STAg联合蜂胶佐剂鼻内免疫小鼠抗弓形虫感染的保护作用

Intranasal Immunization with STAg Plus Propolis Adjuvant Protects Mice against Toxoplasma gondii Infection

目的探讨可溶性速殖子抗原(STAg)联合蜂胶佐剂鼻内免疫小鼠抗弓形虫感染的保护作用及蜂胶的适宜剂量。方法将60只BALB/c小鼠随机分为5组,每组12只,分别用20μgSTAg、20μgSTAg+5μg蜂胶、20μgSTAg+10μg蜂胶、20μgSTAg+20μg蜂胶及20μgSTAg+40μg蜂胶鼻内免疫小鼠2次,间隔14d。末次免疫后第10天,用RH株弓形虫速殖子灌胃攻击,4×104个/只,观察小鼠存活情况。攻击后第30天处死全部小鼠,分离计数小鼠脑、肝组织内速殖子和肠系膜淋巴结淋巴细胞(MLNL)、脾T淋巴细胞;ELISA法检测小鼠肺冲洗液、粪便弓形虫特异性sIgA和血清IgG抗体水平。结果随着蜂胶剂量的增加,小鼠脑、肝速殖子数呈下降趋势,20μgSTAg+40μg蜂胶组显著低于20μgSTAg组,脑、肝组织减虫率分别为46.10%和60.11%;MLNL和脾T淋巴细胞增殖活性提高,其中20μgSTAg+40μg蜂胶组小鼠MLNL和脾T淋巴细胞数分别为(2.09±0.24)×107和(1.89±0.21)×107,均显著高于20μgSTAg组;肺冲洗液、粪便弓形虫特异性sIgA和血清IgG抗体水平呈增高趋势,但各组间差异无统计学意义。结论STAg联合蜂胶佐剂鼻内免疫小鼠可有效诱导抗弓形虫感染的保护作用,适宜的蜂胶剂量为40μg。

Objective To investigate the protective effect of intranasal immunization with soluble tachyzoite antigen （STAg） plus propolis adjuvant against Toxoplas gondii infection and optimize the dosage of propolis as an adjuvant. Methods Sixty BALB/c mice were divided into five groups randomly, 12 for each, and immunized twice with 20 μg STAg, 20 μg STAg ＋ 5 μg propolis, 20 μg STAg ＋ 10 μg propolis, 20 μg STAg ＋ 20μg propolis and 20μg STAg ＋ 40μg propolis by intranasal drip respectively, at an interval of 14 d. Each mouse was orally challenged with 4 × 10^4 tachyzoites of Toxoplasma gondii RH strain in a volume of 0. 5 ml on day 10 after the second dose and observed for survival. All the mice were killed on day 30 after challenge and counted for tachyzoites in brain and liver tissues, mesenteric lymph node lymphocytes （MLNLs） and splenic lymphocytes. The Toxoplasma gondii-specific sIgA in lung washes and feces as well as IgG in sera of mice were determined by ELISA. Results The counts of tachyzoites in brain and liver tissues of mice showed a decreasing tendency with the increasing dosage of propolis, which was significantly lower in 20 μg STAg ＋ 40 μg propolis group than in 20 μg STAg group. The decrease rates of tachyzoites in brain and liver tissues were 46. 10% and 60. 11% respectively. The proliferation activities of MLNLs and splenic lymphocytes increased significantly. The counts of MLNLs and splenic lymphocytes in 20 μg STAg ＋ 40 μg propolis group were （2. 09 ± 0.24） × 10^7 and （1. 89 ± 0. 21）× 10^7 respectively, which were significantly higher than those of 20μg STAg group. The Toxoplasma gondii-speeific sIgA in lung washes and feces as well as IgG in sera of mice showed an increasing tendency, while showed no significant difference in various groups. Conclusion The intranasal immunization with STAg plus propolis adjuvant induced protection against Toxoplasma gondii effectively. The optimal dosage of propolis as an adjuvant was 40 μg.