Release of Membrane-Bound Trails by Trypanosoma cruzi Amastigotes onto Modified Surfaces and Mammalian Cells

Upon incubation at 37° C onto glass coverslips coated with Concanavalin A, poly‐L‐lysine, or a monoclonal antibody (1D9) directed to the parasite major surface glycoprotein Ssp‐4, extracellular Trypanosoma cruzi amastigotes release trails of material barely visible by light microscopy. This release is not associated with parasite movements. Immunolabeling studies confirmed that the material is derived from the parasite's membrane since thin section through samples labeled with 1D9 revealed that the trails are membrane‐bound structures. Scanning electron microscopy showed that the ∼0.1‐μm thick trails of material emerging from the amastigotes can be uniform or beaded, indicating a tendency to vesiculation. The trails are preferentially released from the flagellar pocket region and/or at the opposite posterior end of the parasite body, and seem to be devoid of microtubules. The release is time and temperature‐dependent and fixed parasites do not form trails. All attempts to inhibit trail release using drugs (antimycin A, sodium azide, cytochalasin D, nocodazole, genistein, staurosporine, EGTA) failed. The observation of trails associated with intracellular parasites and amastigotes invading Vero cells suggests that this is probably a physiological process.