Browsing by Author "De Niz, Mariana"
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- Immunopathology and Trypanosoma congolense parasite sequestration cause acute cerebral trypanosomiasisPublication . De Niz, Mariana; Silva Pereira, Sara; Serre, Karine; Ouarné, Marie; Coelho, Joana E; Franco, Claudio; Figueiredo, Luisa M.Trypanosoma congolense causes a syndrome of variable severity in animals in Africa. Cerebral trypanosomiasis is a severe form, but the mechanism underlying this severity remains unknown. We developed a mouse model of acute cerebral trypanosomiasis and characterized the cellular, behavioral, and physiological consequences of this infection. We show large parasite sequestration in the brain vasculature for long periods of time (up to 8 hr) and extensive neuropathology that associate with ICAM1-mediated recruitment and accumulation of T cells in the brain parenchyma. Antibody-mediated ICAM1 blocking and lymphocyte absence reduce parasite sequestration in the brain and prevent the onset of cerebral trypanosomiasis. Here, we establish a mouse model of acute cerebral trypanosomiasis and we propose a mechanism whereby parasite sequestration, host ICAM1, and CD4+ T cells play a pivotal role.
- Intravital imaging of host–parasite interactions in skin and adipose tissuesPublication . De Niz, Mariana; Meehan, Gavin R.; Brancucci, Nicolas M. B.; Marti, Matthias; Rotureau, Brice; Figueiredo, Luisa M.; Frischknecht, FriedrichIntravital microscopy allows the visualisation of how pathogens interact with host cells and tissues in living animals in real time. This method has enabled key advances in our understanding of host-parasite interactions under physiological conditions. A combination of genetics, microscopy techniques, and image analysis have recently facilitated the understanding of biological phenomena in living animals at cellular and subcellular resolution. In this review, we summarise findings achieved by intravital microscopy of the skin and adipose tissues upon infection with various parasites, and we present a view into possible future applications of this method.
- N6-methyladenosine in poly(A) tails stabilize VSG transcriptsPublication . Viegas, Idálio; Macedo, Juan; Serra, Lúcia; De Niz, Mariana; Temporão, Adriana; Silva Pereira, Sara; Mirza, Aashiq H.; Bergstrom, Ed; Rodrigues, Joao A.; Aresta Branco, Francisco; Jaffrey, Samie R.; Figueiredo, Luisa M.RNA modifications are important regulators of gene expression1. In Trypanosoma brucei, transcription is polycistronic and thus most regulation happens post-transcriptionally2. N6-methyladenosine (m6A) has been detected in this parasite, but its function remains unknown3. Here we found that m6A is enriched in 342 transcripts using RNA immunoprecipitation, with an enrichment in transcripts encoding variant surface glycoproteins (VSGs). Approximately 50% of the m6A is located in the poly(A) tail of the actively expressed VSG transcripts. m6A residues are removed from the VSG poly(A) tail before deadenylation and mRNA degradation. Computational analysis revealed an association between m6A in the poly(A) tail and a 16-mer motif in the 3' untranslated region of VSG genes. Using genetic tools, we show that the 16-mer motif acts as a cis-acting motif that is required for inclusion of m6A in the poly(A) tail. Removal of this motif from the 3' untranslated region of VSG genes results in poly(A) tails lacking m6A, rapid deadenylation and mRNA degradation. To our knowledge, this is the first identification of an RNA modification in the poly(A) tail of any eukaryote, uncovering a post-transcriptional mechanism of gene regulation.
- Organotypic endothelial adhesion molecules are key for Trypanosoma brucei tropism and virulencePublication . De Niz, Mariana; Brás, Daniela; Ouarné, Marie; Pedro, Mafalda; Nascimento, Ana M.; Henao Mišíková, Lenka; Franco, Claudio; Figueiredo, Luisa M.Trypanosoma brucei is responsible for lethal diseases in humans and cattle in Sub-Saharan Africa. These extracellular parasites extravasate from the blood circulation into several tissues. The importance of the vasculature in tissue tropism is poorly understood. Using intravital imaging and bioluminescence, we observe that gonadal white adipose tissue and pancreas are the two main parasite reservoirs. We show that reservoir establishment happens before vascular permeability is compromised, suggesting that extravasation is an active mechanism. Blocking endothelial surface adhesion molecules (E-selectin, P-selectins, or ICAM2) significantly reduces extravascular parasite density in all organs and delays host lethality. Remarkably, blocking CD36 has a specific effect on adipose tissue tropism that is sufficient to delay lethality, suggesting that establishment of the adipose tissue reservoir is necessary for parasite virulence. This work demonstrates the importance of the vasculature in a T. brucei infection and identifies organ-specific adhesion molecules as key players for tissue tropism.
