SARS-CoV-2 Virus like Particles produced by a single recombinant baculovirus generate potent neutralizing antibody that protects against variant challenge

  1. Edward Sullivan
  2. Po-Yu Sung
  3. Weining Wu
  4. Neil Berry
  5. Sarah Kempster
  6. Deborah Ferguson
  7. Neil Almond
  8. Ian M. Jones
  9. Polly Roy

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Abstract

The Covid-19 pandemic caused by SARS-CoV-2 infection has highlighted the need for the rapid generation of efficient vaccines for emerging disease. Virus-like particles, VLPs, are an established vaccine technology that produces virus-like mimics, based on expression of the structural proteins of a target virus that can stimulate strong neutralizing antibody responses. SARS-CoV-2 is a coronavirus where the basis of VLP formation has been shown to be the co-expression of the spike, membrane and envelope structural proteins. Here we describe the generation of SARS-CoV-2 VLPs by the co-expression of the salient structural proteins in insect cells using the established baculovirus expression system. VLPs were heterologous ∼100nm diameter enveloped particles with a distinct fringe that reacted strongly with SARS-CoV-2 convalescent sera. In a Syrian hamster challenge model, a non-adjuvanted VLPs induced neutralizing antibodies to the VLP-associated Wuhan S protein, reduced virus shedding following a virulent challenge with SARS-CoV-2 (B.1.1.7 variant) and protected against disease associated weight loss. Immunized animals showed reduced lung pathology and lower challenge virus replication than the non-immunized controls. Our data, using an established and scalable technology, suggest SARS-CoV-2 VLPs offer an efficient vaccine that mitigates against virus load and prevents severe disease.

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  1. ScreenIT

    SciScore for 10.1101/2021.11.29.470349: (What is this?)

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

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variableImmunogenicity studies: Five female Golden hamsters were administered 300µL (10μg) of non-adjuvanted VLP preparation under the skin on two occasions, 4 weeks apart.
    Randomizationnot detected.
    BlindingThe samples were scored blinded.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Gels were either stained with Coomassie brilliant blue or subjected to Western blot using appropriate antibodies: rabbit polyclonal anti-SARS-CoV-2 S antibody (Abcam ab272504) or rabbit polyclonal anti-SARS-CoV/CoV2 M antibody (Novus Biologicals NB100-56569).
    anti-SARS-CoV-2 S
    suggested: None
    anti-SARS-CoV/CoV2 M
    suggested: None
    Transmission Electron Microscopy (TEM): Peak fractions from the sucrose gradient, identified by western blot with an anti-S antibody, were diluted 4-fold in PBS and concentrated to 10% of their original volume using spin filters with a cut-off of 1MDa.
    anti-S
    suggested: None
    After three washes, the bound antibody was detected with goat anti-human Ig (γ chain specific)-HRP conjugated secondary antibody (Thermo Fisher Scientific) diluted 1:10,000 in blocking buffer.
    anti-human Ig (γ chain specific)-HRP
    suggested: None
    Antibodies were diluted to their optimal staining concentration in Bond primary antibody diluent (Leica, AR9352) as follows: SARS-CoV-2 Spike protein: 1:1000 (Leica, AR9961) 30minutes, (Rabbit PAb 40150-T62-COV2-SIB, Stratech Scientific/SinoBiologicals), SARS-CoV-2 Nucleoprotein: 1:2000 (Leica, AR9961) 30minutes, (Mouse Mab 40143-MM05-SIB, Stratech Scientific/SinoBiologicals).
    AR9961
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    Culture from swabs: 20µL of the VTM sample was added to duplicate cultures of VeroTMPRSS2 cells either neat or diluted 1:2 in VTM.
    VeroTMPRSS2
    suggested: JCRB Cat# JCRB1818, RRID:CVCL_YQ48)
    Recombinant DNA
    SentencesResources
    Construction of recombinant baculoviruses: A codon optimized sequence encoding the S protein of the original Wuhan SARS-CoV-2 isolate (QHD43416.1) was obtained from Integrated DNA Technologies as described (23) and cloned in place if the resident SARS S protein in vector pACVC3-SARS-S-E (9), leaving the E open reading frame unchanged.
    pACVC3-SARS-S-E
    suggested: None
    Similarly, an optimized SARS-CoV-2 M gene, was purchased from Eurofins Genomics and cloned into the baculovirus expression vector pAcYB2 (24).
    pAcYB2
    suggested: None
    A single baculovirus expressing the 3 proteins was generated by co-transfection of pACVC3-SARS-E-Covid19-S and pAcYB2-Covid19-M with Bsu36I linearized AcMNPV DNA (25).
    pACVC3-SARS-E-Covid19-S
    suggested: None
    pAcYB2-Covid19-M
    suggested: None
    Software and Algorithms
    SentencesResources
    The pixel density in each dot was assessed using Image J (27).
    Image J
    suggested: (ImageJ, RRID:SCR_003070)
    9 and SigmaPlot v12.5. qRT-PCR: Total nucleic acid was extracted from a 200µL sample using the MagnaPure24 (Roche) External Lysis Pathogen 200 protocol with elution into 50 µL.
    SigmaPlot
    suggested: (SigmaPlot, RRID:SCR_003210)

    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.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  2. Version published to 10.1101/2021.11.29.470349v1 on bioRxiv