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Anti-serum validation for use in immunohistochemistry for Trypanosoma cruzi detection.

INTRODUCTION
The detection of Trypanosoma cruzi in tissue samples is important in many situations, such as testing of the reactivation of the infection. The detection of T. cruzi nests in endomyocardial biopsies (EMB) may be useful to evaluate graft rejection. Given their scarcity, such nests are not routinely identified. To increase the diagnosis sensitivity, immunohistochemistry (IHC) may serve as a promising strategy. Here, we validate an antiserum for the detection of T. cruzi infection by IHC.


METHODS
We used 1) positive controls (PCs) - 13 EMB, 12 skin biopsies, and 1 heart with T. cruzi nests as sections stained with hematoxylin and eosin (HE); 2) negative controls - a) 10 explant hearts and 10 EMB with no amastigote nests or clinical/laboratory signs of chagasic infection; and b) eight samples with leishmaniasis, toxoplasmosis, or histoplasmosis; and 3) Cases - 31 EMB of chagasic patients with no parasite nests in HE sections but detected positive for T. cruzi DNA by polymerase chain reaction. As a primary antibody, a hyperimmune serum from T. cruzi-infected rabbits was used.


RESULTS
IHC results were positive for 21 of 26 PCs (80.8%) and one case of cutaneous leishmaniasis. In 4 of 31 cases, IHC revealed nests (12.9%), which were undetected by conventional histological examination.


CONCLUSIONS
This study shows that IHC with the tested antiserum increases the sensitivity of the diagnosis and may be recommended for routine use in EMB analyses of cardiac transplant patients with Chagas disease.