INFLUENCE OF TREATMENT WITH IMMUNOSUPPRESSIVE DRUGS IN MICE CHRONICALLY INFECTED WITH TRYPANOSOMA-CRUZI

Latent Trypanosoma cruzi infection may be reactivated in immunosuppres sed individuals, with unusual clinical patterns, such as meningoenceph alitis, pseudo neoplastic lesions in the central nervous system, and m yocarditis with numerous parasites in the heart muscle. To investigate this problem 68 Swiss mice chronically infected with different strain s of T. cruzi were treated with different combinations of immunosuppre ssive drugs (azathioprine, cyclosporine and betamethasone), in such a way as to imitate the situation during post transplantation treatment. Mortality varied from 6 to 25% in treated mice. There were no deaths in untreated controls. Normal mice have been submitted to the same sch edules of immunosuppression as controls of treatment and no deaths wer e registered during treatment. Chronically infected mice showed signif icant elevation of total number of leukocytes and lymphocytes in compa rison with intact controls; a significant decrease in blood leukocytes and lymphocytes occurred post-treatment in two of the treated experim ental groups. Exacerbation of myocarditis and myositis and a high inci dence of brain lesions, with focal necrosis, granulomatous lesions and glial proliferation even in the absence of parasites were present in immunosuppressed mice but not in infected controls. Although differing in some aspects from Chagas' disease in immunosuppressed humans, the murine model did show some features that resembled it, especially the peculiar pattern of central nervous system involvement.