Copyright © 1997, American Society for Microbiology Effects of 29,39-Dideoxyinosine on Toxoplasma gondii Cysts in Mice

The activity against Toxoplasma gondii of 2*,3 * dideoxyinosine (ddI), an anti-human immunodeficiency virus drug, was examined in an in vitro and in vivo study. Cell cultures infected with a strain known to cause chronic infections were used to show the dose-dependent effect of this drug compared with spiramycin and sulfadiazine. When a dose of 4 mg/ml was used, no infected THP-1 cells or parasites were found after 60 h of incubation. An electron-microscopic study confirmed that after 12 h at 1 mg/ml, the few parasites observed were severely altered. The treatment of chronically infected mice 3 months postinfection showed that a 30-day treatment with 2 mg of ddI/ml induced a significant reduction in the number of T. gondii cysts in the cerebral tissue. These cysts were not viable, as confirmed by immunofluorescence and reinfection experiments. These experiments suggest a possible role for ddI in the treatment of toxoplasmosis, and this possibility deserves further investigation. Toxoplasma gondii, a coccidian protozoan, is an important pathogen in immunosuppressed patients, especially human im-munodeficiency virus (HIV)-positive patients. Reactivation of cysts in tissue is a major pathogenic event and represents a life-threatening complication (15). Cerebral toxoplasmosis oc