Isolation of viable Toxoplasma gondii cysts from brain samples for oral infection.

AIM: A method was developed to separate contaminant-free viable Toxoplasma gondii cysts from brain samples of infected mice for molecular biology studies and reinfection. MATERIALS AND METHODS: The mice brains were homogenized and washed with phosphate buffered saline (PBS) Tween 80 prior to fractionation using 19-22% dextran solution. Finally, the supernatant was purified by two-step membrane filtration (100-160 microm and < 10 microm) to obtain pure T. gondii cyst. The isolates were analyzed through microscopic observation, qPCR and by reinfection of new batch of mice. RESULTS: T. gondii cysts were best isolated with 21% dextran solution and two step filtration. CONCLUSIONS: The method was observed not to disrupt the integrity of the cysts containing bradyzoites. In addition, the isolated cysts in the filtrate were found to be contaminant-free, viable and able to infect healthy mice when introduced orally; which, mimics the natural infectivity pathway.

Use of prednisolone to aid propagation of Toxoplasma gondii in mice.

AIM: To determine the usefulness of prednisolone in increasing the number of Toxoplasma (T.) gondii tachyzoites and bradyzoites in mice. MATERIALS AND METHODS: The mice were water-fasted prior to being immunosuppressed with oral inoculation of prednisolone. Tachyzoites of 7T gondii RH strain were inoculated into mice and the number of the parasites in the intraperitoneal fluids was then determined at 96 hs post-infection. In addition, tachyzoites of T. gondii ME49 strains were orally introduced into mice and the number of brain cysts formed was observed by microscopic observation at 45 days post-infection. RESULTS: T. gondii propagation was found to be significantly improved by introduction of the prednisolone (p = 0.0004); and the number of parasite showed positive correlation with the increment in dosage of prednisolone (r = 0.9051). CONCLUSIONS: The use of prednisolone greatly improved the number of parasite formed in mice: both tachyzoite and cyst forms.