Department of Medical Microbiology, University of Manitoba, Winnipeg, Canada.
MAbs. 2010 Jan-Feb;2(1):53-66. doi: 10.4161/mabs.2.1.10788. Epub 2010 Jan 27.
Neutralizing antibody responses to the surface glycoproteins of enveloped viruses play an important role in immunity. Many of these glycoproteins, including the severe acute respiratory syndrome-coronavirus (SARS-CoV) spike (S) protein form trimeric units in the membrane of the native virion. There is substantial experimental and pre-clinical evidence showing that the S protein is a promising lead for vaccines and therapeutics. Previously we generated a panel of monoclonal antibodies (mAbs) to whole inactivated SARS-CoV which neutralize the virus in vitro. Here, we define their specificity and affinity, map several of their epitopes and lastly characterise chimeric versions of them. Our data show that the neutralizing mAbs bind to the angiotensin-converting enzyme 2 (ACE2) receptor-binding domain (RBD) of the SARS S protein. Three of the chimeric mAbs retain their binding specificity while one conformational mAb, F26G19, lost its ability to bind the S protein despite high level expression. The affinity for recombinant S is maintained in all of the functional chimeric versions of the parental mAbs. Both parental mAb F26G18 and the chimeric version neutralize the TO R2 strain of SARS-CoV with essentially identical titres (2.07 and 2.47 nM, respectively). Lastly, a comparison with other neutralizing mAbs to SARS-CoV clearly shows that the dominance of a 33 amino acid residue loop of the SARS-CoV RBD is independent of repertoire, species, quaternary structure, and importantly, the technology used to derive the mAbs. In cases like this, the dominance of a compact RBD antigenic domain and the central role of the S protein in pathogenesis may inherently create immunoselection pressure on viruses to evolve more complex evasion strategies or die out of a host species. The apparent simplicity of the mechanism of SARS-CoV neutralization is in stark contrast to the complexity shown by other enveloped viruses.
中和抗体对包膜病毒表面糖蛋白的反应在免疫中起着重要作用。这些糖蛋白中的许多，包括严重急性呼吸系统综合症冠状病毒（SARS-CoV）的刺突（S）蛋白，在天然病毒粒子的膜中形成三聚体单位。有大量的实验和临床前证据表明，S 蛋白是疫苗和治疗药物的一个很有前途的先导。以前，我们生成了一组针对全灭活 SARS-CoV 的单克隆抗体（mAbs），这些 mAbs 在体外中和该病毒。在这里，我们定义了它们的特异性和亲和力，绘制了它们的几个表位图谱，并最后对它们的嵌合版本进行了特征描述。我们的数据表明，中和 mAbs 与 SARS-CoV 的 S 蛋白的血管紧张素转换酶 2（ACE2）受体结合域（RBD）结合。三个嵌合 mAbs 保留了它们的结合特异性，而一个构象 mAb，F26G19，尽管表达水平很高，但丧失了与 S 蛋白结合的能力。所有功能嵌合版本的亲本 mAbs 都保持了对重组 S 的亲和力。亲本 mAb F26G18 和嵌合版本均以基本相同的效价（分别为 2.07 和 2.47 nM）中和 SARS-CoV 的 TO R2 株。最后，与其他针对 SARS-CoV 的中和 mAb 的比较清楚地表明，SARS-CoV RBD 的 33 个氨基酸残基环的优势独立于 repertoire、物种、四级结构，并且重要的是，独立于用于衍生 mAb 的技术。在这种情况下，S 蛋白在发病机制中的 RBD 抗原域的优势和核心作用可能会对病毒产生固有选择压力，使其进化出更复杂的逃避策略，或者从宿主物种中灭绝。SARS-CoV 中和的机制的明显简单性与其他包膜病毒显示出的复杂性形成鲜明对比。
