[New molecular approaches to the diagnosis and prevention of toxoplasmosis]

Toxoplasmosis, a world wide distributed parasitic disease, is known to cause severe complications in foetuses or newborns from mothers acutely infected during pregnancy. More recently, an increased interest for Toxoplasma infection has come from the high incidence of Toxoplasma encephalitis in patients suffering from AIDS. For many years, research aiming at the development of a vaccine strategy has been concentrating on the identification and molecular characterization of surface antigens of the proliferative stage of the parasite, the tachyzoite. On the basis of our previous experience in other parasitic diseases we have based our research strategy with a particular emphasis given to excretory-secretory antigens (ES), to common epitopes expressed both on tachyzoites and bradyzoites, and to isotype selection. The development of a novel experimental model based on the use of athymic (nude) rats has, on the other hand, allowed by selective reconstitutions with antibodies or cells a detailed analysis of the effector mechanisms involved in resistance. Passive transfer experiments of antibodies or T cells from animals immunized with ES antigens have shown their remarkable immunogenicity whereas direct immunization with ES has led to a highly significant degree of protection in mice. Four major immunogens of 43 kD, 39 kD, 28.5 kD and 23 kD have been identified in E.S. products and shown by various techniques including colloidal gold labelling using monoclonal antibodies, to be common to the tachyzoite and bradyzoite stages and localized in their dense granules. Molecular cloning of proteins has been undertaken.(ABSTRACT TRUNCATED AT 250 WORDS)