Toxoplasma gondii: 'Stadienkonversion und Reaktivierung der Infektion: Einfluss von parasitaeren und immunologischen Faktoren'. Teilprojekt: Immunhistologische und elektronenmikroskopische Analyse der Stadienkonversion Abschlussbericht

Abstract

The kinetics and stage conversion of Toxoplasma gondii was studied in vivo in three different mouse strains (BALB/c, C57Bl/6, NMRI) using three strains of T. gondii (RH-virulent, NED-intermediate, Gail-non virulent) for infection. The expression of tachyzoite (TA)-specific, bradyzoite (BA)-specific, and cyst wall (CW)-specific proteins was studied by using various immunohistological and cytochemical procedures. Additional morphological studies were performed by electron microscopy. TA protein expression was found in all examined organs up to day 12 pi. BA-specific and/or CW-specific proteins appeared from day 14 pi onwards together with cyst formation. TA-specific proteins were detectable in the brains up to 30-40 days pi, in the lungs up to 14 days pi. During the acute infection stage there was a limited time of dual expression of TA-specific and BA-/or CW-specific proteins at one infection site. However, the kinetics of Toxoplasma, the parasite load, stage specific protein expression, and cyst formation seen in mice depended on the combination of murine and parasite strains used for infection. The early cyst formation in vivo and in vitro (brain-cell cultures) provided to be very similar. The expression site of an excretory 29 kDa antigen was identified cytochemically. Intermediate stages expressing both TA- and CW-specific markers were also found in the brain tissue of AIDS patients with Toxoplasma encephalitis (TE). However, neither in murine nor human brains tissue was evidence of cyst rupture. During acute TE most of the disseminating parasites expressed the TA-specific protein P30. The results of serological studies did rule out secondary infection as a possible cause for parasite dissemination in AIDS patients. The findings of a strain and host specific regulation of stage conversion and cyst formation requires defined models for use in immunological and therapeutical Toxoplasma research. (orig.)SIGLEAvailable from TIB Hannover: F98B1791 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman