不同剂量STAg滴鼻免疫小鼠诱导的抗弓形虫感染作用

目的观察不同剂量可溶性速殖子抗原(soluble tachyzoite antigen,STAg)滴鼻免疫小鼠诱导抗弓形虫感染作用,确定STAg滴鼻免疫最佳剂量。方法BALB/c小鼠50只随机分为5组,实验组分别用5μg、10μg、20μg、30μg STAg/只滴鼻免疫小鼠2次,间隔2周,对照组用PBS滴鼻。末次免疫后第14d,用4×104个速殖子/只灌胃攻击全部小鼠,观察小鼠健康和死亡情况,记录体重。攻击后第30d检测粪便IgA和血清IgG,计数脾、脑组织内弓形虫速殖子,分离并计数小肠上皮内淋巴细胞(intraepithelial lymphocyte,IEL)。结果20μg和30μg组小鼠存活率高于5μg、10μg及对照组。攻虫后对照组小鼠体重逐渐降低,而5μg组,10μg组(P<0.05),20μg组(P<0.05)和30μg组(P<0.05)小鼠体重仍呈增高趋势。20μg和30μg组脾、脑组织内虫荷(速殖子数)显著低于5μg、10μg组和对照组(P<0.05),实验组粪便IgA,血清IgG及IEL数量高于对照组。结论不同剂量STAg滴鼻免疫小鼠均可诱导抗弓形虫感染,20μg或30μgSTAg滴鼻免疫可诱导更有效的抗弓形虫感染保护作用

Effect of intranasal immunization with different doses of the soluble tachyzoite antigen on the protection of mice against Toxoplasma gondii

To investigate the effect of intranasal immunization with different doses of the soluble tachyzoite antigen (STAg) on the protection of mice against Toxoplasma gondii, BALB/c mice were immunized intranasally with 5, 10, 20 or 30 μg of STAg per mouse twice at interval of 2 weeks, and those mice receiving PBS were to be used as controls.On day 14 after last immunization, all mice were challenged intragastrically with 4×104 tachyzoites per mouse. The conditions of the infected mice about health or death were observed, and the body weights of mice were recorded every day after challenges. The infected mice were killed almost on 30 th day after challenges, and tachyzoites in the spleens and brains of the dead mice were counted. Meanwhile, the levels of serum IgG and IgA in feces were detected by ELISA, and the intraepithelial lymphocytes(IEL) were countered. The results in this study showed that the survival rates of mice immunized with 20 and 30 μg of STAg were higher than those immunized with 5 or 10μg of STAg and the control group of mice. The body weight of the control mice gradually decreased after challenges, while those of mice immunized with different doses of STAgs remained steadily growing. In comparison with the 5 μg and 10 μg dose immunized groups of mice and the control group, the tachyzoite loads in spleens and brains in the 20 and 30 μg dose immunized groups were significantly lower. The levels of serum IgG, IgA in feces and IEP in all the immunized mice were higher than that of the control. It is evident that the intranasal immunization with different doses of STAg of T.gondii can induce protective immune responses against this parasite, in which the protective effect induced with 20 and 30 μg of STAg were mostly significant.