TOXOPLASMA-GONDII - ACQUIRED OCULAR TOXOPLASMOSIS IN THE MURINE MODEL, PROTECTIVE ROLE OF TNF-ALPHA AND IFN-GAMMA

DNA and mRNA amplification by the polymerase chain reaction (PCR), imm unohistochemical, and histopathology were performed in the eyes and br ains from C57BL/6 mice infected with an avirulent strain of Toxoplasma gondii (ME49). Focal ocular inflammation and retinal pigment epitheli al involvement were commonly observed after 15 days of infection. Four weeks after infection a stable number of cysts was observed in the br ain but rarely in the eye, and they did not elicit an inflammatory res ponse. In most of the ocular lesions the presence of the parasite coul d not be demonstrated even with the PCR technique. B1 DNA fragments of T. gondii were detected in only 4 of 11 eyes tested by PCR and Southe rn blot hybridization. Treatment of mice with mAbs against T cells (CD 4 plus CD8) or cytokines (IFN-gamma or TNF-alpha) resulted in a marked increase of ocular lesions, more often associated with the presence o f the parasite and the severity of inflammatory response. This model a nd the techniques utilized here can improve our understanding of the r espective roles of parasite proliferation and immune mechanisms involv ed in the pathogenesis of acquired ocular totoplasmosis. (C) 1994 Acad emic Press, Inc.