Figure 3.

Affinity-matured nanobodies potently neutralize SARS-CoV-2 pseudovirus and live virus

(A) Neutralization results for nanobodies as bivalent Fc-fusion proteins (KA1, KC3, KA1.ep1, KC3.ep3, KC3.ep5, and Ty1) and an antibody (CB6) for inhibiting pseudovirus infectivity in a luciferase-based, HEK293T reporter cell line. Pseudovirus particles were preincubated with antibodies and added to reporter cells, and luciferase signal was measured after 48 h.

(B) Neutralization results for nanobodies as bivalent Fc-fusion proteins (KC3.ep3, Ty1) and antibodies (CB6) for inhibiting live virus infection of VeroE6 cells. Nanobody and antibody dilutions were tested in eight replicate wells each. After cells were incubated with virus and nanobodies or antibody for 3 days, the cells were examined microscopically for visible cytopathic effect. Wells with any degree of visible, virus-induced cytopathic effect were scored as positive for infection. In (A), the data are averages of four or five repeats, and the error bars are standard deviations. In (B), the data are averages of two to four repeats, and the error bars are standard deviations.