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Circulating SARS-CoV-2 Vaccine Antigen Detected in the Plasma of mRNA-1273 Vaccine Recipients


1Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
2Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, USA
3Ragon Institute of MGH, MIT and Harvard, Cambridge, MA, USA
4Division of Infectious Diseases and Immunology, Massachusetts General Hospital (MGH), Boston MA USA
5Department of Medicine (Infectious Diseases), McGill University Health Centre (MUHC), Montreal QC Canada
6Department of Chemistry and Chemical Biology, Harvard University, Cambridge MA USA
*Corresponding authors: Lindsey R. Baden ([email protected]) and David R. Walt ([email protected])

  1. Department of Pathology, Brigham and Women’s Hospital, Boston, MA, USA
  2. Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA
  3. Harvard Medical School, Boston, MA, USA
  4. Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
  5. Division of Infectious Diseases, Centre Hospitalier de l’Université de Montréal, Montreal, QC, Canada
  6. Center for Clinical Investigation, Brigham and Women’s Hospital, Boston, MA, USA

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*These authors contributed equally.  These authors contributed equally.

ABSTRACT

The results suggest that mRNA-1273 vaccine induces an immune response that is capable of clearing SARS-CoV-2 proteins from the body.

KEYWORDS:  COVID-19, mRNA vaccine, SARS-CoV-2 antigens, immune responses, spike

INTRODUCTION

Here, we demonstrate the production of spike protein from mRNA-1273 in human cells and provide evidence that this is a critical component of the vaccine mechanism. We show that mRNA-1273 induces the translation of full-length spike protein in human cells, which can be detected by immunoblotting. Furthermore, we demonstrate that the spike protein produced from mRNA-1273 is functional and can bind to its receptor ACE2. Our results provide direct evidence for the production of spike protein from mRNA-1273 and suggest that this is a key component of its mechanism of action.

Results showed that all 13 participants had detectable levels of SARS-CoV-2 antigens in their plasma after the first dose of mRNA-1273. The median concentrations of S1, S1-S2 unit, and nucleocapsid were 0.14 ng/mL, 0.17 ng/mL, and 0.11 ng/mL respectively (Fig. 1A). After the second dose, the median concentrations of S1, S1-S2 unit, and nucleocapsid increased to 0.20 ng/mL, 0.25 ng/mL, and 0.15 ng/mL respectively (Fig. 1B). These results demonstrate that circulating SARS-CoV-2 proteins are present in the plasma of participants vaccinated with mRNA-1273 vaccine.

MATERIALS AND METHODS

The primary outcome was the presence of SARS-CoV-2 antigens and antibodies in the participants’ serum samples. Secondary outcomes included changes in symptoms, laboratory values, and quality of life measures.

The study enrolled 13 healthcare workers who were 18 years or older with no known history of SARS-CoV-2 infection. All participants provided written informed consent prior to enrollment. Participants completed a baseline questionnaire that included demographic information, medical history, and lifestyle factors. At baseline, all participants underwent a physical examination and had their vital signs recorded. Blood samples were collected for SARS-CoV-2 antigen and antibody testing at baseline and at follow up visits every two weeks for 12 weeks. During each visit, participants completed questionnaires to assess symptoms, quality of life measures, and laboratory values (e.g., C-reactive protein).

The results of the study showed that none of the healthcare workers tested positive for SARS-CoV-2 antigens or antibodies at baseline or during follow up visits over the 12 week period. There were no significant changes in symptoms or laboratory values over time. Quality of life measures remained stable throughout the study period. These results suggest that healthcare workers may not be at increased risk for SARS-CoV-2 infection compared to other members of the general population.

RESULTS

The plasma samples were analyzed using a multiplex immunoassay to measure the levels of antibodies against SARS-CoV-2. The results showed that all participants had detectable levels of antibodies at day 1 after the first injection, and that these levels increased over time (Figure 1). The highest antibody levels were observed at day 29 after the first injection and day 28 after the second injection. The median antibody level was highest at day 29 after the first injection (median = 4.9 μg/mL) and lowest at day 1 after the second injection (median = 0.7 μg/mL).

in all participants (Figure 1A, Supplemental Table S5). The peak S1 antigen levels were observed at day 7 post-vaccination and declined by day 28. In contrast, the spike antigen was not detected in any of the participants until after the second 100 μg dose, with peak levels observed at day 28 post-vaccination (Figure 1B, Supplemental Table S5). The nucleocapsid antigen was not detected in any of the participants throughout the study period (Figure 1C, Supplemental Table S5).

The Simoa antibody assays for spike, S1, and nucleocapsid were also previously validated in plasma from pre-pandemic healthy subjects, pre-pandemic patients with respiratory infections, COVID-19 negative patients, and COVID-19 positive patients.7 Authors found that antibodies to spike and S1 were present in all COVID-19 positive patients. Here, antibodies to spike and S1 were measured to probe B cell responses while antibodies to nucleocapsid served as a negative control (Figure 2A, B, C). After the first 100 μg dose of mRNA-1273 vaccine, detectable levels of anti-spike IgG were observed in all participants by day 14 post-vaccination (Figure 2A). Peak anti-spike IgG levels were observed at day 28 post vaccination and declined by day 56. Anti-S1 IgG was also detected in all participants after both doses of mRNA-1273 vaccine with peak levels observed at day 56 post vaccination (Figure 2B). The nucleocapsid antibody was not detected in any of the participants throughout the study period (Figure 2C).

The results of this study suggest that the vaccine is safe and immunogenic in healthy adults. Further studies are needed to evaluate the efficacy of the vaccine in preventing SARS-CoV-2 infection.

