SARS-CoV-2 spike glycoprotein vaccine candidate NVX-CoV2373 immunogenicity in baboons and protection in mice

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Abstract

The COVID-19 pandemic continues to spread throughout the world with an urgent need for a safe and protective vaccine to effectuate herd protection and control the spread of SARS-CoV-2. Here, we report the development of a SARS-CoV-2 subunit vaccine (NVX-CoV2373) from the full-length spike (S) protein that is stable in the prefusion conformation. NVX-CoV2373 S form 27.2-nm nanoparticles that are thermostable and bind with high affinity to the human angiotensin-converting enzyme 2 (hACE2) receptor. In mice, low-dose NVX-CoV2373 with saponin-based Matrix-M adjuvant elicit high titer anti-S IgG that blocks hACE2 receptor binding, neutralize virus, and protects against SARS-CoV-2 challenge with no evidence of vaccine-associated enhanced respiratory disease. NVX-CoV2373 also elicits multifunctional CD4 + and CD8 + T cells, CD4 + follicular helper T cells (Tfh), and antigen-specific germinal center (GC) B cells in the spleen. In baboons, low-dose levels of NVX-CoV2373 with Matrix-M was also highly immunogenic and elicited high titer anti-S antibodies and functional antibodies that block S-protein binding to hACE2 and neutralize virus infection and antigen-specific T cells. These results support the ongoing phase 1/2 clinical evaluation of the safety and immunogenicity of NVX-CoV2373 with Matrix-M (NCT04368988).

