Sara Silva Pereira

The cause of hypoglycaemia in African trypanosomiasis remains unresolved. We found that infected mice show normal carbohydrate digestion, intestinal glucose absorption, and tissue glucose uptake, but a profound reduction of host glucose production via gluconeogenesis. Liver transcriptomics uncovered coordinated repression of gluconeogenic pathways alongside inflammatory activation. Infection of Rag2⁻/⁻ mice showed that adaptive immunity contributes only minimally to suppression of host gluconeogenesis. In contrast, therapeutic parasite clearance completely restored host glycaemia and gluconeogenesis despite persistent immune activation. These results demonstrate that live parasites directly repress gluconeogenesis in vivo. Using a co-culture assay, we showed that T. brucei is sufficient to directly repress gluconeogenic gene expression in primary hepatocytes in vitro. Finally, we found that providing glycerol in drinking water to infected animals stimulated gluconeogenesis, elevated glycaemia, and improved survival without impacting parasitaemia. This study reveals a previously unrecognised pathogenic strategy in which a eukaryotic parasite directly suppresses host gluconeogenesis.

The brain vasculature is a critical barrier to maintain central nervous system (CNS) homeostasis. Parasitic infections can profoundly disrupt the brain vasculature, with consequences ranging from subtle neurological alterations to severe, life‐threatening pathologies. In this review, we explore the diverse mechanisms by which endoparasites interact with, modulate and breach CNS blood and lymphatic vessels. We highlight how these pathogens manipulate endothelial function, alter barrier permeability and exploit vascular surface molecules to access or influence the brain. These interactions often trigger local inflammation, endothelial activation and blood–brain barrier breakdown, with significant implications for parasite survival and host pathology. Here, we review the molecular and cellular mechanisms underlying these processes, providing an integrative view of parasite‐vascular crosstalk in the brain and identifying emerging research areas. Understanding these interactions offers new insights into brain vascular disease pathogenesis and may inform future strategies for intervention.

Microphysiological systems (MPS) replicate the dynamic interactions between cells, tissues, and fluids. They have emerged as transformative tools for biology and have been increasingly applied to host–parasite interactions. Offering a better representation of cellular behavior compared with traditional in vitro models, MPS can facilitate the study of parasite tropism, immune evasion, and life cycle transitions across diverse parasitic diseases. Applications span multiple host tissues and pathogens, leveraging advanced bioengineering and microfabrication techniques to address long-standing knowledge gaps. Here, we review recent advances in MPS applied to parasitic diseases and identify persisting challenges and opportunities for investment. By refining these systems and integrating host multicellular models and parasites, MPS hold vast potential to revolutionize parasitology, enhancing our ability to combat parasitic diseases through deeper mechanistic understanding and targeted interventions.

In the mammalian host, Trypanosoma congolense cytoadheres, or sequesters, to the vascular endothelium. Although sequestration influences clinical outcome, disease severity and organ pathology, its determinants and mediators remain unknown. Challenges such as the variability of animal models, the only-recently developed tools to genetically manipulate the parasite, and the lack of physiologically-relevant in vitro models have hindered progress. Here, we engineered brain and cardiac 3D bovine endothelial microvessel models that mimic the bovine brain microvasculature and the bovine aorta, respectively. By perfusing these models with two T. congolense strains, we investigated the roles of flow for parasite sequestration and tropism for different endothelial beds. We discovered that sequestration is dependent on cyclic adenosine monophosphate (cAMP) signalling, closely linked to parasite proliferation, but not associated with parasite transmission to the tsetse fly vector. Finally, by comparing the expression profiles of sequestered and non-sequestered parasites collected from a rodent model, we showed gene expression changes in sequestered parasites, including of surface variant antigens. This work presents a physiologically-relevant platform to study trypanosome interactions with the vasculature and provides a deeper understanding of the molecular and biophysical mechanisms underlying T. congolense sequestration.

