Marked enhancement of neutralizing antibody and IFN-γ T-cell responses by GX-19N DNA booster in mice primed with inactivated vaccine

  1. Yong Bok Seo
  2. Duckhyang Shin
  3. You Suk Suh
  4. Juyoung Na
  5. Ji In Ryu
  6. Young Chul Sung

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Abstract

In response to the COVID-19 pandemic, an unprecedented level of vaccine development has occurred. As a result, various COVID-19 vaccines have been approved for use. Among these, inactivated virus particle (VP) vaccines have been widely used worldwide, but additional vaccination strategies are needed because of the short duration of immune responses elicited by these vaccines. Here, we evaluated homologous and heterologous prime–boost regimens using a VP vaccine and GX-19N DNA vaccine for their ability to enhance the protective immune response against SARS-CoV-2. We demonstrated that a heterologous prime–boost regimen with the VP vaccine and GX-19N DNA vaccine resulted in enhanced S RBD - & N-specific antibody responses, compared to the homologous VP vaccine prime–boost vaccination. In addition, the neutralizing antibody response was significantly improved with the heterologous VP prime–DNA boost regimen, and the neutralizing antibody induced with the heterologous prime–boost regimen did not decrease against the SARS-CoV-2 variant of concern (VOC). The heterologous VP prime–DNA boost regimen not only significantly increased S- and N-specific IFN-γ T-cell responses, but also induced an equivalent level of T-cell response against SARS-CoV-2 VOCs. Our results provide new insights into prophylactic vaccination strategies for COVID-19 vaccination.

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  1. ScreenIT

    SciScore for 10.1101/2021.11.02.467026: (What is this?)

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

    Table 1: Rigor

    Ethicsnot detected.
    Sex as a biological variableMouse immunizations: Female BALB/c mice aged 6–8 weeks (Central Lab Animal) were intramuscularly immunized with 0.4 μg/ animal VP vaccine at week 0 and boosted with 12 μg/animal GX-19N, in a total volume of 50 μL PBS, into the tibialis anterior muscle with in vivo electroporation with the OrbiJector® system (SL VAXiGEN Inc.) at week 4.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Surrogate virus-neutralization assay: Surrogate virus neutralization test (sVNT) analyzed the binding ability of RBD to ACE2 after neutralizing RBD with antibodies in serum.
    ACE2
    suggested: None
    The reciprocal of the dilution resulting in a binding inhibition rate of 20% or more (PI20) was defined as the neutralizing antibody titer.
    PI20
    suggested: None
    ELISPOT plates were coated with purified anti-mouse IFN-γ capture antibody and incubated overnight at 4 °C.
    anti-mouse IFN-γ
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    The inactivated SARS-CoV-2 vaccine produced from Vero cells contains 4 μg of viral antigens and 0.225 mg of aluminum hydroxide adjuvant in a 0.5-mL dose.
    Vero
    suggested: RRID:CVCL_A5BG)
    Experimental Models: Organisms/Strains
    SentencesResources
    Mouse immunizations: Female BALB/c mice aged 6–8 weeks (Central Lab Animal) were intramuscularly immunized with 0.4 μg/ animal VP vaccine at week 0 and boosted with 12 μg/animal GX-19N, in a total volume of 50 μL PBS, into the tibialis anterior muscle with in vivo electroporation with the OrbiJector® system (SL VAXiGEN Inc.) at week 4.
    BALB/c
    suggested: None
    Recombinant DNA
    SentencesResources
    Vaccines: The COVID-19 DNA vaccine, consisting of GX-19 and GX-21 at a 1:2 ratio, was constructed by inserting the antigen genes of SARS-CoV-2 into the pGX27 vector.
    pGX27
    suggested: None
    GX-19 (pGX27-SΔTM/IC) contains the SARS-CoV-2 spike (S) gene lacking the transmembrane (TM)/intracellular (IC) domain, and GX-21 (pGX27-SRBD-F/NP) is designed to express the fusion protein of the receptor binding domain (RBD) of the spike protein, the T4 fibritin C-terminal foldon (SRBD-Foldon), and the nucleocapsid protein (N).
    pGX27-SΔTM/IC
    suggested: None
    pGX27-SRBD-F/NP
    suggested: None
    Software and Algorithms
    SentencesResources
    Statistical analysis: Data analyses were performed using GraphPad Prism 7 (GraphPad Software).
    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.
    • No funding statement was detected.
    • 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 10.1101/2021.11.02.467026 on bioRxiv