泡沫病毒（FV）具有独特的基因表达调控机制和特殊的进化地位，可能是以HIV为代表的正反转录病毒和以HBV为代表的嗜肝DNA病毒（副反转录病毒）之间进化的桥梁，同时可作为构建反转录病毒基因转移载体良好的出发毒株。牛泡沫病毒（BFV）感染细胞后释放到上清中的病毒颗粒少，感染力低，病毒只能通过cell-to-cell的方式传播。本实验室前期筛选出一株具有较高释放能力的BFV毒株，可通过cell-free方式感染新的细胞，并已构建获得相应的感染性克隆。本项目拟探究上述两株毒株释放能力差异的原因，通过片段互换和定点突变寻找决定病毒选择cell-free和cell-to-cell传播的关键点，探究BFV出芽释放的分子机制，为解析泡沫病毒出芽释放机制及进化地位提供依据，并为全面认识反转录病毒及相关重要致病病毒的致病机理提供新视角，同时作为将泡沫病毒改造为基因转移载体的必备理论基础。

Foamy virus (FV) has unique biological characteristics, and probably bridges the gap between retroviruses (HIV) and the Hepadnaviridae (HBV). FV is also a good starting strain to construct retroviral gene transfer vectors. Bovine foamy virus (BFV) infected cells to release less virus particles in the supernatant, the infection capacity is low, the spread of the virus is not spread by way of cell-free, only by way of cell-to-cell. We constructed the infectious clone based on the cell-free BFV before. In this project, to indentify the key genes and sites that affect the cell-free and cell-to-cell spread of BFV, we compare the sequence of cell-free BFV and cell-to-cell BFV, and construct chimeric and point mutations BFV infectious clones. Furthermore, clarifying the molecular mechanism of BFV particle release is to provide the basis of FV unique release and evolutionary status, to provide a new perspective for a comprehensive understanding of retroviruses and related important pathogenic virus pathogenesis, as well as to provide the theoretical basis of converting FV into an essential gene transfer vector.