Development of neutralizing nanobodies against SARS-CoV-2

在疫情期间，何医生评估了开发抗体的挑战， 针对SARS-Cov-2的治疗方法，并撰写了综述/展望文章[Ho Antibody Therapeutics 2020; PMID：32566896]。SARS-CoV-2通过其刺突进入人体细胞 (S)与血管紧张素转换酶2（ACE 2）结合的蛋白。因此，S蛋白是 中和抗体的主要目标。于2022财政年度，我们总结了我们在隔离 单峰骆驼纳米抗体抗SARS-CoV-2，并在PNAS上发表了数据[Hong等人，Proc.Sci.2004， 美国国家科学院2022年]。随着SARS-CoV-2变种的出现，迫切需要 来开发广泛中和的抗体我们分离了两种VHH纳米抗体（7A 3和8A 2）， 单峰骆驼的噬菌体展示，具有高亲和力的受体结合域 (RBD)对SARS-CoV-2及其新出现的变异株具有广泛的中和活性。 Cryo-EM复合物结构显示，8A 2以其向上模式结合RBD，7A 3抑制RBD。 通过独特地靶向刺突中高度保守和深埋的位点来结合受体 无论RBD构象状态如何。剂量为5 mg/kg的7A 3有效地保护 K18-hACE 2转基因小鼠在B.1.351或B.1.617.2致死性攻毒中的存活率，表明 这种纳米抗体具有很好的治疗潜力，可以遏制COVID-19的激增， SARS-CoV-2变种。

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.