Immune Correlates of Protection by mRNA-1273 Immunization against SARS-CoV-2 Infection in Nonhuman Primates

TLDR: In this article, a nonhuman primate (NHP) model of SARS-CoV-2 infection replicates key features of human infection and may be used to define immune correlates of protection following vaccination.

Abstract: Immune correlates of protection can be used as surrogate endpoints for vaccine efficacy. The nonhuman primate (NHP) model of SARS-CoV-2 infection replicates key features of human infection and may be used to define immune correlates of protection following vaccination. Here, NHP received either no vaccine or doses ranging from 0.3 – 100 μg of mRNA-1273, a mRNA vaccine encoding the prefusion-stabilized SARS-CoV-2 spike (S-2P) protein encapsulated in a lipid nanoparticle. mRNA-1273 vaccination elicited robust circulating and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly reduced in bronchoalveolar lavages and nasal swabs following SARS-CoV-2 challenge in vaccinated animals and was most strongly correlated with levels of anti-S antibody binding and neutralizing activity. Consistent with antibodies being a correlate of protection, passive transfer of vaccine-induced IgG to naive hamsters was sufficient to mediate protection. Taken together, these data show that mRNA-1273 vaccine-induced humoral immune responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP. One-Sentence Summary mRNA-1273 vaccine-induced antibody responses are a mechanistic correlate of protection against SARS-CoV-2 infection in NHP.

Figures

Fig. 3. Efficacy of mRNA-1273 against upper and lower respiratory viral replication. Rhesus macaques were immunized and challenged as described in Fig. S1C. BAL (A) and nasal swabs (NS) (B) were collected on days 2 (squares), 4 (triangles), and 7 (diamonds) post-challenge, and viral replication was assessed by detection of SARS-CoV-2 N-specific sgRNA. (A-B) Boxes and horizontal bars denote the IQR and medians, respectively; whisker end points are equal to the maximum and minimum values. (C-E) Correlations shown between BAL and NS sgRNA at days 2 (C), 4 (D), and 7 (E) post-challenge are Spearman’s correlation coefficients (r) and corresponding p-values. Symbols represent individual NHP and may overlap, ie. n=6 animals plotted at assay limit (dotted line) for both BAL and NS in (E).

Fig. 2. Correlations of humoral antibody analyses. Rhesus macaques were immunized according to Fig. S1C. Plots show correlations between SARS-CoV-2 S-specific IgG, RBDspecific IgG, ACE2 binding inhibition, lentiviral-based pseudovirus neutralization, VSV-based pseudovirus neutralization, and EHC-83E focus reduction neutralization at 4 weeks post-boost. Circles represent individual NHP, where colors indicate mRNA-1273 dose as defined in Fig. S1C. Dotted lines indicate assay limits of detection. Black and gray lines indicate linear regression and 95% confidence interval, respectively. 'r’ represents Spearman’s correlation coefficients, and ‘p’ the corresponding p-values.

Fig. 5. Passive transfer of mRNA-1273 immune NHP IgG into Syrian hamsters. (A) Sera were pooled from all NHP that received 100 µg of mRNA-1273 in a primary vaccination series. (B) mRNA-1273 immune NHP IgG (2 mg, yellow or 10 mg, orange) or pre-immune NHP IgG (10 mg, gray) was passively transferred to Syrian hamsters (n = 8/group) 24 hours prior to SARSCoV-2 challenge. Twenty-three hours post-immunization, hamsters were bled to quantify circulating S-specific IgG (C) and SARS-CoV-2 pseudovirus neutralizing antibodies (D). Following challenge, hamsters were monitored for weight loss (E). (C-D) Circles represent individual NHP. Bars and error bars represent GMT and geometric SD, respectively. Asterisks at the axis represent animals that did not receive adequate IgG via passive transfer and were thus excluded from weight loss analyses. (D) The dotted line indicates the neutralization assay limit of detection. (E) Circle and error bars represent mean and SEM, respectively.

Fig. 1. Antibody responses following mRNA-1273 immunization. Rhesus macaques were immunized according to Fig. S1 with PBS (gray) or mRNA-1273 (0.3 µg – green, 1 µg – purple, 3 µg – orange, 10 µg – blue, 30 µg – pink, or 100 µg – red). Sera collected 4 weeks post-boost, immediately before challenge, were assessed for SARS-CoV-2 S-specific (A) and RBD-specific (B) IgG by MULTI-ARRAY ELISA, inhibition of ACE2 binding to RBD (C), SARS-CoV-2 lentiviral-based pseudovirus neutralization (D), SARS-CoV-2 VSV-based pseudovirus

