EXPERIMENTAL MYOCARDITIS INDUCED IN SWISS MICE BY HOMOLOGOUS HEART IMMUNIZATION RESEMBLES CHRONIC EXPERIMENTAL CHAGAS HEART-DISEASE

The Swiss mouse is considered a satisfactory model for experimental chronic chagasic myocarditis and there is some evidence of an immunopathologic mechanism in the development of this disease. To further support this conjecture, 45-day-old albino Swiss mice (40 animals) were immunized with homologous heart in complete Freund''s adjuvant. As controls, 20 animals were likewise inoculated with allogeneic testis, as "non-related" antigen. Three mice from the former group died suddenly at 19-21 days postinoculation while the survivors were sacrificed at 60 days for serum samples, and histologic analysis of the heart and skeletal muscle. ECG records were taken at Days 0, 30, and 60 postinoculation. Of myocardium-inoculated animals and testis-inoculated mice 33/37 (89%) and 1/20 (5%), respectively, exhibited myocarditis (P < 0.001). Histologic lesions were highly reminiscent of those observed in chronic experimental Chagas'' disease of Swiss mice. Antimuscle antibodies were seen, by indirect immunofluorescence employing cryostat sections, in 30/33 (91%) of the former group and in 3/20 (15%) of the latter (P < 0.001), some of which recognized a surface antigen of primary cultured fetal rat myocardiocytes. Mice inoculated with myocardium also exhibited ECG abnormalities consisting in QRS interval widening. Following an autoimmune experimental design, the main features of chronic chagasic myocarditis may be reproduced in the Swiss mouse. This agrees with the likely role of an immunopathologic mechanism in heart damage due to Trypanosoma cruzi infection.