Mixed signals - how Trypanosoma cruzi exploits host-cell communication and signaling to establish infection.

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Chagas disease (American trypanosomiasis) is a 'neglected' pathology that affects millions of people worldwide, mainly in Latin America. Trypanosoma cruzi, the causative agent, is an obligate intracellular parasite with a complex and diverse biology that infects several mammalian species, including humans. Because of genetic variability among strains and the presence of four biochemically and morphologically distinct parasite forms, the outcome of T. cruzi infection varies considerably depending on host cell type and parasite strain. During the initial contact, cellular communication is established by host-recognition-mediated responses, followed by parasite adherence and penetration. For this purpose, T. cruzi expresses a variety of proteins that modify the host cell, enabling it to safely reach the cytoplasm. After entry into the host cell, T. cruzi forms a transitory structure termed 'parasitophorous vacuole' (PV), followed by its cytoplasmic replication and differentiation after PV rupture, and subsequent invasion of other cells. The success of infection, maintenance and survival inside host cells is facilitated by the ability of T. cruzi to subvert various host signaling mechanisms. We focus in this Review on the various mechanisms that induce host cytoskeletal rearrangements, activation of autophagy-related proteins and crosstalk among major immune response regulators, as well as recent studies on the JAK-STAT pathway.