Full text

Title: Immune Correlates of Protection by mRNA-1273 Immunization against
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SARS-CoV-2 Infection in Nonhuman Primates
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Authors: Kizzmekia S. Corbett
1#
, Martha C. Nason
2#
, Britta Flach
1
, Matthew Gagne
1
, Sarah O’
4
Connell
1
, Timothy S. Johnston
1
, Shruti N. Shah
1
,
Venkata Viswanadh Edara
3
, Katharine Floyd
3
,
5
Lilin Lai
3
, Charlene McDanal
4
, Joseph R. Francica
1
, Barbara Flynn
1
, Kai Wu
5
, Angela Choi
5
,
6
Matthew Koch
5
, Olubukola M. Abiona
1
, Anne P. Werner
1
, Gabriela S. Alvarado
1
, Shayne F.
7
Andrew
1
, Mitzi M. Donaldson
1
, Jonathan Fintzi
1
, Dillon R. Flebbe
1
, Evan Lamb
1
, Amy T. Noe
1
,
8
Saule T. Nurmukhambetova
1
, Samantha J. Provost
1
, Anthony Cook
6
, Alan Dodson
6
, Andrew
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Faudree
6
, Jack Greenhouse
6
, Swagata Kar
6
, Laurent Pessaint
6
, Maciel Porto
6
, Katelyn
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Steingrebe
6
, Daniel Valentin
6
, Serge Zouantcha
6
,
Kevin W. Bock
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, Mahnaz Minai
7
, Bianca M.
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Nagata
7
, Juan I. Moliva
1
, Renee van de Wetering
1
, Seyhan Boyoglu-Barnum
1
, Kwanyee Leung
1
,
12
Wei Shi
1
, Eun Sung Yang
1
, Yi Zhang
1
, John-Paul M. Todd
1
, Lingshu Wang
1
, Hanne Andersen
6
,
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Kathryn E. Foulds
1
, Darin K. Edwards
5
, John R. Mascola
1
, Ian N. Moore
7
, Mark G. Lewis
6
,
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Andrea Carfi
5
, David Montefiori
4
, Mehul S. Suthar
3,8
, Adrian McDermott
1
, Nancy J. Sullivan
1
,
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Mario Roederer
1
, Daniel C. Douek
1
, Barney S. Graham
1
*, and Robert A. Seder
1
*
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Affiliations:
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1
Vaccine Research Center; National Institute of Allergy and Infectious Diseases; National
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Institutes of Health; Bethesda, Maryland, 20892; United States of America
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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 23, 2021. ; https://doi.org/10.1101/2021.04.20.440647doi: bioRxiv preprint

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Biostatistics Research Branch, Division of Clinical Research, National Institute of Allergy and
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Infectious Diseases, National Institutes of Health; Bethesda, Maryland, 20892; United States of
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America
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Center for Childhood Infections and Vaccines of Children's Healthcare of Atlanta, Department
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of Pediatrics, Department of Microbiology and Immunology, Emory Vaccine Center, Emory
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University, Atlanta, Georgia, 30322, United States of America
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4
Department of Surgery, Duke University Medical Center, Durham, North Carolina, 27708;
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United States of America.
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5
Moderna Inc., Cambridge, MA, 02139; United States of America
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6
Bioqual, Inc.; Rockville, Maryland, 20850; United States of America
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Infectious Disease Pathogenesis Section;
National Institute of Allergy and Infectious Diseases;
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National Institutes of Health; Bethesda, Maryland, 20892; United States of America
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Department of Microbiology and Immunology; Emory University; Atlanta, Georgia, 30329,
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United States of America
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#
Authors have equal contribution to this study
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*Correspondence: rseder@mail.nih.gov and bgraham@nih.gov
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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 23, 2021. ; https://doi.org/10.1101/2021.04.20.440647doi: bioRxiv preprint

Abstract: Immune correlates of protection can be used as surrogate endpoints for vaccine
39
efficacy. The nonhuman primate (NHP) model of SARS-CoV-2 infection replicates key features
40
of human infection and may be used to define immune correlates of protection following
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vaccination. Here, NHP received either no vaccine or doses ranging from 0.3 – 100 µg of
42
mRNA-1273, a mRNA vaccine encoding the prefusion-stabilized SARS-CoV-2 spike (S-2P)
43
protein encapsulated in a lipid nanoparticle. mRNA-1273 vaccination elicited robust circulating
44
and mucosal antibody responses in a dose-dependent manner. Viral replication was significantly
45
reduced in bronchoalveolar lavages and nasal swabs following SARS-CoV-2 challenge in
46
vaccinated animals and was most strongly correlated with levels of anti-S antibody binding and
47
neutralizing activity. Consistent with antibodies being a correlate of protection, passive transfer
48
of vaccine-induced IgG to naïve hamsters was sufficient to mediate protection. Taken together,
49
these data show that mRNA-1273 vaccine-induced humoral immune responses are a mechanistic
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correlate of protection against SARS-CoV-2 infection in NHP.
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One-Sentence Summary: mRNA-1273 vaccine-induced antibody responses are a mechanistic
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correlate of protection against SARS-CoV-2 infection in NHP.
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54
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 23, 2021. ; https://doi.org/10.1101/2021.04.20.440647doi: bioRxiv preprint

