Immunofluorescence as an adjunct to the histopathologic diagnosis of Chagas' disease

We have developed a new indirect immunofluorescence procedure for identifying Trypanosoma cruzi amastigotes in sections of Formalin-fixed, paraffin-embedded tissue pretreated with a 0.25% trypsin solution to enhance immunofluorescence. In sections of human and mouse myocardia infected with T. cruzi and stained by this procedure, both intact amastigotes and phagocytosed amorphous antigen were intensely fluorescent and easily detected; nonspecific background fluorescence was absent or minimal. No staining occurred in similarly treated sections of Formalin-fixed, paraffin-embedded tissue that contained Histoplasma capsulatum var. capsulatum, Toxoplasma gondii, or Leishmania donovani to control specificity. Because pathology laboratories usually receive Formalin-fixed tissues for evaluation, this rapid and reliable procedure can be used to extend the diagnostic capability of conventional histopathology.