[Antigenic differentiation among 3 life-cycle stages of Toxoplasma gondii using fluorescent antibodies]

Antigenic differentiation between three stages of the life cycle of Toxoplasma gondii by fluorescent antibodies. Antisera were prepared in three groups of twenty mice each with three different antigens of Toxoplasma gondii: the first group was inoculated with tachyzoites of RH strain and received sulfadiazine treatment; the second with tissue cysts of T-100-cat-6751 strain and the third with oocysts of the same strain, both without treatment. In the indirect immunofluorescent antibody technique each antigen was tested with its homologous and heterologous antisera, determining qualitative and quantitative antigenic differences according to the fluorescence patterns. Some stages of Toxoplasma when reacting with their heterologous antibodies showed a central, partial posterior or total fluorescence during a certain period of development. The difference in fluorescence was sufficient to distinguish whether the origin of the infection was via cyst, oocysts and/or via tachyzoite when observation was made before day 65 post-infection.