EFFECT OF CORTICOSTEROIDS ON REACTIVATION OF TOXOPLASMA GONDII IN A MURINE MODEL
Mamdouh M. Hegazy* Eman M. Elhamshary, Hanan Z. Rayan and Sherine M. Omar
Departments of Parasitology, Faculties of Medicine, Suez Canal and *Mansoura Universities, Egypt
Two regimens of corticosteroid drugs were tried for reactivation of chronic toxoplasmosis in a murine model, dexamethazone (DXM) alone and in combination with cortisone acetate (CA). Forty five Swiss-albino mice infected 8 weeks previously with cysts of the Me49 strain of Toxoplasma gondii were used. They were divided into 3 groups (15 mice each). G1: infected and treated with DXM, G2: infected and treated with DXM in combination with CA, G3: infected untreated control group. Two additional control groups (15 mice each) were also used; G4: uninfected mice treated with DXM and G5: uninfected untreated mice. The mice were observed for 7 weeks and the reactivation was assessed regarding clinical signs of reactivation, mortality rate, brain cyst burden, spleen/body mass ratio and histopathological changes in various organs. Both regimens of corticosteroids induced reactivation with appearance of neurological signs compatible with toxoplasmic encephalitis (TE) and paralysis in 20% (6/30) of the infected treated mice. No deaths occurred among the infected untreated mice. Mortality in both G1 and G2 was significantly increased compared to G3 and G4. Moreover, mice with clinical signs of TE died after a significantly shorter time as compared to mice which did not develop signs of TE. In G1 and G2, the mean cyst count was significantly higher compared to G3. Additionally, it was significantly higher in mice with signs of TE compared to mice which did not develop signs of TE. The spleen/body mass ratios of G1 and G2 were lower compared to G3 indicating the immunosuppressive effect of corticosteroids. Both infected treated groups showed marked histopathological changes in the brain, liver and spleen. In conclusion, the presented animal model is simple to perform and can be used in various parasitological, pathological, immunological and chemotherapeutics studies. Additionally, it could be concluded that Toxoplasma serologic profile should be initially assessed and monitored in patients about to receive corticosteroid drugs or immunosuppressive medication.