Structural Characterization of a Neutralizing Nanobody With Broad Activity Against SARS-CoV-2 Variants.
Front Microbiol
; 13: 875840, 2022.
Article
in English
| MEDLINE | ID: covidwho-1903080
ABSTRACT
SARS-CoV-2 and its variants, such as the Omicron continue to threaten public health. The virus recognizes the host cell by attaching its Spike (S) receptor-binding domain (RBD) to the host receptor, ACE2. Therefore, RBD is a primary target for neutralizing antibodies and vaccines. Here, we report the isolation and biological and structural characterization of a single-chain antibody (nanobody) from RBD-immunized alpaca. The nanobody, named DL28, binds to RBD tightly with a K D of 1.56 nM and neutralizes the original SARS-CoV-2 strain with an IC50 of 0.41 µg mL-1. Neutralization assays with a panel of variants of concern (VOCs) reveal its wide-spectrum activity with IC50 values ranging from 0.35 to 1.66 µg mL-1 for the Alpha/Beta/Gamma/Delta and an IC50 of 0.66 µg mL-1 for the currently prevalent Omicron. Competition binding assays show that DL28 blocks ACE2-binding. However, structural characterizations and mutagenesis suggest that unlike most antibodies, the blockage by DL28 does not involve direct competition or steric hindrance. Rather, DL28 may use a "conformation competition" mechanism where it excludes ACE2 by keeping an RBD loop in a conformation incompatible with ACE2-binding.
Full text:
Available
Collection:
International databases
Database:
MEDLINE
Topics:
Vaccines
/
Variants
Language:
English
Journal:
Front Microbiol
Year:
2022
Document Type:
Article
Affiliation country:
Fmicb.2022.875840
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