Evaluation of the systemic and mucosal immune response induced by COVID-19 and the BNT162b2 mRNA vaccine for SARS-CoV-2

  1. Olaf Nickel
  2. Alexandra Rockstroh
  3. Johannes Wolf
  4. Susann Landgraf
  5. Sven Kalbitz
  6. Nils Kellner
  7. Michael Borte
  8. Corinna Pietsch
  9. Jasmin Fertey
  10. Christoph Lübbert
  11. Sebastian Ulbert
  12. Stephan Borte

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Abstract

The currently used SARS-CoV-2 mRNA vaccines have proven to induce a strong and protective immune response. However, functional relevance of vaccine-generated antibodies and their temporal progression are still poorly understood. Thus, the central aim of this study is to gain a better understanding of systemic and mucosal humoral immune response after mRNA vaccination with BNT162b2.

Methods

We compared antibody production against the S1 subunit and the RBD of the SARS-CoV-2 spike protein in sera of BNT162b2 vaccinees, heterologous ChAdOx1-S/BNT162b2 vaccinees and COVID-19 patients. We monitored the neutralizing humoral response against SARS-CoV-2 wildtype strain and three VOCs over a period of up to eight months after second and after a subsequent third vaccination.

Results

In comparison to COVID-19 patients, vaccinees showed higher or similar amounts of S1- and RBD-binding antibodies but similar or lower virus neutralizing titers. Antibodies peaked two weeks after the second dose, followed by a decrease three and eight months later. Neutralizing antibodies (nAbs) poorly correlated with S1-IgG levels but strongly with RBD-IgGAM titers. After second vaccination we observed a reduced vaccine-induced neutralizing capacity against VOCs, especially against the Omicron variant. Compared to the nAb levels after the second vaccination, the neutralizing capacity against wildtype strain and VOCs was significantly enhanced after third vaccination. In saliva samples, relevant levels of RBD antibodies were detected in convalescent samples but not in vaccinees.

Conclusions

Our data demonstrate that BNT162b2 vaccinated individuals generate relevant nAbs titers, which begin to decrease within three months after immunization and show lower neutralizing potential against VOCs as compared to the wildtype strain. Large proportion of vaccine-induced S1-IgG might be non-neutralizing whereas RBD-IgGAM appears to be a good surrogate marker to estimate nAb levels. A third vaccination increases the nAb response. Furthermore, the systemic vaccine does not seem to elicit readily detectable mucosal immunity.

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  1. Version published to 10.1371/journal.pone.0263861
  2. ScreenIT

    SciScore for 10.1101/2022.01.29.22270066: (What is this?)

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

    Table 1: Rigor

    EthicsIRB: The ethics committee of the Saxonian medical chamber approved the study (registry number EK-allg-37/10–1) and informed consent was obtained from all volunteers.
    Consent: The ethics committee of the Saxonian medical chamber approved the study (registry number EK-allg-37/10–1) and informed consent was obtained from all volunteers.
    Sex as a biological variableAnother 11 study participants (63.6 % females, median age 31 [IQR 26-37]) received a heterologous ChAdOx1-S vector based prime (EMA fact sheet [10]) and BNT162b2 boost vaccination (AZ/BNT).
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Commercial assays for the detection of antibodies against S1 and Nucleocapsid: All serum samples were tested for IgG against SARS-CoV-2 S1 (Anti-SARS-CoV-2-QuantiVac-ELISA, S1 Quant IgG; cut-off ≥25.6 BAU/ml) and for IgA against SARS-CoV-2 S1 (S1 IgA, Euroimmun, Lübeck, Germany; cut-off ratio ≥0.8).
    Anti-SARS-CoV-2-QuantiVac-ELISA
    suggested: None
    SARS-CoV-2
    suggested: None
    S1
    suggested: None
    In addition, baseline sera were screened for IgG antibodies against SARS-CoV-2 nucleocapsid (Virotech, Rüsselsheim, Germany; cut-off ≥11 VE/ml)
    SARS-CoV-2 nucleocapsid (Virotech,
    suggested: None
    Sera (diluted 1:100) were incubated for 1.5 h at room temperature and binding antibodies were detected using a HRP-conjugated secondary goat anti human IgG antibody (Dianova, 1:20,000) or goat anti human IgG+IgM+IgA H&L antibody (Abcam, 1:10,000) for 1 h at room temperature.
    anti human IgG
    suggested: None
    anti human IgG+IgM+IgA
    suggested: None
    SARS-CoV-2 focus forming units were stained using a monoclonal rabbit anti-S1 antibody (CR3022, abcam, 1:1,000) and a secondary goat anti-rabbit IgG HRP-conjugated antibody (Dianova, 1:1,000).
    CR3022
    suggested: None
    anti-rabbit IgG
    suggested: None
    After another wash step, beads were resuspended in 500 µl of BD sheath fluid and analyzed using a BD FACS Lyric flow cytometer (BD Biosciences, San Jose, CA, U.S.) with PMT voltage settings adapted to discriminate beads specific for Spike S1- and Spike RBD-specific IgA antibodies.
    IgA
    suggested: None
    Therefore, we compared FRNT-suggested nAb titers in matched serum samples with calculated concentrations of neutralizing surrogate antibodies in DBS and found a high degree of correlation (S3).
    S3
    suggested: None
    Experimental Models: Cell Lines
    SentencesResources
    RBD protein (AA residues 329-538 of spike protein, strain Wuhan-Hu-1) was expressed in Drosophila S2 cells and purified from cell culture supernatants with tandem immobilized metal affinity and size exclusion chromatography using the ÄKTA pure 25 l chromatography system (GeHealthcare).
    S2
    suggested: None
    SARS-CoV-2 neutralization assay: Focus reduction neutralization assays (FRNT) were performed according to Rockstroh et. al. 2021.[3] Briefly, heat-inactivated human serum samples were serially diluted in DMEM without FCS from 1:2.5 to 1:5120 and incubated with 50-150 focus forming units of SARS-CoV-2 wt, B.1.1.7 or B.1.351 for 1 h at 37°C before addition to confluent Vero E6 monolayers in 96-well plates.
    Vero E6
    suggested: None
    Experimental Models: Organisms/Strains
    SentencesResources
    SARS-CoV-2 viral stocks: SARS-CoV-2 wildtype virus (wt) (isolate BetaCoV/Germany/BavPat1/2020, obtained from the European Virus Archive Global, EVAg)[11], SARS-CoV-2 B.1.1.7 (isolate MUC1-IMB1-CB, kindly provided by Klaus Überla from the Institute of Clinical and Molecular Virology, University of Erlangen-Nürnberg) and SARS-CoV-2 B.1.351 (SARS-CoV-2/human/Germany/LE-B14HXA2/2021 kindly provided by Corinna Pietsch from the Institute of Virology, University Hospital Leipzig) were propagated in VeroE6 cells.
    SARS-CoV-2
    suggested: None
    Software and Algorithms
    SentencesResources
    Statistical analysis: SPSS version 21 (IBM, Armonk, NY, USA) and GraphPad PRISM version 6 (GraphPad Software, San Diego, CA, USA) were used for statistical calculations and generation of figures.
    SPSS
    suggested: (SPSS, RRID:SCR_002865)
    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.

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

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  3. Version published to 10.1101/2022.01.29.22270066v1 on medRxiv