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Title: Efficacy and breadth of adjuvanted SARS-CoV-2 receptor-binding domain nanoparticle
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vaccine in macaques
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Authors: Hannah A. D. King,
a,b,c,1
M. Gordon Joyce,
b,c,1
Ines Elakhal Naouar,
c,d
Aslaa
4
Ahmed,
e
Camila Macedo Cincotta,
c,d
Caroline Subra,
a,b,c
Kristina K. Peachman,
d
Holly H.
5
Hack,
c,d
Rita E. Chen,
f,g
Paul V. Thomas,
b,c
Wei-Hung Chen,
b,c
Rajeshwer S. Sankhala,
b,c
Agnes
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Hajduczki,
b,c
Elizabeth J. Martinez,
b,c
Caroline E. Peterson,
b,c
William C. Chang,
b,c
Misook
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Choe,
b,c
Clayton Smith,
h
Jarrett A. Headley,
b,c
Hanne A. Elyard,
i
Anthony Cook,
i
Alexander
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Anderson,
a,b,c
Kathryn McGuckin Wuertz,
a
Ming Dong,
a,b,c
Isabella Swafford,
a,b,c
James B.
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Case,
f
Jeffrey R. Currier,
e
Kerri G. Lal,
a,b,c
Mihret F. Amare,
b,c
Vincent Dussupt,
a,b,c
Sebastian
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Molnar,
a,b,c
Sharon P. Daye,
j
Xiankun Zeng,
k
Erica K. Barkei,
l
Kendra Alfson,
m
Hilary M. Staples,
m
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Ricardo Carrion,
m
Shelly J. Krebs,
a,b,c
Dominic Paquin-Proulx,
a,b,c
Nicos Karasavvas,
c,d
Victoria R.
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Polonis,
a
Linda L. Jagodzinski,
d
Sandhya Vasan,
a,b,c
Paul T. Scott,
b
Yaoxing Huang,
n
Manoj S.
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Nair,
n
David D. Ho,
n
Natalia de Val,
h
Michael S. Diamond,
f,g
Mark G. Lewis,
i
Mangala Rao,
a
Gary
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R. Matyas,
a
Gregory D. Gromowski,
e
Sheila A. Peel,
d
Nelson L. Michael,
j,2
Kayvon
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Modjarrad
b,2.3
and Diane L. Bolton
a,b,c,2,3
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Author Affiliations:
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a
US Military HIV Research Program, Walter Reed Army Institute of Research (WRAIR), Silver Spring
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MD 20910, USA.
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b
Emerging Infectious Diseases Branch, WRAIR, Silver Spring MD 20910, USA.
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c
Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda MD 20817, USA.
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d
Diagnostics and Countermeasures Branch, WRAIR, Silver Spring MD 20910, USA.
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e
Viral Diseases Branch, WRAIR, Silver Spring MD 20910, USA.
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f
Department of Medicine and
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Pathology & Immunology, Washington University, St. Louis, MO
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63130, USA.
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h
Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, National
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Institutes of Health, Frederick, MD 21702, USA.
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i
BIOQUAL, Inc., Rockville, MD 20850, USA.
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j
Center for Infectious Diseases Research, WRAIR, Silver Spring MD 20910, USA.
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k
Division of Pathology, United States Army Medical Research Institute of Infectious Diseases,
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Frederick, MD 21702, USA.
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l
Veterinary Pathology Branch, WRAIR, Silver Spring MD 20910, USA.
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m
Disease Intervention and Prevention, Texas Biomedical Research Institute, San Antonio TX 78227,
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USA.
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n
Aaron Diamond AIDS Research Center, Columbia University Vagelos College of Physicians and
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Surgeons, New York, NY, USA.
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1
These authors contributed equally to this work.
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2
These authors contributed equally to this work.
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3
To whom correspondence may be addressed: Dr. Kayvon Modjarrad and Dr. Diane L. Bolton,
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Emerging Infectious Diseases Branch and US Military HIV Research Program, WRAIR, 503 Robert
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Grant Ave, Silver Spring, MD 20910 USA. Phone: 301-319-3054 and 301-319-3151. E-mail:
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kayvon.modjarrad.civ@mail.mil and dbolton@hivresearch.org
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (whichthis version posted April 10, 2021. ; https://doi.org/10.1101/2021.04.09.439166doi: bioRxiv preprint
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ABSTRACT
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Emergence of novel variants of the severe acute respiratory syndrome coronavirus-2 (SARS-
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CoV-2) underscores the need for next-generation vaccines able to elicit broad and durable
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immunity. Here we report the evaluation of a ferritin nanoparticle vaccine displaying the
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receptor-binding domain of the SARS-CoV-2 spike protein (RFN) adjuvanted with Army
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Liposomal Formulation QS-21 (ALFQ). RFN vaccination of macaques using a two-dose regimen
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resulted in robust, predominantly Th1 CD4+ T cell responses and reciprocal peak mean
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neutralizing antibody titers of 14,000-21,000. Rapid control of viral replication was achieved in
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the upper and lower airways of animals after high-dose SARS-CoV-2 respiratory challenge, with
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undetectable replication within four days in 7 of 8 animals receiving 50 µg RFN. Cross-
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neutralization activity against SARS-CoV-2 variant B.1.351 decreased only ~2-fold relative to
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USA-WA1. In addition, neutralizing, effector antibody and cellular responses targeted the
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heterotypic SARS-CoV-1, highlighting the broad immunogenicity of RFN-ALFQ for SARS-like
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betacoronavirus vaccine development.
