Immunogenicity and efficacy of the COVID-19 candidate vector vaccine MVA SARS 2 S in preclinical vaccination

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Abstract

The severe acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) has emerged as the infectious agent causing the pandemic coronavirus disease 2019 (COVID-19) with dramatic consequences for global human health and economics. Previously, we reached clinical evaluation with our vector vaccine based on vaccinia virus MVA against the Middle East respiratory syndrome coronavirus (MERS-CoV), which causes an infection in humans similar to SARS and COVID-19. Here, we describe the construction and preclinical characterization of a recombinant MVA expressing full-length SARS-CoV-2 spike (S) protein (MVA-SARS-2-S). Genetic stability and growth characteristics of MVA-SARS-2-S, plus its robust synthesis of S antigen, make it a suitable candidate vaccine for industrial scale production. Vaccinated mice produced S antigen-specific CD8+ T cells and serum antibodies binding to S glycoprotein that neutralized SARS-CoV-2. Prime-boost vaccination with MVA-SARS-2-S protected mice sensitized with a human ACE2-expressing adenovirus from SARS-CoV-2 infection. MVA-SARS-2-S is currently being investigated in a phase I clinical trial as aspirant for developing a safe and efficacious vaccine against COVID-19.

Significance Statement

The highly attenuated vaccinia virus MVA is licensed as smallpox vaccine, and as vector it is a component of the approved Adenovirus-MVA-based prime-boost vaccine against Ebola virus disease. Here we provide results from testing the COVID-19 candidate vaccine MVA-SARS-2-S, a poxvirus-based vector vaccine that proceeded to clinical evaluation. When administered by intramuscular inoculation, MVA-SARS-2-S expresses and safely delivers the full-length SARS-CoV-2 spike (S) protein, inducing balanced SARS-CoV-2-specific cellular and humoral immunity, and protective efficacy in vaccinated mice. Substantial clinical experience has already been gained with MVA vectors using homologous and heterologous prime-boost applications, including the immunization of children and immunocompromised individuals. Thus, MVA-SARS-2-S represents an important resource for developing further optimized COVID-19 vaccines.

