title: Real-time RT-PCR on SAG1 and BAG1 gene expression during stage conversion in immunosuppressed mice infected with Toxoplasma gondii Tehran strain.
abstract: Toxoplasmic encephalitis is caused by reactivation of bradyzoites to rapidly dividing tachyzoites of the apicomplexan parasite Toxoplasma gondii in immunocompromised hosts. Diagnosis of this life-threatening disease is problematic, because it is difficult to discriminate between these 2 stages. Toxoplasma PCR assays using gDNA as a template have been unable to discriminate between an increase or decrease in SAG1 and BAG1 expression between the active tachyzoite stage and the latent bradyzoite stage. In the present study, real-time RT-PCR assay was used to detect the expression of bradyzoite (BAG1)- and tachyzoite-specific genes (SAG1) during bradyzoite/tachyzoite stage conversion in mice infected with T. gondii Tehran strain after dexamethasone sodium phosphate (DXM) administration. The conversion reaction was observed in the lungs and brain tissues of experimental mice, indicated by SAG1 expression at day 6 after DXM administration, and continued until day 14. Bradyzoites were also detected in both organs throughout the study; however, it decreased at day 14 significantly. It is suggested that during the reactivation period, bradyzoites not only escape from the cysts and reinvade neighboring cells as tachyzoites, but also converted to new bradyzoites. In summary, the real-time RT-PCR assay provided a reliable, fast, and quantitative way of detecting T. gondii reactivation in an animal model. Thus, this method may be useful for diagnosing stage conversion in clinical specimens of immunocompromised patients (HIV or transplant patients) for early identification of tachyzoite-bradyzoite stage conversion.
authors.affiliation: Department of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Monavar
authors.initials: M
authors.lastname: Selseleh
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Modarressi
authors.forename: Mehdi
authors.initials: M
authors.lastname: Mohebali
authors.forename: Saeedeh
authors.initials: S
authors.lastname: Shojaee
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Eshragian
authors.forename: Mina
authors.initials: M
authors.lastname: Selseleh
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Azizi
authors.forename: Hossein
authors.initials: H
authors.lastname: Keshavarz
mesh_terms: D000818:Animals; D000953:Antigens, Protozoan / Q000096:biosynthesis*; D001921:Brain / Q000469:parasitology; D005260:Female; D015870:Gene Expression; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D016867:Immunocompromised Host; D008018:Life Cycle Stages; D008168:Lung / Q000469:parasitology; D051379:Mice; D015800:Protozoan Proteins / Q000096:biosynthesis*; D060888:Real-Time Polymerase Chain Reaction; D014122:Toxoplasma / Q000235:genetics* / Q000502:physiology; D014124:Toxoplasmosis, Animal
chemical_list: D000953:Antigens, Protozoan; C106179:BAG1 protein, Toxoplasma; D006360:Heat-Shock Proteins; D015800:Protozoan Proteins; C047168:SAG1 antigen, Toxoplasma