complex in the trafficking fast lane?

Extracellular vesicles (EVs) provide a central mechanism of cell-cell communication. While EVs are found in most organisms, their pathogenesis-promoting roles in parasites are of particular interest given the potential for medical insight and consequential therapeutic intervention. Yet, a key feature of EVs in human parasitic protozoa remains elusive: their mechanisms of biogenesis. Here, we survey the current knowledge on the biogenesis pathways of EVs secreted by the four main clades of human parasitic protozoa: apicomplexans, trypanosomatids, flagellates, and amoebae. In particular, we shine a light on findings pertaining to the Endosomal Sorting Complex Required for Transport (ESCRT) machinery, as in mammals it plays important roles in EV biogenesis. This review highlights the diversity in EV biogenesis in protozoa, as well as the related involvement of the ESCRT system in these unique organisms.

Anxiety, depression, and memory loss in Chagas disease: a puzzle far beyond neuroinflammation to be unpicked and solved

Mental disorders such as anxiety, depression, and memory loss have been described in patients with chronic Chagas disease (CD), a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi. Social, psychological, and biological stressors may take part in these processes. There is a consensus on the recognition of an acute nervous form of CD. In chronic CD patients, a neurological form is associated with immunosuppression and neurobehavioural changes as sequelae of stroke. The chronic nervous form of CD has been refuted, based on the absence of histopathological lesions and neuroinflammation; however, computed tomography shows brain atrophy. Overall, in preclinical models of chronic T. cruzi infection in the absence of neuroinflammation, behavioural disorders such as anxiety and depression, and memory loss are related to brain atrophy, parasite persistence, oxidative stress, and cytokine production in the central nervous system. Interferon-gamma (IFNγ)-bearing microglial cells are colocalised with astrocytes carrying T. cruzi amastigote forms. In vitro studies suggest that IFNγ fuels astrocyte infection by T. cruzi and implicate IFNγ-stimulated infected astrocytes as sources of TNF and nitric oxide, which may also contribute to parasite persistence in the brain tissue and promote behavioural and neurocognitive changes. Preclinical trials in chronically infected mice targeting the TNF pathway or the parasite opened paths for therapeutic approaches with a beneficial impact on depression and memory loss. Despite the path taken, replicating aspects of the chronic CD and testing therapeutic schemes in preclinical models, these findings may get lost in translation as the chronic nervous form of CD does not fulfil biomedical model requirements, as the presence of neuroinflammation, to be recognised. It is hoped that brain atrophy and behavioural and neurocognitive changes are sufficient traits to bring the attention of researchers to study the biological and molecular basis of the central nervous system commitment in chronic CD.

Extracellular vesicles from Trypanosoma cruzi-dendritic cell interaction show modulatory properties and confer resistance to lethal infection as a cell-free based therapy strategy

Extracellular vesicles (EVs) include a heterogeneous group of particles. Microvesicles, apoptotic bodies and exosomes are the most characterized vesicles. They can be distinguished by their size, morphology, origin and molecular composition. To date, increasing studies demonstrate that EVs mediate intercellular communication. EVs reach considerable interest in the scientific community due to their role in diverse processes including antigen-presentation, stimulation of anti-tumoral immune responses, tolerogenic or inflammatory effects. In pathogens, EV shedding is well described in fungi, bacteria, protozoan and helminths parasites. For Trypanosoma cruzi EV liberation and protein composition was previously described. Dendritic cells (DCs), among other cells, are key players promoting the immune response against pathogens and also maintaining self-tolerance. In previous reports we have demonstrate that T. cruzi downregulates DCs immunogenicity in vitro and in vivo. Here we analyze EVs from the in vitro interaction between blood circulating trypomastigotes (Tp) and bone-marrow-derived DCs. We found that Tp incremented the number and the size of EVs in cultures with DCs. EVs displayed some exosome markers and intracellular RNA. Protein analysis demonstrated that the parasite changes the DC protein-EV profile. We observed that EVs from the interaction of Tp-DCs were easily captured by unstimulated-DCs in comparison with EVs from DCs cultured without the parasite, and also modified the activation status of LPS-stimulated DCs. Noteworthy, we found protection in animals treated with EVs-DCs+Tp and challenged with T. cruzi lethal infection. Our goal is to go deep into the molecular characterization of EVs from the DCs-Tp interaction, in order to identify mediators for therapeutic purposes.

