Science - USA (2022-03-04)

OC43 and HKU1 S proteins at both sampling
time points. At the preboost time point, we de-
tected significantly elevated serum antibody
titers to both OC43 and HKU1 relative to pre-
pandemic sera samples, suggesting a“back-
boosting”of preexisting cross-reactive MBCs
induced by seasonalb-CoV infections (Fig. 1,
F and G). However, this response was not fur-
ther amplified after homologous or heterolo-
gous booster immunization.
We next evaluated serum neutralizing ac-
tivity against authentic SARS-CoV-2 D614G,
B.1.617.2/Delta, B.1.351/Beta, and B.1.1.529/

Omicron variants at both sampling time points.

At the preboost time point, the vast majority

of donors (87%) displayed weak or undetect-

able serum neutralizing activity against SARS-

CoV-2 D614G, with 50% neutralization titers

ranging from <16 to 66 (Fig. 1H), and none

of the donors showed detectable serum neu-

tralization against Beta, Delta, or Omicron

(Fig. 1, I to K). Homologous ChAdOx1 booster

immunization resulted in an overall 4.6-fold

increase in serum neutralizing activity against

SARS-CoV-2 D614G (geometric mean titer =

82), but neutralizing titers remained at the

lower limit of detection in 21% (6 of 28) of

donors (Fig. 1H). In about half of the individuals,

we also observed a small but significant (1.5 to

2.4-fold) rise in serum neutralizing activity

against Beta and Delta after ChAdOx1 booster

immunization (Fig. 1, I and J), but none of the

donor sera exhibited detectable neutralization

against Omicron (Fig. 1K). In contrast to the

relatively weak serum neutralizing responses

observed after two doses of ChAdOx1, hete-

rologous mRNA-1273 booster vaccination sig-

nificantly enhanced serum neutralizing titers

to SARS-CoV-2 D614G, Beta, and Delta in all

1044 4 MARCH 2022•VOL 375 ISSUE 6584 science.orgSCIENCE

ChAdOx1:ChAdOx1 ChAdOx1:mRNA-1273

1 2 3 4 1 2 3 4

A B

CD

E

0.1

10

>100

0

20

40

60

80

100

S-2P K^1

(nM)D

Proportion of antibodies (%)

Proportion of antibodies (%)

ChAdOx1:

ChAdOx1

ChAdOx1:

mRNA-1273

(55%) (41%)

UM-1UM-2UM-3UM-4UM-5UM-6UM-7UM-8

<50%

50-80%

>80%

% Neutralization

at 1 μg/ml

ChAdOx1:ChAdOx1 ChAdOx1:mRNA-1273

0

20

40

60

80

100

UM-1UM-2UM-3UM-4UM-5UM-6UM-7UM-8

NTD

RBD - ACE2

competitive

RBD - ACE2

noncompetitive

S2

K417NE484KF490SL452RG446VK378NACE2Neut. K417NE484KF490SL452RG446VK378N

Antibody class:

RBD mutant:

ChAdOx1:ChAdOx1 ChAdOx1:mRNA-1273

ADI-69654

ADI-69496

ADI-69611

ADI-69677

ADI-69547

ADI-69705

ADI-69550

ADI-69766

ADI-69742

ADI-69688

ADI-69785

ADI-69652

ADI-69828

ADI-69527

ADI-69835

ADI-69843

ADI-69772

ADI-69717

ADI-69799

ADI-69568

ADI-69480

ADI-69661

ADI-69818

ADI-69715

ADI-69503

ADI-69836

ADI-69704

ADI-69626

ADI-69721

ADI-69987

ADI-69905

ADI-70147

ADI-69889

ADI-70032

ADI-69960

ADI-69936

ADI-69918

ADI-69941

ADI-70026

ADI-70156

ADI-70052

ADI-70048

ADI-70194

ADI-69963

ADI-70082

ADI-70034

ADI-69916

ADI-69965

ADI-69932

ADI-70149

ADI-70040

ADI-70171

ADI-70008

ADI-70232

ADI-69973

ADI-69964

ADI-70080

ADI-69996

ADI-70139

ADI-69882

ADI-70186

ADI-69979

ADI-70172

ADI-69978

ADI-69982

ADI-70133

ADI-70176

ADI-70246

ADI-70037

ACE2Neut.

Fold change

in KD

<2

2-10

>10 <50%

50-80%

>80%

% Neutralization

No

Yes

ACE2

competition

ChAdOx1:ChAdOx1 ChAdOx1:mRNA-1273

(^2940)
Antibody class
1
1/2
2
2/3
3
4
Donor ID:
Donor ID:
Fig. 3. Binding and neutralization properties of monoclonal antibodies isolated
from ChAdOx1- and mRNA-1273Ðboosted donors.(A) Fab binding affinities for
S-2P, as determined with BLI. Antibodies with no detectable monovalent binding
activity are excluded, and those with weak binding affinities that could not be fit to
a 1:1 binding model are plotted asKd>100 nM. Black bars indicate medians. Values in
parentheses indicate the percentage of antibodies withKd>100 nM. (B) Proportion
of antibodies exhibiting <50%, 50 to 80%, and >80% neutralization activity against
MLV-SARS-CoV-2 Wuhan-1 at a concentration of 1mg/ml. (C) Proportion of S-2PÐ
reactive antibodies directed to each of the indicated subdomains within prefusion S.
Competitive hACE2 binding was determined by using a BLI-based competition assay.
(D) Heatmaps displaying fold change in binding affinity of antibodies to RBD to
variant RBDs containing the indicated single point mutations. Competitive hACE2
binding activity and percentage neutralization against MLV-SARS-CoV-2 Wuhan-1 at
a concentration of 1mg/ml are shown in the bars on the right. (E) Summary of the
distribution of antibodies to RBD belonging to each of the indicated classes. The
numbers in the center of the pies indicate the total number of antibodies analyzed.
Statistical comparisons were made by mewans of (A) two-sided Mann-Whitney
Utests.KD,equilibrium dissociation constant. **P< 0.01.
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