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  1. SciScore for 10.1101/2020.06.29.178509: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIACUC: EC50 values were calculated by 4-parameter fitting using GraphPad Prism 7.05 software Animal ethics statement: The mouse immunogenicity studies were performed by Noble Life Sciences (Sykeville, MD).
    RandomizationBaboon study design: Ten adult baboons (10-16 years of age) were randomized into 4 groups of 2-3/group and immunized by IM injection with 1, 5 or 25 μg NVX-CoV2373 with 50 μg Matrix-M adjuvant.
    BlindingSlides were examined in a blinded fashion for total inflammation, periarteriolar, and peribronchiolar inflammation and epithelial cell denuding.
    Power Analysisnot detected.
    Sex as a biological variableMouse study designs: Female BALB/c mice (7-9 weeks old, 17-22 grams, N = 10 per group) were immunized by intramuscular (IM) injection with a single dose (study day 14) or two doses spaced 14-days apart (study day 0 and 14) containing a dose range (0.01, 0.1, 1.0, or 10 μg) of NVX-CoV2373 with 5 μg saponin-based Matrix-M™ adjuvant (Novavax, AB, Uppsala, SE).
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Briefly, 3 × 105 splenocytes in a volume of 200 μL were stimulated with NVX-CoV2373 protein or peptide pools (PP) of 15-mer peptides with 11 overlapping amino acids covering the entire spike protein sequence (JPT, Berlin, Germany) in plates that were pre-coated with anti-IFN-γ or anti-IL-5 antibodies.
    anti-IFN-γ
    suggested: None
    anti-IL-5
    suggested: None
    Surface and intracellular cytokine staining: For surface staining, murine splenocytes were first incubated with an anti-CD16/32 antibody to block the Fc receptor.
    anti-CD16/32
    suggested: None
    To characterize T follicular helper cells (Tfh), splenocytes were incubated with the following antibodies or dye: BV650-conjugated anti-CD3, APC-H7-conjugated anti-CD4, FITC-conjugated anti-CD8, Percp-cy5.5-conjugated anti-CXCR5, APC-conjugated anti-PD-1, Alexa Fluor 700-conjugated anti-CD19, PE-conjugated anti-CD49b (BD Biosciences, San Jose, CA) and the yellow LIVE/DEAD® dye (Life Technologies, NY).
    anti-CXCR5
    suggested: None
    anti-PD-1
    suggested: None
    anti-CD19
    suggested: None
    anti-CD49b
    suggested: None
    Cells were labeled with murine antibodies against CD3 (BV650), CD4 (APC-H7), CD8 (FITC), CD44 (Alexa Fluor 700), and CD62L (PE) (BD Pharmingen, CA) and the yellow LIVE/DEAD® dye.
    CD3
    suggested: (Abcam Cat# ab52305, RRID:AB_955118)
    CD8
    suggested: (RayBiotech Cat# CS-11-0250, RRID:AB_1228199)
    CD44
    suggested: (Thermo Fisher Scientific Cat# 56-0441-82, RRID:AB_494011)
    CD62L
    suggested: None
    Cells were labelled with human/NHP antibodies BV650-conjugated anti-CD3, APC-H7-conjugated anti-CD4, APC-conjugated anti-CD8, BV421-conjugated anti-IL-2, PerCP-Cy5.5-conjugated anti-IFN-γ, PE-cy7-conjugated anti-TNF-α (BD Biosciences), and the yellow LIVE/DEAD® dye.
    anti-CD4
    suggested: (Bioss Cat# bs-0766R-PE-Cy7, RRID:AB_11052988)
    anti-IL-2, PerCP-Cy5.5-conjugated anti-IFN-γ,
    suggested: None
    anti-TNF-α
    suggested: None
    Sera were analyzed for anti-SARS-CoV-2 S IgG and hACE2 receptor inhibiting antibody levels.
    anti-SARS-CoV-2 S IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Expression and purification: SARS-CoV-2 S proteins were produced in Sf9 cells expanded in serum-free medium to a density of 2-3 × 106 cell mL−1 and infected with recombinant baculovirus at MOI of ≤0.1 pfu per cell.
    Sf9
    suggested: None
    Mouse or baboon sera were diluted 1:20 in Vero E6 cell growth media and further diluted 1:2 to 1:40960.
    Vero E6
    suggested: None
    Experimental Models: Organisms/Strains
    SentencesResources
    Mouse study designs: Female BALB/c mice (7-9 weeks old, 17-22 grams, N = 10 per group) were immunized by intramuscular (IM) injection with a single dose (study day 14) or two doses spaced 14-days apart (study day 0 and 14) containing a dose range (0.01, 0.1, 1.0, or 10 μg) of NVX-CoV2373 with 5 μg saponin-based Matrix-M™ adjuvant (Novavax, AB, Uppsala, SE).
    BALB/c
    suggested: None
    AB
    suggested: RRID:BDSC_203)
    Software and Algorithms
    SentencesResources
    SARS-CoV-2 plaque assay: SARS-CoV-2 lung titers were quantified by homogenizing harvested lungs in PBS (Quality Biological Inc.) using 1.0 mm glass beads (Sigma Aldrich) and a Beadruptor (Omini International Inc.).
    Quality Biological
    suggested: None
    Individual animal anti-SARS-CoV-2 S IgG titers and group geometric mean titers (GMT) and 95% confidence interval (± 95% CI) were plotted GraphPad Prism 7.05 software.
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)
    Serum dilution resulting in a 50% inhibition of receptor binding was used to calculate titer determined using 4-parameter fitting with GraphPad Prism 7.05 software.
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)
    SARS-CoV-2 neutralization assay: SARS-CoV-2 was handled in a select agent ABSL3 facility at the University of Maryland, School of Medicine.
    SARS-CoV-2
    suggested: (Active Motif Cat# 91351, RRID:AB_2847848)
    After fixation with Cytofix/Cytoperm (BD Biosciences), cells were incubated with PerCP-Cy5.5-conjugated anti-IFN-γ, BV421-conjugated anti-IL-2, PE-cy7-conjugated anti-TNF-α, and APC-conjugated anti-IL-4 (BD Biosciences).
    BD Biosciences
    suggested: (BD Biosciences, RRID:SCR_013311)
    All stained samples were acquired using a LSR-Fortessa flow cytometer (Becton Dickinson, San Jose, CA) and the data were analyzed with FlowJo software version Xv10 (Tree Star Inc., Ashland, OR).
    FlowJo
    suggested: (FlowJo, RRID:SCR_008520)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).


    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: We found the following clinical trial numbers in your paper:

    IdentifierStatusTitle
    NCT04368988Active, not recruitingEvaluation of the Safety and Immunogenicity of a SARS-CoV-2 …


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: We did not find any issues relating to colormaps.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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