C5a/C5aR信号在约氏疟原虫减毒子孢子疫苗诱导小鼠产生保护性免疫中的作用和机制

It is well known that CSP-specific CD8+T cells are the dominant effector of the sterile protective immunity induced by irradiation-attenuated sporozoites. However, the underlined mechanism of CSP-specific CD8+T cells induced by irradiation-attenuated sporozoite is still largely unknown. Our preliminary data showed that the protective efficacy of C5aR-/- mice against sporozoite challenge was largely impaired, and the frequency of IFN-γ secreted CSP-specific CD8+T cells was also significantly reduced after immunization of irradiation-attenuated sporozoites. Thus, in this project, we would like to investigate the influence of C5aR deficiency on the CSP-specific CD8+ and CD4+ T cells response and the anti-CSP antibody production following immunization. Then, we'll also observe the effect of C5aR deficiency on DC maturation and its ability to allostimulate CD4+ T cells, and the frequecy of CD4+ CD25+Foxp3 T cells and its ability to suppress CD4+ T cells activation after immunization. Finally, we'll test whether C5a/C5aR signaling is essential for the full activation of DC or/ and the expansion of CD4+ CD25+Foxp3 T cells stimulated with sporozoites in vitro. The project will not only help us to understand the underlined mechanism of protective immunity induced by irradiation-attenuated sporozoites, but will also guide us to design effective malaria subunit vaccine.

疟原虫CSP特异CD8+T是减毒子孢子疫苗的主要效应细胞，但减毒子孢子活化和调节CSP特异CD8+T细胞机制尚不清楚。我们前期研究发现，在C5aR缺失情况下，减毒子孢子免疫小鼠抵御野生子孢子攻击和产生的分泌IFN-γ的CSP特异CD8+T细胞的能力显著减低。因此，本项目拟在前期研究基础上，进一步观察C5aR缺失对减毒子孢子免疫后小鼠抵御子孢子攻击能力、CD8+ 和CD4+T细胞反应、以及抗CSP抗体产生的影响；并比较免疫后C5aR-/- 和野生小鼠在DC成熟及其功能、以及Treg细胞频率和功能方面的差别；然后通过体外实验观察C5a/C5aR信号对子孢子活化DC和/或Treg的影响；探讨C5aR缺失是否通过调节DC和/或Treg功能抑制减毒子孢子诱导小鼠CD8+T细胞反应及其抗子孢子攻击能力，这不但有助于理解减毒子孢子疫苗诱导的保护性免疫机制，而且可为设计有效的疟疾亚单位提供重要理论依据。

疟疾仍然是世界上危害最为严重的三大传染病之一。随着抗性株疟原虫和按蚊的出现和蔓延，现有的疟疾防治措施受到了严重挑战，迫切需要发展新的防控手段。本项目就宿主抗红外期疟原虫固有免疫机制，以及红外期DNA疫苗和红内期全虫灭活疫苗在防控疟疾中的作用和机制进行了深入的探讨。本项目的研究发现，子孢子裂解产物能被TLR2受体所识别，而TLR2 信号通路的活化能有效地抑制红外期疟原虫的发育，其中的机制与子孢子裂解产物能通过活化TLR2刺激肝脏产生大量的促炎因子密切相关。这可为免疫预防疟原虫的感染提供新思路。本项目还构建了gp96NTD-csp DNA疫苗，发现该疫苗免疫后不但能诱导小鼠产生CSP特异性抗体和CD8+T细胞反应，而且能部分保护免疫小鼠抗子孢子的攻击。另外，我们还发现红内期全虫灭活疫苗不但能抗红内期疟原虫的攻击，而且能以CD8+T 细胞依赖的方式交叉抗子孢子的攻击；另外，该红内期全虫灭活疫苗所诱导的疟原虫特异的抗体和MCP-1还能有效抑制疟原虫在按蚊体内的发育；从而首次报道一种集治疗、预防和阻断传播的疟疾疫苗，这可为疟疾的防控提供一种潜在的有效手段。