Development of neutralizing nanobodies against SARS-CoV-2

在大流行期间，何博士评估了开发针对SARS-Cov-2的抗体疗法所面临的挑战，并撰写了一篇综述/观点文章[Ho antibody therapeutics 2020；PMID: 32566896)。SARS-CoV-2通过其刺突(S)蛋白与血管紧张素转换酶2 （ACE2）结合进入人体细胞。因此，S蛋白是中和抗体的主要靶点。在2022财年，我们总结了我们在分离单峰骆驼纳米体对抗SARS-CoV-2方面的工作，并在PNAS上发表了相关数据[Hong等]。[j].科学通报，2010。随着SARS-CoV-2变体的出现，迫切需要开发广泛中和的抗体。我们通过噬菌体展示从单峰骆驼中分离出两个VHH纳米体（7A3和8A2），它们对受体结合域（RBD）具有高亲和力，对SARS-CoV-2及其新变体具有广泛的中和活性。Cryo-EM复合物结构显示，8A2以其上向模式结合RBD，而7A3通过独特地靶向RBD中高度保守和深埋的位点来抑制受体结合，而不管RBD的构象状态如何。5mg /kg剂量的7A3可有效保护K18-hACE2转基因小鼠免受B.1.351或B.1.617.2的致命攻击，这表明该纳米体在抑制新出现的SARS-CoV-2变体的COVID-19激增方面具有良好的治疗潜力。

During the pandemic, Dr Ho has evaluated the challenges for developing antibody therapeutics targeting SARS-Cov-2 and wrote a review/perspective article [Ho Antibody Therapeutics 2020; PMID: 32566896]. SARS-CoV-2 gains entry to human cells through its spike (S) protein binding to angiotensin-converting enzyme 2 (ACE2). Therefore, the S protein is the primary target for neutralizing antibodies. In FY2022, we summarized our work on isolation of dromedary camel nanobodies against SARS-CoV-2 and published the data in PNAS [Hong et al. Proc Natl Acad Sci U S A. 2022]. With the emergence of SARS-CoV-2 variants, there is an urgent need to develop broadly neutralizing antibodies. We isolated two VHH nanobodies (7A3 and 8A2) from dromedary camels by phage display, which have high affinity for the receptor-binding domain (RBD) and broad neutralization activities against SARS-CoV-2 and its emerging variants. Cryo-EM complex structures reveal that 8A2 binds the RBD in its up mode and 7A3 inhibits receptor binding by uniquely targeting a highly conserved and deeply buried site in the spike regardless of the RBD conformational state. 7A3 at a dose of 5 mg/kg efficiently protects K18-hACE2 transgenic mice from the lethal challenge of B.1.351 or B.1.617.2, suggesting that the nanobody has promising therapeutic potential to curb the COVID-19 surge with emerging SARS-CoV-2 variants.