Detection of Trypanosoma cruzi with the Polymerase Chain Reaction and in Situ Hybridization in Infected Murine Cardiac Tissue

Chagas' disease is caused by the hemoflagellate protozoan Trypanosoma cruzi, which is predominantly found in South and Central America and Mexico. Although the parasite is present in the United States, confirmed cases of human disease are rare. The most serious manifestation of chronic Chagas' disease is a progressive inflammatory cardiomyopathy. However, T. cruzi has not been consistently demonstrated with histologic techniques in inflammatory cardiac lesions. In this study, we used both polymerase chain reaction (PCR) amplification of extracted DNA from hematoxylin and eosin-stained tissue scrapings, and in situ hybridization to detect the presence of T. cruzi in infected murine cardiac tissue sections. Three T. cruzi-specific DNA sequences were used: a 122-basepair (bp) sequence localized within the minicircle network (MCS), a 188-bp nuclear repetitive sequence (RS), and a 177-bp sequence within the open reading frame of a gene coding for a flagellar protein (FPS). We found that all three sequences are amplifiable from scrapings of murine cardiac tissue. The MCS and RS are detected at 0.167 and 0.24 amastigote DNA equivalents, while FPS is barely detected at 0.24 amastigote DNA equivalents. On the other hand, in situ hybridization with all three sequences allowed for the detection of T. cruzi amastigotes within the tissue. The MCS and FPS, however, consistently yielded a more intense signal. These results indicate that PCR and in situ hybridization may prove useful in establishing the prevalence of T. cruzi in human chagasic cardiomyopathy.