甲3(H3N2)亚型流感病毒相变异分子生物学基础的研究

Studies on the basis of molecular biology of the phase change of influenza A(H3N2) viruses

目的弄清甲３（Ｈ３Ｎ２）亚型流感病毒相变异的分子生物学基础。方法病毒粒ＲＮＡ经逆转录合成ｃＤＮＡ，经聚合酶链反应（ＰＣＲ）扩增，产物纯化，采用双脱氧链末端终止法进行核苷酸序列测定。结果３５株甲３（Ｈ３Ｎ２）亚型流感病毒的ＨＡ１区基因长度均为９８４个核苷酸，它们间无发生任何核苷酸丢失或插入并发现ＨＡ１蛋白分子上氨基酸序列多变点主要在ＨＡ蛋白的顶部，尤其抗原决定簇Ｂ区和受体结合部位（ＲＢＳ），这进一步证实了，ＨＡ蛋白分子上氨基酸替换主要是人群免疫压力所造成。同时还发现了半胱氨酸和脯氨酸具有高保守性及糖基化位点主要集中在ＨＡ１区的Ｎ和Ｃ端，尤其Ｎ端。糖基化位点如此分布在病毒基因进化和流行病学上意义至今不清楚。结论Ｈ３Ｎ２亚型病毒“Ｏ”相毒株的出现与其蛋白分子上第２２６位氨基酸发生替换密切相关并推测“Ｏ”相毒株ＨＡ蛋白三维结构与“Ｄ”相的不同。

The analysis of nucleotide sequences on HA1 domain of 35 strains of influenza A(H3N2) virus showed that their HA1 genes all were 984 nucleotides in length coding for a HA1 protein with 328 amino acides and there was not any occurrence of insertion or deletion of nucleotides on HA1 genes among them. The appearance of “O” phase strain of influenza A(H3N2) virus was closely related with substitution at 226 position of amino acid on HA1 protein molecule and the three-dimensional structural change of HA protein. The results in this paper indicaded that the positions with multiple changes on HA1 protein molecule located at the top of HA protein, especially at antigenic determinant B site or receptor binding site. These further demonstrated that the substitution of amino acid on HA1 protein molecule was casued mainly by suppress of herd immunity. This study also showed that the position of the cysteine and proline residues on the HA1 protein molecule were conservative and that the glycosylation sites located at N and C terminals, especially at N terminal of the HA1 protein The significance of such a distrib△ of glycosylation sites in the evolution of viral genes and epidemiology still remain unknown.