Immunological response to re-infections with clones of the Colombian strain of Trypanosoma cruzi with different degrees of virulence: influence on pathological features during chronic infection in mice

Re-infections with Trypanosoma cruzi are an aggravating factor forChagas disease morbidity. The Colombian strain of T. cruzirepresents multiclonal populations formed by clonally propagating organisms withdifferent tropisms and degrees of virulence. In the present study, the influence ofsuccessive inoculations with clones of the Colombian strain, exhibiting differentdegrees of virulence, on chronic myocarditis and the humoral and cellular immuneresponses (Col-C1 high virulence, Col-C8 medium virulence and Col-C5 low virulence)were demonstrated. Mice from three groups with a single infection were evaluatedduring the acute (14th-30th day) and chronic phases for 175 days. Animmunofluorescence assay, ELISA and delayed type hypersensitivity (DTH) cutaneoustest were also performed. Mice with a triple infection were studied on the115th-175th days following first inoculation. The levels of IgM and IgG2a were higherin the animals with a triple infection. DTH showed a higher intensity in theinflammatory infiltrate based on the morphometric analysis during a 48 h period ofthe triple infection and at 24 h with a single infection. The histopathology of theheart demonstrated significant exacerbation of cardiac inflammatory lesions confirmedby the morphometric test. The humoral responses indicate a reaction to the tripleinfection, even with clones of the same strain.