[Isolation of anti-SARS-CoV-2 neutralizing monoclonal antibodies cross effective to variants aiming at antibody therapy].

We isolated five mAbs with potent neutralizing activities against SARS-CoV-2 from two convalescent COVID-19 patients infected with prototype virus. Among them, the 9-105 antibody that have a highest affinity for the receptor-binding domain (RBD), cross-neutralize variants, such as B.1.1.7 (alfa), mink cluster 5 variant, B.1.351 (beta), P.1 (gamma), C.37 (lambda), B.1.617.1 (kappa), B.1.617.2 (delta) and B.1.621 (mu). A single amino acid mutation at K417 of RBD decreased neutralization sensitivity of 9-105. A 9-105 homology model revealed that 9-105 light chain binds to RBD including K417 by the same angle as ACE2.