调节性B细胞在控制小鼠疟疾免疫病理中的作用及机制研究

发布时间：2018-04-12 09:10

本文选题：疟疾 + 调节性B细胞　；参考：《中国科学技术大学》2013年博士论文

【摘要】：疟疾是由原虫类寄生虫——疟原虫(Plasmodium spp.)感染引起的流行性疾病,是全球三大主要传染性疾病之一。流行病学调查数据表明,目前在世界许多地区,疟疾仍然呈现高发病率和高死亡率,特别是在撒哈拉以南的非洲地区；易感人群多为5岁以下的儿童,其感染后常表现严重的病理变化和症状,例如脑疟、严重贫血和肺功能衰竭等。然而,我们对疟疾感染所诱导的主要免疫病理变化—脑疟—及其调控机理尚未完全了解。在疟疾流行区,感染疟疾后的人群虽然能获得部分保护性免疫,但是这种免疫力维持时间短,并且在个体离开疟疾流行区后保护力快速消失。目前治疗疟疾的主要手段是药物治疗,可是由于疟原虫耐药性的产生及药物的不及时使用严重降低抗疟药的效果,所以疫苗被认为是目前应对疟疾的最理想方式。然而在疟疾疫苗研发方面我们仍然面临巨大的挑战,其原因之一是我们尚未完全探明疟原虫病原与宿主之间的复杂免疫学关系。在本论文报告的研究中,我们采用小鼠伯氏疟原虫(Plasmodium berghei)疟疾模型,(1)分析研究了与疟疾相关的主要免疫病理变化—脑疟的发生和调节机制；(2)比较和分析了诱导有效免疫保护力的疟疾疫苗的不同免疫策略。 1.调节性B细胞与脑疟疟原虫感染诱发的神经系统功能障碍—脑疟,是疟疾感染时产生的主要病理变化和致死原因之一。大约有1%的恶性疟原虫感染个体可发生脑疟；其中,10%到20%的脑疟患者发生死亡。脑疟是免疫失调所导致的脑组织免疫病理反应。目前认为,其主要的诱发原因与感染疟原虫的红细胞粘附在脑组织毛细血管壁,并引起局部毛细血管堵塞和炎性细胞招募有关。淋巴细胞浸润、免疫杀伤性NK细胞和细胞毒性CD8+T细胞等破坏毛细血管壁和血脑屏障,导致脑组织出血和神经系统功能受损。免疫调节性细胞因子IL-10在维持免疫自身稳定和控制感染诱导的免疫病理如脑疟的过程中发挥关键作用。近年来有大量实验表明,可分泌IL-10的调节性B细胞具有免疫调节功能,并证实其在维持免疫自身耐受和抑制免疫病理中发挥着重要作用。据此,本课题采用伯氏疟原虫感染C57BL/6小鼠的疟疾模型,研究了调节性B细胞在疟疾感染过程中调控过度免疫反应和脑疟病理的作用。研究结果表明,伯氏疟原虫感染后可诱导血清中IL-10水平的增高；同时观察到小鼠脾脏细胞中可分泌IL-10的调节性B细胞比率显著增高。体内转输实验证实,IL-10+调节性B细胞明显抑制脑组织微血管出血性病理变化,并显著降低疟疾感染小鼠的死亡率；进一步研究发现,调节性B细胞能抑制免疫杀伤细胞向脑组织迁移,但对疟原虫血虫水平没有显著影响。用IL-10受体抗体阻断IL-10信号后,调节性B细胞抑制脑疟发生的作用消失,这说明调节性B细胞抑制脑疟发生是由IL-10介导的。我们还发现,转输CD4+CD25+调节性T细胞对脑疟发生没有显著作用。以上结果表明调节性B细胞,而不是调节性T细胞,抑制疟原虫感染的小鼠脑疟病理的发生。此项研究的成果不仅揭示疟疾病理新的调控机制,还对制定脑疟预防策略及抗疟疾药物研发提供重要理论依据。 2.疟疾活虫疫苗的免疫效能目前疫苗被认为是控制疟疾最有效的方式。近半个多世纪以来人们尝试用各种疫苗方式来预防疟疾,然而到目前为止还没有成功的抗疟疾疫苗在临床上应用。亚单位疫苗被人们寄予厚望,但近三十年来许多亚单位疟疾疫苗临床试验都以失败告终,这可能与这些疫苗缺乏危险信号进而不能有效激活免疫应答和免疫保护力相关。人们发现放射线致弱和基因改造的减毒子孢子能够诱导针对疟疾的完全保护力,可是这种疫苗难以在体外大规模获得从而限制了在临床上的应用。在本研究中,我们分析两种疫苗免疫策略诱导的免疫应答和保护力水平。一种是短期活虫感染加药物终止模拟活虫疫苗的方式,另一种是全虫抗原加佐剂的疫苗方式。研究目的是鉴定两种疫苗策略的免疫应答差异以及与有效保护力相关的免疫应答标志物。实验结果表明,短期活虫感染免疫可诱导较强的免疫保护力。二全虫抗原家佐剂仅可诱导部分保护。与全虫抗原加佐剂组相比,短期活虫感染加药物阻断组诱导更高的疟原虫特异的抗体水平和树突状细胞激活水平以及更强的CD4+T细胞应答。Thl型、Th2型和调节性细胞因子表达水平在两种疫苗策略之间都有类似的显著性差异。进一步的研究将验证这些免疫因素和保护力之间的相互联系。本项研究有助于设计出更理性的疟疾疫苗方案。
[Abstract]:Malaria is a protozoan parasite Plasmodium (Plasmodium spp.) infection caused by epidemic disease, is one of the three major infectious diseases worldwide. Epidemiological data show that in many parts of the world, malaria still has high morbidity and mortality, especially in sub Saharan Africa; the susceptible population is children under the age of 5, after its infection often show pathological changes and serious symptoms, such as cerebral malaria, severe anemia and lung failure. However, we change to the main immune pathology of malaria infection induced by cerebral malaria and its regulation mechanism is not yet fully understood. In malaria endemic areas, malaria infection after the crowd although we can obtain some protective immunity, but the immunity of short duration, and in individual leaves in malaria endemic area after the protection force quickly disappeared. The main therapy for the treatment of malaria The drug treatment, but because of the drug resistance of Plasmodium and not using seriously reduce the antimalarial effect, so the vaccine is considered to be the ideal way to deal with malaria at present. However, in the aspect of malaria vaccine development we still face enormous challenges, one of the reasons is that we have not yet fully proved the complex immunological relationship between Plasmodium the pathogen and host. In this research report, we used mouse Plasmodium berghei malaria model (Plasmodium berghei), (1) analysis of the occurrence of cerebral malaria changes mainly immunopathology associated with malaria and regulatory mechanisms; (2) comparison and analysis of different immunization strategies effective malaria vaccine induced immune protection force.
1. regulatory B cells and brain malaria
The dysfunction of brain nervous system induced by malaria Plasmodium infection, is the main pathological changes in malaria infection and cause of death. The occurrence of cerebral malaria infected individuals about 1% of Plasmodium falciparum; among them, 10% to 20% of the deaths occurred in patients with cerebral malaria. Malaria is the brain pathological immune response immune disorders caused by brain tissue. At present, red cell adhesion and its main causes and infection of Plasmodium in brain capillary wall, and cause local capillary congestion and inflammatory cell recruitment. Lymphocyte infiltration, immune killer NK cells and cytotoxic CD8+T cells destroy the capillary wall and the blood-brain barrier, leading to bleeding and neurological damage of brain.
