Sartorius_May21_NeutAntiMakingTheir - 38

Octet® Bio-Layer Interferometry Systems

CoV-2 Secto domain (KD = 10.8 nM) although similar

to SARS CoV-2 S protein. To gain more insight on

binding affinities were reported for binding

the epitopes recognized by the panel of mAbs, an

to the SARS CoV and SARS CoV-2 RBD binding

Octet® epitope binning assay was carried out to

domains, further validating the differences in

map the antigenic sites present on the SARS CoV

epitope accessibility between the two virus

and, SARS-CoV-2 RBDs.

receptor binding motif (RBM) conformations.

Octet® epitope binning analysis identified

Additionally, as in other cases reported thus far,

four antigenic regions within the RBD of

47D11 did not compete with the SARS CoV or

SARS CoV where the mAbs were targeting.

SARS CoV-2 RBD, implying neutralization through

Based on these findings, mAb combinations

a mode that is different from receptor blocking.

that targeted different antigenic regions were

This cross-neutralizing antibody reportedly

tested for neutralization potencies and possible

targets a communal epitope and offers potential

synergistic effects where data indicated that

for prevention and treatment of SARS CoV-2.

either S304 or S315 in combination with S309

Pinto et al. screened for nAbs from a SARS CoV

enhanced neutralization potencies against

survivor7. Eight mAbs from the screen bound

SARS CoV-2. S309 identified in this work showed

to both SARS CoV and SARS CoV-2 S protein-

broad neutralization activity against multiple

transfected CHO cells, out of which mAbs S303,

sarbecoviruses showing promise as an effective

S304, S309 and S315 recognized both SARS

therapeutic candidate.

CoV and SARS CoV-2 RBDs. Octet® system data

Pan et al. used the SARS CoV-2 RBD domain

indicated S309 binding to both S domains with

to produce neutralization antibodies in horse

similar nanomolar affinities and also showed

antisera6. F(ab')2s isolated from horse antisera

comparable neutralization potencies against

reportedly showed neutralization activity against

both SARS CoV and CoV-2 pseudo- viruses and

SARS CoV-2 with an EC80 of ~25 µg/mL. Octet®

authentic SARS-CoV-2. According to structural

BLI kinetic analysis also confirmed SARS CoV-2

data, S309 recognizes a protein/glycan epitope

receptor binding to F(ab')2 with an affinity of 76

on the SARS CoV-2 RBD distinct from the

nM. Affinity purification of F(ab')2 from antisera

receptor-binding motif (RBM) and seems to be

improved neutralization activity against SARS

accessible to both up and down states.

CoV-2 (EC80 = 0.18 µg/mL) and increased

Octet® BLI competition assays showed that

binding affinity (0.76 nM) measured by Octet® BLI,

binding of S309 Fab and IgG forms to SARS CoV-2

highlighting RBD-specific F(ab')2 as a potential

RBD did not discourage ACE2 receptor binding

therapeutic candidates for SARS CoV-2.

38 |


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