Toxoplasma gondii na interface materno-fetal: prospecção de novos candidatos terapêuticos e efeitos de vesículas extracelulares placentárias sobre células endoteliais cerebrais

Abstract

Toxoplasmosis is a disease caused by the protozoan Toxoplasma gondii. Infection during pregnancy can lead to congenital toxoplasmosis, which is associated with severe outcomes, such as neurological problems, fetal abnormalities, stillbirths, and spontaneous abortion. Current treatment options for congenital toxoplasmosis have several limitations, including low efficacy during the chronic phase of the disease and potential fetal toxicity, with bone marrow suppression and teratogenic effects. Therefore, there is an urgent need for more effective and safer therapeutic alternatives. In Chapter I, three compounds from the Medicines for Malaria Venture Pathogen Box were evaluated: MMV675968, MMV022478, and MMV021013, regarding their ability to control T. gondii infection in human trophoblast cells (BeWo) and third-trimester placental villous explants. The toxicity of the compounds, their effects on the parasite's lytic cycle (including adhesion and invasion), changes in parasite morphology, and the host immune response through cytokine quantification were evaluated. Non-toxic concentrations of the three compounds irreversibly inhibited parasite proliferation and interfered with the initial stages of the lytic cycle. In addition, treated T. gondii tachyzoites exhibited membrane disruption, cytoplasmic degradation, and organelle disorganization. The cytokine profile indicated that treatment with the compounds promoted an anti-inflammatory immune response, mainly through a reduction in IL-8 levels. Importantly, these compounds also effectively controlled T. gondii infection in human placental explants without inducing cytotoxicity. These findings support the potential of MMV675968, MMV022478, and MMV021013 as promising drug candidates for the treatment of congenital toxoplasmosis. MMV021013 stands out as the most promising compound, combining predicted high gastrointestinal absorption and blood-brain barrier permeability, with no predicted mutagenic, tumorigenic, irritant, or reproductive effects. In the second chapter, drugs included in the Relação Nacional de Medicamentos Essenciais (RENAME) were evaluated regarding their potential for drug repurposing in the treatment of congenital toxoplasmosis. Among the drugs investigated, metronidazole and acyclovir exhibited a favorable selectivity profile, with antiparasitic activity associated with the preservation of BeWo cell viability, standing out as candidates for further studies. In the third chapter, the influence of extracellular vesicles derived from placental explants exposed to the soluble antigen of T. gondii tachyzoites (STAg) on human brain microvascular endothelial cells was investigated. Vesicles obtained from placental villi exposed to STAg exhibited changes in their characteristics, including increased size and reduced Syncytin-1 expression. In addition, STAg treatment contributed to lower particle uptake by endothelial cells and influenced the inflammatory response of recipient cells, with changes in IL-6 production, highlighting the involvement of these vesicles in intercellular communication. Taken together, the results of the three chapters expand our understanding of the potential of drug repurposing for the control of congenital toxoplasmosis and the mechanisms of communication between the placenta and the cerebral endothelium.