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  1. SciScore for 10.1101/2021.01.09.426032: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board StatementIRB: For use of patient serum ethical approval was granted by the Ethics Committee at the Medical Faculty of LMU Munich (vote 20-225 KB) in accordance with the guidelines of the Declaration of Helsinki.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableVaccination experiments in mice: Female BALB/c mice (6 to 10 week-old) were purchased from Charles River Laboratories (Sulzfeld, Germany).
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    The blots were blocked in a phosphate buffered saline (PBS) buffer containing 5% Bovine Serum Albumin (BSA) (Sigma-Aldrich, Taufkirchen, Germany) and 0.1% Tween-20 (Sigma-Aldrich, Taufkirchen, Germany) and incubated for 60 min with primary antibody, monoclonal anti-HAtag antibody (1:8000; HA Tag mAb 2-2.2.14, Thermo Fisher Scientific, Planegg, Germany) or COVID-19 patient serum (1:200).
    anti-HAtag
    suggested: (InvivoGen Cat# ab-hatag, RRID:AB_391833)
    Permeabilized cells were probed with a monoclonal antibody against the HA-tag epitope (1:1000; HA Tag mAb 2-2.2.14, Thermo Fisher Scientific, Planegg, Germany) to detect SARS-2-S protein.
    HA-tag epitope
    suggested: None
    Non-permeabilized cells were stained with a mouse monoclonal antibody obtained against the S protein of SARS-CoV-1 (SARS-1-S; 1:200; GeneTex) before fixation with PFA.
    SARS-1-S
    suggested: None
    Polyclonal goat anti-mouse secondary antibody (1:1000; Life Technologies, Darmstadt, Germany) was used to visualize S-specific staining by red fluorescence.
    anti-mouse
    suggested: None
    Surrogate virus neutralization assay (sVNT): To test for the presence of neutralizing anti-SARS-CoV-2-S serum antibodies we used surrogate virus neutralization test as described before with slight modifications (25).
    anti-SARS-CoV-2-S
    suggested: None
    Plates were extensively washed with phosphate-buffered saline/0.05% Tween-20 (PBST), followed by incubation for 1h at 37°C with an HRP-conjugated anti-His-tag antibody (1.2 μg/ml; clone HIS 3D5).
    anti-His-tag
    suggested: (MBL International Cat# M136-3, RRID:AB_11125943)
    To remove background effects, the mean percentage of inhibition from non-specific mouse serum (Invitrogen) was deducted from sample values and neutralizing anti-SARS-CoV2-S antibodies titres were determined as serum dilution that still had binding reduction > mean + 2 SD of values from sera of vehicle-treated mice.
    anti-SARS-CoV2-S
    suggested: None
    After incubation, we fixed the cells with 4% formaldehyde/phosphate-buffered saline (PBS) and stained the cells with polyclonal rabbit anti-SARS-CoV antibody (Sino Biological, https://www.sinobiological.com) and a secondary peroxidase-labeled goat anti-rabbit IgG (Dako, https://www.agilent.com).
    anti-SARS-CoV
    suggested: None
    anti-rabbit IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Human A549 cells (ATCC® CCL-185™) (LGC standards) were maintained in DMEM with high glucose and 10% FBS.
    A549
    suggested: None
    The replicative capacity of recombinant MVA was tested in multi-step-growth experiments on monolayers of DF-1, HaCat, HeLa or A549 cells grown in 6-well-tissue-culture plates.
    HaCat
    suggested: None
    HeLa
    suggested: None
    Western Blot analysis of recombinant protein: To monitor production of the recombinant SARS-2-S protein, DF-1 cells were infected at MOI 10 with recombinant or non-recombinant MVA or remained uninfected (mock).
    DF-1
    suggested: None
    Immunostaining of recombinant SARS-2-S protein: Vero cells were infected with 0.05 MOI MVA-SARS-2-S or non-recombinant MVA and incubated at 37 °C.
    Vero
    suggested: None
    We then added 50 μL of virus suspension (400 plaque-forming units) to each well and incubated at 37°C for 1 h before placing the mixtures on Vero-E6 cells.
    Vero-E6
    suggested: None
    Cytopathic effects (CPE) on VeroE6 cells (ATCC CRL1586) were analyzed 4 days after infection.
    VeroE6
    suggested: JCRB Cat# JCRB1819, RRID:CVCL_YQ49)
    Experimental Models: Organisms/Strains
    SentencesResources
    Vaccination experiments in mice: Female BALB/c mice (6 to 10 week-old) were purchased from Charles River Laboratories (Sulzfeld, Germany).
    BALB/c
    suggested: None
    Software and Algorithms
    SentencesResources
    After incubation, we fixed the cells with 4% formaldehyde/phosphate-buffered saline (PBS) and stained the cells with polyclonal rabbit anti-SARS-CoV antibody (Sino Biological, https://www.sinobiological.com) and a secondary peroxidase-labeled goat anti-rabbit IgG (Dako, https://www.agilent.com).
    https://www.sinobiological.com
    suggested: (Sino Biological, RRID:SCR_003697)
    https://www.agilent.com
    suggested: (Agilent Technologies, RRID:SCR_013575)
    Next, cells were permeabilized using Intracellular Staining Permeabilization Wash Buffer (Perm Wash buffer; Biolegend; dilution 1:10), and stained intracellularly in 100 μl/well of anti-mouse IFN-γ (clone XMG1.2, 1:200, Biolegend) plus anti-mouse TNF-α (clone MP6-XT22, 1:200, Biolegend) diluted in Perm Wash buffer for 30 min at room temperature.
    Biolegend
    suggested: (BioLegend, RRID:SCR_001134)
    For each antibody, single colour controls were prepared using OneComp eBeads™ Compensation Beads (eBioscience, Thermo Fisher Scientific) and cells for the viability dye Zombie Aqua.
    OneComp
    suggested: None
    Data was acquired by the MACSQuant VYB Flow Analyser (Miltenyi Biotec) and analyzed using FlowJo (FlowJo LLC, BD Life Sciences, Ashland, OR, USA).
    FlowJo
    suggested: (FlowJo, RRID:SCR_008520)
    Statistical analysis: Data were prepared using GraphPad Prism version 5 (GraphPad Software Inc., San Diego CA, USA) and expressed as mean ± standard error of the mean (SEM).
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)

    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: No clinical trial numbers were referenced.


    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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