In Vitro and In Vivo Potential of RH Strain of Toxoplasma gondii (Type I) in Tissue Cyst Forming.
BACKGROUND
Based on recent studies, there are controversial reports on the capacity of tissue cyst forming of Toxoplasma gondii RH strain. In this study, the capacity was evaluated by in vivo and in vitro experiments.


METHODS
RH strain was subcutaneously inoculated to ten Wistar rats. After one month, their blood, brain, tongue and diaphragm were collected and evaluated by MAT, PCR, pathological and bioassay methods. The parasite was cultivated in the cell monolayer. To change to bradyzoite, the media pH was altered to 6.8. Biological aspect of the bradyzoites was evaluated by incubation in acidic pepsin and it's inoculation in ten BALB/c mice.


RESULTS
All rats showed antibodies to Toxoplasma at titers ≥1:320 but no DNA and tissue cyst were detected in the tissues. Following intraperitoneal inoculation of rats' brain homogenate into BALB/c mice, no infection was established in none of the animals. During presence of cell culture, in acid media for a 3-5 days period, cyst-like structures were noticed when they were stained with PAS. The visible bradyzoites in the cysts that were incubated in acid pepsin medium were not able to kill any mice.


CONCLUSIONS
This study confirmed that Iranian RH strain has lost the potential of tissue cyst forming in rats and bradyzoites cultivated in cell culture lost their resistance to acidic condition, so this strain can be a candidate for future vaccine researches.
Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Qasem
Q
Asgari
Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ; Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran.
Hossein
H
Keshavarz
Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Saeedeh
S
Shojaee
Dept. of Medical Parasitology and Mycology, Faculty of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.
Mohammad Hossein
MH
Motazedian
Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ; Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran.
Mehdi
M
Mohebali
Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
Ramin
R
Miri
Stem Cell and Transgenic Technology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
Davood
D
Mehrabani
Dept. of Medical Parasitology and Mycology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran ; Center for Research of Endemic Parasites of Iran, Tehran University of Medical Sciences, Tehran, Iran.
Mostafa
M
Rezaeian
RH strain; Tissue cyst; Toxoplasma gondii; in vitro; in vivo