The coronavirus SARS-CoV-2 is the cause of the ongoing COVID-19 pandemic. Therapeutic neutralizing antibodies constitute a key short-to-medium term approach to tackle COVID-19. However, traditional antibody production is hampered by long development times and costly production. Here, we report the rapid isolation and characterization of nanobodies from a synthetic library, known as sybodies (Sb), that target the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. Several binders with low nanomolar affinities and efficient neutralization activity were identified of which Sb23 displayed high affinity and neutralized pseudovirus with an IC 50 of 0.6 µg/ml. A cryo-EM structure of the spike bound to Sb23 showed that Sb23 binds competitively in the ACE2 binding site. Furthermore, the cryo-EM reconstruction revealed an unusual conformation of the spike where two RBDs are in the ‘up’ ACE2-binding conformation. The combined approach represents an alternative, fast workflow to select binders with neutralizing activity against newly emerging viruses. Here, the authors isolate several nanobodies from a synthetic library that bind the receptor-binding domain (RBD) of SARS-CoV-2 spike protein (S) and neutralize S pseudotyped viruses. Cryo-EM structure of Spike with one nanobody and further biophysical analysis shows competition with ACE2 binding.
【저자키워드】 Infectious diseases, Biochemistry, Molecular medicine, structural biology, Biophysics, 【초록키워드】 COVID-19, viruses, neutralizing antibody, spike, COVID-19 pandemic, coronavirus SARS-CoV-2, Spike protein, Neutralizing activity, nanobody, pseudovirus, RBD, SARS-CoV-2 spike protein, Isolation, cryo-EM, Pseudotyped viruses, Analysis, ACE2 binding, antibody production, ACE2 binding site, high affinity, nanomolar affinity, neutralization activity, sybody, approach, cryo-EM structure, neutralize, neutralized, bind, the receptor-binding domain, costly, the SARS-CoV-2, 【제목키워드】 SARS-CoV-2, Selection, Structural analysis, neutralize, synthetic nanobody,