Study of Trypanosoma Cruzi trypomastigotes egress from infected cells

Abstract

The flagellated protozoan Trypanosoma cruzi is the causative agent of Chagas' disease, which affects about 7 million people worldwide. T. cruzi trypomastigotes infect host cells and differentiate into intracellular amastigotes; after replication, they differentiate into bloodstream trypomastigotes that disrupt the host cell accessing the extracellular medium. Over the years, several studies addressed cell invasion by T. cruzi but less is known about its egress. Some researches demonstrate that, similar to other intracellular pathogens, disruptions occur in the three cytoskeleton-forming filaments during intracellular parasite development. Others suggest that in the late stages of infection, calcium influx may occur due to increased cell permeability, promoting release of parasite proteases. Literature also describes that adherent infected cells releases trypomastigotes through ruptures at the edges; however, rounded cells were also observed prior to parasite egress. These different morphologies during the egress may be related to different mechanisms of cell death; some reports demonstrate that egress mediated by host cell apoptosis may favor maintenance of infection, although the role of cell death is controversial in the literature. In our laboratory, using scanning electron microscopy we observed at the time of egress, clearly lysed cells with parasites enclosed by a filament meshwork; we also found cells with apparent intact membrane, presenting however apertures that exposed trypomastigotes, possibly in "pre egress" stage. Based on the current data and our preliminary results, the aims of this project are: to investigate whether parasites modulate their egress through changes in cytoskeleton and host cell membrane; evaluate if increased permeability of infected cells occurs by the action of pore-forming proteins; and verify whether parasite modulate metabolic or signaling pathways and host cell enzymatic activity during the course of infection until egress stage. (AU)