Figure 2. Persistence of T. cruzi in chronically infected rhesus monkeys.

The persistence of T. cruzi parasite and antigens was evaluated by immunohistochemistry, PCR and antibody response. (A) Photomicrographs of section of myocardium of left ventricle of monkey #95 (20 ypi). Immunohistochemistry for T. cruzi antigens (black arrows and insert) associated (dotted square) or not associated (black arrow) with focal inflammation. Inflammatory infiltrates lacking parasite antigens (white arrow heads). B–C. PCR for T. cruzi kDNA (∼330 bp) in blood of noninfected controls (NI) and T. cruzi-infected rhesus monkeys at (B) 16–20 ypi and (C) 20–23 ypi. (D) PCR for T. cruzi kDNA (∼330 bp) in fragments of the left ventricle (LV) of the heart of noninfected controls and T. cruzi-infected rhesus monkeys at 20–23 ypi. Negative (−) and positive (+) controls were heart fragments of noninfected and T. cruzi-infected C57BL/6 mice, respectively. (E) Real time qPCR for the T. cruzi satellite DNA sequences Cruzi1/Cruzi2 in heart and spleen of noninfected controls and T. cruzi-infected rhesus monkeys at 20–23 ypi. (F) Standard curve of 10-fold serial dilution of DNA of epimastigote forms of the Colombian T. cruzi strain (10⁶ to 10 parasites/mL) used for the absolute quantification by real time qPCR. The linear regression curve, coefficient of determination (r² = 0.995) and qPCR efficiency (E = 80%) are indicated. The melting curve is also shown. (G) Serology for IgG anti-T. cruzi in rhesus monkeys prior to infection, during the acute phase (AP), when parasitemia was positive (+) and negative (−), and during the chronic phase (CP; at the end-point 20 ypi). Bar = 100 µm; Bar = 25 µm in insert in (A).