EFFECTS OF 2',3'-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,vith a strain known to caus e chronic infections were used to show the dose-dependent effect of th is drug compared with spiramycin and sulfadiazine. When a dose of 4 mu g/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 mu g/ml, the few parasites observed were severely altered, The treatment of chronically infected mice 3 months postinfection show ed that a 30-day treatment with 2 mg of ddI/ml induced a significant r eduction in the number of T. gondii cysts in the cerebral tissue, Thes e cysts were not viable, as confirmed by immunofluorescence and reinfe ction experiments, These experiments suggest a possible role for ddI i n the treatment of toxoplasmosis, and this possibility deserves furthe r investigation.