Nanobody cocktails potently neutralize SARS-CoV-2 D614G N501Y variant and protect mice

Neutralizing antibodies are important for immunity against SARS-CoV-2 and as therapeutics for the prevention and treatment of COVID-19. Here, we identified high-affinity nanobodies from alpacas immunized with coronavirus spike and receptor-binding domains (RBD) that disrupted RBD engagement with the human receptor angiotensinconverting enzyme 2 (ACE2) and potently neutralized SARS-CoV-2. Epitope mapping, X-ray crystallography, and cryo-electron microscopy revealed two distinct antigenic sites and showed two neutralizing nanobodies from different epitope classes bound simultaneously to the spike trimer. Nanobody-Fc fusions of the four most potent nanobodies blocked ACE2 engagement with RBD variants present in human populations and potently neutralized both wild-type SARS-CoV-2 and the N501Y D614G variant at concentrations as low as 0.1 nM. Prophylactic administration of either single nanobodyFc or as mixtures reduced viral loads by up to 104-fold in mice infected with the N501Y D614G SARS-CoV-2 virus. These results suggest a role for nanobody-Fc fusions as prophylactic agents against SARS-CoV-2.

Automated summary

Neutralizing antibodies, particularly nanobodies, play a crucial role in immunity against SARS-CoV-2 and in the development of therapeutics for COVID-19. Researchers have identified high-affinity nanobodies that effectively disrupt the interaction between the virus and the human host cell receptor ACE2, offering promising prophylactic potential against SARS-CoV-2. Studies have shown that nanobody-Fc fusions can block viral engagement with host cells and significantly reduce viral loads in infected mice, suggesting their use as preventive agents against COVID-19.