Identification and characterization of extracellular vesicles from red cells infected with Babesia divergens and Babesia microti

Babesiosis is a zoonosis and an important blood-borne human parasitic infection that has gained attention because of its growing infection rate in humans by transfer from animal reservoirs. Babesia represents a potential threat to the blood supply because asymptomatic infections in man are common, and blood from such donors can cause severe disease in certain recipients. Extracellular vesicles (EVs) are vesicles released by cells that contain a complex mixture of proteins, lipids, glycans, and genetic information that have been shown to play important roles in disease pathogenesis and susceptibility, as well as cell–cell communication and immune responses. In this article, we report on the identification and characterization of EVs released from red blood cells (RBCs) infected by two major human Babesia species—Babesia divergens from in vitro culture and those from an in vivo B. microti mouse infection. Using nanoparticle tracking analysis, we show that there is a range of vesicle sizes from 30 to 1,000 nm, emanating from the Babesia-infected RBC. The study of these EVs in the context of hemoparasite infection is complicated by the fact that both the parasite and the host RBC make and release vesicles into the extracellular environment. However, the EV frequency is 2- to 10-fold higher in Babesia-infected RBCs than uninfected RBCs, depending on levels of parasitemia. Using parasite-specific markers, we were able to show that ~50%–60% of all EVs contained parasite-specific markers on their surface and thus may represent the specific proportion of EVs released by infected RBCs within the EV population. Western blot analysis on purified EVs from both in vivo and in vitro infections revealed several parasite proteins that were targets of the host immune response. In addition, microRNA analysis showed that infected RBC EVs have different microRNA signature from uninfected RBC EVs, indicating a potential role as disease biomarkers. Finally, EVs were internalized by other RBCs in culture, implicating a potential role for these vesicles in cellular communication. Overall, our study points to the multiple functional implications of EVs in Babesia–host interactions and support the potential that EVs have as agents in disease pathogenesis.

Molecular Recognition of Surface Trans-Sialidases in Extracellular Vesicles of the Parasite Trypanosoma cruzi Using Atomic Force Microscopy (AFM)

Trans-sialidases (TS) are important constitutive macromolecules of the secretome present on the surface of Trypanosoma cruzi (T. cruzi) that play a central role as a virulence factor in Chagas disease. These enzymes have been related to infectivity, escape from immune surveillance and pathogenesis exhibited by this protozoan parasite. In this work, atomic force microscopy (AFM)-based single molecule-force spectroscopy is implemented as a suitable technique for the detection and location of functional TS on the surface of extracellular vesicles (EVs) released by tissue-culture cell-derived trypomastigotes (Ex-TcT). For that purpose, AFM cantilevers with functionalized tips bearing the anti-TS monoclonal antibody mAb 39 as a sense biomolecule are engineered using a covalent chemical ligation based on vinyl sulfonate click chemistry; a reliable, simple and efficient methodology for the molecular recognition of TS using the antibody-antigen interaction. Measurements of the breakdown forces between anti-TS mAb 39 antibodies and EVs performed to elucidate adhesion and forces involved in the recognition events demonstrate that EVs isolated from tissue-culture cell-derived trypomastigotes of T. cruzi are enriched in TS. Additionally, a mapping of the TS binding sites with submicrometer-scale resolution is provided. This work represents the first AFM-based molecular recognition study of Ex-TcT using an antibody-tethered AFM probe.

Multi-therapeutic strategy targeting parasite and inflammation-related alterations to improve prognosis of chronic Chagas cardiomyopathy: a hypothesis-based approach

Chagas disease (CD), caused by infection by the protozoan parasite Trypanosoma cruzi, presents as main clinical manifestation the chronic chagasic cardiomyopathy (CCC). CCC afflicts millions of people, mostly in Latin America, and vaccine and effective therapy are still lacking. Comprehension of the host/parasite interplay in the chronic phase of T. cruzi infection may unveil targets for rational trait-based therapies to improve CCC prognosis. In the present viewpoint, I critically summarise a collection of data, obtained by our network of collaborators and other groups on CCC and preclinical studies on pathogenesis, targeting identification for intervention and the use of drugs with immunomodulatory properties to improve CCC. In the last two decades, models combining mouse lineages and T. cruzi strains allowed replication of crucial clinical, histopathological, and immunological traits of CCC. This condition includes conduction changes (heart rate changes, arrhythmias, atrioventricular blocks, prolongation of the QRS complex and PR and corrected QT intervals), ventricular dysfunction and heart failure, CD8-enriched myocarditis, tissue remodeling and progressive fibrosis, and systemic inflammatory profile, resembling "cytokine storm". Studies on Chagas' heart disease pathogenesis begins to unveil the molecular mechanisms underpinning the inflammation-related cardiac tissue damage, placing IFNγ, TNF and NFκB signaling as upstream regulators of miRNAs and mRNAs associated with critical biological pathways as cell migration, inflammation, tissue remodeling and fibrosis, and mitochondrial dysfunction. Further, data on preclinical trials using hypothesis-based tools, targeting parasite and inflammation-related alterations, opened paths for multi-therapeutic approaches in CCC. Despite the long path taken using experimental CD models replicating relevant aspects of CCC and testing new therapies and therapeutic schemes, these findings may get lost in translation, as conceptual and economical challenges, underpinning the valley of death across preclinical and clinical trials. It is hoped that such difficulties will be overcome in the near future.