Lu Yun, Ding Jian, Liu Wanli, Chen Ying-Hua
Laboratory of Immunology, Research Centre for Medical Science and Department of Biology, Tsinghua University, and Protein Science Laboratory of the Ministry of Education, Beijing, China.
Int Arch Allergy Immunol. 2002 Mar;127(3):245-50. doi: 10.1159/000053869.
The hemagglutinin (HA) of influenza viruses is one of the major targets of the humoral response. The role of serum antibody to HA in the protection against infection has been demonstrated by long-standing observation. In previous studies, we suggested that an epitope vaccine might be a new strategy against the virus.
HA sequences of 491 H3 subtype strains from the influenza sequence database were compared and analyzed. To acquire information on the immunogenicity of the F3 epitope, F3-epitope-specific antibody levels in 81 patient sera infected with influenza virus were tested by ELISA. Based on the theory of the epitope vaccine, we designed an epitope peptide F3 (C-KAYSNCYPYDVPDY-G-KAYSNCYPYDVPDY), which contains the repeated F3 epitope KAYSNCYPYDVPDY (aa92-105) on HA (H3N2). The specificity and the titer of the antibodies induced by the epitope vaccine were determined by ELISA. The neutralizing activities of these anti-F3 antibodies were shown by inhibiting influenza virus infection of MDCK cells.
Comparison of HA sequences of 491 H3 subtype strains indicates that this epitope is highly conservative. Analysis of the sera from influenza virus-infected patients revealed a very low level of F3 epitope-specific antibodies, suggesting the poor immunogenicity of the F3 epitope on influenza virus. The epitope vaccine based on the F3 epitope induced high levels of F3 epitope-specific antibodies recognizing the epitope peptide F3 (antibody titer in antisera up to 1:25,600). Besides, the antisera could also recognize the natural HA in Western blotting. Interestingly, these antisera induced by the epitope vaccine could inhibit infection of MDCK cells by influenza virus (strain A/Wuhan/359/95) in the neutralization assay. These results suggest that the epitope vaccine can intensively increase the immunogenicity of neutralizing epitopes and may provide a new way to develop an effective vaccine against influenza virus.
流感病毒的血凝素（HA）是体液免疫反应的主要靶点之一。长期观察已证实血清中针对HA的抗体在预防感染中的作用。在先前的研究中，我们提出表位疫苗可能是对抗该病毒的一种新策略。
对流感序列数据库中491株H3亚型毒株的HA序列进行比较和分析。为获取有关F3表位免疫原性的信息，采用酶联免疫吸附测定法（ELISA）检测了81例流感病毒感染患者血清中F3表位特异性抗体水平。基于表位疫苗理论，我们设计了一种表位肽F3（C-KAYSNCYPYDVPDY-G-KAYSNCYPYDVPDY），其包含HA（H3N2）上重复的F3表位KAYSNCYPYDVPDY（氨基酸92 - 105）。通过ELISA测定表位疫苗诱导产生的抗体的特异性和效价。这些抗F3抗体的中和活性通过抑制MDCK细胞的流感病毒感染来显示。
491株H3亚型毒株HA序列的比较表明该表位高度保守。对流感病毒感染患者血清的分析显示F3表位特异性抗体水平极低，表明流感病毒上F3表位的免疫原性较差。基于F3表位的表位疫苗诱导产生了高水平的识别表位肽F3的F3表位特异性抗体（抗血清中的抗体效价高达1:25,600）。此外，抗血清在蛋白质印迹法中也能识别天然HA。有趣的是，在中和试验中，这些由表位疫苗诱导产生的抗血清能够抑制流感病毒（A/武汉/359/95株）对MDCK细胞的感染。这些结果表明表位疫苗可显著提高中和表位的免疫原性，并可能为开发有效的抗流感病毒疫苗提供一种新方法。