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of
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coronavirus disease 2019 (COVID-19), has led to more than 138 million infections and 3 million
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deaths worldwide as of April 15, 2021 (1). Mass vaccination offers the most efficient public
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health intervention to control the pandemic. Two mRNA-based vaccines, Moderna’s mRNA-
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1273 and Pfizer/BioNTech’s BNT 162b2, both of which encode the prefusion-stabilized spike
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glycoprotein (S-2P) (2, 3), showed >94% efficacy against symptomatic COVID-19 in interim
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Phase 3 analyses (4, 5) and are currently being administered globally. Several other vaccines
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have shown 60-80% efficacy against COVID-19 in Phase 3 trials (6, 7), and a number of
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candidate vaccines are in earlier stages of clinical development (8). A critical issue for
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optimizing the use of COVID-19 vaccines is defining an immune correlate of protection. This
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surrogate of vaccine efficacy can be used to inform potential dose reduction, advance approval of
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other vaccine candidates in lieu of Phase 3 efficacy data, extend indications for use to other age
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groups, and provide insights into the immune mechanisms of protection (9).
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The nonhuman primate (NHP) model has been used to demonstrate immunogenicity and
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protective efficacy against SARS-CoV-2 with a number of vaccine candidates (10-13). The high
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level of protection achieved with mRNA vaccines in NHP using clinically relevant dose
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regimens has been consistent with results from human trials. This model exhibits upper and
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lower airway infection and pathology similar to clinical presentations of mild COVID-19 disease
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in humans (14). While assessment of immune correlates of viral load after primary infection has
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been completed in NHP (15), there are no studies to date that have specifically defined immune
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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 23, 2021. ; https://doi.org/10.1101/2021.04.20.440647doi: bioRxiv preprint

correlates of protection in upper and lower airways after vaccination with any product approved
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for use in humans.
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We used immunogenicity and protection assessments from our previous NHP mRNA-1273
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vaccine study (13) to hypothesize that serum antibody measurements serve as immune correlates
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of protection. Here, in a dose de-escalation study, we evaluated how multiple measurements of
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humoral and cellular immunity correlate with the reduction of viral replication in the upper and
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lower airway following challenge. Antibody analyses were also performed on bronchoalveolar
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lavages (BAL) and nasal washes after vaccination to assess site-specific immune correlates. Last,
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we demonstrated the ability of passively transferred IgG from mRNA-immunized NHP to
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mediate protection in a highly pathogenic Syrian hamster SARS-CoV-2 challenge model.
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Together, these studies support spike (S)-specific antibodies as a correlate of protection,
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highlight the ability of localized mucosal antibodies to control upper and lower airway viral
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replication, and confirm mRNA-1273-induced IgG to be sufficient for protection against SARS-
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CoV-2 infection in preclinical models.
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Results
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mRNA-1273 vaccination elicits robust antibody responses in a dose-dependent manner
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We previously demonstrated dose-dependency of serum antibody responses in NHP following
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vaccination with 10 or 100 µg of mRNA-1273, with high-level protection against SARS-CoV-2
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challenge in both dose groups (Fig. S1A) (13). These and other immunogenicity outcomes from
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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 23, 2021. ; https://doi.org/10.1101/2021.04.20.440647doi: bioRxiv preprint

Frequently asked questions

Q1. What are the contributions in "Title: immune correlates of protection by mrna-1273 immunization against 1 sars-cov-2 infection in nonhuman primates" ?

The nonhuman primate ( NHP ) model of SARS-CoV-2 infection replicates key features 40 of human infection and may be used to define immune correlates of protection following 41 vaccination. Here, NHP received either no vaccine or doses ranging from 0. 3 – 100 μg of 42 mRNA-1273, a mRNA vaccine encoding the prefusion-stabilized SARS-CoV-2 spike ( S-2P ) 43 protein encapsulated in a lipid nanoparticle. 51 One-Sentence Summary: mRNA-1273 vaccine-induced antibody responses are a mechanistic 52 correlate of protection against SARS-CoV-2 infection in NHP. 53 54 was not certified by peer review ) is the author/funder.