In the mammalian host, Trypanosoma congolense cytoadheres to the vascular endothelium in a process known as sequestration. Although sequestration influences clinical outcome, disease severity and organ pathology, its determinants and mediators remain unknown. Challenges such as the variability of animal models, the only-recently developed tools to genetically manipulate the parasite, and the lack of physiologically relevant in vitro models have hindered progress. Here, we engineered brain and cardiac 3D bovine endothelial microvessel models that mimic the bovine brain microvasculature and the bovine aorta, respectively. By perfusing these models with two T. congolense strains, we simulated physiologically relevant conditions and investigated the roles of flow for parasite sequestration and tropism for different endothelial beds. We discovered that sequestration is dependent on cyclic AMP signalling, closely linked to parasite proliferation, but not associated with parasite transmission to the tsetse fly vector. Finally, by comparing the expression profiles of sequestered and non-sequestered parasites collected from a rodent model, we showed gene expression changes in sequestered parasites, including of the surface variant antigens. This work presents a physiologically-relevant platform to study trypanosome interactions with the vasculature and provides a deeper understanding of the molecular and biophysical mechanisms underlying T. congolense sequestration.

N6-methyladenosine (m ⁶ A) is a mRNA modification with important roles in gene expression. In African trypanosomes, this post-transcriptional modification is detected in hundreds of transcripts and it affects the stability of the variant surface glycoprotein (VSG) transcript in the proliferating blood stream form. However, how m6A landscape varies across the life cycle remains poorly defined. Using full-length, non-fragmented RNA, we immunoprecipitated and sequenced m ⁶ A-modified transcripts across three life cycle stages of Trypanosoma brucei – slender (proliferative), stumpy (quiescent), and procyclic forms (proliferative). We found that 1037 transcripts are methylated in at least one of these three life cycle stages. While 21% of methylated transcripts are common in the three stages of the life cycle, globally each stage has a distinct methylome. Interestingly, 47% of methylated transcripts are detected in the quiescent stumpy form only, suggesting a critical role for m ⁶ A when parasites exit the cell cycle and prepare for transmission by the Tsetse fly. In this stage, we found that a significant proportion of methylated transcripts encodes for proteins involved in RNA metabolism, which is consistent with their reduced transcription and translation. Moreover, we found that not all major surface proteins are regulated by m ⁶ A, as procyclins are not methylated, and that, within the VSG repertoire, not all VSG transcripts are demethylated upon parasite differentiation to procyclic form. This study reveals that the m ⁶ A regulatory landscape is specific to each life cycle stage, becoming more pervasive as T. brucei exits the cell cycle. Summary: African trypanosome parasites adapt to mammalian and insect hosts by adjusting gene expression, morphology, and metabolism. In this study, we focus on how N6-methyladenosine (m ⁶ A), a post-transcriptional modification, affects the parasite’s transcriptome throughout its differentiation from the mammalian host to the fly. We found that methylation is differentially regulated as the life cycle progresses, being particularly prevalent in the non-proliferative stumpy form, as more methylated transcripts are found at this insect-infective stage than in slender and procyclic forms. We further show that the not all parasite surface proteins are regulated by m ⁶ A and that the previously identified link between m ⁶ A methylation and the expression level of the major surface protein of bloodstream forms applies to the active variant surface glycoprotein, but not always to silent genes, suggesting two distinct regulatory mechanisms of (de)methylation.

Multiple blood-borne pathogens infecting mammals establish close interactions with the host vascular endothelium as part of their life cycles. In this work, we investigate differences in the interactions of three Trypanosoma species: T. brucei, T. congolense and T. vivax with the blood vasculature. Infection with these species results in vastly different pathologies, including different effects on vascular homeostasis, such as changes in vascular permeability and microhemorrhages. While all three species are extracellular parasites, T. congolense is strictly intravascular, while T. brucei is capable of surviving both extra- and intravascularly. Our knowledge regarding T. vivax tropism and its capacity of migration across the vascular endothelium is unknown. In this work, we show for the first time that T. vivax parasites sequester to the vascular endothelium of most organs, and that, like T. congolense, T. vivax Y486 is largely incapable of extravasation. Infection with this parasite species results in a unique effect on vascular endothelium receptors including general downregulation of ICAM1 and ESAM, and upregulation of VCAM1, CD36 and E-selectin. Our findings on the differences between the two sequestering species ( T. congolense and T. vivax ) and the non-sequestering, but extravasating, T. brucei raise important questions on the relevance of sequestration to the parasite’s survival in the mammalian host, and the evolutionary relevance of both sequestration and extravasation.

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.