Uptake of host cell transforming growth factor-ß by Trypanosoma cruzi amastigotes in cardiomyocytes: potential role in parasite cycle completion.
Résumé
Transforming growth factor-β (TGF-β) is a cytokine that plays various functions in the control of Trypanosoma cruzi infectivity and in the progression of Chagas disease. When we immunostained Trypanosoma cruzi-infected cardiomyocytes (following either in vivo or in vitro infections) for TGF-β, we observed stronger immunoreactivity in parasites than in host cells. TGF-β immunoreactivity evolved during parasite cycle progression: intense staining in amastigotes versus very faint staining in trypomastigotes. TGF-β was present on the surface of amastigotes, in the flagellar pocket and in intraparasitic vesicles as revealed by electron microscopy. However, no ortholog TGF-β gene could be identified in the genome of Trypanosoma cruzi by in silico analysis or by extensive PCR and RT-PCR studies. Immunoreactive TGF-β was most probably taken up by the parasite from the host cell cytoplasm since such an internalization process of biotinylated TGF-β could be observed in axenic amastigotes in vitro. These observations represent the first example of a novel mechanism by which a primitive unicellular protozoan can use host cell TGF-β to control its own intracellular cycle.
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