Immunoregulatory cytokine IL-10 play a key role in the process of maintaining immune homeostasis and immune control of infection induced such as cerebral malaria. In recent years a large number of experiments show that the secretion of IL-10 regulatory B cells have immune regulatory function, and confirmed in maintaining immunological self tolerance and plays an important role in inhibiting immune pathology in this paper. Accordingly, the malaria model C57BL/6 mice infected with Plasmodium berghei, studied the regulatory B cells control excessive immune response and pathological cerebral malaria in malaria infection process.
The results show that the increase of Plasmodium berghei infection can induce IL-10 level in serum; at the same time observed in mouse spleen cells can secrete IL-10 regulatory B cell ratio was significantly increased. In vivo transfer experiment confirmed that IL-10+ regulatory B cells inhibit hemorrhagic cerebral microvascular pathological changes, and significantly reduce malaria infection the death rate of mice; further study found that regulatory B cells can inhibit the immune cell migration into the brain, but had no significant effect on parasite blood worms level. Blocking IL-10 signal with IL-10 receptor antibodies after disappearance of regulatory B cells inhibit cerebral malaria occurred, suggesting that regulatory B cells inhibit cerebral malaria occurs mediated by IL-10. We also found that the transfer of CD4+CD25+ regulatory T cells on cerebral malaria has no significant effect. The above results show that regulatory B cells, rather than inhibition of regulatory T cells. The occurrence of cerebral malaria in mice infected with Plasmodium falciparum can not only reveal the new regulation mechanism of malaria pathology, but also provide important theoretical basis for formulating strategies for preventing cerebral malaria and developing anti malaria drugs.
2. immune efficacy of a live worm vaccine
The vaccine is considered to be the most effective way to control malaria. For more than half a century of people trying to use various methods to prevent malaria vaccine, but so far there is no anti malaria vaccine successfully applied in clinic. The subunit vaccine were high hopes, but in the past thirty years many subunit malaria vaccine clinical trials ended in failure, which may be related to the lack of effective vaccine danger signals and can not activate the immune response and protective immunity. People find complete protection of radiation induced reduction of sub toxic spores and weak genetic modification can induce the vaccine against malaria, but difficult to obtain large scale in vitro which limits the clinical application.
In this study, we analyzed two kinds of strategies of vaccine induced immune immune response and protection level. One is to terminate the simulation of living vaccine and drug short live insect infection, the other is a vaccine plus whole worm antigen adjuvant. The purpose of the study is to identify two kinds of differences in immune response and immune vaccine strategies the response associated with the effective protection of the marker. The experimental results show that the short live insects infection can induce strong immune protection. Two whole antigens can only be induced home adjuvant protection. Compared with the whole antigens plus adjuvant group, short live insects infected with drugs blocking antibody level and dendritic cells to induce specific higher group the activation level of Plasmodium and stronger CD4+T cell response to.Thl, the expression level of Th2 and regulatory cytokines have significant differences between the two kinds of similar vaccine strategy further. The study will verify the interlink between these immune factors and protective power. This study helps to design a more rational scheme for malaria vaccine.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：R531.3

【共引文献】