CAS Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Virol Sin. 2021 Dec;36(6):1600-1610. doi: 10.1007/s12250-021-00454-z. Epub 2021 Oct 11.
Ebola virus (EBOV) belongs to the Filoviridae family and causes severe illnesses such as hemorrhagic fever with a high mortality rate up to 90%. Now two antibody drugs termed Inmazeb and Ebanga have been approved for treating EBOV infection. However, clinical studies have demonstrated that the mortality rate of the patients who received these two antibody drugs remains above 30%. Therefore, novel therapeutics with better efficacy is still desired. The isolated human IgG1 constant domain 2 (CH2 domain) has been proposed as a scaffold for the development of C-based single domain antibodies (C-sdAbs) as therapeutic candidates against viral infections and other diseases. Here, we screened and identified a novel C-sdAb termed M24 that targets EBOV glycoprotein (GP) from a C-sdAb phage display library. M24 neutralizes the pseudotype EBOV with IC of 0.8 nmol/L (12 ng/mL) and has modest neutralizing activity against authentic EBOV. Epitope determination, including molecular docking and site mutation analysis, discloses that M24 binds to the internal fusion loop (IFL) within GP2, a transmembrane subunit of GP. Interestingly, we found that the binding of M24 to GP at pH 5.5 has dramatically decreased compared to the binding at pH 7.5, which may lead to weak efficacy in the neutralization of authentic EBOV. Since no sdAb against EBOV infection has been reported to date, our results not only give a proof of concept that sdAbs could be utilized for the development of potential therapeutic candidates against EBOV infection, but also provide useful information for the discovery and improvement of anti-EBOV agents.
埃博拉病毒（EBOV）属于丝状病毒科，可引起严重疾病，如出血热，死亡率高达 90%。目前，两种名为 Inmazeb 和 Ebanga 的抗体药物已被批准用于治疗 EBOV 感染。然而，临床研究表明，接受这两种抗体药物治疗的患者死亡率仍高于 30%。因此，仍需要更好疗效的新型疗法。分离的人 IgG1 恒定区 2（CH2 区）已被提议作为基于 C 的单域抗体（C-sdAb）的开发支架，作为针对病毒感染和其他疾病的治疗候选物。在这里，我们从 C-sdAb 噬菌体展示文库中筛选并鉴定了一种针对 EBOV 糖蛋白（GP）的新型 C-sdAb，称为 M24。M24 中和假型 EBOV 的 IC 为 0.8 nmol/L（12 ng/mL），对真实 EBOV 具有适度的中和活性。表位测定，包括分子对接和位点突变分析，揭示 M24 结合到 GP2 中的内部融合环（IFL）内，GP2 是 GP 的跨膜亚基。有趣的是，我们发现 M24 与 GP 在 pH 5.5 下的结合与在 pH 7.5 下的结合相比显著降低，这可能导致对真实 EBOV 的中和效果减弱。由于迄今为止尚未报道针对 EBOV 感染的 sdAb，我们的结果不仅证明了 sdAb 可用于开发针对 EBOV 感染的潜在治疗候选物，而且为发现和改进抗 EBOV 药物提供了有用信息。
