| Objective This study was performed to study the mucosal and systemic immune responses after intranasal immunization with STAg plus CT adjuvant and the effects on protection of mice against Toxoplasma gondii. Methods This study included three parts. First part was to study the effects of STAg intranasally immunized with different doses on protection of mice against Toxoplasma gondii and determine the optimal dose of STAg for intranasal immunization. BALB/c mice were intranasally immunized with 5μg, 10μg, 20μg, 30μg STAg per mouse twice at an internal of 2 weeks, while mice intranasally administrated with PBS were control. All mice were challenged intragastrically with 4×10~4 tachyzoites per mouse on day 14 after the last immunization. The condition of mice infected about health and death was observed and the weight of mice was recorded every day after challenge. The tachyzoites of spleens and brains were counted on the 30th day after challenge. Serum IgG and sIgA in feces were detected by ELISA. Lymphocytes of IEL were counted. Second part was to study the effects of intranasal immunization with STAg plus CT adjuvant on protection of mice against Toxoplasma gondii and determine the optimal procedure for intranasal immunization. BALB/c mice were intranasally immunized with 20μg STAg plus 1μg CT per mouse once, twice, three times, respectively. All mice were challenged intragastrically with 4×10~4 tachyzoites per mouse on day 14 after the last immunization. The condition of mice about health and death were observed after challenge. The tachyzoites of the livers and brains were counted on the 30th day after challenge, and serum IgG and sIgA in feces were detected by ELISA. Lymphocytes in spleen and PP were counted. Third part was to observe the mucosal and systemic immune responses after intranasal immunization with STAg and CT adjuvant and the duration of the responses. BALB/c mice were intranasally immunized with 20μg STAg and 1μg CT per mouse twice at an internal of two weeks, while control mice were given PBS solution instead. Six mice of each group were killed on week 1, 2, 3, 4, 6, 8, 10, 12 after the last immunization. Serum IgG antibodies and sIgA in feces and nasopharynx washes were detected by ELISA. Lymphocytes in PP, spleen, IEL, NALT, and NC were isolated and counted. Percentage of CD4~+ and CD8+ T cells in these sites were determined by ICC. Results In 20μg group and 30μg group, the weight of mice still remained increasing after challenge (P<0.05). The survival of mice was higher than that of 5μg group, 10μg group and control (P>0.05). Compared with 5μg group, 10μg group and control, the tachyzoite load in spleens and brains in 20μg group and 30μg group was significantly lower (P<0.05). In mice immunized twice or three times, the survival was higher than that of mice immunized once (P<0.05), while the tachyzoite load in livers and brains was significantly lower (P<0.001). The levels of IgG and sIgA increased in mice immunized twice or three times (P>0.05). Thymic weight of mice immunized had been decreasing during six weeks after immunity (P<0.05). The weight of mice spleen increased on week1, 2, 3, 4 (P<0.05). sIgA antibodies in nasopharynx washes were much more than that of the control during twelve weeks (P<0.0001) getting its highest level on week 1. sIgA in feces increased on week 2, 3, 4 (P<0.05) reaching its peak on week 2. Serum IgG antibodies were higher from first week to 8th week (P<0.05) reaching its maximum value on week 3. Lymphocytes in PP, spleen, IEL, NALT and NC significantly increased after immunity. Lymphocytes in PP were higher than that of control on week 1, 2, 3 (P<0.05) getting its maximum number on week 2 after immunity. Lymphocytes in spleen increased on week 1, 2 (P<0.01). The number of IEL was highest on week 2 increasing significantly on week 1, 2, 3, 4 (P<0.01). Lymphocytes of NALT increased on week 1, 2, 6, 8, 12 (P<0.05), while lymphocytes in NC had been increasing during ten weeks after immunity(P<0.01). The subsets of T lymphocytes in various lympho...
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