流感病毒血凝素氨基酸变异造成抗原性差异的结构基础

Genetic mutations of hemagglutinin (HA) give rise to antigenic variation of influenza virus frequently. Obvious antigenic variation can be seen when only a few residues mutate, which leads to weaken or abolished cross immune neutralization reaction between viral antigens and anti-serum. The rationale of this phenomena is yet to be elucidated. In the current project, Re-5 and Re-8, two vaccinal strains from a same evolutional clade, to be selected to research. Reverse genetics and immunological techniques will be performed to find out key residues with antigenic importance; Through comparing structures of these two HA proteins, influence of key residues to structures of epitopes will be analyzed, which will reveal the connections between key residues and antigenicity preliminarily. Then structures of complexes of monoclonal antibody Fab fragments and HAs will be resolved and the fine structure of the binding surface of antigen and antibody will be analyzed. The structural fundamental of the weaken and abolished binding between Re-8 HA and MAbs will be worked out. Through this project, the mechanism why mutation of only a few amino acids will lead to obvious antigenic variation for HA will be elucidated, which will provide a theoretical support for objective evaluation to vaccine application and national preventing measurements made against H5 subtypes influenza viruses.

流感病毒血凝素氨基酸（HA）的变异可以引起抗原性的改变，然而H5亚型禽流感病毒HA发生少数的氨基酸变异，其抗原性就可能发生显著改变，导致病毒抗原与血清交叉免疫中和反应很弱甚至不能发生反应，然而，产生这一现象的结构学基础尚不清楚。本研究以我国临床应用的同一进化分支H5亚型禽流感Re-5和Re-8疫苗毒株为研究对象，通过反向遗传学和免疫学技术，筛选出抗原性相关的关键氨基酸；通过对HA蛋白晶体结构比较研究，解析关键氨基酸对抗原表位结构的影响，初步揭示关键氨基酸改变抗原性的可能结构机制；进一步通过制备单抗Fab抗原抗体复合物，解析HA蛋白-单抗Fab复合物抗原抗体结合部分的精细结构，明确关键氨基酸导致Re-8 HA不结合单抗或与单抗结合变弱的结构基础，阐明少数氨基酸突变即可造成抗原性显著改变的结构基础，为科学评估疫苗免疫作用以及国家制定H5亚型禽流感防控措施提供理论支撑。