Immunization of mice with a Trypanosoma cruzi-like strain isolated from a bat: predictive factors for involvement of eosinophiles in tissue damage.

The granules of eosinophiles are cytotoxic to Trypanosoma cruzi trypomastigote and amastigote forms and to several cell types of the host, revealing their role in either parasite elimination or the production of tissue lesions. In this study, we evaluated the biological characteristics of T. cruzi infection that are responsible for the increase in tissue eosinophile levels in mice previously immunized with a bat isolated T. cruzi-like strain that does not infect mice. Nonisogeneic mice were divided into 24 groups that received from zero to three inoculations of T. cruzi-like RM1 strain, with or without adjuvant, followed by challenge with T. cruzi VIC or JG strains. Uni- and multivariate comparisons were performed comparing the tissue eosinophile levels with the parasitemia peak, severity of myositis in skeletal muscle, phase of infection, and the immunization strategies induced by the T. cruzi-like strain (adjuvant, number of reinoculations, and parasites). Although the severity of inflammation was higher in the acute phase, the score of tissue eosinophiles was similar in the acute and chronic phases of infection. In addition, there was a positive correlation among eosinophile levels and parasitemia peak. In the chronic phase, a greater eosinophile count was accompanied by an augmentation of myositis. Regardless of the phase of infection, we observed a positive correlation between the intensity of eosinophile infiltration and the number of sensitizations with T. cruzi-like strain. The multivariate analysis showed that the peak of parasitemia, number of inoculations with the T. cruzi-like strain, and severity of myositis were associated with greater tissue eosinophilia, in comparison with adjuvant, T. cruzi strains used in the challenge or tissue parasitism. Therefore, tissue eosinophile levels proved to be an important parameter in the pathogenesis of experimental Chagas disease in the acute and chronic phases of infection and might be related to reinfections, parasite multiplication ability, and severity of inflammatory process.