Oral delivery of SARS-CoV-2 DNA vaccines using attenuated Salmonella typhimurium as a carrier in rat

  1. Dan Zhu
  2. Yue Meng
  3. Aaodeng Qimuge
  4. Bilige Bilige
  5. Tegexi Baiyin
  6. Temuqile Temuqile
  7. Shana Chen
  8. Siqin Bao
  9. Huricha Baigude
  10. Dezhi Yang

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Abstract

The 2019 novel coronavirus disease (COVID-19) is the disease that has been identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but the prophylactic treatment of SARS-CoV-2 is still under investigation. The effective delivery of eukaryotic expression plasmids to the immune system’s inductive cells constitutes an essential requirement for the generation of effective DNA vaccines. Here, we have explored the use of Salmonella typhimurium as vehicles to deliver expression plasmids orally. Attenuated Salmonella phoP harboring eukaryotic expression plasmids that encoded spike protein of SARS-CoV-2 was administered orally to Wistar rats. Rats were immunized orally with Salmonella that carried a eukaryotic expression plasmid once a week for three consecutive weeks. The efficiency of the vaccination procedure was due to the transfer of the expression plasmid from the bacterial carrier to the mammalian host. Evidence for such an event could be obtained in vivo and in vitro. Our results showed that all immunized animals generated humoral immunity against the SARS-CoV-2 spike protein, indicating that a Salmonella -based vaccine carrying the Spike gene can elicit SARS-CoV-2-specific humoral immune responses in rats, and may be useful for the development of a protective vaccine against SARS-CoV-2 infection.

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  1. ScreenIT

    SciScore for 10.1101/2020.07.23.217174: (What is this?)

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

    Table 1: Rigor

    Institutional Review Board Statementnot detected.
    RandomizationSARS-CoV-2-S DNA immunization delivered by attenuated S. typhimurium: A total of 18 female Wistar rats were randomly divided into two groups, with nine rats each.
    Blindingnot detected.
    Power Analysisnot detected.
    Sex as a biological variableSARS-CoV-2-S DNA immunization delivered by attenuated S. typhimurium: A total of 18 female Wistar rats were randomly divided into two groups, with nine rats each.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Protein samples were separated by 8% SDS-PAGE and transferred to PVDF membranes (Amersham), then proteins were monitored with ECL Western blotting substrate (Pierce) after incubation with anti-SARS-CoV-2-S-RBD (Sino Biological, China) or anti-β-actin antibody (Solarbio, China).
    anti-SARS-CoV-2-S-RBD
    suggested: None
    anti-β-actin
    suggested: None
    Enzyme linked immunosorbant assay (ELISA): As previously described, the sera were used to test the anti-SARS-CoV-2-S IgG antibodies by enzyme-linked immunosorbent assay (ELISA).
    anti-SARS-CoV-2-S IgG
    suggested: None
    Then the HRP conjugated rabbit anti-goat IgG antibodies (1:3000, Solarbio, China) were added, and incubation continued at 37°C for one hour.
    anti-goat IgG
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    . 293T cells were propagated in Dulbecco’s modified Eagle medium (DMEM) (HyClone, USA) supplemented with 10% fetal bovine serum (Gibco, USA) and maintained in a humidified incubator at 37°C with 5% CO2.
    293T
    suggested: None
    Experimental Models: Organisms/Strains
    SentencesResources
    SARS-CoV-2-S DNA immunization delivered by attenuated S. typhimurium: A total of 18 female Wistar rats were randomly divided into two groups, with nine rats each.
    Wistar
    suggested: RRID:MGI:5657554)
    Software and Algorithms
    SentencesResources
    Statistical analyses: Statistical analyses were performed with one-way ANOVA using GraphPad Prism 6.0.
    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.
    • 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

    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 10.1101/2020.07.23.217174 on bioRxiv