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Keywords: SARS-CoV-2, vaccine, receptor-binding domain
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Significance Statement
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The emergence of SARS-CoV-2 variants of concern (VOC) that reduce the efficacy of current
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COVID-19 vaccines is a major threat to pandemic control. We evaluate a SARS-CoV-2 Spike
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receptor-binding domain ferritin nanoparticle protein vaccine (RFN) in a nonhuman primate
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challenge model that addresses the need for a next-generation, efficacious vaccine with increased
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pan-SARS breadth of coverage. RFN, adjuvanted with a liposomal-QS21 formulation (ALFQ),
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (whichthis version posted April 10, 2021. ; https://doi.org/10.1101/2021.04.09.439166doi: bioRxiv preprint
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elicits humoral and cellular immune responses exceeding those of current vaccines in terms of
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breadth and potency and protects against high-dose respiratory tract challenge. Neutralization
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activity against the B.1.351 VOC within two-fold of wild-type virus and against SARS-CoV-1
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indicate exceptional breadth. Our results support consideration of RFN for SARS-like
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betacoronavirus vaccine development.
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (whichthis version posted April 10, 2021. ; https://doi.org/10.1101/2021.04.09.439166doi: bioRxiv preprint
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INTRODUCTION
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The coronavirus infectious disease 2019 (COVID-19) pandemic, precipitated by severe acute
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respiratory syndrome coronavirus-2 (SARS-CoV-2), continues to threaten global public health
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and economies. Threats of future outbreaks also loom, as evidenced by three emergent SARS-
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like diseases caused by zoonotic betacoronaviruses in the last two decades. While several
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emergency use authorized (EUA) vaccines currently in use are expected to curb both disease and
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transmission of SARS-CoV-2 (1-6), the emergence of circulating variants of concern (VOC) less
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sensitive to vaccine-elicited immunity has raised concerns for sustained vaccine efficacy (7).
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Logistic challenges of vaccine production, distribution, storage and access for these vaccines will
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need to be resolved equitably to achieve resolution to the pandemic (8, 9). The rapid and
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unparalleled spread of SARS-CoV-2 has driven an urgent need to deploy scalable vaccine
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platforms to combat the ongoing pandemic and mitigate future outbreaks.
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Current vaccines primarily focus the immune response to the spike glycoprotein (S) on the virion
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surface as it mediates host cell viral fusion and entry. The receptor-binding domain (RBD) of S
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engages the primary host cell receptor, Angiotensin-converting enzyme 2 (ACE2), for both
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SARS-CoV-2 and SARS-CoV-1, making RBD a promising domain for vaccine elicited immune
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focus (10-12). Moreover, many of the potently neutralizing monoclonal antibodies isolated
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against SARS-CoV-2 target the RBD (13, 14). Vaccination of nonhuman primates with RBD-
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encoding RNA or DNA protects against respiratory tract challenge, indicating that immune
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responses to the RBD can prevent viral replication (15, 16). RBD vaccination also elicits cross-
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reactive responses to circulating SARS-CoV-2 VOC in both animals and humans (17, 18), with
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decrements against the more difficult to neutralize B.1.351 variant similar to that seen with S
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (whichthis version posted April 10, 2021. ; https://doi.org/10.1101/2021.04.09.439166doi: bioRxiv preprint
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immunogens (19). The breadth of RBD immunogenicity is further supported by the ability of
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RBD-specific monoclonal antibodies isolated from SARS-CoV-1 convalescent individuals to
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cross-neutralize SARS-CoV-2 (20, 21). These findings suggest potential for RBD-based
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vaccines being efficacious against SARS-CoV-2 variants and other coronavirus species.
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Approaches to improve immunogenicity of S or RBD protein vaccines include optimizing
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antigen presentation and co-formulating with adjuvants to enhance the protective immunity. One
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common approach to enhance the elicitation of adaptive immune responses is the multimeric
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presentation of antigen, for example, on the surface of nanoparticles or virus-like particles (22).
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Presenting RBD in ordered, multivalent arrays on the surface of self-assembling protein
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nanoparticles is immunogenic and efficacious in animals (23-28), with improved
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immunogenicity relative to monomeric soluble RBD and cross-reactive responses to variants (17,
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24, 26). However, it is unknown whether RBD nanoparticle vaccines are able to protect against
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infection in primates, which have become a standard model for benchmarking performance of
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vaccine candidates. Liposomal adjuvants incorporating QS-21, such as that used in the
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efficacious varicella zoster vaccine, SHINGRIX
®
, may augment protective immunity to SARS-
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CoV-2 vaccines. Such adjuvants have previously demonstrated superior humoral and cellular
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immunogenicity relative to conventional adjuvants (29, 30).
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Here, we evaluate the use of a ferritin nanoparticle vaccine presenting the SARS-CoV-2 RBD
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(RFN) adjuvanted with the Army Liposomal Formulation QS-21 (ALFQ) (31). Both ferritin
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nanoparticles and ALFQ have been evaluated for vaccination against multiple pathogens in
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humans in phase 1 clinical trials (32-34). We demonstrate in a nonhuman primate model that
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was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
The copyright holder for this preprint (whichthis version posted April 10, 2021. ; https://doi.org/10.1101/2021.04.09.439166doi: bioRxiv preprint