PATHOLOGY OF TOXOPLASMA-GONDII INFECTION IN THE NUDE RAT

Genetically athymic nu/nu (nude) rats, deficient in T cells, die from infection with various Toxoplasma gondii strains, including RH and Pru gniaud strains. In contrast, these strains cause chronic infections wi thout apparent symptoms in immunocompetent non-nude rats. We show here that nude rats die in two to three weeks after RH infection and three to four weeks after Prugniaud infection. Histological examination of brains from nude rats at different time points after infection, reveal ed an absence of lesions after RH strain infection and cysts with usua lly no inflammation after Prugniaud infection. Lungs from nude rats de veloped a fibrin alveolitis using either strain, whereas myocarditis w ith focal areas of necrosis were observed only after Prugniaud infecti on. Cysts and, in some cases, tachyzoites in the necrotic lesions were easily identifiable. The two strains of ?: gondii elicited in nude ra ts a granulomatous hepatitis that only differed in intensity. Spleen a nd mesenteric lymph nodes appeared totally non reactive in both cases. This model allows immunological and parasitological studies by compar ison with immunocompetent rat infection. Published data concerning tox oplasma pathology in AIDS, therefore, suggest that acute toxoplasma in fection in nude rats may be a useful model for studying disseminated f orms of toxoplasma infection found in AIDS patients.