The induction of host cell autophagy triggers defense mechanisms against Trypanosoma cruzi infection in vitro

A Review on the Immunological Response against Trypanosoma cruzi

Chagas disease is a chronic systemic infection transmitted by Trypanosoma cruzi. Its life cycle consists of different stages in vector insects and host mammals. Trypanosoma cruzi strains cause different clinical manifestations of Chagas disease alongside geographic differences in morbidity and mortality. Natural killer cells provide the cytokine interferon-gamma in the initial phases of T. cruzi infection. Phagocytes secrete cytokines that promote inflammation and activation of other cells involved in defence. Dendritic cells, monocytes and macrophages modulate the adaptive immune response, and B lymphocytes activate an effective humoral immune response to T. cruzi. This review focuses on the main immune mechanisms acting during T. cruzi infection, on the strategies activated by the pathogen against the host cells, on the processes involved in inflammasome and virulence factors and on the new strategies for preventing, controlling and treating this disease.

In vitro evaluation of Resveratrol as a potential pre-exposure prophylactic drug against Trypanosoma cruzi infection

Chagas' disease or American trypanosomiasis, caused by Trypanosoma cruzi infection, is an endemic disease in Latin America, which has spread worldwide in the past years. The drugs presently used for treatment have shown limited efficacy due to the appearance of resistant parasites and severe side effects. Some of the most recent studies on anti-parasitic drugs have been focused on protein acetylation, a reversible reaction modulated by Acetyl Transferases (KATs) and Deacetylases (KDACs). We have previously reported the anti-parasite activity of resveratrol (RSV), an activator of KDACs type III (or sirtuins), and showed that this drug can reduce the growth of T. cruzi epimastigotes and the infectivity of trypomastigotes. Since RSV is now widely used in humans due to its beneficial effects as an antioxidant, it has become an attractive candidate as a repurposing drug. In this context, the aim of the present study was to evaluate the ability of this drug to protect three different types of host cells from parasite infection. RSV treatment before parasite infection reduced the percentage of infected cells by 50-70% depending on the cell type. Although the mammalian cell lines tested showed different sensitivity to RSV, apoptosis was not significantly affected, showing that RSV was able to protect cells from infection without the activation of this process. Since autophagy has been described as a key process in parasite invasion, we also monitored this process on host cells pretreated with RSV. The results showed that, at the concentrations and incubation times tested, autophagy was not induced in any of the cell types evaluated. Our results show a partial protective effect of RSV in vitro, which justifies extending studies to an in vivo model to elucidate the mechanism by which this effect occurs.

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

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.