茯苓多糖PCP-Ⅰ增强抗原特异性体液免疫反应的机制研究

Mechanism of a Polysaccharides PCP-Ⅰ from Poria cocos on Enhancing Antigen-Specific Humoral Immune Response

目的:以炭疽芽孢杆菌保护性抗原(PA)为模式抗原,对茯苓多糖PCP-Ⅰ作为疫苗佐剂增强抗原特异性体液免疫反应的机制进行研究。方法:PCP-Ⅰ混合PA免疫BALB/c小鼠,分别采用ELISA和毒素中和实验,检测免疫后小鼠血清中PA特异性(anti-PA)抗体和炭疽毒素中和抗体;采用流式细胞术检测树突状细胞(DC)经PCP-Ⅰ体外刺激后的成熟情况,及二免后7 d小鼠脾脏中生发中心(GC)B细胞和滤泡状辅助T细胞(Tfh)的频率。结果:相对于单独PA免疫组,200μg PCP-Ⅰ能够显著提高二免后2周小鼠血清中anti-PA抗体和毒素中和抗体的水平(5.38×10~3vs 6.48×10~1,8.7×10~1vs 1.54×10~1)。PCP-Ⅰ与PA混合刺激培养DC,CD80和MHC-Ⅱ分子阳性细胞频率(82.2%,74.9%)显著高于PA刺激组(51.7%,46.8%)。二免后7 d,PA+PCP-Ⅰ组小鼠脾脏中Tfh细胞频率略高于PA组(4.97%vs 4.20%),GC B细胞频率显著高于PA组(7.73%vs 6.30%)。结论:PCP-Ⅰ可通过促进DC成熟和增强生发中心反应来增强抗原特异性体液免疫反应。

Objective： To investigate the mechanism of a polysaccharides PCP-Ⅰ from Poria cocos as a vaccine adjuvant on enhancing antigen-specific humoral immune response by using anthrax protective antigen（PA） as a model antigen.Methods： BALB/c mice were immunized by PCP-Ⅰ mixed with PA, followed by ELISA for anti-PA antibody, and toxin neutralization assay for anthrax toxin-neutralizing antibody. Flow cytometry was used to detect maturation of dendritic cells（DC） after in vitro stimulation as well as the frequency of germinal center（GC） B cell and follicular helper T cells（Tfh） in spleen at 7 days after the second immunization.Results： Compared with PA control group, 200 μg PCP-Ⅰ combination group improved the level of anti-PA antibody and toxin neutralizing antibody in serum of mice after immunization（5.38×10^3 vs 6.48×10^1, 8.7×10^1 vs 1.54×10^1）. The positive rate of CD80 and MHC-Ⅱ in DC were significantly increased by stimulation of PCP-Ⅰ plus PA（82.2%, 74.9%）, higher than those of PA group（51.7%, 46.8%）. The frequency of Tfh cells in spleen of PA plus PCP-Ⅰ group was slightly higher than that in PA group（4.97% vs 4.20%）, and the frequency of GC B cells was significantly higher than that of PA group（7.73% vs 6.30%）.Conclusion： PCP-Ⅰ may enhance antigen-specific humoral immune responses by promoting DC maturation and enhancing germinal center response.