The effect of passively transferred heterologous serum on Toxoplasma gondii in NMRI mice. Influence of the treatment on course of infection and cyst formation.

Anti-Toxoplasma serum from rabbits or normal Toxoplasma negative serum from humans was administered to NMRI mice by intraperitoneal, intravenous or oral routes. Transfer of immune serum intrapertioneally 48 hours before lethal challenge with cyst forming Alt strain conferred significant resistance to normal recipients as assessed by a 55% reduction in the number of brain cysts and 89% survival rate. Survivors of the groups receiving oral administration of immune or normal serum 48 hours prior to challenge also showed a reduction in the number of brain cysts of 50% and 21% respectively. Animals given immune serum by intrapertioneal or oral routes 48 hours after, or a small intravenous dose one day before challenge showed higher survival rates in comparison to controls but had an "enchancement" of infection as revealed by increased number of brain cysts.