STUDIES ON SCHISTOSOMIASIS AND CHAGAS DISEASE

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Chagas' Disease, parasitic infection caused by the protozoan Trypanosoma cruzi, affects 16-18 million people primarily in Central and South America. While autochthonous cases are rare in the United States, Chagas' Disease may represent an increasing public health problem with increasing immigration of Latin Americans. The major causes of morbidity and mortality in Chagas' Disease is secondary to cardiac and gastrointestinal involvement. Both occur, late, 10 or more years after acute infection. Pathologically both exhibit focal lymphocytic infiltrates which are associated with scarring and loss of myocardial cells in Chagasic cardiomyopathy and neuronal degeneration leading to deinnervation and pathologic dilatation in Chagasic megaesophagus and megacolon. In both Chagasic cardiomyopathy and intestinal Chagas', organisms are rarely found which has questioned the role of parasite persistence in late complications of infection. Chagasic cardiomyopathy and megasyndromes usually do not occur in the same patient and exhibit striking geographic variation in their relative frequency. Recent molecular genetic studies have demonstrated the presence of a 188-bp segment of a repetitive 195-bp DNA sequence adjacent to inflammatory foci in 18 or 21 paraffin-embedded autopsy sections of heart muscle from 7 patients with Chagasic cardiomyopathy. We propose to extend these investigations to identify the cells containing parasite DNAs using in situ PCR techniques and to study the form of parasite DNA by amplifying other T. cruzi-specific DNA sequences. In megasyndromes where inflammatory foci are much more dispersed we will amplify the 195 base repetitive DNA sequence in scrapings of lesions microdissected from H & E-stained sections of esophagus or colon obtained at autopsy or surgery. One possible explanation for the variation in the relative geographic distribution in the late cardiac and gastrointestinal manifestations of Chagas' Disease is that different pathologic mechanisms of injury may be at work. We have previously identified a granzyme-positive CD8 T-cell as the predominant cell in inflammatory cardiac lesions. Additional studies have demonstrated upregulation of MHC class I molecules on myocardial cells and enhanced-expression of MHC class II antigens, E Selectin and CD44 on endothelial cells. We would extend these immunohistochemical studies to the megasyndromes. Finally, epicardial inflammation with pericardial effusion is an almost invariant finding in Chagasic cardiomyopathy. These effusions contain viable lymphocytes and have been recently shown to contain T. cruzi-specific antibodies. Pericardial fluid could provide a window to study humoral and cellular immune responses in Chagasic cardiomyopathy. We would extend earlier studies of humoral responses in pericardial fluid first by characterizing lymphocyte populations immunohistochemically and then using cloning techniques to expand B- and T-cell lymphocyte populations for investigation of B-cell specificity and T-cell function and receptor specificity.