Figure 7.

Recently internalized parasites are highly motile and protrude from host cells. (A) Time lapse of T. cruzi internalization and intracellular movement in a HeLa cell (Video 3). The arrow indicates the invading trypomastigote. Bars, 10 µm. (B) Time-lapse images of the same cell in A (initiated ∼15 min after the last frame of the previous video), showing that the trypomastigote remains highly motile and then protrudes from the host cell. The arrow indicates the intracellular trypomastigote. Bars, 10 µm. (C) Confocal images of a trypomastigote protruding from the host cell surface 30 min after invasion of a HeLa cell transduced with the plasma membrane marker GPI-YFP (red) and Lamp1-RFP (green). After infection, cells were fixed and DNA was stained with DAPI (blue). The arrow indicates an internalized parasite already within a Lamp1-positive compartment, protruding from the GPI-labeled host cell plasma membrane. Bar, 10 µm. (D–G) Scanning EM images of protruding trypomastigotes. HeLa cells exposed to trypomastigotes for 20 min were washed and incubated for an additional 15 min before fixation and processing for scanning electron microscopy. Bars, 5 µm. Arrowheads indicate the continuity between the plasma membrane and the protrusion, and arrows indicate sites where the plasma membrane was fractured, revealing the parasitophorous vacuole membrane. These results are representative of two independent experiments.