Background

Antibody-dependent cell-mediated cytotoxicity (ADCC) is one of the mechanisms connecting humoral immunity and cellular immunity and has been well-demonstrated in recent studies. Neutralizing antibodies and antibodies can mediate ADCC effects and both build a strong defense against H7N9 influenza virus infection. In our previous study, we found that H7N9 patients’ plasma displayed low neutralizing activities that were not sufficient for host protection; however, the plasma of some patients can mediate strong ADCC effects.

Methods

Based on the plasma samples of H7N9 infected patients collected, we measured the ADCC activities of these samples and selected the best to locate the dominant epitopes on H7N9 hemagglutinin (HA) protein that can elicit antibodies and strong ADCC activities. We constructed a yeast surface-display H7N9 HA protein epitope library and screened this library against plasma samples with different potencies in mediating ADCC effects.

Results

Two dominant epitopes were selected from the screening. Plasma samples with depleted antibodies that were specific to the epitopes showed reduced ADCC activities. The serum of mice immunized with the epitopes elicited strong ADCC activities. Three monoclonal antibodies were isolated which showed high ADCC effects in vitro. Vaccination with isolated ADCC activating epitopes can provide partial protection from influenza infection in mouse model. And mice with vaccinated with combination of epitopes and extracellular domain can provide full protection from influenza infection in the same mouse model.

Conclusions

In this study, the epitopes isolated on H7N9 HA were immunogenic and elicited antibodies and strong ADCC activities in mice. Although the protective effect of the epitopes is partial, the combination of epitopes and extracellular domain can provide 100% protection from influenza virus infection in the same mouse model. Our study provides information on the potential use of epitope vaccine design against H7N9 viral infection.

中文翻译：

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H7N9血凝素新蛋白表位的鉴定，可引发强烈的抗体依赖性细胞介导的细胞毒活性，并能抵抗小鼠模型中的流感病毒感染

背景

抗体依赖性细胞介导的细胞毒性（ADCC）是连接体液免疫和细胞免疫的机制之一，在最近的研究中已得到充分证明。中和抗体和抗体可以介导ADCC的作用，并且都可以针对H7N9流感病毒感染建立强大的防御力。在我们以前的研究中，我们发现H7N9患者的血浆显示出低中和活性，不足以保护宿主。但是，某些患者的血浆可以介导ADCC的强效作用。

方法

基于收集的H7N9感染患者的血浆样本，我们测量了这些样本的ADCC活性，并选择了最佳的方法来定位H7N9血凝素（HA）蛋白上的显性表位，该表位可以引发抗体和强大的ADCC活性。我们构建了酵母表面展示H7N9 HA蛋白表位文库，并针对介导ADCC效应的具有不同效力的血浆样品筛选了该文库。

结果

从筛选中选择两个显性表位。具有对表位特异的抗体减少的血浆样品显示出降低的ADCC活性。用表位免疫的小鼠血清引起强烈的ADCC活性。分离到了三种单克隆抗体，它们在体外具有较高的ADCC效应。分离的ADCC激活表位的疫苗接种可以在小鼠模型中提供部分保护，使其免受流感感染。接种了表位和胞外域组合疫苗的小鼠可以在同一小鼠模型中提供针对流感感染的全面保护。

结论

在这项研究中，在H7N9 HA上分离的表位具有免疫原性，并在小鼠中引发抗体和强大的ADCC活性。尽管表位的保护作用是部分的，但在同一小鼠模型中，表位和细胞外结构域的组合可以提供100％的保护，以防止流感病毒感染。我们的研究提供了有关针对H7N9病毒感染的表位疫苗设计潜在用途的信息。