Susceptibility of Brazilian isolates of Trypanosoma evansi to suramin sodium: test in experimentally infected mice.

This study aimed to evaluate the susceptibility of Brazilian isolates of Trypanosoma evansi to suramin sodium. For this purpose, three isolates of T. evansi (LPV-2005, LPV-2009 and LPV-2010) and seventy mice were used, with the animals divided in 10 groups (A, B, C, D, E, F, G, H, I and J) with seven animals each group. Mice of groups A, B, and C were infected with LPV-2005; Groups D, E and F with LPV-2009 and the groups G, H and I with LPV-2010. The group J was composed by healthy mice or uninfected. The parasitemia was monitored daily through blood smear, and the treatment of all groups was performed three days post-infection (PI), when all mice showed increased parasitemia. Groups A, D and G represented the positives controls, while groups B, E and H received a single dose of suramin sodium at 10 mgkg(-1) intramuscularly. Groups C, F and I were treated with three doses of suramin sodium at 10 mgkg(-1), respecting an interval of 24 h between each dose. Negative blood smears from all animals were obtained 24 h after treatment (AT), status maintained until the end of the experiment (50 days PI). The specific PCR for T. evansi was carried out from blood, showing negative results AT. Therefore, this study showed that a single dose of suramin sodium at 10 mgkg(-1) has the same efficacy of three doses, as recommended by the therapeutic literature. Furthermore, we observed that Brazilian isolates did not show resistance to the drug.

Biochemistry detection of acetylcholinesterase activity in Trypanosoma evansi and possible functional correlations.

Several chemical and immunohistochemical techniques can be used for the detection of acetylcholinesterase (AChE) activity. In this experiment we aimed to detect AChE activity in Trypanosoma evansi. For this, the parasites were isolated from the blood of experimentally infected rats using a DEA-cellulose column. Enzymatic activity was determined in trypomastigote forms at 0, 0.2, 0.4, 0.8 and 1.2 mg/mL of protein concentrations by a standard biochemical protocol. At all concentrations tested, the study showed that T. evansi expresses the enzyme AChE and its activity was proportional to the concentration of protein, ranging between 0.64 and 2.70 µmol of AcSCh/h. Therefore, we concluded that it is possible to biochemically detect AChE in T. evansi, an enzyme that may be associated with vital functions of the parasite and also can be related to chemotherapy treatments, as further discussed in this article.

Biochemical detection of adenosine deaminase in Trypanosoma evansi.

Biochemical and molecular research on parasites has increased considerably in trypanosomes in the recent years. Many of them have the purpose of identify areas, proteins and structures of the parasite which are vulnerable and could be used in therapy against the protozoan. Based on this hypothesis this study aimed to detect biochemically the enzyme adenosine deaminase (ADA) in Trypanosoma evansi, and to adapt an assay to the measurement of its activity in trypomastigotes. Firstly, the parasites were separated from the blood of mice experimentally infected with a DEAE-cellulose column. The ADA activity in trypomastigotes was evaluated at concentrations of 0.1, 0.2, 0.5, 0.6 and 0.8mg of protein by spectrophotometry. ADA activity was observed in the parasites at all concentrations tested and its activity was proportional to the concentration of protein, ranging between 0.64 and 2.24U/L in the lowest and highest concentration of protein, respectively. Therefore, it is possible to detect biochemically ADA in T. evansi, an enzyme that may be associated with vital functions of the parasite, similar to what occurs in mammals. This knowledge may be useful in the association of the chemotherapic treatment with specific inhibitors of the enzyme, in future studies.

Susceptibility of mice to Trypanosoma evansi treated with human plasma containing different concentrations of apolipoprotein L-1.

The aim of this study was to test the susceptibility of mice to Trypanosoma evansi treated with human plasma containing different concentrations of apolipoprotein L-1 (APOL1). For this experiment, a strain of T. evansi and human plasma (plasmas 1, 2, and 3) from 3 adult males clinically healthy were used. In vivo test used 50 mice divided in 5 groups (A to E) with 10 animals in each group. Animals of groups B to E were infected, and then treated with 0.2 ml of human plasma in the following outline: negative control (A), positive control (B), treatment with plasma 1 (C), treatment with plasma 2 (D), and treatment with plasma 3 (E). Mice treated with human plasma showed an increase in longevity of 40.9 ± 0.3 (C), 20 ± 9.0 (D) and 35.6 ± 9.3 (E) days compared to the control group (B) which was 4.3 ± 0.5 days. The number of surviving mice and free of the parasite (blood smear and PCR negative) at the end of the experiment was 90%, 0%, and 60% for groups C, D, and E, respectively. The quantification of APOL1 was performed due to the large difference in the treatments that differed in the source plasma. In plasmas 1, 2, and 3 was detected the concentration of 194, 99, and 115 mg/dl of APOL1, respectively. However, we believe that this difference in the treatment efficiency is related to the level of APOL1 in plasmas.