B7-1、B7-2分子在免疫诱导过程中发挥不同的作用，本项目拟通过体外、体内两部分研究探寻B7-1、B7-2在靶向防龋DNA疫苗增强免疫反应过程中的作用机制。体外研究评价在CTLA4融合蛋白和非融合蛋白刺激下，抗原提呈细胞（APC）对两种蛋白的摄取能力，APC的共刺激分子表达、细胞因子产生和信号通路活化，以及T细胞向Th1、Th2和Th17分化能力。体内研究采用靶向和非靶向防龋DNA疫苗免疫小鼠，比较抗原在免疫局部引流淋巴结的表达水平，血清和唾液中的特异性抗体水平，血清IgG亚型，以及脾细胞产生的Th1/Th2/Th17细胞因子水平。研究中拟使用野生型小鼠及B7-1、B7-2、B7-1/2基因敲除鼠做比较，明确B7-1、B7-2如何参与CTLA4靶向疫苗的免疫诱导过程。该项目有助于深入了解B7-1、B7-2分子在免疫调控中的不同作用，可能为靶向B7分子的疫苗的设计提供新的理论依据。

B7-1 and B7-2 play different roles in the induction of immune response. This project is designed to disclose the different effects of B7-1 and B7-2 in the enhanced immune response induced by a targeted fusion anti-caries DNA vaccine. In vitro studies will be conducted to evaluate the ability of antigen-presenting cells (APC) to capture proteins, the expression of costimulatory molecules on APC, the production of cytokines by APC, the activation of signaling pathways in APC, and the differentiation potential of Th0 cells to Th1, Th2 or Th17 cells in the context of the stimulation of CTLA4 fusion protein and non-fusion protein. In vivo studies will be performed to compare the expression of antigen in draining lymph nodes, the levels of specific antibodies in serum and saliva, the levels of IgG subtypes in serum, and the Th1/Th2/Th17 cytokines produced by splenocytes following immunization of mice with targeted anti-caries DNA vaccine versus with non-targeted anti-caries DNA vaccine. For the purpose of delineating how B7-1 and B7-2 are differently involved in the induction of immune response induced by CTLA4 targeted DNA vaccine, four types of mice including wild-type, B7-1 knockout, B7-2 knockout and B7-1/2 double knockout mice will be used in the above studies. This project would help to deepen our understanding on the differential aspects between B7-1 and B7-2 in the induction of immune response and provide new supportive evidences for the designing of B7-targeted vaccines.