Immunogenicity of Chitosan, Montanide and Aluminum hydroxide as an adjuvants in Toxoplasma gondii experimental vaccine in sheep

Toxoplasma gondii is a zoonoses protozoan parasite that causes toxoplasmosis. This parasite causes severe economic losses in the sheep industry. The aim of this study was to evaluate the immunogenicity of the live attenuated vaccine with different adjuvants in sheep. 20 two-month-old pregnant Iranian Qashqaeian serum-negative sheep for Toxoplasma gondii were randomly divided into five groups of four. Group one injected with media and served as control. Three experimental groups were immunized subcutaneously with 1 ml of 25 ×106 inactivate tachyzoites formulated with Montanide, alum, and chitosan, respectively. Last group was inoculated with live attenuated tachyzoite with the same dose. Immunization was performed once. After 21 days, blood samples were collected for ELISA test to evaluate the humoral and cellular immune response. The highest antibody titer was obtained in the group immunized with montanide adjuvant, which was significantly different from other groups (P <0.05). However, the highest cellular immunity according to gamma interferon measurements was related to live attenuated vaccine which was significantly different from other groups, followed by chitosan or aluminum hydroxide adjuvant. It should b notice that all immunized groups had a significant difference with the control group (P <0.05). According to the successful immune response in the live attenuated vaccine, we concluded that this strain can be used for immunization of sheep as the target host and use in higher numbers of sheeps.