- Slow growing behavior in African trypanosomes during adipose tissue colonizationPublication . Trindade, Sandra; De Niz, Mariana; Sequeira, Mariana; Rebelo, Tiago; Bento, Fabio; Dejung, Mario; Narciso, Marta Valido; Escobar, Lara; Ferreira, João; Butter, Falk; Bringaud, Frédéric; Gjini, Erida; Figueiredo, Luisa M.When Trypanosoma brucei parasites, the causative agent of sleeping sickness, colonize the adipose tissue, they rewire gene expression. Whether this adaptation affects population behavior and disease treatment remained unknown. By using a mathematical model, we estimate that the population of adipose tissue forms (ATFs) proliferates slower than blood parasites. Analysis of the ATFs proteome, measurement of protein synthesis and proliferation rates confirm that the ATFs divide on average every 12 h, instead of 6 h in the blood. Importantly, the population of ATFs is heterogeneous with parasites doubling times ranging between 5 h and 35 h. Slow-proliferating parasites remain capable of reverting to the fast proliferation profile in blood conditions. Intravital imaging shows that ATFs are refractory to drug treatment. We propose that in adipose tissue, a subpopulation of T. brucei parasites acquire a slow growing behavior, which contributes to disease chronicity and treatment failure.
- Surgical and intravital microscopy protocol to image Trypanosoma brucei–host interactions in live rodent modelsPublication . De Niz, Mariana; Figueiredo, Luisa M.Intravital microscopy (IVM) involves surgical procedures to expose the internal organs of live anesthetized animals to visualize fluorescently labeled components in situ, in vivo at subcellular resolution. Here, we provide an IVM protocol for time-lapse imaging of dynamic Trypanosoma brucei-host interactions in ten mammalian organs and in systemic circulation. We describe intraperitoneal or intradermal injection of mice with T.brucei. We then detail surgical procedures to prepare ten organs for IVM, followed by imaging of host-T. brucei interactions. For complete details on the use and execution of this protocol, please refer to De Niz et al. (2021).
- Tissue tropism in parasitic diseasesPublication . Silva Pereira, Sara; Trindade, Sandra; De Niz, Mariana; Figueiredo, Luisa M.Parasitic diseases, such as sleeping sickness, Chagas disease and malaria, remain a major cause of morbidity and mortality worldwide, but particularly in tropical, developing countries. Controlling these diseases requires a better understanding of host-parasite interactions, including a deep appreciation of parasite distribution in the host. The preferred accumulation of parasites in some tissues of the host has been known for many years, but recent technical advances have allowed a more systematic analysis and quantifications of such tissue tropisms. The functional consequences of tissue tropism remain poorly studied, although it has been associated with important aspects of disease, including transmission enhancement, treatment failure, relapse and clinical outcome. Here, we discuss current knowledge of tissue tropism in Trypanosoma infections in mammals, describe potential mechanisms of tissue entry, comparatively discuss relevant findings from other parasitology fields where tissue tropism has been extensively investigated, and reflect on new questions raised by recent discoveries and their potential impact on clinical treatment and disease control strategies.
- Toolbox for In Vivo imaging of host–parasite interactions at multiple scalesPublication . De Niz, Mariana; Spadin, Florentin; Marti, Matthias; Stein, Jens V.; Frenz, Martin; Frischknecht, FriedrichAnimal models have for long been pivotal for parasitology research. Over the last few years, techniques such as intravital, optoacoustic and magnetic resonance imaging, optical projection tomography, and selective plane illumination microscopy developed promising potential for gaining insights into host-pathogen interactions by allowing different visualization forms in vivo and ex vivo. Advances including increased resolution, penetration depth, and acquisition speed, together with more complex image analysis methods, facilitate tackling biological problems previously impossible to study and/or quantify. Here we discuss advances and challenges in the in vivo imaging toolbox, which hold promising potential for the field of parasitology.