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.