Multi-Parametric Evaluation of Trypanosoma cruzi Infection Outcome in Animal Models

Motility patterns of Trypanosoma cruzi trypomastigotes correlate with the efficiency of parasite invasion in vitro

Numerous works have demonstrated that trypanosomatid motility is relevant for parasite replication and sensitivity. Nonetheless, although some findings indirectly suggest that motility also plays an important role during infection, this has not been extensively investigated. This work is aimed at partially filling this void for the case of Trypanosoma cruzi. After recording swimming T. cruzi trypomastigotes (CL Brener strain) and recovering their individual trajectories, we statistically analyzed parasite motility patterns. We did this with parasites that swim alone or above monolayer cultures of different cell lines. Our results indicate that T. cruzi trypomastigotes change their motility patterns when they are in the presence of mammalian cells, in a cell-line dependent manner. We further performed infection experiments in which each of the mammalian cell cultures were incubated for 2 h together with trypomastigotes, and measured the corresponding invasion efficiency. Not only this parameter varied from cell line to cell line, but it resulted to be positively correlated with the corresponding intensity of the motility pattern changes. Together, these results suggest that T. cruzi trypomastigotes are capable of sensing the presence of mammalian cells and of changing their motility patterns accordingly, and that this might increase their invasion efficiency.

Transmigration of Trypanosoma cruzi trypomastigotes through 3D cultures resembling a physiological environment

To disseminate and colonise tissues in the mammalian host, Trypanosoma cruzi trypomastogotes should cross several biological barriers. How this process occurs or its impact in the outcome of the disease is largely speculative. We examined the in vitro transmigration of trypomastigotes through three-dimensional cultures (spheroids) to understand the tissular dissemination of different T. cruzi strains. Virulent strains were highly invasive: trypomastigotes deeply transmigrate up to 50 μm inside spheroids and were evenly distributed at the spheroid surface. Parasites inside spheroids were systematically observed in the space between cells suggesting a paracellular route of transmigration. On the contrary, poorly virulent strains presented a weak migratory capacity and remained in the external layers of spheroids with a patch-like distribution pattern. The invasiveness-understood as the ability to transmigrate deep into spheroids-was not a transferable feature between strains, neither by soluble or secreted factors nor by co-cultivation of trypomastigotes from invasive and non-invasive strains. Besides, we demonstrated that T. cruzi isolates from children that were born congenitally infected presented a highly migrant phenotype while an isolate from an infected mother (that never transmitted the infection to any of her children) presented significantly less migration. In brief, we demonstrated that in a 3D microenvironment each strain presents a characteristic migration pattern that can be associated to their in vivo behaviour. Altogether, data presented here repositionate spheroids as a valuable tool to study host-pathogen interactions.