Abstract
Trypanosoma cruzi infection may be caused by different strains with distinct discrete typing units (DTUs) that can result in variable clinical forms of chronic Chagas disease. The present study evaluates the immune response and cardiac lesions in dogs experimentally infected with different T. cruzi strains with distinct DTUs, namely, the Colombian (Col) and Y strains of TcI and TcII DTU, respectively. During infection with the Col strain, increased levels of alanine aminotransferase, erythrocytes, haematocrit and haemoglobin were observed. In addition, CD8+ T-lymphocytes isolated from the peripheral blood produced higher levels of interleukin (IL)-4. The latter suggests that during the acute phase, infection with the Col strain may remain unnoticed by circulating mononuclear cells. In the chronic phase, a significant increase in the number of inflammatory cells was detected in the right atrium. Conversely, infection with the Y strain led to leucopoenia, thrombopoenia, inversion of the ratio of CD4+/CD8+ T-lymphocytes and alterations in monocyte number. The Y strain stimulated the production of interferon-γ by CD4+ and CD8+ T-lymphocytes and IL-4 by CD8+ T-cells. In the chronic phase, significant heart inflammation and fibrosis were observed, demonstrating that strains of different DTUs interact differently with the host.
Highlights
Chagas disease is caused by the flagellate protozoan Trypanosoma cruzi and is transmitted by blood-sucking insects of the subfamily Triatominae (Chagas 1909)
Haematological alterations resulting from T. cruzi infection - When analysing the haematological alterations, it was observed that the erythrocyte and haematocrit levels were increased in the Colombian strain (Col) group at 30, 90 and 240 d.a.i. compared to day 0
A reduction in peripheral blood monocytes was observed at nine and 240 d.a.i. with the Y strain compared to day 0, whereas this was observed at 90 d.a.i. for the Col group (Supplementary data, Table II)
Summary
Chagas disease is caused by the flagellate protozoan Trypanosoma cruzi and is transmitted by blood-sucking insects of the subfamily Triatominae (Chagas 1909). The T. cruzi heterogenic nomenclature is based on grouping the populations into six discrete typing units (DTUs): TcI, TcII, TcIII, TcIV, TcV and TcVI (Zingales et al 2009). Canine experimental infection with T. cruzi shares many of the characteristics of human Chagas disease, including the occurrence of an acute, an indeterminate asymptomatic and a symptomatic chronic phase. They share clinical and serological aspects, including patent parasitaemia, parasitism of myocytes, myocardium inflammation, fibrosis and fatty replacement in the cardiac conduction system, with electrocardiographic alteration, evolution to cardiac dysfunction and congestive heart failure. 1006 Different responses to T. cruzi strains Ana Luiza Cassin Duz et al.1980, 1984, Laranja & Andrade 1980, Tafuri et al 1988, Morris et al 1991, de Lana et al 1992, Guedes et al 2002, Diniz et al 2010, Caldas et al 2013)
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