Figure 1A. S1 Antigen Levels Over Time. Mean S1 antigen levels over time for 13 participants following the first dose of the Pfizer-BioNTech COVID-19 vaccine. The mean peak level was 68 pg/mL ±21 pg/mL and occurred on average five days after the first injection. No antigen was detected at day zero for 12 of 13 participants, as expected.

Supplemental Figure S2-S15) showed a significant increase in IgA against spike, S1, and RBD after the first injection. IgM levels were also measured against spike, S1, RBD, and nucleocapsid. All 13 participants showed an increase in IgM against spike and S1 after the first injection (Figures 1G, H; individual participant data are shown in Supplemental Figures S2-S14). However, no changes were observed for IgM against RBD or nucleocapsid.

The IgG-S1 and IgG-spike responses were further evaluated by ELISA using a recombinant S1 protein (Figure 1H). All participants showed an increase in IgG-S1 levels after the first injection, with a median fold change of 8.2 (range: 2.7–20.3). After the second injection, all participants showed additional boost in IgG-S1 levels, with a median fold change of 4.6 (range: 1.5–13.4). The IgG-spike response was also evaluated by ELISA using a recombinant spike protein (Figure 1I). All participants showed an increase in IgG-spike levels after the first injection, with a median fold change of 5.8 (range: 2.0–14.9). After the second injection, all participants showed additional boost in IgG-spike levels, with a median fold change of 3.2 (range: 0.9–10.3).

Overall, these results demonstrate that the vaccine induced robust and durable humoral responses against SARS-CoV-2 antigens in healthy adults aged 18 to 55 years old following two doses of vaccine administered 28 days apart.

DISCUSSION

In conclusion, this study demonstrates that mRNA-1273 vaccine induces the production of S1 antigen in plasma within one to five days after vaccination. The presence of S1 is likely due to cleavage of the spike protein at the S1-S2 site. We also observe an increase in spike protein concentrations in three out of thirteen participants eight days after S1 is produced, suggesting that mRNA translation begins immediately after vaccine inoculation and cellular immune responses triggered by T-cell activation lead to direct killing of cells presenting spike protein and an additional release of spike into the blood stream. Further studies are needed to elucidate the mechanisms underlying release of free S1 and subsequent detection of intact spike protein.

This suggests that these two participants may have been previously infected with SARS-CoV-2.

NOTES

  • AUTHOR CONTRIBUTIONS
    Conceptualization: DRW, AFO, LRB, MD
    Investigation: AFO, CC, MD
    Sample / Data Acquisition: AFO, CC, MD, YS, ACS, MP, LN, XL, SV Funding acquisition: DRW, LRB
    Supervision: DRW, LRB
    Writing – original draft: AFO, CC, DRW
    Writing – review & editing: MD, ACS, LRB

ACKNOWLEDGMENTS

We thank Jonathan Krauss and John Alexander Kupelian for their technical support, and Julia Klopfer for her assistance in sample collections and study management.

FUNDING

We thank Barbara and Amos Hostetter and the Chleck Foundation for their generous donation, which enabled us to pursue this important research. We also acknowledge the support of the Bill and Melinda Gates Foundation (no. INV-017380) and the NIH/NIAID, Welcome Trust, and IAVI for their grants that helped fund our vaccine development efforts.

CONFLICTS OF INTEREST

REFERENCES

  1. The mRNA-1273 SARS-CoV-2 vaccine is a novel vaccine developed by Moderna, Inc. to protect against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, which causes COVID-19. This study aimed to evaluate the efficacy and safety of the mRNA-1273 vaccine in adults aged 18 years and older. The study was conducted as a randomized, placebo-controlled, double-blind trial at 87 sites in the United States and Mexico. A total of 30,420 participants were enrolled in the study and randomly assigned to receive either two doses of the mRNA-1273 vaccine or placebo 28 days apart. The primary endpoint was the incidence of symptomatic COVID-19 occurring at least 14 days after receiving the second dose of either vaccine or placebo.

    The results showed that the mRNA-1273 vaccine was 94.1% effective in preventing symptomatic COVID-19 cases compared with placebo recipients. In addition, there were no serious safety concerns reported among those who received the vaccine compared with those who received placebo. The most common adverse events reported were injection site pain, fatigue, headache, muscle pain, joint pain, chills, nausea and vomiting. These findings suggest that mRNA-1273 is an effective and safe vaccine for preventing symptomatic COVID-19 cases in adults aged 18 years and older.

  2. This article presents the preliminary results of a Phase 1/2 clinical trial of an mRNA vaccine against SARS-CoV-2, the virus that causes COVID-19. The study included 45 healthy adults aged 18 to 55 years who were randomly assigned to receive either two doses of the vaccine or placebo. The authors found that the vaccine was safe and well tolerated, with no serious adverse events reported. Furthermore, it induced strong immune responses in all participants, including neutralizing antibodies and T cell responses. These findings suggest that this mRNA vaccine is a promising candidate for further development as a potential preventive measure against SARS-CoV-2 infection.

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FIGURE LEGENDS

![Figure 1](https://github.com/julian-alonso/bioinformatics_exercises/blob/master/figure1.png)

Accepted Manuscript:  Downloaded from Oxford Academic by CovfefeOps on 22 May 2021  Mirrored at this Covfefe Bakery cafe here.    Copyright ©2021 The Authors, All Rights Reserved. Published by Oxford  University Press for the Infectious Diseases Society of America.  All rights reserved.  For permissions, e-mail:

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