抗体选择压作用下H9N2亚型禽流感病毒HA基因的变异

摘要：【目的】了解H9N2亚型禽流感病毒(AIV)在抗体选择压作用下的遗传变异。【方法】将制备疫苗用的LG1株H9N2亚型AIV分别接种含有母源抗体鸡胚(A组)和不含有母源抗体的SPF鸡胚(B组)，并连续传代。其中A组再分为4 个独立的传代系列A1-4，B组再分为2 个独立传代系列B1-2。在每个传代系列，分别对第10，20，30，40，50 代病毒的HA基因进行扩增克隆测序，并与原始病毒的序列比较。【结果】LG1株H9N2在没有抗体的鸡胚的传代过程中，仅发生少数碱基的不稳定随机变异，且多为无义突变。在2 个传代系列的10 个代次病毒，共出现了29 个位点变异，有义突变(NS)与无义突变(S)比值NS/S为1.42 。但在有抗体的鸡胚的传代过程中，发生了多个呈现稳定遗传的有义突变。在4 个传代系列的20 个代次病毒，共出现了45 个位点变异，有义突变(NS)与无义突变(S)比值NS/S为3.46。【结论】在鸡胚传代过程中母源抗体提供的免疫选择压确实能影响H9N2的HA基因的变异。同时表明，带有母源抗体的鸡胚是实验室条件下研究免疫选择压对病毒抗原性变异影响的一种有效的实验模型。

Mutations of the hemagglutinin gene of H9N2 subtype avian influenza viruses under selective pressure of antibody

Abstract: [Objective] To understand mutations of avian influenza virus (AIV) under the antibody selective pressures. [Methods] We continuously passed an H9N2-AIV strain LG1 in embryos with or without maternal antibody to LG1 in 6 separate serials. At the 10th, 20th, 30th, 40th and 50th passages in each serial, H9 hemagglutinatin gene (HA) sequences were determined and compared to the original LG1 strain. [Results] Only unstable random mutations happened in 29 sites with nonsynonymous vs synonymous (N/S) mutation ratio of 1.42 during 50 passages in 2 serials without maternal antibodies. However, multiple stable nonsynonymous mutations were detected gradually during 50 passages of 4 serials in embryos with maternal antibody to LG1 strain, and the NS/S ratio was as high as 3.46 among 45 mutated sites. [Conclusion] The results suggested that the antibody selective pressure influenced mutations of H9N2 AIV HA gene during the passages in embryos with maternal antibody. Embryos with maternal antibody to certain viruses could be used as experimental models to study the immune selective pressures on viral mutations.