口蹄疫病毒（FMDV）3A蛋白是病毒毒力相关因子,我们前期研究发现FMD弱毒疫苗ZB株减毒过程中，3A蛋白内3个氨基酸位点突变发挥了重要作用。O型FMD云南太保减毒(YNTBa)株减毒不完全，而该毒株在3A蛋白内相关位点没有发生突变。本项目以现有YNTBa株感染性克隆分子为骨架，根据FMD弱毒疫苗ZB株研究结果，对YNTBa株3A基因进行替换和突变多个位点，构建嵌合病毒和一系列特定变异位点的突变病毒，测定这些病毒的生物学特性，验证3A蛋白突变对病毒毒力的影响；进一步，利用突变病毒，研究FMDV和3A蛋白互作宿主因子（DCTN3、KTN1、ZG16B、UBQLN1、WHAMM和BAG6蛋白因子）之间的相互作用，阐明3A蛋白突变对YNTBa减毒的影响，探索3A-宿主因子相互作用对病毒毒力变异可能的作用机制，为揭示FMDV致病机理提供科学依据。

Foot-and-mouth disease virus (FMDV) is a highly contagious viral disease agent. Review of existing research indicates the non-structural protein 3A of FMDV is a virulence factor in cattle and host range determinant of FMDV. In our previous study, we found that three amino acid sites in 3A protein played an important role during the attenuation process of the FMD attenuated ZB vaccine strain. But another FMDV serotype O Yunnan Taibao attenuated strain (YNTBa), a rabbit-passaged attenuated strain, had been not successfully used as a live FMD vaccine strain owing to its attenuation not completely. The three key amino acid sites in the YNTBa via suckling rabbit-passaged attenuation didn`t mutation in the appropriated positions of 3A protein of ZB strain though contrasted 3A protein sequences of ZB and YNTBa. We suspect that these mutations are likely to be the major determinants of attenuation, and the host factors of specific binding partner for 3A protein is critical role for mediating the interaction that may contribute to virulence attenuation in cattle. In this project, a chimerical virus in which the 3A protein coding region of the full-length cDNA clone of YNTBa strain will replaced by that of 3A gene of ZBatt vaccine virus, and some mutants bearing above mutations in 3A protein will derived by site-directed mutagenesis. The viral biological characters of the chimerical virus and those mutants will assay to explore the effects on virulence of mutations in 3A protein. Furthermore, the host factor which proved that 3A protein of FMDV interacted with DCTN3、KTN1、ZG16B、UBQLN1、WHAMM and BAG6, will also explore how they interact with those mutates virus. The project can help understand the role of 3A protein on the virulence of YNTBa and the relationship of 3A protein mutation and virulent attenuation. The project will highlight the important of 3A-host interaction in FMDV virulence and reveal the pathogenic mechanism of FMDV.