Abstract Background: Autologous whole blood (AWB) administration is described as alternative/complementary medical practice widely employed in medical and veterinary therapy against infections, chronic pathologies and neoplasias. Our aim is to investigate in vivo biological effect of AWB using healthy murine models under the course of Trypanosoma cruzi acute infection. Methods: The first set of studies consisted of injecting different volumes of AWB and saline (SAL) into the posterior region of quadriceps muscle of healthy male Swiss mice under distinct therapeutic schemes evaluating: animal behavior, body and organ weight, hemogram, plasmatic biochemical markers for tissue damage and inflammatory cytokine levels and profile. To assess the impact on the experimental T. cruzi infection, different schemes (prior and post infection) and periods of AWB administration (from one up to 10 days) were conducted, also employing heterologous whole blood (HWB) and evaluating plasma cytokine profile. Results: No major adverse events were observed in healthy AWB-treated mice, except gait impairment in animals that received three doses of 20 μL AWB in the same hind limb. AWB and SAL triggered an immediate polymorphonuclear response followed by mononuclear infiltrate. Although SAL triggered an inflammatory response, the kinetics and intensity of the histological profile and humoral mediator levels were different from AWB, the latter occurring earlier and more intensely with concomitant elevation of plasma IL-6. Inflammatory peak response of SAL, mainly composed of mononuclear cells with IL-10, was increased at 24 h. According to the mouse model of acute T. cruzi infection, only minor decreases (< 30%) in the parasitemia levels were produced by AWB and HWB given before and after infection, without protecting against mortality. Rises in IFN-gamma, TNF-alpha and IL-6 were detected at 9 dpi in all infected animals as compared to uninfected mice but only Bz displayed a statistically significant diminution (p= 0.02) in TNF-alpha levels than infected and untreated mice. Conclusions: This study revealed that the use of autologous whole blood (AWB) in the acute model employed was unable to reduce the parasitic load of infected mice, providing only a minor decrease in parasitemia levels (up to 30%) but without protecting against animal mortality. Further in vivo studies will be necessary to elucidate the effective impact of this procedure.

Trypanosoma cruzi is a parasite that causes Chagas disease, which affects millions of individuals in endemic areas of Latin America. One hundred years after the discovery of Chagas disease, it is still considered a neglected illness because the available drugs are unsatisfactory. Aromatic compounds represent an important class of DNA minor groove-binding ligands that exhibit potent antimicrobial activity. This study focused on the in vitro activity of 10 aromatic dicationic compounds against bloodstream trypomastigotes and intracellular forms of T. cruzi. Our data demonstrated that these compounds display trypanocidal effects against both forms of the parasite and that seven out of the 10 compounds presented higher anti-parasitic activity against intracellular parasites compared with the bloodstream forms. Additional assays to determine the potential toxicity to mammalian cells showed that the majority of the dicationic compounds did not considerably decrease cellular viability. Fluorescent microscopy analysis demonstrated that although all compounds were localised to a greater extent within the kinetoplast than the nucleus, no correlation could be found between compound activity and kDNA accumulation. The present results stimulate further investigations of this class of compounds for the rational design of new chemotherapeutic agents for Chagas disease.

Proline racemase is an important enzyme of Trypanosoma cruzi and has been shown to be an effective mitogen for B cells, thus contributing to the parasite's immune evasion and persistence in the human host. Recombinant epimastigote parasites overexpressing TcPRAC genes coding for proline racemase present an augmented ability to differentiate into metacyclic infective forms and subsequently penetrate host-cells in vitro. Here we demonstrate that both anti T. cruzi proline racemase antibodies and the specific proline racemase inhibitor pyrrole-2-carboxylic acid significantly affect parasite infection of Vero cells in vitro. This inhibitor also hampers T. cruzi intracellular differentiation.

Chagas disease, which is caused by the intracellular parasite Trypanosoma cruzi, is a neglected illness with 12-14 million reported cases in endemic geographic regions of Latin America. While the disease still represents an important public health problem in these affected areas, the available therapy, which was introduced more than four decades ago, is far from ideal due to its substantial toxicity, its limited effects on different parasite stocks, and its poor activity during the chronic phase of the disease. For the past 15 years, our group, in collaboration with research groups focused on medicinal chemistry, has been working on experimental chemotherapies for Chagas disease, investigating the biological activity, toxicity, selectivity and cellular targets of different classes of compounds on T. cruzi. In this report, we present an overview of these in vitro and in vivo studies, focusing on the most promising classes of compounds with the aim of contributing to the current knowledge of the treatment of Chagas disease and aiding in the development of a new arsenal of candidates with anti-T. cruzi efficacy.