弓形虫复合黏膜疫苗滴鼻免疫小鼠诱导的肠IEL持续性免疫应答

Immune Responses of Intestinal Intraepithelial Lymphocytes Induced by Intranasal Immunization with Mucosal Vaccine for Toxoplasma gondii

目的采用可溶性速殖子抗原(solubletachyzoiteantigen,STAg)和霍乱毒素(choleratoxin,CT)佐剂制备弓形虫复合黏膜疫苗,观察经滴鼻免疫BALB/c小鼠后诱导的肠上皮内淋巴细胞(intraepitheliallymphocytes,IEL)免疫应答及持续时间,探讨其抗弓形虫感染的作用机制。方法BALB/c小鼠96只随机分为实验组和对照组,实验组以免疫原性好的STAg(20μg/只)为抗原和CT(1μg/只)为佐剂滴鼻免疫,对照组以PBS滴鼻。滴鼻2次(间隔2周)后分别于第1、2、3、4、6、8、10、12周处死小鼠。制备肠IEL细胞悬液,计数并涂片;免疫细胞化学法(immunocytochemistry,ICC)检测CD4+T、CD8+T细胞亚群水平。结果免疫后肠IEL显著增生,第2周达高峰,第1周至第4周(P<0.01)高于对照组。其中以CD8+T细胞增生为主,CD8+T细胞水平第2周达高峰,第1周至第6周增高显著(P<0.01),CD4+T细胞也略有增生,第2、3周(P<0.05)有显著性,CD4+/CD8+比值倒置,第1、2周明显低于对照组(P<0.05)。结论弓形虫复合黏膜疫苗滴鼻免疫BALB/c小鼠可有效诱导肠IEL免疫应答,且可持续较长时间,在预防弓形虫感染中起重要作用。

Objective To study the mucosal immune responses of IEL after intranasal immunization with mucosal vaccine for Toxoplasma gondii, and to observe the duration of the responses. Methods BALB/c mice were randomly divided into two groups：immunlzed group and control group, with 48 mice per group. Mice were intranasally immunized with 20 μg STAg and 1 μg 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 respectively at week 1, 2, 3, 4, 6, 8, 10, or 12 after the last immunization. IEL were isolated and counted. Percentage of CD4^＋ and CD8^＋ T cells was determined by ICC. Results The number of IEL in mice immunized increased at highest level on week 2 （P〈0.01）. There was an increase in CD8^＋ T cells at week 1, 2, 3 （P〈0.0001） 4, 6 （P〈0.01） and peaked at week 2, while the levels of CD4^＋ T cells were higher than control at week 2, 3 （P〈0.05）. The ratio of CD4^＋ and CD8^＋ T was reversed with significance at week 1 and 2 （P〈0.05）. Conclusion Intranasal immunization with mucosal vaccine for Toxoplasma gondii can effectively induce immune responses of IEL. And the responses can persist for a comparatively long time and protect mice against Toxoplasma gondii.