Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 10 2 2015 06 15 171 180 EN Qasem Asgari Dept. of Parasitology and Mycology, Shiraz University of Medical Sciences, Shiraz, Iran. Hossein Keshavarz Dept. of Parasitology and Mycology, Tehran University of Medical Sciences, Tehran, Iran. Mostafa Rezaeian Dept. of Parasitology and Mycology, Tehran University of Medical Sciences, Tehran, Iran. Hossein Sadeghpour Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran AND Dept. of Medicinal Chemistry of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran. Ramin Miri Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran AND Dept. of Medicinal Chemistry of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran. Mohammad Hossein Motazedian Dept. of Parasitology and Mycology, Shiraz University of Medical Sciences, Shiraz, Iran. 2015 10 14 Background:This study was undertaken to evaluate the viability, infectivity and immunity of Toxoplasma gondii tachyzoites exposed to 2-(naphthalene-2-ylthio)-1H-indole.  Methods:Tachyzoites of RH strain were incubated in various concentrations of 2- (naphthalene-2-ylthio)-1H-indole (25-800μM) for 1.5 hours. Then, they were stained by PI and analyzed by Fluorescence-activated cell sorting (FACS). To eval-uate the infectivity, the tachyzoites exposed to the different concentrations of the compound were inoculated to 10 BALB/c mice groups. For Control, parasites ex-posed to DMSO (0.2% v/v) were also intraperitoneally inoculated into two groups of mice. The immunity of the exposed tachyzoites was evaluated by inoculation of the naïve parasite to the survived mice. Results:The LD50 of 2-(naphthalene-2-ylthio)-1H-indole was 57 μmol. The lon-gevity of mice was dose dependent. Five mice out of group 400μmol and 3 out of group 800μmol showed immunization to the parasite.  Conclusion:Our findings demonstrated the toxoplasmocidal activity of the com-pound. The presence of a well-organized transporter mechanism for indole com-pounds within the parasite in conjunction with several effective mechanisms of these compounds on Toxoplasma viability would open a window for production of new drugs and vaccines. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/335 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/335/464