Sistema FMUSP-HC: Faculdade de Medicina da Universidade de São Paulo (FMUSP) e Hospital das Clínicas da FMUSPFERREIRA-FILHO, Julio Cesar RenteBRAZ, Lucia Maria AlmeidaANDRINO, Marcos Luiz AlvesYAMAMOTO, LidiaKANASHIRO, Edite Hatsumi YamashiroSILVA, Ana Maria Goncalves daKANUNFRE, Kelly AparecidaOKAY, Thelma Suely2021-02-182021-02-182021PARASITOLOGY INTERNATIONAL, v.80, article ID 102210, 5p, 20211383-5769https://observatorio.fm.usp.br/handle/OPI/39308Quantification of parasites in the context of Chagas disease is required to monitor the treatment with benznidazole, disease-associated cardiomyopathies and graft rejection after heart transplantation. As parasitological exams lack sensitivity, Real Time Polymerase Chain Reaction (rt-PCR) has emerged to evaluate the parasite load in blood samples and cardiac biopsies. However, despite its higher sensitivity, rt-PCR does not provide information on the location and distribution of amastigote nests within infected tissues, the characterization of inflammatory infiltrates or changes to tissue architecture. On the contrary, a sensitive immunohistochemistry technique (IHC) could fill these gaps. In the present study, a quantitative IHC exam was standardized and validated by testing adipose and cardiac tissues of experimentally infected mice containing variable parasite load levels of T. cruzi assessed by a sensitive Sybr Green rt-PCR with kDNA primers. Tissues were divided into four groups according to the parasite load: group A100 parasites/50 ng of DNA; group B-10 parasites; group C - around 1 parasite and group D less than 1 parasite/50 ng/DNA. IHC was able to detect T. cruzi in the four groups, even in group D tissues containing fractions of a single parasite/50 ng of DNA sample according to rt-PCR. In conclusion, a highly sensitivity and reliable quantitative immunohistochemistry technique was developed and is proposed to estimate the percentage of T. cruzi-infected tissue area in chagasic patients presenting with cardiomyopathies, as a complementary test to rt-PCR.engrestrictedAccessCardiomyopathyCardiac biopsiesEndomyocardial biopsiesAnti-T. cruzi antibodieschagas-diseaseparasitismarticleCopyright ELSEVIER IRELAND LTD10.1016/j.parint.2020.102210Parasitology1873-0329