新型甲型H7N9流感病毒PB1-F2蛋白基因进化和变异分析

目的：对新型甲型H7N9流感病毒PB1-F2蛋白基因的进化和变异进行分析，为进一步研究致病性禽流感的致病机制和毒力因子奠定基础。方法：从IRD数据库中下载2013年2月19日至2013年10月31日的H7N9流感病毒PBl基因序列63条，运用MEGA5．2．1软件进行序列分析，用邻接法构建基因进化树；通过氨基酸序列分析PB1基因95～367片段的PB1-F2蛋白氨基酸位点变化；应用Excel表格对氨基酸构成进行计算；运用Predictive Analytics Software（PASW）18．0软件对氨基酸构成改变进行统计分析。结果：63株甲型H7N9毒株中有17株毒株的PB1-F2蛋白在其氨基酸序列第25位后发生断裂。新型甲型H7N9的进化主要分为两个系别，系别I主要由完整型PB1-F2蛋白毒株构成，系别Ⅱ主要由52aa截短型PB1-F2蛋白毒株构成。完整型PB1-F2蛋白与截短型PB1-F2蛋白各类氨基酸构成存在差异。结论：H7N9流感毒株中存在着截短型PB1-F2蛋白毒株，并且H7N9流感病毒毒株PB1-F2蛋白断裂位点均在25位氨基酸后，这将成为H7N9流感毒株进化过程中重要的特征。完整型PB1-F2蛋白与截短型PB1-F2蛋白氨基酸构成的差异对于甲型H7N9流感病毒致病性的影响有待进一步研究。

Gene evolution and mutation analysis on the PB1-F2 protein of novel influenza A/H7N9 virus

Objective： This study based on the analysis of the evolution and mutation of the new influenza A/ H7N9 virus protein PB1-F2 gene, in order to lay a foundation for further study of the pathogenic mechanism of pathogenic avian influenza and its virulence. Methods： The H7N9 flu virus PB1 gene sequences were downloaded from the NIAID Influenza Research Database （IRD） online from Feb 19,2013 to Oct 31,2013, sequences were analyzed by molecular evolutionary genetics analysis （MEGA） version 5.2. 1. The genetic evolutionary tree was build by adjacency. The change of the amino acid sequence of PB1- F2 protein at the 95 - 367 segments of PBI gene was analyzed through amino acid sequence; the amino acid composition was calculated by excel;The change of the amino acid composition was analyzed by the Predictive Analytics Software （PASW） version 18.0. There differences of amino acid composition between complete PB1-F2 protein type and truncated PB1-F2 protein type. Results： The mutation in PB1-F2 protein at the 25th after fracture of PB1-F2 protein amino acid sequence was found in 17out of 63 strains of influenza A/H7N9 strains. The evolution of the new influenza A/H7N9 mainly divides into two department, department I mainly consisted of complete PB1-F2 protein strain, department 11 mainly made up of truncated protein PB1-F2 strain which contain 52 amino acid. Conclusion： Truncated PB1-F2 protein strains exist in H7N9 influenza strains, and the fracture sites are at H7N9 flu strain PB1-F2 protein after 25 amino acid, it will be an important characteristics in the process of evolution of H7N9 flu strain. In addition, the differences of amino acid composition between complete PB1- F2 protein type and truncated PB1- F2 protein type effect on the pathogenic of influenza A/H7N9 virus needs further study.