CDCD4^+CDCD25^+调节性T细胞对日本血吸虫病疫苗保护性效果的影响及机制研究

Effect and mechanism of CD4^+CD25^+ regulatory T cells on protective efficacy of protein vaccine against Schistosoma japonicum in mice

目的探讨CD4^+CD25^+调节性T细胞(Tregs)对日本血吸虫病疫苗保护性效果的影响及其机制。方法雌性BALB/c小鼠随机分成5组,即正常对照组、感染对照组、抗CD25单克隆抗体(anti-CD25 m Ab)组、谷胱甘肽-S-转移酶(Gluthatione-S-transferase,GST)免疫组和GST/anti-CD25 m Ab联合组。分别在感染后2、3、4、5周剖杀小鼠,收集脾细胞及培养上清,采用流式细胞术检测脾细胞中CD4^+CD25^+Tregs比例,双抗夹心ELISA法测定脾细胞培养上清中的IFN-γ、IL-2、IL-4、IL-5和TGF-β水平。感染后5周杀鼠,门静脉冲虫,统计每只小鼠虫荷及每克肝脏虫卵数;肝组织石蜡切片HE染色观察虫卵肉芽肿病理变化。结果感染后5周,GST免疫组小鼠减虫率为24.98%,而GST/anti-CD25 m Ab联合组减虫率达43.13%;GST免疫组小鼠脾细胞中CD4^+CD25^+Foxp3+比例显著高于感染对照组(P<0.05),而anti-CD25 m Ab组小鼠脾细胞中CD4^+CD25^+Foxp3+比例显著低于感染对照组(P<0.01)。使用anti-CD25 m Ab后2周,GST/anti-CD25 m Ab联合组小鼠脾细胞培养上清中IL-4、IL-5、IFN-γ和IL-2含量均较其他组高;各组小鼠肝脏病理变化和脾细胞培养上清中TGF-β水平间差异均无统计学意义(P均>0.05)。结论 GST疫苗可引起日本血吸虫感染宿主CD4^+CD25^+Tregs明显上升,从而导致其保护性效果欠佳;anti-CD25 m Ab部分封闭CD4^+CD25^+Tregs后有利于增强日本血吸虫病疫苗的免疫保护性效果,其机制可能与Th1、Th2型免疫反应增强有关。

Objective To explore the effect and mechanism of CD4^＋CD25^＋Tregs（Tregs）on the protective efficacy of gluthatione-S-transferase（GST）against Schistosoma japonicum in mice. Methods Female BALB/c mice were divided randomly into five groups：a normal control group,an infected control group,an anti-CD25 m Ab group,a GST immunization group and a combination group with GST immunization and anti-CD25 m Ab. The GST group and combination group were injected percutaneously with GST 50 μg each mouse,the other two groups were injected with equal volume PBS. The immunization was performed for 3times for two-week interval,and 2 weeks after the last immunization,each mouse was challenged with 40 S. japonicum cercaria.Two weeks post-infection,the combination group and anti-CD25 m Ab group were injected intraperitoneally with 300 μg antiCD25 m Ab each mouse. The mice were succumbed 2 weeks,3 weeks,4 weeks and 5 weeks post-infection respectively. The percentages of CD4^＋CD25^＋Tregs in splenocytes of mice were measured with flow cytometer. The levels of IFN-γ,IL-2,IL-4,IL-5and TGF-β in cell cultural supernatants were determined by sandwich-ELISA after stimulation with Con A. The liver sections were stained with hematoxylin and eosin. Results The worm burden in the combination group（15.80±2.74）was significantly lower than those of the infected control group（27.78±3.15）,anti-CD25 m Ab group（21.50±4.21）,and GST group（20.84±6.46）. Compared to those of the infected control group,the percentages of CD4^＋CD25^＋Tregs were significantly higher in the GSTgroup,while the percentages of CD4^＋CD25^＋ Tregs were significantly lower post.anti.CD25 mAb.administration. Regardless of GST administration,the levels of IFN.γ,IL.2,IL.4 and IL.5 after anti.CD25 mAb were significantly higher than those of the in.fected control groups. There were no significant differences of egg granuloma and the level of TGF.β between each group. Con.clusion CD4^＋CD25^＋ Tregs could be partially blocked by anti.CD25 mAb while Th1 and Th2 type immunization response could be enhanced,which plays a role in improving the protective efficacy of GST against of S. japonicum.