目前仍缺乏理想的HBV感染模型，种种迹象表明树鼩对HBV易感，但短暂病毒血症后迅速被免疫清除。本研究拟借用其它病毒的生存策略，通过制备复制型HBV载体，赋予其免疫抑制功能，使树鼩形成慢性HBV感染。首先,在表达野生型HBV质粒基础上构建复制型HBV载体，利用基因工程方法把相互重叠的HBV C与P蛋白分开，在C、P蛋白间插入外源基因，利用2个小的强效IRES分别表达外源基因和P蛋白，揭示其分子生物学特性；其次，制备3种理论上具有免疫抑制功能的HBV载体（分别表达EB病毒IL-10、巨细胞病毒IL-10、仙台病毒C蛋白N端23肽与一种小荧光蛋白的融合蛋白），在细胞培养条件下筛选出对树鼩具有免疫抑制活性者；最后，利用具有免疫抑制功能的重组HBV颗粒感染树鼩，观察树鼩体内慢性HBV感染情况。本研究除新型HBV载体在HBV分子生物学方面具有广泛用途外，将有望提供首个高病毒载量慢性HBV自然感染模型。

Up to now, there is no ideal Hepatitis B virus (HBV) infection model available. Evidences indicated that tupaia is susceptibile to HBV infection, but HBV is rapidly cleared by the immune system after just transient Viremia. Based on the survival strategy from other virus, we want to induce tupaia chronic HBV infection through giving HBV immunosuppression function by constructing of a replication-competent HBV vector. First, we will construct a replication-competent HBV vector on the basis of wild-type HBV expression plasmid by gene engineering method. The overlapping region of HBV Core and Polymerase will be separated and then an exogenous gene will be inserted between them. Double small internal ribosome entry site (IRES) sequences will be employed for the translation of exogenous gene and the polymerase repectively. The molecular biological characteristics of the HBV vector will be analysed in detail. Second, HBV vectors with theoreticly immunosuppression function (expressions of Epstein-Barr (EB) virus interleukin 10 (IL-10), Cytomegalovirus (CMV) IL-10 and a fusion protein of the N terminal 1-23 peptide of Sendai virus C protein with a small fluorescent protein "miniSOG" respectively) will be constructed and selected for the performance in tupaia cells. Finally, the viral particle from the recombinant HBV vectors with immunosuppressive function is planed to be used for the infection of tupaia in vivo. Characteristics of tupaia model of chronic HBV infection will be observed. In addition to that the new HBV vector will have wide application in HBV molecular biology, this project is expected to provide the first chronic HBV infection model with high viral load.