title: Is stage conversion the initiating event for reactivation of Toxoplasma gondii in brain tissue of AIDS patients?
abstract: Reactivation of chronic toxoplasmosis resulting in Toxoplasma encephalitis (TE) is a common event in acquired immune deficiency syndrome (AIDS) patients. Conversion from Toxoplasma gondii bradyzoites to tachyzoites is a prerequisite for reactivation. Until recently, the study of stage conversion in human tissue was not possible due to the lack of antibodies that recognize stage-specific epitopes after long-term formaldehyde fixation. Using the combination of a polyclonal anti-T. gondii antibody, the cyst-stage-specific monoclonal antibody CC2, and a tachyzoite-specific polyclonal antibody (anti-SAG1, recombinant), we tried to demonstrate parasite differentiation in the brain tissue of 10 AIDS patients with clinically suspected TE. Double labeling of the stage-specific antibodies enabled us to demonstrate interconversion between tachyzoites and bradyzoites for the first time in human tissue. The study confirmed that the transformation process is nonsynchronous and that the manifestation of TE depends on the degree and site of tissue destruction caused by invading tachyzoites. The original source of tachyzoites could never be located, but a few samples suggested that tachyzoites may invade by dissemination across the blood-brain barrier. Cyst rupture as the first event in the process of reactivation was not seen. We conclude that the initial site(s) of reactivation will be destroyed by tissue-destructive tachyzoites long before clinical symptoms occur.
authors.affiliation: Institute of Medical Parasitology, University of Bonn, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Reiter-Owona
authors.forename: H
authors.initials: H
authors.lastname: Seitz
authors.forename: U
authors.initials: U
authors.lastname: Gross
authors.forename: M
authors.initials: M
authors.lastname: Sahm
authors.forename: J K
authors.initials: JK
authors.lastname: Rockstroh
authors.forename: H M
authors.initials: HM
authors.lastname: Seitz
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000469:parasitology* / Q000473:pathology; D000328:Adult; D000818:Animals; D001921:Brain / Q000469:parasitology* / Q000473:pathology / Q000648:ultrastructure; D000939:Epitopes / Q000032:analysis; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D012008:Recurrence; D013045:Species Specificity; D014122:Toxoplasma / Q000276:immunology / Q000502:physiology* / Q000648:ultrastructure; D016781:Toxoplasmosis, Cerebral / Q000469:parasitology* / Q000473:pathology
chemical_list: D000939:Epitopes