H9N2禽流感病毒血凝素蛋白的主要特性及B/T细胞抗原表位预测分析

Characteristics and prediction of B-and T-cell epitopes of hemagglutinin from avian influenza A(H9N2)

目的应用生物信息学方法分析人源和禽源H9N2禽流感病毒血凝素蛋白(hemagglutinin,HA)的主要特性,预测可能的B/T细胞抗原表位。方法以H9N2禽流感病毒HA蛋白的氨基酸序列一级结构为基础分析其保守性,采用ProtParam预测H9N2禽流感病毒HA蛋白的理化特性,SOPMA预测其二级结构,MotifScan预测翻译后修饰位点,DNAStar分析其序列的亲水性指数、柔韧性指数、可及性参数以及抗原指数并推测B细胞抗原表位的可能位置,采用SYFPEITHI的T细胞表位预测工具分别预测CTL和Th细胞表位。结果人源和禽源H9N2禽流感病毒HA蛋白氨基酸序列分别有90和75个变异位点,其中有38个突变位点与氨基酸置换均相同,有14个突变位点相同但氨基酸置换不同。人源和禽源毒株中还各有38和23个特异性突变位点。HA蛋白存在多个糖基化、酰胺化及磷酸化等翻译后修饰位点。除了蛋白激酶C磷酸化位点外,其他类型的翻译后修饰位点在人源和禽源毒株中均有一些变化。经综合各种单参数,HA蛋白均为亲水性蛋白。人源和禽源H9N2禽流感病毒HA蛋白含有4个B细胞表位,8个CTL细胞表位和6个Th细胞表位,以人源和禽源的B细胞和Th细胞表位差异较大,而CTL细胞表位有部分序列相同。结论人源和禽源H9N2禽流感病毒HA蛋白的氨基酸序列有一定差异,其B/T细胞抗原表位的不同,可为H9N2禽流感病毒疫苗的研制提参考。

Objective To predict and compare the main characteristics and B- and T-cell epitopes of the hemagglutinin （HA） protein from avian influenza A （HgN2） infecting humans and birds. Methods Analysis of the extent to which the HA protein of influenza A （H9N2） was conserved performed based on its primary structure, the physical and chemi- cal properties of which were predicted using ProtParam, and its secondary structure was predicted using the SOPMA on- line server. Post translation sites were predicted using MotifScan software. B-cell epitopes were analyzed using DNAStar software, which determined the hydrophilicity, flexible regions, surface probability, and antigenic index of the protein. T-cell epitopes were analyzed using SYFPEITHI. Results The H9N2 virus infecting humans had 90 mutations while the H9N2 virus infecting birds had 75 mutations, including 38 mutations causing the same amino acid substitution, and 14 mutations causing different amino acid substitutions. Thirty-eight mutations were specific to the H9N2 virus infecting hu- mans and 23 were specific to the H9N2 virus infecting birds. In addition, the HA protein was found to have multiple post translational modification sites. With the exception of 13 protein kinase C phosphorylation sites, other post-transla- tional modification sites differed between the two types of H9N2 virus, such as 9 N-glycosylation sites in the H9N2 virus infecting humans and 7 N-glyeosylation sites in the H9N2 virus infecting birds, 6 casein kinase II phosphorylation sites in the H9N2 virus infecting humans and 7 casein kinase II phosphorylation sites in the H9N2 virus infecting birds, 1 kinase phosphorylation site in the H9N2 virus infecting humans and 2 kinase phosphorylation sites in the H9N2 virus infecting birds, and 10 N-myristoylation sites in both the H9N2 virus infecting humans and the H9N2 virus infecting birds. How- ever, mutations at these sites differed. In addition, 4 potential B-cell epitopes, 8 potential CTL cell epitopes, and 6 Thcell epitopes of the HA protein were predicted for the H9N2 virus infecting humans and the H9N2 virus infecting birds. The predicted potential B-cell epitopes and potential CTL cell epitopes of the HA protein differed widely between the two types of H9N2 virus, though the Th cell epitopes of the HA protein were similar. Coneluslon The amino acid se- quences of the H9N2 virus infecting humans and the H9N2 virus infecting differ somewhat. Specific prediction of the characteristics and B- and T-cell epitopes of the HA protein might help to develop vaccines against H9N2 based on pep tides of human and avian strains of the H9N2 virus.