关键词: 弓形虫, 黏膜疫苗, 鼻内免疫, 可溶性抗原, 霍乱毒素

Abstract: 【Abstract】 Objective To study the mucosal and systemic immune response after intranasal immunization with mucosal complex vaccine for Toxoplasma gondii， and to observe the protective effect on mice. Methods The mucosal complex vaccine was made of soluble tachyzoite antigen （STAg） and cholera toxin （CT）， which were mixed and dissolved in PBS （1 ml PBS containing 1 mg STAg and 50 μg CT）. Fifty-two BALB/c mice were randomly divided into two groups： immunized group and control. Mice were intranasally immunized with 20 μl mucosal complex vaccine （20 μg STAg and 1 μg CT） per mouse twice at an interval of two weeks， while the control mice were given PBS solution instead. Six mice of each group were killed by dislocation of cervical vertebra on day 14 after the last immunization. The specific IgG antibodies in serum and IgA in feces were detected by ELISA. Lymphocytes in spleen， Peyer's patches (PP) and intestinal intraepithelial lymphocyte(IEL) were isolated and counted. Percentage of CD4⁺ and CD8⁺ T cells was determined by immunocytochemistry. Other mice were challenged intragastrically each with 4×10⁴ tachyzoites of RH strain Toxoplasma gondii on day 14 after the last immunization. Their health condition was observed and the number of tachyzoites in liver and brain was determined microscopically on the 30 th day after challenge. Results IgG antibodies in serum and IgA antibodies in feces of immunized mice were higher than the control （P<0.05）. Lymphocytes in spleen， PP and IEL significantly increased after immunization （P<0.01）. The CD4⁺ and CD8⁺ T cells were both higher than that of the control （P<0.05） in spleen and PP. The number of CD8⁺ T cells in IEL increased significantly （P<0.01）， and the ratio of CD4⁺ and CD8⁺ T cells was reversed with significance （P<0.05）. On the day 30 after challenge， the survival rate of immunized mice was higher than that of control （P<0.05）， while the tachyzoite load in liver and brain was significantly smaller （P<0.05）， which corresponds to 86.3%， 86.7% protection， respectively. Conclusion Intranasal inoculation with mucosal complex vaccine effectively induces the mucosal and systemic immune response, and protects mice against Toxoplasma gondii.

Key words: Toxoplasma gondii, Mucosal vaccine, Intranasal immunization, Soluble antigen, Cholera toxin