A lipid nanoparticle RBD-hFc mRNA vaccine protects hACE2 transgenic mice against lethal SARS-CoV-2 infection

  1. Uri Elia
  2. Shahar Rotem
  3. Erez Bar-Haim
  4. Srinivas Ramishetti
  5. Gonna Somu Naidu
  6. David Gur
  7. Moshe Aftalion
  8. Ma’ayan Israeli
  9. Adi Bercovich-Kinori
  10. Ron Alcalay
  11. Efi Makdasi
  12. Theodor Chitlaru
  13. Ronit Rosenfeld
  14. Tomer Israely
  15. Sharon Melamed
  16. Inbal Abutbul Ionita
  17. Dganit Danino
  18. Dan Peer
  19. Ofer Cohen

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Abstract

The current global COVID-19 pandemic led to an unprecedented effort to develop effective vaccines against SARS-CoV-2. mRNA vaccines were developed very rapidly during the last year, and became the leading immunization platform against the virus, with highly promising phase-3 results and remarkable efficacy data. Since most animal models are not susceptible to SARS CoV-2 infection, pre-clinical studies are often limited to infection-prone animals such as hamsters and non-human primates. In these animal models, SARS-CoV-2 infection results in viral replication and a mild disease disease. Therefore, the protective efficacy of the vaccine in these animals is commonly evaluated by its ability to elicit immunologic responses, diminish viral replication and prevent weight loss. Our lab recently reported the design of a SARS-CoV-2 human Fc-conjugated receptor-binding domain (RBD-hFc) mRNA vaccine delivered via lipid nanoparticles (LNPs). These experiments demonstrated the development of a robust and specific immunologic response in RBD-hFc mRNA-vaccinated BALB/c mice. In the current study, we evaluated the protective effect of this RBD-hFc mRNA vaccine by employing the K18-hACE2 mouse model. We report that administration of RBD-hFc mRNA vaccine to K18-hACE2 mice led to a robust humoral response comprised of both binding and neutralizing antibodies. In accordance with the recorded immunologic immune response, 70% of vaccinated mice were protected against a lethal dose (3000 plaque forming units) of SARS-CoV-2, while all control animals succumbed to infection. To the best of our knowledge, this is the first non-replicating mRNA vaccine study reporting protection of K18-hACE2 against a lethal SARS-CoV-2 infection.

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  1. ScreenIT

    SciScore for 10.1101/2021.03.29.436639: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    RandomizationFemale K18-hACE2 (B6.CgTg(K18ACE2)2Prlmn/J HEMI) mice (6–8 weeks old) were obtained from Jackson and randomly assigned into cages in groups of 10 animals.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableFemale K18-hACE2 (B6.CgTg(K18ACE2)2Prlmn/J HEMI) mice (6–8 weeks old) were obtained from Jackson and randomly assigned into cages in groups of 10 animals.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    RBD-hFc was detected by incubation of the membrane with purified IgG fraction from serum of rabbit immunized with SARS-CoV-2 spike protein for over-night at 4°C, followed by a secondary antibody IRDye 680RD goat anti-rabbit (LIC-92668071) incubation of 1 h at RT.
    anti-rabbit
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Cells and animals: HEK293T cells (ATCC CRL-3216) and Vero E6 cells (ATCC CRL-1586) were maintained at 37°C, 5% CO2 in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal bovine serum (FBS)
    HEK293T
    suggested: None
    Vero E6
    suggested: None
    Evaluation of in vitro RBD-hFc expression in transfected HEK293 cells was performed essentially as described above.
    HEK293
    suggested: CLS Cat# 300192/p777_HEK293, RRID:CVCL_0045)
    Experimental Models: Organisms/Strains
    SentencesResources
    Female K18-hACE2 (B6.CgTg(K18ACE2)2Prlmn/J HEMI) mice (6–8 weeks old) were obtained from Jackson and randomly assigned into cages in groups of 10 animals.
    B6.CgTg(K18ACE2)2Prlmn/J HEMI )
    suggested: None
    The purified protein was sterile-filtered and stored in PBS. Animal Vaccination Experiments: For RBD-hFc mRNA vaccination studies, groups of 6–8 week old female K18-hACE2 mice were administered intramuscularly (50 μL in both hind legs) with SARS-CoV-2 RBD-hFc mRNA (5 μg) encapsulated with LNP formulation #14.
    K18-hACE2
    suggested: RRID:IMSR_GPT:T037657)
    Software and Algorithms
    SentencesResources
    Images were recorded on a Cooled Falcon IIIEC (FEI) Direct Detection Device by TIA software attached to the Talos or a Gatan MultiScan 791 camera by DigitalMicrograph software (Gatan, U.K.) on the Tecnai.
    DigitalMicrograph
    suggested: None
    The number of plaques in each well was scored and the NT50 (Serum dilution at which the plaque number was reduced by 50%, compared to plaque number of the control, in the absence of serum) was calculated using the Prism software version 8 (
    Prism
    suggested: (PRISM, RRID:SCR_005375)
    (GraphPad Software Inc., USA).
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)
    All statistical analyses were performed using GraphPad Prism 8 statistical software.
    GraphPad Prism
    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.
    • No funding statement was detected.
    • No protocol registration statement was detected.

    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.

  2. Version published to 10.1101/2021.03.29.436639 on bioRxiv