Acute Trypanosoma cruzi infection: IL-12, IL-18, TNF, sTNFR and NO in T. rangeli-vaccinated mice.

We have developed an experimental model of vaccination against the infection with the protozoa Trypanosoma cruzi, the agent of Chagas disease in Latin America. Vaccination was performed with Trypanosoma rangeli, a non-pathogenic protozoa sharing many antigens with T. cruzi. It strongly protected BALB/c mice, sharply reducing parasitaemia and mortality rate of the acute T. cruzi infection. The aim of the present work was to complete our previous study on the production of IFN-gamma and IL-10 in this vaccination model by investigating the production of IL-12p35 and p40, IL-18, TNF, TNF soluble receptors (sTNFR), and nitric oxide (NO), factors known to play a key role in the outcome of T. cruzi infection. We show that the protection obtained against the acute T. cruzi infection was surprisingly associated with reduced circulating levels of IL-18 and NO, whereas the release of IL-12p40 was enhanced in comparison to non-vaccinated infected animals. IL-12p35 remained undetectable in infected animals, vaccinated or not. The balance between sTNFR and TNF suggested a decrease of TNF bioactivity in vaccinated mice. These results show that the protection induced by the vaccination with T. rangeli against a challenging infection with T. cruzi is not associated with the strong type 1 immune response usually involved in the control of intracellular pathogens, particularly questioning the protective role of NO during the acute phase of T. cruzi infection.

[Chronic Chagas' disease: effects of treatment nn the levels of antibodies to crude and partially purified Trypanosoma cruzi antigens]. / Enfermedad de Chagas crónica: efectos del tratamiento en los niveles de anticuerpos hacia antígenos crudos y semipurificados del Trypanosoma cruzi.

The specific therapy in Chagas' disease is useful in acute and neonatal infection and in children under three years old. The results of antiparasitic treatment during chronic infection are still controversial. It will be interesting to analyze the serological behavior in patients treated during chronic infection, to advance in the search of evolutive markers and markers of therapeutic efficacy. In the present work we have measured the antibody response by conventional serology and the response to partially purified T. cruzi antigens in chagasic patients who received nifurtimox or benznidazol 2 to 20 years before. The results showed that, by indirect immunofluorescence in 29% of treated patients the antibody levels were below the established cut off (1:32). By indirect hemagglutination 55% of treated patients showed this serological behavior. In this group a high number of discordant results was observed. By immunoenzimatic assay it was possible to detect a significative decrease of serologic reactivity to a partially purified acidic antigen (F IV) and to exoantigen of T. cruzi. It will be interesting to perform longitudinal surveys employing these antigens, to go further in the knowledge of possible immunological evolutive markers in Chagas' disease.

[Chagas disease. Serologic response to crude and semipurified T. cruzi antigens in different clinical groups of patients]. / Enfermedad de Chagas. Reactividad serológica hacia antígenos crudos y semipurificados del T. cruzi en distintos grupos clínicos de pacientes.

The immune response of people infected by the protozoan parasite Trypanosoma cruzi varies in indeterminate or chronic periods of infection, according to the course of the disease. Apparently, the antibody pattern is different in asymptomatic patients than in patients with cardio-myopathy. The study of those differences for clinical purposes depends on the availability of adequate antigenic preparations. We studied the behavior of crude and partially purified antigens of T. cruzi in acute and chronically infected patients. The level of total antibodies was measured by conventional serology (indirect immunofluorescence, IF, and indirect hemagglutination, HA) and the level of antibodies against different fractions of antigens obtained by analytical chroma-tofocusing, by using enzymatic immunoassay (ELISA). Chronic patients were classified according to Kuschnir et al. in: Group 0 (G0) or Group 1 (G1) according to the absence or presence of electrocardiographic alterations. In acute patients, conventional serology was negative in most cases. However, the ELISA performed with the soluble fraction of the lysate of parasites, showed positive results in 60% of patients. By classical serology, the behavior of chronic patients sera was different in the two groups when assayed by IF; G1 showing more elevated titles than G0. On the other hand, by HA the results were similar in both groups. When the sera were studied by ELISA using the different fractions, the fraction collected at pH 4-4.5, named F IV, detected distinct reactivity in some of, but not in all, the patients of G1. In that subgroup, the highest ELISA indes (optical density of sera vs OD of negative controls) was observed. By associating IF plus FIV-ELISA the results became more apparent: 22% of sera showed titles by IF equal or more than 1:128 and ELISA index equal or more than 3.5, whereas only 2% of G0 showed this characteristic and all the sera with index equal or more than 4 belonged to G1. With lesser antibody titles it was not possible to differentiate between the two groups. It can be concluded that the study of the pattern of antibodies by using different antigens and serological methodologies can offer useful information in the different periods of Chagas disease, by adding the higher sensitivity of methods using crude antigens with the more specific and discriminative results obtained by the use of purified or synthetic antigens.